CN111613496B - Graphene-coated barium-tungsten cathode and preparation method thereof - Google Patents
Graphene-coated barium-tungsten cathode and preparation method thereof Download PDFInfo
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- CN111613496B CN111613496B CN202010522203.2A CN202010522203A CN111613496B CN 111613496 B CN111613496 B CN 111613496B CN 202010522203 A CN202010522203 A CN 202010522203A CN 111613496 B CN111613496 B CN 111613496B
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- H01—ELECTRIC ELEMENTS
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- 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
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- 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
- H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
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- 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
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- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
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Abstract
The invention discloses a graphene-coated barium-tungsten cathode and a preparation method thereof. The preparation method comprises the following steps: preparing a B-type barium-tungsten cathode; (2) Covering a TRT (Top gas trap transistor) on one side of a substrate on which graphene grows, removing the substrate through solution corrosion, retaining the graphene, cleaning the TRT covered with the graphene, and drying; (3) And placing the graphene/TRT film on a temperature control table, inverting the B-type barium-tungsten cathode, controlling the temperature to reach the TRT thermal stripping temperature, taking the cathode away, and attaching the graphene to the surface of the cathode. The invention is beneficial to reducing the work function of the surface of the barium-tungsten cathode, the work function is estimated to be less than 1.9eV, and compared with a B-type cathode, the emission capability can be improved, or the working temperature is reduced to prolong the service life of the cathode.
Description
Technical Field
The invention relates to the technical field of microwave vacuum electronics, in particular to a graphene coated barium-tungsten cathode and a preparation method thereof.
Background
Vacuum electronic devices have been widely used in various devices and systems such as various power microwave systems, precision detection devices, etc. for communication, display, medical CT, nondestructive detection, particle accelerators, free electron lasers, electron microscopes, etc. because of their characteristics of high frequency, high output power, etc. The cathode is used as an electron source of a vacuum microelectronic device, and the emission capability of the cathode directly influences the performance indexes of the device and a system. The hot cathode has the obvious advantages of large emission current, long service life and the like, and is widely applied. Further improvement of the emission capability or extension of the cathode life is a constant development direction of cathodes.
The interdiffusion between the M-type cathode surface film layer and the substrate material can significantly change the cathode surface work function, and the optimal ratio is maintained during the preparation and use processes. An M-type cathode in the existing hot cathode is a cathode with better emission capability and service life, lower work function is realized by coating a layer of osmium or iridium or ruthenium film on the surface of a B-type or S-type cathode, the emission capability is improved, but the surface work function of the M-type cathode and the component ratio of a cathode surface film layer are greatly related, the interdiffusion of the cathode surface film layer and a base metal under a hot working condition can cause the change of the cathode surface component, the change of the cathode surface work function and the change of the emission current density under the same working condition are caused, and the interdiffusion between the cathode surface and the base in the using process influences the working stability and the service life of the M-type cathode.
Disclosure of Invention
The purpose of the invention is as follows: in order to improve the emission performance of the cathode, simplify the preparation process and improve the working stability, the invention aims to provide the graphene coated barium tungsten cathode for improving the emission capability and the working stability, and the invention also aims to provide the preparation method of the graphene coated barium tungsten cathode with simple process.
The technical scheme is as follows: the graphene-coated barium-tungsten cathode comprises a graphene layer and a B-type barium-tungsten cathode layer, wherein the graphene layer is coated on the upper surface of the B-type barium-tungsten cathode layer, the B-type barium-tungsten cathode layer is arranged in a supporting cylinder, and a filament is arranged below the B-type barium-tungsten cathode layer in the supporting cylinder to form a hot cathode.
The graphene layer is single-layer or double-layer graphene. The graphene layer is isolated from the grid electrode through an insulating medium layer or vacuum. The grid is annular or mesh-shaped.
The graphene-coated barium-tungsten cathode can be used as an electron source in a hot cathode vacuum electronic device and a hot-photocathode vacuum electronic device. When the graphene-coated barium-tungsten cathode is used as an electron source in a heat-light comprehensive emission vacuum electronic device, the anode adopts a net structure, so that cathode excitation light can be incident to the cathode from the back of the anode. When the graphene-coated barium-tungsten cathode is used as an electron source in a thermal-optical integrated emission vacuum electronic device, the wavelength of cathode excitation light is shorter than 690 nanometers.
