Cellulose-based composite aerogel and preparation method thereof

Abstract

The invention relates to cellulose-based composite aerogel and a preparation method thereof, and belongs to the field of heat dissipation materials. The cellulose-based composite aerogel comprises cellulose and a high-molecular polymer containing hydroxyl, and the cellulose-based composite aerogel has a layered structure. According to the preparation method, compression treatment is added, the aerogel obtained after compression treatment has a layered structure, crosslinking and blending of cellulose and a high-molecular polymer containing hydroxyl are facilitated, connection of a liquid metal network is facilitated, the thermal conductivity of the aerogel can be improved, and the thermal resistance can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat dissipation materials, and in particular relates to a cellulose-based composite aerogel and a preparation method thereof. Background Art

[0002] With the continuous miniaturization, high integration and multifunctionality, the power density of electronic devices has increased significantly, resulting in a sharp increase in operating temperature. How to remove excess heat to maintain the normal operation of equipment and systems is becoming an urgent problem to be solved. Thermal interface materials play an important role in guiding and dissipating heat. Therefore, flexible thermal interface materials with high thermal conductivity and low thermal resistance are beneficial to solving problems such as overheating of electrical equipment and systems. Cellulose nanocomposites are widely used in the production of substrates for flexible thermal conductive materials due to their light weight, environmental friendliness and excellent mechanical properties. The Chinese patent with publication number CN117417729A discloses a cellulose thermal conductive phase change composite material, which can enhance the thermal conductivity of the cellulose film by constructing a three-dimensional network of cellulose and loading diamonds.

[0003] Room-temperature liquid metals are widely used as heat dissipation fluids due to their excellent fluidity, machinability, and outstanding thermal conductivity and stability. Chinese patent publication number CN116581094A discloses a liquid metal heat dissipation device that effectively enhances heat transfer in pipes. However, the addition of fluid heat dissipation systems to many devices complicates the equipment and increases manufacturing costs.

[0004] Judging from the currently disclosed patents, it is still a major challenge to prepare thermal interface materials with both high thermal conductivity and low thermal resistance by compounding cellulose and liquid metal. Summary of the Invention

[0005] In order to improve the above-mentioned deficiencies, the present invention provides a cellulose-based composite aerogel, which significantly enhances the thermal conductivity of the cellulose-based aerogel and reduces the thermal resistance of the cellulose-based aerogel.

[0006] Correspondingly, the present invention also provides a method for preparing the above-mentioned cellulose-based composite aerogel.

[0007] The present invention adopts the following technical solutions:

[0008] A cellulose-based composite aerogel comprises cellulose and a hydroxyl-containing polymer, and has a layered structure. The hydroxyl-containing polymer has a molecular weight of 50,000 to 100,000; the hydroxyl-containing polymer is preferably polyvinyl alcohol or polyethylene glycol. The cellulose may be carboxylated cellulose, hydroxyalkyl cellulose, methyl cellulose, or other cellulose ethers.

[0009] Preferably, the cellulose-based composite aerogel also includes liquid metal. The cellulose-based composite aerogel has a layered structure with a liquid metal network connecting the layers, and a liquid metal aggregation network forms at the bottom of the cellulose membrane. This liquid metal network between the layers enhances the aerogel's thermal conductivity. Upon compression, the liquid metal particles in the aerogel form pathways within the cellulose nanofiber and polyvinyl alcohol network, and a layer of liquid metal accumulates at the bottom of the aerogel, significantly enhancing the aerogel's thermal conductivity and reducing its thermal resistance. The liquid metal can be a bismuth-based alloy, a sodium-potassium alloy, a tin-indium alloy, or the like.

[0010] Preferably, the cellulose-based composite aerogel further includes magnetic particles. The cellulose-based composite aerogel has a layered structure with a liquid metal network connecting the layers. A liquid metal aggregation network is formed at the bottom of the cellulose membrane, and the magnetic particles are dispersed in the aerogel network. The magnetic particles can be neodymium iron boron particles, ferrite magnetic particles, iron chromium cobalt magnetic particles, etc.

