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

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

1996-02-28

1998-07-28

Wyszomierski, George

Specialized metallurgical processes, compositions for use therei

Processes

Producing or purifying free metal powder or producing or...

75369, 75371, 419 4, 419 63, B22F 924

Patent

active

057857318

ABSTRACT:
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.

REFERENCES:
patent: 5072147 (1991-12-01), Pugh et al.
patent: 5087299 (1992-02-01), Fukuchi et al.
"The Metallurgy of Doped/Non-Sag Tungsten", edited by Erwin Pink and Laszlo artha, Elsevier Applied Science, London (1989), pp. 4-19, 30-35, 84-99.
"Bubbles--Chemische Untersuchungen zur Herstellung kaliumdotierter Wolframpulver fur die Gluhlampenproduktion" (Bubbles--Chemical Investigations Relating to the Manufacture of Potassium Doped Tungsten Powder for the Production of Incandescent Lamps, Thesis by Alfred Gahn, Ludwig-Maximilians-University, Munich, 1986.

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