A heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres and a preparation method thereof

Abstract

The present invention belongs to the technical field of ceramic fibers, and discloses a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres and a preparation method thereof. The preparation includes: preparing ceramic fibers through an electrospinning process; preparing an impregnation solution of hollow silica microspheres; vacuum-impregnating the prepared ceramic fibers in the prepared impregnation solution of hollow silica microspheres, and then performing freeze-drying to obtain a heat-insulating and noise-reducing ceramic composite fiber with a three-dimensional network structure similar to a grape bunch. The preparation process of the present invention is simple and rapid. In addition, due to the modification of the fiber surface by hollow silica microspheres, the optimization of the pore structure, and the synergistic effect of material vibration, the heat-insulating and noise-reducing ceramic composite fiber has excellent sound absorption performance and medium-high temperature heat insulation performance.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic fibers, and in particular relates to a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres and a preparation method thereof. Background Art

[0002] In the early days, airplanes were limited by their low flight speeds, and the noise of airplanes mainly came from the rotation of propellers. In the 1940s, with the birth of jet engines and their widespread application in the field of civil aviation, the aviation industry ushered in rapid development. This progress also brought new noise problems: the strong aerodynamic noise generated by the frequent takeoffs and landings of airplanes seriously affected the lives of residents near the airport. In addition, during the high-altitude flight of the airplane, the turbulent noise generated by the air flowing over the cabin surface and the engine noise were transmitted into the cabin through the cabin wall panels, resulting in excessive noise in the cabin, which not only reduced the riding comfort of passengers, but also may cause anxiety and fatigue of passengers. More seriously, strong aerodynamic noise may also cause resonance of the aircraft structure. Long-term exposure to such high sound intensity environment may cause fatigue damage to the fuselage structure, posing a safety hazard. Therefore, effectively reducing aircraft noise has far-reaching technical significance.

[0003] Porous sound-absorbing materials have become one of the important means to reduce aircraft noise due to their high porosity and good high-frequency (> 1000 Hz) sound absorption ability. Applying these materials in key locations inside the aircraft cabin and near the engine can not only effectively reduce the noise level in the cabin, but also significantly improve the riding comfort of passengers. However, due to the single internal structure of porous sound-absorbing materials, they have poor absorption of medium and low-frequency noise. To overcome this defect, the traditional approach is usually to increase the thickness or density of the material. However, this method has certain limitations: too thick materials will cause high-frequency noise waves to be reflected when entering the material, which will weaken its sound absorption effect on high-frequency noise; at the same time, considering the space limitations in the cabin, the thickness of the material cannot be increased indefinitely. In addition, significantly increasing the density of the material will increase fuel consumption, which is contrary to the design concept of energy conservation and emission reduction. Given that sound-absorbing materials should also have good flame retardant properties, there is an urgent need to develop a new type of material that is both resistant to high temperatures and can achieve efficient sound absorption in the low-frequency range. Summary of the invention

[0004] In view of the technical deficiencies of existing porous sound-absorbing materials in aspects such as high-temperature resistance and low-frequency sound absorption, the present invention provides a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres and a preparation method thereof. Benefiting from the modification of the fiber surface by hollow silica microspheres, the optimization of the pore structure, and the synergistic effect of material vibration, the composite material has excellent sound-absorbing performance and medium-high temperature heat-insulating performance; the preparation method is based on the preparation of ceramic fibers by electrospinning technology, and a high-performance heat-insulating and noise-reducing ceramic composite fiber with a grape-like three-dimensional network structure is obtained through solution vacuum impregnation and freeze-drying.

[0005] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0006] The first aspect of the present invention provides a preparation method of a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres, and the steps are as follows:

[0007] Step 1, electrospinning: Mix a silica sol and a polyvinyl alcohol solution with a mass ratio of (1~2):1 evenly, place it on an electrospinning machine for electrospinning to prepare polymer nanofibers, then place them in an oven for curing, and finally calcine them in an inert atmosphere in a tube furnace to obtain C-SiO2 ceramic nanofibers;

[0008] Step 2, preparation of the impregnating solution: Stir and ultrasonically treat a hollow silica microsphere powder and an ethanol-water blend solution with a mass ratio of 0.2~0.4:20~40 to obtain a hollow silica microsphere impregnating solution; the particle size of the hollow silica microsphere powder is 600~700 nm;

[0009] Step 3, vacuum impregnation and freeze-drying: Vacuum impregnate the C-SiO2 nanofibers in the hollow silica microsphere impregnating solution, then freeze them with liquid nitrogen and perform freeze-drying to obtain a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres, and the mass ratio of the C-SiO2 nanofibers to the hollow silica microsphere impregnating solution is (1~5):(20~40).

