Composite coating on surface of carbon fiber hard insulation felt and preparation method of composite coating

Abstract

The invention provides a composite coating on the surface of a carbon fiber hard insulation felt and a preparation method of the composite coating. The preparation method of the composite coating on the surface of the carbon fiber hard insulation felt comprises the following steps: uniformly stirring a mixture consisting of resin R1, SiC powder, Si powder, C powder and a diluent X1 to form slurry M1, then uniformly brushing the slurry M1 on the surface of the carbon fiber hard insulation felt, and finally forming a pre-coating layer A on the surface of the carbon fiber hard insulation felt through curing treatment; the method comprises the following steps: uniformly stirring a mixture consisting of resin R2, Si powder and a diluent X2 to form slurry M2, uniformly brushing the slurry M2 on the surface of a pre-coating layer A formed on the surface of a carbon fiber hard insulation felt, then carrying out curing treatment, and finally forming a pre-coating layer B on the surface of the pre-coating layer A on the surface of the carbon fiber hard insulation felt, and carrying out vacuum high-temperature sintering heat treatment on the carbon fiber hard insulation felt with the pre-coating A and the pre-coating B, and finally forming a SiC / C composite coating on the surface of the carbon fiber hard insulation felt.

Description

Technical Field

[0001] The present application belongs to the technical field of high temperature resistant coating preparation, and relates to a composite coating on the surface of a carbon fiber hard thermal insulation felt and a preparation method thereof. Background Art

[0002] As a new type of high-temperature resistant thermal insulation material, carbon fiber rigid insulation felt can be widely used in photovoltaic single crystal silicon thermal field, semiconductor, aerospace and other high-end equipment manufacturing fields due to its low density, low thermal conductivity, high strength and good processing performance. It is usually used as thermal insulation material for the internal thermal field of high-temperature furnaces to achieve the production and preparation of semiconductors such as single crystal silicon, silicon carbide and gallium nitride. At the same time, due to its low thermal conductivity, it can effectively reduce the energy consumption of the entire production and preparation. For high-temperature furnaces themselves, which are high-energy consumption equipment, this also plays a role in energy saving and cost reduction.

[0003] However, for some high-temperature furnaces containing silicon vapor, such as: pulling furnaces for producing single crystal silicon or high-temperature furnaces for preparing silicon carbide semiconductors, carbon fiber rigid insulation felt, as its insulation material, is in an atmosphere of silicon vapor for a long time, which will cause the carbon fiber rigid insulation felt to be corroded and powder to fall off, which will eventually affect the quality of the products such as single crystal silicon or silicon carbide semiconductors produced.

[0004] In order to solve the problem that carbon fiber rigid insulation felt is easily corroded by silicon vapor, protective coatings such as silicon carbide coating or carbon coating are usually prepared on the surface of carbon fiber rigid insulation felt to solve the problem that carbon fiber rigid insulation felt is easily corroded by silicon vapor. Considering that silicon carbide coating has better high temperature resistance, corrosion resistance and wear resistance than carbon coating, silicon carbide coating has more advantages than carbon coating as a protective coating for carbon fiber rigid insulation felt.

[0005] The current preparation technologies for silicon carbide coatings mainly include: CVD or thermal spraying technology, but the cost of preparing silicon carbide coatings using CVD or thermal spraying technology is high, and the bonding strength between the prepared silicon carbide coating and the surface of the carbon fiber hard insulation felt is weak, and the coating is prone to fall off during use.

[0006] Patent CN114907144B proposes an improvement plan: using resin, silicon source (such as single Si or SiO 2 ) and a diluent, and then the slurry is coated on the surface of the carbon fiber hard insulation felt through a coating process, and then cured and high-temperature sintered in sequence, and finally a SiC-C composite high-temperature coating is obtained on the hard felt surface. Considering the Si or SiO in the slurry coating 2 Direct reaction with C (formed after carbonization of resin) will cause a certain volume shrinkage, as shown in the following chemical reaction formula:

[0007]

[0008] Through reaction formula ①, it can be calculated that there will be a certain volume shrinkage before and after the reaction, and the volume shrinkage rate is 30.85%.

[0009] It can also be seen from reaction formula ② that the reaction will also bring about a certain volume shrinkage before and after, and the volume shrinkage rate is 62.55%.

