Dispersion Coating Containing High Content of Diamond Particles in a Nickel Matrix Using Azobenzene Surfactant

Abstract

The influence of a redox active surfactant (4-Ethylazobenzene-4’-(oxyethyl)trimethylammonium bromide, AZTAB) and a redox inactive surfactant (n-Dodecyltrimethylammonium bromide, DTAB) on the codeposition of diamond particles with nickel has been investigated. A nickel bath containing DTAB did not deposit a higher amount of diamond particles with nickel, whereas the nickel bath containing AZTAB deposited more than twice the amount of the particles (45.5 vol.%) that were deposited by the former bath (21.6 vol.%). An electrochemical investigation showed that AZTAB is reduced during the nickel deposition. Therefore, it has been assumed here that the reduction of free AZTAB at the cathode surface leads to desorption of AZTAB adsorbed on the particles in the vicinity of the cathode. As a result, deposition of these particles at the cathode surface takes place before these particles are being entrapped in the layer of growing nickel.
The wear resistance of the Ni/diamond composite coatings containing various volumetric content of particles was also investigated. This showed that a higher degree of wear resistance accompanied increased particle content.