DE535091C - Process for the production of glow cathodes in which barium is deposited directly on the core wire by distillation - Google Patents

Description

Process for the production of hot cathodes, in which barium is produced by distillation is deposited immediately on the core wire. It is already proposed been made, the active layer of hot cathodes by distilling appropriate Metals, for example barium. These metals are mostly used during pumping out the tube by decomposing a suitable metal compound, which has usually been applied to the anode. So that after the cathode overdistilled layer material adheres as firmly as possible or has not evaporated it has already been proposed to provide the core wire with a thin layer of oxide. In the case of filaments made of oxidizable metals such as tungsten, However, one must proceed very carefully when oxidizing the core wire in order to avoid a avoid excessive oxidation and destruction of the wire.

This difficulty can be avoided by using the wire with a Protective layer made of a noble metal, such as platinum, provides and on this protective layer a thin layer of a relatively easily oxidizing metal, such as copper, applies. The copper adheres very firmly to the underlying platinum protective layer and is converted into the oxide by suitable treatment. The copper layer will chosen only as strong as is necessary to hold on to the active metal. This However, the procedure is very time consuming.

The disadvantages inherent in all known processes can be eliminated avoid if you according to the invention, the core wire made of an alloy one when glowing in an oxygen-containing atmosphere of non-oxidizing metal, like platinum, iridium, and a more easily oxidizing metal like 1, tickel, cobalt, manufactures. The percentage of oxidizable metal must not be more than 5 ° 1o. Such a core wire can be used without any special precautions Glow in the presence of oxygen and then get a layer of oxide, which is a good one Connection between the core wire and the active layer to be applied subsequently guaranteed. There is no risk that the strength of the core wire suffers too much in the case of oxidation, because the oxidation only affects the easily oxidized Part of the alloy captured. In addition, the resulting oxide protects the deeper layers of the core wire before oxidation. The core wire alloys used in accordance with the invention can also be easily processed into wires.

The use of a platinum-nickel alloy with 5 ° 1o nickel content as a core wire for hot cathodes is known per se. Such alloys were but so far only used in connection with other manufacturing processes which the active layer by applying a paste on the not yet oxidized Platinum-nickel wire, so don't overdistill on the already before oxidized wire. One of these known processes is oxidizing of the core wire more difficult to carry out. It can also increase the strength of the core wire in the subsequent oxidation.

Claims (1)

PATENTANSPRTJCH Process for the production of hot cathodes, in which Barium is deposited directly on the core wire by distillation and in which the core wire is oxidized immediately prior to distillation, characterized in that, that as core wire material up to 5 °, l, a base oxidizable metal, z. B. nickel, an alloy containing one upon annealing in an oxygen-containing one Atmosphere of non-oxidizable metal, e.g. B. platinum is used.