Synthesis of Nanostructured Ni-TiO2 Composite Coatings by Sol-Enhanced Electroplating

A Ni-TiO2 composite film was prepared by electrodeposition containing Ti precursor sol (sol-enhanced deposition). The electrochemical process, microstructures, and properties of the sol-enhanced and traditional composite coatings were studied and compared. The sol-enhanced Ni-TiO2 composite coating possessed a smooth surface and a compact microstructure and showed higher mechanical properties (430 HV100) compared with the traditional coatings (360 HV100). It is believed that the strengthening effects resulted from the high dispersion of TiO2 nanoparticles. The sol added coatings also showed slower growth of Ni grains along the [220] direction but did not change the orientation. It is suggested that the sol addition reduced the thickness of the diffusion layer and increased the limited current density. Therefore, the polarization control in the sol-enhanced process changed from the traditional concentration polarization to electrochemical polarization, avoiding the formation of loose and dendritic structures at high current density. (C) 2010 The Electrochemical Society. [DOI:10.1149/1.3442366] All rights reserved.