Method of making a long life high current density cathode from tungsten and iridium powders using a quaternary compound as the impregnant
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsLouis E. Branovich, Bernard Smith, Gerard L. Freeman, Donald W. Eckart
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Abstract
A long life high current density cathode is made from a mixture of tungsten nd iridium powders by processing the mixture of powders with an activator into a porous billet, and then impregnating the billet with a quaternary compound including barium, oxygen, a metal selected from the group consisting of osmium, iridium, rhodium, and rhenium, and a metal selected from the group consisting of strontium, calcium, scandium and titanium, by firing the billet in a dry hydrogen furnace at a temperature at which the impregnant melts.
Claims8
Method of making a long life high current density cathode suitable for operation in microwave devices from tungsten and iridium powders using a quaternary compound including barium, oxygen, a metal selected from the group consisting of osmium, iridium, rhodium, and rhenium, and a metal selected from the group consisting of strontium, calcium, scandium, and titanium as the impregnant, said method including the steps of:
- (A) mixing the tungsten and iridium powders in a weight ratio of about 60 weight percent tungsten to about 39 weight percent iridium,
- (B) adding about 1 percent by weight of zirconium hydride to the mixture,
- (C) ball milling the mixture for about 8 hours,
- (D) pressing the ball milled mixture into a billet at about 48,000 psi in a die,
- (E) sintering the billet at about 1800.degree. C. for about 1/2 hour in dry hydrogen of less than -100 dewpoint,
- (F) backfilling the billet with copper in dry hydrogen at about 1150.degree. C.,
- (G) machining the billet to the desired geometry,
- (H) removing the copper by etching in nitric acid,
- (I) thoroughly rinsing in deionized water, methanol and then drying,
- (J) firing the billet in dry hydrogen to about 1400.degree. C. for about 15 minutes,
- (K) impregnating the billet with a quaternary compound including barium, oxygen, a metal selected from the group consisting of osmium, iridium, rhodium and rhenium, and a metal selected from the group consisting of strontium, calcium, scandium, and titanium as the impregnant by firing the billet in a dry hydrogen furnace at a temperature at which the impregnant melts,
- (L) removing the billet from the furnace after the furnace is cooled, and
- (M) removing any loose pieces of impregnant from the billet.
Method of making a long life high current density cathode suitable for operation in microwave devices from tungsten and iridium powders using the quaternary compound, Ba.sub.2 ScOsO.sub.6, as the impregnant, said method including the steps of:
- (A) mixing the tungsten and iridium powders in a weight ratio of about 60 weight percent tungsten to about 39 weight percent iridium,
- (B) adding about 1 percent by weight of zirconium hydride to the mixture,
- (C) ball milling the mixture for about 8 hours,
- (D) pressing the ball milled mixture into a billet at about 48,000 psi in a die,
- (E) sintering the billet at about 1800.degree. C. for about 1/2 hour in dry hydrogen of less than -100 dewpoint,
- (F) backfilling the billet with copper in dry hydrogen at about 1150.degree. C.,
- (G) machining the billet to the desired geometry,
- (H) removing the copper by etching in nitric acid,
- (I) thoroughly rinsing in deionized water, methanol and then drying,
- (J) firing the billet in dry hydrogen to about 1400.degree. C. for about 15 minutes,
- ((K)) impregnating the billet with the quaternary compound, Ba.sub.2 ScOsO.sub.6, by firing the billet in a dry hydrogen furnace at about 1000.degree. C. for about 2 minutes,
- (L) removing the billet from the furnace after the furnace is cooled, and
- (M) removing any loose pieces of impregnant from the billet.
- (L) removing the billet from the furnace after the furnace is cooled, and
- (M) removing any loose pieces of impregnant from the billet.
Dependencies are inferred from the claim text.