第四代核能系统用碳化锆陶瓷的缺陷和微结构调控及辐照性能研究

Zirconium carbide (ZrC) has good physical and chemical properties such as high melting point, good thermal stability, high thermal conductivity, low neutron absorption cross-section as well as good resistance to the corrosion of nuclear fission products. Due to its favorable high temperature characteristics mentioned above, ZrC is being considered as one of the candidate materials for the production of the inert matrix for some fuel components of the generation-IV nuclear reactor systems such as gas-cooled fast reactor and high temperature gas reactor. However, it is very hard to sinter ZrC to be dense owing its strong covalent bonding and low diffusion coefficient. Therefore high sintering temperature is generally needed, which also caused the coarse microstructures in the obtained ceramics. The poor microstructures limited its irradiation property improvement and its application as the inert matrix materials. Ultra-fine and pure ZrC powder is synthesized by the solution-based processing method using soluble metal-organic (zirconium-bearing) precursor and organic carbon-bearing precursors as the raw materials. High pressure spark plasma sintering is chosen to promote the sintering ZrC ceramics with fine microstructures at moderate temperature. Additives such as Zr and VC are used to enhance carbon defects and solid solution defects in the lattice of ZrC. The microstructures are tailored by controlling the diffusion process of defects, the solution and precipitation processes of additives. Effects of the defects and microstructures on the irradiation properties of ZrC are investigated. The relationship between high temperature properties and microstructure is also studied. This proposal supplies important knowledge accumulations, data and technique supports about the ZrC-based ceramics as the inert matrix materials.

碳化锆(ZrC)具有高熔点、良好的高温热稳定性、耐核裂变产物腐蚀、高热导率及较低的中子吸收截面等优良的物理、化学性能，是第四代核能系统用惰性基体燃料的重要候选材料。但目前ZrC的烧结温度高、材料显微结构粗化严重，限制了辐照性能的提升及在核能系统中的应用。本研究拟以含锆和碳的有机前驱体为原料，采用湿法合成制备高纯、超细ZrC粉体，结合高压放电等离子体烧结技术实现ZrC在温和温度下的致密化及细晶化。通过添加剂（Zr、VC等）的引入在碳化锆晶格中增加碳缺陷、固溶缺陷，以此促进烧结过程中的扩散传质，并通过添加剂的固溶-析出机制来调控材料的微结构。重点研究材料的缺陷及微结构等对辐照缺陷的捕获及复合机制，并考察材料辐照前后的高温力学、热学、蠕变等性能，阐明材料特性与辐照性能及高温性能的关系。本研究将形成具有自主知识产权的ZrC惰性基体材料，为其在核能上的应用提供重要的知识积累、数据支撑和技术支持。

碳化锆（ZrC）具有高熔点、良好的高温热稳定性、耐核裂变产物腐蚀、高热导率及较低的中子吸收截面等优良的物理、化学性能，是第四代核能系统用惰性基体燃料的重要候选材料。但目前ZrC的烧结温度高、材料显微结构粗化严重，限制了辐照性能的提升及在核能系统中的应用。本项目以有机前驱体氧氯化锆和蔗糖为原料，采用湿法合成并结合发泡辅助工艺制备了平均粒径为180nm、且粒径分布较窄的ZrC粉体，对前驱体的裂解过程、产物相组成、粉体形貌和粒径等特性进行了研究。以Si、Al、Zr为添加剂结合热压技术实现ZrC的低温（1500-1600℃）致密化、缺陷和微结构调控。利用添加剂与基体ZrC原位反应而生成碳缺位型ZrC1-x促进烧结中的扩散传质，原位反应生成具有增强作用的第二相SiC和Zr3Al3C5不但有利于调控材料的微结构，还有利于改善材料的常温综合力学性能。重点研究了材料的缺陷及微结构与材料Xe离子辐照性能的关系，阐明了材料特性对辐照缺陷的捕获及复合机制。研究了过渡金属碳化物WC添加剂通过与基体ZrC形成固溶体对材料高温力学（内耗、弹性模量、抗弯强度）和热学性能的影响机制及其作用机理，WC掺杂可以提升ZrC陶瓷的高温抗弯强度和高温弹性模量。理论计算和实验结果都表明 (Zr, W)C固溶体的形成可以促进氧进入ZrC晶格，起到净化ZrC陶瓷的晶界的作用。项目也初步考察了ZrC基陶瓷的耐熔盐腐蚀性能。本研究为ZrC惰性基体材料在第四代先进核能系统中的应用提供重要的技术支持和理论指导。