No abstract

The first quasicrystal (QC) structure was observed in 1984. QCs possess long-range orientational and translational order while lacking the periodicity of crystals. An overview is given on some physical properties of QCs. It begins with group theory and symmetry. Then the thermodynamics of equilibrium properties and physical property tensors are discussed. Finally, the generalized elasticity theory of QCs and the elasticity theory of dislocations in QCs are presented.

To understand the origin of the second long-length scale in SrTiO 3 , we studied structural defects in Verneuil-grown single crystals by transmission electron microscopy. The density of the dislocations was observed to decrease with increasing depth from the original cut surface of the crystals. The high density of dislocations in the skin region is most likely responsible for the second length scale. [S0031-9007(98)05447-7]

A low-cost impregnation method was developed to prepare PtRu catalysts highly dispersed on carbon support. As clearly revealed by the HRTEM image, even with high metal loadings (up to 40 wt % Pt + 20 wt % Ru) the average particle diameter was 1.5 nm with a narrow distribution ((0.5 nm). Based on EDAX, XRD, XPS, and TGA/DTA analyses, the structure of the PtRu catalyst was deduced to be composed of PtRu alloy and amorphous ruthenium compounds, predominantly hydrous ruthenium oxide, RuO x H y . The PtRu catalyst thusprepared exhibited excellent performance for methanol oxidation.

No abstract