Method for preparing lightweight high-temperature-resistant SiBCN composite aerogel under assistance of ultraviolet curing

Abstract

The invention relates to a method for preparing light high-temperature-resistant SiBCN composite aerogel under the assistance of ultraviolet curing. A photosensitive monomer and a photoinitiator are introduced into a SiBCN system, a plurality of photosensitive groups in a molecular structure of the SiBCN system are subjected to a cross-linking reaction under ultraviolet irradiation, and then monomers are initiated to polymerize to form a three-dimensional network structure, so that the effect of auxiliary enhancement by ultraviolet curing is achieved. On the basis, a high-entropy carbide precursor can be further introduced in a solvothermal process, and a carbon nano tube / graphene oxide nano carbon material or h-BN / SiC / mullite ceramic fiber can be selectively introduced in a wet gel slurry mixing process to realize compounding; a main body framework structure is converted into a cross-linked network structure from a SiBCN aerogel particle accumulation network, and the SiBCN composite aerogel with more excellent comprehensive performance is prepared. The light high-temperature-resistant SiBCN composite aerogel material is applied to the high-temperature fields of aerospace, energy, traffic, chemical engineering and the like.

Description

Technical Field

[0001] This invention relates to lightweight, high-temperature resistant composite aerogels for applications in aerospace, energy, transportation, and chemical industries. The main applications include structural fields such as thermal protection systems, nuclear industry, and thermal management, and it can also be extended to functional fields such as catalyst supports, water treatment, energy storage / nuclear energy, and electromagnetic absorption / shielding. In particular, it relates to a method for preparing lightweight, high-strength, high-temperature resistant, oxidation-resistant, and large-size composite aerogels using ultraviolet light curing. Background Technology

[0002] With the rapid development of my country's aerospace industry, hypersonic vehicles are evolving towards higher speeds and longer operating times, placing new demands on high-temperature insulation materials. For example, the insulation layers of aerospace vehicles not only need to be lightweight, high-strength, and possess excellent thermal insulation capabilities, but also need to withstand the high-temperature environments during takeoff and reentry. Therefore, the development of lightweight porous SiBCN insulation materials with excellent comprehensive performance has attracted researchers' attention in recent years. Precursor-converted SiBCN aerogel possesses low density, high porosity, excellent thermal stability, high-temperature oxidation resistance, and high-temperature creep resistance. Its application in (ultra)high-temperature environments has garnered widespread attention from researchers both domestically and internationally in recent years, making it an ideal ultra-high-temperature insulation material with the potential application in thermal protection systems in the aerospace field.

[0003] Previously, SiBCN aerogels were mostly prepared by solvothermal crosslinking of polyborosilazane precursors combined with different drying methods (such as freeze-drying and supercritical drying) and high-temperature pyrolysis. Building on this, researchers added reinforcing phases to SiBCN aerogels to form chemical bonds. Based on the method of combining SiBCN with reinforcing phases to enhance the network system, nanomaterials such as graphene, HNTs, and SiC nanofibers were introduced into SiBCN aerogels to improve their high-temperature performance, strength, or enhance their functional properties (Ceramics International 2020, 46, 7001; Ceramics International 2021, 47, 9083; Ceramics International 2023, 49, 38351). However, due to limitations in preparation technology and insufficient structural controllability, currently obtained SiBCN aerogels suffer from problems such as limited size, high density, limited strength, and insufficient high-temperature performance. This is because the necking between aerogel particles is weak, and internal stress is generated during the solvothermal assembly process, making the aerogel extremely prone to cracking. This limits its application and development, resulting in the application of SiBCN aerogels being confined to functional fields such as structural materials, catalysts, and electromagnetic absorption / shielding (Ceramics International 2016, 42, 12323; New Journal of Chemistry 2014, 38, 1923; Ceramics International 2018, 44, 22830), while its application in high-end thermal insulation is significantly insufficient. Therefore, developing new assembly methods for SiBCN composite aerogels and improving their performance is key to expanding their application in the field of ultra-high temperature thermal insulation.

