US2246162A - Thermionic cathode treatment - Google Patents

Thermionic cathode treatment Download PDF

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Publication number
US2246162A
US2246162A US289923A US28992339A US2246162A US 2246162 A US2246162 A US 2246162A US 289923 A US289923 A US 289923A US 28992339 A US28992339 A US 28992339A US 2246162 A US2246162 A US 2246162A
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cathodes
sulphur
nickel
thermionic
thermionic cathode
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US289923A
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Benjamin Mark
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General Electric Co
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General Electric Co
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus 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
    • H01J9/02Manufacture of electrodes or electrode systems
    • H01J9/04Manufacture of electrodes or electrode systems of thermionic cathodes

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  • the present invention is an improvement in thermionic cathodes of the activated type in which the base material consists of nickeliferous material, that is, nickel or an alloy of nickel.
  • Oxide-coated cathodes sometimes known as Wehnelt cathodes, when employed in gaseous discharge lamps, in cathode ray tubes, or in other thermionic devices, after a period of use lose their electron emissivity. In some cases cathodes which no longer are effectively electron-emissive can be observed still to be coated with oxide.
  • the accompanying drawing illustrates conventionally a thermionic device to which my invention is applicable.
  • the nickeliferous material is heated in contact with a reagent which is reactive towards sulphur at high temperature.
  • a reagent which is reactive towards sulphur at high temperature.
  • the wire strip, wire or other article of nickel, or one of its alloys is heated at a temperature of about 1000 C. while embedded in an oxygenous alkaline earth compound which is sulphur-reactive, the heating preferably taking place in an inert atmosphere or in a vacuum.
  • Finely divided carbonate of barium or other alkaline earth metals, and similarly the oxides of such metals in powdered form, may be used as the sulphur-reactive reagent.
  • the length of time of heating will vary with the thickness of the nickeliferous material. For a material having a thickness of about 0.5 millimeter or less, good results can be obtained by heat treatment under the described conditions continued for about 1 hour.
  • Nickel or nickel alloy metal after having been subjected to this process, is fabricated into form suitable for the production of cathodes and is coated with activating material, for example, a
  • the coating subsequently is converted to an oxide and is treated to become active or electron-emitting in accordance with well understood methods.
  • the drawing illustrates a rectifier as one form of thermionic cathode device to which my invention is applicable. It comprises a container I in which is mounted a cathode assembly 2 and an anode 3. 'The cathode assembly comprises a heat shield 4, in which are disposed a heater 5 and an oxide-coated ribbon cathode 6 which is wound on a support 1. The cathode is treated in accordance with the present invention. The heater and ribbon cathode are connected electrically as usual to external contacts 8 which are mounted on a base 9. The anode 3 is connected to an external contact Ill.
  • the container contains an appropriate gas filling. A charge of mercury (not shown) which furnishes vapor during operation commonly is used. Electrons emitted from the heated cathode 6 pass through an opening in the shield 4 (not shown) to the anode 3.
  • Cathodes made from sulphur-free metal have longer useful operating lives in thermionic devices than cathodes containing cores or base metal made of commercial metal which contains sulphur.
  • the step in the process of manufacturing oxide-coated cathodes which consists in subjecting the nickeliferous base metal for such cathodes to a heat treatment at about 1000 C. while packed in oxygenous alkaline earth compound until the residual sulphur in such metal has been substantially eliminated.
  • a step in the manufacture of oxide-coated thermionic cathodes comprising nickeliferous base metal which comprises heating base metal for such cathodes to about 1000 C. while packed in barium carbonate and preliminary to coating such material with an oxide layer.