The preparation method of the graphene coated barium-tungsten cathode comprises the following steps:
(1) Preparing a B-type barium-tungsten cathode;
(2) Covering TRT on one side of the substrate to grow graphene, and then passing through FeCl 3 Corroding with a corrosive solution, removing the substrate, reserving the graphene on the TRT, cleaning the TRT coated with the graphene in deionized water, and drying;
(3) And (3) placing the graphene/TRT film obtained in the step (2) on a temperature control table, inverting the B-type barium-tungsten cathode, controlling the temperature of the temperature control table to reach a TRT hot stripping temperature, enabling the TRT to lose viscosity, then removing the cathode, and enabling the graphene to be attached to the surface of the cathode to obtain the graphene-coated barium-tungsten cathode.
In addition, the surface emission of the cathode can be adjusted by adding a grid on the surface of the cathode, the grid adopts a ring-shaped or net-shaped structure, the grid and the cathode are isolated by an insulating layer medium or vacuum, and the adjustment of the emission capability of the cathode can be realized by adjusting the voltage of the grid.
Has the advantages that: compared with the prior art, the invention has the following remarkable characteristics:
1. the surface work function of the barium-tungsten cathode can be reduced, and compared with a B-type cathode, the emission capability can be improved, or the working temperature can be reduced to prolong the service life of the cathode;
2. compared with an M-type cathode, the graphene is adopted to replace the surface coating of the M-type cathode, so that the preparation process is simplified, the stability is enhanced, and the cost is reduced.
3. In the case of an additional gate, the cathode emission capability can be adjusted by adjusting the gate voltage.
Drawings
FIG. 1 is a schematic structural view of the present invention;
fig. 2 is a schematic structural diagram of the gate of the present invention.
Detailed Description
In the following examples, the starting materials were all commercially available.
The position relationship between the graphene film-coated barium tungsten cathode 6 and the anode 7 is shown in figure 1, a graphene layer 1 is coated on the surface of a traditional B-type barium tungsten cathode, the graphene film-coated barium tungsten cathode 6 is supported by a supporting cylinder 3, and a hot wire is filled below the graphene film-coated barium tungsten cathode. The graphene-coated barium-tungsten cathode 6 and the graphene-coated barium-tungsten anode 7 can be of a flat plate structure or a curved surface structure.
A schematic diagram of a gate control structure of the graphene-coated barium tungsten cathode 6 and a position relationship between the graphene-coated barium tungsten cathode 6 and an anode 7 is shown in fig. 2, a grid 4 is added on the surface of the graphene-coated barium tungsten cathode 6 to adjust surface emission of the graphene-coated barium tungsten cathode 6, the grid 4 is in an annular or net-shaped structure, and the grid 4 and the graphene-coated barium tungsten cathode 6 are isolated by an insulating medium layer 5 or vacuum.
The measured value of the (unsaturated) emission current density of the graphene-coated barium-tungsten cathode 6 reaches 0.235A/cm under the working temperature condition of 1080K and the cathode-anode spacing of 1-2mm when the cathode-anode voltage is 160V 2 The work function is estimated to be not more than 1.9eV. The literature (Work function distribution for a B category and an M category in life. (From: T.J. Grant,Technical Digest1986 IEDM 1986 IEEE)) showed that the B-type barium tungsten cathode layer 2 had a work function of about 2.1eV and the M-type cathode had a work function of about 1.95 eV; the work function of the domestic Os-coated film M-type cathode can reach about 1.87 eV; therefore, the emission performance of the graphene coated barium-tungsten cathode 6 provided by the invention is better than that of a B-type cathode (about 2.1 eV), and is not inferior to that of an M-type cathode (about 1.9 eV). Experience has shown that the working life can be doubled for every 10 ℃ reduction in the working temperature of the hot cathode. Therefore, the service life of the low-work-function graphene-coated barium-tungsten cathode 6 can be effectively prolonged by the reduction of the working temperature corresponding to the same emission current density.
