Ultrasonic-assisted electrodeposition of Ni/diamond composite coatings and its structure and electrochemical properties.

Ni/diamond composite coatings have been synthesized by ultrasonic-assisted electrodeposition in a Ni electroplating bath containing diamond nanoparticles. The influences of current density and ultrasonic agitation on the coating composition, morphology, topography, phase structure, and electrochemical characteristics of the electrodeposits were evaluated. Ultrasonic agitation was provided using an external ultrasonic bath at a frequency of 40 kHz and acoustic power of 300 W. Coating samples were also prepared under magnetic stirring for comparison with the ultrasonic-assisted deposits. This work reveals that the diamonds have been incorporated and evenly distributed in the composites. The coatings exhibit dense, granular like morphology with pyramid-like grains. As current density increases, the diamond amount of ultrasonic-assisted electrodeposits first increased to maximum of 11.4 wt% at 3 A dm-2 and then decreases to 9.9 wt% at 5 A dm-2, and the RTC of the preferred orientation (200) plane increases from 76.3% up to 93.4%. The crystallite size was 60-80 nm and the Ra of the magnetic and ultrasonic agitations were 116 nm, 110 nm, respectively. The maximum Rp of 39.9, 50.3 kΩ cm2 was obtained at 4 A dm-2 when respectively immersed 30 min and 7 days, illustrating the best corrosion resistance of the coatings of 4 A dm-2. The effects of mechanical and ultrasonic agitations on the mechanism of the co-electrodeposition process were both proposed. The incorporation of diamond particles enhances the hardness and wear-resisting property of the electrodeposits. The ultrasonic-assisted electrodeposited Ni/diamond coating has better corrosion resistance than that prepared under mechanical stirring conditions.

Ultrasonic-assisted electrodeposition of Ni-Cu/TiN composite coating from sulphate-citrate bath: Structural and electrochemical properties.

Ni-Cu/TiN nanocomposites were electrodeposited by incorporation of TiN nanoparticles in Ni-Cu matrix from sulphate-citrate bath with additives. Ultrasonic assistance was performed in an external ultrasonic bath at ultrasonic frequency of 40 KHz and acoustic power of 300 W. The effects of current density on surface morphology, structural and electrochemical properties of Ni-Cu/TiN nanocomposites were examined. Results indicated that the presence of TiN changes the texture of nickel coating. Corrosion resistance of the composite deposit was enhanced by ultrasonic-assisted electrodeposition. The average roughness value (Ra) of Ni-Cu/TiN is 26-34 nm, which is rougher than Ni-Cu alloy (Ra = 4-5 nm). Not only the ultrasonic agitation, but also the current density affects the corrosion properties of the products. Ni-Cu/TiN nanocomposite electrodeposited at 5 A dm-2 has the highest corrosion resistance.