Fabrication of Porous SiC Ceramics Using Glass Beads

摘要

Porous SiC ceramics have been fabricated by using SiO_2-Al_2O_3 based glass beads. SiC powder with the anerage grain size of 0.6 #mu#m was mixed with 5-20 wt. percent glass beads by dry mixing. The average particle size of the glass beads was about 45 #mu#m. The mixed powder was compressed into plate form and sinterd at 1970 deg C for 2 hours in Ar atmosphere. The resultant materials had porosities ranging from 25 to 50 percent. Large spherical pores connecting through micro-sized open pores were observed in their microstructures. It has been concluded that the occurence of open pores was orginated in the formation of gas phase through the reaction SiC+2SiO_2->3SiO(g)+CO(g), in Ar atmosphere. The alumina element in the glass beads contributed to the densification of SiC matrix through the formation of liquid phase and as a result, the materials had high bending strength in spite of their high porosity.