[0010] Further, the silica sol in Step 1 is obtained by mixing 15~20 parts of deionized water, 20~25 parts of tetraethyl orthosilicate, and 0.01~1 part of phosphoric acid and stirring for 2~3 h.

[0011] When too little tetraethyl orthosilicate is added, the relative molecular weight of the polymer is too small, resulting in insufficient solution viscosity and difficulty in forming fibers through electrostatic action, and it can only be ejected in the form of small droplets or atomized particles.

[0012] When too much tetraethyl orthosilicate is added, the phenomenon of uneven dispersion will occur in the spinning solution, and the needle will be blocked during spinning and normal spinning cannot be carried out.

[0013] When too little phosphoric acid is added, the acidity of the solution is weak, which will affect the gelation time of silica sol and is not conducive to the stability and continuity of electrospinning.

[0014] When too much phosphoric acid is added, the acidity of the solution will be too strong, the viscosity of the spinning solution will increase sharply, the fluidity will decrease, and normal spinning cannot be carried out.

[0015] Further, the polyvinyl alcohol solution in step 1 is obtained as follows: 1 to 5 parts of polyvinyl alcohol powder are dissolved in 20 to 40 parts of deionized water, the stirring temperature is 70-90 °C, and the stirring time is 2-3 h.

[0016] Further, the main process parameters of the electrospinning in step 1 are: the voltage is 10-20 kV, the rotating drum speed is 100-200 rpm, the receiving distance is 15-25 cm, the feeding speed is 0.1-5 mL / h, the spinning temperature is 10-40 °C, and the environmental humidity is 40%-70%.

[0017] Further, the curing temperature in step 1 is 80 °C to 150 °C, and the time is 3-6 h. When the curing temperature is too low, the evaporation rate of water and solvent is too slow, prolonging the curing time; when the curing temperature is too high, stress may be generated inside the fiber, causing shrinkage and cracks, affecting the integrity and performance of the fiber.

[0018] The calcination is carried out in a nitrogen atmosphere, and the heating rate is 5-8 °C·min -1 , and the termination temperature is 600 °C to 800 °C.

[0019] When the temperature is too high, there are some broken and unbonded Si-OH in the Si-O-Si covalent bond network of amorphous SiO2. This structure makes the Si-O-Si bond more likely to break, resulting in an increase in the macroscopic brittleness of the fiber.

[0020] Further, the stirring time in step 2 is 2-4 h, the ultrasonic time is 1-2 h, and the mass ratio of ethanol to water in the ethanol-water blend solution is 1-10:30-40.

[0021] Further, the time for vacuum impregnation in step 3 is 30-60 min.

[0022] Too short impregnation time will cause the microspheres to not fully penetrate the fiber surface, and the microspheres are not firmly bonded to the fiber and are easy to fall off, so that the composite material cannot fully play its role; too long impregnation time will cause the microspheres to deposit too thickly on the fiber surface, reducing the mechanical properties and sound absorption properties of the material.

[0023] Furthermore, the time for liquid nitrogen freezing is 10 - 30 min, and the time for freeze-drying is 12 - 36 h.

[0024] The second aspect of the present invention provides a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres prepared by the above-mentioned preparation method, which is a grape-like three-dimensional network structure with uniformly distributed hollow silica microspheres on the surface of ceramic fibers. The diameter of the ceramic fibers is uniform, with a diameter of 180 - 220 nm, and the diameter of the hollow silica microspheres is 600 - 700 nm.

