CN114340124A - Sodium ion emitter and preparation method thereof - Google Patents
Sodium ion emitter and preparation method thereof Download PDFInfo
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- CN114340124A CN114340124A CN202111668067.9A CN202111668067A CN114340124A CN 114340124 A CN114340124 A CN 114340124A CN 202111668067 A CN202111668067 A CN 202111668067A CN 114340124 A CN114340124 A CN 114340124A
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- sodium ion
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- 229910001415 sodium ion Inorganic materials 0.000 title claims abstract description 41
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title abstract description 7
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 143
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 113
- 239000010937 tungsten Substances 0.000 claims abstract description 113
- 229910000503 Na-aluminosilicate Inorganic materials 0.000 claims abstract description 53
- 235000012217 sodium aluminium silicate Nutrition 0.000 claims abstract description 53
- 239000000429 sodium aluminium silicate Substances 0.000 claims abstract description 53
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 53
- 239000000758 substrate Substances 0.000 claims abstract description 52
- 239000000463 material Substances 0.000 claims abstract description 30
- 238000000576 coating method Methods 0.000 claims abstract description 21
- 239000000203 mixture Substances 0.000 claims abstract description 21
- 239000011248 coating agent Substances 0.000 claims abstract description 20
- 239000002002 slurry Substances 0.000 claims abstract description 14
- 239000000843 powder Substances 0.000 claims description 49
- 238000010438 heat treatment Methods 0.000 claims description 39
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 15
- 238000005245 sintering Methods 0.000 claims description 14
- 239000000919 ceramic Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 13
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 239000003292 glue Substances 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 8
- 239000002243 precursor Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 239000012466 permeate Substances 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 6
- 238000003825 pressing Methods 0.000 claims description 6
- 238000011049 filling Methods 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims 1
- 239000002994 raw material Substances 0.000 claims 1
- 230000009471 action Effects 0.000 abstract description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 6
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 6
- 230000035515 penetration Effects 0.000 abstract 1
- 150000002500 ions Chemical class 0.000 description 10
- 238000005336 cracking Methods 0.000 description 5
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 239000011812 mixed powder Substances 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 238000010884 ion-beam technique Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000006138 lithiation reaction Methods 0.000 description 2
- 239000011268 mixed slurry Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000000295 emission spectrum Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000002431 hydrogen Chemical group 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
Images
Abstract
The invention provides a sodium ion emitter and a preparation method thereof, which have compact structure and greatly increase the thickness of a sodium aluminosilicate coating and the adhesion of the whole structure. The sodium ion emitter adopts tungsten as a framework, a porous structure sintered by a tungsten powder 1:1 mixture with the diameter of 10 microns and 100 microns is used as a substrate, and the chamfer structure of the framework greatly increases the binding force of the two materials and can not fall off under the action of high temperature and electrostatic force. The porous tungsten with the porosity of 25 percent is sintered with the emission material attached to the surface along with the penetration of the emission slurry, so that the adhesion strength of the emission material and the whole structure is further enhanced, and the coating can not be peeled off under the action of electrostatic force under the action of high voltage. The enhancement of the adhesion force of the emission coating can greatly increase the coating thickness, further increase the emission capability and the service life of the sodium ion source, the service life of the sodium ion emitter is more than 10 times of that of the original lithium ion source, and the beam density is more than 2 times of that of the lithium ion source.
Description
Technical Field
The invention relates to a sodium ion emitter for alkali metal plasma generation, material treatment and an ion accelerator, in particular to a sodium ion emitter and a preparation method thereof.
Background
High ion temperature sodium ions are an important tool for plasma generation and for studying ion-plasma interactions. The density and the potential distribution of the boundary plasma obtained without interference are indispensable important physical quantities for researching the plasma. Internationally, interference-free spot measurement of plasma electron density and potential distribution using high-energy sodium neutral beams is becoming a hot spot. The lithium ion source used at present is limited by the problems of poor spatial resolution, short service life, cracking of an emitting material caused by negative thermal expansion coefficient of a coating material, peeling from a porous tungsten substrate and the like. To solve these problems, it is often done by reducing the thickness of the coating and reducing the current emission capability. Thinner emissive coatings result in poor ion emission capability of the ion source, short lifetime, frequent maintenance requirements, and greatly increased system operating costs. The poor current emission capability results in poor signal-to-noise ratio of the system, which is more difficult to operate effectively under lithiated wall processing conditions.
