Gas Sensitivity And Simulation Studies On Au-deposited And Nitrogen-doped TiO₂ Nanotubes Detecting SF₆ Decomposed Components

Gas insulated switchgear?GIS?using Sulfur hexafluoride?SF₆?as insulating medium has strong application potential in power transmission and distribution of electrical industry.GIS based on SF₆ gas possesses obvious advantages such as compact structure,low land coverage,flexible installment,high stability and reliability.With the number of GIS which has been manufactured and operated increases,the role of GIS for electrical system is more important.The operating stability of GIS is certain to influence that of the whole electrical system.Partial discharge is the characteristic of insulation fault of GIS,also the key cause for acceleration of insulation fault.It is essential to monitor and evaluate the partial discharge inside GIS in order to find the potential insulation defects in time,thus avoiding further severe insulation breakdown in sequence.It is reported that SF₆ gas will decompose and react with moisture water,oxygen and insulation materials under the energy of partial discharge.Several components will come into being including SO₂,SOF₂,and SO₂F₂,et al.Online monitoring of these products provides new method of detecting partial discharge inside GIS and evaluating the operating condition of GIS.The research of this paper is supported by the National Natural Science Foundation program.The main aim of the research is to investigate surface-modified TiO₂ nanotube sensors by experiments and simulation and the main content includes two aspects,those are noble metal doping and non metal doping.TiO₂ nanotubes thin film was treated by Au and N doping,with experimental and simulational results compared to study the gas-sensing micro-mechanism of different elements doped TiO₂ nanotubes.Study of noble metal Au deposited TiO₂ nanotubes.Au,one type of noble metal,was chosen as deposition element and deposited on TiO₂ nanotubes which was fabricated by means of anodic oxidation method.Gas-sensing properties of Au-deposited TiO₂ nanotubes to SO₂,SOF₂,and SO₂F₂ were tested through gas-sensing test platform.Results show that Au deposition changes the response of TiO₂ nanotubes to three types of gases,with response to SO₂ decreasing,response to SO₂F₂ enhanced,and that to SOF₂ almost unchanged.After expetimental research,simulation model of Au-deposited anatase TiO₂?101?surface was built,with adsorption parameters including adsorption energy,charge transfer,and density of states calculated when three types of gases approach this surface.Gas-sensing mechanism of Au-deposited TiO₂ nanotubes was analyzed.Prediction based on simulation was consistent with experimental behaviors.Study of nonmetal N-doped TiO₂ nanotubes.On the basis of reports about modification effects of nonmetal doping on narrowing energy gap and enhancing properties of TiO₂ nanotubes,N doping was selected for modification of TiO₂ nanotubes.Plasma treatment produced by dielectric barrier discharge was used for surface modification of TiO₂ nanotubes,with treatment platform built and modification process conducted.Surface characterization methods like SEM,XRD,and XPS were utilized to estimate the effect of nitrogen plasma,showing that N-doped TiO₂ nanotubes were successfully produced.Gas-sensing experiments indicate N-doping does not change sensing response to SO₂,enhance sensing response to SOF₂,decreasing sensing response to SO₂F₂.Simulation of N-doped TiO₂ nanotubes to three types of gases was conducted based on the previous simulation of Au-deposited TiO₂ nanotubes,with adsorption models built and key parameters calculated.Explanation of the gas-sensing phenomenon in experiments on the basis of micro simulation was satisfactory.Through comparison of experimental and simulational study of Au-deposited and N-doped TiO₂ nanotubes with that of intrinsic TiO₂ nanotubes,it is preliminarily confirmed which type of gas among SO₂,SOF₂,SO₂F₂ is more suitable for detection through intrinsic,Au-deposited and N-doped TiO₂ nanotubes,which can provide support for detection of SF₆ decomposition components and lay experimental and theoretical foundation for the fabrication and application of sensor arrays detectiong SF₆ decomposed products.