CN103952677A - Method for coating inner wall of electron-enhanced plasma discharge tube - Google Patents

Abstract

A method for coating the inner wall of an electronically enhanced plasma discharge tube, which has six major steps: 1. Cleaning treatment before coating the inner wall of the treated tube; 2. Assembling an electronically enhanced plasma discharge tube inner wall coating device; 3. Complete the vacuuming of the vacuum chamber, feed the inert gas through the inert gas feeding pipeline, and then enter the insulating cover through the tube to be treated, and control the flow of the inert gas into the vacuum chamber through the mass flow controller; The negative pulse voltage is provided by the cathode target platform, and the predetermined voltage value and duty cycle are set to complete the cleaning of the inner wall of the tube; 5. The particles for deposition in the gaseous or vapor state are fed through the particle feeding pipeline, and the cathode is supplied by an external power supply. The target stage provides a negative pulse voltage, and sets a predetermined voltage value and duty cycle to complete the coating on the inner wall of the tube; 6. Complete the deflation of the vacuum chamber, take out the tube to be processed, and complete the coating on the inner wall of the tube. The invention has practical value in the field of surface material modification.

Description

A method for electronically enhancing the inner wall coating of a plasma discharge tube

technical field

The invention belongs to the technical field of material surface modification in the field of low-temperature plasma physics and chemistry, and relates to a method for electronically enhancing the inner wall coating of a plasma discharge tube. It can be used for internal surface modification of metal and non-metallic capillary tubes, military gun barrels, offshore drilling and natural gas transmission systems, pipelines and valves for transporting corrosive materials, automotive engine cylinders and piston components, etc.

Background technique

In industrial production, there is a large demand for coating the inner wall of metal pipes, especially for tubular workpieces, such as oil pump barrels in the petroleum industry, chemical pipelines, oil pipelines, and military fields, especially naval guns on naval ships. The inner walls of gun barrels and torpedo tubes that work in harsh environments are in urgent need of strengthening treatment, and ordinary treatment methods cannot meet the internal surface strengthening requirements. In the electronics, medical, and optical industries, non-metallic tubular workpieces such as quartz capillaries are one of the necessary materials for key components of gas chromatography, capillary electrophoresis, capillary liquid chromatography and microfluidics. These workpieces are due to the inner wall Early failure occurs due to wear, corrosion, and oxidation. Therefore, the development of anti-wear, anti-corrosion, and anti-oxidation surface modification technologies and processes is an urgent problem in the field of pipe inner wall coatings. Compared with the outer surface of the workpiece, the technical difficulties of coating the inner wall of the tubular workpiece are: First, because the area to be treated is located inside the tube, some treatment methods are difficult to implement. The second is that even if the method is implemented, it is difficult to obtain a good effect, especially for some very long or thin or special-shaped tubes, the uniformity of film thickness and the bonding force of the film base cannot be guaranteed. For the inner wall coating of metal pipes, it was first proposed to use electroplating and electroless plating for treatment. However, electroless plating pollutes the environment due to the frequent use of harmful chemicals; although electroplating reduces the use of harmful chemicals and improves the coating effect to a certain extent, it still has the problem of poor bonding and easy peeling during use. Ma Zhibin, Wang Jianhua, Wan Jun, He Aihua, and Zhang Lei from Wuhan Engineering University invented a method and device for coating (like) diamond films on the inside or outside of quartz tubes (invention patent: 200710051833.0). In this method, microwaves are used to excite working gas discharge to generate cylindrical plasma between two coaxially placed quartz tubes, and then plasma chemical vapor deposition technology is used to coat the outer wall of the inner quartz tube or the inner wall of the outer quartz tube. Diamond or diamond-like films. However, in this method, the length of the plasma region generated by electron cyclotron resonance is short, and the film can only be coated in a very short region, so it is not suitable for long tubes. At the same time, the implementation of the method is complex, requires a high-power microwave power supply, and costs a lot. Zhao Yanhui, Yu Baohai, and Xiao Jinquan from the Institute of Metal Research, Chinese Academy of Sciences invented a method of depositing thin films on the inner surface of long tubes by plasma-enhanced chemical vapor deposition (PECVD) (invention patent: 201310329125.4). In this method, the slender metal tube to be processed is placed in a tube-shaped vacuum chamber, a tungsten wire electrode is placed axially in the center of the metal tubular workpiece, and the working gas is introduced into the metal tube, and the tungsten wire electrode is applied between the tungsten wire electrode and the wall of the vacuum chamber. A pulse of DC or a radio frequency signal stimulates the discharge to create the plasma. In this method, the inner wall of the tube is used as an electrode for generating plasma, and the tube must be a conductor, so it can only be deposited on the inner wall of the metal tube. At present, composite materials are more and more widely used in industry, and this method cannot coat composite materials. At the same time, in PECVD technology, when the inner diameter of the tube becomes smaller and smaller, the glow discharge is difficult to maintain inside the tube, so that this method can only be used to deposit tubes with a diameter greater than 10 mm. Ralph Stein of Germany invented a plasma-assisted chemical vapor deposition method and device (a method and device for plasma-assisted chemical vapor deposition on the inner wall of a hollow body. Patent of this invention: 200780026008.3), which is to be processed The hollow main body is put into the vacuum chamber, and the large-area radio frequency electrode is placed inside the vacuum chamber. The gas burner is put into the hollow main body. After the gas is injected, the plasma cavity is ignited by applying a radio frequency electric field to the RF electrode. The tip of the spray gun forms a plasma cloud that coats the inner walls of the hollow body. The device can deposit DLC, TiO _x , SiO ₂ and other coatings. However, due to the limitation of the outer diameter of the gas fuel spray gun, the inner wall of the tube whose inner diameter is less than 20mm cannot be coated.

