Nickel nanopowders were synthesized by a chemical reduction of nickel ions with hydrazine hydrate at pH ∼12.5. Sonication of the solutions created a temperature of 54-65 ∘ C to activate the reduction reaction of nickel nanoparticles. The solution pH affected the composition of the resulting nanoparticles. Nickel hydroxide nanoparticles were formed from an alkaline solution (pH∼10) of nickel-hydrazine complexed by dropwise titration. X-ray diffraction of the powder and the analysis of the resulting Williamson-Hall plots revealed that the particle size of the powders ranged from 12 to 14 nm. Addition of polyvinylpyrrolidone into the synthesis decreased the nickel nanoparticle size to approximately 7 nm. Dynamic light scattering and scanning electron microscopy confirmed that the particles were in the nanometer range. The structure of the synthesized nickel and nickel hydroxide nanoparticles was identified by X-ray diffraction and Fourier transform infrared spectroscopy.

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Nickel-layered silicates were electrochemically deposited from acidic bath solutions. Citrate was used as a ligand to stabilize nickel (II) ions in the plating solution. The silicate, montmorillonite, was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta-potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The solution particles at pH 2.5 (−22.2 mV) and pH 3.0 (−21.9 mV) were more stable than at pH 1.6 (−10.1 mV) as shown by zeta-potential analysis of the nickel-citrate-montmorillonite plating solution.Ecorrfor the films ranged from −0.32 to −0.39 V with varying pH from 1.6 to 3.0. The films were immersed in 3.5% NaCl and the open circuit potential monitored for one month. The coatings deposited at pH 3.0 were stable 13 days longer in the salt solution than the other coatings. X-ray diffraction showed a change in the (111)/(200) ratio for the coatings at the various pHs. The scanning electron microscopy and hardness results also support that the electrodeposition of nickel-montmorillonite at pH 3.0 (234 GPa) had improved hardness and morphology compared to pH 2.5 (174 GPa) and pH 1.6 (147 GPa).