High-temperature-resistant composite coating and preparation method thereof

Abstract

The application discloses a high-temperature-resistant composite coating and a preparation method thereof, and relates to the technical field of ceramic coating. A traditional ceramic coating is composed of a binder, a curing agent, aggregate and a functional additive. However, the traditional ceramic coating is brittle, has poor toughness and lubricity, and thus has poor wear resistance. In order to overcome the defects, the application uses modified aluminum dihydrogen phosphate as the binder, zinc oxide as the curing agent, and polytetrafluoroethylene as the functional additive, and further introduces silane-modified carbon fibers, so that the finally-prepared coating has the characteristics of wear resistance, corrosion resistance and high-temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of ceramic coating technology, specifically to a high-temperature resistant composite coating and its preparation method. Background Technology

[0002] Ceramic coatings are widely used in industrial equipment protection due to their high-temperature resistance and corrosion resistance. Traditional systems use aluminum dihydrogen phosphate as a binder, zinc oxide as a curing agent, and alumina as aggregate, with polytetrafluoroethylene (PTFE) added to improve lubricity. However, this type of coating has three inherent defects: First, the carbon fiber and ceramic matrix are only physically interlocked, resulting in weak interfacial bonding and easy debonding under alternating loads, leading to insufficient toughness; second, PTFE is prone to agglomeration, failing to form a continuous lubricating film, and its wear resistance deteriorates rapidly in high-temperature friction environments; third, aluminum dihydrogen phosphate is easily hydrolyzed in acidic or humid environments, causing binder failure. These problems result in coating lifespans generally less than 6 months in high-temperature multiphase flow and corrosive environments, making it difficult to meet the long-term protection requirements of thermal power, chemical, and other fields.

[0003] Addressing the inherent weaknesses of traditional coatings—brittleness, abrasion, and corrosion—this application achieves a breakthrough through a triple modification: First, aluminum dihydrogen phosphate is modified with silane, utilizing the active groups generated by acidic hydrolysis to condense with phosphate ions, forming a chemically bonded structure and enhancing the binder's resistance to environmental aging. Second, carbon fibers undergo surface roughening and silane coupling treatment to improve their dispersibility and interfacial bonding strength with ceramic aggregates, inhibiting crack propagation. Finally, through the synergistic effect of the hydrophobic groups in the polytetrafluoroethylene and silane system, a low-friction, corrosion-resistant composite functional layer is constructed on the coating surface. This modification strategy systematically improves the overall performance of the coating from three aspects: binder strengthening, enhanced phase interface optimization, and functional filler synergy. It solves the core problems of poor toughness, easy wear, and insufficient corrosion resistance in traditional ceramic coatings, providing a new solution for equipment protection in high-temperature and complex environments. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature resistant composite coating and its preparation method to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A high-temperature resistant composite coating and its preparation method are disclosed. The high-temperature resistant composite coating comprises the following components in parts by mass: 30-40% modified aluminum dihydrogen phosphate, 18-20% ceramic aggregate, 0.4-0.6% zinc oxide powder, 4-8% silane-modified carbon fiber, and the remainder being polytetrafluoroethylene dispersion emulsion.

[0007] Preferably, the modified aluminum dihydrogen phosphate is prepared by hydrolysis and polycondensation of methyltriethoxysilane and aluminum dihydrogen phosphate.

[0008] Preferably, the ceramic aggregate is one, two or more of silicon carbide, alumina, zirconium oxide, ceramic powder and tungsten carbide.

[0009] Preferably, the ceramic aggregate is alumina.

[0010] Preferably, the silane-modified carbon fiber is prepared by implanting seed crystals into the surface of carbon fiber after surface oxidation and then catalyzing seed crystal growth to obtain carbon fiber with zinc oxide attached to the surface. Subsequently, the carbon fiber with zinc oxide attached is modified by using silane coupling agent KH-570 to obtain silane-modified carbon fiber.

[0011] Preferably, the polytetrafluoroethylene dispersion emulsion has a mass fraction of 60%.

