Preparation And Properties Of Zirconia Nano Powders And Coatings

Zirconium dioxide possess excellent performance,such as high hardness,good toughness,strong oxidation resistance,low thermal conductivity,high thermal expansion coefficient,good corrosion resistance,high wear resistance and excellent chemical,mechanical and thermal stability and so on.So that it is widely used in structural ceramics,functional ceramics,nuclear technology and biomedical fields.For example,it can be used as cutting tools and abrasive,oxygen sensors,solid oxide fuel cells,high temperature heating material,nuclear fuel cladding,pressure pipe and tube shell,ceramic zircon dental implants and dental coatings.In this paper,zirconia materials,including nano-powders and coatings,were prepared by pure water-based sol-gel method.The thermal properties of sol,micro properties of nano-powders and mechanical properties of coatings were studied.The heating decomposition of zirconia sol was analyzed by thermo gravimetry/differential scanning calorimeters(TGA/DSC),to determine the calcination temperature of nano-powders and the annealing temperature of coatings.For zirconia nano-powders,they were subjected to X-ray diffraction(XRD)to analysis the effects of temperature on the phase transition,it has been completely crystallized into tetragonal structure when the calcination temperature is 430?.The morphology,grain size and phase structure of the powders were analyzed by field emission scanning electron microscope(SEM)and high resolution transmission electron microscopy(TEM).The results show that the spherical particles with uniform size of the powder,and the average grain size is 5-10 nm.Finally,the absorbance characteristic of the nano-powders was analyzed by UV-Vis absorption absorber.The band gap width of ZrO2 nano-powder is 5.34 eV calculated by UV-Vis absorption spectroscopy,which is consistent with the band gap width of t-ZrO2 nano-powder reported in most papers.For zirconia nano-coatings,the thickness is about 350 nm.Then grazing incidence X-ray diffraction(GIXRD)is used to characterize crystal structure,it shows amorphous state when the annealing temperature is 450?,which has been fully crystallized into tetragonal structure when the annealing temperature reaches 600?.The hardness and elastic modulus of zirconia coatings were tested,crystalline ZrO2 coating is higher than the titanium alloy substrate,and it improves wear resistance of titanium alloy.The binding force of zirconia coatings and titanium alloy substrate was analyzed by the scratch test combined with the scratch morphology.The result shows coating is combined with the substrate firmly,which is not easy to peel off,and the higher of binding force with the increase of annealing temperature.Finally,the corrosion resistance of the coating was tested by electrochemical corrosion test,and the results of analyzing dynamic potential polarization curve show that amorphous ZrO2 coating has the best corrosion resistance,and it improves the corrosion property of titanium alloy.