Preparation method of high-oxidation-resistance pyrolytic carbon coating of carbon fiber thermal insulation material

Abstract

The application relates to a preparation method of a high-oxidation-resistance pyrolytic carbon coating of a carbon fiber thermal insulation material, which comprises the following steps: 1) performing carbon hardening treatment on the surface of the carbon fiber thermal insulation material to obtain a carbon hardened layer; 2) uniformly coating coating glue 1 on the surface of the carbon hardened layer to form a first transition coating layer; 3) coating coating glue 2 on the surface of the first transition coating layer to form a second transition coating layer; and 4) performing carbon vapor deposition on the first transition coating layer and the second transition coating layer, and then depositing a more dense vapor deposition pyrolytic carbon coating (with a density of 1.5-2.2 g / cm 3 ) on the second transition coating layer. The carbon fiber thermal insulation material prepared by the method has excellent heat insulation performance and strong oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of functional coating material preparation technology, and in particular to a method for preparing a highly antioxidant pyrolytic carbon coating for carbon fiber insulation materials. Background Technology

[0002] With the rapid development of aerospace, photovoltaic, and semiconductor industries, the demand for high-efficiency thermal insulation materials is increasing. Carbon fiber insulation materials, due to their excellent thermal insulation performance, high purity, low density, low specific heat, and ability to maintain high strength at high temperatures, have become one of the preferred materials for high-efficiency thermal insulation. Currently, monocrystalline silicon, as a photovoltaic power generation material, has high photoelectric conversion efficiency and significant commercial advantages, and has become the mainstream material for solar photovoltaic power generation. The thermal field system is the most important component of the monocrystalline furnace. The thermal field is mainly composed of graphite materials, carbon-carbon composite materials, and carbon fiber insulation materials. During the Czochralski process of growing monocrystalline silicon, the melting of silicon material generates silicon vapor and molten silicon splashes, causing silicification erosion of the carbon-carbon thermal field material. This severely affects the mechanical properties and service life of the carbon-carbon thermal field material, easily leading to cracking and pulverization of carbon-carbon components. Furthermore, the epitaxial growth of third-generation silicon carbide causes severe corrosion and oxidation of both graphite and carbon fiber insulation materials, easily causing product cracking and brittle pulverization, significantly shortening their service life.

[0003] To address these issues, researchers have attempted to prepare protective coatings on the surface of carbon fiber insulation materials. Common methods include attaching graphite foil, large-tow carbon cloth, or carbon-based coatings to the material surface. However, these methods still have some limitations, such as the coatings being prone to cracking and peeling, and graphite foil and carbon cloth being prone to delamination and peeling, making it difficult to simultaneously meet the performance requirements of insulation, ablation resistance, and oxidation resistance under high-temperature environments.

[0004] Pyrolytic carbon coatings have become the preferred surface coating for carbon-carbon thermal field materials due to their excellent thermal shock resistance and wear resistance. However, their application in low-density carbon fiber insulation materials cannot be simply replicated. Issues need to be addressed, such as the impact of pyrolytic carbon infiltration into the substrate on the insulation performance of the carbon fiber, preventing excessive pyrolytic carbon deposition on the fiber surface, affecting the coating thickness and density uniformity, and matching thermal expansion. Therefore, a method is needed to develop a stable coating with strong oxidation resistance on the surface of carbon fiber insulation materials, effectively improving the material's high-temperature oxidation resistance and resisting the erosion of reactive gases. This is currently a key research focus and challenge. This is because it is necessary to address not only the interfacial bonding between the coating and the substrate but also factors such as coating thickness uniformity and density control to meet the performance requirements of different application scenarios.

[0005] Regarding the question of how to improve the hardness and coating density of carbon-carbon materials, some research results have been achieved. For example:

[0006] Chinese patent application CN111807853A discloses "a carbon-carbon composite material and its preparation process and application." The prepared carbon-carbon composite material comprises, by weight, 20%–36% carbon fiber, 28%–45% vapor-deposited carbon, and 26%–48% impregnated carbon. The preparation process includes preform preparation, impregnating agent raw material preparation, and multi-stage densification reaction. The prepared carbon-carbon composite material can maintain its mechanical properties, thermal properties, and tribological properties at room temperature in high-temperature and ultra-high-temperature environments. However, there are still issues regarding the carbon fiber modification, such as the need for further optimization of the impregnating agent formulation and modification process. For example, the use of additives containing metals and boron, such as LiAlH4, NaBH4, and i-Bu2AlH, can affect the purity of the product, limiting its application in high-purity environments. Moreover, it is mainly designed for the preparation of high-density carbon-carbon materials and is not suitable for the preparation of low-density carbon fiber insulation materials.

