高熵晶界修饰ZrO2基纳米玻璃陶瓷的制备及其组织与性能的热稳定性

纳米陶瓷由于具有大量处于高能状态的晶界而不稳定，在热环境中易出现晶粒粗化现象，导致其纳米特性减弱，甚至完全丧失。针对此问题，本课题将高熵晶界理念引入纳米陶瓷领域，利用溶质原子共偏析在快速烧结中形成高熵晶界，降低晶界能，阻碍晶界移动，抑制纳米晶粒粗化，提高纳米陶瓷在烧结和中/高温服役双过程中的晶粒尺寸稳定性，从而稳定其性能。本课题拟向ZrO2-SiO2纳米玻璃陶瓷复合添加五元在ZrO2晶界具有强烈偏析倾向的溶质原子，经放电等离子体烧结形成高熵晶界，然后对由高熵晶界修饰的纳米玻璃陶瓷进行烧结后热处理，探究高熵晶界在烧结和热处理双过程中抑制ZrO2纳米晶粒粗化的效果和机理，考察晶界高熵化对力学性能的影响；采用电镜技术观察高熵晶界内各溶质原子的偏析情况，建立溶质原子偏析与纳米晶粒尺寸稳定性之间的联系。本课题既拓展了高熵理念的应用领域，也为设计和制备具有组织和性能热稳定性的新型纳米陶瓷提供重要借鉴。

Nanoceramics are metastable due to the existence of large quantity of high-energy grain boundary. Grain coarsening phenomenon occurs easily under high-temperature condition, resulting in the weakening or even completely loss of nano features. To solve this problem, this study introduces high entropy grain boundary (HEGB) concept to the field of nanoceramics. Co-segregation formed by addition of multi dopants is utilized to form HEGB, which could simultaneously reduce the energy and mobility of grain boundary, and thereby improving the grain size stability of nanoceramics in both sintering and post heat treatment processes. This study will add five dopants to a ZrO2-SiO2 nanocrystalline glass-ceramic. The added dopants show strong segregation tendency at the grain boundaries of ZrO2-SiO2 nanocrystalline glass-ceramic. The glass-ceramic decorated by HEGB will be sintered by spark plasma sintering, followed by post heat treatments. The effects and mechanisms of HEGB on improving the coarsening resistance of nanograins in both sintering and post heat treatment processes will be studied. Meanwhile, the effects of HEGB on the mechanical properties of the glass-ceramic will also be investigated. Furthermore, advanced microscopy techniques will be utilized to characterize the distribution of dopants and the distribution information will be used to build the relationship between grain size stability and the distribution of dopants. This project will not only extend the application of HEGB concept, but also provides useful guidance to design and prepared novel nanoceramics that shows excellent microstructure and properties thermal stability at high temperatures.