Effect of Some Operating Variables on the Characteristics of Electrodeposited Ni-α-Al_2O_3 and Ni-TiO_2 Composites

摘要

The electrodeposition of Ni-α-Al_2O_3 and Ni-TiO_2 composites was studied from baths containing 100 NiSO_4.7H_2O, 40 NiCl_2. 6H_2O,25 H_3BO_3 and Na_2SO_4. 10H_2O with either 1-20 α-Al_2O_3 or 1-20 gl~(-1) TiO_2 particles suspended in the bath. During electrodeposition, the cathodic polarization increased with increase of both the size and concentration of the inert particle in the bath. An explanation of the mechanism of codeposition of the inert particles with nickel has been presented. The current efficiency of nickel electrodeposition is relatively high (95%) and is not affected by inclusion of the inert particles. As revealed by scanning electron microscopy, the growth morphology of the nickel deposit is affected by the inert particle content, the deposition current density and pH of the bath. The microhardness of the nickel deposit (116 kgf mm~(-2)) increased with increase of the inert particle content and increase of the deposition current density until it reached 243 kgf mm~(-2) as a maximum. The data obtained revealed that the microhardness of the deposit is a morphological-sensitive property.