A low cost preparation of C/SiC composites by infiltrating molten Si into gelcasted pure porous carbon preform

C/SiC composites were prepared by infiltrating molten Si into gelcasted pure porous carbon preforms derived from mesocarbon microbeads (MCMBs). First large size flaw-free carbon preforms with smooth surfaces were produced by gelcasting method. The porosity and pore size of the carbonized preforms can be adjusted by changing the solid loading (MCMBs) ranging from 40 to 65 wt%. Subsequently, C/SiC composites were fabricated by liquid silicon infiltration of the porous carbon preforms. The results show that the preforms with solid loading from 40 to 50 wt% were completely infiltrated with Si and formed a C/SiC with homogeneous microstructure. While "SiC shell - black carbon core" structures were observed for the C/SiC composites with solid loading above 50 wt%, indicating that the Si infiltrating process was stopped in the surface of the preform. Reaction and infiltration mechanism analysis reveals that the siliconization process of porous carbon preform and the microstructures of the C/SiC samples were mainly affected by the reaction activity of carbon materials and pore structures of carbon preforms.