Cellulose-based composite aerogel and method of making the same

Abstract

The present application relates to a 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 hydroxyl-containing high polymer, and has a layered structure.In the preparation method, a compression treatment is added.The aerogel obtained after the compression treatment has a layered structure, which is conducive to the cross-linking and blending of the cellulose and the hydroxyl-containing high polymer, and is conducive to the connection of the liquid metal network, and can improve the thermal conductivity of the aerogel and reduce the thermal resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat dissipation materials, and particularly relates to a cellulose-based composite aerogel and a preparation method thereof. BACKGROUND

[0002] With continuous miniaturization, high integration and multifunctionality, the power density of electronic equipment is significantly improved, leading to a sharp rise in operating temperature. How to remove excess heat to maintain the normal operation of equipment and systems is becoming a 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 solve the problem of overheating of electrical equipment and systems. Cellulose nanocomposites are widely used as substrates for making flexible thermal conductive materials due to their lightweight, environmental friendliness and excellent mechanical properties. The cellulose thermal conductive phase change composite disclosed in Chinese Patent No. CN117417729A can enhance the thermal conductivity of the cellulose film by constructing a three-dimensional network with cellulose and loading diamond.

[0003] Room temperature liquid metal is widely used in heat dissipation fluid materials due to its excellent fluidity, good mechanical processing type and excellent thermal conductivity and thermal stability. The liquid metal heat dissipation device disclosed in Chinese Patent No. CN116581094A can effectively enhance the heat transfer effect of the pipeline. However, the addition of a fluid heat dissipation system to many devices will lead to equipment and complexity, increasing the manufacturing cost.

[0004] From the currently disclosed patents, it is still a great challenge to prepare a thermal interface material with high thermal conductivity and low thermal resistance by compounding cellulose and liquid metal. SUMMARY

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

[0006] Correspondingly, the application also provides a preparation method of the above-mentioned cellulose-based composite aerogel.

[0007] The application adopts the following technical solutions:

[0008] A cellulose-based composite aerogel, the cellulose-based composite aerogel comprises cellulose and a hydroxyl-containing high molecular polymer, and the cellulose-based composite aerogel has a layered structure. The molecular weight of the hydroxyl-containing high molecular polymer is 50000-100000; the hydroxyl-containing high molecular polymer is preferably polyvinyl alcohol or polyethylene glycol. The cellulose can be carboxylated cellulose, hydroxyalkyl cellulose, methyl cellulose and other cellulose ethers.

[0009] Preferably, the cellulose-based composite aerogel further comprises liquid metal, and the cellulose-based composite aerogel has a layered structure, a liquid metal connecting network between layers, and a liquid metal aggregation network at the bottom of the cellulose film. The liquid metal connecting network between layers enhances the thermal conductivity of the aerogel. Through compression, the liquid metal particles in the aerogel form a channel in the cellulose nanofiber and polyvinyl alcohol network, and a layer of liquid metal is aggregated at the bottom of the aerogel, thereby significantly enhancing the thermal conductivity of the aerogel and reducing the thermal resistance value of the aerogel. The liquid metal can be a bismuth-based alloy, a sodium-potassium alloy, a tin-indium alloy, etc.

[0010] Preferably, the cellulose-based composite aerogel further comprises magnetic particles, and the cellulose-based composite aerogel has a layered structure, a liquid metal connecting network between layers, and a liquid metal aggregation network at the bottom of the cellulose film, and the magnetic particles are dispersedly distributed in the aerogel network. The magnetic particles can be neodymium-iron-boron particles, ferrite magnetic particles, iron-chromium-cobalt magnetic particles, etc.

[0011] The preparation method of the above cellulose-based composite aerogel comprises the following steps:

[0012] The required raw materials are prepared into a 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 temperature of the mixed solution from being too high;

[0013] The mixed solution is subjected to directional freezing treatment to obtain an oriented aerogel;

[0014] The oriented aerogel is subjected to drying treatment to obtain a dried oriented aerogel;

[0015] The dried oriented aerogel is subjected to compression treatment, and the cellulose-based composite aerogel is obtained.

[0016] The cellulose-based composite aerogel of the present application is prepared by ultrasonic dispersion of cellulose hydrogel and polyvinyl alcohol and the like to prepare a mixed solution, and then freeze-drying and compression molding.

[0017] The directional freezing treatment is carried out at a temperature of -70 to -50℃. Specifically, the directional freezing treatment is to pour the mixed solution into a mold, place the mold above a metal plate, place the metal plate on a cold trap containing liquid nitrogen, control the temperature of the metal plate at -70 to -50℃, freeze for 30 minutes, and obtain an oriented frozen aerogel. The metal plate can be a copper plate, an iron plate, an aluminum plate, etc.