[0012] A method for preparing a high-temperature resistant composite coating, applicable to the high-temperature resistant composite coating mentioned above, includes the following steps:

[0013] S1. Add silane coupling agent KH-570 to an ethanol aqueous solution with a mass fraction of 70-80% at 14-16 times the mass of silane coupling agent KH-570, adjust the pH to 3.5-4.5, then add modified carbon fiber at 0.5-0.8 times the mass of silane coupling agent KH-570, stir and react for 30-40 minutes at a temperature of 30-40℃, filter and dry to obtain silane modified carbon fiber;

[0014] S2. Add methyltriethoxysilane to aluminum dihydrogen phosphate at 0.1 to 0.15 times the mass of methyltriethoxysilane, stir for 30 to 40 minutes at a temperature of 25 to 35°C, let stand for 15 to 20 minutes after stirring, and take off the lower layer of liquid to obtain modified aluminum dihydrogen phosphate.

[0015] S3. Weigh the modified aluminum dihydrogen phosphate, ceramic aggregate, zinc oxide powder, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion according to the above mass fractions. First, mix the ceramic aggregate and zinc oxide powder. After mixing, ultrasonically vibrate for 15-20 minutes. After ultrasonication, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion in sequence. Stir for 25-35 minutes at a temperature of 25-35℃ to obtain a high-temperature resistant coating.

[0016] Preferably, the modified carbon fiber comprises the following preparation steps: adding a zinc sulfate solution of 25-28% by mass to a sodium hydroxide solution of 12-15% by mass, which is 1.25-1.4 times the mass of the zinc sulfate solution; stirring and then filtering and drying; adding the dried filtered product to a sodium hydroxide solution of 7-8% by mass, which is 30-35 times the mass of the filtered product; then adding seed carbon fibers of 3-5 times the mass of the filtered product; stirring at a temperature of 25-35°C for 1-1.2 hours; then raising the temperature to 75-85°C and stirring for 2-2.5 hours; and finally filtering and drying to obtain the modified carbon fiber.

[0017] Preferably, the seed carbon fiber comprises the following preparation steps: adding zinc acetate dihydrate to anhydrous ethanol at 80-90 times its mass, ultrasonically dispersing for 30-35 min, then stirring at 25-35℃ for 1.5-2 h, adding surface-oxidized carbon fiber at 0.9-1.2 times its mass, and uniformly adding 0.1-0.125 mol / L sodium hydroxide ethanol solution at 0.9-1.2 times its mass, over 30-40 min. After the addition is complete, stirring continues for 10-15 min, followed by filtration, and drying the filtered product at 180-200℃ for 1-2 h to obtain the seed carbon fiber.

[0018] Preferably, the surface-oxidized carbon fiber includes the following preparation steps: placing the carbon fiber in an environment at a temperature of 400-450℃ for 1.5-2 hours, then taking it out and transferring it to a 0.1-0.15 mol / L sodium hydroxide solution with a mass of 50-60 times that of the carbon fiber, stirring for 1.5-2 hours, filtering out the solution, and drying it in an environment at a temperature of 55-65℃ for 12-14 hours to obtain the surface-oxidized carbon fiber.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] Traditional ceramic coatings consist of binders, curing agents, aggregates, and functional additives; however, they are brittle, lack toughness and lubricity, resulting in insufficient wear resistance. To overcome these shortcomings, this application uses modified aluminum dihydrogen phosphate as a binder, zinc oxide as a curing agent, and polytetrafluoroethylene as a functional additive, while also introducing silane-modified carbon fibers, aiming to give the final coating wear-resistant, corrosion-resistant, and high-temperature-resistant properties.

[0021] Specifically, aluminum dihydrogen phosphate is first modified using methyltriethoxysilane. Since aluminum dihydrogen phosphate is acidic, methyltriethoxysilane hydrolyzes in an acidic environment to generate active functional groups (hydroxyl groups). When the two are mixed, hydrolysis and condensation reactions occur, leading to their chemical bonding. This process improves upon the shortcomings of traditional aluminum dihydrogen phosphate, which is susceptible to the synergistic effects of alternating loads and corrosion, resulting in a shortened coating life.

