化学镀Pd膜的结构及其对Nb-Ti-Ni体系氢分离膜的氢渗透催化研究

采用碱性化学镀在Nb-Ti-Ni合金膜片表面和载玻片上沉积了Pd膜,利用X射线衍射(XRD),能谱(EDS)、扫描电子显微镜(SEM),示差扫描量热仪(DSC)等手段对Pd沉积膜的相结构、成分、形貌及热稳定性进行了分析。结果表明,制备的Pd沉积膜为非晶态结构,膜层呈现球状颗粒密排沉积形态,颗粒尺寸在1μm左右,膜中的P含量在3%～4%(质量分数,下同)。膜的热稳定性研究表明,在经675K热处理后,膜层仍保持其初始的颗粒密排沉积特征,随着温度的升高,颗粒尺寸有轻微增大的趋势,出现Pd相和Pd6P相。电化学测试结果表明,制备的非晶态Pd膜可显著提高合金膜片的氢渗透电流密度,相应的氢扩散系数增大,而非晶膜层经热处理后,其氢扩散系数有较明显的降低。     

Nb-Ti-Ni体系氢分离合金膜的抗弯性能研究（英文）

开展了Nb-Ti-Ni体系氢分离合金膜的结构和抗弯性能研究。采用XRD/SEM分析了合金膜的结构和组织特征,利用三点弯曲法测定了合金膜的抗弯强度。实验结果表明,制备的Nb-Ti-Ni合金主要由bcc-Nb(Ni,Ti)固溶体和(bcc-Nb(Ni,Ti)+β2-Ni Ti)共晶相构成,前者是渗氢功能相,后者是结构支撑相。经渗氢实验后,合金试样的抗弯性能均有下降,具有网状结构特征的合金有较好的抗弯性能。经磁场热处理后,合金微结构出现晶粒细化、晶粒沿磁场方向定向排列、固溶体相区分布改变等明显变化,合金膜的抗弯强度有不同程度的改善,其中N7试样经0°和45°磁热处理,N5试样经90°磁热处理,其抗弯性能改善明显,说明通过磁热处理可对合金微结构进行调制,从而提高其抗弯强度。     

氢渗透合金膜的研究现状及发展趋势

氢渗透合金膜是一种重要的氢气提纯材料。本文简要介绍了目前存在的几种氢渗透合金膜的研究进展和各自的优缺点,重点讨论了氢渗透合金膜的工作原理、氢渗透性能和制备方法;详细分析了影响氢渗透性能的关键因素,包括氢渗透系数、氢扩散系数、氢溶解系数和氢脆性,提出了通过改善氢渗透合金膜的微观结构以提高膜材料的抗氢脆性、提高氢渗透系数和扩散系数的方法,最后对合金膜的发展趋势进行了探讨。     

Nb-Ni-Ti体系氢分离合金膜的结构和渗氢性能研究

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。     

Nb—Ti—Ni合金的显微组织与氢渗透性能

研究了Nb50Ti25Ni25及Nb40Ti30Ni30合金的显微组织及氢渗透性能,并与贵金属Pd、Pd-Ag合金及纯Nb的氢渗透性能进行了比较.两种合金的显微组织均由先析出的bcc-Nb(Ti,Ni)固溶体和bcc-Nb(Ti,Ni) B2-TiNi共晶组成.随Ni、Ti合金元素含量增加,合金中共晶相的含量增加.氢渗透温度为673 K时,两种合金的氢渗透系数分别为1.71×10-8和1.03×10-8mol·in-1·s-1·Pa-0.5,接近Pd的氢渗透系数,略低于Pd-Ag合金的氢渗透系数.共晶相的比例增加有利于提高合金的抗氢脆性能,增加先析出相的比例可提高合金的氢渗透系数.适当调整合金元素含量可获得综合性能良好的氢渗透合金.     

透氢合金膜的开发

熔体快淬Ni-X-Zr非晶膜的氢渗透性隔膜分离法有可能成为大量生产纯氢的一种既节能有比较低廉的技术,因此,对于当前透氢性最好的Ni-Nb-Zr三元非晶态合金薄膜进行了研究改进,研究了添加Nb和Zr以及添加其他元素取代Zr时对于Ni-Nb-Zr非晶合金性能的影响。     

氢分离合金冷轧成膜组织演变及透氢性能研究进展

第VB族（Nb、V、Ta）难熔金属与商用Pd比不但具有较高的氢渗透率而且价格低廉,成为人们青睐的新一代可替代钯的新型氢分离膜材料。为了规模化制备高通量的氢分离合金膜,研究者们对铸锭合金先进行冷轧变形以获得大尺寸平面膜,然后通过退火处理提高渗透率从而达到合金膜通量效率提升的目的。本文从合金的冷轧成形性、轧态及后续退火态组织演变以及透氢性能三方面的研究进展进行综述,分析了冷轧成膜的成分效应,阐述铸态、冷轧态和退火态的微观组织与渗透率的关系。讨论了通过轧态后续退火改善组织结构,进而开发高通量氢分离合金膜研究所面临的问题,最后对冷轧成膜及后续退火是实现低成本可规模化制备低厚度、高渗透率氢分离合金膜的前景进行展望。     

