High - temperature emissivities of copper , aluminum , and silver

Using a transient calorimetric technique, the total hemispherical emissivities Eh of very pure copper, aluminum, and silver have been measured at various temperatures in the range 335-1100'K. By carrying out measurements on a sphere, a thin circular disk, and a thin square plate all made of the same copper sample, it is shown that the measured (, is practically independent of the shape of the specimen. Measured E,, values of Cu, Al, and Ag show considerable departure from the theoretical predictions of Davisson and Weeks and the data of previous investigators. Eh data are presented in tabular form at 20'K intervals for all three materials in the range 400-1000'K.