贮氢合金的研究和进展

概述了近几年来国内两种主要贮氢材料：AB型贮氢合金和Mg—Ni—RE系贮氢合金的研究和进展，着重阐述了添加不同稀土和采用不同工艺条件对两种贮氢合金的贮氢量、吸放氢速度等贮氢性能的影响，总结了当前的研究现状和需要解决的主要问题，提出了今后应用研究的方向。     

贮氢合金表面处理改善吸放氢性能研究

研究表面改性对La系合金贮氢性能的影响,采用化学镀的方法,对LaNi5和LaNi4.7Al0.3合金进行了镀Pd的表面处理实验.在p-C-T测试系统上研究了镀Pd前后,LaNi5和LaNi4.7Al0.3合金的抗CO毒化性能,进行了动力学性能测试、循环次数测试等.实验结果表明,化学镀Pd后的贮氢合金与未镀Pd的合金相比,吸氢性能得到改善,表现为 平台区域相对变平,吸氢孕育期缩短、循环次数增加,抗CO毒化性能提高.     

稀土-镍系贮氢合金研究与开发现状

稀土-镍系贮氢合金是一类重要的贮氢合金。作为贮氢介质具有贮氢量大、价格便宜及抗中毒等优点。本文详细综述了稀土-镍贮氢合金的氢化性能、改性处理及研究现状。     

V-Ti-Cr-Fe合金吸放氢性能的研究

通过均匀设计法对Ti/(Cr Fe)比的优化控制以及对CdFe比的调整，研究了V-Ti-Cr-Fe系四元贮氢合金。结果表明：Ti/(Cr Fe)比对合金的吸放氢性能产生重要影响。Ti/(Cr Fe)比为1时，Cr/Fe比越偏离2．5，合金有效吸氢量越小，放氢平台压随Fe含量增多而升高。Ti/(Cr Fe)比为1，Cr／Fe比为2．5的V30Ti35Cr25Fe10合金拥有最理想的吸放氢性能。     

稀土镁镍系合金的循环贮氢性能与粉化特性研究

为了研究稀土镁镍系合金的循环贮氢性能与粉化特性,本文以La0.75Mg0.25Ni3.41Co0.2Al0.03Ti0.06合金为研究对象.压力-组成-温度(PCT)曲线与扫描电镜(SEM)分析结果表明,随循环次数增加,合金电极的吸/放氢量、吸/放氢平台压减小;合金氢化物的放氢效率降低.合金的循环前期容量衰减速率比后期...     

纳米Mg2Ni-1.00%Pd的吸放氢特性研究

采用机械合金化法制备了MgaNi-1．00％Pd（质量分数）合金粉末，用XRD及AFM等分析表征了材料吸放氢前后相和微观结构的变化，测定了Mg2Ni-1．00％Pd合金的吸放氢动力学曲线和PCT曲线。结果表明，机械合金化制备的MgaNi-1．00％Pd合金粉末颗粒尺寸在10—50nm之间；添加1．00％Pd机械球磨，可显著地改善纳米Mg2Ni合金的吸，放氢动力学性能，在初始氢压为1．17MPa、温度为423和473K时，同熔炼法制备的合金相比，材料无需活化即可快速吸氢；PCT曲线上有明显的坪台区，而且坪宽较长，有一定的滞后效应且滞后系数随温度的升高而降低；同熔炼法制备的MgaNi合金相比，纳米MgaNi-1．00％Pd合金吸氢时的焓变值减小，放氢时焓变值增加，可逆贮氢容量为3．0％H2。     

稀土-镁-镍系贮氢合金电极材料的最新研究进展

综述了最近几年稀土-镁-镍系贮氢合金电极的最新研究进展,主要包括合金材料的组成、制备方法、微观结构以及吸放氢动力学行为和电化学性能等方面的研究.发现复合体系的放电容量为此类合金中最大的,可达到1014 mA·h·g-1.分析讨论了多元合金的复杂结构,各种替代元素对材料性能影响的原因.指出了稀土-镁-镍系贮氢合金的优缺点以及发展趋势.     

镁系储氢薄膜的研究进展

综述了储氢薄膜的研究进展，包括制备方法、制备原理及影响因素。详细介绍了国内外镁系合金薄膜的研究状况，通过分析Mg-Pd，Mg-V，Mg-Ni，Mg-MmNi5复合薄膜的吸氢性能，指出镁系储氢薄膜的理想发展方向应该是寻找一种价格低廉且活性较好的金属元素取代价格较高的Pd、V，采用与其它类活性好的合金复合等方法，获取吸放氢性能优良的储氢薄膜。     

Ni/MH电池用AB_5型贮氢合金电极研究进展

综述AB_5型贮氢合金电极的研究现状, 总结了目前改善AB_5型稀土系贮氢合金综合性能的方法.详细介绍了合金成分优化,控制合金组织结构,形成第二相和表面处理等方面的研究进展.通过这些途径,可以对AB_5型贮氢合金进行深入研究,从而进一步提高合金的性能.     

