Plasma-enhanced nonlinear conductive coating and method of making and use thereof

Abstract

The application discloses a kind of plasma reinforced nonlinear conductance coating and its preparation method and application, the preparation method includes that composite coating is coated to the surface of insulating substrate, is cured after being handled under the action of electric field to obtain coating;Composite coating includes nonlinear conductance material and coating matrix;Wherein, nonlinear conductance material and / or insulating substrate are treated by plasma process.The nonlinear conductance material of the present application can have good nonlinear conductance characteristics at low doping amount by plasma treatment, and the impact of high-energy particles of plasma can introduce mechanical interlocking, physical adsorption and chemical bonding at the same time, to strengthen the adhesion of coating on the surface of insulating substrate.The coating obtained by the present application can exhibit significant nonlinear conductance characteristics at low filler doping amount, compared with the coating of prior art, has better surface charge control effect, higher surface flashover voltage and stronger basic adhesion.

Description

Technical Field

[0001] This invention relates to the field of technology, and in particular to a plasma-enhanced nonlinear conductive coating, its preparation method, and its application. Background Technology

[0002] The accumulation of surface charge on insulators under DC voltage is a key issue limiting the long-term safe and stable operation of UHVDC gas-insulated equipment. Therefore, finding an effective method to suppress surface charge accumulation is a necessary step in improving the design of UHVDC gas-solid insulation. Currently, coating the insulator surface with a nonlinear conductive coating is considered a charge suppression method with great engineering application potential.

[0003] However, the engineering application of nonlinear conductive coatings still faces the following problems. First, the activation of the nonlinear conductive properties of the coating generally requires doping with inorganic fillers to a level exceeding their percolation threshold. However, high-concentration doping not only poses significant difficulties for sample preparation but also leads to a decrease in the mechanical strength of the finished coating. Furthermore, existing coating construction methods lack consideration for improving adhesion, resulting in low basic adhesion between the coating and the insulator, posing a very high risk of detachment during long-term equipment operation.

[0004] Research on adhesion enhancement of nonlinear conductive coatings is still in its early stages. Only a few scholars have conducted preliminary explorations using mechanical grinding to improve the surface roughness of insulating substrates, but this is far from meeting the requirements of engineering applications. Furthermore, regarding the problem of excessive filler content in nonlinear conductive coatings, some scholars in this field have proposed using an electric field-induced movement of inorganic fillers to form anisotropic functional materials. This results in a gradient distribution of dielectric and physicochemical properties along the direction of the induced electric field, which to some extent reduces the filler doping ratio below the percolation threshold. At the same doping concentration, this method exhibits better charge control than coatings with uniformly dispersed fillers. However, lower filler concentrations often require higher in-situ electric fields to drive particle chain formation, and these higher in-situ electric fields cause severe fluctuations in the coating matrix due to complex electrohydrodynamics, disrupting the particle chain structure. Therefore, the current reduction in particle doping ratio achieved by coatings prepared using electric field-induced techniques is very limited.

[0005] In summary, to promote the application of surface coating in DC gas-insulated equipment, it is necessary to propose a method for preparing nonlinear conductive coatings that combines low filler doping and high adhesion. Summary of the Invention

[0006] To address the problems of existing technologies, this invention utilizes plasma modification to treat the surface of inorganic filler particles and / or insulating substrates. On one hand, it optimizes the chain-forming process of electric field-induced nonlinear conductive material movement by improving the compatibility between the nonlinear conductive material and the coating matrix, further reducing the doping ratio of nonlinear conductive materials capable of stable chain formation. On the other hand, it introduces three bonding modes—mechanical interlocking, physical adsorption, and chemical bonding—at the coating-substrate interface through physical and chemical etching of the insulating substrate surface using plasma, thereby enhancing the adhesion of the coating.

[0007] To achieve the above objectives, the present invention provides a method for preparing a plasma-enhanced nonlinear conductive coating, comprising,

[0008] A composite coating is applied to the surface of an insulating substrate, and then cured under the action of an electric field to obtain the coating.

[0009] The composite coating comprises a nonlinear conductive material and a coating matrix;

[0010] The nonlinear conductive material and / or insulating substrate are subjected to plasma treatment.

