Nb-Ti-Ni系氢分离合金冷坩埚定向凝固相选择特性与渗氢性能

The self-invented cold-crucible directional solidification technology is used to investigate the phase selection characteristics and hydrogen permeability of Nb-Ti-Ni systems making use of its andvantages such as non-conamination of melt, high temperature gradient and ability of preparation of big-sized samples. The low hydrogen permeability of the present alloy is expected to be improved, which is prepared by the conventional free-solidification cast methods causing the random distribution of the hydrogen-permeable phase. Firstly, the equilibrium solidification information of L→Nb(Ti,Ni)+TiNi should be derived by Thermo-Calc of phase diagram. Secondly, The phase selection characteristics of Nb-Ti-Ni ternary eutectic under cold-crucible directional solidification will be investigated, as well as the competitive growth mechanism between primary and eutectic phases. And then, the phase selection model of directionally solidified eutectic alloys with effect of convection should be built by coupled calculations between macroscopic transimission model and microscopic eutectic growth model. Thirdly,the relationship among composition, solidification parameters, microstructure and hydrogen permeability will be characterized for Nb-Ti-Ni systems in cold-crucible directional solidification, and also the hydrogen permeable mechanism.Finally, the most appropriate technological conditions will be determined, deriving both high hydrogen permeability and resistance of hydrogen brittleness of Nb-Ti-Ni systems in cold-crucible directional solidification.

采用自主开发的冷坩埚定向凝固技术研究Nb-Ti-Ni系氢分离合金相选择特性与渗氢性能，发挥其无熔体污染、较高温度梯度、适于制备大尺度试样的优势，解决长久以来采用整体凝固铸造方法制备该合金遇到的渗氢相晶粒随机分布导致渗氢性能低的突出问题。通过相图热力学计算，获得三元Nb-Ti-Ni合金中 "Nb-TiNi共晶沟"相平衡信息，揭示该合金冷坩埚定向凝固相选择特性，分析初生相与共晶相的竞争生长机制，并通过宏观物理场与微观共晶凝固模型相耦合，构建对流作用下定向凝固共晶合金相选择模型，同时揭示合金成分、凝固参数、凝固组织与渗氢性能之间的本征关系，阐明氢渗透机制，确立采用冷坩埚定向凝固技术制备具有高氢渗透度及抗氢脆性能的Nb-Ti-Ni系氢分离合金的技术条件。

高纯氢在电子工业、航空航天、燃料电池和核聚变等领域有非常重要的应用。天然气重整是目前制备氢气的主要途径，但该方法获得的氢气纯度低，必须进一步进行提纯。采用氢分离合金通过膜分离的方法是氢气提纯的重要手段。目前，工业应用的氢分离金属膜材料是非常昂贵的Pd-Ag合金。本项目旨在开发Nb-Ti-Ni系的低成本、高性能氢分离合金。. 本项目通过耦合微观偏析模型的相图热力学计算，获得了三元Nb-Ti-Ni氢分离合金bcc-Nb相区内潜在的凝固路径，确立了可渗氢区域的成分区间及凝固条件。提出了凝固路径预测、凝固组织调控与氢渗透性能优化相结合，开发高性能Nb-Ti-Ni系氢分离合金的新思路。进一步采用元素替代法进行晶格间隙的氢溶解和扩散调控，即Co替代Ni，Hf置换Ti等，开发了Nb-Ti-Ni(Co)，Nb-Ti(Hf)-Ni和Nb-Hf-Co系新型高性能氢分离合金。在此基础上，首次采用定向凝固技术，对晶界结构进行调控，实现了氢渗透和抗氢脆性能的同时提高。由此确立了原子尺度晶格间隙、纳米尺度晶界和微米尺度凝固组织的多尺度结构调控优化氢传输性能的理论和技术体系。本项目研究为开发和制备高性能Nb-Ti-Ni系氢分离合金提供了理论和技术依据，且构建了具有自主知识产权的氢传输行为表征系统和理论体系。. 本项目研究已发表26篇SCI论文，其中4篇论文发表在本领域top1、中科院1区Journal of Membrane Science(影响因子5.557)；另外，在本领域著名国际期刊International Journal of Hydrogen Energy发表5篇论文，受到国际同行的高度评价。目前，与德国耶拿大学相图热力学计算专家Markus Rettenmayr教授、德国哥廷根大学冶金物理学家R. Kirchheim教授、荷兰埃因霍芬理工大学氢分离膜材料研究专家A. Fousto教授建立了深入合作。