热处理工艺对La0.85Ce0.15(NiMnAl)5.30贮氢合金相结构及电化学性能影响

本文研究了无钴La_0.85Ce_0.15(NiMnAl)_5.30贮氢合金在不同热处理工艺下相结构及电化学性能变化规律。衍射分析表明退火参数优化后的合金仍为CaCu5单相,温度升高后结晶度增加但活化性能变差;PCT测试结果显示920℃退火时吸氢量达到0.8902;温度升高后吸氢量呈现降低趋势,放氢压力也明显增加;经过980℃热处理8h后晶体结构改善明显,其吸放氢前后膨胀体积变化最小,抗粉化能力强。无钴合金熔点降低、温度升高后利于体相中元素扩散;活化性能降低的同时合金最大放电容量也有所降低。980℃制备合金电化学性能最优,同时具备较好的贮氢性能。     

Microstructures and hydrogen storage properties of as-cast and copper-mould-cast LaMg4Ni alloys

Phase compositions, morphologies and hydrogen storage properties of the as-cast and copper-mould-cast LaMgaNi alloys were studied. The dehydriding onset temperature of the as-cast alloy hydride was about 500 K, which was at least 50 K higher than that of the copper-mould-cast one, and the copper-mould-cast alloy hydride had a faster dehydriding rate compared with as-cast one. Additionally, the copper-mould-cast alloy could uptake 2.85 wt.% hydrogen, which was 95.0% of saturated hydrogen storage capac- ity at room temperature. While only 1.80 wt.% hydrogen （60% of saturated capacity） was absorbed for the as-cast alloy under the same conditions. The reversible hydrogen storage capacities and plateau hydrogen pressures of the two alloys were close. X-ray dif- fractions and scanning electron microscopy results indicated that similar thermodynamic property of the two alloys should be ascribed to the same hydrogen storage phase, Mg and MgzNi. The better hydrogen sorption kinetics of copper-mould-cast alloy should be as- cribed to the more uniform phase distribution compared with that of the as-cast one.     

硼的添加对Mg2Ni储氢合金吸放氢性能的影响

镁系储氢合金有着价格低廉、储氢量大等优点,作为机载储氢材料有着广泛的应用前景,但其过高的氢分解温度,过慢的分解速度等缺点制约着实际应用.采用机械球磨制备出Mg2 Ni-xB(x =0％,1％,5％,10％,15％)系列储氢合金.通过XRD分析了合金的物相结构,采用P-C-T测试仪测定了合金的吸放氢性能,研究了添加不同含量的B对Mg2Ni合金吸放氢性能的影响.研究结果表明,B的添加对合金在200和300℃下吸放氢性能的改善作用不明显,但添加B的合金在400℃下的吸氢量均较Mg2Ni高,B的添加量由1％增至15％的合金吸氢量分别为3.09％,3.00％,2.81％,2.84％,而Mg2Ni的吸氢量则只有2.60％.随着B含量的增加,含B合金吸氢量略有降低;在含B的试样中,含5％B的合金吸氢速率最大,仅需180 s便能完成吸氢.所有含B合金的放氢平台均较Mg2Ni高且较为平坦.本次实验表明,B的添加量对合金性能的提升存在一个最优值,本次实验结果显示,添加5％B相对较好地改善合金的储氢性能,提高合金吸氢量和放氢平台压的同时能保持较快的吸氢速率.     

Highly ameliorated gaseous and electrochemical hydrogen storage dynamics of nanocrystalline and amorphous LaMg12-type alloys prepared by mechanical milling

Nanocrystalline and amorphous LaMg12-type alloy-Ni composites with a nominal composition of LaMg11 Ni+x wt.% Ni (x=100, 200) were synthesized via ball milling.The influences of ball mill-ing duration and Ni adding amount x on the gaseous and electrochemical hydrogen storage dynamics of the alloys were systematically studied.Gaseous hydrogen storage performances were studied by a differential scanning calorimeter and a Sievert apparatus.The dehydrogenation activation energy of the alloy hydrides was evaluated by Kissinger method.The electrochemical hydrogen storage dynam-ics of the alloys was investigated by an automatic galvanostatic system.The H atom diffusion and ap-parent activation enthalpy of the alloys were calculated.The results demonstrate that a variation in Ni content remarkably enhances the gaseous and electrochemical hydrogen storage dynamics perform-ance of the alloys.The gaseous hydriding rate and high-rate discharge (HRD) ability of the alloys ex-hibit maximum values with varying milling duration.However, the dehydriding kinetics of the alloys is always accelerated by prolonging milling duration.Specifically, rising milling time from 5 to 60 h makes the hydrogen desorption ratio (a ratio of the dehydrogenation amount in 20 min to the saturat-ed hydrogenation amount) increase from 57% to 66% for x=100 alloy and from 57% to 70% for x=200.Moreover, the improvement of gaseous hydrogen storage kinetics is attributed to the descending of dehydrogenation activation energy caused by the prolonging of milling duration and growing of Ni content.     

