Method for preparing graphene through electric pulse at high temperature

Abstract

The invention relates to the field of treatment and resource utilization of high-carbon-content materials, in particular to a method for preparing graphene at high temperature through electric pulses. The method comprises the following steps: mixing a non-graphitized carbon material and a conductive carbon material to obtain a mixture; pulse current is applied to the mixture, so that the temperature of the mixture is increased to 2000-3000 DEG C, and the mixture subjected to electric heat treatment is obtained; and carrying out cooling treatment on the mixture subjected to the electric heat treatment to obtain the graphene, wherein the carbon content in the non-graphitized carbon material is greater than or equal to 50wt%; the heating rate is 103-104 DEG C / s. According to the method, the carbon atom conversion rate is remarkably increased, the graphene preparation cost is greatly reduced, and meanwhile, the environmental problem caused by a traditional incineration or landfill mode is solved through high value-added utilization of the high-carbon-content waste. Compared with a traditional graphene preparation method, low-cost, high-quality and green preparation of graphene is achieved, the method is suitable for high-valued treatment of various high polymer materials and industrial waste, and a new technical path is provided for large-scale preparation and application of graphene.

Description

Technical Field

[0001] The present invention relates to the field of processing and resource utilization of high-carbon content materials, and in particular to a method for preparing graphene by electric pulse high temperature. Background Art

[0002] Materials with high carbon content and not artificially graphitized (such as polyethylene, polypropylene, polyethylene terephthalate (PET), etc.) are one of the most widely used materials in modern industry and daily life, and are widely used in packaging, electronic devices, textiles, industrial components and other fields. However, with the rapid growth in the use of these materials, their waste disposal has gradually become a focus of global attention. At present, the main treatment methods for waste high-carbon materials include landfill, incineration and physical recycling, but these methods all have significant problems. Landfill occupies a large amount of land and pollutes soil and water sources. Incineration not only consumes a lot of energy but also releases a large amount of greenhouse gases. Physical recycling is usually limited to single-component materials, and most of them are downgraded, which is difficult to meet the needs of high-value reuse. These shortcomings seriously limit the resource utilization of waste high-carbon materials.

[0003] Graphitization is a key step to stabilize the carbon element and realize the resource utilization and high-value utilization of high-carbon content materials. Through high-temperature treatment, carbon atoms can be rearranged to form a highly crystallized structure, which significantly improves the electrical conductivity, thermal conductivity and mechanical strength of the material. However, graphitization has high requirements on the carbon content and preliminary treatment of the raw materials. For example, carbonized materials or raw materials with a carbon content of more than 80% are usually required to meet the conditions for graphitization. In addition, existing graphitization technologies generally face problems such as high energy consumption, complex processes and high costs. The heating, graphitization and cooling processes of traditional graphitization furnaces usually take several days, with energy consumption of more than 8000kWh / t. This not only causes huge energy consumption, but also limits the application of graphitization technology on an industrial scale. To this end, the development of an efficient and low-energy graphitization technology that can quickly convert high-carbon content materials into graphitized carbon or graphene has become an urgent need in the field of resource recovery and high-performance material preparation.

[0004] As the most excellent graphitized carbon material currently, graphene has great application potential in energy materials (such as lithium-ion batteries and supercapacitors), thermal management materials (such as heat sinks and thermal conductive films), functional composite materials (such as reinforced plastics and metals), and environmentally friendly materials (such as adsorbents and selective separation membranes) due to its excellent electrical conductivity, thermal conductivity, and mechanical properties. However, existing graphene preparation methods such as redox method and mechanical stripping method have serious pollution and poor quality. Although the chemical vapor deposition method has excellent quality, the cost is too high to meet large-scale industrial needs. Therefore, there is an urgent need for a low-cost, high-efficiency graphitization technology that can directly convert high-carbon content materials into high-quality graphene, providing a feasible solution for the large-scale application of graphene. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present invention provides a method for preparing graphene by electric pulse high temperature, which converts a material with a high carbon content and not artificially graphitized into graphene through rapid electric thermal high temperature treatment. The method has the characteristics of high efficiency, low energy consumption, and green environmental protection, and can achieve rapid carbonization and graphitization of high carbon content materials, providing a new technical path for large-scale low-cost preparation of graphene.

[0006] To this end, the present invention provides a method for preparing graphene by electric pulse high temperature, the method comprising the following steps:

[0007] mixing a non-graphitizable carbon material and a conductive carbon material to obtain a mixture;

[0008] Applying a pulse current to the mixture to heat the mixture to 2000-3000° C. to obtain an electrothermally treated mixture;

[0009] Cooling the mixture subjected to the electrothermal treatment to obtain the graphene;

[0010] Wherein, the carbon content in the non-graphitizable carbon material is ≥50wt%;

[0011] The heating rate is 10 3 -10 4 ℃ / s.

[0012] The present invention aims at the problems existing in the resource utilization of existing high-carbon content materials, graphitization technology and graphene preparation, and provides a method for converting high-carbon content and non-artificially graphitized materials into graphene through rapid electrothermal high-temperature treatment. The method realizes high-temperature treatment of 2000-3000°C by rapid heating with pulsed direct current, and arranges the carbon atoms in the high-carbon content materials in an orderly manner to form a mixture of flaky graphene and highly graphitized carbon particles. The method overcomes the limitations of high energy consumption and long time of traditional graphitization processes, and also realizes efficient utilization of carbon atom resources and minimization of defects, providing a new solution for the large-scale preparation of high-quality graphene and graphitized carbon materials.

[0013] According to an embodiment of the present invention, the cooling rate in the cooling process is 10 2 -10 4 ℃ / s.

[0014] According to an embodiment of the present invention, the mixing mass ratio of the non-graphitizable carbon material and the conductive carbon material is (1-30):1.

[0015] According to an embodiment of the present invention, the non-graphitized carbon material includes at least one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyimide, polyacrylonitrile, polyethylene terephthalate, waste plastics, waste rubber, asphalt, petroleum coke, coke or oil drilling sludge.

[0016] According to an embodiment of the present invention, the conductive carbon material includes at least one of carbon black, graphite or activated carbon.

[0017] According to an embodiment of the present invention, the pulse current is 20-5000A, preferably 100-1000A; the pulse voltage is 30-1000V, preferably 30-500V; and the pulse duration is 0.1-30s.

