A lightweight super-elastic graphene aerogel with a constant positive Gaussian curvature hole structure and a preparation method and application thereof

Abstract

The application discloses a lightweight super-elastic graphene aerogel with a normal positive Gaussian curvature pore structure and a preparation method and application thereof. By using small-size and low-concentration graphene oxide nanosheets, a graphene aerogel pore structure with normal positive Gaussian curvature is constructed on the surface of spherical bubbles. The special pore structure is used to inhibit the slip of graphene sheets, improve the ability of the graphene aerogel to store elastic energy when compressed, and improve the compression elasticity of the graphene aerogel to 93.4%, which is 1.7 times that of a conventional zero-curvature pore structure aerogel, and the graphene aerogel has super-elasticity. Meanwhile, due to the reduced concentration of graphene oxide and the reduced geometric constraint on the initial bubbles, the bulk density of the graphene aerogel can be as low as 1.1 mg / cm 3 , and the graphene aerogel has excellent lightweight characteristics. The method is easy to obtain raw materials and simple in process, and provides a feasible path for the industrialization of graphene materials.

Description

Technical Field

[0001] This invention relates to the field of graphene technology, specifically to a lightweight, superelastic graphene aerogel with a pore structure of constant positive Gaussian curvature, its preparation method, and its applications. Background Technology

[0002] Graphene aerogel, a three-dimensional macroscopic porous material assembled from two-dimensional graphene sheets, combines the excellent intrinsic properties of graphene (such as high conductivity and high temperature resistance) with the lightweight and low-density characteristics of macroscopic porous materials. In recent years, it has shown great application potential in cutting-edge fields such as flexible wearable sensors, piezoresistive devices, high-efficiency adsorption materials, thermal management, and electromagnetic shielding.

[0003] Currently, the mainstream methods for preparing three-dimensional graphene aerogels mainly include template-directed methods, hydrothermal / solvothermal reduction methods, and direct freeze-drying methods. However, graphene aerogels prepared by existing technologies generally suffer from two structural and performance contradictions that are difficult to balance: First, conventional aerogels exhibit poor mechanical stability in their pore wall structure, suffering from severe brittleness and plastic deformation. Pores formed by traditional hydrothermal or freeze-drying methods are mostly based on the random growth of solvent crystals, resulting in pore walls that are predominantly flat polygons or irregular zero-curvature geometries. From a micromechanical perspective, this zero-curvature flat sheet structure is highly susceptible to severe stress concentration at the pore wall junctions when subjected to macroscopic compressive stress. Simultaneously, the lack of effective geometric constraints between the van der Waals stacked graphene sheets makes them highly prone to irreversible interlayer slippage, buckling, and even fracture.

[0004] Second, there is a sharp contradiction between extremely low density and structural integrity. To prevent the basic three-dimensional framework of the aerogel from shrinking and collapsing during freezing, drying, and reduction, existing techniques typically require the use of high concentrations of graphene oxide precursor solutions (usually much greater than 10 mg / mL) or the addition of large amounts of polymers as a supporting framework. This dependence on the initial concentration and supporting materials directly results in the final aerogel's bulk density being difficult to further reduce, typically hovering between a few and tens of mg / cm³. Summary of the Invention

[0005] To address the challenge of balancing low density and high mechanical stability in existing graphene aerogel materials, this invention provides a lightweight, superelastic graphene aerogel with a pore structure exhibiting constant positive Gaussian curvature, along with its preparation method and applications. This invention utilizes small-sized, low-concentration two-dimensional graphene material to construct an aerogel pore structure with constant positive Gaussian curvature on the surface of spherical bubbles. From a topological geometry perspective, the perfect spherical structure with constant positive Gaussian curvature can uniformly distribute external local compressive loads, improve interlayer stress transfer efficiency, and form recoverable elastic microfolds during buckling. This special pore structure suppresses graphene sheet slippage, enhancing the graphene aerogel's ability to store elastic energy under compressive strain. This results in a compressive elasticity 1.7 times (93.4%) that of conventional zero-curvature pore structure aerogels, exhibiting superelasticity. Simultaneously, due to the reduced graphene oxide concentration and decreased geometric constraint on the initial bubbles, the bulk density of this graphene aerogel can be as low as 1.1 mg / cm³. 3 This method possesses excellent lightweight properties. The raw materials are readily available, and the process is simple, providing a practical and feasible path for the industrialization of graphene materials.

