The introduction of La₂O₃ to Mn_0.75Ni_1.25CuO₄ ceramics was studied on the microstructure and electrical properties. The sintered Mn_0.75Ni_1.25CuO₄-xLa₂O₃ (0 ≤ x ≤ 0.3) bodies was typical polycrystalline, with cubic spinel structure of copper manganese oxide, rocksalt structure of nickel copper oxide, along with monoclinic phase of copper oxide and orthorhombic perovskite structure of lanthanum manganese oxide. It is found that La doping reduces the material grain size and changes its morphology from the plate-like form to a spherical staking-like form. The shape and size of the grains are strongly influenced by the addition of La to the system. The X-ray photoelectron spectroscopy analysis corroborates the presence of nonequivalent ions at octahedral sites. The obtained ρ_77K, B_77K/90K constant and activation energy of the negative temperature coefficient (NTC) Mn_0.75Ni_1.25CuO₄-xLa₂O₃ thermistors were in the range of 13.19–30.39 Ω cm, 315–326 K, and 0.0272–0.0281 eV, respectively. This means that the electrical properties can be adjusted to desired values, depending on the La content. Such ceramics could be used as potential candidates for NTC thermistors in a temperature range from 20 K to 90K. So these prepared NTC thermistors were intended to be used under low-temperature conditions.

Using a high-speed and high-resolution-camera system of droplets in glaze sprays and their impact on the surface of a green ceramic body based on silicate tiles have been characterized. The influence of the surface tension of the glaze slips on the droplet size distribution and their wetting behavior on contact with the green silicate body surface have been investigated. The unfired glaze layers have been studied by means of scanning electron microscopy and computer tomography. The impact angle of the droplets as well as the size of the droplets is of great importance for a high glaze surface quality.

Dense (97.3%) zirconium diboride (ZrB₂) ceramics were obtained via gelcasting and pressureless sintering. Four wt% B₄C was used as sintering aid. ZrB₂, SiC, and B₄C can codisperse well in the alkaline region, using a polyacrylate dispersant. Compared with monolithic ZrB₂ (Z), the mechanical properties of ZrB₂-SiC (ZS) were enhanced. The Vickers hardness and fracture toughness of ZS were (13.1 ± 0.6) GPa and (2.5 ± 0.4) MPa m^1/2, respectively.

Graphite foams with low, medium, and high densities were joined to Cu-clad-Mo, 430 stainless steel, titanium, and Inconel 625 using Cusil-ABA^® and Palcusil-5^®. Copper-clad-molybdenum and steel were also joined to SiC-coated foam. Well-bonded joints with partially infiltrated foam and with carbon ligaments enriched with Ti formed in Cusil-ABA joints of coated and uncoated foam. Low-density foams showed greatest braze penetration and penetration distance decreased with increasing foam density. Foam/metal joints with Palcusil-5 showed less penetration than Cusil-ABA. The tension test on foam/Cu-clad-Mo and foam/430 stainless steel joints made using Cusil-ABA revealed that the joints were always stronger than the foam.

In situ reduction of tungstic acid and cobalt chloride by dextrose in silica gel resulted in co-deposition of tungsten carbide-cobalt (WC–Co) nanoparticles with different proportions of cobalt (5–15 wt % of WC). X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy have been used for characterizing these nanoparticles. WC-Co aggregates of 25–30 nm size have been achieved, successfully.

The nanobioactive glass (58SiO₂-33CaO-9P₂O₅) powders were synthesized by simple sol–gel method. The prepared samples reveal amorphous nature, agglomerated spherical morphology with particle size of 100–150 nm. The specific surface area of nanobioactive glass (NBG) particle is 147 m²/g. The NBG samples were coated on titanium (Ti-6Al-4V) alloy through electrochemical deposition method. The particle size of the NBG-coated surface was in the order of 200–300 nm, and it was confirmed by atomic force microscopy (AFM) analysis. In vitro and AFM studies reveal the existence of higher bioactivity and uniform coating of NBG on implants at 80 V for 1 h.

Terbium-activated YAl₃(BO₃)₄ (YAl₃(BO₃)₄:Tb³⁺) phosphors were synthesized by both combustion method and solid-state reaction. It was found that the pure-phase YAl₃(BO₃)₄ phosphors synthesized by combustion method were obtained at 1000°C, which was 200°C lower than that by solid-state reaction. The average particle size of the combustion-derived phosphors increased with increasing temperatures. The luminescence characteristics in ultraviolet (UV) — vacuum ultraviolet (VUV) ranges for the YAl₃(BO₃)₄:Tb³⁺ phosphors were investigated. The bands from 175 nm to 300 nm were attributed to the 4f⁸-4f⁷5d¹ transitions of Tb³⁺. The other strong bands in the region from 125 nm to 175 nm were assigned to host absorption. The emission spectra showed the strongest emission at 542 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺. Moreover, the combustion-derived YAl₃(BO₃)₄:Tb³⁺ phosphors generated more intense luminescence than the solid-state-derived phosphors under UV excitation.

Diopside (CaMgSi₂O₆) ceramics was synthesized and fabricated by a simple solid-state reaction rather than other used processes. This new and economic approach for diopside fabrication consists mainly of replacing the usually used starting materials by other more economic (activated CaO·MgO powders), using conventional sintering and microwave sintering. The P₂O₅ addition (0.5–5.0 wt%) promotes sintering, crystallization, and bioactivity. Additionally, a considerably low weight loss ratio (0.21%) was also obtained for these samples, after 2 days of soaking in lactic acid. Carbonated hydroxyapatite (CHA) formation in simulated body fluid was confirmed for all sintered samples. Both sintering and CHA formation mechanisms were proposed.

Titanium oxide (TiO₂) nanoparticle coatings were deposited on the 316L stainless steel substrates by sol-gel method. The morphology, structure, and corrosion resistance of the coating were analyzed using SEM, AFM, X-ray diffraction, and electrochemical techniques. The deposition parameters employed to realize the anticorrosion performance including calcinations temperature, polyethylene glycol (PEG) content, pH value, and number of dipping cycles were investigated. Taguchi statistical experiments were carried out to determine the influence of the deposition variables on anticorrosion properties and optimal conditions. The results indicated that a higher anticorrosion performance of TiO₂ films could be achieved using 1 g of PEG in a sol with pH in range of 7–9, six cycles of dipping, and calcination temperature at 400°C. The Tafel polarization measurements indicate that i_corr value decreases about 200 times and the R_corr value increases around 57 times compared with uncoated 316L stainless steel.

The activation energies were estimated for conventional and microwave sintering of Zirconia-8 mol% Yttria (8YZ). The results were analyzed to explain the mechanisms responsible for enhancing flux/mass transport during microwave sintering. The activation energies were evaluated using isothermal and nonisothermal methods. The nonisothermal sintering resulted in higher values of activation energies, as compared to isothermal methods. This behavior may be due to the presence of more than one type of diffusion mechanism dominating throughout the process. The nonisothermal method represented activation energy values close to a single densification mechanism (either volume or grain boundary diffusion). A value of 500 ± 25 kJ/mol was observed for nonisothermal sintering of 8YZ with conventional heating. This value was close to the volume diffusion of Zr ion (500 kJ/mol). The microwave sintering (using nonisothermal method) resulted in activation energy values of 200 ± 27 kJ/mol, a value close to the grain boundary diffusion of the Zr ion.

An attempt to enhance both mechanical strength and thermal conductivity of glass-based tapes is described. Flexural strength of ~420 MPa and thermal conductivity of ~10.3 W/m/K have been achieved in fully densified tape comprising calcium aluminoborosilicate glass, aluminum nitride, and silicon carbide whiskers. Silicon carbide whiskers aligned parallel to the casting direction contributed significantly to the reinforcement of the microstructure with accompanying extensive densification over a broad temperature range. These results are compared with the more typical alumina filler substituted for the aluminum nitride.

This article develops a new intuitionistic fuzzy multi-attribute group decision-making model to solve precursor selection problems. The proposed model is based on a hybridization of intuitionistic fuzzy sets theory, grey relational analysis and technique for order performance by similarity to ideal solution method. To better describe the uncertain decision environment, multi-attribute group decision-making method with completely unknown weights of both experts and attributes is proposed in an intuitionistic fuzzy setting. Finally, the selection of the carbon source in synthesis of nanocrystalline titanium carbide powders by sol-gel route as an application example is solved by the proposed model, and the implementation of the model is illustrated completely.

A theoretical relation between processing parameters and porosity (29–56%) of mullite-bonded porous SiC ceramics was derived and validated with experimental data. Porosity-dependent variation of fracture strength (9–34 MPa) and elastic modulus (7–28 GPa) was explained by the minimum solid area model. At room temperature, the Darcian, k₁ (1.2 × 10⁻¹³–1.6 × 10⁻¹² m²) and the non-Darcian, k₂ (4.6 × 10⁻⁹–2.7 × 10⁻⁷ m) permeability coefficients showed linear variation with porosity. Tests conducted up to 650°C indicated an increase in k₁ with temperature and a reverse trend for k₂. Airborne NaCl nanoparticle filtration tests showed good performance of SiC ceramics with fractional collection efficiency of >99% at 46–56% porosity levels.

Effects of postdensification annealing on microwave dielectric properties of Ba([Mg_1−xCo_x]_1/3Nb_2/3)O₃ ceramics have been investigated. The 1:2 ordered complex perovskite structure is obtained in the entire composition range of the as-sintered samples, and the ordering degree decreases with increasing x. With increasing x, the dielectric constant (ε_r) increases, the temperature coefficient of resonant frequency (τ_f) shifts toward negative and can be tuned to near-zero for x = 0.6, while the Q × f value decreases. With postdensification annealing at 1400°C in air for 24 h, the ordering degree increases, and Q × f value can be significantly improved without obvious change in ε_r, while the composition for obtaining near-zero τ_f shifts to x = 0.8. Annealing at 1375°C and 1425°C in air for 24 h does not improve microwave dielectric properties more than annealing at 1400°C. A good combination of microwave dielectric properties of Ba([Mg_1−xCo_x]_1/3Nb_2/3)O₃ ceramics after postdensification annealing at 1400°C in air for 24 h has been obtained for x = 0.8: ε_r = 31.7, Q × f = 76,900 GHz, τ_f = 3.3 ppm/°C.

By sol-gel process, mullite samples doped with 0.002M, 0.02M, 0.1M, 0.15M, and 0.2M of iron, nickel, and copper are prepared. Prepared gels were then dried, grinded, pressed into pellets, and sintered at temperatures 1000°C and 1300°C for 4 h. Mullite densification behavior was analyzed. Our intention is to study the role of metal ions in influencing mullitization behavior in the case of the sol-gel reaction process, to provide useful information of mullite. This study deals with the effect of metal ions on mullite formation, microstructure, and densification behavior in single-phase sol-gel-derived mullite.

The Ceramic Leadership Summit is designed to explore business opportunities, emerging technologies, and critical issues that challenge the ceramic and glass materials community. In 2012, the 3rd Ceramic Leadership Summit was held in conjunction with the 4th International Congress on Ceramics (ICC4). The one-day program focused on technology transfer, entrepreneurship, and product innovation. Important topics discussed included strategies for creating and sustaining a small business, intellectual property protection, technology transfer, and mechanisms for government–university–industry partnerships. International speakers in the case study session addressed these topics from the perspective of their local and national policies and practices. Several of the case study presentations highlighted the use of “waste materials” in the creation and application of new technologies and products.

Preparation and microwave dielectric properties of B₂O₃-doped CaLa₄Ti₄O₁₅ ceramics have been investigated. X-ray diffraction data show that CaLa₄Ti₄O₁₅ ceramic has a trigonal structure coupled with a second phase of CaLa₄Ti₅O₁₇. The CaLa₄Ti₄O₁₅ ceramic with addition of 0.5 wt% B₂O₃, sintered at 1220°C for 4 h, exhibits microwave dielectric properties with a dielectric constant of 45.8, Q × f value of 24,000 GHz, and temperature coefficient of resonant frequency (τ_f) of −19 ppm/^°C. B₂O₃-doped CaLa₄Ti₄O₁₅ ceramics, which have better sintering behavior (decrease in sintering temperature ~ 330°C) and dielectric properties than pure CaLa₄Ti₄O₁₅ ceramics, are candidates for applications in microwave devices.

Most additive manufacturing (AM) techniques have in common that material is spread out as thin layers of a dried powder/granulate by a roller or a shaker system. These layers are mostly characterized by a low packing rate. On the other hand, appreciable densities can be reached by the use of ceramic slurries. In this context, the layer-wise slurry deposition (LSD) has been developed. Specific features of the LSD process are reflected on the basis of already existing additive manufacturing technologies. The microstructure of laser-sintered bodies will be discussed, and strategies for an improved microstructure during sintering will be introduced.

Ferroelectric Ba_0.55Sr_0.4Ca_0.05TiO₃ (BSCT) ceramics with nano-MgO additive have been prepared by typical electrical ceramic technology sintered at 950°C for 2 h. The influence of the additive content on the sintering behaviors of BSCT ceramics is investigated. The results show that the interactions of MgO with BSCT and B₂O₃-Li₂O liquid sintering additive help to form wetting boundaries for accelerating densification process, promote the grain growth of BSCT ceramic. The BSCT ceramic with 20 wt% nano-MgO possesses uniform microstructure, high densification, and superior dielectric properties. The modification mechanism of nano-MgO on BSCT ceramic is summarized as “MgO assisted wetting sintering model.”

BST–ZnO–B₂O₃–composite thick films have been investigated regarding their suitability as low-temperature sintered tunable microwave dielectrics. The investigations showed that already a small amount of ZnO–B₂O₃ additive can remarkably reduce the sintering temperature down to 900°C. Microstructural investigations of the thick films revealed the formation of an amorphous intergranular phase and a clustering of particles for high additive amounts. The microwave characterization showed a reduction in relative permittivity, dielectric loss, and tunability of the thick films with increasing additive content. These results demonstrate the potential to tailor the material abilities by varying the additive content.

Well-crystallized Cobalt ferrite nanoparticles with mean size of 20 nm and high saturation magnetization (82.9 emu/g) were synthesized at a low temperature (≤100°C) by microwave-assisted solid–liquid reaction ball-milling technique without subsequent calcination. CoC₂O₄·4H₂O and Fe powder were used as raw materials and stainless steel or pure iron milling balls with diameter of 1.5 mm were used. As a contrast, solid–liquid reaction ball milling without microwave assistance was also investigated. The results showed that this is a simple, environmentally friendly, and energy-saving technique for ferrite nanocrystal synthesis.

A reddish-orange-emitting SnO₂:Eu³⁺ phosphor for field emission displays (FEDs) was successfully synthesized via a homogeneous precipitation route using urea as a precipitant. The influences of the dopant concentration of Eu³⁺ and calcination temperature on optical properties were investigated. The low-voltage field emission properties of the FED device prepared using the synthesized SnO₂:Eu³⁺ phosphors were reported. Under the UV light, SnO₂:Eu³⁺ phosphors display the strong orange–red emission peaked at 587, 591, and 597 nm due to the ⁵D₀→⁷F₁ magnetic dipole transition of Eu³⁺. The phosphor doped with 1.0 mol% Eu³⁺ possesses the highest photoluminescent (PL) intensity. Under the low-voltage excitation of 300 V, the fabricated FED device exhibits the bright orange–red emission, high-voltage brightness saturation, and high color purity, which has a potential application in low-voltage full color FEDs.

Silicon nitride ceramics were prepared from a high-purity silicon powder doped with 2 mol% Y₂O₃ and 5 mol% MgO as sintering additives via a route of sintering of reaction-bonded silicon nitride (SRBSN). The materials sintered at 1900°C for 3, 6, 12, and 24 h had thermal conductivities of 109, 125, 146, and 154 W/m/K, and four-point bending strengths of 786, 676, 608, and 505 MPa, respectively. The fracture toughness values, determined by the single-edge-precracked-beam (SEPB) method, were 8.4, 8.6, 9.7, and 10.7 MPa m^1/2 for the materials sintered for 3, 6, 12, and 24 h, respectively, which were similar to the results measured by the chevron-notched-beam (CNB) test method. The materials sintered for longer times (12 and 24 h) showed stronger R-curve behaviors over longer range of crack extension, in comparison with the materials sintered for shorter times (3 and 6 h).

Nanoporous LTA-type zeolite membranes were synthesized on α-Al₂O₃ disk as substrate using secondary growth method. A gel formula of 1 Al₂O₃: 2 SiO₂: 3.4 Na₂O: W H₂O in molar basis was chosen while its water content (W) was varied. Four levels of water contents of 140, 155, 175, and 200 were selected for membrane synthesis. The results showed that the best membrane was synthesized with water content of 155. The most efficient zeolite membrane showed a permeation flux of 0.5 kg/m²/h and a separation factor of 3800 in dehydration of a 5/95 (wt%) water/isopropanol mixture at 298 K.

The aim of this study was to prepare and to characterize the structure of Al₂O₃–3YSZ composites with 5% TiO₂ addition as well as the surface modification upon treatments with SnF₂ and NaBF₄, respectively. SEM micrographs showed the controlled densification of the composites as an effect of 3YSZ and TiO₂ addition to alumina matrix. By FTIR and XRD, the characteristics of Al-O and Zr-O vibrations, respectively, the diffractions lines related to α-corundum and zirconia in tetragonal phase were discussed. Qualitative and quantitative results obtained by XPS and ATR FTIR demonstrated that the proposed materials are more sensitive to SnF₂ than to NaBF₄ treatment.

Pure and doped hydroxyapatite (HA) nanocrystalline powders (Ca_10-xMg_x(PO₄)₆OH₂) were synthesized using sol-gel process. For this, calcium nitrate tetrahydrate, magnesium nitrate hexahydrate, and phosphorous pentoxide were used as precursors for Ca, Mg, and P, respectively. Calculated amounts of magnesium ions (Mg⁺²) especially from 0 to 10% (molar ratio) were incorporated as dopant into the calcium sol solution. The structure and morphology of the gels obtained after mixing the phosphorous and (calcium + magnesium) sol solution were different, and their condensations in time depend on the quantities of magnesium added. The several powders resulting from the gels dried and sintered at 500°C for 1 h were characterized by thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and inductively coupled plasma (ICP). Additionally, their agglomeration, morphology, and particle size were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specific surface area of each sample was measured by the Brunauer–Emmett–Teller (BET) gas adsorption technique. The results of XRD, FTIR, and ICP values ranged between 0.45 and 2.11 mg/L indicated that the magnesium added in the calcium solution was incorporated in the lattice structure of HA so prepared, while those obtained by SEM and TEM confirmed the influence of Mg on their morphology (needle and irregular shape) and crystallite size, which is about 30–60 nm. The as-prepared powders had a specific surface area ranged between 6.37 and 27.60 m²/g.

Nano-crystalline Nd_1.8Ce_0.2CuO_4+δ synthesized by combusting mixed precursor materials under microwave heating followed by sintering at 1000°C for 4 h exhibits highest dc conductivity (σ = 2.50 S/cm at 700°C) due to lowest crystallite size (50 nm), which compared with preparation by conventional combustion and solid-state reaction. Symmetric cells configured as electrode/electrolyte/electrode were fabricated by spin coating. The lowest area specific resistance (ASR) value of 0.50 Ω cm² was obtained at a temperature 700°C. Morphology of cathode material is largely dependent on the preparative route, and that influences ASR. Low frequency complex impedance curve was modeled by Gerischer element. The electrochemical performance suggested absorption of oxygen by the Nd_1.8Ce_0.2CuO_4+δ lattice. Combustion of precursors using microwave heating promises to be a potential route for materials preparation to achieve improved electrochemical performance of cathode in intermediate temperature solid oxide fuel cell applications.

