Fabrication and thermal conductivity of UN-UB2 composites fabricated by spark plasma sintering

Abstract

The fabrication and thermal conductivity of mixed-phase UN-UB2 composite pellets has been investigated using the laser flash method. Composites were fabricated by synthesizing UB2 and UN via the carbo/borothermic reduction and hydriding-nitriding-denitriding routes respectively, followed by spark plasma sintering of pellets at 1973 K. Combustion analysis of the synthesized powder showed the existence of C impurity in the synthesized UN. A U-B-N ternary phase formed during SPS fabrication, as an interaction product between the UN and UB2. Analysis of the thermal diffusivity of the composites indicated the partial oxidation of the composites during measurements. The corrected thermal conductivity of the composites was found to increase with increasing UB2 content up to 1073 K (maximum temperature measured). The fabricated composites showed a higher thermal conductivity than the reported UN at low temperatures (673 K). However, the increase was less significant at higher temperatures and the thermal conductivity was found to be lower than UN for composites with low UB2 content (up to 10 wt.%), potentially due to impurities within the synthesised UN.