Morphology and composition of Ni-Co alloy powders electrodeposited from ammoniacal electrolyte

Abstract

In this paper, the morphology and phase structure of Ni-Co powders electrodeposited from ammoniacal electrolyte are investigated as a function of alloy powder composition. Composition of the electrolyte, i.e. the ratio of Ni(2+)/Co(2+) concentration is found to influence both, the phase structure and the morphology of Ni-Co alloy powders. It is shown that the current density practically does not influence the morphology of Ni-Co alloy powders as well as alloy powder composition. At the highest ratio of the Ni(2+)/Co(2+) ions typical spongy particles were obtained. With the decrease of the Ni(2+)/Co(2+) ions ratio agglomerates of the size of about 100 mu m, composed of a large number of fern-like dendrites on their surface were obtained. At the lowest Ni(2+)/Co(2+) concentration ratio, among more dendritic particles, agglomerates typical for pure Co powder deposition were detected. It is also shown that depending on the Ni(2+)/Co(2+) ratio different types of Ni and Co codeposition could be detected: anomalous and irregular. At the Ni(2+)/Co(2+) ions ratio higher than 1 only beta-Ni phase was detected, while at concentration ratios Ni(2+)/Co(2+) LT 1 h.c.p. alpha-Co phase together with beta-Ni phase was detected in the alloy powder deposit.