Hydrogen Treatment Technique And The Hydrogen Absorption-Desorption Properties Of Uranium Alloys

The alloying theory, melting and heat treaUnent, phase transformation and the relationships between the microstructures and the properties of some uranium alloys were reviewed. The hydrogen absorption properties and the effects of hydrogen on the properties of uranium alloys were summarized. The technique of hydrogen treatment of materials was introduced. A new method was proposed to improve the pulverization property of pure uranium metal upon hydrogenation by adding appropriate amount of other elements, such as titanium, zirconium or niobium. The alloys should still retain or enhance most of the superior hydrogen storage properties of uranium metal. The hydrogen absorption-desorption properties of U-l0mass%Zr, U-0.7mass%Ti, U-2.4mass%Nb and U-6.2mass%Nb alloys were investigated in detail at hydrogen pressures up to 0.4 MPa and in the range of temperature from 300 to 723 K, and compared with some other hydrogen storage materials. It was found that these uranium alloys, especially uranium-zirconium alloys, showed high durability against powdering upon hydrogenation and had similar hydrogen desorption properties as uranium metal. The technique of hydrogen treatment of materials (HTM) was used first time to reduce the nonmetal impurities, such as carbon, nitrogen and oxygen, and improve the homogenecity of uranium alloys. The effects of HTM on the microstructure and the properties of uranium alloys were observed and investigated. It was found that, after hydrogen treatment, the content of the nonmetal impurities had largely decreased and the microstructure had changed greatly which resulted in the improvement of the mechanical and anti-corrosion properties of these uranium alloys. At last, the optimized geometries and electronic structures of some gaseous molecules in the uranium-hydrogen and uranium-oxygen-carbon system were calculated with harmonic vibration analyses using quantum mechanical ab initio method. And the potential energy surfaces were constructed based on the single point energy calculations to investigate the interaction process between uranium and CO or 02. It was demonstrated thermodynamically that the initial products with respect to the uranium-hydrogen system included UH, UH2, UH3, U2H2 and U2H4. The potential energy surface analyzing results confirmed that the optimized structures and suggested, theoretically, that the main initial products were UO or linear U02 in the uranium-oxygen system, and uranium monocarbide (UC) or uranium oxycarbides (UCO and CUO) in the uranium-carbon monoxide system, depending on the different interaction mode.