Composite Coated Alumina Ceramics and Its Preparation Method

Abstract

The present invention provides a composite coating alumina ceramic and a preparation method thereof, which relates to the technical field of coated alumina ceramics and is composed of a sealed alumina ceramic component and a composite coating on its surface; the composite coating comprises the following raw materials for preparation in parts by mass: 10-25% charge dissipator, 5-10% zirconium boride nanopowder, 5-15% silicon-modified alumina nanowires, and the balance alumina; the charge dissipator comprises the following raw materials for preparation in parts by mass: 50 parts of flaky hexagonal boron nitride, 50-70 parts of rutile-type nano titanium oxide powder, 3-10 parts of aluminum borate whiskers, 5-15 parts of tetrabutyl titanate, 1-2 parts of dispersant, 0.5-1.5 parts of interfacial modifier, 0.2-0.5 parts of electrostatic stabilizer, and 20-50 parts of solvent. The composite coating of the present invention can provide a good charge dissipation effect for the sealed alumina ceramic component.

Description

Technical Field

[0001] The present invention belongs to the technical field of coated alumina ceramics, and specifically relates to a composite-coated alumina ceramic and a preparation method thereof. Background Art

[0002] Vacuum high-pressure alumina ceramic sealing components have been widely used in fields such as vacuum devices, high-voltage electrical equipment, semiconductor equipment, and aerospace and nuclear industries due to their excellent comprehensive performance. This component can withstand high-pressure and high-temperature environments, while maintaining good airtightness, and has corrosion resistance, wear resistance, and insulation properties.

[0003] Alumina ceramics have a relatively high vacuum breakdown withstand voltage. However, although traditional insulating coatings can achieve extremely high resistivity, their charge dissipation ability is poor, which easily leads to surface electrostatic deposition. This electrostatic deposition phenomenon will reduce the service life of the equipment, interfere with the normal operation of electronic equipment, and may even cause electrostatic breakdown. In addition, the coating materials in the prior art have the problem of excessive leakage current, making it difficult to meet the actual requirements of high-voltage insulation. Summary of the Invention

[0004] In order to overcome the above technical problems, the present invention provides a composite-coated alumina ceramic and a preparation method thereof. The composite coating of the present invention can provide a good charge dissipation effect for the sealed alumina ceramic component.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention provides a composite-coated alumina ceramic, which is composed of a sealed alumina ceramic component and a composite coating on its surface;

[0007] The composite coating includes the following preparation raw materials in parts by mass: 10-25% charge dissipator, 5-10% zirconium boride nanopowder, 5-15% silicon-modified alumina nanowire, and the balance alumina;

[0008] The charge dissipator includes the following preparation raw materials in parts by mass: 50 parts of flaky hexagonal boron nitride, 50-70 parts of rutile-type nano titanium oxide powder, 3-10 parts of aluminum borate whiskers, 5-15 parts of tetrabutyl titanate, 1-2 parts of dispersant, 0.5-1.5 parts of interfacial modifier, 0.2-0.5 parts of electrostatic stabilizer, and 20-50 parts of solvent.

[0009] Preferably, the composite coating includes the following preparation raw materials in parts by mass: 12-20% charge dissipator, 6-9% zirconium boride nanopowder, 7-12% silicon-modified alumina nanowire, and the balance alumina.

[0010] Preferably, the charge dissipating agent comprises the following raw materials in parts by mass: 50 parts of flaky hexagonal boron nitride, 50 - 60 parts of rutile-type nano titanium oxide powder, 3 - 6 parts of aluminum borate whiskers, 5 - 9 parts of tetrabutyl titanate, 1 - 2 parts of dispersant, 0.5 - 1.5 parts of interfacial modifier, 0.2 - 0.5 parts of electrostatic stabilizer, and 20 - 50 parts of solvent.

[0011] Among the raw materials for preparing the charge dissipating agent, the flaky hexagonal boron nitride has high in-plane thermal conductivity and interlayer insulation properties; the rutile-type nano titanium oxide powder has oxygen vacancy conductivity, which can provide a bulk dissipation path, and the nano titanium oxide can also fill the gaps between the flaky hexagonal boron nitride to reduce the interfacial contact resistance. The aluminum borate whiskers bridge the flaky hexagonal boron nitride lamellae, enhance toughness, and assist in charge transport. Tetrabutyl titanate hydrolyzes to form titanium oxide nanoparticles, densifies the coating, and bonds with the silane coupling agent.