Based on the experience of graphene preparation, a graphene film is not suitable for directly growing on a tungsten substrate, so that the graphene needs to be coated on the surface of a barium-tungsten cathode in a transfer mode, but in consideration of the particularity of the cathode, liquid contact needs to be avoided, and therefore, a two-step transfer method of intermediary transfer-Thermal Release Tape (TRT) dry transfer is adopted for coating the graphene on the surface of the barium-tungsten cathode. In the case of using a TRT-based graphene finished product, the first transfer step is not required, and only direct dry transfer is required. The preparation method of the graphene-coated barium-tungsten cathode 6 specifically comprises the following steps:
firstly, adopting an intermediary transfer method to transfer commercial grapheneThe film is transferred from a substrate (e.g., copper base) to a TRT, the TRT is applied to the substrate on the side where graphene layer 1 is grown, and then passed through a solution (e.g., feCl) 3 Solution) etching to remove the substrate while keeping the graphene on the TRT, then cleaning the TRT coated with the graphene layer 1 in deionized water, and then drying;
and secondly, placing the graphene layer 1/TRT film on a temperature control table, inverting the B-type barium-tungsten cathode layer 2 on the temperature control table, controlling the temperature of the temperature control table to reach the TRT thermal stripping temperature, removing the cathode, and attaching graphene to the surface of the cathode to obtain the graphene coated barium-tungsten cathode 6.
Claims (7)
1. A graphene-coated barium-tungsten cathode is characterized in that: the graphene-based high-performance lamp filament comprises a graphene layer (1) and a B-type barium-tungsten cathode layer (2), wherein the graphene layer (1) covers the upper surface of the B-type barium-tungsten cathode layer (2), the B-type barium-tungsten cathode layer (2) is arranged in a supporting cylinder (3), and a lamp filament is arranged below the B-type barium-tungsten cathode layer (2) in the supporting cylinder (3); the graphene layer (1) is single-layer or double-layer graphene;
under the working temperature condition of 1080K, the unsaturated emission current density measured value of the graphene-coated barium-tungsten cathode (6) at the interpolar distance of 1-2mm and the voltage of 160V is 0.235A/cm 2 And the work function is not more than 1.9eV.
2. The graphene-coated barium-tungsten cathode according to claim 1, characterized in that: the graphene layer is characterized by further comprising a grid (4), wherein the grid (4) is isolated from the graphene layer (1) through an insulating medium layer (5) or vacuum.
3. The graphene-coated barium-tungsten cathode according to claim 2, wherein: the grid (4) is annular or net-shaped.
4. The graphene-coated barium-tungsten cathode according to claim 1, characterized in that: when the graphene film-coated barium tungsten cathode is used as an electron source in a thermo-optic integrated emission vacuum electronic device, the anode (7) adopts a net structure, so that excitation light of the graphene film-coated barium tungsten cathode (6) can enter the graphene film-coated barium tungsten cathode (6) from the back of the anode (7).
5. The graphene-coated barium-tungsten cathode according to claim 1, wherein: when the graphene-coated barium-tungsten cathode (6) is used as an electron source in a thermo-optic integrated emission vacuum electronic device, the excitation light of the graphene-coated barium-tungsten cathode (6) has a wavelength shorter than 690 nanometers.
6. The preparation method of the graphene-coated barium-tungsten cathode according to claim 1, characterized by comprising the following steps:
(1) Preparing a B-type barium-tungsten cathode layer (2);
(2) Covering a TRT (true trap transistor) on one side of a substrate growth graphene layer (1), then corroding by a corrosive solution, removing the substrate, reserving the graphene layer (1) on the TRT, cleaning the TRT covered with the graphene layer (1) in deionized water, and drying;
(3) And (3) placing the graphene layer (1)/TRT film obtained in the step (2) on a temperature control table, inverting the B-type barium-tungsten cathode layer (2) on the temperature control table, controlling the temperature of the temperature control table to reach a TRT hot peeling temperature, enabling the TRT to lose viscosity, then removing the B-type barium-tungsten cathode layer (2), and attaching the graphene layer (1) to the surface of the B-type barium-tungsten cathode layer (2) to obtain the graphene coated barium-tungsten cathode (6).
7. The method for preparing the graphene-coated barium-tungsten cathode according to claim 6, wherein the method comprises the following steps: the corrosive solution is FeCl 3 And (3) solution.
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| CN202010522203.2A CN111613496B (en) | 2020-06-08 | 2020-06-08 | Graphene-coated barium-tungsten cathode and preparation method thereof |
| PCT/CN2021/098369 WO2021249304A1 (en) | 2020-06-08 | 2021-06-04 | Graphene-coated barium tungsten cathode and preparation method thereof |
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