Gelcasting of sintered reaction-bonded silicon nitride for improved mechanical properties

摘要

Gelcasting of silicon metal for the production of sintered reaction bonded silicon nitride (SRBSN), was investigated in order to identify associated advantages over conventional forming techniques; i.e., die and isostatic pressing. Compacts were formed from identical powder mixtures by both gelcasting and pressing, and were nitrided and sintered to produce SRBSN ceramics. Characterization of the samples included measurement of green density, green and nitrided pore structure, weight gain during nitridation, final density, microstructure, toughness, and flexural strength. It was found that a more uniform pore structure existed in the green gelcast samples. It is believed that this pore configuration aided in nitridation, and manifested itself in a more uniform final microstructure. In addition, improved mechanical properties were achieved in the gelcast samples. This improvement can be attributed to green microstructure homogeneity.