The present work aims at synthesis and study the bioactivity of porous alumina scaffolds coated with calcium pyrophosphate. Characterization of the formed calcium pyrophosphate and the coated scaffolds was assessed by X-ray diffraction analysis and scanning electron microscope examinations. The in vivo studies revealed the ability of the porous scaffolds to regenerate bone tissue in femur defects of albino rats. Histological analysis showed that the defect is almost entirely filled with new bone. The formed bone is characterized as a mature bone. The produced bone grafts are intended to be used as bone substitute or bone filler.

A novel solution combustion method has been used to prepare Mg-Mn ferrites of various compositions, Mg_0.9Mn_0.1Fe_1-xO₄ where x = 0.2, 0.4, 0.6, 0.8, and the properties were investigated in the present work. Nano-size Mg-Mn ferrite particles with diameter in the range of 8~ 15 nm were successfully formed via this method. The combustion temperature of the oxidation-reduction was apparently occurred at 200°C. The result of X-ray diffraction (XRD) analysis indicated that the as-burnt powder affords a pure single spinel ferrite phase at low temperature. The thermal analysis of nitrate–citrate gels was characterized by DTA-TG. The TEM and SEM observations give the morphology and microstructure of the products. The dielectric properties of the sintered Mg-Mn ferrites were investigated by using HP/Agilent 4291B RF impedence/material analyzer. It was found that there was no maximum dielectric loss within the measured frequency range until 1 GHz due to excellent compositional control in this method.

Reaction-bonded boron carbide was manufactured by infiltrating porous boron carbide preforms at 1273 K with a Mg-Si eutectic alloy. The resulting composite material consists, in addition to the original B₄C, of SiC, Mg₂Si, and a Mg-rich complex boride/carbide Mg_x(Al,Si)_y(B,C)_z phase. The composites display high hardness (1700 HV), Young's modulus (356 MPa) and a moderate bending strength (230 MPa). The ballistic efficiency (of about 6.7), as determined by the depth of penetration method, is much higher than that of alumina and similar to that of silicon-infiltrated reaction-bonded composites.

Two different specific surface area of starting BaCO_3, 10 and 30 m²/g, are used to prepare solid-state BaTiO₃ powder. Pure tetragonal BaTiO₃ was obtained at a lower calcination temperature with smaller BaCO₃, and the kinetic calculations of activation energy also agree with it. A clear, thin, and nano-sized cubic BaTiO₃ clusters on TiO₂ particles were also observed. A narrower particle size distribution of BaTiO₃ powder (350 nm) was obtained from 30 m²/g of starting BaCO₃ at 1000°C. After sintering with reducing atmosphere, the ceramics with potential of X8R or X7R specifications and a clear core–shell microstructure were obtained in this study.

Si₃N₄–SiC composite ceramics used for volumetric receivers were fabricated by pressureless sintering of micrometer SiC, Si₃N₄, andalusite, and other minor additions powders. Mechanical, thermal expansion, thermal conductivity, and thermal shock resistance properties were tested at different sintering temperatures. The best sintering temperature of optimum formula A2 is 1360°C, and the bending strength reaches 79.60 Mpa. And moreover, its thermal expansion coefficient is 6.401 × 10⁻⁶/°C, thermal conductivity is 7.83 W/(m K), and no crack occurs even subjected to 30 cycles thermal shock with a bending strength increase rate of 4.72%. X-ray diffraction results show that the phase constituents of the sintered products mainly consist of SiC, Si₃N₄, mullite, and quartz. Microstructure that is most appropriate and exhibits maximal thermal shock resistance was detected using SEM. The porosity of Si₃N₄–SiC ceramic foam prepared from formula A2 is 95%, which provides a rapid and steady action for the receiver. The evaluation of the present foam shows that Si₃N₄–SiC ceramic composite is a good candidate for volumetric receivers.

Although the utilization of silicon dice in electronic devices has been in place for approximately 50 years, its widespread application has occurred more recently with the rapid expansion of the consumer markets for digital devices such as cameras, personal computers, video players, and smart phones. In particular, due to the recent market drive in the miniaturization and cost reduction of electronic products, silicon dice are often utilized without encapsulation and mounted directly to the substrate by means of conductive adhesives or BGA mounting. Silicon die often need to be thinned to a few hundred micrometers thickness to fit into compact devices and to reduce parasitics. The intrinsic brittle nature of silicon in combination with the lack of mechanical protection such as encapsulation has made fracture of bare dice a typical failure mechanism in handheld electronic devices. In the current work, we tested to failure {100} silicon dice and obtained mirror–mist boundary measurements for correlation to the fracture strengths of the parts. This work will also present various practical examples of how to reliably conduct failure analysis of fractured silicon dice. The intrinsic brittle nature of silicon in combination with the lack of mechanical protection such as encapsulation has made fracture of bare dice a typical failure mechanism in handheld electronic devices such as cameras, portable computers, tablets, media players, and smart phones. In these products, silicon dice are often utilized without encapsulation and are attached directly to the substrate by means of conductive adhesives or ball grid array mounting. Modern silicon dice used in these products typically have small dimensions and higher flexural strength compared to their predecessors. Prior silicon fractographic findings have investigated low strength failures. In the current work, we extend the quantitative fractography of silicon to the high failure stress regime. We have mechanically tested modern silicon dice to failure by four-point bending and obtained mirror–mist boundary measurements for correlation to the fracture strengths of the specimens. Two key areas are addressed which improve the practical application of quantitative fractography to modern silicon dice: (1) application of silicon fractography to high flexural strength regimes and (2) development of a systematic means of reliably measuring fracture surface features.

Heat exchangers are used in gas burners as recuperators. Their efficiency is proportional to their surface which is usually limited by the burner length and diameter. Ceramic recuperators used nowadays in industrial burners are tubular. We studied and developed a new generation of ceramic heat exchanger with the final goal of increasing the efficiency or, at similar efficiencies, of reducing their size and weight. A commercial SiSiC heat exchanger component was used to guarantee safety and robustness. The use of structured textile geometries followed by their conversion into a ceramic is the main innovation of this work.

This study aimed to investigate in vitro the montmorillonite (MMT) as carrier for gemcitabine hydrochloride (dFdU.HCl) and oxaliplatin (DACH-Pt). The maximum adsorption capacities of MMT and their respective mechanisms were determined through a soaking procedure (387.5 mg dFdU.HCl/g MMT were adsorbed in 32 h, 83 mg DACH-Pt/g MMT in 48 h). Release kinetics studies were carried out soaking the samples of loaded MMT in simulated body fluids (SBF). Finally, in an attempt to explain the mechanism of drug delivery, the chemical interactions were studied theoretically, according to the adsorption and release profiles.

A substantial increase in sinterability, high-temperature flexural strength, thermal stability in combination with an average thermal expansion of 0.42 × 10⁻⁶/^°C (30–1000°C) is achieved through magnesium silicate (Mg₃Si₄O₁₀(OH)₂) doping of Aluminum Titanate (Al₂TiO₅) ceramics. Doped specimens exhibited the sintered density of 99% of theoretical density at 1550°C and a maximum enhancement of 169.23% (70 MPa) in flexural strength at 1200°C as compared with 26 MPa measured at 30°C. Enhancement of flexural strength at elevated temperature can be attributed to the increasing extent of thermally activated crack blunting with increasing temperature, which is further evident from the dilatometric hysteresis curve recorded for these samples. XRD investigations of undoped (Al₂TiO₅, AT) samples annealed at 1100°C for 5 and 10 h have shown clear evidence of decomposition to precursor oxides by 7% and 21.13%, respectively. However, the samples of magnesium silicate–doped Al₂TiO₅ (TAT) under identical conditions have shown no sign of decomposition, indicating significantly high thermal stability. TAT formulations were also extrusion processed to investigate the suitability of forming cellular honeycomb structures. TAT formulation with superior thermo-mechanical properties and excellent adaptability for extrusion processing can be explored for the development of next generation diesel particulate filters (DPF).

Amorphous oxide film was prepared on the titanium substrate by plasma electrolytic oxidation (PEO) technology in acidic electrolyte consisting of tungstate and then subject to calcination in air. Films were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and UV-Vis DRS before and after calcination, respectively. Calcined film consisted of anatase and WO₃, showing more open structure compared with uncalcined film. Furthermore, the absorption edge of calcined film was shifted to visible light region and the recombination of photo-induced carriers was inhibited effectively, resulting that WO₃/TiO₂ composite film produced by PEO technology and calcination should be effective as a visible-light-responsive photocatalyst.

This study evaluates the photoactivity of novel zeolite-based TiO₂ composites modified with metal particles for the photoreduction of Cu²⁺, depending on the zeolite and metal particles (Ag or Fe) content and to establish the photoreduction mechanism. The composites have been prepared by incorporating zeolite particles in the sols during the sol-gel preparation of the TiO₂, followed by impregnation of the gels in solutions containing metal ions. The zeolite-based TiO₂ composites have been characterized using X-ray diffraction, Raman and FTIR spectroscopy techniques and TEM microscopy. The role of zeolite particles in the photoreduction process was demonstrated by using different kinetic models. The apparent constant rate for photoreduction increases in direct proportion with the content of zeolite and is higher for the composites modified with Fe than for those modified with Ag nanoparticles. The results demonstrate that composites have a higher photocatalytic efficiency than TiO₂. The experiments in this study reveal that the migration of Cu²⁺ in solution occurs rapidly and that the diffusion through the film on the composite's surface and, subsequently, the photoreduction process are the rate limiting steps. The role of the zeolite in photoreduction is to diminish the recombination rate of the charge carriers.

SrLn₂Al₂O₇ (Ln = La, Nd, Sm) ceramics were proposed and investigated as new candidates for ultra-low loss microwave dielectric materials. These ceramics indicated the Ruddlesden–Popper structure of general formula A_n+1B_nO_3n+1 with n = 2, which was composed by n perovskite layers alternating with one rock-salt layer. Very high Qf value combined with a dielectric constant around 20 was obtained in the present ceramics, where the near-zero temperature coefficient of resonant frequency varied from negative to positive with changing Ln from La to Sm. The best combination of microwave dielectric characteristics was obtained as the following: ε_r = 18.2, Qf = 71,680 GHz, and τ_f = −22.1 ppm/°C for SrLa₂Al₂O₇; ε_r = 20.5, Qf = 65,500 GHz, and τ_f = −4.3 ppm/°C for SrNd₂Al₂O₇; and ε_r = 21.6, Qf = 64,680 GHz, and τ_f = +4.0 ppm/°C for SrSm₂Al₂O₇.

Immobilization of photocatalytic powder is crucial to obtain industrially relevant purification processes. To achieve this goal, self-supporting TiO₂ foams were manufactured by a polyacrylamide gel process. These gels were calcined at different temperatures to study the effect of the calcination temperature on foam characteristics (rigidity, crystallinity, and porosity) and its influence on photocatalytic activity. The results show that an optimal degradation is achieved for those foams calcined between 700 and 800°C. Calcination at higher temperatures results in a steep decrease in activity, explained by stability issues of the material due to formation of Na₂SO₄ phases and a larger rutile fraction.

Understanding the effect of particle size on the optical properties of phosphor is important to increase packaging efficiency in white light-emitting diodes (LEDs). We have investigated the effect of particle size (10–20 μm, 20–25 μm, 25–32 μm) on the optical properties of a yellow silicate phosphor adopted in white LEDs. X-ray diffraction results show negligible modification in crystallinity as the particle size of the yellow silicate phosphor varies, whereas the photoluminescence excitation intensity and quantum yield are enhanced as the particle size increased. LED packages fabricated using phosphors with different mean particle sizes, and their optical properties were analyzed. The radiant flux improved with increasing particle size, whereas the luminous flux increased with decreasing particle size. The effect of immersion on the optical properties of the LED light source has been also measured, and the details are discussed.

La_0.7Sr_0.3MnO_3±δ powders were fabricated by solid-state reaction method at 1473 K for 4 h. The precursors were prepared by ball-milling raw materials for 3, 6, 9, and 12 h, respectively. The crystal structures, particle size, and morphologies of precursors and prepared La_0.7Sr_0.3MnO_3±δ were characterized by XRD, laser particle size analyzer and SEM, respectively. It is found that La_0.7Sr_0.3MnO_3±δ possessed large particle size by ball-milling raw materials for a long time. Results indicated that La_0.7Sr_0.3MnO_3±δ, synthesized by ball-milling raw materials for 3 h, exhibited the optimal microwave absorption properties. The maximum reflection loss was −28.8 dB, and the −6 dB absorption bandwidth was 5.80 GHz.

TiAlN/SiN_x multilayers were fabricated by RF reactive magnetron sputtering. Characterizations by TEM, dark-field images, and SEM revealed the dependence for the thickness of SiN_x (l_SiNx) on the texture and microstructure evolution in multilayers. Epitaxial stabilization in multilayer ameliorated the hardness and H/E ratio. With increasing the l_SiNx, the amorphous SiN_x altered the coherent interfaces and the superlattice structure, leading to an appreciable decrease in hardness. Nevertheless, this fine-grained coating exhibited superior resistance to plastic deformation. In the ball-on-disk wear tests, the observation of coefficient of friction, worn surfaces, and cross-sectional worn scars verified that multilayers showed better tribological resistance than that of TiAlN monolayer. Two antiwear mechanisms on the basis of hardness variation and microstructure evolution were proposed to elucidate the favorable durability of TiAlN/SiN_x multilayers with various l_SiNx.

Dense, highly textured ZrB₂ and ZrB₂–MoSi₂ ceramics were fabricated via a strong magnetic field alignment method followed by spark plasma sintering. Unlike with the previous studies, which only focused on the alignment of single-phase particles, both ZrB₂ and MoSi₂, which exhibited a magnetic anisotropy, have been aligned in this study. The alignment of MoSi₂ in the same direction of ZrB₂ enhanced the degree of orientation of ZrB₂, decreased the grain size, but increased the aspect ratio of the platelet ZrB₂ grains. The microstructure and anisotropic mechanical properties as well as the oxidation resistance in different directions were discussed.

A synthesis of a new dental material, based on nano-structured highly active calcium silicates and calcium carbonates, is described in this paper. Phase analysis of this material, before and after hydration, was performed by X-ray diffraction and showed that active silicate phases were transformed into tobermorite phase, while carbonates remained unchanged. The mechanism of hydration was fully described. The morphology of the sample was studied by SEM, and typical appearance of the present phases was particularly discussed. The mechanical properties and setting time of this material make it very promising for potential application in dental practice.

The recent quest for developing new low carbon footprint construction materials to lower the environmental emissions and implications of infrastructure has imposed many challenges and has created many opportunities for research and development in academia and industrial sectors. The present paper, discusses and summaries these challenges and opportunities and provides a synopsis of the ideas presented in the Infrastructure sessions of the Fourth International Congress on Ceramics (ICC4). This paper also discusses recent advances in the development of sustainable infrastructure materials.

The present article presents first comparative study on three different dry solgel methods of producing new alumina-based dark violet, light pink ceramic nanopigments as well as ruby-red ceramic nanopigment — an alternative to the Purple of Cassius. Gold nanoparticles are built directly on a carrier of an aluminum oxide nanopowder, which finally yields Al₂O₃/Au nanopowders possessing colors ranging from light pink to light violet as well as ruby-red.

The relationship between Sn substitution for Ti and microwave dielectric properties of Mg(Ti_1-xSn_x)O₃ ceramics was investigated. Sn⁴⁺ could substitute for Ti⁴⁺ in MgTiO₃ and increase the crystal volume. All samples exhibited the MgTiO₃-type phase with ilmenite structure as main phase. At the x range from 0 to 0.05, the secondary phase of Mg₂TiO₅ was observed. Upon further increasing Sn content up to 0.15, the SnO₂ phase appeared. When the x value increased from 0 to 0.05, the dielectric constant decreased slightly and the quality factor increased sharply, whereas the dielectric constant increased and the quality factor decreased as the x value varied from 0.05 to 0.15. The temperature coefficient of resonant frequency moved toward positive value with Sn substitution. In particular, at the x range from 0.05 to 0.07, the ceramic sintered at 1360°C for 4 h exhibited excellent microwave dielectric properties of ε_r = 16.8–17.1, Q_f = 298,000–312,000 and τ_f = −53~−50 ppm/°C.

Pyrolytic boron nitride (pBN) was prepared with a nonenergetic chemical vapor deposition. Two tests were performed (i) short time deposition to investigate rate and volume deposition of injected reaction gases and (ii) long time deposition to characterize possible qualitative differences of the formed BN layer. SEM, XRD, FTIR, Raman spectroscopy, and Terahertz time-domain spectroscopy proved that there are small qualitative differences in the pBN deposited at various distances from the blast pipe. The quality of the phase synthesized was resolved with highly sensitive THz-TDS technique, the index of refraction n_pBN varied at 2.0 THz (66.6 cm) from 2.018 ± 0.003 to 2.124 ± 0.005.

Using Al-Si-Ti-C powder mixtures, TiC grains locally reinforced Al-Si matrix composites were produced through self-propagating high-temperature synthesis and casting method. The formation of TiC could be ascribed to the dissolution–reaction–precipitation mechanism. The TiC grains were uniformly distributed in the locally reinforced regions of the Al-Si matrix. With increasing Al-Si content, the size of TiC grains decreased. No pores and cracks were present at the interface between the Al-Si matrix and the reinforced regions. Wear resistance of the locally reinforced regions is significantly improved compared with that of the Al-Si matrix.

Low loss Mg₂TiO₄ (MTO) ceramics have been synthesized by mechanical synthesis method. The effect of processing parameters, on initial particle size, microstructure, relative density, and microwave dielectric properties of MTO ceramics are investigated. The maximum relative density was obtained 97.75%, and uniform microstructure is observed for the sample sintered at 1325°C for 3 h. The driving force for the sintering can be attributed to the surface energy of fine powders and their defect energy. There is not much variation in dielectric constant (ε_r) where as Q × f_o is affected and the values of Q × f_o are in the range of 99,500–155,500.

In this study, the thermal stability of hydroxyapatite was investigated as a function of synthesis factors such as pH, aging time, and calcination temperature. Hydroxyapatite was prepared using calcium hydroxide and orthophosphoric acid and the effect of heat treatment on lead sorption were determined by the batch equilibrium technique. Although the thermal stability of powders was independent from the synthesized condition up to 800°C the material produced at neutral pH and aged during 24 h indicated the suitable stability even at 1000°C. Also, the powder synthesized at above condition completely removed lead compared to that for the other powders.

β-Tricalcium phosphates have been widely used as biomaterials for bone substitutes; however, the poor mechanical properties limit the application in bearing loading bones. In this study, nano-hydroxyapatite has been introduced to improve the mechanical properties for porous bioceramic scaffolds. Nanocomposites containing 0–10 wt% needle-like nano-hydroxyapatite were prepared for investigation. It has been found that needle-like nano-hydroxyapatite improves the toughness, hardness, and compressive strength of the porous β-tricalcium phosphates scaffolds, as well as the microstructure properties. The study provides a reference for the development of safe, excellent bone scaffolds for bone tissue engineering.

Residual stresses were measured on numerous multi-curved, ballistic tiles made from either silicon carbide or boron carbide. Residual stresses were measured at 155 locations to determine what affect parameters such as material, material processing, tile geometry, and manufacturer had on residual stress type and magnitude. 23% of data points had tensile residual stress. The highest residual stresses were measured in tiles with either the largest surface area or smallest plate thickness. Higher stresses were measured in silicon carbide tiles compared with boron carbide tiles. Residual stresses in tiles consolidated by hot pressing measured on average 10 MPa higher than those by pressureless sintering.

Combinatorial composition films of Ba_xSr_1-xTiO₃ were grown on two-inch p-Si by pulsed laser deposition. Large areas of six different combinatorial composition films were grown on the same wafer using three primary target materials. Consequently, the deposition of Ba_0.5Sr_0.5TiO₃ films was obtained from targets BaTiO₃ and SrTiO₃, the deposition of Ba_0.3Sr_0.7TiO₃ films was obtained from targets SrTiO₃ and Ba_0.6Sr_0.4TiO₃, and the Ba_0.8Sr_0.2TiO₃ film was obtained from targets Ba_0.6Sr_0.4TiO₃ and BaTiO₃. The results indicate that the deposited materials are perovskite structures with high dielectric constants ranging from 49.4 to 193.2 and leakage current densities as low as 1.25 × 10⁻⁷ A/cm² at −2V.

