Laser-Induced Thermal Decomposition of Uranium Single-Source Precursors to Form Uranium Ceramics.

Three molecular precursors (uranium amidinate, thioamidate, and amidate) were subjected to laser-based heating to assess how laser irradiation (T > 2000 °C and rapid cooling) changes uranium material formation compared to more mild conditions in furnace heating. Simultaneous thermal analysis was conducted to study mass loss and decomposition profile of the precursors under mild conditions, and suggests formation of uranium nitride, sulfide, and oxide materials. Under laser irradiation, residual gas analysis indicates more fragmentation of ligands with increasing laser power, with small gases such as N2, CO, and small hydrocarbons being the primary gaseous byproducts. Powder X-ray diffraction (PXRD) of the solid-state product formed from an amidinate precursor indicates formation of uranium carbide at lower laser powers, but uranium nitride at higher laser powers. PXRD for amidate and thioamidate precursors reveals nitride and carbides as major products. This suggests that the reactive environment created by the laser and gaseous byproducts is more influential than the pre-existing U-N, U-S, and U-O bonds, which are favored in furnace experiments. Overall, this study demonstrates the varied uses of these molecular precursors when subjected to differing thermal conditions, and their utility for the formation of uranium nitride and uranium carbide under laser irradiation.