Modified carbon fiber hard felt and preparation method and application thereof

Abstract

The application provides a modified carbon fiber hard felt and a preparation method and application thereof.The modified carbon fiber hard felt comprises carbon fibers and silicon carbide and carbon compounded on the carbon fibers.The application is characterized in that a modifier is used to modify and treat the carbon fibers, polymethylphenylsiloxane in the modifier is used as a main material, and a silicon carbide ceramic film can be formed through subsequent high-temperature treatment, and the silicon carbide ceramic film is compounded on the surface of the carbon fibers.The silicon carbide ceramic film can enhance the surface hardness and oxidation resistance of the carbon fibers, improve the wear resistance and high-temperature resistance of the carbon fibers, and thus prolong the service life of the carbon fibers in a vacuum high-temperature furnace.In addition, carbon nanotubes in the modifier can further enhance the mechanical properties of the carbon fibers.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation materials technology, specifically relating to a modified carbon fiber rigid felt, its preparation method, and its application. Background Technology

[0002] Carbon fiber thermal insulation material is a soft felt material made by molding carbon fiber with a certain proportion of binder. Rigid carbon fiber thermal insulation material is then produced by carbonization, graphitization, and machining of the soft felt material. Currently, rigid carbon fiber thermal insulation material (referred to as "carbon fiber rigid felt") has become a focus of research for many scholars due to its high strength, high modulus, high dimensional stability, low density, small coefficient of thermal expansion, resistance to thermal shock, ablation resistance, and good oxidation resistance.

[0003] However, the preparation of carbon fiber rigid felt requires a vacuum high-temperature furnace, and ordinary carbon fibers have a short service life in a vacuum high-temperature furnace, which limits the preparation of carbon fiber rigid felt and makes it impossible to achieve industrial mass production. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a modified carbon fiber rigid felt, its preparation method, and its application. The modified carbon fiber rigid felt has a long service life in a vacuum high-temperature furnace, which is beneficial for industrial-scale mass production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a modified carbon fiber rigid felt comprising carbon fibers and silicon carbide and carbon composited on said carbon fibers.

[0007] Preferably, the carbon fiber is selected from any one or more of polypropylene-based carbon fiber, pitch-based carbon fiber, or viscose-based carbon fiber.

[0008] Preferably, the mass ratio of the carbon fiber, silicon carbide and carbon is 2:(0.5-2):(0.5-2).

[0009] Secondly, the present invention provides a method for preparing the above-mentioned modified carbon fiber rigid felt, comprising:

[0010] The modifier is mixed with carbon fiber to obtain an intermediate. The intermediate is then subjected to hot pressing curing and carbonization in sequence to obtain modified carbon fiber rigid felt.

[0011] The modifier, by mass fraction, comprises: 10-20% polymethylphenylsiloxane, 10-30% viscosity modifier, 1-8% carbon nanotubes, 3-7% oily substances, 10-35% curing agent, and 20-40% pure water.

[0012] Preferably, the modifier comprises, by mass fraction: 12-15% polymethylphenylsiloxane, 15-20% viscosity modifier, 2-6% carbon nanotubes, 4-6% oily substance, 15-25% curing agent, and 25-35% pure water.

[0013] Preferably, the viscosity modifier is selected from one or more of industrial alcohol, acetone, or methanol.

[0014] Preferably, the oily substance is selected from any one or more of kerosene, benzene, or xylene.

[0015] Preferably, the curing agent is selected from any one or more of water-soluble phenolic resin, epoxy resin, or polyester resin.

[0016] Preferably, the water-soluble phenolic resin has a residual carbon content of 30-40% and a viscosity of 10-20 cp.

[0017] Preferably, the hot-press curing process is as follows:

[0018] Ⅰ: The pressure plate is closed, the pressure is 0.1~0.5MPa, the temperature is 40~60℃, and the time is 1~3h;

[0019] II: Heat to 80-95℃, repeatedly open and close the pressure plate, maintaining a pressing rate of 1-5 times / min, with a pressure of 0.1-0.4 MPa and a pressing time of 0.5-1.5 hours;

[0020] III: Heat to 130-160℃ and keep warm for 3-6 hours.

