Fabrication and characterization of reaction-bonded silicon carbide with poly(methyl methacrylate) as pore-forming agent

Reaction-bonded silicon carbide (RBSC) ceramics were prepared by liquid silicon infiltration at 1600°C using a carbon biscuit. The green body was made by slip casting a stabilized carbon powder slurry, followed by pyrolysis in a vacuum furnace at 1000°C for 2h; the density of the biscuit (ρb) was controlled using poly(methyl methacrylate) (PMMA) powder as pore former in mass proportion from 30% to 50% in 5 percentage point intervals. The particle size of the PMMA had significant effects on the microstructure, distribution of residual silicon, and the mechanical properties of the ceramic. For 40mass% PMMA with d50=1.17μm and d50=0.51μm, ρb was 0.81 and 0.82g/mL, with corresponding biscuit porosities of 51% and 50%, which gave peak values of both RBSC ceramic density of 3.07 and 3.10g/mL, and flexural strength of 741 and 794MPa, respectively. XRD analysis showed that the main phase was β-SiC, with a small quantity of α-SiC. Using PMMA with d50=0.51μm, a small quantity of residual Si was well dispersed with grain size