Preparation method and application of bio-based composite nanofiber aerogel material with sandwich structure

Abstract

A preparation method of a bio-based composite nanofiber aerogel material with a sandwich structure comprises the following steps: step 1), heating, stirring and dissolving low-acyl gellan gum and water, step 2), mixing a product obtained in the step 1) with an MXene hot water solution, step 3), freeze-drying the MXene hot water solution to obtain an MXene freeze-dried compressed layer, and step 4), drying the MXene freeze-dried compressed layer to obtain the bio-based composite nanofiber aerogel material with the sandwich structure. (4) covering the product obtained in the step (3) on the outer layer obtained in the step (2), and pouring the gellan gum solution obtained in the step (1) into the outer layer to obtain sandwich-structure composite hydrogel; the method comprises the following steps of (1) preparing a material, (2) preparing a material, (3) preparing a material, (4) preparing a product, (5) soaking the product obtained in the step (4) in a metal salt solution for hardening, (6) soaking the product obtained in the step (5) in an organic solvent solution, and (7) drying the product obtained in the step (6) by a supercritical liquid carbon dioxide drying method to obtain the bio-based composite nanofiber aerogel with the sandwich structure.

Description

Technical Field

[0001] The invention relates to the technical field of aerogel preparation, in particular to a sandwich structure bio-based composite nanofiber aerogel material and a preparation method and application thereof, belonging to the technical field of chemistry. Background Art

[0002] As an open porous material with a three-dimensional nanostructure, aerogel has shown great application potential in the fields of thermal insulation, catalysis, drug release and adsorption due to its unique physical properties - low density, high specific surface area, high porosity and low thermal conductivity. However, despite these excellent properties of aerogel, its insufficient mechanical strength limits the wide range of practical applications. At present, there are relatively few aerogel materials that can be used in practice on the market. For example, although silica aerogel has low thermal conductivity, its mechanical properties are poor and it is difficult to meet the needs of high-strength applications. In contrast, organic aerogels are superior to traditional silica aerogels in formability and mechanical properties, but their synthesis process is complicated and often involves toxic solvents and raw materials, which can easily cause environmental pollution problems. Therefore, researchers have gradually turned their attention to aerogel materials based on natural polymers. Natural polymers are ideal for preparing aerogels due to their good biocompatibility, abundant resources and biodegradable properties. However, pure natural polymer-based aerogels also face the problem of insufficient mechanical properties. Therefore, how to use natural polymer materials to develop an aerogel that is both environmentally friendly and has super insulation and high mechanical strength has become a major challenge in the current technical field. Solving this problem will greatly promote the application of aerogel materials in a wider range of fields.

[0003] Gellan gum (GG) is a water-soluble anionic polysaccharide derived from Sphingomonas paucimobilis, which is prepared by a microbial fermentation process under aerobic conditions. As a new type of microbial polysaccharide, gellan gum is not only non-toxic, but also has excellent biocompatibility and biodegradability. These characteristics make it have important application value in many fields such as food, biomedicine and industry.

[0004] As one of the most promising advanced electromagnetic interference (EMI) shielding materials, transition metal carbonitride (MXene) has attracted much attention due to its excellent conductivity, excellent mechanical properties and high specific surface area. Compared with traditional conductive nanomaterials such as carbon nanotubes, graphene and acetylene black, MXene not only has excellent hydrophilicity, but also has good dispersibility in water. This property makes it easier to combine with bio-based gel materials, providing unique advantages for its application in the field of multifunctional composite materials.

[0005] Chinese patent CN116353126A discloses a method for preparing a composite material for a new energy vehicle battery case suitable for a wide temperature range. The composite material is applied to the thermal insulation and electromagnetic shielding of the battery case of a new energy vehicle using polyamide aerogel as the middle layer and carbon fiber composite material sheet as the outer layer. The maximum electromagnetic shielding efficiency is 56dB. In the process of preparing polyamide aerogel, more toxic and harmful waste will be generated, and a hot pressing process is required to connect the layers. Chinese patent CN108465459A discloses a method for preparing a composite aerogel by freeze-drying a mixture of gellan gum and graphene oxide. However, the pore size range of the aerogel prepared by this method is between tens of microns and hundreds of microns, which fails to reflect the unique nanoporous structure and high specific surface area characteristics of the aerogel. In addition, its microscopic morphology also lacks a typical nano-skeleton structure, which limits its potential in certain high-performance application fields. The method of using gellan gum as a matrix, mixing with MXene and preparing a sandwich structure bio-based composite nanofiber aerogel with both thermal insulation and electromagnetic shielding properties has never been disclosed. . Summary of the invention

[0006] The purpose of the present invention is to provide a sandwich structure bio-based composite nanofiber aerogel material and a preparation method and application thereof, so as to solve the problems in the prior art.