[0006] Specifically, it includes the following steps: (1) Add the surfactant aqueous solution to the mixed solution of reducing agent and graphene oxide, mix evenly, introduce air bubbles with a diameter of 30~250 μm, and make the foaming volume ratio of the mixed solution reach 1.5~3.0 to obtain foamed graphene oxide dispersion; the graphene oxide sheet diameter is 0.8~10 μm; wherein the ratio of the graphene oxide sheet diameter to the diameter of the air bubble is 0.003~0.04.

[0007] The purpose of using a small-diameter, low-concentration two-dimensional graphene material dispersion is to enable the two-dimensional material nanosheets to adhere tightly along the edge of the bubble, avoiding damage to the three-dimensional shape of the bubble, thereby forming a pore structure with a constant positive Gaussian curvature.

[0008] (2) The foamed graphene oxide dispersion is heated at 50~80°C for 2~10 h to obtain pre-reduced graphene oxide hydrogel; the temperature and time within this limit can preliminarily shape the graphene hydrogel skeleton. (3) After freezing the pre-reduced graphene oxide hydrogel, heat it to 90~110°C for 2~10 h to perform a second reduction, and obtain a second-reduced graphene oxide hydrogel. (4) After washing and drying the secondary reduced graphene oxide hydrogel, heat it at 250~400°C for 0.5~4 h to obtain a lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure. Within this temperature and time limit, the two-dimensional graphene material can be reduced relatively thoroughly without destroying the internal microstructure, thereby endowing the aerogel with a unique constant positive Gaussian curvature pore structure and lightweight superelastic properties.

[0009] Among them, graphene oxide includes, but is not limited to, monolayer graphene oxide, few-layer graphene oxide, and graphite oxide.

[0010] Furthermore, the graphene oxide has a sheet diameter of 1~3 μm.

[0011] Furthermore, the reducing agent is one or more of hydroiodic acid, hydrazine hydrate, sodium ascorbate, ethylenediamine, and stannous chloride; the mass ratio of the reducing agent to graphene oxide is 0.1~2.

[0012] Further, the surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, cocamidopropyl betaine, sodium lauroyl amphoteric acetate, polyethylene glycol octylphenyl ether, and polyvinylpyrrolidone; the mass ratio of the surfactant to graphene oxide is 0.5~2.

[0013] Furthermore, the method of introducing air bubbles is one or more of mechanical stirring, magnetic stirring, and air pump inflation. The foaming pore size and foaming rate of the method are adjustable to meet the foaming needs of two-dimensional graphene material dispersions of different volumes.

[0014] Furthermore, in step (4), a mixture of deionized water and anhydrous ethanol is used for cleaning.

[0015] In some embodiments, the preparation method may be: (1) Prepare two-dimensional graphene material dispersion, reducing agent solution and surfactant solution respectively; (2) Add the reducing agent solution obtained in step (1) to the two-dimensional graphene material dispersion and mix evenly to obtain a reducing agent / two-dimensional graphene material mixed dispersion; the sheet diameter of the two-dimensional graphene material is 0.8~10 μm, preferably 1~3 μm; the concentration of the two-dimensional graphene material dispersion is 2~10 mg / mL, preferably 3~6 mg / mL. (3) Slowly add the surfactant solution obtained in step (1) to the mixed dispersion obtained in step (2), stir evenly, and then uniformly introduce air bubbles with a diameter of 30~250 μm into the mixture so that the foaming volume ratio of the mixture reaches 1.5~3.0, and obtain foamed graphene material dispersion. (4) Slowly transfer the foamed graphene material dispersion obtained in step (3) into the mold. After it self-levels, use a smooth stainless steel plate to scrape off the large air bubbles on the surface. Then seal it with plastic wrap and heat it for pre-reduction to obtain pre-reduced graphene hydrogel. (5) The pre-reduced graphene hydrogel obtained in step (4) is completely frozen, and then heated to perform a second reduction to obtain a second-reduced graphene hydrogel. (6) The secondary reduced graphene hydrogel obtained in step (5) is thoroughly solvent-displaced using a mixed solution of deionized water and anhydrous ethanol, followed by heating for drying and final reduction to obtain the lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure. The volume ratio of the deionized water to anhydrous ethanol mixed solution is 100:0~0:100, and the displacement time is controlled within 5~24 h. Within this limited ratio and time, the residual reducing agent and foaming agent in the hydrogel can be replaced more thoroughly, avoiding decomposition and damage to the internal microstructure of the aerogel during the subsequent final reduction. The addition of anhydrous ethanol is intended to accelerate the dissolution of the reducing agent and foaming agent, improve the cleaning efficiency, and reduce the surface tension during the drying process to avoid damage to the internal microstructure of the aerogel. The criterion for complete displacement is that the displacement solution appears clear, transparent, and colorless under 6500K positive white light irradiation.

