Effects of SiC shape and oxidation on the infrared emissivity properties of ZrB2–SiC ceramics

• SiC affected infrared emissivity by changing propagation of electromagnetic waves.
• SiC particle with high surface area decreased infrared emissivity of samples.
• The oxide layer changed the increase rate of infrared emissivity of samples.
• The columnar ZrO2 on the sample surface degenerated the infrared emissivity.

ZrB2–SiC ceramics were prepared by hot-pressing sintering using SiC whiskers and SiC particles and the effects of SiC shape and oxidation on the infrared emissivity properties of ZrB2–SiC ceramics were investigated systematically. SiC whiskers and SiC particles affected the spectral emissivity of ceramics by changing the propagation direction of electromagnetic waves. Compared with SiC particles, SiC whiskers had smaller surface area at the same volume ratio and caused relatively higher infrared emissivity in ceramics. After oxidation at 1300 °C for different time, the total emissivity of ZrB2–SiC ceramics varied in 0.70–1.00. The oxide layer on sample surface slowed down the increase rate of infrared emissivity and the substrate dominated the radiant behavior of ceramics. The investigation also illustrated that the exposed ZrO2 on the samples surface degenerated the infrared emissivity properties of ZrB2–SiC ceramics.