[0007] Chinese invention patent CN103160826B discloses a "method for preparing a pyrolytic carbon / nickel composite coating on the surface of continuous carbon fiber." This method involves preparing a pyrolytic carbon coating on the surface of carbon fibers within a non-woven carbon fiber fabric using chemical vapor deposition (CVD), and then preparing a nickel coating using electroless plating. This effectively prevents fiber oxidation and protects the carbon fibers from damage. However, the use of electroless nickel plating involves solutions containing tin chloride, silver nitrate, sodium hypophosphite, sodium acetate, sodium phosphite, and nickel sulfate, all of which contain metals and phosphorus. This affects the purity and application of the product, particularly in high-end applications such as photovoltaics, semiconductors, and sapphire, where extremely high requirements for metals and phosphorus levels render the product unusable.

[0008] In summary, the existing technology has the following problems:

[0009] 1. After the existing carbon fiber insulation material coating is prepared, the bonding force between the carbon coating and the carbon fiber insulation material matrix is ​​insufficient, which easily leads to cracking and peeling of the coating, affecting the overall performance and service life of the material.

[0010] 2. In high-temperature and oxygen-rich environments, existing thermal protection materials, such as carbon pyrolysis coatings, are easily oxidized due to insufficient density, resulting in reduced thermal protection efficiency and limiting their application range.

[0011] 3. Existing carbon fiber insulation materials have insufficient coating uniformity and thickness control capabilities, making it difficult to meet the requirements for long-term protection of the substrate under high-temperature environments.

[0012] 4. The hardness and coating density of existing carbon fiber insulation materials need to be improved under high temperature environments (affecting the thermal insulation performance and service life of the materials);

[0013] 5. Existing carbon fiber insulation material preparation process parameters, such as deposition temperature and gas flow rate, need to be further optimized to improve product quality and performance. Summary of the Invention

[0014] This invention provides a method for preparing a pyrolytic carbon coating with high oxidation resistance for carbon fiber insulation materials. The carbon fiber insulation material with a pyrolytic carbon coating has excellent thermal insulation performance and strong oxidation resistance. It effectively solves the problems existing in the prior art, such as the carbon coating and the carbon fiber insulation material matrix being prone to cracking and peeling due to insufficient bonding force, uneven coating and poor density leading to local cracking, poor high-temperature oxidation resistance and inability to be used stably for a long time, and coating peeling easily contaminating the product.

[0015] To achieve the above objectives, the present invention employs the following technical solution:

[0016] A method for preparing a highly antioxidant pyrolytic carbon coating for carbon fiber insulation materials includes the following steps:

[0017] 1) Carbon hardening treatment on the surface of carbon fiber insulation material: A hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of carbon fiber insulation material and cured to obtain a carbon hardened layer.

[0018] 2) A coating adhesive composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent and water is uniformly coated onto the surface of the carbon hardened layer formed in step 1) to form a first transition coating.

[0019] 3) A coating adhesive composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water is uniformly coated onto the surface of the first transition coating formed in step 2) to form a second transition coating;

[0020] 4) Carbon vapor deposition is performed on the first and second transition coatings, followed by deposition of a denser vapor-deposited pyrolytic carbon coating on the second transition coating. The density of the vapor-deposited pyrolytic carbon coating is 1.5–2.2 g / cm³. 3 .

[0021] In step 1), the hardening coating adhesive is composed of the following components in parts by weight: 20-60 parts carbon fiber, 10-30 parts carbon nanotubes, 20-60 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 35-360 parts water; the carbon fiber is ground, and the particle size of the ground carbon fiber is 3-6 μm; the preparation process of the hardening coating adhesive is as follows: first, the carbon fiber and carbon nanotubes are mixed evenly, then the dispersant and resin are added and mixed evenly, and finally the crosslinking agent is added and mixed evenly.

[0022] The specific process of step 1) is as follows:

[0023] 1-1. Clean the dust off the surface of the carbon fiber insulation material after processing, and ultrasonically clean it with ethanol and acetone for 15-20 minutes in sequence.

[0024] 1-2. Dry the cleaned carbon fiber insulation material, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, and after the penetration depth reaches 0.5-3mm, cure and shape it at a temperature of 160-200℃, and let it cool naturally to room temperature to obtain a carbon hardened layer with a thickness of 0.5-3mm.

[0025] 1-3. Use sandpaper to sand the surface of the carbon-hardened layer to clean off any particles.

[0026] In step 2), the coating adhesive is composed of the following components in parts by weight: 10-30 parts carbon fiber powder, 20-60 parts coarse graphite powder, 40-80 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 49-408 parts water; the particle size of the carbon fiber powder is 1-4 μm, and the particle size of the coarse graphite powder is 20-80 μm; the preparation process of the coating adhesive is as follows: first, mix the carbon fiber powder and coarse graphite powder, then add water and stir evenly, then add the dispersant and resin and mix evenly, and finally add the crosslinking agent and mix evenly to obtain the coating adhesive.

[0027] The specific process of step 2) is as follows:

[0028] 2-1. After mixing carbon fiber powder, coarse graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive one;

[0029] 2-2. Apply coating adhesive to the surface of the carbon-cured layer, with a coating thickness of 40–120 μm;

[0030] 2-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a first transition coating with a thickness of 40-120μm.

