Effect of reactivity of silicon and magnesium on the preparation of SiC MgAl2O4 composites for immobilizing graphite

SiCMgAl2O4 ceramic has a novel application for immobilizing radioactive graphite. The interface reaction between silicon and magnesium offers a significant challenge in the synthesis of SiCMgAl2O4 composites. In this paper, the effects of silicon source, magnesium source, sintering temperature and holding time on the interface reactivity were investigated by characterizing the phase compositions, microstructures, and hardness. The results show that the reactivity of silicon and magnesium varies with silicon sources and magnesium sources which also have a great effect on the microstructure of SiCMgAl2O4 composites. Either excessive sintering temperature or excessive holding time makes SiCMgAl2O4 composites decomposed into different phases, leading to a decreased hardness value. It is found that silicon as silicon source can contribute to the formation of SiC nanowires, which is in line with VS growth mechanism of SiC. The interface reactivity of element Si and Mg, which is positively correlated with high temperature and long holding time, has a negative effect on the phase compositions and performance of SiCMgAl2O4 ceramic by pressureless sintering.