Advanced Engineering Materials

The cover shows the strand manufactured by stranding 6 single wires (ZEK100) using a polymerical core. In general, magnesium strands constructed with cores consisting of other alloys or materials could also represent an interesting option. In this way, it would be possible to combine various material properties. In doing this, it would be conceivable to use polymer cores which provoke a “Drug Eluting Effect” following the start of magnesium corrosion and thereby differ from current polymer coatings which produce an appropriate release of medication in advance of the magnesium degradation. Further details can be found in the article by Seitz et. al. on page 1087.

The cover shows biocide activity against M. luteus of glass-ceramic compact (middle) and coated with silver nanoparticles (right). Further details can be found in the article by Cabal et. al. on page B462.

Cell-material interaction on biomaterials depends on presented chemical surface groups. The cover shows the low density lipoprotein - uptake of endothelial cells on carboxy-functionalized polymer substrates for tissue engineering applications. More details can be found in the article of Novosel et. al. on page B467.

With the aid of multiple wire drawing passes, the magnesium alloys ZEK100, MgCa0.8, and AL36 were reduced to monofilament wires possessing diameters between 0.5 and 0.1 mm and subsequently twisted into poly-filament suture material using stranding. During the investigations, the alloy ZEK100 exhibited particularly interesting mechanical properties which, owing to its high tensile strengths and fracture strains, are comparable to those of conventional polymer based suture materials.

High resolution X-ray imaging and diffraction modes analogous to those in 2D electron microscopy are combined to form a 3D “crack-tip microscope”. Besides informing on the efficacy of micro- and nano-structural crack-shielding features shown in the figure, the microscope can be used to quantify three measures of the effective crack-tip stress intensity, namely from the overall near tip stress field, from the crack face tractions and from the crack opening displacements.

An experimental setup for in situ investigations under compressive stress using laboratory X-ray computed tomography (XCT) was developed and successfully tested. The rising of observed deformation bands in foams can be explained by the dramatic change of the stress distribution in the neighbor cells after the first brake of a cell wall.

This communication contains five display items and reports that a nanocrystalline bcc Ti_67.4Nb_24.6Zr₅Sn₃ alloy fractures in an intrinsically ductile manner with exceptionally large dimples which are two orders of magnitude greater than the grain size. This large plasticity length scale is attributed to a combination of low shear modulus, high Poisson's ratio, and ultrahigh strength, close to the ideal shear stress, which facilitates ideal shear deformation to promote transgranular shear.

A new selection criterion to explain the activation of the twinning variant in HCP is proposed. This criterion is based on the calculation of the strain energy to create a twin; the effect of grain size is also introduced by a Hall-Petch type relationship. The results are compared with experimental data.

Titanium scrolls are produced by direct writing a flexible mesh, composed of two orthogonal arrays of TiH₂-based ink filaments (250µm in diameter), followed by rolling into scrolls. Heating to 1050°C results in decomposition of the hydride and partial sintering of Ti, yielding three-dimensional reticulated titanium scrolls. This approach provides a low-cost, versatile, and scalable route for fabricating metallic scrolls with tailored filament and pore geometries.

In this paper, spark plasma sintering (SPS) of multi-walled carbon nanotube (CNT) reinforced aluminum matrix composites is reported. Significant improvement in microhardness, nanohardness, and compressive yield strength was observed with 2wt% CNT reinforcement in aluminum matrix composites. The Al-CNT composites further exhibited improved wear resistance and lower friction coefficient due to strengthening and self-lubricating effects of CNTs.

Amongst the aspect of environmental friendly refractory systems this work has observed and shown the interaction of functional ceramic material TiO₂ with the organic binder system. In the centre of this work is the aspect of increased residual carbon content of the binder resin due to TiO₂ addition. The increased residual carbon content of the binder resin connected with improved brick properties due to sub-micro scaled TiO₂ addition offers the feasibility to reduce the total carbon content without downgrading the brick properties.

A novel strain mismatch induced tilted epitaxy method has been demonstrated for producing high quality (000l) hexagonal films on (001) cubic substrates. Highly oriented hexagonal (000l) ZnO films are grown on (001) MgO using Sm_0.28Zr_0.72O_2−δ as a template. The work opens up a new avenue for growing technologically important hexagonal structures on readily available cubic substrates and gives wide possibilities for heteroepitaxial growth of a range of dissimilar materials.

