CN101764007B - Method for producing nano graphite field emission vacuum electronic cathode - Google Patents
Method for producing nano graphite field emission vacuum electronic cathode Download PDFInfo
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- CN101764007B CN101764007B CN201010106572XA CN201010106572A CN101764007B CN 101764007 B CN101764007 B CN 101764007B CN 201010106572X A CN201010106572X A CN 201010106572XA CN 201010106572 A CN201010106572 A CN 201010106572A CN 101764007 B CN101764007 B CN 101764007B
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Abstract
The invention belongs to the field of vacuum electronic element and device production and a method for producing field emission microwave vacuum electronic cathode by using a nano graphite material. The method comprises: processing industrial expanded graphite sheets at high temperature to produce wormlike expanded graphite; processing the wormlike expanded graphite with solution of concentrated sulfuric acid and potassium permanganate to produce nano graphite sheets; washing the nano graphite sheets to remove acid and purifying the nano graphite sheets by using ultrasonic waves and centrifugation; filtering and drying the nano graphite sheets and forming a film; rolling up the film to produce a nano graphite cylinder; and subjecting the nano graphite column to calcining and post treatment to obtain the nano graphite cylindrical cathode. The method has the characteristics that: the production process is simple, reliable, low in energy consumption and high in production efficiency; the produced electronic cathode has a small cross section and high stability, can emit high-intensity current in use, makes the industrial production realized easily; and the like. The method overcome the drawbacks of the prior art such as difficult use in field emission microwave tubes, digital tubes, projection tubes and other tube vacuum electronic elements, complicated production process, low production efficiency, high production cost and the like.
Description
Technical field
The invention belongs to vacuum electronic unit, device production field, particularly a kind of production method that adopts the field launched microwave vacuum electronic cathode of nano-graphite manufacture of materials, this electronic cathode utilizes the edge of film to carry out the field emission, especially is suitable as such as the negative electrode of body class vacuum electron devices such as field launched microwave pipe, charactron, projection tube and uses.
Background technology
Traditional microwave vacuum electronic device negative electrode generally adopts the associated materials of tungsten oxide or tungsten to make, and belongs to the hot cathode emission; Traditional used electron emitting cathode of projection tube electron-like device also is to rely on thermionic emission, thereby exists efficient low, and working temperature is high and need preheating, and defectives such as volume is big, power consumption height; The employing nano-graphite of developing at these defectives as the field-transmitting cathode technology then be utilize chemical vapor deposition growth or disperse with solvent after make film again way obtain the nano-graphite film, and then be made into the membranaceous field emission electron negative electrode of flat thin, i.e. negative electrode by graphite film planar transmit electronics; Though this type of electronic cathode has advantages such as emission effciency is higher, current density is bigger, but generally only be used in cold-cathode field emission flat panel display aspect, and be difficult to use in, and there are disadvantages such as complex manufacturing, production efficiency are low, production cost height such as in the body class vacuum electron devices such as field launched microwave pipe, charactron, projection tube.
Summary of the invention
The production method that the objective of the invention is a kind of nano graphite field emission vacuum electronic cathode of research and design, the field emission vacuum electronic cathode that adopt after filtration, the nano-graphite diaphragm after the dried rolls into column type, effectively reducing its sectional area, to improve the current density and the stability of cathode emission, and simplify production technology, cut down the consumption of energy, realize purpose such as suitability for industrialized production.
Solution of the present invention is at first industrial expanded graphite sheet to be made vermiform expanded graphite, oxidation processes becomes nano graphite flakes then, after disacidify and purification processes, make the oxidation nanometer graphite aqueous solution again, filter film forming, air-dry, roll, promptly make the nano-graphite cylindrical cathode after vacuum calcining is handled.Therefore, the production method of field emission vacuum electronic cathode of the present invention comprises:
A. industrial expanded graphite sheet is placed acidproof and high-temperature resistant container, under 500-1000 ℃ of temperature, heat, it is fully expanded, obtain vermiform expanded graphite;
B. adopt the solution of the concentrated sulfuric acid and potassium permanganate that the vermiform expanded graphite that makes through steps A is carried out chemical oxidation treatment then, with the vermiform expanded graphite be oxidizing to thickness≤1nm, the length of side is the nano graphite flakes (sheet particulate) of 1-10 μ m; In the solution of the concentrated sulfuric acid and potassium permanganate, the content of potassium permanganate is as the criterion with the treating capacity of expanded graphite, expanded graphite: potassium permanganate=1: 0.5-5.0 (percentage by weight); The oxidation processes gained contains the mixed liquor of nano graphite flakes, changes step C;
C. the nano graphite flakes mixed liquor with step B gained filters back, washing deacidification, after placing deionized water to carry out ultrasonicly involving centrifugal purification processes at last, sinking to the bottom separation, collect upper strata feed liquid, the oxidation nanometer graphite flake that obtains disperseing and the suspension of water to impurity;
D. be that the miillpore filter of 0.2-3 μ m filters with the aperture at first with step B gained suspension, again the graphite film that the filter membrane upward filtration is got, through 20-50 ℃ low temperature drying or air-dry after, obtaining thickness is the nano-graphite diaphragm of 1-100 μ m;
E. step D gained nano-graphite diaphragm is wound on a diameter of phi≤0.5mm, length is on the 5-100mm plug, ends when external diameter reaches Φ 100 μ m-10mm, obtains cylindrical nanometer graphite post;
F. the graphite post that step e is obtained places in the vacuum furnace, vacuum atmosphere (condition) and 500-1300 ℃ temperature lower calcination 1-3 hour, with the stove cooling after, flat and segmentation on request promptly gets nano graphite field emission vacuum electronic cathode with two end-grain cutting.
