Abstract: The dielectric stability of a hermetically-sealed solid-electrolyte tantalum capacitor during high temperature storage is improved by the introduction of a small controlled amount of water into the capacitor container before the final sealing step in the manufacture of the capacitor.

Abstract: A dielectric film is formed on tantalum pellets by anodization up to 350 V in an electrolyte of an aqueous solution of an organic carboxylic acid with an ionization constant between 10.sup.-2 and 10.sup.-5. The tantalum pellets are suspended from aluminum-magnesium alloy bars into the electrolytic solution with the bar itself being suspended in the electrolyte. The organic carboxylic acid solute residue from anodization is readily volatile at 200.degree. C. The acid is sometimes combined in the electrolyte with ammonia or an amine having a boiling point less than 200.degree. C.; the electrolyte residues from anodization in these systems are also volatile at 200.degree. C. After anodization, tantalum pellet and aluminum-magnesium bar cleanup is thus accomplished by a brief heat treatment at 200.degree. C., eliminating the need for an extended rinse procedure.

Abstract: The oxygen content of tantalum is reduced by intimately contacting the tantalum with an alkali metal halide, reacting them in a non-oxidizing atmosphere at a maximum temperature of 1200.degree. C. to form and expel the tantalum halide and alkali metal oxide formed by the reaction, and then raising the temperature to 1400.degree. C. for no longer than 10 min. to volatilize any excess alkali metal halide. The tantalum may be in the form of a powder or a porous sintered pellet, and an improved product for electrolytic capacitors, with lower leakage current, is obtained.

Abstract: Aluminum electrolytic capacitor foil is stabilized by passing the foil from an anodization step through a bath containing an aqueous borate solution at a temperature of at least 80.degree. C. and a pH of 8.5 to 9.5. After stabilization, the foil is reanodized.

Abstract: Nodular copper is dissolved from aluminum foil surfaces by contacting the aluminum with a 0.1 to 2 M ammonium persulfate solution. The contacting temperature is 20.degree. to 40.degree. C., preferably 30.degree. C., and the contacting time is 1 to 10 minutes, preferably 2 minutes.

Abstract: An electrolytic capacitor has a cathode electrode produced by depositing aluminum on a porous high surface-area dielectric substrate as a layer at least 2000 A thick on each surface.

Abstract: Residual chlorides are removed from electrochemically etched aluminum foil by coupling the foil to an inert electrode having a low hydrogen overvoltage while contacting the foil with nitric acid.

Abstract: Aluminum electrolytic capacitor foil is etched in a bath containing 1.0 to 1.8 M hydrochloric acid, 0.25 to 0.5 M aluminum chloride, 0.2 to 1.0 M phosphoric acid, and 1.0 to 2.0 M chromium trioxide while subjected to the action of alternating current at 35.degree. to 55.degree. C.

Abstract: In a two-stage differential anodization of valve-metal pellets in which the second stage is carried out at a high voltage and with a different electrolyte than the first, underformed spots on the pellets are eliminated in the second stage by adding 0.01-1.0 wt. % of a nonionic surfactant to the second stage electrolyte.

Abstract: Copper on the surface of etched aluminum foil is electrochemically removed by low-voltage anodization in an electrolytic bath containing up to 5% sodium potassium tartrate or ammonium dihydrogen phosphate.

Abstract: The thickness of a hydrous oxide layer on aluminum capacitor foil is controlled by producing the oxide in a hot, dilute borate solution with a pH of about 6, prior to anodization of the foil.

Abstract: Aluminum electrolytic capacitor foil is treated prior to anodization in a two-step process in which a hydrous oxide film is first formed on the foil and the hydrous oxide is then modified. In the first step the foil is immersed in boiling water to form an appropriate thickness of hydrous oxide and in the second step it is immersed in a boiling aqueous solution containing phosphate, silicate, or tartrate ions, or combinations thereof. This treatment results in a decreased power consumption during anodization and produces a film having higher film capacitance.

Abstract: A dielectric oxide film is modified by the incorporation of a minor amount of carbonaceous material. The modified film is produced by anodizing an aluminum electrolytic capacitor anode in a conventional electrolyte containing a minor amount of an alpha- or ortho- hydroxy carboxylic acid or salt.

Abstract: An electrolytic capacitor contains as a spacer-electrolyte a polymer-liquid electrolyte composite. The composite contains the electrolyte as internal liquid phase and is preferably made of cellulose triacetate. Such a composite has high electrical porosity and reduces the equivalent series resistance of the capacitor.

Abstract: In a two-stage anodization process in which the outer portion of a porous valve-metal sintered body is anodized to a higher voltage than the inner portion, the second-stage anodization is carried out in an electrolyte containing a salt of a weak acid.

Abstract: An electrolytic capacitor is provided with an electrode having a stable aluminum oxide dielectric by anodizing an aluminum foil in a process that includes depolarizing the foil in a bath containing a hydration inhibitor selected from tartrate or citrate or phosphate anions.

Abstract: A quantity of tantalum powder is heated to a temperature greater than 400.degree. C in a non-oxidizing atmosphere to dissolve the tantalum oxide film existing on the surfaces of the tantalum particles. The treated powder without conventional organic binders is compressed to form a unitary pellet in a mold maintained in an inert atmosphere. The pellet is subsequently heated in a vacuum to sinter the particles together and to provide a porous tantalum pellet having carbon-free tantalum surfaces and a large exposed surface area per unit weight of tantalum. Electrolytic capacitors made from these pellets exhibit a larger CV product per unit weight of tantalum and/or a lower leakage current than for comparable capacitors known heretofore.