A method for preparing gradient ceramic nanofiber composite materials and its application

Abstract

This invention relates to the field of fiber technology and provides a method for preparing gradient ceramic nanofiber composite materials and their applications, comprising the following steps: (1) preparing precursor solutions of different concentrations; (2) sequentially jet spinning the precursor solutions of different concentrations in a strong electric field to obtain nanofiber membranes; (3) placing the nanofiber membranes in an oven at 40-50℃ for 30-60 minutes, removing the nanofiber membranes, immersing them in a solution containing a pore-forming agent, and then calcining them in a box furnace to obtain a gradient ceramic nanofiber layer; (4) preparing a porous organic layer using a template method; (5) combining the porous organic layer with the gradient ceramic nanofiber layer to obtain a gradient ceramic nanofiber composite material. The composite material of this invention has a gradient-distributed pore structure, excellent sound absorption and noise reduction performance, achieving broadband sound absorption, and good mechanical properties, thus possessing good market value.

Description

Technical Field

[0001] This invention belongs to the field of fiber technology, specifically relating to a method for preparing gradient ceramic nanofiber composite materials and their applications. Background Technology

[0002] The rapid development of modern transportation and industrialization has led to severe noise pollution, causing disasters for the world economy and human health. Most existing sound-absorbing materials, due to the limitations of their single-pore structure, have difficulty eliminating noise simultaneously.

[0003] Gradient ceramic nanofiber composites, due to their excellent sound absorption and noise reduction properties, can be used in various applications, such as interior decoration of transportation vehicles, walls and ceilings of buildings, and soundproof enclosures for machinery. The introduction of gradient ceramic nanofibers provides a new approach to preparing composite materials with excellent sound absorption properties. The high specific surface area and porosity of nanofibers result in better sound wave absorption and lower sound wave propagation speed; furthermore, the high flexibility and designability of nanofibers make it possible to construct complex porous structures. Porous organic polymers possess advantages such as lightweight, good plasticity, and ease of processing. Combining gradient ceramic nanofibers with porous organic polymers can produce composite materials with good sound absorption properties. These materials not only absorb sound waves through their porous structure but also achieve multiple scattering and interference of sound waves within the material through the gradient structure, thereby improving the sound absorption effect. Currently, there is almost no research on the preparation of gradient ceramic nanofiber composite porous organic layers, making this area worthy of further investigation.

[0004] Chinese patent CN 113135770 A discloses a method for preparing a ceramic sound-absorbing material with a straight-through gradient hole structure. The method involves impregnating a ceramic slurry onto several organic templates with a porous structure, applying carbon powder particles to the surface of the organic templates, stacking the organic templates, and then drying, removing the adhesive, sintering, and performing post-treatment to obtain the ceramic sound-absorbing material. The ceramic sound-absorbing material with the straight-through gradient hole structure of this invention exhibits good compressive strength and a noise reduction coefficient (NRC) of 0.55-0.85. However, the mechanical properties of the ceramic sound-absorbing material need further improvement.

[0005] Therefore, there is an urgent need for a gradient ceramic nanofiber composite material with excellent sound absorption and noise reduction performance and good mechanical properties. Summary of the Invention

