Effect of Bath Temperature on Microstructure of Sulfamate Nickel Electrodeposits

A 70-μm thick nickel was electrodeposited on a copper plate from a sulfamate bath at a current density of 200 A m -2 . The bath temperature was varied from 30 to 60°C at intervals of 10°C to understand how temperature affects electrocrystallization and growth of Ni deposits. Microstructure of Ni deposits was characterized by an optical metallography, and a plane-view and cross-sectional transmission electron microscopy (TEM). The Ni deposit textures were determined by the conventional X-ray diffraction method. The bath temperature proved to have a significant effect on the texture of the Ni deposits. Ni deposited at 50°C exhibited [110] texture, which is an out-growth mode. On the contrary, Ni plated at temperatures lower than 40°C displayed a strong [100] texture, which is typical of lateral growth. The internal grain structure and lattice defects closely corresponded to the texture of the Ni deposits. [110]-oriented deposits consisted of fibrous grains with a high density of dislocations and numerous twins. [100]-oriented deposits exhibited a well-defined columnar grain structure with less lattice defects. In addition, the average grain size of [100]-oriented Ni deposits was larger than that of the [110]-oriented type. The hardness of [100]-oriented deposits is, therefore, lower than that associated with [110] texture.