[0010] It can be seen from reaction equations ① and ② that whether using single Si or SiO 2 As the silicon source of the slurry coating, the final reaction sintering to form SiC will bring about a certain degree of volume shrinkage. The improvement scheme proposed in this technical solution will cause the sintered coating to show a certain degree of cracking. Therefore, the problems existing in this technical solution need to be solved. Summary of the invention

[0011] In view of the above problems, the purpose of this application is to provide a composite coating on the surface of carbon fiber rigid thermal insulation felt and its preparation method. First, a layer of slurry is brushed on the surface of carbon fiber rigid thermal insulation felt and cured to form pre-coating layer A, and then another layer of slurry is brushed and cured to form pre-coating layer B. Through vacuum high-temperature sintering, the components in pre-coating layer B diffuse into pre-coating layer A, react and produce volume expansion. By controlling the sintering conditions and adjusting the degree of reaction, the expansion and contraction offset each other, thereby avoiding cracking of the coating and improving the protective performance of the composite coating.

[0012] The method for preparing the composite coating on the surface of the carbon fiber rigid thermal insulation felt provided in the present application comprises the following steps:

[0013] The resin R 1 , SiC powder, Si powder, C powder and diluent X 1 The mixture is stirred to form a slurry M 1 , then the slurry M 1 Evenly brushing on the surface of the carbon fiber rigid thermal insulation felt, and then curing, finally forming a pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt;

[0014] The resin R 2 , Si powder and diluent X 2 The mixture is stirred to form a slurry M 2 , then the slurry M 2 The pre-coating layer A is evenly applied on the surface of the pre-coating layer A formed on the surface of the carbon fiber rigid thermal insulation felt, and then cured, and finally a layer of pre-coating layer B is formed on the surface of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt;

[0015] The carbon fiber rigid thermal insulation felt with the pre-coating A and the pre-coating B is subjected to vacuum high-temperature sintering heat treatment, and finally a layer of SiC / C composite coating is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0016] The preparation method as described above, wherein the slurry M 1 The mass ratios of the components are: 1 20%~30%; SiC powder 15%~30%; Si powder 40%~50%; C powder 4%~20%, ensuring that the total content of resin, SiC powder, Si powder and C powder is 100%, diluent X 1 The content of the component is 60% to 70% of the total content of the resin, SiC powder, Si powder and C powder.

[0017] The preparation method as described above, wherein the slurry M 2 The mass ratios of the components are: 2 7%~12%, Si powder 88%~93%, ensure that the total content of resin and Si powder is 100%, diluent X 2 The content of the component is 80% to 90% of the total content of the resin and the Si powder.

[0018] The preparation method as described above, wherein the slurry M 1 Resin R 1 is furan resin or phenolic resin, C powder is colloidal graphite powder or carbon fiber powder, diluent X 1 For ethanol or ethylene glycol.

[0019] The preparation method as described above, wherein the slurry M 2 Resin R 2 Furan resin or phenolic resin, diluent X 2 For ethanol or ethylene glycol.

[0020] The preparation method as described above, wherein the slurry M 1 The particle size of SiC powder in the slurry is 5um to 20um, the particle size of Si powder is 5um to 30um, and the particle size of C powder is 5um to 30um. 2 The particle size of Si powder in the process is 1um~20um.

[0021] In the preparation method as described above, the curing temperature of the curing treatment for forming the pre-coating layer A and the pre-coating layer B on the surface of the carbon fiber hard thermal insulation felt is 200° C. to 220° C., and the curing time is 1 hour to 3 hours.

[0022] In the preparation method as described above, the thickness of the pre-coating layer A is 400um to 700um, and the thickness of the pre-coating layer B is 50um to 150um.

[0023] In the preparation method as described above, the vacuum high-temperature sintering heat treatment of the carbon fiber hard insulation felt having the pre-coating layer A and the pre-coating layer B comprises:

[0024] Under a slight positive pressure, the carbon fiber hard insulation felt having the pre-coating layer A and the pre-coating layer B is heated from room temperature to 900°C at a heating rate of 1°C / min to 8°C / min, and kept at 900°C for 1 to 2 hours;

[0025] Under a slight positive pressure, the carbon fiber hard insulation felt with pre-coating A and pre-coating B is heated from room temperature to temperature T at a heating rate of 5°C / min to 15°C / min. After being kept at temperature T for 0.5 to 1 hour, the felt is evacuated to a vacuum degree of ≤0.1Kpa, and then cooled with the furnace;

[0026] The temperature T is 1500°C to 1800°C, the slight positive pressure is 0.3KPa to 0.6KPa greater than the atmospheric pressure, and the room temperature is 20°C±5°C.

[0027] The present application also provides a composite coating prepared by the method for preparing the composite coating on the surface of the above-mentioned carbon fiber hard thermal insulation felt.