[0011] Further, the plasma treatment includes,

[0012] After purging with a mixed gas of oxygen and / or argon at a flow rate of 100-200 mL / min for 1-10 min, dielectric barrier discharge is applied and the gas is treated for 1-10 min at a peak voltage of 1-10 kV.

[0013] Preferably, the dielectric barrier discharge uses parallel plate electrodes; the barrier medium is quartz glass; the dielectric barrier method can be one of high-voltage electrode barrier, ground electrode barrier, or high-voltage electrode-ground electrode dual barrier; the discharge process is driven by a high-voltage power supply, and the power supply waveform is one of high-frequency AC, microsecond pulse, or nanosecond pulse.

[0014] Furthermore, the nonlinear conductive material is silanized before plasma treatment.

[0015] It should be noted that the silanization treatment of the present invention is a conventional operation in the art, which utilizes a silane coupling agent to treat the surface of a nonlinear conductive material. The type of silane coupling agent is not strictly limited and can be at least one of KH501, KH550, KH560, KH580, KH602, etc.; the amount of silane coupling agent used is preferably 0.2%-1%; the dispersion solvent for the nonlinear conductive material and the silane coupling agent can be at least one of water, ethanol, acetone, etc. After coupling and drying, agglomeration may occur. Preferably, the agglomerated particles are ball-milled to ensure that the particle size meets the requirements.

[0016] Furthermore, the insulating substrate undergoes surface cleaning before plasma treatment. The material of the insulating substrate is not strictly limited, but epoxy resin or epoxy-based composite materials are preferred. The specific cleaning process can be as follows: immerse the insulating substrate in ethanol, ultrasonically clean it for 30-60 minutes at a temperature of 40-60℃ and an ultrasonic power of 100-400W, and then remove the insulating substrate and dry it in a constant temperature oven at 20% RH for 24-72 hours.

[0017] Furthermore, the particle size of the nonlinear conductive material is 5-100 μm. The type of nonlinear conductive material is not strictly limited, but preferably it can be at least one of silicon carbide and zinc oxide.

[0018] Furthermore, the coating matrix includes a coating, a curing agent, and an accelerator.

[0019] Preferably, the preparation process of the composite coating follows the operating principle of homogeneous material blending. The nonlinear conductive material should be added to the coating before the curing agent is introduced. The operating temperature of the entire blending process is controlled at 65-75℃. After all raw materials are blended, the composite coating is placed in an environment at 65℃ and vacuumed while stirring for 30-60 minutes. After vacuuming, the composite coating is kept at 65-75℃ for later use. The entire preparation time of the composite coating should not exceed 5 hours.

[0020] In this invention, the type of coating is not strictly limited and can be epoxy resin, polyester resin, silicone rubber, etc. Correspondingly, the curing agent and accelerator are selected as suitable types. The ratio of coating, curing agent, and accelerator can be adjusted as needed and is not strictly limited.

[0021] In this invention, the amount of nonlinear conductive material added does not need to be strictly limited and can be set according to the specific coating requirements. However, it should be noted that adding too much may cause a decrease in the adhesion and stability of the coating. Optionally, the mass of the nonlinear conductive material is 1-10% of the mass of the coating matrix.

[0022] Furthermore, the parameters for the induction treatment are: temperature 80-120℃, voltage amplitude 0.1-1kV, frequency 100-1000Hz, and time 2-12h.

[0023] Furthermore, the curing process employs a stepped temperature increase curing method. Preferably, it can be a two-stage or three-stage stepped curing method, wherein the two-stage step curing is: 90℃ for 2 hours followed by 110℃ for 10 hours; the three-stage step curing is: 90℃ for 2 hours followed by 100℃ for 4 hours, and finally 110℃ for 6 hours.

[0024] The present invention also provides a plasma-enhanced nonlinear conductive coating, which is obtained by the above preparation method.

[0025] The present invention also provides the application of the above-mentioned plasma-enhanced nonlinear conductive coating in DC gas insulation equipment.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) This invention improves the electric field induction method and proposes for the first time to use plasma treatment to optimize the chain formation process of nonlinear conductive materials under the electric field induction, which can enable nonlinear conductive materials to obtain better nonlinear conductive properties with lower doping amount.

