CN114014310B - Multifunctional graphene foam and preparation method thereof - Google Patents
Multifunctional graphene foam and preparation method thereof Download PDFInfo
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- CN114014310B CN114014310B CN202111265022.7A CN202111265022A CN114014310B CN 114014310 B CN114014310 B CN 114014310B CN 202111265022 A CN202111265022 A CN 202111265022A CN 114014310 B CN114014310 B CN 114014310B
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Abstract
The invention relates to the technical field of graphene, in particular to multifunctional graphene foam and a preparation method thereof, and the preparation method comprises the following steps: and immersing the graphene film in a reaction solution, applying external force to assist the reaction solution to keep the reaction solution in a flowing state, and after a certain time of reduction reaction, sequentially performing microwave drying treatment and heat treatment to obtain the multifunctional graphene foam. The preparation method provided by the invention adopts a mode of generating gas by soaking the reaction solution, so that foam products with larger thickness and good structure can be obtained; the microstructure of the foam is porous and fluffy, layers are crosslinked together to form a network, and the structural characteristics can ensure the structural stability of the foam product and provide very good heat and electric conduction channels, so that the foam is excellent in heat and electric conduction functions and the like.
Description
Technical Field
The invention relates to the technical field of graphene, in particular to multifunctional graphene foam and a preparation method thereof.
Background
Various functional foam materials are generally used in electronic products such as mobile phones and computers to solve the problems of heat conduction, electric conduction, shielding and the like in the products. Generally, these functionalized foams are almost all obtained by adding substances such as electric conduction, heat conduction and the like into common foams in the form of additives so as to achieve corresponding product functions; or one or more materials with electric and heat conducting properties are adhered to the common foam by using substances such as adhesive. The foam composition is not single, the product structure is complex, and the performances of heat conduction, electric conduction and the like are easily affected by factors such as uneven mixing, adhesives and the like.
Graphene as a novel carbon material, which has a single-layer structure with very high theoretical thermal conductivity (5300W/mK) and electrical conductivity (electron mobility 15000 cm) 2 and/V.s), and the graphene has the advantages of light weight, corrosion resistance, good mechanical property and the like. The Chinese patent with the publication number of CN 105731438B discloses a preparation method of heat-conducting and electric-conducting graphene foam and an obtained product, wherein the preparation method comprises the following steps: and preparing graphene oxide and a macromolecular long-chain fiber additive by a wet method under the action of a reducing agent, and carrying out heat treatment and reduction at 300-2000 ℃ to obtain the graphene foam. The product obtained by the preparation method has excellent heat conduction and electric conduction performance, the heat conduction performance reaches more than 150W/m.K, and the electric conduction performance reaches 5 x 10 5 S/m. Meanwhile, the graphene foam product has good rebound resilience, a single structure and uniform and stable performance, and can solve the problems. However, this method of preparation has a certain limitation because it "expands" to form bubbles mainly by removing oxygen-containing functional groups in the graphene oxide film by high-temperature heat treatment to generate a large amount of gasCotton structure. However, this method produces very limited amounts of gas that directly affect the "bulking" effect and does not result in thicker foam products; meanwhile, the graphene layers in the 'puffing' structure are discontinuous, so that the heat conduction, electric conduction and other performances of the foam product cannot be further optimized.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a preparation method of multifunctional graphene foam, and the graphene foam prepared by the method has the advantages of strong thickness controllability, good appearance and smooth and uniform surface; the internal structure is porous and fluffy, and the layers are crosslinked together to form a very good electric conduction and heat conduction channel, so that the product has multiple functions of heat conduction, electric conduction, electromagnetic shielding and the like, and has great application value. In addition, the method has simple flow and easy operation, can easily realize batch or large-scale preparation, and is suitable for industrial large-scale production. Another object of the invention is to provide a multifunctional graphene foam which is composed of pure graphene, has a porous and fluffy microstructure, and is crosslinked together in a network shape; the graphene foam has the functions of heat conduction, electric conduction, electromagnetic shielding and the like.
The aim of the invention is achieved by the following technical scheme:
a preparation method of multifunctional graphene foam comprises the following steps: and immersing the graphene film in a reaction solution, applying external force to assist the reaction solution to keep the reaction solution in a flowing state, and after a certain time of reduction reaction, sequentially performing microwave drying treatment and heat treatment to obtain the multifunctional graphene foam.