Therefore, in order to solve the above problems, replacing the lithium ion beam with the sodium ion beam is one of the most effective solutions. The service life of the sodium ion emitter manufactured by the invention is more than 10 times of that of the original lithium ion emitter, the cracking and stripping phenomena caused by the thermal shrinkage of the emitting material can be avoided, the yield of the alkali metal emitter is improved by more than three times, the sodium ion emitter can be effectively used under the treatment condition of a Tokamak lithiation wall, the signal-to-noise ratio is improved by more than 50 times, and the boundary plasma information can be accurately measured.
Disclosure of Invention
The invention aims to provide a sodium ion emitter and a preparation method thereof. The method is a preparation method of a large-area sodium ion emitter suitable for alkali metal plasma generation and sodium beam emission spectrum, so that the long service life of the sodium ion emitter is realized, and the problems that cracking and peeling are caused by thermal contraction of a lithium ion emitting material and thermal expansion of a substrate at high temperature, and the lithium beam has poor signal-to-noise ratio and cannot accurately obtain boundary plasma information in a lithiation wall treatment mode are solved.
In order to achieve the purpose, the invention adopts the technical scheme that:
a sodium ion emitter, comprising: the device comprises a round cup-shaped tungsten bottom plate, a porous tungsten substrate layer, an emission material layer of sodium aluminosilicate and a heating body; wherein the content of the first and second substances,
the heating body comprises aluminum oxide and a conical tungsten wire, and the conical tungsten wire is positioned in the aluminum oxide;
the top of the circular cup-shaped tungsten bottom plate is provided with a top concave cavity, and the bottom of the circular cup-shaped tungsten bottom plate is provided with a bottom concave cavity;
in the top cavity, the porous tungsten substrate layer and the emission material layer of sodium aluminosilicate are sequentially stacked from the bottom of the cavity to the outside;
and the heating body is placed in the bottom concave cavity.
Further, the sodium ion emitter is a monolithic structure formed by heat treatment; preferably, the heat treatment is sintering.
Preferably, the porous tungsten substrate layer is formed by pressing and sintering a mixture formed by mixing tungsten powders with different diameters.
Preferably, the thickness of the porous tungsten substrate is 2-2.5 mm. Preferably, the thickness of the emission material layer of the sodium aluminosilicate is 2-3 mm.
For example, the top cavity depth is 3mm, 4mm, 5mm or 6 mm. The top cavity diameter is 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm or 25 mm.
For example, the depth of the bottom concave cavity is 15-20 mm. For example, the bottom cavity depth is 15mm, 16mm, 17mm, 18mm, 19mm or 20 mm. The bottom cavity diameter is 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm or 29 mm.
Furthermore, an annular step is arranged around the concave cavity at the top of the circular cup-shaped tungsten bottom plate, and a chamfer is formed along the annular step and used for fixing the porous tungsten substrate. For example, the step may be 25mm, 26mm, 27mm or 28mm in diameter and 2mm, 3mm or 4mm in height. Preferably, the chamfer is 45 °. Optionally, the depth of the chamfer structure is 1 mm.
