Structural,electronic,vibrational,and thermodynamic properties of Zr_(1-x)Hf_xCo:A first-principles-based study

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)Hf_x 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(E_f)) 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.     

耐甲醇氧还原催化剂四苯基卟啉-铂的研究

直接甲醇燃料电池;燃料电池;耐甲醇氧还原催化剂四苯基卟啉-铂的研究     

大容量贮氘氚铀床的研制

为了满足重水提氚中大量氘氚气体的安全贮存与转运，设计并加工了大容量氘氚铀床并对其进行了贮氘氚性能的测试。     

α-Al2O3阻氢微观机制研究

采用基于密度泛函理论广义梯度近似下的平面波赝势方法研究了刚玉(α-Al2O3)的阻氢微观机制, 对氢原子在α-Al2O3中的占据结构进行了计算, 发现氢原子占据空隙位置时能量最低, 寻找其过渡态得到活化能为1.59 eV, 利用动力学计算得到了氢原子在α-Al2O3中的扩散系数表达式为D(T)=(3.37×10-7)exp(-1.59/kT). 结果表明, 氢原子占据在α-Al2O3八面体空隙处的结构最稳定; 低温时扩散难以发生; 高温时扩散沿着空隙方向.     

氢中杂质CO对LaNi5,LaNi4.7Al0.3,MlNi4.5Al0.5合金PCT特性的影响

研究了 3种贮氢合金 ,即LaNi5 ,LaNi4.7Al0 .3,MlNi4.5 Al0 .5 在纯氢 ( 99 999% )及含 0 0 1%CO气体杂质氢中毒化前后的PCT特性。对于LaNi5 ,毒化后不出现平台 ;对LaNi4.7Al0 .3及MlNi4.5 Al0 .5 合金 ,平台压升高 ,平台倾斜加剧 ,平台宽度缩小 ,饱和吸氢量减小。LaNi5 中加入少量Al后 ,可以提高其抗毒化能力。分析了PCT平台变短、倾斜的原因。     

Electronic structures and thermodynamic stabilities of aluminum-based deuterides from first principles calculations

The alanates (complex aluminohydrides) have relatively high gravimetric hydrogen densities and are among the most promising solid-state hydrogen-storage materials. In this work, the electronic structures and the formation enthalpies of seven typical aluminum-based deuterides have been calculated by the plane-wave pseudopotential method, these being AlD₃, LiAlD₄, Li₃AlD₆, BaAlD₅, Ba₂AlD₇, LiMg(AlD₄)₃ and LiMgAlD₆. The results show that all these compounds are large band gap insulators at 0 K with estimated band gaps from 2.31 eV in AlD₃ to 4.96 eV in LiMg(AlD₄)₃. The band gaps are reduced when the coordination of Al varies from 4 to 6. Two peaks present in the valence bands are the common characteristics of aluminum-based deuterides containing AlD₄ subunits while three peaks are the common characteristics of those containing AlD₆ subunits. The electronic structures of these compounds are determined mainly by aluminum deuteride complexes (AlD₄ or AlD₆) and their mutual interactions. The predicted formation enthalpies are presented for the studied aluminum-based deuterides.     

杂多酸修饰的电极对于甲醇电氧化的促进作用

采用杂多酸修饰光滑铂电极,研究其对甲醇电催化氧化的作用,发现与未修饰光滑铂电极相比,分别经磷钨酸和硅钨酸修饰的电极上甲醇电催化氧化速率明显增加.     

碳纳米管纯化对Pt/CNTs催化甲醇电化学氧化活性的影响

探索了一种适用于Pt/CNTs催化剂的纯化方法.利用比表面积测定、X射线衍射(XRD)、透射电子显微镜(TEM)和电化学等手段进行了表征.研究结果表明,经该方法纯化的CNTs作为载体制备的阳极催化剂表现出明显优于相应的混酸氧化法纯化的CNTs为载体的催化剂催化性能.     

Fractional Stokes–Einstein relation in TIP5P water at high temperatures

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 T_x= 510 K. The D ～τ~(-1)τis in a fractional form as D ～τξwith ξ =-2.09 for T ≤ T_xand otherwise ξ =τ~(-1).25. The D ～ T/τ is valid with ξ =τ~(-1).01 for T ≤ T_xbut in a fractional form for T T_x. The Stokes–Einstein relation D ～ T/η is satisfied below T_x = 620 K but in a fractional form above T_x. 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.     

固体聚合物电解质水电解进行h/d同位素分离

固体聚合物电解质;水电解;电催化剂;氢同位素;分离