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

Abstract 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 k c ) at an earlier period and diffusion (rate constant k d ) at a later period. Incorporating Zr distinctly slower oxidation rate of the Si containing SiC castables and the k c and k d 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 ZrO 2 reduced the diffusion path and concentration of O 2 , which prevented the loss of SiC and C by forming SiC fibers and reducing CO(g) to graphite, helped absorb SiO 2 to form ZrSiO 4 . It made the SiC castable a self-repairing and enhanced refractory material.