The anti-oxidation behavior and infrared emissivity property of SiC/ZrSiO4–SiO2 coating

Abstract

In order to improve the oxidation resistance and decrease the infrared emissivity of carbon/carbon(C/C) composites, the SiC and SiC/ZrSiO4–SiO2 (SZS) coating were prepared by pack cementation and slurry painting method. The phase compositions and microstructures of the as-prepared coatings were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer. The anti-oxidation property, failure and infrared emissivity of single SiC coating and SZS coating were investigated. The results show that the weight loss of single SiC coated sample reached 2.1 ± 0.025 % after 58 h isothermal oxidation at 1,500 °C. While the SZS coating exhibits superior oxidation resistance and can protect C/C matrix from oxidation for more than 198 h with a weight-gain of 3.67 ± 0.025 %. The failure mechanisms of single SiC coating are mainly resulting from unself-healing defects caused by the CO2 gas which generated during the oxidation process of SiC. The investigation of infrared emissivity property reveals that, the infrared emissivity of SZS coating increases gradually from 0.45 to 0.72 between 3 and 14 μm. The infrared emissivity at 500 °C increases gradually from 0.2 to 0.65 between 3 and 14 μm. The coupled effect between dipole moments and lattice vibration in higher temperature becomes weaker, which in turn lead to the reducing of infrared emissivity in turn. From the anti-oxidation and infrared emissivity property point of view, the SZS coating may be one of the most promising candidates for the anti-oxidation at high temperature and low infrared emissivity of C/C composite.