Improved oxidation resistance and infrared emissivity of tantalum disilicide particles with sol-gel derived SiO2 coatings

Abstract

As an important high-temperature structural material, tantalum disilicide (TaSi2) suffers from performance degradation associated with high temperature oxidation due to the poor oxygen diffusion barring effect of the mixed Ta2O5/SiO2 oxidation scale. In this work, silica coating was prepared on the surface of TaSi2 powder by a sol-gel method. The oxidation resistance was studied by thermogravimetric tests in non-isothermal oxidation and isothermal oxidation, as well as by oxidation treatment in a tube furnace at temperatures ranging from 800 °C to 1400 °C. The spectral emissivity of raw TaSi2, coated TaSi2 and the oxidized ones was compared and analyzed. The amorphous SiO2 coating is composed of numerous nanoparticles and covers most of the surface of TaSi2 particles. The oxidation weight gain of coated TaSi2 during heating from RT to 1200 °C and 1400 °C decreases from 29.8% and 30.9–3.0% and 8.6%, respectively. And the oxidation is controlled by diffusion in the overall process. The coated TaSi2 combines the advantageous radiation property of TaSi2 core and SiO2 coating. Compared with that of raw TaSi2, the emissivity of coated TaSi2 at the wavelength range of 200–2500 nm and 2.5–25 µm has increased by 7.5% and 13.2%, respectively, and the property did not deteriorate after oxidation at 1200 °C, suggesting that the coated TaSi2 is an excellent emitting agent during the entire service life.