A ceramic fiber aerogel blanket and method of making the same

Abstract

The application belongs to the technical field of ceramic fiber composite material preparation, and provides a ceramic fiber aerogel felt and a preparation method thereof; a ceramic fiber felt is used as a framework, a basic sol is prepared through a sol-gel method, and three additives are introduced; the first additive is a boron-silicon oligomer solution, which is used for forming a high-temperature-resistant borosilicate network in the final material; the second additive is a Ti-POSS solution, which is used as an in-situ precursor of a high-temperature infrared light shielding agent and is used for inhibiting the radiation heat transfer of the material at high temperature; the third additive is a phosphazene siloxane solution, which is used for imparting intrinsic flame retardancy and flexibility to the material; subsequently, solvent replacement, surface hydrophobic modification and normal-pressure drying are performed, and a functional conversion and a ceramicization process are completed through heat treatment, so that the obtained ceramic fiber aerogel felt has excellent heat insulation performance and high-temperature structural stability, and has important application value in the field of high-end power battery thermal safety protection.

Description

Technical Field

[0001] This invention belongs to the field of ceramic fiber composite material preparation technology, and relates to a ceramic fiber aerogel felt and its preparation method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the energy density and safety of power batteries have become key technological bottlenecks restricting their further popularization. High-energy-density lithium-ion batteries are highly susceptible to thermal runaway under abuse conditions such as overcharging, short circuits, collisions, or high temperatures, posing a serious threat to the life and property safety of drivers and passengers. Existing battery insulation materials, such as traditional foam and fiberglass, while possessing certain insulation effects, often suffer from insufficient temperature resistance, susceptibility to burn-through, and poor structural strength when faced with the instantaneous high-temperature and high-pressure flame impact generated during thermal runaway of the battery cell.

[0003] Aerogels are considered ideal battery insulation materials due to their extremely low thermal conductivity and lightweight properties. However, pure silica aerogels have two inherent drawbacks: firstly, they are mechanically fragile and brittle; secondly, their insulation performance significantly decreases at high temperatures due to the sintering of nanostructures and the sharp increase in thermal radiation. Simply combining silica aerogels with ceramic fibers can improve their mechanical properties and macroscopic morphology to some extent, but it does not fundamentally solve the problem of their high-temperature insulation performance degradation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a ceramic fiber aerogel felt and its preparation method. By using borosilicate oligomers, Ti-POSS solution, and phosphazene siloxane solution as functional additives, and blending them with a silane precursor to form a composite sol, the sol undergoes surface modification, atmospheric pressure drying, and multi-stage inert atmosphere heat treatment to finally obtain a composite material with excellent thermal insulation and high-temperature structural stability, thereby meeting the needs of actual production.

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

[0006] In a first aspect, the present invention provides a method for preparing ceramic fiber aerogel felt, the method comprising:

[0007] S1, anhydrous ethanol, triethoxysilane and allyl glycidyl ether are mixed and then reacted with Karstedt catalyst. After the reaction is completed, toluene and deionized water are added to react, and then triethoxyboric acid and tetrabutyl titanate are added to react to obtain borosilicate oligomer solution.

[0008] S2, 3,5-dihydroxybenzoic acid is mixed with the first part of anhydrous THF, carbonyl imidazole is added to obtain acyl imidazole activation solution, aminated cage-type silsesquioxane is dispersed in the second part of anhydrous THF, acyl imidazole activation solution is added to the second part of anhydrous THF to react, tetraisopropyl titanate is added to react, and Ti-POSS solution is obtained.

[0009] S3, disperse hexachlorocyclotriphosphazene in the first part of N-methylpyrrolidone to obtain solution A, disperse hydroxyl-terminated polydimethylsiloxane and the first part of anhydrous cesium carbonate in the second part of N-methylpyrrolidone to obtain solution B and add it to solution A, then disperse bisphenol S and the second part of anhydrous cesium carbonate in the third part of N-methylpyrrolidone to obtain solution C, add solution C to solution A to obtain phosphazene siloxane solution;

[0010] S4, mix tetraethoxysilane with anhydrous ethanol, add dilute hydrochloric acid solution to obtain basic sol, add phosphazene siloxane solution, borosilicate oligomer solution, Ti-POSS solution and hexamethylenetetramine in sequence to obtain composite sol, place ceramic fiber felt into composite sol until completely submerged to obtain pretreated ceramic fiber felt.

[0011] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. After displacement, it is immersed in hydrophobic working solution and dried under normal pressure to obtain hydrophobic green felt. The green felt is then heat-treated to obtain a ceramic fiber aerogel felt.

[0012] Specifically, it includes:

[0013] S1, anhydrous ethanol, triethoxysilane and allyl glycidyl ether were mixed and Karstedt catalyst was added. The temperature was adjusted to the first temperature and the reaction was stirred. After the reaction was completed, the temperature was lowered to room temperature and toluene and deionized water were added. The temperature was adjusted to the second temperature and the reaction was refluxed. The temperature was then adjusted to the third temperature and triethoxyboric acid and tetrabutyl titanate were added. The temperature was adjusted to the second temperature and the de-alcoholization condensation reaction was carried out to obtain borosilicate oligomers. The temperature was cooled to the fourth temperature and ethanol was added to adjust to the target solid content. Ethyl p-toluenesulfonate was added and stirred to terminate the reaction and obtain a borosilicate oligomer solution.

[0014] S2, 3,5-Dihydroxybenzoic acid was mixed with the first part of anhydrous THF. Under ice-water bath conditions, carbonyl imidazole was added to obtain an acyl imidazole activated solution. Aminated cage-type silsesquioxane was dispersed in the second part of anhydrous THF. Under ice-water bath conditions, the acyl imidazole activated solution was added to the second part of anhydrous THF and reacted at room temperature. The reaction solution was distilled under reduced pressure to 150 mL. Under ice-water bath conditions, tetraisopropyl titanate was added to react. The reaction solution was then poured into anhydrous diethyl ether to precipitate. The precipitate was filtered, washed with diethyl ether, dried, and redissolved in THF to obtain a Ti-POSS solution.