The aim of this study is to identify the effects of different sterilization methods (autoclave sterilization, dry heat sterilization, gamma sterilization, and ethylene oxide sterilization) on the mechanical properties of LAE442 (Li 4 m.%, Al 4 m.%, RE 2 m.%), MgCa0.8 (Ca 0.8 m.%) magnesium alloys and pure magnesium. Such influences are likely due to the temperatures and media which are used whilst sterilizing. ETO sterilization caused the least changes in the mechanical properties of the alloys.

The in vitro wear performance of dental ceramics, zirconia, or non-precious alloy materials is strongly influenced by the type of material. Glass-ceramic systems provide significantly higher wear in comparison to alloy or zirconia. In contradiction to common expectations, hard zirconia and alloy systems showed even lower antagonistic wear than glass-ceramics.

Aiming at the economic manufacturing of geometrically and mechanically optimized permanent implants, the alloy Ti–6Al–4V was slightly modified by the addition of boron. The new alloy is optimised for the processing by metal injection molding (MIM). Presented mechanical, biological and corrosion tests show that all basic demands on a material for highly loaded permanent implants are fulfilled.

In the present work we show that the proliferation of osteoblasts onto substrates functionalized with chitosan/gelatine multilayer coatings can be significantly increased compared to the uncoated titanium control. We demonstrate that the growth of osteoblasts can be completely suppressed on titanium surfaces functionalized with chitosan/hyaluronic acid multilayers.

Bioactive glass-ceramics made from sintered 45S5 Bioglass® exhibit a biocidal capacity against E. coli and M. luteus, common Gram negative and Gram positive bacteria, respectively. Biocide tests are also carried out on samples coated with glass doped with silver. The antimicrobial activity of the bioactive glass-ceramic scaffolds without silver is high and very promising. The bioactive glass ceramics have a lower biocidal effect on I. orientalis and the silver coating is not found to improve the biocidal effectiveness, although the kinetics of silver release is slow.

The generation of advanced scaffolds for tissue engineering is increasingly implemented by rapid prototyping techniques and therefore designed materials. Two novel polymeric networks based on newly synthesized carboxyfunctionalized polyacrylates were designed to fit the requirements of 3D printing processes regarding viscosity and their surface tension.

The microstructure underneath a wear-induced failure in a non-cross-linked, medical grade UHMWPE subjected to cyclic load is characterized by a gradient in lamellar thickness and orientation. Cross-sectional transmission electron microscopy shows the failure to be amorphous and interconnected to the unmodified UHMWPE by a reorganization zone with an interfacial boundary layer which consists of stacked lamellae with an outstanding orientation.

Cell proliferation, viability, and morphology is observed to be favorably modulated in phase-reversion annealed nanograined/sub-micron grained (N-SM) compared to conventional CG austenitic stainless steel which corroborates the enhanced cellular response in N-SM steel. The improvement in cellular response is ascribed to grain size and hydrophilicity of the substrate.

Novel chitosan-graft-poly(vinyl alcohol) copolymers are proposed as biocompatible polycations to prepare polyelectrolyte smart microcapsules for animal cell entrapment. The microcapsules being stable at long-term cell cultivation can be easily dissolved by slightly rising the pH value of the cultivation medium up to pH 8.0–8.2. This property is of great interest if the release of multicellular spheroids generated within the microcapsules is needed.

Bioinert surface coatings are demanded in the biomedical field in particular as a bioassay or array matrix. Glycerol based polymers of linear and branched architecture with a surface reactive silyl tether can be used to generate monolayers on glass. Such modified glass surfaces have excellent protein, eukaryotic as well as prokaryotic cell resistant properties equivalent to PEG and at the same time offer the possibility for further modification via the multiple hydroxyl groups of polyglycerols.

An osteochondral plug with three distinct layers resembling the naturally occurring cartilage, tidemark, and subchondral zones is produced for application in the regeneration of defects of articular cartilage. The bone layer is constructed from a PLLA/PCL blend using a dual-porogen approach. The upper cartilage layer is made of PGA non-woven felt. Vertical channels facilitate the delivery of the stem cells and blood from the bone marrow when implanted. The biocompatibility is confirmed.

Goal was to engineer biological, arterial grafts with antithrombotic, autologous endothelial luminal surface combined with extraluminal smooth vascular muscle layer and to test them in vivo. After implanting these semiautologious grafts, 9 of 10 showed patency after a follow up period of approximately 3 months, although no anticoagulation was used during this time. Aneurysmatic degeneration was not observed.