Influence of Topological Anisotropy on the Mechanical Properties of Silicate Glasses

拓扑各向异性对硅酸盐玻璃力学性能的影响

• 批准号: 224500468
• 负责人: Professor Dr.-Ing. Erik Bitzek
• 金额: --
• 依托单位: Lehrstuhl für Glaschemie II
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/224500468?language=en
• 关键词: Influence; Topological; Anisotropy; Mechanical; Properties

Although glasses are generally viewed as isotropic material, freezing-in the flow structure of a glass under load can easily be used to produce anisotropic glass components. One example of such a process is the drawing of oxide glass fibers. Macroscopically, the anisotropic nature of the glass manifests itself in the phenomenon of optical birefringence. Moreover, mechanical properties of glass may be strongly affected by anisotropy. Indeed, it was recently shown that topological anisotropy, i.e. a direction dependence in the way the silica tetrahedra are connected with each other, is the main cause for the one order of magnitude higher strength of glass fibers compared to bulk glasses of the same composition. Given the technical relevance of these findings, relatively little is known about the nature of the topological changes which lead to anisotropic properties, and on how topological anisotropy influences the various mechanical properties.The aim of this proposed research project is to study how anisotropy develops in silicate glasses, how it can be characterized on a topological level, and how topological anisotropy affects the stress-strain response and toughness of silicate glasses. For this purpose, we will combine experimental investigations on the macro scale with in-situ nanomechanical testing in the transmission electron microscope (TEM) and atomistic computer simulations.In detail, the key objectives for the experimental work are the production of bulk anisotropic oxide glasses, the detailed characterization of their structure by scattering techniques and fluctuation electron microscopy and the determination of their (direction-dependent) mechanical properties by macroscopic and microscopic tensile tests, fracture experiments and indentation studies. In addition, silica nanostructures (nanospheres, nanofibers) will be rendered anisotropic by in-situ mechanical quenching in the TEM exploiting the recently discovered phenomenon of superplasticiy that can be controlled via electron irradiation.The atomistic simulations will focus on characterizing the topological anisotropy and studying the mechanisms which lead to anisotropy, as well as on determining the direction dependent mechanical properties as function of anisotropy.Throughout the project, the experimental and simulations efforts are closely linked, e.g. by the simulation of electron diffraction patterns and fluctuation electron microscopy images of MD generated samples and comparison to experimental results, or by the comparison of MD simulations of nanomechanical tests with corresponding in-situ experiments.Such knowledge will be used to (a) specifically engineer anisotropic crack propagation by generating dedicated topological anisotropy and (b) understand, on a topological basis, crack propagation in a more complex (multiaxial) field of topological anisotropy and stress. The proposed research will strongly profit from collaborations within the priority programme “Topological Engineering of Ultra-Strong Glasses”, e.g. on the influence of topology on mechanical properties of bulk metallic glasses, where recently similar effects of anisotropy on elastic properties were reported, or on micromechanical testing of oxide glasses.

尽管玻璃通常被视为各向同性材料，但玻璃在负载下的凝固流动结构可容易地用于生产各向异性玻璃部件。这种方法的一个例子是氧化物玻璃纤维的拉伸。宏观上，玻璃的各向异性性质表现为光学双折射现象。此外，玻璃的机械性能可能受到各向异性的强烈影响。事实上，最近表明，拓扑各向异性，即二氧化硅四面体彼此连接的方式的方向依赖性，是玻璃纤维的强度比相同组成的块状玻璃高一个数量级的主要原因。鉴于这些发现的技术相关性，相对较少的是知道的拓扑变化的性质，导致各向异性的性质，以及拓扑各向异性如何影响各种机械性能。本研究项目的目的是研究各向异性如何发展在硅酸盐玻璃，它如何可以在拓扑水平上表征，以及拓扑各向异性如何影响硅酸盐玻璃的应力-应变响应和韧性。为此，我们将结合联合收割机的实验研究，在宏观尺度上与原位纳米力学测试的透射电子显微镜（TEM）和原子计算机模拟。详细地说，实验工作的关键目标是生产块体各向异性氧化物玻璃，通过散射技术和波动电子显微镜对其结构进行详细表征，并确定其通过宏观和微观拉伸试验、断裂实验和压痕研究，对（方向相关）机械性能进行了测试。此外，二氧化硅纳米结构利用最近发现的可以通过电子辐照控制的超塑性现象，在TEM中通过原位机械淬火使纳米球（纳米球，纳米纤维）呈现各向异性。原子模拟将集中于表征拓扑各向异性和研究导致各向异性的机制，以及确定作为各向异性函数的方向相关力学性能。在整个项目中，实验和模拟工作紧密相连，例如通过模拟MD产生的样品的电子衍射图案和波动电子显微镜图像并与实验结果比较，或通过纳米力学测试的MD模拟与相应的原位实验的比较。这些知识将用于（a）通过产生专用拓扑各向异性来具体地设计各向异性裂纹扩展，以及（B）在拓扑基础上理解拓扑各向异性和应力的更复杂（多轴）场中的裂纹扩展。拟议的研究将大大受益于优先方案“超强玻璃拓扑工程”内的合作，例如拓扑结构对大块金属玻璃机械性能的影响，最近报告了各向异性对弹性性能的类似影响，或氧化物玻璃的微观力学测试。