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

[0019] 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 the 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 the solvent added in the mixed solution is 50-85 wt%.

[0023] When the required raw materials include magnetic particles, the preparation method further includes a step of magnetization treatment after the compression treatment; specifically:

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

[0025] In the compression treatment, the applied pressure is 0.3 MPa to 1.8 MPa, and the compression treatment is maintained for 3-5 min. The present application can form an aerogel by applying a pressure of 0.3 MPa to 1.8 MPa to the aerogel material through the compression mold of the material testing machine; preferably, the pressure is 0.3 MPa, 0.6 MPa, 0.9 MPa, 1.2 MPa, 1.5 MPa or 1.8 MPa.

[0026] The present application has the following advantages:

[0027] (1) The present application adds a compression treatment in the preparation method, and the aerogel obtained after the compression treatment has a layered structure, which is beneficial to the crosslinking and blending of cellulose and the high-molecular polymer containing hydroxyl groups, and is beneficial to the connection of the liquid metal network, so that the thermal conductivity of the aerogel can be improved and the thermal resistance can be reduced.

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

[0029] (3) The aerogel prepared by compressing the aerogel has a layered structure, and there is a liquid metal network between the layers, so that the prepared aerogel has high thermal conductivity and good mechanical properties, which can meet the high-strength thermal management of electronic products.

[0030] (4) The introduction of neodymium iron boron particles enables the prepared aerogel to have magnetic driving performance, increasing the selective thermal management capability of the aerogel. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Electron micrograph of a cross-section of the pre-compressed aerogel prepared for Example 9.

[0032] Figure 2 Electron micrograph of a cross-section of the post-compressed aerogel prepared for Example 9.

[0033] Figure 3 Tensile stress-strain curves of cellulose-based aerogels prepared for different polyvinyl alcohol contents of Examples 1 to 5.

[0034] Figure 4 Tensile stress-strain curves of cellulose-based aerogels prepared for different liquid metal contents of Examples 6 to 8.

[0035] Figure 5 Stress-strain curves of cellulose-based aerogels prepared for different neodymium iron boron contents of Examples 9 to 11.

[0036] Figure 6 Magnetic driving bending angles of cellulose-based aerogels prepared for different neodymium iron boron contents of Examples 9 to 11.

[0037] Figure 7 Thermal conductivity test images of cellulose-based aerogels prepared for different neodymium iron boron contents of Examples 1, 9 to 11.

[0038] Figure 8 Thermal resistance test images of cellulose-based aerogels prepared for different neodymium iron boron contents of Examples 1, 9 to 11. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, a more comprehensive description of the present application will be given below in conjunction with specific examples. However, the present application can be implemented in many different forms, and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application.

[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 China Aladdin Chemical Co., Ltd.

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

[0045] (4) Neodymium iron boron particles were purchased from Guangzhou Xin Nuode Transmission Parts Co., Ltd.

[0046] It should be noted that the above raw materials are only examples made to make the technical scheme of the present application clearer, and do not represent that the present application can only use the above raw materials. The specific scope is 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 way of measuring the stress-strain curve of the aerogel material is as follows:

[0049] Uniaxial tensile test was carried out at room temperature using MTS general material testing machine (Criterion Model 43). Aerogel with a size of 30 mm × 5 mm × 0.4 mm was stretched at a strain rate of 0.03 s -1 .

[0050] B. The specific way of measuring the thermal conductivity of the aerogel material is as follows:

[0051] Thermal conductivity and thermal diffusivity analysis was carried out using a laser thermal conductivity instrument (NETZSCH LFA457). The compressed aerogel was cut into a 25 mm × 25 mm disc, and the thermal diffusivity measurement was carried out at room temperature.

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

[0053] The sample was cut into a 40 mm × 5 mm rectangle and placed 5 cm away from the electromagnetic coil. At room temperature, the bending process of the aerogel was recorded.

[0054] Example 1

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

[0056] A preparation method of cellulose / polyvinyl alcohol aerogel, the specific steps are as follows:

[0057] S1, 0.04 g of carboxylated cellulose nanofiber powder (diameter of 4-10 nm, length of 1-3 microns) was added to 4 g of deionized water, and stirred 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 ultrasonicated in an ice water bath for 5 min, 2.4 mL of polyvinyl alcohol solution was added, and ultrasonicated again for 5 min to obtain a cellulose / polyvinyl alcohol mixed solution. In this embodiment, the mass ratio of polyvinyl alcohol to cellulose is 50:1.

