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

Abstract

The invention 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) carrying out carbon hardening treatment on the surface of the carbon fiber thermal insulation material to obtain a carbon hardened layer; 2) uniformly coating the surface of the carbon hardened layer with a coating adhesive I to form a first transition coating; 3) coating the surface of the first transition coating with a coating adhesive II to form a second transition coating; and 4) carrying out carbon vapor deposition on the first transition coating and the second transition coating, and depositing a more compact vapor deposition pyrolytic carbon coating (the density is 1.5-2.2 g / cm < 3 >) on the second transition coating. The prepared carbon fiber thermal insulation material with the pyrolytic carbon coating on the surface has excellent thermal insulation performance and high oxidation resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of functional coating material preparation, and in particular to a method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material. Background Art

[0002] With the rapid development of aerospace, photovoltaics, semiconductors, and other fields, the demand for high-efficiency thermal insulation materials is increasing. Carbon fiber insulation materials, due to their excellent thermal insulation properties, 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, single-crystalline silicon, as a photovoltaic power generation material, has become the mainstream material for solar photovoltaic power generation due to its high photoelectric conversion efficiency and outstanding commercial advantages. The thermal field system is the most important component of the single crystal furnace. The thermal field is mainly composed of graphite materials, carbon-carbon composite materials, and carbon fiber insulation materials. During the Czochralski single crystal silicon pulling process, the melting of silicon material generates silicon vapor and molten silicon splash, which causes silicification corrosion of the carbon-carbon thermal field material, seriously affecting its mechanical properties and service life, and is prone to cracking and pulverization of carbon-carbon components. In addition, the epitaxial growth of third-generation semi-silicon carbide severely corrodes and oxidizes both graphite and carbon fiber insulation materials, which can easily cause cracking, brittleness, and pulverization of the products, significantly shortening their service life.

[0003] To address these issues, researchers have attempted to create protective coatings on carbon fiber insulation materials. Common methods include applying graphite foil, large-tow carbon cloth, or carbon-based coatings to the surface. However, these methods still have limitations, such as coatings that are prone to cracking and flaking, and graphite foil and carbon cloth that are prone to delamination. These methods make it difficult to simultaneously meet the required thermal insulation, ablation resistance, and oxidation resistance in high-temperature environments.

[0004] Pyrolytic carbon coatings have become the first choice for surface coating protection of carbon-carbon thermal field materials due to their excellent thermal shock resistance and wear resistance. However, they cannot be simply borrowed when applied to low-density carbon fiber thermal insulation materials. Problems such as pyrolytic carbon penetrating into the substrate to affect the thermal insulation of the carbon fiber, preventing too much pyrolytic carbon from being deposited on the surface of the fiber, affecting the thickness and density uniformity of the coating, and matching thermal expansion need to be addressed. Therefore, it is necessary to develop a method that can form a stable coating with strong oxidation resistance on the surface of carbon fiber thermal insulation materials, which can effectively improve the material's high-temperature oxidation resistance and resist the erosion of reactive gases. This is also the focus and difficulty of current research. Because not only the interface bonding problem between the coating and the substrate needs to be solved, but also factors such as the thickness uniformity and density control of the coating need to be considered to meet the performance requirements in different application scenarios.

[0005] There are some research results on how to improve the hardness of carbon-carbon materials and the density of coatings. For example:

[0006] Chinese patent application publication number CN111807853A discloses a "carbon-carbon composite material, its preparation process, and application." The prepared carbon-carbon composite material comprises, by mass, 20% to 36% carbon fiber, 28% to 45% vapor-deposited carbon, and 26% to 48% impregnated carbon. The preparation process includes preform preparation, impregnant raw material preparation, and a multi-stage densification reaction. The prepared carbon-carbon composite material maintains mechanical, thermal, and friction and wear properties at room temperature in high and ultra-high temperature environments. However, the carbon fiber modification process still faces challenges: the impregnant formulation and modification process require further optimization. For example, the use of additives containing metals and the element B, such as LiAlH4, NaBH4, and i-Bu2AlH, affects product purity, limiting its application in high-purity environments. Furthermore, the process is primarily targeted at the preparation of high-density carbon-carbon materials and is not suitable for the preparation of low-density carbon fiber insulation materials.