C_f/SiC composites were fabricated using fiber coatings including CNTs and matrix infiltration using the polymer impregnation and pyrolysis process. Interface between fiber and CNTs (CF/CNTs) was tailored to optimize mechanical properties of hybrid composites. The tailored interphases, such as Pyrocarbon (PyC) and PyC/SiC, protect fibers from degradation during the growth of CNTs successfully. Hybrid composites with well-tailored CF/CNTs interface displayed significantly increased mechanical strength (352 ± 21 MPa) compared with that (34 ± 3 MPa) of composites reinforced with CNTs, which grown on carbon fibers directly. The interfacial bonding strength of hybrid composites was improved and optimized by tailoring the CF/CNTs interface. Interfacial failure modes were studied, and a firm interface bonding at the joint where CNTs grown was observed.

Magnetron sputtering has been used to deposit Ni-rich nickel oxide thin films. Based on the switching of lateral current conduction in the nickel oxide thin film between two in-plane electrodes, a planar write-once-read-many-times memory device has been demonstrated. The switching from a low-conductance state (i.e., the OFF state) to a high-conductance state (i.e., the ON state) is induced by a writing voltage, and it is irreversible due to the formation of tilted conductive filaments that are hard to be dissolved by the Joule heating effect. For 80 devices under test, the writing voltage is in a narrow range of 2.0−3.5 V and the ON/OFF resistance ratio is larger than 10⁵ at the reading voltage of 0.3 V. An excellent reading endurance (10⁶ readings) for both ON and OFF states is demonstrated. The device is promising in low-power applications as it can operate at ultra-low voltages (e.g., the reading voltage can be below 100 mV).

Glass infiltrated alumina is one of the popular materials for fabrication of dental prostheses. Achieving complete and uniform glass infiltration is important to achieve desired properties in dental prostheses. This study examined the role of various factors on glass infiltration in sintered porous alumina preforms (porosity ~ 27%). Observations on infiltration in porous alumina samples at a heating rate of 3°C/min at 1100°C for 2 h showed residual glass on the surfaces of the samples indicating incomplete infiltration. Rapid heating of the samples to the peak infiltration temperature by introducing the samples into a preheated furnace resulted in complete infiltration of glass into the samples in <90 min. In addition to heating rate during infiltration, influence of soaking duration and the particle size of glass powder on glass infiltration were also examined.

The dispersion and rheology of aqueous ZrB₂ nanosuspensions were investigated by zeta potential measurements, particle size measurements, sedimentation tests, and rheology measurements, with poly (acrylic acid) (PAA) as dispersant. Results showed that the dispersion and rheology of nanosized ZrB₂ suspensions in aqueous media were dependent on pH value, PAA concentration, solid loading, and ball milling time. Concentrated (up to 30 vol% solid loading) and well-stabilized aqueous ZrB₂ nanosuspension with low viscosity (0.485 Pa s at 60/s) was prepared at pH 10, with 1.0 wt% PAA.

Hydroxyapatite coating was developed with high degree of crystallinity on SS316L substrate by the microplasma spraying technique. Systematic in vitro study of the coating was conducted after the immersion into the simulated body fluid for 1–14 days. Inductively coupled plasma–atomic emission spectroscopy, X-ray diffraction, Fourier transformed infrared spectroscopy, and scanning electron microscopy were utilized for physicochemical and microstructural characterizations. Nanoindentation technique employed to evaluate the nanohardness and Young's modulus of the coating at a constant load of 100 mN. Further, the tribological characteristic was also examined by microscratch testing at a ramping normal load of 10–10.6 N.

Part of the symposium on Nanostructured Materials at the Fourth International Congress on Ceramics (ICC4) dealt with health aspects related to these materials. Major issues discussed included definitions and measurements of nanoparticles, best test protocols, collaboration and communication between, for example, materials scientists and biologists, and the plethora of information and regulations (that is sometimes even conflicting). Emerging opportunities were identified in terms of obtaining uniformity of nomenclature and testing standards, education and training of a new generation of multidisciplinary researchers, and understanding and then fully exploiting the positive aspects of nanomaterials, including improvements to human health.

The goal of this study is to review developments in nanoceramics as discussed during presentations on the subject during the International Ceramic Congress (ICC4) held in Chicago on July 2012. As nanotechnology is such a broad subject affecting many industrial sectors, some presentations in other sessions were included as well. The study has been organized according to the dimensions of the nanoscale material starting with nanoscale entities or particulates followed by nanothin films and finally bulk nanoceramics where the nanoscale character lies in the structure. Developments on hybrid nanocomposites containing at least one ceramic compound were often included in the presentations and are discussed in a separate section. The promise of nanotechnology is also to discover materials with totally new properties or combinations of properties. One such example presented in depth at the conference is presented. The study concludes with a section on issues and opportunities. In general, it can be said that the very large investments that were made more than a decade ago into nanotechnology start to pay off dividends. Products are appearing on the market and can have a substantial impact there. Other commercial applications are on the horizon. Because of the wide scope of the technology, there are still plenty of opportunities for research and development. A particular issue that was mentioned by a number of speakers is that of upscaling, which can be understood literally as interfacing the nanostructure with the micro-, meso-, and macroworld. However, often one means the implementation on the factory floor of processes that have been developed within the laboratory.

CaBi₂Nb₂O₉ ceramic is a promising candidate for high-temperature piezoelectric applications due to its high Curie temperature. However, extremely low piezoelectric properties hinder its application. A combination of Sm³⁺ donor doping and texturing was applied to address this problem. Piezoelectric coefficient, T_c, and resistivity of textured Ca_0.95Sm_0.05Bi₂Nb₂O₉ ceramics (d₃₃ = 23pC/N, T_c = 941°C, ρ = 4.1 × 10⁵Ω cm at 600°C) were obviously higher than those of pure random CaBi₂Nb₂O₉ ceramics (d₃₃ = 6, T_c = 930°C, ρ=0.6 × 10⁵Ω cm at 600°C). Furthermore, it had excellent resistance to depolarization property, with k_p of about 5.9% until 600°C.

A new method to form helical C/SiC spring is proposed. Using paraffin mold as a sacrificial core, unidirectional carbon fiber bundles (infiltrated with resin) are wrapped around the mold to form helical spring, and after resin curing, the mold is removed, leaving a preform of C/SiC spring. Following densification is finished with precursor infiltration and pyrolysis (PIP) process. The spring constant of C/SiC spring reaches 7.88 N/mm and could be regulated by varying composite density and carbon fiber content. The spring properties could be improved by twisting the carbon fibers at 35–50 twist/m. The restoration ratio reaches 100%, but energy dissipation happens during unloading process. After oxidation in air at 1200°C for 10 min, the spring has an 82.4% spring constant remaining ratio.

Flexible aluminum-doped silicon carbide (SiC(Al)) fibrous mats were synthesized by combining electrospinning and polymer-derived ceramic techniques. The mats consist of three-dimensional network structure with randomly distributed fibers of approximately 1.5 μm diameter. The obtained mats exhibited simultaneous fairly good hydrophobic and lipophilic behavior without the need of any posttreatment. Given the intrinsic oxidation/corrosion resistance of Al-doped SiC, the ceramic mats obtained here could be very promising for applications in harsh environments.

Oxygen-deficient BaTiO_3-δ nanoceramics were prepared by spark plasma sintering. Partially reduced raw nanopowders led to unusual dielectric properties. A short postsintering treatment was performed to reach a high ε_r/tan δ, which makes them attractive for industrial applications such as low-frequency capacitors. Surprisingly, our ceramics also remained black even after annealing for 5 days at 850°C in air, indicating the presence of barriers against oxygen diffusion. This exceptional behavior in pure barium titanate was consistent with a core–shell structure made of semiconductive grains and insulating grain boundaries, due to the presence of Ti³⁺/Ti⁴⁺ and oxygen vacancies.

The resistivity, Seebeck coefficients, and power factors of as-prepared RBaCo₂O_5+δ (R112) ceramics with variable R³⁺ ion sizes were investigated systemically. The resistivity of Pr112 and Nd112 exhibits semimetal behavior, which is different with other R112 who have a semiconductor-semimetal transition. At room temperature, Dy112 has the biggest Seebeck coefficient. While at higher temperature, Y112 has best thermoelectric power. In addition, the affects of normalizing temperature on the transport properties of Eu112 ceramic were investigated. Its power factor above room temperature is improved by normalizing, and an optimum normalizing temperature exists at 400°C.

In this study, nanoscale photocatalyst TiO₂ powders were synthesized via sol-gel and flame spray pyrolysis (FSP). Phase structures and ratios were analyzed by X-ray diffractometer (XRD). Size, specific surface area, and morphologies were determined using particle size analyzer, Brunauer-Emmett-Teller theory, and scanning electron microscope, respectively. Anatase phase with some rutile together was obtained in XRD analysis. The degradation rates of aqueous methylene blue (MB) by TiO₂ nanopowders were calculated using UV–vis spectrophotometer. It was found that MB decomposition was successfully achieved with significantly high efficiencies for both sol-gel and FSP-derived powders with small differences.

Alumina micro parts were fabricated using powders in particle sizes of 1 μm, 2.0 μm, and 12.0 μm. The effects of particle size on soft lithography process, green bodies, and sintered characteristics were investigated, including process parameters affecting homogeneous and smooth surface. The effects of particle size were analyzed through suspensions, green, and sintered properties. It was found that the stability of suspensions, sintered density, Vickers micro hardness, surface roughness and edges resolution are significantly improved with the decrease in particle size. On the other hand, suspension viscosity, green density and shrinkage are degraded with the use of finer particles.

The self-reactive quenching technology, which combines flame thermal spraying technology, self-propagating high-temperature synthesis (SHS), and rapid solidification, is a new method for preparation of hollow microspheres. Based on this, the effect of heat released by different exothermic systems on preparation of hollow ceramic microspheres was studied. The results show that for low-exothermic system Si-Sucrose-NH₄Cl, the self-propagating reactions cannot occur, and the quenching products are Si microspheres with porous structure. For the moderate exothermic system Al–SiO₂-Sucrose, the quenching products consist of some grains, which are hollow spherical or nearly spherical particles and irregular powders. Formation of Al₂O₃–Si indicates possible occurrence of SHS reactions. Meanwhile, for high-exothermic system Al–Cr₂O₃-Sucrose-Si-Epoxy Resin, the quenching products consist of internal hollow spherical grains and irregular-shaped porous particles; the phase composition mainly contains Al₂O₃, Cr₃C₂, Cr₇C₃, Cr₃Si, and mullite, showing completeness of SHS reactions. The higher the adiabatic combustion temperature of the system is, the more heat it releases is higher, and the ceramic droplets form easilier.

It is known that several factors can affect the clinical success and durability of fixed partial dentures. Therefore, the aim of the present study was to present a literature review about the longevity, clinical success, and quality, as well as, patients' and dental surgeons' satisfaction of ceramic fixed dentures. High rate of patients' satisfaction has been observed in relation to the esthetic of ceramic crowns. In addition, the literature has shown that dental ceramics can be used in several clinical situations with high success rate and longevity. Despite of failures and complications of ceramic restorations, nowadays, with the improvement of mechanical properties of such materials, ceramic crowns present a favorable prognosis and can be used in several clinical situations with high success rate, clinical quality, and great patients' satisfaction.

Octylamine-coated silver nanoparticles with an average size of 10 nm were synthesized and added to the AZO powder as fillers to increase the density of the sintered target. The resulting Ag–AZO nanocomposite powder was formed into compacts by a uniaxial pressing process. It was found that the addition of octylamine- coated silver nanoparticles can increase the density of AZO powder compacts by ~ 4% after sintering. The optimum content of silver addition is about 0.13 wt%. It is suggested that the melted silver fills the void space between agglomerate pores and enhances the interconnection between nanocrystalline AZO powders. The films deposited using the here-synthesized Ag–AZO target showed lower resistivity and high carrier concentration compared with the one using AZO target.

The broad bandwidth is essential for the ultrasonic transducers because of two main reasons: Firstly, the image axial resolution can be improved by broad bandwidth, and secondly, the ultrasound scanning flexibility can be improved by operating the transducer over a wide range of frequencies. Particularly, nonlinear applications such as biomedical imaging that requires transmitting and receiving in different frequencies can utilize broadband characteristics of transducer efficiently. In this study, a dual-layer piezocomposite transducer was designed by combining two 1–3 piezocomposite transducers with various thicknesses to couple their resonance frequencies and to increase the bandwidth. PZFlex code was used to determine the most promising layer thicknesses for elements of multilayer structure coupling. Finite element analysis showed that the best thickness combination is 1.2 mm and 2 mm. After fabricating multilayer transducers by traditional dice and fill method, their characteristics were examined under water by Labview automated measurement system. Relative sound pressure produced by the transducer was obtained, and their bandwidth was examined at −3 and −6 dB. By varying the individual active layer thicknesses, acoustic impedance of the backing layer and coupling material the best promising broadband transducer design was reported. In addition, ringing characteristics of the transducers were identified by performing the pulse–echo testing. Multilayer transducer with 1.2 mm and 2 mm layer thicknesses and 6 MRayls backing layer gave the best performance in terms of bandwidth and ringing characteristics.

The nature and magnitude of stress in the scales formed on Pt-11Al-3Cr-2Ru (at.%) alloy oxidized in air at 1250°C, for up to 500 h, were determined. This is to establish their long-term viability during high-temperature applications. Residual stress in the scales was measured using luminescence piezospectroscopy and found to be compressive. It decreased gradually with increased oxidation time, before reaching a constant value. The compressive stress was also found to be lower than those of other Ni- and Fe-based superalloys. Thus, the current alloy has a promising potential for high-temperature applications.

The criteria for the formation of a CuAlO₂ reaction phase at the Cu/Al₂O₃ interface are explored. Oxygen solutes up to 2 wt% were introduced into the copper first. The bonding was carried out at 1075°C. The reaction phase was observed only when the oxygen solute in copper before bonding was higher than 1.3 wt%. The CuAlO₂ phase is polycrystalline and covers only part of the interface. The CuAlO₂ grains interact with the crack, which improves the interface strength. As CuAlO₂ is not continuous at the interface, the thermal conductivity of the Al₂O₃/Cu/Al₂O₃ laminate is affected little.

The aim of this work was to evaluate the effect of the two-step sintering process on consolidation of fluoridated hydroxyapatite (FHA). In addition, the effect of fluorine content on sinterability, mechanical properties, and bioactivity of FHA bulks was studied. Nanostructured FHA bulks were obtained under the conditions of 1000 and 900°C for the initial and secondary temperatures, respectively, without any structural decomposition. In addition, by increasing the fluorine content, the sinterability of FHA bulks was decreased and the hardness of FHA bulks was improved. Moreover, FHA bulks showed acceptable bioactivity.

A violet divalent europium-doped strontium aluminate (Sr–Al–O:Eu²⁺) phosphor particle was synthesized from a metal-ethylenediaminetetraacetic acid (EDTA) solution of Sr, Al, Eu, and particulate alumina via spray drying and sintering in a reducing atmosphere. The emission properties, crystal structures, cross-sectional emissions, and elemental distributions of the obtained Sr–Al–O:Eu²⁺ phosphor particles were investigated. The product was determined to be secondary SrAl₁₂O₁₉:Eu²⁺ particles with an average diameter of 20 μm. The violet SrAl₁₂O₁₉:Eu²⁺ emission phase was found in a 1-μm-thick coating of the particles where elemental Al diffusion occurred. These particles are anticipated to find commercial applications such as paints.

Dense ceramics in SrNdAlO₄-Sr₂TiO₄ system were synthesized by a solid-state reaction method, and their microstructures and microwave dielectric characteristics were investigated. The K₂NiF₄-type solid solutions with general formula Sr_1+xNd_1-xAl_1-xTi_xO₄ were obtained in the entire composition range (0.05 ≤ x ≤ 0.9). With increasing x, the dielectric constant ε_r increased from 19.2 to 25, and the temperature coefficient of resonant frequency τ_f was adjusted from −16.7 to 24.6 ppm/°C. The significantly improved Qf value was achieved in the present ceramics with increasing x, and it reached a maximum at x = 0.6. The best combination of microwave dielectric characteristics was achieved at x = 0.6 (ε_r = 23.6, Qf = 86,300 GHz, τ_f = 10.9 ppm/^oC). The reduced interlayer polarization with Sr/Ti cosubstitution in SrNdAlO₄ contributed to the improved Qf, while the decreased tolerance factor and increased inner stress brought the negative effects.

In this study, new refractory coatings based on synthesized cordierite for the casting applications were developed. The investigation included starting raw materials characterization, synthesis of the cordierite, design of the refractory coating as final product, and its application testing. The obtained results pointed out that coating suspension sediment stability was crucial quality parameter. Design and optimization of the coatings composition, with controlled rheological properties included, were achieved by application of different coating components, namely different suspension agents and by alteration of the coating production procedure. Cordierite, used as filler, was obtained by means of synthesis in the solid-state reaction on the basis of talc, kaolin, and alumina. The investigation showed that the application of these particular types of water/alcohol-based coatings has positive influence on surface quality and structural and mechanical properties of the castings of aluminum alloys obtained by casting into sand molds by means of evaporable models method, that is, evaporate pattern casting process.

Dielectric characteristics such as dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ) and real and imaginary parts of electrical modulus (Μ′ and Μ″), and ac electrical conductivity (σ_ac) of Au/ Polyvinyl Alcohol (PVA) (Bi₂O₃-dispersed)/n-Si structures have been investigated by using admittance measurements. Results show that the ε′ values of Au/PVA/n-Si with Bi₂O₃-dispersed PVA interfacial layer are very higher compared with those with pure and other dopant/mixture's of PVA. Thus, PVA is made very compatible for device applications with the enhanced dielectric properties by Bi₂O₃ disperse and its native very high dielectric strength.

For developing excellent microwave attenuation materials in a wide band, two series of SiC-C (graphite) composites with different C additions were fabricated by pressureless sintering, using α-SiC and β-SiC green powder, respectively. β-SBC composites were more suitable for microwave attenuation materials than α-SBC composites. β-SiC composites with 3 wt% C additions exhibited the best microwave absorption: The most significant microwave attenuation was −40.5 dB, and most other attenuations were above −30 dB in the whole X band. The composites were prepared with cost-effective and easily controllable manufacturing process and can be considered as structure–function materials for particular applications.

Ultrafine hafnium diboride (HfB₂) powders were synthesized by the boro/carborthermal reduction process. Fine-scale mixing of the reactants was achieved by solution-based processing using hafnium oxychloride (HfOCl₂·8H₂O) and phenolic resin as the precursor of HfO₂ and carbon respectively. The heat treatment was completed at a temperature range 1300–1500°C for 1h using spark plasma sintering (SPS) apparatus. The crystallite sizes of the synthesized powders were small (<500 nm) and the oxygen content was low (0.85 wt%). The grain growth of HfB₂ could be effectively suppressed using SPS due to the fast heating rate. The effects of temperature and holding time on the synthesis of ultrafine HfB₂ powders were discussed.

A Si–SiC coating was prepared by hot-pressing reactive sintering (HPRS) technique for protecting carbon/carbon (C/C) composites against oxidation. The Si–SiC coating has a dense and crack-free structure with a thickness of 70–90 μm. The Si–SiC coating by HPRS has a higher SiC content and lower Si content than the coating by pressure-less reactive sintering (PRS). It also exhibits better oxidation-protective ability than that prepared by PRS. With hot-pressing, the flexural strength of the Si–SiC coated C/C composites decreases from 121 MPa to 99 MPa, and the interface bonding strength increases from 6 MPa to 10 MPa.