A method for preparing a sodium ion emitter comprises the following steps,
(1) providing a circular cup-shaped tungsten bottom plate, wherein the top of the circular cup-shaped tungsten bottom plate is provided with a top concave cavity, and the bottom of the circular cup-shaped tungsten bottom plate is provided with a bottom concave cavity;
(2) mixing tungsten powders with different diameters to form a mixture, pressing the mixture into the top concave cavity, and sintering the mixture into a porous tungsten substrate layer;
(3) dropping sodium aluminosilicate powder slurry on the surface of the porous tungsten substrate layer to enable the sodium aluminosilicate powder to permeate into the porous tungsten substrate layer;
(4) filling sodium aluminosilicate powder on the surface of the porous tungsten substrate layer in the top concave cavity to obtain a first sodium ion emitter precursor;
(5) heating the first sodium ion emitter precursor in vacuum, and cooling to obtain a second sodium ion emitter precursor;
(6) the sodium ion emitter was prepared by adding a starting material comprising alumina powder to the bottom cavity of a round cup-shaped tungsten base plate of a second sodium ion emitter precursor, placing a conical tungsten wire in the alumina powder, and drying.
Further, in the step (2), the tungsten powders with different diameters are tungsten powder with a diameter of 10 microns and tungsten powder with a diameter of 100 microns respectively. In the mixture, the mass ratio of the tungsten powder with the diameter of 10 microns to the tungsten powder with the diameter of 100 microns is 1: 1.
The purity of the sodium aluminosilicate in the invention is more than 99.5%.
Further, in the step (2), the sintering temperature is 1800-2000 ℃; the sintering atmosphere is hydrogen, and the pressure is 0.01-1.0 pa; the sintering time is 1-2 hours.
Further, in the step (3), the sodium aluminosilicate powder slurry is a mixture of sodium aluminosilicate powder and deionized water.
Further, in the step (3), the sodium aluminosilicate powder slurry is dropped on the surface of the porous tungsten substrate layer, so that the sodium aluminosilicate powder permeates into the porous tungsten substrate layer, and the steps are performed as follows: mixing sodium aluminosilicate powder with deionized water to form slurry, uniformly coating the slurry on the surface of a porous tungsten substrate, and keeping vibration on an ultrasonic vibration platform for 10-20 minutes to enable the sodium aluminosilicate powder to permeate into the porous tungsten substrate; preferably, 2 drops of the slurry are applied per square centimeter of the surface of the porous tungsten substrate.
Further, in the step (4), sodium aluminosilicate powder is uniformly covered on the porous tungsten substrate layer, the thickness is kept at 2-3mm, and the thickness is kept at 150-200 kg/cm2The powder was compacted under pressure and the surface was kept uniform and smooth.
Further, the step (5) specifically includes: the heating is carried out in a vacuum furnace. The heating and cooling steps comprise that the temperature is increased to the highest temperature of 1110-1120 ℃ at the speed of 9-10 ℃ per minute within the range of 0.01-1pa of air pressure, the temperature is maintained at the highest temperature for 5-10 minutes, then the temperature is reduced to the room temperature at the speed of 15-20 ℃ per minute, nitrogen is filled into the air pressure at the speed of 1000-2000 pa/min until the air pressure is increased to 1 atmosphere, and the preparation of the emission coating is completed. The emission coating is an emission material layer of sodium aluminosilicate.
Further, the step (6) specifically includes: and pouring the mixture of the aluminum oxide powder and the ceramic glue into the concave cavity at the deep bottom of the circular cup-shaped tungsten baseplate with the depth of 15-20 mm, and immersing the conical tungsten wire into the mixture of the aluminum oxide powder and the ceramic glue.
Further, in the step (6), the drying and heat treatment comprises: and (3) after injecting a mixture of the alumina powder and the ceramic glue, standing for 24 hours, drying, putting the integral structure into a vacuum oven, baking at 100 ℃ for 5 hours to release residual moisture, and then heating to 300 ℃ for baking for 10 hours.
In the present invention, high purity means a purity of more than 99.5%.
Further, the sodium ion emitter, its main components include: the high-mechanical-strength round-cup-shaped tungsten baseplate comprises a high-mechanical-strength round-cup-shaped tungsten baseplate, a porous tungsten baseplate layer which is formed by mixing, pressing and sintering tungsten powder with the diameter of 10 micrometers and tungsten powder with the diameter of 100 micrometers according to the mass ratio of 1:1, an emission material layer of high-purity sodium aluminosilicate (the purity is more than 99.5%), and a heating body which is composed of aluminum oxide and a conical tungsten wire.