[0022] On the other hand, modifying carbon fibers with zinc oxide adhering to their surface using the silane coupling agent KH-570 effectively improved the problems of agglomeration and uneven dispersion between carbon fibers and ceramic aggregates. Simultaneously, a seeding treatment was applied to the carbon fiber surface to roughen it, enhancing its interfacial bonding performance with other materials. Furthermore, zinc oxide, as a modifying material, promoted reaction curing, significantly improving not only the interfacial peeling ability of carbon fibers in the coating but also enhancing the coating's crack resistance. Moreover, the condensation polymerization between the silane coupling agent KH-570 and methyltriethoxysilane formed chemical bonds, further strengthening the internal bonding strength of the coating. The hydrophobic groups introduced by both, synergistically with polytetrafluoroethylene, improved the overall hydrophobicity of the coating. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] S1. After placing the carbon fiber in an environment at 400℃ for 1.5h, take it out and transfer it to a 0.1mol / L sodium hydroxide solution with 50 times the weight of the carbon fiber. Stir for 1.5h, filter it out, and dry it in an environment at 55℃ for 12h to obtain surface oxidized carbon fiber.

[0026] S2. Add zinc acetate dihydrate to anhydrous ethanol at 80 times the mass of zinc acetate dihydrate, ultrasonically disperse for 30 min, and then stir at 25℃ for 1.5 h. After stirring, add surface-oxidized carbon fiber at 0.9 times the mass of zinc acetate dihydrate. After adding, add 0.1 mol / L sodium hydroxide ethanol solution at 0.9 times the mass of anhydrous ethanol at a uniform rate over 30 min. After adding, continue stirring for 10 min. After stirring, filter and place the filtered product at 180℃ for 1 h to obtain seed carbon fiber.

[0027] S3. Add 25% zinc sulfate solution to 1.25 times the mass of zinc sulfate solution to 12% sodium hydroxide solution. Stir and filter to dry. Add the dried filter product to 30 times the mass of the filter product to 7% sodium hydroxide solution. Add seed carbon fiber to 3 times the mass of the filter product. Stir at 25°C for 1 hour. Then raise the temperature to 75°C and stir for 2 hours. After stirring, filter and dry to obtain modified carbon fiber.

[0028] S4. Add silane coupling agent KH-570 to a 70% ethanol aqueous solution with a mass fraction of 14 times that of silane coupling agent KH-570, adjust the pH to 3.5, then add modified carbon fiber with a mass fraction of 0.5 times that of silane coupling agent KH-570, stir and react for 30 min at a temperature of 30℃, filter and dry to obtain silane modified carbon fiber.

[0029] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate at 0.1 times the mass of methyltriethoxysilane, stir for 30 min at 25℃, let stand for 15 min after stirring, and take off the lower layer of liquid to obtain modified aluminum dihydrogen phosphate.

[0030] S6. Weigh out 30% modified aluminum dihydrogen phosphate, 18% alumina, 0.4% zinc oxide powder, and 4% silane-modified carbon fiber by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, mix the alumina and zinc oxide powder, and then ultrasonically vibrate for 15 minutes. After ultrasonication, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion in sequence. Stir for 25 minutes at 25°C to obtain a high-temperature resistant coating.

[0031] Example 2

[0032] S1. After placing the carbon fiber in an environment at 425℃ for 1.75h, take it out and transfer it to a 0.125mol / L sodium hydroxide solution with 55 times the weight of the carbon fiber. Stir for 1.75h, filter it out, and dry it in an environment at 60℃ for 13h to obtain surface oxidized carbon fiber.

[0033] S2. Add zinc acetate dihydrate to anhydrous ethanol at 85 times its mass and ultrasonically disperse for 32.5 min. Then stir at 30℃ for 1.75 h. After stirring, add surface-oxidized carbon fiber at 1.05 times its mass of zinc acetate dihydrate. After adding, add 0.1125 mol / L sodium hydroxide ethanol solution at 1.05 times its mass of anhydrous ethanol at a uniform rate over 35 min. After adding, continue stirring for 12.5 min. After stirring, filter and dry the filtered product at 190℃ for 1.5 h to obtain seed carbon fiber.

[0034] S3. Add a zinc sulfate solution with a mass fraction of 26.5% to a sodium hydroxide solution with a mass fraction of 13.5% (1.325 times the mass of the zinc sulfate solution), stir, filter and dry. Add the dried filter product to a sodium hydroxide solution with a mass fraction of 7.5% (32.5 times the mass of the filter product), and then add seed carbon fibers with a mass fraction of 4 times the mass of the filter product. Stir at 30°C for 1.1 h, then raise the temperature to 80°C and stir for 2.25 h. After stirring, filter and dry to obtain modified carbon fibers.