[0004] This invention discloses a method for preparing lightweight, high-strength, and high-temperature resistant SiBCN composite aerogels using UV curing. This method utilizes the principle of photosensitive monomers undergoing polymerization and full cross-linking under UV curing, solving the problems of weak neck connections and low skeletal strength in SiBCN aerogel particles. The resulting SiBCN aerogel exhibits low density, high specific surface area, and excellent high-temperature resistance, oxidation resistance, and compressive strength. Its thermal structural stability can reach up to 1800℃, making it applicable to structural fields including aerospace, energy storage / nuclear energy, petrochemicals, and new energy power batteries, as well as functional fields such as catalyst supports, water treatment, and electromagnetic absorption / shielding. Summary of the Invention

[0005] This invention provides a method for preparing lightweight, high-temperature resistant SiBCN composite aerogels using UV curing assistance. Specifically, photosensitive monomers and photoinitiators are introduced into a polyborosilazane precursor system. UV curing enhances the bonds between SiBCN aerogel backbones, such as C-C bonds and Si-C bonds. The photoinitiator generates free radicals, which then initiate cross-linking and curing between photosensitive monomer molecules, forming a three-dimensional network structure. This reduces internal stress generated during pyrolysis and minimizes volume shrinkage during the precursor's pyrolysis-to-ceramic conversion, resulting in lightweight, high-strength, and large-size SiBCN aerogels. Furthermore, high-entropy carbide precursors can be introduced during solvothermal processes, or carbon nanotube / graphene oxide nanomaterials or h-BN / SiC / mullite ceramic fibers can be introduced during wet gel slurry mixing to achieve composite preparation of SiBCN composite aerogels with even superior overall performance. This SiBCN composite aerogel has advantages such as low density and thermal conductivity, high compressive strength, adjustable porosity, and excellent high-temperature stability and oxidation resistance, which can meet the requirements of the next generation of thermal insulation materials in the field of high-temperature thermal protection.

[0006] The present invention relates to a method for preparing lightweight, high-temperature resistant SiBCN composite aerogels using ultraviolet light curing, comprising the following steps:

[0007] 1) Using polyborosilazane (PBSZ) as a ceramic precursor and divinylbenzene (DVB) as a crosslinking agent, the solutions were dissolved in cyclohexane and thoroughly mixed to obtain a homogeneous solution. The solution was then formed by a solvothermal reaction.

[0008] 2) The wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting wet gel slurry is then thoroughly mixed with the organic photosensitive monomer, photoinitiator solution, and cyclohexane. After uniform mixing, a mixed slurry of SiBCN wet gel is obtained. The content of the added organic photosensitive monomer is 3%-60% of the mass of PBSZ; the content of the photoinitiator is 20% of the mass of the photosensitive monomer; and the content of cyclohexane is 30% of the mass of the PBSZ wet gel.

[0009] 3) Pour the slurry obtained in step 2) into a molding mold, and obtain PBSZ aerogel by freeze drying or supercritical drying;

[0010] 4) The PBSZ aerogel obtained in step 3) is then subjected to sufficient ultraviolet light irradiation to allow the photosensitive groups inside the PBSZ aerogel to fully react and crosslink.

[0011] 5) The PBSZ aerogel obtained in step 4) is pyrolyzed at high temperature to obtain SiBCN aerogel.

[0012] In step 1), polyborosilazane (PBSZ) is used as a ceramic precursor, divinylbenzene (DVB) is used as a crosslinking agent, and a high-entropy carbide precursor is added and dissolved in cyclohexane.

[0013] In step 1), the mass percentage of PBSZ is 1%-20%, the mass percentage of DVB is 1%-20%, and the mass percentage of cyclohexane is 60%-98%.

[0014] The high-entropy carbide is a high-entropy material typically composed of five or more elements. The content of the added high-entropy carbide precursor (PHEC) is 1%-300% of the mass of PBSZ. The preferred composition of the PHEC is five transition metal elements: titanium, zirconium, hafnium, tantalum, and niobium. The high-entropy carbide precursor can be prepared using any publicly reported method, and the preparation method mentioned in patent 2024112548449 or the method of the embodiments of this invention can be referred to.

[0015] In step 1), the solvothermal temperature is 100℃-200℃ and the solvothermal time is 10h-20h.

[0016] In step 2), the wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting wet gel slurry is thoroughly mixed with organic photosensitive monomers and photoinitiators, and then a reinforcing agent is introduced, including carbon nanotubes (CNTs) / graphene oxide (GO) nanocarbon materials or h-BN / SiC / mullite ceramic fibers. The content of the added reinforcing agents is 1%-60% of the mass of PBSZ. After uniform mixing, a mixed slurry of SiBCN wet gel is obtained.

