Study On Discharge Decomposition Of C₄F₇N/CO₂ Mixed Gas And Adsorption Of Decomposed Components On Al（110） Surface

SF₆ is widely used in gas-insulated equipment,but there are problems such as high greenhouse effect and large influence of electric field unevenness,which makes domestic and foreign countries start to seek alternative media for SF₆.C₄F₇N excels in dielectric strength,GWP,and time in the atmosphere,which has attracted widespread attention from scholars.Under actual operating conditions,C₄F₇N is mixed with buffer gas CO₂ due to its high liquefaction temperature.However,the discharge decomposition mechanism and decomposition products of C₄F₇N/CO₂ mixed gas are not clear.And the compatibility of C₄F₇N and decomposition products with Al,the shell material of gas insulation equipment,needs further research.Therefore,this paper selected the more common（110）surface of metal Al as the research object of compatibility,proposed an accurate calculation method and constructed an accurate calculation model based on density functional theory,and builded a platform for real discharge under equipment operating conditions.The research on the discharge decomposition of C₄F₇N/CO₂ mixed gas and the adsorption of decomposed components on Al（110）surface was carried.In this paper,the discharge decomposition of C₄F₇N/CO₂ mixed gas was firstly studied:calculated the energy change during the decomposition reaction at normal temperature and pressure,analyzed the difficulty of each reaction and determined the decomposition path and decomposition product;calculated the ionization parameters of the discharge decomposition product,and analyzed insulation performance before and after decomposition;builded a platform for the detection of discharge decomposition products,and used experiments to further verify the simulation calculation results.Subsequently,the compatibility of C₄F₇N with Al（110）surface was studied:the adsorption of C₄F₇N and SF₆ on Al（110）surface was calculated,and the adsorption of these two molecules was analyzed and compared.At the same time,the adsorption of C₄F₇N on Al（110）surface was compared with Al（100）surface and Al（111）surface.Finally,the compatibility of C₄F₇N/CO₂ discharge decomposition products with Al（110）surface was studied:the adsorption of decomposition products（CF₄,CF₃CN,COF₂）on Al（110）surface was calculated,and their adsorption processes on Al（110）surface were analyzed,and its interaction mechanism with Al（110）surface was explored.The research results show that the discharge decomposition of C₄F₇N/CO₂ mixed gas is mainly manifested by the combination of free radicals generated by C₄F₇N,and the decomposition products are CF₄,C₃F₈,CF₃CN,CF₃CF₂CN,CNCN,CO and other gases,which are harmful to the human body.From the perspective of ionization parameters,the insulation performance of C₄F₇N/CO₂ mixed gas after discharge decomposition is slightly weaker than before decomposition.The adsorption strength of C₄F₇N on Al（100）,Al（110）and Al（111）surfaces is weaker than that of SF₆ on Al（110）surface.The interaction between CF₃CN and COF₂ is stronger than that of CF₄ on Al（110）surface,but compared to C₄F₇N,these three gas products are not easily adsorbed on Al（110）surface.When CF₃CN and COF₂are adsorbed on Al（110）surface,orbital hybridization between atoms promotes the formation of chemical bonds between N atoms（CN group）and Al atom,and between O atoms（CO group）and Al atom.C₄F₇N and decomposition products（CF₄,CF₃CN,COF₂）are compatible with Al（110）surface.The research results in this paper can provide data parameters and theoretical basis for the research on the discharge decomposition of C₄F₇N/CO₂ mixed gas,and provide reference and guidance for the application of environmentally friendly insulating medium C₄F₇N and the design of its equipment.It has important theoretical and practical significance.