[0006] To address the existing technical problems, the present invention aims to provide a method for preparing a gradient ceramic nanofiber composite material and its applications. The composite material of the present invention has a gradient-distributed pore structure, excellent sound absorption and noise reduction performance, achieving broadband sound absorption, and also possesses good mechanical properties, giving it significant market value.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing gradient ceramic nanofiber composite materials, comprising the following steps: (1) Preparation of precursor solutions of different concentrations: ① Preparation of spinning aid: Add polyvinyl alcohol and deionized water to the reaction vessel, swell at room temperature for 1-2 hours, and stir for 4-6 hours under water bath heating at 75-85℃ to obtain a polyvinyl alcohol solution with a concentration of 10-30wt%, which is the spinning aid; ② Preparation of composite sol: Add aluminum source, carbon source, silicon source, deionized water, ethanol and hydrochloric acid to the reaction vessel, heat and stir for 5-6 hours to obtain composite sol; ③ Preparation of precursor solutions: Mix the composite sol and spinning aid in different proportions and stir for 2-4 hours to obtain precursor solutions of different concentrations; (2) Electrospinning: The precursor solutions of different concentrations obtained in step (1) are sequentially jet-spun in an electric field to obtain nanofiber membranes; (3) High-temperature calcination: Place the nanofiber membrane obtained in step (2) in an oven at 40-50℃ for 30-60 minutes, immerse it in a solution containing a pore-forming agent, take out the nanofiber membrane, and then place it in a box furnace for calcination to obtain a gradient ceramic nanofiber layer. (4) Preparation of porous organic layer: Porous organic polymer is used to prepare porous organic layer using template method; (5) Composite material: The porous organic layer obtained in step (4) is combined with the gradient ceramic nanofiber layer obtained in step (3) to obtain a gradient ceramic nanofiber composite material.

[0008] The reaction mechanism and function of this invention are as follows: 1. This invention prepares precursor solutions of different concentrations, and utilizes the concentration difference during electrospinning to form nanofiber membranes of different thicknesses, thereby optimizing the sound absorption coefficient of the material, providing sound absorption effects for noise of different frequencies, and improving the overall sound absorption efficiency.

[0009] 2. This invention mixes aluminum, carbon, and silicon sources in a specific mass ratio, which not only synergistically improves the mechanical properties of the fiber, making it more resistant to wear and damage, but also has good chemical stability, resisting corrosion and oxidation, making it suitable for use in harsh environments.

[0010] 3. This invention selects polymethyl methacrylate as a pore-forming agent. Polymethyl methacrylate can decompose uniformly when heated, which can generate a uniform pore structure during sintering. Furthermore, by adjusting the particle size and amount of polymethyl methacrylate, the size and distribution of pores in the final ceramic nanofiber layer can be controlled, thus broadening its application scenarios.

[0011] 4. In the high-temperature calcination process, the present invention controls the temperature range and heating rate to sequentially form different pore sizes in the nanofiber layer, creating a gradient pore structure within the nanofiber layer. This not only creates an acoustic impedance gradient, effectively absorbing sound waves of different frequencies, but also increases the scattering of sound waves within the material, helping to reduce the energy of transmitted sound waves. Simultaneously, the gradient pore size can increase the interaction between sound waves and the material, improving the efficiency of sound energy conversion into heat energy.

[0012] 5. This invention utilizes a template method to fabricate a porous organic layer from an organic polymer. First, a novel porous organic polymer is synthesized, effectively avoiding polymer chain folding during synthesis and enhancing its compressibility through cross-linking. Simultaneously, the highly cross-linked porous organic polymer possesses excellent micropore volume and specific surface area characteristics, endowing it with outstanding sound energy absorption capabilities. Furthermore, by controlling the proportions of the porous organic polymer's pore structure, including pore size and pore distribution, the applicant helps improve sound wave absorption efficiency, thereby enhancing noise reduction and sound absorption performance.

[0013] 6. This invention combines gradient ceramic nanofibers with a porous organic polymer layer for sound absorption and noise reduction, achieving excellent noise reduction effects. On one hand, the acoustic impedance of a material is a key factor determining sound wave absorption efficiency. Gradient ceramic nanofibers and porous organic polymers have different acoustic impedances; when combined, they create a continuously varying acoustic impedance gradient, facilitating better sound wave absorption over a wide frequency range. On the other hand, the gradient ceramic nanofiber layer has different thicknesses and pore sizes, which, combined with the porous organic polymer layer, form a multi-scale porous structure. This structure can provide resonant and frictional sound absorption at different frequencies, enhancing the overall sound absorption effect. Simultaneously, the porosity and pore connectivity of the gradient ceramic nanofiber layer and the porous organic polymer layer are crucial for sound absorption performance; high porosity and good pore connectivity help improve sound wave absorption and scattering. Furthermore, the gradient ceramic nanofibers provide high strength and stiffness, while the porous organic polymer layer provides flexibility. This synergistic effect of mechanical properties helps maintain structural integrity, improves mechanical performance, and allows for effective sound wave absorption.