According to the invention, the external force is applied to assist the reaction solution to keep a flowing state, so that the reaction solution is ensured to fully infiltrate between graphene film layers, the reduction reaction is promoted, bubbles generated by reduction of the graphene oxide film are 'bulging' to form a network-shaped porous structure, and meanwhile, the bubbles formed by the reaction can be influenced by the flowing of liquid to quickly and effectively escape from reaction sites, so that the finally obtained graphene foam has an intact micro-pore structure, and good cross-linking between layers is kept in a network shape, and the structural characteristics are beneficial to the better capabilities of heat conduction, electric conduction, electromagnetic shielding and the like. Therefore, the external force auxiliary means not only simply promotes the reaction or promotes the escape of bubbles, but also reasonably controls the two processes, and the reduction reaction is too severe, so that separation and fracture between layers are easy to occur, thereby being unfavorable for improving the mechanical property and the electrical property; the escape efficiency of bubbles is too low, and the network structure is easily disintegrated and destroyed under long-term pressure, so that the formation of a perfect micro-pore structure is also unfavorable.
In addition, the invention combines the microwave drying mode, utilizes the characteristic of uniform microwave heating to lead the water vapor to escape uniformly, can store the micro-pore structure of the graphene foam to a large extent, and avoids collapse of the network-like structure and damage of channels such as heat conduction, electric conduction and the like; compared with the conventional hot air drying or other heat drying modes, the multilayer structure of the graphene foam is easily damaged by uneven heating and physical action caused by wind power, and a good electric conduction and heat conduction channel cannot be formed; compared with conventional freeze drying, the freeze drying is generally used in a template method, moisture in graphene is frozen below a freezing point and forms an ice frame, the moisture is removed by sublimation, and substances are left in the frozen ice frame, so that a loose and porous graphene structure is formed, but the invention belongs to a self-assembly mode, the structure of graphene is basically formed in a reduction reaction process, the stability of the structure of graphene is mainly considered in the moisture removal process, and the freeze drying can damage the graphene structure formed in the reduction reaction.
Wherein the graphene film is a graphene oxide film, and the carbon-oxygen ratio is 1.2-2.8. The method for obtaining the same is common knowledge in the art. For example, the graphene oxide slurry prepared by the modified Hummers method can be obtained through the steps of blade coating, drying, stripping and the like.
Wherein the reaction solution is a chemical reagent which can react with the oxygen-containing functional group of the graphene oxide and generate gas, such as hydrazine hydrate, dimethylhydrazine, sodium borohydride, thiourea and the like.
Further, the reaction solution is a hydrazine hydrate solution, and the mass concentration of the hydrazine hydrate solution is 1-80%. The hydrazine hydrate has remarkable reduction effect and can reduce more oxygen-containing groups in the graphene oxide.
Wherein the temperature of the reduction reaction is-20 ℃ to 100 ℃, more preferably, the temperature is 0 ℃ to 60 ℃.
Wherein the external force assistance is mechanical stirring, magnetic stirring or ultrasonic vibration.
Further, the external force is assisted by ultrasonic oscillation, and the working power of the ultrasonic oscillation is 500-8000W. By the aid of external force of ultrasonic vibration, bubbles generated by reaction can timely and effectively escape from a reaction site, and damage to a pore wall channel caused by excessive bubble aggregation is avoided, so that the crosslinking property between graphene layers is remarkably improved.
Wherein the working power of the microwave drying treatment is 1 kW-100 kW.
Wherein the heat treatment comprises high-temperature carbonization treatment and graphitization treatment after the high-temperature carbonization treatment, the temperature of the high-temperature carbonization treatment is 950-1300 ℃, and the temperature of the graphitization treatment is 2500-3100 ℃. The high-temperature carbonization treatment and the graphitization treatment are used for gradually removing unreacted complete oxygen-containing functional groups in the graphene foam, and meanwhile, the existing porous network-shaped structure is preserved without being damaged, so that the multifunctional graphene foam with the optimal performance is obtained.
The invention has the beneficial effects that:
(1) The multifunctional foam product with pure graphene as the component is single in structure and good in performance stability; the product has multiple functions of heat conduction, electric conduction, electromagnetic shielding and the like.
