Controllable thermal expansion preparation method of graphene oxide layer

Abstract

The invention discloses a controllable thermal expansion preparation method of a graphene oxide layer. The controllable thermal expansion preparation method comprises the following steps: S1, preparing a modified graphene oxide precursor; s2, preparing a graphene oxide layer preform; s3, gradient heating controllable thermal expansion treatment is carried out; s4, post-treatment shaping is carried out; graphene oxide is modified through an amino silane coupling agent, amino functional groups are introduced, the interlayer acting force of graphene oxide is regulated and controlled, a precursor foundation is provided for subsequent controllable thermal expansion, and the problem that thermal expansion is uncontrollable due to the fact that the interlayer acting force of a traditional precursor is unstable is effectively solved; a gradient heating thermal expansion process is adopted, the heating rate and the constant temperature time are controlled in three stages, moisture removal, functional group decomposition and deep expansion are carried out in order, local excessive expansion or insufficient expansion caused by a single heating rate is avoided, and it is ensured that the graphene oxide layer expands uniformly and the pore structure is controllable.

Description

Technical Field

[0001] This invention belongs to the field of graphene oxide material preparation technology, specifically a method for preparing graphene oxide layers with controllable thermal expansion. Background Technology

[0002] Graphene oxide, as an important derivative of graphene, possesses abundant oxygen-containing functional groups, good dispersibility, and excellent physicochemical properties, making it promising for applications in energy storage materials, composite materials, and adsorption materials. Thermal expansion treatment is one of the key methods for controlling the structure and properties of graphene oxide layers. Through thermal expansion, the interlayer distance of graphene oxide can be increased, forming a porous structure, thereby improving its specific surface area and adsorption performance.

[0003] However, existing methods for preparing graphene oxide layers by thermal expansion generally suffer from uncontrollable thermal expansion processes. This manifests primarily as difficulty in precisely controlling the expansion rate and uneven expansion, resulting in disordered pore structures and poor performance stability in the prepared graphene oxide layers. Traditional methods often employ a single heating rate for thermal expansion, which can easily lead to irreversible aggregation or structural damage of the graphene oxide layer due to sudden localized temperature increases. Furthermore, the lack of effective precursor modification methods prevents precise control of the thermal expansion process by adjusting precursor properties. In addition, the post-processing of samples after thermal expansion in existing methods is simplistic and fails to guarantee the stability of the sample structure, further limiting their application in high-end fields.

[0004] Therefore, developing a method that can precisely control the thermal expansion process and produce graphene oxide layers with uniform structure and stable performance has become an urgent technical problem to be solved in the field of graphene oxide material preparation.

