Apostas Política

Preparation of ultrafine nickel powder by chemical reduction in aqueous solution

Recently, with its good conductivity, high melting point, low cost, it can be used as an inexpensive ceramic capacitor internal electrode. They cause a high degree attention. In order to become the most important electrode material, it must use the more economical method for preparation of electrode material. The molding and sintering is an ideal state that means the nickel powder particles are spherical without agglomeration. The pellets diameter nickel powder has a characteristic of good disperse. Milling, electrical, thermal plasma, polyol method, chemical vapor deposition, chemical deposition in aqueous solution, microwave hydrothermal method and other methods, wet chemical reduction method has been applied to the preparation of fine metal powder. However, these methods are not the best way for mass production of ultra-fine metal powder. According to the needs of the desired properties of metal powder and the economic aspects of the reaction process, one of the possible preparation methods is the use of strong reducing agents to restore the chemical reduction of metal ions from the solution of metal salts. Nickel salts in aqueous solution has a good solubility and intensive, lower reaction temperature and reaction, fine nickel powder prepared in aqueous solution were studied, in this method, the shape and particle size of nickel powder, particle size distribution and degree of agglomeration can be easily controlled by reaction parameters such as solvent composition, nucleating agents, reducing agents, surface active agent. In order to find the impact of surfactants on the particle morphology, fixed N2H4/Ni2 molar ratio of 2.0, nickel ion concentration is 0.8 mol / L at 60  with different amount of surfactants reaction, the reaction time was 45min. Sodium carboxymethyl cellulose concentration of 1.0g / L (a), 2.0 g / L (b), 4.0 g / L (c) and 8.0 g / L, (d). The presence of the modified surface layer formed by the hydrolysis of organic surfactants Group to prevent caking, and the formation of fine spherical particles. Carboxymethyl cellulose sodium concentration of 1.0g / L, respectively, 2.0 g / L, and the mean particle size of 4.0 g / L sample is almost the same, for 0.5¼m. On the other hand, sodium carboxymethyl cellulose concentration of 0.8g / L, the average particle size only than the other concentrations of little freshman. Show that the addition of surfactant on the average particle size of the average particle size of the sample do not add surfactant difference is very small, and not subject to the same amount of surfactant. Surfactant has two basic roles for metal powder supplier: absorption of the surface tension reduction and the role of colloid. In this study, the formation of nickel powder from the aggregation of nickel atoms in aqueous solution. Therefore, the surfactant package on the nickel particles to prevent the growth of single-particle and multiple particles combined. In propanol solvent volume fraction and under the conditions of adding the surfactant, using hydrazine hydrate to restore different concentration of nickel ions. The spherical nickel powder and the required particle size are got. The average particle size of nickel powder increases with the nickel ion concentration. The introduction of surfactant and propanol reduction of the volume fraction does not produce the caking. Due to the characteristics of quickly restore process in hydrazine, the surface of the nickel powder is not completely reduced to nickel. Nickel powder should stay in a hydrogen atmosphere and under the medium temperature it completely removes the Ni (OH) 2.Source:http://www.mhcmp.com

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