氢气净化用PdY合金的热处理工艺及其透氢性能

研究了PdY8合金不同的热处理工艺制度对加工性能的影响及PdY8,PdAgAuNi23-3-0．3合金在不同压差下的氢渗透量及不同温度时透氢率的比较。结果表明,铸锭需经900℃,14h均匀化处理,合金才易于加工;在650～700℃范围内退火、保温1h,合金的塑性加工性能最好;随氢压差和温度的升高,合金的透氢率随之升高,并且PdY8合金升幅较大。     

CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响

在300~450℃范围内,研究氢中加入CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响。结果表明,CO2的加入会大大降低膜的氢渗透率,CO2浓度越高,氢渗透率降低越多;CO2对Pd8Y0.23Ru合金膜存在一定的毒化作用,使氢渗透率下降,450℃下的毒化作用明显强于300℃,但随着时间的延长,渗透率降低速率趋缓。CO2降低氢渗透率还有另外2个因素:当CO2浓度较高(>3%,摩尔分数)时,聚集在膜表面附近的CO2对氢气传质的阻塞作用是氢渗透率降低的主要因素;当CO2浓度较低(<1%)时,CO2在膜表面吸附,占据氢的活性点位,是氢渗透率降低的主要因素。     

国外氢分离及净化用钯膜的研究进展

介绍了氢分离及净化用钯膜的氢选择性机理、影响因素以及制备技术的进展情况,重点阐述了钯合金(如Pd-Cu,Pd-V,Pd-V-Cu,Pd-V-Ni-Co等)以及钯复合膜(如多孔不锈钢、Ni、Fe-A1-Cr基体等)的一些新的研究成果.     

Relationship between activation energy for hydrogen permeation and hydrogen permeation properties of amorphous Cu50Zr50 and Cu65Zr35 membranes

We investigate the role of hydrogen solubility and diffusivity on the activation energy for hydrogen permeability and the relationship between the hydrogen permeability and resistance to hydrogen embrittlement in amorphous membranes, Cu₅₀Zr₅₀ and Cu₆₅Zr₃₅. The membrane with the lower activation energy for permeation showed higher hydrogen permeability, but it showed lower durability under hydrogen atmosphere. This relationship between the two properties is discussed on the basis of the nature of the short-range ordered (SRO) structures constituting amorphous membranes under hydrogen ambient.     

V-Ni-Ti multi-phase alloy membranes for hydrogen purification

Hydrogen-selective membranes formed from body centred cubic alloys can exhibit very high hydrogen permeability, but are prone to brittle failure due to excessive hydrogen absorption. Until issues associated with this are overcome, these materials will not provide a viable alternative to Pd-based membranes. Multi-phase V-Ni-Ti alloys which contain a significant proportion of a BCC component show promise for this application. In order to examine this system in greater detail, alloys of the general form V_85−xTi_xNi₁₅, in which x was varied between 0 and 30 (at.%), were fabricated via arc melting and electrical-discharge wire cutting. Hydrogen permeation measurements of Pd-coated samples at 400 °C showed a monotonic increase in permeability with increasing Ti, reaching a maximum of 1.0 × 10⁻⁷ mol H₂ m⁻¹ s⁻¹ Pa^−0.5 for the V₅₅Ti₃₀Ni₁₅ alloy at 400 °C. The driving force for hydrogen transport is provided by hydrogen absorption, which varies non-linearly with Ti content, and is dependent on the volume fraction of BCC phase, and levels of Ti and Ni solution in the BCC phase. Diffusion coefficients of atomic H through the bulk alloys alloys are dependent largely on microstructure. Whereas the V₈₅Ni₁₅ alloy forms a single phase microstructure, progressive substitution of V with Ti introduced several minor phases; a NiTi-type phase (formed when x ≥ 5), and a NiTi₂-type phase (formed when x ≥ 10), both as V-containing solid solutions. These minor phases act as barriers to hydrogen diffusion, resulting in a significantly reduced diffusion coefficient compared to single-phase BCC alloys. Importantly, the mechanical stability of these alloys appears to be enhanced by the multi-phase microstructure. These alloys therefore show great promise for meeting future flux, cost and durability targets.     

A hydrogen permeation study of cyclically deformed low alloy steel

The effect of the dislocation arrangement on hydrogen permeation in spheroidized low alloy steel (German steel grade 90MnV8, Nr. 1.2842) was studied using the electrochemical permeation technique. The testing material was cyclically deformed in different gaseous environments (hydrogen and ultra-high vacuum) to obtain dislocation structures with different degrees of cell formation. For undeformed material used as a reference the density and mean binding energy of hydrogen traps were evaluated using the trapping theory. The dislocation cell structure formed during fatigue reduces the apparent diffusion coefficient as the trap density is increased. On the other hand, the steady state hydrogen permeation flux is increased as dislocation cores act as short diffusion paths.     