[0016] This invention also provides a lightweight superelastic graphene aerogel with a pore structure of constant positive Gaussian curvature prepared by the above method and its application.

[0017] The density of the graphene aerogel is 1~20 mg / cm³. 3 The pore size is 10~400 μm, and its density is preferably 1~10 mg / cm³. 3 .

[0018] The aerogel thickness ranges from 1 to 4500 mm, and the base area ranges from 0.0001 to 2 m². 2 .

[0019] The beneficial effects of this invention are as follows: By using small-sized, low-concentration two-dimensional graphene materials, a pore topology with constant positive Gaussian curvature is successfully constructed through self-assembly on the surface of spherical bubbles, effectively improving the interlayer stress transfer efficiency and generating recoverable elastic microfolds under pressure. This special pore structure can significantly suppress the relative slippage between graphene sheets, thereby greatly enhancing the aerogel's ability to store elastic energy during compression, increasing its compression elastic recovery rate to approximately 1.7 times (up to 93.4%) that of conventional zero-curvature pore structure aerogels, exhibiting excellent superelasticity. Simultaneously, due to the reduced concentration of two-dimensional graphene materials and the weakened geometric constraint on the initial bubbles, the resulting aerogel can have a volume density as low as 1 mg / cm³, possessing significant lightweight properties. Furthermore, this method has the advantages of readily available raw materials, simple process, and low cost, which helps to accelerate the industrialization of graphene materials. Attached Figure Description

[0020] Figure 1 The mechanism for constructing a hole structure with constant positive Gaussian curvature; Figure 2 The images show scanning electron microscope (SEM) images of the pore structures of the graphene aerogels obtained in Example 1 and Comparative Example 1, with a scale bar of 400 μm. Figure 3 The compression cycle mechanical curves of the graphene aerogels obtained in Example 1 and Comparative Example 1 are shown. Figure 4 An optical photograph of the graphene aerogel obtained in Example 1. Detailed Implementation

[0021] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0022] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0023] The few-layer graphene oxide described in this invention is graphene oxide with 1-10 layers.

[0024] In this invention, the bubble size can be controlled by the rotation speed, and the bubble size is negatively correlated with the rotation speed. During the preparation process, those skilled in the art can observe the bubble size using a microscope and monitor and adjust the rotation speed in real time based on the observation results.

[0025] The embodiments of the present invention will be further described below with reference to several examples.

[0026] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0027] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0028] Example 1 (1) Prepare a 0.5 L volume of monolayer graphene oxide dispersion (0.8 μm diameter) with a concentration of 4 mg / mL, and add 30 mL of sodium ascorbate solution with a mass fraction of 20 wt.% as a reducing agent. Stir the mixture at 800 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain a sodium ascorbate / monolayer graphene oxide mixed dispersion; (2) Prepare 30 mL of sodium dodecylbenzenesulfonate solution with a concentration of 7 wt.% as a surfactant, and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 400 rpm for 5 min at room temperature to make it uniform. Then, increase the stirring speed to 2400 rpm and continue stirring at room temperature for 10 min to introduce bubbles, so that the foaming volume ratio of the mixed solution reaches 2.3 and the initial bubble diameter is 91 μm, to obtain a foamed monolayer graphene oxide dispersion with a bubble structure of constant positive Gaussian curvature; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally and leveles, use a scraper to gently scrape away the large air bubble defects on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 70°C for 6 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -18°C for 5 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 90°C for 6 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 5 L of deionized water and fully displaced for 5 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 5 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 10:90) and further displaced for 5 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) is transferred into an oven and dried at 40°C for 3 h. Then, the temperature is further increased to 320°C for final reduction for 2 h. After the reaction is completed and the material is naturally cooled, the aforementioned lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure is obtained. (7) A lightweight, superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained, with a bottom surface size of 25.4 × 15.7 cm, a thickness of 1.7 cm, and a density of 1.1 mg / cm³. 3 Its average pore size is 355 μm, and its compressive elastic recovery rate is 93.4%.