[0021] Preferably, the carbonization process is as follows:

[0022] Ⅰ: Raise the temperature from 0℃ to 300℃ in 200-250 minutes, and then hold at 300℃ for 1-2 hours;

[0023] II: Raise the temperature from 300℃ to 800℃ in 200-400 minutes, and then hold at 800℃ for 2-4 hours;

[0024] III: Raise the temperature from 800℃ to 1200℃ in 150-250 minutes, and hold at 1200℃ for 1-3 hours;

[0025] IV: Raise the temperature from 1200℃ to 1850℃ over a period of 300-500 minutes, and then hold at 1850℃ for 4-8 hours.

[0026] Thirdly, the present invention provides a thermal insulation material, which includes the modified carbon fiber rigid felt involved in the above-mentioned technical solution.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a modified carbon fiber rigid felt, comprising carbon fibers and silicon carbide and carbon composited on the carbon fibers. In this invention, the modified carbon fiber rigid felt is obtained by mixing a modifier with carbon fibers to obtain an intermediate, which is then subjected to hot pressing curing and carbonization sequentially. This invention modifies the carbon fibers using a modifier, with polymethylphenylsiloxane in the modifier as the main material. Subsequent high-temperature treatment forms a silicon carbide ceramic film, which is then composited onto the surface of the carbon fibers. This silicon carbide ceramic film enhances the surface hardness and oxidation resistance of the carbon fibers, improves their wear resistance and high-temperature resistance, thereby extending their service life in a vacuum high-temperature furnace. Furthermore, carbon nanotubes in the modifier further enhance the mechanical properties of the carbon fibers.

[0029] Tests have shown that the modified carbon fiber rigid felt provided by this invention has a service life of no less than 200 hours and a maximum of 497 hours in a nitrogen-enclosed 2000℃ high-temperature furnace; its thermal conductivity at 1000℃ is no higher than 0.35 W / (m·K); and its density is no higher than 0.25 g / cm³. 3 . Attached Figure Description

[0030] Figure 1 This is a picture of the finished product of the modified carbon fiber rigid felt obtained in Example 1. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] To address the problem that ordinary carbon fibers have a short service life in vacuum high-temperature furnaces and cannot be mass-produced industrially, this invention provides a modified carbon fiber rigid felt, which includes carbon fibers and silicon carbide and carbon composited on the carbon fibers.

[0033] In this invention, the carbon fiber is selected from any one or more of polypropylene-type carbon fiber, pitch-based carbon fiber, or viscose-based carbon fiber. This invention does not impose any particular restriction on the source of the aforementioned carbon fiber; any commercially available product is acceptable.

[0034] In this invention, the mass ratio of carbon fiber, silicon carbide and carbon is 2:(0.5~2):(0.5~2), preferably 2:(1~1.5):(1~1.5).

[0035] This invention involves composite silicon carbide and carbon onto ordinary carbon fibers. Silicon carbide enhances the surface hardness and oxidation resistance of the carbon fibers, improves their wear resistance and high-temperature resistance, thereby extending their service life in vacuum high-temperature furnaces. Furthermore, the presence of carbon further enhances the mechanical properties of the carbon fibers. Therefore, this invention solves the problem of the short service life of ordinary carbon fibers in vacuum high-temperature furnaces in existing technologies, which prevents their industrial-scale mass production.

[0036] The present invention also provides a method for preparing the above-mentioned modified carbon fiber rigid felt, comprising:

[0037] The modifier is mixed with carbon fiber to obtain an intermediate. The intermediate is then subjected to hot pressing curing and carbonization in sequence to obtain modified carbon fiber rigid felt.