[0007] In order to achieve the above-mentioned invention object, the present invention provides the following technical solution: a method for preparing a sandwich structure bio-based composite nanofiber aerogel material, comprising the following steps: Step 1): heating and stirring low acyl gellan gum and water to dissolve to obtain a gellan gum solution; Step 2): the gellan gum solution obtained in step 1) is mixed with a hot MXene aqueous solution at 115° C., and cooled at 5° C. to obtain a gellan gum / MXene hydrogel; The concentration of the MXene solution is 5-30 mg / mL; Step 3): freeze-drying the MXene aqueous solution, and physically extruding and compressing the freeze-dried product to obtain a MXene freeze-dried compressed layer; Step 4): The MXene freeze-dried compressed layer obtained in step 3) is laminated and covered on the outer layer of the gellan gum / MXene hydrogel obtained in step 2), and the gellan gum solution obtained in step 1) is poured into this outer layer, and cooled to obtain a sandwich structure composite hydrogel; Step 5): soaking the sandwich structure composite hydrogel obtained in step 4) in a metal salt solution for hardening to obtain a sandwich structure composite hardened glue; The metal salt solution is a nickel chloride solution, an aluminum chloride solution, or a zirconium oxychloride solution; the concentration of the metal salt solution is 0.01-0.1 mol / L; Step 6) soaking the sandwich structure composite hardened glue obtained in step 5) in an organic solvent solution to obtain a sandwich structure composite organic gel; Step 7) drying the sandwich structure composite organic gel obtained in step 6) by supercritical liquid carbon dioxide drying method to obtain a sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and heat insulation material; In the step 1), the volume ratio of low acyl gellan gum to water is 20 mg:1 mL; The conditions of step 1) heating and stirring include: temperature of 35-115° C., time of 30 min, and stirring speed of 100-800 r / min; The mixing conditions of step 2) include: temperature of 110-130° C., time of 30 min, stirring speed of 100-800 r / min; The cooling time of step 2) is 3 hours and the temperature is 0-10°C; The conditions of the physical extrusion and compression in step 3) include: a pressure of 10-1000N.

[0008] Furthermore, the soaking time in step 5) is 8 hours.

[0009] Further; the organic solvent solution in step 6) is ethanol or methanol or acetone; the soaking conditions are: soaking 3 times, each soaking time is 8 hours, and the organic solvent solution is replaced after each soaking.

[0010] An application of a sandwich structure bio-based composite nanofiber aerogel material, wherein the sandwich structure bio-based composite nanofiber aerogel material is obtained by using a preparation method of a sandwich structure bio-based composite nanofiber aerogel material according to any one of claims 1 to 4, and is characterized in that: the sandwich structure bio-based composite nanofiber aerogel material is applied to electromagnetic shielding or thermal insulation materials, or electromagnetic shielding and thermal insulation materials.

[0011] Furthermore, the sandwich structure bio-based composite nanofiber aerogel material is used for thermal insulation and electromagnetic shielding of new energy vehicle battery boxes.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation process of the present invention is simple and reliable. The raw material gellan gum used is a natural polymer material, which has the characteristics of being environmentally friendly, widely available, excellent in biocompatibility and biodegradable; (2) The thermal conductivity of the aerogel prepared by the present invention under ambient conditions is 16-32 mW / (m·K), and the lowest value is lower than the thermal conductivity of air, so it has great application prospects in the field of thermal insulation; (3) The electromagnetic shielding effectiveness of the aerogel prepared by the present invention in the 8.2-12.5 GHz band is 20-80 dB, so it also has great application prospects in the field of electromagnetic shielding; (4) The present invention utilizes a sandwich structure to organically combine electromagnetic shielding and thermal insulation into one material, providing a solution for application scenarios that require both properties. Compared with CN116353126A, the present invention is not only superior to it in terms of thermal insulation and electromagnetic shielding performance, but also uses pure physical preparation and cross-linking in the preparation process, which is easy to operate, biodegradable and environmentally friendly, and has better performance. Compared with CN108465459A, the gellan gum aerogel prepared by the supercritical liquid carbon dioxide drying method used in the present invention has a pore size of less than 50 nanometers, and the diameter of the nanofiber is less than 100 nanometers, so it has a lower thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a cross-sectional view of the aerogel material prepared in Example 1 of the present invention.

