Study Of The Microstructure And Hydrogen Permeation Performance Of Nb-Zr-Ni(Co) Alloy

Hydrogen energy, a kind of clean and green power, grasps attention of humanincreasingly. Meanwhile, separation and purification of hydrogen is a key link in theprocess of hydrogen utilization. This paper has explored and studied hydrogenseparation membrane materials of Nb-Zr-Ni ternary alloy and Nb-Zr-Ni-Coquaternary alloy, which are used as alternative materials of pure Pd. The paper selects39components to confect and smelt from these two kinds of alloy series, usingscanning electron microscopy (SEM), X-ray diffraction (XRD) to analyze as-castmicrostructure and structure of the alloy. We get the composition range which meetthe hydrogen separation alloy design concept of "multiphase constituting, functionsharing ", and select15components from ideal ingredient range to do hydrogenpermeation experiments. In the end, we have searched hydrogen permeation property,summed the relationship between alloy composition, structure and alloy hydrogenpermeation property. We also analyze the fracture of the alloy, getting the fracturetype of every phase in the alloy.In Nb-Zr-Ni ternary alloy, when the Zr/Ni(at%)=1:1, the hyper-eutecticcomposition (Nb content is greater than13at%) is the ideal hydrogen permeationingredient scope of this article. These alloys contain primary phase Nb and binaryeutectic matrix phase {Nb+ZrNi}, which contribute to hydrogen permeation andresistance to hydrogen embrittlement, respectively. When the Nb content increases,the hydrogen permeability of alloy increases with the increasing of primary phase Nbvolume fraction. On the other hand, the property of resistance to hydrogenembrittlement decreases with the decreasing of binary eutectic matrix phase volumefraction. Nb30Zr35Ni35and Nb40Zr30Ni30alloy membranes shows good coordinationbetween hydrogen permeability and resistance to hydrogen embrittlement, having agood application prospect. When the Zr/Ni(at%)≠1:1, the alloy appears Zr2Ni, ZrNi2,Zr2Ni7, NbNi and other impurities phase, leading to a serious deterioration in theperformance of the alloy resistance to hydrogen embrittlement, which is not suitablefor hydrogen permeation.In Nb-Zr-Ni-Co quaternary alloy, the microstructure of Nb30Zr35Ni35-XCoXandNb40Zr30Ni30-XCoXseries alloy contain primary phase Nb and binary eutectic matrixphase{Nb+ZrNi(Co) or ZrCo(Ni)}, which two phase are relevant to hydrogen permeability. Hydrogen permeability of the alloy increases with the increase of the Cocontent. when Co content is15at%and10at%, respectively, Both series alloy reachthe maximum hydrogen permeability, which is2.3times and2.9times (673K) of purePd, respectively. Meanwhile, the resistance to hydrogen embrittlement of alloy is alsogood. However, When the Co content continues to increase, ternary eutectic phase{Nb+ZrNi(Co) or ZrCo(Ni)+Zr2Ni(Co) or Zr2Co(Ni)} appears in alloy microstructure,the volume fraction of which increases concomitantly. These alloy with ternaryeutectic phase is not suitable for hydrogen permeation, because ternary eutectic phasemake a serious deterioration in the resistance to hydrogen embrittlement.Hydrogen embrittlement of the alloy is mainly caused by embrittlement ofprimary phase Nb in the process of hydrogen permeation. Primary phase Nb showssignificant brittle fracture, while eutectic matrix phase displays morphology of ductilefracture. Moreover, the interface binding capacity of primary phase Nb and eutecticmatrix phase is also an important reason of alloy diaphragm rupture.