[0014] 7. In this invention, the precursor solution is prepared using electrospinning followed by high-temperature calcination. On one hand, selecting appropriate process parameters during electrospinning ensures stable spinning and uniform fiber dispersion; on the other hand, a suitable calcination temperature promotes nanofiber crystallization, improving the fiber's mechanical properties and high-temperature stability.

[0015] In some embodiments, the composite sol in step (1) contains the following raw materials by weight: 9-11 parts aluminum source, 3-5 parts carbon source, 4-7 parts silicon source, 15-20 parts deionized water, 20-30 parts ethanol and 1.5-2.5 parts hydrochloric acid.

[0016] Preferably, the aluminum source is aluminum acetylacetonate, the carbon source is sucrose, and the silicon source is tetraethyl orthosilicate.

[0017] Preferably, the mass ratio of the aluminum source, carbon source, and silicon source is (2-4):1:(1.1-1.5).

[0018] In some embodiments, the mass ratio of the spinning aid to the composite sol in step (1) is 1:(1-4).

[0019] In some embodiments, the electrospinning in step (2) uses a 10ml syringe, the inner diameter of the electrospinning needle is 0.50-0.60mm, the relative humidity is 25%-45%, the extrusion speed is 0.9-1.4mL / h, the voltage is 12-18kV, a metal roller is used as the receiving device, the roller speed is 50-100r / min, the distance between the receiving device and the spinneret is 10-18cm, and the spinning time is 1-4h.

[0020] In some embodiments, the pore-forming agent in step (3) is polymethyl methacrylate.

[0021] In some embodiments, the specific steps of the high-temperature calcination in step (3) are as follows: Disperse the pore-forming agent in the solution for later use; place the nanofibers obtained in step (2) in an oven at 40-50℃ for 30-60 min, immerse them in a solution containing the pore-forming agent, soak for 12-24 h, remove the nanofiber membrane, and then place it in a box furnace for calcination. Raise the temperature to 180-220℃ at a rate of 0.5-2℃ / min, hold for 20-40 min, then raise the temperature to 350-650℃ at a rate of 4-8℃ / min, hold for 1-2 h, introduce an inert gas, and cool to room temperature to obtain a gradient ceramic nanofiber layer.

[0022] In some embodiments, the specific steps for preparing the porous organic layer in step (4) are as follows: S1. 3-(1,1,1-tributylmethanetin)pyrimidine, tetra(triphenylphosphine)palladium, 2,4,6-tribromobenzene-1,3,5-triol, and toluene were added to a reaction vessel. Under an inert gas atmosphere, the mixture was heated to 100-120°C and stirred for 20-28 hours. After cooling, the mixture was extracted, and the organic layer was dried over anhydrous sodium sulfate. The mixture was concentrated under reduced pressure and purified by column chromatography to obtain the intermediate product. S2. Add the intermediate product obtained in step S1, triethylamine, and anhydrous N,N-dimethylacetamide to the reaction vessel, stir in an ice-water bath for 20-40 min, then add 1,3-di(bromomethyl)benzene, continue stirring in an ice-water bath for 20-40 min, heat to 20-25℃ and react for 20-30 min, then heat to 100-120℃ and react for 20-28 h, cool to room temperature, filter, wash, and dry to obtain a porous organic polymer; S3. Use a template method to prepare a porous organic layer from the porous organic polymer obtained in step S2.

[0023] In some embodiments, the molar ratio of 3-(1,1,1-tributylmethanetin)pyrimidine and 2,4,6-tribromobenzene-1,3,5-triol in step S1 is (3.2-3.8):1.

[0024] In some embodiments, the molar ratio of the intermediate product and 1,3-bis(bromomethyl)benzene in step S2 is (0.8-2):1.

[0025] Preferably, the molar ratio of the intermediate product and 1,3-bis(bromomethyl)benzene in step S2 is (1.4-1.6):1.