[0014] Figure 2 The scanning electron microscope images of the aerogel material prepared in Example 1 at different magnifications are shown. DETAILED DESCRIPTION

[0015] In order to more fully explain the implementation of the present invention, implementation examples of the present invention are provided. These implementation examples are merely elaborations of the present invention and do not limit the scope of the present invention.

[0016] In a specific embodiment of the present invention, the low acyl gellan gum is purchased from McLean (manufacturer), G821481 gellan gum, biotechnology grade, low acyl type. In the present invention, the mass of the low acyl gellan gum and the volume ratio of water are preferably 400 mg: 20 mL. In the present invention, the mixing conditions preferably include: temperature of 35-115 ° C, time of 30 min; the temperature is preferably 115 ° C. In the present invention, the gellan gum solution is a uniform transparent solution.

[0017] In the present invention, the MXene aqueous solution is Ti3C2T x Aqueous solution (20 mg / mL) was obtained from a commercial product.

[0018] The present invention freeze-dries the MXene aqueous solution, and physically and mechanically extrude and compress the freeze-dried product to obtain a MXene freeze-dried compressed layer. The freeze-drying process described in the present invention is pre-freezing in a -20°C refrigerator for 5 hours and drying in a freeze dryer for 36 hours. The physical and mechanical extrusion compression pressure described in the present invention is 1000N.

[0019] The present invention soaks the obtained sandwich structure composite hydrogel in a metal salt solution for hardening to obtain a sandwich structure composite hardened glue; the metal salt solution includes a nickel chloride solution, an aluminum chloride solution or a zirconium oxychloride solution; in the present invention, when the metal salt solution is preferably a nickel chloride solution, the concentration is 0.1 mol / L, and in the present invention, when the metal salt solution is preferably an aluminum chloride solution, the concentration is 0.01 mol / L; in the present invention, when the metal salt solution is preferably a zirconium oxychloride solution, the concentration is 0.1 mol / L; in the present invention, the immersion time is preferably 8 hours, and the temperature is preferably 0-40°C.

[0020] The present invention soaks the obtained sandwich structure composite hardening glue in an organic solvent solution to obtain a sandwich structure composite organic gel. In the present invention, the organic solvent solution preferably includes ethanol, methanol or acetone. In the present invention, the soaking conditions preferably include: soaking 3 times, each soaking time is 8 hours, and the organic solvent solution is replaced each time soaking, and the water solvent in the gel is replaced by an alcohol solvent to facilitate subsequent supercritical drying.

[0021] The present invention dries the obtained sandwich structure composite organic gel to obtain a sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and heat insulation material. In the present invention, the drying preferably includes supercritical liquid carbon dioxide drying, and those skilled in the art can follow the conventional method.

[0022] The present invention also provides a sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and heat insulation material obtained by the preparation method described in the above technical solution. In the present invention, the microscopic morphology of the sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and heat insulation material is that nanofibers are interwoven to form a nanoporous structure and wrap staggered and stacked nanosheets, the nanofiber diameter is 10-100 nanometers, the average pore size of the nanopores is 20-70 nanometers, the thickness of the nanosheets is 6-20 nanometers, and the specific surface area of ​​the material is 200-600 m 2 / g, the electromagnetic shielding effectiveness is 20~80 dB, and the thermal conductivity is 16~32 mW / (m·K).

[0023] The present invention also provides the use of the above-mentioned sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material in electromagnetic shielding and thermal insulation, and can be particularly applied to thermal insulation and electromagnetic shielding of new energy vehicle battery boxes.

[0024] In the present invention, GG20 / MX10 means that the solute ratio of the gellan gum solution and the MXene solution after mixing in the step 2) is 20 mg / mL:10 mg / mL, and GG20 / MX0 means that the solute ratio of the gellan gum solution and the MXene solution after mixing in the step 2) is 20 mg / mL:0 mg / mL.

