金属玻璃的多尺度、多维度研究

发布时间：2018-04-16 04:37

本文选题：金属玻璃 + 低维材料　；参考：《中国科学院大学(中国科学院物理研究所)》2017年博士论文

【摘要】：纵观人类社会的发展历程,从石器时代,青铜时代,铁器时代,再到信息时代,我们对材料科学的理解很大程度上代表了人类认识世界,改造世界的能力。而在材料科学发展的过程中,研究的手段与方法则是我们突破以往认知,获得新材料的最重要的手段之一。正如同显微镜的发展让我们对物质的认识从宏观向微观不断深入,一步一步迈向真理的彼岸。在金属玻璃领域,材料的发展更是以制备和表征方式进步的重要节点作为标志。在如今块体非晶材料已经进入大规模市场应用的时代,如何从更深入的角度去理解非晶态物质的本质与特征,从而提高金属玻璃的性能、开拓金属玻璃的新应,用则是目前最重要的问题。在这样的研究背景下,本文采用了一系列不同的研究手段,从多尺度、多维度的角度下对金属玻璃的玻璃形成能力、弛豫等特征进行分析、研究,旨在使用不同的研究手段,在多尺度、多维度的条件下研究金属玻璃的基本问题,以求能够开阔我们对金属玻璃本质与特征的认识。本文首先讨论了低维金属玻璃的制备与表征。我们通过激光脉冲沉积的方法,得到了厚度在原子级别的CuZrAl和CuZr金属玻璃薄膜,并通过球差校正透射电子显微镜等手段对薄膜的性质进行表征。发现Al掺杂能够降低体系扩散系数,导致两种薄膜在退火过程中形核率有明显差异,这也解释了Al掺杂提高玻璃形成能力的现象。我们也制备了尺寸分布在1-5 nm范围的PdSi纳米颗粒,通过对结构随尺寸演化的表征,我们直接观察到了PdSi纳米颗粒的临界核尺寸,从而验证了经典形核理论。本文通过分子动力学模拟研究了玻璃体系弛豫行为的微观起源。我们通过设计具有不同势阱宽度的势函数,得到了具有不同低温弛豫行为的无序体系,发现随着势函数在势阱处变窄,体系的低温弛豫动力学明显增强。在实验上我们同样观察到稀土基金属玻璃普遍具有更明显的?弛豫。并通过其摩尔体积与体弹模量的关系同更窄的势函数建立关联,我们解释了稀土基金属玻璃的弛豫现象。同时,我们对微观动力学的分析显示,无序体系的弛豫行为和动力学非均匀性的强度密切相关。本文进一步采用机器学习方法分析了二元合金玻璃的玻璃形成能力。我们建立了二元非晶形成合金体系的多维数据库,并使用支持向量机对多维数据进行分析,建立了可以预测二元合金玻璃形成能力的模型。通过数据测试,我们证实了该模型对合金的玻璃形成能力好坏具有明显的区分能力。我们通过改变输入数据的种类,考察了不同参量对合金玻璃形成能力的影响,发现合金熔点的信息和玻璃形成能力有明显关联。
[Abstract]:Throughout the development of human society, from the Stone Age, Bronze Age, Iron Age, and then to the Information Age, our understanding of material science represents to a large extent the ability of human beings to understand and transform the world.In the course of the development of material science, the means and methods of research are one of the most important means for us to break through the past cognition and obtain new materials.Just as the development of microscope allows us to understand matter from macro to micro, step by step to the other side of the truth.In the field of metallic glass, the development of materials is marked by the progress of preparation and characterization.Now that bulk amorphous materials have entered the era of large-scale market application, how to understand the nature and characteristics of amorphous materials from a deeper perspective, so as to improve the properties of metallic glass and open up new applications of metallic glass.Use is the most important issue at present.In this research background, this paper uses a series of different research methods to analyze the glass forming ability, relaxation and other characteristics of metallic glass from the angle of multi-scale and multi-dimension. The purpose of this study is to use different research methods.In order to broaden our understanding of the nature and characteristics of metallic glass, the basic problems of metallic glass are studied under multi-scale and multi-dimensional conditions.In this paper, the preparation and characterization of low dimensional metallic glass are discussed.CuZrAl and CuZr metallic glass thin films with atomic thickness were obtained by laser pulse deposition. The properties of the films were characterized by spherical aberration corrected transmission electron microscopy (TEM).It is found that Al doping can decrease the diffusion coefficient of the system, which leads to the obvious difference in nucleation rate between the two films during annealing, which also explains the phenomenon that Al doping can improve the glass forming ability.We have also prepared PdSi nanoparticles with size distribution in the range of 1-5 nm. The critical nucleation size of PdSi nanoparticles has been observed directly through the characterization of the structure evolution with size, thus validating the classical nucleation theory.In this paper, the microscopic origin of relaxation behavior of glass system has been studied by molecular dynamics simulation.By designing potential functions with different potential well widths, we obtain disordered systems with different low-temperature relaxation behaviors. It is found that the low-temperature relaxation kinetics of the system increases with the potential function becoming narrower at the potential well.We also observed that rare earth based metallic glasses are generally more obvious in experiments.Relaxation.The relaxation phenomenon of rare earth based metallic glass is explained by the correlation between the molar volume and bulk elastic modulus and the narrower potential function.At the same time, our analysis of microdynamics shows that the relaxation behavior of disordered systems is closely related to the strength of the dynamic inhomogeneity.In this paper, the glass forming ability of binary alloy glass is analyzed by machine learning method.The multi-dimensional database of binary amorphous alloy system is established and the multi-dimensional data is analyzed by support vector machine (SVM). A model is established to predict the glass forming ability of binary alloy.Through the data test, we confirm that the model has obvious ability to distinguish the glass forming ability of the alloy.By changing the type of input data, we investigate the influence of different parameters on the glass forming ability of the alloy. It is found that the melting point information of the alloy is obviously related to the glass forming ability.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG139.8

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