Hollow silicon dioxide microsphere modified heat insulation and noise reduction ceramic composite fiber and preparation method thereof

Abstract

The invention belongs to the technical field of ceramic fibers, and discloses a hollow silicon dioxide microsphere modified heat insulation and noise reduction ceramic composite fiber and a preparation method thereof, and the preparation method comprises the following steps: preparing a ceramic fiber through an electrostatic spinning technology; preparing a hollow silicon dioxide microsphere impregnation liquid; and impregnating the prepared ceramic fiber in the prepared hollow silicon dioxide microsphere impregnation liquid in vacuum, and then freeze-drying to obtain the heat-insulating and noise-reducing ceramic composite fiber with a grape-string-like three-dimensional network structure. The preparation process is simple and rapid, and in addition, due to the modification of the hollow silicon dioxide microspheres on the fiber surface, the optimization of a pore structure and the synergistic effect of material vibration, the heat-insulation and noise-reduction 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 terms of 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. Thanks 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 composite material has excellent sound absorption performance and medium and high temperature heat insulation performance; its preparation method is to prepare ceramic fibers using electrospinning technology, and obtain high-performance heat-insulating and noise-reducing ceramic composite fibers with a grape-like three-dimensional network structure through solution vacuum impregnation and freeze-drying.

[0005] In order to solve the above technical problems, the present invention is implemented by the following technical solutions:

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

[0007] Step 1, electrospinning: the silica sol and polyvinyl alcohol solution in a mass ratio of (1-2):1 are mixed evenly and then placed on an electrospinning machine for 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 ceramic nanofibers;

[0008] 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;

[0009] Step 3, vacuum impregnation and freeze drying: vacuum impregnate the C-SiO2 nanofibers into the hollow silica microsphere impregnation solution, then freeze with liquid nitrogen and then freeze-dry 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 (1~5): (20~40).

[0010] Furthermore, 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.

[0011] When too little ethyl orthosilicate is added, the relative molecular weight of the polymer is too small, resulting in insufficient solution viscosity, making it difficult to form fibers through electrostatic action, and the solution can only be sprayed out in the form of small droplets or atomized particles.

[0012] When too much ethyl orthosilicate is added, uneven dispersion will occur in the spinning solution, and the needle will be blocked during spinning and spinning will not be possible.

[0013] When too little phosphoric acid is added, the acidity of the solution becomes weaker, which will affect the gelation time of the silica sol and be detrimental 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 will not be possible.

[0015] Furthermore, 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, with a stirring temperature of 70 to 90° C. and a stirring time of 2 to 3 h.

[0016] Furthermore, the main 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 0.1~5 mL / h, spinning temperature of 10~40 °C, and ambient humidity of 40%~70%.

[0017] Furthermore, the curing temperature in step 1 is 80°C to 150°C, and the curing time is 3 to 6 hours. If the curing temperature is too low, the evaporation rate of water and solvent will be too slow, which will extend the curing time; if the curing temperature is too high, stress may be generated inside the fiber, causing shrinkage and cracks, and affecting the integrity and performance of the fiber.

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

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

[0020] Furthermore, in step 2, the stirring time 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.

[0021] Furthermore, the vacuum impregnation time in step 3 is 30 to 60 min.

[0022] If the immersion time is too short, the microspheres will not be able to fully penetrate into the fiber surface, and the microspheres will not be firmly bonded to the fiber and will easily fall off, thus failing to fully exert the effect of the composite material; if the immersion time is too long, the microspheres will be deposited too thickly on the fiber surface, reducing the mechanical properties and sound absorption properties of the material.

[0023] Furthermore, the liquid nitrogen freezing time is 10 to 30 min, and the freeze-drying time is 12 to 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 preparation method, which is a grape-like three-dimensional network structure in which hollow silica microspheres are uniformly distributed on the surface of the ceramic fiber. The ceramic fiber has a uniform diameter of 180-220 nm, and the hollow silica microspheres have a diameter of 600-700 nm.

