A preparation method of a fire-retardant and heat-insulating bamboo-shaped silica / polyimide core-shell structure composite nanofiber aerogel

Abstract

This invention relates to a bamboo-like silica / polyimide core-shell nanofiber aerogel and its preparation method. The aerogel uses bamboo-like silica as the core and polyimide as the shell. Core-shell nanofibers are obtained through coaxial electrospinning, followed by gelation, freeze-drying, and thermal imidization to form a three-dimensional porous network structure with interwoven support and cross-linking. The bamboo-like silica acts as a supporting and reinforcing skeleton within the fibers, improving the aerogel's compression resilience and structural stability, while also enhancing its flame-retardant and thermal insulation properties. The preparation method includes the preparation of a polyamic acid precursor solution, acidic hydrolysis of the silica precursor solution, coaxial electrospinning to form core-shell fibers, pre-imidization, and subsequent thermal imidization steps. The resulting aerogel exhibits low density, high porosity, low thermal conductivity, and excellent thermal stability, making it suitable for applications in thermal insulation, flame retardant protection, and lightweight structural materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and in particular relates to a method for preparing a flame-retardant and heat-insulating bamboo-shaped silica / polyimide core-shell structured composite nanofiber aerogel. Background Technology

[0002] Aerogels are a class of solid materials with a three-dimensional porous network structure, characterized by extremely low bulk density, ultra-high specific surface area, and high porosity, making them widely recognized as lightweight and efficient thermal insulation materials. Their unique nanoporous structure endows aerogels with extremely low thermal conductivity, giving them significant advantages in reducing structural loads, lowering transportation and installation costs, and improving the stability of thermal equipment. With the deepening of aerogel research, its material systems have expanded from traditional inorganic aerogels to various organic aerogel systems. Among various inorganic aerogels, silica aerogels are widely used due to their advantages such as low thermal conductivity, high transparency, and mature preparation methods. However, silica aerogels prepared by the traditional sol-gel method are usually composed of stacked ultrafine nanoparticles with weak interparticle bonds, resulting in high overall brittleness, low mechanical strength, and a tendency to collapse during use. This structural defect significantly limits the further promotion of silica aerogels in applications requiring high reliability and compressibility. In contrast, organic aerogels (such as polyurethane, polyurea, and chitosan aerogels) have certain advantages in flexibility, but generally suffer from poor thermal stability and insufficient high-temperature resistance. Polyimide is a class of high-performance polymers containing imide ring structures in its molecular chain, exhibiting excellent high and low temperature resistance, mechanical properties, and chemical stability. Based on this, polyimide aerogel combines the flexibility of organic aerogels with the high thermal stability of polyimide bulk materials, making it a high-performance lightweight thermal insulation material. However, it is essentially still an organic porous material, thus exhibiting high flammability and insufficient flame retardancy, limiting its application in high-temperature insulation, fire resistance, and safety protection. To address the common brittleness and flame retardancy issues of aerogel materials, researchers often employ fiber reinforcement strategies. Nanofibers, due to their high aspect ratio, high flexibility, and good structural continuity, can construct stable multi-level three-dimensional support networks, effectively improving the mechanical properties of aerogels. However, in existing fiber-reinforced systems, simultaneously ensuring the flame-retardant and thermal insulation properties of the inorganic components and the flexibility and resilience of the organic components remains a technical challenge. In summary, it is of great significance to develop a new type of lightweight aerogel material that combines high mechanical strength, excellent thermal insulation performance, and good flame retardant properties. Summary of the Invention