[0012] In the present invention, the D50 of the alumina is 100 - 250 nm.

[0013] In the present invention, the D50 of the zirconium boride nanopowder is 40 - 60 nm.

[0014] In the present invention, the D50 of the flaky hexagonal boron nitride is 0.5 - 1 μm.

[0015] In the present invention, the D50 of the rutile-type nano titanium oxide powder is 20 - 40 nm.

[0016] In the present invention, the length of the aluminum borate whiskers is 10 - 60 μm, and the diameter is 0.3 - 3 μm.

[0017] In the present invention, the dispersant is polyvinylpyrrolidone or polyetheramine.

[0018] In the present invention, the electrostatic stabilizer is ammonium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, or sodium lignosulfonate.

[0019] In the present invention, the solvent is ethanol and propylene glycol monomethyl ether.

[0020] In the present invention, the interfacial modifier is 3-chloropropyltriethoxysilane (CAS No.: 5089-70-3), 3-chloropropyltrimethoxysilane (CAS No.: 2530-87-2), or 3-chloropropylmethyldimethoxysilane (CAS No.: 18171-19-2).

[0021] In the present invention, the preparation method of the charge dissipating agent: mix and disperse the above-mentioned raw materials to obtain a slurry, cast the slurry into a film, perform low-temperature hot pressing and crushing to obtain the charge dissipating agent.

[0022] Further, the dispersion process is to add flaky hexagonal boron nitride, rutile-type nano-titanium oxide powder, aluminum borate whiskers, a dispersant, and an electrostatic stabilizer into a solvent, ultrasonically disperse and ball-mill them, then add tetrabutyl titanate and an interfacial modifier, adjust the pH to 3 - 4, and obtain a slurry after aging;

[0023] Further, the knife-edge gap for tape casting is 80 - 100 μm.

[0024] Further, the baseband speed for tape casting is 0.3 - 0.6 m / min, for example, 0.5 m / min.

[0025] Further, the drying process for tape casting first heats from 30 - 40 °C to 75 - 85 °C and holds for 2 - 5 min, then cools to 55 - 65 °C and holds for 2 - 5 min; the heating / cooling rate in the drying process is 15 - 20 °C / min.

[0026] Further, the low-temperature hot pressing is to pre-press at 80 - 120 °C and 5 - 12 MPa for 3 - 5 min, hot press at 140 - 170 °C and 13 - 18 MPa for 8 - 12 min, and then hot press at 280 - 320 °C and 45 - 55 MPa for 20 - 30 min, and keep the pressure and cool to below 80 °C before demolding.

[0027] Further, the crushing is carried out by shear dispersion or air flow pulverization, and the discharge particle size is D50 = 5 - 8 μm.

[0028] In the present invention, the preparation method of the silicon-modified alumina nanowires: Place the alumina nanowires in a silane coupling agent solution, and then add ammonia water and react for 0.5 - 2 h.

[0029] In the present invention, the diameter of the alumina nanowires is 15 - 30 nm, and the length of the alumina nanowires is 1 - 3 μm.

[0030] In the present invention, the silane coupling agent is KH550 or KH560.

[0031] In the present invention, the mass concentration of the silane coupling solution is 1 - 5 wt%.

[0032] In the present invention, the mass ratio of the alumina nanowires to the silane coupling solution is 10 - 30:100.

[0033] In the present invention, the concentration of the ammonia water is 5 - 8 wt%, and the concentration of ammonia gas in the reaction kettle is controlled to be 0.5 - 1.0 vol%.

[0034] The present invention also discloses a preparation method of the aforementioned composite coating alumina ceramic, including the following steps:

[0035] S1. Preparation of coating slurry: Mix the raw materials for preparing the composite coating;

[0036] S2. Spraying: Plasma spray the coating slurry onto the surface of the sealed alumina ceramic component;

[0037] S3. Sintering: Sinter at 280 - 350 °C for 0.5 - 1 h, heat up to 750 - 850 °C with nitrogen and sinter for 1.5 - 2 h, then heat up to 1100 - 1200 °C under vacuum and sinter for 30 - 80 min.

[0038] In S1, the solid content of the coating slurry is 40 - 50%.

[0039] In S2, the power of the plasma spraying is 35 - 40 kW.

