CN107804839B - High-elasticity graphene aerogel and preparation method thereof - Google Patents
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Abstract
The invention relates to a high-elasticity aerogel and a preparation method thereof, wherein the preparation method comprises the following steps: (1) preparing graphene oxide sol; (2) preparing graphene hydrogel; (3) a drying step, characterized by further comprising, between step (2) and step (3): (i) reinforcing the skeleton; the step (i) is performed as follows: (a) dissolving a macromolecular compound in a good solvent to prepare a macromolecular solution; (b) soaking the graphene hydrogel prepared in the step (2) in the high polymer solution to obtain graphene gel; (c) soaking the graphene gel in a poor solvent. According to the invention, the graphene sheet layers are wrapped and connected by the macromolecular chains, so that the framework cross-linking points and the framework strength are improved, the elasticity of the graphene aerogel can be effectively improved, and the high-elasticity graphene aerogel material with excellent mechanical properties is prepared.
Description
Technical Field
The invention relates to the technical field of nano materials, in particular to a high-elasticity graphene aerogel and a preparation method thereof.
background
Aerogel materials are also called as 'solid smoke', are known solid materials with the lowest density in the world at present, are formed by stacking nanoparticles on a microstructure to form a nano porous structure, have the characteristics of low density, high specific surface area and low thermal conductivity, and have wide application prospects as heat insulation materials, adsorption materials and the like.
The aerogel material which is the most widely researched and technically mature at present is silicon dioxide aerogel, is prepared by a sol-gel method and then supercritical drying, and has extremely high porosity (not less than 85%), extremely large specific surface area (250-800 m 2/g), lower density (0.03-0.50 g/cm 3) and lower heat conductivity coefficient (0.01-0.03W/(m.K)). however, most of the aerogel including the silicon dioxide aerogel is formed by stacking particles, the contact area between the particles is small, the interaction force is weak, so the characteristics of easy powder falling and high brittleness are presented macroscopically, and the application of the aerogel in the field of elastic heat insulation materials is limited.
Graphene is a sheet-like structure carbon material consisting of a single carbon atom layer, and has excellent mechanical properties and electrical properties. Due to the special lamellar structure, the graphene has certain flexibility and flexibility, so that the graphene is very suitable for being used as a composition unit of an elastic aerogel material. The graphene lamellar structures can be connected through pi-pi interaction to form adjustable interaction force, and the three-dimensional gel with an integral structure is favorably formed. The patent application documents with application publication numbers of CN101941693A, CN102910625A and CN102887508A all relate to the preparation of graphene oxide aerogel materials, but the regulation and characterization of the elastic properties thereof are not mentioned yet. Under the stress condition, the graphene sheet layers are easy to displace, so that the graphene sheet layers move to a new equilibrium position to form a new stable state, and the characteristic that the graphene does not have elasticity or has weaker elasticity after being stressed is shown.
In terms of improving the elasticity of the graphene oxide material, the existing methods include: and (3) reducing graphene oxide by using a weak reducing agent, increasing the wall thickness of the aerogel structural unit and adding a cross-linking agent. The Lihui topic group of Harbin Industrial university adopts ethylenediamine as a reducing agent and sodium tetraborate as a crosslinking agent to prepare elastic Graphene aerogel (Xiaoang Xu, Qiangqiang Zhang, Yikang Yu, Wenli Chen, Han Hu and Hui Li. Naturally doped Graphene Aerogels with super elastic and porous Poisson's ratio. adv. Mater.28,9223-9230 (2016)); the qizhongshan project group at university of major connective engineering selected a microwave reduction method to prepare elastic graphene aerogel (Han Hu, zongbenzhao, Wubo Wan, Yury gootsi, and Jieshan qiu.ultralight and Highly compressive graphene aerogels.adv.mater.25,2219-2223 (2013)). The patent application publication No. CN105692607A discloses that gamma-oxo-1-pyrenebutyric acid is selected as a binder to prepare a graphene compressible aerogel.
The modes have certain requirements on a reducing agent system and a crosslinking system, and a universal method for developing a high-elasticity graphene aerogel material suitable for various systems by modifying a graphene aerogel system is not reported for a long time.
Disclosure of Invention
technical problem to be solved
The invention provides a high-elasticity graphene aerogel and a preparation method thereof, aiming at the problems of poor elasticity of the existing graphene aerogel material and poor general applicability of the existing preparation method for improving the elasticity of the graphene aerogel material. And the elasticity of the graphene aerogel is obviously enhanced after drying.