[0005] Based on this, a method for preparing graphene oxide layers with controllable thermal expansion was designed. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for preparing graphene oxide layers with controllable thermal expansion, which effectively solves the problems mentioned in the background.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a graphene oxide layer with controllable thermal expansion, comprising the following steps: Step S1: Preparation of modified graphene oxide precursor Add natural flake graphite to concentrated sulfuric acid with a mass fraction of 90%-98%, and stir for 30-60 minutes under ice bath conditions, with the ice bath temperature controlled at 0-5℃. Then, add potassium permanganate in batches, with a mass ratio of potassium permanganate to natural flake graphite of 3:1-5:1, at a feeding rate of 0.5-1 g of potassium permanganate per 10 minutes per gram of graphite. During the feeding process, keep the system temperature below 10℃. After the feeding is completed, raise the temperature to 30-40℃ and stir at a constant temperature for 120-180 minutes. Next, deionized water is slowly added at a volume ratio of 3:1 to 5:1 of concentrated sulfuric acid at a rate of 5-10 mL / min. After the addition is complete, the temperature is raised to 90-95℃ and the reaction is maintained at this temperature for 30-60 min. Finally, 30% hydrogen peroxide is added until no more bubbles are produced in the system. The mixture is then filtered, washed 3-5 times with 5%-10% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate is 6.5-7.5. The filtrate is then freeze-dried to obtain graphene oxide. The graphene oxide was added to deionized water and ultrasonically dispersed for 30-60 min at an ultrasonic power of 150-200 W to obtain a graphene oxide dispersion with a mass concentration of 0.5-2 mg / mL. An aminosilane coupling agent was added to the dispersion, with a mass ratio of aminosilane coupling agent to graphene oxide of 0.05:1-0.2:1. The mixture was stirred at 50-70℃ for 60-120 min. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed 3-4 times with deionized water and vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform The modified graphene oxide precursor obtained in step S1 was added to deionized water and ultrasonically dispersed for 20-40 min at an ultrasonic power of 120-180 W to obtain a modified graphene oxide dispersion with a mass concentration of 0.3-1.5 mg / mL. The dispersion was poured onto a filter membrane of a vacuum filtration device with a pore size of 0.22-0.45 μm and vacuum filtered at a vacuum degree of 0.06-0.09 MPa until a uniform graphene oxide membrane was formed on the filter membrane. The graphene oxide membrane and the filter membrane were transferred to a vacuum drying oven and dried at 60-80℃ and a vacuum degree of 0.08-0.1 MPa for 120-180 min. After drying, the filter membrane was peeled off to obtain a graphene oxide layer preform with a thickness of 5-20 μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. Inert gas is first introduced into the tube furnace at a flow rate of 20-50 mL / min for 30-60 min to remove air from the furnace. Then, a gradient temperature increase is carried out. The first temperature increase stage is: from room temperature to 150-200℃, the temperature increase rate is 2-5℃ / min, and the temperature is held for 30-60min. The second heating stage: the temperature is increased from 150-200℃ to 400-500℃ at a rate of 5-10℃ / min, and the temperature is held for 60-90min. The third heating stage: heating from 400-500℃ to 700-850℃ at a rate of 3-6℃ / min, and holding the temperature for 40-80min; During thermal expansion, inert gas is continuously introduced at a flow rate of 20-50 mL / min. Step S4: Post-processing and shaping After thermal expansion, the sample is cooled to room temperature at a rate of 5-8℃ / min and removed. The sample is then immersed in a 1%-3% (w / w) dilute sulfuric acid solution for 20-30 min at a temperature of 25-35℃. After immersion, the sample is washed with deionized water until the pH of the filtrate is 6.8-7.2. The sample is then placed in a vacuum drying oven and dried at 50-70℃ and a vacuum of 0.08-0.1 MPa for 60-90 min to obtain a controllable thermal expansion graphene oxide layer.

[0008] Preferably, the aminosilane coupling agent in step S1 is one or a mixture of two of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane in any proportion.

[0009] Preferably, the inert gas in step S3 is one or a mixture of two of nitrogen and argon in any proportion.

[0010] Preferably, the filter membrane in step S2 is one of polyvinylidene fluoride filter membrane and mixed cellulose ester filter membrane.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention modifies graphene oxide by using an aminosilane coupling agent, introduces amino functional groups, regulates the interlayer interaction force of graphene oxide, and provides a precursor basis for subsequent controllable thermal expansion, effectively solving the problem of uncontrollable thermal expansion caused by unstable interlayer interaction force in traditional precursors. 2. A gradient heating thermal expansion process is adopted, which controls the heating rate and isothermal time in three stages to achieve orderly moisture removal, functional group decomposition and deep expansion. This avoids local over-expansion or under-expansion caused by a single heating rate, and ensures uniform expansion of the graphene oxide layer and controllable pore structure. 3. A precise post-processing technique has been added, in which residual impurities and unstable groups are removed by soaking in dilute sulfuric acid, followed by vacuum drying and shaping, which further improves the stability of the graphene oxide layer structure and the consistency of its performance. 4. The method of this invention has clear steps, well-defined process parameters, strong operability, and is suitable for industrial production. The prepared graphene oxide layer has advantages such as uniform structure, controllable pores, and stable performance, and has broad application prospects in energy storage, adsorption, composite materials and other fields. Detailed Implementation

