MEASUREMENTS OF RADIATIVE PROPERTIES OF CELLULAR CERAMICS AT HIGH-TEMPERATURES

The extinction coefficient and the single scattering albedo of selecte d cellular (reticulated) ceramics that are candidates for use in radia nt burners were determined in the 1200-1400 K temperature range. Total radiation intensities leaving layers of the reticulated material heat ed to steady state in a tube furnace with two different boundary condi tions were measured. An inverse radiation approach involving the two-f lux approximation using a gray, isotropically scattering model was use d to obtain the radiative properties from the measured intensities. Ab ove an optical thickness of unity, this procedure was not sufficiently sensitive to yield the extinction coefficient. For such cases, the ex tinction coefficient was estimated from the geometric optics limit. Th e single scattering albedos varied from 0.68 to 0.88 with an uncertain ty of +/-7%, whereas the extinction coefficients varied from 81 to 270 m(-1) with an uncertainty of +/-11%, depending on the number of pores per centimeter and the sample material. In the range of temperature i nvestigation the variations in the radiation properties were not signi ficant.