Method for depositing continuous gradient thin films by surface dielectric barrier discharge

Abstract

The application discloses a method for depositing a continuous gradient film by surface dielectric barrier discharge, which comprises the following steps: step 1, placing an epoxy resin sample plate in a discharge area of a plasma reactor; step 2, introducing a medium, polydimethylsiloxane, into a gas mixing chamber by a bubbling method with argon as a gas source, and introducing another single argon into the gas mixing chamber, and then the argon and the medium are mixed uniformly in the gas mixing chamber to form working gas; and step 3, continuously blowing the working gas from one side of the epoxy resin sample plate parallel to the upper surface of the epoxy resin sample plate to the discharge area of the plasma reactor. By the method, a continuous gradient film can be deposited on the epoxy resin sample plate, the film is dense, the deposition effect is relatively uniform in the horizontal direction, the thickness of the film gradually decreases in the vertical direction, and the electrical performance of the insulating surface of the epoxy resin sample plate after surface modification is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of high voltage equipment insulating materials, and in particular to a method for depositing a continuous gradient film through surface dielectric barrier discharge. Background Art

[0002] Currently, power systems are developing towards larger capacity and longer distances. At the same time, my country's urbanization has entered a new phase, leading to increased electricity demand and limited transmission corridors. Traditional outdoor overhead transmission lines are no longer able to meet this demand. Furthermore, the insulation performance of overhead transmission lines is highly susceptible to external factors, such as severe weather and temperature fluctuations, significantly reducing equipment lifespan. A gas-insulated transmission line (GIL) is a closed transmission line using sulfur hexafluoride (SF6) as the insulating gas, with insulators and enclosed pipes as the main components. It offers a transmission method that can be installed underground, eliminating the need for surface resources. Compared to traditional outdoor insulation, GIL offers superior stability and can withstand higher voltage levels. However, GIL insulators are exposed to long-term, enclosed, high-voltage operating environments. The mismatch in electrical parameters at the gas-solid interface causes electric field distortion, leading to large charges on the insulator surface, flashovers, and insulation failure. Therefore, surface modification is necessary to improve insulation performance without compromising the original mechanical properties.

[0003] Traditional surface modification methods usually focus on improving the uniformity of modification on the macroscopic surface, which can improve the insulation performance of the material surface to a certain extent compared with unmodified materials. However, uniform modification still cannot solve the problem of mismatched electrical parameters at the gas-solid interface. Therefore, relevant scholars have proposed surface gradient functional materials, that is, depositing a layer of functionally gradient film on the surface of the material to make the electrical parameters (relative dielectric constant, conductivity, etc.) of the material surface change in a gradient, thereby achieving the effect of improving electric field distortion, accelerating charge dissipation, and increasing flashover voltage. Traditional surface gradient modification methods include surface coating, magnetron sputtering, electrospinning, etc. However, these methods can usually only achieve surface step gradients by means of partitioning and timing. The preparation process is complicated and requires expensive equipment such as vacuum pumps.

[0004] Publication No. CN111599553A discloses a flexible gradient surface treatment method for UHV AC GIL pot-type insulators. This method uses electrospinning to create a PVA / BaTiO3 film with a gradient relative dielectric constant distribution on the surface of an epoxy resin substrate. This method achieves the goal of regulating the surface electric field and improving the insulator's electrical resistance. However, this method divides the surface into five regions and controls the treatment time for each region, resulting in a discrete step-type gradient. This results in discontinuous surface parameters and a long treatment cycle.

[0005] Publication No. CN111462961A discloses a method for preparing high-voltage GIL surface functionally graded insulators. Using an F2 / N2 gas mixture for a fluorination reaction, a fluorinated layer with a gradient thickness is formed on the insulator surface, resulting in a continuously graded surface conductivity. This method requires the use of a vacuum pump and multiple injections and exhausts of gas. Residual gas treatment is also required after the process is complete, making the process complex and involving the use of toxic substances.

[0006] Publication No. CN109830347A discloses a rapid industrial treatment method for surface functionally gradient insulators used in high-voltage DC (HVDC) GILs. This method uses a plasma jet method to control the treatment time and perform gradient time treatment on HVDC basin insulators, resulting in HVDC basin insulators with functionally gradient conductivity. However, this method requires shielding other areas while treating certain areas, resulting in a discontinuous gradient.

