The effect of ultrasound on nickel plating

Abstract

The electroless deposition of nickel both in the absence and in the presence of ultrasound has been investigated. In the absence of ultrasound it is found that the rate of deposition goes through a maximum with increase in the concentration of nickel chloride and/or sodium hypophosphite and pH. It is found that with increase in the concentration of nickel ion complexes the rate decreases.

With regard to the properties of the deposit it is found that the as-plated deposit is amorphous, but with heat-treatment at temperatures in the range 200⁰C to 400⁰C recrystallisation followed by grain growth takes place. This heat-treatment initially increases the hardness values due to the dispersion hardening resulting from the formation of Ni3P. At higher temperatures growth of Ni3P particles leads to a decrease in hardness. It is also found that an increase in temperature of the solution leads to a decrease in phosphorus content.

Deposition of electroless nickel in the presence of ultrasound showed that the rate is enhanced at low concentrations of complexing agent whereas at high concentration the rate can even decrease. It is also found that stability of the solution is markedly decreased with the application of ultrasound.

Application of ultrasound is shown to decrease the phosphorus content of the deposit which in turn increased the tendency to obtain crystalline deposits as opposed to amorphous state. The hardness values of as-deposited coatings was shown also to increase with the application of ultrasound due to the decrease in the phosphorus content and the work hardening effect of cavitational collapse on the deposit.

The application of ultrasound to the initial stages of nucleation for the electrocrystallisation of nickel resulted in an infinite rate of nucleation. This was attributed to a change in the activation energy of conversion of a site into a nucleus. The growth rates of electrocrystallised nickel were not affected by ultrasonic irradiation.

Date of Award	1993
Original language	English
Awarding Institution	Coventry University
Supervisor	Timothy Mason (Supervisor) & j Philip Lorimer (Supervisor)