[0003] This invention addresses the technical problems of poor flame retardant and thermal insulation properties of organic polyimide nanofiber gels and the significant fragility of silica aerogels. It develops a method for preparing a bamboo-like silica / polyimide core-shell structured nanofiber aerogel with excellent compression resilience, flame retardancy, thermal insulation, and mechanical stability. The method includes a preparation method for the core-shell structured nanofibers and a molding method for the related nanofiber aerogel. The preparation method of this invention has a simple process, and the resulting aerogel has a low thermal conductivity, good shape designability, and thermal stability, showing promising application prospects. This invention provides a silica / polyimide core-shell nanofiber composite aerogel. The aerogel uses bamboo-like silica / polyimide core-shell nanofibers as the framework structure. The fibers interweave and support each other to form a three-dimensional network structure. The core-shell structure fibers have bamboo-like silica as the core and polyimide as the shell. The bamboo-like silica provides support while maintaining the compressibility and resilience of the aerogel. Furthermore, the polyamic acid spinning solution, the precursor of the polyimide, is prepared by copolymerization of a flexible diamine and a flexible diacid anhydride in a polar solvent. The solid content of the polyamic acid solution is 1-25 wt%, and the dynamic viscosity is 2000-20000 cp. Furthermore, under acidic conditions, the preparation ratio of silica core spinning solution is precursor solution: deionized water = 1:2~20. Furthermore, using coaxial electrospinning technology, silica core spinning solution and polyamic acid shell spinning solution are spun at different feed ratios, resulting in core-shell structured nanofibers with a diameter of 50-1000 nm, preferably 200-500 nm. The silica / polyimide core-shell structured nanofiber aerogel has a density of 2-100 mg / cm³, preferably 5-20 mg / cm³; a porosity of 98% or higher, preferably 99% or higher; a stress of 1-10 kPa at 80% compressive strain, preferably 5-10 kPa; a thermal conductivity of 0.020-0.040 Wm⁻¹K⁻¹, preferably 0.030-0.035 Wm⁻¹K⁻¹; and a thermal decomposition temperature greater than 500 °C. Bamboo-like silica imparts excellent flame-retardant and heat-insulating properties to polyimide nanofiber aerogels. Depending on the proportion of silica added, the elasticity and flame-retardant and heat-insulating properties of the composite aerogel can be improved. A high-compression-resilience, flame-retardant, and heat-insulating silica / polyimide core-shell structured nanofiber composite aerogel comprises the following steps: A: In a three-necked flask, the flexible diamine monomer is completely dissolved in a polar solvent, and the dianhydride monomer is gradually added at 0°C to carry out a polycondensation reaction. After 4-10 h of full reaction, a polyamic acid solution of the polyimide precursor is obtained. B: Prepare a silica precursor solution in a beaker, stir the silica precursor and deionized water at a certain ratio (1:2~20), adjust the pH of the solution to 1~3, and continue the reaction for 12~48 h after the hydrolysis is completed to obtain a silica precursor solution with a small degree of polymerization. C: Using a silica precursor solution as the core spinning solution and a polyamic acid solution as the shell spinning solution, the two solutions were placed in a coaxial electrospinning apparatus. Core-shell structured nanofibers were obtained by applying voltage, precipitation, and air blowing. Pre-iminoization was then performed at 120–200 °C, simultaneously promoting the polymerization reaction of the silica precursor solution in the nanofiber core, thus obtaining partially iminoized core-shell structured nanofibers. D: Partially imidized micro-crosslinked bamboo-like silica / polyamic acid nanofibers were dispersed in a solvent. The resulting core-shell structured nanofiber dispersion was poured into a mold and freeze-dried to obtain a bamboo-like silica / polyamic acid core-shell structured nanofiber aerogel. Finally, a thermal imidization treatment was performed to completely convert it into polyimide and remove residual small molecules, resulting in a bamboo-like silica / polyamic acid core-shell structured nanofiber aerogel. Further, the flexible diamine monomer mentioned in step A is selected from one or more of the diamine being diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), and 4,4'-diaminodiphenylmethane (MDA), and the diacid anhydride used is one or more of the diphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and benzophenone tetracarboxylic dianhydride (BTDA), and the polar solvent is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). Further, the precursor solution in step B is selected from one or more of methyl orthosilicate (TMOS), ethyl orthosilicate (TEOS), and propyl orthosilicate (TPOS). Further, the hydrolysis time in step B is 1-5 h, preferably 2-4 h, and the acidic hydrolysis promoter is one or more of hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), acetic