Synthesis, Microstructure And Properties Of TiO₂/Zn Nanocomposite Coatings

Nanocomposite materials of TiO₂ nanoparticles in Ni,Cu,Ag,Zn nanocrystalline matrixes can be prepared by pluse-electrodeposition.They can be used not only in the area of solar energy cell,air clearing,and killing bacteria but also in the area of corrosion resistant engineering and friction engineering.The a natase structure TiO₂ nanopartMes were prepared with sol-gel method. The results of XRD and TEM reveal that their average grain size is about 20nm.Nanocrystalline zinc coatings with different grain sizes were produced by pluse electrodeposition.The surface morphology of zinc coating was analyzed by optical microscope,The microstructure of zinc coatings was analyzed by SEM.The effect of pulse current density,temperature,and plating time on the grain size of the nanocrystalline zinc were investigated.The dependence of the microhardness and friction coefficient on the grain size was analyzed.The results show that the average grain size of the nanocrystalline Zn which was prepared in different conditions changes in the range 16-45nm,it decreases with increasing pulse current density, increases with increasing temperature,and decreases with increasing plating time. Moreover,the relationship between microhardness and grain size of the nanocrystalline zinc exhibits a conventional Hall-Petch relationship.The microhardness increased to approximately 2-7 times(0.58-1.87GPa)higher than that of pure polycrystalline zinc(0.29GPa).The friction factor of electrodeposited nanocrystalline zinc decreases with decreasing grain size.The friction resistant performance of zinc is improved.Nanocomposite TiO₂/Zn coatings were prepared successfully by the method of pluse-electrodeposition.The surface morphology and microstructure of the TiO₂/Zn nanocomposite coatings was analyzed by SEM.The effects of the pluse current density on TiO₂ content of the coatings were studied.The microhardness and tribology properties of the coatings were analyzed.Results show that TiO₂ content of the coatings increases from 2.2%to 2.8%with increasing of the pluse current density from 1.5 A/cm² to 2.5A/cm².TiO₂ content of the coatings reaches the highest value when pluse current density is 2.5A/cm².then TiO₂ content of the coatings decreases from 2.8%to 1.8%with increasing of the pluse current density from 2.5 A/cm² to 3.5A/cm².The microhardness increases from 0.9 GPa to 1.3 GPa with the increase of TiO₂ content varied from 1.8%to 2.8%.With the microhardness increasing,the wear volume and the friction factor decrease,the wear resistance increase.