[0038] According to the present invention, the modifier is first mixed with carbon fiber, preferably for 1-3 hours, to obtain an intermediate. In the present invention, the modifier comprises, by mass fraction: 10-20% polymethylphenylsiloxane, 10-30% viscosity modifier, 1-8% carbon nanotubes, 3-7% oily substance, 10-35% curing agent, and 20-40% pure water; preferably comprising 12-15% polymethylphenylsiloxane, 15-20% viscosity modifier, 2-6% carbon nanotubes, 4-6% oily substance, 15-25% curing agent, and 25-35% pure water.

[0039] In this invention, the polymethylphenylsiloxane, as the main modifier, forms a silicon carbide film after a subsequent high-temperature process, which is then laminated onto the surface of the carbon fiber. The polymethylphenylsiloxane can be purchased commercially or prepared using methods well-known to those skilled in the art. In this invention, the molecular weight of the polymethylphenylsiloxane is preferably 100-200, more preferably 136.

[0040] The viscosity modifier is used to adjust the solution viscosity of the modifier, and is selected from any one or more of industrial alcohol, acetone, or methanol, preferably industrial alcohol. This invention does not have particular restrictions on the source of the viscosity modifier; any commercially available product is acceptable.

[0041] The oily substance is used to dissolve polymethylphenylsiloxane, and can be selected from any one or more of kerosene, benzene, or xylene, preferably kerosene. This invention does not have particular restrictions on the source of the oily substance; any commercially available product is acceptable.

[0042] The curing agent, used for curing and bonding, is specifically selected from one or more of water-soluble phenolic resin, epoxy resin, or polyester resin, preferably water-soluble phenolic resin. Since the residual carbon content and viscosity of the water-soluble phenolic resin affect the wettability of the modified solution, the present invention preferably uses a water-soluble phenolic resin with a residual carbon content of 30-40%, more preferably 35-38%; and a viscosity of 10-20 cp, more preferably 12-15 cp.

[0043] The carbon nanotubes are used to further enhance the mechanical properties of carbon fibers, and any commercially available product is acceptable.

[0044] The purified water can be used to dissolve the water-soluble phenolic resin, allowing the phenolic resin to be evenly dispersed in the solution; deionized water is sufficient. It should be noted that when epoxy resin or polyester resin is chosen as the curing agent, acetone is generally added to the modifier to ensure even dispersion of both in the solution. The acetone content should be 2-5 wt% of the total modifier system, preferably 3.5 wt%.

[0045] It should be noted that, after screening, the present invention uses a formula including the above-mentioned components as a modifier, and the results show that the service life of the modified carbon fiber rigid felt in the vacuum high-temperature furnace can be significantly extended.

[0046] Since the modifier exists in liquid form, in some embodiments of the present invention, it is preferable to immerse the carbon fiber in the modifier for 1-3 hours, preferably 1.5-2 hours, to ensure that the modifier is fully impregnated in the carbon fiber. In some preferred embodiments of the present invention, the carbon fiber needs to undergo pretreatment, which involves baking the carbon fiber precursor at 300-400°C, preferably 350°C, under nitrogen protection for 5-30 minutes, preferably 10-20 minutes, using a high-temperature dissolution method. After baking, samples are taken and tested using thermogravimetric analysis to ensure that there is no sizing agent residue on the surface of the carbon fiber precursor. Then, the carbon fiber precursor with the sizing agent removed is needle-punched through a cylinder to form a carbon fiber preform with a thickness of 5-10 mm, and then the carbon fiber preform is immersed in the modifier. The purpose of the above pretreatment is to remove the sizing agent, so as to better ensure that the modifier can be impregnated in the carbon fiber and achieve the purpose of modification.

[0047] In this invention, the modifier is mixed with carbon fiber to obtain an intermediate. The intermediate is then preferably subjected to hot pressing curing according to the present invention. The hot pressing curing is preferably carried out in a multilayer press. In this step, the curing agent and polymethylphenylsiloxane are cured and the moisture is eliminated.

[0048] In some embodiments of the present invention, the hot-press curing process is as follows:

[0049] Ⅰ: The pressure plate is closed, the pressure is 0.1~0.5MPa, the temperature is 40~60℃, and the time is 1~3h;

[0050] II: Increase the temperature to 80-95℃, maintain the frequency at 1-5 times / min, the pressure at 0.1-0.4 MPa, and the time at 0.5-1.5 h;

[0051] III: Raise the temperature to 130-160℃ and keep it warm for 3-6 hours.

