Advanced Engineering Materials

Cover image for Vol. 8 Issue 1‐2

February, 2006

Volume 8, Issue 1-2

Pages 3–127

    1. Cover Picture: Platinum Ceramic Composites as new Electrode Materials: Fabrication, Sintering, Microstructures and Properties (Adv. Eng. Mater. 1-2/2006)

      J. Rager, A. Nagel, M. Schwenger, A. Flaig, G. Schneider and F. Mücklich

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200690001

      The economical application of precious metals as electrode materials is an important economic and ecological task. Different platinum composites with 14 vol.% ceramic dispersoids were fabricated. The sintering behaviour and microstructure development was studied in the temperature range between 1000°C and 1760°C. Significant differences were found with respect to the sintering activity and the particle size distribution. Spark erosion tests revealed that the erosion resistance of platinum is degraded by the addition of oxide particles. A new model is proposed to explain the observed erosion behaviour.

    2. Surface and Sub-Surface Quality of Steel after EDM (pages 15–25)

      P. Bleys, J.-P. Kruth, B. Lauwers, B. Schacht, V. Balasubramanian, L. Froyen and J. Van Humbeeck

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500211

      This paper deals with the influence of electrical discharge machining (EDM) on surface and sub-surface quality in the manufacturing of mould and tool steel. The thermal nature of material removal by EDM yields a thermally affected zone at the surface of the manufactured part.. Based on experimental investigations, the influence of process parameters on surface and sub-surface properties is discussed. These include surface roughness, sub-surface micro-structure and composition, micro-hardness and residual stresses. Attention goes to the dangers of surface degradation, yet also to the opportunities to use the EDM process for surface improvement.

    3. Gigahertz and Nanotubes – Perspectives for Innovations with Novel Industrial Microwave Processing Technology (pages 26–32)

      L. Feher, M. Thumm and K. Drechsler

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500148

      A novel industrial microwave system for curing of carbon fibre reinforced plastics is being developed at Forschungszentrum Karlsruhe (FZK). The system, which is scheduled to be in duty at the end of 2005 integrates advantageously the basic processing steps as tooling, tempering of the resin and lay up, the impregnation of the fibres, pre-forming techniques as well as finally the process curing of the composite structures.

    4. Material and Micromachining Aspects of Manufacturing Micromolds for Replication Techniques (pages 33–37)

      T. Gietzelt, L. Eichhorn and K. Schubert

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500215

      Micromolds made of brass and two sorts of maraging steels were micromachined for the replication of micro gearwheels by micro powder injection molding. Different milling strategies are compared. Machining parameters are given and discussed taking into account problems especially relevant for micro machining. Finally, the surface roughness and burr formation of micromolds made of maraging steel before and after electropolishing are compared.

    5. Pressure Free Fabrication of 3D Microcomponents Using Al Powder (pages 38–41)

      J.-S. Kim, K. Jiang and I. Chang

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500190

      This paper presents a new fabrication process of producing 3D microparts using Al microparticle powder. The process does not need high compression pressure and the powder mixture is loosely filled in soft moulds. High density components have been produced through this process. The proposed technology is developed in combination of micro metal injection moulding (μMIM), micro powder injection moulding (μPIM), powder sintering technology and MEMS technology together.

    6. Machining Sequence to Manufacture a γ-TiAl-Conrod for Application in Combustion Engines (pages 41–47)

      K. Weinert, S. Bergmann and C. Kempmann

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500200

      An appropriate fabrication route as well as the testing of γ-TiAl-conrods deployed in a high spinning petrol-operated engine is discussed in this paper. The advantage of deploying γ-TiAl as a conrod consists in the reduction of oscillating masses together with a minimization of engine vibrations. In addition the crank drive improves, resulting in weight and fuel savings and an improved acceleration capability.

    7. Multi-Criteria Material Selection of Monolithic and Multi-Materials in Engineering Design (pages 48–56)

      P. Sirisalee, M. F. Ashby, G. T. Parks and P. John Clarkson

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500196

      Multi-materials are combinations of monolithic materials in a chosen configuration and scale. They can help populate the material property space and fill areas monolithic materials cannot reach. This paper presents a novel approach to compare the performance of monolithic materials and multi-materials in multi-criteria design problems, with the results being visualised through exchange constant charts. In this paper, a particular type of multi-materials, sandwich panels, is selected to demonstrate the approach.

