Unconventional Pathways to Carbide Phase Synthesis via Thermal Decomposition of UI₄(1,4-dioxane)₂

Abstract

UI4(1,4-dioxane)2 was subjected to laser-based heatinga method that enables localized, fast heating (T > 2000 °C) and rapid cooling under controlled conditions (scan rate, power, atmosphere, etc.)to understand its thermal decomposition. A predictive computational thermodynamic technique estimated the decomposition temperature of UI4(1,4-dioxane)2 to uranium (U) metal to be 2236 °C, a temperature achievable under laser irradiation. Dictated by the presence of reactive, gaseous byproducts, the thermal decomposition of UI4(1,4-dioxane)2 under furnace conditions up to 600 °C revealed the formation of UO2, UI x , and U(C1–x O x ) y , while under laser irradiation, UI4(1,4-dioxane)2 decomposed to UO2, U(C1–x O x ) y , UC2–z O z , and UC. Despite the fast dynamics associated with laser irradiation, the central uranium atom reacted with the thermal decomposition products of the ligand (1,4-dioxane = C4H8O2) instead of producing pure U metal. The results highlight the potential to co-develop uranium precursors with specific irradiation procedures to advance nuclear materials research by finding new pathways to produce uranium carbide.

Route to Stabilization of Nanotechnetium in an Amorphous Carbon Matrix: Preparative Methods, XAFS Evidence, and Electrochemical Studies

“…When metallic Tc is formed in situ together with active carbon atoms, both components remain highly reactive and thus capable of forming Tc–C bonds. Note that the thermal decomposition of carbon-containing precursors has been successfully used for the synthesis of high-entropy (Ti, Zr, Hf, Ta, and Nb) carbide powders having great potential and wide application, or uranium carbide …”

“…Note that the thermal decomposition of carbon-containing precursors has been successfully used for the synthesis of highentropy (Ti, Zr, Hf, Ta, and Nb) carbide powders having great potential and wide application, 27 or uranium carbide. 28 A SEM image of the powder obtained by thermal decomposition and its energy dispersive X-ray (EDX) spectrum are given in Figure 3. As one can see, the decomposition products consist of agglomerates, which are merged nanoparticles (d = 100−300 nm).…”

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

“…10,11,29 The passivated surface of the baseplate can also be another source of oxygen, 47 which under reactive environments forms oxidized/reactive compounds (e.g., Ti in methane can form TiO 2 and/or TiH 2 ). 11 Since chlorine compounds were scraped off the baseplate, post-irradiation products will have more UO 2 than the iodine-based compounds. UI 4 (TMEDA) 2 and UCl 4 (TMEDA) 2 behaved similarly under each environment, but the UC content was found to be higher in the products from the thermal degradation of UI 4 (TMEDA) 2 versus UCl 4 (TMEDA) 2 .…”

“…Under laser irradiation, the combination of the rapid heating (up to 2600 °C in less than 1 ms 10,29 ) and the fast cooling rates (10 6 K/s 30,31 ) allows for reaction environments and kinetics rarely achieved via conventional methods. 11 Theoretically, if the byproducts (i.e., through thermal decomposition of the ligand) do not play a role in the ceramic formation, the resulting product should be a uranium metal. On the other hand, if an excess amount of the desired atoms (i.e., C or N), or reactive gaseous products (e.g., methane or nitrogen oxide) are made available to the reactive uranium core via decomposition/ fragmentation of the surrounding ligand groups, uranium ceramics could be formed.…”

“…In a preliminary work, a uranium iodide coordination complex, UI 4 (1,4-dioxane) 2 , was irradiated with a laser to afford uranium oxy-carbide ceramics. 11 These conditions availed a reactive uranium core to ligand fragments/ atoms as the surrounding ligands concomitantly decomposed/ fragmented. The study revealed that, even under a methane atmosphere, the competing influence of the oxygen present in the coordinating ligand prevented the complete elimination of oxygen from the system.…”