[0007] The Chinese invention patent with authorization announcement number CN103160826B discloses "a method for preparing a pyrolytic carbon / nickel composite coating on the surface of continuous carbon fiber". The method uses chemical vapor deposition to prepare a pyrolytic carbon coating on the surface of the carbon fiber in the weftless carbon fiber cloth, and uses chemical plating to prepare a nickel coating, which can effectively prevent the fiber from being oxidized and protect the carbon fiber from being damaged. However, it uses chemical nickel plating, and the production process uses solutions such as tin chloride, silver nitrate, sodium hypophosphite, sodium acetate, sodium phosphite, and nickel sulfate, all of which contain metals and phosphorus. This affects the purity of the product and its application, especially in high-end application fields such as photovoltaics, semiconductors, and sapphire. Due to the extremely high requirements for metal elements and phosphorus, its products cannot be used.

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

[0009] 1. After the existing carbon fiber thermal insulation material coating is prepared, the bonding strength between the carbon coating and the carbon fiber thermal insulation material matrix is insufficient, which easily causes the coating to crack and fall off, affecting the overall performance and service life of the material;

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

[0011] 3. The coating uniformity and thickness control capabilities of existing carbon fiber insulation materials are insufficient, making it difficult to meet the needs of long-term substrate protection in high-temperature environments;

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

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

[0014] The present invention provides a method for preparing a highly resistant pyrolytic carbon coating of a carbon fiber thermal insulation material. The prepared carbon fiber thermal insulation material with a pyrolytic carbon coating on the surface has excellent thermal insulation performance and strong anti-oxidation performance, and effectively solves the problems existing in the prior art such as the carbon coating and the carbon fiber thermal insulation material matrix being prone to cracking and falling off due to insufficient bonding strength, the coating being uneven and having poor density and prone to local cracking, the high-temperature oxidation resistance being poor and unable to be used stably for a long time, and the coating falling off and easily contaminating the product.

[0015] In order to achieve the above object, the present invention adopts the following technical solutions:

[0016] A method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material comprises the following steps:

[0017] 1) Carbon hardening treatment is performed on the surface of the carbon fiber thermal insulation material: a hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of the carbon fiber thermal insulation material, and a carbon hardened layer is obtained after curing;

[0018] 2) using a coating glue composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the carbon hardened layer formed in step 1) to form a first transition coating;

[0019] 3) using a second coating glue composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the first transition coating formed in step 2) to form a second transition coating;

[0020] 4) Carrying out carbon vapor deposition on the first transition coating and the second transition coating, and then depositing a denser vapor deposition pyrolytic carbon coating on the second transition coating, wherein the density of the vapor deposition pyrolytic carbon coating is 1.5 to 2.2 g / cm 3 .

[0021] In the step 1), the hardened coating adhesive is composed of the following components in parts by weight: 20-60 parts of carbon fibers, 10-30 parts of carbon nanotubes, 20-60 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of crosslinking agent, and 35-360 parts of water; the carbon fibers are ground, and the particle size of the ground carbon fibers is 3-6 μm; the preparation process of the hardened coating adhesive is: first, the carbon fibers and carbon nanotubes are evenly mixed, 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 on the surface of the carbon fiber insulation material after processing, and use ethanol and acetone ultrasonic cleaning for 15 to 20 minutes in sequence;

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

[0025] 1-3. Use sandpaper to polish the surface of the carbon hardened layer and clean the particles on the surface.

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

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

[0028] 2-1. The carbon fiber powder, coarse graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue;

[0029] 2-2. Apply a coating glue on the surface of the carbon hardened layer to a coating thickness of 40 to 120 μm;

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

[0031] In the step 3), the coating glue 2 is composed of the following components in parts by weight: 5-20 parts of carbon fiber powder, 30-70 parts of fine graphite powder, 50-90 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of cross-linking agent, and 59-432 parts of 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 glue 2 is: first, the carbon fiber powder and the fine graphite powder are mixed, and then water is added and stirred evenly, and then the dispersant and resin are added and mixed evenly, and finally the cross-linking agent is added and mixed evenly to obtain the coating glue 2.

