Hermann C. Starck Berlin

Uwe Papp

Wolf-Wigand Albrecht

Rudiger Wolf

Axel Hoppe

Dieter Behrens

The invention relates to an improvement of the flowability and an increase in the bulk density of high-surface area valve metal powders by means of the addition of finely divided extraneous metal oxides in quantities of up to 5000 ppm, relative to the quantity of metal, before the powder-metallurgical processing of the valve metal powder.

Process for improving the flowability and increasing the bulk density of

The invention relates to a process for treating the surface of valve metals, in particular niobium and tantalum, in the form of agglomerated or non-agglomerated powders, thin foils or molded articles prepared from powder, for use as electrolytic capacitor electrodes, these metals being heated in at least one stage to temperatures of 300.degree. to 2,000.degree. C. under a high vacuum or an inert gas atmosphere and in the presence of chalcogens or chalcogen compounds, excluding oxygen.

Process for treating the surface of valve metals with chalcogens

To produce valve-metal anodes for electrolytic capacitors, reducing agents are added to the already sintered and/or unsintered anode bodies to improve the electrical properties, whereupon heating is carried out at temperatures above the melting point of the reducing agents and below the temperatures conventionally used for sintering the valve-metal anodes.

Process for producing valve-metal anodes for electrolytic capacitors

A process for the production of valve metal powder, which is doped with boron or boron compounds, for electrolytic capacitors having a low relative leakage current and a high specific charge. The doping with boron or boron compounds in amounts of up to 0.5 percent by weight, relative to the metal content, can take place either during the production of the metal powder or the green valve metal anodes.

Valve metal powder doped with boron

A process for the production of agglomerated valve metal powder which comprises heating an admixture of a valve metal powder and a reducing agent in the presence of an inert gas or under high vacuum for a sufficient time and at a sufficiently elevated temperature that agglomeration of the valve metal powder occurs, and removing the reaction products of the reducing agent and the valve metal and any unreacted reducing agent from the agglomerated valve metal powder by subsequent reaction with an inorganic acid. The agglomerated powder can be sintered to prepare valve metal electrodes, e.g., anodes, which can also be prepared by direct sintering of the admixture of the metal powder and the reducing agent.

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Goslar, Germany

Uwe Papp