Incorporating Zr combined Si and C to achieve self-repairing ability and enhancement of silica sol bonded SiC castables

SiC based refractory is an environment-friendly lining material for high-temperature solid waste gasifier and urgently required longer service life. In this paper, the efficiency of silica sol bonded SiC castables introducing different amounts of Zr combined Si and C was evaluated by considering their sintered properties, mechanical performance, isothermal oxidation behavior, microstructure, and thermodynamics. It was found that the oxidation of SiC castables follows a two-stage kinetic model, controlled by oxidation (rate constant kc) at an earlier period and diffusion (rate constant kd) at a later period. Incorporating Zr distinctly slower oxidation rate of the Si containing SiC castables and the kc and kd were reduced by 18.9% and 9.2% with addition of 0.6 wt% Zr, respectively, compared to the unmodified sample. The Zr-modified SiC castables exhibited good mechanical behavior, increased bulk density, and reduced porosity. The oxidation of Zr to ZrO2 reduced the diffusion path and concentration of O2, which prevented the loss of SiC and C by forming SiC fibers and reducing CO(g) to graphite, helped absorb SiO2 to form ZrSiO4. It made the SiC castable a self-repairing and enhanced refractory material.