[0031] In step 3), the coating adhesive II is composed of the following components in parts by weight: 5-20 parts carbon fiber powder, 30-70 parts fine graphite powder, 50-90 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 59-432 parts water; the particle size of the carbon fiber powder is 0.3-1.5 μm, and the particle size of the fine graphite powder is 0.5-1.2 μm; the preparation process of coating adhesive II is as follows: first, mix the carbon fiber powder and fine graphite powder, then add water and stir evenly, then add the dispersant and resin and mix evenly, and finally add the crosslinking agent and mix evenly to obtain coating adhesive II.

[0032] The specific process of step 3) is as follows:

[0033] 3-1. After mixing carbon fiber powder, fine graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive II;

[0034] 3-2. Apply coating adhesive II to the surface of the first transition coating, with a coating thickness of 20–80 μm;

[0035] 3-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a second transition coating with a thickness of 20-80μm; then graphitize at 1600-2200℃, so that the resin, dispersant and crosslinking agent react fully, and the first transition coating and the second transition coating become a carbon coating.

[0036] In steps 1) to 3), the resin is one or more of epoxy resin, polybutadiene resin, phenolic resin, unsaturated polyester resin, polyurethane resin, unsaturated polyester resin, and furan resin; the crosslinking agent is one or more of dicumyl peroxide, dicumyl peroxide, diethylenetriamine, diethylenetriamine, polyisocyanate, alkyl isocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, polyether, and polyoxyethylene alkylphenol ether.

[0037] The specific process of step 4) is as follows:

[0038] 4-1. Place the carbon fiber insulation material obtained after step 3) into a chemical vapor deposition furnace;

[0039] 4-2. A chemical vapor deposition furnace is introduced with nitrogen and a mixture of methane / propane / propylene gas, the pressure of which is 50–2000 Pa; the flow rate of nitrogen in the mixture is 300–12000 mL / min, and the flow rate of methane / propane / propylene gas is 100–1200 mL / min.

[0040] 4-3. The temperature is raised to 900-1100℃ in a chemical vapor deposition furnace at a heating rate of 1-10℃ / min, and the deposition is carried out for 10-50 hours to achieve a penetration depth of 60-200μm for both the first and second transition coatings. Then, a vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50μm is formed on the second transition coating, and finally, the coating is naturally cooled to room temperature.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] 1) By hardening the carbon fiber insulation material and setting a multi-layer coating structure, the hardness of the product is significantly improved, and the mechanical strength and durability of the product in high temperature environment are enhanced, thereby effectively solving the problems of easy deformation and poor wear resistance of carbon fiber insulation materials in the existing technology.

[0043] 2) Through the synergistic effect of dispersants and crosslinking agents, the dispersibility of graphite powder and fibers in the coating is improved, and the crosslinking of fibers, graphite and binder particles is promoted to form a dense network structure, which effectively prevents particles from falling off the coating and significantly increases the density and uniformity of the coating.

[0044] 3) By strictly controlling parameters such as gas flow rate, gas ratio and vacuum degree, the uniformity and stability of carbon vapor deposition coating are improved, and the problems of uneven coating thickness and poor adhesion in the prior art are solved.

[0045] 4) The coated carbon fiber insulation material prepared by the present invention has an excellent pyrolytic carbon coating structure, forming a dense protective network, which can maintain stable performance for a long time in a high temperature and oxygen environment of 400-500℃, effectively preventing the carbon fiber insulation material from being oxidized and significantly improving the thermal protection efficiency of the product.

[0046] 5) The preparation method described in this invention is simple to operate, easy to scale up, and does not require expensive equipment investment, which greatly reduces production costs and is conducive to promoting the commercial application of carbon fiber insulation materials. Attached Figure Description

[0047] Figure 1 This is an electron microscope image of the surface of the vapor-deposited pyrolytic carbon coating described in this invention.

[0048] Figure 2 This is a cross-sectional electron microscope image of the vapor-deposited pyrolytic carbon coating described in this invention. Detailed Implementation

[0049] The present invention discloses a method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation materials, comprising the following steps:

[0050] 1) Carbon hardening treatment on the surface of carbon fiber insulation material: A hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of carbon fiber insulation material and cured to obtain a carbon hardened layer.

[0051] 2) A coating adhesive composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent and water is uniformly coated onto the surface of the carbon hardened layer formed in step 1) to form a first transition coating.

[0052] 3) A coating adhesive composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water is uniformly coated onto the surface of the first transition coating formed in step 2) to form a second transition coating;

[0053] 4) Carbon vapor deposition is performed on the first and second transition coatings, followed by deposition of a denser vapor-deposited pyrolytic carbon coating on the second transition coating. The density of the vapor-deposited pyrolytic carbon coating is 1.5–2.2 g / cm³. 3 .

[0054] In step 1), the hardening coating adhesive is composed of the following components in parts by weight: 20-60 parts carbon fiber, 10-30 parts carbon nanotubes, 20-60 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 35-360 parts water; the carbon fiber is ground, and the particle size of the ground carbon fiber is 3-6 μm; the preparation process of the hardening coating adhesive is as follows: first, the carbon fiber and carbon nanotubes are mixed evenly, then the dispersant and resin are added and mixed evenly, and finally the crosslinking agent is added and mixed evenly.

