A thermal insulation SiC-BN aerogel felt and its preparation method and application

Abstract

The present invention belongs to the technical field of composite materials, and specifically relates to an insulating SiC‑BN aerogel felt, a preparation method thereof, and an application thereof. The preparation method provided by the present invention comprises the following steps: heating and mixing a nitrogen source, a boron source, a solvent, and a silica aerogel powder to obtain a hot mixture; the solvent is a solvent capable of dissolving the nitrogen source and the boron source; impregnating graphite felt in the hot mixture, and obtaining a gel felt after cooling; removing the solvent from the gel felt to obtain an aerogel felt; and heating the aerogel felt in a protective atmosphere to perform a pyrolysis reaction to obtain the insulating SiC‑BN aerogel felt. The SiC‑BN aerogel felt obtained by the preparation method provided by the present invention has the properties of good thermal insulation, flexibility, easy cutting, flame retardancy, and ultra-high temperature resistance, which overcomes the pain points of the aerogel felt currently on the market, such as easy powder shedding and difficulty in long-term use at high temperatures.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to an insulating SiC-BN aerogel felt and a preparation method and application thereof. Background Art

[0002] The frequent occurrence of fires in new energy vehicles stems from the rapid heating of battery cells due to mechanical, electrical, and thermal factors. This heat releases a large amount of heat into the surrounding area, which in turn can cause combustion of the battery cells, battery packs, and even the entire vehicle, threatening human life. Therefore, installing thermal insulation and flame-retardant materials between battery cells can effectively prevent the spread of combustion and effectively prevent accidents. Thermal insulation and flame-retardant materials can also help insulate power batteries, addressing issues such as reduced capacity and cycle life caused by overcooling. Aerogel, with its superior thermal insulation and flame-retardant properties and lower density compared to traditional insulation materials, is an ideal material for power battery thermal management.

[0003] As a multifunctional aerogel, silica aerogel, like other aerogels, suffers from poor mechanical properties, such as brittleness and easy damage during use. Furthermore, its thermal conductivity increases significantly above 600°C. To overcome these limitations, a study has reported dissolving boric acid and melamine in a 2:1 molar ratio in a 5:7 volume ratio of water and tert-butyl alcohol. The mixture is then heated and stirred at 85°C for approximately 30 minutes until a transparent hot solution is obtained. The hot solution is then cooled to 30°C while ultrasonically treated to produce a white hydrogel. The hydrogel is then freeze-dried to obtain an M·2B precursor. Finally, the M·2B precursor is heated at 1200°C for 3 hours in an NH3 atmosphere to produce a high-surface-area bulk boron nitride (BN) aerogel. This aerogel exhibits a certain elasticity, overcoming the aerogel's brittleness and difficulty in cutting. On this basis, in order to further improve the flexibility of BN aerogel, Chinese patent CN202110413296 dissolves the boron source precursor and the nitrogen source precursor in a solvent to obtain a precursor solution, and then introduces the precursor solution into the internal network of the fiber reinforcement to obtain a fiber-reinforced precursor solution complex, and obtains a fiber-reinforced precursor composite hydrogel through solvent-induced and / or temperature-induced sol-gel transformation. Finally, the fiber-reinforced precursor composite hydrogel is dried and pyrolyzed at high temperature to obtain fiber-reinforced BN aerogel. The fiber reinforcements used in the above patents include glass fiber, polyacrylonitrile pre-oxidized yarn, carbon fiber, polyacrylonitrile fiber, silica fiber, mullite fiber, alumina fiber, etc., but these fibers not only have poor temperature resistance in the air, but also have high thermal conductivity, which will reduce the thermal insulation performance of the composite when compounded with BN aerogel. Summary of the Invention

[0004] The purpose of the present invention is to provide an insulating SiC-BN aerogel felt and its preparation method and application. The insulating SiC-BN aerogel felt provided by the present invention uses SiC nanofibers to improve the mechanical properties and high-temperature resistance of the aerogel felt, thereby having good thermal insulation, flame retardancy and ultra-high temperature resistance, and is also flexible and easy to cut.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a thermally insulating SiC-BN aerogel felt, comprising the following steps:

[0007] heating and mixing a nitrogen source, a boron source, a solvent and silica aerogel powder to obtain a hot mixture; wherein the solvent is a solvent capable of dissolving the nitrogen source and the boron source;

[0008] impregnating graphite felt in the hot mixture and obtaining gel felt after cooling;

[0009] removing the solvent from the gel felt to obtain an aerogel felt;

[0010] The aerogel felt is heated in a protective atmosphere to perform a pyrolysis reaction to obtain the thermal insulation SiC-BN aerogel felt.