[0026] Another aspect of the present invention provides an application of the gradient ceramic nanofiber composite material obtained by the preparation method described above, for the field of sound absorption and noise reduction.

[0027] Furthermore, the gradient ceramic nanofiber composite material obtained by the preparation method is particularly suitable for outdoor noise reduction and aviation noise reduction.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The composite material of the present invention is a composite of gradient ceramic nanofibers and porous organic polymer layers, which has a gradient distribution of pore structure, excellent sound absorption and noise reduction performance, achieves wide-band sound absorption, and has good mechanical properties, thus having good market value.

[0029] 2. This invention prepares precursor solutions of different concentrations, and utilizes the concentration differences to form nanofiber membranes of different thicknesses, thereby optimizing the sound absorption coefficient of the material, providing sound absorption effects for noise of different frequencies, and improving the overall sound absorption efficiency.

[0030] 3. This invention uses polymethyl methacrylate as a pore-forming agent, which can not only generate a uniform pore structure during sintering, but also control the size and distribution of pores in the final ceramic nanofiber layer by adjusting the particle size and amount of polymethyl methacrylate, thus broadening its application scenarios.

[0031] 4. In the high-temperature calcination process, the present invention controls the temperature range and heating rate to form different pore sizes in the nanofiber layer, thereby creating a gradient pore structure within the nanofiber layer, which helps to achieve efficient sound absorption.

[0032] 5. The porous organic layer of the present invention has excellent sound energy absorption capability. The applicant improves the sound absorption and noise reduction performance by controlling the proportion of the porous organic polymer to adjust the pore structure, including pore size and pore distribution. Detailed Implementation

[0033] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0034] Ceramic nanofiber composite materials of various gradients were prepared according to the proportions and preparation methods of each raw material specified in the following examples and comparative examples.

[0035] To facilitate implementation of this invention by those skilled in the art, the manufacturers of some raw materials for the embodiments and comparative examples are described below: Polyvinyl alcohol: purchased from Wuhan Runxingyuan Technology Co., Ltd., model number 1788; Polymethyl methacrylate: purchased from Changping Chahuiyou Plastic Raw Materials Business Department, Dongguan City, brand name V020; Polystyrene: Purchased from Zhongke Leiming (Beijing) Technology Co., Ltd.; Unless otherwise specified, all other raw materials can be purchased from the market.

[0036] Preparation Example 1 The method for preparing porous organic layer A includes the following steps: S1. 35 mmol of 3-(1,1,1-tributylmethanetin)pyrimidine, 1.35 mmol of tetra(triphenylphosphine)palladium, 10 mmol of 2,4,6-tribromobenzene-1,3,5-triol, and 75 mL of toluene were added to a reaction vessel. Under a nitrogen atmosphere, the mixture was heated to 110 °C and stirred for 24 h. After cooling to room temperature, the mixture was extracted, and the organic layer was dried over anhydrous sodium sulfate. The mixture was concentrated under reduced pressure and purified by chromatography (using ethyl acetate and petroleum ether in a volume ratio of 1:20) to obtain the intermediate product. S2. Add 4 mmol of the intermediate product obtained in step S2, 8 mmol of triethylamine, and 200 mmol of anhydrous N,N-dimethylacetamide to a reaction vessel, stir in an ice-water bath at 0°C for 30 min, then add 2.65 mmol of 1,3-di(bromomethyl)benzene, continue stirring in an ice-water bath at 0°C for 30 min, heat to 25°C and react for 30 min, then heat to 110°C and react for 24 h, cool to room temperature, filter, wash three times each with distilled water and tetrahydrofuran, and dry at 105°C for 12 h to obtain porous organic polymer A; S3. Using a template method, the porous organic polymer A obtained in step S2 is used to form a porous organic layer A with a thickness of 1 cm.

[0037] Preparation Example 2 The porous organic layer B was prepared in the same way as in Example 1, except that the amount of 3-(1,1,1-tributylmethanetin)pyrimidine added in step S1 was 25 mmol.