(II) technical scheme
In order to solve the technical problems, the invention provides the following technical scheme:
A preparation method of a high-elasticity graphene aerogel, comprising the following steps of: (1) preparing graphene oxide sol; (2) preparing graphene hydrogel; (3) a drying step, further comprising between the step (2) and the step (3): (i) reinforcing the skeleton; the step (i) is performed as follows:
(a) dissolving a macromolecular compound in a good solvent to prepare a macromolecular solution;
(b) Soaking the graphene hydrogel prepared in the step (2) in the high polymer solution to obtain graphene gel;
(c) And soaking the graphene gel in a poor solvent of a high molecular compound.
Preferably, the polymer compound is selected from any one of polyacrylonitrile compounds, polyacrylamide compounds, polyamide compounds, polyester compounds and polysulfone compounds; and
the molecular weight of the polymer compound is 5000-.
Further preferably, the concentration of the polymer solution is 0.5 to 5 wt%.
further preferably, the good solvent is any one selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, and tetrahydrofuran.
More preferably, the graphene hydrogel is soaked in the polymer solution for not less than 2 times, preferably 2 to 4 times, and the single soaking time is not less than 3 days, preferably 3 to 6 days.
preferably, the poor solvent is selected from liquid alcohol compounds or liquid ketone compounds, preferably from the group consisting of ethanol, isopropanol and acetone.
Further preferably, the soaking times of the graphene gel treated in the step (b) in the poor solvent are not less than 2 times, preferably 2 to 4 times, and the time of single soaking is not less than 3 days, preferably 3 to 5 days.
Preferably, the graphene hydrogel is prepared by a chemical reduction method, and the process conditions are as follows:
the reducing agent used is a reducing agent which is water-soluble per se and the oxidized product of which is also water-soluble, and is preferably selected from hydrazine hydrate, sodium bisulfite, ascorbic acid and ethylenediamine;
The mass ratio of the graphene oxide to the reducing agent is 1: (0.5 to 5);
The temperature for the reduction reaction is 40-200 ℃, and the reaction time is not less than 12 hours, preferably 12-20 hours.
Preferably, the concentration of the graphene oxide sol is 2-15 mg/mL, the pH of the graphene oxide sol is 5-7, the potassium ion content is below 0.04 wt%, the manganese ion content is below 0.07 wt%, the sodium ion number is below 0.05 wt%, the number of graphene oxide sheets is 1-3, the thickness of each sheet is 1-3nm, and the diameter of each sheet is 1-30 μm; and/or
The drying adopts a supercritical drying method.
The invention also provides high-elasticity graphene aerogel prepared by the preparation method.
(III) advantageous effects
The technical scheme of the invention has the following advantages:
(1) According to the invention, the skeleton of the graphene aerogel is enhanced by adopting a macromolecule, the macromolecule is wrapped and connected between graphene sheet layers through conformation transformation in a poor solvent, the number of structural cross-linking points is increased, the elasticity of the graphene aerogel is obviously improved, and the prepared graphene aerogel has high elasticity and a three-dimensional structure and can be used as an elastic thermal insulation material and an electrochemical material.
(2) The framework reinforcement method adopted by the invention is realized by soaking the macromolecular good solvent solution and the macromolecular poor solvent, the process is simple and easy to operate, and the method is suitable for graphene aerogel prepared by different reducing agent systems and has universality.
Drawings
FIG. 1 is a flow chart of a preparation method used in the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
As shown in fig. 1, the preparation method of the high-elasticity graphene aerogel provided by the invention comprises the following steps:
(1) and preparing the graphene oxide sol.