[0017] The photosensitive monomers in step 2) include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and aliphatic polyurethane hexaacrylate.

[0018] The photoinitiator in step 2) is ethyl phenyl (2,4,6-trimethylbenzoyl)-phosphine, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1-hydroxycyclohexylbenzophenone, or benzoin dimethyl ether.

[0019] The ultraviolet light irradiation time in step 4) is in the range of 5 min to 60 min.

[0020] The pyrolysis temperature in step 5) is 1000℃-1800℃, and the pyrolysis is carried out under vacuum conditions or under a protective atmosphere, which is argon or nitrogen.

[0021] This invention provides a method for preparing SiBCN composite aerogels using UV curing. UV curing allows the introduced photosensitive monomers and photoinitiators to undergo polymerization and full cross-linking under UV irradiation. During this process, the photosensitive monomers absorb light energy to form free radicals, which then grow into polymers: monomer + light → free radicals → chain growth → polymer, forming a three-dimensional network structure. This, in turn, triggers intermolecular cross-linking and curing, achieving the effect of enhancing the SiBCN aerogel. Furthermore, a high-entropy carbide precursor (PHEC) can be introduced during the solvothermal process, or carbon nanotubes (CNTs) / graphene oxide (GO) nanomaterials or h-BN / SiC / mullite ceramic fibers can be introduced during the mixing of the wet gel slurry to achieve composite formation. This transforms the main framework structure from a SiBCN aerogel particle stacked network to a cross-linked network structure, preparing a lightweight, high-strength, high-temperature resistant, and oxidation-resistant SiBCN composite aerogel. This method is simple, and the composition, structure, and properties of the resulting SiBCN composite aerogel material are easy to control, which greatly improves the overall performance of the composite aerogel material and broadens its application range in extreme fields such as energy, aerospace, and military.

[0022] The lightweight, high-temperature resistant SiBCN composite aerogel prepared by UV curing assisted by this invention has the following effects:

[0023] (1) Low density (0.1-0.4 g / cm³) 3 High specific surface area (132.77m²) 2 (g), low thermal conductivity (32mW / (m·K)), low linear shrinkage (30%), high compressive strength (~2.1MPa);

[0024] (2) Excellent high temperature stability and oxidation resistance. It can be stable up to 1800℃ in an inert atmosphere and up to 1400℃ in an air atmosphere.

[0025] It can meet the needs of lightweight composite aerogels in aerospace, energy, transportation, chemical and other fields, thus broadening its practical application scenarios. Attached Figure Description

[0026] Figure 1 This is the SEM image of the SiBCN aerogel prepared in Example 1.

[0027] Figure 2 This is the SEM image of the SiBCN composite aerogel prepared in Example 2.

[0028] Figure 3 This is the SEM image of the SiBCN composite aerogel prepared in Example 4.

[0029] Figure 4This is the XRD pattern of the SiBCN composite aerogel prepared in Example 6.

[0030] Figure 5 This is the XRD pattern of the SiBCN composite aerogel prepared in Example 8.

[0031] Figure 6 This is a spectrum of the thermal insulation properties of the SiBCN composite aerogel prepared in Example 9.

[0032] Figure 7 This is the SEM image of the SiBCN composite aerogel prepared in Example 10.

[0033] Figure 8 This is the SEM image of the SiBCN composite aerogel prepared in Example 13. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for illustrative purposes only and not for limiting the scope of the invention. The abbreviations used in the embodiments have the following meanings: polyborosilazane (PBSZ), divinylbenzene (DVB), graphene oxide (GO), and carbon nanotubes (CNTs);

[0035] The high-entropy carbide precursor (PHEC) used is prepared according to the method mentioned in patent 2024112548449.

[0036] The preparation method of this invention is as follows: 0.8g hafnium tetrachloride, 0.58g zirconium tetrachloride, 0.675g niobium pentachloride, 0.895g tantalum pentachloride, 0.85g tetrabutyl titanate, 3g acetylacetone, and 5.23g triethylamine were weighed and dissolved in 150.2g n-butanol. After being heated in an oil bath at 80°C for 2 hours, the mixture was filtered and then rotary evaporated in a water bath at 80°C for 1 hour to obtain a yellow viscous PHEC, which was then applied in the following embodiments of this invention.

