Magnetohydrodynamic Effect On Extending Surface Area Of Anode Aluminum Foil

With the development of mordern technology,aluminum electrolytic capacitors tend to be miniaturized and integrated.It is well known that the key technology for miniaturization and high specific capacitance is to improve the capacitance of anodic aluminum foil.In this paper,the magnetohydrodynamics?MHD?was introduced in etching,tunnel widening and the electrodeposition Al₂O₃-TiO₂ film process to improve the pitting state and the morphology of etching hole by strengthening mass transfer,specific surface area S,dielectric constant ?r,capacitance Cd and corrosion inhibition performance of anodic aluminum foil.The main research contents and results are as follows:?1?Magnetohydrodynamic effect on morphology and capacitance of anode aluminum foil.The MHD was introduced into the direct current electrochemical corrosion process of anodic aluminum foil.The MHD reinforce effect on the inward/outward migration of ions to facilitate pit initiation and the growth of tunnel of aluminum foil was studied in detail.As the result,the MHD effect inhibit the growth of aluminum oxide film,increase the Cl^-adsorption on the surface of anode aluminum foil,reduce the thickness of diffusion layer,strengthen the inward/outward migration of Cl and Al³⁺ within tunnels and decrease the mass transfer resistance of ions in electrolyte.Moreover,the average pore diameter,the unifonnity of etching hole density and the hole depth was further improved and also improving the Cd from 20.83 ?F·cm^-2 up to 39.63 ?F·cm^-2?2?Effect of SDBS coupled with magnetic field on corrosion inhibition performance and specific capacitance of anodic aluminum foilBy introducing magnetic field into the extending surface area process,combined with SDBS as corrosion inhibitor,the effect of MHD on the morphology of etching hole,corrosion inhibition performance and specific capacitance of etched foils was studied systematically.Obviously,the MHD effect increases the mass transfer rate of DBS-/NO₃^-to the etched foil surface/hole in electrolyte,the surface adsorption capacity and distribution unifonnity of SDBS and corrosion inhibition efficiency,as well as the weightlessness reduction.Meanwhile,the inner space of etched hole,the average hole depth and specific surface area are also improved evidently.The specific capacitance increased from 51.66 ?F·cm^-2 to 65.39 ?F·cm,accompanied by extended average hole depth from 63.52 ?m to 70.30 ?m.?3?Magnetohydrodynamic effect on the structure and performance of Al₂O₃-TiO₂ composite oxide film for formed aluminum foil.By introducing magnetic field into the electrodeposition process,the high dielectric constant Al₂O₃-TiO₂ film formed on etched foil surface.The effect of MHD on the ion diffusion behavior in electrolyte was studied,as well as the structure and properties of Al₂O₃-TiO₂ composite oxide film.The results show that MHD effect increases the Ti⁴⁺ diffusion rate in electrolyte,anatase TiO₂ amount and its distribution uniformity on etched foil surface and tunnel.In addition,from the analysis results of its electrochemical performance tests,the MHD effect also enlarges the relative dielectric constant of composite oxide film,reduces the forming power of anodizing process and raise its specific capacitance up to 58.29 ?F·cm2.Compared to the Al₂O₃-TiO₂ formation foil without MHD,its forming power is decreased by 23.1%,accompanied by 10.1%increment of specific capacitance.