[0055] The specific process of step 1) is as follows:

[0056] 1-1. Clean the dust off the surface of the carbon fiber insulation material after processing, and ultrasonically clean it with ethanol and acetone for 15-20 minutes in sequence.

[0057] 1-2. Dry the cleaned carbon fiber insulation material, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, and after the penetration depth reaches 0.5-3mm, cure and shape it at a temperature of 160-200℃, and let it cool naturally to room temperature to obtain a carbon hardened layer with a thickness of 0.5-3mm.

[0058] 1-3. Use sandpaper to sand the surface of the carbon-hardened layer to clean off any particles.

[0059] In step 2), the coating adhesive is composed of the following components in parts by weight: 10-30 parts carbon fiber powder, 20-60 parts coarse graphite powder, 40-80 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 49-408 parts water; the particle size of the carbon fiber powder is 1-4 μm, and the particle size of the coarse graphite powder is 20-80 μm; the preparation process of the coating adhesive is as follows: first, mix the carbon fiber powder and coarse graphite powder, then add water and stir evenly, then add the dispersant and resin and mix evenly, and finally add the crosslinking agent and mix evenly to obtain the coating adhesive.

[0060] The specific process of step 2) is as follows:

[0061] 2-1. After mixing carbon fiber powder, coarse graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive one;

[0062] 2-2. Apply coating adhesive to the surface of the carbon-cured layer, with a coating thickness of 40–120 μm;

[0063] 2-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a first transition coating with a thickness of 40-120μm.

[0064] In step 3), the coating adhesive II is composed of the following components in parts by weight: 5-20 parts carbon fiber powder, 30-70 parts fine graphite powder, 50-90 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 59-432 parts water; the particle size of the carbon fiber powder is 0.3-1.5 μm, and the particle size of the fine graphite powder is 0.5-1.2 μm; the preparation process of coating adhesive II is as follows: first, mix the carbon fiber powder and fine graphite powder, then add water and stir evenly, then add the dispersant and resin and mix evenly, and finally add the crosslinking agent and mix evenly to obtain coating adhesive II.

[0065] The specific process of step 3) is as follows:

[0066] 3-1. After mixing carbon fiber powder, fine graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive II;

[0067] 3-2. Apply coating adhesive II to the surface of the first transition coating, with a coating thickness of 20–80 μm;

[0068] 3-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a second transition coating with a thickness of 20-80μm; then graphitize at 1600-2200℃, so that the resin, dispersant and crosslinking agent react fully, and the first transition coating and the second transition coating become a carbon coating.

[0069] In steps 1) to 3), the resin is one or more of epoxy resin, polybutadiene resin, phenolic resin, unsaturated polyester resin, polyurethane resin, unsaturated polyester resin, and furan resin; the crosslinking agent is one or more of dicumyl peroxide, dicumyl peroxide, diethylenetriamine, diethylenetriamine, polyisocyanate, alkyl isocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, polyether, and polyoxyethylene alkylphenol ether.

[0070] The specific process of step 4) is as follows:

[0071] 4-1. Place the carbon fiber insulation material obtained after step 3) into a chemical vapor deposition furnace;

[0072] 4-2. A chemical vapor deposition furnace is introduced with nitrogen and a mixture of methane / propane / propylene gas, the pressure of which is 50–2000 Pa; the flow rate of nitrogen in the mixture is 300–12000 mL / min, and the flow rate of methane / propane / propylene gas is 100–1200 mL / min.

[0073] 4-3. The temperature is raised to 900-1100℃ in a chemical vapor deposition furnace at a heating rate of 1-10℃ / min, and the deposition is carried out for 10-50 hours to achieve a penetration depth of 60-200μm for both the first and second transition coatings. Then, a vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50μm is formed on the second transition coating, and finally, the coating is naturally cooled to room temperature.

[0074] The electron microscope image of the vapor-deposited pyrolytic carbon coating surface described in this invention is as follows: Figure 1 As shown in the figure, the cross-sectional electron microscope image of the vapor-deposited pyrolytic carbon coating is as follows. Figure 2 As shown.

[0075] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0076] In the following examples, all original reagent materials are commercially available. Experimental methods without specific conditions are conventional methods and conditions well known in the art, or are performed according to the conditions recommended by the instrument manufacturer.

[0077]

Example 1

[0078] In this embodiment, the preparation process of the high oxidation-resistant pyrolytic carbon coating of the carbon fiber insulation material is as follows:

[0079] Step 1: Perform carbon hardening treatment on the surface of the carbon fiber insulation material to form a carbon hardened layer. The specific process is as follows:

[0080] Step 1-1: Clean the dust off the surface of the processed carbon fiber insulation material by ultrasonic cleaning with ethanol and acetone for 20 minutes in sequence.

[0081] Steps 1-2: Mix 30g of carbon fiber with a particle size of 4μm and 20g of carbon nanotubes evenly, add 120g of water and mix evenly, then add 1.6g of polyvinyl alcohol (dispersant), then add 55g of epoxy resin and 1.2g of phthalic anhydride (crosslinking agent), mix evenly and obtain the hardened coating adhesive.

