Ti-V基多相贮氢电极合金的电化学吸放氢机理研究

采用XRD的Rietveld全谱拟合技术以及利用储氢合金吸氢量与其体积膨胀成线形关系的原理,研究了Ti-V基贮氢电极合金的电化学吸放氢机理.结果表明,铸态合金Ti0.8Zr0.2V1.867Mn0.373Cr0.56Ni0.7由C14型Laves相和V基固溶体相构成.在充电过程中,充电时间由3.33增至120 min时,Laves相的晶胞体积膨胀率ΔV/V分别由0.301％增加到2.719％,而V基同溶体相的ΔV/V由0.011％增至1.685％.在放电过程中,放电时间从0 min增加到165 min时,Layes相的ΔV/V从14.542％降到8.119％;而V基固溶体相的△V/V从8.117％减小到6.248％.说明电化学吸氢时,氢首先被Laves相吸收,然后再扩散进入V基固溶体;电化学放氢时, V基固溶体中的氢首先扩散进入Laves相然后再释放.因此,该合金中,Laves相既是吸氢相又是催化相,提高合金中V基固溶体相的利用率,从而使Ti-V基贮氢合金具有较好的综合电化学性能.     

Ti3Al-Ni合金的吸氢和放氢性能

近年来 ,具有大容量的新型储氢材料受到广泛关注。D0 1 9-Ti3Al合金由于质轻和超过 3 %的吸氢容量而成为具有储氢潜质的合金之一。然而 ,Ti3AlHX 合金由于稳定性好 ,即吸氢温度太高而无法实际应用。这就使得降低吸氢温度变得必要和重要起来。最近 ,日本学者S .ManO通过Ni替换Ti75-XAl2 5MX (X =15 %和 2 5 % )合金中的合金元素 ,研究了Ni元素在吸氢前后对Ti3Al合金晶体结构的影响 ,同时分析了吸氢含量和放氢温度的变化。实验用材料选用氩气保护下电弧熔炼的Ti75-XAl2 5MX (X =0～ 2 5mol% )合金 ,经过真空下的 10 73K/180h/3 0…     

几种固溶体储氢合金的研究近况

介绍了Ti-V-Ni，Ti-V-Mn和Ti-V-Cr3种固溶体合金作为储氢合金或电极材料的研究现状。对无电化学活性的基质合金，用元素取代、合成复合合金和多相合金等多种方法，得到一些性能较好的负极材料。同时指出了固溶体合金的特点和研究工作的方向。     

成份调整对V-Ti-Cr-Fe合金吸放氢性能的影响

分别调整Ti／Cr比及V含量，对V-Ti-Cr-Fe系四元合金的室温吸放氢性能进行了研究。结果表明：随V30Ti31＋xCr29-xFe10合金中Ti／Cr增大，合金吸氢量增大，放氢平台压降低，Ti／Cr〉1．2时放氢量减小，298K最大吸氢量3．66％（质量），最大放氢量2．0％（质量）；随Vx（TiCrFe）100-x（Ti-Cr-Fe=7：5：2）中V含量增大，合金吸氢量增大，放氢量增大，放氢平台压降低，V含量20％（原子）的合金中出现Laves相，298K最大吸氢量3．73％（质量），最大放氢量2．08％（质量）。     

Ti-V-Fe系储氢合金的相结构及吸放氢特性

系统研究了Ti100-x-yVxFey（x=54，49，44；y=5，7．5，10）储氢合金的相结构及其吸放氢性能。XRD及SEM分析表明，Ti41V54Fes合金由体心立方（BCC）结构的固溶体主相和少量的α-Ti第二相组成；而Ti43．5V49Fe7．5和Ti46V44Fe10合金均为单一的BCC固溶体相。储氢性能测试表明，3种合金的动力学性能均很好，在室温和4MPa初始氢压条件下，无需氢化孕育期就能快速吸氢：经4次～5次吸放氢循环即能活化，仅2min～3min就能吸氢饱和达到最大吸氢量363．7ml／g-372．4ml／g；在300℃和0．1MPa放氢终压条件下，合金的放氢量在220．3ml／g-238．5ml／g之间。在所研究的合金中，Ti46V44Fe10合金的综合性能最佳，经4次吸放氢循环即活化，室温最大吸氢量可达372．4ml／g，放氢量达到238．5ml／g。     

