| An octangonal cathode was designed and used and the Ni-Al2O3 composite coating was produced in watt' solution with Al2O3 particles in the dissertation. The relationship of the coating thickness and the mount of particles in the composite coatings with the current density, stirring rate and the particle content in electrolyte were studied. Result show that the current density, the speed of the rotation and Al2O3 content in electrolyte influence the content of particles of the composite coatings obviously. The whole tendency is that the more thickness and particle content in the composite coatings, the nearer distance from the anode to the plated layer, the coatings thickness and it's particle content vary with the technological parameters. When the current density was 10 A/dm2 and stirring rate 350r/min, the most amount of particle contents of different coatings gained too as the particle concentration was 80 g/L in the electrolyte.The co-deposition was performed using the directional flowing of the electrolyte with two directions of the perpendicularity and the horizon in order to reduce the thickness of the diffusion layer close to the cathode, enhance the current density, and accelerate the rate of the co-deposition Al2O3 and nickel. Result showed that the rate of co-deposition was increased by means of making the electrolyte flow along the surface of the cathode in certain direction, while it is not obvious how to increase the content of particle in the coating. The inherent principle was needed further study in the future experiments.Under certain current density, stirring rate and Al2O3 particle concentration in the plating solutions, the functional gradient coating with particle continuously distributed in the direction of thickness was prepared by roatating the cathode according to a decided regularity, which provide a new technique for fabrication of functional gradient materials. |
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