This study investigates the microstructure, oxidation kinetics, and electrical behavior of Mn–Co spinel coating for interconnect applications in solid oxide fuel cells. A relatively dense, uniform, and well-adherent Mn–Co (Mn_1.5Co_1.5O₄) spinel coating with good oxidation resistance and stable conductivity was successfully prepared on the surface of Crofer 22 APU stainless steel using electrophoretic deposition followed by sintering at 1150°C. During further thermal treatment at 800°C, the chromium oxide (Cr₂O₃) sublayer formed at the substrate/coating interface during sintering showed a very slow growth, and no chromium penetration was detected in the Mn–Co coating. The oxidation kinetics of the Mn–Co-coated substrate obeyed the parabolic law with the a parabolic rate constant k_p of 5.20 × 10⁻¹⁵ g²/cm⁴/s, which was 1–2 orders of magnitude lower than that of the uncoated Crofer 22 APU stainless steel substrate. For oxidation (at 800°C) times ≥50 h, the area-specific resistance of the Mn–Co-coated Crofer 22 APU substrate became ~17 mΩ·cm² and was almost constant after further oxidation.

The thermal stress resistance (TSR) parameters available in the literature are basically “figures of merit” that should help for the selection of materials for engineering design involving thermal stress fracture. However, they are based on very simplified models. For instance, they neglect or simplify the thermal gradient or rather the stress field that actually exist in practice. The state of stress was analytically calculated and the results implemented in the established thermal stress fracture parameters (R, R″) and damage parameter (). For each of them, an analytical solution and an approximation were derived. The reviewed TSR parameters allow a clearly improved prediction of the resistance to thermal shock for bricks in refractory linings and facilitate the classification of industrial refractories.

Phase evolution and morphology of Fe₃O₄-Si-Al powder mixtures during ball milling from 30 min to 20 h were investigated. A 3-h critical milling was necessary for the occurrence of mechanically activated combustion reaction. The reaction results in the formation of Fe (Si), Fe₃Si, and α-Al₂O₃. During ball milling from 3 to 20 h, Fe (Si) and Fe₃Si were combined into disordered Fe₃Si intermetallic and Fe₃Si-Al₂O₃ composite powder was formed. The presence of in situ formed alumina leads to a decrease in crystallite and particle sizes. The Fe₃Si-Al₂O₃ particles after milling for 20 h had a crystalline size of 10~12 nm.

YBO₃:Eu³⁺ microspheres were synthesized by a hydrothermal method. Size and surface morphology of the spheres were tailored by ion-adding. Phase identification, morphology observation, and photoluminescence (PL) performance of the YBO₃:Eu³⁺ microspheres were characterized byX-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and PL spectrophotometer, respectively. Moderate particles with enlarged size and perfect surface were achieved by adding Li⁺ ion or/and Mg²⁺ ion. PL emissions of such YBO₃:Eu³⁺ phosphors were enhanced. Significantly improved PL intensity was achieved when 1% Li⁺ ion and 5% Mg²⁺ ion were added, which was nearly doubled compared with the reference sample.

In this paper, we present some elements of the lattice compatibility theory (LCT) as plausible explanations to the problem of instability of some ternary ceramics under some circumstances. Particular attention is paid to ceramics nano-scale patterns.

The dielectric and electrical properties of CaCu₃Ti₄O₁₂ ceramics prepared by a simple combustion method were investigated. Fine-grained CaCu₃Ti₄O₁₂ ceramics exhibited good dielectric properties and temperature stability. Very low loss tangents of 0.020–0.016 and high dielectric constant of 5776–6406 (at 1 kHz and 20°C) with temperature coefficient less than ±15% in the temperature range of −70 to 90°C were observed. Dielectric relaxation processes were observed in large-grained CaCu₃Ti₄O₁₂ ceramics. The dielectric relaxation in the temperature range of 60–150°C may be associated with sample–electrode contact. The relaxation in temperatures below −40°C is related to the electrical response at grain boundaries.

The effects of various pH values of sodium phosphate buffer solution (PBS), 4.0, 6.0, 8.0, and 9.0 on calcium phosphate cement (CPC) prepared by mixing monocalcium phosphate monohydrate (MCPM), calcium carbonate, and PBS were studied. The phase evolution takes place in three steps: Firstly, the MCPM and calcium carbonate crystals dissolve in the PBS and precipitate in the form of DCPD crystals. Then, after 12 h, DCPD begins to convert to amorphous calcium phosphate (ACP). Finally, the metastable ACP phase converts into stable CDHA. With an increase in the pH of the PBS, the CDHA content in the CPC increased.

The La₂Ce₂O₇ powder doped with Sr was synthesized by sol-gel method in this study and its dense bulk samples were also prepared by pressureless-sintered at 1600°C for 10 h. Its phase composition, microstructure, and thermophysical property were investigated. Results reveal that pure (La_0.95Sr_0.05)₂Ce₂O_6.95 with single fluorite structure was successfully synthesized. Microstructure of bulk sample is dense. Its thermal expansion coefficient is higher than that of Y₂O₃-stabilized ZrO₂ (YSZ) and its thermal conductivity is lower than that of YSZ. These results show that (La_0.95Sr_0.05)₂Ce₂O_6.95 ceramic can be explored as the candidate material for thermal barrier coatings.

SnO₂ nanosheet–assembled graded continuous films were successfully fabricated in aqueous solutions containing SnF₂ of 250 mM at 90°C. Thickness reached 1200 nm after immersion for 24 h. The nanosheets were 100–500 nm in in-plane sheet size and 5–20 nm in thickness. The graded structures were caused by gradual change in supersaturation degree of the solutions. The films had a-axis orientation, antireflective effect, band gap of 3.63 eV, and superhydrophilic surfaces. In contrast, the films immersed for 20 m showed band gap of 4.04 eV and contact angle of 58°.

To improve the ablation resistance of PIP-C/SiC composites, zirconium carbide (ZrC)-modified SiC coating was prepared by chemical vapor deposition combined with slurry painting, then the ablation capability of the coated composites was tested under an oxy-acetylene torch. Compared with the uncoated composites, linear and mass ablation rates of the coated composites decreased by 73.6% and 76.4%, respectively. The formation of zirconia from the oxidation of ZrC improved the ablation resistance of the composites because of anti-oxidation performance, which absorbed heat from the flame and reduced erosive attack to C/SiC composites. Zirconia also acted as an accelerator for carbon fiber oxidation as it reacted with carbon during ablation. The heterogeneous reactions controlled the ablation of the composites.

Usually, resonating cantilevers come from silicon technology and are activated with pure bending mode. In this work, we suggest to combine high-sensitive cantilever structure with both self-actuated and self-read-out piezoelectric thick-film for high electrical–mechanical coupling. This cantilever is realized through screen-printing deposition associated with a sacrificial layer. It is composed of a PZT layer between two gold electrodes. Optimum performances of piezoelectric ceramics generally imply the use of mechanical pressure and very high sintering temperature that are not compatible with the screen-printing process. Addition of eutectic composition Li₂CO₃-Bi₂O₃-CuO or borosilicate glass-frit to PZT powder and application of isostatic pressure improve the sintering at a given temperature. Firing temperature of 850°C, 900°C, and 950°C is tested. Microstructural, electrical and mechanical characterizations are achieved. In addition to the bending mode, the in-plane 31-longitudinal vibration mode and the out-of-plane 33-thickness resonance mode are revealed. Correlations between experimental results and modeling of the different vibration modes are established. The piezoelectric parameters of PZT cantilevers approach those of ceramics. Quality factors between 300 and 400 associated with the unusual 31-longitudinal mode make screen-printed PZT cantilevers good candidates for detection in liquid and gaseous media.

Ultrasonic time-of-flight (TOF) is investigated as a predictor of density variation across reaction-sintered silicon carbide (SiC) ceramics. The importance of this research is heightened by the fact that the reaction-sintered SiC ceramic tiles being investigated are manufactured using the reaction sintering process that involves the infusion of liquid silicon into a porous ceramic preform. This can potentially lead to the formation of islands of free silicon, small closed areas of un-sintered silicon material as well as conventional porosity. All these defects can result in local variations of density which cannot be detected by conventional bulk density measurement techniques. To study the microstructural differences, the porosity dependence of ultrasonic TOF of the reflected signals was investigated to establish a correlation between the velocity and density across the ceramic tile that aids in characterizing the material. The data suggest that for these ceramic tiles, TOF C-scan mapping surfs as a much better indicator of sample homogeneity than the amplitude of the back wall echo. At the current time, ceramic tiles are inspected offline and this takes time and effort and is very expensive. In particular, this study contains the procedure followed to establish a quantitative method to quantify density variation across selected ceramic tile.

Al₂O₃-stabilized tetragonal ZrO₂ nanoparticles were obtained through hot-air spray pyrolysis and characterized after postsynthesized treatments. The produced nanoparticles were 26 nm in size with surface area of 59 m²/g. A multilayer thermal barrier coating of nanostructured Al₂O₃-ZrO₂-embedded silicate was applied to the mild steel (EN3) specimen using spin-coating technique and characterized comprehensively employing X-ray diffraction and scanning electron microscope. The Al₂O₃-stabilized ZrO₂ with silicate matrix facilitates the formation of zirconium silicate nanostructured surface-protective coating on EN3 specimen. The Al₂O₃-ZrO₂/SiO₂ matrix-based hybrid inorganic coating shows effective thermal barrier for EN3 after firing at a high temperature of 600°C.

A systematic study was conducted of the effect of Al impurities on the mechanical and thermal properties of sintered reaction-bonded silicon nitrides (SRBSNs). 2 mol.% Y₂O₃ and 5 mol.% MgSiN₂ were added as sintering aids to high-purity raw Si powder, followed by respective additions of 0, 0.01, 0.1, 0.2, and 0.4 mass% of Al relative to Si. The prepared powder mixes were press formed and nitrided in a 0.1 MPa nitrogen atmosphere at 1400°C for 8 h. Postsintering of the nitrides was conducted under a pressurized nitrogen atmosphere of 0.9 MPa at 1900°C for 6 h. The SRBSN specimens exhibited hardly any difference in their four-point bending strength, which ranged from 800 to 850 MPa. However, their fracture toughness clearly decreased with increasing additive Al content. This is thought to be due to a reduction in the proportion of coarse prismatic grains improving the toughness with increasing additive Al content. A significant reduction in the thermal conductivity was also observed with increasing additive Al content. This is conjectured to be due to the formation of SiAlON through a substituted solid solution of aluminum (Al) and oxygen (O) in β-Si₃N₄ crystals. An inductively coupled plasma and hot gas extraction method were employed to directly analyze Al and O in β-Si₃N₄ particles. Approximately half of the additive Al was confirmed to be in solid solution in β-Si₃N₄ particles along with the solid solution of O in a chemical formula that nearly corresponds to β-Si_6–zAl_zO_zN_8–z. The chemical analysis results give a Z value range of 0.0006–0.024.

Two different hydroxyapatites with the particle sizes of 3.9 and 1.69 μm were chosen. Slurries with initial hydroxyapatite concentration of 15 vol% were prepared. Different cooling rates from 2 to 14°C/min were utilized. The specimens were sintered at different temperatures of 1250–1350°C. The phase composition (by X-Ray Diffraction), microstructure (by Scanning Electron Microscopy), mechanical characteristics, and the porosity of sintered samples were assessed. The porosity of the sintered samples was in range of ~57–83%, and the compressive strength varied from ~1.7 to 15 MPa. The mechanical strength of the scaffolds increased as a function of cooling rate and sintering temperature.

Low-temperature synthesis of fluorapatite/fluorohydroxyapatite with precursor mixture previously mechanochemically treated is described in this article. Ethylene vinylacetate/versatate copolymer as a surface active substance was mechanically treated to obtain a core-shell system with strongly controlled grain size. Despite usual behavior of mechanically activated systems, only an amorphous phase formed from precursor ions present in the mixture composed of β-Ca₂P₂O₇, CaCO₃, CaF₂, and unreacted Ca(OH)₂ was obtained during milling for 5 min to 8 h. The mixture contained depots of labile F⁻ ions conserved in micelles cages, which are useful for teeth protection from carries. For transformation of these amorphous phases into fluorapatite, an additional low thermal treatment was necessary. The mechanism of the precursor mixture transformation into fluorapatite during milling and thermal treatment was investigated using FTIR spectroscopy and X-ray diffraction. The morphology and size distribution of the obtained powders was studied using SEM and TEM.

The integration of biological and mechanical requirements remains a challenge in developing porous hydroxyapatite (HA) and tri-calcium phosphate (TCP) scaffolds for load-bearing bone implant application. With the newly developed slip-deposition and coating-substrate co-sintering technique, a strong layered HA/TCP-zirconia scaffold composite structure was successfully fabricated. The bending strength (321 MPa) of this composite can match upper strength limit of the natural compact bone. The HA-based scaffold coating has multiple scale porous structures with pore size ranging 1–10 and 20–50 μm. The zirconia-based substrate is also porous with submicropores. Focus ion beam micrographs show most of the micropores in the coating are interconnected. Microindentation and primarily adhesive strength tests demonstrate that the scaffold coating strongly bonds with the zirconia based substrate. In vitro cell culture study indicates that the coatings have no cytotoxicity. It is evident that the strong layered HA–zirconia scaffold composite offers new implant options for bone repairs requiring immediate load bearing capacity.

This article describes a new approach to fabricate various embedded ceramic microstructures. Design geometries of the microstructures are replicated onto a soft reusable polydimethylsiloxane (PDMS) mold. Rapid consolidation of ceramic suspension on the molds using gel-casting technique produces structured ceramic layers. 85% aqueous glycerol solution has been identified as suitable adhesive agent to laminate the ceramic layers. Capability of the approach in fabricating embedded microstructures of 3-dimensional and aspect ratio as high as 20 and 50 has been demonstrated. Ceramic microthruster and Y-shaped microfluidic reactor are fabricated using this new approach to show its potential to construct various ceramic microdevices.

Dense ZrB₂-SiC ceramics containing 40 vol% ZrC particles are fabricated via hot pressing method. Then the sintered ceramics are oxidized in air up to 1500°C, and the oxidation kinetics of the ceramic composites is deduced in combination with the reacted fraction curves. As indicated by the experimental results, the oxidation kinetics changes from reaction-controlled process to diffusion-controlled one with increasing of oxidation temperature. In addition, the oxidation kinetics parameters are obtained, which indicates that the oxidation resistance decays at elevated temperatures. Furthermore, the evolution of surface morphology and oxide scale during oxidation process is clarified.

The thermal shock resistance of four commercially available magnesia-based refractory bricks mainly used in furnace linings were investigated. Thermal stability of the bricks was tested using the water-quench method. The experimental damage was characterised by visual inspection and determining some residual physical and mechanical properties. Cracks were observed after thermal cycling resulting in loss of strength and materials degradation. The results show that thermal stability of magnesia-based refractories depends strongly on their chemical composition. The addition of chrome and spinel improved the thermal stability of magnesia bricks with magnesia–spinel (MgAl₂O₄) having better thermal stability than the magnesia–chrome bricks.

Creep behavior of Si₃N₄ polycrystals containing Y₂O₃-MgO-SiO₂ glass phase (with and without Calcium oxide [CaO] additive) was studied by compression tests between 1500 and 1700°C. We studied the effect of CaO additive on flow stress, microstructural evolutions, and thermal stability of the intergranular glass phase during deformation. While the addition of CaO did not affect grain size, the flow stress decreased with the amount of CaO. This result suggested that the addition of CaO reduced the viscosity of intergranular glass phase. The addition of CaO further improved the thermal stability of the glass phase by suppressing the evaporation at elevated temperatures.

The results of an experimental investigation on epoxy-joined silicon carbide tested in shear mode by seven different configurations of torsion tests are presented and compared to results obtained by asymmetric four-point bending. All samples have been joined by an epoxy adhesive (Araldite AV119) chosen to obtain several joined samples in a reasonable time. Advantages and disadvantages of each configuration are discussed with the aim of finding a suitable method to measure the shear strength of joined components.

The Fe/Al₂O₃ coatings for application as microwave absorbers were deposited by air plasma spraying (APS). The morphologies of powders and cross-section of coatings were characterized by scanning electron microscope (SEM). The investigations of electrical conductivity and complex permittivity properties of coatings were performed. The real part (ε′) of permittivity increases with increasing Fe volume fraction, which is attributed to the space charge polarization, and the imaginary part (ε″) also increases which is ascribed to the increasing electrical conductivity result from the formation of Fe conductive network. The effect of Fe content on dielectric properties and the corresponding mechanisms are analyzed. By measuring the microwave absorption properties of the Fe/Al₂O₃ coatings as a single-layer absorbers, it was find that the reflection loss varies with the changes of thickness and Fe content, due to the deviation of impedance-matching condition.

The diffusion couples of lanthanum-based barium borosilicate glass with high- and low-temperature electrolytes have been heat-treated at 850°C and 800°C, respectively, for 5, 100 and 750 h. These prepared diffusion couples have been characterized using various techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dot mapping, and electron probe microanalysis (EPMA). The thermodynamic parameters like frequency factor, crystallization constants, free volume, and bulk thermal expansion coefficients have been calculated to understand the behavior of glass. Interestingly, glass revealed self-healing tendency with heat treatment duration.

In industrial high-intensity discharge lamps, cracks and delaminations occasionally develop at the interface between SiO₂ and the Mo foil in the seal. Here, functionally graded SiO₂-Mo materials for use in these lamps were fabricated by uniaxial compression casting and pressureless sintering. Consequently, vertical cracks developed across the sintered body layers, and interfacial cracks developed between the 100 wt% SiO₂ and 90 wt% SiO₂-Mo layers. Therefore, the effects of residual stress, difference in the coefficient of thermal expansion (CTE), and difference in the volume shrinkage on these cracks were investigated. Vertical cracks were suppressed when residual stress was relaxed by annealing near the annealing point of silica glass during the cooling step in the sintering process. Interfacial cracks were suppressed when the difference in the CTE of the interface between the 100 wt% SiO₂ and 90 wt% SiO₂-Mo layers was relaxed by inserting layers of 95 wt% SiO₂-Mo between them. Furthermore, the suppression effect became stronger when the difference in the volume shrinkage of the layers was relaxed by sintering to join the separately sintered monolayers. Thus, the development of these cracks was influenced by the residual stress, CTE, and volume shrinkage. Therefore, these cracks can be prevented by optimizing these factors.

The effects of ZnO and B₂O₃ addition on the sintering behavior, microstructure, and the microwave dielectric properties of 5Li₂O-1Nb₂O₅-5TiO₂ (LNT) ceramics have been investigated. With addition of low-level doping of ZnO and B₂O₃, the sintering temperature of the LNT ceramics can be lowered down to near 920°C due to the liquid phase effect. The Li₂TiO₃ss and the “M-phase” are the two main phases, whereas other phase could be observed when co-doping with ZnO and B₂O₃ in the ceramics. And the amount of the other phase increases with the ZnO content increasing. The addition of ZnO does not induce much degradation in the microwave dielectric properties but lowers the τ_f value to near zero. Typically, the good microwave dielectric properties of ε_r = 36.4, Q × f = 8835 GHz, τ_f = 4.4 ppm/°C could be obtained for the 1 wt% B₂O₃ and 4 wt% ZnO co-doped sample sintered at 920°C, which is promising for application of the multilayer microwave devices using Ag as internal electrode.

