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Establishment of new analytical technique applicable for local atomic arrangements in various multi-component materials

建立适用于各种多组分材料中局部原子排列的新分析技术

基本信息

批准号：
10450234
负责人：
OKI Kensuke
金额：
$ 8.45万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

This study aims at establishing a new TEM (transmission electron microscope) techique to analyze local atomic arrangements quantitatively which is applicable for various multi-component systems, such as aluminides or oxides. The optimum experimental conditions and formulations of ALCHEMI (atom location by channelling enhanced microanalysis) for B2 or L1_0 type-ordered aluminides were investigated experimentally and theoretically. The structure factors of superlattice reflections in the aluminides were measured by some different methods, and the preciseness and applicability of the methods were examined. The main conclusions are drawn as follows.1. In case of alloys and compounds containing a large amount of light elements, such as Al or O, the result of ALCHEMI depends strongly on the diffraction condition. If a positive excitation error is set for the channelling condition, the characteristic X-ray intensity may give incorrect occupation probabilities of the constituent elements. The … More fact is mainly due to delocalization of the inner-shell ionization for the X-ray emission and absorption of the X-rays within the specimen. The differences between the experimental values of occupation probabilities and the correct ones become large for alloys and compounds which have considerable small structure factors of superlattice reflections, such as B2-ordered Ti-Al-Mo.2. A new procedure of ALCHEMI which gives reliable data for such aluminides are proposed as follows : (1) set the crystal orientation into the systematic row excitation. (2) measure the characteristic X-ray intensity of constituent elements with tilting the incident electron beam to obtain a "diffraction condition-characteristic X-ray intensity" profile, as well as the foil thickness. (3) fit the profile by the computer simulation of ALCHEMI to determine the occupation probabilities of the constituent elements which give the best fitting result.3. The simulation of ALCHEMI must consider (i) dynamical diffraction of elastic-scattered electrons attenuated by inelastic scattering, (ii) characteristic X-ray emission by the elastic- and inelastic-scattered electrons, (iii) delocalization of the inner-shell ionization and (iv) absorption of the X-rays within the specimen.4. For alloys which have small structure factors of superlattice reflections, such as B2-ordered Ti-Al-Mo, the quantitative electron diffraction and its fitting-simulation using the many-beam dynamical diffraction theory give much reliable values of the structure factors than the intersecting Kikuchi-line method and the thickness-fringe one. Less

本研究旨在建立一种新的透射电子显微镜（TEM）技术来定量分析局域原子排列，该技术适用于各种多组分体系，如铝化物或氧化物。从实验和理论上研究了B_2和L_1_0型有序铝化合物的ALCHEMI（原子定位沟道增强显微分析）的最佳实验条件和配方。用不同的方法测量了铝化物超晶格反射的结构因子，并对这些方法的准确性和适用性进行了检验。主要结论如下：1.在合金和化合物含有大量的轻元素，如铝或O的情况下，ALCHEMI的结果强烈依赖于衍射条件。如果为沟道条件设置正激励误差，则特征X射线强度可能给出组成元素的不正确的占据概率。的 ...更多信息事实上，主要是由于离域的内壳层电离的X射线发射和吸收的X射线在试样内。对于具有相当小的超晶格反射结构因子的合金和化合物，如B2-有序Ti-Al-Mo，占据几率的实验值与正确值之间的差异变得很大。本文提出了一种新的ALCHEMI方法，它能给出这类铝化物的可靠数据：（1）将晶体取向置于系统行激发中。(2)通过倾斜入射电子束来测量组成元素的特征X射线强度，以获得“衍射条件-特征X射线强度”轮廓以及箔厚度。(3)通过ALCHEMI的计算机模拟对轮廓进行拟合，确定最佳拟合结果的组成元素的占位概率. ALCHEMI的模拟必须考虑（i）由非弹性散射衰减的弹性散射电子的动态衍射，（ii）弹性和非弹性散射电子的特征X射线发射，（iii）内壳层电离的离域和（iv）X射线的吸收。4.对于具有较小超晶格反射结构因子的合金，如B_2有序Ti-Al-Mo合金，用多束动态衍射理论进行定量电子衍射及其拟合模拟，得到的结构因子值比相交菊池线法和厚度条纹法可靠得多。少