[0059] S3, directional freezing treatment: the cellulose / polyvinyl alcohol mixed solution was poured into a square silica gel mold, the bottom of the mold was in contact with a brass plate, and the brass plate was placed above a dewar flask containing liquid nitrogen; the surface temperature of the brass plate was controlled in the range of -70~-50℃, and the ice crystals inside the dispersion liquid were driven to grow along the plate surface direction by the low-temperature copper plate.

[0060] S4, drying treatment: the completely frozen cellulose and polyvinyl alcohol solution was placed in a freeze dryer (-50 °C and 10 Pa) for 5 hours to obtain a 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, which was named CNF / PVA 0.6 .

[0062] Example 2

[0063] This embodiment uses the same implementation as Example 1, and the difference from Example 1 is 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 finally obtained in this embodiment is named CNF / PVA 0.2 .

[0065] Example 3

[0066] This embodiment uses the same implementation as Example 1, and the difference from Example 1 is that the volume of polyvinyl alcohol in step S2 is 1.6 mL. In this embodiment, the mass ratio of polyvinyl alcohol to cellulose is 34:1. The cellulose / polyvinyl alcohol aerogel finally obtained in this embodiment is named CNF / PVA 0.4 .

[0067] Example 4

[0068] The same implementation as example 1 was adopted in this example, with the difference that the volume of polyvinyl alcohol in step S2 was 3.2 mL. The mass ratio of polyvinyl alcohol to cellulose in this example was 67:1.

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

[0070] Example 5

[0071] The same implementation as example 1 was adopted in this example, with the difference that the volume of polyvinyl alcohol in step S2 was 4 mL. The mass ratio of polyvinyl alcohol to cellulose in this example was 84:1. The cellulose / polyvinyl alcohol aerogel obtained in this example was named CNF / PVA 1.0 .

[0072] Example 6

[0073] The cellulose-based composite aerogel prepared in this example was a cellulose / polyvinyl alcohol / liquid metal aerogel.

[0074] A method for preparing a cellulose / polyvinyl alcohol / liquid metal aerogel, with the specific steps as follows:

[0075] S1. 0.04 g of carboxylated cellulose nanofiber powder was taken and added to 4 g of deionized water, and stirred on a magnetic stirring platform for 20 min (400 rpm) to obtain a transparent cellulose hydrogel, which was not affected by the pH of the solution.

[0076] S2. 2.576 g of liquid metal (gallium-indium alloy, melting point 16 °C) was taken and added to the cellulose hydrogel, and ultrasonicated in an ice water bath for 5 min, then 2.4 mL of polyvinyl alcohol solution was added and ultrasonicated again for 5 min to obtain a cellulose / polyvinyl alcohol / liquid metal mixed solution. The mass ratio of cellulose, polyvinyl alcohol and liquid metal in this example was 1:50:64.

[0077] S3. Directional freezing treatment: the mixed solution was poured into a square rubber mold with a qualitative shape, the bottom of the mold was in contact with a brass plate, and the brass plate was placed above a dewar flask filled with liquid nitrogen. The surface temperature of the brass plate was controlled in the range of -70~-50 °C, and the ice crystals inside the dispersion liquid were driven to grow along the plate surface direction by the low-temperature copper plate.

[0078] S4. Drying treatment: the completely frozen mixed solution was placed in a freeze dryer (-50 °C and 10 Pa) for 5 hours to obtain a 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, which was named CNF / PVA / LM. 0.3 .

[0080] Example 7

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

[0082] Example 8

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

[0084] Example 9

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

[0086] A method for preparing a cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel, the specific steps of which are as follows:

[0087] S1. 0.04 g of carboxylated cellulose nanofiber powder was added to 4 g of deionized water, and stirred on a magnetic stirring platform for 20 min (400 rpm) to obtain a transparent cellulose hydrogel, which was not affected by the pH.

[0088] S2. 2.567 g of liquid metal and 1.515 g of neodymium iron boron particles (particle size 5 μm) were added to the cellulose hydrogel, and shaken and mixed in an ice water bath for 5 min of uniform ultrasonic, 2.4 mL of polyvinyl alcohol solution was added, and ultrasonic was performed again for 5 min to obtain a cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron mixed solution. The mass ratio of cellulose, polyvinyl alcohol, liquid metal, and neodymium iron boron in this example was 1:50:64:38.