    8. Increasing the Strength/Toughness Combination of High Volume Fraction Particulate Metal Matrix Composites using an Al-Ag Matrix Alloy (pages 56–62)

      A. Miserez, R. Müller and A. Mortensen

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500185

      Ceramic reinforced metals, despite superior properties such as specific stiffness, are often considered as too brittle for structural applications. We show that despite a high ceramic particle content (60 vol.%), aluminium matrix composites can be made to exhibit a fracture toughness matching that of unreinforced aluminium alloys, provided critical microstructural parameters are controlled. We here use an unconventional Al-Ag matrix to simultaneously increase the strength and the toughness of this class of composite.

    9. Carbon Nanotubes Strengthened Nanophase WC-Co Hard Alloys (pages 62–72)

      G.-L. Tan, X.-J. Wu and Z.-Q. Li

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500194

      A novel approach employing C2H2 instead of CO as carburization agent has been applied to fabricate nanophase WC-Co composite alloys being strengthened by carbon nanotubes and nanorods, which were formed in-situ during C2H2 carburization process. The sintered composite alloys show exceptionally high microhardness. Carbon nanotubes are supposed to play roles on strengthening the matrix and prohibiting growth of WC grains, thus greatly improving the mechanical properties of the matrix.

    10. Influence of the Surface Treatment on the Deposition of Platinum Nanoparticles on the Carbon Nanotubes (pages 73–77)

      C. Xu, J. Chen, Y. Cui, Q. Han, H. Choo, P. K. Liaw and D. Wu

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500179

      The influence of the pretreatment of carbon nanotubes (CNTs) on the deposition of Pt-n noparticles is investigated. The results show that refluxing CNTs by the mixture solution of sulfuric and nitric acids, or immersing them in the H2O2 solution are effective ways for depositing Pt-nanoparticles on the CNTs. The hybrid process yields the best results and obtained the Pt-nanoparticles with a size of about 3 nm on the CNTs surface.

    11. Formation of Nanostructured Titania: Effect of Thickness on Oxidation Kinetics of Titanium Thin Films in Aqueous Hydrogen Peroxide (pages 77–80)

      D. M. DeRosa, A. S. Zuruzi and N. C. MacDonald

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500186

      The oxidation kinetics of Ti films in aqueous hydrogen peroxide was investigated. Oxidation of Ti films is dependent on both film thickness and average grain size. Films of thickness 50 nm or less exhibit Stage I oxidation while thicker films exhibit both Stages I and II. The difference in oxidation rates and dependencies on grain size observed in these two stages are attributed to different mechanisms controlling oxide growth.

    12. Platinum Ceramic Composites as new Electrode Materials: Fabrication, Sintering, Microstructures and Properties (pages 81–88)

      J. Rager, A. Nagel, M. Schwenger, A. Flaig, G. Schneider and F. Mücklich

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500192

      The economical application of precious metals as electrode materials is an important economic and ecological task. Different platinum composites with 14 vol.% ceramic dispersoids were fabricated. The sintering behaviour and microstructure development was studied in the temperature range between 1000°C and 1760°C. Significant differences were found with respect to the sintering activity and the particle size distribution. Spark erosion tests revealed that the erosion resistance of platinum is degraded by the addition of oxide particles. A new model is proposed to explain the observed erosion behaviour.

    13. Creation of Porous Ceria by Sublimation of Tin Dioxide during Sintering (pages 89–93)

      Y. Liu and M. Liu

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500212

      Highly porous CeO2 was prepared by natural sublimation of SnO2 during firing of a CeO2-SnO2 nanocomposite powder synthesized using combustion CVD. Unlike the conventional strategies, the new method requires neither time consuming chemical leaching nor following-up gas reduction procedures. This approach is attractive to fabrication of porous structures for solid oxide fuel cells, gas separation, and catalysis since no chemical leaching or gas reduction is involved.

    14. Microstructural Bases for the Superior Densification of Gels doped with Alumina Nanoseeds (pages 93–97)

      J. Tartaj and P. Tartaj

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500198

      The densification behavior of alumina gels has been studied. We have found that in addition to the effect of volume transformed, the thermal history of gels plays an important role in their densification process. Particularly, prior to the θ- to α transformation, the nanoseeded gels preserve a close packed and evenly distributed porous structure that helps to achieve full density at lower temperatures.