[0082] Steps 1-3: Dry the carbon fiber insulation material after cleaning in step 1-1, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, control the penetration depth to 2mm, then cure and shape it at 180℃, and let it cool naturally to room temperature to obtain a 2mm thick carbon hardened layer.

[0083] Steps 1-4: Use sandpaper to sand the surface of the carbon-hardened layer and clean off any remaining particles.

[0084] Step 2: Prepare coating adhesive one using carbon fiber powder, coarse graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive one evenly to the surface of the carbon-cured layer to form the first transition coating. The specific process is as follows:

[0085] Step 2-1: Mix 30g of carbon fiber powder with a particle size of 2μm and 40g of coarse graphite powder with a particle size of 50μm evenly, then add 80g of water and mix evenly. Add 2g of starch (dispersant) and stir evenly. Then add 60g of phenolic resin and 1.2g of phthalic anhydride (crosslinking agent), mix evenly and obtain coating adhesive one.

[0086] Step 2-2: Apply the coating adhesive evenly to the surface of the carbon hardened layer, controlling the coating thickness to be 80μm;

[0087] Steps 2-3: Dry at 80℃ for 1 hour, then heat to 150℃ for 3 hours, and then carbonize at 800℃ to form the first transition coating.

[0088] Step 3: Prepare coating adhesive II using carbon fiber powder, fine graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive II evenly to the surface of the first transition coating to form the second transition coating. The specific process is as follows:

[0089] Step 3-1: Mix 15g of carbon fiber powder with a particle size of 0.5μm and 40g of fine graphite powder with a particle size of 0.5μm evenly, then add 150g of water and mix evenly. Add 2.2g of starch (dispersant) and stir evenly. Then add 70g of phenolic resin and 1.2g of phthalic anhydride (crosslinking agent), mix evenly and obtain coating adhesive II.

[0090] Step 3-2: Apply coating adhesive 2 evenly to the surface of the first transition coating, with a coating thickness of 30μm;

[0091] Step 3-3: Dry at 80℃ for 1.5h, then heat to 150℃ for 3h, followed by carbonization at 800℃ to form a second transition coating with a thickness of 30μm. Then, graphitize at 1800℃, allowing the resin, dispersant, and crosslinking agent to fully react, turning the first and second transition coatings into carbon coatings.

[0092] Step 4: Perform carbon vapor deposition on the surfaces of the first and second transition coatings, and then deposit carbon on the second transition coating to form a denser vapor-deposited carbon coating; the specific process is as follows:

[0093] Step 4-1: Place the carbon fiber insulation material after step 3 into a chemical vapor deposition furnace;

[0094] Step 4-2: After the designed furnace temperature is reached, a mixture of nitrogen and methane is introduced. The pressure of the mixture is 1200 Pa, and the gas flow ratio is 6:1, with the nitrogen flow rate at 1200 ml / min and the propane flow rate at 200 ml / min.

[0095] Step 4-3: Heat to 1100℃ at a heating rate of 5℃ / min, deposit for 30 hours, and the thickness of both the first and second transition coatings is 100μm. Then, deposit a denser vapor-deposited carbon pyrolysis coating with a thickness of 30μm on the second transition coating. Allow to cool naturally to room temperature. The density of the vapor-deposited carbon pyrolysis coating is 2.1g / cm³. 3 .

[0096] In this embodiment, the vapor-deposited pyrolytic carbon coating on the surface of the carbon fiber insulation material sample is smooth, without cracks or powder shedding, and has a hardness of 92HA (in contrast, the hardness of ordinary graphite coating is 78HA). In the oxidation resistance test at 550℃, the weight loss after burning at 550℃ for 8 hours in air is 0.04%, with no powder shedding (in contrast, the weight loss of ordinary graphite coating after burning at 550℃ for 8 hours in air is 9.2%, and severe powder shedding occurs).

[0097] Conclusion: The carbon fiber insulation material with a vapor-deposited pyrolytic carbon coating prepared in this embodiment can prevent air from directly contacting the surface of the carbon fiber insulation material, preventing its oxidation and ablation, giving it excellent anti-oxidation and anti-corrosion properties, and significantly improving the service life of the carbon fiber insulation material.

[0098]

Example 2

[0099] In this embodiment, the preparation process of the high oxidation-resistant pyrolytic carbon coating of the carbon fiber insulation material is as follows:

[0100] Step 1: Perform carbon hardening treatment on the surface of the carbon fiber insulation material to form a carbon hardened layer. The specific process is as follows:

[0101] Step 1-1: Clean the dust off the surface of the processed carbon fiber insulation material by ultrasonic cleaning with ethanol and acetone for 20 minutes in sequence.

[0102] Steps 1-2: Mix 30g of carbon fiber with a particle size of 4μm and 20g of carbon nanotubes evenly, then add 100g of water and mix evenly. Add 0.5g of polyvinyl alcohol (dispersant), then add 55g of epoxy resin, and finally add 1.0g of diethylenetriamine (dispersant). After mixing evenly, a hardened coating adhesive is obtained.