[0037] Example 1

[0038] 1) Preparation of PBSZ wet gel: Take 20wt% PBSZ, 20wt% DVB, and 60wt% cyclohexane. Under the protection of a flowing inert gas, add 3g of PBSZ and 3g of DVB to 9g of cyclohexane and stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 100℃ for solvothermal treatment for 10h to obtain PBSZ wet gel.

[0039] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 3 wt% of PBSZ trimethylolpropane triacrylate, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0040] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0041] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0042] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1000℃ for 2 hours under nitrogen protection to obtain SiBCN composite aerogel.

[0043] The density of the SiBCN composite aerogel was measured to be 0.2-0.3 g / cm³. 3 Its specific surface area is 132.77 m². 2 / g, with a compressive strength of approximately 0.35 MPa. Further, after heat treatment at 1400℃ for 2 hours, SEM images revealed that the typical pearl necklace-like structure of the aerogel remained intact at the microscopic level, demonstrating excellent high-temperature resistance, such as... Figure 1 As shown. The density reaches the currently reported values ​​for PDCs aerogels (0.16-0.51 g / cm³). 3 While maintaining a high level of performance, it also possesses high compressive strength and high-temperature stability, meeting the application requirements of high-temperature thermal protection systems.

[0044] Example 2

[0045] 1) Preparation of PBSZ wet gel: Take 10wt% PBSZ, 10wt% DVB, and 80wt% cyclohexane. Under the protection of a flowing inert gas, add 3g of PBSZ and 3g of DVB to 24g of cyclohexane and stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 150℃ for solvothermal treatment for 20h to obtain PBSZ wet gel.

[0046] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 5 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0047] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0048] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0049] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under nitrogen protection to obtain SiBCN composite aerogel.

[0050] Tests showed that this SiBCN composite aerosol exhibited a low density (0.15-0.25 g / cm³). 3) High compressive strength (~2.1 MPa). Further heat treatment at 1400℃ for 2 hours resulted in a linear shrinkage of only about 40%. SEM images showed that the microscopic porous structure remained intact, demonstrating excellent high-temperature resistance. Figure 2 As shown, the density of PDCs aerogels, such as SiBCN, SiCN, SiOC, and SiOCN, reaches the reported values ​​of 0.065-0.240 g / cm³. 3 At the same time, it has high compressive strength and high temperature stability, meeting the application requirements of high temperature thermal protection systems.

[0051] Example 3

[0052] 1) Preparation of PBSZ wet gel: Take 1 wt% PBSZ, 1 wt% DVB, and 98 wt% cyclohexane. Under the protection of a flowing inert gas, add 0.5 g of PBSZ and 0.5 g of DVB to 49 g of cyclohexane and stir with a magnetic stirrer for 1 h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20 h to obtain PBSZ wet gel.

[0053] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 10 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester, 5 wt% of PBSZ CNTs, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0054] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0055] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 30 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0056] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0057] Example 4

[0058] 1) Preparation of PBSZ wet gel: Take 10wt% PBSZ, 10wt% DVB, and 80wt% cyclohexane. Under the protection of a flowing inert gas, add 3g of PBSZ and 3g of DVB to 24g of cyclohexane and stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20h to obtain PBSZ wet gel.

[0059] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 20 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester, 1 wt% of PBSZ GO, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0060] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0061] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) was uniformly irradiated under a UV high-pressure mercury lamp for 60 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0062] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1800℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0063] Tests showed that this SiBCN composite aerosol exhibited a low density (0.15-0.3 g / cm³). 3 It exhibits high compressive strength (0.7-1.06 MPa). Furthermore, after heat treatment at 1400℃ for 2 hours, the linear shrinkage of this SiBCN aerogel is less than 30%. SEM images show that the microscopic porous structure remains intact, demonstrating excellent high-temperature resistance. Figure 3 As shown, it meets the application requirements of high-temperature thermal protection systems.

[0064] Example 5

[0065] 1) Preparation of PBSZ wet gel: Take 5wt% PBSZ, 5wt% DVB, and 90wt% cyclohexane. Under the protection of a flowing inert gas, add 3g of PBSZ and 3g of DVB to 54g of cyclohexane and stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20h to obtain a wet gel.

