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

Abstract

The application discloses a preparation method of a sandwich structure bio-based composite nanofiber aerogel material, and comprises the following steps: step 1), heating and stirring to dissolve low acyl gum; step 2), mixing the product obtained in step 1) with a hot aqueous solution of MXene; step 3), freeze-drying treatment of the aqueous solution of MXene to obtain a compressed layer of MXene; step 4), pasting and covering the product obtained in step 3) on an outer layer obtained in step 2), pouring the gum solution obtained in step 1) into the outer layer to obtain a sandwich structure composite hydrogel; step 5), soaking the product obtained in step 4) in a metal salt solution to harden; step 6), soaking the product obtained in step 5) in an organic solvent solution; and step 7), drying the product obtained in step 6) by using a supercritical liquid carbon dioxide drying method to obtain the sandwich structure bio-based composite nanofiber aerogel. The material has low thermal conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel preparation, and particularly relates to a sandwich structure bio-based composite nanofiber aerogel material, a preparation method and application thereof, and belongs to the technical field of chemistry. BACKGROUND

[0002] As an open porous material with three-dimensional nanostructure, aerogel has shown great application potential in thermal insulation, catalysis, drug release and adsorption due to its unique physical properties, such as low density, high specific surface area, high porosity and low thermal conductivity. However, although aerogel has these excellent properties, the lack of mechanical strength limits the universality of its practical application. At present, there are relatively few aerogel materials that can be practically applied on the market. For example, although silica aerogel has low thermal conductivity, its mechanical properties are poor and it is difficult to meet the demand of high-strength application. In contrast, organic aerogel is superior to traditional silica aerogel in formability and mechanical properties, but its synthesis process is complex 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 have become an ideal choice 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 environmentally friendly aerogel with super insulation and high mechanical strength has become a major challenge in the current technical field. The solution to 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 microbial fermentation 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 properties make it have important application value in food, biomedical and industrial fields.

[0004] Transition metal carbonitride (MXene) is one of the most potential advanced electromagnetic interference (EMI) shielding materials, which has attracted much attention due to its excellent electrical 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 can achieve good dispersion in water, which makes it easier to combine with bio-based gel materials, providing a unique advantage for its application in multifunctional composite materials.

[0005] Chinese patent CN116353126A discloses a method for preparing a composite material suitable for new energy vehicle battery cases with a wide temperature range. The composite material uses a polyamide aerogel as a middle layer and a carbon fiber composite sheet as an outer layer. The resulting composite material provides thermal insulation and electromagnetic shielding for new energy vehicle battery cases, achieving a maximum electromagnetic shielding efficiency of 56 dB. However, the polyamide aerogel preparation process generates a significant amount of toxic and hazardous waste, and hot pressing is required to connect the layers. Chinese patent CN108465459A discloses a method for preparing composite aerogels by freeze-drying a mixture of gellan gum and graphene oxide. However, the pore size of the aerogels produced by this method ranges from tens to hundreds of microns, failing to exhibit the unique nanoporous structure and high specific surface area characteristics of aerogels. Furthermore, their micromorphology lacks a typical nano-skeleton structure, limiting their potential for certain high-performance applications. A method for preparing a sandwich-structured bio-based composite nanofiber aerogel with both thermal insulation and electromagnetic shielding properties, using gellan gum as a matrix and mixing it with MXene, 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 its preparation method and application, so as to solve the problems in the prior art.

[0007] In order to achieve the above-mentioned object of the invention, 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:

[0008] Step 1): heating and stirring low acyl gellan gum and water to dissolve to obtain a gellan gum solution;

[0009] Step 2): mixing the gellan gum solution obtained in step 1) with a hot MXene aqueous solution at 115° C. and cooling at 5° C. to obtain a gellan gum / MXene hydrogel;

[0010] The concentration of the MXene solution is 5-30 mg / mL;

[0011] 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;

[0012] Step 4): The freeze-dried compressed MXene 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;

[0013] Step 5): soaking the sandwich structure composite hydrogel obtained in step 4) in a metal salt solution to harden it, thereby obtaining a sandwich structure composite hardened glue;

[0014] 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 to 0.1 mol / L;