[0018] According to an embodiment of the present invention, the electrothermal treatment is performed in an inert atmosphere.

[0019] According to an embodiment of the present invention, the electrothermal treatment is performed at 100 Pa-10 KPa.

[0020] According to an embodiment of the present invention, the method further comprises: pulverizing and acid-washing the non-graphitizable carbon material to obtain non-graphitizable carbon particles, and mixing the non-graphitizable carbon particles with a conductive carbon material to obtain a mixture.

[0021] According to an embodiment of the present invention, the pickling treatment includes mixing the crushed non-graphitizable carbon material with an acid solution.

[0022] According to an embodiment of the present invention, the number of layers of the graphene is ≤10, and the Raman spectrum of the graphene is D / I G ≤0.5, I 2D / I G ≥0.5.

[0023] The beneficial effects of the present invention are as follows:

[0024] (1) Wide adaptability to raw materials

[0025] The present invention can directly process polymer materials and wastes with a carbon content of ≥50wt% and not artificially graphitized, such as polyethylene (PE), polypropylene (PP), PET, waste plastics, waste rubber, etc. At the same time, the technology is applicable to complex systems, including mixed wastes doped with metal and ceramic impurities, providing the possibility for high-value utilization of various waste high-carbon materials;

[0026] (2) Efficient conversion and utilization of carbon atoms

[0027] The present invention achieves orderly rearrangement and complete conversion of carbon atoms in a high temperature environment of 2000-3000°C through precise and rapid temperature rise and fall control. The carbon utilization efficiency in the preparation process reaches more than 90%, avoiding the waste of resources caused by by-products or incomplete reactions in traditional technologies. This high conversion efficiency not only improves the utilization rate of raw materials, but also significantly reduces waste emissions, further reflecting the advantages of green environmental protection and efficient resource utilization;

[0028] (3) Preparation of high-quality graphene

[0029] Through the rapid temperature rise and fall technology, the number of graphene sheets prepared is controllable (preferably ≤10 layers), the defect rate is low, the specific surface area is high, and it has excellent dispersibility and electrical and thermal conductivity, which is suitable for multi-field applications of high-performance materials;

[0030] (4) Significant energy-saving effect

[0031] The present invention uses flash Joule heating technology to heat the 3 -10 4 ℃ / s) to achieve high temperature treatment of 2000-3000℃, and energy consumption is reduced to ≤1000kWh / t, which greatly reduces energy consumption compared with traditional graphitization process;

[0032] (5) Efficient time control

[0033] The traditional graphitization process usually takes several days to complete the heating, graphitization and cooling process, while the present invention can complete the entire conversion process within seconds, greatly shortening the process time and improving production efficiency;

[0034] (6) Green and environmentally friendly features

[0035] No solvents or catalysts are used in the preparation process, and no wastewater or exhaust gas is discharged, achieving a zero-pollution green process that meets current environmental protection and sustainable development requirements;

[0036] (7) Extensive industrial application potential

[0037] The graphene and graphitized carbon materials prepared by the present invention have excellent properties and can be widely used in energy materials (such as lithium-ion batteries and supercapacitors), thermal management materials (such as thermal conductive sheets and heat dissipation films), functional composite materials (such as reinforced plastics and ceramic composites) and environmentally friendly materials (such as adsorbents and selective separation membranes).

[0038] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0040] Figure 1 A physical picture of the polypropylene powder in Example 1 of the present invention is shown;

[0041] Figure 2 It shows the temperature-time curve of the rapid electrothermal high temperature treatment process of polypropylene powder in Example 1 of the present invention;

[0042] Figure 3 The Raman spectra of the polypropylene powder in Example 1 of the present invention after being subjected to different electrothermal high-temperature treatments are shown;

[0043] Figure 4 The SEM image of the polypropylene powder in Example 1 of the present invention after being subjected to 2650° C. electrothermal high temperature treatment is shown;

[0044] Figure 5 The XRD pattern of the polypropylene powder in Example 1 of the present invention after being subjected to 2650° C. electrothermal high temperature treatment is shown;

[0045] Figure 6 The figure shows the 2.5wt% NMP dispersion obtained by rapid electrothermal high temperature treatment of polypropylene in Example 1 (electrothermal treatment temperature of 2000°C), polyacrylonitrile in Example 2 (electrothermal treatment temperature of 2800°C), polyimide in Example 3 (electrothermal treatment temperature of 2250°C), waste PET in Example 4 (electrothermal treatment temperature of 2600°C) and waste mobile phone plastic in Example 5 (electrothermal treatment temperature of 2850°C) after standing for one week;

[0046] Figure 7 A physical picture of the polyacrylonitrile powder in Example 2 of the present invention is shown;

[0047] Figure 8 The temperature-time curve of the rapid electrothermal high-temperature treatment process of polyacrylonitrile powder in Example 2 of the present invention is shown;

[0048] Fig. 9 The Raman spectra of the polyacrylonitrile powder in Example 2 of the present invention after being subjected to different electrothermal high-temperature treatments are shown;

[0049] Fig.10 The SEM image of the polyacrylonitrile powder after being subjected to 2650° C. electrothermal high temperature treatment in Example 2 of the present invention is shown;

[0050] Fig.11 The low magnification TEM image of the polyacrylonitrile powder after electrothermal high temperature treatment at 2650° C. in Example 2 of the present invention is shown, and the scale is 50 nm;

[0051] Fig.12 The middle magnification TEM image of the polyacrylonitrile powder after electrothermal high temperature treatment at 2650° C. in Example 2 of the present invention is shown, and the scale is 20 nm;

[0052] Fig.13 The high-magnification TEM image of the polyacrylonitrile powder after electrothermal high-temperature treatment at 2650° C. in Example 2 of the present invention is shown, and the scale is 5 nm;

[0053] Fig.14 The SAED pattern of the polyacrylonitrile powder after electrothermal high temperature treatment at 2650° C. in Example 2 of the present invention is shown, with a scale of 5 and a unit of 1 / nm;

[0054] Fig.15 The XRD pattern of the polyacrylonitrile powder in Example 2 of the present invention after being subjected to 2650° C. electrothermal high temperature treatment is shown;

[0055] Fig.16 A physical picture of the polyimide powder in Example 3 of the present invention is shown;