[0066] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 60 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 5 wt% of PBSZ h-BN whiskers, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0067] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0068] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0069] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0070] Example 6

[0071] 1) Preparation of PBSZ wet gel: 7.5 wt% PBSZ, 7.5 wt% DVB, and 85 wt% cyclohexane were added to 34 g of cyclohexane under a flowing inert gas atmosphere. The mixture was stirred with a magnetic stirrer for 1 h to obtain a homogeneous solution. The obtained solution was transferred to a hydrothermal reactor and placed in an oven at 180 °C for solvothermal treatment for 20 h to obtain a wet gel.

[0072] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 5 wt% of PBSZ trimethylolpropane trimethacrylate solution, 20 wt% of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide solution, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0073] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0074] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0075] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0076] Tests showed that this SiBCN composite aerosol exhibited a low density (0.15-0.25 g / cm³). 3) The SiBCN aerogel exhibits high compressive strength (~1 MPa), and after heat treatment at 1400℃ for 2 hours, its linear shrinkage is only about 30%. XRD analysis shows that the composite aerogel did not form a high-entropy solid solution at 1400℃, demonstrating excellent high-temperature stability and resistance to crystallization. Figure 4 As shown, it meets the application requirements of high-temperature thermal protection systems.

[0077] Example 7

[0078] 1) Preparation of PBSZ wet gel: Take 5 wt% PBSZ, 5 wt% DVB, and 90 wt% cyclohexane. Under the protection of a flowing inert gas, add 3 g PBSZ, 3 g DVB, and 1 wt% PBSZ of PHEC to 54 g cyclohexane. Stir with a magnetic stirrer for 1 h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 200℃ for solvothermal treatment for 20 h to obtain a wet gel.

[0079] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 10 wt% of PBSZ mass of 1,6-hexanediol diacrylate solution, 20 wt% of photoinitiator 1-hydroxycyclohexylbenzophenone solution, 10 wt% of PBSZ mass of mullite whiskers, and 30 wt% of PBSZ wet gel mass of cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0080] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0081] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) was uniformly irradiated under a UV high-pressure mercury lamp for 60 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0082] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1000℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0083] Example 8

[0084] 1) Preparation of PBSZ wet gel: 7.5 wt% PBSZ, 7.5 wt% DVB, and 85 wt% cyclohexane were added to 34 g of cyclohexane under a flowing inert gas atmosphere. The mixture was stirred with a magnetic stirrer for 1 h to obtain a homogeneous solution. The obtained solution was transferred to a hydrothermal reactor and placed in an oven at 180 °C for solvothermal treatment for 20 h to obtain a wet gel.

[0085] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 20 wt% PBSZ polyethylene glycol diacrylate solution, 20 wt% photoinitiator benzoin dimethyl ether solution, 5 wt% PBSZ SiC whiskers, and 30 wt% PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0086] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0087] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) was uniformly irradiated under a UV high-pressure mercury lamp for 60 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0088] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1600℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0089] The prepared SiBCN composite aerogel has a low density (0.1-0.25 g / cm³). 3 After heat treatment at 1600℃ for 2 hours, the linear shrinkage rate was only about 33%, demonstrating excellent high-temperature stability. XRD analysis showed that this composite aerogel exhibited excellent high-temperature stability and anti-crystallization properties. Figure 5 As shown, it meets the application requirements of high-temperature thermal protection systems.

[0090] Example 9

[0091] 1) Preparation of PBSZ wet gel: 6 wt% PBSZ, 18 wt% DVB, and 76 wt% cyclohexane were mixed. Under a flowing inert gas atmosphere, 3 g PBSZ, 9 g DVB, and 50 wt% PBSZ-containing PHEC were added to 38 g cyclohexane. The mixture was stirred with a magnetic stirrer for 1 h to obtain a homogeneous solution. The obtained solution was transferred to a hydrothermal reactor and placed in an oven at 200℃ for solvothermal treatment for 20 h to obtain a wet gel.

