The Effects of Electrolyte S Cobalt and Sodium Dodecyl Sulfate Contents on Microstructural

THE EFFECTS OF ELECTROLYTES COBALT AND SODIUM DODECYL SULFATE CONTENTS ON MICROSTRUCTURAL HOMOGENITY AND HARDNESS OF ELECTRODEPOSITED Cu-Co/WC NANOCOMPOSITE COATING

Shila Khaleghpanah1, Parvin Abachi 2, Abolghasem Dolati3 , Tom W.Coyle4

1,3Dept. of Materials Sci. & Eng., Sharif Uni. of Tech., P.O.Box: 9466-11365, Tehran-Iran 2,4Center for Advanced Coating Technologies, Uni. of Toronto, Toronto-Canada 1 [email protected], [email protected], [email protected], [email protected],

ABSTRACT

The Cu-Co/WC nano-composite coating was synthesized on CP-copper substrate using direct current (DC) electrodeposition method. At this work, it was tried to increase the hardness of surface without losing copper's specific physical properties such as electrical- and thermal-conductivity at the substrate. The effects of cobalt sulfate concentration and sodium dodecyl sulfate (SDS) content as surfactant on homogeneity and hardness of coating were investigated. The copper plates with the thickness of 0.5 mm and purity of 99.99% were used as cathode (substrate) and anode. The cathode exposed surface area was considered as 1 cm2. The electrolyte consists of WC particles, copper sulfate (200 g/l), sulfuric acid (50 g/l), cobalt sulfate and SDS. The concentration of latter ones in the electrolyte varied in the range of (25-75 g/l) and (0.1-0.5 g/(g of WC)), respectively. The particle size of WC powder was in the range of 40-70 nm. The pH and WC content of electrolyte, current density and the temperature of deposition were considered as 1.25, 10 g/l, 60 mA/cm2 and 50˚C, correspondingly. The distribution of WC particles in coating was studied using FESEM. Micro-hardness measurement was performed in Vickers scale. The resultant coating thickness was 60 µm after 30 min.The results showed that there are optimum values for Co 2+ and SDS in the electrolyte (cobalt sulfate 50 g/l and SDS 0.3 g/(g of WC)) which result in better distribution of WC nano-particles in the coating. Fig. 1(a & b) shows distribution of WC particles on the surface of Cu-Co/WC nano-composite coating prepared with different concentrations of cobalt sulfate. Fig. 1.c. reveals roughly homogenous distribution of W on the coating surface at optimum concentration of cobalt sulfate (50 g/l). The coating hardness was improved from 110 to 130 HV in comparison with that of pure copper.

KEYWORDS

Nano-composite coating, Electrodeposition, Cobalt sulfate, SDS, Homogeneity, Hardness a b c

WC Cu-Co

Figure1- FESEM images showing the distribution of WC particles on the surface of Cu-Co/WC nano-composite coating using electrolytes having different contents of cobalt sulfate:(a) 25 g/l and (b) 50 g/l (c) FESEM-MAP-50 g/l

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