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 Ni²⁺/Co²⁺ 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 Ni²⁺/Co²⁺ ions typical spongy particles were obtained. With the decrease of the Ni²⁺/Co²⁺ ions ratio agglomerates of the size of about 100 μm, composed of a large number of fern-like dendrites on their surface were obtained. At the lowest Ni²⁺/Co²⁺ concentration ratio, among more dendritic particles, agglomerates typical for pure Co powder deposition were detected. It is also shown that depending on the Ni²⁺/Co²⁺ ratio different types of Ni and Co codeposition could be detected: anomalous and irregular. At the Ni²⁺/Co²⁺ ions ratio higher than 1 only β-Ni phase was detected, while at concentration ratios Ni²⁺/Co²⁺<1 h.c.p. α-Co phase together with β-Ni phase was detected in the alloy powder deposit.