[0011] The method for preparing the above-mentioned cellulose-based composite aerogel comprises the following steps:

[0012] The required raw materials are prepared into a uniform mixed solution; the preparation process of the mixed solution is preferably carried out in an ice water bath to reduce the temperature and prevent the mixed solution from being too high;

[0013] performing directional freezing treatment on the mixed solution to obtain oriented aerogel;

[0014] performing a drying process on the oriented aerogel to obtain a dry oriented aerogel;

[0015] The cellulose-based composite aerogel can be obtained by compressing the dried oriented aerogel.

[0016] The cellulose-based composite aerogel of the present invention is a product obtained by preparing a mixed solution by ultrasonic dispersion of raw materials such as cellulose hydrogel and polyvinyl alcohol, and then freeze-drying and compression molding.

[0017] The directional freezing treatment is performed at a temperature between -70°C and -50°C. Specifically, the mixed solution is poured into a mold, which is placed on a metal plate. The metal plate is placed on a cold trap filled with liquid nitrogen. The metal plate is kept at a temperature between -70°C and -50°C and frozen for 30 minutes to obtain an oriented frozen aerogel. The metal plate can be a copper plate, iron plate, aluminum plate, or the like.

[0018] The compression direction of the compression treatment is the same as the orientation direction of the oriented aerogel.

[0019] Wherein, the required raw materials are cellulose and polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the cellulose is 16-84:1;

[0020] The required raw materials are cellulose, polyvinyl alcohol and liquid metal, and the mass ratio of cellulose, polyvinyl alcohol and liquid metal is 1:16-84:16-152; preferably 1:50:16-152;

[0021] The required raw materials are cellulose, polyvinyl alcohol, liquid metal and magnetic particles, and the mass ratio of the cellulose, polyvinyl alcohol, liquid metal and magnetic particles is 1:16-84:16-152:11-72; preferably 1:50:64:11-72.

[0022] The amount of solvent added to the mixed solution is 50-85 wt %.

[0023] Wherein, when the required raw materials include magnetic particles, after the compression process, the preparation method further includes a magnetization process step; specifically, the following steps:

[0024] The cellulose-based composite aerogel obtained by compression treatment is magnetized in a magnetic field; the magnetic field intensity of the magnetization treatment is 1-2 T, and the magnetization treatment time is 15-30 min.

[0025] The pressure applied during the compression process is 0.3 MPa to 1.8 MPa, and the compression process is maintained for 3-5 minutes. In the present invention, the aerogel material can be formed by applying pressure to the aerogel material through a compression mold of a material testing machine, and the applied pressure is 0.3 MPa to 1.8 MPa; preferably, the pressure is 0.3 MPa, 0.6 MPa, 0.9 MPa, 1.2 MPa, 1.5 MPa, or 1.8 MPa.

[0026] Beneficial effects of the present invention:

[0027] (1) The present invention adds a compression process to the preparation method. The aerogel obtained after the compression process has a layered structure, which is conducive to the cross-linking and blending of cellulose and hydroxyl-containing polymers, and is conducive to the connection of liquid metal networks, which can improve the thermal conductivity of the aerogel and reduce the thermal resistance;

[0028] (2) The present invention ultrasonically mixes the raw materials in an ice-water bath, and the cellulose hydrogel and polyvinyl alcohol are interconnected by hydrogen bonds to form a hydrogen bond network. After freeze-drying, the ultrasonically dispersed liquid metal droplets are fixed in the aerogel network.

[0029] (3) The aerogel prepared by compressed aerogel has a layered structure with a liquid metal network between the layers, which makes the prepared aerogel have high thermal conductivity and good mechanical properties that can meet the high-intensity thermal management of electronic products.

