| Nanotechnology has been considered as one of the most promising science frontiers and hot spots since 1980s. Magnetic nickel nanoparticles, due to their unique physical and chemical properties, could be widely used in catalysts, magnetic materials, conductive paste, nano coating materials, battery materials, and cemented carbide binder etc., so they have attracted a great deal of attention and been the subject of intensive researches over past decades.Various techniques have been developed for synthesis of magnetic nickel nanoparticles, among them, liquid-phase reduction (except for electrodeposition, which usually conducted in aqueous bath) is the one being widely used in laboratory and industrial production because of the advantages of simple operation, high yield, easy control of the powder size and morphology. Reducing agents are essential to liquid-phase reduction. At present, the usually used ones are hydrazine hydrate, NaBH4 or KBH4, polyhydric alcohols and sodium phosphite, which have disadvantages in one way or another. For example, hydrazine hydrate and NaBH4 or KBH4 are toxic substance, polyhydric alcohols would lead to a very slow reaction and sodium phosphite would bring in impurity (Na). Synthesis of nickel particles by electrodeposition from non-aqueous bath is a good way to solve these problems, since there is no need to use reducing agents, the non-aqueous bath could avoid oxidation and improve dispersion at the same time.This paper introduces synthesis of nano nickel powders by electrodeposition method from non-aqueous bath of NiCl2-6H2O. It contains researches on the effects of technological parameters of NiCl2·6H2O initial concentration, voltage, surfactant type and concentration to phase structure of nickel powders, average grain size, morphology and magnetic properties. With the help of X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) and Fourier infrared spectrometer characterization, the following conclusions are drawn:Nickel powders synthesized are of face-centered cubic structure, under 100nm in grain size, shape like dendrite and ferromagnetic.1) With the increasing of NiCl2·6H2O initial concentration in ethanol, the average grain size of nickel powders and saturation magnetization (Ms) increase gradually, and remanence ratio (Mr/Ms) decreases obviously. There exists a minimum value for the coercive force.2) With the increasing of voltage, the average grain size of nickel powders without apparent change in morphology reduces. Moreover, saturation magnetization, remanent magnetization, coercive force and remanence ratio show a similar change trend:surge to the maximum value from the minimum value, then drop quickly and finally increase steadily.3) No matter adding PVP or SDS as surfactant, phase structure of nickel powders, average grain size and grain orientation are of highly similar, except that the nickel powders from adding SDS own a higher magnetism. With the increasing of SDS concentration, the average grain size fluctuates around 25±5nm, and the number of the branches decreases and the dendrites get shorter as well. When the SDS concentration is below 11.67mg/L, saturation magnetization, remanent magnetization and coercive force decrease with SDS concentration increasing. For the SDS concentration over 11.67mg/L, to the contrary, they rise gradually with SDS concentration increasing. Remanence ratio always keeps growing during the concentration range.4) Different from electrodeposition of aqueous solution, we have found in this paper that ethanol molecules have taken part in the discharge process of anode without forming aldehyde oxide and acid. Ethanol molecule could also protect nickel particles form oxidation to some extent. |
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