Effect of acrylate gel maker factors on properties of B۴C preforms for thefabrication of RBBC Ceramics

In this study, acrylate gel maker monomers (MAM and MBAM) were utilized in gel-castingprocess to fabricate boron carbide porous preform. In this research, by investigation ofrheological behavior of the suspension, the effects of dispersant quantity on the viscosity of B۴Cslurries were examined. It was found that optimum amount of TMAH was about ۰.۲ Wt.% ofceramic powder in such a low-toxic system. The green bodies were pyrolyezed at ۶۰۰ °C andinfiltrated by molten silicon at ۱۶۰۰ °C for ۱ h under vacuum. The influence of the amount ofmonomers (MAM+ MBAM) and also the ratio between monomers (MAM/MBAM) on thestrength of dried green body was evaluated. The flexural strength of the green body is highest atan optimum value of the monomers ratio (RM=۵), and increases with increasing monomercontent, reaching ۳۲ MPa when monomer content is ۲۵ Wt.%. The results show that moltensilicon infiltration in porous B۴C preforms produced by gel-casting process is possible and fullydense RBBC ceramics were fabricated by this method. The microstructure of the RBBCceramics consists of boron carbide particles with a core-rim structure, β-SiC and some residualsilicon. The SiC carbide particles have a polygonal shape in composites fabricated in thepresence of free carbon.

Keywords:

Gel-casting , Preform , Boron carbide , Infiltration , RBBC ceramics.