A method for manufacturing a field emission cathode and a field emission cathode

Abstract

The application discloses a preparation method of a field emission cathode and the field emission cathode and relates to the technical field of vacuum electron devices; the method comprises the following steps: providing a field emission paste and a field emission base; the field emission base is provided with a groove; the field emission paste is filled into the groove; the field emission base filled with the field emission paste is placed in a sealed reaction container; the sealed reaction container is subjected to heat treatment, and the pressure in the sealed reaction container is controlled to be a preset pressure, so that a heat-treated field emission base is obtained; the preset pressure is 0.3 MPa-0.6 MPa; the heat-treated field emission base is subjected to annealing and surface treatment, so that the field emission cathode is obtained. The pressure in the sealed reaction container is set to 0.3 MPa-0.6 MPa, the field emission paste is extruded to discharge the bubbles in the field emission paste, the gap of the field emission paste is fully compressed, the residual holes in the contact interface between the field emission paste and the field emission base are eliminated, and the interface bonding force between the emission layer in the field emission cathode and the field emission base is effectively improved.

Description

Technical Field

[0001] This application relates to the technical field of vacuum electronic devices, specifically to a method for preparing a field emission cathode and the field emission cathode itself. Background Technology

[0002] In vacuum electronic devices, the electron emission cathode is a core component, and its current emission capability, stability, and resistance to ion impact directly determine the overall performance of the device. In recent years, cold cathode materials, represented by carbon nanotubes, have been widely used due to their superior performance. Currently, the mainstream fabrication processes for carbon nanotube field emission cathodes mainly include chemical vapor deposition and screen printing. However, both of these processes generally face technical bottlenecks such as weak bonding between the cathode emitter and the conductive substrate, and poor interfacial conductivity.

[0003] Taking screen printing as an example, the process involves the preparation of field emission paste, screen printing, and subsequent heat treatment steps such as degassing and annealing. During this process, microscopic pores are generated at the contact interface between the field emission film and the conductive base. These pores lead to poor adhesion and poor conductivity at the interface. Poor conductivity causes heat to easily accumulate at the bonding site when the cathode emitter is working, and under long-term high-power operation, the cathode emitter is prone to detachment, causing the electron emission cathode to fail. Summary of the Invention

[0004] The first aspect of this application discloses a method for preparing a field emission cathode, comprising the following steps: The system provides field emission slurry and field emission base; wherein the field emission slurry includes cold cathode emission material, conductive particles, thickener and dispersant, and the field emission base is provided with grooves; Fill the groove with field emission slurry; A field emission base filled with field emission slurry is placed in a sealed reaction vessel. The sealed reaction vessel is then heat-treated, and the pressure inside the sealed reaction vessel is controlled at a preset pressure to obtain a heat-treated field emission base. The preset pressure is 0.3 MPa to 0.6 MPa. The heat-treated field emission base is annealed and surface-treated to obtain the field emission cathode.

[0005] In some optional embodiments of the first aspect of this application, the closed reaction vessel includes a first closed reaction vessel and a second closed reaction vessel; The field emission base filled with field emission slurry is placed in a sealed reaction vessel. The sealed reaction vessel is then heat-treated, and the pressure inside the sealed reaction vessel is controlled to a preset pressure, including: The field emission base filled with field emission slurry is placed in the first sealed reaction container, and the first sealed reaction container is placed in the second sealed reaction container. The second sealed reaction container is heat-treated and inert gas is introduced into the second sealed reaction container to control the pressure of the first sealed reaction container to a preset pressure.

[0006] In some optional embodiments of the first aspect of this application, heat treatment of the second sealed reaction vessel includes: heat treatment of the second sealed reaction vessel at 80°C to 160°C for 240 min to 300 min.

[0007] In some optional embodiments of the first aspect of this application, annealing the heat-treated field emission base includes: The heat-treated field emission base is placed in a vacuum environment and kept at 560℃~850℃ for 2h~4h to obtain the annealed field emission base.

