SUPPRESSION OF RADIATIONS AT HIGH TEMPERATURES BY MEANS OF CERAMIC COATINGS*

A method was developed for measuring the emissivities of ceramic coatings and ceramic-coating materials with respect to oxidized stainless steel. The emissivities in the visible-red and near-infrared spectral regions were studied over a temperature range of 800° to 1600°F. The numerous materials investigated were found to cover an emissivity range from more than 100% to less than 10%. Lepidolite was the highest emitter, Uverite the lowest. Transmission of radiant energy decreased with coat thickness according to established laws. The transmission of radiant energy through coat-bonding glasses could be greatly influenced by composition. Every material has a characteristic tendency to emit radiations at a given temperature. High-temperature ceramic paints were found to be effective radiation suppressors and thermal insulators.