[0052] In some preferred embodiments of the present invention, the hot-press curing process is as follows:

[0053] Ⅰ: The pressure plate is closed, with a pressure of 0.2-0.3 MPa; a temperature of 45-50℃; and a time of 1.5-2 hours.

[0054] II: Heat to 90℃, repeatedly open and close the pressure plate, maintaining a pressing speed of 2-3 times / min, with a pressure of 0.2-0.3 MPa; for 1 hour;

[0055] III: Increase the temperature to 140-150℃ and keep it warm for 4-5 hours.

[0056] In this invention, the repeated opening and closing of the pressure plate at 80-95°C, preferably 90°C, in step II above is crucial. During the repeated opening and closing process, the gas generated during curing is released, reducing the generation of internal stress in the hard felt.

[0057] After hot pressing and curing, the resulting product needs to be carbonized. In this step, polymethylphenylsiloxane is cracked, silicon atoms rearrange and carbonize, and the molecular structure gradually transforms into a silicon carbide structure. In some embodiments of the present invention, the carbonization process is as follows:

[0058] Ⅰ: Raise the temperature from 0℃ to 300℃ in 200-250 minutes, and then hold at 300℃ for 1-2 hours;

[0059] II: Raise the temperature from 300℃ to 800℃ in 200-400 minutes, and then hold at 800℃ for 2-4 hours;

[0060] III: Raise the temperature from 800℃ to 1200℃ in 150-250 minutes, and hold at 1200℃ for 1-3 hours;

[0061] IV: Raise the temperature from 1200℃ to 1850℃ over a period of 300-500 minutes, and then hold at 1850℃ for 4-8 hours.

[0062] In some preferred embodiments of the present invention, the carbonization process is as follows:

[0063] Ⅰ: Raise the temperature from 0℃ to 300℃ in 220-230 minutes, and then hold at 300℃ for 1.5-2 hours;

[0064] II: Raise the temperature from 300℃ to 800℃ over a period of 200–300 minutes, and then hold at 800℃ for 2.5–3.5 hours.

[0065] III: Raise the temperature from 800℃ to 1200℃ over a period of 180–200 minutes, and then hold at 1200℃ for 1.5–2 hours.

[0066] IV: Raise the temperature from 1200℃ to 1850℃ over a period of 350–400 minutes, and then hold at 1850℃ for 5–6 hours.

[0067] After the above carbonization is completed, natural cooling will yield modified carbon fiber rigid felt.

[0068] It should be noted that the oily substances and viscosity modifiers will gradually volatilize during the preparation process, and the carbon nanotubes will turn into carbon during the carbonization process, and then be combined with carbon fibers.

[0069] The method for preparing modified carbon fiber rigid felt provided by this invention is simple, convenient, and easy to implement.

[0070] Tests have shown that the modified carbon fiber rigid felt provided by this invention has a service life of no less than 200 hours and a maximum of 497 hours in a nitrogen-enclosed 2000℃ high-temperature furnace; its thermal conductivity at 1000℃ is no higher than 0.35 W / (m·K); and its density is no higher than 0.25 g / cm³. 3 .

[0071] Based on this, the present invention also provides a thermal insulation material, which includes the modified carbon fiber rigid felt described in the above technical solution.

[0072] To further illustrate the present invention, the following embodiments are provided for detailed description. The carbon fiber precursor used in the following embodiments of the present invention is 12K carbon fiber, purchased from Zhongfu Shenying Co., Ltd.; the molecular weight of polymethylphenylsiloxane is 136, purchased from Orion Chemical Co., Ltd.; the molecular weight of polydimethylsiloxane is 322, purchased from Guijing New Materials Co., Ltd.; and the molecular weight of polycarbosilane is 1323, purchased from Alpha Chemical Co., Ltd.

