The vacuum arc melting method was used to prepare ZrCo1-xCrx(x=0,0.025,0.05,0.075,0.1)alloys.Afterward,the crystal structure,hydrogenation kinetics,thermodynamic properties,and disproportionation performance of ZrCo1-...The vacuum arc melting method was used to prepare ZrCo1-xCrx(x=0,0.025,0.05,0.075,0.1)alloys.Afterward,the crystal structure,hydrogenation kinetics,thermodynamic properties,and disproportionation performance of ZrCo1-xCrx(x=0-0.1)alloys were investigated.The x-ray diffraction spectra demonstrated that ZrCo1-xCrx(x=0-0.1)alloys contained ZrCo and ZrCo2 phases,and their corresponding hydrides consisted of ZrCoH3 and ZrH phases.The activation behaviors of Cr-substituted samples were significantly promoted.The activation time of ZrCo was 7715 s while that of ZrCo0.9Cr0.1 was 195 s.The improvement of kinetics can be attributed to the catalytic hydrogenation of ZrCr2.The activation energy for the hydrogenation of ZrCo was 44.88-kJ·mol^-1 H2 and decreased to 40.34-kJ·mol^-1 H2 for ZrCo0.95Cr0.05.The plateau pressure and width of the pressure-composition-temperature curves decreased slightly as Cr content increased.The extent of disproportionation of ZrCo was 83.68%after being insulated at 798 K for 10 h and decreased slightly to 70.52%for ZrCo0.9Cr0.1.The improvement of anti-disproportionation performance can be attributed to increase in the activation energy of disproportionation from 167.46-kJ·mol^-1 H2 for ZrCo to 168.28-kJ·mol^-1 H2 for ZrCo0.95Cr0.05.展开更多
The physical properties including structural,electronic,vibrational and thermodynamic properties of Zr1-xHfx Co（x is the concentration of constituent element Hf,and changes from 0 to 1） are investigated in terms of ...The physical properties including structural,electronic,vibrational and thermodynamic properties of Zr1-xHfx Co（x is the concentration of constituent element Hf,and changes from 0 to 1） are investigated in terms of the ABINIT program.The results reveal that all of Zr（1-x）Hfx Co have similar physical properties.When Hf concentration x gradually increases from 0.0 to 1.0,the lattice constant decreases from 3.217°A to 3.195°A very slowly.The calculated density of states（DOS）indicates that the metallic nature is enhanced and the electrical conductivity turns better with the increase of Hf.Moreover,as Hf concentration increases from 0 to 1,the Fermi energy gradually increases from-6.96 e V to-6.21 e V,and the electronic density of states at the Fermi level（N（Ef）） decreases from 2.795 electrons/e V f.u.down to 2.594 electrons/e V f.u.,both of which imply the decrease of chemical stability.The calculated vibrational properties show that the increase of Hf concentration from 0 to 1 causes the maximum vibrational frequency to decrease gradually from about 223 cm^-1 to 186 cm^-1,which suggests a lower dispersion gradient and lower phonon group velocities for these modes.Finally,the phonon related thermodynamic properties are obtained and discussed.展开更多
Fractional Stokes–Einstein relation described by D ～（τ/T）~ξ is observed in supercooled water, where D is the diffusion constant, τ the structural relaxation time, T the temperature, and the exponent ξ =τ^（-1...Fractional Stokes–Einstein relation described by D ～（τ/T）~ξ is observed in supercooled water, where D is the diffusion constant, τ the structural relaxation time, T the temperature, and the exponent ξ =τ^（-1）. In this work, the Stokes–Einstein relation in TIP5 P water is examined at high temperatures within 400 K–800 K. Our results indicate that the fractional Stokes–Einstein relation is explicitly existent in TIP5P water at high temperatures, demonstrated by the two usually adopted variants of the Stokes–Einstein relation, D ～τ^（-1）τand D ～ T/τ, as well as by D ～ T/η, where η is the shear viscosity. Both D ～τ^（-1）τand D ～ T/τ are crossed at temperature Tx= 510 K. The D ～τ^（-1）τis in a fractional form as D ～ τ ξwith ξ =-2.09 for T ≤ Txand otherwise ξ =τ^（-1）.25. The D ～ T/τ is valid with ξ =τ^（-1）.01 for T ≤ Txbut in a fractional form for T Tx. The Stokes–Einstein relation D ～ T/η is satisfied below Tx = 620 K but in a fractional form above Tx. We propose that the breakdown of D ～ T/η may result from the system entering into the super critical region, the fractional forms of D ～τ^（-1）τand D ～ T/τ are due to the disruption of the hydration shell and the local tetrahedral structure as well as the increase of the shear viscosity.展开更多
基金the National Natural Science Foundation of China(Grant Nos.21573200,2017YFE0301505,21601165,21401173,21573200,and 51731002).
