SPECTRAL EMITTANCE AND REFLECTANCE OF POWDERS
AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA
Pagination or Media Count:
The emittance of well-sized corundum powders in the range between 1- 30 microns was measured by infrared interferometry in the 7.5-25 micron region of the spectrum wavenumber 400-1300. The spectral features persist for all particle sizes with some interesting relative intensity variations. The temperature of the radiating surface is determined by setting the emittance equal to unity at wave number 1035. At this point it is known that both orientations of corundum have a refractive index close to unity and the absorption coefficient is quite small. Thus both the volume and the surface reflectance terms are negligible and hence the emittance is approximately 1. The same powders have been measured in reflectance using a Cary-White spectrometer. A quantitative comparison is made between the two techniques and Kirchoffs law is shown to apply experimentally.