Heat-insulating composite aerogel as well as preparation method and application thereof

Abstract

The invention relates to heat-insulating composite aerogel as well as a preparation method and application thereof. The heat-insulating aerogel comprises a framework silicon dioxide nanofiber, and a network interpenetrating porous structure formed by interweaving cellulose nanofiber and silicon dioxide nanofiber. Specific surface functionalization treatment is adopted to promote the interfacial compatibility between SiO2-NF and TOCNF, nano polystyrene microspheres are added, and finally annealing treatment is performed to precisely regulate and control the pores of the aerogel, so that uniform dispersion and network interpenetration of the aerogel in the nanoscale are realized; and the porous structure of the obtained composite network is effectively maintained by using a freeze-drying technology. The final product shows ultralow thermal conductivity, excellent lightweight characteristic and mechanical properties of rigidity and softness. The process is controllable, the raw materials can be selected from biomass, and the obtained aerogel has important application value in the fields of building energy-saving enclosure, aerospace thermal protection and the like.

Description

Technical Field

[0001] The invention relates to a heat-insulating aerogel with low thermal conductivity, a preparation method and application thereof, and belongs to the technical field of functional composite materials. Background Art

[0002] Aerogel, a nanoporous material with ultra-high porosity (typically 80%-99.8%) and extremely low thermal conductivity, derives its thermal insulation properties from its unique three-dimensional network structure. This structure confines air within the pores, inhibiting gas molecular motion and convective heat transfer. At the same time, the complex pore design significantly increases the tortuosity of the heat conduction path, achieving an insulation effect close to that of static air.

[0003] In high-temperature or variable-temperature scenarios such as new energy battery insulation and building energy conservation, the pore structure characteristics of aerogels (including pore size distribution, pore connectivity and specific surface area) directly determine the stability and efficiency of their thermal management performance. However, the traditional aerogel manufacturing process has significant limitations: a single pore size distribution (mostly micropore range) and insufficient structural uniformity, resulting in a sharp decline in performance in complex thermal environments (especially when there is radiation heat transfer or temperature and humidity fluctuations). For example, in CN207880305U, the designer attempted to improve thermal insulation safety by combining a flexible aerogel layer (containing aerogel fine powder) with an external fire-retardant coating. However, the structure exposes two key defects caused by the pore structure: uneven pore size exacerbates the thermal bridge effect. For example, CN114316375A attempts to create a reinforced structure using a ternary composite of carboxycellulose, chitosan, and sodium alginate. However, the pore structure formed by its freeze-drying process still presents a serious problem: the large number of hydroxyl groups in the cellulose backbone makes the pore walls highly hydrophilic. Under high humidity conditions, water molecules penetrate into the nanopores and generate capillary forces, leading to irreversible pore collapse and further reducing the effective insulating porosity. Therefore, there is an urgent need to develop a high-performance insulating aerogel with low thermal conductivity. Summary of the Invention

[0004] Purpose of the Invention: In view of the problem that aerogel materials in the prior art are difficult to simultaneously achieve nano-porosity, light weight and good thermal insulation effects, one object of the present invention is to provide an insulating aerogel product with low thermal conductivity. Another object of the present invention is to provide a method for preparing the insulating aerogel. The last object of the present invention is to provide the application of the insulating aerogel in the field of thermal protection.

[0005] Technical solution: The thermal insulation composite aerogel described in the present invention comprises a skeleton silica nanofiber, a network interpenetrating porous structure in which cellulose nanofibers (CNF) and silica nanofibers are interwoven with each other.

[0006] Furthermore, the cellulose nanofibers are TEMPO-oxidized cellulose.

[0007] The method for preparing the thermal insulation composite aerogel of the present invention comprises the following steps:

[0008] (1) preparing a silica film by electrospinning, and homogenizing the silica film into a fibrous dispersion to obtain a silica nanofiber dispersion;

[0009] (2) Adding the cellulose nanofiber dispersion to the silica nanofiber dispersion, stirring and mixing, adding polystyrene, continuing to stir and mix, freeze-drying, and annealing.