[0030] (4) The introduction of NdFeB particles gives the prepared aerogel magnetic driving properties, which increases the selective thermal management capability of the aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an electron microscope image of the cross section of the aerogel prepared in Example 9 before compression.

[0032] Figure 2 This is an electron microscope image of the cross section of the compressed aerogel prepared in Example 9.

[0033] Figure 3 These are the tensile stress-strain curves of cellulose-based aerogels prepared with different polyvinyl alcohol contents in Examples 1 to 5.

[0034] Figure 4 These are the tensile stress-strain curves of the cellulose-based aerogels with different liquid metal contents prepared in Examples 6 to 8.

[0035] Figure 5 These are the stress-strain curves of cellulose-based aerogels with different NdFeB contents prepared in Examples 9 to 11.

[0036] Figure 6 The magnetically driven bending angles of the cellulose-based aerogels with different NdFeB contents prepared in Examples 9 to 11.

[0037] Figure 7 Thermal conductivity test graphs of cellulose-based aerogels with different NdFeB contents prepared in Examples 1 and 9 to 11.

[0038] Figure 8 Graphs showing the thermal resistivity of cellulose-based aerogels with different NdFeB contents prepared in Examples 1 and 9 to 11. DETAILED DESCRIPTION

[0039] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0042] (1) Cellulose nanofiber powder was purchased from Guilin Qihong Technology Co., Ltd.

[0043] (2) Polyvinyl alcohol (PVA-1799) was purchased from Aladdin Chemical Co., Ltd., China;

[0044] (3) Liquid metal was purchased from Dongguan Dingguan Metal Technology Co., Ltd.;

[0045] (4) NdFeB particles were purchased from Guangzhou Xinnod Transmission Components Co., Ltd.

[0046] It should be noted that the above raw materials are only examples made to make the technical solution of the present invention clearer, and do not mean that the present invention can only adopt the above raw materials. The specific scope shall be subject to the claims.

[0047] The performance parameters of the samples prepared in the following examples were tested according to the following test methods:

[0048] A. The specific method for measuring the stress-strain curve of aerogel materials is as follows:

[0049] Uniaxial tensile tests were performed at room temperature using an MTS universal materials testing machine (Criterion Model 43). Aerogels with dimensions of 30 mm × 5 mm × 0.4 mm were tested at a speed of 0.03 s -1 strain rate stretching.

[0050] B. The specific method for measuring the thermal conductivity of aerogel materials is as follows:

[0051] Thermal conductivity and thermal diffusivity were analyzed using a laser thermal conductivity meter (NETZSCH LFA457). The compressed aerogel was cut into 25 mm × 25 mm discs and thermal diffusivity measurements were performed at room temperature.

[0052] C. The specific method for measuring the magnetic bending angle of aerogel is as follows:

[0053] The magnetic field strength was controlled by adjusting the output current of a programmable power supply (IT8500) to attract or repel the aerogel. The sample was cut into a 40 mm × 5 mm rectangle and placed 5 cm from the electromagnetic coil. The bending process of the aerogel was recorded at room temperature.

[0054] Example 1:

[0055] The cellulose-based composite aerogel prepared in this example is cellulose / polyvinyl alcohol aerogel.

[0056] A method for preparing cellulose / polyvinyl alcohol aerogel, comprising the following specific steps:

[0057] S1. Take 0.04 g of carboxylated cellulose nanofiber powder (diameter 4-10 nm, length 1-3 μm) and add it to 4 g of deionized water. Stir on a magnetic stirring platform for 20 min (400 rpm) to obtain a transparent cellulose hydrogel.

[0058] S2. The cellulose hydrogel prepared in S1 was sonicated in an ice-water bath for 5 minutes, 2.4 mL of polyvinyl alcohol solution was added, and sonicated again for 5 minutes to obtain a cellulose / polyvinyl alcohol mixed solution. In this example, the mass ratio of polyvinyl alcohol to cellulose was 50:1.

