Method of making cathode heaters
AssigneeVarian Associates, Inc.
InventorPaul D. Williams
Life of this patent
Estimating the term…
Abstract
A method of improving the thermal emmissivity of a cathode heater wire to allow lower temperature operation of the heater without an attendant lowering in the cathode operating temperature, in which method the surface of a tungsten or molybdenum wire is oxidized, then coated with a salt of a refractory metal, and finally heated to reduce the salt and oxide to their metallic forms thereby causing the heater wire to be roughened and darkened.
Claims8
A method for the manufacture of a heater for an indirectly heated cathode of an electron tube which comprises:
- (a) oxidizing the surface of a heater wire in the presence of an oxidizing gas to form an oxidized exposed surface on said wire, said wire being composed of a refractory metal selected from the group consisting of tungsten and molybdenum;
- and
- (b) reducing the exposed oxidized surface of the wire formed by step (a) to the metallic state of the refractory metal to form a rough, black surface on the wire, step (b) being the final step for forming the heater for the indirectly heated cathode.
A method for the manufacture of a heater for an indirectly heated cathode of an electron tube which comprises the steps of:
- (a) oxidizing the surface of a heater wire by heating the wire in the presence of an oxidizing gas to form an exposed oxidized surface on said wire, said wire being composed of a refractory metal selected from the group consisting of tungsten and molybdenum;
- (b) coating the exposed oxidized surface of the wire with alumina;
- (c) heating the coated wire in the presence of hydrogen to reduce the refractory oxides on the surface of the wire and to sinter the alumina to the wire to form a resulting wire;
- (d) coating the resulting wire with a soluble salt of a refractory metal;
- and
- (e) heating the wire formed by step (d) in a reducing atmosphere to form a rough, black surface on the wire.
A method for the manufacture of a heater for an indirectly heated cathode of an electron tube which comprises:
- (a) oxidizing the surface of a heater wire by heating the wire in the presence of an oxidizing gas to form an exposed oxidized surface on said wire, said wire being composed of a refractory metal selected from the group consisting of tungsten and molybdenum;
- (b) coating the exposed oxidized wire with a soluble salt of a refractory metal;
- and
- (c) reducing the coating and the oxidized surface of the wire in the presence of hydrogen to their metallic states to form a rough, black surface on the wire.
Dependencies are inferred from the claim text.