[0010] Furthermore, in step (1), preparing the silicon dioxide film by electrospinning comprises the following steps:

[0011] Dissolve ethyl orthosilicate and oxalic acid in a mixed solution of deionized water and anhydrous ethanol, stir, add polyvinyl alcohol, continue stirring to prepare a precursor solution, use the precursor solution for electrospinning, and calcine.

[0012] Furthermore, the mass ratio of ethyl orthosilicate, oxalic acid, deionized water, anhydrous ethanol, and polyvinyl alcohol in the precursor solution is (0.5-2): (0.02-0.1): (1-2): (4-10): (0.005-0.015), preferably (0.6-1.8): (0.03-0.08): (1.2-1.9): (5-8): (0.008-0.013), more preferably (0.9-1.5): (0.035-0.05): (1.5-18): (6-7): (0.009-0.011), and most preferably 1: 0.04: 10: 6: 0.01. The speed of stirring and continued stirring is 200-800 rpm, preferably 300-500 rpm, and more preferably 400 rpm. The stirring time is 5 to 8 hours, preferably 6 to 7 hours; the stirring time is continued for 4 to 8 hours, preferably 5 to 6 hours. The voltage applied for electrospinning is 15 to 25 kV, the temperature is 15 to 30 ° C, the humidity is 10 to 50%, and the spinning distance is 15 to 30 cm. Preferably, the voltage is 17 to 22 kV, the temperature is 18 to 25 ° C, the humidity is 20 to 40%, and the spinning distance is 18 to 25 cm. More preferably, the voltage is 18 to 20 kV, the temperature is 25 ° C, the humidity is 30%, and the spinning distance is 20 to 22 cm. The calcination parameters are: a heating rate of 2 to 8 ° C / min, a calcination temperature of 800 to 1000 ° C, and a calcination time of 1 to 2 hours. Preferably, the heating rate is 3 to 6 ° C / min, the calcination temperature is 850 to 950 ° C, and the calcination time is 1.5 hours.

[0013] Furthermore, in step (1), the electrospun silica membrane is cut into pieces and dispersed in pure water, and a homogenizer is used to prepare a uniform silica nanofiber dispersion, wherein the concentration of the silica nanofibers in the silica nanofiber dispersion is 0.5-3 wt %, preferably 1-2.5 wt %, and most preferably 1.5 wt %. In step (2), the cellulose nanofiber dispersion is a dispersion of carboxyl-modified cellulose obtained by TEMPO oxidation, having a solid content of 0.5-2 wt %, and the mass ratio of the silica nanofiber dispersion to the cellulose nanofiber dispersion to the polystyrene is (5-10):(1-5):(0.5-1), preferably (6-9):(1.5-4.5):(0.6-0.9), and more preferably (7-8):(2-3):(0.7-0.8). The stirring and mixing speeds and the continued stirring and mixing speeds are both 11000-16000 rpm, preferably 14000-15000 rpm, and more preferably 14400 rpm; the stirring and mixing time and the continued stirring and mixing time are both 20-60 min, preferably 30 min; 10-30 mL of the mixed nanofiber dispersion is poured on a mold with a length, width and height of 2.5 cm and then freeze-dried. The freeze-drying parameters are: pressure 3-8.0 MPa, temperature -50--80°C, freeze-drying time 48-72 h, preferably pressure 3-5 MPa, temperature -56--80°C, and freeze-drying time 50-65 h. The high temperature heating rate is 2-8°C / min, preferably 3-6°C / min, and more preferably 5°C / min. The annealing temperature is 300-600°C, preferably 400-550°C, and more preferably 450-500°C. The high temperature time is 20-60 minutes, preferably 30-50 minutes, and more preferably 35-40 minutes. The high temperature atmosphere is argon.

[0014] Application of the thermal insulation composite aerogel of the present invention in the field of thermal protection.

[0015] Furthermore, the protection field and the aerospace field.

