Thermal and mechanical properties of zirconium hydride

The physico-chemical properties of zirconium hydride such as mechanical and thermal properties have been studied in the present study. The zirconium h ydride specimens in the form of pellets (6 mm phi x 10 mm 1) had the hydrog en contents with 1.5-1.7 H/Zr, which were fabricated directly from zirconiu m metal in a modified UHV Sieverts apparatus. All the zirconium hydrides pr epared in the present study showed CaF2 type delta ZrH2-x. The lattice para meter slightly increased with the hydrogen content. The thermal expansion c oefficients of the zirconium hydrides evaluated from high-temperature X-ray diffraction data were larger than that of zirconium metal and increased wi th the hydrogen content. The longitudinal and shear sound velocities of the zirconium hydride were slightly different from those of zirconium metal, w hich enabled us to estimate the elastic properties. The zirconium hydride h ad higher elastic moduli than zirconium metal and the elastic moduli slight ly depended on the hydrogen content. The microhardness of the zirconium hyd ride was much higher than that of zirconium metal and decreased with increa sing hydrogen content. The Debye temperature of the zirconium hydride estim ated from the sound velocities was larger than that of pure zirconium metal . The heat capacity was also estimated from the sound velocities and the th ermal expansion data. (C) 1999 Elsevier Science S.A. All rights reserved.