Contents of the invention

1. Purpose: The purpose of the present invention is to provide a method for electron-enhanced plasma discharge tube inner wall coating in view of the above-mentioned deficiencies and defects in the background technology, so as to solve the problem that the existing methods are not suitable for straight long thin tubes and special-shaped tubes , can only be used to deposit pipes with a diameter greater than 10mm, the deposition speed is slow, and it can only be coated on the inner wall of metal pipes, but not on the inner wall of non-metallic pipes.

2. Technical solution

One end of the pipe to be treated is connected with the insulating short pipe, and then connected to the outlet of the gas feeding pipe which is grounded and made of conductive material. The other end is connected with the insulating cover with a hole in the center of the end face, and the insulating cover is placed on the cathode target platform. All the above devices are placed in a vacuum chamber. When the present invention works, the pre-evacuation of the system is first completed, and the gaseous or vaporous particles for deposition are introduced through the gas feed pipe, and then enter the insulating cover through the pipe to be treated. Inert gas can be used as a carrier to maintain a high gas density in the tube to be treated. The negative pulse high voltage provided by the external power supply to the workbench and the outlet of the grounded gas feed pipe become point-shaped hollow anodes and large-area cathodes respectively, and a focused electric field is formed between the two. When the voltage is greater than the ignition voltage, the anode and cathode A glow discharge is generated in the plasma, the ions in the plasma near the target are accelerated, and the electrons are driven away to form a plasma sheath. The ions are accelerated through the sheath and injected into the target while generating secondary electrons. Under the action of the focused electric field, the electrons move toward the point-like hollow anode and gain enough energy, and enter the tube to be treated. In the tube to be treated with a high gas density, the electrons collide with the particles used for deposition to generate a strong glow discharge, and the tube to be treated is at a suspended potential so that the plasma generated by the glow discharge can be maintained in the tube, so that the ions Deposited on the inner wall of the tube to complete the process of coating the inner wall of the tube. The vacuum degree throughout the surface modification process is maintained by a vacuum system.

In summary, the present invention provides a method for electron-enhanced plasma discharge tube inner wall coating. The specific steps of the method are as follows:

Step 1: Clean the inner wall of the pipe to be treated before coating: clean the pipe to be treated with an ultrasonic cleaning machine, and then dry the inner wall of the pipe with an air pump.

