Morphology of nickel powder contactly precipitated on magnesium in aqueous solutions
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MORPHOLOGY OF NICKEL POWDER CONTACTLY PRECIPITATED ON MAGNESIUM IN AQUEOUS SOLUTIONS O. I. Kuntyi, O. B. Masyk, and R. V. Minakova
UDC 621.785
We analyze the morphology of nickel powders obtained by contact precipitation on magnesium and establish the hierarchy of the shape of particles. We show that in the concentration range of nickel salt of 0.2 – 2.0 M and at the temperature range 20 – 95°C, elementary precipitated round particles form rings, arcs, and polygonal conglomerations of the second level of formation. The reproduction of the magnesium surface occurs at the third level. The greater the specific yield of nickel, the better this reproduction. We establish that the value of the specific yield of nickel increases with increase in the temperature and concentration of nickel ions in the solution.
Properties of powder materials are structure-sensitive and, in the process of formation of structure, they inherit morphological and other properties of the original powders whose characteristics depend on methods of their production and technological parameters of the process. One of the methods of production of dispersed metals, which are characterized by a low energy capacity and simple technology, is based on their contact precipitation in aqueous solutions [1 – 5]. Problems of contact precipitation of conditioned copper powders and the possibility of their application to powder metallurgy have been studied most completely [3, 5, 6]. Due to the considerable amount of secondary nickel raw material [7] and the relative ease of leaching of this metal [8], it is important to investigate the possibilities of contact precipitation of metal nickel in the dispersed form. This is given only in [4] where reduction is performed on aluminum but the morphology of the obtained dispersed metal is not studied. The authors of [9] show that, using magnesium, it is possible to obtain a dispersed high-purity metal. In the present work, we continue investigations of contact precipitation of metal powders on magnesium and the influence of the main technological parameters on their morphology. Experimental Procedure We obtain nickel powders from aqueous systems that simulate solutions of leaching of nickel from secondary raw material. We perform contact precipitation by the following method: We added 1 g of a magnesium chip ∼ 0.1 × 5 × 10 mm in size or scrap of fraction of 0.9 – 1.0 mm to 0.5 liter of a solution of (NH4 ) 2 SO4 (0.5 M), NiSO4 ⋅ 7H2 O (0.2 – 2.0 M), NH3 ⋅ H2 O (up to pH 7.5) in a thermostable beaker and mixed it intensely with an electromechanical mixer. Experiments were carried out at the temperature range 20 – 95°C. After cessation of gas release, which points to the completion of contact precipitation of nickel, we removed it from the solution, washed it with water and ethanol, and dried it in a drying chamber. We study the morphology of nickel powders with an electron scanning microscope (JSM Superprobe-733, JEQL). Results of Testing and Discussion The main parameters of contact precipitation, in particular, the
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