acid (CH3COOH), and formic acid (HCOOH). Furthermore, in step C, the core-shell spinning solution injection ratio is 1:1~10, preferably 1:2~5, and the spinning voltage is 10~30kV. Further, the solvent used for dispersion in step D is one or more of phenol, ethylene glycol, glycerol, tert-butanol, and water; preferably, it is an aqueous solution of tert-butanol. Further, the high-temperature thermal imidization treatment in step D involves heating from room temperature to 120~160 ℃, preferably 130~150 ℃, holding at that temperature for 0.1~2 h, preferably 0.5 h; then heating to 180~350 ℃, preferably 200~300 ℃, holding at that temperature for 0.1~5 h, preferably 0.5~3 h; the heating rate is 1~5 ℃ / min, preferably 2~3 ℃ / min. This invention encapsulates silica within polyimide nanofibers and obtains bamboo-like silica through the polymerization reaction of silica precursor solution in a nanoscale microreactor. This bamboo-like silica skeleton plays a supporting role in the core structure of the polyimide nanofibers, helping to reduce the shrinkage generated during the preparation of the nanofiber aerogel. At the same time, the bamboo-like silica provides greater flexibility during the compression and rebound process of the aerogel. This allows the bamboo-like silica / polyimide core-shell structured nanofiber aerogel to combine the excellent compression and rebound performance and chemical stability of polyimide nanofiber aerogel with the beneficial flame-retardant and heat-insulating properties of silica aerogel. Beneficial effects (1) The manufacturing process of the present invention is simple, easy to operate, requires less time, is highly efficient, and has industrial scalability. (2) The coaxial electrospinning method used in this invention injects the silica precursor into the interior of polyimide nanofibers and allows it to polymerize in the nanofibers. The nanofibers serve as nanoreactors to form bamboo-shaped silica, which plays a supporting role inside the polyimide fibers. At the same time, the bamboo-shaped silica can also provide a certain degree of flexibility when the fibers are bent, which is beneficial to the compression and rebound of the aerogel. Meanwhile, the encapsulation of polyimide prevents the silica from falling off to a certain extent. (3) This invention combines the flexible resilience of polyimide nanofiber aerogel with the excellent flame retardant and heat insulation properties of silica. (4) The bamboo-shaped silica / polyimide core-shell structured nanofiber aerogel obtained by this preparation method has good shape designability during the preparation process. Different shapes of aerogels can be prepared according to different molds, which are suitable for various occasions. Attached Figure Description Figure 1 These are physical appearance images of the bamboo-like silica / polyimide core-shell structured nanofiber aerogel in Example 4 and TEM projection images of the core-shell structured nanofibers. Figure 2 This is a SEM microstructure image of the bamboo-like silica / polyimide core-shell structured nanofiber aerogel in Example 4. Figure 3 These are the stress values ​​of the bamboo-like silica / polyimide core-shell structured nanofiber aerogel in Example 4 under different strain conditions; Figure 4 The TGA thermal analysis diagrams are of the bamboo-like silica / polyimide core-shell structured nanofiber aerogels in Comparative Example 1 and Examples 1-4. Figure 5 This is a comparison of combustion experiments of pure polyimide nanofiber aerogel and bamboo-shaped silica / polyimide core-shell structured nanofiber aerogel in Comparative Example 1 and Example 4 (ignition time was 15 s for both). Detailed Implementation The invention will be further illustrated below with reference to specific embodiments. It should be noted that the following embodiments are merely illustrative of the invention and not intended to limit the technical solutions described herein. Therefore, although this specification has described the invention in detail with reference to the following embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the invention; and all technical solutions and improvements that do not depart from the spirit and scope of the invention should be covered within the scope of the claims of the invention. Example 1 (1) Weigh 9.95 g of pyromellitic dianhydride (BPDA) and 6.77 g of 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1. Add all of the ODA to 100 ml of N,N-dimethylformamide (DMF) solvent. After it is completely dissolved, add PMDA in batches under ice-water bath conditions. After mechanical stirring for 4-6 h, a 15 wt% polyamic acid solution is obtained. (2) Add tetraethyl orthosilicate (TEOS) and deionized water in a molar ratio of 1:8 to a beaker, adjust the pH to 2~3 with hydrochloric acid (HCl), stir at room temperature for 1~2 h to complete hydrolysis, and then continue stirring for 12~48 h to obtain a semi-polymerized silica precursor solution. (3) Two spinning solutions were transferred into syringes respectively, and core-shell structured nanofiber membranes were obtained by coaxial electrospinning. Pre-imidization was carried out at 135 °C to