[0059] S3. Directional freezing treatment: The cellulose / polyvinyl alcohol mixed solution is poured into a square silicone mold with the bottom of the mold in contact with a brass plate placed above a Dewar flask filled with liquid nitrogen. The surface temperature of the brass plate is controlled in the range of -70 to -50°C. The low-temperature copper plate drives the ice crystals in the dispersion to grow in a directional manner along the plate normal surface.

[0060] S4. Drying treatment: The completely frozen cellulose and polyvinyl alcohol solution was placed in a freeze dryer (-50°C and 10 Pa) and dried for 5 hours to obtain cellulose / polyvinyl alcohol aerogel.

[0061] S5. Compression treatment: The obtained cellulose / polyvinyl alcohol aerogel was placed in a compression mold and a pressure of 1.5 MPa was applied from above to obtain a cellulose / polyvinyl alcohol aerogel named CNF / PVA. 0.6 .

[0062] Example 2:

[0063] This embodiment adopts the same implementation as that of Example 1, except that the volume of polyvinyl alcohol in step S2 is 0.8 mL. In this embodiment, the mass ratio of polyvinyl alcohol to cellulose is 17:1.

[0064] The cellulose / polyvinyl alcohol aerogel obtained in this example is named CNF / PVA 0.2 .

[0065] Example 3:

[0066] This example adopts the same implementation method as Example 1, except that the volume of polyvinyl alcohol in step S2 is 1.6 mL. The mass ratio of polyvinyl alcohol to cellulose in this example is 34:1. The cellulose / polyvinyl alcohol aerogel finally obtained in this example is named CNF / PVA. 0.4 .

[0067] Example 4:

[0068] This embodiment adopts the same implementation as that of Example 1, except that the volume of polyvinyl alcohol in step S2 is 3.2 mL. In this embodiment, the mass ratio of polyvinyl alcohol to cellulose is 67:1.

[0069] The cellulose / polyvinyl alcohol aerogel obtained in this example is named CNF / PVA 0.8 .

[0070] Example 5:

[0071] This example adopts the same implementation method as Example 1, except that the volume of polyvinyl alcohol in step S2 is 4 mL. The mass ratio of polyvinyl alcohol to cellulose in this example is 84:1. The cellulose / polyvinyl alcohol aerogel finally obtained in this example is named CNF / PVA. 1.0 .

[0072] Example 6:

[0073] The cellulose-based composite aerogel prepared in this embodiment is cellulose / polyvinyl alcohol / liquid metal aerogel.

[0074] A method for preparing cellulose / polyvinyl alcohol / liquid metal aerogel, comprising the following specific steps:

[0075] S1. Add 0.04 g of carboxylated cellulose nanofiber powder to 4 g of deionized water and stir on a magnetic stirring platform (400 rpm) for 20 min to obtain a transparent cellulose hydrogel whose dissolution is not affected by pH.

[0076] S2. Add 2.576 g of liquid metal (gallium-indium alloy, melting point 16°C) to the cellulose hydrogel and sonicate in an ice-water bath for 5 minutes. Then, add 2.4 mL of polyvinyl alcohol solution and sonicate again for 5 minutes to obtain a cellulose / polyvinyl alcohol / liquid metal mixed solution. In this example, the mass ratio of polyvinyl alcohol to cellulose and liquid metal is 1:50:64.

[0077] S3. Directional Freezing: The mixed solution is poured into a square rubber mold with a defined surface. The bottom of the mold is in contact with a brass plate, which is placed above a Dewar flask filled with liquid nitrogen. The surface temperature of the brass plate is controlled between -70°C and -50°C. The low temperature of the plate drives ice crystals within the dispersion to grow in a directional pattern normal to the plate.

[0078] S4. Drying treatment: The completely frozen mixed solution was placed in a freeze dryer (-50 °C and 10 Pa) and dried for 5 hours to obtain cellulose and polyvinyl alcohol aerogel.