The step can adopt a Hummers method to prepare graphene oxide. The used preparation raw materials comprise graphite powder (particles with the granularity of less than 30 mu m, the content is more than 95 percent, the carbon content is more than 99 percent), concentrated sulfuric acid (95 to 98 percent), potassium permanganate, sodium nitrate, hydrogen peroxide (30 percent), hydrochloric acid, barium chloride and hydrazine hydrate (80 percent). The method specifically comprises the following steps: a250 mL reaction bottle is assembled in an ice-water bath, a proper amount of concentrated sulfuric acid is added, a solid mixture of 2g of graphite powder and 1g of sodium nitrate is added under stirring, 6g of potassium permanganate is added in times, the reaction temperature is controlled not to exceed 20 ℃, the mixture is stirred and reacted for a period of time, then the temperature is raised to about 35 ℃, the mixture is continuously stirred for 30min, a certain amount of deionized water is slowly added, and after the mixture is continuously stirred for 20min, a proper amount of hydrogen peroxide is added to reduce the residual oxidant, so that the solution becomes bright yellow. The hot solution was filtered and washed with 5% HCl solution and deionized water until no sulfate was detected in the filtrate. And finally, putting the filter cake in a vacuum drying oven at 60 ℃ for full drying to obtain graphite oxide, and storing for later use. 100mg of graphite oxide is dispersed in 100g of aqueous solution to obtain a brownish yellow suspension, and then dispersed for 1 hour under the ultrasonic condition to obtain a stable dispersion. And then moving the graphene oxide into a four-mouth flask, heating to 80 ℃, dropwise adding 2mL of hydrazine hydrate, reacting for 24h under the condition, filtering, sequentially washing the obtained product with methanol and water for multiple times, fully drying in a vacuum drying oven at 60 ℃ to obtain graphene oxide with the number of layers of 1-3, the thickness of the sheet layer of 1-3nm and the diameter of the sheet of 1-30 microns, and storing for later use.
And adding water into the graphene oxide to prepare the graphene oxide hydrosol with the concentration of 2-15 mg/mL for subsequent steps.
(2) And preparing the graphene hydrogel.
According to the invention, the graphene hydrogel can be prepared by a chemical reduction method, a reducing agent with a certain content is added into the graphene oxide hydrosol, and after the graphene oxide hydrosol is uniformly mixed, the graphene oxide hydrosol undergoes a reduction reaction at a certain temperature and is gelled to form the graphene hydrogel. The reducing agent can reduce graphene oxide, remove oxygen-containing groups (such as epoxy groups, hydroxyl groups and carboxyl groups) on the surface of the graphene oxide, reduce the graphene oxide into graphene, and stack graphene sheets due to pi-pi interaction so as to form gel. The reducing agent used may be a reducing agent which is water-soluble in itself and the oxidized product is also water-soluble, such as any of hydrazine hydrate, sodium bisulfite, ascorbic acid, ethylenediamine. The mass ratio of the graphene oxide to the reducing agent may be 1: (0.5 to 5), for example, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1: 5. The temperature for the reduction reaction is 40-200 ℃, and the reaction time is not less than 12 hours, preferably 12-20 hours.
Besides the chemical reduction method, the graphene hydrogel can be prepared by other self-assembly methods. Such as ultrasonic dispersion. The method specifically comprises the following steps: ultrasonically dispersing the graphene oxide hydrosol in an ultrasonic cleaner for more than 12 hours, then sealing the graphene oxide hydrosol in a container, transferring the container into an oven, and keeping the container at 85 ℃ for 72 hours to obtain the graphene hydrogel.
Different from the existing graphene oxide aerogel preparation steps, the method adds the step (i) after the step (2): and (5) reinforcing the framework.
The method comprises the following steps:
(a) Dissolving a macromolecular compound in a good solvent to prepare a macromolecular solution;
(b) soaking the graphene hydrogel prepared in the step (2) in the high polymer solution to obtain graphene gel;
(c) And (c) soaking the graphene gel obtained after the treatment in the step (b) in a poor solvent of a high molecular compound.
Dissolving the macromolecular compound in a good solvent to prepare a solution, wherein the macromolecular compound is in an extended conformation. And soaking the graphene hydrogel obtained in the step into the graphene hydrogel, wherein the high molecules are diffused into the gel framework and are arranged in a stretched conformation in the gel pore channel. The high molecular compound refers to any one of polyacrylonitrile compounds, polyacrylamide compounds, polyamide compounds, polyester compounds and polysulfone compounds, and the molecular weight is 5000-200000. The good solvent comprises water-soluble solvents such as N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran and the like, has good dissolving capacity for high polymers, and enables high molecular chains to stretch in the good solvent. The polymer solution has a mass concentration of 0.5 to 10% (for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%). The graphene hydrogel is soaked in the polymer solution for multiple times, so that the polymer completely enters the interior of the gel framework, the soaking time is more than or equal to 2 times and can be 2-4 times, the single soaking time is more than or equal to 3 days, preferably 3-6 days, and the mass fraction of water in the soaked graphene gel is less than or equal to 1%.