[0056] Fig.17 The temperature-time curve of the rapid electrothermal high-temperature treatment process of polyimide powder in Example 3 of the present invention is shown;

[0057] Fig.18 The Raman spectra of the polyimide powder in Example 3 of the present invention after being subjected to different electrothermal high-temperature treatments are shown;

[0058] Fig.19 The SEM image of the polyimide powder in Example 3 of the present invention after being subjected to 2250° C. electrothermal high temperature treatment is shown;

[0059] Fig. 20 The XRD pattern of the polyimide powder in Example 3 of the present invention after being subjected to an electrothermal high temperature treatment at 2500° C. is shown;

[0060] Fig.21 The comparative physical pictures of the waste PET plastic before and after crushing in Example 4 of the present invention are shown;

[0061] Fig. 22 The temperature-time curve of the rapid electrothermal high-temperature treatment process of waste PET plastic in Example 4 of the present invention is shown;

[0062] Fig.23 The Raman spectra of the waste PET plastics after different electrothermal high-temperature treatments in Example 4 of the present invention are shown;

[0063] Fig.24 The SEM image of the waste PET plastic after being subjected to 2100°C electric heating high temperature treatment in Example 4 of the present invention is shown;

[0064] Fig.25 The XRD pattern of the waste PET plastic after being subjected to 2600°C electric heating high temperature treatment in Example 4 of the present invention is shown;

[0065] Fig.26 A physical picture showing the waste mobile phone plastic powder before pickling treatment in Example 5 of the present invention;

[0066] Fig. 27 A physical picture showing the waste mobile phone plastic powder after acid washing in Example 5 of the present invention;

[0067] Fig.28 The XRD comparison diagram of the waste mobile phone plastic powder before and after the acid washing treatment in Example 5 of the present invention is shown;

[0068] Fig.29 The element content distribution diagram of the waste mobile phone plastic powder before the acid washing treatment in Example 5 of the present invention is shown;

[0069] Fig.30 The element content distribution diagram of the waste mobile phone plastic powder after acid washing in Example 5 of the present invention is shown;

[0070] Fig.31 The temperature-time curve of the rapid electrothermal high-temperature treatment process of waste mobile phone plastic powder in Example 5 of the present invention is shown;

[0071] Fig.32 The Raman spectra of the waste mobile phone plastic powder after being subjected to different electrothermal high-temperature treatments in Example 5 of the present invention are shown;

[0072] Fig.33 The SEM image of the waste mobile phone plastic powder after being subjected to 2850°C electrothermal high temperature treatment in Example 5 of the present invention is shown;

[0073] Fig.34 The XRD diagram of the waste mobile phone plastic powder after being subjected to 2400°C electric heating high temperature treatment in Example 5 of the present invention is shown;

[0074] Fig.35 The Raman spectra of the polypropylene powder after electrothermal high temperature treatment at 2650°C in Example 1 of the present invention, the Raman spectra of the polyacrylonitrile powder after electrothermal high temperature treatment at 2650°C in Example 2, the Raman spectra of the polyimide powder after electrothermal high temperature treatment at 2000°C in Example 3, the Raman spectra of the waste PET plastic after electrothermal high temperature treatment at 2600°C in Example 4, and the Raman spectra of the waste mobile phone plastic powder after electrothermal high temperature treatment at 2150°C in Example 5 are shown;

[0075] Fig.36 The temperature-time curve of the rapid electrothermal high-temperature treatment process of polypropylene powder in Comparative Examples 1-3 of the present invention is shown;

[0076] Fig.37 The Raman spectra of the polypropylene powders in Comparative Examples 1-3 of the present invention after being subjected to different electrothermal high-temperature treatments are shown. DETAILED DESCRIPTION

[0077] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0078] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0079] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0080] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0081] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0082] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0083] According to an embodiment of the present invention, the present invention provides a method for preparing graphene by electric pulse high temperature, comprising the following steps:

[0084] mixing a non-graphitizable carbon material and a conductive carbon material to obtain a mixture;

[0085] Applying a pulse current to the mixture to heat the mixture to 2000-3000° C. to obtain an electrothermally treated mixture;

[0086] Cooling the mixture subjected to the electrothermal treatment to obtain the graphene;

[0087] Wherein, the carbon content in the non-graphitizable carbon material is ≥50wt%;

[0088] The heating rate is 10 3 -10 4 ℃ / s.

[0089] The present invention converts a high-carbon-content, non-graphitized material into graphene by rapid electrothermal high-temperature treatment, wherein the high-temperature treatment provides sufficient kinetic energy to carbon atoms to promote their transformation from a disordered amorphous structure to an ordered sp 2 The rapid heating can accelerate the migration and rearrangement of carbon atoms, effectively shorten the time required to form a highly graphitized structure, and avoid material degradation or impurity diffusion caused by long-term heating in traditional graphitization processes. During high-temperature treatment, non-carbon elements (such as O, H, and N) in the material escape in the form of gas, significantly reducing the impact of residual impurities on the graphitized structure. Specifically, H atoms react with O atoms to generate water vapor (H2O), or are directly discharged in the form of hydrogen (H2); O atoms are mostly released in the form of carbon monoxide (CO) or carbon dioxide (CO2); N atoms usually form nitrogen (N2). These reaction products are quickly discharged under the vacuum or inert atmosphere of the reaction chamber, thereby further improving the purity and quality of the final product. In addition, rapid cooling can fix the stable structure formed under high temperature conditions, prevent further lattice dislocation or defect generation, and inhibit the recombination of incompletely converted elements, providing high purity and low defect characteristics for graphene and graphitized carbon materials.