[0008] In some optional embodiments of the first aspect of this application, the surface treatment includes orienting the cold cathode emitting material in the annealed field emission base to vertically upward.

[0009] In some optional embodiments of the first aspect of this application, the cold cathode emitting material includes carbon nanotubes and graphene.

[0010] In some optional embodiments of the first aspect of this application, the carbon nanotubes have a length of 50 μm to 100 μm and a diameter of 10 nm to 30 nm.

[0011] In some optional embodiments of the first aspect of this application, the carbon nanotubes are selected from at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0012] In some optional embodiments of the first aspect of this application, the graphene monolayer thickness is 0.55nm~1.2nm, the graphene diameter is 0.5μm~3μm, and the number of graphene layers is 1 to 5.

[0013] In some optional embodiments of the first aspect of this application, the conductive particles are selected from at least one of copper, titanium, cobalt, molybdenum, iron, nickel and silver.

[0014] In some optional embodiments of the first aspect of this application, the particle size of the conductive particles is 50 nm to 100 nm.

[0015] In some optional embodiments of the first aspect of this application, the mass ratio of cold cathode emitting material to dispersant is 1:(150~300). The mass ratio of conductive particles to dispersant is 1:(20~40). The mass ratio of thickener to dispersant is 1:(80~120).

[0016] In some optional embodiments of the first aspect of this application, the method for preparing the field emission slurry is as follows: Conductive particles are added to a dispersant and ball-milled for 60 to 80 minutes at a ball mill speed of 300 r / min to 550 r / min and a ball mill power of 250 W to 350 W to obtain the first slurry. The cold cathode emission material is added to the first slurry and ball-milled for 180 min to 240 min at a ball mill speed of 400 r / min to 550 r / min and a ball mill power of 300 W to 400 W to obtain the second slurry. Thickener is added to the second slurry, and the mixture is ball-milled for 120 min to 180 min at a ball mill speed of 500 r / min to 600 r / min and a ball mill power of 350 W to 450 W to obtain the field emission slurry.

[0017] In some optional embodiments of the first aspect of this application, the material of the field emission base is selected from at least one of elemental iron, iron alloy, elemental copper, copper alloy, elemental nickel, and nickel alloy.

[0018] The second aspect provides a field emission cathode, which is prepared by the above-described method for preparing a field emission cathode.

[0019] Beneficial effects: The method for preparing a field emission cathode provided in the first aspect of this application involves filling a groove in a field emission base with a field emission paste using screen printing equipment. The field emission base filled with the paste is then placed in a sealed reaction vessel. The sealed reaction vessel is heat-treated while controlling the pressure range within the vessel to be 0.3 MPa to 0.6 MPa. Following this, the heat-treated field emission base is annealed and surface-treated to obtain a field emission cathode containing an emission layer. Setting the pressure within the sealed reaction vessel to 0.3 MPa to 0.6 MPa allows for the expulsion of air bubbles from the field emission paste, ensuring sufficient compression of the paste gaps. This eliminates residual pores at the contact interface between the paste and the base, effectively improving the interfacial bonding between the emission layer and the base. Simultaneously, it prevents the paste from being squeezed out from the groove edges, ensuring uniform emission layer thickness and guaranteeing the quality of the field emission cathode. Attached Figure Description

[0020] Figure 1 This is a flowchart of the preparation method in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a field launcher base in one embodiment of this application; Figure 3This is a schematic diagram of the long-term operating current stability of the field emission cathode in Embodiment 1 of this application.

[0021] Figure 2 The attached diagram is labeled as: 1. Groove. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the present application.

[0023] In one embodiment, such as Figure 1 As shown, a method for preparing a field emission cathode is provided, comprising the following steps: Field emission slurry and field emission base are provided; wherein, the field emission slurry includes cold cathode emission material, conductive particles, thickener and dispersant, and the field emission base is provided with groove 1; Fill the groove 1 with field emission slurry; A field emission base filled with field emission slurry is placed in a sealed reaction vessel. The sealed reaction vessel is then heat-treated, and the pressure inside the sealed reaction vessel is controlled at a preset pressure to obtain a heat-treated field emission base. The preset pressure is 0.3 MPa to 0.6 MPa. The heat-treated field emission base is annealed and surface-treated to obtain the field emission cathode.

