基于键价模型的MgAl_(2)O_(4)透明陶瓷热机械性能预测

Predicting Thermomechanical Properties of MgAl_(2)O_(4) Transparent Ceramic Based on Bond Valence Models

尖晶石型陶瓷具有优异的热机械性能,在高温结构材料领域具有良好的应用前景。本研究将键价模型与高温机械性能理论表征模型相结合,建立了从变温晶体结构出发预测尖晶石型陶瓷高温热机械性能的方法,阐明了晶体结构与高温热机械性能之间的关系。采用该方法预测了MgAl_(2)O_(4)透明陶瓷的高温断裂强度和断裂韧性,其预测结果与实验值吻合。研究表明,MgAl_(2)O_(4)中阳离子反位率、化学键硬度和体模量随温度的变化在800℃上下存在显著差异,然而由于配位多面体的耦合作用,阳离子反位的温度效应不会显著影响MgAl_(2)O_(4)透明陶瓷的高温热机械性能。

Spinel-type ceramics have great application prospects owing to their excellent thermomechanical properties in the field of high-temperature structural materials.In this study,a new approach that combined bond valence models with high-temperature mechanical theoretical characterization models was established to predict the high-temperature thermomechanical properties of spinel-type ceramics based on temperature-dependent crystal structure.Furthermore,the relationship between crystalline structure and high-temperature properties was clarified.The high-temperature fracture strength and fracture toughness of MgAl_(2)O_(4)transparent ceramic,were predicted by this approach,which agreed well with the experimental values.It is shown that the ratio of cation inversion,hardness and bulk modulus of chemical bonds in MgAl_(2)O_(4)vary significantly with temperature around 800℃.However,due to coupling effect of the coordinated polyhedra,the temperature-dependent cation inversion can hardly affect the high-temperature thermomechanical properties of MgAl_(2)O_(4)transparent ceramic.