[0016] The aerogel of this invention utilizes silica nanofibers (SiO2-NF) and TEMPO-oxidized cellulose nanofibers (TOCNF) as key structural elements, constructed through an innovative in-situ composite strategy. The key elements of this method include: a specific surface functionalization treatment to promote interfacial compatibility between the SiO2-NF and TOCNF; the addition of nano-polystyrene microspheres; and precise control of the aerogel's porosity through annealing. Uniform dispersion and interpenetration of the aerogel at the nanoscale are achieved; and freeze-drying is employed to effectively maintain the porous structure of the resulting composite network. The resulting product exhibits ultra-low thermal conductivity, excellent lightweight properties, and mechanical properties that combine rigidity and flexibility. The silica nanofiber skeleton provides excellent thermal stability and structural support, while the CNF network effectively inhibits solid-phase heat conduction, enhances toughness, and refines pores. The nano-polystyrene further modulates the aerogel's nanopores. The synergistic coupling effect of these three elements is one of the keys to achieving excellent comprehensive thermal insulation performance. The process is controllable, and the raw materials can be selected from biomass. The resulting aerogel has important applications in building energy-saving enclosures, aerospace thermal protection, and other fields.

[0017] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: (1) The thermal insulation composite aerogel of the present invention has the characteristics of low density, low thermal conductivity, high flame retardancy and high strength, which overcomes the defects of the existing thermal insulation aerogel that high strength, light weight and good thermal insulation are difficult to coordinate, has great application potential in the field of thermal insulation, and provides a new idea for the preparation of high-strength thermal insulation aerogel. (2) The present invention combines two lightweight materials - silica nanofibers and cellulose nanofibers and nano-polystyrene into thermal insulation aerogel, among which silica nanofibers provide excellent thermal stability and structural support as a skeleton, while the TOCNF network effectively inhibits solid-phase heat conduction, enhances toughness and refines pores, and nano-polystyrene further regulates the nano-pores of the aerogel. The synergistic coupling effect of the three is to achieve excellent comprehensive thermal insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a macroscopic morphology image of the thermal insulation composite aerogel obtained in Example 1;

[0019] Figure 2 This is the flame retardant image of the thermal insulation composite aerogel obtained in Example 1;

[0020] Figure 3 This is a microscopic morphology image of the thermal insulation composite aerogel product obtained in Example 1;

[0021] Figure 4 This is a flame retardant image of the thermal insulation composite aerogel product obtained in Example 2;

[0022] Figure 5This is a microscopic morphology image of the thermal insulation composite aerogel product obtained in Example 2;

[0023] Figure 6 This is the flame retardant image of the thermal insulation composite aerogel obtained in Example 3;

[0024] Figure 7 This is a microscopic morphology image of the thermal insulation composite aerogel obtained in Example 3;

[0025] Figure 8 This is the flame retardant image of the aerogel product obtained in Example 4;

[0026] Figure 9 This is a microscopic morphology image of the aerogel product obtained in Example 4;

[0027] Figure 10 The flame retardant and macroscopic images of the silica film product obtained in Comparative Example 1, wherein a is a macroscopic image of the silica film product, and b is a flame retardant image of the silica film product;

[0028] Figure 11 The flame retardant and macroscopic images of the cotton-like silica product obtained in Comparative Example 2, wherein a is a macroscopic image of the cotton-like silica product, and b is a flame retardant image of the cotton-like silica product;

[0029] Figure 12 This is a macroscopic image of the silica particle aerogel obtained in Comparative Example 3. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] The reagents used in the following examples are all commercially available. The cellulose nanofiber dispersion was purchased from Weifang Qi'ang Nanotechnology and is a dispersion of TEMPO-oxidized cellulose with a solid content of 0.5-2 wt%.

[0032] Example 1

[0033] (1) Dissolve 1g of ethyl orthosilicate and 0.04g of oxalic acid in a mixed solution of 10g of deionized water and 6g of anhydrous ethanol. After stirring for 3h, add 0.01g of polyvinyl alcohol (1799 type) and stir magnetically at 300rpm for 4h at room temperature to obtain a clear solution with a certain viscosity. The above solution is used for electrospinning. The parameters used for electrospinning are: voltage 20kV, temperature 25℃, humidity 30%, and spinning distance 22cm. The nanofiber cotton obtained by spinning is calcined at a high temperature with a calcination heating rate of 5℃ / min, a calcination temperature of 900℃, and a calcination time of 1.5h to obtain a silica nanofiber membrane. The preparation is repeated.

