Electrolytic method of preparation of composite cobalt-nickel powder
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A new process has been developed for the electrolytic production of composite cobalt-nickel powder, in which separate cobalt and nickel anodes are used, and the currents passing through time are independently regulated. This process ensures that the solution composition remains constant during electrolysis, as a result of which composite powders of predetermined composition, with component ratios ranging from pure cobalt to pure nickel, can be produced in a continuous manner.
A study was made of the influence of cathode current density, as well as of solution temperature, concentration, and acidity on the current yield, composition, and structure of resultant composite powder. The following optimum electrolysis parameters were established. Electrolyte composition: CoSO4 +NiSO4 with a combined Co + Ni content of 10–16 g/liter and a (Co/Ni)sol ratio equal to (Co/Ni)pow; NH4Cl = 20–30 g/liter; NaCl = 30–50 g/liter; pH 3.5–5.0; Dc = 5000–20,000 A/m2, Da(Co) = 100–200 A/m2; Da(Ni) = 100–200 A/m2; ia(Co)/ia(Ni) = (Co/Ni)sol; t = 20–35° C.
It was established that the composite powders are solid solutions of cobalt and nickel, and consist mainly of fine-fraction particles (less than 150 gm). Depending on their composition, the powders contain about 0.02 % hydrogen and between 0.5 and 1.8% oxygen. With increasing nickel content, the amount of oxygen in the powder decreases. The oxygen and hydrogen contents of the powder may be markedly decreased by reduction annealing in a hydrogen atmosphere.
The method evolved may be successfully employed for the preparation of other composite powders of various chemical compositions (iron-nickel, iron-cobalt, iron-nickel-cobalt, etc.).
KeywordsCobalt Composite Powder NiSO4 Cathode Current Density CoSO4
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