[0090] Compared with the traditional graphene preparation method (oxidation-reduction method or chemical vapor deposition method, etc.), the graphene prepared by the present invention has low defects, high specific surface area and good dispersibility, and is suitable for energy materials (electrode materials for lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, supercapacitors and fuel cells, which significantly improve the performance of energy storage devices by improving conductivity, energy density and cycle life), thermal management materials (including thermal conductive materials, heat absorbing materials, heat dissipating materials and electric heating materials, which are suitable for flexible electric heating sheets, solar collectors, high-efficiency heat sinks, thermal conductive pastes and electronic equipment thermal management systems), functional composite materials (including conductive plastics, reinforced metals and their alloys, ceramic composites and carbon-carbon composites, which are used to improve the mechanical strength, conductivity, corrosion resistance and high temperature resistance of the matrix material), environmental and adsorption materials (used as adsorption materials (such as oil adsorption and pollutant removal), selection The fields of application include: separation materials (such as desalination, air purification and gas separation membranes) and barrier materials (such as moisture and oxygen permeation resistance, suitable for environmental protection and industrial applications), functional coatings (including fire retardant coatings, anti-corrosion coatings, electronic shielding coatings, hydrophobic coatings and conductive inks, used in building protection, industrial coatings and the manufacture of flexible electronic devices), high-tech cutting-edge materials (including semiconductor materials (such as graphene field effect transistors, sensor elements), optical materials (such as transparent conductive films), communication materials (such as high-frequency antennas) and flexible electronic materials (such as flexible electrodes and wearable devices)), biomedical materials (including antibacterial coatings, drug delivery materials and tissue repair scaffolds, used in medical devices, bioimplants and biomedical engineering), standards and others (used for standard reference materials (such as nano-thickness calibrants, spectral calibrants, specific surface area standards) and other potential industrial applications).

[0091] According to a specific embodiment of the present invention, the type of the non-graphitized carbon material is not particularly limited, and includes but is not limited to polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyimide, polyacrylonitrile, polyethylene terephthalate, waste plastics, waste rubber, asphalt, petroleum coke, coke or drilling sludge, etc.

[0092] According to a specific embodiment of the present invention, the method further comprises: pulverizing and acid-washing the non-graphitizable carbon material to obtain non-graphitizable carbon particles, and mixing the non-graphitizable carbon particles with a conductive carbon material to obtain a mixture.

[0093] Specifically, the pulverization process can achieve a non-graphitized carbon material particle size of 1-1000 μm, so as to ensure that it is suitable for the reaction chamber filling and reaction requirements for subsequent electrothermal treatment. The pulverization method is not particularly limited, including but not limited to mechanical pulverization, ball milling or other mechanical mixing methods.

[0094] Specifically, the pickling treatment includes mixing the crushed non-graphitized carbon material with an acid solution or an alkaline solution to dissolve some non-carbon elements and compounds in the material and remove impurities to further increase the carbon content.

[0095] According to a specific embodiment of the present invention, the type of the conductive carbon material is not particularly limited, and includes but is not limited to carbon black, graphite, and activated carbon.

[0096] According to a specific embodiment of the present invention, the mixing mass ratio of the non-graphitizable carbon material and the conductive carbon material is (1-30):1, so as to ensure that the mixture has good electrical conductivity and uniform heat transfer characteristics during the reaction.

[0097] According to a specific embodiment of the present invention, the resistance of the mixture is 0.1-100Ω, and the average particle size of the mixture is 0.1-1000 μm, so as to ensure good electrical conductivity and uniform heat transfer characteristics.

[0098] According to a specific embodiment of the present invention, the heating rate in the electrothermal treatment is 10 3 -10 4 ℃ / s, so the extremely high heating and cooling rate plays a key role in reducing the defect density, that is, under high temperature environment, the diffusion rate of carbon atoms is significantly improved, and the amorphous carbon area is converted into a graphitized lattice. The electrothermal treatment can achieve high-temperature rapid carbonization and graphitization reactions, realize the rearrangement of carbon atoms, and form flake graphene with a hexagonal honeycomb structure.

[0099] According to a specific embodiment of the present invention, the pulse current is 20-5000A, preferably 100-1000A; the pulse voltage is 30-1000V, preferably 30-500V, and the pulse duration is 0.1-30s. The power determines the quality of the reactants. Specifically, I 2 Rt=cm(T2-T1). The temperature settings in the laboratory and pilot or mass production are the same, and the resistance is also similar, all around 1-5Ω. The settings here can meet the requirements of 1g-1kg of reactants per reaction.

[0100] Specifically, the pulse current is provided by a pulsed DC power supply, which may include a current control module and a temperature feedback module to achieve precise reaction temperature control.

[0101] According to a specific embodiment of the present invention, the electrothermal treatment may specifically include: filling the mixture into a reaction chamber, and connecting it to a pulsed DC power supply via a graphite or high temperature resistant metal electrode.

[0102] Specifically, the reaction chamber is made of high temperature resistant materials, including but not limited to quartz, corundum, mullite, concrete or other refractory materials, and the reaction chamber has anti-oxidation properties.

[0103] Specifically, the graphite electrode is preferably made of high-purity graphite, and its resistivity is ≤10 μΩ·m.

[0104] According to a specific embodiment of the present invention, the electrothermal treatment is carried out in an inert atmosphere, which includes but is not limited to nitrogen, argon, etc. The inert atmosphere inside the cavity can be adjusted at a flow rate of 1-100L / min to prevent the occurrence of oxidation reaction.

[0105] According to a specific embodiment of the present invention, the electrothermal treatment is performed at 100 Pa-10 KPa. In the present invention, the pressure is absolute pressure.

[0106] According to a specific embodiment of the present invention, the cooling rate in the cooling process is 10 2 -10 4 ℃ / s to reduce the degree of graphitization of the flakes and form a mixture of flaky graphene and highly graphitized carbon particles.

[0107] Specifically, the cooling process can be achieved through natural cooling, a gas cooling module or a liquid cooling module.

[0108] According to a specific embodiment of the present invention, the method may further include: characterizing the product obtained by the cooling process to confirm that its structure and quality meet expectations. Characterization methods include but are not limited to X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy (Raman).

[0109] According to a specific embodiment of the present invention, the method may further include: post-processing the product obtained by the cooling treatment to further improve the purity, layer number control and dispersion performance of the graphene.

[0110] Specifically, the post-treatment includes but is not limited to pickling treatment, ultrasonic dispersion treatment or centrifugal separation treatment.

[0111] Specifically, the pickling treatment may be to mix the product obtained by the cooling treatment with an acidic reagent, wherein the acidic reagent includes but is not limited to hydrochloric acid, sulfuric acid, and the like.

[0112] Specifically, the ultrasonic frequency and treatment time in the ultrasonic dispersion treatment are not particularly limited. As some specific examples, an ultrasonic frequency of 20-40 kHz and a treatment time of 5-30 min may be used.

