A field emission cathode coating preparation system

Abstract

The application relates to a field emission cathode coating preparation system, which comprises an electrophoretic deposition assembly, a cleaning assembly and a drying assembly. The electrophoretic deposition assembly comprises an electrophoretic tank, cathode and anode plates arranged in the electrophoretic tank and a power supply electrically connected with the cathode and anode plates. The power supply is used for adjusting the voltage / current between the cathode and anode plates. A nickel base plate is detachably arranged at the lower end of the cathode plate. The cleaning assembly comprises a spraying unit arranged at the top of the electrophoretic tank and an ultrasonic cleaning unit arranged at the bottom of the electrophoretic tank. The drying assembly comprises an air flow blowing unit arranged at the top of the electrophoretic tank, a vacuum pumping unit and a heating unit arranged at the bottom of the electrophoretic tank. The system can clean and dry the coating after the field emission coating is generated on the cathode. The whole process is automatically carried out, the tedious process of manually transferring the field emission cathode material is avoided, the labor and operation cost of coating solidification treatment are reduced, and the preparation efficiency and yield of the field emission cathode material are improved.

Description

Technical Field

[0001] This application belongs to the field of field emission cathode material preparation technology, and specifically relates to a field emission cathode coating preparation system. Background Technology

[0002] Field emission, also known as field-induced electron emission, refers to the electron emission phenomenon where, when a strong electric field is applied to the surface of a metal or semiconductor material, the surface electron barrier height decreases and the width narrows, causing electrons to escape from the surface through a tunneling effect. Field emission displays developed based on this phenomenon and principle are characterized by small size, low power consumption, and large viewable area. Among them, nano-ZnO thin films are considered an ideal field emission cathode material due to their low surface electron affinity and large aspect ratio, as well as their excellent emission characteristics such as high stability and low threshold electric field in field emission performance studies. To prepare this material, in existing technologies, the prepared nano-ZnO powder is first formulated into an electrophoretic solution, and then a uniform ZnO coating is formed on the cathode surface by electrophoretic deposition using an electrophoretic deposition device. This coating is deposited and adhered to the cathode surface in the form of a thin film, allowing the cathode to be used as a field emission cathode for preparing field emission structures or for field emission performance testing. For example, the utility model patent CN204039531U discloses an electrophoretic deposition device for conductive surfaces. Although this device can improve the uniformity of the coating on the conductive metal surface during electrophoretic deposition, when applied to the preparation of nano-ZnO coatings, it is prone to cause the coating, which is attached to the cathode surface by van der Waals forces alone, to fall off. It is also necessary to perform chemical vapor deposition to cure the field emission cathode material prepared by the electrophoretic deposition device. However, this process not only makes the preparation process more complicated, but also requires manual operation to transfer the field emission cathode material between the electrophoretic deposition device, cleaning device, drying device and other equipment. The field emission cathode material can only be placed in the tube furnace for chemical vapor deposition after cleaning and drying after electrophoresis. This process increases the amount of labor and preparation cost, and is not conducive to improving the preparation efficiency. Summary of the Invention

[0003] Based on the aforementioned technical needs, this application provides a field emission cathode coating preparation system, which can solve the problems faced by the prior art in preparing field emission cathode materials. It requires manual operation to transfer the field emission cathode material between equipment such as electrophoretic deposition device, cleaning device, and drying device, so that the field emission cathode material can be cleaned and dried after electrophoresis before being placed in a tube furnace for curing treatment by chemical vapor deposition, resulting in high labor intensity, preparation cost and low preparation efficiency.

[0004] To achieve the above objectives, the technical solution of this application is as follows:

[0005] A field emission cathode coating preparation system includes an electrophoretic deposition assembly, a cleaning assembly, and a drying assembly. The electrophoretic deposition assembly includes an electrophoresis tank, a cathode plate and an anode plate spaced apart within the electrophoresis tank, and a power supply electrically connected to both the cathode plate and the anode plate. The power supply is used to adjust the voltage / current between the cathode plate and the anode plate. A nickel substrate plate is detachably mounted on the lower end of the cathode plate. The cleaning assembly includes a spray unit located at the top of the electrophoresis tank and an ultrasonic cleaning unit located at the bottom of the electrophoresis tank. The spray unit is used to spray cleaning fluid into the electrophoresis tank. The drying assembly includes an airflow purging unit and a vacuum unit located at the top of the electrophoresis tank and a heating unit located at the bottom of the electrophoresis tank. The airflow purging unit is used to provide a drying airflow into the electrophoresis tank. The vacuum unit is used to extract cleaning fluid vapor from the electrophoresis tank. The heating unit is used to heat the internal space of the electrophoresis tank.