[0040] In S2, the Ar flow rate of the plasma spraying is 30 - 40 L / min and the H2 flow rate is 10 - 20 L / min.

[0041] In S2, the powder feeding rate of the plasma spraying is 15 - 20 g / min.

[0042] In S3, the heating rate during the sintering process is 5 - 10 °C / min.

[0043] In S3, after sintering, cool down to ≤80 °C in a nitrogen atmosphere and then take out of the furnace to obtain the composite - coated alumina ceramic.

[0044] On the basis of conforming to the common knowledge in the art, the above - mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] For the composite - coated alumina ceramic of the present invention, due to the good charge dissipation performance of the composite coating on the surface, electrostatic discharge can be achieved efficiently and rapidly under vacuum high - voltage conditions. In this composite coating, the conductive network provided by the charge dissipator can achieve electrostatic dissipation; zirconium boride nanoflakes have strong antioxidant ability at high temperatures, which can improve the thermal stability of the coating; silicon - modified alumina nanowires can improve the fracture toughness of the coating, enhancing the durability and adhesion of the coating.

[0047] The raw materials for preparing the composite coating have a reasonable formula, providing good charge dissipation performance, heat dissipation ability and mechanical properties for the coating. Among them, flaky hexagonal boron nitride acts as an insulating skeleton, and together with rutile - type nano - titanium oxide powder, forms a conductive - insulating network to promote charge dissipation; aluminum borate whiskers bridge the flaky hexagonal boron nitride lamellae, thereby enhancing the toughness of the coating and simultaneously improving the mechanical and electrical properties.

[0048] The surface resistivity of the composite coating alumina ceramic of the present invention in vacuum is 3 - 8× 10 10 Ω; the leakage current under high vacuum voltage is 2.2 - 4.5 nA / cm 2 , and in some preferred embodiments it is 3.5 - 4.5 nA / cm 2 ; the adhesion force ≥ 65 MPa, and in some preferred embodiments it is 70 - 80 MPa. Detailed implementation manners

[0049] For the convenience of understanding the present invention, the following will describe the present invention more comprehensively and meticulously in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0050] Unless otherwise defined, all the professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0051] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also anticipated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all anticipated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0052] If there is no special instruction, all the implementation manners and optional implementation manners of the present invention can be combined with each other to form new technical solutions.

[0053] If there is no special instruction, all the technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0054] Unless otherwise specified, all steps of the present invention can be carried out sequentially or randomly, preferably sequentially. For example, the method comprising steps (a) and (b) means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0055] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present invention mean open-ended, and can also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or contained, or may only include or contain the listed components.

[0056] Unless otherwise specified, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0057] The raw material information used in the following examples is as follows:

[0058] The D50 of zirconium boride nanopowder is 50 nm, and the specific surface area is 45 m 2 / g;

[0059] Aluminum oxide was purchased from Yumu New Materials YM-A1203-N200. The D50 of aluminum oxide is 200 nm, the crystal form of aluminum oxide is α / γ phase, and the microscopic morphology is spherical-like;

[0060] Aluminum oxide nanowires were purchased from Zhongke Leiming. The diameter of the aluminum oxide nanowires is 20 nm, and the (average) length is 1 μm;

[0061] Flaky hexagonal boron nitride was purchased from Zhejiang Yamei Nano Technology Co., Ltd., and D50 = 500 nm;

[0062] Rutile-type nano-titanium oxide powder was purchased from Zhongke Keyou ZKKY-T220, with a content of 99.9%, D50 = 20 nm, and a specific surface area of 60 m 2 / g;

[0063] Aluminum borate whiskers were purchased from Shanghai Fengzhu Composite New Materials. The composition of the aluminum borate whiskers is 9Al2O3·2B2O3. The length of the aluminum borate whiskers is 10 - 60 μm, the diameter is 0.3 - 3 μm, and the density is 2.93 g / cm 3;

[0064] The polyetheramine Mn (number average molecular weight) = 1000.

[0065] Example 1

[0066] 1. The composite coating alumina ceramic of this example is composed of a sealed alumina ceramic component and a composite coating on its surface.

[0067] The composite coating includes the following raw materials for preparation by mass: 15% charge dissipator, 7.5% zirconium boride nanopowder, 11.5% silicon-modified alumina nanowires, and the balance alumina.

