Characterization of cubic γ-phase uranium molybdenum alloys synthesized by ultrafast cooling

► U-Mo alloys prepared by splat cooling. ► A small amount of γ-phase was preserved in pure splat-cooled uranium specimen. ► Crystal structure characterized by X-ray diffraction and EBSD. ► A stability of γ-phase for alloys with 11–15at.% Mo. ► Superconducting transition, Tc=1.24K (pure-U) to 2.11K (...

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Bibliographic Details
Published in:Journal of alloys and compounds 2012-09, Vol.534, p.101-109
Main Authors: Tkach, I., Kim-Ngan, N.-T.H., Mašková, S., Dzevenko, M., Havela, L., Warren, A., Stitt, C., Scott, T.
Format: Article
Language:English
Subjects:
Alloys
Condensed matter: structure, mechanical and thermal properties
Cooling
Electrical resistivity
Electron back scatter diffraction
Exact sciences and technology
Inorganic compounds
Molybdenum base alloys
Physics
Scanning electron microscopy
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
Superconductivity
U-Mo alloys
Uranium
γ-Uphase
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Summary:► U-Mo alloys prepared by splat cooling. ► A small amount of γ-phase was preserved in pure splat-cooled uranium specimen. ► Crystal structure characterized by X-ray diffraction and EBSD. ► A stability of γ-phase for alloys with 11–15at.% Mo. ► Superconducting transition, Tc=1.24K (pure-U) to 2.11K (U-15at.% Mo). U-Mo alloys with Mo concentration in the range of 0–15at.% Mo were prepared using a splat-cooling technique. Phase analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD) revealed the presence of a small amount of γ-U phase retained at room temperature alongside the majority α-U phase and opening the possibility of stabilizing the γ-phase at room temperature in uranium metal by ultrafast cooling. The double-phase (α+γ) structure with predominance of the α-phase was obtained in the alloys with 0–10at.% Mo. Increasing further Mo doping leads to the γ° phase (for 11–12at.% Mo) and pure cubic γ phase (for 15at.% Mo). The superconducting transition was investigated by low-temperature resistivity measurements down to 0.3K in magnetic fields up to 5T. All the splats become superconducting with Tc in the range from 1.24K (pure U splat) to 2.11K (U-15at.% Mo). The superconductivity in the γ-phase alloys exhibited a much higher upper critical field than for α-phase material. Electrical resistivity of the γ-alloys (⩾11at.% Mo) exhibited a negative temperature coefficient from room temperature down to the superconducting transition.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2012.04.028