[0006] Preferably, the bottom of the electrophoresis tank is provided with a first drain port, a second drain port and an exhaust port, the first drain port and the second drain port are respectively provided with drain valves, and the exhaust port is provided with an exhaust valve.

[0007] Preferably, one side of the electrophoresis tank is connected to an infusion tube, one end of which is connected to a first infusion pump. The inlet of the first infusion pump is connected to an electrophoresis solution pre-storage chamber, and the first infusion pump is used to transport the electrophoresis solution stored in the electrophoresis solution pre-storage chamber to the electrophoresis tank.

[0008] Preferably, the top of the electrophoresis tank is sealed with a cover plate, and the spray unit includes a pre-storage chamber for cleaning liquid, a second infusion pump and a nozzle. The nozzle is provided at the bottom of the cover plate, the outlet of the second infusion pump is connected to the nozzle, and the inlet of the second infusion pump is connected to the pre-storage chamber for cleaning liquid.

[0009] Preferably, there are several ultrasonic cleaning units, which are symmetrically distributed at the bottom of the electrophoresis tank.

[0010] Preferably, a liquid level sensor is provided in the electrophoresis tank, and the liquid level sensor is electrically connected to the ultrasonic cleaning unit. The liquid level sensor is used to obtain the liquid level height of the cleaning liquid in the electrophoresis tank.

[0011] Preferably, the airflow purging unit includes an air supply pipe and a plurality of jet nozzles, the plurality of jet nozzles being arranged circumferentially around the electrophoresis tank and positioned higher than the cathode plate and the anode plate, and the air supply pipe being connected to the jet nozzles.

[0012] Preferably, the side of the electrophoresis tank is cylindrical, the bottom of the electrophoresis tank is inverted conical, the number of air nozzles is at least four, the four air nozzles are centrally symmetrically distributed around the side of the electrophoresis tank, and the air jet direction of any air nozzle is tangent to the side of the electrophoresis tank. The air nozzles are used to form a downward swirling flow in the electrophoresis tank.

[0013] Preferably, the vacuum unit includes a negative pressure tube and a vacuum pump, with one end of the negative pressure tube extending from outside the electrophoresis tank into the electrophoresis tank and the other end connected to the vacuum pump.

[0014] Preferably, the heating unit includes an electric heating block or electric heating wire embedded in the bottom of the electrophoresis tank and a temperature controller, wherein the temperature controller is electrically connected to the electric heating block or electric heating wire. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the field emission cathode coating preparation system in the embodiment.

[0016] Figure 2 This is a partial cross-sectional view AA of the field emission cathode coating preparation system in the embodiment.

[0017] In the figure: Electrophoretic deposition assembly 10, electrophoresis tank 11, first drain port 111, second drain port 112, exhaust port 113, drain valve 114, exhaust valve 115, infusion pipe 116, first infusion pump 117, electrophoretic solution pre-storage chamber 118, cathode plate 12, anode plate 13, power supply 14, nickel substrate plate 15, cover plate 16, cleaning assembly 20, spray unit 21, cleaning solution pre-storage chamber 211, second infusion pump 212, nozzle 213, ultrasonic cleaning unit 22, ultrasonic generator 221, liquid level sensor 222, drying assembly 30, airflow purging unit 31, air supply pipe 311, air nozzle 312, support 313, vacuum unit 32, negative pressure pipe 321, vacuum pump 322, heating unit 33, electric heating wire 331, temperature controller 332. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of this application will be further described below with reference to the accompanying drawings of the embodiments, and this application is not limited to the following specific implementation methods.

[0019] It should be understood that the same or similar reference numerals in the accompanying drawings of the embodiments correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "inner," "outer," "left," "right," "front," "rear," "top," and "bottom" indicate directions or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the structure or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms describing positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limitations on this patent. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0020] The following is in conjunction with the appendix Figure 1 To be continued Figure 2 The present application will be further described in detail with reference to specific embodiments.

