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 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 ZrO2 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 SiO2 to form ZrSiO4. It made the SiC castable a self-repairing and enhanced refractory material. (C) 2017 Elsevier B.V. All rights reserved.