Kinetic Characteristics of the Process of Synthesis of Nickel Nanopowder by the Chemical Metallurgy Method
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Kinetic Characteristics of the Process of Synthesis of Nickel Nanopowder by the Chemical Metallurgy Method T. H. Nguyena,b, V. M. Nguyenc,*, V. N. Danchuka, M. H. Nguyenb, H. V. Nguyena, and X. D. Tangd a National
University of Science and Technology “MISiS,” Moscow, 119991 Russia b Le Quy Don Technical University, Hanoi, 100000 Vietnam c Institute of Research and Development, Duy Tan University, Danang, 550000 Vietnam d Vietnam–Russia Tropical Centre, Hanoi, 100000 Vietnam *e-mail: [email protected]; [email protected] Received May 18, 2020; revised May 18, 2020; accepted May 29, 2020
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. DOI: 10.1134/S1995078020020160
INTRODUCTION At present, the production of Ni nanopowder (NP) with the desired properties is of great practical importance [1]. Nickel NP is widely used in various fields of technology and industry, for example, the creation of magnetic materials; preparation of elastic layered electroconductive materials; creation of fine coatings on ceramic, quartz, metal, plastic, and composite items of any complex shape; activation of sintering processes for powder materials; creation of effective catalysts and adsorbents; and production of capacitors, electronic microcircuits, etc. [2–12]. Nickel NP are produced using various mechanical and physicochemical methods, most of which are characterized by high energy consumption and low productivity. The chemical metallurgy method consisting in the chemical deposition of oxygen-containing metal compounds with their subsequent thermal decomposition and reduction has a number of advantages, such as low costs, environmental friendliness, and the possibility of controlling the properties of products during their syntheses [13–15]. Reduction is the longest and mo
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