US2559530A - Cathode coatings - Google Patents
Cathode coatings Download PDFInfo
- Publication number
- US2559530A US2559530A US553959A US55395944A US2559530A US 2559530 A US2559530 A US 2559530A US 553959 A US553959 A US 553959A US 55395944 A US55395944 A US 55395944A US 2559530 A US2559530 A US 2559530A
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- US
- United States
- Prior art keywords
- cathode
- coating
- carbonate
- peroxide
- earth metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/14—Solid thermionic cathodes characterised by the material
- H01J1/142—Solid thermionic cathodes characterised by the material with alkaline-earth metal oxides, or such oxides used in conjunction with reducing agents, as an emissive material
Definitions
- This invention relates to an electron-emissive coating for thermionic type cathodes and to the method of producing coated cathodes of this type.
- An object of this invention is to produce a thermionic cathode which shall have a substantially increased thermionic emission.
- Another object is to increase the intensity with which the coating adheres to the core metal of the cathode and thus increase the life of the cathode under severe load conditions.
- alkaline earth metal carbonate coating mixture which may, for example, consist of barium carbonate and strontium carbonate, a hydrated barium peroxide (BaO2I-I2O2). While I prefer to use hydrated barium peroxide (BaO2H2O2), any other peroxide in which the barium is replaced by any other alkaline earth metal may be used. I prefer that the peroxide shall constitute about per cent by weight of the total mixture of dry ingredients. To the above mixture may be added the usual vehicles, such as, amyl-acetate and nitrocellulose lacquer. In accordance with my present understandin of the invention the peroxide performs the function of a binder. However, it may perform additional functions in view of the remarkable results which are secured as a result of its use.
- a thermionic cathode either of the indirectly heated or of the filamentary type, may be coated with the above coating material, either by painting, spraying, dipping, or the like, until the core metal of the cathode carries a sufiiciently heavy layer of coating. The coating is then dried in air. It is then assembled and sealed into the electronic tube in which it is to be utilized. Thereupon the tube is exhausted to a relatively high vacuum and the cathode heated to a temperature of about 450 centigrade. At this point, fusing of the peroxide takes place and some of the carbonate appears to dissolve in the molten peroxide. However, an insufficient amount of peroxide is used to dissolve completely all of the carbonate.
- the cathode temperature is raised to about 880 Centigrade. At this temperature the carbonates, as well as any other compounds remaining, break down so as to leave a residuum of barium oxide strontium oxide as the final cathode coating.
- the coating of the cathode as prepared above consists of a mass of finely interlocking crystals which are in extremely close thermal and electrical contact with the cathode core metal. Also the crystals throughout the mass of coating itself are in similarly close thermal and electrical contact with each other.
- cathodes are constructed in accordance with my invention, as described above, I have been able to obtain therefrom copius thermionic emission at temperatures corresponding to below red heat. As the temperature of the cathode is increased beyond this point, an extraordinarily large degree of thermionic emission is obtained. As compared with cathodes coated in accordance with heretofore commercial practice, cathodes constructed in accordance with the present invention have had their emission increased about two and one-half times at corresponding operating temperatures.
- a cathode-coating material consisting of an amyl acetate-nitrocellulose lacquer containing the carbonate of an alkaline-earth metal and a substantial amount of BaO2H20z.
- a cathode-coating material consisting of an amyl acetate-nitrocel1ulose lacquer containing the carbonate of an alkaline-earth metal as a major component and a substantial amount of BaozHzOz as a minor component.
- a cathode-coating material consisting of an amyl acetate-nitrocellulose lacquer containing a mixture of about of the carbonate of an alkaline-earth metal and about 25 of BaOcI-IzOz.
Description
Patented July 3, 1951 CATHODE COATINGS Carl W. Becker, Arlington, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware No Drawing. Application September 13, 1954, Serial No. 553,959
3 Claims. 1
This invention relates to an electron-emissive coating for thermionic type cathodes and to the method of producing coated cathodes of this type.
An object of this invention is to produce a thermionic cathode which shall have a substantially increased thermionic emission.
Another object is to increase the intensity with which the coating adheres to the core metal of the cathode and thus increase the life of the cathode under severe load conditions.
The foregoing and other objects of this inven tion will be best understood from the following description of exemplifications thereof.