[0028] The beneficial effects of the present application are as follows: by adopting the "slurry method", the slurry M composed of resin, SiC powder, Si powder, C powder and diluent is 1 , by first brushing a layer of slurry M on the surface of the carbon fiber hard insulation felt 1 , then apply the slurry M by brush 1 The carbon fiber rigid thermal insulation felt is cured to form a pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt, and then a slurry M composed of resin, silicon powder and diluent is applied. 2 , continue to brush a layer of slurry M on the surface of pre-coating A 2Then, a curing treatment is performed, and finally a layer of pre-coating B is formed on the surface of the pre-coating A. Finally, the carbon fiber rigid thermal insulation felt with the pre-coating A and the pre-coating B on the surface is subjected to high-temperature sintering treatment under vacuum, and finally a SiC / C composite coating is formed on the surface of the carbon fiber rigid thermal insulation felt. During the vacuum high-temperature sintering process, the Si component in the pre-coating B will diffuse into the pre-coating A. At this time, the Si component that enters the pre-coating A through diffusion will react with the C component in the pre-coating A to produce SiC, which will bring about a certain volume expansion. The volume expansion rate generated by theoretical calculation is 107.67%. Therefore, by controlling the temperature and insulation time of vacuum high-temperature sintering, the content of the Si component diffused from the pre-coating B to the pre-coating A is adjusted, and finally the volume expansion brought about by the reaction of the Si component diffused from the pre-coating B to the pre-coating A and the C component in the pre-coating A is just consistent with the volume contraction brought about by the reaction of the Si component contained in the pre-coating A itself with the C component, and finally the prepared SiC / C composite coating does not crack, thereby achieving the improvement of the protective effect of the SiC / C composite coating on the carbon fiber rigid thermal insulation felt. DETAILED DESCRIPTION

[0029] The embodiment of the present application provides a composite coating on the surface of a carbon fiber rigid thermal insulation felt and a preparation method thereof, so as to meet the quality requirements for the protective effect of the composite coating on the carbon fiber rigid thermal insulation felt when the carbon fiber rigid thermal insulation felt is used as a thermal insulation material in a high-temperature furnace.

[0030] The embodiments of the present application are based on the following technical concepts: through the reasonable design of each component in the pre-coating layer A and the pre-coating layer B on the surface of the carbon fiber hard insulation felt, and combined with the control of the sintering process parameters, the volume shrinkage caused by the reaction of the Si component in the pre-coating layer A with the C component and the volume expansion caused by the reaction of the C component in the pre-coating layer A with the Si component diffused into the pre-coating layer A through diffusion during high-temperature sintering are basically consistent, which can effectively improve the problem of coating cracking.

[0031] The method for preparing the composite coating on the surface of carbon fiber carbon fiber hard thermal insulation felt provided in the embodiment of the present application comprises the following steps:

[0032] The resin R 1 , SiC powder, Si powder, C powder and diluent X 1 The mixture is stirred to form a slurry M 1 , then the slurry M 1 It is evenly brushed on the surface of the carbon fiber rigid thermal insulation felt, and then cured (the curing temperature is 200℃~220℃, and the curing time is 1 hour~3 hours), and finally a pre-coating layer A with a thickness of 400um~700um is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0033] Among them, the slurry M 1 The mass ratios of the components are: 1 20%~30%; SiC powder 15%~30%; Si powder 40%~50%; C powder 4%~20%, ensuring that the total content of resin, SiC powder, Si powder and C powder is 100%, diluent X 1 The content of the component is 60% to 70% of the total content of the resin, SiC powder, Si powder and C powder.

[0034] The resin R1 in the slurry M1 is preferably furan resin or phenolic resin, the C powder is preferably colloidal graphite powder or carbon fiber powder, and the diluent X1 is preferably ethanol or ethylene glycol.

[0035] Among them, the slurry M 1 The particle size of the SiC powder is preferably 5um to 20um, the particle size of the Si powder is preferably 5um to 30um, and the particle size of the C powder is preferably 5um to 30um.

[0036] The resin R 2 , Si powder and diluent X 2 The mixture is stirred to form a slurry M 2 , then the slurry M 2 The pre-coating layer A is evenly brushed on the surface of the carbon fiber rigid thermal insulation felt, and then cured (the curing temperature is 200°C to 220°C, and the curing time is 1 hour to 3 hours). Finally, a pre-coating layer B with a thickness of 50um to 150um is formed on the surface of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt.

[0037] Among them, the slurry M 2 The mass ratios of the components are as follows: 2 7%~12%, Si powder 88%~93%, ensure that the total content of resin and Si powder is 100%, diluent X 2 The content of the component is 80% to 90% of the total content of the resin and the Si powder.