[0024] In the above technical solution, field emission paste is filled into the groove 1 of the field emission base by screen printing equipment, and then the field emission base filled with field emission paste is placed in a sealed reaction container. The sealed reaction container is heat-treated and the pressure range inside the sealed reaction container is controlled to be 0.3MPa~0.6MPa. After that, the heat-treated field emission base is annealed and surface-treated to obtain a field emission cathode containing an emission layer.

[0025] The pressure inside the sealed reaction vessel can be controlled by heating; alternatively, heating and the introduction of inert gas can be used simultaneously to control the pressure. Setting the pressure inside the sealed reaction vessel to 0.3 MPa~0.6 MPa allows for the extrusion of air bubbles from the field emission slurry, ensuring sufficient compression of the slurry gaps. This eliminates residual voids at the contact interface between the slurry and the field emission base, effectively improving the interfacial bonding between the emission layer and the field emission base in the field emission cathode. Simultaneously, it prevents the field emission slurry from being squeezed out from the edge of groove 1, thus ensuring uniform emission layer thickness and guaranteeing the quality of the field emission cathode.

[0026] Specifically, the pressure inside the closed reaction vessel can be set to 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, or a range selected from any two of the above values.

[0027] It should be noted that, as Figure 2 As shown, the groove 1 is located at the top of the field emission base, with the opening of the groove 1 facing upwards. The groove 1 can be machined or laser-etched at the center of the upper surface of the field emission base; after machining the groove 1, the field emission base is cleaned with ethanol and deionized water to remove machining stains; after cleaning, the field emission base is cleaned with an acid solution to remove the oxide layer, and then cleaned with deionized water.

[0028] In some optional embodiments of this application, the closed reaction vessel includes a first closed reaction vessel and a second closed reaction vessel; The field emission base filled with field emission slurry is placed in a sealed reaction vessel. The sealed reaction vessel is then heat-treated, and the pressure inside the sealed reaction vessel is controlled to a preset pressure, including: The field emission base filled with field emission slurry is placed in the first sealed reaction container, and the first sealed reaction container is placed in the second sealed reaction container. The second sealed reaction container is heat-treated and inert gas is introduced into the second sealed reaction container to control the pressure of the first sealed reaction container to a preset pressure.

[0029] In some optional embodiments of this application, heat treatment of the second sealed reaction vessel includes: heat treatment of the second sealed reaction vessel at 80°C to 160°C for 240 min to 300 min.

[0030] In the above scheme, the temperature for heat treatment of the second sealed reaction vessel is set to 80℃~160℃. Within the range of 80℃~160℃, the dispersant in the field emission slurry in the first sealed reaction vessel and the inert gas in the second sealed reaction vessel expand steadily, increasing the pressure in the first sealed reaction vessel to compact the field emission slurry, thereby expelling the voids at the interface between the field emission slurry and the substrate, without generating new pores, realizing the pre-curing of the field emission slurry, completely preserving the emission structure of the cold cathode emission material, and obtaining a dense and uniform emission layer.

[0031] Specifically, the temperature for heat treatment of the sealed reaction vessel can be set to 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, or a range selected from any two of the above values.

[0032] In some optional embodiments of this application, the first and second sealed reaction containers are reaction vessels. Specifically, the first sealed reaction container is the inner vessel, and the second sealed reaction container is the outer vessel. The inner vessel can be made of acid- and alkali-resistant materials such as nylon or polytetrafluoroethylene, while the outer vessel is made of stainless steel. A field emission base filled with field emission slurry is placed in the inner vessel, which is then placed inside the outer vessel. Inert gas is introduced into the outer vessel while heating is performed, and the pressure in the inner vessel is controlled to be 0.3 MPa to 0.6 MPa.