complete the polymerization of silica, resulting in partially imidized bamboo-like silica / polyimide core-shell structured nanofibers. The spinning temperature was room temperature, the ambient humidity was 20~30%, the spinning solution propulsion speed was silica precursor solution: polyamic acid solution = 0.11 mL / h: 0.89 mL / h, the voltage was 20~25 KV, the roller speed was 400 rpm, and the distance from the needle to the receiving plate was 18~20 cm. (4) 1 g of bamboo-like silica / polyimide core-shell structured nanofibers were cut and dispersed in 100 g of tert-butanol aqueous solution. The mass fraction of the nanofibers was 1 wt%. After uniform dispersion, a bamboo-like silica / polyimide core-shell structured nanofiber dispersion was obtained. (5) The dispersion of bamboo-like silica / polyimide core-shell nanofibers was poured into a mold and pre-frozen at -80℃ for 12 h. After freeze-drying (vacuum degree of 0~1 Pa, drying time of 72 h), bamboo-like silica / polyimide core-shell nanofiber aerogel was prepared. The aerogel was placed in a hot furnace and heated from room temperature to 150℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h. Then, the temperature was increased to 300℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h, thereby obtaining bamboo-like silica / polyimide core-shell nanofiber aerogel with complete imidization and removal of other small molecule impurities. Example 2: (1) Weigh 9.95 g of pyromellitic dianhydride (BPDA) and 6.77 g of 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1. Add all of the ODA to 100 ml of N,N-dimethylformamide (DMF) solvent. After it is completely dissolved, add PMDA in batches under ice-water bath conditions. After mechanical stirring for 4-6 h, a 15 wt% polyamic acid solution is obtained. (2) Add tetraethyl orthosilicate (TEOS) and deionized water in a molar ratio of 1:8 to a beaker, adjust the pH to 2~3 with hydrochloric acid (HCl), stir at room temperature for 1~2 h to complete hydrolysis, and then continue stirring for 12~48 h to obtain a semi-polymerized silica precursor solution. (3) Two spinning solutions were transferred into syringes respectively, and core-shell structured nanofiber membranes were obtained by coaxial electrospinning. Pre-imidization was carried out at 135 °C to complete the polymerization of silica, resulting in partially imidized bamboo-like silica / polyimide core-shell structured nanofibers. The spinning temperature was room temperature, the ambient humidity was 20~30%, the spinning solution propulsion speed was silica precursor solution: polyamic acid solution = 0.14 mL / h: 0.86 mL / h, the voltage was 20~25 KV, the roller speed was 400 rpm, and the distance from the needle to the receiving plate was 18~20 cm. (4) 1 g of bamboo-like silica / polyimide core-shell structured nanofibers were cut and dispersed in 100 g of tert-butanol aqueous solution. The mass fraction of the nanofibers was 1 wt%. After uniform dispersion, a bamboo-like silica / polyimide core-shell structured nanofiber dispersion was obtained. (5) The dispersion of bamboo-like silica / polyimide core-shell nanofibers was poured into a mold and pre-frozen at -80℃ for 12 h. After freeze-drying (vacuum degree of 0~1 Pa, drying time of 72 h), bamboo-like silica / polyimide core-shell nanofiber aerogel was prepared. The aerogel was placed in a hot furnace and heated from room temperature to 150℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h. Then, the temperature was increased to 300℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h, thereby obtaining bamboo-like silica / polyimide core-shell nanofiber aerogel with complete imidization and removal of other small molecule impurities. Example 3 (1) Weigh 9.95 g of pyromellitic dianhydride (BPDA) and 6.77 g of 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1. Add all of the ODA to 100 ml of N,N-dimethylformamide (DMF) solvent. After it is completely dissolved, add PMDA in batches under ice-water bath conditions. After mechanical stirring for 4-6 h, a 15 wt% polyamic acid solution is obtained. (2) Add tetraethyl orthosilicate (TEOS) and deionized water in a molar ratio of 1:8 to a beaker, adjust the pH to 2~3 with hydrochloric acid (HCl), stir at room temperature for 1~2 h to complete hydrolysis, and then continue stirring for 12~48 h to obtain a semi-polymerized silica precursor solution. (3) Two spinning solutions were transferred into syringes respectively, and core-shell structured nanofiber membranes were obtained by coaxial electrospinning. Pre-imidization was carried out at 135 °C to complete the polymerization of silica, resulting in partially imidized bamboo-like silica / polyimide core-shell structured nanofibers. The spinning temperature was room temperature, the ambient humidity was 20~30%, the spinning solution propulsion speed was silica precursor solution: polyamic acid solution = 0.2 mL / h: 0.8 mL / h, the voltage was 20~25 KV, the roller speed was 400 rpm, and the distance from the needle to the receiving plate was 18~20 cm. (4) 1 g of bamboo-like silica / polyimide core-shell structured nanofibers were cut and dispersed in 100 g of tert-butanol aqueous solution. The