[0038] Among them, the slurry M 2 Resin R 2 Preferably furan resin or phenolic resin, diluent X 2 Preferred are ethanol or ethylene glycol.

[0039] Among them, the slurry M 2 The particle size of Si powder in the mixture is preferably 1 um to 20 um.

[0040] The carbon fiber hard insulation felt with pre-coating A and pre-coating B is subjected to vacuum high temperature sintering heat treatment, specifically:

[0041] Under a slight positive pressure, the carbon fiber hard insulation felt having the pre-coating layer A and the pre-coating layer B is heated from room temperature to 900°C at a heating rate of 1°C / min to 8°C / min, and kept at 900°C for 1 to 2 hours;

[0042] Under a slight positive pressure, the carbon fiber hard insulation felt with pre-coating A and pre-coating B is heated from room temperature to temperature T at a heating rate of 5°C / min to 15°C / min. After being kept at temperature T for 0.5 to 1 hour, the felt is evacuated to a vacuum degree of ≤0.1Kpa, and then cooled with the furnace;

[0043] The temperature T is 1500°C to 1800°C, the slightly positive pressure is 0.3KPa to 0.6KPa greater than the atmospheric pressure, and the room temperature is 20°C ± 5°C.

[0044] Finally, a layer of SiC / C composite coating is formed on the surface of the carbon fiber hard insulation felt.

[0045] The present application is further described below in conjunction with specific embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0046] Example 1

[0047] 1. Slurry M 1 Preparation of Resin R 1 Furan resin with a residual carbon rate of 60% is selected, C powder is colloidal graphite powder, and diluent X 1 Ethanol is selected, and the specific mass ratio of each component is: furan resin 20%; SiC powder with a particle size of 5um 15%; Si powder with a particle size of 30um 50%; colloidal graphite powder with a particle size of 5um 15%. The mass of the diluent ethanol added to the slurry M1 is slurry M 1 70% of the total of furan resin, SiC powder, Si powder and colloidal graphite powder are added, and then all the above components are mixed evenly by a mixer for standby use.

[0048] 2. Slurry M 1 Brush coating: First, sand the surface of the carbon fiber hard insulation felt with sandpaper to remove the powder impurities on the surface, and then mix the slurry M 1 Apply evenly on the surface of carbon fiber hard insulation felt to ensure that the slurry M 1 The coating thickness is consistent and there is no slurry accumulation.

[0049] 3. Slurry M 1 Coating curing: brush the surface with slurry M 1The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 220° C. for 1 hour, and finally a pre-coating layer A with a thickness of 400 μm is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0050] 4. Slurry M 2 Preparation of Resin R 2 Furan resin with a residual carbon content of 60% was also selected, and the diluent X 2 Ethanol was selected, and the specific mass ratio of each component was: furan resin 7%, Si powder with a particle size of 10um 93%, and diluent X was added. 2 The mass of ethanol is the slurry M 2 Add 90% of the total amount of furan resin and Si powder, and then mix all the above components evenly with a mixer for standby use.

[0051] 5. Slurry M 2 Brushing: On the basis of the pre-coating A formed on the surface of the carbon fiber hard insulation felt, continue to brush a layer of slurry M 2 , and also ensure that the thickness of the brushed coating is consistent and there is no accumulation of slurry.

[0052] 6. Slurry M 2 Coating curing: Slurry M will be applied on the surface of pre-coating A. 2 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 200°C for 3 hours, and finally a pre-coating layer B with a thickness of 50 um is formed on the basis of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt.

[0053] 7. Coating sintering: The pre-coating layer A and the pre-coating layer B sequentially formed on the surface of the carbon fiber hard insulation felt are subjected to vacuum high-temperature sintering treatment, wherein the sintering treatment parameters are:

[0054] ①Room temperature (20℃±5℃)~900℃, heating rate is 8℃ / min, slightly positive pressure (0.3KPa higher than atmospheric pressure);

[0055] ②900℃, keep warm for 1 hour, slightly positive pressure (0.3KPa higher than atmospheric pressure);

[0056] ③900℃~1500℃, heating rate is 15℃ / min, slightly positive pressure (0.3KPa higher than atmospheric pressure);

[0057] ④1500℃, keep warm for 1 hour, evacuate, vacuum degree ≤100Pa;

[0058] ⑤ Cool down along with the furnace.

[0059] Through the above steps, a layer of SiC / C composite coating can be finally formed on the surface of the carbon fiber hard insulation felt.

[0060] Comparative Example 1

[0061] Comparative Example 1 is compared with Example 1, except that the content of furan resin in the first step is adjusted to 15%, the SiC powder with a particle size of 5 um is adjusted to 17%, and the colloidal graphite powder is adjusted to 18%, the other preparation process parameters and processes are consistent with Example 1.

