耐核辐照损伤的SiC/SiC复合材料连接及抗辐照机理研究

SiC/SiC composite is an important fuel cladding material with require high radiation tolerant for the next generation fission reactor and fusion reactor. However, the research of robust joining and mechanism of nuclear irradiation resistance of the joint of the SiC/SiC composite is not enough. Two systems of glass solder (SiO2-Al2O3-Re2O3（Re：Y、Yb、Nd、Lu）and CaO-Al2O3) and three systems of solder (Ti3SiC2, Ti+Si and TiC+Si) are designed to join SiC/SiC composite. The addition of SiC and Si3N4 powders into the solder to form the composite solder will also be investigated. The effect of solder compositions, joining environment and parameters on the microstructure and mechanical properties of the joints will be studied systematically through experiments and simulations, and the joining mechanism of SiC/SiC composite will be revealed. The irradiation resistance of the joints will be researched using In-situ Ion Irradiation Transmission Electron Microscope (I3-TEM) and Ultra-High Voltage Electron Microscope (HVEM). The irradiation synergistic effect of different phases in the joints will also be studied. Combined with the finite element model of temperature and stress fields, the composition of solders can be optimized, and finally solders with good high temperature resistance and irradiation resistance will be obtained. The results will provide theoretical guidance and technical assistance for the joining technology of SiC/SiC cladding materials.

SiC/SiC复合材料是针对下一代核裂变反应堆和聚变反应堆对更高事故裕度需求的关键包壳材料之一，然而SiC/SiC的连接及接头抗辐照损伤研究刚刚起步。本项目拟采用SiO2-Al2O3-Re2O3（Re：Y、Yb、Nd、Lu）、CaO-Al2O3两种体系的玻璃-陶瓷焊料；Ti3SiC2、Ti+Si、TiC+Si三个Ti-Si-C体系焊料连接SiC/SiC，并在以上焊料体系中加入SiC和Si3N4粉末构成复合焊料，利用试验和理论计算方法，系统研究焊料成分和连接参数对接头组织和性能的影响规律。利用原位离子辐照透射电镜和高压电镜原位电子辐照，观察连接样品的抗辐照行为，分析接头内部构成相的辐照协同效应，结合应力场和热场计算，指导焊料成分设计，优化抗高温核辐照的焊料体系，揭示接头内构成相的有效调控机制，阐明SiC/SiC复合材料接头的抗辐照机理。为SiC/SiC包壳材料的连接提供理论指导和技术支持。

以建立耐辐照损伤的SiC陶瓷连接接头作为指导思想，设计了并制备了Y2O3-Al2O3-SiO2、CaO-Al2O3-SiO2、CaO-Al2O3-SiO2-LiO2三种玻璃-陶瓷焊料体系，通过对玻璃焊料的析晶处理，分析焊料的析晶行为。利用SRIM程序模拟了SiC母材以及焊料中析出晶相LiAlSi2O6、CaSiO3和CaAl2Si2O8的He离子辐照损伤结果，发现三种结晶产物的耐辐照损伤能力与SiC母材相当。通过调整焊料成分来调节焊料与母材的CTE匹配，以降低接头的残留应力。通过优化连接工艺参数，在1240℃保温10min条件下，所获得预氧化SiC接头的剪切强度达到127MPa。对接头进行400℃下300keV的He离子辐照试验，随着辐照剂量由4dpa增加到12dpa，接头界面保持完整，未发现辐照缺陷。SiC陶瓷母材的辐照损伤程度高于微晶玻璃焊缝，辐照产生的缺陷以及He泡在SiC内部距表面950nm的辐照损伤峰值区域聚集,导致SiC母材逐渐非晶化并出现微裂纹。而微晶玻璃内部的辐照损伤以及He泡分布更加均匀分散，展现出更好的辐照抗性。基于Raman光谱法对不同辐照条件下接头中SiC陶瓷一侧表面的残余应力进行测量，发现SiC表面的应力随着辐照剂量的增加，由压应力向拉应力转变。