Study On Electrolytic Capacitor Anode Of Titanium Suboxide

Electrolytic capacitors are used expensively with a large market. Due to the influence of properties, resource and cost, anode material of electrolytic capacitor changed from Al to Ta, Nb and suboxide in turn. Thus, study on the anode material of electrolytic capacitor is very important. Titanium is resourceful and cheaper as compared with other materials. But it is difficult to form the oxide layer on the Titanium anode. The electrolytic capacitor anode of Titanium suboxide concerned in this paper have the advantage of high capacity, little leakage current, resourceful and low cost.For the first time titanium suboxide is used as electrolytic capacitor anode and the preparation of titanium suboxide powder by solid-solid reaction between Ti (TiH₂) and TiO₂ is studied. The manufacture of titanium suboxide anode is studied in detail by orthogonal experiments and analysis of variance and the technological conditions are further optimized according to the technological process of sinter electrolytic capacitors: powder pressing, sinter and oxidation of the titanium anode. The specific capacity of titanium suboxide anode prepared is 40000¹20000μF.V.g^-1, leakage current (value of K) is 0.1⁰.005μA.μF^-1.V^-1.The preparation of titanium suboxide powder by solid-solid reaction of Ti (TiH₂) and TiO₂ have the advantages that the products are free from pollution and the oxygen content can be easily controlled. Kinetic analysis shows that the reaction is controlled by the diffusion of oxide in different phases, so milling, mixing and roasting in high temperature can facilitate the reaction.Based on the theories of quantum chemistry and structural chemistry, the stability and conductive mechanism of TiO are analysed . It can be proved that TiO is stable due to the out shell electron structure, ionization potential, characteristics of orbit separating of the Ti and free energy of disproportionation reaction of TiO and TiO₂. The band theory in quantum chemistry illustrates that TiO crystal has excellent electrical properties and it can meet with the demand of electrolytic capacitor on conductivities of anode.The relationship between oxygen content of titanium suboxide, particle size, doped NbO and its electrical properties is studied. The results indicate that oxygen content of titanium suboxide and particle size have great influences on theelectrical properties of anode and doped NbO can enhance the electrical properties of the anode.Investigation of the forming solution shows that the time-voltage curve of titanium suboxide is a half parabola as to most of forming solutions and the ammonium pentaborate or its mixing solution with boracic acid is the best forming solution for the titanium suboxide. The formed titanium suboxide anode shows different interference color (i.e., color code) along with the change of formation voltage.The microscopic appearance of titanium suboxide powder during anode sintering and forming are investigated by SEM in detail. Energy spectrum and X-ray diffraction analysis show that titanium suboxide film is unformed TiC>2.It is the first time that the anode oxidation of titanium suboxide in the mixing solution of 5% boracic acid and 1% ammonium pentaborate is investigated in detail by cyclic voltammetry and AC impedance method. The results indicate that titanium suboxide has the obvious characters of valve metals and there is a peak of oxygen evolution during anode oxidising of titanium suboxide, the reaction is mixed controlled.According to the manufacture craft and anode testing results, titanium suboxide prepared in this paper have some advantages such as high specific capacity, simple manufacture craft and low cost, although its current leakage is similar to aluminum and the problem of dielectric loss isn't insolved. It is believed that electrolytic capacitor using titanium suboxide as anode may become a new-style electrolytic capacitor by continuous improvement.