Step 2: Assembling a device for coating the inner wall of an electron-enhanced plasma discharge tube, the element used for deposition is solid or liquid, as shown in Figure 1, the device consists of a gas cylinder, a mass flow controller, an inert gas feed pipeline, and a heating Chamber, heating device, outer shielding cover of heating chamber, valve heating device, mass flow controller, particle feeding pipeline insulation device, flange plate, particle feeding pipeline, insulating short tube, waiting tube, insulating cover, vacuum chamber, cathode Composed of target stage, workbench support, vacuum pump exhaust port, insulating ceramics, gas outlet of the tube to be processed, and point-like anodes. The position connection relationship between them is: one end of the tube to be treated is connected to the insulating cover with a hole in the center of the end face, the insulating cover is placed on the cathode target platform supported by the workbench support, and the insulating ceramic is located between the workbench support and the vacuum chamber. The above components are all placed in the vacuum chamber, and the vacuum chamber is brought to a vacuum state through the mechanical pump and the molecular pump, and the gas is discharged through the exhaust port of the vacuum pump. In addition, the workbench support is connected to the negative pulse power supply outside the vacuum chamber. The other end of the tube to be treated is connected to the grounded particle feed pipe through an insulating short pipe, and the particle feed pipe is connected to the vacuum chamber through a flange. The solid or liquid elements used for deposition are placed in the heating chamber, and the heating chamber There is a heating device on the outside, and the outer shield of the heating chamber is outside the heating chamber. The solid or liquid elements used for deposition are heated and evaporated and then enter the vacuum chamber through the particle feeding pipeline. The flow rate is controlled by a mass flow controller and equipped with valves. A heating device, the outer wall of the particle feeding pipeline is provided with a particle feeding pipeline heat insulating device. In addition, an inert gas is introduced into the heating chamber through a gas feed pipe, and the flow rate is controlled by a flow controller. For the element used for deposition is gas, as shown in Figure 2, the relationship between them is: the part in the vacuum chamber is consistent with that shown in Figure 1, and outside the vacuum chamber, the gas used for deposition is in the gas cylinder, and the gas particles The gas feed pipe leads into the vacuum chamber, the gas flow rate is controlled by a mass flow controller, and the gas feed pipe and the vacuum chamber are connected by a flange.

Step 3: Complete the vacuuming of the vacuum chamber, feed the inert gas through the inert gas feeding pipeline, then enter the insulating cover through the pipe to be processed, and control the flow of the inert gas passing into the vacuum chamber through the mass flow controller;

Step 4: Provide a negative pulse voltage to the cathode target platform through an external power supply, and set a predetermined voltage value and duty cycle to complete the cleaning of the inner wall of the tube.

Step 5: Introduce gaseous or vaporized particles for deposition through the particle feeding pipeline, then enter the insulating cover through the tube to be treated, control the gas flow into the vacuum chamber through the mass flow controller, and supply the cathode target platform with an external power supply Provide a negative pulse voltage, and set a predetermined voltage value and duty cycle to complete the coating on the inner wall of the tube.

Step 6: Complete the deflation of the vacuum chamber, take out the tube to be processed, and complete the coating on the inner wall of the tube.

Wherein, the material of the pipe to be treated in step 1 is conductive material or insulating material; the inner wall of the pipe to be treated is cleaned by an ultrasonic cleaning machine, and the cleaning time is 10-20 minutes;

Wherein, the completion of the vacuuming of the vacuum chamber described in step 3 has a vacuum degree of 10 ⁻³ Pa;

Wherein, the inert gas described in step 3 refers to argon; its flow rate is 40 sccm;

Among them, in step 4, the negative pulse voltage is provided to the cathode target platform through an external power supply, and an appropriate voltage value and duty cycle are set. The specific parameter ranges are: voltage value 10-14KV, duty cycle 0.1%-0.5 %. Cleaning time 10-20min;

Wherein, the gaseous or vaporous deposition particles described in step 5 are selected according to the requirements of the tube inner wall coating; the gas flow rate passed into the vacuum chamber is related to the inner diameter of the tube to be processed;

Among them, step 5 provides negative pulse voltage to the cathode target platform through an external power supply, and sets a suitable voltage value and duty cycle. The specific parameter range is: voltage value 10-14KV, duty cycle 0.1%-0.5 %. The deposition time is related to the inner diameter of the tube.

3, effect and benefit of the present invention:

A large-area cathode generated by a high-voltage pulse power supply and a grounded point-shaped anode generate stable glow plasma in the tube. Due to the use of electron-enhanced plasma discharge, it can be coated on the inner wall of the tube of conductive material and the inner wall of the tube of insulating material. The overall shape of the pipeline can be a straight tube or a special-shaped tube, and the equipment is simple and does not require an additional ion source. In addition, the plasma density generated by the present invention is high, and the deposition rate of the film is fast.

Description of drawings

Figure 1 is a schematic diagram of the device structure for coating the inner wall of an electron-enhanced plasma discharge tube (the elements used for deposition are solid or liquid, and the tube to be treated is a straight tube).