[0113] Specifically, the rotation speed and centrifugation time of the centrifugal separation treatment are not particularly limited. As some specific examples, the rotation speed may be 5000-10000 rpm and the centrifugation time may be 10-30 min.

[0114] According to a specific embodiment of the present invention, the number of layers of the graphene is ≤10, and the Raman spectrum of the graphene is D / I G ≤0.5, I 2D / I G ≥0.5. Thus, the graphene has low defects, excellent conductivity and specific surface area. At the same time, the graphene also has a high specific surface area and good dispersibility, and can be stable in a 2.5wt% N-methylpyrrolidone (NMP) dispersion for at least 1 week without precipitation, and is suitable for the preparation of dispersed slurries, electrode materials and composite materials.

[0115] According to a specific embodiment of the present invention, the average particle size of the highly graphitized carbon particles is 50-500 nm, and the crystallinity is characterized by low defect rate and high order, which conforms to the structural characteristics of a high degree of graphitization.

[0116] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. In the embodiments, if no specific techniques or conditions are indicated, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially. The heating process in the following embodiments and comparative examples, if not otherwise specified, is carried out in a vacuum chamber.

[0117] Example 1

[0118] This embodiment provides a method for converting polypropylene into graphene by rapid electrothermal high-temperature treatment. The method comprises the following steps:

[0119] 1. Prepare raw materials: Select analytical pure polypropylene powder, whose supplier is Shanghai MacLean Biochemical Technology Co., Ltd. Figure 1 shown.

[0120] 2. Mixing process: polypropylene powder and conductive carbon black are mixed in a mass ratio of 3:1, and ground evenly by a manual mortar to prepare a mixture.

[0121] 3. Reactant loading and atmosphere control: Place the mixture in a rapid electric heating high temperature reaction chamber and evacuate it to below 10KPa to prevent oxidation reaction from affecting the graphitization effect.

[0122] 4. Electrical heat treatment: In a vacuum environment, a high current pulse (discharge voltage intensity of 75V, current intensity of 150A, duration of 1s) is applied to instantly heat the sample to 2650°C, and then quickly cool it to room temperature. The temperature changes under different discharge conditions are as follows: Figure 2As shown in the figure, the temperature reaches the target value and the duration does not exceed 1s. In order to explore the effect of temperature on graphitization, the discharge voltage is adjusted to 65V and 60V, and the temperature is raised to 2300℃ and 2000℃ respectively.

[0123] 5. Product collection and characterization: The processed product is taken out and ground, and various characterization analyses are performed:

[0124] (1) Raman spectroscopy (see Figure 3 ): Under the treatment condition of 2650℃, sample I D / I G The ratio is 0.37, indicating that there are fewer defects; I 2D / I G The ratio is 0.86, indicating that the graphene sheet has a clear structure. Compared with 2300℃ and 2000℃, the higher temperature significantly reduces the defect density;

[0125] (2) SEM images (see Figure 4 ): After treatment at 2650℃, the surface of the product presents a flake graphene structure with evenly stacked flakes, indicating that high temperature promotes the orderly arrangement of carbon atoms;

[0126] (3) XRD pattern (see Figure 5 ): After treatment at 2650℃, the characteristic peak (002) of graphite has significant crystal plane intensity and good crystal structure.

[0127] 6. Post-treatment: Add the treated product to NMP solvent and ultrasonicate for 5 minutes to prepare a dispersion mainly composed of few-layer or single-layer graphene. The dispersion was left to stand for one week without obvious sedimentation (see Figure 6 ). This result shows that the graphene prepared by this method has excellent dispersion stability.

[0128] 7. Discussion of experimental results:

[0129] (1) Effect of temperature: As the treatment temperature increases from 2000°C to 2650°C, the D / I G The ratio is significantly reduced and defects are reduced; 2D / I G The ratio approaches the ideal value, indicating that the graphene sheets are more regular.

[0130] (2) Purity of raw materials: Polypropylene raw materials are of high purity, with very few oxygen and hydrogen impurities, which is suitable for the formation of high-quality graphene. This also means that raw materials with high impurity content (such as waste mobile phone plastics) need to be pre-treated to improve their purity.

[0131] Example 2

[0132] This embodiment provides a method for converting polyacrylonitrile into graphene by rapid electrothermal high-temperature treatment. The method comprises the following steps:

[0133] 1. Prepare raw materials: Select analytical pure polyacrylonitrile powder, whose supplier is Shanghai Aladdin Biochemical Technology Co., Ltd. Figure 7 shown.

[0134] 2. Mixing process: Mix polyacrylonitrile powder and conductive carbon black in a mass ratio of 3:1, grind evenly, and prepare a mixture.

[0135] 3. Reactant loading and atmosphere control: Place the mixture in a rapid electric heating high-temperature reaction chamber and evacuate it to below 10KPa to prevent the occurrence of high-temperature oxidation reactions.

[0136] 4. Electrical heat treatment: Apply high current pulses (discharge voltage intensity of 75V, current intensity of 150A, duration of 1s) in a vacuum environment to rapidly heat the sample to 2800°C, and then rapidly cool it to room temperature. Adjusting the discharge voltage to 65V and 60V can make the temperature reach 2650°C and 2300°C respectively. The specific temperature curves are as follows: Figure 8 As shown in the figure, the temperature reaches the target value and the duration does not exceed 1s.

[0137] 5. Product collection and characterization:

[0138] (1) Raman spectroscopy: analysis results (see Fig. 9 ) shows that I D / I G The ratio decreases with increasing temperature. At 2650℃, I D / I G The ratio is 0.20, indicating that the sample has few defects. 2D / I G The ratio is 1.11, indicating the formation of high-quality graphene.

[0139] (2) Scanning electron microscopy (SEM): Fig.10 The flaky structure of the product surface after treatment at 2650°C is shown, and the interlayer stacking is uniform, which further verifies the promoting effect of high temperature treatment on graphitization.

[0140] (3) Transmission electron microscopy (TEM): low magnification (see Fig.11 ), medium times (see Fig.12 ) and high power (see Fig.13)TEM photos show that the product has typical flake graphene characteristics. Low-magnification images show that the flake structure is evenly distributed, with a large area and some areas overlapping, indicating that the sample has successfully formed flake graphene; medium-magnification images further show clear and flat flake edges, and wrinkles in some areas indicate that the flake thickness is thin; lattice fringes can be seen in high-magnification images, with a spacing of 0.34nm, corresponding to the characteristic crystal plane (002) of graphene, further confirming that the sample has a high degree of graphitization and good crystal order.