(2) Compared with the preparation method of graphene foam which generates gas by high-temperature heat treatment and the like, the preparation method provided by the patent adopts a mode of generating gas by soaking the reaction solution, so that foam products with larger thickness and good structures can be obtained; the microstructure of the foam is porous and fluffy, layers are crosslinked together to form a network, and the structural characteristics can ensure the structural stability of the foam product and provide very good heat and electric conduction channels, so that the foam is excellent in heat and electric conduction functions and the like.
(3) The preparation method provided by the patent adopts the external force auxiliary disturbance reaction solution and the microwave drying treatment means, is very favorable for obtaining stable and intact porous microstructure foam products, has the heat conduction performance of 180W/m K and the electric conductivity of 8 x 10 5 S/m, and the electromagnetic shielding effectiveness can reach 113.2dB.
(4) The preparation method provided by the patent has simple flow, can easily realize industrial large-scale production, and generates practical economic benefit.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
Fig. 1 is an SEM image of graphene foam obtained in example 1, with a magnification of 100.
Fig. 2 is an SEM image of graphene foam obtained in example 1, with a magnification of 1000.
Fig. 3 is an electromagnetic shielding performance curve of the graphene foam obtained in example 1 in the electromagnetic wave frequency range of 30MHz to 10 GHz.
Fig. 4 is an SEM image of graphene foam obtained in example 2, with a magnification of 100.
Fig. 5 is an SEM image of graphene foam obtained in comparative example 1, at a magnification of 25.
Detailed Description
The present invention is further described below with reference to examples and fig. 1 for the understanding of those skilled in the art, and the description of the embodiments is not intended to limit the present invention.
Example 1
Graphene oxide coated film (purchased from Yunnan cloud) with carbon-oxygen ratio of 1.4Tian-Rui technology Co., ltd.) is placed in a reaction vessel with ultrasonic oscillation function, hydrazine hydrate is selected as a reaction solution, and the volume ratio of the graphene oxide coating film to the hydrazine hydrate solution is 1:3, a step of; the reaction temperature is constant at 40 ℃, the working power of ultrasonic vibration is set to 2000W, and the wet graphene foam is obtained through reaction. And then placing the graphene foam into a microwave drying oven, setting the working power to be 60kW, and obtaining the dried graphene foam with the thickness of about 7mm after 3 min. After high-temperature carbonization at 1200 ℃ and graphitization at 2800 ℃ in sequence, as shown in fig. 1, a low-multiple SEM image can see the perfect porous structure in the graphene foam, and the pore size distribution is 60-120 μm. Further, the SEM image at a magnification shown in fig. 2 clearly shows that graphene layers are crosslinked together to form a network, and effective electric and heat conduction channels are formed between the holes. The thermal conductivity of the graphene foam is 180W/m.K, and the conductivity is 8.0 x 10 5 S/m; the electromagnetic shielding effect curve of the graphene foam prepared by the embodiment shown in fig. 3 in the frequency range of 30 MHz-10 GHz can reach 113.2dB at maximum.