And (c) soaking the graphene gel obtained after the treatment in the step (b) in a poor solvent, and performing solvent replacement. The graphene aerogel with the macromolecules diffused therein is placed in a poor solvent for solvent replacement, when the poor solvent is diffused into the gel, the macromolecules are subjected to conformation transformation and are transformed from an unfolded conformation to a coiled conformation, so that the graphene aerogel is attached to a graphene gel framework, the framework cross-linking point and the framework strength are increased, the energy barrier required by deformation of the graphene aerogel under the condition of external force is increased, and the graphene aerogel is easier to recover to the initial position after deformation. The poor solvent is water-soluble solvent, and the polymer has poor solubility in the poor solvent, including alcohols and ketones, such as ethanol, isopropanol, acetone, etc. The graphene gel is soaked in the poor solvent of the high polymer for multiple times, so that the high polymer is completely converted into a coiled conformation, the soaking time is more than or equal to 2 times, for example, 2-4 times, and the single soaking time is more than or equal to 3 days, for example, 3-5 days.
(3) And drying the graphene gel to obtain the graphene aerogel. The drying method in the step can be a supercritical drying method, and the method specifically comprises the following steps: and (2) taking carbon dioxide as a drying medium, putting the wet gel (namely the graphene gel soaked with the poor solvent) into a drying kettle, introducing carbon dioxide gas, pressurizing to 2-4 MPa, slowly heating to 50 ℃, and continuously pressurizing to 10-15 MPa to enable the carbon dioxide to enter a supercritical state. And (3) carrying an alcohol or ketone solvent in the graphene gel into a separation kettle by using carbon dioxide for separation, and after the solvent is completely carried out, reducing the pressure at a speed of 1-6 MPa/h until the pressure is restored to normal pressure, thus obtaining the high-elasticity graphene aerogel.
The invention also provides a high-elasticity graphene aerogel prepared by the preparation method, wherein the density of the graphene aerogel is 0.032-0.081 g/cm 3, the specific surface area is 156-317 m 2/g, the maximum rebound compression amount is 20-60%, and the rebound rate is high.
The following are examples of the present invention.
Example 1
And S11, preparing the graphene oxide sol.
Graphene oxide was prepared by Hummers method. The used preparation raw materials comprise graphite powder (particles with the granularity of less than 30 mu m, the content is more than 95 percent, the carbon content is more than 99 percent), concentrated sulfuric acid (95 to 98 percent), potassium permanganate, sodium nitrate, hydrogen peroxide (30 percent), hydrochloric acid, barium chloride and hydrazine hydrate (80 percent). The method specifically comprises the following steps: a250 mL reaction bottle is assembled in an ice-water bath, a proper amount of concentrated sulfuric acid is added, a solid mixture of 2g of graphite powder and 1g of sodium nitrate is added under stirring, 6g of potassium permanganate is added in times, the reaction temperature is controlled not to exceed 20 ℃, the mixture is stirred and reacted for a period of time, then the temperature is raised to about 35 ℃, the mixture is continuously stirred for 30min, a certain amount of deionized water is slowly added, and after the mixture is continuously stirred for 20min, a proper amount of hydrogen peroxide is added to reduce the residual oxidant, so that the solution becomes bright yellow. The hot solution was filtered and washed with 5% HCl solution and deionized water until no sulfate was detected in the filtrate. And finally, putting the filter cake in a vacuum drying oven at 60 ℃ for full drying to obtain graphite oxide, and storing for later use. 100mg of graphite oxide is dispersed in 100g of aqueous solution to obtain a brownish yellow suspension, and then dispersed for 1 hour under the ultrasonic condition to obtain a stable dispersion. And then moving the graphene oxide into a four-mouth flask, heating to 80 ℃, dropwise adding 2mL of hydrazine hydrate, reacting for 24h under the condition, filtering, sequentially washing the obtained product with methanol and water for multiple times, fully drying in a vacuum drying oven at 60 ℃ to obtain graphene oxide with the number of layers of 1-3, the thickness of the sheet layer of 1-3nm and the diameter of the sheet of 1-30 microns, and storing for later use.
And adding water into the graphene oxide to prepare the graphene oxide hydrosol with the concentration of 10mg/mL for subsequent steps.
S12, preparing the graphene hydrogel through a chemical reduction method.