[0025] The present invention adopts vacuum impregnation and freeze drying to prepare the 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 fiber are effectively removed, and the tiny pores between the fibers form a capillary effect, which helps the microspheres to penetrate into the surface and inside of the fiber. When the microspheres are in close contact with the fiber surface, since the distance between molecules is shortened to a certain extent, a strong adsorption effect will be generated, so that the microspheres are firmly attached to the fiber surface. The impregnated fiber is frozen in a liquid nitrogen low-temperature environment. During the freezing process, the moisture and solvent in the fiber will gradually solidify into ice crystals, and the microspheres will be further fixed between the fibers. The frozen fiber material is placed in a vacuum environment for drying. Under vacuum conditions, ice crystals will directly sublimate from a solid state to a gas state (i.e., a sublimation process) without going through a liquid stage. In this process, the moisture and solvent in the fiber material are effectively removed, and the hollow microspheres can be closely combined with the fiber by physical adsorption and chemical bonding. The hollow silica microspheres are evenly distributed on the fiber surface, significantly increasing the roughness of the fiber, so that the sound waves are more obstructed and friction when passing through the material, resulting in increased 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 reflection and scattering of sound waves between fibers, thereby increasing the contact area and interaction time between sound waves and materials, and thus 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. This vibration can further consume the energy of the sound waves 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 and ultra-high temperature thermal insulation properties;

[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 a wide source of raw materials and a simple operation process.

[0028] 2. Good high temperature stability: The heat insulation and noise reduction 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 anti-ablation performance, which can maintain the normal temperature in the cabin while resisting the impact of high temperature and other harsh environments on the sound absorption performance of the material, thereby extending 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, which significantly increases the roughness of the fiber surface, causing more obstruction and friction when sound waves pass through the heat-insulating and noise-reducing ceramic fibers, increasing the loss of sound energy. In addition. The hollow silica microspheres further optimize the pore structure between the fibers, forming a complex and changeable internal network, so that the sound waves are reflected and scattered multiple times when propagating between the fibers, enhancing the interaction between the sound waves and the material, resulting in a slow wave effect. In addition, when the sound waves act on the material, the microspheres and fibers will vibrate, and this vibration can further consume the energy of the sound waves, and the vibration of the microspheres will in turn drive the surrounding microspheres to vibrate, resulting in sound delay. Compared with pure fibers, the sound absorption peak of the composite material moves to low frequencies and the sound absorption peak is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of preparing hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers according to the present invention;

[0031] Figure 2 The SEM images of the heat-insulating and noise-reducing ceramic composite fibers prepared by the present invention, wherein (a) and (b) are respectively the SEM images and the enlarged images of the heat-insulating and noise-reducing ceramic composite fibers prepared by Example 1, (c) and (d) are respectively the SEM images and the enlarged images of the heat-insulating and noise-reducing ceramic composite fibers prepared by Example 2 of the present invention, (e) and (f) are respectively the SEM images and the enlarged images of the heat-insulating and noise-reducing ceramic composite fibers prepared by Comparative Example 1 of the present invention, and (g) and (h) are respectively the SEM images and the enlarged images of the heat-insulating and noise-reducing ceramic composite fibers prepared by Comparative Example 2 of the present invention;

[0032] Figure 3 The thermal conductivity images of the heat-insulating and noise-reducing ceramic composite fibers prepared in Comparative Examples 1 to 4 and Examples 1 to 2 of the present invention;

[0033] Figure 4 The sound absorption performance diagram of the heat-insulating and noise-reducing ceramic composite fibers prepared in Examples 1 to 2 of the present invention and Comparative Examples 1 to 4;

[0034] Figure 5 This is a diagram of the sound absorption mechanism of the heat-insulating and noise-reducing ceramic composite fiber prepared in the present invention. DETAILED DESCRIPTION