掺杂对氢化燃烧合成镁基储氢合金性能的影响

借助XRD、SEM和自制放氢量的测试装置研究了掺杂对氢化燃烧合成镁镍储氢合金性能的影响。结果表明：三种掺杂中以掺富铈镧系金属产生的镁镍氢化物最多,掺铜产生镁镍氢化物的晶格畸变最为明显。晶胞分析显示Mg_2NiH_4的晶胞参数都有一定的变化。300℃、0．1 MPa下放氢速率的测量显示,掺杂降低了放氢温度,放氢速率一般为6～10 min。掺铜放氢量为2．68％,掺钛放氢量为2．35％,掺富铈镧系金属放氢量为3．10％,掺钛、掺富铈镧系金属活化可适当提高吸放氢量。     

Enhanced hydrogen storage performance of Mg-Cu-Ni system catalyzed by CeO_2 additive

In this paper,the as-cast Mg_(85)Cu_5Ni_(10) alloy and Mg_(85)Cu_5Ni_(10)-x wt% CeO_2(x=0,4,8) alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail.The results show that the Mg_(85)Cu_5Ni_(10) alloys with CeO_2 additive have faster hydrogenation/dehydrogenation kinetics and better thermodynamic properties.The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt% CeO_2.CeO_2 contributes to producing structural defects,nanocrystallines,grain boundaries,partial amorphous,lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process.Meanwhile,CeO_2 additive weakens the bond energy of Mg-H.These micro structural changes caused by CeO_2 additive improve the hydrogen storage performance of Mg_(85)Cu_5Ni_(10) markedly.     

Microstructure and improved hydrogen storage properties of Mg based alloy powders prepared by modified milling method

Abstract

In this study, the modified preparation method of combining planetary and vibratory ball milling was proposed to prepare Mg based hydrogen storage alloy powders. The comparison of micromorphology and hydrogen storage behaviour between Mg₂Ni prepared using the modified and conventional preparation methods were investigated experimentally. The comparison results showed that the combination of first planetary and then vibratory ball milling has more favourable effect on improving both the kinetics and the thermodynamics of ball milled Mg₂Ni alloys. The sample synthesised by first planetary milling for 40 h and then vibratory milling for 30 h has faster hydrogen absorption kinetics and lower dehydriding onset temperature than those prepared by the single method of planetary or vibratory milling and hydriding combustion synthesis owing to its popcorn-like microstructure. Moreover, this kind of modified method reduces the reaction enthalpy and activation energy by up to ～18 and 22% respectively.     

镁基合金的储氢功能

镁及其合金独特的热力学性质可使其用作充电电池的电极材料以及储氢材料,这不仅因为它的价格相对低廉,而且对环境不造成威胁,更重要的是它的优异的储氢功能.该文综述并预测了镁基合金在储氢材料上的应用前景.     

A comparison study of hydrogen storage performances of SmMg11Ni alloys prepared by melt spinning and ball milling

The melt spinning(MS) and ball milling(BM) technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_(11)Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_(Ms)(des) = 82.51 kJ/mol and ΔH_(BM)(des) = 81.68 kJ/mol, respectively, viz.ΔH_(MS)(des) ΔH_(BM)(des). The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.     

Hydriding/dehydriding behaviors of La2Mg17-10 wt.%Ni composite prepared by mechanical milling

The structure and hydriding/dehydriding behaviors of La2Mg17-10 wt.%Ni composite prepared by mechanical milling were investigated. Compared with the un-milled sample, the as-milled alloys were ready to be activated and the kinetics of hydrogen absorption was relatively fast even at environmental temperature. The composite milled for 10 h absorbed 3.16 wt.% hydrogen within 100 s at 290 K. The kinetic mechanisms of hydriding/dehydriding reactions were analyzed by using a new model. The results showed that hydrogenation processes for all composites were controlled by hydrogen diffusion and the minimum activation energy was 15.3 kJ/mol H2 for the composite milled for 10 h. Mechanical milling changed the dehydriding reaction rate-controlling step from surface penetration to diffusion and reduced the activation energy from 204.6 to 87.4 kJ/mol H2. The optimum milled duration was 5 h for desorption in our trials.     

AB5型贮氢合金结构分析

贮氢合金的电极性能取决于贮氢合金的微结构。从晶体结构、电子结构及化学键结构等各方面对市场上广泛应用的AB5型贮氢合金的结构进行综述，同时讨论合金结构与合金吸放氢性能之间的关系。