Ni-P-TiO2 Composite coatings on copper produced by sol-enhanced electroplating

Abstract

Ni-P-TiO2 composite coatings were prepared on copper substrate by TiO2 sol-enhanced electroplating. A systematic study of Ni-P-X coatings with different sol concentrations (TiO2 concentration X from 0 to 50 mL/L) has been conducted in order to understand the effect of TiO2 sol addition and the strengthening mechanism. The sol-enhanced coatings show significantly improved mechanical properties comparing with the traditional composite coatings. The optimal mechanical properties can be achieved when the sol concentration is 12.5 mL/L. In this case, the microhardness of Ni-P-12.5 mL/L TiO2 composite coatings can reach ~710 HV while the Ni-P is ~520 HV. It is observed that the TiO2 nanoparticles tend to aggregate and the voids may emerge in the coatings when excess sol was added into the electrolyte, decreasing the dispersion strengthen effect. Correspondingly, the mechanical property of Ni-P-50 ml/L TiO2 coating declined.