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Dislocations in quasicrystals

准晶体中的位错

基本信息

批准号：
11650674
负责人：
EDAGAWA Keiichi
金额：
$ 2.62万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650674/
关键词：
quasicrystal dislocation mechanical property plasticily phason icosahedra phase decagonal phase

项目摘要

In quasicrystals, we can define a dislocation whose Burgers vector is a lattice translational vector of a 4D or higher dimensional lattice. Such a dislocation is a novel type of structural defect inherent to quasicrystal in the sense that it is accompanied not only by a conventional strain but also by a strain named phason strain which is caused by a lattice distortion in a complementary space orthogonal to real space. We performed the following researches for the purpose of clarifying the properties of such a dislocation. First, we perfomed plastic deformation experiments for icosahedra (i-) Al-Pd-Mn and decagonal (d-) Al-Ni-Co. For both samples, work softening, which is generally seen for quasicrystals, was observed. As a result of thermal activation analysis, we analyzed the data at various temperatures systematically on the assumption of temperature-dependent dragging stress for a dislocation. Second, we investigated structure and properties of phasons, which play an important role in the dynamical property of the dislocation in quasicrystals. Here, i) we observed the structure of a phason defect by STM, ii) we measured specific heat at high temperatures to investigate thermally equilibinium phasons and iii) we observed the phasons in motion at high temperatures by in-situ high-temperature HRTEM. In i), we observed a frozen-in phason defect in d-Al-Ni-Co by STM. In ii), we measured specific heat (Cp) of i-Al-Pd-Mn and d-Al-Cu-Co by DSC. we observed an upward deviation of Cp from the Dulong-Petit value of 3k/atom (k : Boltzman's constant) and it reached 5k at about 800℃. This can be interpreted as a thermal excitation of phasons. We calculated the entropy change from the increment of Cp and compared it with the result of the computer simulations previously done. In iii), we observed directly phasons in motion by HRTEM for the first time.

在准晶体中，我们可以定义一个位错，其伯格斯矢量是 4D 或更高维晶格的晶格平移矢量。这种位错是准晶体固有的一种新型结构缺陷，因为它不仅伴随着常规应变，而且还伴随着称为相子应变的应变，该应变是由与实空间正交的互补空间中的晶格畸变引起的。为了阐明这种位错的性质，我们进行了以下研究。首先，我们对二十面体 (i-) Al-Pd-Mn 和十面体 (d-) Al-Ni-Co 进行了塑性变形实验。对于这两个样品，都观察到了准晶常见的加工软化现象。作为热激活分析的结果，我们假设位错的拖曳应力与温度相关，系统地分析了不同温度下的数据。其次，我们研究了相子的结构和性质，它在准晶位错的动力学性质中起着重要作用。在这里，i）我们通过 STM 观察了相子缺陷的结构，ii）我们测量了高温下的比热以研究热平衡相子，iii）我们通过原位高温 HRTEM 观察了高温下运动的相子。在 i) 中，我们通过 STM 观察到 d-Al-Ni-Co 中的冻结相子缺陷。在ii)中，我们通过DSC测量了i-Al-Pd-Mn和d-Al-Cu-Co的比热(Cp)。我们观察到Cp相对于Dulong-Petit值3k/atom（k：玻尔兹曼常数）向上偏差，并在800℃左右达到5k。这可以解释为相子的热激发。我们根据 Cp 的增量计算了熵变化，并将其与之前进行的计算机模拟的结果进行了比较。在 iii) 中，我们首次通过 HRTEM 直接观察到运动中的相子。