Abstract

The kinetic characteristics of the process of synthesis of Ni nanopowder (NP) by the chemical metallurgy method are studied. Nickel NP is obtained by reduction of NiO nanopowder with hydrogen in a tubular furnace at temperatures in the range from 240 to 280°C. Nickel oxide nanopowder is prepared by thermal decomposition of nickel hydroxide Ni(OH)₂ at 300°C, which has been synthesized in advance by chemical precipitation from aqueous solutions of nickel nitrate 10 wt % and alkali NaOH 10 wt % with pH 9 at room temperature. It is found that NiO NP is more readily reduced at temperatures above 250°C. The rate constant of the reduction process at 280°C is about 2.5 times higher than in the case of reduction at 240°C. The duration of the reduction process at 280°C is shorter by a factor of more than two in comparison with the case of reduction at 240°C. Based on the results of calculation of the activation energy of the reduction process from isothermal data, an assumption is made about the kinetically controlled rate-limiting regime of the reduction of NiO NP. It is revealed that Ni nanoparticles obtained by hydrogen reduction of nickel oxide have an average size in the range of 60–120 nm, and each of them is connected to several adjacent particles by necks.

中文翻译：

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化学冶金法合成镍纳米粉的过程动力学特性

摘要

研究了化学冶金法合成镍纳米粉（NP）过程的动力学特性。镍NP通过在240至280°C的温度下在管式炉中用氢气还原NiO纳米粉获得。氧化镍纳米粉是通过氢氧化镍Ni（OH）_2的热分解制备的在室温下，通过化学沉淀预先从10重量％的硝酸镍和10重量％的碱式NaOH的水溶液中化学沉淀而合成的，在300℃下。发现在高于250℃的温度下NiO NP更容易还原。280℃下的还原过程的速率常数比240℃下的还原过程的速率常数高约2.5倍。与在240℃下还原的情况相比，在280℃下还原过程的持续时间缩短了两倍以上。根据等温数据计算还原过程的活化能的结果，对NiO NP还原的动力学控制的限速机制进行了假设。结果表明，通过氧化镍氢还原制得的镍纳米粒子的平均粒径为60-120 nm，