[0103] Steps 1-3: Dry the carbon fiber insulation material after cleaning in step 1-1, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, control the penetration depth to 2mm, then cure and shape it at 180℃, and let it cool naturally to room temperature to obtain a 2mm thick carbon hardened layer.

[0104] Steps 1-4: Use sandpaper to sand the surface of the carbon-hardened layer and clean off any remaining particles.

[0105] Step 2: Prepare coating adhesive one using carbon fiber powder, coarse graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive one evenly to the surface of the carbon-cured layer to form the first transition coating. The specific process is as follows:

[0106] Step 2-1: Mix 30g of carbon fiber powder with a particle size of 2μm and 40g of coarse graphite powder with a particle size of 50μm evenly, then add 70g of water and mix evenly. Add 2g of polyvinyl alcohol (dispersant) and stir evenly. Then add 60g of epoxy resin and 1g of diethylenetriamine (crosslinking agent) and mix evenly to obtain coating adhesive one.

[0107] Step 2-2: Apply the coating adhesive evenly to the surface of the carbon hardened layer, controlling the coating thickness to be 80μm;

[0108] Steps 2-3: Dry at 80℃ for 1 hour, then heat to 150℃ for 3 hours, and then carbonize at 800℃ to form the first transition coating.

[0109] Step 3: Prepare coating adhesive II using carbon fiber powder, fine graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive II evenly to the surface of the first transition coating to form the second transition coating. The specific process is as follows:

[0110] Step 3-1: Mix 15g of carbon fiber powder with a particle size of 0.5μm and 40g of fine graphite powder with a particle size of 0.5μm evenly, then add 100g of water and mix evenly. Add 2g of polyvinyl alcohol (dispersant) and stir evenly. Then add 70g of epoxy resin and 1.2g of phthalic anhydride (crosslinking agent), mix evenly and obtain coating adhesive II.

[0111] Step 3-2: Apply coating adhesive 2 evenly to the surface of the first transition coating, and control the coating thickness to 30μm;

[0112] Step 3-3: Dry at 80℃ for 1.5h, then heat to 150℃ for 3h, and then carbonize at 600℃ to form a second transition coating with a thickness of 30μm. Then, graphitize at 1800℃ to allow the resin, dispersant, and crosslinking agent to react fully, so that the first and second transition coatings become carbon coatings.

[0113] Step 4: Perform carbon vapor deposition on the surfaces of the first and second transition coatings, and then deposit carbon on the second transition coating to form a denser vapor-deposited carbon coating; the specific process is as follows:

[0114] Step 4-1: Place the carbon fiber insulation material after step 3 into a chemical vapor deposition furnace;

[0115] Step 4-2: After the designed furnace temperature is reached, a mixture of nitrogen and methane is introduced. The pressure of the mixture is 1200 Pa, and the gas flow ratio is 6:1, with the nitrogen flow rate at 1200 ml / min and the propane flow rate at 200 ml / min.

[0116] Step 4-3: Heat to 1100℃ at a heating rate of 5℃ / min, deposit for 35 hours, penetrating to a depth of 105μm in both the first and second transition coatings. Then, deposit a denser vapor-deposited carbon pyrolysis coating with a thickness of 50μm on the second transition coating. Allow to cool naturally to room temperature. The density of the vapor-deposited carbon pyrolysis coating is 2.1g / cm³. 3 .

[0117] In this embodiment, the vapor-deposited pyrolytic carbon coating on the surface of the carbon fiber insulation material sample is smooth, without cracks or powder shedding, and has a hardness of 94HA (in contrast, the hardness of ordinary graphite coating is 78HA). In the oxidation resistance test at 550℃, the weight loss after burning at 550℃ for 8 hours in air is 0.04%, with no powder shedding (in contrast, the weight loss of ordinary graphite coating after burning at 550℃ for 8 hours in air is 9.27%, and severe powder shedding occurs).

[0118] Conclusion: The carbon fiber insulation material with a vapor-deposited pyrolytic carbon coating prepared in this embodiment can prevent air from directly contacting the surface of the carbon fiber insulation material, preventing its oxidation and ablation, giving it excellent anti-oxidation and anti-corrosion properties, and significantly improving the service life of the carbon fiber insulation material.

[0119]

Example 3

[0120] In this embodiment, the preparation process of the high oxidation-resistant pyrolytic carbon coating of the carbon fiber insulation material is as follows:

[0121] Step 1: Perform carbon hardening treatment on the surface of the carbon fiber insulation material to form a carbon hardened layer. The specific process is as follows:

[0122] Step 1-1: Clean the dust off the surface of the processed carbon fiber insulation material by ultrasonic cleaning with ethanol and acetone for 20 minutes in sequence.

[0123] Steps 1-2: Mix 30g of carbon fiber with a particle size of 4μm and 20g of carbon nanotubes evenly, then add 120g of water and mix evenly, then add 1.6g of gelatin (dispersant), then add 55g of furan resin, then add 1.0g of diethylenetriamine (dispersant), mix evenly and obtain the hardened coating adhesive.