[0015] S3, hexachlorocyclotriphosphazene is dispersed in the first part of N-methylpyrrolidone to obtain solution A. Hydroxyl-terminated polydimethylsiloxane and the first part of anhydrous cesium carbonate are dispersed in the second part of N-methylpyrrolidone. The solution is pre-activated at the first temperature to obtain solution B, which is then added to solution A. The solution is aged at the first temperature. Bisphenol S and the second part of anhydrous cesium carbonate are then dispersed in the third part of N-methylpyrrolidone to obtain solution C. The temperature is adjusted to the third temperature, and solution C is added to solution A. The solution is kept at the third temperature, and then the temperature is adjusted to the second temperature and kept at the second temperature to obtain a reaction solution. The reaction solution is poured into a methanol aqueous solution while hot to precipitate. The solution is filtered, washed, dried, and dissolved again in anhydrous tetrahydrofuran to obtain a phosphazene siloxane solution.

[0016] S4. Tetraethoxysilane and anhydrous ethanol are mixed, and dilute hydrochloric acid solution is added under ice-water bath conditions. The temperature is adjusted to the first temperature and refluxed to obtain a basic sol. The temperature is lowered to the fourth temperature, and phosphazene siloxane solution, borosilicate oligomer solution, Ti-POSS solution and hexamethylenetetramine are added in sequence to obtain a composite sol. The ceramic fiber felt is placed in a vacuum tank, and after vacuuming, the composite sol is introduced until it is completely submerged and maintained. After returning to normal pressure, the temperature is kept constant at the fourth temperature, and then the temperature is adjusted to the first temperature for aging. During the aging period, the sol is replaced with ethanol / THF working solution once every 24 hours to obtain a pretreated ceramic fiber felt.

[0017] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. After displacement, it is immersed in hydrophobic working solution and impregnated at the fourth temperature. After rinsing with anhydrous n-hexane, it is dried under normal pressure to obtain hydrophobic green felt. The green felt is then heat-treated to obtain a ceramic fiber aerogel felt.

[0018] In step S1, the silane-hydrogen bonds in the triethoxysilane molecule undergo addition with the carbon-carbon double bonds of allyl glycidyl ether under the action of a Karstedt catalyst, covalently attaching the organic segment containing the epoxy functional group to the silicon atom. Subsequently, water is introduced, causing hydrolysis of some of the silylethoxy bonds in the triethoxysilane to generate silanol groups. The introduced triethoxyboric acid undergoes a dealcoholization condensation reaction with the silanol groups already generated in the system. Under the condition of tetrabutyl titanate as a Lewis acid catalyst, the oxygen atom of the silanol group acts as a nucleophile to attack the boron center, or the oxygen atom of the borate ester attacks the silicon center, forming a thermodynamically stable silicon-oxygen-boron bond. By introducing an acidic substance, a small portion of the epoxy groups undergo a ring-opening reaction. Ethanol in the system acts as a nucleophile to attack the protonated epoxy ring, generating additional hydroxyl and ether bonds.

[0019] In step S2, carbonyl diimidazole reacts with the carboxyl group of 3,5-dihydroxybenzoic acid to generate a highly reactive acyl imidazolium intermediate. The primary amine group of the aminated cage-like silsesquioxane acts as a nucleophilic center, attacking the carbonyl carbon of the acyl imidazolium. The imidazolium then leaves as a leaving group, forming a stable amide bond. The aromatic ring structure containing a phenolic hydroxyl group is covalently grafted onto the inorganic cage core of the silsesquioxane. After grafting, the introduced tetraisopropyl titanate acts as a Lewis acid center. Following amidation, the aromatic ring phenolic oxygen and / or the adjacent amide carbonyl oxygen coordinate with Ti, achieving bridged coordination of Ti through multiple ligands.

[0020] In step S3, highly basic cesium carbonate deprotonates the terminal hydroxyl groups of hydroxyl-terminated polydimethylsiloxane, forming a silanolate anion with strong nucleophilicity. This silanolate nucleophilically attacks the phosphorus atom of hexachlorocyclotriphosphazene, replacing the chloride ion and introducing the flexible polydimethylsiloxane segment onto the rigid phosphazene ring. Next, bisphenol S also forms a phenoxy anion under the action of cesium carbonate. This bifunctional nucleophile continues to attack the remaining phosphorus-chlorine bonds on the phosphazene ring, acting as a chain growth unit to connect multiple siloxane-substituted phosphazene rings, forming a high-molecular-weight linear or branched polymer.

[0021] In step S4, tetraethoxysilane undergoes hydrolysis and preliminary condensation under acid catalysis to form a basic sol. Subsequently, the three additive solutions synthesized above are added sequentially in a specific order. The hydroxyl / residual alkoxy groups on the additive molecules can partially co-condense with the silanols in the basic sol, while hydrogen bonding and physical entanglement provide synergistic fixation. The latent catalyst, hexamethylenetetramine, is chemically inert at room temperature, but slowly hydrolyzes under subsequent mild heating, uniformly releasing ammonia as a base catalyst. This causes a uniform sol-to-gel phase transition throughout the pores of the ceramic fiber felt, forming a solvent-filled solid three-dimensional network.

[0022] In step S5, the hydrophilic silanol groups on the surface of the gel framework react with modifiers such as trimethylchlorosilane, making the entire network surface hydrophobic and effectively preventing the collapse of the nanoporous structure during drying. Subsequent high-temperature heat treatment under an inert atmosphere causes the organic components in the additive molecules to pyrolyze, while the inorganic framework undergoes reconstruction and ceramization. The borosilicate oligomer transforms into a borosilicate phase with high-temperature sintering resistance; titanium-functionalized silsesquioxanes generate in-situ titanium-based ceramic nanophases with infrared absorption and scattering capabilities through solid-phase reactions such as carbothermal reduction; and the phosphazene siloxane hybrid polymer releases flame-retardant gases while forming dispersed phosphorus-silicon-oxygen glassy ceramic nanophases, distributed in a point-like / thin-layer pattern within the framework, improving temperature resistance / sintering resistance without inducing overall densification.