[0011] Preferably, the nitrogen source is one or more of dicyandiamide, (NH4)2SO4, melamine and urea; the boron source is one or more of boron trioxide, ammonium borate, borax, boric acid and NaBH4; the solvent is a mixed solvent, and the mixed solvent includes water and a hydroxyl compound; the hydroxyl compound includes one or more of methanol, ethanol, ethylene glycol, benzyl alcohol, tert-butyl alcohol, phenol and cresol;

[0012] The molar ratio of the nitrogen source, the boron source and the water is (1-5):(0.2-6):(70-750).

[0013] Preferably, the temperature of the hot mix is 80-95°C;

[0014] The immersion is ultrasonic oscillation immersion, and the time of the ultrasonic oscillation immersion is 1 to 20 minutes;

[0015] The cooling temperature is -196 to 60°C.

[0016] Preferably, the silica aerogel powder includes single-component silica aerogel and / or silica composite aerogel;

[0017] The mass ratio of the silica aerogel powder to the boron source is (1-10):(1-10).

[0018] Preferably, the graphite felt includes any one of asphalt-based graphite felt, polyacrylonitrile-based graphite felt and viscose-based graphite felt.

[0019] Preferably, the specific surface area of the graphite felt is 100 to 1500 m 2 / g, and the bulk density is 0.05~0.5g / cm 3 .

[0020] Preferably, the desolventizing method includes any one or a combination of two or more of supercritical drying, atmospheric pressure drying and freeze drying; the temperature of the atmospheric pressure drying is 80 to 150°C, and the time is 24 to 72 hours; the pre-freezing temperature of the freeze drying is -80 to 0°C, the pre-freezing time is 1 to 12 hours, and the freeze drying time is 12 to 72 hours; the temperature of the supercritical drying is 35 to 45°C, the pressure is 9 to 14 MPa, and the time is 8 to 36 hours.

[0021] Preferably, the protective atmosphere is one or more of argon atmosphere, nitrogen atmosphere, vacuum and ammonia atmosphere; the temperature of the pyrolysis reaction is 1050-1650° C., and the insulation reaction time is 0.5-4 h.

[0022] The present invention provides a thermal insulation SiC-BN aerogel felt prepared by the preparation method described in the above technical solution, comprising a felt body formed of graphite and SiC nanofibers, and BN supported on the felt body.

[0023] The present invention provides the use of the thermal insulation SiC-BN aerogel felt described in the above technical solution as a heat-dissipating, heat-insulating and flame-retardant material.

[0024] The invention provides a preparation method of a thermally insulating SiC-BN aerogel felt, comprising the following steps: heating and mixing a nitrogen source, a boron source, a solvent and silica aerogel powder to obtain a hot mixture; the solvent is a solvent capable of dissolving the nitrogen source and the boron source; impregnating graphite felt in the hot mixture and obtaining a gel felt after cooling; removing the solvent from the gel felt to obtain an aerogel felt; and heating the aerogel felt in a protective atmosphere to perform a pyrolysis reaction to obtain the thermally insulating SiC-BN aerogel felt. The preparation method provided by the present invention introduces silica aerogel and graphite felt, causing the silica aerogel to pyrolyze under heating conditions to produce SiO and CO gases, which react with the graphite felt: SiO(g) + 2C(s) → SiC(s) + CO(g), SiO2(s) + CO(g) → SiO(g) + CO2(g), generating SiC nanofibers. The remaining unreacted graphite and the generated SiC nanofibers together form a felt body. Simultaneously, a nitrogen source and a boron source react under heating conditions to generate BN, which is loaded on the formed felt body, thereby obtaining a SiC-BN aerogel felt. The SiC nanofibers generated by the present invention can improve the mechanical properties and high-temperature resistance of the aerogel felt. As a result, the SiC-BN aerogel felt obtained by the preparation method provided by the present invention has good thermal insulation, flexibility, easy cutting, flame retardancy, ultra-high temperature resistance, and other properties, overcoming the pain points of the aerogel felt currently on the market, such as easy powder shedding and difficulty in long-term use at high temperatures.