In an alternative embodiment, the porous tungsten substrate layer has a porosity of 25%.
Furthermore, the porous tungsten substrate layer has a thermal expansion coefficient of sodium aluminosilicate close to that of the porous tungsten substrate layer, so that the coating stripping phenomenon caused by different expansion sizes at the use temperature of 1000-1100 ℃ is avoided.
Further, the mixture of sodium aluminosilicate powder and deionized water is vibrated on the ultrasonic platform for a long time, so that the sodium aluminosilicate can enter the porous tungsten to form a compact structure, and the sodium aluminosilicate cannot fall off due to the action of electrostatic force in the using process.
Furthermore, the annular chamfer of the tungsten support baseplate can ensure that the porous tungsten and the tungsten support baseplate are combined more firmly, and a large gap or separation phenomenon caused by slight difference of thermal expansion coefficients of two materials can be avoided.
Furthermore, sodium aluminosilicate is uniformly covered on the surface of the porous tungsten substrate by adopting dry powder, and the sodium aluminosilicate with the diameter of 2-10 microns can generate a large number of micro holes, so that sodium ions can overflow the surface of the emitter as soon as possible to generate the sodium ions, and the emission capability of the emitter is improved.
Furthermore, the sintering temperature is 1100 ℃ and is maintained for 20 minutes, the sodium aluminosilicate can not be fully changed into liquid when being sintered together, a large number of micro-hole structures of the emission material are reserved, stress caused by heating expansion is favorably released, and the cracking phenomenon of the emission material caused by expansion is effectively inhibited.
In the invention, the porous tungsten substrate layer is in a porous tungsten cake structure.
Has the advantages that:
1. according to the invention, a concave cavity with the circular depth of 5mm is processed at the top of a firm and high-temperature-resistant cup-shaped tungsten framework, chamfering processing is carried out at the bottom of the concave cavity, tungsten powder with the diameter of 10 microns and tungsten powder with the diameter of 100 microns are mixed in a ratio of 1:1, and are pressed and sintered together with a tungsten base to form a porous tungsten cake structure with the thickness of 2mm and the porosity of 25%, and the structure can effectively solve the problem of cracks or falling-off phenomenon at high temperature due to different thermal expansion coefficients of tungsten and porous tungsten.
2. The mixed slurry of sodium aluminosilicate powder with the diameter of 2-10 microns and deionized water can penetrate into the porous tungsten substrate under the action of ultrasonic vibration, and the mixed slurry and the sodium aluminosilicate powder on the surface are sintered together, so that the adhesive force of the surfaces of the two materials can be increased, and the two materials cannot be peeled off under the action of electrostatic force.
3. The sodium aluminosilicate powder is uniformly laid on the surface of the substrate, a concave cavity with the depth of about 3mm is filled, and the pressure is 200kg/cm2The material is compacted under pressure, thus an emitting material coating with a porous structure can be formed after sintering at 1100 ℃, the stress caused by thermal expansion can be effectively released, and further the phenomena of cracking or powder part falling off caused by expansion are avoided.
4. The thermal expansion coefficient of the porous tungsten cake is smaller than that of tungsten and is close to that of porous sodium aluminosilicate, so that the problem that the contact surface material is cracked under stress caused by expansion caused by heat and contraction caused by cold of the two materials can be effectively solved.
5. Adopt tungsten heater strip and alumina ceramics integral structure, realized the insulation of heater strip promptly, change original thermal radiation heating structure into heat-conduction heating emitter simultaneously, heating efficiency is higher.
Drawings
FIG. 1 is a cross-sectional view of the structure of the present invention;
fig. 2 is an exploded view of a sodium ion emitter.
Wherein: 1 is a tungsten framework, 2 is a chamfer, 3 is a porous tungsten substrate, 4 is a sodium aluminosilicate cake, 5 is an alumina ceramic body, and 6 is a tungsten heating wire.