[0034] (2) 1.5 g of SiO2 nanofiber membrane was cut into 1 × 1 cm pieces using scissors and dispersed in 98.5 mL of pure water. A Y25G homogenizer was used at 14,400 rpm for 30 minutes to prepare a uniform nanofiber dispersion to obtain a 1.5% silica nanofiber dispersion.

[0035] (3) 3 g of TEMPO-oxidized cellulose nanofibers (CNF) were added to 8 g of silica nanofiber dispersion and stirred for 30 minutes. 0.75 g of polystyrene (50 nm particle size) was then added and stirred for another 30 minutes to obtain a mixed nanofiber dispersion.

[0036] (4) The prepared mixed nanofiber dispersion was poured onto a mold with a length, width and height of 2.5 cm. It was frozen using liquid nitrogen and then freeze-dried. The freeze-drying parameters were: pressure 5 MPa, temperature -70 ° C, and freeze-drying time of 65 h. After freeze-drying, the sample was subjected to high-temperature thermal annealing in an argon atmosphere. The high-temperature thermal annealing heating rate was 5 ° C / min, the high-temperature thermal annealing temperature was 500 ° C, and the high-temperature thermal annealing time was 40 min. A composite thermal insulation aerogel with a size of 2.5 × 2.5 × 2.5 cm was obtained, as shown Figure 1 shown.

[0037] The heat-insulating composite aerogel prepared in this example was burned at 1300°C for 1 minute. Figure 2 As shown, the aerogel did not burn significantly, demonstrating excellent flame retardancy. The thermal conductivity of the dried sample was measured using the flat plate method, and the measured thermal conductivity of the sample was 0.033 W / (m·K).

[0038] The morphology of the two-phase interface of the thermal insulation composite aerogel prepared in this example was characterized using a scanning transmission microscope. Figure 3 As shown. By observing Figure 3 The microscopic image at the aerogel interface shows that the fibers are tightly entangled together, which can provide good mechanical synergy and a composite thermal insulation reinforcement network.

[0039] Example 2

[0040] The experimental process is the same as that of Example 1, except that the amount of cellulose nanofibers used is different.

[0041] (1) Dissolve 1g of ethyl orthosilicate and 0.04g of oxalic acid in a mixed solution of 10g of deionized water and 6g of anhydrous ethanol. After stirring for 3h, add 0.01g of polyvinyl alcohol (1799 type) and stir magnetically at 300rpm for 4h at room temperature to obtain a clear solution with a certain viscosity. The above solution is used for electrospinning. The parameters used for electrospinning are: voltage 20kV, temperature 25℃, humidity 30%, and spinning distance 22cm. The nanofiber cotton obtained by spinning is calcined at a high temperature with a calcination heating rate of 5℃ / min, a calcination temperature of 900℃, and a calcination time of 1.5h to obtain a silica nanofiber membrane. The preparation is repeated.

[0042] (2) 1.5 g of SiO2 nanofiber membrane was cut into pieces and dispersed in 98.5 mL of pure water. A uniform nanofiber dispersion was prepared using a Y25G homogenizer at 14,400 rpm for 30 minutes to obtain a 1% silica nanofiber dispersion.

[0043] (3) 8 g of TEMPO-oxidized cellulose nanofibers (TOCNF) were added to 8 g of silica nanofiber dispersion and stirred for 30 minutes. 0.75 g of polystyrene (50 nm particle size) was then added and stirred for another 30 minutes to obtain a mixed nanofiber dispersion.

[0044] (4) The prepared mixed nanofiber dispersion was cast on a mold with a length, width and height of 2.5 cm. It was frozen using liquid nitrogen and then freeze-dried. The freeze-drying parameters were: pressure 5 MPa, temperature -70°C, and freeze-drying time 65 h. After freeze-drying, the sample was thermally annealed in an argon atmosphere. The high-temperature thermal annealing heating rate was 5°C / min, the temperature was 500°C, and the high-temperature thermal annealing time was 40 min. A composite thermal insulation aerogel with a size of 2.5×2.5×2.5 cm was obtained.

