Effect of Co-W-WC Proportion on the Microstructure and Optical Properties of SiO₂ Film Prepared by HVOF for Sensor

The absorption layers of CO-W-WC with different ratios were prepared by supersonic flame spraying(HVOF). Then the SiO₂ composite film was prepared on the surface of the absorption layer by the sol-gel method,and its microstructure and optical properties were tested. The results show that characteristic peaks of Co,W,and WC are formed in the composite film,and some Hcp-Co particles transform into Fcc-Co structure in the spraying stage. After gradually increasing the amount of WC,fewer dispersive unmelted particles were formed on the surface of the composite film,and a smooth and dense structure was obtained. When W:WC reaches 1:1,it helps to reduce the surface roughness and make the absorption layer obtain lower emissivity. After gradually reducing the ratio of W/WC,the reflectivity increases and the absorption decreases,indicating that W has a stronger spectral absorption capacity than WC. SiO₂ thin films have a low refractive index,which facilitates the transmission of shortwave light so that the absorption layer can obtain more incident light. After 100 h heat treatment,the absorptivity increased to 0.915 and the emissivity reached 0.2516. No composite film shedding was observed,indicating that the SiO₂ composite film has stable optical properties.