[0025] Furthermore, in the present invention, the nitrogen source is one or more of dicyandiamide, (NH4)2SO4, melamine, and urea; the boron source is one or more of boron trioxide, ammonium borate, borax, boric acid, and NaBH4; the solvent is a mixed solvent, and the mixed solvent includes water and a hydroxyl compound; the hydroxyl compound includes one or more of methanol, ethanol, ethylene glycol, benzyl alcohol, tert-butyl alcohol, phenol, and cresol; and the molar ratio of the nitrogen source, the boron source, and the water is (1-5):(0.2-6):(70-750). The present invention uses inexpensive nitrogen and boron sources as gel raw materials, and the preparation method omits the solvent replacement step, shortens the preparation cycle, and reduces the preparation cost.

[0026] The present invention provides a thermally insulating SiC-BN aerogel felt prepared by the preparation method described in the above technical solution, comprising a felt body formed of graphite and SiC nanofibers, and BN supported on the felt body. The aerogel provided by the present invention combines a felt body containing SiC nanofibers with BN, and utilizes SiC nanofibers to assist the formation of BN. The SiC-BN aerogel can improve the mechanical properties and high-temperature resistance of the aerogel felt. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A schematic flow chart of a method for preparing a thermally insulating SiC-BN aerogel felt provided in an embodiment of the present invention;

[0028] Figure 2 This is a SEM photo of the thermal insulation SiC-BN aerogel felt prepared in Example 1 of the present invention;

[0029] Figure 3 This is a SEM photograph of the BN aerogel prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a thermally insulating SiC-BN aerogel felt, comprising the following steps:

[0031] heating and mixing a nitrogen source, a boron source, a solvent and silica aerogel powder to obtain a hot mixture; wherein the solvent is a solvent capable of dissolving the nitrogen source and the boron source;

[0032] impregnating graphite felt in the hot mixture and obtaining gel felt after cooling;

[0033] removing the solvent from the gel felt to obtain an aerogel felt;

[0034] The aerogel felt is heated in a protective atmosphere to perform a pyrolysis reaction to obtain the thermal insulation SiC-BN aerogel felt.

[0035] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0036] The present invention heats and mixes a nitrogen source, a boron source, a solvent and silicon dioxide aerogel powder to obtain a hot mixed material; the solvent is a solvent that can dissolve the nitrogen source and the boron source.

[0037] In the present invention, the nitrogen source is preferably one or more of dicyandiamide, (NH4)2SO4, melamine and urea, more preferably melamine.

[0038] In the present invention, the boron source is preferably one or more of boron trioxide, ammonium borate, borax, boric acid and NaBH4, more preferably boric acid.

[0039] In the present invention, the solvent is preferably a mixed solvent, and the mixed solvent preferably includes water and a hydroxyl compound; the hydroxyl compound preferably includes one or more of methanol, ethanol, ethylene glycol, benzyl alcohol, tert-butanol, phenol and cresol, more preferably tert-butanol.

[0040] In the present invention, the water is preferably deionized water.

[0041] In the present invention, the molar ratio of the nitrogen source, the boron source and the water is preferably (1-5):(0.2-6):(70-750).

[0042] The present invention has no special requirements on the volume ratio of water to the hydroxy compound in the mixed solvent.

[0043] In the present invention, the silica aerogel powder preferably includes single-component silica aerogel and / or silica composite aerogel.

[0044] In the present invention, the silica aerogel is preferably a hydrophobic silica aerogel.

[0045] In the present invention, the particle size of the silica aerogel powder is preferably ≤5 μm, more preferably 5 μm.

[0046] In the present invention, the mass ratio of the silica aerogel powder to the boron source is preferably (1-10):(1-10), more preferably (1.5-8):(1.5-8), and even more preferably (2-7):(2-7).

[0047] In the present invention, the mixing preferably includes the following steps: dissolving the nitrogen source and the boron source in a hot solvent to obtain a hot mixed solution A; and stirring and mixing the silica aerogel powder and the hot mixed solution A to obtain a hot mixed material. In the present invention, the temperature of the hot solvent is preferably 80 to 95°C; the dissolution is preferably carried out under stirring, and the stirring time is preferably 5 to 30 minutes.

[0048] After obtaining the hot mixed material, the present invention immerses the graphite felt in the hot mixed material, and obtains the gel felt after cooling.

[0049] In the present invention, the graphite felt preferably includes any one of asphalt-based graphite felt, polyacrylonitrile-based graphite felt and viscose-based graphite felt.

