Model for the prediction of thermomechanical bulk properties of multicomponent oxide glasses based on a combined quantum mechanical and thermodynamic approach

本项目的灵感来自于深入理解科学概念中玻璃的化学成分、结构和热机械性能之间的关系。目标是开发一种模型，能够定量探索具有突出机械性能的区域的组成空间，并随后在材料设计中使用。该模型应针对多组分氧化物玻璃的块体机械块体性能。它从这种玻璃中的结构短程有序群和在等化学晶态中发现的相应结构的等效性这一工作假设出发。然而，这一假设在热化学性质方面得到了很好的证实，但在机械性质方面却没有得到充分的利用，部分原因是缺乏对晶体基本数据的了解--甚至是可用性。设想的模型试图通过组合的方法建立从单晶到多组分玻璃的宽桥。首先，这是一种基于量子力学的从头算方法；它旨在评估晶体结构和性质，以及理解为什么某些结构在其性质方面突出。其次，这是一种热力学方法，旨在评估单组分玻璃和等化学晶体在现象量方面的差异，并将这些数据叠加到多组分玻璃基质的性质上。这里，项目意义上的“多”是指大多数工业玻璃产品中常见的典型&gt；5功能氧化物成分。以MgO-CaO-Al_2O_3-SiO_2-P_2O_5系为组成基础。为该项目设想的实验工作首先旨在从现象学的角度评估选定的单晶与其等化学物之间的差异。由于这些差异最敏感地反映在低温热容的差异上，因此应进行低温微量热法(外部合作)。单组分玻璃的机械体积性能的实验测定也有同样的目的。这些特性应通过脉冲激励技术以声学方式确定。同样的技术将被应用于广泛验证多组分矩阵的模型预测。该模型对材料设计的实用性应在项目结束时通过几个案例进行演示。

The present project is inspired by the motivation to deeply root the understanding of the relation among chemical composition, structure, and thermomechanical properties of glasses in scientific concepts. The objective is the development of a model enabling quantitative exploration of compositional space for areas with outstanding mechanical properties, and its consequent use in materials design. The model shall be directed towards the bulk mechanical bulk properties of multicomponent oxide glasses. It starts from the working hypothesis of equivalency of structural short-range order groupings in such glasses, and the corresponding structures found in the isochemical crystalline states. This hypothesis is well substantiated with respect to thermochemical properties, however, yet unexploited with respect to mechanical properties, in part because of a lack of understanding – or even availability – of fundamental data for the crystals. The envisaged model attemps to establish the wide bridge from single crystals to multicomponent glasses by a combined approach. This is, firstly, a quantum mechanics based ab initio approach; it is directed towards the assessment of crystal structures and properties as well as towards an understanding why certain structures stand out with respect to their properties. This is, secondly, a thermodynamic approach directed towards assessing the differences between one-components glasses and isochemical crystals in terms of phenomenological quantities, and towards the superimposition of such data to the properties of multicomponent glass matrices. Here, “multi” in the sense of the project refers to typically > 5 functional oxide components as found in most industrial glass products. The system MgO-CaO-Al2O3-SiO2-P2O5 is depicted as compositional basis. The experimental work envisaged for this project aims, firstly, at a phenomenological assessment of the differences between selected single crystals and their isochemical counterparts. As these differences are most sensitively reflected by the differences in low-T heat capacities, low-T microcalorimetry shall be performed (external cooperation). The experimental determination of the mechanical bulk properties of one-component glasses serves the same purpose. These properties shall be determined acoustically by impuls excitation technique. The same technique will be applied to extensively verify model predictions for multicomponent matrices. The usefulness of the model for materials design shall be demonstrated at the end of the project for a few cases.