Total Normal And Total Hemispherical Emittance Of Polished Metals - Part II

Abstract:
The total hemispherical emittance, the total normal emittance, the spectral emittance at 0.65 microns and the electrical resistivity were measured on freshly rolled and polished surfaces of molybdenum in a vacuum over a temperature range from 1100°K to 1800°K. The total hemispherical emittance was obtained from the measured power dissipation at the center of an electrically heated strip suspended in a vacuum while its temperature was measured using a themocouple. The total normal emittance was measured using a radiation thermopile. The ratio of total hemispherical to total normal emittance was also calculated directly from the angular distribution of radiation obtained by revolving the detector about an axis through the ribbon.

Observations were also made on the time variation of the total hemispherical emittance of platinum. Small increases were noted in the emittance while thermal etching of the boundaries between the crystals was followed by time lapse photomicroscopy of the heated surface.