mass fraction of the nanofibers was 1 wt%. After uniform dispersion, a bamboo-like silica / polyimide core-shell structured nanofiber dispersion was obtained. (5) The dispersion of bamboo-like silica / polyimide core-shell nanofibers was poured into a mold and pre-frozen at -80℃ for 12 h. After freeze-drying (vacuum degree of 0~1 Pa, drying time of 72 h), bamboo-like silica / polyimide core-shell nanofiber aerogel was prepared. The aerogel was placed in a hot furnace and heated from room temperature to 150℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h. Then, the temperature was increased to 300℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h, thereby obtaining bamboo-like silica / polyimide core-shell nanofiber aerogel with complete imidization and removal of other small molecule impurities. Example 4 (1) Weigh 9.95 g of pyromellitic dianhydride (BPDA) and 6.77 g of 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1. Add all of the ODA to 100 ml of N,N-dimethylformamide (DMF) solvent. After it is completely dissolved, add PMDA in batches under ice-water bath conditions. After mechanical stirring for 4-6 h, a 15 wt% polyamic acid solution is obtained. (2) Add tetraethyl orthosilicate (TEOS) and deionized water in a molar ratio of 1:8 to a beaker, adjust the pH to 2~3 with hydrochloric acid (HCl), stir at room temperature for 1~2 h to complete hydrolysis, and then continue stirring for 12~48 h to obtain a semi-polymerized silica precursor solution. (3) Two spinning solutions were transferred into syringes respectively, and core-shell structured nanofiber membranes were obtained by coaxial electrospinning. Pre-imidization was carried out at 135 °C to complete the polymerization of silica, resulting in partially imidized bamboo-like silica / polyimide core-shell structured nanofibers. The spinning temperature was room temperature, the ambient humidity was 20~30%, the spinning solution propulsion speed was silica precursor solution: polyamic acid solution = 0.25 mL / h: 0.75 mL / h, the voltage was 20~25 KV, the roller speed was 400 rpm, and the distance from the needle to the receiving plate was 18~20 cm. (4) 1 g of bamboo-like silica / polyimide core-shell structured nanofibers were cut and dispersed in 100 g of tert-butanol aqueous solution. The mass fraction of the nanofibers was 1 wt%. After uniform dispersion, a bamboo-like silica / polyimide core-shell structured nanofiber dispersion was obtained. (5) The dispersion of bamboo-like silica / polyimide core-shell nanofibers was poured into a mold and pre-frozen at -80℃ for 12 h. After freeze-drying (vacuum degree of 0~1 Pa, drying time of 72 h), bamboo-like silica / polyimide core-shell nanofiber aerogel was prepared. The aerogel was placed in a hot furnace and heated from room temperature to 150℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h. Then, the temperature was increased to 300℃ at a heating rate of 2℃ / min and held at that temperature for 0.5 h, thereby obtaining bamboo-like silica / polyimide core-shell nanofiber aerogel with complete imidization and removal of other small molecule impurities. Comparative Example 1 (1) Weigh 9.95 g of pyromellitic dianhydride (BPDA) and 6.77 g of 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1. Add all of the ODA to 100 ml of N,N-dimethylformamide (DMF) solvent. After it is completely dissolved, add PMDA in batches under ice-water bath conditions. After mechanical stirring for 4-6 h, a 15 wt% polyamic acid solution is obtained. (2) The spinning solution was transferred into a syringe, and a nanofiber membrane was obtained by electrospinning. The nanofiber was pre-imidized at 135 °C to obtain partially imidized polyimide nanofibers. The spinning temperature was room temperature, the ambient humidity was 20-30%, the spinning solution feed rate was 1 mL / h, the voltage was 20-25 KV, the roller speed was 400 rpm, and the distance from the needle to the receiving plate was 18-20 cm. (3) 1 g of polyimide nanofibers were cut and dispersed in 100 g of tert-butanol aqueous solution. The mass fraction of polyimide nanofibers was 1 wt%. After uniform dispersion, a bamboo-like silica / polyimide core-shell structured nanofiber dispersion was obtained. (4) The polyimide nanofiber dispersion was poured into a mold and pre-frozen at -80 °C for 12 h. After freeze-drying (vacuum degree of 0~1 Pa, drying time of 72 h), polyimide nanofiber aerogel was prepared. The aerogel was placed in a hot furnace and heated from room temperature to 150 °C at a heating rate of 2 °C / min and held at that temperature for 0.5 h. Then, the temperature was increased to 300 °C at a heating rate of 2 °C / min and held at that temperature for 0.5 h, thereby obtaining a polyimide nanofiber aerogel that was fully imidized and free of other small molecule impurities. The flame retardant effect of the aerogel obtained in Comparative Example 1 was compared with that of the composite aerogel obtained in Example 4. After ignition with an alcohol torch for 15 seconds, the flame retardant effect was... Figure 5 It is evident that the internal inorganic gel network significantly enhances the flame-retardant properties of the aerogel.