And adding 100mg of ethylenediamine into 10mL of graphene oxide hydrosol with the concentration of 10mg/mL, and uniformly stirring. And (3) sealing the hydrosol in a hydrothermal kettle, and heating at 120 ℃ for 14h to fully perform reduction reaction and generate gel.
and S13, reinforcing the framework.
Weighing a certain mass of polyacrylonitrile with the number average molecular weight of 30000, dissolving in N, N-dimethylformamide, and preparing into a macromolecular solution with the mass concentration of 1%. The graphene hydrogel is soaked in a polymer solution with the volume of 10 times of that of the graphene hydrogel, and the polymer solution is replaced once every 3 days for 3 times in total. Then, the graphene gel was soaked in 10 times volume of ethanol, and the ethanol was replaced every 3 days for 3 times in total.
S14, drying the graphene gel to obtain the graphene aerogel.
And (3) putting the graphene gel treated by the S13 into supercritical drying equipment, introducing carbon dioxide until the pressure reaches 3MPa, heating the equipment to 50 ℃, continuously pressurizing to 15MPa, and taking out the ethanol solvent by using the supercritical carbon dioxide. And after the ethanol is completely removed, reducing the pressure to normal pressure at the speed of 2MPa/h, and taking out the sample to obtain the graphene aerogel material.
Through detection, the density of the high-elasticity graphene oxide aerogel prepared by the embodiment is 0.05g/cm 3, the specific surface area is 188m 2/g, the maximum rebound compression amount is 50%, and the rebound rate is more than or equal to 90%.
Example 2
And S21, preparing the graphene oxide sol.
Graphene oxide was prepared by Hummers method. The used preparation raw materials comprise graphite powder (particles with the granularity of less than 30 mu m, the content is more than 95 percent, the carbon content is more than 99 percent), concentrated sulfuric acid (95 to 98 percent), potassium permanganate, sodium nitrate, hydrogen peroxide (30 percent), hydrochloric acid, barium chloride and hydrazine hydrate (80 percent). The method specifically comprises the following steps: a250 mL reaction bottle is assembled in an ice-water bath, a proper amount of concentrated sulfuric acid is added, a solid mixture of 2g of graphite powder and 1g of sodium nitrate is added under stirring, 6g of potassium permanganate is added in times, the reaction temperature is controlled not to exceed 20 ℃, the mixture is stirred and reacted for a period of time, then the temperature is raised to about 35 ℃, the mixture is continuously stirred for 30min, a certain amount of deionized water is slowly added, and after the mixture is continuously stirred for 20min, a proper amount of hydrogen peroxide is added to reduce the residual oxidant, so that the solution becomes bright yellow. The hot solution was filtered and washed with 5% HCl solution and deionized water until no sulfate was detected in the filtrate. And finally, putting the filter cake in a vacuum drying oven at 60 ℃ for full drying to obtain graphite oxide, and storing for later use. 100mg of graphite oxide is dispersed in 100g of aqueous solution to obtain a brownish yellow suspension, and then dispersed for 1 hour under the ultrasonic condition to obtain a stable dispersion. And then moving the graphene oxide into a four-mouth flask, heating to 80 ℃, dropwise adding 2mL of hydrazine hydrate, reacting for 24h under the condition, filtering, sequentially washing the obtained product with methanol and water for multiple times, fully drying in a vacuum drying oven at 60 ℃ to obtain graphene oxide with the number of layers of 1-3, the thickness of the sheet layer of 1-3nm and the diameter of the sheet of 1-30 microns, and storing for later use.
And adding water into the graphene oxide to prepare the graphene oxide hydrosol with the concentration of 10mg/mL for subsequent steps.
S22, preparing the graphene hydrogel through a chemical reduction method.
And adding 100mg of ethylenediamine into 10mL of graphene oxide hydrosol with the concentration of 10mg/mL, and uniformly stirring. And (3) sealing the hydrosol in a hydrothermal kettle, and heating at 120 ℃ for 14h to fully perform reduction reaction and generate gel.
And S23, reinforcing the framework.
Weighing a certain mass of polysulfone with the number average molecular weight of 50000, dissolving the polysulfone in N, N-dimethylformamide, and preparing a macromolecular solution with the mass concentration of 0.5%. The graphene hydrogel is soaked in a polymer solution with the volume of 10 times of that of the graphene hydrogel, and the polymer solution is replaced once every 3 days for 3 times in total. Then, the graphene gel was soaked in 10 times volume of ethanol, and the ethanol was replaced every 3 days for 3 times in total.