In accordance with invention I add to the usual alkaline earth metal carbonate coating mixture, which may, for example, consist of barium carbonate and strontium carbonate, a hydrated barium peroxide (BaO2I-I2O2). While I prefer to use hydrated barium peroxide (BaO2H2O2), any other peroxide in which the barium is replaced by any other alkaline earth metal may be used. I prefer that the peroxide shall constitute about per cent by weight of the total mixture of dry ingredients. To the above mixture may be added the usual vehicles, such as, amyl-acetate and nitrocellulose lacquer. In accordance with my present understandin of the invention the peroxide performs the function of a binder. However, it may perform additional functions in view of the remarkable results which are secured as a result of its use.
A thermionic cathode, either of the indirectly heated or of the filamentary type, may be coated with the above coating material, either by painting, spraying, dipping, or the like, until the core metal of the cathode carries a sufiiciently heavy layer of coating. The coating is then dried in air. It is then assembled and sealed into the electronic tube in which it is to be utilized. Thereupon the tube is exhausted to a relatively high vacuum and the cathode heated to a temperature of about 450 centigrade. At this point, fusing of the peroxide takes place and some of the carbonate appears to dissolve in the molten peroxide. However, an insufficient amount of peroxide is used to dissolve completely all of the carbonate. During this heating process, some gas is evolved from the cathode coating. I believe that under these conditions the peroxide breaks down, at least partially, into the dioxide form, such as BaOz. After the above heating process has been completed, the cathode temperature is raised to about 880 Centigrade. At this temperature the carbonates, as well as any other compounds remaining, break down so as to leave a residuum of barium oxide strontium oxide as the final cathode coating.
I have found that the coating of the cathode as prepared above consists of a mass of finely interlocking crystals which are in extremely close thermal and electrical contact with the cathode core metal. Also the crystals throughout the mass of coating itself are in similarly close thermal and electrical contact with each other.
When cathodes are constructed in accordance with my invention, as described above, I have been able to obtain therefrom copius thermionic emission at temperatures corresponding to below red heat. As the temperature of the cathode is increased beyond this point, an extraordinarily large degree of thermionic emission is obtained. As compared with cathodes coated in accordance with heretofore commercial practice, cathodes constructed in accordance with the present invention have had their emission increased about two and one-half times at corresponding operating temperatures.
What is claimed is:
1. A cathode-coating material consisting of an amyl acetate-nitrocellulose lacquer containing the carbonate of an alkaline-earth metal and a substantial amount of BaO2H20z.
2. A cathode-coating material consisting of an amyl acetate-nitrocel1ulose lacquer containing the carbonate of an alkaline-earth metal as a major component and a substantial amount of BaozHzOz as a minor component.
3. A cathode-coating material consisting of an amyl acetate-nitrocellulose lacquer containing a mixture of about of the carbonate of an alkaline-earth metal and about 25 of BaOcI-IzOz.
CARE W. BECKER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,874,785 Miller et a1 Aug. 30, 1932 2,018,993 Braselton Oct. 29, 1935
Claims (1)
1. A CATHODE-COATING MATERIAL CONSISTING OF AN AMYL ACETATE-NITROCELLULOSE LACQUER CONTAINING THE CARBONATE OF AN ALKALINE-EARTH METAL AND A SUBSTANTIAL AMOUNT OF BAO2H2O2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US553959A US2559530A (en) | 1944-09-13 | 1944-09-13 | Cathode coatings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US553959A US2559530A (en) | 1944-09-13 | 1944-09-13 | Cathode coatings |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2559530A true US2559530A (en) | 1951-07-03 |
Family
ID=24211476
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US553959A Expired - Lifetime US2559530A (en) | 1944-09-13 | 1944-09-13 | Cathode coatings |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2559530A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2963450A (en) * | 1958-03-17 | 1960-12-06 | Interlectric Corp | Filament coating composition |
| US2985548A (en) * | 1957-12-26 | 1961-05-23 | Sylvania Electric Prod | Method of making a low density coating for an electron discharge device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1874785A (en) * | 1930-06-23 | 1932-08-30 | Grigsby Grunow Co | Oxide coatings and method of preparing the same |
| US2018993A (en) * | 1930-06-03 | 1935-10-29 | Sirian Lamp Co | Electrical discharge material and method of manufacturing it |
-
1944
- 1944-09-13 US US553959A patent/US2559530A/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2018993A (en) * | 1930-06-03 | 1935-10-29 | Sirian Lamp Co | Electrical discharge material and method of manufacturing it |
| US1874785A (en) * | 1930-06-23 | 1932-08-30 | Grigsby Grunow Co | Oxide coatings and method of preparing the same |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2985548A (en) * | 1957-12-26 | 1961-05-23 | Sylvania Electric Prod | Method of making a low density coating for an electron discharge device |
| US2963450A (en) * | 1958-03-17 | 1960-12-06 | Interlectric Corp | Filament coating composition |
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