[0021] This application discloses a field emission cathode coating preparation system (hereinafter referred to as the "system"), including an electrophoretic deposition assembly 10, a cleaning assembly 20, and a drying assembly 30. The electrophoretic deposition assembly 10 includes an electrophoresis tank 11 for introducing electrophoretic solution, a stainless steel cathode plate 12 and a stainless steel anode plate 13 spaced apart within the electrophoresis tank 11, and a power supply 14 electrically connected to both the cathode plate 12 and the anode plate 13. The power supply 14 is used to adjust the voltage / current between the cathode plate 12 and the anode plate 13. Specifically, the power supply 14 is preferably a DYY7-C type electrophoresis apparatus, which can set a voltage of 5 to 50 Ω between the cathode plate 12 and the anode plate 13. To better utilize the cathode... The effect of electrophoretic deposition is that a nickel substrate 15 is detachably installed at the lower end of the cathode plate 12 via a clip made of conductive material. This allows the nickel substrate 15 to serve as an emergency component. Utilizing the high conductivity and good mechanical properties of metallic nickel, ZnO in the electrophoretic solution can be deposited onto the nickel substrate 15 under electrophoretic deposition to form a nano-ZnO coating. The cleaning assembly 20 includes a spray unit 21 at the top of the electrophoresis tank 11 and an ultrasonic cleaning unit 22 at the bottom of the electrophoresis tank 11. The spray unit 21 sprays cleaning fluid, such as deionized water or anhydrous ethanol, into the electrophoresis tank 11 to remove residual organic matter (residual electrophoretic solution) from the inner wall of the electrophoresis tank 11 and the surface of the nickel substrate 15. The system is designed to prevent residual electrophoretic solution from reacting with the coating or nickel base material during subsequent heating and drying processes, thus ensuring the purity of the coating and preventing the residual electrophoretic solution on the nano-ZnO thin film from carbonizing at high temperatures, which could lead to increased porosity or localized damage to the coating film. An ultrasonic cleaning unit 22 generates low-frequency ultrasound (e.g., 40 to 80 kHz) below the cleaning liquid surface to assist the spraying unit 21 in deep cleaning of the residual electrophoretic solution adhering to the surface of the nickel substrate 15, removing residual liquid and most loose impurity particles. The drying assembly 30 includes an airflow purging unit 31 and a vacuum unit 32 located at the top of the electrophoresis tank 11, and a heating unit 33 located at the bottom of the electrophoresis tank 11. The purging unit 31 can blow dry airflow (such as nitrogen) into the electrophoresis tank 11 to remove residual cleaning liquid from the walls of the electrophoresis tank 11 and the surfaces of the cathode plate 12, anode plate 13, and nickel substrate 15. The vacuum unit 32 is used to perform vacuum treatment in the electrophoresis tank 11 after the airflow purging and drying. This not only removes residual suspended cleaning liquid vapor in the electrophoresis tank 11, but also works with the heating unit 33 to dry and clean the space inside the electrophoresis tank 11, removing residual cleaning liquid and possible oxygen, impurities, etc. from the gaps in the nano-coating, further improving the purity of the coating. As the heating unit 33 gradually increases the temperature and heats for a period of time, the coating bondes more firmly to the nickel substrate 15.

[0022] When using the above-described field emission cathode coating preparation system, an electrophoretic solution prepared from isobutanol and nano-ZnO powder is first introduced into the electrophoresis tank 11. Metallic nickel is cut into rectangular thin slices of 12mm × 10mm, coarsely and finely polished and cleaned, and then placed at the lower end of the cathode plate 12. The distance between the cathode plate 12 and the anode plate 13 is adjusted to 1cm. After the cathode plate 12 and anode plate 13 are immersed below the surface of the electrophoretic solution, an electrophoretic effect is generated between the cathode plate 12 and the anode plate 13 using a power supply 14 at a set voltage / current, such as 30V for 1 minute. After the deposition reaction is complete, the residual electrophoretic solution is discharged from the electrophoresis tank 11, and then... The spray unit 21 sprays anhydrous ethanol cleaning solution to clean the nickel substrate 15. After the cleaning solution immerses the nickel substrate 15, the ultrasonic cleaning unit 22 is turned on to improve the cleaning effect with a set 40KHz low-frequency ultrasonic wave. After ultrasonic cleaning for 30 seconds, the electrophoresis tank 11 and the nickel substrate 15 are purged with dry nitrogen gas at a flow rate of 10 to 20 L / min by the airflow purging unit 31 for 30 seconds for preliminary drying. Then, the vacuum pump 322 is started to evacuate the internal space of the electrolytic cell and the heating unit 33 is turned on and controlled to gradually heat to 150°C to ensure that the nickel substrate 15 is fully and uniformly dried. After that, the nickel substrate 15 is removed and the relevant procedures of chemical vapor deposition are performed.