[0015] Step 6) soaking the sandwich structure composite hardened adhesive obtained in step 5) in an organic solvent solution to obtain a sandwich structure composite organogel;

[0016] 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 electromagnetic shielding and thermal insulation material;

[0017] In step 1), the volume ratio of low acyl gellan gum to water is 20 mg:1 mL;

[0018] The conditions for heating and stirring in step 1) include: temperature of 35-115° C., time of 30 min, and stirring speed of 100-800 r / min;

[0019] The mixing conditions in step 2) include: temperature of 110-130° C., time of 30 min, and stirring speed of 100-800 r / min;

[0020] The cooling time of step 2) is 3 hours, and the temperature is 0-10°C;

[0021] The conditions for the physical extrusion and compression in step 3) include: a pressure of 10-1000N.

[0022] Furthermore, the soaking time in step 5) is 8 hours.

[0023] Furthermore, in step 6), the organic solvent solution is ethanol, 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.

[0024] 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 the 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 used in electromagnetic shielding or thermal insulation materials, or electromagnetic shielding and thermal insulation materials.

[0025] Furthermore, the sandwich structure bio-based composite nanofiber aerogel material is used for thermal insulation and electromagnetic shielding of new energy vehicle battery boxes.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The preparation process of the present invention is simple and reliable. The raw material gellan gum used is a natural polymer material with the characteristics of being environmentally friendly, widely available, biocompatible and biodegradable. (2) The thermal conductivity of the aerogel prepared by the present invention is 16-32 mW / (m·K) under ambient conditions, and the lowest value is lower than the thermal conductivity of air. It has great application prospects in the field of thermal insulation. (3) The electromagnetic shielding effectiveness of the aerogel prepared by the present invention is 20-80 dB in the 8.2-12.5 GHz band. It also has great application prospects in the field of electromagnetic shielding.

[0028] (4) The present invention utilizes a sandwich structure to organically combine electromagnetic shielding and thermal insulation properties into one material, providing a solution for applications that require both properties. Compared with CN116353126A, the present invention not only outperforms CN116353126A in terms of thermal insulation and electromagnetic shielding performance, but also uses pure physical preparation and cross-linking in the preparation process, 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 a nanofiber diameter of less than 100 nanometers, thus having a lower thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a cross-sectional view of the aerogel material prepared in Example 1 of the present invention.

[0030] Figure 2 These are scanning electron microscope images of the aerogel material prepared in Example 1 at different magnifications. DETAILED DESCRIPTION

[0031] 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.

[0032] In a specific embodiment of the present invention, the low-acyl gellan gum is purchased from Maclean (manufacturer), G821481 gellan gum, biotech grade, low-acyl type. In the present invention, the mass-to-volume ratio of the low-acyl gellan gum to water is preferably 400 mg:20 mL. In the present invention, the mixing conditions preferably include: a temperature of 35-115°C for 30 minutes; the temperature is preferably 115°C. In the present invention, the gellan gum solution is a homogeneous, transparent solution.

[0033] In the present invention, the MXene aqueous solution is Ti3C2T x Aqueous solution (20 mg / mL) was obtained from a commercial product.

[0034] The present invention freeze-dries the MXene aqueous solution, and then physically and mechanically extrudes and compresses the freeze-dried product to produce a freeze-dried compressed MXene layer. The freeze-drying process described in the present invention involves pre-freezing in a -20°C refrigerator for 5 hours and then drying in a freeze dryer for 36 hours. The physical and mechanical extrusion compression pressure used in the present invention is 1000N.

[0035] 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; 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.

[0036] The present invention soaks the obtained sandwich-structured composite hardened adhesive in an organic solvent solution to produce a sandwich-structured composite organogel. In the present invention, the organic solvent solution preferably comprises ethanol, methanol, or acetone. In the present invention, the soaking conditions preferably include: soaking three times, each soaking lasting 8 hours, with the organic solvent solution being replaced each time to replace the aqueous solvent in the gel with an alcohol solvent, facilitating subsequent supercritical drying.

[0037] The present invention dries the obtained sandwich structure composite organic gel to obtain a sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material. In the present invention, the drying preferably includes supercritical liquid carbon dioxide drying, which can be conventionally performed by those skilled in the art.