[0045] The heat-insulating composite aerogel prepared in this example was burned at 1300°C for 1 minute. Figure 4 As shown, the aerogel has a serious burning phenomenon and poor thermal insulation and flame retardancy. The thermal conductivity of the dried sample was measured using the flat plate method, and the thermal conductivity of the sample was measured to be 0.044W / (m·K).

[0046] The morphology of the two-phase interface of the thermal insulation aerogel prepared in this example was characterized using a scanning transmission microscope. Figure 5 As shown in the figure, the increased cellulose nanofiber content leads to intertwining, forming a flocculent structure. This leads to uneven skeleton distribution, potentially causing agglomeration or a discontinuous network, which reduces heat reflection and gas confinement capabilities. Furthermore, excessive cellulose nanofibers can carbonize or shrink at high temperatures, destroying the original structure and compromising thermal insulation performance at high temperatures.

[0047] Example 3

[0048] The experimental process is the same as that of Example 1, except that the amount of silica nanofibers used is different.

[0049] (1) Dissolve 1g of ethyl orthosilicate and 0.04g of oxalic acid in a mixed solution of 10g of deionized water and 6g of anhydrous ethanol. After stirring for 3h, add 0.01g of polyvinyl alcohol (1799 type) and stir magnetically at 300rpm for 4h at room temperature to obtain a clear solution with a certain viscosity. The above solution is used for electrospinning. The parameters used for electrospinning are: voltage 20kV, temperature 25℃, humidity 30%, and spinning distance 22cm. The nanofiber cotton obtained by spinning is calcined at a high temperature with a calcination heating rate of 5℃ / min, a calcination temperature of 900℃, and a calcination time of 1.5h to obtain a silica nanofiber membrane. The preparation is repeated.

[0050] (2) 1.5 g of SiO2 nanofiber membrane was cut into pieces and dispersed in 98.5 mL of pure water. A uniform nanofiber dispersion was prepared using a Y25G homogenizer at 14,400 rpm for 30 minutes to obtain a silica nanofiber dispersion with a concentration of 1.5%.

[0051] (3) 3 g of TEMPO-oxidized cellulose nanofibers (TOCNF) were added to 15 g of silica nanofiber dispersion and stirred for 30 minutes. 0.75 g of polystyrene (50 nm particle size) was then added and stirred for another 30 minutes to obtain a mixed nanofiber dispersion.

[0052] (4) The prepared mixed nanofiber dispersion was cast on a mold with a length, width and height of 2.5 cm. It was frozen using liquid nitrogen and then freeze-dried. The freeze-drying parameters were: pressure 5 MPa, temperature -70°C, and freeze-drying time 65 h. After freeze-drying, the sample was thermally annealed in an argon atmosphere. The high-temperature thermal annealing heating rate was 5°C / min, the temperature was 500°C, and the high-temperature thermal annealing time was 40 min. A composite thermal insulation aerogel with a size of 2.5×2.5×2.5 cm was obtained.

[0053] The heat-insulating composite aerogel prepared in this example was burned at 1300°C for 1 minute. Figure 6 The thermal conductivity of the dried sample was measured using a flat plate method, and the measured thermal conductivity of the sample was 0.030 W / (m·K).

[0054] The morphology of the two-phase interface of the thermal insulation aerogel prepared in this example was characterized using a scanning transmission microscope. Figure 7As shown in Figure 2, with increasing silica nanofiber content, the material structure becomes denser and the skeleton network more continuous, effectively improving thermal insulation and flame retardancy. However, excessive inorganic fiber content also leads to a decrease in organic-inorganic interface bonding strength and poor interfacial compatibility, potentially leading to localized microcracks or stress concentrations, affecting the overall structural stability of the material.

[0055] Example 4

[0056] The experimental process is the same as that of Example 1, except that the amount of polystyrene used is different.

