Thermodynamic analysis on synthesis of fibrous Ni-Co alloys precursor and Ni/Co ratio control  

纤维状镍钴合金前驱体制备热力学分析与镍钴配比的控制(英文)

作　　者：湛菁[1,2] 贺跃辉[1] 周涤非[2] 张传福[2] 

机构地区：[1]中南大学粉末冶金国家重点实验室,长沙410083 [2]中南大学冶金科学与工程学院,长沙410083

出　　处：《Transactions of Nonferrous Metals Society of China》2011年第5期1141-1148,共8页中国有色金属学报（英文版）

基　　金：Project (20090162120080) supported by Research Fund for the Doctoral Program of Higher Education of China; Project (20070410989) supported by China Postdoctoral Science Foundation; Project (2010FJ3012) supported by the Program of Science and Technology of Hunan Province, China; Project (09JJ4028) supported by Natural Science Foundation of Hunan Province, China

摘　　要：According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni（II）-Co（II）-C2O4^2--NH3-NH4^＋-H2O system at ambient temperature were deduced. The diagrams of logarithm ion concentrations versus pH values at different solution compositions were drawn. The results show that Ni^2＋ and Co^2＋ can completely precipitate at pH less than 5.0 and the predefined Ni/Co ratios can be well kept in the precursor. The precursor morphology is granular aggregation. However, rod aggregation precursor is obtained in the pH range of 5.0-8.0, and fibre-shape precursor is got at pH value higher than 8.0. The Ni/Co ratios in the above two precursors are not reproduced as that in the feed due to the formhtion of multi-coordinated Ni（NH3）n^2＋ and Co（NH3）n^2＋ （n=1-6）. Modification of precipitation medium is favorable for the precursors to keep the predefined Ni/Co ratios of the feed in the pH range of 2.0-8.6. Meanwhile, the precursors with fibrous morphology can be obtained.根据同时平衡原理和质量守恒原理,推导Ni(II)-Co(II)-C2O42--NH3-NH4+-H2O反应体系中金属离子和草酸盐在常温水溶液中的热力学平衡方程,计算并绘制该体系的lg[Me2+]T—pH图。结果表明,在水溶液中,当pH值小于5.0时,溶液中镍离子和钴离子以设定配比转移到前驱体粉末中,前驱体的形貌为粒状聚集体;当pH值大于5.0时,由于Ni(NH3)n2+和Co(NH3)n2+(n=1-6)离子的形成,前驱体粉末中镍钴配比不能维持料液中设定的配比值,前驱体在pH为5.0-8.0范围内呈现棒状形貌,而在pH>8.0时为纤维状形貌。改变沉淀介质可以在pH为2.0-8.6范围内获得配比准确、成分均匀的纤维状镍钴合金前驱体。

关 键 词：thermodynamic analysis nickel-cobalt alloy nickel-cobalt oxalate precursor predefined Ni/Co ratio fibre-shape 

分 类 号：TG146.15[一般工业技术—材料科学与工程]