[0025] The present invention uses vacuum impregnation and freeze-drying to prepare a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres. Under vacuum conditions, the air and moisture on the surface and inside of the fibers are effectively removed, and the capillary effect is formed in the tiny pores between the fibers, which helps the microspheres to penetrate to the surface and inside of the fibers. When the microspheres are in close contact with the fiber surface, due to the shortening of the intermolecular distance to a certain extent, a strong adsorption force will be generated, making the microspheres firmly adhere to the fiber surface. The impregnated fibers are frozen in a liquid nitrogen low-temperature environment. During the freezing process, the water and solvents in the fibers will gradually solidify into ice crystals, and at the same time, the microspheres are further fixed between the fibers. The frozen fiber material is placed in a vacuum environment for drying. Under vacuum conditions, the ice crystals will directly sublime from the solid state to the gaseous state (i.e., the sublimation process) without passing through the liquid phase. During this process, the water and solvents in the fiber material are effectively removed, and at the same time, the hollow microspheres can be tightly combined with the fibers through physical adsorption and chemical bonding. The hollow silica microspheres are evenly distributed on the fiber surface, significantly increasing the roughness of the fibers, so that the sound waves are more hindered and frictioned when passing through the material, resulting in an increase in sound energy loss. In addition, the introduction of hollow silica microspheres changes the pore structure between the fibers to a certain extent, forming a more complex and tortuous pore network, prolonging the propagation path of sound waves inside the material, causing more reflections and scattering of sound waves between the fibers, thereby increasing the contact area and interaction time of sound waves with the material, and further enhancing the sound absorption effect. In addition, the hollow silica microspheres themselves have a certain mass and elasticity. When sound waves act on the material, the microspheres will vibrate together with the fibers, and this vibration can further consume the sound wave energy and effectively reduce low-frequency noise. The modification of the fiber surface by hollow silica microspheres, the optimization of the pore structure, and the synergistic effect of material vibration make the composite material have excellent sound absorption performance and ultra-high temperature heat insulation performance;

[0026] The beneficial effects of the present invention are:

[0027] 1. The preparation process of the present invention is simple: The present invention loads hollow silica microspheres on silica ceramic fibers through vacuum impregnation and freeze-drying processes, which has the advantages of wide raw material sources and simple operation processes.

[0028] 2. Good high-temperature stability: The heat-insulating and noise-reducing ceramic fiber of the present invention has a low thermal conductivity (0.0345 W·m -1 ·K -1 ~0.0356 W·m -1 ·K -1 ), and excellent ablation resistance. It can maintain the normal temperature in the cabin while resisting the influence of harsh environments such as high temperature on the sound absorption performance of the material, and extend the service life of the material.

[0029] 3. Excellent sound absorption performance: The hollow silica microspheres of the present invention are attached to the fiber surface, significantly increasing the roughness of the fiber surface. This causes more hindrance and friction when sound waves pass through the heat-insulating and noise-reducing ceramic fiber, increasing the loss of sound energy. In addition, the hollow silica microspheres further optimize the pore structure between the fibers, forming a complex and variable internal network, which causes multiple reflections and scattering of sound waves when they propagate between the fibers, enhancing the interaction between the sound waves and the material, resulting in the slow wave effect. Additionally, when sound waves act on the material, the microspheres and fibers vibrate. This vibration can further consume the sound wave energy, and the vibration of the microspheres will in turn drive the vibration of the surrounding microspheres, resulting in the sound delay phenomenon. Compared with pure fibers, the sound absorption peak of the composite material shifts to lower frequencies and the sound absorption peak increases. Description of the Drawings

[0030] Figure 1 is the flow chart for preparing the heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres of the present invention;

[0031] Figure 2 is the SEM image of the heat-insulating and noise-reducing ceramic composite fiber prepared by the present invention. Among them, (a) and (b) are the SEM image and its enlarged view of the heat-insulating and noise-reducing ceramic composite fiber prepared in Example 1 respectively, (c) and (d) are the SEM image and its enlarged view of the heat-insulating and noise-reducing ceramic composite fiber prepared in Example 2 of the present invention respectively, (e) and (f) are the SEM image and its enlarged view of the heat-insulating and noise-reducing ceramic composite fiber prepared in Comparative Example 1 of the present invention respectively, and (g) and (h) are the SEM image and its enlarged view of the heat-insulating and noise-reducing ceramic composite fiber prepared in Comparative Example 2 of the present invention respectively;

[0032] Figure 3 is the thermal conductivity image of the heat-insulating and noise-reducing ceramic composite fiber prepared in Comparative Examples 1-4 and Examples 1-2 of the present invention;