[0012] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] This invention provides a method for preparing a graphene oxide layer with controllable thermal expansion, comprising the following steps: Step S1: Preparation of modified graphene oxide precursor Add natural flake graphite to concentrated sulfuric acid with a mass fraction of 90%-98%, and stir for 30-60 minutes under ice bath conditions, with the ice bath temperature controlled at 0-5℃. Then, add potassium permanganate in batches, with a mass ratio of potassium permanganate to natural flake graphite of 3:1-5:1, at a feeding rate of 0.5-1 g of potassium permanganate per 10 minutes per gram of graphite. During the feeding process, keep the system temperature below 10℃. After the feeding is completed, raise the temperature to 30-40℃ and stir at a constant temperature for 120-180 minutes. Next, deionized water is slowly added at a volume ratio of 3:1 to 5:1 of concentrated sulfuric acid at a rate of 5-10 mL / min. After the addition is complete, the temperature is raised to 90-95℃ and the reaction is maintained at this temperature for 30-60 min. Finally, 30% hydrogen peroxide is added until no more bubbles are produced in the system. The mixture is then filtered, washed 3-5 times with 5%-10% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate is 6.5-7.5. The filtrate is then freeze-dried to obtain graphene oxide. The graphene oxide was added to deionized water and ultrasonically dispersed for 30-60 min at an ultrasonic power of 150-200 W to obtain a graphene oxide dispersion with a mass concentration of 0.5-2 mg / mL. An aminosilane coupling agent was added to the dispersion, with a mass ratio of aminosilane coupling agent to graphene oxide of 0.05:1-0.2:1. The mixture was stirred at 50-70℃ for 60-120 min. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed 3-4 times with deionized water and vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform The modified graphene oxide precursor obtained in step S1 was added to deionized water and ultrasonically dispersed for 20-40 min at an ultrasonic power of 120-180 W to obtain a modified graphene oxide dispersion with a mass concentration of 0.3-1.5 mg / mL. The dispersion was poured onto a filter membrane of a vacuum filtration device with a pore size of 0.22-0.45 μm and vacuum filtered at a vacuum degree of 0.06-0.09 MPa until a uniform graphene oxide membrane was formed on the filter membrane. The graphene oxide membrane and the filter membrane were transferred to a vacuum drying oven and dried at 60-80℃ and a vacuum degree of 0.08-0.1 MPa for 120-180 min. After drying, the filter membrane was peeled off to obtain a graphene oxide layer preform with a thickness of 5-20 μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. Inert gas is first introduced into the tube furnace at a flow rate of 20-50 mL / min for 30-60 min to remove air from the furnace. Then, a gradient temperature increase is carried out. The first temperature increase stage is: from room temperature to 150-200℃, the temperature increase rate is 2-5℃ / min, and the temperature is held for 30-60min. The second heating stage: the temperature is increased from 150-200℃ to 400-500℃ at a rate of 5-10℃ / min, and the temperature is held for 60-90min. The third heating stage: heating from 400-500℃ to 700-850℃ at a rate of 3-6℃ / min, and holding the temperature for 40-80min; During thermal expansion, inert gas is continuously introduced at a flow rate of 20-50 mL / min. Step S4: Post-processing and shaping After thermal expansion, the sample is cooled to room temperature at a rate of 5-8℃ / min and removed. The sample is then immersed in a 1%-3% (w / w) dilute sulfuric acid solution for 20-30 min at a temperature of 25-35℃. After immersion, the sample is washed with deionized water until the pH of the filtrate is 6.8-7.2. The sample is then placed in a vacuum drying oven and dried at 50-70℃ and a vacuum of 0.08-0.1 MPa for 60-90 min to obtain a controllable thermal expansion graphene oxide layer.

[0014] In step S1 of this embodiment, the aminosilane coupling agent is one or a mixture of two of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane in any proportion.

[0015] In step S3 of this embodiment, the inert gas is one or a mixture of two of nitrogen and argon in any proportion.

[0016] In step S2 of this embodiment, the filter membrane is one of polyvinylidene fluoride filter membrane and mixed cellulose ester filter membrane.