[0033] For example, the outer vessel is configured as a large reactor, inside which multiple inner vessels (which can be configured as multiple small reactors) are placed side by side. The outer vessel is equipped with a heating jacket (electric heating or oil bath mode can be selected) for heating both the outer and inner vessels. An inert gas inlet with a flow meter is located at the top of the outer vessel for introducing inert gas into the closed chamber inside the outer vessel; simultaneously, a pressure sensor and a pressure relief valve are also installed at the top of the outer vessel for real-time monitoring and pressure relief regulation. Each inner vessel is also equipped with an independent pressure gauge on its top cover for real-time monitoring of the pressure within each inner vessel. By combining the inert gas flow rate, the heating jacket heat treatment temperature, and the pressure monitoring data of each inner vessel, precise control of the inner vessel pressure is achieved.

[0034] During the heat treatment at 80℃~160℃, the dispersant in the field emission slurry in the inner vessel and the inert protective gas in the outer vessel expand steadily, thereby increasing the pressure in the inner vessel to compact the field emission slurry and thus expel the voids between the inside of the field emission slurry and the substrate interface; at the same time, the outer vessel plays a protective role.

[0035] In some optional embodiments of this application, annealing the heat-treated field emission base includes: The heat-treated field emission base is placed in a vacuum environment and kept at 560℃~850℃ for 2h~4h to obtain the annealed field emission base.

[0036] In the above scheme, the vacuum annealing temperature is set to 560℃~850℃. Within the range of 560℃~850℃, organic additives such as dispersants and thickeners in the field emission slurry are removed to eliminate insulating impurities. At the same time, a continuous conductive path is formed by high-temperature sintering of nanoscale conductive particles, which allows the cold cathode emission material to be tightly bonded to the field emission base, reducing the interface resistance, releasing film stress, and improving the cathode's conductivity, thermal conductivity, impact resistance, and high-current emission stability.

[0037] Specifically, the vacuum annealing temperature can be set to 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, or a range selected from any two of the above values.

[0038] In some optional embodiments of this application, the surface treatment includes orienting the cold cathode emitting material in the annealed field emission base to vertically upward.

[0039] In the above scheme, a flexible silicone head can be used to orient the cold cathode emitting material in the annealed field emission base to vertically upward.

[0040] In some optional embodiments of this application, the cold cathode emitting material includes carbon nanotubes and graphene.

[0041] In some optional embodiments of this application, the carbon nanotubes have a length of 50 μm to 100 μm and a diameter of 10 nm to 30 nm.

[0042] Specifically, the length of the carbon nanotubes can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, or a range selected from any two of the above values. The diameter of the carbon nanotubes can be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, or a range selected from any two of the above values.

[0043] In some optional embodiments of this application, the carbon nanotubes are selected from at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0044] In some optional embodiments of this application, the graphene monolayer thickness is 0.55nm~1.2nm, the graphene diameter is 0.5μm~3μm, and the number of graphene layers is 1~5.

[0045] Specifically, the thickness of a graphene monolayer can be 0.55 nm, 0.65 nm, 0.75 nm, 0.85 nm, 0.95 nm, 1.05 nm, 1.15 nm, 1.20 nm, or a range selected from any two of the above values. The diameter of the graphene can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, or a range selected from any two of the above values. The number of graphene layers can be 1, 2, 3, 4 or 5.

[0046] In some optional embodiments of this application, the conductive particles are selected from at least one of copper, titanium, cobalt, molybdenum, iron, nickel and silver.

[0047] In some optional embodiments of this application, the size of the conductive particles is 50nm~100nm.

[0048] Specifically, the size of the conductive particles is 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, or a range selected from any two of the above values.

[0049] In some optional embodiments of this application, the mass ratio of cold cathode emitting material to dispersant is 1:(150~300). The mass ratio of conductive particles to dispersant is 1:(20~40). The mass ratio of thickener to dispersant is 1:(80~120).