Above-mentioned industrial expanded graphite sheet, its thickness are that 0.1-40 μ m, the length of side are 10-100 μ m.The described concentrated sulfuric acid, its concentration are that percent concentration 〉=70%, purity are the concentrated sulfuric acid of technical pure and above purity thereof; And the middle and high potassium manganate of the solution of the concentrated sulfuric acid and potassium permanganate: the concentrated sulfuric acid=1.0g: 200-1000ml.And describedly carry out the ultrasonic centrifugal purification processes that involves, wherein frequency of ultrasonic be 100KHz (KHz), centrifuge power be 40-100W (watt).Described is that the miillpore filter of 0.2-3 μ m filters with the aperture, and its filter type is a vacuum filtration.
The present invention at first makes vermiform expanded graphite with industrial expanded graphite sheet, oxidation processes becomes nano graphite flakes then, after disacidify and purification processes, make the oxidation nanometer graphite aqueous solution again, filter film forming, air-dry, roll, after vacuum calcining is handled forms.Thereby it is simple, reliable to have production technology, and energy consumption is low, production efficiency is high, and institute's electronic cathode sectional area of producing is little, the current density of launching in the use greatly, good stability, and be easy to realize characteristics such as suitability for industrialized production.
Description of drawings
Fig. 1 is field emitting electronic source shaft section X100 of the present invention (doubly) electron microscope scanning figure;
Fig. 2 is a field emitting electronic source structural representation of the present invention.
Among the figure: 1, substrate, 1.1, graphite film (layer), 2. plug.
Embodiment
A. the industrial expanded graphite 4.0g that with thickness is 0.1-100 μ m puts into high-temperature resistant container, and heating is fully expanded it under 800 ± 20 ℃ of temperature, obtains vermiform expanded graphite;
B. be after 96% industrial concentrated sulfuric acid 500ml and 1.0g potassium permanganate are mixed with solution with concentration, add steps A gained expanded graphite, oxidation processes to thickness≤1nm, the length of side is the nano graphite flakes (sheet particulate) of 1-10 μ m, and the mixed liquor that gained contains nano graphite flakes changes step C;
C. step B gained mixed liquor is filtered back, washing deacidification, placing deionized water then is after 100KHz and power are to carry out ultrasonic and centrifugal purification processes under the condition of 50W, sink to the bottom separation to impurity, to collect upper strata feed liquid, the oxidation nanometer graphite flake that obtains disperseing and the suspension of water in ultrasonic frequency;
D. the suspension that step C is obtained is that the micropore nylon leaching film of 0.25 μ m carries out vacuum and filters with the aperture, remove anhydrate after with gained graphite film on the filter membrane, behind 40 ℃ of temperature dryings, obtaining average thickness is the thick nano-graphite diaphragms of 30 μ m;
E. step D gained nano-graphite diaphragm is wound on a diameter of phi 0.1mm, length is on the plug of 50mm, ends when external diameter reaches Φ 0.8mm, obtains cylindrical nanometer graphite post;
F. the graphite post that step e is obtained places in the vacuum furnace, be lower than 10Pa and 1100 ℃ of temperature lower calcinations 1.5 hours in vacuum degree, with the stove cooling after, two end-grain cutting are flat and by segmentation, promptly get the nano graphite field emission vacuum electronic cathode goods.
