Thermal emissivity and high-temperature stability of thermal insulating materials produced by mixing powdered porous MgAl2O4 ceramics with commercial insulating castable
Journal of the Ceramic Society of Japan
Conventional industrial thermal insulating materials have a porous structure and provide resistance to thermal conduction. However, this structure permits heat transfer through radiation. Hence, they exhibit high thermal conductivity at temperatures higher than 1000°C. To achieve high total-thermal-insulation efficiency, we recently developed new insulating materials, called THERMOSCATT TM , which greatly suppress radiation heat transfer. Their thermal conductivity was measured to be less than
... ed to be less than 0.3 W/(m·K) at 1500°C. These insulating materials consist of porous MgAl 2 O 4 ceramics having 15¯m pores which restrain heat transfer through radiation, which was consistent with the Mie scattering theory. From the thermal emissivity estimated from reflectance measurements, the porous MgAl 2 O 4 ceramics had near-zero hemispherical spectral emissivity values in the wavelength range of 0.355¯m. Mixing these powdered porous MgAl 2 O 4 ceramics with a conventional commercial insulating castable ceramics is shown to successfully reduce heat transfer through radiative Mie scattering. This report describes the experimental result of the powdered porous MgAl 2 O 4 ceramics mixed into the commercial insulating castable.