[0038] The present invention also provides a sandwich-structured bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material obtained by the preparation method described in the above technical solution. In the present invention, the microscopic morphology of the sandwich-structured bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material is a nanoporous structure formed by interweaving nanofibers and wrapped with staggered 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).

[0039] The present invention also provides the application of the above-mentioned sandwich structure bio-based composite nanofiber aerogel electromagnetic shielding and thermal insulation material in electromagnetic shielding and thermal insulation, which can be particularly applied to the thermal insulation and electromagnetic shielding of new energy vehicle battery boxes.

[0040] In the present invention, GG20 / MX10 means that the solute ratio of the gellan gum solution and the MXene solution after mixing in 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 step 2) is 20 mg / mL:0 mg / mL.

[0041] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] 400 mg of low-acyl gellan gum was added to 10 mL of deionized water and stirred at 115°C for 30 minutes until the low-acyl gellan gum was completely dissolved, resulting in a homogeneous, transparent solution. 10 mL of MXene aqueous solution was added, and the mixture was heated to 115°C and stirred for 30 minutes until the MXene and gellan gum solutions were completely mixed, resulting in a homogeneous, black solution. The solution was poured into a mold, cooled, and allowed to stand for 3 hours to obtain a composite hydrogel. 7 mL of the MXene aqueous solution was freeze-dried and the freeze-dried product was mechanically compressed. The resulting freeze-dried, compressed MXene layer was laminated to the outer layer of the composite hydrogel. Gellan gum solution was then poured onto this outer layer to stabilize and protect the sandwich structure. After cooling for 1 hour, the sandwich composite hydrogel was immersed in a 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) for 8 hours. The sandwich-structured composite hydrogel was then immersed in anhydrous ethanol (with a volume ratio of anhydrous ethanol to hydrogel greater than 5) three times for 8 hours each time, with the solution replaced between soaks. The resulting sandwich-structured composite hydrogel was then dried using supercritical liquid carbon dioxide to obtain the final aerogel sample (GG20 / MX10).

[0044] Example 2

[0045] 400 mg of low-acyl gellan gum was added to 14 mL of deionized water and stirred at 115°C for 30 minutes until the low-acyl gellan gum was completely dissolved, resulting in a homogeneous, transparent solution. 6 mL of MXene aqueous solution was added, and the mixture was heated to 115°C and stirred for 30 minutes until the MXene and gellan gum solutions were completely mixed, resulting in a homogeneous, black solution. The solution was poured into a mold, cooled, and allowed to stand for 3 hours to obtain a composite hydrogel. 7 mL of the MXene aqueous solution was freeze-dried and the freeze-dried product was mechanically extruded. The resulting freeze-dried, compressed MXene layer was laminated to the outer layer of the composite hydrogel. Gellan gum solution was then poured onto this outer layer to stabilize and protect the sandwich structure. After cooling for 1 hour, the sandwich composite hydrogel was immersed in a 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) for 8 hours. The sandwich-structured composite hydrogel was then immersed in anhydrous ethanol (with a volume ratio of anhydrous ethanol to hydrogel greater than 5) for three 8-hour soaks, with the solution replaced between soaks. The resulting sandwich-structured composite hydrogel was then dried using supercritical liquid carbon dioxide to obtain the final aerogel sample (GG20 / MX6).

[0046] Example 3

[0047] 400 mg of low-acyl gellan gum was added to 18 mL of deionized water and stirred at 115°C for 30 minutes until the low-acyl gellan gum was completely dissolved, resulting in a homogeneous, transparent solution. 2 mL of MXene aqueous solution was added, and the mixture was heated to 115°C and stirred for 30 minutes until the MXene and gellan gum solutions were completely mixed, resulting in a homogeneous, black solution. The solution was poured into a mold, cooled, and allowed to stand for 3 hours to obtain a composite hydrogel. 7 mL of the MXene aqueous solution was freeze-dried and the freeze-dried product was mechanically compressed. The resulting freeze-dried, compressed MXene layer was laminated to the outer layer of the composite hydrogel. Gellan gum solution was then poured onto this outer layer to stabilize and protect the sandwich structure. After cooling for 1 hour, the sandwich composite hydrogel was immersed in a 0.1 M ZrOCl2·8H2O solution (the volume ratio of ZrOCl2·8H2O solution to hydrogel was greater than 5) for 8 hours. The sandwich-structured composite hydrogel was then immersed in anhydrous ethanol (with a volume ratio of anhydrous ethanol to hydrogel greater than 5) for three 8-hour soaks, with the solution replaced between soaks. The resulting sandwich-structured composite alcohol gel was then dried using supercritical liquid carbon dioxide to obtain the final aerogel sample (GG20 / MX2).