[0062] Example 2

[0063] 1. Slurry M 1 Preparation of Resin R 1 Use phenolic resin with a residual carbon rate of 60%, carbon fiber powder as C powder, and diluent X 1 Ethylene glycol is selected, and the specific mass ratio of each component is: phenolic resin 30%; SiC powder with a particle size of 20um 17%; Si powder with a particle size of 5um 46%; carbon fiber powder with a particle size of 15um 7%. The mass of the diluent ethylene glycol added to the slurry M1 is slurry M 1 60% of the total of furan resin, SiC powder, Si powder and colloidal graphite powder are added, and then all the above components are mixed evenly by a mixer for standby use.

[0064] 2. Slurry M 1 Brush coating: First, sand the surface of the carbon fiber hard insulation felt with sandpaper to remove the powder impurities on the surface, and then mix the slurry M 1 Apply evenly on the surface of carbon fiber hard insulation felt to ensure that the slurry M 1 The coating thickness is consistent and there is no slurry accumulation.

[0065] 3. Slurry M 1 Coating curing: brush the surface with slurry M 1 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 200° C. for 3 hours, and finally a pre-coating layer A with a thickness of 700 μm is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0066] 4. Slurry M 2 Preparation of Resin R 2 The phenolic resin with a residual carbon content of 60% was also selected, and the diluent X 2 Use ethylene glycol, the specific mass ratio of each component is: phenolic resin 12%, Si powder with a particle size of 20um 88%, add diluent X 2 The mass of ethylene glycol is the slurry M 2 80% of the total amount of furan resin and Si powder is added, and then all the above components are mixed evenly by a mixer for standby use.

[0067] 5. Slurry M 2Brushing: On the basis of the pre-coating A formed on the surface of the carbon fiber hard insulation felt, continue to brush a layer of slurry M 2 , and also ensure that the thickness of the brushed coating is consistent and there is no accumulation of slurry.

[0068] 6. Slurry M 2 Coating curing: Slurry M will be applied on the surface of pre-coating A. 2 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 220°C for 1 hour, and finally a pre-coating layer B with a thickness of 150 um is formed on the basis of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt.

[0069] 7. Coating sintering: The pre-coating layer A and the pre-coating layer B sequentially formed on the surface of the carbon fiber hard insulation felt are subjected to vacuum high-temperature sintering treatment, wherein the sintering treatment parameters are:

[0070] ①Room temperature (20℃±5℃)~900℃, heating rate is 1℃ / min, slightly positive pressure (0.5KPa higher than atmospheric pressure);

[0071] ②900℃, keep warm for 2 hours, slightly positive pressure (0.5KPa higher than atmospheric pressure);

[0072] ③900℃~1800℃, heating rate is 5℃ / min, slightly positive pressure (0.5KPa higher than atmospheric pressure);

[0073] ④1800℃, keep warm for 0.5 hours, evacuate, vacuum degree ≤50Pa;

[0074] ⑤ Cool down along with the furnace.

[0075] Through the above steps, a layer of SiC / C composite coating can be finally formed on the surface of the carbon fiber hard insulation felt.

[0076] Comparative Example 2

[0077] Comparative Example 2 is compared with Example 2, except that the content of furan resin in the first step is adjusted to 35%, SiC powder with a particle size of 20 um is 15%, and colloidal graphite powder is adjusted to 4%, the other preparation process parameters and processes are consistent with Example 2.

[0078] Example 3

[0079] 1. Slurry M 1 Preparation of Resin R 1 Furan resin with a residual carbon rate of 60% is selected, C powder is colloidal graphite powder, and diluent X 1Ethanol was selected, and the specific mass ratio of each component was: phenolic resin 22%; SiC powder with a particle size of 8um 25%; Si powder with a particle size of 20um 43%; colloidal graphite powder with a particle size of 20um 10%, and added to the slurry M 1 The mass of the diluent ethanol in the slurry M 1 68% of the total of furan resin, SiC powder, Si powder and colloidal graphite powder are added, and then all the above components are mixed evenly by a mixer for standby use.

[0080] 2. Slurry M 1 Brush coating: First, sand the surface of the carbon fiber hard insulation felt with sandpaper to remove the powder impurities on the surface, and then mix the slurry M 1 Apply evenly on the surface of carbon fiber hard insulation felt to ensure that the slurry M 1 The coating thickness is consistent and there is no slurry accumulation.

