Thermal diffusivity, thermal conductivity and spectral emissivity of uranium dicarbide at high temperatures

Thermal diffusivity and thermal conductivity between 600 and 20700C, and spectral emissivity at 0.65 and at 2.3 micron between 1000 and 20700C have been determined for UC2 samples with C/U approximately equal to 1.8 with a modulated-electron-beam thermal-diffusivity apparatus. Some associated thermophysical properties are discussed in accordance with metallographic microscopic examinations and x-ray diffraction analysis. The transformation of the samples into the (UC + UC2) cubic solid-solution phase is clearly observable through the four measured quantities. Formation of U2C3, between 1100 and 16000C, was accompanied by an increase of the diffusivity and, indirectly, through cracks and holes, of the emissivities, but the conductivity remained unchanged. A simple but reliable procedure for correcting temperature measurements with a two-colour pyrometer when the sample cannot be regarded as a gray body, as is the case for UC2, is described. (author)