[0057] (1) Dissolve 1g of ethyl orthosilicate and 0.04g of oxalic acid in a mixed solution of 10g of deionized water and 6g of anhydrous ethanol. After stirring for 3h, add 0.01g of polyvinyl alcohol (1799 type) and stir magnetically at 300rpm for 4h at room temperature to obtain a clear solution with a certain viscosity. The above solution is used for electrospinning. The parameters used for electrospinning are: voltage 20kV, temperature 25℃, humidity 30%, and spinning distance 22cm. The nanofiber cotton obtained by spinning is calcined at a high temperature with a calcination heating rate of 5℃ / min, a calcination temperature of 900℃, and a calcination time of 1.5h to obtain a silica nanofiber membrane. The preparation is repeated.

[0058] (2) 1.5 g of SiO2 nanofiber membrane was cut into pieces and dispersed in 98.5 mL of pure water. A uniform nanofiber dispersion was prepared using a Y25G homogenizer at 14,400 rpm for 30 minutes to obtain a silica nanofiber dispersion with a concentration of 1.5%.

[0059] (3) 3 g of TEMPO-oxidized cellulose nanofibers (TOCNF) were added to 8 g of silica nanofiber dispersion and stirred for 30 minutes. Subsequently, 2 g of polystyrene (50 nm particle size) was added and stirred for another 30 minutes to obtain a mixed nanofiber dispersion.

[0060] (4) The prepared mixed nanofiber dispersion was cast on a mold with a length, width and height of 2.5 cm. It was frozen using liquid nitrogen and then freeze-dried. The freeze-drying parameters were: pressure 5 MPa, temperature -70°C, and freeze-drying time 65 h. After freeze-drying, the sample was thermally annealed in an argon atmosphere. The high-temperature thermal annealing heating rate was 5°C / min, the temperature was 500°C, and the high-temperature thermal annealing time was 40 min. A composite thermal insulation aerogel with a size of 2.5×2.5×2.5 cm was obtained.

[0061] The heat-insulating composite aerogel prepared in this example was burned at 1300°C for 1 minute. Figure 8As shown, the aerogel has good thermal insulation and fire protection performance. The thermal conductivity of the dried sample was measured using the flat plate method, and the thermal conductivity of the sample was measured to be 0.036W / (m·K).

[0062] The morphology of the two-phase interface of the composite thermal insulation aerogel prepared in this example was characterized using a scanning transmission microscope. The results are as follows: Figure 9 As shown in the figure, the amount of polystyrene used affects the microscopic pore size of the aerogel. Excessive polystyrene particles will leave a large number of holes after high-temperature pyrolysis, weakening the effective connection between fibers, resulting in a loose aerogel skeleton, reduced mechanical properties, and affected thermal insulation performance.

[0063] Comparative Example 1:

[0064] The silica nanofiber membrane was prepared by the electrospinning method in step (1) of Example 1. The front side of the silica nanofiber membrane was burned at 1300°C for 1 minute. Figure 10 As shown in Figure a, although it has certain fireproof and heat-insulating properties, its application as a thin film is relatively narrow and lacks in large-scale three-dimensional application scenarios. Figure 10 As shown in b. Figure 10 It can be seen that the electrospun silica in this comparative example assembled into a membrane, which was interwoven with countless silica fibers, but could not assemble into a three-dimensional structure.

[0065] Comparative Example 2:

[0066] Using the preparation method in step (1) of Example 1, cage-shaped electrospinning was prepared by changing the receiving device to obtain cotton-like silica fibers, such as Figure 11 As shown in a. The sample was burned at 1300℃ for 1 minute on the front side, and it also has certain fireproof and heat insulation properties, but its macroscopic pores and lack of mechanical strength limit its application. The actual picture of electrospun silica fiber after being burned at 1300℃ is shown in Figure 11 As shown in b. The thermal conductivity of the dried sample was measured using the plate method, and the thermal conductivity of the sample was measured to be 0.039W / (m·K). Figure 11 As can be seen, although the cotton-like structure electrospun in this comparative example resembles an aerogel, its pore size is macroscopic, not an aerogel, and its thermal conductivity is poor. Therefore, a silica nanodispersion must be prepared to assemble into an aerogel.

