Reference EPFL-ARTICLE-184271doi:10.1016/j.compositesa.2012.08.001View record in Web of Science Record created on 2013-02-27, modified on 2017-05-10

Composites Part A: Applied Science and Manufacturing

Composites. Part B, Engineering

HRTEM image of a single Ge nanocrystal. The image has been rotationally filtered to improve clarity. The lattice fringes imaged are for Ge 〈111〉, with a d spacing of 3.27 A. Reaction between the Zintl salt NaGe and GeCl4 is shown to produce Ge nanocrystals. The reaction proceeds readily in refluxing diglyme at ambient pressure. The nanocrystals produced may be surface-terminated by reaction with RLi or RMgBr and demonstrate quantum confinement.

Solution Synthesis of Germanium Nanocrystals Demonstrating Quantum Confinement

Transient liquid phase sintering was examined for Fe-Ti powder mixtures. The experimental plan included the effects of several processing variables, such as green density, particle size, composition, heating rate, sintering temperature, and sintering time. During heating, pores form at the Ti particle sites. At the first eutectic temperature (1085 °C), liquid spreading is inhibited by a surrounding intermetallic envelope, leading to swelling. At the second eutectic temperature (1289 °C), the liquid penetrates along the iron grain boundaries and provides densification. The amount of densification depends on the amount of liquid formed at the second eutectic temperature and its duration as determined by the titanium content and heating rate.

Processing of iron-titanium powder mixtures by transient liquid phase sintering

The Cu-based metal powder has been successfully sintered without protection and pre-heating. Bonding mechanisms and the influences of the liquid volume fraction of binder on the density and mechanical properties of direct laser-sintered parts have been investigated. It was found that with the increase in the amount of the binder in the powder mixture, the density of the sintered parts increases and the microstructure become denser. Mechanical properties in terms of tensile strength, impact toughness, and transverse rupture strength have also been studied, showing the increased mechanical properties with the increase in the amount of binder. However, at a high volume of binder, mechanical properties showed a decrease. The low mechanical properties may be caused by the high porosity.

Influence of binder’s liquid volume fraction on direct laser sintering of metallic powder

Three types of commercially used iron powder of different specific surfaces and compressibilities were cold compacted with 10wt-%Cu over a range of pressures before sintering at a temperature of 1140°C. A study of dimensional changes during sintering showed that swelling was inversely related to the specific surface of the powder, but directly proportional to the compacting pressure. Metallo- graphie, dilatometric, and microprobe studies showed that the observed swelling in the compacts was almost totally due to grain boundary penetration by liquid Cu, while diffusion of Cu into grains made only a small contribution. However, analyses of the relevant experimental parameters have shown that the particle internal micropores are energetically more favourable for attracting and accommodating the liquid Cu than the grain boundaries, and therefore, when present, they inhibit volumetric growth. In support of the above, it has been shown that the vol.%, change for various powders compacted over the range ...

Dimensional Changes During Liquid Phase Sintering of Fe–Cu Compacts

Pseudoplastic deformation pits on polished ceramics due to cavitation erosion

In this work, the fracture toughness of rotationally molded polyethylene (PE) and polypropylene (PP) was measured using J integral methods at static loading rates and at room temperature. Two different commercially available rotational molding grades PE and PP were tested in this study which have been used in various rotationally molded products such as small leisure craft, water storage tanks, and so on. Scanning electron microscope (SEM), optical microscope, differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance (solid-state NMR), and X-ray scattering were used to investigate the microstructure, fracture surfaces, and compare toughness properties of these materials. In PE, higher molecular weight and broader molecular weight distribution, larger amorphous and crystal region thicknesses are found to be related to higher toughness values. High molecular weight favors higher number of entanglements that improve fracture energy and broader distribution increases long chain branching of higher molecular weight fractions which creates higher entanglements at the branch sites. Larger amorphous regions promote microvoiding more easily compared to thinner amorphous regions, leading to greater plastic deformation and energy absorption. Higher crystal thickness also contributes to microvoiding in the amorphous region. For PP, greater plastic deformation observed in the fracture surfaces is related to higher fracture toughness values. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

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Fracture toughness of rotationally molded polyethylene and polypropylene

Design and development of a new acetabular cup prosthesis

The interplay between materials science and sports equipment takes many forms. Certainly a broad cross section of materials is used in sporting equipment to improve performance and safety, and to reduce cost. The new materials used in sports equipment originate from a long history of innovation, drawing from and contributing to other technologies. Amateurs and professionals play sports, so rules on the use of new technology vary immensely. This allows for a short circuit of new technology into the market-place in some cases and restriction or prohibition of opportunities in others. Also materials selection and development for sports equipment must stretch beyond consideration of the object itself to include the human interface and design of a system that best makes use of the materials. Sports after all are about human capability and interaction. The equipment is just a facilitator. Certainly more efficient ways exist of placing a ball into a hole than hitting it with a long metal stick from hundreds of yards away. This is perhaps the most unique element of materials development for sports. The rules governing materials development are not just laws of science and of government but rules put into place just for “sport.” Because of the connection of sports to the lives of so many people, either as participants or spectators, materials science of sporting equipment is also a great platform for educating students about materials selection and behavior.

Kamran Tabeshfar

Papers

Dimensional Changes During Liquid Phase Sintering of Fe–Cu Compacts

Pseudoplastic deformation pits on polished ceramics due to cavitation erosion

Fracture toughness of rotationally molded polyethylene and polypropylene

Design and development of a new acetabular cup prosthesis

Materials for Sports