[0141] (4) Selected area electron diffraction (SAED): Fig.14 The selected area electron diffraction image of the prepared graphene is shown. The annular diffraction pattern shows clear (002) diffraction rings, and the corresponding interplanar spacing is 0.34nm, indicating that there is high-crystallinity flake graphene in the sample. The uniformity and intensity of the diffraction rings indicate that the sample is graphitized uniformly and the grain size distribution is relatively consistent.

[0142] (5) X-ray diffraction (XRD): Fig.15 The XRD results show that the characteristic peak of graphite (002) has significant crystal plane intensity, indicating that the crystal structure is good.

[0143] 6. Post-treatment: Add the treated product to NMP solvent and ultrasonicate for 5 minutes to prepare a dispersion mainly composed of few-layer or single-layer graphene. The dispersion was left to stand for one week without obvious sedimentation (see Figure 6 ). This result shows that the graphene prepared by this method has excellent dispersion stability.

[0144] 7. Results and Discussion:

[0145] High temperature treatment effectively promotes the orderly arrangement of carbon atoms, especially at 2650℃, I D / I G Ratio and I 2D / I G The ratios all reached the optimum, indicating the highest degree of graphitization. TEM and SAED results further confirmed the high degree of graphitization and polycrystalline nature of the samples, and the proportion of flake graphene in the product was significantly increased. Comparing the experimental results at different temperatures, it can be seen that the higher the temperature, the fewer defects, but too high a temperature may cause some carbon to volatilize, and optimization should be carried out by comprehensively considering the raw material characteristics and energy costs. Polyacrylonitrile raw materials contain a small amount of nitrogen, and nitrogen atoms are partially released during the high temperature process, which may help repair defects during the graphitization process.

[0146] Implementation effect: This method combines multiple analytical methods such as SEM, TEM, SAED and XRD, proving that polyacrylonitrile can be efficiently converted into high-quality graphene through rapid high-temperature electrothermal treatment, providing an important basis for subsequent industrial preparation and high-end applications.

[0147] Example 3

[0148] This embodiment provides a method for converting polyimide into graphene by rapid electrothermal high-temperature treatment. The method comprises the following steps:

[0149] 1. Prepare raw materials: Select analytically pure polyimide powder, whose supplier is Shanghai Aladdin Biochemical Technology Co., Ltd. Fig.16 shown.

[0150] 2. Mixing treatment: polyimide powder and conductive carbon black are mixed in a mass ratio of 3:1, and ground evenly using a manual mortar to prepare a mixture.

[0151] 3. Reactant loading and atmosphere control: Place the mixture in a rapid electric heating high-temperature reaction chamber and evacuate it to below 10KPa to avoid high-temperature oxidation reactions.

[0152] 4. Electrothermal treatment: Apply high current pulses (discharge voltage intensity of 70V, current intensity of 150A, duration of 1s) in a vacuum environment to rapidly heat the sample to 2500°C, and then rapidly cool it to room temperature. By adjusting the discharge voltage to 60V and 55V, the sample can be heated to 2250°C and 2000°C, respectively. The specific temperature curve is as follows: Fig.17 As shown in the figure, the temperature reaches the target value and the duration does not exceed 1s.

[0153] 5. Product collection and characterization:

[0154] (1) Raman spectroscopy (see Fig.18 ): Under the treatment condition of 2000℃, the I D / I G The ratio is 0.18, indicating that the sample has a low defect density; while I 2D / I G The ratio is 1.06, the highest value at all temperatures, showing that the intensity of the 2D peak is higher than that of the G peak, indicating that the number of graphene layers in the sample is small and the quality is higher. In contrast, under the treatment conditions of 2250℃ and 2500℃, although I D / I G The ratios were lower (0.18 and 0.05, respectively), indicating that the defects were further reduced, but I 2D / I G The ratios dropped to 0.75 and 0.25, respectively, reflecting that high temperature may lead to increased stacking of flakes and a decrease in the proportion of few-layer graphene. In summary, 2000°C is the optimal temperature for polyimide to achieve high-quality graphene preparation under this experimental condition, which not only ensures low defects (I D / I G The ratio is moderate), and the quality of graphene layers is significantly improved (I 2D / I G than the highest).

[0155] (2) Scanning electron microscopy (SEM) (see Fig.19 ): SEM images show that after treatment at 2250°C, the sample presents a flaky structure with less stacking between the lamellae, indicating that high temperature effectively promotes the formation of graphitized carbon.

[0156] (3) X-ray diffraction (XRD) (see Fig. 20 ): The XRD spectrum of the graphite characteristic peak (002) of the sample treated at 2500℃ has significant crystal plane intensity, indicating that the sample has a good crystal structure.

[0157] 6. Post-treatment: Add the treated product to NMP solvent and ultrasonicate for 5 minutes to prepare a dispersion mainly composed of few-layer or single-layer graphene. The dispersion was left to stand for one week without obvious sedimentation (see Figure 6 ). The results show that graphene prepared by rapid high-temperature electrothermal treatment has excellent dispersion stability.

[0158] 7. Results and Discussion:

[0159] (1) The influence of raw materials on the results: Polyimide raw materials contain a small amount of oxygen and nitrogen elements. During the high-temperature treatment process, these impurity atoms are gradually removed. This process may promote the orderly arrangement of carbon atoms, reduce structural defects, and thus improve the degree of graphitization of the sample. In addition, the benzene ring chemical structure contained in polyimide itself provides a high-carbon content and high-quality precursor, which is an ideal material for preparing high-quality graphene.

[0160] (2) Temperature optimization: Experimental results show that 2000°C is the optimal temperature for preparing low-defect, high-layer quality graphene. However, the processing temperature needs to be optimized according to specific application requirements and raw material characteristics. Although too high a temperature (such as 2500°C) further reduces the defect density, it may also lead to increased stacking of graphene layers and partial carbon loss. Therefore, it is necessary to comprehensively consider the impact of temperature on quality and yield.