[0050] Specifically, the mass ratio of cold cathode emitting material to dispersant can be 1:150, 1:160, 1:170, 1:180, 1:190, 1:200, 1:210, 1:220, 1:230, 1:240, 1:250, 1:260, 1:270, 1:280, 1:290, 1:300, or a range selected from any two of the above values.

[0051] The mass ratio of conductive particles to dispersant can be 1:20, 1:22, 1:24, 1:26, 1:28, 1:30, 1:32, 1:34, 1:36, 1:38, 1:40, or a range selected from any two of the above values.

[0052] The mass ratio of thickener to dispersant can be 1:80, 1:85, 1:90, 1:95, 1:100, 1:105, 1:110, 1:115, 1:120, or a range selected from any two of the above values.

[0053] In some optional embodiments of this application, the thickener is selected from ethyl cellulose, and the dispersant is selected from at least one of terpineol, ethylene glycol, and glycerol.

[0054] In some optional embodiments of this application, the preparation method of the field emission slurry is as follows: Conductive particles are added to a dispersant and ball-milled for 60 to 80 minutes at a ball mill speed of 300 r / min to 550 r / min and a ball mill power of 250 W to 350 W to obtain the first slurry. The cold cathode emission material is added to the first slurry and ball-milled for 180 min to 240 min at a ball mill speed of 400 r / min to 550 r / min and a ball mill power of 300 W to 400 W to obtain the second slurry. Thickener is added to the second slurry, and the mixture is ball-milled for 120 min to 180 min at a ball mill speed of 500 r / min to 600 r / min and a ball mill power of 350 W to 450 W to obtain the field emission slurry.

[0055] In some optional embodiments of this application, the material of the field emission base is selected from at least one of elemental iron, iron alloy, elemental copper, copper alloy, elemental nickel, and nickel alloy.

[0056] In some optional embodiments of this application, the field emission base may also be made of stainless steel.

[0057] In another embodiment, a field emission cathode is provided, which is prepared by the above-described method for preparing a field emission cathode.

[0058] The present application is further illustrated below with reference to embodiments and comparative examples. Unless otherwise specified, the raw materials, reagents, materials and equipment used in this application are all commercially available products conventionally used in the art.

[0059]

Example 1

[0060] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The thickness of a single graphene layer is 1.2 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0061] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0062] S2. Screen print the field emission paste into the groove 1 of the field emission base. The field emission base is made of stainless steel.

[0063] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 120℃ for 240 minutes, and control the pressure in the reactor to be 0.45MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0064] S4. After the heat-treated field emission base is naturally cooled, it is placed in a vacuum environment at 700℃ for 2 hours for annealing. Then, the cold cathode emission material in the annealed field emission base is activated by vertical orientation using a silicone head to obtain the field emission cathode.

[0065]

Example 2

[0066] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 70 μm to 100 μm and a diameter of 15 nm to 20 nm, and three layers of graphene. The thickness of a single graphene layer is 0.8 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0067] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0068] S2, Same as Example 1.

[0069] S3, Same as Example 1.

[0070] S4, Same as in Example 1.

[0071]

Example 3

[0072] The dispersant includes terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are a mixture of silver powder, copper powder, and titanium powder with a particle size of 100 nm; the cold cathode emitting material includes multi-walled carbon nanotubes with a length of 50 μm and a diameter of 10 nm to 20 nm and three layers of graphene, with a single layer thickness of 0.8 nm and a graphene diameter of 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0073] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0074] S2, Same as Example 1.

[0075] S3, Same as Example 1.

[0076] S4, Same as in Example 1.

[0077]

Example 4

[0078] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The thickness of a single graphene layer is 1.2 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0079] The mass ratio of conductive particles to dispersant is 1:20, the mass ratio of cold cathode emitting material to dispersant is 1:150, and the mass ratio of thickener to dispersant is 1:80.

[0080] S2, Same as Example 1.

[0081] S3, Same as Example 1.

[0082] S4, Same as in Example 1.

[0083]

Example 5

[0084] S2, Same as Example 1.