In the figure: 1 gas cylinder, 2 mass flow controller, 3 inert gas feeding pipe, 4 heating chamber, 5 heating device, 6 outer shielding cover of heating chamber, 7 valve heating device, 8 mass flow controller, 9 particle feeding pipe insulation Device, 10 flange, 11 particle feed pipeline, 12 short insulating tube, 13 tube to be treated (conductive material), 14 insulating cover, 15 vacuum chamber, 16 cathode target stage, 17 workbench support, 18 vacuum pump exhaust port, 19 insulating ceramics, 20 gas outlet of the pipe to be treated, 21 dotted anodes

Figure 2 is a schematic diagram of the device structure of the electron-enhanced plasma discharge tube inner wall coating (the element used for deposition is gas, the tube to be treated is a straight tube, and the part in the vacuum chamber is consistent with Figure 1).

In the figure: 22 gas cylinders, 23 mass flow controllers, 24 flanges, 25 gas feed pipes, 26 vacuum chambers

Fig. 3 is a flow chart of the present invention

specific implementation plan

See Fig. 3, the present invention is a method for electron-enhanced plasma discharge tube inner wall coating.

Embodiment 1: Taking the molybdenum coating on the inner wall of the pipe as an example, a straight pipe with an inner diameter of 4 mm and a length of 100 mm is selected as the pipe to be treated. The straight pipe is made of insulating material quartz. The insulating short tube is made of quartz. Take the device in Fig. 1, the specific steps of the method are as follows:

Step 1: cleaning the inner wall of the tube 13 to be treated before coating: ultrasonically clean the tube to be treated with absolute ethanol for 10 minutes, and then dry the inner wall of the tube with an air pump.

Step 2: the coating device is connected, one end of the tube 13 to be treated is connected to the insulating cover 14 with a hole in the center of the end face, the insulating cover 14 is placed on the cathode target platform 16 supported by the workbench support 17, and the insulating ceramic 19 is located on the workbench support Between the vacuum chamber and the vacuum chamber, the above components are placed in the vacuum chamber 15, and the vacuum chamber is brought to a vacuum state through a mechanical pump and a molecular pump, and the gas is discharged through the vacuum pump exhaust port 18. In addition, the workbench support and the negative pulse power supply outside the vacuum chamber connect. The other end of the tube to be treated 13 is connected to the grounded particle feed pipeline 11 through an insulating short tube 12, the particle feed pipeline 11 and the vacuum chamber 15 are connected by a flange 10, and molybdenum hexafluoride is placed in the heating chamber 4, There is a heating device 5 outside the heating chamber 4, and the outer shielding cover 6 of the heating chamber is outside the heating device 5. After being heated and evaporated, the solid or liquid elements used for deposition pass into the tube 13 to be treated through the particle feeding pipeline 11 and then enter the insulating cover 14. , its flow rate is controlled by a mass flow controller 8, and is equipped with a valve heating device 7, and the outer wall of the particle feed pipe 11 has a particle feed pipe insulation device 9. In addition, the inert gas in the gas cylinder 1 enters the heating chamber 4 through the inert gas feed pipe 3 and then enters the insulating cover 14 through the pipe to be treated 13 , and the gas flow rate is controlled by the flow controller 2 .

Step 3: complete the vacuuming of the vacuum chamber 15, so that the vacuum degree in the vacuum chamber reaches the level of 10 ⁻³ Pa, feed the inert gas argon through the inert gas feeding pipeline 3, and then enter the insulating cover 14 through the pipe 13 to be processed, and pass Mass flow controllers 2 and 8 control the flow rate of argon gas fed into the vacuum chamber 15, and the flow rate of argon gas is 40 sccm.

Step 4: Provide a negative pulse voltage to the cathode target platform 16 through an external power supply, and set a predetermined voltage value and duty cycle. The voltage value is 12KV, the duty cycle is 0.5%, and the processing time is 10 minutes, and the cleaning of the inner wall of the tube is completed. .

Step 5: Heat the heating chamber filled with molybdenum hexafluoride liquid through the heating device 5, feed molybdenum hexafluoride gas through the particle feeding pipeline 11, and then enter the insulating cover 14 through the tube 13 to be treated, and feed the argon gas through the inert gas The pipeline 3 leads into the heating cavity 4, and then enters the insulating cover 14 through the pipe 13 to be treated. The flows of the two are controlled by mass flow controllers 8 and 2 respectively. The negative pulse voltage is provided to the cathode target platform 16 through an external power supply, and a predetermined voltage value and duty cycle are set. The voltage value is 12KV, the duty cycle is 0.5%, and the processing time is 10 minutes. The coating on the inner wall of the tube is completed.