[0038] Preparation Example 3 The porous organic layer C was prepared in the same way as in Example 1, except that the amount of 1,3-di(bromomethyl)benzene added in step S2 was 1.75 mmol.

[0039] Example 1 A method for preparing a gradient ceramic nanofiber composite material includes the following steps: (1) Preparation of precursor solutions of different concentrations: ① Preparation of spinning aid: Add 3g of polyvinyl alcohol and 13.6g of deionized water to the reaction vessel, swell at room temperature for 1 hour, and stir in a magnetic stirrer heated in an 80℃ water bath for 5 hours to obtain an 18wt% polyvinyl alcohol solution, which is the spinning aid. ② Preparation of composite sol: Add 10.5g aluminum acetylacetonate, 4g sucrose, 5.5g tetraethyl orthosilicate, 17.5g deionized water, 25g ethanol and 2.9g 68wt% hydrochloric acid solution to the reaction vessel, heat to 50℃ and stir for 6h to obtain composite sol; ③ Preparation of precursor solutions: 5g of composite sol was mixed with 8g, 12g and 15g of spinning aid in different proportions and stirred for 3h to obtain precursor solutions of different concentrations; (2) Electrospinning: The precursor solutions of different concentrations obtained in step (1) are sequentially sprayed and spun in an electric field of 3 kV / cm to obtain nanofiber membranes; The electrospinning process used a 10ml syringe, an electrospinning needle with an inner diameter of 0.50mm, a relative humidity of 35%, an extrusion speed of 1.2mL / h, a voltage of 14kV, a metal roller as the receiving device, a roller speed of 75r / min, a distance of 14cm between the receiving device and the spinneret, and a spinning time of 3h. (3) High-temperature calcination: 10g of polymethyl methacrylate was dispersed in 100ml of acetone to obtain a solution containing a pore-forming agent for later use; the nanofiber membrane obtained in step (2) was placed in a 45℃ oven for 50min to remove static electricity, then immersed in the solution containing the pore-forming agent for 18h, the nanofiber membrane was removed, and then placed in a box furnace for calcination. The temperature was increased to 200℃ at a rate of 1℃ / min and held for 30min, then increased to 550℃ at a rate of 5℃ / min and held for 1h. Nitrogen gas was introduced and cooled to room temperature to obtain a gradient ceramic nanofiber layer. (4) Preparation of porous organic layer A; (5) Composite material: The porous organic layer A is combined with the gradient ceramic nanofiber layer and then cold-pressed to obtain the gradient ceramic nanofiber composite material.

[0040] Example 2 A method for preparing a gradient ceramic nanofiber composite material includes the following steps: (1) Preparation of precursor solutions of different concentrations: ① Preparation of spinning aid: Add 3g of polyvinyl alcohol and 27g of deionized water to the reaction vessel, let it swell at room temperature for 1 hour, and stir in a magnetic stirrer heated in an 80℃ water bath for 5 hours to obtain a 10wt% polyvinyl alcohol solution, which is the spinning aid. ② Preparation of composite sol: Add 9g aluminum acetylacetonate, 3g sucrose, 4g tetraethyl orthosilicate, 15g deionized water, 20g ethanol and 2.3g 68wt% hydrochloric acid solution to the reaction vessel, heat to 50℃ and stir for 6h to obtain composite sol; ③ Preparation of precursor solutions: 5g of composite sol was mixed with 15g, 15g and 20g of spinning aid in different proportions and stirred for 3h to obtain precursor solutions of different concentrations; (2) Electrospinning: The precursor solutions of different concentrations obtained in step (1) are sequentially sprayed and spun in an electric field of 3 kV / cm to obtain nanofiber membranes; The electrospinning process used a 10ml syringe, an electrospinning needle with an inner diameter of 0.50mm, a relative humidity of 30%, an extrusion speed of 1.1mL / h, a voltage of 16kV, a metal roller as the receiving device, a roller speed of 80r / min, a distance of 12cm between the receiving device and the spinneret, and a spinning time of 3h. (3) High-temperature calcination: 10g of pore-forming agent polymethyl methacrylate was dispersed in 100ml of acetone for later use; the nanofiber membrane obtained in step (2) was placed in a 40℃ oven for 60min to remove static electricity, then immersed in a solution containing the pore-forming agent for 12h, the nanofiber membrane was removed, and then placed in a box furnace for calcination. The temperature was increased to 180℃ at a rate of 0.5℃ / min and held for 30min, then increased to 350℃ at a rate of 4℃ / min and held for 1h. Nitrogen gas was introduced and cooled to room temperature to obtain a gradient ceramic nanofiber layer. (4) Preparation of porous organic layer A; (5) Composite material: The porous organic layer A is combined with the gradient ceramic nanofiber layer and then cold-pressed to obtain the gradient ceramic nanofiber composite material.