[0033] Figure 4 is the sound absorption performance graph of the heat-insulating and noise-reducing ceramic composite fiber prepared in Examples 1-2 and Comparative Examples 1-4 of the present invention;

[0034] Figure 5 is the sound absorption mechanism diagram of the heat-insulating and noise-reducing ceramic composite fiber prepared by the present invention. Detailed Embodiments

[0035] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0036] Example 1

[0037] A preparation method of a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres, the preparation process is as Figure 1 shown, including the following steps:

[0038] 1) Electrospinning: 0.098 g of phosphoric acid (H3PO4) was quickly dropped into a mixture of 18 g of water and 20.8 g of tetraethyl orthosilicate (TEOS), and stirred for 2 h to form a silica sol; 4 g of polyvinyl alcohol (PVA) powder was added to 36 g of deionized water and dissolved at 90 °C, and stirred for 3 h to form a 10 wt% PVA solution; 20 g of the PVA solution was mixed with 20 g of the silica sol and stirred for 2 h to form a stable spinning solution. The mixed spinning solution was placed on an electrospinning machine, the electrospinning process parameters were adjusted, the high-voltage power supply was turned on, and the electrospinning process was started, and the obtained polymer nanofibers were received by a collecting device; among them, the electrospinning process parameters were: the voltage was 18 kV, the rotating drum speed was 150 rpm, the receiving distance was 20 cm, the feeding speed was 0.8 mL / h, the ambient temperature was 25±2 °C, and the ambient humidity was 45±5%; the polymer nanofibers obtained by electrospinning were cured in a vacuum oven at 80 °C for 3 h to remove moisture, and then placed in a muffle furnace to calcine to remove organic components, and the heating rate was 5 °C·min -1 , and the termination temperature was 800 °C to obtain C-SiO2 ceramic nanofibers.

[0039] 2) Preparation of the impregnating solution: 5 g of anhydrous ethanol was added to 35 g of deionized water, and after stirring evenly, 0.2 g of hollow silica microsphere powder with a particle size of 600-700 nm was added to the ethanol-water blend system and stirred vigorously for 3 h and sonicated for 1 h to obtain a uniformly dispersed hollow silica microsphere impregnating solution.

[0040] 3) Vacuum impregnation and freeze-drying: 1 g of the prepared C-SiO2 ceramic nanofibers was vacuum-impregnated in 40 g of the hollow silica microsphere impregnating solution for 30 min; frozen with liquid nitrogen for 30 min, and finally placed in a freeze-dryer and dried for 24 h to obtain a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres.

[0041] Example 2

[0042] A preparation method of hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers. The preparation method is the same as that of Example 1, except for the preparation of the impregnating solution: Add 5 g of absolute ethanol to 35 g of deionized water, stir evenly, and then add 0.3 g of hollow silica microsphere powder with a particle size of 600-700 nm to the ethanol-water blend system, stir vigorously for 3 h and ultrasonicate for 1 h to obtain a uniformly dispersed hollow silica microsphere impregnating solution.

[0043] Comparative Example 1

[0044] A preparation method of hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers. The preparation method is the same as that of Example 1, except for the preparation of the impregnating solution: Add 5 g of absolute ethanol to 35 g of deionized water, stir evenly, and then add 0.1 g of hollow silica microsphere powder to the ethanol-water blend system, stir vigorously for 3 h and ultrasonicate for 1 h to obtain a uniformly dispersed hollow silica microsphere solution.

[0045] Comparative Example 2

[0046] A preparation method of hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers. The preparation method is the same as that of Example 1, except for the preparation of the impregnating solution: Add 5 g of absolute ethanol to 35 g of deionized water, stir evenly, and then add 0.5 g of hollow silica microsphere powder to the ethanol-water blend system, stir vigorously for 3 h and ultrasonicate for 1 h to obtain a uniformly dispersed hollow silica microsphere solution.

[0047] Comparative Example 3

[0048] A preparation method of hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers. The preparation method is the same as that of Example 1, except for step 3, immersing the C-SiO2 nanofibers in the hollow silica microsphere impregnating solution at normal temperature.

