CN111774276A - Preparation method of calcium aluminate derivative thermal emission cathode crystal - Google Patents
Preparation method of calcium aluminate derivative thermal emission cathode crystal Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 39
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical class [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 238000002360 preparation method Methods 0.000 title claims description 18
- 239000011521 glass Substances 0.000 claims abstract description 48
- 239000002002 slurry Substances 0.000 claims abstract description 46
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 42
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 40
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 40
- 239000010439 graphite Substances 0.000 claims abstract description 40
- 238000003756 stirring Methods 0.000 claims abstract description 36
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 27
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 21
- 239000011812 mixed powder Substances 0.000 claims abstract description 18
- 239000011858 nanopowder Substances 0.000 claims abstract description 18
- 239000008367 deionised water Substances 0.000 claims abstract description 15
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 239000002994 raw material Substances 0.000 claims abstract description 10
- 238000005245 sintering Methods 0.000 claims abstract description 10
- 230000001680 brushing effect Effects 0.000 claims abstract description 9
- 239000011248 coating agent Substances 0.000 claims abstract description 9
- 238000000576 coating method Methods 0.000 claims abstract description 9
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 7
- 230000018044 dehydration Effects 0.000 claims abstract description 7
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 7
- 229920000609 methyl cellulose Polymers 0.000 claims abstract description 7
- 239000001923 methylcellulose Substances 0.000 claims abstract description 7
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000007789 sealing Methods 0.000 claims abstract description 7
- 239000011230 binding agent Substances 0.000 claims description 18
- 239000000843 powder Substances 0.000 claims description 14
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 7
- 235000010981 methylcellulose Nutrition 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 150000001450 anions Chemical class 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- -1 oxygen ions Chemical class 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 150000001721 carbon Chemical class 0.000 description 2
- 239000012776 electronic material Substances 0.000 description 2
- 238000003760 magnetic stirring Methods 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 239000010937 tungsten Substances 0.000 description 2
- 150000004645 aluminates Chemical class 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010891 electric arc Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000000615 nonconductor Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- DECCZIUVGMLHKQ-UHFFFAOYSA-N rhenium tungsten Chemical compound [W].[Re] DECCZIUVGMLHKQ-UHFFFAOYSA-N 0.000 description 1
- 102220040233 rs79219465 Human genes 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/28—Processes for applying liquids or other fluent materials performed by transfer from the surfaces of elements carrying the liquid or other fluent material, e.g. brushes, pads, rollers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
- B05D3/002—Pretreatement
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
- B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
- B05D3/0254—After-treatment
- B05D3/0272—After-treatment with ovens
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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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D2203/00—Other substrates
- B05D2203/30—Other inorganic substrates, e.g. ceramics, silicon
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Abstract
A method for preparing a calcium aluminate derivative thermal emission cathode crystal, comprising the steps of: 1) mixing calcium carbonate nano powder and alumina nano powder, then adding methyl cellulose, and fully and uniformly stirring to obtain mixed powder; 2) adding deionized water into the mixed powder, and stirring uniformly to fully mix the raw materials to obtain slurry; 3) taking a molybdenum sheet or a high-purity graphite sheet with a polished surface as a slide glass, uniformly brushing the slurry on the surface of the slide glass, heating, cooling, and dehydrating and drying the slurry; 4) and (3) placing the slide glass coated with the slurry obtained by dehydration and drying in a graphite crucible, sealing, sintering at high temperature, and cooling to room temperature to obtain the carrier glass containing the calcium aluminate derivative C12A7: C-/C crystal coating, i.e. calcium aluminate derivative heat emitting cathode crystals. The material has lower work function and good conductive performance, and can be used as a novel material for a hot cathode coating in a thermionic emission device.
Description
Technical Field
The invention relates to a preparation method of a calcium aluminate derivative thermal emission cathode crystal, belonging to the technical field of thermal cathode electron emission materials.