[0067] Comparative Example 3

[0068] (1) 3 g of TEMPO-oxidized cellulose nanofibers (TOCNF) were added to 8 g of 1.5% silica nanoparticles and stirred for 30 minutes. 0.75 g of polystyrene (50 nm in diameter) was then added and stirred for another 30 minutes to obtain a mixed nanofiber dispersion.

[0069] (4) The prepared mixed nanofiber dispersion was cast on a mold with a length, width and height of 2.5 cm. It was frozen using liquid nitrogen and then freeze-dried. The freeze-drying parameters were: pressure 5 MPa, temperature -70°C, and freeze-drying time 65 h. After freeze-drying, the sample was thermally annealed in an argon atmosphere. The high-temperature thermal annealing heating rate was 5°C / min, the temperature was 500°C, and the high-temperature thermal annealing time was 40 min. A thermal insulating aerogel with a size of 2.5×2.5×2.5 cm was obtained.

[0070] The thermal insulation composite aerogel prepared in this embodiment is as Figure 12 As shown, significant collapse occurs. The adsorption between silica particles and nanofibers relies primarily on van der Waals forces or hydrogen bonds, lacking crosslinking. This prevents them from interweaving like silica fibers and cellulose nanofibers. During heat treatment, particles tend to desorb or redistribute from the fiber surface, leading to network support failure and structural collapse.

Claims

1. A thermal insulation composite aerogel, characterized in that: The thermal insulation aerogel comprises a skeleton of silica nanofibers, a network interpenetrating porous structure in which cellulose nanofibers and silica nanofibers are interwoven with each other.

2. The thermal insulation composite aerogel according to claim 1, characterized in that The cellulose nanofibers are TEMPO-oxidized cellulose.

3. The method for preparing the thermal insulation composite aerogel according to claim 1 or 2, characterized in that: The following steps are involved: (1) preparing a silica film by electrospinning, and homogenizing the silica film into a fibrous dispersion to obtain a silica nanofiber dispersion; (2) Adding the cellulose nanofiber dispersion to the silica nanofiber dispersion, stirring and mixing, adding polystyrene, continuing to stir and mix, freeze-drying, and annealing.

4. The preparation method according to claim 3, characterized in that In step (1), preparing the silicon dioxide film by electrospinning comprises the following steps: Dissolve ethyl orthosilicate and oxalic acid in a mixed solution of deionized water and anhydrous ethanol, stir, add polyvinyl alcohol, continue stirring to prepare a precursor solution, use the precursor solution for electrospinning, and calcine.

5. The preparation method according to claim 4, characterized in that The mass ratio of tetraethyl orthosilicate, oxalic acid, deionized water, anhydrous ethanol, and polyvinyl alcohol in the precursor solution is (0.5-2): (0.02-0.1): (1-2): (4-10): (0.005-0.015); the voltage applied for electrospinning is 15-25 kV, the calcination temperature is 800-1000° C., and the calcination time is 1-2 h.

6. The preparation method according to claim 3, characterized in that In step (1), the electrospun silica membrane is cut into pieces and dispersed in pure water, and a homogenizer is used to prepare a uniform silica nanofiber dispersion liquid, wherein the concentration of silica nanofibers in the silica nanofiber dispersion liquid is 0.5-3 wt%.

7. The preparation method according to claim 3, characterized in that In step (2), the mass ratio of the silica nanofiber dispersion, the cellulose nanofiber dispersion and the polystyrene is (5-10): (1-5): (0.5-1).

8. The preparation method according to claim 3, characterized in that In step (2), the stirring and mixing time is more than 30 minutes, and the stirring and mixing time is continued for more than 30 minutes. The freeze-drying parameters are: pressure 3.0 to 8.0 MPa, temperature -50 to -80°C.

9. The preparation method according to claim 3, characterized in that In step (2), the high temperature heating rate is 2-5°C / min, the annealing temperature is 300-600°C, the high temperature time is 20-60min, and the high temperature atmosphere is argon.

10. Use of the thermal insulation composite aerogel according to claim 1 or 2 in the field of thermal protection.

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