With the present embodiment resulting product, by simple diode mechanism checkout area emitting performance in the transmitting station of high vacuum field.Background vacuum pressure is 7 * 10 during test
-5Pa; Utilize a cylindrical stainless steel as anode; The nano-graphite goods vertically are fixed on the anode below as field-transmitting cathode, and the distance between negative electrode and the anode is 400 μ m.Its current density of test gained reaches 470mA/cm
2Opening the field, is 10 μ A/cm corresponding to current density
2The time electric field be about 3.3V/ μ m; Threshold field, corresponding emission are 10 μ A/cm
2The time electric field strength be about 4.7V/ μ m.
Claims (5)
1. the production method of a nano graphite field emission vacuum electronic cathode comprises:
A. industrial expanded graphite sheet is placed acidproof and high-temperature resistant container, under 500-1000 ℃ of temperature, heat, it is fully expanded, obtain vermiform expanded graphite;
B. adopt the solution of the concentrated sulfuric acid and potassium permanganate that the vermiform expanded graphite that makes through steps A is carried out chemical oxidation treatment then, with the vermiform expanded graphite be oxidizing to thickness≤1nm, the length of side is the nano graphite flakes of 1-10 μ m; In the solution of the concentrated sulfuric acid and potassium permanganate, the content of potassium permanganate is as the criterion with the treating capacity of expanded graphite, by weight percentage, expanded graphite: potassium permanganate=1: 0.5-5.0; The oxidation processes gained contains the mixed liquor of nano graphite flakes, changes step C;
C. the nano graphite flakes mixed liquor with step B gained filters back, washing deacidification, after placing deionized water to carry out ultrasonicly involving centrifugal purification processes at last, sinking to the bottom separation, collect upper strata feed liquid, the oxidation nanometer graphite flake that obtains disperseing and the suspension of water to impurity;
D. be that the miillpore filter of 0.2-3 μ m filters with the aperture at first with step C gained suspension, again the graphite film that the filter membrane upward filtration is got, through 20-50 ℃ low temperature drying or air-dry after, obtaining thickness is the nano-graphite diaphragm of 1-100 μ m;
E. step D gained nano-graphite diaphragm is wound on a diameter of phi≤0.5mm, length is on the 5-100mm plug, ends when external diameter reaches Φ 100 μ m-10mm, obtains cylindrical nanometer graphite post;
F. the graphite post that step e is obtained places in the vacuum furnace, vacuum atmosphere and 500-1300 ℃ temperature lower calcination 1-3 hour, with the stove cooling after, flat and segmentation on request promptly gets nano graphite field emission vacuum electronic cathode with two end-grain cutting.
2. by the production method of the described nano graphite field emission vacuum electronic cathode of claim 1, it is characterized in that described industrial expanded graphite sheet, its thickness is that 0.1-40 μ m, the length of side are 10-100 μ m.
3. by the production method of the described nano graphite field emission vacuum electronic cathode of claim 1, percent concentration 〉=70%, the purity that it is characterized in that the described concentrated sulfuric acid is technical pure and above purity thereof; And the middle and high potassium manganate of the solution of the concentrated sulfuric acid and potassium permanganate: the concentrated sulfuric acid=1.0g: 200-1000ml.
4. by the production method of the described nano graphite field emission vacuum electronic cathode of claim 1, it is characterized in that the described ultrasonic centrifugal purification processes that involves of carrying out, wherein frequency of ultrasonic is that 100KHz, centrifuge power are 40-100W.
5. by the production method of the described nano graphite field emission vacuum electronic cathode of claim 1, it is characterized in that described is that the miillpore filter of 0.2-3 μ m filters with the aperture, and its filter type is a vacuum filtration.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201010106572XA CN101764007B (en) | 2010-02-03 | 2010-02-03 | Method for producing nano graphite field emission vacuum electronic cathode |
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| CN101764007B true CN101764007B (en) | 2011-04-27 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102024635B (en) | 2010-11-29 | 2012-07-18 | 清华大学 | Electron emitter and electron emission component |
| CN102024639B (en) * | 2010-11-29 | 2012-11-21 | 清华大学 | Method for manufacturing electron emitter |
| CN102013376B (en) | 2010-11-29 | 2013-02-13 | 清华大学 | Field emission unit and field emission pixel tube |
| CN102024636B (en) | 2010-11-29 | 2012-10-10 | 清华大学 | Electron emitter and electron emitting element |
| CN102024654B (en) | 2010-11-29 | 2013-02-13 | 清华大学 | Field emission pixel tube |
| TWI427673B (en) * | 2010-12-06 | 2014-02-21 | Hon Hai Prec Ind Co Ltd | A method fro making a electron emitter |
| TWI427659B (en) * | 2010-12-06 | 2014-02-21 | Hon Hai Prec Ind Co Ltd | Electron emitter and electron emitting element |
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