[0029] Example 2 (1) Prepare a 0.5 L volume of graphene oxide dispersion (4 μm diameter) with a concentration of 7 mg / mL, and add 20 mL of 20 wt.% hydrazine hydrate solution as a reducing agent. Stir the mixture at 800 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain a hydrazine hydrate / graphene oxide mixed dispersion. (2) Prepare 40 mL of a 15 wt.% cocamidopropyl betaine solution as a surfactant and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 400 rpm for 5 min at room temperature to make it uniform. Then, increase the stirring speed to 2400 rpm and continue stirring at room temperature for 10 min to introduce bubbles, so that the foaming volume ratio of the mixed solution reaches 1.8 and the initial bubble diameter is 162 μm, to obtain a foamed few-layer graphene oxide dispersion with a bubble structure of constant positive Gaussian curvature; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally and leveles, use a scraper to gently scrape away the large air bubble defects on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 75°C for 8 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -23°C for 5 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 95°C for 6 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 5 L of deionized water and fully displaced for 5 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 5 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 20:80) and further displaced for 5 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) is transferred into an oven and dried at 50°C for 3 h. Then, the temperature is further increased to 330°C for final reduction for 2 h. After the reaction is completed and the material is naturally cooled, the aforementioned lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure is obtained. (7) A lightweight, superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained, with a bottom surface size of 24.2 × 16.8 cm, a thickness of 1.3 cm, and a density of 3.2 mg / cm³. 3 Its average pore size is 395 μm, and its compressive elastic recovery rate is 91.2%.

[0030] Example 3 (1) Prepare a 0.5 L volume of graphite oxide dispersion (10 μm diameter) with a concentration of 3 mg / mL, and add 30 mL of 25 wt.% hydroiodic acid solution as a reducing agent. Stir the solution at 800 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain a hydroiodic acid / graphite oxide mixed dispersion; (2) Prepare 40 mL of a 15 wt.% polyvinylpyrrolidone solution as a surfactant and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 400 rpm for 5 min at room temperature to make it uniform. Then, use a mobile air compressor to connect a porous bubble stone, immerse the bubble stone in the mixed dispersion, and introduce bubbles by aeration for 0.5 min at room temperature, so that the foaming volume ratio of the mixed solution reaches 3.0 and the initial bubble diameter is 246 μm, to obtain a foamed graphite oxide dispersion with a bubble structure of constant positive Gaussian curvature; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally, use a scraper to gently scrape away the large air bubble defects on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 80°C for 8 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -28°C for 5 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 100°C for 6 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 10 L of deionized water and fully displaced for 6 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 10 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 40:60) and further displaced for 6 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) is transferred into an oven and dried at 60°C for 3 h. Then, the temperature is further increased to 350°C for final reduction for 2 h. After the reaction is completed and the material is naturally cooled, the aforementioned lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure is obtained. (7) A lightweight, superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained, with a bottom surface size of 25.2 × 15.8 cm, a thickness of 1.0 cm, and a density of 6.5 mg / cm³. 3 Its average pore size is 371 μm, and its compressive elastic recovery rate is 86.2%.

[0031] Example 4 (1) Prepare a 0.5 L graphene oxide dispersion (5 μm in diameter) with a concentration of 2 mg / mL, and add 30 mL of ethylenediamine solution with a mass fraction of 20 wt.% as a reducing agent. Stir the mixture at 500 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain an ethylenediamine / monolayer graphene oxide mixed dispersion; (2) Prepare 30 mL of a 10 wt.% polyethylene glycol octylphenyl ether solution as a surfactant and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 400 rpm for 5 min at room temperature to make it uniformly mixed. Then, increase the stirring speed to 1800 rpm and continue stirring at room temperature for 5 min to introduce bubbles, so that the foaming volume ratio of the mixed solution reaches 1.8 and the initial bubble diameter is 194 μm, thus obtaining a foamed graphite oxide dispersion with a bubble structure of constant positive Gaussian curvature; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally, use a scraper to gently scrape away the large air bubbles on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 50°C for 10 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -23°C for 3 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 110°C for 2 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 5 L of deionized water and fully displaced for 5 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 5 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 30:70) and further displaced for 5 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) was transferred into an oven and dried at 35°C for 5 h. Then the temperature was further increased to 400°C for final reduction for 0.5 h. After the reaction was completed and the mixture was naturally cooled, the aforementioned lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained. (7) A lightweight, superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained, with a bottom surface size of 25.5 × 15.7 cm, a thickness of 0.7 cm, and a density of 10.6 mg / cm³. 3 Its average pore size is 274 μm, and its compressive elastic recovery rate is 82.7%.