[0041] Example 3 A method for preparing a gradient ceramic nanofiber composite material includes the following steps: (1) Preparation of precursor solutions of different concentrations: ① Preparation of spinning aid: Add 3g polyvinyl alcohol and 7g deionized water to the reaction vessel, swell at room temperature for 1 hour, and stir in a magnetic stirrer heated in an 80℃ water bath for 5 hours to obtain a 30wt% polyvinyl alcohol solution, which is the spinning aid. ② Preparation of composite sol: Add 11g aluminum acetylacetonate, 5g sucrose, 7g tetraethyl orthosilicate, 20g deionized water, 30g ethanol and 3.6g 68wt% hydrochloric acid solution to the reaction vessel, heat to 50℃ and stir for 6h to obtain composite sol; ③ Preparation of precursor solutions: 5g of composite sol was mixed with 5g, 8g and 12g of spinning aid in different proportions and stirred for 3h to obtain precursor solutions of different concentrations; (2) Electrospinning: The precursor solutions of different concentrations obtained in step (1) are sequentially sprayed and spun in an electric field of 3 kV / cm to obtain nanofiber membranes; The electrospinning process used a 10ml syringe, an electrospinning needle with an inner diameter of 0.60mm, a relative humidity of 40%, an extrusion speed of 1.4mL / h, a voltage of 12kV, a metal roller as the receiving device, a roller speed of 160r / min, a distance of 16cm between the receiving device and the spinneret, and a spinning time of 4h. (3) High-temperature calcination: 10g of pore-forming agent polymethyl methacrylate was dispersed in 100ml of acetone solution for later use; the nanofiber membrane obtained in step (2) was placed in a 50℃ oven for 30min to remove static electricity, then immersed in a solution containing the pore-forming agent for 24h, the nanofiber membrane was removed, and then placed in a box furnace for calcination. The temperature was increased to 220℃ at a rate of 2℃ / min and held for 40min, then increased to 650℃ at a rate of 8℃ / min and held for 2h. Nitrogen gas was introduced and cooled to room temperature to obtain a gradient ceramic nanofiber layer. (4) Preparation of porous organic layer A; (5) Composite material: The porous organic layer A is combined with the gradient ceramic nanofiber layer and then cold-pressed to obtain the gradient ceramic nanofiber composite material.

[0042] Example 4 A method for preparing a gradient ceramic nanofiber composite material, the specific implementation method is the same as in Example 1, except that a porous organic layer B of equal thickness is used instead of a porous organic layer A.

[0043] Example 5 A method for preparing a gradient ceramic nanofiber composite material, the specific implementation method is the same as in Example 1, except that a porous organic layer C of equal thickness is used instead of a porous organic layer A.

[0044] Example 6 A method for preparing a gradient ceramic nanofiber composite material, the specific implementation method is the same as in Example 1, except that an equal amount of polystyrene is used instead of polymethyl methacrylate.

