Study On The Controllable Preparation Of TiO₂ Nanotubes And The Nano-size Effect

In this paper,TiO₂ nanotube was prepared by anodic oxidation.The electrolyte is composed of ethylene glycol,different mass fraction of NH ₄F and 2 Vol%deionized water.First,the relationship between the parameters of the process and the size of TiO₂ nanotube was studied,and the samples were characterized by F-SEM,EDS spectra,XRD and Raman spectroscopy.Then,the size effect model of tubular nanomaterials was established,and the model was verified by molecular dynamics simulation.The effect of particle size effect on surface energy,vacancy formation energy and diffusion activation energy was analyzed.Finally,the electrochemical properties,UV absorption behavior,photocatalytic properties and wetting behavior of TiO₂ nanotubes with different oxidation time were anal yzed,and the reasons for the performance difference were analyzed by the established model.The main results are as follows:The growth of TiO₂ nanotube film consists mainly of two:The process of initial oxidation film toward the titanium substrate and t he process of F^-dissolution of the initial oxide film at a certain speed.If the dissolution of F^-on the initial oxide film is less than or equal to the rate of the initial oxide film pushing to the substrate,the TiO₂ nanotube film will continue to grow.When the mass concentration of ammonium fluoride is 0.5 wt.%,the thin tube diameter of TiO₂ nanotubes at the preparation is not uniform,and the surface is uneven.When NH₄F concentration reaches 0.75 wt.%,the nanotube structure can not be formed.With the increase of oxidation time,the outer diameter of the nanotubes,wall thickness and length increased gradually.The longer the anodization time,the larger the outer diameter and the length of TiO₂ nanotubes.When the time exceeds 24 h the growth of the TiO₂ nanotube length will be limited.At the same time,it is found that the pore size of the porous membrane on the TiO₂ surface will increase gradually,and the coverage range of the porous membrane will gradually shrink,and the crys tallinity of the anatase in the TiO₂ nanotube film will be improved to a certain extent.Using the energy change during the process of extracting nanoscale from the perfect cuboid crystal surface,the tube metal nano size effect model was established:???The number of atoms of nanoscale and nanoscale nanoparticles with different particle sizes was calculated by this model,and the results were verified with the molecular dynamics model.It was found that the model was highly reliable.The effect of the size of nanoparticles on the surface energy was studied by the nano size effect model of the tubular metal.It is found that the size effect of the surface energy can be generated by the decrease of the particle size.At the same time,the space formation energy and diffusion activation energy of metal nanoparticles were calculated by the size effect model.The results show that the smaller the size of the nanoparticles,the more obvious the effect of the space formation e nergy and the present size effect of the diffusion activation energy.The corrosion resistance of TiO₂ nanotube film was better than that of pure titanium,and when the anodic oxidation time was controlled from 30 min to 60 min,the corrosion resistance was the best.The tube wall of the TiO₂ nanotube decreases with the increase of the oxidation gold.The absorbability of the visible light,the photocatalytic performance and the wetting performance of the deionized water are improved by the TiO₂ nanotube,which is in agreement with the calculated results of the nanoscale effect.