Detailed Description
The technical scheme of the invention is explained in detail in the following with the accompanying drawings of the specification.
As shown in fig. 1-2, a sodium ion emitter (i.e., a sodium ion source) suitable for an ion accelerator, material treatment and plasma generation includes a tungsten skeleton 1 having a high mechanical strength, a porous tungsten substrate 3 formed by pressing and sintering a tungsten powder mixture having a diameter of 10 μm and a diameter of 100 μm in a mass ratio of 1:1, a tungsten skeleton chamfer 2 for fixing the porous tungsten substrate 3, a high purity sodium aluminosilicate sintered ceramic body (high purity means purity of more than 99.5%), a tungsten heater wire 6 for performing heating and insulating functions, and a columnar alumina ceramic body 5. The tungsten heating wire 6 is positioned in the columnar alumina ceramic body 5, and the tungsten heating wire 6 and the columnar alumina ceramic body 5 form a heating body. The tungsten heating wire 6 is a conical tungsten wire. The distance between the tungsten heating wire 6 and the tungsten framework 1 is more than 2mm, and two ends of the tungsten heating wire are connected with a heating power supply.
The ceramic body sintered by the high-purity sodium aluminosilicate is a sodium aluminosilicate cake 4. The sodium aluminosilicate cake 4 is a ceramic body sintered by sodium aluminosilicate with the purity of more than 99.5 percent.
The porous tungsten substrate 3 is a porous tungsten cake. The porosity of the porous tungsten substrate 3 is 25%. The porous tungsten cake with the porosity of 25 percent and the sodium aluminosilicate ceramic body have similar thermal expansion coefficients, so that the adhesion of the emission material on the substrate can be ensured, and simultaneously, the emission material can not crack due to thermal expansion. The tungsten skeleton and the porous tungsten which are sintered together in the chamfer structure ensure that the two materials cannot fall off at high temperature due to different thermal expansion coefficients, and meanwhile, the porous tungsten cake cannot be peeled off due to the action of electrostatic force in the discharging process.
The tungsten framework with high mechanical strength is made of high-hardness tungsten materials and is in a circular cup shape. The top of the tungsten skeleton is provided with a top concave cavity and an annular chamfer structure. The top cavity is a cavity with a diameter of 20mm and a depth of 5 mm. The bottom of the tungsten skeleton 1 is provided with a bottom concave cavity with the diameter of 25mm and the depth of 20 mm. The annular chamfering structure is arranged as follows: an annular step is arranged around the concave cavity at the top, the diameter of the step is 28mm, the height of the step is 3mm, and a chamfer 2 is formed along the annular step to form an annular chamfer structure which is used for being fixed with an auxiliary structure of the ion source and ensuring good electric contact of the ion source. Optionally, the chamfer 2 is 45 ° and the depth of the chamfer structure is 1 mm. In the top concave cavity, a porous tungsten substrate 3 and a sodium aluminosilicate cake 4 are sequentially stacked from the bottom of the concave cavity to the outside. And the heating body is placed in the bottom concave cavity.
Mixing tungsten powder with diameter of 10 microns and 100 microns according to the mass ratio of 1:1 to form mixed powder, wherein the mass ratio of the mixed powder to the tungsten powder is 10T/cm2And pressing the mixed powder into the cavity at the top under pressure, placing the structure in an environment with the gas pressure of 0.01pa hydrogen and the temperature of 2000 ℃ for firing for 2 hours until the structure is sintered to form a porous structure substrate, and then slowly cooling to the room temperature to form a porous tungsten substrate 3 with the porosity of about 25%. The tungsten skeleton 1 and the porous tungsten substrate 3 are sintered together, because the tungsten skeleton 1 and the porous tungsten substrate 3The components are the same, so the expansion coefficients are close, and the separation of the framework and the substrate caused by the difference of the thermal expansion coefficients is relieved. The thickness of the porous tungsten substrate is 2.5 mm.