[0023] The field emission cathode coating preparation system described in this application has the following advantages:

[0024] The above system allows electrophoretic deposition, coating cleaning, and drying to all be carried out within the same electrophoresis tank 11. During this process, there is no need to frequently transfer the field emission cathode material prepared by electrophoretic deposition, which reduces the complexity and cost of coating preparation and pretreatment such as cleaning and drying, and helps to improve the preparation efficiency and yield of field emission cathode materials.

[0025] Based on the above embodiments, this application also provides some specific implementation methods to improve the above solutions.

[0026] In one embodiment, the bottom of the electrophoresis tank 11 is provided with a first drain port 111, a second drain port 112, and an exhaust port 113. The first drain port 111 and the second drain port 112 are each equipped with a drain valve 114, and the exhaust port 113 is equipped with an exhaust valve 115. Preferably, the drain valves 114 and 115 are both solenoid valves, which are opened or closed by corresponding control circuits. For example, after electrophoretic deposition is completed, only the drain valve 114 of the first drain port 111 is opened to allow the electrophoretic solution to drain from the electrophoresis tank. 11; After closing the drain valve 114, the cleaning solution is sprayed into the electrophoresis tank 11. After cleaning, the drain valve 114 of the second drain port 112 is opened to drain the cleaning solution, so that the cleaning solution and the electrophoresis solution are discharged separately for disposal; then the drain valve 114 of the second drain port 112 is closed and the exhaust valve 115 of the exhaust port 113 is opened. The exhaust port 113 serves as the outlet for dry gas, allowing the dry gas to be blown out of the electrophoresis tank 11 through the exhaust valve 115; then the exhaust valve 115 is closed so that the vacuum unit 32 can perform vacuum treatment on the electrophoresis tank 11.

[0027] To ensure that the required electrophoresis solution can be introduced into the electrophoresis tank 11, preferably, an infusion pipe 116 is connected to one side of the electrophoresis tank 11. One end of the infusion pipe 116 is connected to a first infusion pump 117. The inlet of the first infusion pump 117 is connected to an electrophoresis solution pre-storage chamber 118 via a pipeline. The electrophoresis solution pre-storage chamber 118 is used to pre-store or prepare the required electrophoresis solution. The first infusion pump 117 is used to transport the electrophoresis solution stored in the electrophoresis solution pre-storage chamber 118 into the electrophoresis tank 11.

[0028] To improve the cleaning effect of the spray unit 21, preferably, the opening at the top of the electrophoresis tank 11 is sealed with a cover plate 16. The spray unit 21 includes a cleaning liquid pre-storage chamber 211, a second delivery pump, and a nozzle 213. The nozzle 213 is located at the bottom of the cover plate 16. The outlet of the second delivery pump is connected to the nozzle 213 through a pipeline. The inlet of the second delivery pump 212 is connected to the cleaning liquid pre-storage chamber 211. The second delivery pump 212 is used to pressurize the cleaning liquid in the cleaning liquid pre-storage chamber 211 and spray it out through the nozzle 213. Under the diversion and atomization effect of the nozzle 213, the cleaning liquid is sprayed in the form of droplet groups at various positions in the electrophoresis tank 11 to rinse the nickel substrate 15 and the inner wall of the electrophoresis tank 11.

[0029] To further improve the auxiliary cleaning effect of the ultrasonic cleaning unit 22, there are several ultrasonic cleaning units 22, and these units are symmetrically distributed at the bottom of the electrophoresis tank 11. Preferably, at least one pair of ultrasonic cleaning units 22 are used. Each ultrasonic cleaning unit 22 includes an ultrasonic generator 221 (such as a low-frequency piezoelectric ceramic) and a power supply circuit. The low-frequency piezoelectric ceramic is sealed and embedded in the wall of the electrophoresis tank 11. When the cleaning fluid level in the electrophoresis tank 11 is higher than the low-frequency piezoelectric ceramic and the nickel substrate 15, the synchronous vibration of each low-frequency piezoelectric ceramic can uniformly and at a low frequency vibrate the nickel substrate 15, thereby removing loose particles and crystalline impurities from the surface of the nickel substrate 15.