[0032] Example 5 (1) Prepare a 0.5 L graphene oxide dispersion (2 μm in diameter) with a concentration of 10 mg / mL, and add 30 mL of 25 wt.% hydrazine hydrate solution as a reducing agent. Stir the mixture at 600 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain a hydrazine hydrate / monolayer graphene oxide mixed dispersion; (2) Prepare 30 mL of sodium lauroylamphoacetate solution with a concentration of 5 wt.% as a surfactant, and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 300 rpm for 5 min at room temperature to make it uniformly mixed. Then, increase the stirring speed to 1600 rpm and continue stirring at room temperature for 5 min to introduce bubbles, so that the foaming volume ratio of the mixed solution reaches 1.5 and the initial bubble diameter is 42 μm, to obtain a foamed graphite oxide dispersion with a bubble structure of constant positive Gaussian curvature; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally and leveles, use a scraper to gently scrape away the large air bubble defects on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 80°C for 2 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -15°C for 6 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 90°C for 10 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 5 L of deionized water and fully displaced for 5 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 5 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 20:80) and further displaced for 5 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) is transferred into an oven and dried at 50°C for 4 h. Then, the temperature is further increased to 250°C for final reduction for 4 h. After the reaction is completed and the material is naturally cooled, the aforementioned lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure is obtained. (7) A lightweight, superelastic graphene aerogel with a constant positive Gaussian curvature pore structure was obtained, with a bottom surface size of 25.8 × 14.4 cm, a thickness of 0.4 cm, and a density of 19.8 mg / cm³. 3 Its average pore size is 287 μm, and its compressive elastic recovery rate is 77.2%.

[0033] Comparative Example 1 (1) Prepare a 0.5 L volume of monolayer graphene oxide dispersion (30 μm diameter) with a concentration of 10 mg / mL, and add 60 mL of sodium ascorbate solution with a mass fraction of 20 wt.% as a reducing agent. Stir the mixture at 800 rpm for 10 min at room temperature using a magnetic stirrer to ensure uniform mixing and obtain a sodium ascorbate / monolayer graphene oxide mixed dispersion; (2) Prepare 30 mL of sodium dodecylbenzenesulfonate solution with a concentration of 7 wt.% as a surfactant, and slowly add it to the mixed dispersion obtained in step (1). Use a magnetic stirrer to initially stir at 400 rpm for 5 min at room temperature to make it uniformly mixed. Then, increase the stirring speed to 2400 rpm and continue stirring at room temperature for 10 min to introduce bubbles, so that the foaming volume ratio of the mixed solution reaches 1.5, and obtain a foamed monolayer graphene oxide dispersion; (3) Slowly pour the foamed dispersion obtained in step (2) into a stainless steel mold with a bottom surface size of 30×20 cm. After it flows naturally and leveles, use a scraper to gently scrape away the large air bubble defects on the surface of the system. Then, tightly cover the surface of the mold with a sealing plastic wrap and transfer the whole thing into an oven. Pre-reduction at 70°C for 6 h to obtain pre-reduced graphene hydrogel. (4) The pre-reduced graphene hydrogel obtained in step (3) was transferred to a low-temperature freezer and frozen at -18°C for 5 h to further fix its internal structure. Then it was transferred to an oven and reduced again at 90°C for 6 h to obtain a secondary reduced graphene hydrogel; (5) The secondary reduced graphene hydrogel obtained in step (4) was completely immersed in 5 L of deionized water and fully displaced for 5 h (complete immersion was achieved by placing a stainless steel pressure block on top of the hydrogel). Then it was transferred and completely immersed in 5 L of deionized water / anhydrous ethanol mixed solution (the mass ratio of the mixed solution was 10:90) and further displaced for 5 h to obtain the displaced graphene hydrogel; (6) The replaced graphene hydrogel obtained in step (5) is transferred into an oven and dried at 40°C for 3 h. Then, the temperature is further increased to 320°C for final reduction for 2 h. After the reaction is completed and the material is naturally cooled, the graphene aerogel with the aforementioned conventional zero-curvature pore structure can be obtained. (7) The graphene aerogel obtained had a bottom surface size of 25×15 cm, a thickness of 1.2 cm, and a density of 13.5 mg / cm³. 3 Its average pore size is 524 μm, and its compressive elastic recovery rate is 54.3%.

