Normal emittance measurements by a transient temperature technique

Abstract

Normal spectral emittance measurements from 5000 to 400 cm−1, and normal total emittance measurements, were made for sapphire and polycrystalline aluminas using Fourier-transform infrared spectroscopy. Samples were dropped from a furnace into the nitrogen ambient of the spectrometer to the position where the internal global source is normally focused. Radiance was measured as the alumina cooled to derived emittances from 900 to 1450 K. The temperatures were determined from radiance measurements at 1027 cm−1 where alumina has zero reflectivity and transmittance. Standard deviations of total normal emittance measurements averaged over three drops were ≤0.3% of the averages.