X-Ray Diffraction Studies of Quasicrystals and Other Crystalline Materials

Colella将对Al-Pd-Mn的二十面体相进行各种x射线衍射实验。由于该合金可以制成具有高质量晶格结构的准晶体，因此动态衍射是可行的。“原子在哪里？”这个基本问题仍然存在，在发现准晶体12年后，这个问题还没有得到完全的回答。在普渡大学和同步加速器光源（nssls和CHESS）进行的实验将包括对异常传输（博尔曼效应）、驻波和圆偏振x射线使用的定量研究。本章将探讨中心对称的基本问题。实验将确定在两个对构空间群中可以找到的苄基分子晶体的空间群，并将光学活性与结构联系起来。各种x射线衍射技术，包括在国家同步加速器光源和康奈尔高能同步加速器源的实验，将用于研究准晶体中的原子排列。这些新材料不像大多数其他固体物质那样表现出长范围的周期性。它们的高强度、低密度、低表面摩擦和良好的抗氧化性使其成为表面涂层的理想选择。法国的一家公司已经建立了一条用准晶体涂层代替特氟龙的煎锅生产线。一些准晶体具有特殊的储氢品质。＊＊＊

w:\awards\awards96\*.doc 9625585 Colella Various x-ray diffraction experiments will be carried out on the icosahedral phase of Al-Pd-Mn. Since this alloy can be made into a quasicrystal with a high quality lattice structure, dynamical diffraction is feasible. The basic question still remains, "Where are the atoms?" and twelve years after the discovery of quasicrystals this question has not been fully answered. Experiments at Purdue and at the synchrotron light sources, NSLS and CHESS, will include quantitative studies of anomalous transmission (the Borrman effect), standing waves, and the use of circularly polarized x-rays. The basic issue of the centrosymmetry will be examined. An experiment will be carried out to determine the space group of the benzil molecular crystal that can be found in two enantiomorphic space groups and correlate optical activity with structure. %%% Various x-ray diffraction techniques, including experiments at the National Synchrotron Light Source and the Cornell High Energy Synchrotron Source, will be used to investigate the atomic arrangements in quasicrystals. These are new materials that do not exhibit long range periodicity as do most other solid substances. Their high strength, low density, low surface friction, and good oxidation resistance make them ideal for surface coatings. A company in France has set up a production line for using quasicrystalline coatings in frying pans instead of Teflon. Applications are envisaged for ball bearings, Some quasicrystals have exceptional qualities for hydrogen storage. ***