Influence of additives on the mechanical and protective properties of electrodeposited Ni/AI_2O_3 composite coatings

摘要

Electrochemical composite deposition is a method of codepositing inert particles in an electrodeposited metal matrix. One of the most applied composite coatings due to its high abrasion and heat resistance is the Ni/Al_2O_3 system. Until now, most of the works were carried out using AI_2O_3 microparticles. However, the recently emergence of nanotechnologies has lead to scientific and technological interest on the electrodeposition of N1/AI2O3 composite coatings with AI_2O_3 particles smaller than 100 nm, mainly devoted to increase the abrasion resistance ef metal surfaces in mierodevieea. Despite rapid advanees in naneeomposite coatings research, certain aspects concerning the agglomeration of particles in the electrolyte, the low content of nanoparticles in the composite coating and the non uniformity of particles distribution in the metal matrix remain to be solved. To cope with these problems, some attempts have been made, such as to apply ultrasonic energy before and during the electrodeposition process, to modulate the deposition current or to use additives as chemical dispersion agents for the particles.