Background
Calcium aluminate 12CaO·7Al2O3(C12A7) is a good electrical insulator and is commonly used commercially as a component of aluminate cements. Due to their unusual crystal structure, the preparation and property studies of their derivatives are of great interest. The unit cell of C12A7 can be represented as [ Ca24Al28O64 ]]4++2O2-The former part represents a positively charged lattice framework with 12 cages, with an internal diameter of 0.4 nm. The latter part, the oxygen ions outside the two frameworks, occupies two of the 12 cages in a unit cell to compensate for the positive charge of the cage frameworks, while the other 10 cages remain empty. Oxygen ion O occupying vacancy in cage2-C12A7 derivatives which can be substituted with other anions, such as e-, NH2-, OH-, H-, or O-, etc., have unique properties when free oxygen ions are replaced with foreign anions.
To date, C12a7 and its derivatives have attracted much research, but most are directed to C12a7: e-and OH-, O-, NH 2-and other common anions, wherein the ratio of C12A7: e-is much studied, but there is no study on the preparation of carbon derivatives of C12A 7.
In the prior art, the methods for preparing C12a7 and derivatives thereof include a hybrid sintering method, an ammonia heat treatment method, a czochralski-smelting zone method and the like, wherein the C12a7 prepared by the hybrid sintering method contains more impurities and is generally used for building materials rather than electronic materials, and the ammonia heat treatment method and the czochralski-smelting zone method respectively correspond to the methods of C12a7: e-and C12A7: preparation of NH 2-. Prepared using the czochralski method to give C12a7: in the e-process, a carbon derivative of C12a7 is produced as an intermediate product, but a stable product thereof cannot be obtained. The technology of the invention improves the raw material proportion and the reaction condition aiming at the problem, optimizes the preparation steps, reduces the preparation cost, and simultaneously ensures that the final product can obtain the stable calcium aluminate derivative C12A7: C-/C.
Disclosure of Invention
The technical problem is as follows: the invention mainly aims to provide a preparation method of a calcium aluminate derivative thermal emission cathode crystal. The method solves the problems that C12A7: C-/C.
The technical scheme is as follows: the invention provides a preparation method of a calcium aluminate derivative thermal emission cathode crystal, which is characterized by comprising the following steps of: the method comprises the following steps:
1) mixing alumina nano powder and calcium carbonate nano powder according to the mass ratio of 1: 1.67-1.69, then adding methyl cellulose as a binder, and fully and uniformly stirring to obtain mixed powder, wherein the mass ratio of the alumina powder to the calcium carbonate to the binder is 1: 1.67-1.69: 0.008-0.009;
2) adding deionized water into the mixed powder obtained in the step 1), and stirring uniformly to fully mix the raw materials to obtain slurry;
3) uniformly brushing the slurry obtained in the step 2) on the surface of a slide glass by using a molybdenum sheet or a high-purity graphite sheet with a polished surface as the slide glass, heating the slide glass coated with the slurry to be close to 90 ℃, and then cooling to dehydrate and dry the slurry;
4) placing the slide glass coated with the slurry obtained by dehydration and drying in the step 3) in a graphite crucible, sealing, then stably placing the crucible in a high-temperature furnace, sintering at the high temperature of 1000-1600 ℃ for 25-40 min, taking out the graphite crucible, cooling to room temperature, opening the crucible, and taking out the slide glass to obtain the slide glass containing the calcium aluminate derivative C12A7: C-/C crystal coating, i.e. calcium aluminate derivative heat emitting cathode crystals.
Wherein:
the purity of the calcium carbonate nano powder in the step 1) is 99.5 to 99.9 weight percent, and the purity of the aluminum oxide nano powder is 99.5 to 99.9 weight percent; the mixed powder obtained by fully and uniformly stirring is stirred for 15-20 min at a speed of 1200-1500 r/min by using a magnetic stirrer.
