Cubic γ-phase U–Mo alloys synthesized by splat-cooling

Nhu.-T.H. Kim-Ngan, I Tkach, S Maskova, L. Havela, A D Warren, Thomas Bligh Scott

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Abstract

U–Mo alloys are the most promising materials fulfilling the requirements of using low enriched uranium (LEU) fuel in research reactors. From a fundamental standpoint, it is of interest to determine the basic thermodynamic properties of the cubic γ-phase U–Mo alloys. We focus our attention on the use of Mo doping together with ultrafast cooling (with high cooling rates ≥106 K s−1), which helps to maintain the cubic γ-phase in U–Mo system to low temperatures and on determination of the low-temperature properties of these γ-U alloys. Using a splat cooling method it has been possible to maintain some fraction of the high-temperature γ-phase at room temperature in pure uranium. U-13 at.% Mo splat clearly exhibits the pure γ-phase structure. All the splats become superconducting with Tc in the range from 1.24 K (pure U splat) to 2.11 K (U-15 at.% Mo). The γ-phase in U–Mo alloys undergoes eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and tetragonal γ'-phase upon annealing at 500 °C, while annealing at 800 °C has stabilized the initial γ phase. The α-U easily absorbs a large amount of hydrogen (UH3 hydride), while the cubic bcc phase does not absorb any detectable amount of hydrogen at pressures below 1 bar and at room temperature. At 80 bar, the U-15 at.% Mo splat becomes powder consisting of elongated particles of 1–2 mm, revealing amorphous state.
Original languageEnglish
Article number035006
Number of pages10
JournalAdvances in Natural Sciences: Nanoscience and Nanotechnology
Volume4
Issue number3
Early online date14 Jun 2013
DOIs
Publication statusPublished - Sep 2013

Keywords

  • cubic γ -U
  • U–Mo alloys
  • splat cooling
  • superconductivity
  • hydride

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