Nb-Ni-Ti体系氢分离合金膜的结构和渗氢性能研究

Microstructure and Hydrogen Permeability of Nb-Ni-Ti Alloy Membranes for Hydrogen Separation

摘要:

开展了Nb-Ni-Ti体系氢分离合金膜的结构和渗氢性能研究。采用XRD、SEM分析膜片的相结构和组织特征，利用Devanathan-Stachurski双电解池法测定膜片的氢扩散系数，考察膜片厚度、成分和结构组织对其氢扩散系数的影响。实验结果表明：氢分离膜的氢扩散系数均随膜片厚度的增加而增大。制备的Nb-Ni-Ti体系合金膜都具有两相结构，即先析出相（bcc-Nb（Ni，Ti）固溶体）和共晶相（bcc-Nb（Ni，Ti）+β2-NiTi），个别成分点有少量的第三相NiTi2生成。膜片成分和组织结构对氢扩散系数影响显著，当合金中先析出固溶体相比例增加时，合金中的氢扩散系数也随着增大，而Ni，Ti含量的变化引起共晶相变化，NiTi相及NiTi2相都不同程度增加了共晶相的相比例而引起氢扩散系数的降低，但同时在结构上改善了合金在吸氢膨胀过程中发生的氢脆现象。氢在Nb-Ni-Ti体系氢分离膜中的扩散系数在10-9数量级范围。

Abstract:

Microstructure and hydrogen permeability of Nb-Ni-Ti alloy membranes for hydrogen separation were investigated. XRD and SEM were employed to characterize the phases and microstructure of Nb-Ni-Ti ternary alloys; hydrogen diffusion coefficients of these membranes with different thickness, composition or microstructure, were measured in Devanathan-Stachurski dual-cell system. The results indicate that hydrogen diffusion coefficient increases with the increasing thickness of these membranes. Basically these alloys are all of two-phase, i.e. the primary bcc-Nb(Ni,Ti) solid solution phase and the eutectic phase of bcc-Nb(Ni,Ti)+β2-NiTi, while just a small amount of NiTi2 phase is observed in very few samples. Microstructure and composition play an important role on hydrogen diffusion. Hydrogen diffusion coefficient is increased with the increase of the content of solid solution phase; the addition of Ni and Ti lead to the variety of eutectic phase composition; the presence of NiTi phase and NiTi2 phase decreases the hydrogen diffusion coefficient, but benefits the resistance to hydrogen embrittlement induced by the crystal expansion/contraction during atomic hydrogen permeation/release. Hydrogen diffusion coefficient of Nb-Ni-Ti alloy membranes falls in the magnitude of 10-9 m2/s.