元素粉末法合成多元合金碳化物的热稳定提高机制研究

熔点超过3000℃的金属碳化物超高温陶瓷被认为是在航空航天耐超高温领域最具应用前景的材料之一。新近研究表明，在二元碳化物中添加多个IV-V过渡族金属制备成多元合金碳化物被认为是提高碳化物热稳定性能非常有效的新途径，但关于熔点和抗氧化两方面的热稳定提高机制未得到系统揭示，不利于其成分和性能的深度优化。本项目拟以Hf、Zr、Ta等过渡族金属和碳为原料，采用本团队发明的“元素粉末法”合成纯度高的不同组分比例和不同碳空位浓度的多元合金碳化物粉体，再将其烧结成致密体；系统分析碳化物晶体结构，测量碳化物的氧化/烧蚀性能以及熔点变化规律；建立金属和空位等组元及其比例跟碳化物氧化/烧蚀性能以及熔点变化的内在关系；基于热力学计算、晶体模型和实验结果，系统揭示多元合金碳化物熔点和抗氧化方面的热稳定提高机制，为新型合金碳化物的优化设计奠定理论基础，亦为我国空间飞行器的耐热结构部件的选材提供科学依据与技术支撑

The ultra-high temperature metal carbide ceramics with a melting point exceeding 3000°C are considered to be one of the most promising materials for high temperature applications in aerospace field. Recent studies have shown that fabricating multi-component alloy carbide by adding multiple IV-V transition metal elements into binary carbide is considered to be an effective novel method to improve the thermal stability of carbide. However, the improvement mechanism of the thermal stability of melting point and oxidation resistance has not been systematically revealed, which is not conducive to the deep optimization of its composition and performance. This project intends to use Hf, Zr, Ta and other transition metals and carbon as raw materials, and exploit the "elemental powder method" which was invented by our team to synthesize high pure multicomponent carbide powder with different carbon vacancy concentration and compositions; and then this multicomponent carbide powder is sintered into compact body. Moreover, the crystal structure of carbides will be systematically analyzed, and the oxidation/ablation properties and melting point of carbides will be measured; This project also aims to establish the intrinsic relationship between the metal elements, vacancy and their proportions with the oxidation/ablation properties and melting point of carbides; More importantly, based on the thermodynamic calculation, crystal model and experimental results, the improvement mechanism of thermal stability including melting point and oxidation resistance of multi-component alloy carbides will be systematically revealed; which would lay a theoretical foundation for the optimal design of novel multi-component alloy carbides, and provide scientific basis and technical support for the material selection of heat-resistant structural components of space vehicles in China.