关键词: 反应烧结碳化硅, 凝胶注模, 酚醛树脂, 环氧树脂

Abstract: This work aims to explore a low-cost and environmentally friendly shaping method to prepare reaction-bonded silicon carbide (RBSC) materials,SiC fine powder and micropowder,phenolic resin,and epoxy resin were used as the main raw materials,tetramethylammonium hydroxide as the dispersant to prepare SiC ceramic slurries with a solid loading of 55 mass% and phenolic resin mass fractions of 13.5%,18%,22.5%,and 27%,respectively.The green bodies prepared by gelcasting and cured were heat treated at 800 ℃ for 2 h,followed by heat treatment at 1 760 ℃ for 3 h in vacuum to form the RBSC materials.The curing mechanism of the green bodies and the effect of the phenolic resin addition on the microstructure,phase composition,and physical properties of the samples were studied.The results show that:(1)the curing mechanism of the green body is that the hydroxymethyl groups in the phenolic/epoxy resin undergo cross-linking via condensation reactions with ortho-para hydrogen atoms in the aromatic ring,forming a high-strength bonding network;(2)with the increasing phenolic resin addition,the residual carbon in the resin system reacts with molten silicon,the cold modulus of rupture of the fired sample first increases and then decreases;when the addition of phenolic resin is 18%,the cold modulus of rupture of the sample is the highest,reaching 79.9 MPa;the apparent porosity and bulk density of the sample are 1.1% and 2.88 g·cm^-3,respectively.

Key words: reaction-bonded silicon carbide, gelcasting, phenolic resin, epoxy resin