[0161] Implementation effect: This example successfully converts polyimide into high-quality graphene through rapid electrothermal high-temperature treatment. Combined with multiple characterization methods such as Raman, SEM and XRD, the high degree of graphitization and excellent performance of the sample are verified. The product has the characteristics of low defects and regular layers, and can be used in the fields of thermal conductive materials, high-performance composite materials and energy storage.

[0162] Example 4

[0163] This embodiment provides a method for converting waste PET plastic into graphene by rapid electrothermal high-temperature treatment. The method comprises the following steps:

[0164] 1. Prepare the raw materials: Select the PET plastic sheets from discarded beverage bottles and crush them into powder using a crusher (Baihaojia grinder, 34000rpm, 15min). The morphology of the sample before and after crushing is as follows: Fig.21 shown.

[0165] 2. Mixing treatment: Mix the waste PET powder and conductive carbon black in a mass ratio of 3:1, grind evenly, and obtain a mixture.

[0166] 3. Reactant loading and atmosphere control: Place the mixture in a rapid electric heating high-temperature reaction chamber and evacuate it to below 10KPa to prevent the occurrence of high-temperature oxidation reactions.

[0167] 4. Electrical heat treatment: In a vacuum environment, a high current pulse (discharge voltage of 68V, current intensity of 150A, duration of 1s) is applied to rapidly heat the sample to 2600°C, and then rapidly cool it to room temperature. By adjusting the discharge voltage (60V and 58V), the temperature reaches 2100°C and 2000°C respectively. The temperature change curve is shown in Figure 2. Fig. 22 shown.

[0168] 5. Product characterization:

[0169] (1) Raman spectrum: Raman analysis results (see Fig.23 ) shows that the I D / I G and I 2D / I G The ratios change significantly: 2000℃: D / G ratio is 0.60, 2D / G ratio is 1.18, indicating that lamellar graphene is formed, but with more defects; 2100℃: D / G ratio is 0.14, with the least defects; 2D / G ratio is 0.56, and the lamellar structure is not significant enough; 2600℃: D / G ratio is 0.16, with fewer defects; 2D / G ratio is 1.20, indicating that the lamellar regularity and degree of graphitization are optimal.

[0170] (2) Scanning electron microscopy (SEM): SEM images (see Fig.24 ) shows that after treatment at 2100℃, the surface of the sample is mainly granular, with porous and irregular features, and clusters formed in local areas. Different from the flake stacking structure, this morphology indicates that waste PET is more inclined to generate granular graphitized carbon during the decomposition and recombination process at high temperature. This result further shows that although high-temperature treatment promotes carbonization and graphitization, the raw material characteristics of waste PET may limit the formation of flake graphene.

[0171] (3) XRD spectrum: XRD results (see Fig.25 ) showed that the graphite characteristic peak (002) of the sample treated at 2600℃ had significant crystal plane intensity, further proving that the sample had a good crystal structure and degree of graphitization.

[0172] 6. Post-treatment: Add the treated product to NMP and ultrasonicate for 5 minutes to form a dispersion mainly composed of a few or single layers of graphene. The dispersion was left to stand for a week without significant sedimentation (see Figure 6 ).

[0173] 7. Results and Discussion:

[0174] (1) Effect of temperature on graphitization: When treated at 2000℃, although the graphene sheets are well formed (I 2D / I G The ratio is 1.18), but the sample has many defects (I D / I G When treated at 2100℃, the sample has the least defects (I D / I G ratio is 0.14), but the lamellar structure is not clear enough (I 2D / I G When treated at 2600℃, the sample has fewer defects (I D / I G ratio of 0.16) and a regular lamellar structure (I 2D / I G ratio is 1.20), showing the best degree of graphitization.

[0175] (2) Influence of raw material complexity: Waste PET raw materials contain a lot of oxygen elements, which are partially volatilized during high-temperature treatment and may play a certain role in defect repair, but its complexity may limit the further improvement of the quality of graphene sheets.

[0176] Implementation effect: By optimizing the processing temperature, this method successfully converts waste PET plastic into high-quality graphene. Especially at 2600°C, the product has low defects, high degree of graphitization and excellent lamellar structure, which is suitable for the preparation and resource utilization of high-performance materials.

[0177] Example 5

[0178] This embodiment provides a method for converting polymer material waste mobile phone plastic into graphene by rapid electrothermal high temperature treatment, the method comprising the following steps:

[0179] 1. Prepare raw materials: Select discarded mobile phone materials containing plastic and metal, crush them into powder using a crusher, and then crush the samples into powder. Fig.26 To remove metal impurities in the powder, the powder was immersed in a 12wt% hydrochloric acid solution for pickling. Fig. 27 The XRD comparison diagram before and after pickling is shown in Fig.28As shown in Figure 2, it shows that after pickling, the metal phase is significantly reduced, only a small amount of oxide remains, and the carbon content ratio of the sample is significantly increased (see Figure 29-30 ).

[0180] 2. Mixing treatment: Mix the acid-washed waste mobile phone plastic powder and conductive carbon black in a mass ratio of 3:1, and grind them evenly in a mortar to prepare a mixture.

[0181] 3. Reactant loading and atmosphere control: Place the mixture in a rapid electric heating high-temperature reaction chamber and evacuate the device to below 10KPa to prevent the occurrence of high-temperature oxidation reactions.

[0182] 4. Electric heat treatment: Apply two continuous high current pulses to the two stages of the reaction chamber under vacuum (the first discharge voltage intensity is 45V, the current intensity is 150A, and the duration is 1s; the second discharge voltage intensity is 70V, the current intensity is 150A, and the duration is 1s) to instantly heat the sample to 2850°C, and then quickly cool it to room temperature. Changing the first discharge voltage to 50V and the second discharge voltage to 60V, while keeping the current intensity and duration unchanged, the sample temperature can be raised to 2400°C. Changing the first discharge voltage to 50V and the second discharge voltage to 50V, while keeping the current intensity and duration unchanged, the sample temperature can be raised to 2150°C. The temperature-time curve is shown in the figure below. Fig.31 shown.

[0183] 5. Product characterization:

[0184] (1) Element content distribution: Comparison of element content before and after pickling Figure 29-30 As shown, the carbon content increased from 57.11% before pickling to 63.12%, further indicating that the removal effect of metal and non-metal impurities was significant.