Claims

1. A buckytube-like silica / polyimide core-shell structure nanofiber aerogel, characterized in that, The aerogel is composed of a three-dimensional porous network of bamboo-shaped silica / polyimide core-shell nanofibers; the nanofibers are composed of a bamboo-shaped silica core and a polyimide shell covering the outside of it; the bamboo-shaped silica core forms a structure with periodic nodes inside the fiber, which provides support for the aerogel and improves its compression resilience.

2. The aerogel of claim 1, wherein: Density 2-100 mg / cm 3 , preferably 5-20 mg / cm 3 ; porosity > 98%, preferably > 99%; stress at 80% compression strain 1-10 kPa, preferably 5-10 kPa; Thermal conductivity 0.020-0.040 W-m -1 K"1, preferably 0.030-0.035 W-m -1 K"1; thermal decomposition temperature > 500°C.

3. The aerogel of claim 1, wherein: The diameter of the core-shell structured nanofibers is 50–1000 nm, preferably 200–500 nm.

4. The aerogel of claim 1, wherein: The silica core is obtained by acid hydrolysis of one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

5. The aerogel of claim 1, wherein: The polyimide shell is formed by imidization of polyamic acid, which is prepared by solution polymerization of a flexible diamine monomer and a flexible diacid anhydride in a polar solvent; the flexible diamine monomer is selected from one or more of diaminodiphenyl ether, p-phenylenediamine, and 4,4′-diaminodiphenylmethane; the diacid anhydride is selected from one or more of biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, and benzophenone tetracarboxylic dianhydride; and the polar solvent is selected from one or more of NMP, DMF, DMAc, and DMSO.

6. The aerogel of claim 1, wherein: The bamboo-shaped silica core is used to provide support and deformation flexibility during compression, thereby reducing aerogel structure shrinkage and enhancing compression resilience.

7. A method of making the bamboo-like silica / polyimide core-shell structure nanofiber aerogel of claim 1, characterized by Includes the following steps: (1) Dissolve the flexible diamine monomer in a polar solvent, and gradually add the diacid anhydride at 0°C to carry out a polycondensation reaction. After reacting for 4 to 10 hours, a polyamic acid solution with a solid content of 1 to 25 wt% and an apparent viscosity of 2000 to 20000 cp is obtained. (2) Mix silicon precursor with deionized water at a mass ratio of 1:2 to 20, hydrolyze under acidic conditions for 1–5 h, and continue the reaction for 12–48 h to obtain a silicon dioxide precursor solution with a certain degree of polymerization. (3) Core-shell structured nanofibers were prepared by coaxial electrospinning with a feed ratio of 1:1 to 10 and a spinning voltage of 10 to 30 kV using silica precursor solution as core spinning solution and polyamic acid solution as shell spinning solution. The nanofibers were then pre-iminoized at 120 to 200 °C. (4) Partially imidized nanofibers were dispersed in a solvent and freeze-dried in a mold to obtain fiber aerogel; (5) The obtained aerogel was subjected to segmented heating and heat preservation treatment at 120-160℃ and 180-350℃, with the heating rate controlled at 1-5℃ / min, so that the polyamic acid was completely imidized and small molecules were removed, resulting in bamboo-like silica / polyimide core-shell structured nanofiber aerogel.

8. The method of claim 7, wherein: The acidic hydrolysis accelerator is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, or formic acid.

9. The method of claim 7, wherein: The dispersing solvent in step (4) is one or more of phenol, ethylene glycol, glycerol, tert-butanol or water, preferably an aqueous solution of tert-butanol.

10. A nanofiber aerogel containing any one of claims 1 to 9, comprising the bamboo-like silica / polyimide core-shell structure as described in any one of claims 1 to 9, and the product thereof.

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