Study of hydrogen migration mechanisms in materials with complex crystal textures

用气体渗透法在超高真空装置上测量了Pd、Fe、Ni膜的氢渗透率。超高真空装置的使用使我们能够在低压、低温和薄箔中进行测量。结果表明，Pd膜的氢渗透受样品表面污染的影响很大。通过在低温下的短暂老化，将污染物从Pd表面去除。表面清洗后，氢气渗透量增加，并呈线性阿累尼乌斯关系，说明该方法适用于多层样品的氢气渗透实验。因此，在Pd基板上测量了不同层数和不同厚度的Pd-Fe和Pd-Ni多层膜的氢渗透量，即使在清洗了Pd表面后，通过Pd-Ni多层膜的氢渗透量也不是线性的阿累尼乌斯关系，而是大于采用镍的体属性值的模型计算的结果。从实验结果和模型计算可以看出，Pd-Ni多层膜的渗透不受中间层和边界层的影响。Pd表面清洗后，Pd-Fe多层膜的渗氢量呈线性阿累尼乌斯关系，但与Fe层厚度和层数的关系复杂。对于这个系统，必须进行进一步的调查。与Pd-Ni系不同，Pd-Fe多层膜的渗透量比模型计算得到的要少。用俄歇电子能谱对Pd箔进行了表面分析，氢气通过Pd的渗透被可能来自碳氢化合物的C原子抑制。

The hydrogen permeability measurements in Pd, Fe, Ni membranes have been done by the gas permeation method by an ultrahigh vacuum apparatus. The use of an ultrahigh vacuum apparatus enables us to measure at low pressure and temperature and at thin foil. It is shown that the hydrogen permeation through Pd membrane is exceedingly affected by the surface contamination of the specimen. The contaminants are taken off from the Pd surface by short aging at low temperatures. After this surface cleaning, the amount of hydrogen permeation increases and shows linear-like Arrhenius relation.From above results, our permeation method is suitable for hydrogen permeation experiment of multi-layers specimen. Therefore, the permeation of hydrogen is measured for various number of layers and thickness of multi-layers in Pd-Fe and Pd-Ni systems on Pd base plate.Even after cleaning the Pd surface, the amount of hydrogen permeation through Pd-Ni multi-layers does not show linear-like Arrhenius relation and is larger than that from model calculation in which the bulk property values of Ni are used. From the experimental results and model calculations, it is concluded that the permeation through Pd-Ni multi-layers is not affected by inter Pd layers and boundary layers. Enhanced hydrogen permeation is caused by high grain boundary permeation through small grained Ni layers.After cleaning the Pd surface, the permeation amount through Pd-Fe multi-layers showed linear-like Arrhenius relation, but the dependence for the thickness and number of Fe layers was complex. Further investigation must be needed for this system. The amount through Pd-Fe multi-layers decreased than those obtained from model calculation different from the case of Pd-Ni system.Surface analysis of Pd foil is done by Auger electron spectroscopy and hydrogen gas permeation through Pd is suppressed by C atoms which may come from hydrocarbons.