High-temperature-resistant composite coating and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant composite coating and a preparation method thereof, and relates to the technical field of ceramic coatings. A traditional ceramic coating is composed of a binder, a curing agent, aggregate and a functional additive, but the traditional ceramic coating is high in brittleness and poor in toughness and lubricity, so that the wear resistance is insufficient. In order to overcome the defects, modified aluminum dihydrogen phosphate is used as a binder, zinc oxide is used as a curing agent, polytetrafluoroethylene is used as a functional additive, and silane modified carbon fibers are introduced, so that the finally prepared coating has the characteristics of wear resistance, corrosion resistance and high temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic coatings, and particularly to a high-temperature resistant composite coating and a preparation method thereof. Background Art

[0002] Ceramic coatings are widely used in the protection of industrial equipment due to their high temperature resistance and corrosion resistance. The traditional system uses aluminum dihydrogen phosphate as a binder, zinc oxide as a curing agent, alumina as an aggregate, and polytetrafluoroethylene is added to improve lubricity. However, such coatings have three inherent defects: First, the carbon fiber and the ceramic matrix are only physically embedded, the interfacial bonding is weak, and debonding is likely to occur under alternating loads, resulting in insufficient toughness; Second, polytetrafluoroethylene is prone to agglomeration and cannot form a continuous lubricating film, and the wear resistance decays rapidly in a high-temperature friction environment; Third, aluminum dihydrogen phosphate is prone to hydrolysis in an acidic or humid and hot environment, resulting in the failure of the binder. The above problems lead to the service life of the coating being generally less than 6 months in a high-temperature multiphase flow and corrosive environment, and it is difficult to meet the long-term protection requirements in fields such as thermal power and chemical engineering.

[0003] In view of the "brittleness, abrasion, and corrosion" pain points of traditional coatings, this application achieves a breakthrough through triple modification: First, aluminum dihydrogen phosphate is modified with silane. The active groups generated by acid hydrolysis are polycondensed with phosphate groups to form a chemical bonding structure, enhancing the environmental aging resistance of the binder; Second, the carbon fiber is subjected to surface roughening and silane coupling treatment to improve its dispersibility and interfacial bonding strength with the ceramic aggregate and inhibit crack propagation; Finally, through the synergy of the hydrophobic groups of polytetrafluoroethylene and the silane system, a low-friction and corrosion-resistant composite functional layer is constructed on the coating surface. This modification strategy systematically improves the comprehensive performance of the coating from three aspects: binder strengthening, enhanced phase interface optimization, and functional filler synergy, solves the core problems of poor toughness, easy wear, and insufficient corrosion resistance of traditional ceramic coatings, and provides a new solution for the protection of equipment in high-temperature and complex environments. Summary of the Invention

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

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] A high-temperature resistant composite coating and a preparation method thereof, the mass fractions of the components of the high-temperature resistant composite coating are as follows: modified aluminum dihydrogen phosphate 30-40%, ceramic aggregate 18-20%, zinc oxide powder 0.4-0.6%, silane-modified carbon fiber 4-8%, and the rest is a 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 a combination of more of silicon carbide, aluminum oxide, zirconium oxide, porcelain powder and tungsten carbide.

[0009] Preferably, the ceramic aggregate is aluminum oxide.

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

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

[0012] A preparation method of a high-temperature resistant composite coating, which is applied to the high-temperature resistant composite coating in the above, includes the following steps:

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

[0014] S2. Add methyltriethoxysilane to aluminum dihydrogen phosphate that is 0.1-0.15 times the mass of methyltriethoxysilane, and under the condition of a temperature of 25-35 °C, stir for 30-40 min. After stirring, let it stand for 15-20 min, and take the lower layer liquid to obtain the 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 the zinc oxide powder, and after mixing, perform ultrasonic vibration for 15-20 min. After ultrasonic vibration, add the modified aluminum dihydrogen phosphate, silane-modified carbon fiber and polytetrafluoroethylene dispersion emulsion in sequence. Under the condition of a temperature of 25-35 °C, stir for 25-35 min to obtain the high-temperature resistant coating.