[0028] (2) This invention proposes for the first time to use plasma modification treatment to optimize the bonding process between the nonlinear conductive coating and the insulating substrate. The impact of high-energy plasma particles can simultaneously introduce three bonding effects on the surface of the coating and the insulating substrate: mechanical interlocking, physical adsorption, and chemical bonding, thereby strengthening the adhesion of the coating on the surface of the insulating substrate.

[0029] (3) The present invention achieves the actual effect of high nonlinear conductivity and high bonding strength of coating without using special chemical reagents. The processing method is simple, environmentally friendly and does not affect the formulation system of the coating itself.

[0030] (4) The coating obtained by the present invention has excellent charge and electric field control capabilities, and its DC surface resistance is better than that of existing coatings. Furthermore, the low doping filler properties also ensure the excellent mechanical strength of the coating body, taking into account both the functional effectiveness and structural effectiveness of the coating. It has great application potential in high voltage DC gas insulation equipment. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating a method for preparing a plasma-enhanced nonlinear conductive coating according to an embodiment of the present invention is shown;

[0033] Figure 2 The electrical conductivity characteristics of the coatings prepared in Example 1, Comparative Example 2, and Comparative Example 3 are shown in the diagram.

[0034] Figure 3 The diagram shows the surface charge accumulation of the coatings prepared in Examples 1, 2, and 3 during the 2-hour pressurization process;

[0035] Figure 4 The DC surface flashover voltage results of the coatings prepared in Example 1, Comparative Example 2, and Comparative Example 3 are shown in the figure.

[0036] Figure 5 The adhesion test results of Examples 1-3 and Comparative Example 1 are shown in the figure. Detailed Implementation

[0037] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, a method for preparing a plasma-enhanced nonlinear conductive coating includes the following steps:

[0041] ① Plasma treatment of nonlinear conductive materials:

[0042] 1) β-silicon carbide with a particle size of 5 μm and KH550 were dispersed in ethanol, and then stirred for 25 min at 25 °C and ultrasonic power of 200 W. The mass of KH550 was 0.5% of the mass of β-silicon carbide. After stirring, the resulting mixture was transferred to a heating chamber and dried at 100 °C for 12 h. After drying, the agglomerated sample was removed and ground in a ball mill to obtain 5 μm silane-coupled β-silicon carbide. This was then transferred to a plasma discharge chamber, which was a transparent device with quartz glass covers on both sides, with a diameter of 20 cm and a thickness of 5 cm.

[0043] 2) Select a mixture of oxygen and argon as the background gas for plasma treatment. First, perform a gas washing process inside the chamber. The gas washing process is completed using a DC flow controller. The flow ratio of oxygen to argon is 1:9, and the process lasts for 5 minutes. The total gas flow rate is maintained at 100 mL / min.

[0044] 3) Connect the high-frequency sinusoidal AC power supply to begin plasma treatment, using dielectric barrier discharge (DBD) with parallel flat electrodes; the barrier medium is quartz glass; the dielectric barrier method is high-voltage electrode-ground electrode double barrier, the power supply frequency is set to 10kHz, the peak voltage is set to 5kV, and the treatment time lasts for 5 minutes. After plasma treatment, transfer to a beaker for later use.

[0045] ② Plasma treatment of insulating substrate:

[0046] 1) The insulating substrate was selected as a sheet-like insulating sample made of alumina / epoxy resin. The insulating substrate was first cleaned, i.e., subjected to ultrasonic pretreatment. Specifically, the insulating substrate was placed in a beaker filled with alcohol, and the beaker was placed in a water bath of an ultrasonic disperser for ultrasonic cleaning. The cleaning power was 150W, the treatment time was 30 minutes, and the cleaning temperature was 45℃. After treatment, the insulating substrate was removed from the alcohol and placed in a constant temperature oven for drying. The oven temperature was set to 60℃, the humidity was controlled at 20%RH, and the drying time was 36 hours.

