Hydrogen Embrittlement of Metal Membrane Detected by In-situ Measurement under Hydrogen Permeation and Elucidation of Embrittlement Mechanism of Niobium based Metal Membranes

本研究的目的在于：（1）建立金属透氢膜氢脆的原位测试方法;（2）阐明溶解氢对透氢膜力学性能的影响;（3）提出可承受氢压差的新型金属透氢膜的设计原则。研究结果如下：1.利用自行研制的原位小冲孔试验装置，研究了纯铌金属膜在氢渗透下的氢脆机理.通过一系列原位小冲杆试验和PCT测量（Sievert方法）确定钯涂覆的铌膜的韧脆转变的覆盖率。与以往文献提出的边界相比，实验测得的边界向低氢含量区偏移较大.在673 K时，降低氢压，引入约10%的晶格收缩，膜容易变形和断裂，此时脱氢反应进行顺利.虽然在实际氢压条件下，纯铌溶解大量的氢，造成显著的氢脆，但降低溶解氢浓度可以控制氢脆.为了在膜两侧获得高的氢浓度差而设计的合金设计可以成为既具有氢渗透性又具有强的抗氢脆性的新铌膜。例如，当将钯添加到铌中时，溶解的氢的量减少，并且钯的添加有助于提供抗氢脆性6。本研究结果将为抗氢脆铝基渗透膜的设计提供线索。

This research aims at (1) establishment of the hydrogen embrittlement in-situ measuring method of the metallic hydrogen permeable membranes, (2) elucidation of the effects of dissolved hydrogen on the mechanical properties and (3) suggestion some guidelines of a new metallic membrane design which can be sustainable hydrogen pressure difference. The results are as follows.1. By using a newly developed in-situ small punch apparatus, the mechanism of hydrogen embrittlement of pure niobium metal membrane was investigated under hydrogen permeation.2. The coverage for the ductile-brittle transition of the palladium-coated niobium membrane was determined by a series of the in-situ small punch test and the PCT measurements (Sievert's method). Compared with the one proposed by previous reports, the measured boundary showed great shift to the lower hydrogen content region.3. The membrane was deformed and fractured easily when about 10% lattice contraction was introduced to it by lowering the hydrogen pressure at 673K, at which the dehydrogenation reaction progressed smoothly.4. Although, under the practical hydrogen pressure conditions, pure niobium dissolves a great amount of hydrogen and causes remarkable embrittlement, the reduction of dissolving hydrogen concentration can control the proof hydrogen embrittlement.5. An alloy design planned so as to obtain high hydrogen concentration difference on both sides of the membrane can become a new niobium membrane provided with both hydrogen permeability and strong resistance against hydrogen embrittlement. For instance, when palladium was added to niobium, the amount of dissolved hydrogen decreased, and palladium addition contributed to giving the resistance to hydrogen embrittlement6. The present results will provide us with a clue to the design of niobium-based permeable membrane against the hydrogen embrittlement.