[0035] S4. Add silane coupling agent KH-570 to a 75% ethanol aqueous solution with a mass fraction of 15 times that of silane coupling agent KH-570, adjust the pH to 4, then add modified carbon fiber with a mass fraction of 0.65 times that of silane coupling agent KH-570, stir and react for 35 min at a temperature of 35℃, filter and dry to obtain silane modified carbon fiber.

[0036] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate at 0.125 times the mass of methyltriethoxysilane, stir for 35 min at 30℃, let stand for 17.5 min after stirring, and take off the lower layer of liquid to obtain modified aluminum dihydrogen phosphate.

[0037] S6. Weigh out 35% modified aluminum dihydrogen phosphate, 19% alumina, 0.5% zinc oxide powder, and 6% silane-modified carbon fiber by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, mix the alumina and zinc oxide powder, and then ultrasonically vibrate for 17.5 min. After ultrasonication, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion in sequence. Stir for 30 min at 30℃ to obtain a high-temperature resistant coating.

[0038] Example 3

[0039] S1. After placing the carbon fiber in an environment at 450℃ for 2 hours, remove it and transfer it to a 0.15mol / L sodium hydroxide solution with 60 times the mass of the carbon fiber. Stir for 2 hours, filter and remove it. Dry it in an environment at 65℃ for 14 hours to obtain surface oxidized carbon fiber.

[0040] S2. Add zinc acetate dihydrate to anhydrous ethanol at 90 times the mass of zinc acetate dihydrate, ultrasonically disperse for 35 min, and then stir at 35℃ for 2 h. After stirring, add surface-oxidized carbon fiber at 1.2 times the mass of zinc acetate dihydrate. After adding, add 0.125 mol / L sodium hydroxide ethanol solution at 1.2 times the mass of anhydrous ethanol at a uniform rate over 40 min. After adding, continue stirring for 15 min. After stirring, filter and place the filtered product at 200℃ for 2 h to obtain seed carbon fiber.

[0041] S3. Add 28% zinc sulfate solution to 1.4 times the mass of zinc sulfate solution to 15% sodium hydroxide solution. Stir and filter to dry. Add the dried filter product to 35 times the mass of the filter product to 8% sodium hydroxide solution. Add 5 times the mass of the filter product to seed carbon fiber. Stir at 35°C for 1.2 hours. Then raise the temperature to 85°C and stir for 2.5 hours. After stirring, filter and dry to obtain modified carbon fiber.

[0042] S4. Add silane coupling agent KH-570 to an 80% ethanol aqueous solution with a mass fraction of 16 times that of silane coupling agent KH-570, adjust the pH to 4.5, then add modified carbon fiber with a mass fraction of 0.8 times that of silane coupling agent KH-570, stir and react for 40 min at a temperature of 40℃, filter and dry to obtain silane modified carbon fiber.

[0043] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate at 0.15 times the mass of methyltriethoxysilane, stir for 40 min at 35℃, let stand for 20 min after stirring, and take off the lower layer of liquid to obtain modified aluminum dihydrogen phosphate.

[0044] S6. Weigh out 40% modified aluminum dihydrogen phosphate, 20% alumina, 0.6% zinc oxide powder, and 8% silane-modified carbon fiber by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, mix the alumina and zinc oxide powder, and then ultrasonically vibrate for 20 minutes. After ultrasonication, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion in sequence. Stir for 35 minutes at a temperature of 35°C to obtain a high-temperature resistant coating.

[0045] Example 4

[0046] The difference from Example 2 is only in step S6: 35% aluminum dihydrogen phosphate, 19% alumina, 0.5% zinc oxide powder, and 6% silane-modified carbon fiber are weighed by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, the alumina and zinc oxide powder are mixed, and after mixing, the mixture is ultrasonically vibrated for 17.5 min. After ultrasonication, aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion are added in sequence. The mixture is stirred for 30 min at a temperature of 30°C to obtain a high-temperature resistant coating.

[0047] Example 5

[0048] The difference from Example 2 is only in step S6: 35% modified aluminum dihydrogen phosphate, 19% alumina, 0.5% zinc oxide powder, and 6% modified carbon fiber are weighed by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, the alumina and zinc oxide powder are mixed, and after mixing, the mixture is ultrasonically vibrated for 17.5 min. After ultrasonication, the modified aluminum dihydrogen phosphate, modified carbon fiber, and polytetrafluoroethylene dispersion emulsion are added sequentially. The mixture is stirred for 30 min at a temperature of 30°C to obtain a high-temperature resistant coating.