[0017] Example 1: A method for preparing a graphene oxide layer with controllable thermal expansion includes the following steps: Step S1: Preparation of modified graphene oxide precursor 10g of natural flake graphite was added to 200mL of 98% concentrated sulfuric acid and stirred in an ice bath at 0℃ for 60min. Then, 40g of potassium permanganate was added in batches at a rate of 0.8g of potassium permanganate per gram of graphite per 10min, keeping the system temperature below 10℃ during the addition process. After addition, the temperature was raised to 35℃ and stirred for 150min. Next, 800mL of deionized water was slowly added at a rate of 8mL / min. After addition, the temperature was raised to 92℃ and reacted for 45min. Finally, 30% hydrogen peroxide was added until no more bubbles were produced. The mixture was filtered, washed four times with 8% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate reached 7.0. The filtrate was then freeze-dried to obtain graphene oxide. 5g of the graphene oxide was added to 2500mL of deionized water and ultrasonically dispersed for 45min at an ultrasonic power of 180W to obtain a graphene oxide dispersion with a mass concentration of 2mg / mL. 0.5g of γ-aminopropyltriethoxysilane was added to the dispersion and stirred at 60℃ for 90min. After the reaction was completed, the mixture was centrifuged, the precipitate was washed four times with deionized water, and vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform Add 3g of the modified graphene oxide precursor obtained in step S1 to 3000mL of deionized water and ultrasonically disperse for 30min at an ultrasonic power of 150W to obtain a modified graphene oxide dispersion with a mass concentration of 1mg / mL. Pour the dispersion onto a polyvinylidene fluoride filter membrane in a vacuum filtration device. The filter membrane has a pore size of 0.22μm and is vacuum filtered at a vacuum degree of 0.08MPa until a uniform graphene oxide membrane is formed on the filter membrane. Transfer the graphene oxide membrane together with the filter membrane to a vacuum drying oven and dry it at 70℃ and a vacuum degree of 0.09MPa for 150min. After drying, peel off the filter membrane to obtain a graphene oxide layer preform with a thickness of 12μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. Nitrogen gas is first introduced into the tube furnace at a flow rate of 35 mL / min for 45 min to remove air from the furnace. Then, a gradient temperature increase was carried out. The first temperature increase stage was: from room temperature to 180℃, with a heating rate of 3℃ / min, and held at the temperature for 45min. Second heating stage: heating from 180℃ to 450℃ at a heating rate of 8℃ / min, and holding the temperature for 75min. The third heating stage: heating from 450℃ to 780℃ at a rate of 5℃ / min, and holding the temperature for 60min. During the thermal expansion process, nitrogen gas is continuously introduced at a flow rate of 35 mL / min. Step S4: Post-processing and shaping After thermal expansion, the sample was cooled to room temperature at a rate of 6℃ / min and removed. The sample was then immersed in a 2% (w / w) dilute sulfuric acid solution for 25 min at a temperature of 30℃. After that, it was washed with deionized water until the pH of the filtrate was 7.0. The sample was then placed in a vacuum drying oven and dried at 60℃ and a vacuum of 0.09 MPa for 75 min to obtain a graphene oxide layer with controllable thermal expansion.

[0018] Example 2: A method for preparing a graphene oxide layer with controllable thermal expansion includes the following steps: Step S1: Preparation of modified graphene oxide precursor 8g of natural flake graphite was added to 160mL of 95% concentrated sulfuric acid and stirred in an ice bath at 3°C ​​for 45min. Then, 32g of potassium permanganate was added in batches at a rate of 0.6g of potassium permanganate per gram of graphite per 10min, keeping the system temperature below 10°C during the addition process. After addition, the temperature was raised to 32°C and stirred for 130min. Next, 640mL of deionized water was slowly added at a rate of 6mL / min. After addition, the temperature was raised to 90°C and reacted for 50min. Finally, 30% hydrogen peroxide was added until no more bubbles were produced. The mixture was filtered, washed three times with 6% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate reached 6.8. The filtrate was then freeze-dried to obtain graphene oxide. 4g of the graphene oxide was added to 3200mL of deionized water and ultrasonically dispersed for 35min at an ultrasonic power of 160W to obtain a graphene oxide dispersion with a mass concentration of 1.25mg / mL. 0.4g of γ-aminopropyltrimethoxysilane was added to the dispersion and stirred at 55℃ for 100min. After the reaction was completed, the mixture was centrifuged, the precipitate was washed three times with deionized water, and vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform 2g of the modified graphene oxide precursor obtained in step S1 was added to 2000mL of deionized water and ultrasonically dispersed for 25min at an ultrasonic power of 130W to obtain a modified graphene oxide dispersion with a mass concentration of 1mg / mL. The dispersion was poured onto a mixed cellulose ester filter membrane in a vacuum filtration device with a pore size of 0.45μm and vacuum filtered at a vacuum degree of 0.07MPa until a uniform graphene oxide membrane was formed on the filter membrane. The graphene oxide membrane and the filter membrane were transferred to a vacuum drying oven and dried at 65℃ and a vacuum degree of 0.08MPa for 140min. After drying, the filter membrane was peeled off to obtain a graphene oxide layer preform with a thickness of 8μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. Argon gas is first introduced into the tube furnace at a flow rate of 25 mL / min for 35 min to remove air from the furnace. Then, a gradient temperature increase was carried out. The first temperature increase stage was: from room temperature to 160℃, with a heating rate of 2℃ / min, and held at the temperature for 50min. Second heating stage: heating from 160℃ to 420℃ at a heating rate of 6℃ / min, and holding at the temperature for 80min; The third heating stage: heating from 420℃ to 720℃ at a rate of 4℃ / min, and holding the temperature for 50min. During the thermal expansion process, argon gas is continuously introduced at a flow rate of 25 mL / min. Step S4: Post-processing and shaping After thermal expansion, the sample was cooled to room temperature at a rate of 5℃ / min and removed. The sample was then immersed in a 1.5% (w / w) dilute sulfuric acid solution for 22 min at a temperature of 28℃. After that, it was washed with deionized water until the pH of the filtrate was 6.9. The sample was then placed in a vacuum drying oven and dried at 55℃ and a vacuum of 0.08 MPa for 80 min to obtain a graphene oxide layer with controllable thermal expansion.