[0124] Steps 1-3: Dry the carbon fiber insulation material after cleaning in step 1-1, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, control the penetration depth to 2mm, then cure and shape it at 180℃, and let it cool naturally to room temperature to obtain a 2mm thick carbon hardened layer.

[0125] Steps 1-4: Use sandpaper to sand the surface of the carbon-hardened layer and clean off any remaining particles.

[0126] Step 2: Prepare coating adhesive one using carbon fiber powder, coarse graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive one evenly to the surface of the carbon-cured layer to form the first transition coating. The specific process is as follows:

[0127] Step 2-1: Mix 25g of carbon fiber powder with a particle size of 2μm and 45g of coarse graphite powder with a particle size of 50μm evenly, then add 80g of water and mix evenly. Add 2g of diethylenetriamine (dispersant) and stir evenly. Then add 60g of furan resin and 1g of diethylenetriamine (crosslinking agent) and mix evenly to obtain coating adhesive one.

[0128] Step 2-2: Apply coating adhesive evenly to the surface of the carbon hardened layer, controlling the coating thickness to be 90μm;

[0129] Steps 2-3: Dry at 80℃ for 1 hour, then heat to 150℃ for 3 hours to cure, and then carbonize at 800℃ to form the first transition coating.

[0130] Step 3: Prepare coating adhesive II using carbon fiber powder, fine graphite powder, resin, dispersant, and crosslinking agent. Apply coating adhesive II evenly to the surface of the first transition coating to form the second transition coating. The specific process is as follows:

[0131] Step 3-1: Mix 17g of carbon fiber powder with a particle size of 0.5μm and 35g of fine graphite powder with a particle size of 0.5μm evenly, then add 150g of water and mix evenly. Add 2g of diethylenetriamine (dispersant) and stir evenly. Then add 70g of furan resin and 1.2g of phthalic anhydride (crosslinking agent), and mix evenly to obtain coating adhesive II.

[0132] Step 3-2: Apply coating adhesive 2 evenly to the surface of the first transition coating, and control the coating thickness to be 40μm;

[0133] Step 3-3: Dry at 80℃ for 1.5h, then heat to 150℃ for 3h, and then carbonize at 700℃ to form a second transition coating with a thickness of 40μm. Then, graphitize at 1800℃, allowing the resin, dispersant, and crosslinking agent to react fully, so that the first and second transition coatings become carbon coatings.

[0134] Step 4: Perform carbon vapor deposition on the surfaces of the first and second transition coatings, and then deposit carbon on the second transition coating to form a denser vapor-deposited carbon coating; the specific process is as follows:

[0135] Step 4-1: Place the carbon fiber insulation material after step 3 into a chemical vapor deposition furnace;

[0136] Step 4-2: After the designed furnace temperature is reached, a mixture of nitrogen and methane is introduced. The pressure of the mixture is 1000 Pa, and the gas flow ratio is 7:1, with the nitrogen flow rate being 1540 ml / min and the propane flow rate being 220 ml / min.

[0137] Step 4-3: Heat to 1100℃ at a heating rate of 5℃ / min, deposit for 40 hours, and the thickness of both the first and second transition coatings is 125μm. Then, deposit a denser vapor-deposited carbon pyrolysis coating with a thickness of 50μm on the second transition coating. Allow to cool naturally to room temperature. The density of the vapor-deposited carbon coating is 2.1g / cm³. 3 .

[0138] In this embodiment, the vapor-deposited pyrolytic carbon coating on the surface of the carbon fiber insulation material sample is smooth, without cracks or powder shedding, and has a hardness of 78HA (in contrast, the hardness of ordinary graphite coating is 78HA). In an oxidation resistance test at 550°C, the weight loss after burning at 550°C for 8 hours in air was 0.02%, with no powder shedding (in contrast, the weight loss of ordinary graphite coating after burning at 550°C for 8 hours in air was 9.2%, and severe powder shedding occurred).

[0139] Conclusion: The carbon fiber insulation material with a vapor-deposited pyrolytic carbon coating prepared in this embodiment can prevent air from directly contacting the surface of the carbon fiber insulation material, preventing its oxidation and ablation, giving it excellent anti-oxidation and anti-corrosion properties, and significantly improving the service life of the carbon fiber insulation material.

[0140] The above embodiments demonstrate that the carbon fiber insulation material with high oxidation resistance pyrolytic carbon coating prepared according to the method of the present invention has excellent thermal insulation performance and strong oxidation resistance, and can avoid or reduce the phenomenon of cracking and peeling of pyrolytic carbon coating.