[0050] In the present invention, the specific surface area of the graphite felt is preferably 100 to 1500 m 2 / g, more preferably 300 to 1000 m 2 / g, more preferably 350 to 800 m 2 / g; the bulk density of the graphite felt is preferably 0.05 to 0.5 g / cm 3 , more preferably 0.1 to 0.4 g / cm 3 , more preferably 0.15 to 0.3 g / cm 3 .

[0051] In the present invention, the immersion is preferably ultrasonic oscillation immersion, and the time of the ultrasonic oscillation immersion is preferably 1 to 20 minutes, more preferably 5 to 15 minutes.

[0052] In the present invention, the cooling temperature is preferably -196 to 60°C, more preferably -100 to 30°C.

[0053] After obtaining the gel felt, the present invention removes the solvent from the gel felt to obtain the aerogel felt.

[0054] In the present invention, the solvent removal method preferably includes any one of supercritical drying, atmospheric pressure drying, and freeze drying, or a combination of two or more thereof.

[0055] In the present invention, the temperature of the atmospheric pressure drying is preferably 80 to 150° C., more preferably 85 to 140° C.; the holding time of the atmospheric pressure drying is preferably 24 to 72 hours, more preferably 36 to 48 hours.

[0056] In the present invention, the pre-freezing temperature of the freeze-drying is preferably -80 to 0°C, more preferably -30 to -5°C, and further preferably -25 to -10°C; the pre-freezing time is preferably 1 to 12 hours, more preferably 2 to 10 hours; and the freeze-drying time is preferably 12 to 72 hours, more preferably 36 to 48 hours.

[0057] In the present invention, the supercritical drying temperature is preferably 35-45° C., more preferably 38-42° C.; the pressure is preferably 9-14 MPa, more preferably 10-13 MPa; and the time is preferably 8-36 h, more preferably 12-24 h.

[0058] After obtaining the aerogel felt, the present invention heats the aerogel felt in a protective atmosphere to perform a pyrolysis reaction to obtain the thermal insulation SiC-BN aerogel felt.

[0059] In the present invention, the protective atmosphere is preferably one or more of argon atmosphere, nitrogen atmosphere, vacuum and ammonia atmosphere, more preferably argon atmosphere.

[0060] In the present invention, the temperature of the pyrolysis reaction is 1050-1650°C, more preferably 1100-1600°C, and further preferably 1150-1400°C; the time of the insulation reaction is preferably 0.5-4h, more preferably 1-3.5h, and further preferably 1.5-3h.

[0061] In the present invention, during the pyrolysis reaction, the silica aerogel is pyrolyzed at high temperature to produce SiO and CO gas, which react with the graphite felt: SiO(g)+2C(s)→SiC(s)+CO(g), SiO2(s)+CO(g)→SiO(g)+CO2(g).

[0062] The present invention provides a thermal insulation SiC-BN aerogel felt prepared by the preparation method described in the above technical solution, comprising a felt body formed of graphite and SiC nanofibers, and BN supported on the felt body.

[0063] The present invention provides the use of the thermal insulation SiC-BN aerogel felt described in the above technical solution as a heat-dissipating, heat-insulating and flame-retardant material.

[0064] The thermal insulation SiC-BN aerogel felt provided by the present invention has good thermal insulation, flexibility, easy cutting, flame retardancy, ultra-high temperature resistance and other properties, overcoming the pain points of the aerogel felt currently on the market that is easy to shed powder and difficult to use for a long time at high temperatures.

[0065] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1

[0067] like Figure 1 As shown, the present embodiment provides a method for preparing a high-temperature resistant thermal insulation SiC-BN aerogel felt, comprising the following steps:

[0068] S1. Heat a mixed solvent of 50 mL of deionized water and 70 mL of tert-butanol to 85° C., then dissolve 1.2 g of melamine and 1.2 g of boric acid in the mixed solvent, and stir to obtain a mixed solution A.

[0069] S2. Add 0.5 g of a single silica aerogel to the mixed solution A and stir to obtain a mixed solution B; the temperature of the mixed solution B is 85° C.;

[0070] S3, pour the mixed solution B obtained in S2 into a crucible, then immerse the graphite felt in it, and make B evenly dispersed in the graphite felt by ultrasonic vibration, and cool it to induce the formation of gel C; wherein: the graphite felt is selected with a specific surface area of 451m 2 / g, and the bulk density is 0.17g / cm 3 Asphalt-based graphite felt, cooling temperature is 25 ° C, ultrasonic vibration time is 5 minutes;

[0071] S4, freeze-drying the gel C obtained in S3, with the pre-freezing temperature at -20°C and the freeze-drying time at 48 hours to obtain aerogel felt D;

[0072] S5. The aerogel felt D obtained in S4 is subjected to a high-temperature reaction of B, N, SiO2, and graphite felt in a protective atmosphere to obtain a high-temperature resistant and insulating SiC-BN aerogel felt; the protective atmosphere is Ar gas, the high-temperature reaction temperature is 1200°C, and the high-temperature reaction holding time is 3h. The obtained high-temperature resistant and insulating SiC-BN aerogel felt is marked as sample 1.