Adding deionized water into the mixed powder obtained in the step 1) in the step 2), wherein the mass ratio of the aluminum oxide to the calcium carbonate to the binder to the deionized water is 1: 1.67-1.69: 0.008-0.009: 22-23; the raw materials are fully mixed by uniform stirring to obtain slurry, the uniform stirring refers to stirring for 20-25 min at 1500-2000 r/min in a magnetic stirrer, and the rotation direction of a rotor is adjusted every 4-6 min.
And 3) uniformly brushing the slurry obtained in the step 2) in the surface of the slide glass, wherein the thickness of the slurry on the surface of the slide glass is 1-1.5 mm.
And 3) heating the slide glass coated with the slurry to be close to 90 ℃, and then cooling, namely placing the slide glass coated with the slurry on a heating plane of a stirring meter, heating to 85-90 ℃ at 50-60W, stopping heating, and waiting for the temperature of a heating table to be reduced to 30-40 ℃, so that the slurry is fully dehydrated and dried.
The work function of the calcium aluminate derivative thermal emission cathode crystal prepared by the method can reach 0.6-1.5 eV.
Has the advantages that: compared with the prior art, the invention has the following advantages:
in the prior art, the common high-temperature sintering method can only prepare calcium aluminate with lower purity, and the calcium aluminate is used as a material in the aspect of construction and is difficult to be directly used for electronic materials. Other preparation methods generally aim at the anion derivative of C12A7, have higher preparation difficulty and are only suitable for preparation and use in laboratories.
The invention has the characteristics of simple process and low cost, is relatively easy to prepare, can directly obtain a relatively uniform C12A7: C-/C crystal coating, has low work function which can reach 0.6-1.5 eV, and can be used as a material of a thermionic emitter.
Drawings
FIG. 1 is a device for firing calcium aluminate derivative thermal emission cathode crystals in an electric arc furnace, and the device is provided with a tungsten-rhenium thermocouple 1 for monitoring the furnace temperature, a tungsten needle electrode 2, a tungsten needle 3, a high-temperature resistant insulating layer 4, a graphite electrode 5, a slide 6, a graphite crucible 7 and an insulating ceramic sleeve 8.
FIG. 2 is an x-diffraction pattern of the prepared calcium aluminate derivative thermionic emission cathode crystal, with diffraction angle on the abscissa and diffraction intensity on the surface of the sample on the ordinate.
Detailed Description
The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1:
a preparation method of calcium aluminate derivative thermal emission cathode crystal is characterized in that: the method comprises the following steps:
1) mixing alumina nano powder (with the purity of 99.5 wt%) and calcium carbonate nano powder (with the purity of 99.5 wt%) according to the mass ratio of 1:1.67, then adding methyl cellulose as a binder, then fully stirring in a magnetic stirrer, and stirring at 1200r/min for 15min to uniformly mix the powders to obtain mixed powder, wherein the mass ratio of the alumina powder, the calcium carbonate powder and the binder is 1:1.67: 0.008;
2) adding deionized water (the mass ratio of the aluminum oxide to the calcium carbonate to the binder to the deionized water is 1:1.67:0.008:22) into the mixed powder obtained in the step 1), fully and uniformly stirring in a magnetic stirrer, stirring at 1500r/min for 20min, and adjusting the rotation direction of a rotor every 5min to fully mix the raw materials to obtain slurry;
3) taking a molybdenum sheet with a polished surface as a slide glass 6, uniformly brushing the slurry obtained in the step 2) on the surface of the slide glass 6, wherein the thickness of the slide glass 6 is 1mm, then placing the slide glass 6 coated with the slurry on a heating plane of a stirring meter, heating to 85 ℃ at 50W, stopping heating, waiting for a heating table to cool to 40 ℃, and fully dehydrating and drying the slurry;
4) carefully clamping the slide glass 6 from two sides of the slide glass 6 coated with the slurry obtained by dehydration and drying by using tweezers, placing the slide glass 6 in a graphite crucible 7, sealing the graphite crucible 7, stably placing the graphite crucible 7 in a high-temperature furnace, sintering the graphite crucible 7 at the high temperature of 1000 ℃ for 25min, taking out the graphite crucible 7, cooling the graphite crucible 7 to the room temperature, opening the graphite crucible 7, and taking out the slide glass to obtain the carrier glass containing C12A7: C-/C crystal coating, i.e. calcium aluminate derivative thermionic emission cathode crystal, the work function of the crystal can reach 1.5 eV.