[0049] Example 6

[0050] The difference from Example 2 is only in step S6: 35% modified aluminum dihydrogen phosphate, 19% alumina, 0.5% zinc oxide powder, and 6% carbon fiber are weighed by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, the alumina and zinc oxide powder are mixed, and after mixing, the mixture is ultrasonically vibrated for 17.5 min. After ultrasonication, the modified aluminum dihydrogen phosphate, carbon fiber, and polytetrafluoroethylene dispersion emulsion are added in sequence. The mixture is stirred for 30 min at a temperature of 30°C to obtain a high-temperature resistant coating.

[0051] Example 7

[0052] The difference from Example 2 is only in step S4: 35% aluminum dihydrogen phosphate, 19% alumina, 0.5% zinc oxide powder, and 6% carbon fiber are weighed by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. First, the alumina and zinc oxide powder are mixed, and after mixing, the mixture is ultrasonically vibrated for 17.5 min. After ultrasonication, aluminum dihydrogen phosphate, carbon fiber, and polytetrafluoroethylene dispersion emulsion are added in sequence. The mixture is stirred for 30 min at a temperature of 30°C to obtain a high-temperature resistant coating.

[0053] Example 8

[0054] The difference from Example 2 is only in step S6: 35% modified aluminum dihydrogen phosphate, 19% alumina, and 0.5% zinc oxide powder are weighed by mass fraction, with the remainder being polytetrafluoroethylene dispersion emulsion. The alumina and zinc oxide powder are mixed first, and then ultrasonically vibrated for 17.5 min. After ultrasonication, the modified aluminum dihydrogen phosphate and polytetrafluoroethylene dispersion emulsion are added in sequence, and the mixture is stirred for 30 min at 30°C to obtain a high-temperature resistant coating.

[0055] Example 9

[0056] The high-temperature resistant coatings prepared in Examples 1-8 were sprayed onto the substrate surface by air spraying. After spraying, the coatings were allowed to stand for 24 hours. After standing, step curing was performed. The step curing temperatures were 50°C for 30 minutes; 100°C for 30 minutes; 150°C for 15 minutes; 250°C for 105 minutes; and 350°C for 15 minutes. After curing, the coatings were cooled to room temperature to obtain the high-temperature resistant coating.

[0057] Hardness test

[0058] The Vickers microhardness tester was used. The measuring indenter was a diamond square pyramid with an angle of 136° between the opposite faces. The applied load was 980.7 mN and the holding time was 12 s. Six points were measured for each sample. The measurement results were obtained by removing the maximum and minimum values ​​and taking the average value as the coating hardness.

[0059] Combined strength test

[0060] According to GB / T9286-2021, the bonding strength of the coating is evaluated using the cross-cut test, and finally the bonding strength of the coating is graded and evaluated according to the evaluation criteria.

[0061] Hydrophobicity measurement

[0062] Deionized water was dropped onto the coating surface, and the contact angle was measured using an image analysis method with a contact angle meter. Five measurements were taken at each location, and the average value was taken as the coating contact angle.

[0063] The experimental results are shown in Table 1 below;

[0064] Table 1

[0065]

[0066]

[0067] A comparison of the experimental data from Examples 1 to 3 in Table 1 shows that the high-temperature resistant coating prepared by the present invention has good hardness, bonding strength and hydrophobic properties.

[0068] Examples 4-7 show a gradual decrease in hardness and hydrophobicity. In Example 4, aluminum dihydrogen phosphate was not modified; in Example 5, modified carbon fiber was not modified; in Example 6, carbon fiber was used as a substitute; and in Example 7, neither aluminum dihydrogen phosphate nor carbon fiber was modified. The data shows that the performance of the high-temperature resistant coating gradually decreased, with the most significant decrease in Example 8, which was due to the absence of carbon fiber. However, the contact angle increased somewhat, mainly because adding carbon fiber without modification after reaching a certain content would affect the hydrophobicity of the coating.