[0034] The mechanism of constructing aerogels with constant positive Gaussian curvature pore structure in this invention is as follows: Figure 1 As shown. In conventional preparation methods, to improve the stability of the aerogel structure, large-diameter, high-concentration two-dimensional graphene materials are often selected as precursors. In this case, the bubbles are subject to greater geometric constraints, and the pore structure undergoes significant deformation. This invention, by using small-sized, low-concentration two-dimensional graphene materials as precursors, greatly reduces the geometric constraints on the bubbles during the foaming process, allowing the two-dimensional nanosheets to be tightly arranged along the bubble edges. This enables the successful construction and locking of a pore structure with constant positive Gaussian curvature at extremely low densities. Figure 2 ).like Figure 3 As shown, compared to the 54.3% compressive elasticity (compression recovery rate, calculated as: elastic recovery segment strain / total strain) of conventional zero-curvature porous aerogels, the graphene aerogel of this invention achieves a compressive elasticity as high as 93.4% (an improvement of approximately 1.7 times), exhibiting extremely superior energy storage and deformation recovery capabilities. This indicates that this characteristic structure can uniformly disperse external local compressive loads, improve interlayer stress transfer efficiency, and effectively suppress graphene sheet slippage. Furthermore, as... Figure 4 As shown, this process has good scalability and good potential for engineering fabrication.

[0035] In summary, this invention eliminates the need for complex and demanding molding conditions, achieving precise control of microstructure through a simple process to construct a lightweight, superelastic graphene aerogel with a pore structure exhibiting constant positive Gaussian curvature. This method utilizes readily available raw materials, allows for flexible control of the prepared size, and facilitates the industrial-scale mass production of large-scale bulk materials, laying a solid foundation for the practical applications of high-performance graphene aerogels in areas such as actuation component cushioning, building material sound absorption, and flexible sensing.

[0036] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A method for preparing a lightweight, superelastic graphene aerogel with a pore structure of constant positive Gaussian curvature, characterized in that, It includes the following steps: (1) Add the surfactant aqueous solution to the mixed solution of reducing agent and graphene oxide, mix evenly, introduce air bubbles with a diameter of 30~250 μm, and make the foaming volume ratio of the mixed solution reach 1.5~3.0 to obtain foamed graphene oxide dispersion; the graphene oxide sheet diameter is 0.8~10 μm; the graphene oxide concentration is 2~10 mg / mL; wherein the ratio of the graphene oxide sheet diameter to the diameter of the air bubble is 0.003~0.04; (2) The foamed graphene oxide dispersion was heated at 50~80°C for 2~10 h to obtain a pre-reduced graphene oxide hydrogel; (3) After freezing the pre-reduced graphene oxide hydrogel, heat it to 90~110°C for 2~10 h to perform a second reduction, and obtain a second-reduced graphene oxide hydrogel. (4) After washing the secondary reduced graphene oxide hydrogel, it is dried and heated at 250~400°C for 0.5~4 h to obtain a lightweight superelastic graphene aerogel with a pore structure of constant positive Gaussian curvature.

2. The method according to claim 1, characterized in that, The graphene oxide sheets have a diameter of 1~3 μm.

3. The method according to claim 1, characterized in that, The mass ratio of reducing agent to graphene oxide is 0.1~2; the mass ratio of surfactant to graphene oxide is 0.5~2.

4. The method according to claim 1, characterized in that, The surfactant is one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, cocamidopropyl betaine, sodium lauroyl amphoteric acetate, polyethylene glycol octylphenyl ether, and polyvinylpyrrolidone; the reducing agent is one or more of hydroiodic acid, hydrazine hydrate, sodium ascorbate, ethylenediamine, and stannous chloride.

5. The method according to claim 1, characterized in that, The method of introducing air bubbles is one or more of mechanical stirring, magnetic stirring, and air pump inflation.

6. The method according to claim 1, characterized in that, In step (4), a mixture of deionized water and anhydrous ethanol is used for cleaning.

7. A lightweight superelastic graphene aerogel with a pore structure having constant positive Gaussian curvature prepared by the method described in claim 1.

8. The lightweight superelastic graphene aerogel with a pore structure of constant positive Gaussian curvature according to claim 7, characterized in that, Density is 1~20 mg / cm³ 3 The pore size is 10~400 μm.

9. The lightweight superelastic graphene aerogel with a constant positive Gaussian curvature pore structure according to claim 7, characterized in that, The aerogel thickness ranges from 1 to 4500 mm, and the base area ranges from 0.0001 to 2 m². 2 .

10. An application of the lightweight, superelastic graphene aerogel as described in claim 7.

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