Example 2:
a preparation method of calcium aluminate derivative thermal emission cathode crystal is characterized in that: the method comprises the following steps:
1) mixing the alumina nano powder (with the purity of 99.5 wt%) and the calcium carbonate nano powder (with the purity of 99.5 wt%) according to the mass ratio of 1:1.67, then adding methyl cellulose as a binder, then fully stirring in a magnetic stirrer, and stirring at 1300r/min for 15min to uniformly mix the powders to obtain mixed powder, wherein the mass ratio of the alumina to the calcium carbonate powder to the binder is 1:1.68: 0.008;
2) adding deionized water (the mass ratio of the aluminum oxide to the calcium carbonate to the binder to the deionized water is 1:1.68:0.008:22) into the mixed powder obtained in the step 1), fully and uniformly stirring in a magnetic stirrer, stirring at 1600r/min for 20min, and adjusting the rotation direction of a rotor every 5min to fully mix the raw materials to obtain slurry;
3) taking a molybdenum sheet with a polished surface as a slide 6, uniformly brushing the slurry obtained in the step 2) on the surface of the slide 6, wherein the thickness of the slide 6 is 1mm, then placing the slide 6 coated with the slurry on a heating plane of a stirring meter, heating the slide 6 to 87 ℃ at 55W, stopping heating, waiting for the temperature of a heating table to be reduced to 35 ℃, and fully dehydrating and drying the slurry;
4) carefully clamping the slide glass 6 from two sides of the slide glass 6 coated with the slurry obtained by dehydration and drying by using tweezers, placing the slide glass 6 in a graphite crucible 7, sealing the graphite crucible 7, stably placing the graphite crucible 7 in a high-temperature furnace, sintering the graphite crucible 7 at the high temperature of 1200 ℃ for 30min, taking out the graphite crucible 7, cooling the graphite crucible 7 to the room temperature, opening the graphite crucible 7, and taking out the slide glass to obtain the carrier glass containing C12A7: C-/C crystal coating, i.e. calcium aluminate derivative thermionic emission cathode crystal, the work function of the crystal can reach 1.1 eV.
Example 3:
a preparation method of calcium aluminate derivative thermal emission cathode crystal is characterized in that: the method comprises the following steps:
1) mixing the alumina nano powder (with the purity of 99.9 wt%) and the calcium carbonate nano powder (with the purity of 99.9 wt%) according to the mass ratio of 1:1.69, then adding methyl cellulose as a binder, then fully stirring in a magnetic stirring meter, and stirring for 15min at 1400r/min to uniformly mix the powders to obtain mixed powder, wherein the mass ratio of the alumina powder, the calcium carbonate powder and the binder is 1:1.69: 0.009;
2) adding deionized water (the mass ratio of the alumina to the calcium carbonate to the binder to the deionized water is 1:1.69:0.009:23) into the mixed powder obtained in the step 1), fully and uniformly stirring in a magnetic stirring meter, stirring at 1800r/min for 25min, and adjusting the rotation direction of a rotor every 5min to fully mix the raw materials to obtain slurry;
3) taking a molybdenum sheet with a polished surface as a slide 6, uniformly brushing the slurry obtained in the step 2) on the surface of the slide 6, wherein the thickness of the slide 6 is 1.5mm, then placing the slide 6 coated with the slurry on a heating plane of a stirring meter, heating to 90 ℃ at 60W, stopping heating, waiting for the temperature of a heating table to be reduced to 40 ℃, and fully dehydrating and drying the slurry;
4) carefully clamping the slide glass 6 from two sides of the slide glass 6 coated with the slurry obtained by dehydration and drying by using tweezers, placing the slide glass 6 in a graphite crucible 7, sealing the graphite crucible 7, stably placing the graphite crucible 7 in a high-temperature furnace, sintering the graphite crucible 7 at the high temperature of 1400 ℃ for 30min, taking out the graphite crucible 7, cooling the graphite crucible 7 to the room temperature, opening the graphite crucible 7, and taking out the slide glass to obtain the carrier glass containing C12A7: C-/C crystal coating, i.e. calcium aluminate derivative thermionic emission cathode crystal, the work function of which can reach 0.6 eV.