Step 6: Complete the degassing of the vacuum chamber 15, take out the tube 13 to be processed, and complete the coating on the inner wall of the tube.

Supplementary note: For the inner wall coating of straight pipes with conductive materials and the inner wall coatings of special-shaped pipes with conductive or insulating materials, the methods and steps are the same as above. related.

Embodiment 2: Taking the diamond-like carbon film (DLC) coating on the inner wall of the pipe as an example, a straight pipe with an inner diameter of 4mm and a length of 100mm is selected as the pipe to be treated. The straight pipe is made of insulating material quartz. The insulating short tube is made of quartz. Take the device in Fig. 2, the vacuum chamber part in the Fig. 2 device is consistent with Fig. 1, and the specific steps of the method are as follows:

Step 1: cleaning the inner wall of the tube 13 to be treated before coating: ultrasonically clean the tube to be treated with absolute ethanol for 10 minutes, and then dry the inner wall of the tube with an air pump.

Step 2: the coating device is connected, the part in the vacuum chamber is consistent with that shown in Figure 1, and the part outside the vacuum: the gas in the gas cylinder 22 is passed into the vacuum chamber 26 through the particle feed pipeline 25, and the particle feed pipeline 25 is connected to the vacuum chamber 26 Connection via flange 24 . The gas flow is controlled by a gas flow controller 23 .

Step 3: complete the vacuuming of the vacuum chamber 26, so that the vacuum degree in the vacuum chamber reaches the level of 10 ⁻³ Pa, feed the inert gas argon through the gas feeding pipeline 25, and then enter the insulating cover 14 through the pipe to be processed 13, and pass the mass Flow controller 23 controls the flow rate of the argon gas that passes into the vacuum chamber 26, and the flow rate of argon gas is 40 sccm;

Step 4: Provide a negative pulse voltage to the cathode target platform 16 through an external power supply, and set a suitable voltage value and duty cycle. The voltage value is 12KV, the duty cycle is 0.5%, and the processing time is 10 minutes, and the cleaning of the inner wall of the tube is completed. .

Step five: feed acetylene gas through the gas feed pipeline 25, then enter the insulating cover 14 through the pipe to be treated 13, and control the flow of the acetylene gas passing into the vacuum chamber 26 through the mass flow controller 23. The power supply provides negative pulse voltage to the cathode target platform 16, and sets the appropriate voltage value and duty cycle. The voltage value is 12KV, the duty cycle is 0.5%, and the processing time is 10 minutes. The coating on the inner wall of the tube is completed.

Step 6: Complete the deflation of the vacuum chamber 26, take out the tube 13 to be processed, and complete the coating on the inner wall of the tube.

For the inner wall coating of straight pipes with conductive material and the inner wall coating of special-shaped pipes with conductive or insulating materials, the method and steps are the same as above, and the flow rate of particles used for gaseous or vapor deposition is related to the inner diameter of the pipe to be treated.

One end of the pipe 13 to be treated is connected to a short insulating pipe 12 with a similar inner diameter, and the other end is connected to an insulating cover 14 with a hole in the center of the end face. The diameter of the end face hole of the insulating cover 14 is slightly larger than the outer diameter of the tube 13 to be processed. The other end of the insulating short tube 12 is connected to the outlet of the particle feeding pipeline 11 in the vacuum chamber 15, and the particle feeding pipeline 11 is made of conductive material and grounded. The insulating cover 14 is placed on the cathode target platform 16 in the vacuum chamber 15 . Use a mechanical pump and a molecular pump to pump the vacuum chamber down to about 10 ^-3 Pa, and then pass in gaseous or vaporous particles for deposition. Inert gas can be used as a carrier. The gas flow rate and mixing ratio are controlled by a mass flow meter, and the flow rate of the mixed gas is related to the length and diameter of the pipe 13 to be treated. The gas feeding pipeline is made of conductive material and grounded, and a high-voltage pulse power supply is used to apply negative pulse high voltage to the workbench support 17 and the cathode target platform 16, so that the glow plasma fills the inside of the tube. The voltage provided by the high-voltage pulse power supply is about 12-15KV, and the duty cycle is about 0.1%-1%.