[0023] As a preferred embodiment of the present invention, in S1, the mass ratio of anhydrous ethanol, triethoxysilane, allyl glycidyl ether, Karstedt catalyst, toluene, deionized water, triethoxyboric acid, tetrabutyl titanate, and ethyl p-toluenesulfonate is (700-800):(300-320):(45-50):(1-2):(300-350):(18-20):(76-80):(0.3-0.8):( 2-3), for example, could be (700, 710, 720, 730, 740, 750, 760, 770, 780, 790 or 800): (300, 302, 304, 306, 308, 310, 312, 314, 316, 318 or 320): (45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5 or 50): (1.0, 1.1, 1.2) 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0: (300, 305, 310, 315, 320, 325, 330, 335, 340, 345 or 350): (18.0, 18.2, 18.4, 18.6, 18.8, 19.0, 19.2, 19.4, 19.6, 19.8 or 20.0): (76, 76.4, 76.8, 77.2, 77. 6, 78.0, 78.4, 78.8, 79.2, 79.6 or 80: (0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75 or 0.8): (2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0024] In some alternative embodiments, the first temperature is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the stirring reaction time at the first temperature is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In some alternative embodiments, the second temperature is 110-115°C, for example, it can be 110°C, 110.5°C, 111°C, 111.5°C, 112°C, 112.5°C, 113°C, 113.5°C, 114°C, 114.5°C or 115°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the reflux reaction time is 3-3.5 h, for example, it can be 3.0 h, 3.05 h, 3.1 h, 3.15 h, 3.2 h, 3.25 h, 3.3 h, 3.35 h, 3.4 h, 3.45 h or 3.5 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] In some alternative embodiments, the third temperature is 90-95°C, for example, it can be 90°C, 90.5°C, 91°C, 91.5°C, 92°C, 92.5°C, 93°C, 93.5°C, 94°C, 94.5°C or 95°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the time for the dealcoholization condensation reaction is 6-7 h, for example, 6.0 h, 6.1 h, 6.2 h, 6.3 h, 6.4 h, 6.5 h, 6.6 h, 6.7 h, 6.8 h, 6.9 h or 7.0 h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0030] In some alternative embodiments, the fourth temperature is 40-45°C, for example, it can be 40°C, 40.5°C, 41°C, 41.5°C, 42°C, 42.5°C, 43°C, 43.5°C, 44°C, 44.5°C or 45°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the target solid content is 29-31 wt.%, for example, it can be 29.0 wt.%, 29.2 wt.%, 29.4 wt.%, 29.6 wt.%, 29.8 wt.%, 30.0 wt.%, 30.2 wt.%, 30.4 wt.%, 30.6 wt.%, 30.8 wt.%, or 31.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0032] As a preferred embodiment of the present invention, in S2, the mass ratio of 3,5-dihydroxybenzoic acid, anhydrous THF, and carbonyl imidazole is (14-15):(350-400):(9-10), for example, it can be (14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9 or 15.0):(350, 355, 360, 365, 370, 375, 380, 385, 390, 395 or 400):(9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or 10.0), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the mass ratio of 3,5-dihydroxybenzoic acid, amino-modified cage-like silsesquioxane, the second part of anhydrous THF, and tetraisopropyl titanate is (14-15):(20-21):(150-200):(10-11), for example, (14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, or 15.0):(20.0, 20.1, 20.2, 20.3). 20.4, 20.5, 20.6, 20.7, 20.8, 20.9 or 21.0: (150, 155, 160, 165, 170, 175, 180, 185, 190, 195 or 200): (10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.0), but not limited to the listed values, other unlisted values ​​within this range also apply.

[0034] In some optional embodiments, the room temperature reaction time is 16-17 h, for example, it can be 16.0 h, 16.1 h, 16.2 h, 16.3 h, 16.4 h, 16.5 h, 16.6 h, 16.7 h, 16.8 h, 16.9 h or 17.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the reaction time for adding tetraisopropyl titanate is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the solid content of the Ti-POSS solution is 10-11 wt.%; for example, it can be 10.0 wt.%, 10.1 wt.%, 10.2 wt.%, 10.3 wt.%, 10.4 wt.%, 10.5 wt.%, 10.6 wt.%, 10.7 wt.%, 10.8 wt.%, 10.9 wt.%, or 11.0 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] As a preferred embodiment of the present invention, in S3, the mass ratio of the hexachlorocyclotriphosphazene, the first part of N-methylpyrrolidone, the hydroxyl-terminated polydimethylsiloxane, the first part of anhydrous cesium carbonate, the second part of N-methylpyrrolidone, bisphenol S, the second part of anhydrous cesium carbonate, and the third part of N-methylpyrrolidone is (28-29):400:(64-65):(21-22):200:(17-18):(22-23):200, for example, it can be (28, 28.1, 28.2, 28.3, 28.4, 28.5, 28.6, 28.7, 28.8, 28.9 or 29):400:(64, 64.1, 64.2, 64). 3, 64.4, 64.5, 64.6, 64.7, 64.8, 64.9 or 65): (21, 21.1, 21.2, 21.3, 21.4, 21.5, 21.6, 21.7, 21.8, 21.9 or 22): 200; (17, 17.1, 17.2, 17.3, 17.4, 17.5, 17.6, 17.7, 17.8, 17.9 or 18): (22, 22.1, 22.2, 22.3, 22.4, 22.5, 22.6, 22.7, 22.8, 22.9 or 23): 200, but not limited to the listed values, other unlisted values ​​within this range also apply.