[0092] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 10 wt% of PBSZ aliphatic polyurethane hexaacrylate solution, 20 wt% of photoinitiator phenyl (2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 30 wt% of PBSZ GO, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0093] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0094] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0095] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0096] The prepared SiBCN composite aerogel has a low density (0.2-0.35 g / cm³). 3 It exhibits high compressive strength (~1 MPa), low shrinkage (~30%), and a thermal conductivity of 32 mW / (m·K). The thermal insulation performance spectrum shows that after 5 minutes of ablation, the composite aerogel maintained its original shape without any burn marks, cracks, or shrinkage, demonstrating excellent thermal insulation and ablation resistance. Figure 6 As shown, this expands its application potential in the field of high-temperature thermal insulation. Its thermal conductivity is lower than that of previously reported PDCs aerogels (52-147 mW / (m·K)), meeting the application requirements of high-temperature thermal protection systems.

[0097] Example 10

[0098] 1) Preparation of PBSZ wet gel: Take 10wt% PBSZ, 20wt% DVB, and 70wt% cyclohexane. Under the protection of a flowing inert gas, add 3g PBSZ, 6g DVB, and PHEC (100wt% PBSZ) to 21g cyclohexane. Stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20h to obtain a wet gel.

[0099] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 60 wt% of PBSZ aliphatic polyurethane hexaacrylate solution, 20 wt% of photoinitiator phenyl (2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 60 wt% of PBSZ CNTs, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0100] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0101] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) was uniformly irradiated under a UV high-pressure mercury lamp for 60 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0102] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0103] The prepared SiBCN composite aerogel has a low density (0.21-0.32 g / cm³). 3 It exhibits high compressive strength (~1.6 MPa) and low shrinkage (35%). SEM images show that after heat treatment at 1800℃, the composite aerogel retains its typical pearl necklace-like structure, with its micropores remaining intact, demonstrating excellent high-temperature structural stability. Figure 7 As shown, it meets the application requirements of high-temperature thermal protection systems.

[0104] Example 11

[0105] 1) Preparation of PBSZ wet gel: Take 5 wt% PBSZ, 5 wt% DVB, and 90 wt% cyclohexane. Under the protection of a flowing inert gas, add 3 g PBSZ, 3 g DVB, and 300 wt% PHEC (based on the mass of PBSZ) to 54 g cyclohexane. Stir with a magnetic stirrer for 1 h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20 h to obtain a wet gel.

[0106] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 60 wt% PBSZ polyethylene glycol diacrylate solution, 20 wt% photoinitiator benzoin dimethyl ether solution, 30 wt% PBSZ SiC whiskers, and 30 wt% PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0107] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0108] 4) UV curing of PBSZ aerogel: The PBSZ mixed slurry obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 30 minutes to allow the photosensitive groups to undergo polymerization reaction and fully crosslink.

[0109] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0110] Example 12

[0111] 1) Preparation of PBSZ wet gel: 7.5 wt% PBSZ, 7.5 wt% DVB, and 85 wt% cyclohexane were added to 34 g of cyclohexane under a flowing inert gas atmosphere. The mixture was stirred with a magnetic stirrer for 1 h to obtain a homogeneous solution. The obtained solution was transferred to a hydrothermal reactor and placed in an oven at 180 °C for solvothermal treatment for 20 h to obtain a wet gel.

[0112] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 60 wt% of PBSZ 1,6-hexanediol diacrylate solution, 20 wt% of photoinitiator 1-hydroxycyclohexylbenzophenone solution, 20 wt% of PBSZ mullite whiskers, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0113] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0114] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 30 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0115] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0116] Example 13

[0117] 1) Preparation of PBSZ wet gel: Take 10wt% PBSZ, 10wt% DVB, and 80wt% cyclohexane. Under the protection of a flowing inert gas, add 3g of PBSZ, 3g of DVB, and 10wt% PHEC (by weight of PBSZ) to 24g of cyclohexane. Stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20h to obtain a wet gel.

[0118] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 60 wt% of PBSZ in 2,4,6-trimethylbenzoyl diphenylphosphine oxide solution, 20 wt% of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide solution, 60 wt% of PBSZ in h-BN whiskers, and 30 wt% of PBSZ wet gel in cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0119] 3) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 2) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0120] 4) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 3) is uniformly irradiated under a UV high-pressure mercury lamp for 5 minutes to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0121] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1400℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0122] The prepared SiBCN composite aerogel has a low density (0.3-0.4 g / cm³). 3It exhibits high compressive strength (~2MPa) and low shrinkage (30%). Further, after heat treatment at 1400℃ for 2 hours, SEM images revealed that the microstructure of the composite aerogel remained intact, retaining its pearl necklace-like structure. rGO bridged the cracks between the aerogel particles, significantly improving strength and demonstrating excellent overall performance. Figure 8 As shown, this expands its application potential in the field of high-temperature insulation and meets the application requirements of high-temperature thermal protection systems.