[0016] Preferably, the modified carbon fiber includes the following preparation steps: adding a zinc sulfate solution with a mass fraction of 25-28% into a sodium hydroxide solution with a mass fraction of 12-15% and a mass 1.25-1.4 times that of the zinc sulfate solution, stirring, filtering, and drying; adding the dried filtered product into a sodium hydroxide solution with a mass fraction of 7-8% and a mass 30-35 times that of the filtered product, adding seeded carbon fiber with a mass 3-5 times that of the filtered product, stirring at 25-35°C for 1-1.2 h, then heating to 75-85°C and stirring for 2-2.5 h, filtering and drying after stirring to obtain the modified carbon fiber.

[0017] Preferably, the seeded carbon fiber includes the following preparation steps: adding zinc acetate dihydrate into absolute ethanol with a mass 80-90 times that of the zinc acetate dihydrate, ultrasonically dispersing for 30-35 min, stirring at 25-35°C for 1.5-2 h, adding surface oxidized carbon fiber with a mass 0.9-1.2 times that of the zinc acetate dihydrate after stirring, uniformly dropping a 0.1-0.125 mol / L sodium hydroxide ethanol solution with a mass 0.9-1.2 times that of the absolute ethanol within 30-40 min after adding, continuing to stir for 10-15 min after dropping, filtering, and drying the filtered product at 180-200°C for 1-2 h to obtain the seeded carbon fiber.

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

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

[0020] The traditional ceramic coating is composed of a binder, a curing agent, an aggregate, and a functional additive. However, it has high brittleness, poor toughness and lubricity, resulting in insufficient wear resistance. To overcome these defects, the present application uses modified aluminum dihydrogen phosphate as the binder, zinc oxide as the curing agent, polytetrafluoroethylene as the functional additive, and introduces silane-modified carbon fiber, aiming to make the finally prepared coating have the characteristics of wear resistance, corrosion resistance, and high temperature resistance;

[0021] Specifically, aluminum dihydrogen phosphate was first modified with methyltriethoxysilane. Given that aluminum dihydrogen phosphate is acidic, methyltriethoxysilane will hydrolyze to form active functional groups of hydroxyl in an acidic environment, and hydrolysis and polycondensation reactions will occur when the two are mixed, and then they will be combined in the form of chemical bonds. This process improves the drawback that traditional aluminum dihydrogen phosphate is easily affected by the combined action of alternating loads and corrosion, resulting in a shortened coating life.

[0022] On the other hand, carbon fibers with zinc oxide attached to the surface were modified with silane coupling agent KH-570, effectively improving the problems of agglomeration and uneven dispersion between carbon fibers and ceramic aggregates. At the same time, the surface of the carbon fibers was roughened by seeding treatment, enhancing its interfacial bonding performance with other materials. In addition, zinc oxide as a modification material can promote reaction curing, not only significantly improving the interfacial peeling ability of carbon fibers in the coating, but also enhancing the crack resistance of the coating. Moreover, a chemical bond will be generated by the polycondensation between silane coupling agent KH-570 and methyltriethoxysilane, further enhancing the internal bonding strength of the coating. The hydrophobic groups introduced by the two and polytetrafluoroethylene synergistically improve the hydrophobic ability of the overall coating. Specific implementation mode

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0024] Example 1

[0025] S1. The carbon fibers were placed in an environment at a temperature of 400 °C for 1.5 h and then taken out, transferred to a 0.1 mol / L sodium hydroxide solution 50 times the mass of the carbon fibers, stirred for 1.5 h and then filtered out, and dried at a temperature of 55 °C for 12 h to obtain surface-oxidized carbon fibers;

[0026] S2. Zinc acetate dihydrate was added to absolute ethanol 80 times the mass of zinc acetate dihydrate, ultrasonically dispersed for 30 min, and then stirred at a temperature of 25 °C for 1.5 h. After stirring, surface-oxidized carbon fibers 0.9 times the mass of zinc acetate dihydrate were added. After adding, a 0.1 mol / L sodium hydroxide ethanol solution 0.9 times the mass of absolute ethanol was uniformly added dropwise within 30 min. After dropwise addition, stirring was continued for 10 min. After stirring, suction filtration was carried out, and the filtered product was placed at a temperature of 180 °C and dried for 1 h to obtain seeded carbon fibers;