[0073] Example 1

[0074] This embodiment provides a modified carbon fiber rigid felt, the preparation method of which is as follows:

[0075] (1) Using the high temperature dissolution method, the carbon fiber precursor is baked in a nitrogen-protected environment at 340℃ for 25 minutes. After completion, samples are taken and tested by thermogravimetric analysis to ensure that there is no sizing agent residue.

[0076] (2) The carbon fiber precursor with the sizing agent removed is opened, laid up and needle-punched by a cylinder to form a preform with a thickness of 10mm.

[0077] (3) Soak the preform in the modification solution for 3 hours. The specific components of the modification solution by mass fraction are: 15% polymethylphenylsiloxane, 30% industrial alcohol, 5% carbon nanotubes, 5% kerosene, 20% water-soluble phenolic resin (phenolic resin has a residual carbon content of 35% and a viscosity of 14cp), and 25% pure water.

[0078] (4) Place the soaked preform into a multi-layer press for hot pressing and curing. The curing process is as follows: I: Close the press plate, pressure 0.2 MPa, temperature 45℃ and constant temperature for 1 hour; II: After the constant temperature of step I is completed, raise the temperature to 90℃ and repeatedly open and close the press plate, keeping the number of times at 4 times / min, press with a pressure of 0.3 MPa to ensure that excess glue and water can be squeezed out of the felt. The process takes 1.5 hours; III: Raise the temperature to 150℃ and keep it for 5 hours to complete the curing.

[0079] (5) Place the cured resin board into a high-temperature integrated carbonization furnace. The carbonization process is as follows: Ⅰ: 0~300℃, heating time 200min, holding time 2h; Ⅱ: 300~800℃, heating time 200min, holding time 3h; Ⅲ: 800~1200℃, heating time 250min, holding time 3h; Ⅳ: 1200℃~1850℃, heating time 400min, holding time 8h. After natural cooling, the modified carbon fiber hard felt is obtained.

[0080] The finished product image of the modified carbon fiber rigid felt obtained in this embodiment is shown below. Figure 1 As shown.

[0081] Example 2

[0082] This embodiment provides a modified carbon fiber rigid felt, the preparation method of which is as follows:

[0083] (1) Using the high temperature dissolution method, the carbon fiber precursor is baked in a nitrogen-protected environment at 340℃ for 25 minutes. After completion, samples are taken and tested by thermogravimetric analysis to ensure that there is no sizing agent residue.

[0084] (2) The carbon fiber precursor with the sizing agent removed is opened, laid up and needle-punched by a cylinder to form a preform with a thickness of 10mm.

[0085] (3) Soak the preform in the modified solution for 3 hours. The modified solution is composed of the following components by mass fraction: 10% polymethylphenylsiloxane, 30% industrial alcohol, 1% carbon nanotubes, 3% kerosene, 10% water-soluble phenolic resin (phenolic resin has a residual carbon content of 48% and a viscosity of 152cp), and 46% pure water.

[0086] (4) Place the soaked preform into a multi-layer press for hot pressing and curing. The curing process is as follows: I: Close the press plate, pressure 0.2 MPa, temperature 50℃ for 2 hours; II: After the temperature is constant in step I, raise the temperature to 90℃ and repeatedly open and close the press plate, keeping the number of times at 2 times / min, pressure 0.2 MPa, to ensure that excess glue and water can be squeezed out of the felt. This process takes 1 hour; III: Raise the temperature to 140℃ and keep it for 4 hours to complete the curing.

[0087] (5) Place the cured resin board into a high-temperature integrated carbonization furnace. The carbonization process is as follows: Ⅰ: 0~300℃, heating time 220min, holding time 1.5h; Ⅱ: 300~800℃, heating time 280min, holding time 3h; Ⅲ: 800~1200℃, heating time 180min, holding time 1.5h; Ⅳ: 1200℃~1850℃, heating time 450min, holding time 5h. After natural cooling, the modified carbon fiber hard felt is obtained.