[0079] S5. Compression treatment: The cellulose / polyvinyl alcohol / liquid metal aerogel was placed in a compression mold and a pressure of 1.5 MPa was applied from above to obtain the cellulose / polyvinyl alcohol / liquid metal aerogel, named CNF / PVA / LM. 0.3 .

[0080] Example 7:

[0081] This example uses the same implementation as Example 6, with the difference from Example 6 being that the mass of the liquid metal in step S2 is 0.67 g. The mass ratio of polyvinyl alcohol, cellulose, and liquid metal in this example is 1:50:17. The cellulose / polyvinyl alcohol / liquid metal aerogel obtained in this example is named CNF / PVA / LM 0.1 .

[0082] Example 8:

[0083] This example uses the same implementation as Example 6, with the difference from Example 6 being that the mass of the liquid metal in step S2 is 6.01 g. The mass ratio of polyvinyl alcohol, cellulose, and liquid metal in this example is 1:50:150. The cellulose / polyvinyl alcohol / liquid metal aerogel obtained in this example is named CNF / PVA / LM 0.5 .

[0084] Example 9:

[0085] The cellulose-based composite aerogel prepared in this embodiment is cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel.

[0086] A method for preparing cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel, comprising the following steps:

[0087] S1. Add 0.04 g of carboxylated cellulose nanofiber powder to 4 g of deionized water and stir on a magnetic stirring platform (400 rpm) for 20 min to obtain a transparent cellulose hydrogel whose dissolution is not affected by pH.

[0088] S2. Add 2.567 g of liquid metal and 1.515 g of NdFeB particles (5 μm in diameter) to the cellulose hydrogel, shake and mix, and sonicate evenly in an ice-water bath for 5 minutes. Add 2.4 mL of polyvinyl alcohol solution and sonicate again for 5 minutes to obtain a cellulose / polyvinyl alcohol / liquid metal / NdFeB mixed solution. In this example, the mass ratio of polyvinyl alcohol, cellulose, liquid metal, and NdFeB is 1:50:64:38.

[0089] S3. The mixed solution is poured into a square silicone mold, with the bottom of the mold in contact with a brass plate placed above a Dewar flask filled with liquid nitrogen. The surface temperature of the brass plate is controlled between -70°C and -50°C. The low temperature of the brass plate drives the ice crystals within the dispersion to grow in a directional pattern along the plate's normal surface.

[0090] S4. The completely frozen mixed solution was placed in a freeze dryer (-50°C and 10 Pa) and dried for 5 hours to obtain cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel.

[0091] S5. Place the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel in a compression mold and apply a pressure of 1.5 MPa from above to obtain the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel.

[0092] S6, magnetization treatment: The aerogel obtained in step S5 was placed in a magnetic field with an intensity of 1.4 T and magnetized for 15 minutes to obtain a magnetically driven aerogel, named M 0.15 CPL.

[0093] Example 10:

[0094] This example adopts the same implementation method as Example 9, with the difference from Example 9 being that the mass of NdFeB in step S2 is 0.452 g. The mass ratio of polyvinyl alcohol, cellulose, liquid metal and NdFeB in this example is 1:508:648:118. The cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel finally obtained in this example is named M 0.05 CPL.

[0095] Example 11:

[0096] This embodiment adopts the same implementation method as that of embodiment 9, except that the mass of NdFeB in step S2 is 2.862 g. The mass ratio of polyvinyl alcohol, cellulose, liquid metal and NdFeB in this embodiment is 1:508:648:72. The cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel finally obtained in this embodiment is named M 0.25 CPL.

[0097] Example 12:

[0098] This embodiment adopts the same implementation as that of Example 1, and differs from Example 1 in that: polyvinyl alcohol in step S2 is replaced with polyethylene glycol, the pressure applied for the compression treatment in step S5 is 0.3 MPa, and the compression treatment time is 3 minutes.