Stirring 0.5 g of sodium aluminosilicate powder with the purity of more than 99.5 percent by using 2ml of deionized water to form a slurry body, dripping the slurry body on the surface of the porous tungsten substrate 3, dripping 2 drops per square centimeter, uniformly coating, placing on an ultrasonic vibration platform, keeping vibrating for 20 minutes, and allowing the sodium aluminosilicate powder to permeate into the porous tungsten body. Mixing deionized water and dry sodium aluminosilicate powder at a mass ratio of 1:10, stirring, and filling into a cavity at the top of the tungsten skeleton at 200kg/cm2The powder is compacted under pressure to the same height as the surface of the cavity and to maintain a uniform and smooth surface. By adopting the structure, the thickness of the surface sodium aluminosilicate coating can reach 2-3 mm. Since the current emission capability is proportional to the coating thickness, the emission capability is higher. And (3) slowly drying the surface coating in the shade for 48 hours in a room temperature environment, so that the powder coating does not crack and the ion source framework is prepared.
And (3) putting the prepared ion source framework into a vacuum furnace, and keeping the air pressure at about 0.01pa to inhibit the evaporation of the sodium aluminosilicate at high temperature. Slowly heating the skeleton structure, keeping the temperature rise rate at 10 ℃ per minute, keeping the temperature for 10 minutes after the temperature reaches 1110 ℃ until a liquid glass-like object is formed on the surface, and then slowly cooling the skeleton structure by a vacuum furnace at 20 ℃ per minute until the skeleton structure is in a room temperature state. And (3) filling nitrogen into the vacuum chamber at the speed of 1000pa/min until the pressure is raised to 1 atmosphere, and finishing the firing of the emission coating through the steps. The emission coating is the sodium aluminosilicate cake 4. The thickness of the emission coating was 3 mm.
The method comprises the steps of enabling a concave cavity at the bottom of a tungsten framework to face upwards, adding a mixture of high-purity aluminum oxide powder (with the purity of 99.9%) and 1400-DEG C-resistant inorganic ceramic glue in a mass ratio of 2:1 into the tungsten framework, injecting the mixture into the tungsten framework to the thickness of 2mm, drying the tungsten framework for 24 hours, placing a conical tungsten heating wire 6 in the center of the concave cavity at the bottom, injecting the mixture of the aluminum oxide powder and the ceramic glue again until the tungsten heating wire 6 is completely covered, standing the tungsten heating wire for 24 hours, drying the tungsten heating wire, placing the integral structure into a vacuum oven, baking the tungsten heating wire for 5 hours at the temperature of 100 ℃ to release residual water, heating the tungsten heating wire to 300 ℃ to bake for 10 hours, discharging residual organic impurities, and hardening the aluminum oxide powder condensate until the manufacturing of the sodium ion source is finished, so that the sodium ion source can be heated and used. Wherein the alumina powder agglomerates harden to form a columnar alumina ceramic body 5.
When the sodium ion emitter prepared by the invention is used, the ion source is heated to 1000-1100 ℃, and the bias voltage of-10 to-1 kV is added relative to the emitter, so that 1-7mA/cm can be led out2The sodium ion stream.
Although illustrative embodiments of the present invention have been described above to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but various changes may be apparent to those skilled in the art, and it is intended that all inventive concepts utilizing the inventive concepts set forth herein be protected without departing from the spirit and scope of the present invention as defined and limited by the appended claims.
Claims (9)
1. A sodium ion emitter, comprising: the device comprises a round cup-shaped tungsten bottom plate, a porous tungsten substrate layer, an emission material layer of sodium aluminosilicate and a heating body; wherein the content of the first and second substances,
the heating body comprises aluminum oxide and a conical tungsten wire, and the conical tungsten wire is positioned in the aluminum oxide;
the top of the circular cup-shaped tungsten bottom plate is provided with a top concave cavity, and the bottom of the circular cup-shaped tungsten bottom plate is provided with a bottom concave cavity;
in the top cavity, the porous tungsten substrate layer and the emission material layer of sodium aluminosilicate are sequentially stacked from the bottom of the cavity to the outside;
and the heating body is placed in the bottom concave cavity.
