【作者】 侯雪燕；

【导师】 韩选利；

【作者基本信息】 西安建筑科技大学 ， 应用化学， 2006， 硕士

【摘要】 本文首先对各种贮氢合金的研究开发现状进行了概述，进而确定以稀土-镁-镍系贮氢合金为研究对象，以改善贮氢合金的综合电化学性能为主要目的，着重从很少有人研究的La侧成分优化方面进行，用Ce、Pr和Nd替代La_0.7Mg_0.3Ni_3.5和La_0.7Mg_0.3Ni_2.65Co_0.75Mn_0.1中的La，分别制备了La_0.7-xM_xMg_0.3Ni_3.5系列合金和La_0.7-xM_xMg_0.3Ni_2.65Co_0.75Mn_0.1（M=Ce、Pr和Nd）系列合金，对它们的综合电化学性能进行了比较系统地研究，得到了改变合金综合电化学性能的一些实验关系。运用X射线衍射分析（XRD）、扫描电镜分析（SEM）等方法探讨了稀土-镁-镍系贮氢合金的相结构、微观组织形貌对其电化学性能的联系。本文还研究了La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1合金经简易真空封装和未经真空封装条件下分别放置0-7天，其电化学性能的变化状况，为探寻简易可行的保存方法提供了依据。对La_0.7-xM_xMg_0.3Ni_3.5系列合金和La_0.7-xM_xMg_0.3Ni_2.65Co_0.75Mn_0.1系列合金的研究表明：当采用不同的取代元素和不同的取代量都会引起合金的活化次数、最大放电容量和容量衰减率的变化。用Ce替代时，合金的活化次数有所减少，合金的循环稳定性趋于良好，最大放电容量有所减小。用Pr替代时，能够提高合金的最大放电容量，当Pr含量达0.4时，合金最大放电容量达最大值，合金的活化性能基本没有影响，合金的循环稳定性随Pr元素取代量的增大而减小。用Nd替代时，也能提高合金的最大放电容量，合金的活化性能基本没有影响，合金的循环稳定性增强。经过比较La_0.3Pr_0.4Mg_0.3Ni_3.5和La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1合金的综合电化学性能较好，合金的活化次数分别为11次和8次，最大放电容量分别为238mA·h·g^-1和251mA·h·g^-1 La_0.3Pr_0.4Mg_0.3Ni_3.5经过100次循环充放电后合金的容量衰减率为12.6％，La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1经过150次循环充放电后合金的容量衰减率为5.6％。合金的主相MgNi₂相和LaNi₅相，与合金的充放电容量关系密切。La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1合金中还有Nd₂Ni₁₇相和La₄Co₃相可能使得合金的循环稳定性增强，Ni₆Mn₈相可能有增大合金放电容量的作用。对合金的简易封装方法进行了实验探索。结果表明：真空封装的合金放置后与刚制备出的合金的电化学性能大致相同，说明该方法是一种简单、有效、成本低廉的贮氢合金保存方法。未放入真空保存的合金，放置时间越长，合金的循环稳定性越差。放置后的合金出现了Nd₂O₃相、Ni相、La（OH）₃相和Ni（OH）₂相。合金的微观组织形貌变成非单一的形状。更多还原

【Abstract】 In this paper, sorts of hydrogen alloys have been extensively reviewed and analyzed, and on this basis, the RE-Mg-Ni hydrogen storage electrode alloys were selected as the subject of this study. The study aimed to improve the overall electrochemical properties of the alloys, emphasizing to optimize the lanthanum side which was seldom studied.The lanthanum of La_0.7Mg_0.3Ni_3.5 and La_0.7Mg_0.3Ni_2.65Co_0.75 Mn_0.1 alloys were substituted by cerium, praseodymium and neodymium, respectively and the La_0.7-xM_xMg_0.3Ni_3.5 and La_0.7-xM_xMg_0.3Ni_2.65Co_0.75Mn_0.1 （M=Ce、 Pr and Nd） alloys were prepared. We systematically studied the overall electrochemical properties of the alloys and gained some useful clues to improve the overall electrochemical properties of the alloys. The phase structures, microcosmic form the alloys were studied by XRD, SEM. The changes of the electrochemical properties of the La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1 alloys were studied when they were packed and kept in different ways, for exploring a simple and viable conservation method of the alloys.The La_0.7-xM_xMg_0.3Ni_3.5 and La_0.7-xM_xMg_0.3Ni_2.65Co_0.75Mn_0.1 were studied and the result showed that: different elemental substitutions and different substituted amount affect the discharge capacity, the activity number and the rate of capacity decay of the alloys. When La was substituted by Ce, activity number of alloys was decreased, cyclic stability of alloy electrodes was effectively improved and discharge capacity was decreased. When substituted by Pr, activity number of alloys was almost not changed and the cyclic stability of the alloy electrodes decreased, discharge capacity of the alloys can be increased to the peak when x equals 0.4. When substituted by Nd, activity number of alloys was almost not changed, cyclic stability of alloy electrodes was effectively improved and discharge capacity was increased. The La_0.3Pr_0.4Mg_0.3Ni_3.5 and La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75 Mn_0.1 had better comprehensive electrochemical properties compared with other hydrogen storage alloys studied in this paper.The activity number of the alloys were eleven and eight, and the maximum discharge capacity were 238mA·h·g^-1 and 251mA·h·g^-1, respectively. The rate of capacity decay of La_0.3Pr_0.4Mg_0.3Ni_3.5 alloy was 12.6% after 100 cycles. The rate of capacity decay of La_0.2Nd_0.5Mg_0.3Ni_2.65Co_0.75Mn_0.1 was 5.6% after 150 cycles. Structure analyses showed that the main phases of alloys were MgNi₂ and LaNi₅ phases that had the close connection with the charge discharge capacity of the alloys. LaCo₅ phase and LaCo₃ phase content increased with increasing Co content. The Lao.2Ndo.5Mgo.3Ni2.65Coo.75 Mn_0.1 also had Nd₂Ni₁₄ phase and La₄Co₃ phase which may improve the cyclic stability of the alloy; Ni₆Mn₈ phase may increase the discharge capacity of the alloys.The sample sealing method of the alloys was experimental explored. The alloy encapsulated and conserved for about a week showed the same properties as the alloy which was just made. So it was a simple, effective and cheap consrvation method to seal and kept hydrogen storage electrode alloys in vacuum bags. While the alloy was kept not in vacuum bag, the longger placed, the worse the cyclic stability of the alloys. The placed alloys had the Nd₂O₃ phase, Ni phase, La（OH）₃ phase and Ni（OH）₂ phase. The microcosmic form of the alloys was not the single figure.更多还原