[0047] 2) The insulating substrate that has undergone ultrasonic oscillation pretreatment is transferred to the plasma discharge chamber. A mixture of oxygen and argon is selected as the background gas for plasma treatment. First, the gas washing process inside the chamber is carried out. The gas washing process is completed using a DC flow controller. The flow ratio of oxygen to argon is 1:9, which lasts for 5 minutes, and the total gas flow rate is maintained at 100 mL / min.

[0048] 3) Connect the high-frequency sinusoidal AC power supply to begin plasma treatment, using dielectric barrier discharge with parallel flat electrodes; the barrier medium is quartz glass; the dielectric barrier method is a high-voltage electrode-ground electrode double barrier, the power frequency is set to 10kHz, the peak voltage is set to 5kV, and the treatment time lasts for 5 minutes. After plasma treatment, transfer the plasma to a room temperature storage cabinet for later use.

[0049] ③ Coating material blending and in-situ electric field induction:

[0050] 1) Heat E51 epoxy resin to 100℃ to reduce viscosity. Add the plasma-treated silane-coupled β-silicon carbide obtained in step ① to the E51 epoxy resin, then cool to 65℃ and stir for 1 hour. After stirring, add the curing agent methylhexahydrophthalic anhydride, then continue stirring at 65℃ for 2 hours, add the accelerator phenol, and stir and mix at 65℃ for 1 hour. Finally, transfer to a vacuum oven and vacuum for 1 hour to obtain the composite coating, and place it in a 65℃ constant temperature oven for later use. The mass of silane-coupled β-silicon carbide is 5% of the mass of the composite coating, and the mass ratio of E51 epoxy resin, methylhexahydrophthalic anhydride, and phenol is 100:80:0.5.

[0051] 2) To adapt to the structure of the sheet-like alumina / epoxy resin insulating substrate, a self-designed assembly structure is adopted. The assembly structure includes an upper insulating plate, a lower insulating plate, and fasteners. Both the upper and lower insulating plates have grooves, electrode pre-reserved slots, and fixing holes. When the upper and lower insulating plates are assembled, they can confine the insulating substrate in the grooves and reserve space for coating. The groove of the upper insulating plate is also provided with a liquid injection hole for injecting composite coating into the coating space. The electrode pre-reserved slot is used to install patch electrodes. In this embodiment, the upper and lower insulating plates are made of the same material, PEEK insulating plates. After the plasma-treated insulating substrate is placed into the assembly structure, it is fixed with fasteners. Composite coating is injected through the liquid injection hole. After the composite coating is injected, patch electrodes are installed in the electrode pre-reserved slots and connected to a power source that can generate high-frequency sinusoidal AC power.

[0052] 3) Turn on the power and perform in-situ electric field induction for 2 hours at a temperature of 90℃, a voltage amplitude of 500V, and a frequency of 1000Hz.

[0053] ④ Stepped high-temperature curing

[0054] After the in-situ electric field induction is completed, the coated assembly structure system is transferred to a constant temperature oven and set to a two-stage stepped curing process, which is carried out at 90℃ for 2 hours and then transferred to 110℃ for 10 hours.

[0055] After completing the above steps, the insulating substrate is removed from the assembly structure, and a plasma-enhanced nonlinear conductive coating is formed on the surface of the insulating substrate.

[0056] Example 2

[0057] The process is basically the same as the example, except that the plasma treatment time for the insulating substrate in step ② is 2 minutes.

[0058] Example 3

[0059] The process is basically the same as in the example, except that the plasma treatment time for the insulating substrate in step ② is 3 minutes.

[0060] Comparative Example 1

[0061] The process is basically the same as the previous example, except that the plasma treatment time for the insulating substrate in step ② is 0 min.

[0062] Comparative Example 2

[0063] A method for preparing a nonlinear conductive coating, comprising the following steps:

[0064] ①Silane-coupled nonlinear conductive materials:

[0065] β-silicon carbide with a particle size of 5 μm and KH550 were dispersed in ethanol, and then stirred at 25 °C and ultrasonic power of 200 W for 25 min. The mass of KH550 was 0.5% of the mass of β-silicon carbide. After stirring, the resulting mixture was transferred to a heating oven and dried at 100 °C for 12 h. After drying, the agglomerated sample was removed and ground in a ball mill to obtain 5 μm silane-coupled β-silicon carbide.

