Complex structure reaction-bonded silicon carbide (RB-SiC) can be prepared by reactive melt infiltration (RMI) and digital light processing (DLP). However, the strength and modulus of RB-SiC prepared by DLP are not sufficient, due to its low solid content (around 40 vol.%), compared with the traditional fabrication techniques (solid content > 60 vol.%). With this understanding, a new method to improve the properties of RB-SiC was proposed, by the impregnation of composite precursor into the porous preform. The composite precursor was composed of phenolic (PF) resin and furfuryl alcohol (FA). PF and FA were pyrolyzed at 1850 °C to obtain amorphous carbon and graphite into the porous preform, respectively. The effects of multiphase carbon on the microstructure and performance of RB-SiC was studied. When the mass ratio of PF to FA was 1/4, the solid content of RB-SiC increased from 40 vol.% to 68.6 vol.%. The strength, bulk density and modulus were 323.12 MPa, 2.94 g/cm3 and 348.83 Gpa, respectively. This method demonstrated that the reaction process between liquid Si and carbon could be controlled by the introduction of multiphase carbon into the porous preforms, which has the potential to regulate the microstructure and properties of RB-SiC prepared by additive manufacturing or other forming methods.
Keywords: impregnation; mechanical performance; microstructure; multiphase carbon; reaction-bonded silicon carbide.