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

[0033] 3-1. The carbon fiber powder, fine graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue II;

[0034] 3-2. The second coating glue is applied to the surface of the first transition coating, with a coating thickness of 20 to 80 μm;

[0035] 3-3. Dry at 60-80°C for 0.5-2 hours, then heat to 140-160°C and cure for 2-4 hours. Then carbonize at 600-900°C to obtain a second transition coating with a thickness of 20-80 μm. Then, graphitize at 1600-2200°C to allow the resin, dispersant, and cross-linking agent to fully react, so that 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 hydroperoxide, diethylenetriamine, diethylenetriamine, polyisocyanate, alkyl isocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, polyethers, and polyoxyethylene alkylphenol ether.

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

[0038] 4-1. The carbon fiber insulation material obtained in step 3) is placed in a chemical vapor deposition furnace;

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

[0040] 4-3. The temperature in a chemical vapor deposition furnace is raised to 900-1100°C at a heating rate of 1-10°C / min and deposited for 10-50 hours, so that the penetration depth of the first transition coating and the second transition coating reaches 60-200 μm. A vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50 μm is then formed on the second transition coating, and the coating is finally naturally cooled to room temperature.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1) By hardening the carbon fiber insulation material and providing 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 environments are enhanced, thereby effectively solving the problems of easy deformation and poor wear resistance of carbon fiber insulation materials in the prior art;

[0043] 2) Through the synergistic effect of the dispersant and cross-linking agent, the dispersion of graphite powder and fiber in the coating is improved, and the cross-linking of fiber, graphite and binder particles is promoted to form a dense network structure, which effectively prevents the particles in the coating from falling off and significantly increases the density and uniformity of the coating;

[0044] 3) By strictly controlling parameters such as gas flow, gas ratio and vacuum degree, the uniformity and stability of the carbon vapor deposition coating are improved, solving the problems of uneven coating thickness and poor adhesion in the existing technology;

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

[0046] 5) The preparation method of the present invention is simple to operate, easy to achieve large-scale production, and does not require expensive equipment investment, which greatly reduces production costs and is conducive to promoting the commercial application of carbon fiber thermal insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0048] Figure 2 This is an electron microscope image of a cross section of the vapor-deposited pyrolytic carbon coating of the present invention. DETAILED DESCRIPTION

[0049] The method for preparing a highly oxidative-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to the present invention comprises the following steps:

[0050] 1) Carbon hardening treatment is performed on the surface of the carbon fiber thermal insulation material: a hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of the carbon fiber thermal insulation material, and a carbon hardened layer is obtained after curing;

[0051] 2) using a coating glue composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the carbon hardened layer formed in step 1) to form a first transition coating;

[0052] 3) using a second coating glue composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the first transition coating formed in step 2) to form a second transition coating;

[0053] 4) Carrying out carbon vapor deposition on the first transition coating and the second transition coating, and then depositing a denser vapor deposition pyrolytic carbon coating on the second transition coating, wherein the density of the vapor deposition pyrolytic carbon coating is 1.5 to 2.2 g / cm 3 .

[0054] In the step 1), the hardened coating adhesive is composed of the following components in parts by weight: 20-60 parts of carbon fibers, 10-30 parts of carbon nanotubes, 20-60 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of crosslinking agent, and 35-360 parts of water; the carbon fibers are ground, and the particle size of the ground carbon fibers is 3-6 μm; the preparation process of the hardened coating adhesive is: first, the carbon fibers and carbon nanotubes are evenly mixed, 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 on the surface of the carbon fiber insulation material after processing, and use ethanol and acetone ultrasonic cleaning for 15 to 20 minutes in sequence;

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

[0058] 1-3. Use sandpaper to polish the surface of the carbon hardened layer and clean the particles on the surface.

