Ti基和稀土基金属玻璃高压下的结构演变研究

发布时间：2018-03-02 08:15

本文关键词： 金属玻璃非晶多形态转变高压双体分布函数逆向蒙特卡罗　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：金属玻璃材料作为玻璃家族的新成员,因其具有的无序结构和所表现出来的特性引起了材料科学和凝聚态物理学的广泛研究。具有网状结构的传统玻璃态物质曾经被报道过存在由原子配位数的增加引起的压致非晶多形态相变,例如冰、石英和硅等材料。金属玻璃是由与传统玻璃截然不同的无方向性金属键构成的,因其空间密堆结构和具有的最大配位数被认为不可能存在压致非晶多形态相变。然而金属玻璃高压下的相变现象在近年来被发现和并进行了深入研究。本论文利用高压技术结合多种分析手段对金属玻璃的高压结构演化进行了研究,其中包括不存在相变的过渡元素Ti基体系和存在相变现象的镧系基金属玻璃,得到的主要研究结果如下:(1)采用原位高能X射线散射实验结合双体分布函数分析和逆向蒙特卡罗拟合对二元金属玻璃Ti_(62)Cu_(38)的高压结构进行了研究。在长程尺度上,体系相对原子体积在压力作用下呈现出平滑的连续性变化曲线,通过状态方程拟合得到其等温体积模量B0=132(3)GPa,B0'=5.8(0.4)。在短程尺度上,由RMC拟合获得的压缩状态的原子密堆结构表明体系的短程拓扑序为变形二十面体并且在压力作用下保持稳定状态。由体系相对体积与配位球尺寸变化率的关系确定Ti_(62)Cu_(38)金属玻璃的原子间距前四个峰尺度范围内存在维数为2.5的分形行为。(2)采用原位高压同步辐射X射线散射实验研究了Yb基金属玻璃的压缩行为,观察到了体系由低密度态向高密度态的转变,并伴随由等温体积模量不连续性变化反映的体积坍塌。体系的体积塌缩是由变形二十面体短程序在压力作用下向正二十面体转变引起的,该压致非晶多形态相变现象与压缩条件下Yb元素所含有的4f电子的离域化效应相关,并与原位高压电子输运性能测量的结果相符合。Yb基金属玻璃具有非晶多形态相变的现象结合相关研究报导表明压致多形态现象是镧系基金属玻璃的普遍性行为。(3)Yb基金属玻璃的压致非晶多形态相变现象表明镧系基金属玻璃含有的镧系溶剂原子对其电子结构具有继承性,那么金属玻璃中的镧系溶质原子是否具有电子结构的继承性?采用原位高压X射线散射实验对含有Pr溶质原子的La_(43.4)Pr_(18.6)Al_(14)Cu_(24)金属玻璃进行了结构研究,结果显示该体系产生了伴随着体积塌缩的低密度态向该密度态转变的压致非晶多形态相变。同时出现了局域结构向正二十面体变化的趋势,短程序尺度的P-r1关系和中程序尺度的P-Q1关系都表征了体系的结构存在变化。由于体系不可能发生由配位数增加引起的相变,且其包含的La元素不含有4f电子,因此认为体系的非晶多形态相变是由溶质原子Pr的4f电子离域化效应引起的,由此可以确定金属玻璃体系内含有的溶剂原子和溶质原子都对其电子结构具有继承性。该发现进一步补充了镧系基金属玻璃的研究,并为含有镧系元素的金属玻璃的非晶多形态研究提供了新的思路和方向。综上所述,本论文首次在实验上发现了金属玻璃体系遵循的2.5幂律关系在实空间内超出最近邻范围;Yb基金属玻璃存在压致非晶多形态的现象表明非晶相变是Ln系基金属玻璃的普遍特性,同样证实了Ln系基金属玻璃的Ln系元素具有电子结构继承性;La_(43.4)Pr_(18.6)Al_(14)Cu_(24)金属玻璃的高压结构研究表明镧系溶质原子也具有4f电子结构继承性,首次发现了Ln系溶质原子引起的非晶多形态相变。本论文的研究成果促进了金属玻璃材料的高压研究进展,并为其提供了新的研究方向和前景。
[Abstract]:The metallic glass material as a new member of the glass family, because of its disordered structure and behavior caused extensive research in materials science and condensed matter physics. The traditional glass material with network structure has been reported to have caused by the atomic coordination number increases the pressure induced polyamorphous transition. Such as ice, quartz and silicon and other materials. The metal glass is composed of non directional metal bond is quite different from the traditional glass, because the maximum coordination number of the space lattice structure and has not considered possible pressure induced polyamorphous transition. However, phase transition metallic glass under high pressure was found in recent years and in-depth study. This paper combine many kinds of analysis means of evolution high-pressure structure of metallic glass was studied by using high technology, including the absence of transitional element transformation in Ti matrix The Department and the lanthanide based metallic glass transition phenomenon, the main research results are as follows: (1) using in situ high-energy X ray scattering experiment combined with pair distribution function analysis and reverse Monte Carlo fitting of two yuan of metallic glass Ti_ (62) Cu_ (38) high voltage structure were studied. In the long term scale. System of relative atomic volume under pressure curve showing continuous changes smoothly, the isothermal bulk modulus B0=132 by equation (3) GPa, B0'=5.8 (0.4). In the short distance scale, short topological order compression obtained by fitting the RMC atom close packed structure shows that the system for surface deformation of twenty and keep a steady state under pressure. The system of relative volume and coordination sphere size rate of change