Figure 1 shows a schematic diagram of coating the inner wall of a solid material element tube with a low melting point and a high vapor pressure by using the method. When the element or one of the elements used for deposition is derived from a specific solid or liquid substance, it is first necessary to evaporate and vaporize the substance to obtain the particles used for deposition. Evaporation takes place in the heating chamber 4 . The evaporated particles for deposition are loaded under the carrying condition of an inert gas. The carrying gas can be a substance that participates in deposition, or an inert gas that does not participate in deposition, or a mixed gas. The carrier gas is provided by the gas cylinder 1, and the flow rate is controlled by the mass flow controller 2. The use of carrier gas can help the transport of solid matter after vaporization on the one hand, and can regulate the concentration of particles for deposition on the other hand. At the same time, the carrier gas can also promote the ionization of particles for deposition, providing a self-glow plasma formation The required air pressure provides guarantee for the smooth progress of ionization and deposition. For the vapor particles of the evaporated solid elements, the particle feed pipeline 11 used for transmission adopts the particle feed pipeline thermal insulation device 9 to ensure that the particles are fed into the vacuum chamber 15, and prevent the evaporated particles from freezing in the particle feed pipeline 11 due to being cooled. Inside. In FIG. 1, the particles for deposition are transported into the vacuum chamber 15, first pass through the point-shaped anode 21, and then enter the insulating cover through the tube 13 to be treated. The ionization and deposition working chamber comprises at least one point-shaped anode 21 and at least one large-area cathode target platform 16, the large-area cathode target platform 16 is connected to the negative pole of the power supply, and the point-shaped anode 21 is connected to the positive pole of the power supply, so that the point-shaped anode 21 and the An electric field with electron focusing effect on the anode is formed between the large-area cathode target stage 16. During the subsequent gas discharge process, the electrons in the plasma and the secondary electrons generated by ion injection into the cathode target stage 16, Under the action of the electric field, the electrons are focused near the gas outlet 20 of the tube to be processed, and an electron focusing area is formed near the place. This place increases the voltage drop value of the anode potential drop region in the normal gas discharge, further increasing the energy of the electrons at this place. The deposited particles are ionized by the electrons in the accumulation area, so that the ionization of the particles has a higher ionization rate than ordinary gas discharge, forming a plasma with a high ionization rate. The electrons and secondary electrons in the plasma in the focused area continue to move toward the point-like anode 21 and enter the tube 13 to be processed under the action of the electric field. In the tube 13 to be treated with a relatively high gas density, electrons collide with the particles used for deposition to generate a strong glow discharge, and an insulating short tube 12 is connected between the tube 13 to be treated and the particle feeding pipeline 11 grounded, The potential of the tube 13 to be treated is suspended, so that the plasma generated by the glow discharge can be maintained in the tube 13 to be treated, so that ions are deposited on the inner wall of the tube, and the process of coating the inner wall of the tube is completed.

Fig. 2 shows a schematic diagram of coating the inner wall of gaseous or vaporous substance element tubes by using the method. For particles that are in the gaseous or vapor state at the working temperature, it is not necessary to heat and evaporate solid or liquid substances as shown in FIG. 1 , but can be shown in FIG. 2 . The gas cylinder 22 is directly connected to the gas feed pipe 25 through the flange 24, and the particles required for deposition are directly introduced into the vacuum chamber 26 through the gas feed pipe 25, and its flow rate is controlled by the mass flow controller 23, and the gas feed pipe does not need As shown in Figure 1, thermal insulation or heating measures are adopted. For the loading of gaseous or vaporous substances, other gaseous substances can also be used as carriers to mix with them before loading. In this case, the main function of adding other gaseous substances for carrying is to dilute the deposition gas or vapor Particles, so that the deposition can be carried out according to the corresponding proportion.

