| The physical and chemical characteristics of electrodeposited nickel and nickel alloys, such as their structure and inclusions in the deposit, are influenced by plating conditions. Nickel electroplating from a Watt's solution at high potential is accompanied by the production of H{dollar}sb2{dollar}, O{dollar}sb2{dollar}, and Cl{dollar}sb2{dollar} gases. In addition to nickel ion reduction, Ni{dollar}sp{lcub}2+{rcub}{dollar}, nickel hydride, NiH, and molecular hydrogen, H{dollar}sb2{dollar}, are formed. The former results in a microstructural transformation while the latter produces macroscopic internal stresses. Nickel lattice spacing increases with the addition of hydrogen atoms, as nickel hydride, to the unit cell. Crystal size would decrease as the amount of nickel hydride increases in the deposit. A transformation from FCC to nanocrystalline structure has been detected by x-ray analysis. The influences of gravity and the electrode's orientation with, or without, a ceramic frit shielded cathode have been studied to investigate the mechanism of this phenomenon. If a frit shielded cathode is used, convection enhancement and blocking of the cathode surface by O{dollar}sb2{dollar} and Cl{dollar}sb2{dollar} gaseous evolution are greatly reduced. This results in increased hydride inclusion, deposition efficiency and corrosion resistance.; Electrodeposition of Ni-Co alloy from aqueous solution has been hypothesized to proceed via anomalous codeposition mechanism. Diffusion and/or kinetic control can predominate. The flux of electrochemical species to the electrode surface is governed by diffusion and convection. This was investigated by depositing the alloy under low gravity environment to study the effect of diffusion with minimized convection. Ni-Co alloy deposition was found to proceed with Ni{dollar}sp{lcub}2+{rcub}{dollar} reduction under kinetic control, while Co{dollar}sp{lcub}2+{rcub}{dollar} reduction, and H{dollar}sb2{dollar} evolution were under diffusion control. Nickel deposition is inhibited as cobalt is codeposited. Using specially designed electrochemical cells, various electrode orientations and agitation effects on alloy composition and properties were used to study the codeposition mechanism. |
