Influence of surface oxidation on the radiative properties of ZrB 2 -SiC composites

•Surface component affected radiative properties of ZrB2-SiC composites significantly.•Emissivity in long-wave range gradually increased with the thickness of oxide scale.•The surface temperature had a little effect on radiative properties of composites.•Influence of surface roughness on emissivity could be negligible.•Covering the surface with glass is a method for improving radiative properties.