[0089] S3. Pour the mixed solution into a square silica gel mold, with the bottom of the mold in contact with a brass plate placed above a Dewar flask containing liquid nitrogen. The surface temperature of the brass plate is controlled in the range of -70 ~ -50 ℃, and the ice crystals inside the dispersion liquid are driven by the low-temperature copper plate to grow in the direction of the plate surface.

[0090] S4. Dry the completely frozen mixed solution in a freeze dryer (-50 °C and 10 Pa) for 5 hours to obtain cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel.

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

[0092] S6, Magnetization treatment: Place the aerogel obtained in step S5 in a magnetic field with a strength of 1.4 T, and magnetize for 15 minutes to obtain a magnetically drivable aerogel, designated as M 0.15 CPL.

[0093] Example 10:

[0094] This example uses the same implementation as Example 9, with the difference that the mass of neodymium iron boron in step S2 is 0.452 g. In this example, the mass ratio of cellulose, polyvinyl alcohol, liquid metal, and neodymium iron boron is 1:50:64:11. The cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel obtained in this example is designated as M 0.05 CPL.

[0095] Example 11:

[0096] This example uses the same implementation as Example 9, with the difference that the mass of neodymium iron boron in step S2 is 2.862 g. In this example, the mass ratio of cellulose, polyvinyl alcohol, liquid metal, and neodymium iron boron is 1:50:64:72. The cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel obtained in this example is designated as M 0.25 CPL.

[0097] Example 12:

[0098] This example uses the same implementation as Example 1, with the difference that the polyvinyl alcohol in step S2 is replaced by polyethylene glycol, and the compression treatment in step S5 applies a pressure of 0.3 MPa for 3 minutes.

[0099] Example 13:

[0100] The same implementation as example 6 is adopted, and the difference from example 6 is that the liquid metal (gallium-indium alloy) in step S2 is replaced by liquid metal (sodium-potassium alloy), the compression treatment in step S5 is applied with a pressure of 1.8 MPa, and the compression treatment time is 5 min, to obtain cellulose / polyvinyl alcohol / liquid metal aerogel.

[0101] Example 14:

[0102] The same implementation as example 9 is adopted, and the difference from example 9 is that the magnetic field strength in the magnetization treatment in step S6 is 2 T, and the magnetization treatment time is 30 min.

[0103] Figure 1 The electron microscope image of the cross section of the cellulose / polyvinyl alcohol / liquid metal / neodymium-iron-boron aerogel before compression during the preparation of example 9 is shown. It can be seen that the cellulose / polyvinyl alcohol / liquid metal / neodymium-iron-boron aerogel after freeze-drying has a clear porous structure and presents a clear longitudinal orientation. The liquid metal is dispersed into droplets with a diameter of about 3-5 μm under the action of ultrasound, and an oxidation shell is rapidly generated on the surface of the liquid metal droplets under oxygen, which reduces the Gibbs free energy, improves the stability of the liquid metal droplets, and increases the interaction between CNF / PVA and LM through chemical bonds, so that it is wrapped in the CNF / PVA aerogel network.

[0104] Figure 2 The electron microscope image of the cross section of the cellulose / polyvinyl alcohol / liquid metal / neodymium-iron-boron aerogel after compression during the preparation of example 9 is shown. The cellulose / polyvinyl alcohol / liquid metal / neodymium-iron-boron aerogel after compression presents a layered structure, and a liquid metal network is formed between and within the layers under the action of pressure, and a liquid metal aggregation network is formed at the bottom of the cellulose film (as shown by the red line in the part marked in Figure 2 ).

[0105] Figure 3 The tensile stress-strain curve of the cellulose / polyvinyl alcohol aerogel with different polyvinyl alcohol contents in example 1 to example 5 is shown. The breaking strain in example 1 is 36.9%, and the breaking strength is 6.1 MPa. With the increase of the content of polyvinyl alcohol, the strain of the prepared cellulose / polyvinyl alcohol aerogel increases, while the maximum tensile strength presents a trend of first increasing and then decreasing, indicating that excessive polyvinyl alcohol has a negative effect on the tensile strength of the cellulose / polyvinyl alcohol aerogel. The more appropriate mass ratio of polyvinyl alcohol to cellulose is 40-60:1.