[0030] Furthermore, to precisely control the activation timing of the ultrasonic cleaning unit 22, a liquid level sensor 222 is installed inside the electrophoresis tank 11. The liquid level sensor 222 is electrically connected to the ultrasonic cleaning unit 22 and forms a control loop to automatically activate the ultrasonic cleaning unit 22. The liquid level sensor 222 is used to detect the liquid level of the cleaning solution in the electrophoresis tank 11. When it detects that the liquid level has reached a position higher than the low-frequency piezoelectric ceramic and the nickel substrate 15, the ultrasonic cleaning unit 22 is activated to perform auxiliary cleaning.

[0031] In one embodiment, the aforementioned airflow purging unit 31 includes an air supply pipe 311 and a plurality of nozzles 312. Each nozzle 312 is circumferentially embedded within the electrophoresis tank 11 and is higher than the positions of the cathode plate 12 and the anode plate 13. The outlet of the nozzle 312 faces the interior of the electrophoresis tank 11, and the inlet of each nozzle 312 is connected to the air supply pipe 311. The air supply pipe 311 is used to inject compressed and dried nitrogen gas into the electrophoresis tank 11 through the nozzles 312. Preferably, the nitrogen gas flow from the plurality of nozzles 312 located above the nickel substrate plate 15, circumferentially sprayed around the inner wall of the electrophoresis tank 11, is discharged downward through the exhaust port 113. During the flow of the nitrogen gas, the cathode plate 12, the anode plate 13, and the nickel substrate plate 15 are purged, and the residual cleaning liquid on their surfaces is dried and removed.

[0032] Furthermore, to improve the efficiency and effect of nitrogen purging, the side of the electrophoresis tank 11 is cylindrical and the bottom is inverted conical. The number of the jet nozzles 312 is preferably four. The four jet nozzles 312 are evenly distributed in a centrally symmetrical manner around the side wall of the electrophoresis tank 11, and the jet direction of any jet nozzle 312 is tangent to the side of the electrophoresis tank 11. The jet nozzles 312 can form a vortex from top to bottom in the electrophoresis tank 11. The synchronous jetting of the evenly distributed jet nozzles 312 improves the stability and uniformity of the vortex, and can increase the purging area and airflow velocity of the airflow, so that the residual cleaning liquid on the surface of various parts of the electrophoresis tank 11 is efficiently removed. Specifically, to facilitate the jet nozzle 312 to jet in a fixed direction and connect with the air supply pipe 311, the airflow purging unit 31 also includes a bracket 313. The bracket 313 is annular and is circumferentially sleeved around the side of the electrophoresis tank 11 at the top of the electrophoresis tank 11. The bracket 313 has a mounting hole that runs through it circumferentially. One end of the air inlet of each jet nozzle 312 extends into one side of the mounting hole, so that the jet direction of each jet nozzle 312 is fixed. The air supply pipe 311 extends into the other end of the mounting hole and connects to the jet nozzle 312, thus avoiding the problem of poor air supply caused by bending or loosening of the air supply pipe 311 and the jet nozzle 312.

[0033] In one embodiment, the vacuum unit 32 includes a negative pressure pipe 321 and a vacuum pump 322. One end of the negative pressure pipe 321 extends from outside the electrophoresis tank 11 into the electrophoresis tank 11, and the other end is connected to the vacuum pump 322. After nitrogen purging is completed, the exhaust port 113 is closed and the vacuum pump 322 is turned on, which can extract the residual electrophoresis liquid or cleaning liquid vapor from the electrophoresis tank 11.

[0034] To enhance the drying effect in conjunction with the vacuum unit 32, the heating unit 33 includes an electric heating block or electric heating wire 331 embedded in the bottom of the electrophoresis tank 11 and a temperature controller 332. The temperature controller 332 is electrically connected to the electric heating block or electric heating wire 331 and can regulate the heating temperature of the electrophoresis tank 11, so that the temperature inside the electrophoresis tank 11 gradually increases. This not only allows the residual cleaning liquid that was missed during the cleaning process to evaporate into vapor and be discharged from the electrophoresis tank 11 under the action of the vacuum unit 32, but also gradually solidifies the coating, enhancing the adhesion and density of the cathode coating film.