[0038] In some optional embodiments, the pre-activation time is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the aging time at the first temperature is 1-2 hours, for example, it can be 1.0 hours, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0040] In some optional embodiments, the time for maintaining the third temperature is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In some optional embodiments, the second temperature holding time is 1-2 hours, for example, it can be 1.0h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2.0h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0042] In some optional embodiments, the volume ratio of methanol to deionized water in the methanol-water solution is 7:3.

[0043] In some optional embodiments, the solid content of the phosphazene siloxane solution is 19-21 wt.%, for example, it can be 19.0 wt.%, 19.2 wt.%, 19.4 wt.%, 19.6 wt.%, 19.8 wt.%, 20.0 wt.%, 20.2 wt.%, 20.4 wt.%, 20.6 wt.%, 20.8 wt.%, or 21.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] As a preferred embodiment of the present invention, in S3, the mass ratio of tetraethoxysilane, anhydrous ethanol, dilute hydrochloric acid solution, phosphazene siloxane solution, borosilicate oligomer solution, Ti-POSS solution, and hexamethylenetetramine is (400-410):3000:(200-210):(40-50):(100-110):(70-80):(5-8), for example, it can be (400, 401, 402, 403, 404, 405, 406, 407, 408, 409 or 410):3000:(200, 201, 202, 203, 204, 205...). 206, 207, 208, 209 or 210: (40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50): (100, 101, 102, 103, 104, 105, 106, 107, 108, 109 or 110): (70, 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80): (5.0, 5.3, 5.6, 5.9, 6.2, 6.5, 6.8, 7.1, 7.4, 7.7 or 8.0), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0045] In some optional embodiments, the concentration of the dilute hydrochloric acid solution is 0.01M.

[0046] In some alternative embodiments, the reflux reaction time is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some optional embodiments, the duration of maintenance is 30-40 minutes, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes or 40 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] In some alternative embodiments, the time for holding the fourth temperature is 2-4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0049] In some optional embodiments, the aging time at the first temperature is 70-72 hours, for example, it can be 70.0 hours, 70.2 hours, 70.4 hours, 70.6 hours, 70.8 hours, 71.0 hours, 71.2 hours, 71.4 hours, 71.6 hours, 71.8 hours or 72.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0050] In some optional embodiments, the volume ratio of ethanol to THF in the ethanol / THF working solution is 7:3.

[0051] As a preferred technical solution of the present invention, in S5, the stepwise replacement is carried out according to the volume ratio of ethanol to n-hexane of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step taking 4 hours and a total of 20 hours.

[0052] In some optional embodiments, the hydrophobic working fluid is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane and triethylamine in a volume ratio of 100:50:850:1.5.

[0053] In some optional embodiments, the atmospheric pressure drying is performed by heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours.

[0054] In some optional embodiments, the heat treatment is carried out in an argon atmosphere, with the temperature raised to 350°C and held for 1 hour, then raised to 800°C and held for 1 hour, then raised to 1200°C and held for 1 hour, and finally cooled naturally to room temperature.

[0055] Secondly, the present invention provides a ceramic fiber aerogel felt prepared by the preparation method described in the first aspect and the preparation method thereof.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows: by forming a borosilicate network in situ at high temperature through borosilicate oligomers, the high-temperature structural stability of the aerogel felt is improved, effectively suppressing the sintering shrinkage of traditional aerogels at high temperatures; secondly, by generating a titanium-based nanophase in situ in the aerogel skeleton, a high-temperature infrared shielding system is constructed, reducing heat transfer through radiation and enhancing the material's heat insulation capability in the high-temperature region; the introduction of phosphazene siloxane hybrid polymer and the synergistic effect of phosphorus and nitrogen elements provide the material with a dual flame-retardant mechanism in both the gas phase and solid phase. Detailed Implementation

[0057] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0058] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment. Example

[0059] This embodiment provides a ceramic fiber aerogel felt and its preparation method, the preparation method specifically includes the following steps:

[0060] S1, 700g anhydrous ethanol, 310g triethoxysilane and 50g allyl glycidyl ether were mixed and 1g Karstedt catalyst was added. The temperature was adjusted to 70 °C and stirred for 2h. After the reaction was completed, the temperature was lowered to room temperature and 350g toluene and 18g deionized water were added. The temperature was adjusted to 115 °C and refluxed for 3h. The temperature was then adjusted to 95 °C and 76g triethoxyboric acid and 0.8g tetrabutyl titanate were added. The temperature was adjusted to 110 °C and de-alcoholized for 7h to obtain borosilicate oligomers. The mixture was cooled to 40 °C and ethanol was added to adjust the solid content to 31wt.%. 3g ethyl p-toluenesulfonate was added and stirred to terminate the reaction, resulting in a borosilicate oligomer solution.

[0061] S2, 15g of 3,5-dihydroxybenzoic acid was mixed with 350g of the first portion of anhydrous THF. Under ice-water bath conditions, 11g of carbonyl imidazole was added to obtain an acyl imidazole activation solution. 21g of amino-modified cage-like silsesquioxane was dispersed in 150g of the second portion of anhydrous THF. Under ice-water bath conditions, the acyl imidazole activation solution was added to the second portion of anhydrous THF, and the reaction was carried out at room temperature for 16h. The reaction solution was then distilled under reduced pressure to 150 mL. Under ice-water bath conditions, 10g of tetraisopropyl titanate was added, and the reaction was carried out for 2h. The reaction solution was then poured into anhydrous diethyl ether to precipitate the precipitate. The precipitate was filtered, washed with diethyl ether, dried, and redissolved in THF to obtain a Ti-POSS solution with a solid content of 11 wt.%.