[0081] 3. Slurry M 1 Coating curing: brush the surface with slurry M 1 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 210° C. for 2 hours, and finally a pre-coating layer A with a thickness of 500 μm is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0082] 4. Slurry M 2 Preparation of Resin R 2 Use phenolic resin with a residual carbon rate of 60%, diluent X 2 Use ethylene glycol, the specific mass ratio of each component is: phenolic resin 10%, Si powder with a particle size of 1um 90%, add diluent X 2 The mass of ethylene glycol is the slurry M 2 83% of the total amount of phenolic resin and Si powder is added, and then all the above components are mixed evenly by a mixer for standby use.

[0083] 5. Slurry M 2 Brushing: On the basis of the pre-coating A formed on the surface of the carbon fiber hard insulation felt, continue to brush a layer of slurry M 2 , and also ensure that the thickness of the brushed coating is consistent and there is no accumulation of slurry.

[0084] 6. Slurry M 2 Coating curing: Slurry M will be applied on the surface of pre-coating A. 2 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 200°C for 2 hours, and finally a pre-coating layer B with a thickness of 120 um is formed on the basis of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt.

[0085] 7. Coating sintering: The pre-coating layer A and the pre-coating layer B sequentially formed on the surface of the carbon fiber hard insulation felt are subjected to vacuum high-temperature sintering treatment, wherein the sintering treatment parameters are:

[0086] ①Room temperature (20℃±5℃)~900℃, heating rate is 3℃ / min, slightly positive pressure (0.4KPa higher than atmospheric pressure);

[0087] ②900℃, keep warm for 1.5 hours, slightly positive pressure (0.4KPa higher than atmospheric pressure);

[0088] ③900℃~1600℃, heating rate is 8℃ / min, slightly positive pressure (0.4KPa higher than atmospheric pressure);

[0089] ④1600℃, keep warm for 0.9 hours, evacuate, vacuum degree ≤60Pa;

[0090] ⑤ Cool down along with the furnace.

[0091] Through the above steps, a layer of SiC / C composite coating can be finally formed on the surface of the carbon fiber hard insulation felt.

[0092] Comparative Example 3

[0093] Compared with Example 3, Comparative Example 3 performs slurry M in the first step. 1 When the configuration is 1 The mass ratio of each component is adjusted as follows: phenolic resin 22%; SiC powder with a particle size of 8 um 28%; Si powder with a particle size of 20 um 43%; colloidal graphite powder with a particle size of 20 um 7%, and other process parameters and process flow are consistent with Example 3.

[0094] Example 4

[0095] 1. Slurry M 1 Preparation of Resin R 1 Use phenolic resin with a residual carbon rate of 60%, carbon fiber powder as C powder, and diluent X 1 Use ethylene glycol, the specific mass ratio of each component is: phenolic resin 27%; SiC powder with a particle size of 17um 15%; Si powder with a particle size of 8um 50%; carbon fiber powder with a particle size of 20um 8%, add slurry M 1 The mass of the diluent ethylene glycol in the slurry M 1 63% of the total of furan resin, SiC powder, Si powder and colloidal graphite powder are added, and then all the above components are mixed evenly by a mixer for standby use.

[0096] 2. Slurry M 1Brush coating: First, sand the surface of the carbon fiber hard insulation felt with sandpaper to remove the powder impurities on the surface, and then mix the slurry M 1 Apply evenly on the surface of carbon fiber hard insulation felt to ensure that the slurry M 1 The coating thickness is consistent and there is no slurry accumulation.

[0097] 3. Slurry M 1 Coating curing: brush the surface with slurry M 1 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 200° C. for 3 hours, and finally a pre-coating layer A with a thickness of 600 μm is formed on the surface of the carbon fiber rigid thermal insulation felt.

[0098] 4. Slurry M 2 Preparation of Resin R 2 Use phenolic resin with a residual carbon rate of 60%, diluent X 2 Ethanol was selected, and the specific mass ratio of each component was: 9% phenolic resin, 91% Si powder with a particle size of 15um, and diluent X was added. 2 The mass of ethanol is the slurry M 2 82% of the total amount of phenolic resin and Si powder was added, and then all the above components were mixed evenly by a mixer for standby use.

[0099] 5. Slurry M 2 Brushing: On the basis of the pre-coating A formed on the surface of the carbon fiber hard insulation felt, continue to brush a layer of slurry M 2 , and also ensure that the thickness of the brushed coating is consistent and there is no accumulation of slurry.

[0100] 6. Slurry M 2 Coating curing: Slurry M will be applied on the surface of pre-coating A. 2 The coated carbon fiber rigid thermal insulation felt is cured at a temperature of 200°C for 3 hours, and finally a pre-coating layer B with a thickness of 130 um is formed on the basis of the pre-coating layer A on the surface of the carbon fiber rigid thermal insulation felt.