[0035] Combining the various structures and features in the above embodiments, the corresponding functions of the above-mentioned field emission cathode coating preparation system are improved, enabling it to form a field emission coating on the nickel substrate 15 of the cathode by electrophoretic deposition, and then clean and dry the coating in a timely manner. The whole process is carried out automatically, avoiding the tedious process of manually transferring the field emission cathode material, reducing the labor and operating costs of coating curing treatment, and helping to improve the preparation efficiency and yield of field emission cathode material.

[0036] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A field emission cathode coating preparation system, characterized in that, The system includes an electrophoretic deposition assembly, a cleaning assembly, and a drying assembly. The electrophoretic deposition assembly includes an electrophoresis tank, a cathode plate and an anode plate spaced apart within the electrophoresis tank, and a power supply electrically connected to both the cathode plate and the anode plate. The power supply is used to adjust the voltage / current between the cathode plate and the anode plate. A nickel substrate plate is detachably mounted on the lower end of the cathode plate. The cleaning assembly includes a spray unit located at the top of the electrophoresis tank and an ultrasonic cleaning unit located at the bottom of the electrophoresis tank. The spray unit is used to spray cleaning fluid into the electrophoresis tank. The drying assembly includes an airflow purging unit and a vacuum unit located at the top of the electrophoresis tank and a heating unit located at the bottom of the electrophoresis tank. The airflow purging unit is used to provide a drying airflow into the electrophoresis tank. The vacuum unit is used to extract cleaning fluid vapor from the electrophoresis tank. The heating unit is used to heat the internal space of the electrophoresis tank.

2. The field emission cathode coating preparation system as described in claim 1, characterized in that, The bottom of the electrophoresis tank is provided with a first drain port, a second drain port, and an exhaust port. The first drain port and the second drain port are respectively provided with drain valves, and the exhaust port is provided with an exhaust valve.

3. The field emission cathode coating preparation system as described in claim 1, characterized in that, One side of the electrophoresis tank is connected to an infusion tube, and one end of the infusion tube is connected to a first infusion pump. The inlet of the first infusion pump is connected to an electrophoresis solution pre-storage chamber. The first infusion pump is used to transport the electrophoresis solution stored in the electrophoresis solution pre-storage chamber to the electrophoresis tank.

4. The field emission cathode coating preparation system as described in claim 1, characterized in that, The top of the electrophoresis tank is sealed with a cover plate. The spray unit includes a pre-storage chamber for cleaning fluid, a second infusion pump, and a nozzle. The nozzle is located at the bottom of the cover plate. The outlet of the second infusion pump is connected to the nozzle, and the inlet of the second infusion pump is connected to the pre-storage chamber for cleaning fluid.

5. The field emission cathode coating preparation system as described in claim 1, characterized in that, There are several ultrasonic cleaning units, which are symmetrically distributed at the bottom of the electrophoresis tank.

6. The field emission cathode coating preparation system as described in claim 5, characterized in that, A liquid level sensor is installed inside the electrophoresis tank. The liquid level sensor is electrically connected to the ultrasonic cleaning unit and is used to obtain the liquid level height of the cleaning liquid in the electrophoresis tank.

7. The field emission cathode coating preparation system according to any one of claims 1 to 6, characterized in that, The airflow purging unit includes an air supply pipe and several jet nozzles. The jet nozzles are arranged circumferentially around the electrophoresis tank and are positioned higher than the cathode plate and the anode plate. The air supply pipe is connected to the jet nozzles.

8. The field emission cathode coating preparation system as described in claim 7, characterized in that, The side of the electrophoresis tank is cylindrical, and the bottom of the electrophoresis tank is inverted conical. The number of air nozzles is at least four. The four air nozzles are centrally symmetrically distributed around the side of the electrophoresis tank, and the air jet direction of any air nozzle is tangent to the side of the electrophoresis tank. The air nozzles are used to form a downward swirling flow in the electrophoresis tank.

9. The field emission cathode coating preparation system as described in claim 1, characterized in that, The vacuum unit includes a negative pressure tube and a vacuum pump. One end of the negative pressure tube extends from outside the electrophoresis tank into the electrophoresis tank, and the other end is connected to the vacuum pump.

10. The field emission cathode coating preparation system as described in claim 1, characterized in that, The heating unit includes an electric heating block or electric heating wire embedded in the bottom of the electrophoresis tank and a temperature controller, wherein the temperature controller is electrically connected to the electric heating block or electric heating wire.

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