Ti—Ⅴ基多相贮氢电极合金的电化学吸放氢机理研究

采用XRD的Rietveld全谱拟合技术以及利用储氢合金吸氢量与其体积膨胀成线形关系的原理，研究了Ti—Ⅴ基贮氢电极合金的电化学吸放氢机理．结果表明，铸态合金Ti0.8Zr0.2V1.867Mn0．373Cr0．56Ni0.7由C14型Laves相和Ⅴ基固溶体相构成在充电过程中，充电时间由3．33增至120min时，Laves相的晶胞体积膨胀率△Ⅴ／Ⅴ分别由0．301％增加到2．719％，而Ⅴ基固溶体相的△Ⅴ／Ⅴ由0．011％增至1．685％．在放电过程中，放电时间从0min增加到165min时，Laves相的△Ⅴ／Ⅴ从14．542％降到8．119％；而Ⅴ基固溶体相的△Ⅴ／Ⅴ从8．117％减小到6．248％．说明电化学吸氢时，氢首先被Laves相吸收，然后再扩散进入Ⅴ基固溶体；电化学放氢时，Ⅴ基固溶体中的氢首先扩散进入Laves相然旨再释放．因此，该合金中，Laves相既是吸氢相又是催化相，提高合金中Ⅴ基固溶体相的利用率，从而使Ti—Ⅴ基贮氢合金具有较好的综合电化学性能。     

（LPCCa）2（MgNi）17合金的吸放氢性能

研究了用部分Ca取代LPC（LPC为无钕镧镨铈混合稀土金属），同时用部分Ni取代Mg的（LPCCa）2（MgNi）17合金的吸放氢性能。比较了不同温度下，不同成分配比对合金贮氢性能的影响。其中，（LPC）1.9Ca0.1Mg15Ni2合金具有相对较低的放氢温度和较大的放氢节，住275℃的放氢量达3．43％（质量分数）。分析了（LPC）1.9Ca0.1Mg15Ni2的微观结构，同时对合金放氢温度降低的原冈进行了讨论。     

FeTi1.3（Mn）y合金的贮氢性能及其吸放氢机理研究

系统研究了ＦｅＴｉ１．３（Ｍｎ）ｙ（ｙ＝０，０．０１３，０．０２６，０．０２９，０．０５２）合金的贮氢性能。研究结果表明，在ＦｅＴｉ１．３合金中添加少量的富Ｃｅ混合稀土Ｍｍ可以显著改善合金铁活化性能，使未经任何活化处理的合金在室温下经较短孕育的期就能吸放氢。这主要是因为，在合金中分别以β－Ｔｉ和颗粒夹杂形式存在的过量的Ｔｉ和少量的Ｍｎ在氢化过程中首先与氢反应，伴随着的晶格膨胀导致合金中出现大量的显     

Investigation of solid solution hardening in molybdenum alloys

Mechanical properties of pure molybdenum like yield strength, hardness and creep strength can be modified by alloying elements. The alteration of properties can be described as a result of different mechanisms like solid solution hardening (SSH), particle as well as grain boundary hardening. The aim of this work is to quantify the solid solution hardening effect of different solutes. Therefore the influences of other strength affecting mechanisms like grain boundary hardening or particle hardening have been excluded. Based on the powder metallurgical manufacturing route different molybdenum alloys with Cr, Re, Ta, Ti or W additions were prepared. Vickers hardness measurements at room temperature and tensile tests at 500 °C were performed to quantify the hardening effect. Additionally the modulus of rigidity was measured by ultrasonic inspection and the dynamical resonance method. Lattice parameters were measured by means of X-ray diffraction experiments. Applying existing theories of solid solution hardening an attempt was made to separate and quantify dielastic and parelastic effects.     