[0066] ②Preparation of coating raw materials

[0067] E51 epoxy resin was heated to 100℃ to reduce its viscosity. The silane-coupled β-silicon carbide obtained in step ① was added to the E51 epoxy resin, and then the temperature was lowered to 65℃ and stirred for 1 hour. After stirring, the curing agent methylhexahydrophthalic anhydride was added, and then stirring was continued at 65℃ for 2 hours. The accelerator phenol was then added, and the mixture was stirred and blended at 65℃ for 1 hour. Finally, the mixture was transferred to a vacuum oven and vacuumed for 1 hour to obtain a composite coating, which was then placed in a 65℃ constant temperature oven for later use. The mass of the silane-coupled β-silicon carbide was 5% of the mass of the composite coating, and the mass ratio of E51 epoxy resin, methylhexahydrophthalic anhydride, and phenol was 100:80:0.5.

[0068] ③ Stepped high-temperature curing

[0069] The selection of the insulating substrate and the cleaning method are the same as in Example 1, and will not be repeated here. The composite coating obtained in step ② is applied to the surface of the insulating substrate, and then transferred to a constant temperature oven, set to a two-stage stepped curing process, and then heated to 90°C for 2 hours and then to 110°C for 10 hours to form a nonlinear conductive coating on the surface of the insulating substrate.

[0070] In Comparative Example 1 and Example 1, the coatings formed have the same thickness.

[0071] Comparative Example 3

[0072] A method for preparing an in-situ electric field-induced nonlinear conductive coating, comprising the following steps:

[0073] ①Silane-coupled nonlinear conductive materials:

[0074] β-silicon carbide with a particle size of 5 μm and KH550 were dispersed in ethanol, and then stirred at 25 °C and ultrasonic power of 200 W for 25 min. The mass of KH550 was 0.5% of the mass of β-silicon carbide. After stirring, the resulting mixture was transferred to a heating oven and dried at 100 °C for 12 h. After drying, the agglomerated sample was removed and ground in a ball mill to obtain 5 μm silane-coupled β-silicon carbide.

[0075] ②Preparation of coating raw materials

[0076] E51 epoxy resin was heated to 100℃ to reduce its viscosity. The silane-coupled β-silicon carbide obtained in step ① was added to the E51 epoxy resin, and then the temperature was lowered to 65℃ and stirred for 1 hour. After stirring, the curing agent methylhexahydrophthalic anhydride was added, and then stirring was continued at 65℃ for 2 hours. The accelerator phenol was then added, and the mixture was stirred and blended at 65℃ for 1 hour. Finally, the mixture was transferred to a vacuum oven and vacuumed for 1 hour to obtain a composite coating, which was then placed in a 65℃ constant temperature oven for later use. The mass of the silane-coupled β-silicon carbide was 5% of the mass of the composite coating, and the mass ratio of E51 epoxy resin, methylhexahydrophthalic anhydride, and phenol was 100:80:0.5.

[0077] ③ In-situ electric field induction and stepped high-temperature curing

[0078] 1) The selection of insulating substrate and cleaning method are the same as in Example 1, and will not be repeated here. Because an electric field needs to be applied, the same assembly structure as in Example 1 is adopted. For the specific structure, please refer to Example 1, and will not be repeated here. After the composite coating obtained in step ② is injected, the patch electrode is set in the electrode pre-reserved groove, and the power supply is connected and turned on to perform in-situ electric field induction for 2 hours at a temperature of 90°C, a voltage amplitude of 500V, and a frequency of 1000Hz.

[0079] 2) After the in-situ electric field induction is completed, the coated assembly structure system is transferred to a constant temperature oven and set to a two-stage stepped curing process, which is carried out at 90℃ for 2 hours and then transferred to 110℃ for 10 hours. The insulating substrate is then removed from the assembly structure, and a nonlinear conductive coating is formed on the surface of the insulating substrate.