氢分离单相V基合金膜研究进展

Pd-Ag合金膜作为分离高纯H2的金属膜目前已经商业化应用,但由于Pd-Ag合金膜的材料成本高,限制其大规模应用。 单相V基合金膜拥有比钯银合金膜更高的H渗透率、机械强度和较低的成本,且氢脆抗力较纯V得到很大提高,塑性和H渗透率也比多相V基合金膜高,因此成为替代Pd-Ag合金膜的潜在材料之一。 本文综述了氢分离单相V基合金膜的研究进展,包括V基合金膜种类及H渗透性能、微观结构对H渗透性能的影响、合金膜失效机制等,并对氢分离单相V基合金膜未来的发展趋势进行了简单的展望。     

Microstructural effects on the hydrogen permeation of an Inconel alloy 690

In the present work, hydrogen permeability tests were carried out in Inconel 690 in the as-received (AR) condition and after heat treating. The heat treatments promoted total solid solution (SA) or a microstructure full of grain boundary (gb) coverage with M₂₃C₆ carbides (A800). first and second polarization hydrogen transients were determined and used in disclosing the role of reversible and irreversible hydrogen trapping. It was found that in the SA condition, the permeation rates were the highest but they were significantly reduced in the AR condition, particularly in the A800 due to the presence of gb M₂₃C₆ carbides.     

Influence of tensile straining on the permeation of hydrogen in low alloy Cr-Mo steels

The effect of dynamic tensile straining on hydrogen permeation through low alloy Cr-Mo steel samples was studied with the electrochemical permeation technique. The hydrogen steady-state permeation current through large flat tensile specimens mounted between the two compartments of an electrochemical permeation cell undergoes different types of changes, depending on the charging conditions, on the steel’s composition and microstructure and on the strain rate. Dynamic trapping of hydrogen to strain-induced dislocations which leads to a deviation of the permeation current below the initial steady-state value is mostly observed when the external hydrogen activity and the strain rate are large. However, the hydrogen permeation current through Cr-Mo steels with a bainitic microstructure appears to be less sensitive to tensile straining up to large deformation levels than a lower alloyed Cr-Mo steel with a ferrito-pearlitic microstructure. On the other hand, the enhancement of the steady-state hydrogen permeation current observed during tensile straining if specific experimental conditions are met strongly suggests a mechanism of hydrogen transport by mobile dislocations which contributes to hydrogen permeation.     

Structure and hydrogen absorbing properties of ScCrMn alloy

The crystal structures of ScCrMn alloy and its hydride are determined by XRD Rietveld analysis and TEM examination. The ScCrMn alloy exhibits a rarely ideal close-packed C14 type hexagonal Laves phase structure with lattice parameters a = 5.064(1), c = 8.263(2) Å, deviating from the ANOE dependent rule on Laves phase structure. The hydrogenation of the alloy to ScCrMnH_3.9 results in significant lattice expansion of 27%, but does not alter the matrix lattice structure. The XRD pattern of the hydride also shows close-packed structure with little line broadening, comparable to that of the alloy, indicating a high degree of crystallinity, where the hydrogen atoms are homogeneously distributed in evenly distributed interstitials with minimal defects. The alloy demonstrates extremely easy activation property. The alloy can be activated at a low pressure of 0.46 kPa and exhibit very fast absorption rate at sub-atmosphere at room temperature. The hydrogenation thermodynamics of the alloy are evaluated by P-C-T measurements at different temperatures. At hydrogen concentration H/M = 0.66 corresponding to a defined room temperature plateau pressure, the relative partial molar enthalpy ΔH and entropy ΔS derived by Van’t Hoff equation are −63 kJ/mol and −111 J/mol K, respectively. These results manifest that the hydride stability of the ScCrMn alloy is comparable to those of the hydrogen isotope storage alloys of ZrCo and ZrTi_0.2V_1.8, and would be superior on relevant applications. The DSC-TG measurements of the hydride reveal that the total release of hydrogen can basically be achieved at 653 K, accompanied by an oxidation reaction with residual oxygen to form water vapor. The results indicate that the alloy is an effective catalyst for the dissociation of hydrogen and combination of oxygen.     

新型Ti-Fe-Mo-Mn-Nb-Zr系钛合金的力学性能

在纯钛中加入Fe,Mo,Mn,Nb和Zr强化元素制成新型Ti-Fe-Mo-Mn-Nb-Zr系钛合金,测定了该材料的硬度、压缩强度及弹性模量等性能,考察了加入元素对硬度、压缩强度的影响规律.实验结果表明该合金形成了等轴α+β组织,与其它现有牙科用钛合金相比,硬度、弹性模量更接近牙本质的,且压缩性能明显优于其它牙科用钛合金.