共沉淀法制备Fe-Ni合金粉末的热力学分析

Thermodynamic analysis on synthesis of Fe-Ni alloy by chemical Co-precipitation

通过共沉淀-热分解还原法,研究了一种容易实现的大规模制备Fe-Ni合金粉末的方法,根据质量守恒和同时平衡原理,建立了Ni^(2+)-Fe2^(2+)-C_2O_4^(2)--C_2N_2H_8-H_2O体系的热力学分析模型,并根据模型进行了相关计算,绘制了溶液中金属离子浓度对数-pH图,系统研究了沉淀过程中溶液pH值对溶液中各离子浓度的影响。结果表明,当pH值为3.5时,溶液中镍离子和亚铁离子的总浓度[Ni^(2+)]T、[Fe^(2+)]T达到一致,镍离子和亚铁离子的沉淀率相同,且沉淀基本完全,此时能够得到成分均匀性良好的Fe-Ni前驱体粉末。然后,将前驱体粉末在氢氩混合气氛中进行热分解还原,最终得到符合预期Ni/Fe摩尔比的合金粉末。

We have developed a facile strategy for the mass-production techniques of Fe-Ni alloy powder by a coprecipitation - thermal decomposition reduction method. According to the principle of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in the system at ambient temperature were deduced. The diagrams of logarithm ion concentrations versus pH values at different solution compositions were drawn based on the calculation results. The effects of pH value on the concentration of ions in solution were investigated. At about pH 3.5, the values of [Ni2＋]T and [Fe2＋]T were almost the same; the Ni2＋ and Fe2＋ were nearly completely precipitated, and the precipitation rate of these two type of ions were almost the same. Thus, homogeneous Fe-Ni alloys precursor can be obtained under such conditions. And then, the precur- sor was decomposed and reduced in flowing H2/Ar atmosphere. Finally, Fe-Ni alloy powders can be obtained.