[0027] S3. Add a zinc sulfate solution with a mass fraction of 25% to a sodium hydroxide solution with a mass fraction of 12% that is 1.25 times the mass of the zinc sulfate solution. After stirring, filter and dry. Then add the dried filtered product to a sodium hydroxide solution with a mass fraction of 7% that is 30 times the mass of the filtered product. Add carbon fiber seeds that are 3 times the mass of the filtered product. Stir at 25 °C for 1 h, then raise the temperature to 75 °C and stir for 2 h. After stirring is completed, filter and dry to obtain modified carbon fiber;

[0028] S4. Add silane coupling agent KH-570 to an aqueous ethanol solution with a mass fraction of 70% that is 14 times the mass of silane coupling agent KH-570. Adjust the pH to 3.5. Then add modified carbon fiber that is 0.5 times the mass of silane coupling agent KH-570. Stir and react at 30 °C for 30 min, then filter and dry to obtain silane-modified carbon fiber;

[0029] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate that is 0.1 times the mass of methyltriethoxysilane. Stir at 25 °C for 30 min. After stirring is completed, let it stand for 15 min and take the lower layer liquid to obtain modified aluminum dihydrogen phosphate;

[0030] S6. Weigh 30% of modified aluminum dihydrogen phosphate, 18% of alumina, 0.4% of zinc oxide powder, and 4% of silane-modified carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder. After mixing is completed, perform ultrasonic vibration for 15 min. After ultrasonic vibration is completed, add modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion in sequence. Stir at 25 °C for 25 min to obtain a high-temperature resistant coating.

[0031] Example 2

[0032] S1. Place the carbon fiber in an environment at 425 °C for 1.75 h and then take it out. Transfer it to a 0.125 mol / L sodium hydroxide solution that is 55 times the mass of the carbon fiber. Stir for 1.75 h and then filter and take out. Dry in an environment at 60 °C for 13 h to obtain surface-oxidized carbon fiber;

[0033] S2. Add zinc acetate dihydrate to absolute ethanol that is 85 times the mass of zinc acetate dihydrate. Ultrasonically disperse for 32.5 min, then stir at 30 °C for 1.75 h. After stirring is completed, add surface-oxidized carbon fiber that is 1.05 times the mass of zinc acetate dihydrate. After adding, uniformly drip a 0.1125 mol / L sodium hydroxide ethanol solution that is 1.05 times the mass of absolute ethanol within 35 min. After dripping is completed, continue to stir for 12.5 min. After stirring is completed, filter, and place the filtered product at 190 °C and dry for 1.5 h to obtain carbon fiber seeds;

[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% that is 1.325 times the mass of the zinc sulfate solution. Stir, then filter and dry. Add the dried filtered product to a sodium hydroxide solution with a mass fraction of 7.5% that is 32.5 times the mass of the filtered product. Then add seed carbon fibers that are 4 times the mass of the filtered product. Stir at 30 °C for 1.1 h, then raise the temperature to 80 °C and stir for 2.25 h. After stirring is complete, filter and dry to obtain modified carbon fibers;

[0035] S4. Add silane coupling agent KH-570 to an aqueous ethanol solution with a mass fraction of 75% that is 15 times the mass of silane coupling agent KH-570. Adjust the pH to 4. Then add modified carbon fibers that are 0.65 times the mass of silane coupling agent KH-570. Stir and react at 35 °C for 35 min, then filter and dry to obtain silane-modified carbon fibers;

[0036] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate that is 0.125 times the mass of methyltriethoxysilane. Stir at 30 °C for 35 min. After stirring is complete, let it stand for 17.5 min and take the lower layer liquid to obtain modified aluminum dihydrogen phosphate;

[0037] S6. Weigh 35% of modified aluminum dihydrogen phosphate, 19% of alumina, 0.5% of zinc oxide powder, and 6% of silane-modified carbon fibers by mass fraction. The rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder. After mixing is complete, perform ultrasonic vibration for 17.5 min. After ultrasonic vibration is complete, add modified aluminum dihydrogen phosphate, silane-modified carbon fibers, and polytetrafluoroethylene dispersion emulsion in sequence. Stir at 30 °C for 30 min to obtain a high-temperature resistant coating.