S24, drying the graphene gel to obtain the graphene aerogel.
And (3) putting the graphene gel treated by the S13 into supercritical drying equipment, introducing carbon dioxide until the pressure reaches 3MPa, heating the equipment to 50 ℃, continuously pressurizing to 15MPa, and taking out the ethanol solvent by using the supercritical carbon dioxide. And after the ethanol is completely removed, reducing the pressure to normal pressure at the speed of 2MPa/h, and taking out the sample to obtain the graphene aerogel material.
Through detection, the density of the high-elasticity graphene oxide aerogel prepared by the embodiment is 0.035g/cm 3, the specific surface area is 195m 2/g, the maximum rebound compressibility is 55%, and the rebound resilience is more than or equal to 90%.
Example 3
and S31, preparing the graphene oxide sol.
Graphene oxide was prepared by Hummers method. The used preparation raw materials comprise graphite powder (particles with the granularity of less than 30 mu m, the content is more than 95 percent, the carbon content is more than 99 percent), concentrated sulfuric acid (95 to 98 percent), potassium permanganate, sodium nitrate, hydrogen peroxide (30 percent), hydrochloric acid, barium chloride and hydrazine hydrate (80 percent). The method specifically comprises the following steps: a250 mL reaction bottle is assembled in an ice-water bath, a proper amount of concentrated sulfuric acid is added, a solid mixture of 2g of graphite powder and 1g of sodium nitrate is added under stirring, 6g of potassium permanganate is added in times, the reaction temperature is controlled not to exceed 20 ℃, the mixture is stirred and reacted for a period of time, then the temperature is raised to about 35 ℃, the mixture is continuously stirred for 30min, a certain amount of deionized water is slowly added, and after the mixture is continuously stirred for 20min, a proper amount of hydrogen peroxide is added to reduce the residual oxidant, so that the solution becomes bright yellow. The hot solution was filtered and washed with 5% HCl solution and deionized water until no sulfate was detected in the filtrate. And finally, putting the filter cake in a vacuum drying oven at 60 ℃ for full drying to obtain graphite oxide, and storing for later use. 100mg of graphite oxide is dispersed in 100g of aqueous solution to obtain a brownish yellow suspension, and then dispersed for 1 hour under the ultrasonic condition to obtain a stable dispersion. And then moving the graphene oxide into a four-mouth flask, heating to 80 ℃, dropwise adding 2mL of hydrazine hydrate, reacting for 24h under the condition, filtering, sequentially washing the obtained product with methanol and water for multiple times, fully drying in a vacuum drying oven at 60 ℃ to obtain graphene oxide with the number of layers of 1-3, the thickness of the sheet layer of 1-3nm and the diameter of the sheet of 1-30 microns, and storing for later use.
And adding water into the graphene oxide to prepare graphene oxide hydrosol with the concentration of 6mg/mL for subsequent steps.
S32, preparing the graphene hydrogel through a chemical reduction method.
0.18 ascorbic acid was added to 10mL of 6mg/mL graphene oxide hydrosol, and the mixture was stirred well. And (3) sealing the hydrosol in a hydrothermal kettle, and heating at 40 ℃ for 18h to fully perform reduction reaction and generate gel.
And S33, reinforcing the framework.
Weighing a certain mass of polyacrylamide with the number average molecular weight of 60000, dissolving the polyacrylamide in N, N-dimethylformamide, and preparing into a high polymer solution with the mass concentration of 0.5%. The graphene hydrogel is soaked in a polymer solution with the volume of 10 times of that of the graphene hydrogel, and the polymer solution is replaced once every 3 days for 3 times in total. Then, the graphene gel was soaked in 10 times volume of ethanol, and the ethanol was replaced every 3 days for 3 times in total.
s34, drying the graphene gel to obtain the graphene aerogel.
And (3) putting the graphene gel treated by the S13 into supercritical drying equipment, introducing carbon dioxide until the pressure reaches 3MPa, heating the equipment to 50 ℃, continuously pressurizing to 15MPa, and taking out the ethanol solvent by using the supercritical carbon dioxide. And after the ethanol is completely removed, reducing the pressure to normal pressure at the speed of 2MPa/h, and taking out the sample to obtain the graphene aerogel material.
