Electroless Deposition Of Nickel On Alumina Powders And Its Application In Preparation Of Ni-Al₂O₃ Composite Coatings

Ni-Al₂O₃ composite materials are widely used in many engineering fields such as aeronautical manufacture,shipbuilding and heated parts in industrial gas turbine,etc.due to its high strength combined with good flexibility,good antioxidation and corrosion resistance.In this study,raw alumina powders and nickel coated alumina powders by electroless deposition were used to prepare Ni-Al₂O₃ composite coatings,and the coating structure and properlity were investigated.Ni coated Al₂O₃ were prepared by electroless plating and the Ni-Al₂O₃ composite coatings were prepared through electrodeposition.The surfactants used include sodium dodecyl sulfate?SDS?,Triton X-100 and hexadecyl trimethyl ammonium bromide?CTAB?.The stability of particles in the plating bath was evaluated through sedimentation test and particle size measurement.Hardness tests were taken with different concentrations and species of surfactants.Composite coating was produced by deposition in watts bath.Polarizing microscopy and scanning electron microscopy?SEM?were used to characterize the structure of coatings.The results indicate that the plating electrolyte containing nickle-coated alumina powders is more stable with sufactants which have positive influence on the deposition of coated alumina compared with the little influence on original alumina powders.By comparison,SDS plays a greater role in influence of the stability of solution.Single dispersant has no influence on original alumina powder particle,and combined addition of two kinds of dispersants produces negative effect.CTAB also has little influence on the size of Ni-Al₂O₃ coating,but Triton X-100 can make the Ni coated Al₂O₃ particle size smaller,and SDS have the better influence on it.