Abstract
Thermal emissivity of commercial nuclear graphites (IG-110, PCEA, IG-430 and NBG-18) following changes in oxidation degrees were examined. Specimens were oxidized to 0%, 5%, and 10% in air flow of 5l/min at <TEX>$600^{\circ}C$</TEX> using a furnace, and the thermal emissivities were measured using an infrared spectrum analyzer. The measuring temperatures for the thermal emissivity were <TEX>$100^{\circ}C$</TEX>, <TEX>$200^{\circ}C$</TEX>, <TEX>$300^{\circ}C$</TEX>, <TEX>$400^{\circ}C$</TEX> <TEX>$500^{\circ}C$</TEX>. Also density and porosity of the specimens were observed to compare with thermal emissivity. Results showed that emissivity increased with oxidation, and the 10% oxidized NBG-18 showed the highest emissivity (0.890) which value is larger for 24% than the value of as-received specimen. Investigation of factors affecting the emissivity revealed that increases in the surface roughness and porosity due to oxidation were responsible for the increase in emissivity after oxidation.
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