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

[0036] Example 1

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

[0038] 1) Electrospinning: 0.098 g of phosphoric acid (H3PO4) was quickly added dropwise to a mixture of 18 g of water and 20.8 g of tetraethyl orthosilicate (TEOS), and the mixture was 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 the mixture was stirred for 3 h to form a PVA solution with a concentration of 10 wt %. 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, the electrospinning process began, and the obtained polymer nanofibers were received by a collecting device; the electrospinning process parameters were as follows: voltage of 18 kV, drum speed of 150 rpm, receiving distance of 20 cm, feeding speed of 0.8 mL / h, ambient temperature of 25±2℃, and ambient humidity of 45±5%; the polymer nanofibers obtained by electrospinning were cured in a vacuum oven at 80℃ for 3 h to remove moisture, and then placed in a muffle furnace for calcination to remove organic components, and the heating rate was 5℃·min -1 , the termination temperature is 800 ℃, and C-SiO2 ceramic nanofibers are obtained.

[0039] 2) Preparation of impregnation solution: Add 5 g of anhydrous ethanol to 35 g of deionized water and stir evenly. Then, add 0.2 g of hollow silica microsphere powder with a particle size of 600-700 nm to the ethanol-water blend system and stir vigorously for 3 h and ultrasonicate for 1 hour to obtain a uniformly dispersed hollow silica microsphere impregnation solution.

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

[0041] Example 2

[0042] A method for preparing a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres. The preparation method is the same as that in Example 1, except that an impregnation solution is prepared as follows: 5 g of anhydrous ethanol is added to 35 g of deionized water and stirred evenly, and then 0.3 g of hollow silica microsphere powder with a particle size of 600-700 nm is added to the ethanol-water blend system, and the mixture is vigorously stirred for 3 h and ultrasonicated for 1 hour to obtain a uniformly dispersed hollow silica microsphere impregnation solution.

[0043] Comparative Example 1

[0044] A method for preparing a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres. The preparation method is the same as that in Example 1, except that an impregnating solution is prepared: 5 g of anhydrous ethanol is added to 35 g of deionized water and stirred evenly, and then 0.1 g of hollow silica microsphere powder is added to the ethanol-water blend system, vigorously stirred for 3 h and ultrasonicated for 1 hour to obtain a uniformly dispersed hollow silica microsphere solution.

[0045] Comparative Example 2

[0046] A method for preparing a heat-insulating and noise-reducing ceramic composite fiber modified with hollow silica microspheres. The preparation method is the same as that in Example 1, except that an impregnating solution is prepared: 5 g of anhydrous ethanol is added to 35 g of deionized water and stirred evenly, and then 0.5 g of hollow silica microsphere powder is added to the ethanol-water blend system, vigorously stirred for 3 h and ultrasonicated for 1 hour to obtain a uniformly dispersed hollow silica microsphere solution.

[0047] Comparative Example 3

[0048] A method for preparing hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers, the preparation method is the same as that in Example 1, the only difference being that step 3 is to immerse the C-SiO2 nanofibers in the hollow silica microsphere impregnation solution at normal temperature.

[0049] Comparative Example 4

[0050] A method for preparing hollow silica microsphere-modified heat-insulating and noise-reducing ceramic composite fibers, the preparation method is the same as that of Example 1, the only difference being that in step 3, the C-SiO2 nanofibers are vacuum-impregnated in the hollow silica microsphere impregnation solution and then dried.

[0051] Performance test results:

[0052] The morphology of the samples in Example 1-2 and Comparative Example 1-2 was analyzed using a JSM-7800F field emission scanning electron microscope. Figure 2 As shown. Figure 2In (b), it can be seen that the silica fiber has 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 extremely narrow particle size, with a diameter of about 600-700 nm. Figure 2 From (a) to (d), it can be seen that the microspheres with regular morphology and smooth surface are evenly distributed on the surface of the nanofibers, showing a good interface bonding state. Figure 2 The low to high magnification scanning electron micrographs of Comparative Example 1 shown in (e) and (f) show that when the content of hollow silica microspheres is low, the microspheres on the fiber surface are sparsely distributed, and only a few microspheres are attached to the surface of some fibers. Figure 2 As shown in (g) and (h), the fiber is completely covered by the microspheres, and microspheres agglomerate.