[0007] Research has shown that the electric field averaging effect of a continuous gradient surface is far superior to that of a step gradient. Therefore, it is of great significance to propose an energy-saving and efficient method for surface continuous gradient modification. Plasma surface modification is currently a hot research topic in the field of surface modification, in which surface dielectric barrier discharge can generate gradient plasma on the surface.

[0008] Therefore, in response to the demand for surface continuous gradient functionalization, the present invention proposes a method for depositing continuous gradient films by surface dielectric barrier discharge. The functional film is gradiently deposited on the material surface using atmospheric pressure plasma driven by a nanosecond pulse excitation source, thereby improving its insulation performance in a short time. Summary of the Invention

[0009] 1. Technical problems to be solved:

[0010] In response to the above technical problems, the present invention provides a method for depositing a continuous gradient thin film by surface dielectric barrier discharge.

[0011] 2. Technical solution:

[0012] A method for depositing a continuous gradient thin film using surface dielectric barrier discharge, comprising the following steps:

[0013] Step 1: Place the epoxy resin sample plate in the discharge area of ​​the plasma reactor;

[0014] Step 2: Using argon as the gas source, the medium polydimethylsiloxane is brought into the mixing chamber by bubbling, and another separate argon gas is introduced into the mixing chamber. The argon and the medium are evenly mixed in the mixing chamber to form a working gas;

[0015] Step 3: The working gas is evenly and continuously blown out from one side of the epoxy resin sample plate parallel to the upper surface of the epoxy resin sample plate to the discharge area of ​​the plasma reactor;

[0016] Step 4: The nanosecond pulse excitation source works to generate an electric field in the discharge area of ​​the plasma reactor. The working gas generates a plasma plume under the action of the electric field, and the plasma plume deposits a continuous gradient film on the surface of the epoxy resin sample plate.

[0017] Preferably, the voltage amplitude of the nanosecond pulse excitation source is 8 kV, and the power frequency is 1 kHz.

[0018] Preferably, the argon flow rate for bringing the medium polydimethylsiloxane into the gas mixing chamber by bubbling is 13-15 mL / min, and the argon flow rate of another separate channel is 1.8-2 L / min.

[0019] Preferably, the nanosecond pulse excitation source starts working 1 minute after the working gas is blown out.

[0020] Preferably, the time for depositing the continuous gradient film on the epoxy resin sample plate is 5 minutes.

[0021] Preferably, the size of the epoxy resin sample plate is 100×100×1 mm.

[0022] Preferably, the viscosity of the medium polydimethylsiloxane is 50 cst.

[0023] More specifically, the method of the present invention is based on a surface dielectric barrier discharge modification platform, which includes an argon gas cylinder, a mixing chamber and a plasma reactor. The argon gas cylinder is connected to a two-way joint, which is connected to two flow meters, one of which is directly connected to the mixing chamber, and the other is connected to an anti-backflow bottle, which is connected to a medium bottle, which is connected to the mixing chamber. The gas flow rates of the two flow meters are controlled by a flow rate controller, and the mixing chamber is connected to a porous air inlet module of the plasma reactor. The air outlet of the porous air inlet module faces the discharge area of ​​the plasma reactor, and the working gas is blown out evenly from the porous air inlet module. The air outlet of the porous air inlet module is slightly higher than the upper surface of the epoxy resin sample plate, and the plasma reactor is connected to a nanosecond pulse excitation source.

[0024] The working principle of the present invention is as follows: When the nanosecond pulse excitation source is working, it generates an electric field. Argon gas generates plasma under the action of the electric field. The plasma contains a large number of active particles. The active particles will decompose the medium polydimethylsiloxane (PDMS) into silicon-containing active groups such as Si-O-Si and Si-CH3. The decomposition process is shown in formula (1):

[0025] (1);

[0026] At the same time, a large number of active particles in the plasma bombard the surface of the epoxy resin sample plate, breaking the OH chemical bond on one side of the epoxy resin. Then, the silicon-containing active groups in the plasma undergo grafting and cross-linking reactions with the epoxy resin under the action of discharge to form Si-O-Si polymers. The process is shown in Equation 2.

[0027] (2).