[0101] 7. Coating sintering: The pre-coating layer A and the pre-coating layer B sequentially formed on the surface of the carbon fiber hard insulation felt are subjected to vacuum high-temperature sintering treatment, wherein the sintering treatment parameters are:

[0102] ②Room temperature (20℃±5℃)~900℃, heating rate is 6℃ / min, slightly positive pressure (0.6KPa higher than atmospheric pressure);

[0103] ②900℃, keep warm for 1.8 hours, slightly positive pressure (0.6KPa higher than atmospheric pressure);

[0104] ③900℃~1700℃, heating rate is 10℃ / min, slightly positive pressure (0.6KPa higher than atmospheric pressure);

[0105] ④1700℃, keep warm for 0.6 hours, evacuate, vacuum degree ≤30Pa;

[0106] ⑤ Cool down along with the furnace.

[0107] Through the above steps, a layer of SiC / C composite coating can be finally formed on the surface of the carbon fiber hard insulation felt.

[0108] Comparative Example 4

[0109] Compared with Example 4, Comparative Example 4 performs slurry M in the first step. 1 When the configuration is 1 The mass ratio of each component is adjusted as follows: phenolic resin 27%; SiC powder with a particle size of 17um 12%; Si powder with a particle size of 8um 50%; carbon fiber powder with a particle size of 20um 11%. Other process parameters and process flow are consistent with Example 4.

[0110] Table 1 Appearance of coatings in various embodiments and comparative examples

[0111] Coating appearance Example 1 Dense, no cracking Comparative Example 1 Shedding Example 2 Dense, no cracking Comparative Example 2 Cracking Example 3 Dense, no cracking Comparative Example 3 Cracking Example 4 Dense, no cracking Comparative Example 4 Cracking

[0112] Table 1 shows the results of the samples obtained in the above embodiments and comparative examples, and the above obtained verification results are analyzed:

[0113] For Example 1 and Comparative Example 1, since the slurry M in Comparative Example 1 1 Resin R 1 The content is too low, and at this time the resin R 1 The pre-coating A acts as both a carbon source and a binder in the pre-coating A. Therefore, when the slurry M1 is cured, the resin R 1 Too low a content will result in insufficient adhesion between the slurry M1 and the surface of the carbon fiber rigid thermal insulation felt, making it easy for the pre-coating A to separate from the carbon fiber rigid thermal insulation felt matrix during the carbonization process, and eventually causing the coating obtained by the sintering process to fall off;

[0114] For Example 2 and Comparative Example 2, if the slurry M 1 If the resin content is too high, the resin R1 in the pre-coating A will show a certain degree of cracking, so the coating obtained after sintering will also show a certain degree of cracking;

[0115] Therefore, according to the verification results of Example 1 and Comparative Example 1 and Example 2 and Comparative Example 2, the slurry M 1 Resin R 1The content mass ratio is controlled in the range of 20% to 30%.

[0116] For Example 3 and Comparative Example 3, when the Si component in the slurry M1 remains unchanged, the total amount of carbon source (including resin carbon formed by resin carbonization and colloidal graphite carbon contained in the slurry) decreases, when the pre-coating layer A formed by curing the slurry M1 is sintered, the proportion of carbon source in the pre-coating layer A used to react with Si in the pre-coating layer B also decreases accordingly, so that the volume expansion caused by the reaction of carbon in the pre-coating layer A with Si in the pre-coating layer B is not enough to balance the volume shrinkage caused by the reaction of Si component in the pre-coating layer A itself with component C, which will eventually lead to cracking of the sintered coating layer;

[0117] Similarly, for Example 4 and Comparative Example 4, for slurry M 1 When the Si component in the pre-coating A remains unchanged, when the carbon source component in the pre-coating A (including resin carbon formed by resin carbonization and the colloidal graphite carbon contained in the pre-coating A) increases, a part of the carbon in the pre-coating A will react with the Si component contained in the pre-coating A first, and the relatively excess carbon will react with the Si component diffused from the pre-coating B to the pre-coating A, which will eventually lead to a mismatch between the volume shrinkage caused by the silicon-carbon reaction in the pre-coating A itself and the volume expansion caused by the reaction of the excess carbon in the pre-coating A with the Si component diffused from the pre-coating B to the pre-coating A, which will eventually lead to cracking of the coating obtained by sintering.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application, rather than to limit it. Although the present application has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solution described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. These modifications or replacements are within the scope of protection of the present invention.

