Colloidal processing of temperature shock resistant SiC with tailored porosity

Abstract

From aqueous slurries containing SiC powder coated with nano-scaled carbon black, green bodies were prepared by slip casting. On slip cast green bodies the densification , microstrucural development and mechanical properties were investigated. Depending on the sintering temperature and boron carbide content samples with different relative densities between 0.90 and 0.988 were obtained after pressureless sintering. In all samples a homogeneous microstructure (distribution of the residual pores and grain morphology) was observed. Due to this homogeneity the sintered samples showed high amount of fracture strength of about 500 MPa, even at large residual porosities of 10%. The thermal shock resistance of samples with different porosities measured by water quenching revelaed the critical temperature difference to be around 700 K.