Copper powder particles formed by electrolysis under different quantities of evolved hydrogen were analyzed using the scanning electron microscopy (SEM) technique. It was found that the structure of the powder particles strongly depended on the quantity of evolved hydrogen that is, two types of powder particles were formed, depending on the quantity of evolved hydrogen. One type of particle was formed during the electrodeposition of copper when the quantity of evolved hydrogen was insufficient to change the hydrodynamic conditions in the near-electrode layer. This particle type comprised dendrites constructed of corncob-like structures as the basic element. The other type of particle was cauliflower-like and was formed when the quantity of evolved hydrogen was sufficient to change the hydrodynamic conditions in the near-electrode layer. However, both types of particle consisted of agglomerates of copper grains. The only difference lay in the size of the copper grains of which the agglomerates were constituted. The size of the grains was a function of the electrodeposition overpotential and, consequently, the quantity of evolved hydrogen, with a tendency to attain a steady value when the electrodeposition overpotential was increased. (C) 2007 Elsevier B.V. All rights reserved.