[0038] Example 3

[0039] S1. Place carbon fibers in an environment at 450 °C for 2 h, then take them out and transfer them to a 0.15 mol / L sodium hydroxide solution that is 60 times the mass of the carbon fibers. Stir for 2 h, then filter and take out. Dry in an environment at 65 °C for 14 h to obtain surface-oxidized carbon fibers;

[0040] S2. Add zinc acetate dihydrate to absolute ethanol that is 90 times the mass of zinc acetate dihydrate, and ultrasonically disperse for 35 min. Then, stir at 35 °C for 2 h. After stirring, add surface oxidized carbon fiber that is 1.2 times the mass of zinc acetate dihydrate. After adding, uniformly dropwise add a 0.125 mol / L sodium hydroxide ethanol solution that is 1.2 times the mass of absolute ethanol within 40 min. After dropwise addition, continue to stir for 15 min. After stirring, filter by suction, and place the filtered product at 200 °C for drying for 2 h to obtain seed carbon fiber;

[0041] S3. Add a zinc sulfate solution with a mass fraction of 28% to a 15% sodium hydroxide solution that is 1.4 times the mass of the zinc sulfate solution. Stir, filter by suction, and dry. Then, add the dried suction-filtered product to an 8% sodium hydroxide solution that is 35 times the mass of the suction-filtered product, and add seed carbon fiber that is 5 times the mass of the suction-filtered product. Stir at 35 °C for 1.2 h, then raise the temperature to 85 °C and stir for 2.5 h. After stirring is completed, filter by suction and dry to obtain modified carbon fiber;

[0042] S4. Add silane coupling agent KH-570 to an 80% ethanol aqueous solution that is 16 times the mass of silane coupling agent KH-570, and adjust the pH to 4.5. Then, add modified carbon fiber that is 0.8 times the mass of silane coupling agent KH-570. Stir and react at 40 °C for 40 min, then filter by suction and dry to obtain silane-modified carbon fiber;

[0043] S5. Add methyltriethoxysilane to aluminum dihydrogen phosphate that is 0.15 times the mass of methyltriethoxysilane. Stir at 35 °C for 40 min. After stirring, let it stand for 20 min, and take the lower layer liquid to obtain modified aluminum dihydrogen phosphate;

[0044] S6. Weigh 40% of modified aluminum dihydrogen phosphate, 20% of alumina, 0.6% of zinc oxide powder, and 8% of silane-modified carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, ultrasonically vibrate for 20 min. After ultrasonic treatment, sequentially add modified aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion. Stir at 35 °C for 35 min to obtain a high-temperature resistant coating.

[0045] Example 4

[0046] The difference from Example 2 is only in step S6: Weigh 35% of aluminum dihydrogen phosphate, 19% of alumina, 0.5% of zinc oxide powder, and 6% of silane-modified carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, perform ultrasonic vibration for 17.5 min. After the ultrasonic treatment, sequentially add aluminum dihydrogen phosphate, silane-modified carbon fiber, and polytetrafluoroethylene dispersion emulsion respectively, and stir at a temperature of 30 °C for 30 min to obtain a high-temperature resistant coating;

[0047] Example 5

[0048] The difference from Example 2 is only in step S6: Weigh 35% of modified aluminum dihydrogen phosphate, 19% of alumina, 0.5% of zinc oxide powder, and 6% of modified carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, perform ultrasonic vibration for 17.5 min. After the ultrasonic treatment, sequentially add modified aluminum dihydrogen phosphate, modified carbon fiber, and polytetrafluoroethylene dispersion emulsion respectively, and stir at a temperature of 30 °C for 30 min to obtain a high-temperature resistant coating;

