Characterization of electrodeposited powders of the system Ni-Mo-O

Abstract

The electrodeposition of the Ni-Mo-O alloy powders from ammonium chloride containing electrolytes for different Ni/Mo ions concentration ratios was investigated by the polarization measurements. The morphology, chemical composition and phase composition of the electrodeposited Ni-Mo-O alloy powders were investigated using DSC, TGA, SEM, EDS and XRD analysis. According to the EDS results, the powder composition depends on the Ni/Mo ions concentration ratio. However, some deviations in the composition of the as-deposited powders, as the result of the position of the EDS analysis, revealed that the composition of such powders is not homogeneous. The as-deposited alloy powders were nanocrystalline showing only one broad XRD peak around 44 degrees. Their morphology was found to depend on the Ni/Mo ions concentration ratio. After annealing of the Ni-Mo-O powders for 2 h in N-2 atmosphere at 600 degrees C, well-defined crystals for all powders were detected by SEM. The presence of the NiMoO4 phase only or NiMoO4 and MoO3 phases in these powders (XRD), depending on the Ni/Mo ions concentration ratio, was identified. The additional EDS analysis on different recrystallized grains revealed the influence of the annealing on a composition of the alloy powders. (c) 2008 Elsevier Ltd. All rights reserved.