Near-infrared optical properties of a porous alumina ceramics produced by hydrothermal oxidation of aluminum

•The transport scattering albedo is retrieved from the normal-reflectance measurements.•The known data for absorption coefficient of alumina in a wide temperature range are used.•The absorption coefficient is obtained using the additive hypothesis for porous ceramics.•The Mie theory for grains in porous ceramics is used to estimate near-infrared scattering.

The measured spectral normal–hemispherical reflectance of an optically thick sample of porous alumina ceramics produced by hydrothermal oxidation of aluminum and subsequent high-temperature treatment of boehmite (or böhmite), AlO(OH), is used in a combination with the published data for absorption coefficient of alumina to retrieve the near-infrared optical properties of the alumina ceramics at both room and elevated temperatures. The spectral emissivity of porous alumina ceramics is also determined. An approximate model based on the Mie theory for single grains is suggested to estimate the transport scattering coefficient and the radiative conductivity of the material at high temperatures.