[0123] Example 14

[0124] 1) Preparation of PBSZ wet gel: Take 5 wt% PBSZ, 5 wt% DVB, and 90 wt% cyclohexane. Under the protection of a flowing inert gas, add 3 g PBSZ, 3 g DVB, and 150 wt% PHEC (by weight of PBSZ) to 54 g cyclohexane. Stir with a magnetic stirrer for 1 h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 180℃ for solvothermal treatment for 20 h to obtain a wet gel.

[0125] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 20 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 60 wt% of PBSZ GO, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0126] 3) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 2) was uniformly irradiated under a UV high-pressure mercury lamp for 30 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0127] 4) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 3) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0128] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1600℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0129] Example 15

[0130] 1) Preparation of PBSZ wet gel: Take 15wt% PBSZ, 15wt% DVB, and 70wt% cyclohexane. Under the protection of a flowing inert gas, add 3g PBSZ, 3g DVB, and PHEC (100wt% PBSZ) to 14g cyclohexane. Stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 200℃ for solvation for 20h to obtain a wet gel.

[0131] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 20 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 60 wt% of PBSZ SiC whiskers, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0132] 3) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 2) was uniformly irradiated under a UV high-pressure mercury lamp for 30 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0133] 4) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 3) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0134] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1800℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0135] Example 16

[0136] 1) Preparation of PBSZ wet gel: Take 10wt% PBSZ, 10wt% DVB, and 80wt% cyclohexane. Under the protection of a flowing inert gas, add 3g PBSZ, 3g DVB, and 50wt% PHEC (by weight of PBSZ) to 24g cyclohexane. Stir with a magnetic stirrer for 1h to obtain a homogeneous solution. Transfer the obtained solution to a hydrothermal reactor and place it in an oven at 200℃ for solvation for 20h to obtain a wet gel.

[0137] 2) Mixing of slurry: The PBSZ wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting PBSZ wet gel slurry is thoroughly mixed with 20 wt% of PBSZ trimethylolpropane triacrylate solution, 20 wt% of photoinitiator phenyl(2,4,6-trimethylbenzoyl)-phosphinic acid ethyl ester solution, 60 wt% of PBSZ mullite whiskers, and 30 wt% of PBSZ wet gel cyclohexane to form a uniform slurry, which is then placed in a slurry molding mold.

[0138] 3) UV curing of PBSZ aerogel: The PBSZ aerogel obtained in step 2) was uniformly irradiated under a UV high-pressure mercury lamp for 30 min to allow the photosensitive groups to undergo a polymerization reaction and fully crosslink.

[0139] 4) Drying of PBSZ aerogel: The PBSZ mixed slurry obtained in step 3) was placed in a refrigerator and frozen for 30 min, and then transferred to a freeze dryer and dried at 0 °C for 48 h to obtain PBSZ aerogel.

[0140] 5) Pyrolysis of PBSZ aerogel: The photocured PBSZ aerogel obtained in step 4) was placed in a tube furnace and pyrolyzed at 1600℃ for 2 hours under argon protection to obtain SiBCN composite aerogel.

[0141] This invention relates to a method for preparing lightweight, high-temperature resistant SiBCN composite aerogels using UV curing. By introducing photosensitive monomers and photoinitiators into a PBSZ system, the photosensitive monomer molecules undergo free radical polymerization under photoexcitation, achieving intermolecular cross-linking and curing to form a three-dimensional network structure, thus aiding in the preparation of lightweight, high-temperature resistant SiBCN composite aerogels. Furthermore, a high-entropy carbide precursor (PHEC) can be introduced during the solvothermal process, or carbon nanotubes (CNTs) / graphene oxide (GO) nanomaterials or h-BN / SiC / mullite ceramic fibers can be introduced as reinforcing phases during the mixing of the wet gel slurry to prepare SiBCN composite aerogels with superior overall performance. This SiBCN composite aerogel exhibits low density, high porosity, low thermal conductivity, and high compressive strength, maintaining ultra-high temperature structural stability in an inert environment up to 1800℃, as well as excellent thermal and mechanical properties. This invention provides an auxiliary preparation method for lightweight, high-temperature resistant SiBCN aerogel, which improves its compressive strength and upper temperature resistance while reducing the density of SiBCN aerogel, thus broadening its application range in extreme environments. In particular, it meets the requirements of the future high-end thermal insulation field for a new generation of thermal insulation materials.