[0085] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce argon gas into the outer vessel, and place the outer vessel into a heating furnace under an argon protective atmosphere and keep it at 120℃ for 240 minutes. Control the pressure in the reactor to be 0.3MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0086] S4, Same as in Example 1.

[0087]

Example 6

[0088] S2, Same as Example 1.

[0089] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 120℃ for 240 minutes, and control the pressure in the reactor to be 0.6MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0090] S4, Same as in Example 1.

[0091]

Example 7

[0092] S2, Same as Example 1.

[0093] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 80℃ for 240 minutes, and control the pressure in the reactor to be 0.45MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0094] S4, Same as in Example 1.

[0095]

Example 8

[0096] S2, Same as Example 1.

[0097] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 160℃ for 240 minutes, and control the pressure in the reactor to be 0.45MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0098] S4, Same as in Example 1.

[0099] Comparative Example 1 The difference between this comparative example and Example 1 lies in the different heat preservation temperature and control of the reactor pressure in S3. The specific steps are as follows: S1 is the same as in Example 1.

[0100] S2, Same as Example 1.

[0101] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 60°C for 240 minutes, and control the pressure in the reactor to be 0.22 MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0102] S4, Same as in Example 1.

[0103] Comparative Example 2 The difference between this comparative example and Example 1 lies in the different heat preservation temperature and control of the reactor pressure in S3. The specific steps are as follows: S1 is the same as in Example 1.

[0104] S2, Same as Example 1.

[0105] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 180℃ for 240 minutes, and control the pressure in the reactor to be 0.72MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0106] S4, Same as in Example 1.

[0107] Comparative Example 3 The difference between this comparative example and Example 1 lies in the different heat preservation temperature and control of the reactor pressure in S3. The specific steps are as follows: S1 is the same as in Example 1.

[0108] S2, Same as Example 1.

[0109] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 120℃ for 240 minutes, and control the pressure in the reactor to be 0.25MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0110] Comparative Example 4 The difference between this comparative example and Example 1 lies in the different heat preservation temperature and control of the reactor pressure in S3. The specific steps are as follows: S1 is the same as in Example 1.

[0111] S2, Same as Example 1.

[0112] S3. Place the field emission base filled with field emission slurry flat in the inner vessel; place the inner vessel in the outer vessel, introduce a certain amount of argon gas into the outer vessel, and place the outer vessel in a heating furnace with an argon protective atmosphere. Keep it at 120℃ for 240 minutes, and control the pressure in the reactor to be 0.68MPa. After the heat treatment is completed, the heat-treated field emission base is obtained.

[0113] Comparative Example 5 The difference between this comparative example and Example 1 is that the cold cathode emission material parameters are different in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0114] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 20 μm and a diameter of 60 nm and three layers of graphene, with a single layer thickness of 0.8 nm and a graphene diameter of 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0115] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0116] S2, Same as Example 1.

[0117] S3, Same as Example 1.

[0118] S4, Same as in Example 1.

[0119] Comparative Example 6 The difference between this comparative example and Example 1 is that the cold cathode emission material parameters are different in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0120] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 70 μm and a diameter of 20 nm and 10 layers of graphene, with a single layer thickness of 3 nm and a graphene diameter of 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0121] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0122] S2, Same as Example 1.

[0123] S3, Same as Example 1.

[0124] S4, Same as in Example 1.

[0125] Comparative Example 7 The difference between this comparative example and Example 1 lies in the particle size of the conductive particles in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0126] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 300 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The graphene single layer has a thickness of 1.2 nm and a diameter of 1 μm. The mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0127] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0128] S2, Same as Example 1.

[0129] S3, Same as Example 1.

[0130] S4, Same as in Example 1.

[0131] Comparative Example 8 The difference between this comparative example and Example 1 lies in the particle size of the conductive particles in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0132] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 20 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The graphene single layer has a thickness of 1.2 nm and a diameter of 1 μm. The mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0133] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0134] S2, Same as Example 1.

[0135] S3, Same as Example 1.

[0136] S4, Same as in Example 1.

