SiC/C界面辐照性能的分子动力学研究*

摘要

Continuous silicon carbide (SiC) fiber-reinforced SiC (SiCf/SiC) composites have been considered to be used as structural materials in advanced nuclear reactors for its excellent properties. Their mechanical properties have been greatly improved during the last decade. But the radiation damage at the SiC and pyrolytic carbon interface would degrade the mechanical integrity of the composites, while the mechanism of degradation is remaining unknown at present. In this study, molecular dynamics simulations have been used to model the irradiation cascade of five SiC/C composite systems. According to the angle between the graphite layer and the interface, the models are marked as M0, M28, M56, M77 and M90, in which the number represents the angle. Forty primary knock-on atoms (PKAs) at different positions in each composite system are used to bombard the interface. In each run a collision cascade may be initiated by giving one of the 40 atoms 1.5 keV kinetic energy. The relationships between the distribution of defects and simulation time and PKA position are systematically studied, and compared with those in bulk SiC, which are marked as MW. Results show that the radiation damage resistance of SiC/C interface is significantly lower than bulk SiC, and the interface structure has an impact on the number of defects. Radial distribution function (RDF) is employed to examine the coordination of interfacial atoms. The results show that the higher the density of graphite atoms in the interface, the larger impact the irradiation on the RDF and coordination.%本文通过分子动力学模拟的方法，研究了5种含不同空间结构的SiC/C界面的材料受辐照后的缺陷分布随时间以及PKA位置的变化关系，并与单质SiC中缺陷分布情况进行对比。利用径向分布函数分析了辐照对界面原子排列情况的影响。研究结果表明， SiC/C界面的抗辐照能力明显低于SiC内部，不同的空间结构对界面缺陷数量存在一定影响。由径向分布函数推得界面区域石墨原子密度高则界面原子排列情况受辐照影响越大。