Method of coating cathode heaters
AssigneeGTE Sylvania Incorporated
InventorsMartha J. B. Thomas, Richard A. Fowler, Robert C. Larson
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Abstract
A solution containing dissolved tungsten and dissolved aluminum is spray dried to recover a tungsten-and-aluminum containing powder. The powder is then fired to eliminate hydrated water and volatiles and to convert the aluminum compound into alumina. The powder is next fired at a higher temperature in a reducing atmosphere to reduce the tungsten compound to elemental tungsten. A coating suspension containing the tungsten-alumina powder is then prepared and electrophoretically deposited on cathode heaters.
Claims8
In the process of coating heaters for use with indirectly heated cathodes of electron tubes the steps which comprise:
- preparing a solution containing dissolved tungsten and dissolved aluminum;
- atomizing said solution in a stream heated above the boiling point of water to yield dry particles containing an aluminum compound and a tungsten compound;
- first firing said particles to eliminate volatiles and convert said aluminum compound to alumina;
- second firing said particles at a higher temperature in a reducing atmosphere to reduce said tungsten compound to elemental tungsten;
- third firing said particles at a still higher temperature in a reducing atmosphere to crystallize said particles;
- dispersing said particles in a coating suspension and electrophoretically coating said heaters therewith.
Dependencies are inferred from the claim text.