[0141] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation materials, characterized in that, Includes the following steps: 1) Carbon hardening treatment of carbon fiber insulation material surface: A hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of carbon fiber insulation material and cured to obtain a carbon hardened layer; the hardening coating adhesive is composed of the following components by weight: 20-60 parts carbon fiber, 10-30 parts carbon nanotubes, 20-60 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 35-360 parts water; the carbon fiber is ground to a particle size of 3-6 μm; the preparation process of the hardening coating adhesive is as follows: first, the carbon fiber and carbon nanotubes are mixed evenly, then the dispersant and resin are added and mixed evenly, and finally the crosslinking agent is added and mixed evenly. 2) A coating adhesive, composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent, and water, is uniformly coated onto the surface of the carbon-hardened layer formed in step 1) to form a first transition coating. The coating adhesive consists of the following components in parts by weight: 10-30 parts carbon fiber powder, 20-60 parts coarse graphite powder, 40-80 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent, and 49-408 parts water. The particle size of the carbon fiber powder is 1-4 μm, and the particle size of the coarse graphite powder is 20-80 μm. The preparation process of the coating adhesive is as follows: first, the carbon fiber powder and coarse graphite powder are mixed and then water is added and stirred evenly. Then, the dispersant and resin are added and mixed evenly. Finally, the crosslinking agent is added and mixed evenly to obtain the coating adhesive. 3) A second coating is formed by uniformly coating the surface of the first transition coating formed in step 2) with a coating adhesive II composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water. The coating adhesive II is composed of the following components in parts by weight: 5-20 parts carbon fiber powder, 30-70 parts fine graphite powder, 50-90 parts resin, 0.2-3 parts dispersant, 0.1-1.5 parts crosslinking agent and 59-432 parts water. The particle size of the carbon fiber powder is 0.3-1.5 μm and the particle size of the fine graphite powder is 0.5-1.2 μm. The preparation process of the coating adhesive II is as follows: first, the carbon fiber powder and fine graphite powder are mixed and then water is added and stirred evenly. Then, the dispersant and resin are added and mixed evenly. Finally, the crosslinking agent is added and mixed evenly to obtain the coating adhesive II. 4) Carbon vapor deposition is performed on the first and second transition coatings, followed by deposition of a denser vapor-deposited pyrolytic carbon coating on the second transition coating. The density of the vapor-deposited pyrolytic carbon coating is 1.5–2.2 g / cm³. 3 .

2. The method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation material according to claim 1, characterized in that, The specific process of step 1) is as follows: 1-1. Clean the dust off the surface of the carbon fiber insulation material after processing, and ultrasonically clean it with ethanol and acetone for 15-20 minutes in sequence. 1-2. Dry the cleaned carbon fiber insulation material, apply the hardening coating adhesive evenly to the surface of the carbon fiber insulation material, and after the penetration depth reaches 0.5-3mm, cure and shape it at a temperature of 160-200℃, and let it cool naturally to room temperature to obtain a carbon hardened layer with a thickness of 0.5-3mm. 1-3. Use sandpaper to sand the surface of the carbon-hardened layer to clean off any particles.

3. The method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation material according to claim 1, characterized in that, The specific process of step 2) is as follows: 2-1. After mixing carbon fiber powder, coarse graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive one; 2-2. Apply coating adhesive to the surface of the carbon-cured layer, with a coating thickness of 40–120 μm; 2-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a first transition coating with a thickness of 40-120μm.

4. The method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation material according to claim 1, characterized in that, The specific process of step 3) is as follows: 3-1. After mixing carbon fiber powder, fine graphite powder, resin, water, dispersant and crosslinking agent according to the ratio and order, stir for 4-6 hours to obtain coating adhesive II; 3-2. Apply coating adhesive II to the surface of the first transition coating, with a coating thickness of 20–80 μm; 3-3. Dry at 60-80℃ for 0.5-2 hours, then heat to 140-160℃ for 2-4 hours, and then carbonize at 600-900℃ to obtain a second transition coating with a thickness of 20-80μm; then graphitize at 1600-2200℃, so that the resin, dispersant and crosslinking agent react fully, and the first transition coating and the second transition coating become a carbon coating.

5. The method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation material according to claim 1, characterized in that, In steps 1) to 3), the resin is one or more of epoxy resin, polybutadiene resin, phenolic resin, unsaturated polyester resin, polyurethane resin, and furan resin; the crosslinking agent is one or more of dicumyl peroxide, dicumyl peroxide, diethylenetriamine, diethylenetriamine, polyisocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, and polyether.

6. The method for preparing a high-oxidation-resistant pyrolytic carbon coating for carbon fiber insulation material according to claim 1, characterized in that, The specific process of step 4) is as follows: 4-1. Place the carbon fiber insulation material obtained after step 3) into a chemical vapor deposition furnace; 4-2. A chemical vapor deposition furnace is introduced with nitrogen and a mixture of methane / propane / propylene gas, the pressure of which is 50–2000 Pa; the flow rate of nitrogen in the mixture is 300–12000 mL / min, and the flow rate of methane / propane / propylene gas is 100–1200 mL / min. 4-3. The temperature is raised to 900-1100℃ in a chemical vapor deposition furnace at a heating rate of 1-10℃ / min, and the deposition is carried out for 10-50h. Then, a vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50μm is formed on the second transition coating, and finally the coating is naturally cooled to room temperature.

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