Claims

1. A method for preparing a composite coating on the surface of a carbon fiber rigid thermal insulation felt, characterized in that: The steps include: A mixture consisting of resin R1, SiC powder, Si powder, C powder and diluent X1 is stirred evenly to form slurry M1, and then the slurry M1 is evenly brushed on the surface of the carbon fiber hard insulation felt, and then cured to finally form a pre-coating layer A on the surface of the carbon fiber hard insulation felt; A mixture consisting of resin R2, Si powder and diluent X2 is stirred evenly to form slurry M2, and then the slurry M2 is evenly brushed on the surface of the pre-coating layer A formed on the surface of the carbon fiber hard thermal insulation felt, and then cured, and finally a layer of pre-coating layer B is formed on the surface of the pre-coating layer A on the surface of the carbon fiber hard thermal insulation felt; The carbon fiber rigid thermal insulation felt with the pre-coating A and the pre-coating B is subjected to vacuum high-temperature sintering heat treatment, and finally a layer of SiC / C composite coating is formed on the surface of the carbon fiber rigid thermal insulation felt.

2. The method for preparing the composite coating on the surface of the carbon fiber hard thermal insulation felt according to claim 1, characterized in that: The mass ratios of the components in the slurry M1 are: resin R1 20% to 30%; SiC powder 15% to 30%; Si powder 40% to 50%; C powder 4% to 20%, ensuring that the total content of the resin, SiC powder, Si powder and C powder is 100%, and the content of the diluent X1 component is 60% to 70% of the total content of the resin, SiC powder, Si powder and C powder.

3. The method for preparing the composite coating on the surface of the carbon fiber hard thermal insulation felt according to claim 2, characterized in that: The mass ratios of the components in the slurry M2 are: resin R27%-12%, Si powder 88%-93%, ensuring that the total content of the resin and Si powder components is 100%, and the content of the diluent X2 component is 80%-90% of the total content of the resin and Si powder components.

4. The method for preparing the composite coating on the surface of carbon fiber hard thermal insulation felt according to claim 1, characterized in that: The resin R1 in the slurry M1 is furan resin or phenolic resin, the C powder is colloidal graphite powder or carbon fiber powder, and the diluent X1 is ethanol or ethylene glycol.

5. The method for preparing the composite coating on the surface of carbon fiber hard thermal insulation felt according to claim 1, characterized in that: The resin R2 in the slurry M2 is furan resin or phenolic resin, and the diluent X2 is ethanol or ethylene glycol.

6. The method for preparing the composite coating on the surface of the carbon fiber hard thermal insulation felt according to any one of claims 1 to 5, characterized in that: The particle size of the SiC powder in the slurry M1 is 5um-20um, the particle size of the Si powder is 5um-30um, the particle size of the C powder is 5um-30um, and the particle size of the Si powder in the slurry M2 is 1um-20um.

7. The method for preparing the composite coating on the surface of carbon fiber hard thermal insulation felt according to claim 6, characterized in that: The curing temperature of the curing treatment for forming the pre-coating layer A and the pre-coating layer B on the surface of the carbon fiber hard thermal insulation felt is 200° C. to 220° C., and the curing time is 1 hour to 3 hours.

8. The method for preparing the composite coating on the surface of carbon fiber hard thermal insulation felt according to claim 6, characterized in that: The thickness of the pre-coating layer A is 400um to 700um, and the thickness of the pre-coating layer B is 50um to 150um.

9. The method for preparing the composite coating on the surface of carbon fiber hard thermal insulation felt according to claim 6, characterized in that: The vacuum high-temperature sintering heat treatment of the carbon fiber hard insulation felt having the pre-coating layer A and the pre-coating layer B comprises: Under a slight positive pressure, the carbon fiber hard insulation felt having the pre-coating layer A and the pre-coating layer B is heated from room temperature to 900°C at a heating rate of 1°C / min to 8°C / min, and kept at 900°C for 1 to 2 hours; Under a slight positive pressure, the carbon fiber hard insulation felt with pre-coating A and pre-coating B is heated from room temperature to temperature T at a heating rate of 5°C / min to 15°C / min. After being kept at temperature T for 0.5 to 1 hour, the felt is evacuated to a vacuum degree of ≤0.1Kpa, and then cooled with the furnace; The temperature T is 1500°C to 1800°C, the slight positive pressure is 0.3KPa to 0.6KPa greater than the atmospheric pressure, and the room temperature is 20°C±5°C.

10. A composite coating prepared by the method for preparing a composite coating on the surface of a carbon fiber rigid thermal insulation felt according to any one of claims 1 to 9.

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