Calorimetric Determinations of Thermal Radiation Characteristics

High-temperature emissivities of copper, aluminum, and silver

“…His results for aluminum were very much higher than the theoretically predicted values. The measurements on copper by Butler and Inn,' 4 Gaumer et al , 15 and Thaler et al ,16 and those on silver by Zimmermann, 1 7 Butler et al , 18 and Thaler et al were also unsatisfactory for one or more of several reasons. Some of these are (a) use of low-purity commercial grade materials with high intrinsic p values, (b) use of a coating of an absorbing material like Parson's black on the inner wall of the vacuum chamber, which results in a considerable increase in outgassing and in a higher ultimate pressure, (c) formation of a high-resistivity surface layer on the metal due to prolonged annealing at T > 1000 K in an inadequate vacuum, and (d) use of large hollow specimens with seams, enclosing electricalheating assemblies which could produce a nonuniform specimen temperature, a large correction term on account of the power leads, and a large systematic error.…”