    15. Biomimetic Formation of Hydroxyapatite/collagen Matrix Composite (pages 97–100)

      Y. Wang, C. Yang, X. Chen and N. Zhao

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500220

      A composite of collagen (COL) and hydroxyapatite(HA) was prepared using a biomimetic approach, which performs a direct nucleation of HA on self- assembled collagen matrix. This research may be helpful to understand the possible mechanisms for collagen-mediated mineralization in general and the COL/HCA composite can be considered a new particularly attractive material for human bone tissue implantation.

    16. Comparison of Shape Memory Metals and Polymers (pages 101–106)

      E. Hornbogen

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500193

      Both, metals and polymers can show the one-way shape memory effect or rubber-like elasticity. The origin of these effects in the two types of materials is discussed. It is shown that there is an analogy between the high temperature phases β: crystalline austenite in metals and random coils in polymers. There are differences in the low temperature phases α: a domain structure is typical for metallic martensite, and stretched chains for polymers. Prerequisite for memory and superelastic effects is a complete structural reversibility during a β – α transformation cycle.

    17. Effect of Heat Treatment and Thermochemical Treatment on Linear Recovery Property of TiNi Shape Memory Alloy (pages 107–111)

      G. Wang, G. Yang, Y. Huang and J. Wang

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500145

      A new concept of linear recovery behavior in TiNi shape memory alloy (SMA) is proposed in this article. Effects of heat treatment and thermochemical treatment including “Ceriuming” and “Samariuming” on the linear recovery property of TiNi SMA were investigated through measuring the thermal reversion curves. The results indicates that the linear recovery properties can be modified by both heat treatment and thermochemical treatment.

    18. Thermal Oxidation Study on Lead-free Solders of Sn-Ag-Cu and Sn-Ag-Cu-Ge (pages 111–114)

      S. Wan Cho, K. Han, Y. Yi, S. J. Kang, K.-H. Yoo, K. Jeong and C.-N. Whang

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500188

      At present, the electronic packaging industry is actively searching for lead-free (Pb-free) solders due to environmental concerns over Pb-containing solders. For a successful transition to Pb-free manufacturing in electronics assembly, it is critical to understand the behavior of Pb-free solders. We report the surface oxidation mechanism of Pb-free solder in this paper. This mechanism has been investigated after using X-ray photoelectron spectroscopy.

    19. Correlating Interfacial Moisture Content and Adhesive Fracture Energy of Polymer Coatings on Different Surfaces (pages 114–118)

      E. P. O'Brien, C. C. White and B. D. Vogt

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500164

      The adhesion of polymer film of PMMA to different surfaces was measured using the shaft-loaded blister test. The exposure of the films to saturated water vapor generally leads to a decrease in adhesive strength. The adhesion loss was directly related to the moisture accumulation at the polymer/substrate interface as measured using neutron reflectivity.

    20. Early Stage of Diffusional Formation of Carbide Coatings on Steels (pages 119–123)

      A. Młynarczak

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500149

      Despite much research on different aspects of the formation of diffusion carbide coatings (DCC) there is still no complex description of the early stage of the formation of chromium, vanadium and titanium carbides. However, the knowledge of this stage of diffusional processes enables the control the useful coating properties. This paper presents new insights for better understanding of the mechanism of the early stage of V, Ti, Cr DCC growth on a steel matrix.

    21. Influence of pH of Phosphating Bath on the Zinc Phosphate Coating on AZ91D Magnesium Alloy (pages 123–127)

      G. Y. Li, J. S. Lian, L. Y. Niu and Z. H. Jiang

      Version of Record online: 13 FEB 2006 | DOI: 10.1002/adem.200500095

      Suitable pH of the phosphating bath is crucial to restrain resolving rate of magnesium and obtain high quality phosphate coatings because of the high activity of magnesium. In this investigation a compact zinc phosphate coatings on AZ91D were successfully obtained from the phosphating bath with pH=2.15∼2.5. This figure indicated that the slab-like phosphate crystals were entirely covered the substrate when the pH of the phosphating bath is 2.5.

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