Claims (7)

1. A method for electron-enhanced plasma discharge tube inner wall coating, characterized in that: the method concrete steps are as follows: Step 1: Clean the inner wall of the pipe to be treated before coating: clean the pipe to be treated with an ultrasonic cleaning machine, and then dry the inner wall of the pipe with an air pump; Step 2: Assembling a device for coating the inner wall of an electron-enhanced plasma discharge tube. The element used for deposition is solid or liquid. The device consists of a gas cylinder, a mass flow controller, an inert gas feeding pipeline, a heating chamber, and a heating device. Heating chamber outer shielding cover, valve heating device, mass flow controller, particle feeding pipeline insulation device, flange plate, particle feeding pipeline, insulating short tube, tube to be processed, insulating cover, vacuum chamber, cathode target platform, workbench support , the exhaust port of the vacuum pump, insulating ceramics, the gas outlet of the tube to be processed, and a point-shaped anode; one end of the tube to be processed is connected to the insulating cover with a hole in the center of the end face, and the insulating cover is placed on the cathode target platform supported by the workbench bracket. Insulating ceramics are located between the workbench support and the vacuum chamber, and the above components are placed in the vacuum chamber. The vacuum chamber is brought to a vacuum state through a mechanical pump and a molecular pump, and the gas is discharged through the exhaust port of the vacuum pump. In addition, the workbench support and the vacuum chamber The other end of the tube to be treated is connected to the grounded particle feeding pipeline through an insulating short tube, the particle feeding pipeline is connected to the vacuum chamber through a flange, and the solid or liquid elements used for deposition are placed in the heating chamber Among them, there is a heating device outside the heating chamber, and the outer shield of the heating chamber is outside the heating chamber. The solid or liquid elements used for deposition are heated and evaporated, and then enter the vacuum chamber through the particle feeding pipeline, and the flow rate is determined by the mass flow controller. control, and is equipped with a valve heating device, and the outer wall of the particle feeding pipe has a particle feeding pipe insulation device; in addition, the inert gas is passed into the heating chamber through the gas feeding pipe, and the flow rate is controlled by a flow controller; the element used for deposition is gas, vacuum The indoor part is consistent with the above. Outside the vacuum chamber, the gas used for deposition is in the gas cylinder. The gas particles enter the vacuum chamber through the gas feed pipe. The gas flow is controlled by the mass flow controller. The gas feed pipe and the vacuum chamber pass through a method LAN connection; Step 3: Complete the vacuuming of the vacuum chamber, feed the inert gas through the inert gas feeding pipeline, then enter the insulating cover through the pipe to be processed, and control the flow of the inert gas passing into the vacuum chamber through the mass flow controller; Step 4: Provide a negative pulse voltage to the cathode target platform through an external power supply, and set a predetermined voltage value and duty cycle to complete the cleaning of the inner wall of the tube; Step 5: Introduce gaseous or vaporized particles for deposition through the particle feeding pipeline, then enter the insulating cover through the tube to be treated, control the gas flow into the vacuum chamber through the mass flow controller, and supply the cathode target platform with an external power supply Provide negative pulse voltage, and set a predetermined voltage value and duty cycle to complete the coating on the inner wall of the tube; Step 6: Complete the deflation of the vacuum chamber, take out the tube to be processed, and complete the coating on the inner wall of the tube. 2. the method for a kind of electron enhanced plasma discharge tube inner wall coating according to claim 1, is characterized in that: the material of the tube to be treated described in step 1 is conductive material or insulating material; The inner wall of the tube is cleaned, and the cleaning time is 10-20 minutes. 3 . The method for coating the inner wall of an electron-enhanced plasma discharge tube according to claim 1 , characterized in that: in step 3, the vacuum chamber is vacuumed to a degree of 10 ⁻³ Pa. 4 . 4. A method for coating the inner wall of an electron-enhanced plasma discharge tube according to claim 1, characterized in that: the inert gas described in step 3 refers to argon; its flow rate is 40 sccm. 5. The method for coating the inner wall of an electron-enhanced plasma discharge tube according to claim 1, characterized in that: step 4 provides a negative pulse voltage to the cathode target stage through an external power supply, and sets a predetermined voltage Value and duty cycle, the specific parameter range is: voltage value 10-14KV, duty cycle 0.1%-0.5%, cleaning time 10-20min. 6. A method for electron-enhanced plasma discharge tube inner wall coating according to claim 1, characterized in that: the gaseous or gaseous deposition particles in step 5 are selected according to the requirements of the tube inner wall coating ; The gas flow into the vacuum chamber is related to the inner diameter of the tube to be treated. 7. A method for coating the inner wall of an electron-enhanced plasma discharge tube according to claim 1, characterized in that: step 5 provides a negative pulse voltage to the cathode target stage through an external power supply, and sets a predetermined voltage Value and duty cycle, the specific parameter range is: voltage value 10-14KV, duty cycle 0.1%-0.5%, deposition time is related to the inner diameter of the tube.