[0088] Example 3

[0089] This embodiment provides a modified carbon fiber rigid felt, the preparation method of which is as follows:

[0090] (1) Using the high temperature dissolution method, the carbon fiber precursor is baked in a nitrogen-protected environment at 340℃ for 25 minutes. After completion, samples are taken and tested by thermogravimetric analysis to ensure that there is no sizing agent residue.

[0091] (2) The carbon fiber precursor with the sizing agent removed is opened, laid up and needle-punched by a cylinder to form a preform with a thickness of 10mm.

[0092] (3) Soak the preform in the modified solution for 3 hours. The modified solution consists of the following components by mass fraction: 20% polymethylphenylsiloxane, 10% industrial alcohol, 8% carbon nanotubes, 7% kerosene, 35% water-soluble phenolic resin (phenolic resin has a residual carbon content of 52% and a viscosity of 6246cp), and 20% pure water.

[0093] (4) Place the soaked preform into a multi-layer press for hot pressing and curing. The curing process is as follows: I: Close the press plate, pressure 0.4 MPa, temperature 55℃ for 2.5 h; II: After the temperature is constant in step I, raise the temperature to 85℃ and repeatedly open and close the press plate, keeping the number of times at 3 times / min, pressure 0.4 MPa, to ensure that excess glue and water can be squeezed out of the felt. This process takes 1 h; III: Raise the temperature to 140℃ and keep it for 4 h to complete the curing.

[0094] (5) Place the cured resin board into a high-temperature integrated carbonization furnace. The carbonization process is as follows: I: 0-300℃, heating time 250min, holding time 1.5h; II: 300-800℃, heating time 350min, holding time 3.5h; III: 800-1200℃, heating time 200min, holding time 2.5h; IV: 1200℃-1850℃, heating time 350min, holding time 7.5h. After natural cooling, the modified carbon fiber hard felt is obtained.

[0095] Example 4

[0096] This embodiment provides a modified carbon fiber rigid felt. Compared with Example 1, the only difference is that the curing process in step (4) is as follows: I: The pressure plate is closed, the pressure is 0.5 MPa, and the temperature is 60℃ for 3 hours; II: After the constant temperature of step I is completed, the temperature is raised to 95℃ and the pressure plate is repeatedly opened and closed, with the number of times maintained at 3 times / min. The pressure is 0.4 MPa to ensure that the excess glue and water can be squeezed out of the felt. The process takes 1.5 hours; III: The temperature is raised to 145℃ and kept for 4 hours to complete the curing. The remaining parameters and steps are consistent with those of Example 1.

[0097] Comparative Example 1

[0098] This comparative example provides a modified carbon fiber rigid felt, which differs from Example 1 only in that the modified solution is replaced with: 25% polydimethylsiloxane, 20% industrial alcohol, 5% zirconium oxide, 10% glycerol, 20% water-soluble phenolic resin (phenolic resin residual carbon content is 35%, viscosity is 14CP), and 20% pure water. The remaining parameters and steps are consistent with those of Example 1.

[0099] Comparative Example 2

[0100] This comparative example provides a modified carbon fiber rigid felt, which differs from Example 1 only in that the modified solution is replaced with: 20% polycarbosilane, 15% industrial alcohol, 9% alumina, 6% methyl chloride, 20% water-soluble phenolic resin (phenolic resin residual carbon content is 35%, viscosity is 14cp), and 30% pure water. The remaining parameters and steps are consistent with those of Example 1.

[0101] Performance testing

[0102] The modified carbon fiber rigid felts obtained in Examples 1-4 and Comparative Examples 1-2 were tested using the following methods:

[0103] For methods of testing thermal conductivity, refer to YB / T4130-2005;

[0104] For density testing methods, refer to GB / T 24528-2009.

[0105] The test results are shown in Table 1 below:

[0106] Table 1

[0107]

[0108] As shown in Table 1, the products obtained in the examples have a significantly longer service life in a 2000°C high-temperature furnace under nitrogen atmosphere and exhibit lower thermal conductivity, indicating good heat preservation performance. In particular, the product obtained in Example 1 has the longest service life in the high-temperature furnace and the lowest thermal conductivity.

