Aqueous gelcasting of solid-state-sintered SiC ceramics with the addition of the copolymer of isobutylene and maleic anhydride

Abstract

As a nontoxic and eco-friendly gelling agent, the copolymer of isobutylene and maleic anhydride (PIBM) was successfully used for aqueous gelcasting of dense solid-state-sintered SiC (S-SiC) ceramics. We acquired low-viscosity SiC-B4C-C slurry with an ultrahigh solid loading of 55 vol% through a synergy strategy of surface modification and particle grading of fine (D50 =˜ 0.5 μm) and coarse (D50 = ˜4.6 μm) SiC powders. With the addition of a low amount (0.3 wt%) of PIBM, the slurries were in-situ solidified to form green bodies after kept 2 h at room temperature. Gelcasted S-SiC ceramics were sintered at 2160 °C and densified with relative densities of ≥95.9%. The sintered bulks possessed fine equiaxed grains of uniform size owing to the pinning effect of coarse SiC particles, and presented a moderate flexure strength of 291 ± 8 MPa and a high fracture toughness of 4.55 ± 0.46MPam1/2.