[0053] Using the transient hot wire method, the samples with flat cross sections prepared in Examples 1, 2 and Comparative Examples 1 to 4 were placed on the upper and lower surfaces of the sensor of a thermal conductivity tester (TC3000E, XIA TECH) to measure the thermal conductivity. Figure 3 As shown. Figure 3 It can be seen that with the increase of the content of hollow silica microspheres, 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 between the matrix material, and the heat needs to overcome additional thermal resistance when passing through the interface of different materials. In addition, the introduction of microspheres reduces the pore size between the fiber skeletons, reduces the gas heat conduction of the material, and thus reduces 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 pores between the fibers being blocked, the direct contact between the fibers is increased, and the thermal bridge effect is enhanced, thereby increasing the thermal conductivity of the material. Among them, the thermal conductivity of the ceramic composite fiber in Example 2 in which the hollow silica microspheres are uniformly distributed is the lowest, which is 0.0345 W·m -1 ·K -1 , indicating that the material has good thermal insulation ability. The thermal conductivity of Comparative Examples 3 and 4 increased slightly, because the microspheres were not strongly bonded due to the room temperature impregnation and drying method, and there was a phenomenon of falling off, so the thermal conductivity increased slightly.

[0054] The sound absorption test of the samples of Examples 1-2 and Comparative Examples 1-4 was conducted using SW4201 & 4601 impedance tubes. Round fibers with diameters of 10 cm and 2.9 cm were prepared respectively. During the test, the samples were placed close to the rigid wall of the impedance tube to avoid the influence of the cavity behind on the sound absorption performance. After the test was completed, the curves of different frequency bands were fitted using the test software, and the test data was output according to 1 / 3 octave. Finally, the sound absorption curves of Examples 1-2 and Comparative Examples 1-4 at 160-6300 Hz were combined to obtain Figure 4 .Depend on Figure 4 It can be seen that the heat-insulating and noise-reducing ceramic composite fibers modified with hollow silica microspheres prepared in Examples 1 to 2 of the present invention have a more excellent sound absorption effect in the low-frequency range. The improvement in sound absorption performance is mainly attributed to the fact that the hollow silica microspheres are evenly distributed on the fiber surface, which significantly increases the roughness of the fiber, causing more obstruction and friction when the sound waves pass through the material, resulting in increased 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, extending the propagation path of the sound waves inside the material, causing more reflection and scattering of the sound waves between the fibers, thereby increasing the contact area and interaction time between the sound waves and the material, thereby enhancing the sound absorption effect. In addition, the hollow silica microspheres themselves have a certain mass and elasticity. When the sound waves act on the material, the microspheres will vibrate with the fibers. This vibration can further consume the energy of the sound waves and effectively reduce low-frequency noise. The sound absorption mechanism is as follows: Figure 5 As shown. 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 low, only a few microspheres are attached to the fiber surface, and the noise reduction effect cannot be fully exerted; when the content of microspheres is high, the excessive hollow silica microspheres block part of the pore structure between the fibers, causing the fibers to reflect some noise waves, so the sound absorption performance is slightly reduced. At the same time, Figure 4 It can also be seen that the sound absorption coefficient of Comparative Examples 3 and 4 also decreased after the process was changed. This is mainly because the use of room temperature impregnation and drying results in uneven 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-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the invention spirit and claims, which all fall within the scope of protection 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, then freeze with liquid nitrogen and then freeze-dry 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 (1~5):(20~40).

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, with a stirring temperature of 70 to 90° C. and a stirring time of 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 main 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 0.1~5 mL / 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 vacuum impregnation time of C-SiO2 nanofibers is 30-60 min, the liquid nitrogen freezing time is 10-30 min, and the freeze-drying time is 12-36 h.

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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