Thermolysis of cesium hexa(carboxylato)ferrate(III) precursors, Cs₃[Fe(L)₆].xH₂O (L = formate, acetate, propionate, butyrate), has been carried out in flowing air atmosphere from ambient temperature to 1000°C. Various physico-chemical techniques, that is, simultaneous TG-DTG-DTA, XRD, TEM, IR, Mössbauer spectroscopy, have been employed to characterize the intermediates and end products. After dehydration, the anhydrous precursors undergo exothermic decomposition to yield various intermediates, that is, cesium carbonate/propionate/butyrate and α-Fe₂O₃. A subsequent decomposition of these intermediates leads to the formation of cesium ferrite above 800°C. Similar ferrite has been prepared by the combustion method at comparatively lower temperature (600°C) and in less time than that of conventional ceramic method.

CIGSe solar cells with an ink-printing absorber layer were prepared on Mo-coated alumina substrates. The use of alumina substrates can extend the process window to higher temperatures. The inks contained single-phase CIGSe powder, which was formed by firing different selenide powders of Cu₂Se, In₂Se₃, and Ga₂Se₃ at 800°C. All these powders were synthesized with an environment-friendly and cost-effective powder process. The printed inks were sintered at 600–800°C. The solar cells had power conversion efficiency of 0.50%, an open-circuit voltage of 27 mV, a short-circuit current density of 37 mA/cm², and a fill factor of 0.50.

This study demonstrated that a long silicon nitride pipe of several meters with adequately strong joints can be fabricated by a local-heating joining technique. Commercially available silicon nitride ceramic pipes sintered with Y₂O₃ and Al₂O₃ additives were used for parent material, and powder slurry of Si₃N₄-Y₂O₃-Al₂O₃-SiO₂ system was brush-coated on the rough or uneven end faces of the pipes. Joining was carried out by locally heating the joint region at different temperatures from 1500°C to 1650°C for 1 h with a mechanical pressure of 5 MPa in N₂ flow; using a horizontal electrical furnace specially designed for this experiment. The silicon nitride pipe 3-m long was successfully fabricated without voids or cracks in the joint region, and the microstructure of the joint region was similar to that of the parent one. The joint strength was examined in flexure using specimens cut from the joined pipes, and those joined at 1600°C and 1650°C indicated the highest strength of about 680 MPa, which was almost the same as that of the parent material. This study also indicated that the slurry brush-coating technique is advantageous to easily joining ceramic pipes with rough or uneven end faces, which is essentially important for practical use.

Eight mol% Yttria-stabilized zirconia, the most commonly employed electrolyte material for solid oxide fuel cells (SOFC), was shaped into honeycomb structures by thermally induced gelation of aqueous zirconia slurry containing methyl cellulose using microwave irradiation. The green honeycomb samples were subjected to green density and green compressive strength measurements revealing a uniform gelation and hence a relatively higher strength for microwave irradiated samples. The green honeycomb samples were further sintered to crack-free dense honeycombs (>99% TD) at 1525°C for 1 h. Honeycomb samples were characterized for their physical, cellular, and electrical properties. A relatively high ionic conductivity value of 0.07 S/cm at 800°C and corresponding low activation energy of 0.61 eV in the temperature range 700–800°C provide opportunities to explore the development of novel designs for SOFC application.

Nanostructures are the building blocks of future nanodevices and thus methods for fabricating nanostructures of various materials in various forms are fundamentally important. Among those nanostructures ZnO has received much attention over the past few years due to the wide range of research by many different groups focused on different novel nanostructures with different properties. Although ZnO nanowires have been intensively studied, there are only a few methods that showed promising characteristics for practical applications. Without much effort, it can be grown in many different nanostructure forms, thus allowing various novel devices to be achieved. In this study, we intend to review those methods that enable nanostructure growth to be more controllable and feasible for applications. The methods for fabricating ZnO nanostructures are introduced in the first part. In the second part, the application of those nanostructures are mentioned and explained. Finally, the future realization of nanodevices is discussed.

Currently, the pyrolysis of hydrocarbons for the production of light olefins is almost exclusively carried out in steam crackers operating around 900–1000°C. However, cracking hydrocarbons at much higher temperature results in high selectivity to acetylene, which can be converted into many petrochemical products including ethylene. The desired hydropyrolysis reaction from hydrocarbons to acetylene can be realized in a reverse-flow reactor at very high temperatures (>1700°C) in a scalable manner. The reactor elements include ceramic components that are placed in the hottest regions of the reactor and must withstand a temperature that is in the range of 1500–2000°C. In addition, the temperature rises and falls with the reverse-flow cycle; a fluctuation that could be as high as 100–500°C over a period of several seconds. Moreover, the materials in the hot zone are exposed alternately to a regeneration (heat addition) step that is mildly oxidizing, and a pyrolysis (cracking) step that is strongly reducing with a correspondingly high carbon activity. This article addresses the thermodynamic stability of selected ceramic materials based on alumina, zirconia, and yttria for such an application. Results from laboratory tests involving the exposure of these ceramic materials to simulated process conditions followed by their microstructural characterization are compared with expectations from thermodynamic predictions.

Systematic investigation has been made on the structure and dielectric properties of MnCO₃-doped barium titanate-based X8R ceramics, to reveal the relationship between the manufacturing process and dielectric properties. The dielectric ceramic sintered at 950°C showed high permittivity and low dielectric loss, meeting X8R specifications. Transmission electron microscopy and EDS analysis were used. The results suggested that the temperature-stable BaTiO₃-based X8R ceramics with the good dielectric properties can be prepared through the BaTiO₃ calcined at 1150°C and doped with 0.7 wt% MnCO_3.

Reticulated silicon carbide (SiC) ceramic filters are prepared with modified coatings in an attempt to improve mechanical properties of the sintered filter. Two classes of coatings are used: mixtures of non-SiC ceramic and sintering aid and mixtures of SiC and glass. Various candidate ceramics, sintering aids, and glasses are screened. The most promising coatings are determined to be silica with 5 wt% bismuth oxide and SiC with ≤10 wt% Spruce Pine Batch glass. Filters with these coatings are prepared and subjected to mechanical abuse. Both coatings improve the ruggedness of the filter relative to the standard uncoated SiC type. Filters with <10 wt% glass additive were subjected to molten metal impingement and filtration of liquid gray iron at 1510°C. Those with 5 wt% glass or more softened during filtration. Those with 2.5 wt% glass or less survived without failure.

The study deals with the effect of the SPS parameters and LiF doping on the mechanical and optical properties polycrystalline magnesium aluminate spinel (PMAS) with emphasis on the grain size of the final product. Sintering at 1300°C of undoped powder yielded fully dense submicrometer (0.4–0.6 μm) samples with elevated mechanical properties (1600HV and 300MPa bending strength). Doped samples had a larger, 40 μm grain size, lower, 1450HV, hardness and 150MPa bending strength. The transmittance of the doped samples (80% at 500 nm wavelength) was higher than that of the undoped ones. Thus, the required functionality of the ceramic dictates the choice of parameters for the fabrication of dense transparent PMAS.

This contribution describes the development of tape casting for solid oxide fuel cells (SOFCs) anode supports starting with the characterization of the powders and ending with manufacturing of cells for stack testing. After casting the support, full cells were prepared by screen printing and sintering of the functional layers. The results of single-cell and stack tests of the novel SOFC will be discussed. The new cell showed excellent electrochemical performance in single-cell tests with more than 1.5 A/cm² (800°C, 0.7 V). Furthermore, stack tests showed no significant difference from earlier standard cells when operated at 800°C with a current density of 0.5 A/cm².

The mullite ceramic/fiber brick system was bonded by two kinds of phosphate adhesives. The specimens were treated from 200 to 1400°C. The mechanical properties were tested at room temperature and at high temperature, and the relevant bonding mechanism was also discussed. The results show that the addition of silicon can greatly improve the adhesive's mechanical properties. The room-temperature shear strength of the component bonded by adhesive with the silicon calcined at 800°C can reach 6.58 MPa. The shear strength of the adhesive with silicon tested at 800°C can reach 0.42 MPa.

The effect of B₂O₃ addition on the microwave dielectric properties and microstructure of Li₂ZnTi₃O₈ ceramics prepared using conventional solid-state reaction was investigated for low-temperature co-fired ceramic (LTCC) applications. X-ray diffraction and scanning electron microscopy were used to investigate the effect of B₂O₃ addition on the sintering process. The Li₂ZnTi₃O₈ ceramic sintered at 875°C with 0.5 wt% B₂O₃ for 4 h showed good microwave dielectric properties including ε_r = 25, Q × f = 50,917 GHz, and τ_f = −17.8 ppm/°C. Silver was found to be unreactive toward the 0.5 wt% B₂O₃ doped Li₂ZnTi₃O₈ ceramic under the above sintering conditions.

In the present study, we examined how the active aluminum nano-oxide in the gamma form used as a neutral carrier for the nanoparticles of various metals (as Ag, Pr) affected their toxic behavior. Our experiments have shown that exposure to metal nanoparticles can be reduced by binding the nanoparticles to alumina nanoparticles and the aluminum nano-oxide is suitable to function as the nano-stabilizer for the Ag and Pr nanoparticles. We have managed to manufacture new alumina-stabilized silver and praseodymium nanoparticles using dry sol-gel method that are not phyto- and eco-toxic.

Porous SiC ceramics were synthesized by oxidation bonding of compacts of commercial α-SiC powder at 1300°C. Different volume fractions of petroleum coke powder were used for variation of porosity of ceramics from 36% to 56%. The material exhibited variations of pore size from 3 to 15 μm, flexural strength from 5.5 to 29.5 MPa, and elastic modulus from 3.3 to 27.6 GPa. Air permeation behavior was studied at 26–650°C. At room temperature Darcian (k₁) and non-Darcian (k₂) permeability parameters vary from 1.64 to 18.42 × 10⁻¹³ m² and 0.58 to 2.95 × 10⁻⁷ m, respectively. Temperature dependence of permeability was explained from structural changes occurring during test conditions.

Trivalent dysprosium-doped strontium zirconate perovskite (SrZrO₃) phosphors were prepared by gel-combustion synthesis using citric acid as fuel and ammonium nitrate as oxidizer. X-ray diffraction patterns confirmed the formation of orthorhombic phase of SrZrO₃ with minor impurity, which completely disappears at high temperature. The morphological investigation was carried out using scanning electron microscopy (SEM). Photoluminescence studies showed that no emission from the host is observed, indicating the efficient energy transfer from the ZrO₃²⁻ group to Dy³⁺ ions. The emission line is purely because of f–f transitions of Dy³⁺. Moreover, these phosphors predominantly exhibit near white light emission, when excited by 229 nm UV light due to strong ⁴F_9/2→⁶H_13/2 transition at 577 nm (yellow), strong ⁴F_9/2→⁶H_15/2 transition at 482 nm (blue), and weak ⁴F_9/2→⁶H_9/2 transition at 677 nm (red). Enhancement in emission intensity was observed with increase in the annealing temperature of the phosphor. The CIE chromaticity coordinates of the SrZrO₃:Dy³⁺ phosphors were observed to fall in the white light domain of the chromaticity diagram, which indicate that such fine tuning might be possible after varying the temperature of annealing.

The bactericidal action of silver nanoparticles has been observed by many researchers since few years. In this study, we have developed an antibacterial ceramics (ACs) by absorbing synthesized silver nanoparticles within the ceramic matrix developed by us from an abundantly available coal fly ash, an extremely hazardous by-product of thermal power plants. Nanoparticles dispersions of different particle sizes were made absorbed in to the ceramic matrix to evaluate its bactericidal activity against both Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria, taken as the model microorganisms. This study showed that the total bactericidal action of ACs depends on the size of absorbed nanoparticles and the content of nanoparticles in the dispersions within the ceramic matrix. ACs thus developed release very slowly a minute amount of nanoparticles and show strong and prolonged bactericidal activity against pathogenic strain of both types of bacteria. The concentration of prepared nanoparticles in dispersion and the concentration of released nanoparticles in aqueous medium from the absorbed ceramic matrix were measured using inductively coupled plasma spectrophotometer. The mechanism of the antibacterial action was also studied using transmission electron microscopy image analysis of the bacterial cross-section of both types of bacteria.

The aim of this investigation was the surface functionalization of industrial ceramic tiles by sol-gel technique to improve at the same time the cleanability and the antibacterial activity of surfaces. This objective was pursued through the design and preparation of nanostructured titania-silver coating that was deposited on glazed, unglazed, and polished tiles by air-brushing. The obtained results showed that the applied coatings are transparent, show a good adhesion, and a remarkable antibacterial activity under the tested conditions. The surface photocatalicity was optimized with the higher thermal treatments (200°C) even if photodegradation process is clearly affected by the sample surface roughness.

The flaw propagation in Lead zirconate titanate (PZT) multilayer ceramics under mechanical load was examined using impedance spectroscopy and three-point bending studies. Initial flaws were generated by applying a positive sinusoidal electric field to the specimens. The cracks were sequentially propagated and after the release of the external mechanical load, impedance spectroscopy was conducted. The shift in the resonance frequencies and the subresonance height of the impedance spectroscopy were used as a measure of flaw extension. A functional dependence of the resonance frequency and the phase shift on the crack length was found. The crack propagation was studied on flaws starting at the positive and negative electrode, respectively. The maximum fracture strength, as well as the crack path, depends on the electrode potential. The variation in the fracture strength was caused by different observed fracture mode: interface cracking, matrix-cracking, or a combination of both. The morphology of the fracture surfaces was ascribed to a textured microstructure, which is created by the sample processing, for example, by the poling process. A modified poling procedure with a lower poling temperature was analyzed, which yielded a reduction of the anisotropy of the electrode strength. Impedance spectroscopy was found to be a reliable measurement tool for automated flaw detection in PZT multilayer ceramics.

Using BaO–B₂O₃–SiO₂ (BBS)-based frit as sintering aid, the K_0.49Na_0.51NbO₃ (KNN) + x wt% BBS (x = 1.0, 1.5, 2.0 and 2.5) lead-free piezoelectric ceramics were successfully fabricated by solid-state reaction method under low-sintering temperature of 1000°C. The effect of BBS frit doping amount on the structure and electrical properties of the ceramics was investigated. The KNN ceramics with 1.5 wt% BBS frit showed optimal properties as follows: piezoelectric constant d₃₃ = 108 pC/N, planar electromechanical coupling coefficient k_p = 41%, mechanical quality factor Q_m = 225, relative dielectric constant ε_r = 410, dielectric loss tanδ = 0.57% and Curie temperature T_c = 400°C. This ceramic sample should be a good lead-free candidate for actuators or high temperature sensors application due to its ultra-low tanδ, relatively high Q_m and T_c.

The sintering behaviors and dielectric properties of Ba_0.6Sr_0.4TiO₃ ceramics were investigated as a function of B₂O₃ and CuO content. The addition of both B₂O₃ and CuO reduced the sintering temperature of Ba_0.6Sr_0.4TiO₃ about 500°C. It was suggested that a liquid phase BaCu(B₂O₅) was formed and assisted the densification of Ba_0.6Sr_0.4TiO₃ ceramics. Ba_0.6Sr_0.4TiO₃ ceramics co-doped with 3.0 mol% B₂O₃, and 2.0 mol% CuO, sintered at 950°C for 5 h, had a dense microstructure and showed good microwave dielectric properties of a moderate dielectric constant (ε = 1048), low dielectric loss (0.0090) and high tunability (42.2%) at dc electric field of 30 kV/cm.

The effect of impurities and LiF sintering additive on the microstructure and optical properties of hot-pressed transparent MgAl₂O₄ spinel was investigated. A lower and a higher purity powder were hot pressed with and without LiF and process parameters varied. Microstructure was examined using optical and electron microscopy, optical properties using spectrophotometry, and chemistry using various spectroscopic techniques. Impurities present in parts-per million were found to segregate at grain boundaries and form an amorphous phase, restricting grain growth and causing scatter and opacity. It was found that LiF reacts with impurities to form volatile species that can be removed with proper processing, resulting in larger grain size and increased transmittance. LiF also counteracts absorption caused by reduction of spinel, but results in MgO loss, grain boundary embrittlement, and if trapped in higher concentration, restricts grain growth and causes scatter and opacity.

Failing implants lead to osseous defects. Guided tissue regeneration made of bioactive ceramics has been used to promote bone formation in osseous deformation. The aim of this study was to prepare and to characterize the fluorapatite/forsterite nanocomposite powder for treatment of oral bone defects. In this study, these composite powders with different contents of forsterite nanopowder were prepared via sol-gel process. Characterization of prepared nanocomposite powders and their cytotoxicity evaluation were done and compared with pure forsterite and fluorapatite powders. Results showed that nanocomposite powders with crystallite size of about 21–24 nm were fabricated successfully by gel calcination at 600°C. Besides the non-toxicity effects of powders, nanocomposite containing 20 wt% forsterite significantly increased cell viability compared with control groups. According to these results, these nanocomposite powders might be suitable as bioactive material for oral bone defect.

Power mode is one of the most important factors in the plasma electrolytic oxidation (PEO) technique, which greatly influences the structure and performances of the prepared ceramic coatings. The aim of this work was to investigate effects of three kinds of power modes (constant voltage (Mode 1), constant current (Mode 2), and constant power (Mode 3)) on the structure and corrosion resistance of the PEO ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology, and the element distribution of the coatings was studied using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, respectively. The electrochemical impedance spectrum was measured to evaluate the structure and the corrosion resistance. The polarizing curves were measured to evaluate the corrosion resistance. The results show that the coatings are of porous structure and mainly composed of MgO. The thickness and surface roughness of three kinds of coatings abide by the following sequences: Mode 1 > Mode 2 > Mode 3. By comparison, “equivalent circuit” mode R_s{Q₁[R₁(Q₂R₂)]} is the most proper to reflect the structure of such coatings, including the surface roughness, the outer layer pore structure, and the inner layer structure. The coatings prepared under Mode 1 are of maximum thickness and high density, and therefore have the best general corrosion resistance. And the coatings prepared under Mode 3 are of the smallest surface roughness and higher density, which leads to the best pitting corrosion resistance.

Titania-doped chromium oxide (CTO) can serve as an active gas-sensing material. It has been successful in commercial gas sensors due to its good gas-sensing performance and stability in humid environment; especially with respect of volatile organic compounds (VOCs). CTO fibers with reticular structure were prepared by electrospinning technology and the sensing behavior upon exposure to ethanol was characterized in this report. The gas sensors made of CTO fibers show a good response to ethanol and stability for a long term at operating temperature of 400°C. The experimental results have been analyzed and simulated using the response equations. The humidity effects on the sensor performance were also evaluated. The results indicate that the CTO fibers could be used in practical applications.

A novel approach to prepare dense AlN ceramics with high thermal conductivity was proposed. The aluminum isopropoxide (AIP) was introduced to prepare dense AlN ceramics possessing enhanced thermal conductivity via in situ reaction. The effect of AIP and sintering temperatures on the microstructure and properties of AlN ceramics were investigated. Results indicate that AIP is beneficial for the densification of AlN ceramics, and particularly, when the addition of AIP reaches 1 wt%, the density and thermal conductivity could reach up to 3.29 g/cm³, 182 W/mK, respectively. Finally, the mechanism of the in situ reaction was proposed.

Glass composite dielectrics consisting of calcium aluminoborosilicate glass and nitride fillers such as aluminum nitride, boron nitride, and silicon nitride (AlN, BN, and Si₃N₄) were investigated. Densification and crystallization behavior depended on the type of filler, filler content, and firing temperature. AlN was most promising in generating desirable densification and dielectric properties (k of ~7.2 and tanδ of ~0.003) at 850°C with progressive crystallization of common anorthite phase. BN tended to show no significant densification and suppression of crystallization. Si₃N₄ resulted in abnormal behavior of densification, which can be highlighted with certain expansion at higher temperatures, as well as unexpected crystallization of CaSiO₃ and CaAl₂SiO₆.

