Reflectance Variables of Compacted Powders
Numerous factors were found to modify the spectral reflectance of compacted powders in the 0.23 to 2.65µ range. Particular variables of importance were opacity of the particles, degree of compaction, chemical composition and temperature. Other variables studied included particle size, liquid impurities, and effect of vacuum. Transparent particles, such as white oxides, underwent a large decrease in reflectance with increasing compaction, while opaque particles, such as metals and dark nonoxides, underwent a small increase. Particle size variations from 30 to 105µ did not change the reflectance of compacted pure materials. However, particle size was of importance when considering mixtures, since it controlled the relative surface areas of the components. Equations were developed to enable approximate calculation of the reflectance of compacted powder mixtures. Liquid additions to the powders were found to decrease the reflectance of the compacts, and the decrease was greatest for materials having transparent particles. Heating of compacted oxides resulted in either a decrease or increase in reflectance depending on the material and the temperature. Exposure of specimens to vacuum usually resulted in random small variations in reflectance.
KeywordsSpectral Reflectance Compaction Pressure Dibutyl Phthalate Compact Powder Ethyl Benzoate
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