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

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

[0061] 2-1. The carbon fiber powder, coarse graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue;

[0062] 2-2. Apply a coating glue on the surface of the carbon hardened layer to a coating thickness of 40 to 120 μm;

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

[0064] In the step 3), the coating glue 2 is composed of the following components in parts by weight: 5-20 parts of carbon fiber powder, 30-70 parts of fine graphite powder, 50-90 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of cross-linking agent, and 59-432 parts of 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 glue 2 is: first, the carbon fiber powder and the fine graphite powder are mixed, and then water is added and stirred evenly, and then the dispersant and resin are added and mixed evenly, and finally the cross-linking agent is added and mixed evenly to obtain the coating glue 2.

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

[0066] 3-1. The carbon fiber powder, fine graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue II;

[0067] 3-2. The second coating glue is applied to the surface of the first transition coating, with a coating thickness of 20 to 80 μm;

[0068] 3-3. Dry at 60-80°C for 0.5-2 hours, then heat to 140-160°C and cure for 2-4 hours. Then carbonize at 600-900°C to obtain a second transition coating with a thickness of 20-80 μm. Then, graphitize at 1600-2200°C to allow the resin, dispersant, and cross-linking agent to fully react, so that 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 hydroperoxide, diethylenetriamine, diethylenetriamine, polyisocyanate, alkyl isocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, polyethers, and polyoxyethylene alkylphenol ether.

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

[0071] 4-1. The carbon fiber insulation material obtained in step 3) is placed in a chemical vapor deposition furnace;

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

[0073] 4-3. The temperature in a chemical vapor deposition furnace is raised to 900-1100°C at a heating rate of 1-10°C / min and deposited for 10-50 hours, so that the penetration depth of the first transition coating and the second transition coating reaches 60-200 μm. A vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50 μm is then formed on the second transition coating, and the coating is finally naturally cooled to room temperature.

[0074] The surface electron microscope image of the vapor deposition pyrolytic carbon coating of the present invention is as follows Figure 1 As shown, the cross-section electron microscope image of the vapor deposition pyrolytic carbon coating is as follows Figure 2 shown.

[0075] In order to more intuitively embody the present invention, the embodiments of the present invention are further described in conjunction with examples. The following examples are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solution that can be obviously obtained by a person skilled in the art within the technical scope disclosed in the present invention, including simple changes or equivalent replacements, is within the scope of protection of the present invention.

[0076] In the following examples, all raw reagents and 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 highly oxidative-resistant pyrolytic carbon coating of the carbon fiber thermal insulation material is as follows:

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

[0080] Step 1-1, clean the dust on the surface of the processed carbon fiber thermal insulation material, and use ethanol and acetone ultrasonic cleaning for 20 minutes in sequence;

[0081] Step 1-2: 30 g of carbon fiber with a particle size of 4 μm and 20 g of carbon nanotubes were mixed evenly, and then added to 120 g of water and mixed evenly. Then, 1.6 g of polyvinyl alcohol (dispersant) was added, followed by 55 g of epoxy resin and 1.2 g of phthalic anhydride (crosslinking agent). After mixing evenly, a hardened coating adhesive was obtained.

[0082] Step 1-3: Dry the carbon fiber thermal insulation material cleaned in step 1-1, evenly apply the hardened coating glue to the surface of the carbon fiber thermal insulation material, control the penetration depth to 2 mm, and then cure it at 180° C. and naturally cool it to room temperature to obtain a 2 mm thick carbon hardened layer;

[0083] Steps 1-4: Use sandpaper to polish the surface of the carbon hardened layer and clean the remaining particles after polishing.

[0084] Step 2: Carbon fiber powder, coarse graphite powder, resin, dispersant, and cross-linking agent are used to prepare a coating adhesive. The coating adhesive is evenly applied to the surface of the carbon hardened layer to form a first transition coating. The specific process is as follows:

[0085] Step 2-1: 30 g of 2 μm carbon fiber powder and 40 g of 50 μm coarse graphite powder were mixed evenly, then added to 80 g of water and mixed evenly, 2 g of starch (dispersant) was added and stirred evenly, and then 60 g of phenolic resin and 1.2 g of phthalic anhydride (crosslinking agent) were added and mixed evenly to obtain coating glue 1;

[0086] Step 2-2, evenly apply the coating glue 1 on the surface of the carbon hardened layer, and control the coating thickness to be 80 μm;

[0087] Step 2-3: drying at 80° C. for 1 hour, then heating to 150° C. for curing for 3 hours, and then carbonizing at 800° C. to form a first transition coating.

