【作者】 周晓满；

【导师】 井晓天； 卢正欣；

【作者基本信息】 西安理工大学 ， 材料学， 2004， 硕士

【摘要】 本文分别通过X射线衍射分析（XRD）、金相观察、扫描电镜检测（SEM）、能谱分析（EDS）、透射电镜分析（TEM）以及电化学测试（ET）等不同手段，对采用常规电弧熔炼工艺制备的一系列进行B侧合金化的MlNi_5-xM_x（M=Co、Mn、Al）贮氢合金铸锭以及通过单辊快淬得到的快淬态贮氢合金薄带从合金相结构、微观组织形貌、微区成分分析、衍射斑点标定和电化学性能等不同方面进行了较为系统的研究，研究结果表明： 1、XRD分析表明：B侧合金化之后，铸态与快淬态MlNi_5-xM_x贮氢合金的主相仍旧保持CaCu₅型六方晶体结构；快淬合金的衍射谱线中第二相强度明显减弱；Co、Mn、Al元素对Ni的取代导致合金晶格发生膨胀，相应点阵常数a、c增加；与铸态相比，快淬态合金的点阵常数a略有缩短，c略有伸长。 2、铸态合金熔炼过程中产生离异共晶，致使微量镍在晶界偏析；而快淬使合金晶粒细化，并有效抑制元素偏析和第二相产生，提高合金成分均匀性；改善贮氢合金的电化学循环稳定性，但导致活化性能恶化，放电容量降低。西安理工大学硕士学位论文3、Co能够改善电极循环稳定性，但在一定程度上引起了合金活化性能的 衰减;Mn能够提高合金电极放电容量，但过量的Mn易造成偏析，恶 化合金的循环稳定性:Al能够提高电极在碱液中的耐蚀性，从而提高 电极的循环稳定性，但过量Al会使电极活化次数增加，放电容量减小。4、在本试验中LaNi 5-xM、贮氢合金氢化物标准生成烙△H“的最佳范围在 一32.0一33.3 kJ/m 01之间。5、本实验中电极是由气孔、液孔和固相三种网格交织组成的复合体系;贮 氢合金的本征容量受颗粒尺寸‘、合金吸氢量以及扩散系数D。的影响: 实用化电极的放电容量由氢化物电极在充放电循环过程中的活化和衰 退两大效应共同作用决定。更多还原

【Abstract】 In this paper, the as-cast ingots and rapidly quenched thin strips of a series of hydrogen storage alloys MlNi5.xMx (M = Co, Mn, Al) were obtained by traditional arc-melting technics and rapid quenching (melt-spinning) respectively. The influence of B-side elements and the rapid quenching technics on the crystal structure, phase structure, morphology, microstructure, micro-scale element contents distribution and electrochemical properties were systematically investigated by means of X-ray diffraction analysis, metallography, SEM examination, energy dispersive spectrum analysis, TEM examination, electrochemical method and so on. The results are showed as follow:(1) The analysis of XRD indicates that after alloyed by the B side elements, the main phase of as-cast and rapid quenched hydrogen storage alloys MlNi5.xMx still maintain the CaCu5 type hexagonal structure. At the same time, the intensity of the diffraction peaks of the second phase obviously decreases for rapid quenched alloys. It is calculated that the substitution of Co, Mn, Al for Ni causes the lattic of the alloys to expand, which brings about the increase in corresponding crystal constants a, c; In comparison to those of as-cast alloys, the crystal constants of rapidly quenched alloys change slightly: the a axis contracts and the c axis extends.(2) During the solidification process of as-cast alloys nonequilibrium eutectic occurred, which led to small amount of Ni segregation at interdentritic boundary. Rapid quenching can decrease the crystal particles size and effectively suppress the element segregations and the precipitation of the second phase, so that the homogeneity of all alloy elements is improved. Rapid quenching can effectivelypromote the electrochemical cycle stability of hydrogen storage alloys, but it can also make the activation capacity deteriorated and discharge capacity decrease.(3) Co can improve the cycle stability of alloy electrode, but cause the activation capacity of alloys to decay to some degree; Mn can increase the discharge capacity, however excessive Mn may lead to segregation and deteriorate the cycle stability of alloy electrode; Al can improve the resistance corrosion in alkaline solutions, so as to increase electrode cycle stability, but with the amount of Al increasing the number of electrode activation increases and the discharge capacity decrease.(4) In the experiment the optimal range of AH?of MlNi5-xMx hydrogen storage alloys hydride is -32.0 ~ -33.3 kJ/mol.(5) In this paper the electrodes are a three-dimensional network-shape compound system made up of gas, liquid and solid phase. The intrinsic capacity of hydrogen storage alloys is influenced by the size of particles (ro), the diffusion coefficient (Da) and the capacity of hydrogen absorption of alloys. The discharge capacity of practical electrodes depends on both the activation and the decay of hydride electrodes during the charge - discharge cycles.更多还原