[0028] The working gas is blown out evenly through the porous air inlet module, and the blown working gas forms a plasma plume under the action of the electric field, covering the upper surface of the epoxy resin sample plate; affected by the surface adsorption of the material and the deposition reaction, the number of active particles in the plasma and the concentration of silicon-containing active groups produced by PDMS decomposition will gradually decrease with the development of the plasma plume, and this reduction obeys the "concentration boundary layer" law, that is, the number of active particles closer to the porous air inlet module is large, the grafting and cross-linking reactions of the silicon-containing active groups are more complete, and the formed film is thicker. As the distance increases, the number of active particles farther away from the porous air inlet module decreases, the deposition effect weakens, and the film thickness decreases. Therefore, continuous gradient thin film deposition on the surface of the insulating material can be achieved.

[0029] 3.Beneficial effects:

[0030] (1) The method of the present invention can deposit a continuous gradient film on the epoxy resin sample plate. The film is dense, the deposition effect in the horizontal direction is relatively uniform, and the thickness of the film in the vertical direction gradually decreases.

[0031] (2) The electrical properties of the insulating surface of the epoxy resin sample plate after surface modification by the method of the present invention are greatly improved. The flashover voltage of the untreated sample plate is 8~9kV, and the flashover voltage of the sample plate after traditional uniform thin film deposition treatment is increased to 11~12kV. The flashover voltage of the sample plate treated by the method of the present invention is further increased to 12~14kV. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a surface dielectric barrier discharge modification platform according to an embodiment of the present invention;

[0033] Figure 2 This is an epoxy resin sample plate before surface modification treatment according to an embodiment of the present invention;

[0034] Figure 3 This is the epoxy resin sample plate after surface modification treatment according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings.

[0036] As attached Figure 1 To the attached Figure 3 As shown, Specific embodiment:

[0038] A method for depositing a continuous gradient thin film by surface dielectric barrier discharge, the method being achieved by a surface dielectric barrier discharge modification platform; Figure 1 As shown, the surface dielectric barrier discharge modification platform includes an argon gas cylinder 1, a gas mixing chamber 8 and a plasma reactor 9. The argon gas cylinder 1 is connected to a two-way joint 2, the two-way joint 2 is connected to a flow meter A3 and a flow meter B4, the flow meter A3 is directly connected to the gas mixing chamber, the flow meter B4 is connected to an anti-backflow bottle 6, the anti-backflow bottle 6 is connected to a medium bottle 7, the medium bottle 7 is connected to the gas mixing chamber, the gas flow rates of the flow meters A3 and B4 are controlled by a flow rate controller 5, the gas mixing chamber 8 is connected to a porous gas inlet module 10 of the plasma reactor 9, the gas outlet of the porous gas inlet module 10 is directly facing the discharge area of ​​the plasma reactor 9, and the plasma reactor 9 is connected to a nanosecond pulse excitation source 13;

[0039] The method comprises the following steps:

[0040] Step 1: correctly place the epoxy resin sample plate 12 with a size of 100×100×1 mm in the discharge area of ​​the plasma reactor 9;

[0041] Step 2: Open the pressure reducing valve on argon bottle 1. The argon is split into two streams: one enters mixing chamber 8 through flowmeter A3, and the other enters the medium bottle through flowmeter B4. This creates bubbles, bringing the medium polydimethylsiloxane (PDMS) into mixing chamber 8. The viscosity of PDMS is 50 cSt. During operation, first adjust the flow rate of flowmeter B4 to 15 mL / min and observe whether bubbles steadily appear in medium bottle 7. After 1 minute of bubbling, adjust the flow rate of flowmeter A3 to 2 L / min. The two gases are thoroughly mixed in mixing chamber 8 to form the working gas.

[0042] Step 3: The working gas is evenly blown out from one side of the epoxy resin sample plate 12 parallel to the upper surface of the epoxy resin sample plate 12 to the discharge area of ​​the plasma reactor 9 through the porous air inlet module 10; the air outlet position of the porous air inlet module 10 is generally slightly higher than the upper surface of the epoxy resin sample plate 12.

[0043] Step 4: After the working gas is introduced for 1 minute, the nanosecond pulse excitation source is operated with the parameters set to a voltage amplitude of 8 kV and a power frequency of 1 kHz. An electric field is generated in the discharge area of ​​the plasma reactor 9. Under the action of the electric field, the working gas generates a plasma plume 11, which deposits a continuous gradient thin film on the upper surface of the epoxy resin sample plate for 5 minutes.