[0062] S3, 29g of hexachlorocyclotriphosphazene was dispersed in 400g of N-methylpyrrolidone to obtain solution A. 64g of hydroxyl-terminated polydimethylsiloxane and 22g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone and pre-activated at 70 °C for 1h to obtain solution B, which was then added to solution A. The mixture was aged at 60 °C for 2h. Then, 18g of bisphenol S and 22g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone to obtain solution C. The temperature was adjusted to 95 °C, and solution C was added to solution A. The mixture was kept at 90 °C for 3h, and then the temperature was adjusted to 115 °C and kept at 1h to obtain a reaction solution. The reaction solution was poured into a methanol-water solution while hot to precipitate the precipitate. The volume ratio of methanol to deionized water in the methanol-water solution was 7:3. The solution was filtered, washed, dried, and redissolved in anhydrous tetrahydrofuran to obtain a phosphazene siloxane solution with a solid content of 19 wt.%.

[0063] S4, 400g of tetraethoxysilane and 2000g of anhydrous ethanol were mixed, and 210g of 0.01M dilute hydrochloric acid solution was added under ice-water bath conditions. The temperature was adjusted to 60 °C and refluxed for 3h to obtain a basic sol. The temperature was lowered to 45 °C, and 130g of phosphazene siloxane solution, 11g of borosilicate oligomer solution, 390g of Ti-POSS solution and 5g of hexamethylenetetramine were added sequentially to obtain a composite sol. The ceramic fiber felt was placed in a vacuum tank, and after vacuuming, the composite sol was introduced until it was completely submerged and maintained for 30min. After returning to normal pressure, the temperature was kept constant at 45 °C for 2h, and then the temperature was adjusted to 70 °C and kept for 70h. During the aging period, the sol was replaced once every 24h with ethanol / THF working solution. The volume ratio of ethanol to THF in the ethanol / THF working solution was 7:3 to obtain the pretreated ceramic fiber felt.

[0064] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. The stepwise displacement is performed at ethanol:n-hexane volume ratios of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step lasting 4 hours, for a total of 20 hours. After displacement, a hydrophobic working solution is added. This working solution is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane, and triethylamine in a volume ratio of 100:50:850:1.5, and impregnated at 40 °C for 24 hours. h, after rinsing with anhydrous n-hexane, it is dried at atmospheric pressure. The atmospheric pressure drying is carried out by heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours to obtain a hydrophobic green felt. The green felt is then subjected to heat treatment in an argon atmosphere, heated to 350°C and held for 1 hour, then heated to 800°C and held for 1 hour, then heated to 1200°C and held for 1 hour, and finally naturally cooled to room temperature to obtain a ceramic fiber aerogel felt. Example

[0065] This embodiment provides a ceramic fiber aerogel felt and its preparation method, the preparation method specifically includes the following steps:

[0066] S1, 800g anhydrous ethanol, 300g triethoxysilane and 45g allyl glycidyl ether were mixed and 2g Karstedt catalyst was added. The temperature was adjusted to 60 °C and stirred for 3h. After the reaction was completed, the mixture was cooled to room temperature and 300g toluene and 20g deionized water were added. The temperature was adjusted to 110 °C and refluxed for 3.5h. The temperature was then adjusted to 90 °C and 80g triethoxyboric acid and 0.3g tetrabutyl titanate were added. The temperature was adjusted to 115 °C and de-alcoholized for 6h to obtain borosilicate oligomers. The mixture was cooled to 45 °C and ethanol was added to adjust the solid content to 29wt.%. 2g ethyl p-toluenesulfonate was added and stirred to terminate the reaction, resulting in a borosilicate oligomer solution.

[0067] S2, 14g of 3,5-dihydroxybenzoic acid was mixed with 400g of the first portion of anhydrous THF. Under ice-water bath conditions, 10g of carbonyl imidazole was added to obtain an acyl imidazole activation solution. 20g of amino-modified cage-like silsesquioxane was dispersed in 200g of the second portion of anhydrous THF. Under ice-water bath conditions, the acyl imidazole activation solution was added to the second portion of anhydrous THF, and the reaction was carried out at room temperature for 17h. The reaction solution was then distilled under reduced pressure to 150 mL. Under ice-water bath conditions, 9g of tetraisopropyl titanate was added and the reaction was carried out for 3h. The reaction solution was then poured into anhydrous diethyl ether to precipitate the precipitate. The precipitate was filtered, washed with diethyl ether, dried, and redissolved in THF to obtain a Ti-POSS solution with a solid content of 10wt.%.

[0068] S3, 28g of hexachlorocyclotriphosphazene was dispersed in 400g of N-methylpyrrolidone to obtain solution A. 65g of hydroxyl-terminated polydimethylsiloxane and 21g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone and pre-activated at 60 °C for 2h to obtain solution B, which was then added to solution A. The mixture was aged at 70 °C for 1h. Then, 17g of bisphenol S and 23g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone to obtain solution C. The temperature was adjusted to 90 °C, and solution C was added to solution A. The mixture was kept at 95 °C for 2h, and then adjusted to 110 °C for 2h to obtain a reaction solution. The reaction solution was poured into a methanol-water solution while hot to precipitate the precipitate. The volume ratio of methanol to deionized water in the methanol-water solution was 7:3. The solution was filtered, washed, dried, and redissolved in anhydrous tetrahydrofuran to obtain a phosphazene siloxane solution with a solid content of 21 wt.%.

[0069] S4, 410g of tetraethoxysilane and 2000g of anhydrous ethanol were mixed, and 200g of 0.01M dilute hydrochloric acid solution was added under ice-water bath conditions. The temperature was adjusted to 70 °C and refluxed for 2h to obtain a basic sol. The temperature was lowered to 40 °C, and 120g of phosphazene siloxane solution, 12g of borosilicate oligomer solution, 380g of Ti-POSS solution and 8g of hexamethylenetetramine were added sequentially to obtain a composite sol. The ceramic fiber felt was placed in a vacuum tank, and after vacuuming, the composite sol was introduced until it was completely submerged and maintained for 40min. After returning to normal pressure, the temperature was kept constant at 40 °C for 4h, and then the temperature was adjusted to 60 °C and kept for 72h. During the aging period, the ethanol / THF working solution was replaced once every 24h. The volume ratio of ethanol to THF in the ethanol / THF working solution was 7:3 to obtain the pretreated ceramic fiber felt.