[0068] The charge dissipator includes the following raw materials for preparation by mass: 50 parts of flaky hexagonal boron nitride, 55 parts of rutile-type nano titanium oxide powder, 5 parts of aluminum borate whiskers, 8 parts of tetrabutyl titanate, 1.2 parts of dispersant (polyvinylpyrrolidone), 0.7 part of interfacial modifier (3-chloropropylmethyldimethoxysilane), 0.28 part of electrostatic stabilizer (ammonium polyacrylate), and 30 parts of solvent (ethanol / propylene glycol methyl ether volume ratio 7:3)

[0069] Preparation method of the charge dissipator:

[0070] (1) Mixing and dispersion: Add flaky hexagonal boron nitride, rutile-type nano titanium oxide powder, aluminum borate whiskers, dispersant, and electrostatic stabilizer into the solvent according to the above ratio, ultrasonically disperse, ball mill, then add tetrabutyl titanate and interfacial modifier, adjust the pH to 3.5 with acetic acid, and stir and ripen at 25°C for 24 h to obtain a slurry;

[0071] (2) Casting into film: Cast the slurry into a film, the knife gap is 80 μm, the baseband speed is 0.5 m / min, and the drying process of casting into film is with a heating / cooling rate of 20°C / min, first heat from 40°C to 80°C, hold at 80°C for 2 min, and then cool to 60°C and hold for 2 min;

[0072] (3) Low-temperature hot pressing: Pre-press at 100°C and 10 MPa for 5 min, hot press at 150°C and 15 MPa for 10 min, then hot press at 300°C and 50 MPa for 30 min, and keep the pressure and cool to below 80°C to remove the mold;

[0073] (4) Crushing: Use shear dispersion until the D50 of the discharge particle size is 7 μm.

[0074] Preparation method of silicon-modified alumina nanowires:

[0075] The alumina nanowires were placed in a 2.5 wt% silane coupling agent KH550 solution, and then 5 wt% ammonia water was added and reacted for 1 h, controlling the ammonia concentration in the reaction kettle to be 0.5 vol%; the mass ratio of alumina nanowires to silane coupling solution was 15:100.

[0076] 2. The preparation method of the composite coating alumina ceramic in this example is as follows:

[0077] S1. Prepare the coating slurry: Add water to the mixture of the composite coating to make a coating slurry with a solid content of 45%.

[0078] S2. Spraying: Plasma spray the coating slurry onto the surface of the sealed alumina ceramic component; the plasma spraying power is 35 kW, the Ar flow rate during plasma spraying is 40 L / min, the H2 flow rate is 10 L / min, and the powder feeding rate is 20 g / min.

[0079] S3. Sintering: The heating rate during sintering is 10 °C / min, heat up to 300 °C at 20 °C and sinter for 1 h, then heat up to 800 °C by introducing nitrogen and sinter for 2 h, heat up to 1200 °C under vacuum and sinter for 30 min, and cool down to below 80 °C by filling nitrogen and then take out of the furnace.

[0080] Example 2

[0081] The difference between this example and Example 1 is as follows:

[0082] The composite coating includes the following raw materials by mass: 20% charge dissipator, 6.1% zirconium boride nanopowder, 7.4% silicon-modified alumina nanowires, and the balance alumina.

[0083] All other raw materials, steps, and parameters are the same as those in Example 1.

[0084] Example 3

[0085] The difference between this example and Example 1 is as follows:

[0086] The charge dissipator includes the following raw materials by mass: 50 parts of flaky hexagonal boron nitride, 60 parts of rutile-type nano-titanium oxide powder, 6 parts of aluminum borate whiskers, 5 parts of tetrabutyl titanate, 1.8 parts of dispersant (polyetheramine), 1.4 parts of interfacial modifier (3-chloropropyltrimethoxysilane), 0.49 part of electrostatic stabilizer (sodium polystyrene sulfonate), and 40 parts of solvent.

[0087] All other raw materials, steps, and parameters are the same as those in Example 1.

[0088] Example 4

[0089] The difference between this example and Example 1 is as follows:

[0090] The charge dissipator comprises the following raw materials for preparation in parts by mass: 50 parts of flaky hexagonal boron nitride, 30 parts of rutile-type nano titanium oxide powder, 5 parts of aluminum borate whiskers, 7.2 parts of tetrabutyl titanate, 1.8 parts of dispersant, 1.1 parts of interfacial modifier, 0.44 parts of electrostatic stabilizer and 30 parts of solvent.

