Formation of Oxides Upon Thermal Debinding and Their Role in Obtaining Reaction-Bonded Silicon Carbide

A study has been made of the formation of silicon oxides on the surface of silicon carbide upon thermal removal of a paraffin binder from a powder silicon-carbide casting in an air atmosphere at a temperature of 600–900°C. An optimum temperature of 630°C of the process was determined which allows obtaining the SiC base with maximum porosity and a mechanical bending strength of 0.5 MPa. It has been shown that surface oxides are reduced by solid carbon in the process of manufacture of the composite C–SiC at the stage of pyrolysis in vacuum at 1600°C and exert no influence on the following process of liquid-phase C–SiC siliconizing when reaction-bonded silicon-carbide ceramics is obtained. The amount of solid carbon expended on reducing the oxides makes up an appreciable part of the carbon introduced into the pores of the SiC base when C–SiC is prepared for siliconizing and must be taken account of as a correction in calculations of the composition of the intermediate and final materials of the ceramics.