The Preparation Of TiO₂ Crystals By Dual-frequency Atmospheric Pressure Cold Plasma Jet

In recent years,as a wide band gap n type semiconductor photocatalyst material,TiO₂ has been widely used in many fields,especially in the treatment of water pollution.Compared with many other semiconductor photocatalysts,TiO₂ has many advantages.For example,it has high photocatalytic activity,good stability,corrosion resistance to light,chemical corrosion resistance,innocuity and harmlessness,and low cost.Therefore,TiO₂ is considered to be one of the most promising photocatalysts in twenty-first century.However,TiO₂ also has some defects,for example,it has smaller specific surface area,no light response in the visible region?380-780 nm?and higher recombination rate of photo generated carriers.There are many methods to prepare titanium dioxide.With the rapid development of plasma technology,the atmospheric pressure cold plasma technology has been applied in many fields of science.Energy transfer is achieved by electron impact in atmospheric pressure cold plasma,high enough energy can promote the excitation,dissociation and ionization of reactant molecules and atmospheric pressure cold plasma possess low ion and gas temperature.The reaction process is carried out at low temperature under normal pressure,which reduces the energy consumption of the reaction system.In this paper,a needle ring electrode was designed and used to prepare the titanium dioxide by dual-frequency atmospheric pressure cold plasma jet.At the same time,in order to enhance the photocatalytic activity of titanium dioxide,the nonmetallic elements were doped to the prepared titanium dioxide.And the hollow sphere structure with larger surface area was prepared.The main work consists of the following two parts:Frst part,the titanium tetraisopropoxide?TTIP?carried by N₂ in the argon/oxygen atmospheric pressure plasma jet was studied.In the experiment,the electrode of the plasma discharge is a self-made coaxial needle-ring structure electrode.The needle electrode is connected with the low frequency power source?100 kHz?and the ring electrode is connected with the radio frequency power source?100 MHz?.The atmospheric pressure dual-frequency?DF?cold plasma jet can one step deposit high quality TiO2 films.The experiment was explored by changing the flow of N₂.The results show that the mixed crystal phase titanium dioxide containing anatase and rutile phase was prepared under different conditions,and all of them exhibit hollow sphere structure.In the plasma environment,C and N elements were successfully doped into TiO₂ and narrowed the band gap,so that it have light response in the visible range.Second part,the titanium tetraisopropoxide?TTIP?carried by N₂ in the Ar/O₂atmospheric pressure plasma jet was studied.The experiment was still driven by dual frequency power source.The effect of different low frequency discharge voltage and radio frequency discharge power on the surface morphology of TiO₂ was investigated in the experiment.The results show that,the TiO₂ prepared under different discharge parameters showed different morphologies,such as nano fibrous,sphere and collapse sphere.The characteristics of different discharge conditions were analyzed.