[0099] Example 13:

[0100] This embodiment adopts the same implementation method as Example 6, and differs from Example 6 in that: the liquid metal (gallium-indium alloy) in step S2 is replaced with liquid metal (sodium-potassium alloy), the pressure applied during the compression treatment in step S5 is 1.8 MPa, and the compression treatment time is 5 minutes, thereby producing cellulose / polyvinyl alcohol / liquid metal aerogel.

[0101] Example 14:

[0102] This embodiment adopts the same implementation as that of Example 9, but differs from Example 9 in that the magnetic field intensity in the magnetization treatment in step S6 is 2 T, and the magnetization treatment time is 30 minutes.

[0103] Figure 1 This is an electron micrograph of a cross-section of the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel before compression during the preparation process of Example 9. It can be seen that the freeze-dried cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel has a distinct porous structure and exhibits a distinct longitudinal orientation. Under ultrasound, the liquid metal disperses into droplets approximately 3-5 μm in diameter. Oxygen rapidly forms an oxidation shell on the droplet surface, reducing the Gibbs free energy and improving the stability of the liquid metal droplets. Furthermore, chemical bonding between CNF / PVA and LM results in its encapsulation within the CNF / PVA aerogel network.

[0104] Figure 2 This is an electron microscope image of the cross-section of the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel after compression during the preparation process of Example 9. The compressed cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel exhibits a layered structure, with liquid metal networks forming within and between layers under pressure, and a liquid metal aggregation network forming at the bottom of the cellulose membrane (e.g., Figure 2 (marked with red lines in the figure).

[0105] Figure 3 The tensile stress-strain curves of cellulose / PVA aerogels with varying PVA contents from Examples 1 to 5 are shown. In Example 1, the fracture strain was 36.9% and the fracture strength was 6.1 MPa. As the PVA content increased, the strain of the prepared cellulose / PVA aerogels increased, while the maximum tensile strength initially increased and then decreased, indicating that excessive PVA has a negative impact on the tensile strength of the cellulose / PVA aerogels. A suitable PVA:cellulose mass ratio is 40-60:1.

[0106] Figure 4Tensile stress-strain curves for cellulose / polyvinyl alcohol / liquid metal aerogels prepared in Examples 6 to 8 with varying liquid metal contents. In Example 6, the fracture strain was 27.7%, and the fracture strength was 0.79 MPa. In Example 7, the fracture strain was 37.44%, and the fracture strength was 1.28 MPa. In Example 8, the fracture strain was 13.98%, and the fracture strength was 0.694 MPa. As the liquid metal content increased, the strain of the cellulose / polyvinyl alcohol / liquid metal aerogel decreased. The maximum tensile strength (fracture strength) of Example 8 was greater than that of Example 6 because the liquid metal formed more liquid metal networks within the aerogel network. The combined action of the liquid metal and cellulose networks increased the maximum tensile strength of the cellulose / polyvinyl alcohol / liquid metal aerogel. A suitable liquid metal to cellulose mass ratio is 50-70:1.

[0107] Figure 5 Stress-strain curves of cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogels with different NdFeB contents prepared in Examples 9 to 11. In Example 9, the fracture strain was 13%, and the fracture strength was 0.65 MPa. In Example 10, the fracture strain was 18.94%, and the fracture strength was 0.389 MPa. In Example 11, the fracture strain was 5.94%, and the fracture strength was 1.18 MPa. As the NdFeB content increases, the maximum tensile strength of the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel increases, while the fracture strain decreases.

[0108] Figure 6 Figure 1 shows the magnetically actuated bending angles of the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogels with different NdFeB contents prepared in Examples 9 to 11. As the NdFeB content increases, the bending angle of the cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel increases at the same magnetic field strength.

[0109] Figure 7 The thermal conductivity of cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogels with different NdFeB contents prepared in Examples 1, 9, and 11. The thermal conductivity of Example 9 is 1.63 W / (m K), compared with 0.646 W / (m The thermal conductivity of cellulose aerogel (K) was enhanced by 2.5 times. This proves that the addition of an appropriate amount of NdFeB can significantly improve the thermal conductivity of cellulose aerogel in synergy with the liquid metal network.

