Morphological and functional effects of graphene on the synthesis of uranium carbide for isotopes production targets

Abstract

The development of tailored targets for the production of radioactive isotopes represents an active field in nuclear research. Radioactive beams find applications in nuclear medicine, in astrophysics, matter physics and materials science. In this work, we study the use of graphene both as carbon source for UO2 carbothermal reduction to produce UCx targets, and also as functional properties booster. At fixed composition, the UCx target grain size, porosity and thermal conductivity represent the three main points that affect the target production efficiency. UCx was synthesized using both graphite and graphene as the source of carbon and the target properties in terms of composition, grain size, porosity, thermal diffusivity and thermal conductivity were studied. The main output of this work is related to the remarkable enhancement achieved in thermal conductivity, which can profitably improve thermal dissipation during operational stages of UCx targets.

Effect of graphite and graphene oxide on thorium carbide microstructural and thermal properties

“…As in SEM, not many structural differences can be observed between the two materials. No evidence of a discrepancy in carbon distribution around thorium carbide grains is found, contrary to what reported for uranium carbide 17 . The analysis of ring diffraction patterns suggests, however, that the crystalline part of the ThCx–GO sample is polyphasic, with the onset of a cubic phase (ThO 2 ) and a monoclinic one (ThC 2 ), whereas ThCx–graphite is found to be monophasic.…”

“…Both show a microstructure composed of a dispersion of residual carbon (dark grains) in a partially sintered thorium carbide matrix. In ThCx–GO, carbon is clearly visible, contrary to what was found in UC x –graphene in another study 17 , but it is equally well dispersed. It must be remarked that in this case graphene oxide was used instead of pure graphene.…”

“…It must be remarked that in this case graphene oxide was used instead of pure graphene. ThCx–graphite microstructure resembles that of previously obtained carbides using the very same graphite 17 , 19 , whose size is in the order of tens of μm.

Figure 6 SEM images taken on the surface and along thickness of ( a , b ) ThCx–GO and ( c , d ) ThCx–graphite.

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“…The powders were then further mixed in the ball mill (3 h at 3000 rpm). The pressing conditions and the heat treatment conditions were similar to those reported in 17 . At least five pellets of 13 mm diameter and about 1 mm thickness were prepared for each batch (ThO 2 –Graphite and ThO 2 –GO).…”

“…Composites materials demonstrated 16 better thermal properties and thus are of interest for our application. In our previous collaborative work, graphene had the effect of improving thermal properties of uranium carbide–carbon composites 17 . In the present study, graphene oxide was used, with the aim of exploiting its low-temperature reduction 18 and the related gas release during thermal treatment, thought to be beneficial for the creation of interconnected micro- and meso-porosity, and consequently for obtaining a high SSA.…”