[0073] The SEM photo of the high temperature resistant thermal insulation SiC-BN aerogel felt obtained in this embodiment is as follows: Figure 2 shown.

[0074] Example 2

[0075] The preparation method is basically the same as that of Example 1, except that the asphalt-based graphite felt in step S3 of Example 1 is replaced with viscose-based graphite felt; and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 2.

[0076] Example 3

[0077] The preparation method is basically the same as that of Example 1, except that the asphalt-based graphite felt in step S3 of Example 1 is replaced with polyacrylonitrile-based graphite felt; and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 3.

[0078] Example 4

[0079] The preparation method is basically the same as that of Example 1, except that the holding temperature in step S5 of Example 1 is changed to 1250° C.; the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 4.

[0080] Example 5

[0081] The preparation method is basically the same as that of Example 4, except that the asphalt-based graphite felt in step S3 of Example 4 is replaced with viscose-based graphite felt; and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 5.

[0082] Example 6

[0083] The preparation method is basically the same as that of Example 4, except that the asphalt-based graphite felt in step S3 of Example 4 is replaced with polyacrylonitrile-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 6.

[0084] Example 7

[0085] The preparation method is basically the same as that of Example 4, except that: 1.2g of boric acid in step S1 of Example 4 is replaced with 1g of boron trioxide; and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as Sample 7.

[0086] Example 8

[0087] The preparation method is basically the same as that of Example 7, except that the asphalt-based graphite felt in step S3 of Example 7 is replaced with viscose-based graphite felt; and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 8.

[0088] Example 9

[0089] The preparation method is basically the same as that of Example 7, except that the asphalt-based graphite felt in step S3 of Example 7 is replaced with polyacrylonitrile-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 9.

[0090] Example 10

[0091] The preparation method is basically the same as that of Example 4, except that: 1.2 g of boric acid in step S1 of Example 4 is replaced with 0.9 g of ammonium borate, and the insulation temperature in step S5 of Example 4 is changed to 1150°C. The obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 10.

[0092] Example 11

[0093] The preparation method is basically the same as that of Example 10, except that the asphalt-based graphite felt in step S3 of Example 10 is replaced with viscose-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 11.

[0094] Example 12

[0095] The preparation method is basically the same as that of Example 10, except that the asphalt-based graphite felt in step S3 of Example 10 is replaced with polyacrylonitrile-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 12.

[0096] Example 13

[0097] The preparation method is basically the same as that in Example 1, except that the mixed solvent of 50 mL of deionized water and 70 mL of tert-butanol in step S1 of Example 1 is changed to a mixed solvent of 70 mL of deionized water and 50 mL of tert-butanol, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is labeled as Sample 13.

[0098] Example 14

[0099] The preparation method is basically the same as that of Example 13, except that the asphalt-based graphite felt in step S3 of Example 13 is replaced with viscose-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 14.

[0100] Example 15

[0101] The preparation method is basically the same as that of Example 13, except that the asphalt-based graphite felt in step S3 of Example 13 is replaced with polyacrylonitrile-based graphite felt, and the obtained high-temperature resistant insulating SiC-BN aerogel felt is marked as sample 15.

[0102] Comparative Example 1

[0103] S1. Heat 90 mL of deionized water to 85° C., dissolve 1.63 g of melamine and 1.58 g of boric acid therein, and stir to obtain a mixed solution.

[0104] S2, cooling the mixed solution naturally to room temperature while ultrasonically vibrating to form a gel;

[0105] S3, pre-freezing the gel at -20°C and freeze-drying it for 48 h to obtain a BN aerogel precursor;

[0106] S4. The BN aerogel precursor is kept at 1200° C. in Ar gas for 3 h to obtain a high-temperature resistant and insulating BN aerogel.

[0107] The SEM photograph of the BN aerogel obtained in this comparative example is shown in FIG. Figure 3 shown.