[0110] Figure 8 The thermal resistivity of cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogels with different NdFeB contents prepared in Examples 1, 9, and 11. The thermal resistance of Example 9 is 0.316 × 10 -3 (m2 K) / W, while the thermal resistance of the pure cellulose / polyvinyl alcohol aerogel in Example 1 is 0.485 × 10 -3 (m 2 K) / W, proving that the liquid metal network inside the compressed cellulose / polyvinyl alcohol / liquid metal / NdFeB aerogel effectively reduces the thermal resistance of the cellulose aerogel.

[0111] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0112] Any portions not described in detail in this specification are known in the art. The above embodiments are provided for illustrative purposes only and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications that do not depart from the spirit and principles of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. A cellulose-based composite aerogel, characterized in that: The cellulose-based composite aerogel comprises cellulose and a high molecular polymer containing hydroxyl groups, and the cellulose-based composite aerogel has a layered structure.

2. The cellulose-based composite aerogel according to claim 1, characterized in that The cellulose-based composite aerogel also includes liquid metal. The cellulose-based composite aerogel has a layered structure with a liquid metal connection network between layers, and a liquid metal aggregation network is formed at the bottom of the cellulose membrane.

3. The cellulose-based composite aerogel according to claim 2, characterized in that The cellulose-based composite aerogel also includes magnetic particles. The cellulose-based composite aerogel has a layered structure with a liquid metal connection network between layers. A liquid metal aggregation network is formed at the bottom of the cellulose membrane, and the magnetic particles are dispersed in the aerogel network.

4. The method for preparing the cellulose-based composite aerogel according to any one of claims 1 to 3, characterized in that: The steps include: Prepare the required raw materials into a uniform mixed solution; performing directional freezing treatment on the mixed solution to obtain oriented aerogel; performing a drying process on the oriented aerogel to obtain a dry oriented aerogel; The cellulose-based composite aerogel can be obtained by compressing the dried oriented aerogel.

5. The method for preparing the cellulose-based composite aerogel according to claim 4, characterized in that: The directional freezing treatment is performed at a temperature of -70°C to -50°C.

6. The method for preparing the cellulose-based composite aerogel according to claim 4, characterized in that: The compression direction of the compression process is the same as the orientation direction of the oriented aerogel.

7. The method for preparing a cellulose-based composite aerogel according to any one of claims 4 to 6, characterized in that: The required raw materials are cellulose and polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the cellulose is 16-84:1; The required raw materials are cellulose, polyvinyl alcohol and liquid metal, and the mass ratio of cellulose, polyvinyl alcohol and liquid metal is 1:16-84:16-152; The required raw materials are cellulose, polyvinyl alcohol, liquid metal and magnetic particles, and the mass ratio of cellulose, polyvinyl alcohol, liquid metal and magnetic particles is 1:16-84:16-152:11-72; The amount of solvent added to the mixed solution is 50-85 wt %.

8. The method for preparing the cellulose-based composite aerogel according to claim 7, characterized in that: When the required raw materials include magnetic particles, after the compression process, the preparation method further includes a magnetization process; specifically, the following steps: The cellulose-based composite aerogel obtained by compression treatment is magnetized in a magnetic field; the magnetic field intensity of the magnetization treatment is 1-2 T, and the magnetization treatment time is 15-30 min.

9. The method for preparing the cellulose-based composite aerogel according to claim 7, characterized in that: The liquid metal is a gallium-indium alloy, the cellulose is carboxylated cellulose nanofibers, and the magnetic particles are neodymium-iron-boron particles.

10. The method for preparing the cellulose-based composite aerogel according to claim 7, characterized in that: The pressure applied during the compression treatment is 0.3 MPa to 1.8 MPa, and the compression treatment is maintained for 3-5 minutes.

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