Example 4:
a preparation method of calcium aluminate derivative thermal emission cathode crystal is characterized in that: the method comprises the following steps:
1) mixing the alumina nano powder (with the purity of 99.9 wt%) and the calcium carbonate nano powder (with the purity of 99.9 wt%) according to the mass ratio of 1:1.69, then adding methyl cellulose as a binder, then fully stirring in a magnetic stirrer, and stirring at 1500r/min for 20min to uniformly mix the powders to obtain mixed powder, wherein the mass ratio of the alumina powder to the calcium carbonate powder to the binder is 1:1.69: 0.008;
2) adding deionized water (the mass ratio of the aluminum oxide to the calcium carbonate to the binder to the deionized water is 1:1.69:0.008:23) into the mixed powder obtained in the step 1), fully and uniformly stirring in a magnetic stirrer, stirring at 2000r/min for 25min, and adjusting the rotation direction of a rotor every 5min to fully mix the raw materials to obtain slurry;
3) taking a molybdenum sheet with a polished surface as a slide 6, uniformly brushing the slurry obtained in the step 2) on the surface of the slide 6, wherein the thickness of the slide 6 is 1.5mm, then placing the slide 6 coated with the slurry on a heating plane of a stirring meter, heating to 90 ℃ at 60W, stopping heating, waiting for the temperature of a heating table to be reduced to 30 ℃, and fully dehydrating and drying the slurry;
4) carefully clamping the slide glass 6 from two sides of the slide glass 6 coated with the slurry obtained by dehydration and drying by using tweezers, placing the slide glass 6 in a graphite crucible 7, sealing the graphite crucible 7, stably placing the graphite crucible 7 in a high-temperature furnace, sintering the graphite crucible 7 at a high temperature of 1600 ℃ for 40min, taking out the graphite crucible 7, cooling the graphite crucible 7 to room temperature, opening the graphite crucible 7, and taking out the slide glass to obtain the carrier glass containing C12A7: C-/C crystal coating, i.e. calcium aluminate derivative thermionic emission cathode crystal, the work function of the crystal can reach 0.9 eV.
Claims (6)
1. A preparation method of calcium aluminate derivative thermal emission cathode crystal is characterized in that: the method comprises the following steps:
1) mixing alumina nano powder and calcium carbonate nano powder according to the mass ratio of 1: 1.67-1.69, then adding a trace amount of methylcellulose serving as a binder, and fully and uniformly stirring to obtain mixed powder, wherein the mass ratio of the alumina powder to the calcium carbonate powder to the binder is 1: 1.67-1.69: 0.008-0.009;
2) adding deionized water into the mixed powder obtained in the step 1), and stirring uniformly to fully mix the raw materials to obtain slurry;
3) taking a molybdenum sheet or a high-purity graphite sheet with a polished surface as a slide glass (6), uniformly brushing the slurry obtained in the step 2) on the surface of the slide glass, heating the slide glass (6) coated with the slurry to a temperature close to 90 ℃, and then cooling to dehydrate and dry the slurry;
4) placing the slide glass coated with the slurry obtained by dehydration and drying in the step 3) in a graphite crucible (7), sealing, then stably placing the graphite crucible (7) in a high-temperature furnace, sintering at the high temperature of 1000-1600 ℃ for 20-40 min, taking out the graphite crucible (7), cooling to room temperature, opening the graphite crucible (7), and taking out the slide glass to obtain the slide glass containing the calcium aluminate derivative C12A7: C-/C crystal coating, i.e. calcium aluminate derivative heat emitting cathode crystals.