[0019] Example 3: A method for preparing a graphene oxide layer with controllable thermal expansion includes the following steps: Step S1: Preparation of modified graphene oxide precursor 12g of natural flake graphite was added to 240mL of 92% concentrated sulfuric acid and stirred in an ice bath at 4℃ for 50min. Then, 54g of potassium permanganate was added in batches at a rate of 0.9g of potassium permanganate per gram of graphite per 10min, keeping the system temperature below 10℃ during the addition process. After addition, the temperature was raised to 38℃ and stirred for 160min. Next, 960mL of deionized water was slowly added at a rate of 9mL / min. After addition, the temperature was raised to 94℃ and reacted for 35min. Finally, 30% hydrogen peroxide was added until no more bubbles were produced. The mixture was filtered, washed five times with 9% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate reached 7.2. The filtrate was then freeze-dried to obtain graphene oxide. 6g of the graphene oxide was added to 4000mL of deionized water and ultrasonically dispersed for 50min at an ultrasonic power of 190W to obtain a graphene oxide dispersion with a mass concentration of 1.5mg / mL. A mixture of 0.9g of γ-aminopropyltriethoxysilane and 0.3g of γ-aminopropyltrimethoxysilane was added to the dispersion and stirred at 65℃ for 110min. After the reaction was completed, the mixture was centrifuged, the precipitate was washed four times with deionized water, and then vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform 4g of the modified graphene oxide precursor obtained in step S1 was added to 4000mL of deionized water and ultrasonically dispersed for 35min at an ultrasonic power of 170W to obtain a modified graphene oxide dispersion with a mass concentration of 1mg / mL. The dispersion was poured onto a polyvinylidene fluoride filter membrane in a vacuum filtration device with a pore size of 0.3μm and vacuum filtered at a vacuum degree of 0.09MPa until a uniform graphene oxide membrane was formed on the filter membrane. The graphene oxide membrane and the filter membrane were transferred to a vacuum drying oven and dried at 75℃ and a vacuum degree of 0.1MPa for 160min. After drying, the filter membrane was peeled off to obtain a graphene oxide layer preform with a thickness of 18μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. A mixture of nitrogen and argon (volume ratio 1:1) is first introduced into the tube furnace at a flow rate of 45 mL / min for 55 min to remove air from the furnace. Then, a gradient temperature increase was carried out. The first temperature increase stage was: from room temperature to 190℃, with a heating rate of 4℃ / min, and held at the temperature for 35min. Second heating stage: heating from 190℃ to 480℃ at a heating rate of 9℃ / min, and holding at the temperature for 65min; The third heating stage: heating from 480℃ to 820℃ at a rate of 6℃ / min, and holding the temperature for 70min. During the thermal expansion process, the mixed gas is continuously introduced at a flow rate of 45 mL / min.

[0020] Step S4: Post-processing and shaping After thermal expansion, the sample was cooled to room temperature at a rate of 7℃ / min and removed. The sample was then immersed in a 2.5% (w / w) dilute sulfuric acid solution for 28 min at a temperature of 32℃. After that, it was washed with deionized water until the pH of the filtrate was 7.1. The sample was then placed in a vacuum drying oven and dried at 65℃ and a vacuum of 0.1 MPa for 70 min to obtain a graphene oxide layer with controllable thermal expansion.

