Investigation of Formation, Stability, Structure and Hydrogen Storage Properties of Ti-Quasicrystals and Related Crystalline Phases

钛基准晶体和相关相的原子结构，准晶体和近似晶体的可成形性，杂质在相形成中的作用，以及连接准晶体和近似晶体的相变的性质，目前还知之甚少。在过去的资助期内取得了成功，这些观点在钛和锆基准晶体和相关的晶相中进行了探索。课题包括：(1)间隙杂质对二十面体相形成作用的研究；(2)准晶、相关晶相和非晶相的加氢特性，以及氢/准晶相图和压力/成分等温线；(3) x射线和中子衍射测定TiZrTM合金中稳定晶体近似物的原子装饰；(4) TiCrSiO、TiZrNi和TiZrFe合金相形成顺序的研究；(5) TiZrNi合金稳定二十面体相与合理近似相之间相变的性质。一些合作正在进行中，包括与英国剑桥大学合作，通过滴管实验辅助研究相形成；与华盛顿大学的科学家合作，通过磁化率测量来研究杂质的稳定作用；与密苏里大学研究反应堆（MURR）和法国萨克莱合作的氢化（和氘化）准晶体的中子散射研究；在伊利诺伊州诺克斯学院对样品进行核磁共振研究。弹性中子散射和核磁共振研究有助于更好地理解TiZrNi准晶体中含氢位点的分布、对称性和化学性质。这些数据将用于改进由确定的晶体近似相结构构建的准晶体模型。非弹性中子和核磁共振研究允许估计氢在准晶体中的扩散速率。这项研究为准晶合金作为储氢材料的潜力提供了基础知识。＊＊＊

9705202 Kelton The atomic structures of titanium-based quasicrystals and related phases, the formability of the quasicrystal and crystal approximants, the role of impurities in phase formation, and the nature of the phase transitions connecting the quasicrystal and the crystal approximants, are as yet poorly understood. Pursuing successes under the past grant period, these points are explored in titanium and zirconium-based quasicrystals and related crystal phases. Subjects include: (1) the investigation of the role of interstitial impurities on icosahedral phase formation; (2) the hydrogenation characteristics of quasicrystals, related crystalline and amorphous phases, and the hydrogen/quasicrystal phase diagram and pressure/composition isotherms; (3) X-ray and neutron diffraction to determine the atomic decoration of stable crystal approximants in TiZrTM alloys; (4) investigations of the sequence of phase formation in TiCrSiO, TiZrNi, and TiZrFe alloys; and (5) the nature of the phase transitions between the stable icosahedral-phase and the rational approximant phases in TiZrNi alloys. Several collaborations are underway, including studies of phase formation aided by drop-tube experiments in collaboration with Cambridge University, UK; the stabilizing role of impurities by magnetic susceptibility measurements in collaboration with scientists at Washington University; neutron scattering studies of hydrogenated (and deuterated) quasicrystals in collaboration with Missouri University Research Reactor (MURR), and Saclay, France; NMR studies of samples with Knox College, IL. The elastic neutron scattering and NMR studies lead to a better understanding of the distribution, symmetry and chemistry of the hydrogen containing sites in the TiZrNi quasicrystals. These data will be used to refine quasicrystal models constructed from determined structures for the crystal approximant phases. Inelastic neutron and NMR studies allow estimates to be made to hydrogen diffusion rates in the quasicrystal. %%% This research provides fundamental knowledge related to the potential for quasicrystal alloys to function as hydrogen storage materials. ***