[0109] In contrast, Comparative Examples 1 and 2, which used modifiers with different formulations, showed that the products had a significantly shorter service life in a nitrogen-enclosed 2000°C high-temperature furnace than the examples. This indicates that the modified carbon fiber rigid felt prepared using the modifier formulation provided by this invention has long-term high-temperature usability and low density, making it easy to use as a thermal insulation material.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A modified carbon fiber rigid felt, characterized in that, Includes carbon fibers and silicon carbide and carbon composited on the carbon fibers; The modified carbon fiber rigid felt was prepared according to the following method: The modifier is mixed with carbon fiber to obtain an intermediate. The intermediate is then subjected to hot pressing curing and carbonization in sequence to obtain modified carbon fiber rigid felt. The modifier, by mass fraction, comprises: 10-20% polymethylphenylsiloxane, 10-30% viscosity modifier, 1-8% carbon nanotubes, 3-7% oily substances, 10-35% curing agent, and 20-40% pure water.

2. The modified carbon fiber rigid felt according to claim 1, characterized in that, The carbon fiber is selected from any one or more of polypropylene carbon fiber, pitch-based carbon fiber, or viscose-based carbon fiber.

3. The modified carbon fiber rigid felt according to claim 1 or 2, characterized in that, The mass ratio of the carbon fiber, silicon carbide, and carbon is 2:(0.5~2):(0.5~2).

4. A method for preparing modified carbon fiber rigid felt according to any one of claims 1 to 3, characterized in that, include: The modifier is mixed with carbon fiber to obtain an intermediate. The intermediate is then subjected to hot pressing curing and carbonization in sequence to obtain modified carbon fiber rigid felt. The modifier, by mass fraction, comprises: 10-20% polymethylphenylsiloxane, 10-30% viscosity modifier, 1-8% carbon nanotubes, 3-7% oily substances, 10-35% curing agent, and 20-40% pure water.

5. The preparation method according to claim 4, characterized in that, The modifier, by mass fraction, comprises: 12-15% polymethylphenylsiloxane, 15-20% viscosity modifier, 2-6% carbon nanotubes, 4-6% oily substances, 15-25% curing agent, and 25-35% pure water.

6. The preparation method according to claim 4 or 5, characterized in that, The viscosity modifier is selected from any one or more of industrial alcohol, acetone, or methanol; The oily substance is selected from any one or more of kerosene, benzene, or xylene; The curing agent is selected from any one or more of water-soluble phenolic resin, epoxy resin, or polyester resin.

7. The preparation method according to claim 6, characterized in that, The water-soluble phenolic resin has a residual carbon content of 30-40% and a viscosity of 10-20 cp.

8. The preparation method according to claim 6, characterized in that, The hot-press curing process is as follows: Ⅰ: The pressure plate is closed, the pressure is 0.1~0.5 MPa, the temperature is 40~60℃, and the time is 1~3 h; II: Heat to 80~95℃ and repeatedly open and close the pressure plate, maintaining a pressing rate of 1~5 times / min, with a pressure of 0.1~0.4 MPa and a pressing time of 0.5~1.5h; III: Heat to 130~160℃ and keep warm for 3~6 hours.

9. The preparation method according to claim 6, characterized in that, The carbonization process is as follows: Ⅰ: Raise the temperature from 0℃ to 300℃ in 200~250 minutes, and hold at 300℃ for 1~2 hours; II: Raise the temperature from 300℃ to 800℃ in 200~400 min, and hold at 800℃ for 2~4 h; III: Raise the temperature from 800℃ to 1200℃ in 150-250 minutes, and hold at 1200℃ for 1-3 hours; IV: Raise the temperature from 1200℃ to 1850℃ over a period of 300-500 minutes, and then hold at 1850℃ for 4-8 hours.

10. A thermal insulation material, characterized in that, It includes the modified carbon fiber rigid felt according to any one of claims 1 to 3 or the modified carbon fiber rigid felt prepared by the preparation method according to any one of claims 4 to 9.

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