Sintering behavior and properties of SiC/Si^sub 3^N^sub 4^ composite

SiC/Si^sub 3^N^sub 4^ composite was pressureless sintered using self-propagating high-temperature combustion synthesis [alpha]-Si^sub 3^N^sub 4^ powder and appropriate amount of [beta]-SiC powder. Both of the sintering additive systems were used, which were YAN (Y^sub 2^O3-Al^sub 2^O3-AlN) and YN (Y^sub 2^O3-AlN). The influences of [beta]-SiC content on sintering behavior of SiC/Si^sub 3^N^sub 4^ composite were investigated. The results show that the density, shrinkage, bending strength, hardness, and fracture toughness of the samples with two sintering additive systems increase first with the increase of the contents of [beta]-SiC and then decrease even when [beta]-SiC contents continually increase. The tendency of weight loss of the samples is opposite. The [beta]-SiC content of the samples with the best mechanical properties is different in two systems. For YAN system, the best mechanical properties of the samples are gained when [beta]-SiC content reaches 10 %, while as for YN system it is 5 %. The properties of YN samples are superior to YAN samples. J phase (2Y^sub 2^O3·Si^sub 2^N2O) forms in YN system easily. A small amount of M phase (Y^sub 2^O3·Si^sub 3^N^sub 4^) is observed in YAN system.