Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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Transactions of Nonferrous Metals Society of China

Vol. 21    No. 5    May 2011

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Thermodynamic analysis on synthesis of fibrous Ni-Co alloys precursor and Ni/Co ratio control
ZHAN Jing1, 2, HE Yue-hui1, ZHOU Di-fei2, ZHANG Chuan-fu2

1. State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083, China;
2. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China

Abstract:According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni(II)−Co(II)−C2O42−−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 Ni2+ and Co2+ 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 formation of multi-coordinated Ni(NH3)n2+ and Co(NH3)n2+ (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.


Key words: thermodynamic analysis; nickel-cobalt alloy; nickel-cobalt oxalate precursor; predefined Ni/Co ratio; fibre-shape

ISSN 1004-0609
CN 43-1238/TG

ISSN 1003-6326
CN 43-1239/TG

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