文摘The vacuum arc melting method was used to prepare ZrCo1-xCrx(x=0,0.025,0.05,0.075,0.1)alloys.Afterward,the crystal structure,hydrogenation kinetics,thermodynamic properties,and disproportionation performance of ZrCo1-xCrx(x=0-0.1)alloys were investigated.The x-ray diffraction spectra demonstrated that ZrCo1-xCrx(x=0-0.1)alloys contained ZrCo and ZrCo2 phases,and their corresponding hydrides consisted of ZrCoH3 and ZrH phases.The activation behaviors of Cr-substituted samples were significantly promoted.The activation time of ZrCo was 7715 s while that of ZrCo0.9Cr0.1 was 195 s.The improvement of kinetics can be attributed to the catalytic hydrogenation of ZrCr2.The activation energy for the hydrogenation of ZrCo was 44.88-kJ·mol^-1 H2 and decreased to 40.34-kJ·mol^-1 H2 for ZrCo0.95Cr0.05.The plateau pressure and width of the pressure-composition-temperature curves decreased slightly as Cr content increased.The extent of disproportionation of ZrCo was 83.68%after being insulated at 798 K for 10 h and decreased slightly to 70.52%for ZrCo0.9Cr0.1.The improvement of anti-disproportionation performance can be attributed to increase in the activation energy of disproportionation from 167.46-kJ·mol^-1 H2 for ZrCo to 168.28-kJ·mol^-1 H2 for ZrCo0.95Cr0.05.
基金Project supported by the National Natural Science Foundation of China(Grant No.21573200)
文摘The physical properties including structural,electronic,vibrational and thermodynamic properties of Zr1-xHfx Co（x is the concentration of constituent element Hf,and changes from 0 to 1） are investigated in terms of the ABINIT program.The results reveal that all of Zr（1-x）Hfx Co have similar physical properties.When Hf concentration x gradually increases from 0.0 to 1.0,the lattice constant decreases from 3.217°A to 3.195°A very slowly.The calculated density of states（DOS）indicates that the metallic nature is enhanced and the electrical conductivity turns better with the increase of Hf.Moreover,as Hf concentration increases from 0 to 1,the Fermi energy gradually increases from-6.96 e V to-6.21 e V,and the electronic density of states at the Fermi level（N（Ef）） decreases from 2.795 electrons/e V f.u.down to 2.594 electrons/e V f.u.,both of which imply the decrease of chemical stability.The calculated vibrational properties show that the increase of Hf concentration from 0 to 1 causes the maximum vibrational frequency to decrease gradually from about 223 cm^-1 to 186 cm^-1,which suggests a lower dispersion gradient and lower phonon group velocities for these modes.Finally,the phonon related thermodynamic properties are obtained and discussed.
基金supported by the National Natural Science Foundation of China(Grant No.2153200)the China Postdoctoral Science Foundation(Grant No.2016M602712)
文摘Fractional Stokes–Einstein relation described by D ～（τ/T）~ξ is observed in supercooled water, where D is the diffusion constant, τ the structural relaxation time, T the temperature, and the exponent ξ =τ^（-1）. In this work, the Stokes–Einstein relation in TIP5 P water is examined at high temperatures within 400 K–800 K. Our results indicate that the fractional Stokes–Einstein relation is explicitly existent in TIP5P water at high temperatures, demonstrated by the two usually adopted variants of the Stokes–Einstein relation, D ～τ^（-1）τand D ～ T/τ, as well as by D ～ T/η, where η is the shear viscosity. Both D ～τ^（-1）τand D ～ T/τ are crossed at temperature Tx= 510 K. The D ～τ^（-1）τis in a fractional form as D ～ τ ξwith ξ =-2.09 for T ≤ Txand otherwise ξ =τ^（-1）.25. The D ～ T/τ is valid with ξ =τ^（-1）.01 for T ≤ Txbut in a fractional form for T Tx. The Stokes–Einstein relation D ～ T/η is satisfied below Tx = 620 K but in a fractional form above Tx. We propose that the breakdown of D ～ T/η may result from the system entering into the super critical region, the fractional forms of D ～τ^（-1）τand D ～ T/τ are due to the disruption of the hydration shell and the local tetrahedral structure as well as the increase of the shear viscosity.