[0049] Comparative Example 4

[0050] A preparation method of hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers. The preparation method is the same as that of Example 1, except for step 3, vacuum-immersing the C-SiO2 nanofibers in the hollow silica microsphere impregnating solution and then drying.

[0051] Performance test results:

[0052] The morphologies of the samples in Examples 1-2 and Comparative Examples 1-2 were analyzed using a JSM-7800F field emission scanning electron microscope, as Figure 2 shown. From Figure 2It can be seen from Fig. (b) that the silica fibers exhibit a cylindrical structure with a relatively uniform diameter of about 200 nm. The fiber surface is smooth without obvious defects. The hollow silica microspheres attached to the fiber surface have perfect sphericity and a very narrow particle size, with a diameter of about 600 - 700 nm. From Figure 2 It can be seen from Fig. (a)-(d) that the microspheres with regular morphology and smooth surface are uniformly distributed on the nanofiber surface, showing a good interfacial bonding state. Figure 2 From the low-magnification to high-magnification scanning electron microscope images of Comparative Example 1 shown in Fig. (e) and (f), it can be seen that when the content of hollow silica microspheres is low, the distribution of microspheres on the fiber surface is relatively sparse, and only a few microspheres are attached to the surface of some fibers. The low-magnification to high-magnification scanning electron microscope images of Comparative Example 2, Figure 2 as shown in Fig. (g) and (h), the fibers are completely covered by microspheres, and microsphere agglomeration occurs.

[0053] Using the transient hot wire method, the samples with flat cross-sections prepared in Examples 1 and 2 and Comparative Examples 1 - 4 were placed in contact with the upper and lower surfaces of the sensor of a thermal conductivity tester (TC3000E, XIA TECH), and the thermal conductivities were measured as Figure 3 shown. It can be seen from Figure 3 that as the content of hollow silica microspheres increases, the thermal conductivity shows a trend of first decreasing and then increasing. This is because when the microspheres are loaded on the fiber surface, many new interfaces are formed with the matrix material, and heat needs to overcome additional thermal resistance when passing through the interfaces of different materials. Moreover, the introduction of microspheres reduces the pore size between the fiber skeletons, reducing the gas thermal conduction of the material, thereby reducing the thermal conductivity. However, when the content of hollow silica microspheres is too high, the microspheres are too densely distributed on the fiber surface, resulting in the blockage of the pores between the fibers, an increase in the direct contact between the fibers, and an enhanced thermal bridge effect, thus increasing the thermal conductivity of the material. Among them, the ceramic composite fiber in Example 2 with uniformly distributed hollow silica microspheres has the lowest thermal conductivity of 0.0345 W·m -1 ·K -1 , indicating that the material has good heat insulation ability. The thermal conductivities of Comparative Examples 3 and 4 increased slightly because the adhesion of the microspheres was not strong due to the normal-temperature impregnation and drying methods, resulting in the phenomenon of shedding, so the thermal conductivity increased slightly.

[0054] The SW4201&4601 impedance tubes were used to conduct sound absorption tests on the specimens of Examples 1-2 and Comparative Examples 1-4. Circular fibers with diameters of 10 cm and 2.9 cm were prepared respectively. During the test, the specimens were closely attached to the rigid wall of the impedance tube to avoid the influence of the back cavity on the sound absorption performance. After the test was completed, the test software was used to fit the curves in different frequency bands, and the test data was output according to the 1 / 3 octave. Finally, the sound absorption curves of Examples 1-2 and Comparative Examples 1-4 in the range of 160-6300 Hz were combined to obtain Figure 4 . It can be seen from Figure 4 that the heat-insulating and noise-reducing ceramic composite fibers modified with hollow silica microspheres prepared in Examples 1-2 of the present invention have more excellent sound absorption effects in the low-frequency range. The improvement of the sound absorption performance is mainly attributed to the uniform distribution of hollow silica microspheres on the fiber surface, which significantly increases the roughness of the fiber, causing more obstacles and friction when sound waves pass through the material, resulting in an increase in sound energy loss. In addition, the introduction of hollow silica microspheres changes the pore structure between fibers to a certain extent, forming a more complex and tortuous pore network, extending the propagation path of sound waves inside the material, causing more reflections and scattering of sound waves between fibers, thereby increasing the contact area and interaction time between sound waves and the material, and further enhancing the sound absorption effect. In addition, the hollow silica microspheres themselves have a certain mass and elasticity. When sound waves act on the material, the microspheres will vibrate with the fibers, and this vibration can further consume the sound wave energy, effectively reducing the low-frequency noise. The sound absorption mechanism is as shown in Figure 5 . When the content of hollow microspheres is too low or too high, the sound absorption coefficient decreases. This is mainly because when the content of microspheres is small, only a few microspheres are attached to the fiber surface, and their noise reduction effect cannot be fully exerted; when the content of microspheres is high, the excessive hollow silica microspheres block some of the pore structures between the fibers, causing some noise waves to be reflected by the fibers, so the sound absorption performance decreases slightly. At the same time, it can also be seen from Figure 4 that after the processes of Comparative Example 3 and Comparative Example 4 were changed, the sound absorption coefficient also decreased. This is mainly because the use of normal-temperature impregnation and drying results in non-uniform distribution of microspheres on the fiber surface, and the fiber structure is easily changed during the drying process, thus affecting the sound absorption effect.

