STUDY OF PHYSICAL, THERMAL AND MECHANICAL PROPERTIES OF SOME CERAMIC MATERIAL

Abstract

The applications of RB-Si-SiC and RB-Si-SiC-MoSi2 are based on a reaction sintering process, whereby a compacted body of(a-SiC + C/Cf) and (a-SiC + C/Cf+ Mol MoSi2) respectively are sintered and then infiltrated by silicon which impregnates the body, converting both carbon powder or carbon fibers to 13-SiC or fibrous 13-SiC respectively which bond the original alpha grains and transforms Mo3C2 produced by sintering to

MoSi2

The dependence of the green density on both uniaxial pressing and grain size of SiC powder was investigated. The results obtained from these measurements revealed that the green density increases as the pressure increases up to 300 MPa, after this point the green density remains constant with increasing pressure. The green density increases as the grain size of SiC powder increases. The effect of the green density on sintered and infiltrated density was investigated. However the sintered and infiltrated densities are improved by increasing the green density. X-ray diffraction patterns were used to find out the different phases formed in the specimens after sintering and infiltration. The obtained results showed that the Mo3C2 formed after sintering due to the addition ofMo or MoSi2, disappeared after infiltration through the formation ofMoSi2 . The results showed also that with increasing the content of carbon powder or carbon fibers, the volume of secondary SiC after infiltration increases on the expense of residual free silicon. Finally, these results showed no evidence of carbon particles, carbon fibers and Si02 phases after infiltration.