[0080] Test case

[0081] The conductivity of the nonlinear conductive coating under high voltage is particularly important for its performance. The conductivity characteristics of the coatings prepared in the examples and comparative examples were tested, and the results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the nonlinear conductive coating of Comparative Example 2 does not show a significant increase in conductivity under electric field strength of 1-10 kV / m, which may be due to the insufficient addition of the nonlinear conductive material silane-coupled β-silicon carbide. Comparative Example 3, which undergoes in-situ electric field induction, exhibits more obvious nonlinear conductive characteristics under varying electric field. This is because applying an AC electric field causes the silane-coupled β-silicon carbide to align into chains along the electric field direction, resulting in a coating with good nonlinear conductive characteristics even at low doping concentrations. However, Example 1, which undergoes plasma strengthening and in-situ electric field induction, exhibits significant nonlinear conductive characteristics under varying electric field. This is because plasma strengthening optimizes the chain formation process of silane-coupled β-silicon carbide under electric field induction, and also optimizes the bonding process between the nonlinear conductive coating and the insulating substrate.

[0082] The coatings of the examples and comparative examples were subjected to a voltage of +15 kV for 2 hours, and the charge accumulation on the coating surface was recorded. The results are as follows: Figure 3 As shown. From Figure 3 As can be seen from the data, the plasma-enhanced nonlinear conductive coating prepared in Example 1 exhibits minimal surface charge accumulation performance during the pressurized period, which is due to the better arrangement of β-silicon carbide particles.

[0083] The DC surface flashover voltage of the coatings in the examples and comparative examples was tested, and the results are as follows: Figure 4 As shown, the coatings prepared by in-situ electric field induction, plasma strengthening, and in-situ electric field induction exhibit higher flashover voltages compared to those prepared by direct coating.

[0084] The adhesion of coatings prepared on insulating substrates under different plasma treatment times was also tested, and the results are as follows: Figure 5 As shown, compared to Comparative Example 1 without plasma treatment, the adhesion strength of Examples 1-3 after plasma treatment is significantly greater and shows an increasing trend over time. This is because plasma modification treatment optimizes the bonding process between the nonlinear conductive coating and the insulating substrate. By utilizing the impact of high-energy plasma particles, three bonding effects—mechanical interlocking, physical adsorption, and chemical bonding—can be introduced simultaneously on the surfaces of the coating and the insulating substrate, thereby enhancing the adhesion of the coating to the insulating substrate surface.

[0085] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a plasma-enhanced nonlinear conductive coating, characterized in that, include, A composite coating is applied to the surface of an insulating substrate, and then cured under the action of an electric field to obtain the coating. The composite coating comprises a nonlinear conductive material and a coating matrix; The nonlinear conductive material and the insulating substrate are subjected to plasma treatment. Nonlinear conductive materials undergo silanization treatment before plasma treatment; The coating matrix is ​​composed of coating, curing agent and accelerator; The nonlinear conductive material constitutes 1-10% of the mass of the coating matrix; The plasma treatment includes rinsing the gas for 1-10 minutes in a mixed gas of oxygen and / or argon with a gas flow rate of 100-200 mL / min, followed by dielectric barrier discharge and treatment for 1-10 minutes at a voltage peak of 1-10 kV. Plasma treatment optimizes the chain formation process of nonlinear conductive materials under the influence of electric field, enabling nonlinear conductive materials to obtain better nonlinear conductivity characteristics at lower doping levels. Plasma performs physical and chemical etching on the surface of the insulating substrate to introduce three bonding modes—mechanical interlocking, physical adsorption, and chemical bonding—at the coating-substrate interface, thereby enhancing the adhesion of the coating.

2. The method for preparing the plasma-enhanced nonlinear conductive coating according to claim 1, characterized in that, The insulating substrate is also cleaned before plasma treatment.

3. The method for preparing the plasma-enhanced nonlinear conductive coating according to claim 1, characterized in that, The particle size of the nonlinear conductive material is 5-100 μm.

4. The method for preparing the plasma-enhanced nonlinear conductive coating according to claim 1, characterized in that, The parameters for the induction treatment are: temperature 80-120℃, voltage amplitude 0.1-1kV, frequency 100-1000Hz, and time 2-12h.

5. A plasma-enhanced nonlinear conductive coating, characterized in that, It is obtained by the preparation method described in any one of claims 1-4.

6. The application of the plasma-enhanced nonlinear conductive coating of claim 5 in DC gas-insulated equipment.

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