[0070] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. The stepwise displacement is performed at ethanol:n-hexane volume ratios of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step lasting 4 hours, for a total of 20 hours. After displacement, a hydrophobic working solution is added. This working solution is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane, and triethylamine in a volume ratio of 100:50:850:1.5, and impregnated at 45 °C for 24 hours. h, after rinsing with anhydrous n-hexane, it is dried at atmospheric pressure. The atmospheric pressure drying is carried out by heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours to obtain a hydrophobic green felt. The green felt is then subjected to heat treatment in an argon atmosphere, heated to 350°C and held for 1 hour, then heated to 800°C and held for 1 hour, then heated to 1200°C and held for 1 hour, and finally naturally cooled to room temperature to obtain a ceramic fiber aerogel felt. Example

[0071] This embodiment provides a ceramic fiber aerogel felt and its preparation method, the preparation method specifically includes the following steps:

[0072] S1, 750 g anhydrous ethanol, 320 g triethoxysilane and 48 g allyl glycidyl ether were mixed and 1.5 g Karstedt catalyst was added. The temperature was adjusted to 65 °C and the mixture was stirred for 2.5 h. After the reaction was completed, the mixture was cooled to room temperature and 320 g toluene and 19 g deionized water were added. The temperature was adjusted to 112 °C and the mixture was refluxed for 3.2 h. The temperature was then adjusted to 92 °C and 78 g triethoxyboric acid and 0.5 g tetrabutyl titanate were added. The mixture was then adjusted to 112 °C and the mixture underwent a de-alcoholization condensation reaction for 6.5 h to obtain borosilicate oligomers. The mixture was cooled to 42 °C and ethanol was added to adjust the solid content to 30 wt.%**. 2.5 g ethyl p-toluenesulfonate was added and stirred to terminate the reaction, resulting in a borosilicate oligomer solution.

[0073] S2, 14.5 g of 3,5-dihydroxybenzoic acid was mixed with 380 g of the first portion of anhydrous THF. Under ice-water bath conditions, 10.5 g of carbonyl imidazole was added to obtain an acyl imidazole activated solution. 20.5 g of amino-modified cage-like silsesquioxane was dispersed in 180 g of the second portion of anhydrous THF. Under ice-water bath conditions, the acyl imidazole activated solution was added to the second portion of anhydrous THF. The reaction was carried out at room temperature for 16.5 h. The reaction solution was then distilled under reduced pressure to 150 mL. Under ice-water bath conditions, 10 g of tetraisopropyl titanate was added and the reaction was carried out for 2.5 h. The reaction solution was then poured into anhydrous diethyl ether to precipitate the precipitate. The precipitate was filtered, washed with diethyl ether, dried, and redissolved in THF to obtain a Ti-POSS solution with a solid content of 10.5 wt.%.

[0074] S3, 28.5g of hexachlorocyclotriphosphazene was dispersed in 400g of N-methylpyrrolidone to obtain solution A. 65g of hydroxyl-terminated polydimethylsiloxane and 21.5g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone and pre-activated at 65 °C for 1.5h to obtain solution B, which was then added to solution A and aged at 65 °C for 1.5h. Then, 17g of bisphenol S and 22.5g of anhydrous cesium carbonate were dispersed in 200g of N-methylpyrrolidone to obtain solution C. The temperature was adjusted to 92 °C and solution C was added to solution A. The mixture was kept at 92 °C for 2.5h, and then the temperature was adjusted to 112 °C. The reaction solution was kept at °C for 1.5 h to obtain a reaction solution. While still hot, the reaction solution was poured into a methanol-water solution to precipitate the precipitate. The volume ratio of methanol to deionized water in the methanol-water solution was 7:3. The solution was filtered, washed, and dried. Anhydrous tetrahydrofuran was added to redissolve the precipitate, yielding a phosphazene siloxane solution with a solid content of 20 wt.%.

[0075] S4, 405g of tetraethoxysilane and 2000g of anhydrous ethanol were mixed, and 205g of 0.01M dilute hydrochloric acid solution was added under ice-water bath conditions. The temperature was adjusted to 65 °C and refluxed for 2.5h to obtain a basic sol. The temperature was lowered to 42 °C, and 125g of phosphazene siloxane solution, 11.5g of borosilicate oligomer solution, 385g of Ti-POSS solution and 6.5g of hexamethylenetetramine were added sequentially to obtain a composite sol. The ceramic fiber felt was placed in a vacuum tank, and after vacuuming, the composite sol was introduced until it was completely submerged and maintained for 35min. After returning to normal pressure, the temperature was kept constant at 42 °C for 3h, and then the temperature was adjusted to 65 °C and kept for 71h. During the aging period, the ethanol / THF working solution was replaced once every 24h. The volume ratio of ethanol to THF in the ethanol / THF working solution was 7:3 to obtain the pretreated ceramic fiber felt.

[0076] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. The stepwise displacement is performed at ethanol:n-hexane volume ratios of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step lasting 4 hours, for a total of 20 hours. After displacement, a hydrophobic working solution is added. This working solution is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane, and triethylamine in a volume ratio of 100:50:850:1.5, and impregnated at 42 °C for 24 hours. h, after rinsing with anhydrous n-hexane, it is dried at atmospheric pressure. The atmospheric pressure drying is carried out by heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours to obtain a hydrophobic green felt. The green felt is then subjected to heat treatment in an argon atmosphere, heated to 350°C and held for 1 hour, then heated to 800°C and held for 1 hour, then heated to 1200°C and held for 1 hour, and finally naturally cooled to room temperature to obtain a ceramic fiber aerogel felt. Example

[0077] This embodiment provides a ceramic fiber aerogel felt and its preparation method, the preparation method specifically includes the following steps:

[0078] S1, 720g anhydrous ethanol, 305g triethoxysilane and 46g allyl glycidyl ether were mixed and 1.2g Karstedt catalyst was added. The temperature was adjusted to 62 °C and the mixture was stirred for 2.2h. After the reaction was completed, the temperature was lowered to room temperature and 310g toluene and 19.5g deionized water were added. The temperature was adjusted to 114 °C and the mixture was refluxed for 3.4h. The temperature was then adjusted to 94 °C and 79g triethoxyboric acid and 0.6g tetrabutyl titanate were added. The temperature was adjusted to 114 °C and the mixture was subjected to a de-alcoholization condensation reaction for 6.2h to obtain borosilicate oligomers. The mixture was cooled to 44 °C and ethanol was added to adjust the solid content to 30.5wt.%**. 2.8g ethyl p-toluenesulfonate was added and stirred to terminate the reaction, resulting in a borosilicate oligomer solution.

