Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/02—Manufacture of electrodes or electrode systems
  • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
  • H01J9/042—Manufacture, activation of the emissive part

Definitions

• This invention relates to a method of preparing thermionic cathodes, the cathode base, generally a metal such as tungsten or nickel, being coated with a mixture of alkaline earth carbonates and a compound of a metal of good conductivity, said compound being decomposed during the conversion of the carbonates to oxide and the subsequent electroforrning of the cathode in a manner such that finely divided metal is left in the oxide layer of the cathode.
• the invention relates to a thermionic valve comprising a cathode made by the said method.
• nickel oxalate It has been suggested before to use nickel oxalate for the purpose above indicated but there is a limitation in that nickel oxalate is not always wholly decomposed to metallic nickel, occlusions of nickel oxide being left.
• the object of the invention is to improve the above method so that the added compound is decomposed to metal as far as possible.
• the added compound in a method of preparing a thermionic cathode which is coated with a mixture consisting of one or more alkaline earth carbonates and a compound of a metal of good conductivity which compound during the decomposition of the carbonates to oxide and the subsequent formation of the cathode is converted into a finely divided metal of good conductivity contained in the oxide layer, the added compound is constituted by the formate of one or more of the metals nickel, cobalt, tungsten, molybdenum, platinum, iridium, osmium, palladium, rhodium and ruthenium.
• the added quantity of metal compound may be from mol. percent to 90 mol. percent, preferably from 20 mol. percent to 60 mol percent measured on the added metal and the alkaline earth metals.
• the quantity of added metal depends on the manner of coating the cathode with the carbonates and upon the purpose for which the valve (a vacuum or gas discharge valve, a valve for pulsatory or for continuous operation) is required.
• One advantage of the addition of metal to the oxide layer of the cathode resides inter alia in that it mitigates against the formation of silicate layers of high resistance between the oxide grains.
• Example 1 This example relates to a paste in which cathodes are oxide-coated by dipping.
• the paste consists of:
• barium-strontium carbonate 50 mol. percent BaCOs
• nickel formate anhydrous
• binder A 480 parts by volume butyl acetate where binder A contains 50 parts by weight nitrocellulose 130 parts by volume diethyl oxalate 530 parts by volume amyl acetate 60 parts by volume ethyl alcohol.
• the cathodes prepared therewith contain 20 mol. percent nickel in the oxide layer.
• Example 2 This example relates to a paste required to be applied to the cathode by spraying.
• the paste consists of:
• nitrocellulose binder obtained from 66 parts by weight nitrocellulose and 1,000 parts by volume amyl acetate
• diethyl oxalate parts by volume methyl alcohol The milling operation is effected in the same manner as in Example 1.
• a thermionic cathode the steps of, coating a refractory metal base with a layer of a mixture of at least one alkaline earth carbonate and a formate of a refractory metal of good conductivity, and reducing the alkaline earth carbonate to a. layer of the corresponding oxide.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Solid Thermionic Cathode (AREA)
• Catalysts (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9967000

Family Applications (1)

Country Status (6)

Cited By (1)

Citations (3)

• 0
  • NL NL89643D patent/NL89643C/xx active
  • BE BE511131D patent/BE511131A/xx unknown
• 1951
  • 1951-05-03 GB GB10393/51A patent/GB699977A/en not_active Expired
• 1952
  • 1952-04-29 DE DEN5441A patent/DE911876C/de not_active Expired
  • 1952-05-01 CH CH307771D patent/CH307771A/de unknown
  • 1952-05-01 US US285562A patent/US2748033A/en not_active Expired - Lifetime

Patent Citations (3)

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