[0021] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0022] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a graphene oxide layer with controllable thermal expansion, characterized in that, Includes the following steps: Step S1: Preparation of modified graphene oxide precursor Add natural flake graphite to concentrated sulfuric acid with a mass fraction of 90%-98%, and stir for 30-60 minutes under ice bath conditions, with the ice bath temperature controlled at 0-5℃. Then, add potassium permanganate in batches, with a mass ratio of potassium permanganate to natural flake graphite of 3:1-5:1, at a feeding rate of 0.5-1 g of potassium permanganate per 10 minutes per gram of graphite. During the feeding process, keep the system temperature below 10℃. After the feeding is completed, raise the temperature to 30-40℃ and stir at a constant temperature for 120-180 minutes. Next, deionized water is slowly added at a volume ratio of 3:1 to 5:1 of concentrated sulfuric acid at a rate of 5-10 mL / min. After the addition is complete, the temperature is raised to 90-95℃ and the reaction is maintained at this temperature for 30-60 min. Finally, 30% hydrogen peroxide is added until no more bubbles are produced in the system. The mixture is then filtered, washed 3-5 times with 5%-10% hydrochloric acid solution, and then washed with deionized water until the pH of the filtrate is 6.5-7.

5. The filtrate is then freeze-dried to obtain graphene oxide. The graphene oxide was added to deionized water and ultrasonically dispersed for 30-60 min at an ultrasonic power of 150-200 W to obtain a graphene oxide dispersion with a mass concentration of 0.5-2 mg / mL. An aminosilane coupling agent was added to the dispersion, with a mass ratio of aminosilane coupling agent to graphene oxide of 0.05:1-0.2:

1. The mixture was stirred at 50-70℃ for 60-120 min. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed 3-4 times with deionized water and vacuum dried to obtain the modified graphene oxide precursor. Step S2: Preparation of graphene oxide layer preform The modified graphene oxide precursor obtained in step S1 was added to deionized water and ultrasonically dispersed for 20-40 min at an ultrasonic power of 120-180 W to obtain a modified graphene oxide dispersion with a mass concentration of 0.3-1.5 mg / mL. The dispersion was poured onto a filter membrane of a vacuum filtration device with a pore size of 0.22-0.45 μm and vacuum filtered at a vacuum degree of 0.06-0.09 MPa until a uniform graphene oxide membrane was formed on the filter membrane. The graphene oxide membrane and the filter membrane were transferred to a vacuum drying oven and dried at 60-80℃ and a vacuum degree of 0.08-0.1 MPa for 120-180 min. After drying, the filter membrane was peeled off to obtain a graphene oxide layer preform with a thickness of 5-20 μm. Step S3: Gradient heating and controllable thermal expansion treatment The graphene oxide layer preform obtained in step S2 is placed in a tube furnace. Inert gas is first introduced into the tube furnace at a flow rate of 20-50 mL / min for 30-60 min to remove air from the furnace. Then, a gradient temperature increase is carried out. The first temperature increase stage is: from room temperature to 150-200℃, the temperature increase rate is 2-5℃ / min, and the temperature is held for 30-60min. The second heating stage: the temperature is increased from 150-200℃ to 400-500℃ at a rate of 5-10℃ / min, and the temperature is held for 60-90min. The third heating stage: heating from 400-500℃ to 700-850℃ at a rate of 3-6℃ / min, and holding the temperature for 40-80min; During thermal expansion, inert gas is continuously introduced at a flow rate of 20-50 mL / min. Step S4: Post-processing and shaping After thermal expansion, the sample is cooled to room temperature at a rate of 5-8℃ / min and removed. The sample is then immersed in a 1%-3% (w / w) dilute sulfuric acid solution for 20-30 min at a temperature of 25-35℃. After immersion, the sample is washed with deionized water until the pH of the filtrate is 6.8-7.

2. The sample is then placed in a vacuum drying oven and dried at 50-70℃ and a vacuum of 0.08-0.1 MPa for 60-90 min to obtain a controllable thermal expansion graphene oxide layer.

2. The method for preparing a controllable thermal expansion layer of graphene oxide according to claim 1, characterized in that, The aminosilane coupling agent mentioned in step S1 is one or a mixture of two of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane in any proportion.

3. The method for preparing a controllable thermal expansion layer of graphene oxide according to claim 1, characterized in that, The inert gas mentioned in step S3 is one or a mixture of two of nitrogen and argon in any proportion.

4. The method for preparing a controllable thermal expansion layer of graphene oxide according to claim 1, characterized in that, The filter membrane mentioned in step S2 is one of polyvinylidene fluoride filter membrane and mixed cellulose ester filter membrane.