[0079] S2, 14.2 g of 3,5-dihydroxybenzoic acid was mixed with 360 g of the first portion of anhydrous THF. Under ice-water bath conditions, 10.8 g of carbonyl imidazole was added to obtain an acyl imidazole activated solution. 20.8 g of amino-modified cage-like silsesquioxane was dispersed in 160 g of the second portion of anhydrous THF. Under ice-water bath conditions, the acyl imidazole activated solution was added to the second portion of anhydrous THF. The reaction was carried out at room temperature for 16.2 h. The reaction solution was then distilled under reduced pressure to 150 mL. Under ice-water bath conditions, 9.8 g of tetraisopropyl titanate was added and the reaction was carried out for 2.8 h. The reaction solution was then poured into anhydrous diethyl ether to precipitate the precipitate. The precipitate was filtered, washed with diethyl ether, dried, and redissolved in THF to obtain a Ti-POSS solution with a solid content of 10.8 wt.%.

[0080] S3, 28.8 g of hexachlorocyclotriphosphazene was dispersed in 400 g of N-methylpyrrolidone to obtain solution A. 64.5 g of hydroxyl-terminated polydimethylsiloxane and 21.2 g of anhydrous cesium carbonate were dispersed in 200 g of N-methylpyrrolidone and pre-activated at 62 °C for 1.8 h to obtain solution B, which was then added to solution A. The mixture was aged at 68 °C for 1.2 h. Then, 17.5 g of bisphenol S and 22.8 g of anhydrous cesium carbonate were dispersed in 200 g of N-methylpyrrolidone to obtain solution C. The temperature was adjusted to 94 °C, and solution C was added to solution A. The mixture was kept at 94 °C for 2.2 h, and then the temperature was adjusted to 114 °C. The mixture was kept at °C for 1.8 h to obtain a reaction solution. While still hot, the reaction solution was poured into a methanol-water solution to precipitate the precipitate. The volume ratio of methanol to deionized water in the methanol-water solution was 7:3. The precipitate was filtered, washed, and dried. Anhydrous tetrahydrofuran was added to redissolve the precipitate, yielding a phosphazene siloxane solution with a solid content of 20.5 wt.%.

[0081] S4, 408g of tetraethoxysilane and 2000g of anhydrous ethanol were mixed, and 208g of 0.01M dilute hydrochloric acid solution was added under ice-water bath conditions. The temperature was adjusted to 68 °C and refluxed for 2.8h to obtain a basic sol. The temperature was lowered to 44 °C, and 128g of phosphazene siloxane solution, 11.8g of borosilicate oligomer solution, 388g of Ti-POSS solution and 7g of hexamethylenetetramine were added sequentially to obtain a composite sol. The ceramic fiber felt was placed in a vacuum tank, and after vacuuming, the composite sol was introduced until it was completely submerged and maintained for 38min. After returning to normal pressure, the temperature was kept constant at 44 °C for 3.5h, and then the temperature was adjusted to 68 °C and kept for 71.5h. During the aging period, the ethanol / THF working solution was replaced once every 24h. The volume ratio of ethanol to THF in the ethanol / THF working solution was 7:3 to obtain a pretreated ceramic fiber felt.

[0082] S5, the pretreated ceramic fiber felt is sequentially placed in ethanol / n-hexane for stepwise displacement. The stepwise displacement is performed at ethanol:n-hexane volume ratios of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step lasting 4 hours, for a total of 20 hours. After displacement, a hydrophobic working solution is added. This working solution is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane, and triethylamine in a volume ratio of 100:50:850:1.5, and impregnated at 44 °C for 24 hours. h, after rinsing with anhydrous n-hexane, it is dried at atmospheric pressure. The atmospheric pressure drying is carried out by heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours to obtain a hydrophobic green felt. The green felt is then subjected to heat treatment in an argon atmosphere, heated to 350°C and held for 1 hour, then heated to 800°C and held for 1 hour, then heated to 1200°C and held for 1 hour, and finally naturally cooled to room temperature to obtain a ceramic fiber aerogel felt.

[0083] Comparative Example 1

[0084] This comparative example provides a ceramic fiber aerogel felt and its preparation method. The difference between this example and Example 1 is that the mass of the borosilicate oligomer solution in S4 is 0, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0085] Comparative Example 2

[0086] This comparative example provides a ceramic fiber aerogel felt and its preparation method. The difference between this example and Example 1 is that the mass of the Ti-POSS solution in S4 is 0, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0087] Comparative Example 3

[0088] This comparative example provides a ceramic fiber aerogel felt and its preparation method. The difference between this example and Example 1 is that the mass of the phosphazene siloxane solution in S4 is 0, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0089] The test method for thermal conductivity (at 300℃) is GB / T 10294-2008; the test method for flame retardancy rating is GB / T8624-2012; the burn-through resistance test is to use a butane spray gun to burn a 2mm thick ceramic fiber aerogel felt and observe its burn-through time.

[0090] The test results are shown in Table 1.

