Fabrication of reaction-bonded silicon carbide via phenolic/epoxy resin gelcasting
This work aims to explore a low-cost and environmentally friendly shaping method to prepare re-action-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 trea-ted 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 microstruc-ture,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 car-bon in the resin system reacts with molten silicon,the cold modulus of rupture of the fired sample first in-creases 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.
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