Shock-induced phase transitions among SiC polytypes

A series of recovery experiments was conducted using a propellant single-stage gun on starting materials of both α-SiC and β-SiC. X-ray examination on the recovered samples indicated that obvious polytype transformations among 3C, 6H, and 15R took place. To the α-SiC starting material, 15R tends to increase and 6H tends to decrease, while a small amount of α-SiC form transforms to 3C type, along with increasing the shock temperature and pressure. X-ray diffraction analysis showed that the β-SiC polytype is transformed into rhombohedral forms. From results of both types of SiC samples, rhombohedral polytypes seem to be the favored shock modification. The effects of shock pressure and shock temperature and their heterogeneous distribution on these polytype transitions are discussed in detail. Analysis showed that these polytype transitions resulted from the stacking sequence changes of SiC atom layers.