Synthesis and high-temperature oxidation resistance of SiC-ZrB2 composite powders via carbothermal reduction
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SiC-ZrB2 composite powders were synthesized via carbothermal reduction using silica sol (SiO2·nH2O), graphite (C), boric acid(H3BO3), and zirconium dioxide (ZrO2) as raw materials. The effect of calcination temperature on the synthesis process wasinvestigated by holding the mixture at temperatures ranging from 1450 to 1600 °C for 1 h. Composite powders synthesizedunder optimized conditions was subsequently selected to systematically evaluate its high-temperature oxidation resistance. Results indicate that holding at 1600 °C for 1 h represents the optimal synthesis condition, producing high-purity SiCZrB2composite powders. The powder exhibits a heterogeneous microstructure comprising near-spherical particles, columnarparticles, irregularly structured particles, and whiskers. Stepwise oxidation testing revealed the following: At 800 °C, ZrB2 wascompletely oxidized to ZrO2, while a small amount of SiC reacted with oxidation products to form zircon (ZrSiO4). Above1200 °C, the oxidation of SiC increased substantially, accompanied by significant sintering, leading to the formation of denseagglomerates. Notably, SiC remained stable at 1500 °C, exhibiting markedly superior oxidation resistance compared to ZrB2.
Abstract
SiC-ZrB2 composite powders were synthesized via carbothermal reduction using silica sol (SiO2·nH2O), graphite (C), boric acid(H3BO3), and zirconium dioxide (ZrO2) as raw materials. The effect of calcination temperature on the synthesis process wasinvestigated by holding the mixture at temperatures ranging from 1450 to 1600 °C for 1 h. Composite powders synthesizedunder optimized conditions was subsequently selected to systematically evaluate its high-temperature oxidation resistance. Results indicate that holding at 1600 °C for 1 h represents the optimal synthesis condition, producing high-purity SiCZrB2composite powders. The powder exhibits a heterogeneous microstructure comprising near-spherical particles, columnarparticles, irregularly structured particles, and whiskers. Stepwise oxidation testing revealed the following: At 800 °C, ZrB2 wascompletely oxidized to ZrO2, while a small amount of SiC reacted with oxidation products to form zircon (ZrSiO4). Above1200 °C, the oxidation of SiC increased substantially, accompanied by significant sintering, leading to the formation of denseagglomerates. Notably, SiC remained stable at 1500 °C, exhibiting markedly superior oxidation resistance compared to ZrB2.