Emissivity and structure of anodized beryllium

Results are presented on the emissivity of anodized beryllium between $400$ and $1000$ degree K in relation to the thickness and structure of the oxide layer. A stable emissivity is found for anodized beryllium bearing an oxide film annealed in air. Metastable structures in the oxide film alter the emissivity of anodized beryllium considerably. An amorphous oxide layer reduces the integral normal degree of blackness relative to equilibrium $\rm BeO$, whereas a hydrated film deficient in oxygen increases the value.