[0091] All other raw materials, steps and parameters are the same as those in Example 1.

[0092] Example 5

[0093] The difference between this example and Example 1 lies in:

[0094] In the low-temperature hot pressing in step (3) of the preparation method of the charge dissipator: pre-press at 120 °C and 10 MPa for 3 min, hot press at 160 °C and 13 MPa for 8 min, and then hot press at 280 °C and 50 MPa for 20 min, and keep the pressure and cool to below 80 °C to remove the mold.

[0095] All other raw materials, steps and parameters are the same as those in Example 1.

[0096] Example 6

[0097] The difference between this example and Example 1 lies in:

[0098] Preparation method of silicon-modified alumina nanowires:

[0099] Place the alumina nanowires in a 3.0 wt% solution of silane coupling agent KH560, then add 8 wt% ammonia water and react for 0.5 h, controlling the ammonia concentration in the reaction kettle to be 0.5 vol%; the mass ratio of alumina nanowires to silane coupling solution is 10:100.

[0100] All other raw materials, steps and parameters are the same as those in Example 1.

[0101] Comparative Example 1

[0102] This comparative example does not add rutile-type nano titanium oxide powder. The difference between this comparative example and Example 1 lies in:

[0103] The charge dissipator comprises the following raw materials for preparation in parts by mass: 50 parts of flaky hexagonal boron nitride, 5 parts of aluminum borate whiskers, 5 parts of tetrabutyl titanate, 1.2 parts of dispersant, 1.0 part of interfacial modifier, 0.2 parts of electrostatic stabilizer and 25 parts of solvent.

[0104] All other raw materials, steps and parameters are the same as those in Example 1.

[0105] Comparative Example 2

[0106] This comparative example does not add aluminum borate whiskers. The difference between this comparative example and Example 1 lies in:

[0107] The charge dissipating agent comprises the following raw materials for preparation in parts by mass: 50 parts of flaky hexagonal boron nitride, 60 parts of rutile-type nano titanium oxide powder, 6 parts of tetrabutyl titanate, 1.3 parts of dispersant, 1.4 parts of interfacial modifier, 0.28 part of electrostatic stabilizer and 35 parts of solvent.

[0108] Other raw materials, steps and parameters are the same as those in Example 1.

[0109] Comparative Example 3

[0110] The difference between this comparative example and Example 1 lies in:

[0111] S3. Sintering: The heating rate during the sintering process is 10 °C / min, and it is sintered at 1200 °C for 40 min.

[0112] Other raw materials, steps and parameters are the same as those in Example 1.

[0113] Test Example

[0114] The composite coating alumina ceramics prepared in the above examples and comparative examples are tested for insulation performance and leakage current performance, and the test results are shown in Table 1.

[0115] The test method for surface resistivity refers to GB / T 1410, and the test is carried out in a vacuum environment of 10 -3 Pa;

[0116] The test method for leakage current refers to GB / T 5594.4, and the test is carried out under the vacuum high voltage conditions of 10 -3 Pa and 20 kV / mm;

[0117] The test method for adhesion refers to ISO 20502.

[0118] .

[0119] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods. The specific embodiments described above further illustrate the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Composite coating alumina ceramics, characterized in that, It consists of a sealed alumina ceramic component and a composite coating on its surface; The composite coating comprises the following raw materials in parts by mass: 10 - 25% charge dissipator, 5 - 10% zirconium boride nanopowder, 5 - 15% silicon-modified alumina nanowires, and the balance alumina; The charge dissipator comprises the following raw materials in parts by mass: 50 parts of flaky hexagonal boron nitride, 50 - 70 parts of rutile-type nano titanium oxide powder, 3 - 10 parts of aluminum borate whiskers, 5 - 15 parts of tetrabutyl titanate, 1 - 2 parts of dispersant, 0.5 - 1.5 parts of interfacial modifier, 0.2 - 0.5 parts of electrostatic stabilizer, and 20 - 50 parts of solvent.

2. The composite coating alumina ceramic according to claim 1, characterized in that, Meet at least one of the following conditions ① - ⑤: ① The D50 of the alumina is 100 - 250 nm; ② The D50 of the zirconium boride nanopowder is 40 - 60 nm; ③ The D50 of the flaky hexagonal boron nitride is 0.5 - 1 μm; ④ The D50 of the rutile-type nano titanium oxide powder is 20 - 40 nm; ⑤ The length of the aluminum borate whiskers is 10 - 60 μm and the diameter is 0.3 - 3 μm.