[0108] The properties of the aerogels prepared in Examples 1 to 15 and Comparative Example 1 are shown in Table 1. It can be seen that the high-temperature resistant thermal insulation SiC-BN aerogel felt prepared in the present invention has excellent thermal insulation performance and temperature resistance.

[0109] Table 1. Performance parameters of high temperature resistant thermal insulation SiC-BN aerogel felt obtained in Examples 1 to 15

[0110] Example <![CDATA[Specific surface area (m 2 / g)]]> Temperature resistance in air (℃) <![CDATA[Thermal conductivity (Wm -1 K -1 )]]> 1 432.25 1200 0.0261 2 368.57 1200 0.0263 3 402.56 1200 0.0268 4 682.32 1300 0.0235 5 623.54 1300 0.0237 6 642.32 1300 0.0231 7 653.32 1300 0.0215 8 598.32 1300 0.0221 9 613.23 1300 0.0213 10 456.36 1250 0.0255 11 432.12 1250 0.0252 12 495.23 1250 0.0253 13 351.23 1200 0.0271 14 384.56 1200 0.0269 15 342.11 1200 0.0272

[0111] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an insulating SiC-BN aerogel felt, characterized in that: The following steps are involved: heating and mixing a nitrogen source, a boron source, a solvent and silica aerogel powder to obtain a hot mixture; wherein the solvent is a solvent capable of dissolving the nitrogen source and the boron source; impregnating graphite felt in the hot mixture and obtaining gel felt after cooling; removing the solvent from the gel felt to obtain an aerogel felt; In a protective atmosphere, the aerogel felt is heated to perform a pyrolysis reaction to obtain the thermal insulation SiC-BN aerogel felt.

2. The preparation method according to claim 1, characterized in that The nitrogen source is one or more of dicyandiamide, (NH4)2SO4, melamine and urea; the boron source is one or more of boron trioxide, ammonium borate, borax, boric acid and NaBH4; the solvent is a mixed solvent, and the mixed solvent includes water and a hydroxyl compound; the hydroxyl compound includes one or more of methanol, ethanol, ethylene glycol, benzyl alcohol, tert-butyl alcohol, phenol and cresol; The molar ratio of the nitrogen source, the boron source and the water is (1-5):(0.2-6):(70-750).

3. The preparation method according to claim 1, characterized in that the temperature of the hot mix is 80-95°C; The immersion is ultrasonic oscillation immersion, and the time of the ultrasonic oscillation immersion is 1 to 20 minutes; The cooling temperature is -196 to 60°C.

4. The preparation method according to claim 1, characterized in that The silica aerogel powder includes single-component silica aerogel and / or silica composite aerogel; The mass ratio of the silica aerogel powder to the boron source is (1-10):(1-10).

5. The preparation method according to claim 1, characterized in that The graphite felt includes any one of asphalt-based graphite felt, polyacrylonitrile-based graphite felt and viscose-based graphite felt.

6. The preparation method according to claim 1 or 5, characterized in that The specific surface area of the graphite felt is 100 to 1500 m 2 / g, and the bulk density is 0.05~0.5g / cm 3 .

7. The preparation method according to claim 1, characterized in that The desolventizing method includes any one of supercritical drying, atmospheric pressure drying and freeze drying, or a combination of two or more thereof; the atmospheric pressure drying temperature is 80 to 150° C., and the time is 24 to 72 hours; the pre-freezing temperature of the freeze drying is -80 to 0° C., the pre-freezing time is 1 to 12 hours, and the freeze drying time is 12 to 72 hours; the supercritical drying temperature is 35 to 45° C., the pressure is 9 to 14 MPa, and the time is 8 to 36 hours.

8. The preparation method according to claim 1, characterized in that The protective atmosphere is one or more of argon atmosphere, nitrogen atmosphere and ammonia atmosphere; the temperature of the pyrolysis reaction is 1050-1650° C., and the insulation reaction time is 0.5-4 hours.

9. The preparation method according to claim 1, characterized in that The protective atmosphere is replaced with a vacuum environment; the temperature of the pyrolysis reaction is 1050-1650° C., and the insulation reaction time is 0.5-4 hours.

10. The thermal insulation SiC-BN aerogel felt prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The invention comprises a felt body formed of graphite and SiC nanofibers, and BN supported on the felt body.

11. Use of the thermal insulation SiC-BN aerogel felt according to claim 10 as a heat-dissipating, heat-insulating and flame-retardant material.

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