[0048] Example 4

[0049] 400 mg low acyl kollagen was added into 20 mL deionized water, then stirred at 115℃ for 30 min until the low acyl kollagen was completely dissolved to obtain a uniform transparent solution. The above solution was poured into a mold, and after cooling and standing for 3 h, a composite hydrogel was obtained. 7 mL MXene aqueous solution was freeze-dried, and the freeze-dried product was physically and mechanically extruded and compressed to obtain a MXene freeze-dried and compressed layer, which was attached to the outer layer of the composite hydrogel, and then kollagen solution was poured into the outer layer to stabilize and protect the overall sandwich structure. After cooling for 1 h, the sandwich structure composite hydrogel was soaked in a 0.1 M ZrOCl2·8H2O solution (the volume ratio of the ZrOCl2·8H2O solution to the hydrogel was greater than 5) for 8 h. Then the soaked sandwich structure composite hydrogel was soaked in anhydrous ethanol (the volume ratio of the anhydrous ethanol to the hydrogel was greater than 5) for 3 times, each time for 8 h, and the solution was replaced each time. The obtained sandwich structure composite alcohol hydrogel was treated by supercritical liquid carbon dioxide drying method to obtain the final aerogel sample (GG20 / MX0).

[0050] The aerogels obtained in the above four examples were subjected to thermal conductivity test, electromagnetic shielding test, and scanning electron microscope test, and the specific results are shown in the attached Figure 1 、 Figure 2 and Table 1. From the results, it can be seen that the sandwich structure biobased composite nanofiber aerogel electromagnetic shielding and heat insulation material can be obtained by using the method, which has a great application prospect in the field of electromagnetic shielding and heat insulation.

[0051]

[0052] Figure 2 The scanning electron microscope image shows that the sandwich structure biobased composite nanofiber aerogel sandwich layer is formed by interweaving nanofibers to form a nanoporous structure and wrapping the staggered and stacked MXene nanosheets.

[0053] As can be seen from Table 1, with the increase of the concentration of MXene, the thermal conductivity of the aerogel gradually increases, and the electromagnetic shielding effectiveness gradually increases. Therefore, the sandwich structure biobased composite nanofiber aerogel material of the present application has a good application prospect in electromagnetic shielding or heat insulation materials, or electromagnetic shielding and heat insulation materials.

[0054] After the embodiments of the present application are described in detail, those skilled in the art can clearly understand that various changes and modifications can be made without departing from the scope and spirit of the above application, and any simple modification, equivalent change and modification made according to the technical essence of the present application to the above examples are within the scope of the technical solution of the present application, and the present application is not limited to the implementation modes shown in the examples.

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): mixing the gellan gum solution obtained in step 1) with a hot MXene aqueous solution at 115° C. and cooling 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 freeze-dried compressed MXene 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 to harden it, thereby obtaining 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 to 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 organogel; 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 step 1), the volume ratio of low acyl gellan gum to water is 20 mg:1 mL; The conditions for heating and stirring in step 1) include: temperature of 35-115° C., time of 30 min, and stirring speed of 100-800 r / min; The mixing conditions in step 2) include: temperature of 110-130° C., time of 30 min, and 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 for 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-structured bio-based composite nanofiber aerogel material, wherein the sandwich-structured bio-based composite nanofiber aerogel material is obtained by the preparation method of a sandwich-structured bio-based composite nanofiber aerogel material according to any one of claims 1 to 3, and is characterized in that: The sandwich structure bio-based composite nanofiber aerogel material is used in electromagnetic shielding or thermal insulation materials, or electromagnetic shielding and thermal insulation materials.

5. The use of a sandwich structure bio-based composite nanofiber aerogel material according to claim 4, characterized in that: The sandwich-structured 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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