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

Description

June 17, 1941. M. BENJAMIN THERMiONIC CATHODE TREATMENT Filed Aug. 12, 1939 Patented June 17, 1941 UETED THERMIONIO GATHODE; TREATIVIENT Mark Benjamin, ,Wembley, England, assignor to General Electric Company, a corporation of New York Application August 12, 1939, Serial No. 289,923 In Great Britain August 17, 1938 3 Claims.
The present invention is an improvement in thermionic cathodes of the activated type in which the base material consists of nickeliferous material, that is, nickel or an alloy of nickel.
Oxide-coated cathodes, sometimes known as Wehnelt cathodes, when employed in gaseous discharge lamps, in cathode ray tubes, or in other thermionic devices, after a period of use lose their electron emissivity. In some cases cathodes which no longer are effectively electron-emissive can be observed still to be coated with oxide.
I have discovered that one of the causes of loss of activity of oxide-coated cathodes is the deleterious effect of sulphur which is present ordinarily in the metal base or core. Commercial nickel contains appreciable quantities of sulphur which known metallurgical processes are not capable of removing sufliciently to avoid such deleterious effect on cathodes made therefrom.
In accordance with the method step constituting my invention, residual sulphur is removed substantially entirely from articles of nickel, such as nickel wire strip or sheet material, or in any event to such extent that any remainder is harmless to electron emission of cathodes made from such material.
The accompanying drawing illustrates conventionally a thermionic device to which my invention is applicable. In carrying out my invention the nickeliferous material is heated in contact with a reagent which is reactive towards sulphur at high temperature. For example, the wire strip, wire or other article of nickel, or one of its alloys, is heated at a temperature of about 1000 C. while embedded in an oxygenous alkaline earth compound which is sulphur-reactive, the heating preferably taking place in an inert atmosphere or in a vacuum. Finely divided carbonate of barium or other alkaline earth metals, and similarly the oxides of such metals in powdered form, may be used as the sulphur-reactive reagent.
The length of time of heating will vary with the thickness of the nickeliferous material. For a material having a thickness of about 0.5 millimeter or less, good results can be obtained by heat treatment under the described conditions continued for about 1 hour.
Nickel or nickel alloy metal, after having been subjected to this process, is fabricated into form suitable for the production of cathodes and is coated with activating material, for example, a
carbonate of barium, strontium, or calcium, or an.
appropriate mixture. The coating subsequently is converted to an oxide and is treated to become active or electron-emitting in accordance with well understood methods.
The drawing illustrates a rectifier as one form of thermionic cathode device to which my invention is applicable. It comprises a container I in which is mounted a cathode assembly 2 and an anode 3. 'The cathode assembly comprises a heat shield 4, in which are disposed a heater 5 and an oxide-coated ribbon cathode 6 which is wound on a support 1. The cathode is treated in accordance with the present invention. The heater and ribbon cathode are connected electrically as usual to external contacts 8 which are mounted on a base 9. The anode 3 is connected to an external contact Ill. The container contains an appropriate gas filling. A charge of mercury (not shown) which furnishes vapor during operation commonly is used. Electrons emitted from the heated cathode 6 pass through an opening in the shield 4 (not shown) to the anode 3.
Cathodes made from sulphur-free metal have longer useful operating lives in thermionic devices than cathodes containing cores or base metal made of commercial metal which contains sulphur.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. The step in the process of manufacturing oxide-coated cathodes which consists in subjecting the nickeliferous base metal for such cathodes to a heat treatment at about 1000 C. while packed in oxygenous alkaline earth compound until the residual sulphur in such metal has been substantially eliminated.
2. A step in the manufacture of oxide-coated thermionic cathodes comprising nickeliferous base metal which comprises heating base metal for such cathodes to about 1000 C. while packed in barium carbonate and preliminary to coating such material with an oxide layer.
3. The method of manufacturing cathodes for electric discharge devices from nickel bases containing sulphur which consists in subjecting said bases to a purifying treatment for aboutone hour at about 1000" C. while packed in oxygenous alkaline earth compound whereby sulphur is substantially eliminated and thereafter coating said bases with activating material.
MARK BENJAMIN.
US289923A 1938-08-17 1939-08-12 Thermionic cathode treatment Expired - Lifetime US2246162A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586768A (en) * 1949-02-24 1952-02-26 Driver Harris Co Vacuum tube electrode element
US2819991A (en) * 1952-08-30 1958-01-14 Rca Corp Carburized thoriated tungsten electrode and method of enhancing its emissivity
US2916652A (en) * 1955-02-04 1959-12-08 Raytheon Co Control of electron emission in cathode assemblies
US3439210A (en) * 1966-01-03 1969-04-15 Hughes Aircraft Co Thermionic emission cathode having reduced frontal area and enlarged emission area for ion bombardment environment
US6333121B1 (en) 1992-10-13 2001-12-25 General Electric Company Low-sulfur article having a platinum-aluminide protective layer and its preparation
US6656605B1 (en) 1992-10-13 2003-12-02 General Electric Company Low-sulfur article coated with a platinum-group metal and a ceramic layer, and its preparation

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586768A (en) * 1949-02-24 1952-02-26 Driver Harris Co Vacuum tube electrode element
US2819991A (en) * 1952-08-30 1958-01-14 Rca Corp Carburized thoriated tungsten electrode and method of enhancing its emissivity
US2916652A (en) * 1955-02-04 1959-12-08 Raytheon Co Control of electron emission in cathode assemblies
US3439210A (en) * 1966-01-03 1969-04-15 Hughes Aircraft Co Thermionic emission cathode having reduced frontal area and enlarged emission area for ion bombardment environment
US6333121B1 (en) 1992-10-13 2001-12-25 General Electric Company Low-sulfur article having a platinum-aluminide protective layer and its preparation
US6656533B2 (en) 1992-10-13 2003-12-02 William S. Walston Low-sulfur article having a platinum-aluminide protective layer, and its preparation
US6656605B1 (en) 1992-10-13 2003-12-02 General Electric Company Low-sulfur article coated with a platinum-group metal and a ceramic layer, and its preparation
US20040123923A1 (en) * 1992-10-13 2004-07-01 Walston William S. Low sulfur article having a platinum-aluminide protective layer, and its preparation
US6797408B2 (en) 1992-10-13 2004-09-28 General Electric Company Low-sulfur article having a platinum-aluminide protective layer, and its preparation
US20050121116A1 (en) * 1992-10-13 2005-06-09 General Electric Company Low-sulfur article having a platinum aluminide protective layer and its preparation
US6969558B2 (en) 1992-10-13 2005-11-29 General Electric Company Low sulfur article having a platinum-aluminide protective layer, and its preparation
US7510779B2 (en) 1992-10-13 2009-03-31 General Electric Company Low-sulfur article having a platinum aluminide protective layer and its preparation

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