3. The composite coating alumina ceramic according to claim 1, characterized in that, Meet at least one of the following conditions ① - ④: ① The dispersant is polyvinylpyrrolidone or polyetheramine; ② The electrostatic stabilizer is ammonium polyacrylate, sodium polystyrene sulfonate, polyethyleneimine, sodium polyacrylate, or sodium lignosulfonate; ③ The solvent is ethanol and propylene glycol methyl ether; ④ The interfacial modifier is 3-chloropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, or 3-chloropropylmethyldimethoxysilane.

4. The composite coating alumina ceramic according to claim 1, characterized in that, The preparation method of the charge dissipator: Mix and disperse the preparation raw materials to obtain a slurry, cast the slurry into a film, perform low-temperature hot pressing and crushing to obtain the charge dissipator.

5. The composite coating alumina ceramic according to claim 4, wherein Meet at least one of the following conditions ① - ⑤: ① The dispersion process is to add flaky hexagonal boron nitride, rutile-type nano titanium oxide powder, aluminum borate whiskers, dispersant, and electrostatic stabilizer into the solvent, ultrasonically disperse and ball mill, then add tetrabutyl titanate and interfacial modifier, adjust the pH to 3 - 4, and age to obtain the slurry; ② The knife-edge gap for casting into a film is 80 - 100 μm, and the baseband speed for casting into a film is 0.3 - 0.6 m / min; ③ The drying process for casting into a film first heats from 30 - 40 °C to 75 - 85 °C and holds for 2 - 5 min, then cools to 55 - 65 °C and holds for 2 - 5 min; the heating / cooling rate in the drying process is 15 - 20 °C / min; ④ The low-temperature hot pressing is pre-pressed at 80 - 120 °C and 5 - 12 MPa for 3 - 5 min, hot-pressed at 140 - 170 °C and 13 - 18 MPa for 8 - 12 min, and then hot-pressed at 280 - 320 °C and 45 - 55 MPa for 20 - 30 min, and the mold is removed after cooling to below 80 °C while maintaining this pressure; ⑤ The crushing is carried out by shear dispersion or air jet milling, and the particle size of the discharged material is D50 = 5 - 8 μm.

6. The composite coating alumina ceramic according to claim 1, characterized in that, The preparation method of the silicon-modified alumina nanowires: Place the alumina nanowires in a silane coupling agent solution, and then add ammonia water and react for 0.5 - 2 h.

7. The composite coating alumina ceramic according to claim 6, wherein, Meet at least one of the following conditions ① - ④: ① The diameter of the alumina nanowires is 15 - 30 nm, and the length of the alumina nanowires is 1 - 3 μm; ② The silane coupling agent is KH550 or KH560; ③ The mass concentration of the silane coupling solution is 1 - 5 wt%; ④ The mass ratio of the alumina nanowires to the silane coupling solution is 10 - 30:

100.

8. The preparation method of the composite coating alumina ceramic according to any one of claims 1 to 7, characterized in that, It includes the following steps: S1. Prepare the coating slurry: Mix the raw materials for preparing the composite coating; S2. Spraying: Plasma spray the coating slurry onto the surface of the sealed alumina ceramic component; S3. Sintering: Sinter at 280 - 350 °C for 0.5 - 1 h, heat up to 750 - 850 °C in nitrogen atmosphere and sinter for 1.5 - 2 h, then heat up to 1100 - 1200 °C under vacuum and sinter for 30 - 80 min.

9. The preparation method of the composite coating alumina ceramic according to claim 8, wherein Meet at least one of the following conditions ① - ④: ① The solid content of the coating slurry is 40 - 50%; ② The power of the plasma spraying is 35 - 40 kW; ③ The Ar flow rate of the plasma spraying is 30 - 40 L / min and the H2 flow rate is 10 - 20 L / min; ④ The powder feeding rate of the plasma spraying is 15 - 20 g / min.

10. The preparation method of the composite coating alumina ceramic according to claim 8, characterized in that, Meet at least one of the following conditions ① - ②: ① The heating rate during the sintering process is 5 - 10 °C / min; ② After sintering, cool down to ≤80 °C in nitrogen atmosphere and then take out of the furnace.