[0049] Example 6

[0050] The difference from Example 2 is only in step S6: Weigh 35% of modified aluminum dihydrogen phosphate, 19% of alumina, 0.5% of zinc oxide powder, and 6% of carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, perform ultrasonic vibration for 17.5 min. After the ultrasonic treatment, sequentially add modified aluminum dihydrogen phosphate, carbon fiber, and polytetrafluoroethylene dispersion emulsion respectively, and stir at a temperature of 30 °C for 30 min to obtain a high-temperature resistant coating;

[0051] Example 7

[0052] The difference from Example 2 is only in step S4: Weigh 35% of aluminum dihydrogen phosphate, 19% of alumina, 0.5% of zinc oxide powder, and 6% of carbon fiber by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, perform ultrasonic vibration for 17.5 min. After the ultrasonic treatment, sequentially add aluminum dihydrogen phosphate, carbon fiber, and polytetrafluoroethylene dispersion emulsion respectively, and stir at a temperature of 30 °C for 30 min to obtain a high-temperature resistant coating;

[0053] Example 8

[0054] The difference from Example 2 is only in step S6: Weigh 35% of modified aluminum dihydrogen phosphate, 19% of alumina, and 0.5% of zinc oxide powder by mass fraction, and the rest is polytetrafluoroethylene dispersion emulsion. First, mix alumina and zinc oxide powder, and after mixing, perform ultrasonic vibration for 17.5 min. After ultrasonic treatment, add modified aluminum dihydrogen phosphate and polytetrafluoroethylene dispersion emulsion in sequence. Under the condition of a temperature of 30 °C, stir for 30 min to obtain a high-temperature resistant coating;

[0055] Example 9

[0056] Spray the high-temperature resistant coatings prepared in Examples 1 - 8 onto the surface of the substrate by air spraying. After spraying, let it stand for 24 h. After standing, perform stepwise curing. The temperatures at each stage of stepwise curing are 50 °C for 30 min; 100 °C for 30 min; 150 °C for 15 min; 250 °C for 105 min; 350 °C for 15 min. After curing, cool to room temperature to obtain a high-temperature resistant coating;

[0057] Hardness test

[0058] Use a Vickers microhardness tester. The indenter is a diamond regular square pyramid with an included angle of 136° between opposite faces. Apply a load of 980.7 mN and a holding time of 12 s. Measure 6 points for each sample. The measurement result is to remove the maximum and minimum values, and take the average value as the coating hardness;

[0059] Adhesion strength test

[0060] According to GB / T9286 - 2021, use the cross - cut method to evaluate the adhesion strength of the coating, and finally grade and evaluate the adhesion strength of the coating according to the evaluation standard.

[0061] Hydrophobicity measurement

[0062] Drop deionized water on the surface of the coating, and use the image analysis method with a contact angle measuring instrument to measure the contact angle. Measure five positions each time, and take the average value as the coating contact angle;

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

[0064] Table 1

[0065]

[0066]

[0067] From the comparison of the experimental data of Examples 1 - 3 in Table 1, it can be found that the high - temperature resistant coating prepared by the present invention has good hardness, adhesion strength, and hydrophobic properties;

[0068] It can be seen from Examples 4 to 7 that the hardness and hydrophobic properties gradually decrease. In Example 4, since aluminum dihydrogen phosphate was not modified, in Example 5, the modified carbon fiber was not further modified, in Example 6, carbon fiber was used for substitution, and in Example 7, neither aluminum dihydrogen phosphate nor carbon fiber was modified. It can be seen from the data that the performance of the high-temperature resistant coating gradually decreases, and the decrease is most obvious in Example 8, which is caused by the absence of carbon fiber addition. However, its contact angle has increased, mainly because adding without modification when the carbon fiber reaches a certain content will affect the hydrophobic property of the coating.

[0069] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed invention.

Claims

1. A high-temperature resistant composite coating and its preparation method, characterized in that, The mass parts of each component of the high-temperature resistant composite coating are as follows: 30-40% of modified aluminum dihydrogen phosphate, 18-20% of ceramic aggregate, 0.4-0.6% of zinc oxide powder, 4-8% of silane-modified carbon fiber, and the rest is polytetrafluoroethylene dispersion emulsion.