[0137] Comparative Example 9 The difference between this comparative example and Example 1 is that the slurry ratio is different in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0138] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The thickness of a single graphene layer is 1.2 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0139] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:350, and the mass ratio of thickener to dispersant is 1:100.

[0140] S2, Same as Example 1.

[0141] S3, Same as Example 1.

[0142] S4, Same as in Example 1.

[0143] Comparative Example 10 The difference between this comparative example and Example 1 is that the slurry ratio is different in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0144] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The thickness of a single graphene layer is 1.2 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0145] The mass ratio of conductive particles to dispersant is 1:50, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:100.

[0146] S2, Same as Example 1.

[0147] S3, Same as Example 1.

[0148] S4, Same as in Example 1.

[0149] Comparative Example 11 The difference between this comparative example and Example 1 is that the slurry ratio is different in S1. The specific steps are as follows: S1. Preparation of field emission slurry: The conductive particles are added to the dispersant and dispersed by ball milling for 80 minutes at a ball milling speed of 500 r / min and a ball milling power of 350 W to obtain the first slurry. The cold cathode emission material was added to the first slurry and ball-milled for 240 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the second slurry. Thickener ethyl cellulose was added to the second slurry, and the mixture was ball-milled for 180 minutes at a ball mill speed of 500 r / min and a ball mill power of 350 W to obtain the field emission slurry.

[0150] The dispersant consists of terpineol and ethylene glycol in a volume ratio of 1:1; the conductive particles are silver powder with a particle size of 70 nm; and the cold cathode emitting material consists of multi-walled carbon nanotubes with a length of 50 μm to 70 μm and a diameter of 10 nm to 15 nm and three layers of graphene. The thickness of a single graphene layer is 1.2 nm, the diameter of the graphene layer is 1 μm, and the mass ratio of multi-walled carbon nanotubes to graphene is 1:1.

[0151] The mass ratio of conductive particles to dispersant is 1:30, the mass ratio of cold cathode emitting material to dispersant is 1:200, and the mass ratio of thickener to dispersant is 1:150.

[0152] S2, Same as Example 1.

[0153] S3, Same as Example 1.

[0154] S4, Same as in Example 1.

[0155] Comparative Example 12 The difference between this comparative example and Example 1 is that the field emission base filled with field emission slurry is not placed in the reactor and subjected to heat treatment. The specific steps are as follows: S1, Same as in Example 1 S2, Same as Example 1.

[0156] S3. Place the field emission base filled with field emission slurry in a vacuum environment at 700℃ for 2 hours for annealing. Then, use a silicone head to vertically orient and activate the cold cathode emission material in the annealed field emission base to obtain the field emission cathode.

[0157] Table 1 summarizes some of the parameters and conditions of each embodiment and comparative example.

[0158] Table 1

[0159] Performance tests were conducted on the field emission cathodes obtained in each embodiment and comparative example. A standard planar diode test structure was used. Under high vacuum, the field emission cathode with a pointed emission structure was placed parallel to the planar metal anode, with a distance d between the two electrodes set to 300 μm. The metal anode was connected to a 0–20 kV high-voltage power supply, and the field emission cathode was grounded. A source meter (SMU) was used to perform current-voltage (IV) curve scanning measurements on the field emission cathode. Furthermore, the resistivity of the field emission cathode was characterized using an equivalent resistance circuit model. The resistance of the field emission cathode is composed of the intrinsic resistance of the carbon nanotubes and the contact resistance between the carbon nanotube bundle and the metal electrode. The intrinsic resistance of the field emission cathode was evaluated using the IV relationship. The test results are shown in Tables 2 and 3.

[0160] Table 2

[0161] Table 3

[0162] As shown in Table 3, the overall performance of each embodiment in terms of maximum emission current and current density is better than that of the comparative example.

[0163] like Figure 3 As shown, in Example 1, the field emission cathode exhibits good long-term operating current stability, with current attenuation of <10% over time.

