Laser-Induced Thermal Decomposition of Uranium Coordination Compounds with Non-oxidic Ligands to Produce Nitride and Carbide Materials

Abstract

The production of ceramics from uranium coordination compounds can be achieved through thermal processing if an excess amount of the desired atoms (i.e., C or N), or reactive gaseous products (e.g., methane or nitrogen oxide) is made available to the reactive uranium metal core via decomposition/fragmentation of the surrounding ligand groups. Here, computational thermodynamic approaches were utilized to identify the temperatures necessary to produce uranium metal from some starting compoundsUI4(TMEDA)2, UCl4(TMEDA)2, UCl3(pyridine) x , and UI3(pyridine)4. Experimentally, precursors were irradiated by a laser under various gaseous environments (argon, nitrogen, and methane) creating extreme reaction conditions (i.e., fast heating, high temperature profile >2000 °C, and rapid cooling). Despite the fast dynamics associated with laser irradiation, the central uranium atom reacted with the thermal decomposition products of the ligands yielding uranium ceramics. Residual gas analysis identified vaporized products from the laser irradiation, and the final ceramic products were characterized by powder X-ray diffraction. The composition of the uranium precursor as well as the gaseous environment had a direct impact on the production of the final phases.

Comparison of the structural, electrochemical, and spectroscopic properties of two cryptates of trivalent uranium

“…1–3 Reported studies in this area provide insight into potential uses of depleted uranium and fundamental knowledge of uranium coordination chemistry involved in applications such as actinide separations in nuclear waste. 4–8 Within this context, there have been widespread reports of redox-active and redox-inactive ligands used to form complexes of U III , 9–16 and one of those ligands, 2.2.2-cryptand, has been widely used to encapsulate metal ions, including U III . 17–19 Further, the coordination chemistry of U III , Np III , and Pu III with 2.2.2-cryptand has been reported recently, 20 expanding cryptand chemistry into the actinides.…”