[0055] Although the preferred embodiments of the present invention are described above, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many specific transformations in form without departing from the spirit of the invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A method for preparing a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres, characterized in that: Here are the steps: Step 1, electrospinning: mixing silica sol and polyvinyl alcohol solution in a mass ratio of (1-2):1 uniformly and then electrospinning to prepare polymer nanofibers, which are then placed in an oven for curing, and finally calcined in a tubular furnace under an inert atmosphere to obtain C-SiO2 nanofibers; Step 2, preparation of an impregnation solution: a hollow silica microsphere powder and an ethanol-water mixed solution having a mass ratio of 0.2-0.4:20-40 are stirred and ultrasonicated to obtain a hollow silica microsphere impregnation solution; the hollow silica microsphere powder has a particle size of 600-700 nm; Step 3, vacuum impregnation and freeze-drying: vacuum impregnate the C-SiO2 nanofibers into the hollow silica microsphere impregnation solution for 30 to 60 min, then freeze-dry the C-SiO2 nanofibers with liquid nitrogen to obtain hollow silica microsphere-modified thermal insulation and noise reduction ceramic composite fibers, wherein the mass ratio of the C-SiO2 nanofibers to the hollow silica microsphere impregnation solution is (1 to 5): (20 to 40).

2. The preparation method according to claim 1, characterized in that: The polyvinyl alcohol solution in step 1 is obtained as follows: 1 to 5 parts of polyvinyl alcohol powder is dissolved in 20 to 40 parts of deionized water, the stirring temperature is 70 to 90° C., and the stirring time is 2 to 3 h.

3. The preparation method according to claim 1, characterized in that: The silica sol in step 1 is obtained by mixing 15 to 20 parts of deionized water, 20 to 25 parts of ethyl orthosilicate, and 0.01 to 1 part of phosphoric acid and stirring for 2 to 3 hours.

4. The preparation method according to claim 1, characterized in that: The process parameters of the electrospinning in step 1 are: voltage of 10~20 kV, drum speed of 100~200 rpm, material collection distance of 15~25 cm, feed speed of 0.1~5mL / h, spinning temperature of 10~40°C, and ambient humidity of 40%~70%.

5. The preparation method according to claim 1, characterized in that: The curing temperature in step 1 is 80°C to 150°C for 3 to 6 hours; the calcination is carried out in a nitrogen atmosphere at a heating rate of 5 to 8°C min -1 , the termination temperature is 600℃~800℃.

6. The preparation method according to claim 1, characterized in that: The stirring time in step 2 is 2-4 h, the ultrasonic time is 1-2 h, and the mass ratio of ethanol to water in the ethanol-water mixed solution is 1-10:30-40.

7. The preparation method according to claim 1, characterized in that: In step 3, the liquid nitrogen freezing time is 10 to 30 minutes, and the freeze-drying time is 12 to 36 hours.

8. The heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It is a grape-like three-dimensional network structure in which hollow silica microspheres are evenly distributed on the surface of ceramic fibers. The diameter of the ceramic fibers is uniform, ranging from 180 to 220 nm, and the diameter of the hollow silica microspheres is 600-700 nm.

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