in the relationship between Ti_ (62) Cu_ (38) atom distance four peak scale metallic glass in the fractal dimension is 2.5 . (2) the compression behavior of Yb based metallic glass in situ high-pressure synchrotron radiation X ray scattering experiment, observed the changes in the system by the state to the low density high density state, and accompanied by the isothermal bulk modulus discontinuity reflects the change in volume collapse. Volume collapse system is composed of twenty surface shrinkage deformation body short program under pressure to change the body surface is twenty, the Yb element of the pressure induced polyamorphous transition phenomenon and compression conditions contained in the 4f electron delocalization effect, and transport properties of in situ measurements with high voltage electronic accord with.Yb based metallic glass is amorphous phase transformation phenomena with the relevant research reports show that the pressure induced multi form phenomenon is a common behavior of lanthanide based metallic glass. (3) Yb based metallic glass pressure induced polyamorphous transition phenomenon indicated that the lanthanide based metallic glass containing lanthanide The solvent atoms have inherited their electronic structure, so the lanthanide solute atoms in metallic glasses have inherited the electronic structure? By in situ high pressure X ray scattering experiments of solute atoms containing Pr La_ (43.4) Pr_ (18.6) Al_ (14) Cu_ (24) in the structure of the metallic glass. The results show that the system produces with the changes of low density state volume collapse to the density of states of pressure induced polyamorphous transition. At the same time there is a trend toward the local structure of twenty face changes, short program scale P-r1 relations and program scale P-Q1 relationship to characterize the system structure change because does not occur by the coordination number caused by the increase of transformation system, which contains La elements and does not contain 4f, so that the polyamorphous transition system is composed of 4f electron delocalization of solute atoms Pr effect caused by this, can be determined. The solvent and solute atoms will contain metallic glass system has inherited its electronic structure. This finding is a supplement to the study of lanthanide based metallic glass, and provides new ideas and direction of amorphous form of metallic glass containing lanthanide elements. To sum up, this thesis for the first time in the experiment found that 2.5 power-law relations follow the metallic glass system beyond the scope of the nearest neighbor in real space; Yb based metallic glass has the phenomenon of pressure induced amorphous morphology showed that the amorphous phase is a common characteristic of Ln based metallic glass, also confirmed the Ln elements Ln based metallic glass has the electronic structure of inheritance; La_ (43.4) Pr_ (18.6) Al_ (14) Cu_ (24) of high-pressure structure of metallic glass shows that lanthanide solute atoms also has the electronic structure of 4f inheritance, first discovered the polyamorphous transition of Ln solute atoms caused. The research achievements of this paper promote the research progress of high pressure metal glass materials, and provide new research direction and prospect for it.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG139.8

【相似文献】