The relationship between structural and surface properties of γ-alumina prepared by various methods has been studied, and the adsorption ability of the powders for cobalt ions from aqueous solution is presented, based on the results of X-ray diffraction, specific surface area, scanning electron microscopy, and surface hydroxyl group concentration of the resulting products. Results show that γ-alumina obtained by solution-combustion method (specific surface area: 232.9 m²/g; morphology: lamellar and mesoporous; hydroxyl group content: 0.24 meq OH⁻/g) exhibited the best Co²⁺ adsorption. Furthermore, the synthesis of γ-alumina is highly helpful to study various structural and surface properties of this material.

The determination of wt% alumina (wa) and pore volume fraction (pv) in alumina-based bioceramics is important in ceramic engineering. This article adopts support vector machine (SVM) and relevance vector machine (RVM) for prediction of wa and pv based on SiC. SVM is firmly based on theory of statistical learning. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. The developed SVM and RVM give equations for prediction of wa and pv. This article gives robust models based on SVM and RVM for prediction of wa and pv.

A radio-frequency atmospheric-pressure plasma process has been applied to the synthesis of ultrafine ZrC powders using ZrCl₄ and CH₄ as precursors. Both thermodynamic analysis and experiments were conducted and the as-prepared samples were characterized by X-ray diffraction, electron microscopy, and laser scattering. Results showed that ZrC powders with particle size <100 nm and surface area of 36.56 M²/g could be obtained. The addition of excess H₂ contributed to the increase in conversion rate. The conversion rate was about 65% when the carrier gas ratio (H₂/CH₄) was set at 4.0 and added axially through the injection probe.

Influence of ethanol treatment of co-precipitated yttrium–zirconium hydroxide on deagglomeration of calcined nano 3YSZ powder was studied. Results indicated that the amount of ethanol used in washing the zirconium hydroxide precipitate had a significant impact on the calcined powder characteristics. Different ratios of ethanol to the water contained within the precipitate were used during washing and the calcined nano 3YSZ powders were characterized in terms of BET specific surface area, tap density, pressure-displacement behavior during powder compaction, nanoindentation of green compacts, green and sintered body microstructures. The results indicated that a minimum ethanol amount of 2–3 times that of water in the precipitate was required to achieve superior deagglomeration of the calcined nano YSZ powders. The powders obtained by washing with optimum ethanol amount resulted in high green density and sintered density of compacts.

The present article describes the creation and immobilization of Polyethylene imine (PEI) capsules on a glass surface. The synthesis and deposition were accomplished by short-time (3 min) one-step reaction. The preparation and immobilization of PEI spheres, was carried out using an environmental friendly method, the ultrasonic emulsification. The ultrasonic technique enables to control size and fulfillment of the internal part of the immobilized PEI spheres. Moreover, the ultrasonic emulsification method showed 100% efficiency in PEI spheres creation, which means no residues of aqueous PEI and oil solvents remained in the reaction flask after the nanosphere's creation. The immobilized PEI spheres have sizes varied from 50 to 500 nm. The PEI spheres were successfully filled either with organic solvent (hydrophobic) or with water (hydrophilic). This method provides us the perspective for future encapsulation of varies molecules which have hydrophobic or hydrophilic nature.

In this study, pressureless sintering of silicon nitride via the addition of chromium oxide was investigated. Silicon nitride samples containing additives from the Cr–Cr₂O₃–SiO₂ system were sintered under different conditions. The phase transformation, the degree of densification and the in situ reactions between Si₃N₄ and chromium compounds were investigated and the reactions were validated thermodynamically. It was found that Si₃N₄ reacts with Cr₂O₃ and Cr and these in situ reactions lead to Si₃N₄ decomposition and consequently formation of a series of chromium silicides including Cr₃Si,Cr₅Si, and CrSi₂. Due to the presence of chromium silicides as liquid phases during sintering, the α-Si₃N₄ to β-Si₃N₄ phase transformation started around 1400°C and was completed around 1800°C. On the other hand, densification of Si₃N₄ samples with chromium oxide addition was not observed. The participation of Cr₂O₃ in these in situ reactions prevents sufficient formation of chromium silicate and leads to insufficient liquid phase with poor wettability during sintering, resulting in poor densification.

This article reports a low-cost yellow-emitting Y₃Al_5-xB_xO_12-xN_x:Ce³⁺ phosphor with an enhanced luminescent intensity and excellent thermal stability for white light-emitting diodes (LEDs). It was synthesized by a simple gas-pressure sintering (GPS) process. The effect of B³⁺–N³⁻ incorporation on the optical properties of Y₃Al₅O₁₂:Ce³⁺ phosphor was investigated. The addition of appropriate amounts of boron nitride (BN) leads to a marked increase in photoluminescent intensity and a slight shift of its emission spectra toward the blue region, which is assigned to the improved crystallinity and increased particle size. Especially, the prepared oxynitride phosphor does not exhibit any thermal quenching under high temperature, and the emission intensity at 250°C even increases up to 175% of that measured at 20°C. Finally, the white LED flat lamp with luminous efficiency as high as 101 lm/W, color rendering index of 72, and correlated color temperature of about 6600 K is successfully realized by using YAG:Ce³⁺ phosphor doped with 0.5 molar ratio BN, which is acceptable and promising for general indoor illuminations to replace fluorescent or incandescent lamps.

The thermal stability and photoluminescence degradation of Mn²⁺ in fluorescent lamps used BaMgAl₁₀O₁₇:Eu²⁺,Mn²⁺ phosphor are investigated. The detection of impurity containing manganese with high valence demonstrates the oxidation of Mn²⁺ during baking process at 700°C and it partly leads to emission degradation of Mn²⁺. The emission of Mn²⁺ mainly originates from the energy transfer of Eu²⁺→Mn²⁺. The oxidation of Eu²⁺ decrease the amount of Eu²⁺ centers and thus finally causes the degradation of Mn²⁺. Some traps are revealed to be induced during baking process and it further weakens energy transfer efficiency of Eu²⁺→Mn²⁺ and decreases the emission of Mn²⁺.

Composites of polyvinyledene fluoride (PVDF) and strontium barium niobate (Sr_xBa_1−xNb₂O₆ for x = 0.53/SBN)/ФSBN − (1 − Ф)PVDF with Ф = 0.1 to 0.3 have been prepared by hot uniaxial press. Structural, morphological, dielectric and pyrolectric properties of the composites have been studied. Self-sustaining thick films with a 0–3 connectivity have been synthesized. The dielectric constant (ε_r) was found to increase with the increase in ceramic volume fraction (Ф) in the composite. The composite with Ф = 0.3 is found to have highest values of pyroelectric coefficient (p_i) ~13.475 μC/m²K, FOM_I ~0.481 μC/m²K and FOM_II ~20.13 μC/m²K with good mechanical flexibility.

Investigation on properties and performance of MoSi₂-based heating elements was carried out using high temperature sintering (HT), low-high temperature sintering (LHT), and low temperature sintering (LT) processes. Flexural strength depends proportionally on the thickness of protective surface scale, which is determined by the sintering temperature. The performance, indicated as critical damage temperature, is significantly correlated with the degree of densification, embodying dramatic deterioration with increasing porosity. LHT is more promising in industrially producing high-performance MoSi₂-based heating elements because of advantages in densification and efficiency compared with HT and LT.

We have developed a hot-pressing method for consolidating garnet scintillator powder of composition Gd₃(Al,Ga)₅O₁₂:Ce. Thermodynamic analysis revealed that gallium oxide, which was a constituent of the garnet scintillator powder, would react with the graphite mold beginning at 950°C and would be reduced to gallium metal. To prevent this reaction during hot-pressing, a reaction barrier material was placed between the graphite mold and the scintillator powder. As for the reaction barrier material, 3GdAlO₃–Al₂O₃ powder calcined at 1100°C was found to be suitable because the material provided two important characteristics: the same thermal expansion coefficient as the scintillator material and good sinterability. The Gd₃(Al,Ga)₅O₁₂:Ce garnet scintillator powder was hot pressed at 1475°C for 4 h in vacuum, followed by annealing at 1300°C for 4 h in oxygen atmosphere. The thus obtained garnet scintillator successfully satisfied the necessary requirements for use in an X-ray computed tomography detector.

The dispersion of highly concentrated Zirconium diboride (ZrB₂) suspension in aqueous media was investigated in terms of zeta potential and rheological measurements, with a salt of polyacrylate polymer (SD-07) as dispersant. The adsorption behavior of SD-07 on ZrB₂ particle surface was also studied. Results showed that acid cleaning improved the fluidity of aqueous ZrB₂ slurry. Concentrated (up to 50 vol%) and well-stabilized suspension was obtained in the alkaline pH region, with 0.60 mg/m² SD-07. On this basis, 50 vol% ZrB₂ gelcasting slurry was prepared. The linear shrinkage and flexural strength of as-casted green body were (3.42 ± 0.13)% and (9.4 ± 0.3) MPa, respectively.

The self-setting behavior of α-calcium sulfate hemihydrate is highly dependent on its morphology that is tuned through the addition of ethanol into CaCl₂ aqueous solutions during a salt solution method. With the increase of the ethanol/water volume ratios, the mean lengths of the formed crystals decreased from 24 to 19 μm, whereas their mean widths increased from 6 to 18 μm. It is also detected that the setting time of α-CSH paste reduced from 120 ± 12.3 to 17 ± 2.1 min as the crystal morphology evolved from rod-like to equiaxial.

A green synthesis of Zr₂(WO₄)(PO₄)₂ ceramics from ZrO₂, WO₃ and P₂O₅ is presented. It is shown that the ceramics can be synthesized by one-step sintering within 60 min. The relative density of the ceramics can be enhanced from about 75% without sintering additives to 99.8% of the theoretical value with 1.0 wt% MgO and 2.0 wt% polyvinyl alcohol. The grain sizes of the ceramics are smaller and more uniform with MgO added in the raw materials than with MgO added in the Zr₂(WO₄)(PO₄)₂ powder. The coefficients of thermal expansion are about −2.325 × 10⁻⁶, −1.406 × 10⁻⁶, −1.509 × 10⁻⁶ and −1.384 × 10⁻⁶°C⁻¹ for the samples without MgO, with MgO added in the raw materials, with MgO added in the Zr₂(WO₄)(PO₄)₂ powder and with MgO and PVA added in the raw materials, respectively.

The influence of BaCu(B₂O₅) (BCB) on densification, phases, microstructure and microwave dielectric properties of ZnNb₂O₆–xTiO₂ (x = 1.70–1.90) composite ceramics have been investigated. Undoped ZnNb₂O₆–1.8TiO₂ ceramics sintered at 1200°C exhibit temperature coefficient of resonant frequency (τ_f) ~9.25 ppm/°C. When BaCu(B₂O₅) was added, the sintering temperature of the ZnNb₂O₆–1.8TiO₂ composite ceramics was effectively reduced to 950°C. The results indicated that the permittivity and Q × f were dependent on the sintering temperature and the amounts of BaCu(B₂O₅). Addition of 3.0 wt% BaCu(B₂O₅) in ZnNb₂O₆–1.8TiO₂ ceramics sintered at 950°C showed excellent dielectric properties of ε_r = 40.9, Q × f = 12,200 GHz (f = 5.015 GHz) and τ_f = +0.3 ppm/°C.

When 1.5 wt% of Li₂O–B₂O₃–SiO₂ and 1.5 wt% of Li₂O–B₂O₃–Al₂O₃ glass-added (Ca_0.7Sr_0.3O)_1.03(Ti_0.1Zr_0.9)O₂ batch was ball milled for 10~30 h followed by sintering at 950°C in flowing N₂-10%H₂ atmosphere, an apparent density of approximately 4.5 g/cm³, a dielectric constant of approximately 26, and a quality factor of roughly about 3300 GHz were demonstrated. A prolonged ball mill time thereafter significantly decreased both of the dielectric properties because of the enhanced reduction of the specimens during sintering. The apparent evidence of a material reaction between the dielectric material and the copper electrode was not observed.

Alkali corrosion has become a problem in industrial furnaces especially because of the increasing use of secondary fuels. In the corroded lining material alkali aluminosilicates such as kalsilite, leucite or nepheline could be identified. According to ternary phase diagrams these substances have very high melting points which would make them suitable for high temperature applications in alkali corrosive environments. This study presents systematic synthesis experiments to produce alkali aluminosilicates by thermal (800°C, 1000°C, 1200°C) and hydrothermal (200°C) treatment starting from the nominal compositions of KAlSi₂O₆, KAlSiO₄, and NaAlSiO₄., KOH NaOH, quartz powder, and Al(OH)₃ were used as raw materials. The phase composition was analyzed by using X-ray diffraction (XRD). The alkali corrosion was tested using alkali salts as corrosive substances. The synthesis experiments resulted in multiphase reaction products. The hydrothermal method yielded only for the initial composition according to the stoichiometry of KAlSiO₄ crystalline phases of the same composition. The thermal method produced for all sets of synthesizing parameters mixtures of stoichiometric and nonstoichiometric alkali aluminosilicates. In the corrosion test, material of the nominal composition of KAlSiO₄ showed the best results. The material was corrosion resistant independently from the initially applied synthesizing parameters.

Preparation of Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) lead-free piezoelectric ceramics with different amounts of LiF (BCZT-xLiF) was done, and the effects of the LiF doping on the phase transition behavior and the electrical properties of the resulting ceramic were investigated. The experimental results showed that the polymorphic rhombohedral-tetragonal phase transition temperature was found shifted toward room temperature with the Li doping. The study showed that BCZT lead-free piezoelectric ceramic with improved performance properties at room temperature can be achieved by shifting the polymorphic phase transition point nearer room temperature through the addition of LiF.

The effects of impurity iron content on characteristics of sintered reaction-bonded silicon nitrides were examined by adding iron powder to a high purity raw Si powder. Powder compacts of the raw Si powder doped with 2 mol% Y₂O₃ and 5 mol% MgSiN₂ as sintering additives and Fe as impurity (0 mass%, 0.1 mass%, 1.0 mass% and 5.0 mass%) were nitrided at 1400°C for 8 h under a N₂ pressure of 0.1 MPa, followed by post-sintering at 1900°C for 6 h under a N₂ pressure of 0.9 MPa. All the SRBSN (Sintered Reaction-Bonded Silicon Nitride) specimens had about the same 4-point bending strength of 730–770 MPa. The fracture toughness of the specimens was gradually decreased with increasing Fe additive amount due to the inhibition of development of rodlike β-Si₃N₄ grains by SiFe_x particles formed during nitridation process. The thermal conductivity was also decreased with an increase in Fe amount. It seems that the increasing oxygen in grain-boundary phase caused by the oxidation of Fe during milling resulted in the increase in lattice oxygen of β-Si₃N₄ grains, which caused phonon scattering and thereby decreased thermal conductivity of β-Si₃N₄. There was little change in the dielectric breakdown strength of the specimens: 24, 22, 22, and 21 kV/mm for the specimens without Fe, and with 0.1 mass%, 1.0 mass% and 5.0 mass% Fe, respectively. The surface resistivity of the specimens with 0 mass%, 0.1 mass% and 1.0 mass% Fe was in the range of 10¹³ Ω, but the specimen with 5 mass% Fe was about one order lower than the others.

An attempt has been made to provide the ranking of piezoelectric and pyroelectric materials using technique for order preference by similarity to ideal solution (TOPSIS) method. To calculate weight (priority) for all the attributes (properties) understudy, entropy method is used. Interestingly my results suggest that dielectric constant is a key parameter (after d₃₃ coefficient) which governs selection of piezoelectric materials. PLZT (8/65/35) and LiTaO₃ ceramics place on first rank among studied piezoelectric and pyroelectric materials, respectively. These materials are classified using hierarchical clustering which shows similarities between the materials irrespective to their ranking obtained using TOPSIS method.

Two different commercial refractory castables based on mullite or magnesia aggregates have been improved through addition of 0–25 wt.% nano-magnesium aluminate spinel (MA) powder. Physico-mechanical and refractory properties were tested at different firing temperatures. The phase composition, thermal analysis, and microstructure of these refractory castables were detected using X-ray diffraction (XRD), differential thermal analysis (DTA), as well as scanning electron microscope (SEM) attached with energy dispersive X-ray unit, respectively. The castable sample mix containing 10 wt.% nano-MA spinel powder was chosen as an optimum composition according to its good sintering, mechanical as well as refractory properties.

The formation of three-dimensional shapes is one of the most important technological steps in low temperature co-fired ceramics (LTCC) process. Channels and chambers qualities and the process speed are strongly affected by the shaping procedure. There are three main machining techniques: laser cutting, punching, and milling. This article is dedicated to end milling process of LTCC tapes. The determined PS/DK 2³ experiment design was used in the investigations and its procedure is described in this article. The used procedure is a very flexible method to achieve much useful information about the influence of the process parameters on the output. The PS/DK 2³ experiment design enables analysis of the influence of: the three input parameters on the output (minimal obtained feature) and the interaction between the input parameters on the output (minimal obtained feature). Moreover, PS/DK 2³ experiment design enables to obtain the mathematical model of the milling process and to decrease the number of measurements demanded to achieve the correct model. Hence, the design is suitable to decrease the time and costs of the experiment. The influence of the following input parameters: spindle rotational speed, spindle feed rate, vertical spindle step, and cutter diameter on minimal obtained feature of LTCC tapes is analyzed in this article.

In this study, TiO₂ nanoparticle suspensions are guided by templated molds to fabricate micrometer feature patterns and arrays. The effects of PEG with different molecular weights on suspension flowability and surface wettability between the PDMS molds and the TiO₂ suspensions on pattern formation are investigated. PEG 400 is the most desirable dispersant. The suspensions have the best wetting on the mold surface with 3 wt% TX-100 addition. Micrometer feature arrays with feature sizes ranging from 750 nm to 1.5 μm are obtained. Fundamental understanding, regarding suspension flowability, wetting, and the ability to make different feature sizes and shapes, is discussed.

Dense nanocomposites consisting of spinel Mn-doped Mg-ferrite and permalloy, (Mg[Fe_1 − xMn_x]₂O₄(0 ≤ x ≤ 0.4)/53Fe–47Ni), have been fabricated from powder mixtures of MgO/α-Fe₂O₃/MnO and N₂-atomized metal particles utilizing high-pressure cold isostatic press (CIP), pulsed electric current pressure sintering (PECPS), and capsule-free hot isostatic pressing (HIP). Metal particles were coated with the mixed oxide powders homogeneously under high shear compression in Ar. The coated powders were densified into relative densities of 83–85% by high pressure CIPing (1 GPa). They were then presintered at 823 K for 3 min under uniaxial pressure of 100 MPa in Ar using a PECPS. The pre-sintered bodies had relative densities of 93–95% composed of spinel ferrite and permalloy; the mixed metal oxides were changed into magnesium ferrites by heating briefly at low temperature. Then, HIP (1123 K/6 h/196 MPa-Ar) was adopted to densify the pre-sintered bodies into a nearly full density; furthermore, a sintering atmosphere control was performed using ferrite muffles to maintain both phases. Sintered materials consisting of granular metal particles (φ 8.5 μm) isolated and surrounded by a thin ferrite discontinuous layer (0.2–1.3 μm) with a relative density ≥99.5% revealed both a saturation magnetization density ≥1 T and moderate permeability values of 30–35 at 1 MHz.

This study demonstrates the synthesis of nanostructured Si₃N₄/SiC composite powders from silica fume, for the first time. The processing approach to convert the waste silica fume to advanced nanocomposites is based on the integrated mechanical and thermal activation (IMTA) process. The synthesized nanostructured Si₃N₄/SiC powders have crystallite sizes as small as 17 nm for SiC and 42 nm for Si₃N₄. It has been shown that the carbothermic reduction and nitridation temperature, as well as the graphite concentration in the starting SiO₂ + C mixture are the important parameters to obtain Si₃N₄ and SiC nanopowders and control their crystal sizes. The synthesis conditions to tailor the relative contents of α-Si₃N₄ and α-SiC (changing from as high as 49 vol.% to as low as 21 vol.% α-SiC) in the final powder mixture have been investigated, and the mechanisms responsible for the observed relationship between processing conditions and the characteristics of the final powder have been identified.

