Press releases
Please quote Nature Materials as the source of these items.
January 2003
Ceramics cushion the load
The word ceramic may conjure up images of decorative tiles or teapots, but probably not of a material as absorbent as wood. Researchers at Drexel University and Oak Ridge National Laboratory, led by Michel Barsoum, have shown that a specific type of ceramic can be compressed repeatedly and fully recover, while absorbing considerable mechanical energy. Such behaviour is more usually seen in non-crystalline materials such as wood or nylon.
Michel Barsoum and colleagues study a ternary carbide, Ti3SiC2, which is related to the binary carbides and nitrides used to make hard coatings for high-temperature products and applications. Mechanically, however, they cannot be more different: they are relatively soft and easily machined, yet remain stiff and highly heat and damage tolerant. This unusual combination of properties led to them being dubbed 'ductile ceramics'.
The ability of these materials to absorb vibrations is vastly superior to other structural ceramics, and so they offer engineers many of the thermal, chemical and electrical advantages of ceramics, with few of their drawbacks, such as brittleness. A material that can absorb mechanical vibrations, and yet remain stiff and lightweight, should find many applications in areas as diverse as automobile and aircraft engine components, precision machine tools and electronic insulators.
Fully reversible, dislocation-based compressive deformation of Ti3SiC2 to 1 GPa pp107-111
M.W. Barsoum, T. Zhen, S.R. Kalidindi, M. Radovic and A. Murugaiah
Published online: 26 January 2003 | doi 10.1038/nmat814
Microassembly of semiconductor three-dimensional photonic crystals
Photonic crystals are the optical analogues of semiconductors. By periodic modulation of their refractive index, materials that selectively prevent the passage of light at certain wavelengths can be designed. Such materials have the potential to give us the same control over light as can be achieved with electrons, with all the practical optoelectronic applications that it implies; but photonic crystals are notoriously difficult to design and construct. In the September issue of Nature Materials, researchers in Japan reported a novel fabrication method that makes it possible to assemble semiconductor three-dimensional (3D) structures at the microscopic scale.
Since the photonic band gap (PBG) concept was launched in 1987, the technological goal has been the design of optical integrated circuits, in which all the components can be assembled on one chip. And although 3D crystals are ideal structures to manipulate light, most research efforts so far have been focused on 2D crystals, because they use conventional semiconductor processing technology.
Now, Kanna Aoki and colleagues have developed an approach that combines integrated circuit processing technology with the remote manipulation of microstructures by mechanical probes. They demonstrate its applicability using indium phosphide, the most important base semiconductor for optoelectronic devices used in fibre-optic communication systems. The authors believe that this technology offers great prospects for the production of optical wavelength photonic crystals.
