氢在钯/石墨烯/铌复合界面的渗透行为

Dense metal membranes have a marked application in hydrogen and its isotopes separation. Palladium has good catalytic ability for hydrogen molecules, and niobium is with high permeability for hydrogen atoms. Palladium-niobium-palladium composite membrane, combining the advantages of both palladium and niobium, has good hydrogen permeation. However, the high temperature interdiffusion of palladium and niobium atoms leads to the serious reduction of hydrogen permeability, which hinders the large-scale application of this composite membrane. Therefore, it is necessary to deposit an intermediate layer to prevent the high temperature interdiffusion of palladium and niobium atoms but not affect the permeation of hydrogen atoms. Graphene, with compact structure and good heat resistance, can hinder the interdiffusion of metal atoms at high temperature. But whether it has some influence on the diffusion of hydrogen atoms is not clear enough, which needs further study. In this research, a palladium-graphene-niobium composite membrane is prepared by depositing a layer of graphene membrane on the surface of clean niobium metal and a layer of palladium membrane on the graphene. The interfacial stability and hydrogen permeation behavior of palladium-graphene-niobium composite membrane is studied and the effect of graphene on the interdiffusion of metal atoms and the hydrogen permeation mechanism is analyzed. Ultimately, we hope to provide some theoretical basis and technical support for the application of palladium-graphene-niobium composite membrane in the field of hydrogen and its isotopic separation and purification.

致密金属膜在氢及其同位素分离领域具有重要应用。钯/铌/钯复合膜充分结合了钯对氢分子的高催化解离能力和铌对氢原子的高体扩散性，氢渗透率较高。但是，钯、铌原子高温互扩散导致复合膜氢渗透率严重降低的问题阻碍了其大规模应用。所以，需要寻找一种能阻隔钯、铌原子高温互扩散且不影响氢原子渗透的中间层。石墨烯膜结构致密、耐热性好，能阻隔金属原子的高温互扩散，但其对氢原子的扩散渗透行为是否存在影响，目前认识的还不够清晰。因此，本项目拟通过在清洁铌表面沉积一层石墨烯膜，并在石墨烯膜表面溅射一层纳米钯膜，形成钯/石墨烯/铌复合膜。通过系统研究钯/石墨烯/铌复合膜的高温界面稳定性和氢渗透行为，获得石墨烯膜对金属原子高温互扩散的影响规律以及氢在复合膜界面的扩散渗透机制，为钯/石墨烯/铌复合膜在氢同位素分离提纯领域的应用提供理论基础和实验依据。

致密金属膜在氢及其同位素分离领域具有重要应用。钯/铌/钯复合膜充分结合了钯对氢分子的高催化活性和铌对氢原子的高体扩散性，氢渗透率较高。但是，钯、铌原子高温互扩散导致的氢渗透率严重降低问题阻碍了其大规模应用。石墨烯膜结构致密、耐热性好，能阻隔金属原子的高温互扩散，但其对氢原子的扩散渗透行为是否存在影响，目前认识的还不够清晰。本文以微（纳）米晶铌膜为研究对象，首先采用机械抛光、电解抛光、超高真空退火、氩离子溅射等对铌膜进行表面处理，研究了不同处理方式下铌表面成分及结构的变化；接着，采用快速转移法在“清洁”铌箔表面转移一层单层石墨烯膜，并采用磁控溅射法在铌膜和铌/石墨烯膜表面沉积一层钯膜，形成钯/铌/钯复合膜和钯/石墨烯/铌复合膜，对复合膜的微观结构进行表征；最后，采用高温气相渗透法研究了铌膜在600~800 ℃、钯/铌/钯和钯/石墨烯/铌复合膜在300~450 ℃范围内渗氘（氢）行为。结果表明：采用机械磨抛与电解抛光、超高真空高温退火或氩离子溅射相结合的方式能有效去除铌表面的氧化层，使其厚度降低到纳米级，获得相对“洁净”的铌表面；表面氧化层对铌膜的渗氘行为具有重要影响，在铌表面沉积一层钯膜有助于增加铌膜的氢同位素渗透性，但表面氧化层和高温热处理导致的钯、铌互扩散，使得钯/铌/钯复合膜的渗透性能严重降低，且铌晶粒度越小，互扩散越严重。在钯/铌界面置入一层单原子层石墨烯膜可以减缓阻止钯、铌原子发生高温互扩散，其稳定存在区间为温度低于600 ℃，继续升高温度，石墨烯膜破裂碎化，使得钯、铌原子相互接触，迅速产生互扩散；但石墨烯膜的存在也降低了其氘渗透性能。通过系统研究钯/铌和钯/石墨烯/铌复合界面的高温稳定性及复合膜的氢渗透行为，获得了石墨烯膜对金属原子高温互扩散的影响规律以及氢在复合界面的渗透机制，为钯/石墨烯/铌复合膜在氢同位素分离提纯领域的应用提供理论基础和实验依据。