A dense SiC coating on carbon particles has been developed using SiO powders as the Si source and a chemical vapor reaction method. The coating process was controlled by atmosphere, coating temperature, time, and weight ratio of SiO/C. The SiC-coated carbon particles, with a mean particle size of 20 μm, were sintered at 2000°C under 40 MPa for 20 min by spark plasma sintering (SPS). The product, called ceramic bonded carbon (CBC), had a unique microstructure, with a 3D micro-network structure consisting of carbon particles covered with 1~5 μm thick SiC boundary layers. The sintering behavior of SiC/CBCs was analyzed in terms of the network formation of SiC boundary layers at over 1800°C and the grain growth of SiC at 2000°C. SiC/CBCs showed a bending strength of 150 MPa and a low shore hardness of 40. These materials could also be easily joined to SiC ceramics using SPS.

We herein describe a set of experiments used to study the effect of heating schedule on phase formation during the fabrication of Ti₃SiC₂-based materials from Ti–SiC powder mixtures by means of pressureless sintering. We found that combustion was initiated at a temperature of about 1330°C, which resulted in the formation of Ti-rich eutectic melt followed by crystallization of Ti₃SiC₂. It was shown that when preannealing was performed at 1150°C, no further combustive process could occur, and an intermediate, nonequilibrium phase composition, consisting of Ti₅Si₃C_x, TiC, and SiC remained until the end of the heat treatment. We herein discuss the mechanistic interpretation of this behavior.

The objective of this study was to develop anti-washout and fast-setting calcium–magnesium phosphate cement (as-CMP) by introducing white dextrin (WD) and magnesium phosphate cement (MPC) to CPC. The results showed that WD imparted anti-washout to the as-CMP paste, whereas MPC simultaneously improved the paste anti-washout and fast-setting. The synergistic effect of MPC and WD obviously shortened the setting time of as-CMP. The WD did not affect the phase evolution and microstructure of the paste. Furthermore, all samples were biocompatible and as-CMP exhibited the best cell metabolic activity, cell attachment, and proliferation, which would provide basic data for the clinical application.

Sodium borosilicate glass powder with the Si:B:Na molar ration of 53:44:6 has been developed and used as the solder to join sintered SiC ceramics. The coefficient of thermal expansion of the glass matches the silicon carbide substrate well at low temperature, and the wettability of the solder on SiC substrate becomes excellent above 1150°C. The 4-point bending strength of the joint reaches 218 ± 23 MPa at room temperature and the joint strength at 400°C can be kept at 154 ± 35 MPa. The microstructure, compositions, and interfacial properties were studied. Results showed that a good adhesion between SiC substrate and the solder layer was achieved.

The conversion of polytitanocarbosilane fibers to SiC has been studied from 1400°C to 1600°C. Thermochemical modeling indicated the stable phases were SiC and TiC. Kinetics were studied with a thermogravimetric method and post heat-treatment phases, and microstructures were studied with X-ray diffraction and scanning electron microscopy. Kinetics exhibit a strong temperature dependence and an activation energy of 443.3 ± 11.7 kJ/mol. This suggests that a chemical reaction step is rate-limiting. X-ray diffraction shows the conversion of an amorphous phase to crystalline SiC. Electron microscopy shows the development of internal porosity and large grains on the fiber surface, particularly at the higher temperatures.

Application of polymer as thickener of precursor solution for preparing boron nitride (BN) nanofibers by electrospinning brings carbon impurity in the nitride products. The control and removal of the carbon impurity are a key step in the synthesis of the BN nanofibers. In this article, the control and removal of the carbon impurity are well realized by introducing O₂ and NH₃ simultaneously. The carbon content in the BN nanofibers can be well controlled by changing O₂/NH₃ ratio, temperature, time, and gas flow rate. The effects of the carbon impurity on the structure of the BN products are investigated systematically.

This article offers a detail description of design, simulation, fabrication and characterization of inductors on different substrate configurations intended for application in radio frequency range. The presented inductors are meander type structures fabricated using low temperature co-fired ceramic technology. Different substrate configurations incorporate placement of an air-gap beneath the inductor. Obtained results present over 30% increase in quality factor and widening of the operating frequency range by over 55% in comparison with inductors on standard substrate configurations.

Epitaxially grown (100) three-axis-oriented (Ba_0.7Sr_0.3)TiO₃ thin film on (100) platinum (Pt) coated (100) magnesium oxide (MgO) substrate and (100) three-axis-oriented BaTiO₃ thin film with BaZrO₃ buffer layer were prepared on an MgO(100) substrate using the chemical solution deposition method. The growth of the film was found to depend on the annealing condition. Transmission electron microscope revealed cube-on-cube epitaxial growth. The thin films exhibited a (100) three-axis-orientation that followed the (100) orientation of the MgO substrate and the (100) orientation of the Pt or BaZrO₃ bottom layer, as observed from an X-ray pole figure measurement and the selected area electron diffraction patterns.

Aligned regular 2D channels were fabricated in alumina via two routes: soft metal and carbon fibers. The soft metal route was accomplished employing centrifugal forces to eject the molten metal from the green matrix. The carbon fiber route was accomplished by burning out the carbon fibers between 450°C and 630°C. In both methods, pressureless sintering followed, yielding the desired 2D channel profiles. Some porous preforms exhibited higher fracture strength than the solid specimens, and this has been attributed to the ability of the channels to reduce the population and distribution of cracks in the porous material.

Development of alumina/glass composites with minimal residual porosity and superior mechanical properties requires systematic studies on glass infiltration into porous alumina. This work has examined the effect of alumina particle size and the resulting pore size distribution on glass infiltration. Samples were prepared by slip-casting a coarser alumina powder and blends of the coarse (d₅₀ ~ 3.4 μm) and a finer (d₅₀ ~ 0.7 μm) alumina powder. After presintering (1200°C) and following a single cycle of infiltration (1100°C), the sample with 50:50 (wt%) coarse and fine alumina showed highest flexural strength. Improvement in flexural strength could be imputed to the better glass infiltration.

The aim of this research was to study the influence of pH (2.5, 7, 10.5), molar ratio of fuel to nitrates (0.36, 0.56, 0.75), and calcination temperature (600, 800, 1000, 1200°C) on the characteristics of CoAl₂O₄ nano pigments synthesized using a solution-based combustion method. Gel formation, morphology, specific surface area, and color of the powder were characterized using TG–DTA (thermogravimetric and differential thermal analysis), XRD (X-ray diffraction), TEM (transmission electron microscopy), BET (Brunauer–Emmett–Teller), and UV–Vis. The results indicate that spinel CoAl₂O₄ was formed independently of the different variables studied and that higher temperature promotes crystallite size. According to the TEM micrographs, most of particles calcined at 800 and 1000°C have average particle sizes <30 and 75 nm, respectively. Consistent with BET results, maximum specific surface area was obtained at pH of 7. Colorability tests demonstrate that the mixtures of glaze and calcined nano pigments are still dark blue after heating up to 1200°C.

The skutterudite/electrode thermoelectric joints were fabricated with the insertion of Ti foil by spark plasma sintering. The interfacial microstructure and reliability of joints were studied during thermal duration test. A multilayer structure, which was composed of intermetallic compounds, was observed at the CoSb₃/Ti interface after thermal aging of 20 days. The interfacial reactions and diffusion path between CoSb₃ and Ti were discussed. The contact resistance of CoSb₃/electrode junction was measured through four-probe method and the thermal contact resistance was calculated based on multilayer mode measurement. Effects of the contact resistivity on the performance of CoSb₃-based device were discussed.

ZnO and Al-doped ZnO ceramics with high density and fine grain size were prepared using a two-step sintering method. ZnO ceramics with a grain size of 1.2 μm and a density greater than 99% were obtained. The kinetic window for a ZnO nanoparticle TSS process was determined in this study. Dense AZO ceramics with homogeneous Al distribution were obtained using a high sintering temperature (T_st) of 1323 K and a low sintering temperature (T_nd) of 1273 K. The activation energies for ZnO and AZO nanoparticle grain growth were determined to be 169 ± 18 kJ/mol and 374 ± 36 kJ/mol, respectively.

Localized mode is an important property of defect electromagnetic band gap (EBG) structure, which plays a key role in the application of EBG structure. The purpose of this article was to study the impact on localized properties by introducing cavities of different shapes into diamond EBG structure. Alumina-based ceramic diamond EBG structures were fabricated using stereolithography (SL), gel-casting and vacuum freeze-drying. When the microwave transmission properties of samples with cavities of different shapes were tested, the resonant peaks appeared within the band gap. By varying the cavity shape, the quality of the localized mode could be adjusted. The results have shown that localized mode with a high quality factor (Q factor) corresponded to the optimal cavity shape in EBG structure. The experimental results agreed well with simulation results. These excellent microwave properties of 3D EBG structure could be directly applied in microwave devices, such as microwave antenna and filter devices.

Ferroelectric film-on-foil capacitors are suitable to replace discrete passive components in the quest to develop electronic devices that show superior performance and are smaller in size. The film-on-foil approach is the most practical method to fabricate such components. Films of Pb_0.92La_0.08Zr_0.52Ti_0.48O₃ (PLZT) were deposited on SrRuO₃ (SRO) buffer films over nickel and silicon substrates. High-quality polycrystalline SRO thin-film electrodes were first deposited by chemical solution deposition. A phase pure, dense, uniform microstructure with grain size <100 nm was obtained in films crystallized at 700°C. The room-temperature resistivity of the SRO films crystallized at 700°C was ~800–900 μΩ-cm. The dielectric properties of sol–gel derived PLZT capacitors on SRO-buffered nickel were evaluated as a function of temperature, bias field, and frequency, and the results were compared to those of the same films on silicon substrates. The comparison demonstrated the integrity of the buffer layer and its compatibility with nickel substrates. Device-quality dielectric properties were measured on PLZT films deposited on SRO-buffered nickel foils and found to be superior to those for PLZT on SRO-buffered silicon and expensive platinized silicon. These results suggest that SRO films can act as an effective barrier layer on nickel substrates suitable for embedded capacitor applications.

Laser cladding of the A₃Ti + TiC preplaced powders on the Ti–6Al–4V alloy can form the Ti₃Al/TiC ceramic layer, which improved the wear resistance of the substrate. In this study, the influence of 7 wt% yttria partially stabilized zirconia (YPSZ) on the surface performance of the Ti₃Al/TiC ceramic layer was researched, and the Al₃Ti + TiC/YPSZ laser-cladded coating has been researched by means of X-ray diffraction, scanning electron microscope, and energy dispersive spectrometer. It was found that laser cladding of YPSZ can control the cracks in the Ti₃Al/TiC ceramic layer. Furthermore, due to the action of YPSZ, stratification was observed in this ceramic layer. The upper layer in this coating consisted of Al₂O_3, Ti₃Al, t-ZrO₂, TiC, TiO₂ and ZrSiO₄, and Ti₃Al/Al₂O₃ were the matrix of this region. This upper layer exhibited an excellent wear resistance due to its phase constituent. During the cladding process, YPSZ had a very marked trend to float on the surface of the coating. Therefore, the upper layer showed better wear resistance than that of the bottom layer due to the action of the high YPSZ content.

The introduction of ceramics into the market of wood cutting tools has been difficult because of the generally low toughness of ceramics which causes brittle failure. That is why the improvement of mechanical performance of ceramics with potential to be used as cutting tools is important. The newly developed Si₃N₄/SiC wood cutting tools have a bending strength of 740 MPa, a fracture toughness of 5.4 MPam^1/2, a hardness of 16.8 GPa and a grain size of 1 μm. These Si₃N₄/SiC tools were tested in a lifetime cutting trial on wood and showed twice as long lifecycles than standard tungsten carbide tools. Furthermore, the static corrosion resistance in tannic acid, the friction coefficients between wood and the tool material and the cutting forces were measured for both the ceramic composite and the tungsten carbide tools.

Thermodynamic equilibrium modeling indicates that the introduction of H₂O in oxidizing environments decreases Si stability due to formation of volatile hydroxide and oxy hydroxides. 3Al₂O₃·2SiO₂ mullite bond offers only slight improvement over pure silica as the thermodynamic activity of silica in mullite is near unity. In reducing atmospheres Si stability is improved by the presence of H₂O and Al₂O₃, transitioning from SiO and silane as the dominant volatile species to hydroxides, oxy hydroxides, and SiO with increasing water vapor partial pressure. Empirical studies reveal initial rapid releases of Si from stationary solid oxide fuel cell refractory materials followed by slower solid-state diffusion limited release.

In Tabor's classical studies of the deformation of metals, the yield stress (Y) and hardness (H) were shown to be related according to H/Y ≈ 3 for complete or fully plastic deformation. Since then it has been anecdotally shown for ceramics that this ratio is <3. Interest exists to explore this further so Hertzian indentation was used to measure the apparent yield stress of numerous ceramics and metals and their results were compared with each material's load-dependent Knoop hardness. The evaluated ceramics included standard reference materials for hardness (silicon nitride and tungsten carbide), silicon carbide, alumina, and glass. Several steel compositions were also tested for comparison. Knoop hardness measurements at 19.6 N (i.e., toward “complete or fully plastic deformation”), showed that 2 < H/Y < 3 for the metals and 0.8 < H/Y < 1.8 for the glasses and ceramics. Being that H/Y ≠ 3 for the ceramics indicates that Tabor's analysis is either not applicable to ceramics or that full plastic deformation is not achieved with a Knoop indentation or both.

Doloma and doloma carbon refractories are the standard refractory systems applied in AOD (argon oxygen decarburization) and VOD (vacuum oxygen decarburization) vessels in the secondary metallurgy to produce stainless steel. This refractory system is connected with metallurgical benefits such as high oxidic stability of its oxides, and the ability to bond sulfur from the hot metal. Production and application of carbon-bonded refractories is directly linked with environmental harmful emissions in the broadest sense. In the center of this work is the aspect of increased residual carbon content of the binder resin due to TiO₂ addition. Furthermore, this work has observed the applicability of TiO₂-treated bricks in AOD converter. The increased residual carbon content of the binder resin connected with improved mechanical, physical, and thermomechanical properties due to sub-micro scaled TiO₂ and metallic antioxidant addition offers the feasibility to reduce the total carbon content without downgrading the brick properties. This aspect has not been observed yet, and is of high interest with respect to reduced emissions and environmental friendly refractories. Previous works have investigated the influence of TiO₂ on other carbon-bonded refractory systems, such as alumina carbon and magnesia carbon. As illustrated in this work and previous work, TiO₂ is working completely different in the doloma carbon system when compared with other systems.

Glass + ceramic composites using lead-free ultralow-softening point glass matrices (brand names G018-249 and G018-250) with alumina fillers are investigated. The composites show good densification with near zero shrinkage at very low sintering temperature and do not show either the formation of secondary crystalline phases or dissolution of alumina. They further show no reactivity with the silver electrodes at a sintering temperature of 650°C and have permittivities of 9.5 and 8.8, loss tangents of 0.0068 and 0.0087 at 1 MHz for the samples containing G018-249 glass and G018-250 glass, respectively.

The La_1−xYb_x(Mg_0.5Sn_0.5)O₃ ceramics were prepared by the conventional solid-state method with various sintering temperatures. The X-ray diffraction patterns of the La_0.97Yb_0.03(Mg_0.5Sn_0.5)O₃ ceramics revealed no significant variation of phase with sintering temperatures. An apparent density of 6.65 g/cm³, a dielectric constant (ε_r) of 20.2, a quality factor (Q × f) of 56,800 GHz, and a temperature coefficient of resonant frequency (τ_f) of −76.9 ppm/°C were obtained for La_0.97Yb_0.03(Mg_0.5Sn_0.5)O₃ ceramics that were sintered at 1550°C for 4 h.

Low-pressure injection molding (LPIM) was used to produce helical alumina springs. Three sets of springs were sintered at 1550°C, 1600°C and 1650°C to observe the effects on spring constant and fracture stress. Sintered alumina springs were obtained with densities ranging from 94.0% to 97.5% of the theoretical limit. Spring constants were measured from room temperature up to 1100°C. Fracture stress data were analyzed according to Weibull statistics and the method of maximum likelihood. Upon increase of sintering temperature from 1550°C to 1650°C, the spring constant and the Weibull characteristic strength of the alumina springs increases by 15% and 32%, respectively. On the other hand, sintering temperature has a negligible influence on Weibull's modulus. This is because internal bubbles and surface defects introduced in the production stage of the ceramic springs — more than the reduction in porosity with increasing sintering temperature — are critical in determining the reliability of the ceramic springs.

Using the solution precursor plasma spray process Eu: Y₂O₃ phosphor coating was deposited. The phase composition, microstructure, and photoluminescent properties of the as-synthesized powders and as-deposited coatings were investigated. XRD analysis indicated that the coating is composed of cubic Y₂O₃. SEM micrographs reveal the as-sprayed coating is porous with a thickness of ~150 μm. Photoluminescent property measurement indicated that the phosphor coating exhibits the strongest emission at 612 nm, which is assigned to ⁵D₀ → ⁷F₂ electric-dipole transition.

Magnesium hydroxide, Mg(OH)₂ (both 99% and 99.99% purity grades), γ-Al₂O₃, and AlOOH have been investigated for the direct production of transparent MgAl₂O₄. The highest average in-line transmittance through 3.5–4 mm thick samples is 84.2 ± 1.0% at 550 nm, attained by using mixtures of 99.99% pure Mg(OH)₂ and γ-Al₂O₃. Other formulations exhibited 77–80% visible transmission, suggesting that further optimization can improve sample consistency. All samples exhibited a Knoop hardness of ~12 GPa, and elastic modulus of ~280 GPa. Biaxial flexural strength measurements ranged from 85 to 136 MPa depending on starting materials.

High densified C_sf/Al₂O₃ ceramic composites were prepared by hot-pressed sintering using α-Al₂O₃ powders and short carbon fibers as starting materials. Dielectric and mechanical properties of these composites were evaluated. The results show that the addition of short carbon fiber (C_sf) conducting fillers renders the composites radar absorbing ability, while the hardness around 90 HRF and strength around 300 MPa are also obtained in these composites. Both the fiber content and the length can be used to optimize the dielectric property at the frequency range 8.2–12.4 GHz. The results indicate that C_sf/Al₂O₃ composite is a promising radar absorbing material with load-bearing ability.

New composites called ceramic-bonded carbon (CBCs), consisting of a three-dimensional structure of carbon particles bonded with thin ceramic boundaries, were developed. To fabricate light and tough CBCs and to understand their reinforcing mechanism, Si₃N₄ and carbon powders (25:75 in volume ratio) were gelcasted and then sintered by spark plasma sintering at temperatures of 1700–1900°C. The ceramic boundary of SiC was formed in situ at above 1700°C by the reaction of Si₃N₄ and C. The sintered CBCs showed a unique microstructure consisting of carbon particles and ceramic boundaries of 15 μm in size and 0.5–3 μm in thickness, respectively. With an increase in sintering temperature, physical bonding of ceramic grains to the carbon particles was enhanced as the grain growth of SiC increased. The SiC/CBCs sintered at 1900°C were highly dense (97% theoretical density), lightweight (2.36 mg/m³), and had both relatively high bending strength and thermal conductivity (135 MPa and 140 W/mK, respectively).

The oxide inclusion and porosity defect structures in a tantalum carbide specimen fabricated from vacuum plasma spraying with postspraying sintering and hot-isostatic pressing has been characterized. The tantalum carbide powders were obtained using a carbothermal reduction process of tantalum oxide precursors. During its fabrication, oxide-based inclusions formed from intrinsic impurities in the powder. Using serial sectioning and three-dimensional reconstruction techniques, interconnected globular oxide inclusions were revealed to be within the matrix phase and in the grain boundaries. The oxide phase was identified to be z-Ta₂O₅ through selected area electron diffraction. The two- and three-dimensional porosity size distribution was compared and accounted for ~2% of the volume.