[0044] like Figure 2As shown in Figure 2, the surface of the epoxy resin sample plate before treatment is smooth and flat without any undulations. Figure 3 As shown, after the surface modification treatment by the method of this embodiment, a white dense film with an area of ​​about 80×80 mm is produced on the surface of the epoxy resin sample plate. The deposition effect in the horizontal direction is relatively uniform, and the thickness and density of the film in the vertical direction gradually decreases, which shows that the method of this embodiment can deposit a thickness gradient film on the surface of the material.

[0045] Further testing of the surface flashover voltage performance of the insulating material showed that the flashover voltage of the untreated sample plate was 8~9kV, while the flashover voltage of the sample plate was increased to 11~12kV after traditional uniform thin film deposition treatment; after surface modification treatment using the method of the present invention, the flashover voltage of the sample plate was further increased to 12~14kV, indicating that the method of this embodiment is more effective in improving the electrical performance of the insulating surface than traditional uniformity modification.

[0046] Although the present invention has been disclosed above in terms of preferred embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims of this application.

Claims

1. A method for depositing a continuous gradient thin film by surface dielectric barrier discharge, characterized in that: The following steps are involved: Step 1: Place the epoxy resin sample plate in the discharge area of ​​the plasma reactor; Step 2: Using argon as the gas source, polydimethylsiloxane (PDMS) with a viscosity of 50 cSt is introduced into the mixing chamber by bubbling. Another separate stream of argon is then introduced into the mixing chamber. The argon and the medium are mixed evenly in the mixing chamber to form the working gas. Step 3: The working gas is evenly blown out from one side of the epoxy resin sample plate parallel to the upper surface of the epoxy resin sample plate to the discharge area of ​​the plasma reactor. The working gas is evenly blown out from the multi-porous air inlet module. The outlet position of the multi-porous air inlet module is slightly higher than the upper surface of the epoxy resin sample plate. The airflow direction of the working gas is consistent with the electric field direction of the plasma reactor. Step 4: The nanosecond pulse excitation source operates to generate an electric field in the discharge region of the plasma reactor. The working gas generates a plasma plume under the action of the electric field, and the plasma plume deposits a continuous gradient film on the surface of the epoxy resin sample plate; The method is based on a surface dielectric barrier discharge modification platform, which includes an argon gas cylinder, a gas mixing chamber, and a plasma reactor. The argon gas cylinder is connected to a two-way joint, which is connected to two flow meters, one of which is directly connected to the gas mixing chamber, and the other is connected to an anti-backflow bottle, which is connected to a medium bottle, which is connected to the gas mixing chamber. The gas flow rates of the two flow meters are controlled by a flow rate controller. The gas mixing chamber is connected to a porous gas inlet module of the plasma reactor, the gas outlet of the porous gas inlet module faces the discharge area of ​​the plasma reactor, the working gas is evenly blown out from the porous gas inlet module, and the gas outlet of the porous gas inlet module is slightly higher than the upper surface of the epoxy resin sample plate. The plasma reactor is connected to a nanosecond pulse excitation source.

2. The method for depositing a continuous gradient thin film by dielectric barrier discharge on a surface according to claim 1, characterized in that: The voltage amplitude of the nanosecond pulse excitation source is 8 kV, and the power frequency is 1 kHz.

3. The method for depositing a continuous gradient thin film by dielectric barrier discharge on a surface according to claim 1, characterized in that: The argon flow rate for bringing the medium polydimethylsiloxane into the gas mixing chamber by bubbling is 13~15mL / min, and the flow rate of another independent argon flow is 1.8~2L / min.

4. The method for depositing a continuous gradient thin film by dielectric barrier discharge on a surface according to any one of claim 1, characterized in that: After the working gas is blown out for 1 minute, the nanosecond pulse excitation source starts working.

5. The method for depositing a continuous gradient thin film by dielectric barrier discharge on a surface according to any one of claims 2 to 4, characterized in that: The time for depositing the continuous gradient film on the epoxy resin sample plate is 5 minutes.

6. The method for depositing a continuous gradient thin film by dielectric barrier discharge on a surface according to claim 5, characterized in that: The size of the epoxy resin sample plate is 100×100×1 mm.

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