[0069] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a high-temperature resistant composite coating, characterized in that, The high-temperature resistant composite coating consists of the following components by mass percentage: 30-40% modified aluminum dihydrogen phosphate, 18-20% ceramic aggregate, 0.4-0.6% zinc oxide powder, 4-8% silane-modified carbon fiber, and the remainder being polytetrafluoroethylene dispersion emulsion. S1. Add silane coupling agent KH-570 to an ethanol aqueous solution with a mass fraction of 70-80% at 14-16 times the mass of silane coupling agent KH-570, adjust the pH to 3.5-4.5, then add modified carbon fiber at 0.5-0.8 times the mass of silane coupling agent KH-570, stir and react for 30-40 minutes at a temperature of 30-40℃, filter and dry to obtain silane modified carbon fiber; S2. Add methyltriethoxysilane to aluminum dihydrogen phosphate at 0.1 to 0.15 times the mass of methyltriethoxysilane, stir for 30 to 40 minutes at a temperature of 25 to 35°C, let stand for 15 to 20 minutes after stirring, and take off the lower layer of liquid to obtain modified aluminum dihydrogen phosphate. S3. Weigh the modified aluminum dihydrogen phosphate, ceramic aggregate, zinc oxide powder, silane-modified carbon fiber and polytetrafluoroethylene dispersion emulsion according to the above mass fractions. First, mix the ceramic aggregate and zinc oxide powder. After mixing, ultrasonically vibrate for 15-20 minutes. After ultrasonication, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber and polytetrafluoroethylene dispersion emulsion in sequence. Stir for 25-35 minutes at a temperature of 25-35℃ to obtain a high-temperature resistant coating. The modified carbon fiber comprises the following preparation steps: adding a zinc sulfate solution of 25-28% by mass to a sodium hydroxide solution of 12-15% by mass, which is 1.25-1.4 times the mass of the zinc sulfate solution; stirring and then filtration and drying; adding the dried filtration product to a sodium hydroxide solution of 7-8% by mass, which is 30-35 times the mass of the filtration product; adding seed carbon fiber, which is 3-5 times the mass of the filtration product; stirring at a temperature of 25-35℃ for 1-1.2 hours; then raising the temperature to 75-85℃ and stirring for 2-2.5 hours; and finally filtration and drying to obtain the modified carbon fiber. The seed carbon fiber comprises the following preparation steps: adding zinc acetate dihydrate to anhydrous ethanol at 80-90 times its mass, ultrasonically dispersing for 30-35 min, and then stirring at 25-35℃ for 1.5-2 h. After stirring, adding surface-oxidized carbon fiber at 0.9-1.2 times its mass of zinc acetate dihydrate, and then uniformly adding 0.1-0.125 mol / L sodium hydroxide ethanol solution at 0.9-1.2 times its mass of anhydrous ethanol over 30-40 min. After adding, stirring is continued for 10-15 min. After stirring, the mixture is filtered, and the filtered product is dried at 180-200℃ for 1-2 h to obtain the seed carbon fiber.

2. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The modified aluminum dihydrogen phosphate was prepared by hydrolysis and polycondensation of methyltriethoxysilane and aluminum dihydrogen phosphate.

3. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The ceramic aggregate is one, two, or a combination of more of the following: silicon carbide, alumina, zirconium oxide, ceramic powder, and tungsten carbide.

4. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The ceramic aggregate is alumina.

5. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The silane-modified carbon fiber is prepared by implanting seed crystals into the surface of carbon fiber after surface oxidation and then catalyzing seed crystal growth to obtain carbon fiber with zinc oxide attached to the surface. Subsequently, the carbon fiber with zinc oxide attached is modified by using silane coupling agent KH-570 to obtain silane-modified carbon fiber.

6. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The polytetrafluoroethylene dispersion emulsion has a mass fraction of 60%.

7. The method for preparing the high-temperature resistant composite coating according to claim 1, characterized in that, The surface-oxidized carbon fiber includes the following preparation steps: carbon fiber is placed in an environment at a temperature of 400~450℃ for 1.5~2h, then taken out and transferred to a sodium hydroxide solution of 0.1~0.15mol / L with a mass of 50~60 times that of the carbon fiber. After stirring for 1.5~2h, it is filtered out and dried in an environment at a temperature of 55~65℃ for 12~14h to obtain surface-oxidized carbon fiber.

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