[0045] Example 7 A method for preparing a gradient ceramic nanofiber composite material, the specific implementation method is the same as in Example 1, the difference being that in step (3) high-temperature calcination: 10g of pore-forming agent polymethyl methacrylate is dispersed in 100ml of acetone solution for later use; the nanofibers obtained in step (2) are placed in a 50℃ oven for 30min to remove static electricity, immersed in a solution containing pore-forming agent, soaked for 24h, and then placed in a box furnace for calcination, heated to 200℃ at a heating rate of 5℃ / min, held for 30min, then heated to 550℃ at a heating rate of 10℃ / min, held for 1h, nitrogen gas is introduced, and cooled to room temperature to obtain a gradient ceramic nanofiber layer.

[0046] Comparative Example 1 A method for preparing a gradient ceramic nanofiber composite material, the specific implementation method is the same as in Example 1, except that 10.5g aluminum acetylacetonate is added to replace 10.5g aluminum acetylacetonate, 4g sucrose and 5.5g tetraethyl orthosilicate.

[0047] Effect evaluation: The gradient ceramic nanofiber composite materials prepared in Examples 1-7 and Comparative Example 1 were tested and analyzed. The specific results are shown in Table 1.

[0048] Performance testing: (1) Compressive strength: Refer to GB / T 1964-2023 "Test method for room temperature compressive strength of porous ceramics"; (2) Noise reduction coefficient: Refer to GB / T 18696.1-2004, "Measurement of sound absorption coefficient and acoustic impedance in acoustic impedance tubes - Part 1: Standing wave ratio method".

[0049] Table 1 As shown in Table 1, the composite materials prepared in Examples 1-3 have better mechanical properties and noise reduction properties, and can be widely used in various applications.

[0050] Compared to Example 1, Example 4 changed the molar ratio of 3-(1,1,1-tributylmethanetin)pyrimidine and 2,4,6-tribromobenzene-1,3,5-triol during the preparation of the porous organic layer. This weakened the porous structure and affected the sound absorption performance.

[0051] Compared to Example 1, Example 5 changed the molar ratio of the intermediate product and 1,3-di(bromomethyl)benzene, which affected its mechanical properties and thus its sound absorption performance.

[0052] Compared to Example 1, the modified pore-forming agent polystyrene in Example 6 is not suitable for high-temperature calcination, making it difficult to form gradient pore sizes and resulting in poor noise reduction effect.

[0053] Compared to Example 1, Example 7 changed the heating rate of high-temperature calcination, which affected the crystallization of nanofibers, resulting in uneven pore size and reduced compressive strength.

[0054] Compared to Example 1, Comparative Example 1 uses only an aluminum source and lacks carbon and silicon sources, which results in poor mechanical properties and consequently affects sound absorption performance.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application in any way. Although the present application discloses the preferred embodiment as described above, it is not intended to limit the present application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of the present application using the disclosed technical content are equivalent to equivalent implementation cases. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for preparing a gradient ceramic nanofiber composite material, characterized in that, It includes the following steps: (1) Preparation of precursor solutions of different concentrations: ① Preparation of spinning aid: Add polyvinyl alcohol and deionized water to the reaction vessel, swell at room temperature for 1-2 hours, and stir for 4-6 hours under water bath heating at 75-85℃ to obtain a polyvinyl alcohol solution with a concentration of 10-30wt%, which is the spinning aid; ② Preparation of composite sol: Add aluminum source, carbon source, silicon source, deionized water, ethanol and hydrochloric acid to the reaction vessel, heat and stir for 5-6 hours to obtain composite sol; ③ Preparation of precursor solutions: Mix the composite sol and spinning aid in different proportions and stir for 2-4 hours to obtain precursor solutions of different concentrations; (2) Electrospinning: The precursor solutions of different concentrations obtained in step (1) are sequentially jet-spun in an electric field to obtain nanofiber membranes; (3) High-temperature calcination: Place the nanofiber membrane obtained in step (2) in an oven at 40-50℃ for 30-60 minutes, immerse it in a solution containing a pore-forming agent, take out the nanofiber membrane, and then place it in a box furnace for calcination to obtain a gradient ceramic nanofiber layer. (4) Preparation of porous organic layer: Porous organic polymer is used to prepare porous organic layer using template method; (5) Composite material: The porous organic layer obtained in step (4) is combined with the gradient ceramic nanofiber layer obtained in step (3) to obtain a gradient ceramic nanofiber composite material.