2. The high-temperature resistant composite coating according to claim 1, wherein The modified aluminum dihydrogen phosphate is prepared by hydrolysis and polycondensation of methyltriethoxysilane and aluminum dihydrogen phosphate.

3. 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 silicon carbide, alumina, zirconia, porcelain powder and tungsten carbide.

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

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

6. The high-temperature resistant composite coating according to claim 1, wherein, The mass fraction of the polytetrafluoroethylene dispersion emulsion is 60%.

7. A preparation method of a high-temperature resistant composite coating, which is applied to the high-temperature resistant composite coating in claims 1 to 6, characterized in that, It includes the following steps: S1. Add silane coupling agent KH-570 to an ethanol aqueous solution with a mass fraction of 70-80% which is 14-16 times the mass of silane coupling agent KH-570, adjust the pH to 3.5-4.5, then add modified carbon fiber which is 0.5-0.8 times the mass of silane coupling agent KH-570, and under the condition of a temperature of 30-40 °C, stir and react for 30-40 min, then filter and dry to obtain silane-modified carbon fiber; S2. Add methyltriethoxysilane to aluminum dihydrogen phosphate which is 0.1-0.15 times the mass of methyltriethoxysilane, stir at a temperature of 25-35 °C for 30-40 min, after stirring, let it stand for 15-20 min, and take the lower layer liquid to obtain modified aluminum dihydrogen phosphate; S3. Weigh 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, and after mixing, carry out ultrasonic vibration for 15-20 min. After ultrasonic vibration, sequentially add modified aluminum dihydrogen phosphate, silane-modified carbon fiber and polytetrafluoroethylene dispersion emulsion respectively, and under the condition of a temperature of 25-35 °C, stir for 25-35 min to obtain the high-temperature resistant coating.

8. The preparation method of the high-temperature resistant composite coating according to claim 7, characterized in that, The preparation steps of the modified carbon fiber include: adding a zinc sulfate solution with a mass fraction of 25-28% to a sodium hydroxide solution with a mass fraction of 12-15% which is 1.25-1.4 times the mass of the zinc sulfate solution, stirring and then filtering and drying, and adding the dried filtered product to a sodium hydroxide solution with a mass fraction of 7-8% which is 30-35 times the mass of the filtered product, then adding seed carbon fiber which is 3-5 times the mass of the filtered product, and under the condition of a temperature of 25-35 °C, stir for 1-1.2 h, then raise the temperature to 75-85 °C and stir for 2-2.5 h. After stirring is completed, filter and dry to obtain modified carbon fiber.

9. The preparation method of the high-temperature resistant composite coating according to claim 8, characterized in that, The seed carbon fiber includes the following preparation steps: Add zinc acetate dihydrate to absolute ethanol that is 80 - 90 times the mass of zinc acetate dihydrate, ultrasonically disperse for 30 - 35 min, then stir at a temperature of 25 - 35 °C for 1.5 - 2 h. After stirring, add surface oxidized carbon fiber that is 0.9 - 1.2 times the mass of zinc acetate dihydrate. After adding, uniformly dropwise add a 0.1 - 0.125 mol / L sodium hydroxide ethanol solution that is 0.9 - 1.2 times the mass of absolute ethanol within 30 - 40 min. After dropwise addition, continue to stir for 10 - 15 min. After stirring, perform suction filtration, and place the filtered product at a temperature of 180 - 200 °C and dry for 1 - 2 h to obtain the seed carbon fiber.

10. The preparation method of the high-temperature resistant composite coating according to claim 9, characterized in that, The surface oxidized carbon fiber includes the following preparation steps: Place the carbon fiber in an environment at a temperature of 400 - 450 °C for 1.5 - 2 h and then take it out, transfer it to a 0.1 - 0.15 mol / L sodium hydroxide solution that is 50 - 60 times the mass of the carbon fiber, stir for 1.5 - 2 h and then filter and take it out, dry in an environment at a temperature of 55 - 65 °C for 12 - 14 h to obtain the surface oxidized carbon fiber.

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