Liquid-Phase Sintering of SiC with Al-B_4C-C as Sintering Aids

SiC ceramics were prepared by pressureless sintering with Al, B and C as sintering aids. The effects of the mol ratio of Al and B, the sintering temperature and sintering time on the relative density and bending strength of the samples were studied. The fracture surface structure and the grain shape of the samples were displayed by SEM photographs. The experimental result shows that the most appropriate sintering time is 1h, and the relative density of the samples reaches to 90% when the sintering temperature is above 1850℃. It also shows that the samples have the best performance when the mol ratio of Al and B is between 3/1 and 4/1. The XRD pattern shows A18B4C7 is in existence, which indicates that Al8B4C7 is produced during sintering, so that the sintering mechanism is liquid-phase sintering.