Osram Sylvania Inc.

Global Tungsten & Powders Corp.

Patent Treuhand Gesellschaft Fur Elektrische Gluhlampen Mbh

Patent-treuhand-gesellschaft Fuer Elektrische Gluehlampen Mbh

Amistec Gmbh & Co. Kg

Hans-Joachim Lunk

Henry J Stevens

Michael Salmen

Martin Fait

Alfred-Georg Gahn

Thomas J Patrician

Dale E Benjamin

Harry D Martin, Iii

Ricky D Morgan

Tuan A Dang

Bernhard Altmann

Joseph-Peter Guggenbichler

Maria B Winnicka

Timothy A Frisk

Anna S Nached

Burkhard Ziemer

Joachim Fuchs

The coating the tungsten powder particles with a ceramic barrier suppresses the leachability of tungsten in aqueous media. Preferably, the ceramic coating substantially encapsulates each particle of tungsten and has a thickness of at least about 30 nm and, more preferable, from about 200 nm to about 500 nm. Examples of ceramic coatings that may be used include, but are not limited to, aluminum oxide (alumina), aluminum oxyhydroxide (AlOOH), zirconium oxide (zirconia), cerium oxide (ceria), hafnium oxide (hafnia), and magnesium oxide (magnesia).

Ceramic-coated tungsten powder

There is described a method of making a nanocrystalline tungsten powder that comprises: (a) heating a tungsten-containing material in a reducing atmosphere at an intermediate temperature of from about 600&#xb0; C. to about 700&#xb0; C. for an intermediate time period; the tungsten-containing material being selected from ammonium paratungstate, ammonium metatungstate or a tungsten oxide; and (b) increasing the temperature to a final temperature of about 800&#xb0; C. to about 1000&#xb0; C. for a final time period.

Method of making nanocrystalline tungsten powder

A boron addition for making potassium-doped tungsten powder is described herein. Boron is added to a potassium-doped starting material, preferably in the form of boric acid, and then the mixture is reduced to form a potassium-doped tungsten powder. The boron addition results in increased potassium incorporation in the potassium-doped tungsten powder and also effects an increase in potassium retention in sintered compacts of the potassium-doped tungsten powder.

Boron addition for making potassium-doped tungsten

A method of making a potassium-doped tungsten powder is described comprising forming a mixture of ammonium paratungstate or ammonium metatungstate and a potassium-containing compound selected from a thermally unstable potassium-containing salt or a potassium tungstate, and reducing the mixture in a single step without adding additional dopants to form a potassium-doped tungsten powder. The potassium-doped tungsten powder produced by the method of this invention can be pressed, sintered and drawn to produce a non-sag tungsten wire.

Method of making non-sag tungsten wire for electric lamps

It has been discovered that potassium retention in NS tungsten processing may be improved by double doping tungsten blue oxide (TBO) prior to reduction. The novel `double-doping` process consists of dry doping standard singly doped K--Al--Si TBO with potassium nitrate, KNO.sub.3, followed by the standard reduction, acid washing, sintering, rolling and drawing steps. In another aspect, the novel method includes an aqueous extraction of heteropolytungstate anion [SiW.sub.11 O.sub.39 ].sup.8- from a sample of the singly doped tungsten blue oxide to predict potassium retention.

Method of making non-sag tungsten wire

To essentially eliminate aluminum and silicon as contaminants in a doped tungsten wire, the tungsten wire is obtained by mechanical working of reduced tungsten blue oxide which contains as a primary or major constituent a special hexagonal ammonium tungsten bronze of the general formula (NH.sub.4).sub.X (NH.sub.3).sub.y WO.sub.3. A liquid doping step is carried out by adding a solution containing potassium nitrate, the special doped ammonium tungsten bronze forming preferably more than 70% by weight of the overall tungsten blue oxide. The special hexagonal ammonium tungsten bronze is made by decomposing ammonium paratungstate in an ammonium atmosphere, preferably at a temperature between about 400.degree. and 550.degree. C.

Method of manufacturing a non-sag tungsten wire for electric lamps

To dope ammonium paratungstate with potassium, essentially devoid of silicon and ammonium, an aqueous potassium containing solution, preferably potassium hydroxide is added to an aqueous solution of ammonium paratungstate (APW), in a mol relationship of potassium to ammonium of between 0.1 and 10. A doped ammonium potassium paratungstate (AKPW) is obtained. This ammonium potassium paratungstate is then converted to tungsten blue oxide, which is reduced, preferably in a hydrogen containing atmosphere and a tungsten powder is then obtained which will be doped with 40 to 120 ppm, preferably about 90 ppm of potassium. Lamps equipped with tungsten wire filaments drawn from so doped tungsten have lifetimes at least 10% more than lamps with conventional tungsten filaments.

Process of making a non-sag tungsten wire for electric lamps

Growing community of inventors

Towanda, PA, United States of America

Hans-Joachim Lunk