Diffusion-controlled growth of solid solution scales on nickel-cobalt alloys

Cation concentration profiles in solid—solution scales on NiCo alloys have been calculated by making use of Wagner's theoretical analysis. As a result of the computation method used, it becomes unnecessary to incorporate experimental values in the calculation for either the parabolic rate constant, k_p, or the boundary conditions of the cation profile. The agreement between the independently determined theoretical and experimental cation profiles provides strong support for Wagner's model. The calculated variation of k_p with alloy composition is also in agreement with the experimental data.     

Fe-23Al合金固溶冷却过程中的匀相转变行为

利用金相、XRD、TEM、HTEM方法研究了Fe-23 Al合金固溶冷却过程中的匀相转变行为.结果表明,匀相转变在固溶冷却过程中迅速发生,即使提高固溶温度水冷也未能抑制.Fe-23Al合金固溶体发生调幅分解形成Al原子富集区,并在Al原子富集区原位形成B2和DO3有序相,其中DO3相的尺寸比B2相略小.     

Phase separation of solid solution in Fe-Ni and Fe-Ni-P alloys during irradiation,deformation, and annealing

Measurements of residual resistivity and thermal expansion coefficient have been used to study processes of phase separation in the solid solution of the Fe-34.7 at % Ni and Fe-34.7 at % Ni-0.1 at % P alloys that occurred during deformation, electron irradiation, and subsequent annealings. It has been shown that during both deformation and irradiation, vacancy clusters appear with various multiplicities. In both the deformed alloys and alloys irradiated at room temperatures, the presence of phosphorus atoms in the solid solution facilitates the formation of the vacancy clusters and increases the fraction of vacancies that survive in the form of vacancy clusters. After deformation, irradiation, and subsequent annealings, the same changes are observed in the electrical resistance and thermal expansion coefficient. A nearly linear dependence of the increment in the electrical resistance on the thermal expansion coefficient has been obtained. The results agree well with the matrix model of the phase separation of the solid solution.     

Decomposition of supersaturated solid solution in rapidly solidified foils of tin-cadmium alloys

The results of a study of the phase composition, grain structure, and microstructure of tin-cadmium alloys produced by rapid solidification are presented. Supersaturated solid solution based on the β-Sn is formed from the melt by ultrarapid quenching. The decomposition processes of that metastable phase are investigated at room temperature. The average grain size, texture, and mechanical properties depend on the concentration of cadmium.     

Decomposition of a supersaturated solid solution in thin foils of Sn-Bi alloys

The morphology of the surface and the microstructure of the cross section of rapidly solidified foils of the Sn-Bi alloys have been investigated. The initial observations have been conducted 5–10 min after preparation of the foil. The formation of thin needle-like precipitates immediately after solidification has been found both on the surface and inside the foil. The mechanism of the formation of these precipitates is suggested. After continuous decomposition, the decomposition by the discontinuous mechanism was observed in the foils. When the boundary of the decomposition zone passes through needle-like precipitates of Bi, their thickness increases. For comparison, the rapidly solidified foils after homogenizing and quenching in air have been investigated. A distinction is that upon quenching in air the process of discontinuous decomposition begins within some time after the commencement of observations and occurs simultaneously with the continuous decomposition, which consists in the formation of few globural inclusions. The experimentally established (upon observations in situ) rate of growth of cells upon discontinuous decomposition in rapidly solidified and air-quenched foils of the Sn-8 at % Bi alloy varies within 1–4 × 10⁻⁹ m/s. The results of X-ray diffraction analysis confirm the occurrence of discontinuous decomposition in the foils.