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Most of the known methods for the chemical production of nickel nano- and microparticles, nickel oxides and hydroxides use various reducing agents and solvents, which are often toxic to the environment. As a rule, these methods are energy-consuming, lengthy and multi-stage, requiring complex equipment. Therefore, the development of a simple and "green" process for the synthesis of nickel-containing particles, including those with magnetic properties, remains one of the priority tasks. In this paper, a new physicochemical method for oxidation-reduction contact deposition of nickel(II) hydroxide nano-microparticles on the surface of magnesium particles from aqueous solutions of nickelcontaining electrolyte is proposed. This method is based on the local corrosion of microgalvanic cells' formation with predominant hydrogen depolarization. The proposed method was used to obtain nickel(II) hydroxide samples and study their morphology using SEM, as well as their phase composition using XRD analysis. It has been proven that the shape and structure of the resulting Ni(OH)2 particles depend on the contact deposition conditions: depending on the surface state of the magnesium particles as a reducing agent, it is possible to obtain both plate-shaped α/β-Ni(OH)2 particles and threedimensional β-Ni(OH)2 "flowers" with different degrees of crystallinity. [ABSTRACT FROM AUTHOR]

Plant-based biogenic silicon dioxide nanoparticles are used to produce catalysts, additives, templates for deposition of other semiconductors and metals, nanomaterials with novel properties, bio-nanocomposites for biomedical, energy and environmental fields. There are too many ways of bio-SiO2 production. Dependent on the way and obtaining condition some properties of the plant-based biogenic silicon dioxide nanoparticles can be changed. The most amount of silicon is accumulated in stalks and husk biomass of rice, buckwheat and oats. The aim of our work was the investigation of physic-chemical properties of the biogenic silicon dioxide obtained from the rice husk by both ecologically- and economically-friendly technology. The fluoric technology was used for silicon dioxide isolation. Our technology allows us to restore used catalysts. Thus this technology is ecologically and economically efficient. The synthesised SiO2 was studied by using the following methods: low-temperature nitrogen sorption–desorption, XRD, XRF, ICP-MS, AFM, FTIR-ATR, SEM-EDS, TGA. It was established that obtained samples had a specific surface area 107 m2/g. The XRD of the powdered SiO2 showed 100% amorphous characteristics of the material. FTIR, XRF SEM-EDS, ICP-MS and X-ray diffraction indicated that samples contain only SiO2. AFM results show obtained silica particles were having shape from spherical to lamellar. According to SEM investigated sample consists of spherical small aggregates. [ABSTRACT FROM AUTHOR]