[0106] Figure 4Tensile stress-strain curves of cellulose / polyvinyl alcohol / liquid metal aerogels with different liquid metal contents prepared for Example 6 to Example 8. The fracture strain in Example 6 is 27.7% and the fracture strength is 0.79 MPa. The fracture strain in Example 7 is 37.44% and the fracture strength is 1.28 MPa. The fracture strain in Example 8 is 13.98% and the fracture strength is 0.694 MPa. With the increase of liquid metal, the strain of cellulose / polyvinyl alcohol / liquid metal aerogel decreases. The reason why the maximum tensile strength (fracture strength) of Example 8 is greater than that of Example 6 is that the liquid metal forms more liquid metal networks in the aerogel network, which increases the maximum tensile strength of cellulose / polyvinyl alcohol / liquid metal aerogel under the joint action of liquid metal network and cellulose network. The more appropriate mass ratio of liquid metal to cellulose is 50-70:1.

[0107] Figure 5 Stress-strain curves of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogels with different neodymium iron boron contents prepared for Example 9 to Example 11. The fracture strain in Example 9 is 13% and the fracture strength is 0.65 MPa. The fracture strain in Example 10 is 18.94% and the fracture strength is 0.389 MPa. The fracture strain in Example 11 is 5.94% and the fracture strength is 1.18 MPa. With the increase of neodymium iron boron content, the maximum tensile strength of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel increases, while the fracture strain decreases.

[0108] Figure 6 Magnetic driving bending angles of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogels with different neodymium iron boron contents prepared for Example 9 to Example 11. With the increase of neodymium iron boron content, the bending angle of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogel under the same magnetic field strength increases.

[0109] Figure 7 Thermal conductivities of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogels with different neodymium iron boron contents prepared for Example 1, Example 9 to Example 11. The thermal conductivity of Example 9 is 1.63 W / (m K), which is 2.5 times higher than that of pure cellulose / polyvinyl alcohol aerogel in Example 1, which is 0.646 W / (m K). It is proved that the addition of appropriate amount of neodymium iron boron can significantly improve the thermal conductivity of cellulose aerogel in cooperation with the liquid metal network.

[0110] Figure 8 Thermal resistivities of cellulose / polyvinyl alcohol / liquid metal / neodymium iron boron aerogels with different neodymium iron boron contents prepared for Example 1, Example 9 to Example 11. The thermal resistance of Example 9 is 0.316 ×10 -3 (m2 K) / W, while the thermal resistance of pure cellulose / polyvinyl alcohol aerogel in Example 1 is 0.485 x 10 -3 (m 2 K) / W, which proves that the liquid metal network in the compressed cellulose / polyvinyl alcohol / liquid metal / neodymium-iron-boron aerogel effectively reduces the thermal resistance of the cellulose aerogel.

[0111] Those skilled in the art will easily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0112] The part of the present application specification not described in detail belongs to the known technology in the art. The above examples are only for the purpose of describing the present application and are not intended to limit the scope of the present application. The scope of the present application is defined by the appended claims. Various equivalent replacements and modifications made without departing from the spirit and principles of the present application shall be included in the scope of the present application.

Claims

1. A method for preparing a cellulose-based composite aerogel, characterized in that, The cellulose-based composite aerogel comprises cellulose, polyvinyl alcohol, liquid metal, and magnetic particles. The cellulose-based composite aerogel has a layered structure with a liquid metal connecting network between the layers, and a liquid metal aggregate network is formed at the bottom of the cellulose membrane. The magnetic particles are dispersed in the aerogel network. The mass ratio of cellulose, polyvinyl alcohol, liquid metal, and magnetic particles is 1:16-84:16-152:11-72. The cellulose-based composite aerogel was prepared by the following steps: Prepare a homogeneous mixture of the required raw materials in an ice-water bath; The mixed solution was subjected to directional freezing treatment to obtain oriented aerogel; The oriented aerogel is dried to obtain a dried oriented aerogel; The dried oriented aerogel is compressed in the same direction as the orientation direction of the oriented aerogel. The cellulose-based composite aerogel obtained by compression treatment can be obtained by magnetizing it in a magnetic field.

2. The method for preparing cellulose-based composite aerogel according to claim 1, characterized in that, The directional freezing process is carried out at a temperature of -70 °C to -50 °C.

3. The method for preparing cellulose-based composite aerogel according to claim 1 or 2, characterized in that, The amount of solvent added to the mixed solution is 50-85 wt%.

4. The method for preparing cellulose-based composite aerogel according to claim 3, characterized in that, The magnetic field strength for the magnetization treatment is 1-2 T, and the magnetization treatment time is 15-30 min.

5. The method for preparing cellulose-based composite aerogel according to claim 3, 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.

6. The method for preparing cellulose-based composite aerogel according to claim 3, characterized in that, The compression process is performed at a pressure of 0.3 MPa to 1.8 MPa, and the compression time is 3-5 min.

Images