NMR studies of hydrogen diffusion in ZrBe2H1.4
NMR studies of hydrogen diffusion in ZrBe2H1.4
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ZrBe2H1.4 中氢扩散的 NMR 研究
DOI：
10.1016/s0925-8388(97)00273-9
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发表时间：
1998
影响因子：
6.2
通讯作者：
A. Mcdowell
中科院分区：
文献类型：
--
作者：
F. Kimmerle;G. Majer;U. Kaess;A. Maeland;M. Conradi;A. Mcdowell
用不同的核磁共振技术研究了氢在金属氢化物ZrBe_2 H_（1.4）中的扩散系数。在27.7MHz和67.7MHz频率下测量了175 - 500 K温度范围内质子自旋-晶格弛豫速率Γ 1。在0.31 ~ 29.2MHz范围内，用场循环（FC）NMR技术研究了四种不同温度下Γ 1的频率依赖性。这些研究表明，氢扩散被限制在两个维度内的粉末样品的每个颗粒。ZrBe_2 H_（1.4）的结构表明氢的扩散发生在Zr原子形成的xy平面内。脉冲场梯度（PFG）自旋回波实验中回波幅度随外加场梯度的变化证实了氢扩散的二维特征。在272 K和478 K之间的PFG数据直接产生xy平面Dxy中的扩散系数。Dy的温度依赖性符合Arrhenius定律，活化焓Ha=（0.25±0.02）eV。该活化焓与从频率和温度依赖性的Γ1推导出的值非常一致。
The diffusivity of hydrogen in the metal-hydride ZrBe2H1.4has been studied by different nuclear magnetic resonance (NMR) techniques. The proton spin-lattice relaxation rate Γ1has been measured at 27.7 MHz and 67.7 MHz in the temperature range from 175 K to 500 K. At four distinct temperatures the frequency dependence of Γ1has been investigated between 0.31 MHz and 29.2 MHz using the field-cycling (FC) NMR technique. These studies indicate that the hydrogen diffusion is restricted to two dimensions within each particle of the powdered sample. The structure of ZrBe2H1.4suggests that the hydrogen diffusion takes place in the xy planes formed by the Zr atoms. The variation of the echo amplitude with the applied field gradient in pulsed-field-gradient (PFG) spin-echo experiments confirmed the two-dimensional character of the hydrogen diffusion. The PFG data taken between 272 K and 478 K yielded directly the diffusivities in the xy plane Dxy. The temperature dependence of Dxyis well represented by an Arrhenius law with an activation enthalpy Ha=(0.25±0.02) eV. This activation enthalpy is in very good agreement with values deduced from both the frequency and the temperature dependence of Γ1.