[0091] Table 1. Test results of ceramic fiber aerogel mats in Examples 1-4 and Comparative Examples 1-3

[0092] Thermal conductivity (W / mK) Flame retardant rating Burn-through resistance (min) Example 1 ≤0.04 A1 >60min Example 2 ≤0.04 A1 >60min Example 3 ≤0.04 A1 >60min Example 4 ≤0.04 A1 >60min Comparative Example 1 ≤0.05 A1 >40min Comparative Example 2 ≤0.06 A1 >35min Comparative Example 3 ≤0.05 A1 >30min

[0093] As shown in Table 1, compared to Example 1, the thermal conductivity of Comparative Example 1 increased, while its burn-through resistance decreased; the thermal conductivity of Comparative Example 2 increased, while its burn-through resistance decreased; and the thermal conductivity of Comparative Example 3 increased, while its burn-through resistance decreased. This is because the mass of the borosilicate oligomer solution in Comparative Example 1 was 0, lacking the borosilicate phase, which reduced the framework's resistance to sintering / softening, leading to faster local structural relaxation and the formation of interconnected thermal channels under flame impact. In Comparative Example 2, the mass of the Ti-POSS solution was 0, lacking the surface absorption-dissipation-shielding of the Ti phase, resulting in faster back-side temperature rise, stronger thermal penetration, and a further shortened burn-through time. In Comparative Example 3, the mass of the phosphazene siloxane solution was 0, lacking the phosphorus-silicon-oxygen nanophase under flame impact, making the locally heated area more prone to pulverization and interconnection, thus reducing its anti-penetration ability.

[0094] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a ceramic fiber aerogel felt, characterized in that, The preparation method includes: S1, anhydrous ethanol, triethoxysilane and allyl glycidyl ether are mixed and then reacted with Karstedt catalyst. After the reaction is completed, toluene and deionized water are added to react. Then triethoxyboric acid and tetrabutyl titanate are added to react. Ethyl p-toluenesulfonate is added and stirred to terminate the reaction, and a borosilicate oligomer solution is obtained. S2, 3,5-dihydroxybenzoic acid is mixed with the first part of anhydrous THF, carbonyl imidazole is added to obtain acyl imidazole activation solution, aminated cage-type silsesquioxane is dispersed in the second part of anhydrous THF, acyl imidazole activation solution is added to the second part of anhydrous THF to react, tetraisopropyl titanate is added to react, and Ti-POSS solution is obtained. S3, disperse hexachlorocyclotriphosphazene in the first part of N-methylpyrrolidone to obtain solution A, disperse hydroxyl-terminated polydimethylsiloxane and the first part of anhydrous cesium carbonate in the second part of N-methylpyrrolidone to obtain solution B and add it to solution A, then disperse bisphenol S and the second part of anhydrous cesium carbonate in the third part of N-methylpyrrolidone to obtain solution C, add solution C to solution A to obtain phosphazene siloxane solution; S4, mix tetraethoxysilane with anhydrous ethanol, add dilute hydrochloric acid solution to obtain basic sol, add phosphazene siloxane solution, borosilicate oligomer solution, Ti-POSS solution and hexamethylenetetramine in sequence to obtain composite sol, place ceramic fiber felt into composite sol until completely submerged to obtain pretreated ceramic fiber felt. S5, the pretreated ceramic fiber felt is sequentially placed in ethanol and n-hexane for stepwise displacement. After displacement, it is immersed in hydrophobic working solution and dried under normal pressure to obtain hydrophobic green felt. The green felt is then heat-treated to obtain a ceramic fiber aerogel felt.

2. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S1: The mass ratio of anhydrous ethanol, triethoxysilane, allyl glycidyl ether, Karstedt catalyst, toluene, deionized water, triethoxyboric acid, tetrabutyl titanate and ethyl p-toluenesulfonate is (700-800):(300-320):(45-50):(1-2):(300-350);(18-20):(76-80):(0.3-0.8):(2-3).

3. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S2: The mass ratio of the 3,5-dihydroxybenzoic acid, the first part of anhydrous THF, carbonyl imidazole and the second part of anhydrous THF is (14-15):(350-400):(9-10):(150-200).

4. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S2: The mass ratio of the 3,5-dihydroxybenzoic acid, the amino-encapsulated silsesquioxane, the second part of anhydrous THF and tetraisopropyl titanate is (14-15):(20-21):(150-200):(10-11).

5. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S3: The mass ratio of the hexachlorocyclotriphosphazene, the first part of N-methylpyrrolidone, the hydroxyl-terminated polydimethylsiloxane, the first part of anhydrous cesium carbonate, the second part of N-methylpyrrolidone, bisphenol S, the second part of anhydrous cesium carbonate, and the third part of N-methylpyrrolidone is (28-29):400:(64-65):(21-22):200:(17-18):(22-23):

200.

6. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S4: The mass ratio of tetraethoxysilane, anhydrous ethanol, dilute hydrochloric acid solution, phosphazene siloxane solution, borosilicate oligomer solution, Ti-POSS solution to hexamethylenetetramine is (400-410): 2000: (200-210): (120-130): (11-12): (385-390): (5-8).

7. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S5: The stepwise replacement is performed at volume ratios of ethanol to n-hexane of 75:25, 50:50, 25:75, 0:100, and 0:100, with each step taking 4 hours and a total of 20 hours.

8. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S5: The hydrophobic working solution is a mixture of trimethylchlorosilane, hexamethyldisilazane, anhydrous n-hexane and triethylamine in a volume ratio of 100:50:850:1.

5.

9. The method for preparing a ceramic fiber aerogel felt according to claim 1, characterized in that, In S5: The atmospheric pressure drying process involves heating to 60°C for 2 hours, then heating to 90°C for 6 hours, and then heating to 120°C for 3 hours. The heat treatment is performed in an argon atmosphere, with the temperature raised to 350°C and held for 1 hour, then raised to 800°C and held for 1 hour, then raised to 1200°C and held for 1 hour, and finally cooled naturally to room temperature.

10. A ceramic fiber aerogel felt obtained by the preparation method according to any one of claims 1-9.