[0025] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0026] Example 1 400 mg of low acyl gellan gum was added to 10 mL of deionized water, and then stirred at 115 ° C for 30 min until the low acyl gellan gum was completely dissolved to obtain a uniform transparent solution. 10 mL of MXene aqueous solution was added, and the mixture was heated to 115 ° C and stirred for 30 min until the MXene aqueous solution and the gellan gum solution were completely mixed to obtain a uniform black solution. The above solution was poured into a mold, cooled and allowed to stand for 3 h to obtain a composite hydrogel. 7 mL of MXene aqueous solution was freeze-dried, and the freeze-dried product was physically and mechanically extruded and compressed. The obtained MXene freeze-dried compressed layer was laminated and covered on the outer layer of the composite hydrogel, and then the gellan gum solution was poured into this outer layer to stabilize and protect the overall sandwich structure. After cooling for 1 h, the sandwich structure composite hydrogel was immersed in 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) and immersed for 8 h. The sandwich structure composite hydrogel was then immersed in anhydrous ethanol (the volume ratio of anhydrous ethanol to hydrogel was greater than 5) for 3 times, each time for 8 hours, and the solution was replaced each time. The obtained sandwich structure composite alcohol gel was treated by supercritical liquid carbon dioxide drying to obtain the final aerogel sample (GG20 / MX10).

[0027] Example 2 400 mg of low acyl gellan gum was added to 14 mL of deionized water, and then stirred at 115 ° C for 30 min until the low acyl gellan gum was completely dissolved to obtain a uniform transparent solution. 6 mL of MXene aqueous solution was added, and the mixture was heated to 115 ° C and stirred for 30 min until the MXene aqueous solution and the gellan gum solution were completely mixed to obtain a uniform black solution. The above solution was poured into a mold, cooled and allowed to stand for 3 h to obtain a composite hydrogel. 7 mL of MXene aqueous solution was freeze-dried, and the freeze-dried product was physically and mechanically extruded and compressed. The obtained MXene freeze-dried compressed layer was laminated and covered on the outer layer of the composite hydrogel, and then the gellan gum solution was poured into this outer layer to stabilize and protect the overall sandwich structure. After cooling for 1 h, the sandwich structure composite hydrogel was immersed in 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) and immersed for 8 h. The sandwich structure composite hydrogel was then immersed in anhydrous ethanol (the volume ratio of anhydrous ethanol to hydrogel was greater than 5) for 3 times, each time for 8 hours, and the solution was replaced each time. The obtained sandwich structure composite alcohol gel was treated by supercritical liquid carbon dioxide drying to obtain the final aerogel sample (GG20 / MX6).

[0028] Example 3 400 mg of low acyl gellan gum was added to 18 mL of deionized water, and then stirred at 115 ° C for 30 min until the low acyl gellan gum was completely dissolved to obtain a uniform transparent solution. 2 mL of MXene aqueous solution was added, and the mixture was heated to 115 ° C and stirred for 30 min until the MXene aqueous solution and the gellan gum solution were completely mixed to obtain a uniform black solution. The above solution was poured into a mold, cooled and allowed to stand for 3 h to obtain a composite hydrogel. 7 mL of MXene aqueous solution was freeze-dried, and the freeze-dried product was physically and mechanically extruded and compressed. The obtained MXene freeze-dried compressed layer was fitted and covered on the outer layer of the composite hydrogel, and then the gellan gum solution was poured into this outer layer to stabilize and protect the overall sandwich structure. After cooling for 1 h, the sandwich structure composite hydrogel was immersed in 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) and immersed for 8 h. The sandwich structure composite hydrogel was then immersed in anhydrous ethanol (the volume ratio of anhydrous ethanol to hydrogel was greater than 5) for 3 times, each time for 8 hours, and the solution was replaced each time. The obtained sandwich structure composite alcohol gel was treated by supercritical liquid carbon dioxide drying to obtain the final aerogel sample (GG20 / MX2).

[0029] Example 4 400 mg of low acyl gellan gum was added to 20 mL of deionized water, and then stirred at 115 ° C for 30 min until the low acyl gellan gum was completely dissolved to obtain a uniform transparent solution. The above solution was poured into a mold, cooled and allowed to stand for 3 h to obtain a composite hydrogel. 7 mL of MXene aqueous solution was freeze-dried, and the freeze-dried product was physically and mechanically extruded and compressed. The obtained MXene freeze-dried compressed layer was laminated and covered on the outer layer of the composite hydrogel, and then the gellan gum solution was poured into this outer layer to firmly protect the overall sandwich structure. After cooling for 1 h, the sandwich structure composite hydrogel was immersed in 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) and immersed for 8 h. The sandwich structure composite hydrogel after immersion was then immersed in anhydrous ethanol (the volume ratio of anhydrous ethanol to hydrogel was greater than 5) for 3 times, each time for 8 h, and the solution was changed each time. The obtained sandwich structure composite alcohol gel was treated by supercritical liquid carbon dioxide drying method to obtain the final aerogel sample (GG20 / MX0).

