Wataru Saiki

Mechanical and thermal properties of uranium intermetallic compounds

Abstract The structures and lattice constants of UFe 2 , UNi 2 , UPd 3 , URh 3 , URu 3 and UNi 5 were examined, and thermal expansion coefficients of the intermetallic compounds were evaluated from high-temperature X-ray diffraction data. The longitudinal and shear sound velocities of the intermetallic compounds were markedly different, which enabled us to estimate the elastic properties. The intermetallic compounds were found to have higher bulk moduli than uranium metal. The values of microhardness of the intermetallic compounds except UFe 2 were much higher than pure uranium. The physico–chemical properties of the intermetallic compounds such as Debye temperature and heat capacity were estimated from the sound velocities and the thermal expansion data, and the correlations between the properties were discussed.

Thermal diffusivity measurement of uranium–thorium–zirconium hydride

Abstract The uranium–thorium mixed zirconium hydrides of UTh 4 Zr 10 H x ( x =20, 24, 27) have been successfully fabricated without large crack by means of a Sieverts apparatus. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses show that UTh 4 Zr 10 H x consist of α-U, ThZr 2 H x , and (δ, e)-ZrH x . The thermal diffusivity measurements of UTh 4 Zr 10 H x have been performed over the temperature ranges to around 773 K by means of a laser-flash method. It is shown that as the hydrogen concentration increases, the thermal diffusivity increases under 600 K and decreases above 600 K. The temperature dependence of the thermal diffusivity can be expressed with the simple equation as functions of composition and temperature. The thermal conductivity of the UTh 4 Zr 10 hydrides has been also evaluated from the measured data of the thermal diffusivity and the density and the estimated data of the specific heat and found to be close to those of U-carbide or -nitride at around 773 K.

Study on the hydrogen solubility in UNiAl

Abstract The hydrogen solubility in UNiAl has been studied at a hydrogen pressure up to 2 MPa at temperatures ranging from 50 to 250°C. In the UNiAl–H system, there exist α (dilute solid solution), β (UNiAlH hydride), and γ (UNiAlH 2 hydride) phases. The enthalpy of solution of hydrogen into the α phase and the standard enthalpy of formation of the β phase were estimated from the equilibrium pressure–hydrogen concentration isotherms. The lattice parameters of the hydride were examined by X-ray diffraction analysis. The anisotropic lattice expansion was observed for the hydrogenation of UNiAl. It was found from DTA and TG analyses that the hydride of UNiAl showed no marked oxidation up to 300°C in air and appears to have excellent thermal stability in air.

Physico-chemical Properties of Fe2P-type Uranium Intermetallic Compounds

The structures and lattice constants of ternary uranium intermetallic compounds of UFeAl, UCoAl, UNiAl and UlrAl were examined, and thermal expansion coefficients of the intermetallic compounds were evaluated from high-temperature X-ray diffraction data. The physico-chemical properties of the intermetallic compounds such as Debye temperature and heat capacity were estimated from the sound velocities and the thermal expansion data, and the correlations between the properties were discussed. The characteristic of the metallic bonding in the intermetallic compounds does not markedly differ from that of pure metals