2. The method for preparing gradient ceramic nanofiber composite material according to claim 1, characterized in that, The composite sol in step (1) contains the following raw materials by weight: 9-11 parts aluminum source, 3-5 parts carbon source, 4-7 parts silicon source, 15-20 parts deionized water, 20-30 parts ethanol and 1.5-2.5 parts hydrochloric acid.

3. The method for preparing gradient ceramic nanofiber composite material according to claim 2, characterized in that, The mass ratio of the spinning aid to the composite sol in step (1) is 1:(1-4).

4. The method for preparing gradient ceramic nanofiber composite material according to claim 1, characterized in that, In step (2), the electrospinning process uses a 10ml syringe, an electrospinning needle with an inner diameter of 0.50-0.60mm, a relative humidity of 25%-45%, an extrusion speed of 0.9-1.4mL / h, a voltage of 12-18kV, a metal roller as the receiving device, a roller rotation speed of 50-100r / min, a distance of 10-18cm between the receiving device and the spinneret, and a spinning time of 1-4h.

5. The method for preparing gradient ceramic nanofiber composite material according to claim 1, characterized in that, The pore-forming agent mentioned in step (3) is polymethyl methacrylate.

6. The method for preparing gradient ceramic nanofiber composite material according to claim 1, characterized in that, The specific steps of the high-temperature calcination in step (3) are as follows: Disperse the pore-forming agent in the solution for later use; place the nanofiber membrane obtained in step (2) in an oven at 40-50℃ for 30-60 min, immerse it in the solution containing the pore-forming agent, soak for 12-24 h, take out the nanofiber membrane, and then place it in a box furnace for calcination. Raise the temperature to 180-220℃ at a rate of 0.5-2℃ / min, hold for 20-40 min, then raise the temperature to 350-650℃ at a rate of 4-8℃ / min, hold for 1-2 h, introduce inert gas, and cool to room temperature to obtain a gradient ceramic nanofiber layer.

7. The method for preparing gradient ceramic nanofiber composite material according to claim 1, characterized in that, The specific steps for preparing the porous organic layer in step (4) are as follows: S1. 3-(1,1,1-tributylmethanetin)pyrimidine, tetra(triphenylphosphine)palladium, 2,4,6-tribromobenzene-1,3,5-triol, and toluene were added to a reaction vessel. Under an inert gas atmosphere, the mixture was heated to 100-120°C and stirred for 20-28 hours. After cooling, the mixture was extracted, and the organic layer was dried over anhydrous sodium sulfate. The mixture was concentrated under reduced pressure and purified by column chromatography to obtain the intermediate product. S2. Add the intermediate product obtained in step S1, triethylamine, and anhydrous N,N-dimethylacetamide to the reaction vessel, stir in an ice-water bath for 20-40 min, then add 1,3-di(bromomethyl)benzene, continue stirring in an ice-water bath for 20-40 min, heat to 20-25℃ and react for 20-30 min, then heat to 100-120℃ and react for 20-28 h, cool to room temperature, filter, wash, and dry to obtain a porous organic polymer; S3. Use a template method to prepare a porous organic layer from the porous organic polymer obtained in step S2.

8. The method for preparing gradient ceramic nanofiber composite material according to claim 7, characterized in that, The molar ratio of 3-(1,1,1-tributylmethanetin)pyrimidine and 2,4,6-tribromobenzene-1,3,5-triol in step S1 is (3.2-3.8):

1.

9. The method for preparing gradient ceramic nanofiber composite material according to claim 7, characterized in that, The molar ratio of the intermediate product and 1,3-bis(bromomethyl)benzene in step S2 is 1:(0.8-2).

10. The application of a gradient ceramic nanofiber composite material obtained by the preparation method according to any one of claims 1-9, characterized in that, Used in the field of sound absorption and noise reduction.

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