Through detection, the density of the high-elasticity graphene oxide aerogel prepared by the embodiment is 0.052g/cm 3, the specific surface area is 156m 2/g, the maximum resilient compression amount is 40%, and the resilient amount is more than or equal to 90%.
examples 4 to 8 were prepared in substantially the same manner as in example 1 except that the differences were as shown in Table 1.
example 9
S91 is the same as S11.
s92, preparing the graphene hydrogel by an ultrasonic dispersion method. Ultrasonically dispersing the graphene oxide hydrosol in an ultrasonic cleaner for 15 hours, then sealing the graphene oxide hydrosol in a container, transferring the container into an oven, and keeping the container at 85 ℃ for 72 hours to obtain the graphene hydrogel.
S93 is the same as S13.
S94 is the same as S14.
In addition to the above examples, several sets of comparative products were prepared according to the present invention.
Example 10
Essentially the same as example 1, except that: no step of reinforcing the skeleton is included.
Example 11
Essentially the same as example 1, except that: in the step of reinforcing the skeleton, solvent substitution with a poor solvent is not performed.
example 12
Polydimethylsiloxane is adopted as a high polymer material, and the polydimethylsiloxane and a curing agent are dissolved in n-hexane to be used as a high polymer solution. The preparation method comprises the following steps:
the aerogel material prepared in example 10 was immersed in the polymer solution for half an hour, and then the aerogel material was placed in a vacuum oven at 120 ℃ for 12 hours.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (6)
1. A preparation method of a high-elasticity graphene aerogel, comprising the following steps of: (1) preparing graphene oxide sol; (2) preparing graphene hydrogel; (3) a drying step, characterized by further comprising, between step (2) and step (3): (i) reinforcing the skeleton; the step (i) is performed as follows:
(a) Dissolving a high molecular compound in a good solvent to prepare a high molecular solution with the concentration of 0.5-5 wt%; the high molecular compound is selected from any one of polyacrylonitrile compounds, polyacrylamide compounds, polyamide compounds, polyester compounds and polysulfone compounds; and the molecular weight of the polymer compound is 5000-; the good solvent is selected from any one of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and tetrahydrofuran;
(b) Soaking the graphene hydrogel prepared in the step (2) in the high polymer solution for not less than 2 times and not less than 3 days to obtain graphene gel, wherein the mass fraction of water in the soaked graphene gel is not more than 1%;
(c) Soaking the graphene gel in a poor solvent of a high molecular compound for not less than 2 times, wherein the time of single soaking is not less than 3 days; the poor solvent is selected from the group consisting of ethanol, isopropanol, and acetone;
Wherein the concentration of the graphene oxide sol is 2-15 mg/mL;
The density of the high-elasticity graphene aerogel is 0.032-0.081 g/cm 3, the specific surface area is 156-317 m 2/g, the maximum rebound compression amount is 20-60%, and the rebound rate is more than or equal to 90%.
2. the preparation method according to claim 1, wherein the graphene hydrogel is soaked in the polymer solution for 2 to 4 times, and the single soaking time is 3 to 6 days.
3. The preparation method according to claim 1, wherein the graphene gel treated in step (b) is soaked in the poor solvent for 2-4 times, and the time of a single soaking is 3-5 days.
4. The production method according to any one of claims 1 to 3, characterized in that the graphene hydrogel is produced by a chemical reduction method;
The process conditions of the chemical reduction method are as follows: the reducing agent is water-soluble and the oxidized product is water-soluble, and is selected from hydrazine hydrate, sodium bisulfite, ascorbic acid and ethylenediamine;
The mass ratio of the graphene oxide to the reducing agent is 1: (0.5 to 5);
The temperature of the reduction reaction is 40-200 ℃, and the reaction time is 12-20 hours.
5. The production method according to any one of claims 1 to 3, characterized in that:
the pH value of the graphene oxide sol is 5-7, the potassium ion content is below 0.04 wt%, the manganese ion content is below 0.07 wt%, the sodium ion number is below 0.05 wt%, the number of graphene oxide sheets is 1-3, the thickness of each sheet is 1-3nm, and the diameter of each sheet is 1-30 mu m; and/or
The drying adopts a supercritical drying method.
6. A high-elasticity graphene aerogel is characterized by being prepared by the preparation method of any one of claims 1 to 5.
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| CN110332857B (en) * | 2019-07-08 | 2021-12-10 | 杭州高烯科技有限公司 | Graphene aerogel interference bomb |
| CN110342498B (en) * | 2019-07-08 | 2021-05-07 | 浙江大学 | Graphene-based elastic structure and preparation method thereof |
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