H.c. Starck Gmbh

H. C. Starck, Gmbh & Co Kg

Josua Löffelholz

Jürgen Hilpert

Christoph Schnitter

Karlheinz Reichert

Hady Seyeda

Rüdiger Wolf

Frank Behrens

Marianne Gottschling

Mathias Albert

Siegfried Schmieder

Günter Sadowski

A valve metal powder having a particle shape factor mean value f, as determined by SEM image analysis, of 0.65&#x2266;f&#x2266;1, said powder has an average agglomerate particle size D50 value, as determined with a MasterSizer in accordance with ASTM B 822, of 40 to 200 &#x3bc;m and wherein the valve metal powder is niobium.

Niobium powders having a particle shape

Processes comprising: melting a mixture comprising a valve metal precursor and a diluting agent in at least one first vessel under a first set of temperature and residence time conditions; transferring the mixture to at least one second vessel; and initiating, in the at least one second vessel, a reaction of the valve metal precursor to form a valve metal under a second set of temperature and residence time conditions; valve metal powder prepared thereby and uses therefor.

Processes for preparing valve metal powders, powders prepared thereby and uses therefor

The invention relates to the production of valve metal powders, in particular, tantalum powders by reduction of a corresponding valve metal compound, for example, KTaF, with an alkali metal in the presence of a diluent salt, whereby the reduction is carried out in the presence of a particle diminution agent, preferably, NaSO, which is added to the reaction mixture continuously or in aliquots.

Production of valve metal powders

A valve metal powder by is prepared by a particular set of sequential steps that involves the use of precursor having preformed morphology. The method by which the valve metal is prepared includes a stabilization step that results in the valve metal powder having secondary and tertiary structures that each corresponds to the secondary and tertiary structures of the precursor. Also described is a method of producing solid electrolyte capacitors that include the valve metal powder of the present invention.

Valve metal powders

Process for the production of shaped articles of niobium or tantalum by electrochemical etching of a niobium or tantalum sheet covered by a structured photoresist mask in an aqueous solution containing hydrofluoric acid, the etching being effected under electrochemical conditions under which strong noise is superposed on the etching current and the etching solution contains a water-soluble polymer.

Process for the production of shaped articles of niobium or tantalum by electrochemical etching

Process for producing a valve metal powder by producing a precursor of desired morphology, converting the precursor into an oxide of the valve metal, stabilizing the structure of the oxide by heat treatment and reducing the stabilized oxide while retaining the morphology. Valve metal powders obtainable in this way, in particular comprising spherical agglomerates with a mean agglomerate size of 10&#x2013;80 &#x3bc;m, preferably 20&#x2013;40 &#x3bc;m, and use of these valve metal powders to produce solid electrolyte capacitors.

Valve metal powders and process for producing them

The process comprises the reduction of niobium and/or tantalum oxides by means of alkaline earth metals and/or rare earth metals, wherein the first reduction stage is carried out as far as an average composition corresponding to (Nb, Ta)O.sub.x where x=0.5 to 1.5 and before the second stage the reduction product from the first stage is freed from alkaline earth oxides and/or rare earth metal oxides which are formed (and optionally from excess alkaline earth metal and/or rare earth metal) by washing with mineral acids.

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Langelsheim, Germany

Josua Löffelholz