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

Al-Ni-Co十角形相受到了广泛的关注，因为十角形准晶体的几种调制，显示出高度有序的衍射图样或几种不同类型的具有超晶格反射的衍射图样，以及一些晶体近似。为了揭示这些十角形准晶体的结构，人们利用电子衍射分析、高分辨率透射电子显微镜（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，以往的研究都是针对个别的十方准晶进行的，并没有对所有Al-Ni-Co十方准晶的结构进行系统的解释。本课题对950℃退火后Al_<72.5>, Ni_<17>, Co_<20.5>的合金中发现的晶体近似物进行了精确的结构分析。这种W-(AlCoNi)相的结构使我们能够详细地讨论Al-Ni-Co十方准晶的结构。这些研究成果可作为准晶体及相关近似晶体的重要结构信息之一，并被邀请参加2001年国际准晶体会议。本研究项目发展了相对较新的单晶异常x射线散射技术，使我们能够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，并使我们了解了Cu在与准晶相关的近似相形成中的结构作用。本课题组还对大二十面体原子团簇的立方近似相结构进行了系统的研究。所得结果在国际准晶体研讨会上作了重点报告。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