[0164] It should be noted that, in this document, "comprising," "including," or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0165] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0166] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a field emission cathode, characterized in that, Includes the following steps: A field emission slurry and a field emission base are provided; wherein the field emission slurry includes a cold cathode emission material, conductive particles, a thickener and a dispersant, and the field emission base is provided with a groove; The field emission slurry is filled into the groove; The field emission base filled with the field emission slurry is placed in a sealed reaction container, the sealed reaction container is heat-treated and the pressure inside the sealed reaction container is controlled to a preset pressure to obtain the heat-treated field emission base; wherein, the preset pressure is 0.3MPa~0.6MPa; The heat-treated field emission base is annealed and surface-treated to obtain the field emission cathode.

2. The method for preparing a field emission cathode as described in claim 1, characterized in that, The sealed reaction vessel includes a first sealed reaction vessel and a second sealed reaction vessel; The step of placing the field emission base filled with the field emission slurry into a sealed reaction vessel, performing heat treatment on the sealed reaction vessel, and controlling the pressure inside the sealed reaction vessel to a preset pressure includes: The field emission base filled with the field emission slurry is placed in the first sealed reaction container, the first sealed reaction container is placed in the second sealed reaction container, the second sealed reaction container is heat-treated and inert gas is introduced into the second sealed reaction container to control the pressure of the first sealed reaction container to a preset pressure.

3. The method for preparing a field emission cathode as described in claim 2, characterized in that, The heat treatment of the second sealed reaction vessel includes: The second sealed reaction vessel was heat-treated at 80℃~160℃ for 240min~300min.

4. The method for preparing a field emission cathode as described in claim 1, characterized in that, The annealing of the heat-treated field emission base includes: The heat-treated field emission base is placed in a vacuum environment and kept at 560℃~850℃ for 2h~4h to obtain the annealed field emission base. The surface treatment includes orienting the cold cathode emitting material in the annealed field emission base to be vertically upward.

5. The method for preparing a field emission cathode according to any one of claims 1 to 4, characterized in that, The cold cathode emitting material includes carbon nanotubes and graphene; The carbon nanotubes have a length of 50μm to 100μm and a diameter of 10nm to 30nm. The carbon nanotubes are selected from at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. The graphene single-layer thickness is 0.55nm~1.2nm, the graphene diameter is 0.5μm~3μm, and the number of graphene layers is 1 to 5.

6. The method for preparing a field emission cathode according to any one of claims 1 to 4, characterized in that, The conductive particles are selected from at least one of copper, titanium, cobalt, molybdenum, iron, nickel and silver; The particle size of the conductive particles is 50nm~100nm.

7. The method for preparing a field emission cathode according to any one of claims 1 to 4, characterized in that, The mass ratio of the cold cathode emitting material to the dispersant is 1:(150~300). The mass ratio of the conductive particles to the dispersant is 1:(20~40). The mass ratio of the thickener to the dispersant is 1:(80~120).

8. The method for preparing a field emission cathode according to any one of claims 1 to 4, characterized in that, The preparation method of the field emission slurry is as follows: The conductive particles are added to the dispersant and ball-milled for 60 to 80 minutes at a ball mill speed of 300 r / min to 550 r / min and a ball mill power of 250 W to 350 W to obtain the first slurry. The cold cathode emitting material is added to the first slurry and ball-milled for 180 min to 240 min at a ball milling speed of 400 r / min to 550 r / min and a ball milling power of 300 W to 400 W to obtain the second slurry. The thickener is added to the second slurry, and the mixture is ball-milled for 120 min to 180 min at a ball mill speed of 500 r / min to 600 r / min and a ball mill power of 350 W to 450 W to obtain the field emission slurry.

9. The method for preparing a field emission cathode according to any one of claims 1 to 4, characterized in that, The material of the field launch base is selected from at least one of elemental iron, iron alloy, elemental copper, copper alloy, elemental nickel, and nickel alloy.

10. A field emission cathode, characterized in that, It is prepared by the method for preparing the field emission cathode according to any one of claims 1 to 9.

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