Spectral Emissivities of Graphite and Carbon

Abstract

The spectral emissivities of graphite and carbon have been determined at a wavelength of 0.653μ in the temperature range of 1285 to 2035°K and have been found to be temperature dependent in accordance with a prediction from a relation between reflectivity and resistivity. For polished graphite of high purity having a resistivity of about 1120 microhm‐cm the value obtained is 0.78; the value obtained for a polished high density graphite having a resistivity of 1740 microhm‐cm is 0.78; and that for polished spectroscopic carbon having a resistivity of 5080 microhm‐cm is 0.79. If graphite is sublimed from a polished surface, the latter becomes roughened, so that the emissivity increases. In one particular experiment it attained a value of 0.90.