Preparation and Microstructure of Pressureless Sintered Si_2ON_2-SiC Ceramic

摘要

This paper introduces Si_2ON_2-SiC ceramic fabricated by pressureless sintering method and studies the effect of additives, nitriding temperatures on bulk density, porosity, phase composition and microstructure. It is discovered that additives MgO, CeO_2 can increase the densities of Si_2ON_2-SiC ceramic apparently, and MgO additive has a better effect than CeO_2. Nitriding temperature also is an important factor. The bulk density of the specimen with MgO additive reaches maximum at 1.91 g/cm~3 when sintered at 1450 °C, and the bulk density of specimen with CeO_2 additive is 1.86 g/cm~3 at the same condition while the bulk density of the specimen without additive is only 1.75 g/cm~3. The X-ray diffraction and scanning electron microscopy of the specimens show that the amount of Si_2N_2O increase with the sintering temperature increase. But when the temperature is higher than 1500 °C the Si_2ON_2 grains will decompose into Si_3N_4, and Si_2ON_2 will vanish at 1550 °C.