2. The sodium ion emitter according to claim 1, wherein an annular step is arranged around the concave cavity at the top of the circular cup-shaped tungsten baseplate and chamfered along the annular step for fixing the porous tungsten baseplate; preferably, the thickness of the porous tungsten substrate is 2-2.5 mm; preferably, the thickness of the emission material layer of the sodium aluminosilicate is 2-3 mm.
3. A method of preparing a sodium ion emitter according to any one of claims 1-2, comprising the steps of,
(1) providing a circular cup-shaped tungsten bottom plate, wherein the top of the circular cup-shaped tungsten bottom plate is provided with a top concave cavity, and the bottom of the circular cup-shaped tungsten bottom plate is provided with a bottom concave cavity;
(2) mixing tungsten powders with different diameters to form a mixture, pressing the mixture into the top concave cavity, and sintering the mixture into a porous tungsten substrate layer;
(3) dropping sodium aluminosilicate powder slurry on the surface of the porous tungsten substrate layer to enable the sodium aluminosilicate powder to permeate into the porous tungsten substrate layer;
(4) filling sodium aluminosilicate powder on the surface of the porous tungsten substrate layer in the top concave cavity to obtain a first sodium ion emitter precursor;
(5) heating the first sodium ion emitter precursor in vacuum, and cooling to obtain a second sodium ion emitter precursor;
(6) the sodium ion emitter is prepared by adding a raw material comprising alumina powder to the bottom cavity of a round cup-shaped tungsten base plate of a second sodium ion emitter precursor, placing a conical tungsten wire in the alumina powder, drying, and heat treating.
4. The method according to claim 3, wherein in the step (2), the sintering temperature is 1800-2000 ℃; the sintering atmosphere is hydrogen, and the pressure is 0.01-1.0 pa; the sintering time is 1-2 hours.
5. The method according to claim 3, wherein in the step (3), the sodium aluminosilicate powder slurry is dripped on the surface of the porous tungsten substrate layer, so that the sodium aluminosilicate powder permeates into the porous tungsten substrate layer, and the method comprises the following steps: mixing sodium aluminosilicate powder with deionized water to form slurry, uniformly coating the slurry on the surface of a porous tungsten substrate, and keeping vibration on an ultrasonic vibration platform for 10-20 minutes to enable the sodium aluminosilicate powder to permeate into the porous tungsten substrate; preferably, 2 drops of the slurry are applied per square centimeter of the surface of the porous tungsten substrate.
6. The method according to claim 3, wherein in the step (4), the sodium aluminosilicate powder is uniformly coated on the porous tungsten substrate layer and is 150-200 kg/cm2The powder was compacted under pressure and the surface was kept uniform and smooth.
7. The method according to claim 3, wherein in step (5), the heating is performed by: raising the temperature to a maximum temperature of 1110-1120 ℃ at a speed of 9-10 ℃ per minute within the range of 0.01-1pa, and maintaining the maximum temperature for 5-10 minutes; the cooling is performed by: the temperature is reduced to room temperature at a rate of 15-20 ℃ per minute, and then nitrogen is filled at a rate of 1000-2000 pa/min until the pressure is raised to 1 atmosphere.
8. The method of claim 1, wherein the step (6) comprises: pouring the mixture of the alumina powder and the ceramic glue into the cavity at the bottom of the round cup-shaped tungsten baseplate, and immersing the conical tungsten wire into the mixture of the alumina powder and the ceramic glue.
9. The method of claim 3, wherein in step (6), the drying and heat treating comprises: and (3) after injecting a mixture of the alumina powder and the ceramic glue, standing for 24 hours, drying, putting the integral structure into a vacuum oven, baking at 100 ℃ for 5 hours to release residual moisture, and then heating to 300 ℃ for baking for 10 hours.
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