Kinetic Characteristics of the Process of Synthesis of Nickel Nanopowder by the Chemical Metallurgy Method

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. © 2020, Pleiades Publishing, Ltd.