2. The method of preparing a calcium aluminate derivative thermionic emission cathode crystal as claimed in claim 1, wherein: the purity of the calcium carbonate nano powder in the step 1) is 99.5 to 99.9 weight percent, and the purity of the aluminum oxide nano powder is 99.5 to 99.9 weight percent; the mixture is fully and uniformly stirred to obtain mixed powder, namely stirring for 15-20 min at 1200-1500 r/min by using a magnetic stirrer.
3. The method of preparing a calcium aluminate derivative thermionic emission cathode crystal as claimed in claim 1, wherein: adding deionized water into the mixed powder obtained in the step 1) in the step 2), wherein the mass ratio of the aluminum oxide to the calcium carbonate to the binder to the deionized water is 1: 1.67-1.69: 0.008-0.009: 22-23; the raw materials are fully mixed by uniform stirring to obtain slurry, the uniform stirring refers to stirring for 20-25 min at 1500-2000 r/min in a magnetic stirrer, and the rotation direction of a rotor is adjusted every 4-6 min.
4. The method of preparing a calcium aluminate derivative thermionic emission cathode crystal as claimed in claim 1, wherein: and 3) uniformly brushing the slurry obtained in the step 2) in the surface of the slide glass, wherein the thickness of the slurry on the surface of the slide glass is 1-1.5 mm.
5. The method of preparing a calcium aluminate derivative thermionic emission cathode crystal as claimed in claim 1, wherein: and 3) heating the slide glass (6) coated with the slurry to be close to 90 ℃, and then cooling, namely placing the slide glass (6) coated with the slurry on a heating plane of a stirring meter, heating to 85-90 ℃ at 50-60W, stopping heating, and waiting for a heating table to cool to 30-40 ℃ to fully dehydrate and dry the slurry.
6. The method of preparing a calcium aluminate derivative thermionic emission cathode crystal as claimed in claim 1, wherein: the work function of the calcium aluminate derivative thermal emission cathode crystal prepared by the method can reach 0.6-1.5 eV.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023017199A1 (en) | 2021-08-10 | 2023-02-16 | Advanced Thermal Devices S.L. | Cathode based on the material c12a7:e− (electride) for thermionic electron emission and method for using same |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1659114A (en) * | 2002-05-01 | 2005-08-24 | 康宁股份有限公司 | Fabrication of low thermal expansion calcium aluminate articles |
| CN1790607A (en) * | 2004-12-15 | 2006-06-21 | 鸿富锦精密工业（深圳）有限公司 | Field emission illuminating light source and its preparing method |
| CN102484031A (en) * | 2009-08-25 | 2012-05-30 | 旭硝子株式会社 | Electrode for discharge lamp, and process for production thereof |
| CN103547547A (en) * | 2011-05-13 | 2014-01-29 | 旭硝子株式会社 | Method for producing conductive mayenite compound |
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2020
- 2020-06-15 CN CN202010541593.8A patent/CN111774276A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1659114A (en) * | 2002-05-01 | 2005-08-24 | 康宁股份有限公司 | Fabrication of low thermal expansion calcium aluminate articles |
| CN1790607A (en) * | 2004-12-15 | 2006-06-21 | 鸿富锦精密工业（深圳）有限公司 | Field emission illuminating light source and its preparing method |
| CN102484031A (en) * | 2009-08-25 | 2012-05-30 | 旭硝子株式会社 | Electrode for discharge lamp, and process for production thereof |
| CN103547547A (en) * | 2011-05-13 | 2014-01-29 | 旭硝子株式会社 | Method for producing conductive mayenite compound |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023017199A1 (en) | 2021-08-10 | 2023-02-16 | Advanced Thermal Devices S.L. | Cathode based on the material c12a7:e− (electride) for thermionic electron emission and method for using same |
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