Fabrication And Properties Of TiN Array Structure Based Nanocapacitors

Compared to batteries and supercapacitors,electrolytic capacitors feature high power density(10⁷ W kg^-1),high cycle life,and low energy density.At present,researchers generally increase the energy density of electrolytic capacitors by organizing nanocapacitor structures,increasing the area of the dielectric film and using dielectric materials with high dielectric constant.This paper proposes to prepare electrolytic capacitors with high energy density by constructing nanostructures and using dielectric materials with high dielectric constan.First,the rapid and controllable preparation of TiO₂ nanotubes was achieved by adding monobutyl phosphate additive to a conventional electrolyte.The best conditions of the constant current anodization were investigated by changing the content of the monobutyl phosphate additive and the process parameter setting of constant current anodization.The addition of monobutyl phosphate additive can increase the growth rate of TiO₂ nanotubes and protect the TiO₂ nanotubes from corrosion at high current densities.When in 2 wt%NH₄F,2 vt%H₂O,0.2 wt%monobutyl phosphate in ethylene glycol electrolyte,oxided at a current density of 30mA cm^-2 for 15 min,TiO₂ nanotube length is 34.5?m,the growth rate of TiO₂nanotubes is 2.3?m min^-1.Then,in order to increase the thickeness of TiN nanotube wall,the anodized TiO₂ nanotubes were hydrothermally treated in tetrabutyl titanate?TBT?solution,and the solution-treated TiO₂ nanotubes were nitrided at high temperature into TiN nanotubes in ammonia gas.The optimum process for preparing thick-tube-wall TiN nanotubes was investigated by changing the concentration of TBT,the concentration of hydrochloric acid and the number of TBT hydrothermal treatments.Heat treatment at 90? for 1 h three times in the TBT solution with a volume ratio of TBT,deionized water and hydrochloric acid of 1:15:4 can thicken the thickness of the TiN nanotube wall from 23 nm to about 62nm,then the oxidation resistance voltage of the TiN nanotubes increases from 3.0 V to 5.5 V.Next,the TiN nanotubes were anodized in a solution of 5 wt%pentaborate and 1wt%boric acid,and TiO₂ dielectric films were prepared on the surface the TiN nanotubes,.Then the TiO₂ dielectric films were converted into BaTiO₃ by an alkaline hydrothermal reaction.The effects of different oxidation conditions on the properties of TiO₂ dielectric films were investigated,and the performance differences between TiO₂ dielectric films and BaTiO₃ dielectric films were compared.Re-oxidation can repair the internal defects of TiO₂ dielectric films.The TiO₂ dielectric films prepared by re-oxidation at 2.5 V have the best performance.At 2.0 V operating voltage,the specific capacitance of TiN nanotube arrays/reoxidized-TiO₂ dielectric films/electrolyte system is 178?F cm^-2,the tan?is 0.73,the leakage current is 0.26mA cm^-2,and the leakage current constant is 0.73?A V^-1?F^-1.The TiO₂ dielectric film can be completely converted into BaTiO₃ by alkaline hydrothermal reaction for 5h.At 3.0 V operating voltage,the specific capacitance of TiN nanotube arrays/BaTiO₃dielectric films/electrolyte system is 97?F cm^-2,the tan?is 0.35,the leakage current is 0.04 mA cm^-2,and the leakage current constant 0.14?A V^-1?F^-1.Compared with the TiO₂ dielectric films,the performance of the TiN nanotube arrays/BaTiO₃dielectric films/electrolyte system has been greatly improved,the tan?is reduced by up to 50%,the leakage current is reduced by up to 84.6%,and the leakage current constant is reduced from 0.73?A V^-1?F^-1 to 0.14?A V^-1?F^-1.