高性能堇青石-氮化硅晶须复相储热陶瓷的低温原位合成机理及性能研究

堇青石储热陶瓷材料被广泛用于太阳能热发电和工业余热回收等领域。本课题针对堇青石陶瓷材质的强度低、韧性差和热导率低等不足，拟在前期材料设计和技术积累的基础上，耦合使用直接氮化法、铝热还原氮化法和碳热还原氮化法等技术方法，设计Si3N4晶须在堇青石的MgO-Al2O3-SiO2系统低温原位合成的反应路线，在堇青石中以原位合成的方式引入低膨胀的Si3N4晶须，旨在利用Si3N4晶须的高强、高韧和高热导率改善堇青石陶瓷的各项性能，获得堇青石-Si3N4晶须复相储热陶瓷材料。本项目将系统地研究堇青石中Si3N4晶须的低温原位合成机理和生长过程，探讨堇青石的三元液相对晶须形貌和生长机制的影响，并通过调控原料共混物的熔融特性，对Si3N4晶须改性堇青石陶瓷材料进行致密化处理。最后，分析复相储热陶瓷材料的组成、结构和各项性能的相关性，揭示其内在规律，为高性能堇青石基复相储热陶瓷材料的制备奠定科学基础。

Cordierite thermal storage ceramics are comprehensively applied for solar thermal power generation and waste heat recovery, etc. In this project, aiming at overcoming the weaknesses in the mechanical and heat conductive properties of cordierite ceramics on the basis of the previous material design and technology accumulation, Si3N4 whiskers of low thermal expansion will be introduced into the cordierite matrix by an in-situ synthesis method through the coupling uses of direct nitridation method, aluminothermic nitridation method and carbothermic nitridation method, from which the technical routes for the in-situ synthesis of Si3N4 whiskers in the MgO-Al2O3-SiO2 ternary system of cordierite are designed. Cordierite-Si3N4 whisker composites for thermal storage applications will be obtained by improving the performances of cordierite matrix with the assistance of Si3N4 whiskers with high strength, high toughness and high thermal conductivity. The low-temperature in-situ synthesis mechanism and the growth processes of Si3N4 whiskers in the cordierite matrix during firing will be investigated systematically and the effects of ternary viscous flow formed by cordierite on the morphology and growth mechanism of Si3N4 whiskers will be studied. The microstructure densification of cordierite ceramics toughed by Si3N4 whiskers will be conducted by adjusting the melting characteristics of ceramic blends. Finally, the relations among the phase compositions, microstructure and properties of Si3N4 whiskers toughed thermal storage composites will be analyzed, in which the inherent laws can be revealed. This project will establish a solid scientific foundation for the preparation of high-performance cordierite-based thermal storage composites.