The emissivities of various niobium surfaces in the temperature range 500-1100° C

The total hemispherical emissivities of various niobium surfaces have been determined in the temperature range 500-1100° C with accuracy to 5% or better. The specimens were in the form of tubes, and the five surfaces were (i) in the as-manufactured condition, (ii) deoxidized and (iii) three types with varying degrees of nitriding. During the investigation, it was found that the emissivities altered with heat treatment. Sets of results are therefore given for both the initial and final conditions, the latter being the state reached when no further change could be detected.