METHOD OF PREPARING CATHODE FOIL AND CATHODE FOIL FOR ELECTOLYTIC CAPACITORS Russian patent published in 2010 - IPC H01G9/58 H01G9/45 

FIELD: chemistry.

SUBSTANCE: method of preparing cathode foil involves direct deposition of a porous layer of a valve metal on both sides of an aluminium base in a vacuum through electron-beam evaporation while continuously moving the aluminium base over the evaporator in a reactive atmosphere of a mixture of gases. Evaporation is carried out simultaneously from at least two evaporators and condensation of the porous layer takes place during combined supply of process gases into the condensation zone through constant flow channels and supply of gas into the vacuum chamber through a vacuum stabilisation channel. The porous layer is deposited on the aluminium base without depositing an intermediate layer. Condensation of the porous layer takes place when a mixture of process gases is fed into the condensation zone through constant flow channels, whereby the said mixture of process gases is a mixture of nitrogen and oxygen. Flow of the mixture of process gases is in the range of (10-50)× 10^-6 m³/s. Content of oxygen in the mixture of gases is between 20 and 80% of the overall composition of the mixture, while content of nitrogen is between 80 and 20%. Inert gas, e.g. argon, is fed into the vacuum chamber through the vacuum stabilisation channel. The cathode foil contains a 7-30 mcm thick aluminium base on both sides of which there is a porous layer which contains crystals and blocks of crystals separated by pores in form of a branching network of channels, which is a titanium metal-titanium nitride-titanium oxide solid solution. Content of titanium metal is between 25 and 35%, content of titanium oxide is between 30 and 40% and content of titanium nitride is between 30 and 40% of the overall composition of the coating. The coating has a column structure in form of tightly joined fibres. The surface of the coating has a hill-like relief, where each hill is the end of the fibre. The coating has developed open porosity between 40 and 60%. Thickness of the porous layer is between 0.3 and 1.5 mcm, and crystals and blocks of crystals have a granular structure and are stretched perpendicular the surface of the aluminium base. The cathode foil has electrostatic capacitance between 400 and 3000 mcF/cm. Obtaining a hill-like relief of the cathode foil with a developed open surface ensures contact with the electrolyte on the entire surface of the coating.

EFFECT: increased reliability of electrolytic capacitors during use.

7 cl, 4 dwg, 2 tbl