Structural study on quasicrystals and their approximants in the Al-Ni-Co alloy system, by means of anomalous X-ray scattering

Al-Ni-Co十次准晶由于具有多种调制方式，呈现出高度有序的衍射花样或几种不同类型的超晶格衍射花样，以及一些近似晶体而受到人们的广泛关注。为了揭示这些十次对称准晶的结构，人们利用电子衍射分析、高分辨透射电子显微镜（HRTEM）和高角度环形探测器暗场扫描透射电子显微镜（HAERDF-STEM）进行了大量的研究。然而，以往的研究都是对单个的十次准晶进行的，没有对所有的Al-Ni-Co十次准晶的结构进行系统的解释。本研究计画对Al_ Ni_ Co_合金中950℃退火后的近似晶体进行了精确的结构分析<72.5><17><20.5>。这种W-（AlCoNi）相的结构使我们能够讨论应力 关于我们 Al-Ni-Co十次准晶的结构。这些研究结果可作为准晶及相关近似晶体最重要的结构信息之一，并被邀请参加2001年国际准晶会议。本研究项目发展了相对较新的单晶反常X射线散射技术，它促使我们了解合金样品中特定元素周围的精细结构。这一新的分析工具成功地表征了Cu在Al-Cu-Fe近似相中的分布，使我们了解了Cu在形成与准晶有关的近似相中的结构作用，本研究组还对具有大二十面体原子团簇的立方近似相的结构进行了系统的研究。所获得的结果在国际准晶体研讨会上作为重点讲座进行了演示。少

The Al-Ni-Co decagonal phase has received much attention, because, of several modulations of decagonal quasicrystals, showing highly-ordered diffraction patterns or several different type of diffraction patterns with super-lattice reflections, and some crystalline approximants. In order to reveal the structures of these decagonal quasicrystals, many studies have been made by electron diffraction analysis, high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAERDF-STEM). However, previous studies have been made on individual decagonal quasicrystals, and no systematic interpretation on the structures of all the Al-Ni-Co decagonal quasicrystals has been performed. This research project has performed precise structural analysis of a crystalline approximant, which is found in alloy around Al_<72.5>Ni_<17>Co_<20.5>, annealed at 950℃. The structure of this W-(AlCoNi) phase, enables us to discuss the str … More uctures of the Al-Ni-Co decagonal quasicrystals in detail. These research results can be referred as one of the most important structural information considering the quasicrystals and related approximant crystals and the head investigator was invited to International Conference of Quasicrystals 2001.The present research project developed the relatively new technique of single crystal anomalous X-ray scattering technique, which prompts us to know fine structure around a specific element in an alloy sample. This, new analytical tool succeeded to characterize the distribution of Cu in the Al-Cu-Fe approximant phase and allowed us to understand the structural role for Cu for the formation of approximant phase related to quasicrystals.The present research group has also performed the systematic research with respect to structures of cubic approximant phase with large icosahedarl atom clusters. The obtained results were demonstrated in the International Workshop for Quasicrystals as a key lecture. Less