[0088] Step 3: Use carbon fiber powder, fine graphite powder, resin, dispersant and cross-linking agent to prepare coating glue 2, and evenly apply the coating glue 2 to the surface of the first transition coating to form a second transition coating. The specific process is as follows:

[0089] Step 3-1: 15 g of carbon fiber powder with a particle size of 0.5 μm and 40 g of fine graphite powder with a particle size of 0.5 μm were mixed evenly, then added to 150 g of water and mixed evenly, 2.2 g of starch (dispersant) was added and stirred evenly, and then 70 g of phenolic resin and 1.2 g of phthalic anhydride (cross-linking agent) were added and mixed evenly to obtain coating glue II;

[0090] Step 3-2, evenly apply the second coating glue on the surface of the first transition coating, with a coating thickness of 30 μm;

[0091] Step 3-3: Dry at 80°C for 1.5 hours, then heat to 150°C for curing for 3 hours, and then carbonize at 800°C to form a second transition coating with a thickness of 30 μm. Graphitization is then performed at 1800°C to allow the resin to fully react with the dispersant and crosslinking agent, transforming the first and second transition coatings into carbon coatings.

[0092] Step 4: performing carbon vapor deposition on the surfaces of the first transition coating and the second transition coating, and then depositing carbon on the second transition coating to form a denser vapor-deposited carbon coating. The specific process is as follows:

[0093] Step 4-1, placing the carbon fiber thermal insulation material after step 3 in a chemical vapor deposition furnace;

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

[0095] Step 4-3: Heat the mixture to 1100°C at a heating rate of 5°C / min and deposit for 30 hours. The thickness of the first transition coating and the second transition coating is 100 μm. Then, a denser vapor-deposited carbon pyrolytic coating with a thickness of 30 μm is deposited on the second transition coating. The mixture is cooled naturally to room temperature. The density of the vapor-deposited carbon pyrolytic coating is 2.1 g / cm 3 .

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

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

[0098] [Example 2]

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

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

[0101] Step 1-1, clean the dust on the surface of the processed carbon fiber thermal insulation material, and use ethanol and acetone ultrasonic cleaning for 20 minutes in sequence;

[0102] Step 1-2: 30 g of carbon fiber with a particle size of 4 μm and 20 g of carbon nanotubes were mixed evenly, then added to 100 g of water and mixed evenly, 0.5 g of polyvinyl alcohol (dispersant) was added, 55 g of epoxy resin was added, and finally 1.0 g of diethylenetriamine (dispersant) was added, and mixed evenly to obtain a hardened coating adhesive;

[0103] Step 1-3: Dry the carbon fiber thermal insulation material cleaned in step 1-1, evenly apply the hardened coating glue to the surface of the carbon fiber thermal insulation material, control the penetration depth to 2 mm, and then cure it at 180° C. and naturally cool it to room temperature to obtain a 2 mm thick carbon hardened layer;

[0104] Steps 1-4: Use sandpaper to polish the surface of the carbon hardened layer and clean the remaining particles after polishing.

[0105] Step 2: Carbon fiber powder, coarse graphite powder, resin, dispersant, and cross-linking agent are used to prepare a coating adhesive. The coating adhesive is evenly applied to the surface of the carbon hardened layer to form a first transition coating. The specific process is as follows:

[0106] Step 2-1: 30 g of carbon fiber powder with a particle size of 2 μm and 40 g of coarse graphite powder with a particle size of 50 μm were mixed evenly, then added to 70 g of water and mixed evenly, 2 g of polyvinyl alcohol (dispersant) was added and stirred evenly, and then 60 g of epoxy resin and 1 g of diethylenetriamine (cross-linking agent) were added and mixed evenly to obtain coating glue 1;

[0107] Step 2-2, evenly apply the coating glue 1 on the surface of the carbon hardened layer, and control the coating thickness to be 80 μm;

[0108] Step 2-3: Dry at 80° C. for 1 hour, then heat to 150° C. for curing for 3 hours, and then carbonize at 800° C. to form a first transition coating.