[0142] By adjusting the process parameters described in this invention, lightweight, high-temperature resistant SiBCN composite aerogels can be prepared, exhibiting performance substantially consistent with the examples. The above descriptions are merely preferred embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing lightweight, high-temperature resistant SiBCN composite aerogel using ultraviolet light curing, characterized in that, Includes the following steps: 1) Using polyborosilazane (PBSZ) as a ceramic precursor and divinylbenzene (DVB) as a crosslinking agent, the solutions were dissolved in cyclohexane and thoroughly mixed to obtain a homogeneous solution. The solution was then formed by a solvothermal reaction. 2) The wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting wet gel slurry is then thoroughly mixed with the organic photosensitive monomer, photoinitiator solution, and cyclohexane. After uniform mixing, a mixed slurry of SiBCN wet gel is obtained. The content of the added organic photosensitive monomer is 3%-60% of the mass of PBSZ; the content of the photoinitiator is 20% of the mass of the photosensitive monomer; and the content of cyclohexane is 30% of the mass of the PBSZ wet gel. 3) Pour the slurry obtained in step 2) into a molding mold, and obtain PBSZ aerogel by freeze drying or supercritical drying; 4) The PBSZ aerogel obtained in step 3) is then subjected to sufficient ultraviolet light irradiation to allow the photosensitive groups inside the PBSZ aerogel to fully react and crosslink. 5) The PBSZ aerogel obtained in step 4) is pyrolyzed at high temperature to obtain SiBCN aerogel.

2. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel using UV curing as described in claim 1, characterized in that, In step 1), polyborosilazane (PBSZ) is used as a ceramic precursor, divinylbenzene (DVB) is used as a crosslinking agent, and a high-entropy carbide precursor is added and dissolved in cyclohexane.

3. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel using UV curing as described in claim 1, characterized in that, In step 1), the mass percentage of PBSZ is 1%-20%, the mass percentage of DVB is 1%-20%, and the mass percentage of cyclohexane is 60%-98%.

4. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 2, characterized in that, The high-entropy carbide is a high-entropy material usually composed of five or more elements. The content of the added high-entropy carbide precursor (PHEC) is 1%-300% of the mass of PBSZ. The composition of PHEC is preferably five transition metal elements: titanium, zirconium, hafnium, tantalum and niobium.

5. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 1 or 2, characterized in that, In step 1), the solvothermal temperature is 100℃-200℃ and the solvothermal time is 10h-20h.

6. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel using UV curing as described in claim 1, characterized in that, In step 2), the wet gel obtained in step 1) is thoroughly pulverized under ultrasonic treatment. The resulting wet gel slurry is thoroughly mixed with organic photosensitive monomers and photoinitiators, and then a reinforcing agent is introduced, including carbon nanotubes (CNTs) / graphene oxide (GO) nanocarbon materials or h-BN / SiC / mullite ceramic fibers. The content of the added reinforcing agents is 1%-60% of the mass of PBSZ. After uniform mixing, a mixed slurry of SiBCN wet gel is obtained.

7. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 1, characterized in that, The photosensitive monomers in step 2) include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate, and aliphatic polyurethane hexaacrylate.

8. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 6, characterized in that, The photoinitiator in step 2) is ethyl phenyl (2,4,6-trimethylbenzoyl)-phosphine, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1-hydroxycyclohexylbenzophenone, or benzoin dimethyl ether.

9. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 2, characterized in that, The ultraviolet light irradiation time in step 4) is in the range of 5 min to 60 min.

10. The method for preparing lightweight, high-temperature resistant SiBCN composite aerogel with UV curing assistance as described in claim 2, characterized in that, The pyrolysis temperature in step 5) is 1000℃-1800℃, and the pyrolysis is carried out under vacuum conditions or under a protective atmosphere, which is argon or nitrogen.

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