THERMAL RADIATION CHARACTERISTICS OF TRANSPARENT SEMI-TRANSPARENT AND TRANSLUCENT MATERIALS UNDER NON-ISOTHERMAL CONDITIONS
LEXINGTON LABS INC CAMBRIDGE MA
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Thermal radiation from refractory oxides is a volume, rather than a surface phenomenon in the wavelength range 0.5-6 microns. Emissivity values were calculated for specially prepared Al2O3, MgO, SiO2 and SrTiO3 samples from appropriate reflectivities, absorption coefficients and scattering coefficients derived from material characteristics index of refraction, single crystal transmissivity, pore size and concentration. Experimental measurements of emissivity for these samples were made at temperatures up to 1200C and at wavelengths from one to fifteen microns. The Hamaker equations for non- isothermal emissivity, which linearize the temperature gradient, were compared with the exact solution by numerical integration. Evaluation of the rotating blackbody slot system indicates it gives results in good agreement with an external blackbody.
- Ceramics, Refractories and Glass