[0030] The aerogels obtained in the above four embodiments were subjected to thermal conductivity test, electromagnetic shielding test and scanning electron microscopy test. The specific results are shown in the attached Figure 1 , Figure 2 As shown in Table 1, it can be seen from the results that by adopting this method, a sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material can be obtained, which has great application prospects in the fields of electromagnetic shielding and thermal insulation.

[0031]

[0032] Figure 2 The scanning electron microscope image shows that the sandwich structure bio-based composite nanofiber aerogel sandwich layer is a nanoporous structure formed by interweaving nanofibers and wrapped with staggered and stacked MXene nanosheets.

[0033] From Table 1, we can see that as the concentration of MXene increases, the thermal conductivity of the aerogel gradually increases, and the electromagnetic shielding effectiveness gradually increases. Therefore, the sandwich structure bio-based composite nanofiber aerogel material of the present invention has a good application prospect in electromagnetic shielding or thermal insulation materials, or electromagnetic shielding and thermal insulation materials.

[0034] After describing the implementation mode of the present invention in detail, people familiar with the technology can clearly understand that various changes and modifications can be made without departing from the scope and spirit of the above-mentioned patent application. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention, and the present invention is not limited to the implementation mode of the examples given in the specification.

Claims

1. A method for preparing a sandwich structure bio-based composite nanofiber aerogel material, characterized in that: The following steps are involved: Step 1): heating and stirring low acyl gellan gum and water to dissolve to obtain a gellan gum solution; Step 2): the gellan gum solution obtained in step 1) is mixed with a hot MXene aqueous solution at 115° C., and cooled at 5° C. to obtain a gellan gum / MXene hydrogel; The concentration of the MXene solution is 5-30 mg / mL; Step 3): freeze-drying the MXene aqueous solution, and physically extruding and compressing the freeze-dried product to obtain a MXene freeze-dried compressed layer; Step 4): The MXene freeze-dried compressed layer obtained in step 3) is laminated and covered on the outer layer of the gellan gum / MXene hydrogel obtained in step 2), and the gellan gum solution obtained in step 1) is poured into this outer layer, and cooled to obtain a sandwich structure composite hydrogel; Step 5): soaking the sandwich structure composite hydrogel obtained in step 4) in a metal salt solution for hardening to obtain a sandwich structure composite hardened glue; The metal salt solution is a nickel chloride solution, an aluminum chloride solution, or a zirconium oxychloride solution; the concentration of the metal salt solution is 0.01-0.1 mol / L; Step 6) soaking the sandwich structure composite hardened adhesive obtained in step 5) in an organic solvent solution to obtain a sandwich structure composite organic gel; Step 7) drying the sandwich structure composite organogel obtained in step 6) by supercritical liquid carbon dioxide drying to obtain a sandwich structure bio-based composite nanofiber aerogel material; In the step 1), the volume ratio of low acyl gellan gum to water is 20 mg:1 mL; The conditions of step 1) heating and stirring include: temperature of 35-115° C., time of 30 min, and stirring speed of 100-800 r / min; The mixing conditions of step 2) include: temperature of 110-130° C., time of 30 min, stirring speed of 100-800 r / min; The cooling time of step 2) is 3 hours and the temperature is 0-10°C; The conditions of the physical extrusion and compression in step 3) include: a pressure of 10-1000N.

2. The method for preparing a sandwich structure bio-based composite nanofiber aerogel material according to claim 1, characterized in that: The soaking time in step 5) is 8 hours.

3. The method for preparing a sandwich structure bio-based composite nanofiber aerogel material according to claim 1, characterized in that: In step 6), the organic solvent solution is ethanol, methanol or acetone; and the soaking conditions are: soaking for 3 times, each soaking time is 8 hours, and the organic solvent solution is replaced after each soaking.

4. Application of a sandwich structure bio-based composite nanofiber aerogel material, wherein the sandwich structure bio-based composite nanofiber aerogel material is obtained by the preparation method of a sandwich structure bio-based composite nanofiber aerogel material according to any one of claims 1 to 4, characterized in that: The sandwich structure bio-based composite nanofiber aerogel material is used in electromagnetic shielding or heat insulation materials, or electromagnetic shielding and heat insulation materials.

5. The use of a sandwich structure bio-based composite nanofiber aerogel material according to claim 4, characterized in that: The sandwich structure bio-based composite nanofiber aerogel material is used for thermal insulation and electromagnetic shielding of a battery box of a new energy vehicle.

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