[0109] Step 3: Using carbon fiber powder, fine graphite powder, resin, dispersant and cross-linking agent to prepare coating glue 2, the coating glue 2 is evenly applied to the surface of the first transition coating to form a second transition coating; the specific process is as follows;

[0110] Step 3-1: 15 g of carbon fiber powder with a particle size of 0.5 μm and 40 g of fine graphite powder with a particle size of 0.5 μm were mixed evenly, then added to 100 g of water and mixed evenly, 2 g of polyvinyl alcohol (dispersant) was added and stirred evenly, and then 70 g of epoxy resin and 1.2 g of phthalic anhydride (cross-linking agent) were added and mixed evenly to obtain coating glue II;

[0111] Step 3-2: evenly apply the second coating glue on the surface of the first transition coating, and control the coating thickness to be 30 μm;

[0112] Step 3-3: Dry at 80°C for 1.5 hours, then heat to 150°C for curing for 3 hours, and then carbonize at 600°C to form a second transition coating with a thickness of 30 μm. Then, graphitize at 1800°C to allow the resin, dispersant, and crosslinker to fully react, turning the first and second transition coatings into carbon coatings.

[0113] Step 4: performing carbon vapor deposition on the surfaces of the first transition coating and the second transition coating, and then depositing carbon on the second transition coating to form a denser vapor-deposited carbon coating. The specific process is as follows:

[0114] Step 4-1, placing the carbon fiber thermal insulation material after step 3 in a chemical vapor deposition furnace;

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

[0116] Step 4-3: Heat the mixture to 1100°C at a heating rate of 5°C / min and deposit for 35 hours. The depth of the first transition coating and the second transition coating is 105 μm. Then, a denser vapor-deposited carbon pyrolytic coating with a thickness of 50 μm is deposited on the second transition coating. The mixture is cooled naturally to room temperature. The density of the vapor-deposited carbon pyrolytic coating is 2.1 g / cm 3 .

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

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

[0119] [Example 3]

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

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

[0122] Step 1-1, clean the dust on the surface of the processed carbon fiber thermal insulation material, and use ethanol and acetone ultrasonic cleaning for 20 minutes in sequence;

[0123] Step 1-2: 30 g of carbon fiber with a particle size of 4 μm and 20 g of carbon nanotubes were mixed evenly, then added to 120 g of water and mixed evenly, followed by addition of 1.6 g of gelatin (dispersant), 55 g of furan resin, and 1.0 g of diethylenetriamine (dispersant), and mixed evenly to obtain a hardened coating adhesive;

[0124] Step 1-3: Dry the carbon fiber thermal insulation material cleaned in step 1-1, evenly apply the hardened coating glue to the surface of the carbon fiber thermal insulation material, control the penetration depth to 2 mm, and then cure it at 180° C. and naturally cool it to room temperature to obtain a 2 mm thick carbon hardened layer;

[0125] Steps 1-4: Use sandpaper to polish the surface of the carbon hardened layer and clean the remaining particles after polishing.

[0126] Step 2: Carbon fiber powder, coarse graphite powder, resin, dispersant, and cross-linking agent are used to prepare a coating adhesive. The coating adhesive is evenly applied to the surface of the carbon hardened layer to form a first transition coating. The specific process is as follows:

[0127] Step 2-1, 25g of carbon fiber powder with a particle size of 2μm and 45g of coarse graphite powder with a particle size of 50μm were mixed evenly, then added to 80g of water and mixed evenly, 2g of diethylenetriamine (dispersant) was added and stirred evenly, and then 60g of furan resin and 1g of diethylenetriamine (cross-linking agent) were added and mixed evenly to obtain coating glue 1;

[0128] Step 2-2, evenly apply the coating glue 1 on the surface of the carbon hardened layer, and control the coating thickness to be 90 μm;

[0129] Step 2-3: Dry at 80° C. for 1 hour, then heat to 150° C. for curing for 3 hours, and then carbonize at 800° C. to form a first transition coating.