The microwave dielectric properties of the (1 − x)(Mg_0.95Ni_0.05)TiO₃–x(Ca_0.8Sr_0.2)TiO₃ ceramic system prepared by mixed oxide route have been investigated. The crystal structures and the microstructures of the ceramics were characterized by means X-ray and scanning electron microscopy. The microwave dielectric properties are strongly related to the density and matrix of the specimen. Combination of (Mg_0.95Ni_0.05)TiO₃ (ilmenite-type structure) and (Ca_0.8Sr_0.2)TiO₃ (perovskite-structured) forms a two-phase system and leads to a near-zero temperature coefficient (τ_f). With increasing x, the quality factor (Q × f) decreased and dielectric constant (ε_r) increased. A new microwave dielectric material 0.95(Mg_0.95Ni_0.05)TiO₃–0.05(Ca_0.8Sr_0.2)TiO₃, possessing excellent microwave dielectric properties with a dielectric constant (ε_r) of 21.68, a quality factor (Q × f) of 94,000 (GHz) and a temperature coefficient (τ_f) of approximately −5.2 ppm/°C at 1275°C for 4 h, is proposed as a suitable candidate material for microwave applications requiring low dielectric loss.

Nanocrystalline calcium substituted magnesium titanate was synthesized through an auto-igniting combustion technique. The phase constitution of the powder was examined using X-ray diffraction, thermal analyses, and spectroscopic studies. The particle size of ~30 nm was obtained, and that could be sintered to 96% of the theoretic density at 1150°C/2 h. The microstructure of the sintered surface was examined using scanning electron microscopy. The quality factor (Q_u × f ) of 65,110 GHz, dielectric constant (ε_r) of 20.25, and temperature coefficient of resonant frequency (τ_f) of ~0 ppm/°C suggest that the sintered sample can be used for microwave applications.

The fabrication of Er-doped ZrO₂-based nanocrystalline phase-separated silica optical preforms by the modified chemical vapor deposition process and solution-doping techniques is presented. Fabricated preform cores are nearly transparent and contain phase-separated rare-earth-doped nanocrystalline particles with diameters mainly in a range from 20 to 80 nm. High concentrations of erbium and aluminum in preform cores of about 0.3 and 14 mol%, respectively, have been achieved without defects on the core–cladding interface. Spectral losses in a range 800–1600 nm and fluorescence spectra of erbium ions around 1550 nm measured on a fiber drawn from the preform are reported.

This article demonstrates a method to fabricate VO₂ powder by annealing a precursor that was obtained by electrochemical intercalation of lithium into layered structured V₂O₅. The method includes three steps. First, Li⁺ was intercalated into interlayers of V₂O₅ through an electrochemical process with precisely controlled electrical discharging currents and intercalation amounts, and at the same time V⁵⁺ would be deoxidized into V⁴⁺. Secondly, the Li⁺-intercalated powder was rinsed in an acid solution to achieve an ion exchanging process of replacing the Li⁺ in the V–O frame with H⁺. Thirdly, the powder was annealed at 800°C in N₂ atmosphere for dehydration and VO₂ crystallization. By DSC investigation, the as-produced final product has a strong endothermic peak at around 68°C in a heating semicycle, which is indicative of the phase transition from VO₂(M) to VO₂(R). This approach can be extended to the fabrication of other sub-valence oxides by lithium intercalation and deoxidization of its higher valence layer-structured precursors.

It remains both a challenge and an opportunity to attract and nurture the best talent in ceramic science and engineering. Success stories in other areas provide examples of how to do it. Research findings reveal behaviors and specific actions that encourage excellence in all individuals, for example, showing support, creating structures that promote interaction, and establishing clear expectations. In developing countries, where the education and research infrastructure are often not as strong and English is not otherwise the language of choice, additional factors come into play. Involving students in research and exchanges—both domestically and internationally—within academe and with other sectors are keys to maintaining a high level of engagement. Students need to identify with the benefits and goals of their career paths. It is imperative that the education curriculum be nimble and incorporate skill development in important and emerging areas such as entrepreneurship and integrated computation and modeling.

This article summarizes the opportunities and challenges for future research in ceramics used in biology and medicine. The summary was prepared from the seven presentations at the 4th International Congress on Ceramics held from July 15 to 19, 2012, in Chicago, USA. The major emerging opportunities identified were as follows: (i) developing fundamental understanding of bioactive ions used in bioceramics, (ii) possibility of using novel manufacturing methods such as 3D printing, (iii) attaching bioceramics to metallic implants, and (iv) enabling collaboration between ceramicist, biologist, industry, and medical professionals.

Aerospace was one of several parallel tracks at the 4th International Congress on Ceramics. Three prominent areas for application of ceramic technology to aerospace were discussed: propulsion and exhaust washed structures, thermal protection systems, and hot primary structure. Whereas ceramics are not new to aerospace, their application heretofore has been rather limited. Beyond directly working the technical maturity of various ceramic matrix composite, thermal protection, and ultra-high-temperature ceramic materials and systems, specific efforts are required to fully transition these materials for aerospace applications, to nurture the technology through to application, and to address affordability.

Design procedure, technology and basic properties of a piezoelectric Low Temperature Co-fired Ceramics (LTCC) accelerometer are presented in this paper. The sensor consists of a LTCC membrane with a seismic mass. Meggitt InSensor^® PZT thick film has been applied as the sensing material. Finite element method (FEM) has been used to analyze the impact of the sensor geometry (membrane thickness, membrane and seismic mass radii) and PZT thick film placement on basic properties (sensitivity and bandwidth) of the device. The LTCC process was optimized in order to create thin and planar ceramic membrane with relatively huge seismic mass. Selected properties of the sensor have been measured and compared with the simulated ones.

Low-temperature co-fired ceramics (LTCC) enable the fabrication of microfluidic elements such as channels and embedded cavities in electrical devices. Hence, LTCC facilitate the realization of complex and integrated microfluidic devices. Examples can be applied in many areas like reaction chambers for synthesis of chemical compounds. However, for many applications it is necessary to have an optically transparent interface to the surroundings. The integration of optical windows in LTCC opens up a wide field of new and innovative applications such as the observation of chemiluminescent reactions. These chemical reactions emit electromagnetic radiation and thus offer a method for noninvasive detection. Thin glasses (≤500 μm) were bonded by thermocompression onto a LTCC substrate. As the bonding agent, a glass frit paste was used. Borosilicate glasses, fused silica as well as silicon were successfully bonded onto LTCC. To join materials with a large coefficient of thermal expansion mismatch (i.e., fused silica and LTCC), it is necessary to limit the heat input to the bond interface. Therefore, a heating structure was integrated into the LTCC substrate beneath the bond interface. This bonding process provides a gas-tight optical port with a high bond strength.

Recent advances in the development of high gauge factor thin films for strain gauges prompt the research on advanced substrate materials. A glass ceramic composite has been developed in consideration of a high coefficient of thermal expansion (9.4 ppm/K) and a low modulus of elasticity (82 GPa) for the application as support material for thin-film sensors. In the first part, constantan foil strain gauges were fabricated from this material by tape casting, pressure-assisted sintering, and subsequent lamination of the metal foil on the planar ceramic substrates. The accuracy of the assembled load cells corresponds to accuracy class C6. That qualifies the load cells for the use in automatic packaging units and confirms the applicability of the low-temperature co-fired ceramic (LTCC) substrates for fabrication of accurate strain gauges. In the second part, to facilitate the deposition of thin-film sensor structures to the LTCC substrates, pressure-assisted sintering step is modified using smooth setters instead of release tapes, which resulted in fabrication of substrates with low average surface roughness of 50 nm. Titanium thin films deposited on these substrates as test coatings exhibited low surface resistances of 850 Ω comparable to thin films on commercial alumina thin-film substrates with 920 Ω. The presented material design and advances in manufacturing technology are important to promote the development of high-performance thin-film strain gauges.

The implementation of thin-film technologies in energy-related applications, such as special fuel cells and gas separation membranes for low-emission power plants, is essential in terms of enhancing the functionality, reducing operating temperatures, and increasing lifetime. Introducing thin electrolyte layers into solid oxide fuel cells (SOFCs) decreases the internal cell resistance and thus drastically enhances the power density. This supports the goal of reducing the operation temperature from ~800°C to temperatures below 700°C. As the operation temperature is lowered, the temperature-activated degradation processes are slowed down, and 40,000 h of operation becomes feasible. Reducing the thickness of the gas separation membranes also reduces internal losses, and therefore, the rate-limiting steps within the layer. Thinner functional layers possess higher permeabilities but also involve a risk of more layer defects. This also holds for the fuel cells. Thus, the manufacturing of the supports and the intermediate layers is also very important. The paper gives an overview of the application of thin-film technologies to SOFCs and gas separation membranes and highlights the efforts to date. Examples include SOFC stacks operated stably for in excess of 40,000 h and submicron-sized membranes with high permeability and good separation factors.

Negative temperature coefficient (NTC) thermistor thick films were fabricated by screen printing on alumina substrates and firing at 900°C. Spinel-type NiMn₂O₄ exhibits limited stability in air between 730 and 970°C only and interacts with the Bi₂O₃ additive. The Zn–Co-substituted spinel Zn_0.75Ni_0.5Co_0.5Mn_1.25O₄ with 3 wt% additive shows complete densification at 900°C; no interaction between spinel and additive was observed. Alternatively, a Cu–Zn–Co-substituted Cu_0.37Zn_0.52Ni_0.44Co_0.44Mn_1.23O₄ spinel with excellent sintering characteristics even without sintering additive was investigated. The thermistor films display a sheet resistance of about 300 kΩ/□ and B = 3300 K. The firing behavior, microstructure formation, and electrical properties of NTC thick films are reported.

In this article, the challenging manufacturing process of a deformable mirror for the wave front correction of a high energy laser is described. During this process, the low temperature co-fired ceramic (LTCC) membrane as the base component with integrated sensors must endure several postfire processes at temperatures of up to 900°C without any degradation of the sensors' characteristics. To optimize the sensors, various combinations of resistor and conductor pastes and different geometries are characterized. The usability and the performance of the sensor elements after temperature treatment are investigated by measuring the resistance and its resistance temperature characteristic.

The article describes technology of the low-temperature co-fired ceramics (LTCC) structure that enables light absorbance measurements of liquid sample. The manufactured ceramic structure contains buried microfluidic channels. The structure consists of two co-fired glass windows that separate the light source and detector from the test solution. A construction of an electronic measurement system is described as well. The signal from three light-emitting diodes (LED)s — red, green, and blue — can be used in the absorbance measurements. The light intensity is measured by the TCS 3414CS (TAOS, Plano, TX) color detector. Optical properties of the fabricated microfluidic LTCC system is investigated with several concentrations of potassium permanganate (KMnO₄) in water solution. The system can be applied in microbiology for constant monitoring of bacterial growth.

For the fabrication of complex, micro-electromechanical systems (MEMS) devices based on low-temperature co-fired ceramic (LTCC), higher firing temperatures and longer times than those proposed by the LTCC producer are needed. These changes to the thermal budget may influence the material properties and consequently its functional properties. The effect of the firing conditions on the LTCC DuPont 951 and thus on the phase composition, that is, the alumina/anorthite ratio and porosity, on the mechanical properties is presented. The samples fired at low temperatures (800°C) had a high porosity (7%), which significantly contributed to the low elastic modulus (100 GPa) and the low mechanical strength of the LTCC (140 MPa). The samples fired at 850°C, which had only 1% of porosity, resulted in an elastic modulus of 122 GPa and a flexural strength of 224 MPa. A further increase in the temperature contributed to a slight decrease in the elastic modulus, while no significant difference in the flexural strength could be observed. The enhancement of the flexural strength with an increasing firing temperature was mainly related to a decrease in the porosity and to a lesser extent to the different ratio of the alumina/anorthite phases. The effect of firing time on the phase composition at selected temperatures (i.e., 100 h at 700 and 800°C) is also discussed.

This work focuses on the fabrication and assembly of cylindrical plasma containment tubes using DuPont's 951 low temperature co-fired ceramics (LTCC) for use in miniature electrostatic thrusters. The tube is used to contain argon plasma, which is generated by a spiral inductively coupled plasma antenna, which is also fabricated in LTCC. The tube also interfaces with two electrically biased grids on the opposite end, which accelerate the plasma out of the tube. These interfaces are highly dependent on the dimensions and tolerances of the containment tube. The development of the fabrication process will be presented for the incorporation of the tubes and grids onto the base as a single structure. This includes constructing the antenna base, shaping the “rolled” LTCC containment tube using a jig and isostatic press, and integrating the tube and antenna base during the firing. Following the fabrication, measurements will be taken to determine tube circularity and hermeticity of the seal at the interface between the tube and the antenna base. The results will be presented and characterized to evaluate the effectiveness of the structure as well as the documentation of the development of a rolled LTCC tube structure integrated with a planar LTCC antenna base.

Titania micropatterns with periodic arrangements were successfully formed on glass substrates for use with electromagnetic wave energy resonance and localizations in terahertz frequency ranges. Geometric arrangements of acrylic polygonal tablets with titania particle dispersions were fabricated by using micropatterning stereolithography. Moreover, periodically arranged full anatase-phase titania tablets were created homogeneously through liquid-phase crystal depositions of water solvent processes, using microtemplates fabricated by using the stereolithography system. The terahertz wave properties were measured and calculated by using a time-domain spectroscopic system and finite-difference time-domain method.

The use of porous materials as a restrictor in aerostatic bearings provides many advantages over conventional restrictors, such as small variation of temperature, high damping, high operational speeds, limited wear, and capacity to support radial, axial, and combined loading. A design of experiment (DOE) was carried out to evaluate cold-pressed cementitious composites as an air restrictor in thrust bearings. The physical and mechanical properties such as the apparent porosity, permeability, and elastic modulus were investigated in this work, thus verifying the structural and flow characteristics of the composites for such application. The composites fabricated with low compacting pressure and small silica particles provided the material requirements for porous bearings.

In this work a study of glass-ceramic laser machining and some functional applications are presented. Firstly, both the effect produced by the machining method as well as how the modification of the reference position influence the machining results have been studied. Secondly, blind holes and special shape cross-section blind holes have been created for functional purposes. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-widths in the nanosecond range has been used. Morphology, depth, and volume obtained by machining grooves have been studied. The variation in the ablation yield when the position of the surface to be machined is modified has also been studied. The composition and microstructure of the machined areas have been described and discussed and thermal tests have been performed to check if the objectives of the functional applications have been achieved.

New dielectric ceramics are prepared by the conventional solid-state ceramic route. Effects of LZB glass on sintering, phase purity, microstructure, and dielectric properties of Li₂ZnTi₃O₈ ceramics have been investigated. Adding LZB lowers sintering temperature from 1050°C to 875°C, and does not induce much degradation of dielectric properties. The 1.0 wt% LZB glass-added ceramic has better properties of ε_r = 23.9, Q × f = 31,608 GHz, τ_f = −14.3 ppm/°C. Additions of TiO₂ markedly improve microwave properties. Typically, the Li₂ZnTi₃O₈ + 1 wt%LZB + 3.5 wt%TiO₂ sintered at 900°C shows ε_r = 26.1, Q × f = 45,168 GHz, τ_f = −4.1 ppm/°C. Compatibility with Ag electrode indicates that this material may be applied to LTCC devices.

A suspension with good rheology and high stability is crucial for slip casting and gelcasting technology. However, a mixed suspension from two or more different powders usually has bad rheology because of the easy agglomeration of mixed powders caused by the attractive force between the powders with heterocharges. We studied the surface modification of the each single-component powders (SiC, Al₂O₃, ZrO₂(3Y) powders) and the SiC-Al₂O₃-ZrO₂(3Y) mixed powders to increase the repulsive force by adjusting the pH value and adding polyacrylic acid (PAA) as dispersant. The PAA addition effects on the SiC-Al₂O₃-ZrO₂(3Y) mixture were investigated in terms of zeta potential, pH range for heterocharge region, dispersion of the mixed powders and rheology of the mixed slurry based on the study of each unary suspensions. The results show that before surface modification the SiC-Al₂O₃-ZrO₂(3Y) mixed powders were agglomerated severely because they were in the heterocharge region with a broad pH range from 3.5 to 8.25, while after surface modification (pH = 10.5, PAA = 0.8wt%) the heterocharge region was narrowed with a relatively narrower pH range from 2.6 to 3.7. The mixed powders with homocharges were dispersed well because of the great electrostatic repulsive force and steric hindrance offered by PAA and the mixed suspensions had favorable rheology.

In order to develop ED-machinable ceramics with high strength, toughness and wear resistance, ZTA was chosen as matrix material. A dispersion of 24 vol% electrically conductive phase (TiC, TiN, TiCN, TiB₂ and WC) was added. These composites were hot pressed for 1 h at 60 MPa and temperatures ranging from 1475°C to 1550°C. Mechanical and electrical properties were investigated. The influence of the electrically conductive phase on the surface quality after EDM was analyzed. The mechanical properties and machining quality were found to depend significantly on the type of conductive phase added. Machining of a complex shaped ZTA-TiC component was demonstrated.

Reaction-bonded silicon carbide ceramics fabricated from tape casting and Si infiltration have been reported in previous studies. To reduce the residual Si content in the sintered bodies, impregnation of phenol–formaldehyde resin (PF) into the porous green preforms before Si infiltration was proposed and studied in this work. The impregnation of PF solution not only helped to reduce the porosity and increase the carbon content of the green preforms, but also improved their strength. As a result, the flexural strength of the RBSC increased a lot and reached 856 ± 161MPa, whereas the residual Si content was reduced to 10 vol%.

The thermal decomposition of Ti₃SiC₂ in vacuum furnace up to 1500°C has been investigated. The results show that the mild decomposition of Ti₃SiC₂ commences at 1300°C and the higher the holding temperature, the larger the volatilization of Si atoms. The Ti₃SiC₂ decomposition occurs simultaneously on the surface and in the bulk. Four phases coexist at 1400°C and 1450°C and the Ti₅Si₃C_x phase appears in the bulk and/or surface. Diffusion distance, rate, and volatilization of Si contribute to the porous structure and the presence of Ti₅Si₃C_x. The evolution of furnace pressure reflects the decomposition kinetics of Ti₃SiC₂.

A wide variety of microstructures have been obtained by vacuum plasma spraying (VPS) 39Ta:61C atomic percent feedstock powders. During processing, the powder feed was fed through a high energy VPS plasma plume, where altering nozzle angle changed the overall retained carbon concentration in the deposited material. The samples were subsequently sintered and hot isostatic pressed to homogenize and consolidate the microstructure. The microstructures consisted of grains that were either equiaxed or acicular. In the samples with less carbon loss, the equiaxed grains were either the TaC phase or a TaC matrix that encased fine laths of Ta₄C₃. In the sample with the most carbon loss, acicular grains were found containing layered and parallel TaC, Ta₂C, and Ta₄C₃ laths along the major-axis of the grains. The phases of the compounds have been determined by using complimentary X-ray diffraction and electron diffraction techniques. Focused ion beam serial sectioning and transmission electron microscopy tilt series tomography were performed to generate three-dimensional reconstructions of the microstructure morphologies. This article addresses how tantalum carbide microstructures are controlled by the overall concentration and phase fraction content in each of these samples.

Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. It was observed up to ~7.16 wt% (~2.67 mol%) of strontium and ~14.46 wt% (~3.56 mol%) of cesium could be simultaneously loaded into NZP formulations without significant changes in the three-dimensional framework structure. The crystal chemistry of Na_1−x(Cs_1.33Sr₁)_xZr₂P₃O₁₂ (x = 0.1–1.0) has been investigated using General Structure Analysis System programming. The CsSrNZP phases crystallize in the space group R-3c and Z = 6. Powder diffraction data have been subjected to Rietveld refinement to arrive at a satisfactory structural convergence of R-factors.