Example 2
And (3) placing the graphene oxide coating film (purchased from Yunnan Tian Rui technology Co., ltd.) with the carbon-oxygen ratio of 1.4 into a container containing hydrazine hydrate reaction solution, providing magnetic stirring disturbance solution in the reaction process, keeping the reaction temperature constant at 40 ℃, and reacting to obtain the wet graphene foam. And then placing the graphene foam into a microwave drying oven, setting the microwave frequency to be 60kW, and obtaining the dried graphene foam with the thickness of about 5mm after 3 min. After high-temperature carbonization at 1200 ℃ and graphitization at 2800 ℃ in sequence, as shown in fig. 4, a partially intact porous structure can be seen by observing the microstructure through a scanning electron microscope, and no obvious cross-linking exists between graphene layers at partial positions. The method is characterized in that the whole fluidity of the reaction solution is inconsistent due to magnetic stirring, the bubble escape rate in each region is different, the graphene layers in the foam structure are poor in crosslinking, and the heat conduction and electric conduction channels are discontinuous. The thermal conductivity coefficient of the graphene foam is 116W/m.K, and the electrical conductivity can reach 8.6 x 10 4 S/m。
Example 3
Carbon is added toThe graphene oxide coating film material with the oxygen ratio of 2.0 is placed in a reaction container with an ultrasonic oscillation function, hydrazine hydrate is selected as a reaction solution, the reaction temperature is constant at 60 ℃, and the wet graphene foam is obtained. Then, the graphene foam is placed in a microwave drying oven, the microwave frequency is set to 80kW, and the graphene foam dried to a thickness of about 11mm is obtained after 2 min. Sequentially carrying out high-temperature carbonization at 1200 ℃ and graphitization treatment at 2800 ℃, wherein the pore diameter is 50-160 mu m; the graphene layers are crosslinked together to form a network shape, and effective electric and heat conduction channels are formed among the holes. The thermal conductivity of the graphene foam is 145W/m K, and the electrical conductivity can reach 5.5 x 10 5 S/m。
Comparative example 1
Comparative example 1 protocol in example 1, a reaction vessel without the function of ultrasonic vibration was used, and the other operation was the same. As shown in fig. 5, since the comparative example is not assisted by external force of ultrasonic vibration, bubbles generated by the reaction cannot timely and effectively "escape" from the reaction site, and excessive bubble aggregation causes the destruction of pore wall channels, so that the crosslinkability between graphene layers is remarkably reduced. The thermal conductivity was measured to be 69W/mK, and the electrical conductivity was measured to be 3.6x10 3 S/m。
Comparative example 2
Comparative example 2 the procedure used in example 1 was a conventional forced air drying with a drying power of 500W, and the other procedure was the same.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above embodiments are preferred embodiments of the present invention, and besides, the present invention may be implemented in other ways, and any obvious substitution is within the scope of the present invention without departing from the concept of the present invention.
Claims (9)
1. A preparation method of multifunctional graphene foam is characterized by comprising the following steps: the method comprises the following steps: and immersing the graphene film in a reaction solution, applying external force to assist the reaction solution to keep the reaction solution in a flowing state, and sequentially performing microwave drying treatment and heat treatment after a certain time of reduction reaction to obtain the multifunctional graphene foam, wherein the external force is assisted by mechanical stirring, magnetic stirring or ultrasonic vibration.
2. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the graphene film is a graphene oxide film, and the carbon-oxygen ratio is 1.2-2.8.
3. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the reaction solution is one or more of hydrazine hydrate, dimethylhydrazine, sodium borohydride and thiourea.
4. The method for preparing the multifunctional graphene foam according to claim 3, wherein the method comprises the following steps: the reaction solution is a hydrazine hydrate solution, and the mass concentration of the hydrazine hydrate solution is 1% -80%.
5. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the temperature of the reduction reaction is-20-100 ℃.
6. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the external force assistance is ultrasonic oscillation, and the working power of the ultrasonic oscillation is 500-8000W.
7. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the working power of the microwave drying treatment is 1 kW-100 kW.
8. The method for preparing the multifunctional graphene foam according to claim 1, which is characterized by comprising the following steps: the heat treatment comprises high-temperature carbonization and graphitization after the high-temperature carbonization, wherein the temperature of the high-temperature carbonization is 950-1300 ℃, and the temperature of the graphitization is 2500-3100 ℃.
9. The utility model provides a multi-functional graphite alkene bubble is cotton, its characterized in that: the method for preparing the multifunctional graphene foam according to any one of claims 1 to 8.
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| US20130314844A1 (en) * | 2012-05-23 | 2013-11-28 | Nanyang Technological University | Method of preparing reduced graphene oxide foam |
| CN105731438B (en) * | 2016-01-27 | 2018-07-10 | 常州富烯科技股份有限公司 | A kind of graphene foam preparation method of thermal conductivity and obtained product |
| CN110357083A (en) * | 2019-07-12 | 2019-10-22 | 淄博联科石墨烯技术服务中心 | The preparation method of polymolecularity graphene powder |
| CN111362256B (en) * | 2020-03-12 | 2021-11-02 | 杭州高烯科技有限公司 | Preparation method of graphene electromagnetic shielding material |
| CN112028058B (en) * | 2020-08-28 | 2021-10-19 | 清华大学深圳国际研究生院 | Preparation method of graphene composite heat-conducting film |
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