[0130] Step 3: Use carbon fiber powder, fine graphite powder, resin, dispersant and cross-linking agent to prepare coating glue 2, and evenly apply the coating glue 2 to the surface of the first transition coating to form a 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, then add them to 150g of water and mix them evenly. Add 2g of diethylenetriamine (dispersant) and stir evenly. Then add 70g of furan resin and 1.2g of phthalic anhydride (cross-linking agent), mix evenly to obtain coating glue II.

[0132] Step 3-2, evenly apply the second coating glue on the surface of the first transition coating, and control the coating thickness to be 40 μm;

[0133] Step 3-3: Dry at 80°C for 1.5 hours, then heat to 150°C for curing for 3 hours, and then carbonize at 700°C to form a second transition coating with a thickness of 40 μm. Then, graphitize at 1800°C to allow the resin to fully react with the dispersant and crosslinking agent, turning the first and second transition coatings into carbon coatings.

[0134] Step 4: performing carbon vapor deposition on the surfaces of the first transition coating and the second transition coating, and then depositing carbon on the second transition coating to form a denser vapor-deposited carbon coating. The specific process is as follows:

[0135] Step 4-1, placing the carbon fiber thermal insulation material after step 3 in a chemical vapor deposition furnace;

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

[0137] Step 4-3: Heat the material to 1100°C at a heating rate of 5°C / min and deposit for 40 hours. The thickness of the first transition coating and the second transition coating is 125 μm. Then, a denser vapor-deposited carbon pyrolytic coating with a thickness of 50 μm is deposited on the second transition coating. The material is naturally cooled to room temperature. The density of the vapor-deposited carbon coating is 2.1 g / cm 3 .

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

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

[0140] The above examples prove that the highly resistant pyrolytic carbon coating for carbon fiber thermal insulation material prepared according to the method of the present invention has excellent thermal insulation performance and strong resistant oxidation performance, and can avoid or reduce the cracking and falling off of the pyrolytic carbon coating.

[0141] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material, characterized in that: The steps include: 1) Carbon hardening treatment is performed on the surface of the carbon fiber thermal insulation material: a hardening coating adhesive composed of carbon fiber, carbon nanotubes, resin, dispersant, crosslinking agent and water is applied to the surface of the carbon fiber thermal insulation material, and a carbon hardened layer is obtained after curing; 2) using a coating glue composed of carbon fiber powder, coarse graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the carbon hardened layer formed in step 1) to form a first transition coating; 3) using a second coating glue composed of carbon fiber powder, fine graphite powder, resin, dispersant, crosslinking agent and water, and evenly applying it to the surface of the first transition coating formed in step 2) to form a second transition coating; 4) Carrying out carbon vapor deposition on the first transition coating and the second transition coating, and then depositing a denser vapor deposition pyrolytic carbon coating on the second transition coating, wherein the density of the vapor deposition pyrolytic carbon coating is 1.5 to 2.2 g / cm 3 .

2. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: In the step 1), the hardened coating adhesive is composed of the following components in parts by weight: 20-60 parts of carbon fibers, 10-30 parts of carbon nanotubes, 20-60 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of crosslinking agent, and 35-360 parts of water; the carbon fibers are ground, and the particle size of the ground carbon fibers is 3-6 μm; the preparation process of the hardened coating adhesive is: first, the carbon fibers and carbon nanotubes are evenly mixed, the dispersant and resin are added and mixed evenly, and finally, the crosslinking agent is added and mixed evenly.

3. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: The specific process of step 1) is as follows: 1-1. Clean the dust on the surface of the carbon fiber insulation material after processing, and use ethanol and acetone ultrasonic cleaning for 15 to 20 minutes in sequence; 1-2. Dry the cleaned carbon fiber insulation material, evenly apply the hardening coating adhesive to the surface of the carbon fiber insulation material to a penetration depth of 0.5 to 3 mm, then cure at 160 to 200°C and cool naturally to room temperature to obtain a carbon hardened layer with a thickness of 0.5 to 3 mm. 1-3. Use sandpaper to polish the surface of the carbon hardened layer and clean the particles on the surface.

4. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: In the step 2), the coating adhesive is composed of the following components in parts by weight: 10 to 30 parts of carbon fiber powder, 20 to 60 parts of coarse graphite powder, 40 to 80 parts of resin, 0.2 to 3 parts of dispersant, and 0.1 to 1.5 parts of cross-linking agent; 49 to 408 parts of water; the particle size of the carbon fiber powder is 1 to 4 μm, and the particle size of the coarse graphite powder is 20 to 80 μm; the preparation process of the coating adhesive is: first, the carbon fiber powder and the coarse graphite powder are mixed, water is added and stirred evenly, then the dispersant and resin are added and mixed evenly, and finally the cross-linking agent is added and mixed evenly to obtain the coating adhesive.

5. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: The specific process of step 2) is as follows: 2-1. The carbon fiber powder, coarse graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue; 2-2. Apply a coating glue on the surface of the carbon hardened layer to a coating thickness of 40 to 120 μm; 2-3. Dry at 60-80°C for 0.5-2h, then heat to 140-160°C for curing for 2-4h, and then carbonize at 600-900°C to obtain a first transition coating with a thickness of 40-120μm.

6. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: In the step 3), the coating glue 2 is composed of the following components in parts by weight: 5-20 parts of carbon fiber powder, 30-70 parts of fine graphite powder, 50-90 parts of resin, 0.2-3 parts of dispersant, 0.1-1.5 parts of cross-linking agent, and 59-432 parts of 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 glue 2 is: first, the carbon fiber powder and the fine graphite powder are mixed, and then water is added and stirred evenly, and then the dispersant and resin are added and mixed evenly, and finally the cross-linking agent is added and mixed evenly to obtain the coating glue 2.

7. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: The specific process of step 3) is as follows: 3-1. The carbon fiber powder, fine graphite powder, resin, water, dispersant and cross-linking agent are mixed in proportion and order, and stirred for 4 to 6 hours to obtain a coating glue II; 3-2. The second coating glue is applied to the surface of the first transition coating, with a coating thickness of 20 to 80 μm; 3-3. Dry at 60-80°C for 0.5-2 hours, then heat to 140-160°C and cure for 2-4 hours. Then carbonize at 600-900°C to obtain a second transition coating with a thickness of 20-80 μm. Then, graphitize at 1600-2200°C to allow the resin, dispersant, and cross-linking agent to fully react, so that the first transition coating and the second transition coating become a carbon coating.

8. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal 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, unsaturated polyester resin, and furan resin; the crosslinking agent is one or more of dicumyl peroxide, dicumyl hydroperoxide, diethylenetriamine, diethylenetriamine, polyisocyanate, alkyl isocyanate, glycidyl ether, phthalic anhydride, and tetrachlorophthalic anhydride; and the dispersant is one or more of gelatin, starch, polyvinyl alcohol, polyethers, and polyoxyethylene alkylphenol ether.

9. The method for preparing a high-oxidation-resistant pyrolytic carbon coating of a carbon fiber thermal insulation material according to claim 1, characterized in that: The specific process of step 4) is as follows: 4-1. The carbon fiber insulation material obtained in step 3) is placed in a chemical vapor deposition furnace; 4-2. A chemical vapor deposition furnace is fed with a mixture of nitrogen and methane / propane / propylene at a pressure of 50 to 2000 Pa; the nitrogen flow rate in the mixture is 300 to 12000 mL / min, and the methane / propane / propylene gas flow rate is 100 to 1200 mL / min; 4-3. The temperature in a chemical vapor deposition furnace is raised to 900-1100°C at a heating rate of 1-10°C / min and deposited for 10-50 hours, so that the penetration depth of the first transition coating and the second transition coating reaches 60-200 μm. A vapor-deposited pyrolytic carbon coating with a deposition thickness of 1-50 μm is then formed on the second transition coating, and the coating is finally naturally cooled to room temperature.

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