Morphology and phase composition of Ni-Co alloy powders electrodeposited from ammonium sulfate-boric acid electrolyte

Abstract

In this paper the morphology of Ni-Co powders electrodeposited from ammonium sulfate-boric acid containing electrolyte is investigated as a function of alloy powder composition. Composition of the electrolyte, i.e. the ratio of Nr2+/Co2+ concentration is found to influence both, the alloy phase composition and the morphology of Ni-Co alloy powders. At the highest ratio of Ni2+/Co ions concentration, typical 2D fern-like dendritic particles were obtained. With decrease of Ni2+/Co 2+ ions ratio among 2D fern-like dendrites, 3D dendrites and different agglomerates of a size of about 100 μm, being either compact (typical for pure Co powder) or composed of a large number of small 3D dendrites on their surface were obtained. According to the X-ray analysis, with decreasing Ni2+/Co2+ concentration ratio the amount of f.c.c. β-Ni phase was found to decrease, while the amount of h.c.p. α-Co phase was found to increase being accompanied by the appearance of the f.c.c. Co phase at Ni2+/Co2+ = 0.33.