Alloying and hydrogenation of u-metal as a probe into the 5f-magnetism

Uranium exists in 3 possible allotropic phasesα-U, β-Uand γ-U. Variation of lattice parameters and inter-uranium distances in different crystal structures can play an important role in electronic properties, in analogy with various U-based compounds. Electronic properties are well known only for α-U, which is stable at room temperature (below 942 K) and crystallizes in an orthorhombic structure. β-phase having a tetragonal structure with large unit cell is stable in the range 942-1049 K. As γ-U phase with a cubic bcc structure is stable at even higher temperatures (1049-1408 K), the low temperature properties remained unknown for γ-U. On the other hand, bcc U can be retained to low temperatures in the form of highly alloyed (Mo, Zr) U for metals fuels, at which the bcc structure provides better mechanical properties and higher resistance to irradiation effects [1]. We decided to use the doping by Mo or Zr in conjunction with the splat-cooling technique, which could help to stabilize γ-U phase to room temperature with minimal amount of dopants in the alloys.In addition, we have studied interaction of these alloys with hydrogen gas, which leads to the formation of hydrides. Hydrogenation can be considered as a "negative" pressure effect, which expands the lattice and therefore also change the inter-uranium distances