[0185] (2) Raman spectroscopy: Raman spectra of samples treated at different temperatures are shown in Figure 2. Fig.32 The results show that sample I treated at 2150℃ D / I G The ratio is 0.32, indicating that its defect density is the lowest and the degree of graphitization is high. 2D / I G The ratio is 0.59, showing a clear lamellar structure. As the temperature rises to 2400℃, I D / I G The ratio increases to 0.60, I 2D / I G The ratio is 0.69, the degree of graphitization decreases, but still maintains good lamellar regularity. Further heating to 2850℃, I D / I G The ratio dropped to 0.47, but I 2D / IG The ratio dropped significantly to 0.46, indicating that too high a temperature may lead to the volatilization of carbon and structural damage, affecting the quality of graphitization. In summary, 2150℃ is the optimal temperature condition for graphitization of waste mobile phone plastics.

[0186] (3) Scanning electron microscopy (SEM): Fig.33 This is the SEM image of the sample after treatment at 2850℃, showing that the surface of the sample is a stacked lamellar structure. The lamellar layers are arranged evenly but there are wrinkles on the edges.

[0187] (4) XRD spectrum: The XRD pattern of the sample after treatment at 2400℃ is as follows Fig.34 As shown, the graphite characteristic peak (002) has obvious crystal plane intensity, indicating that the sample has a good crystal structure, but due to the high impurity content, the crystal integrity is still limited.

[0188] 6. Preparation of dispersion: Add the sample after electrothermal high temperature treatment into NMP solvent and ultrasonicate for 5 minutes to prepare a dispersion mainly composed of few-layer or single-layer graphene. After standing for one week, no obvious sedimentation was observed. The actual dispersion was as follows: Figure 6 shown.

[0189] 7. Results and Discussion:

[0190] (1) Raw material purification effect: Acid washing significantly removed the metal components (such as Al, Zn, etc.) in the waste mobile phone plastic, and the carbon content was increased to 63.12%, providing a purer matrix for high-temperature graphitization.

[0191] (2) Temperature effect: As the treatment temperature increases, the I D / I G Compared with first lowering and then raising, 2400℃ is the optimal temperature. Too high temperature (2850℃) may cause carbon volatilization and affect the quality of graphene.

[0192] (3) Influence of impurities: Compared with high-purity raw materials such as polypropylene, the degree of graphitization of waste mobile phone plastics is significantly limited by residual impurities, but a relatively regular graphene sheet structure is still formed.

[0193] Application potential: Although graphene prepared from waste mobile phone plastics is slightly inferior to high-purity raw materials in purity and defect density, it utilizes waste resources at a low cost and has important environmental significance and economic value.

[0194] Implementation effect:

[0195] By using this method, waste mobile phone plastics were quickly subjected to high-temperature electrothermal treatment and successfully converted into carbon materials with a high degree of graphitization. Experimental results show that at 2850°C, a flaky structure dominated by few-layer graphene was formed in the product, which had good conductivity and dispersion stability. The pickling step effectively removed metal and non-carbon impurities in the raw materials, greatly improving the quality of graphitization. Compared with traditional graphitization processes, this method has the significant advantages of high efficiency and low energy consumption, and provides a feasible technical path for the resource utilization of waste plastics and the low-cost preparation of graphene. The obtained graphene materials can be widely used in conductive composite materials, conductive inks and other fields, showing good application potential.

[0196] The Raman spectra of graphene obtained under relatively ideal experimental conditions in Examples 1-5 are integrated to obtain Fig.35 It can be seen that the method provided by the present invention solves many technical bottlenecks in the resource utilization of high-carbon content materials, graphitization technology and graphene preparation. This method not only significantly improves the process efficiency, but also achieves major breakthroughs in energy saving and consumption reduction, simplified operation procedures and green environmental protection. Utilizing rapid electric heating high-temperature treatment technology, the present invention can directly convert materials with a carbon content ≥50wt% and that have not been artificially graphitized into high-quality graphene and graphitized carbon particles in a very short time (within a few seconds). The entire preparation process does not require the addition of catalysts or solvents, avoiding the complex pretreatment and waste discharge problems in traditional technologies, and achieving clean, efficient and low-cost material conversion.

[0197] Comparative Example 1

[0198] The difference between this comparative example and Example 1 is only that:

[0199] Step 4. Electrothermal treatment: In a vacuum environment, a high current pulse (discharge voltage intensity of 58V, current intensity of 100A, duration of 1s) is applied to instantly heat the sample to 1700°C, and then quickly cool it to room temperature. The temperature change under this discharge condition is as follows: Fig.36 shown.

[0200] The Raman spectrum of the sample is Fig.37 The results show that sample I treated at 1700℃ D / I G The ratio is 0.72, indicating that its defect density is high. 2D / I G The ratio is 0.74, and there is a certain amount of graphitization, indicating that lower temperature will affect the graphitization quality of graphene.

[0201] Comparative Example 2

[0202] The difference between this comparative example and Example 1 is only that:

[0203] Step 4. Electrothermal treatment: In a vacuum environment, a high current pulse (discharge voltage intensity of 53V, current intensity of 100A, duration of 1s) is applied to instantly heat the sample to 1450°C, and then quickly cool it to room temperature. The temperature change under this discharge condition is as follows: Fig.36 shown.

[0204] The Raman spectrum of the sample is Fig.37 The results show that sample I treated at 1450℃ D / I G The ratio is 0.83, indicating that its defect density is high. 2D / I G The ratio is 1.03, and there is a certain amount of graphitization, indicating that lower temperature will affect the graphitization quality of graphene.

[0205] Comparative Example 3

[0206] The difference between this comparative example and Example 1 is only that:

[0207] Step 4. Electrothermal treatment: In a vacuum environment, a high current pulse (discharge voltage intensity of 47V, current intensity of 100A, duration of 1s) is applied to instantly heat the sample to 1150°C, and then quickly cool it to room temperature. The temperature change under this discharge condition is as follows: Fig.36 shown.

[0208] The Raman spectrum of the sample is Fig.37 The results show that sample I treated at 1150℃ D / I G The ratio is 0.89, indicating that its defect density is high. 2D / I G The ratio is 1.01, and there is a certain amount of graphitization, indicating that lower temperature will affect the graphitization quality of graphene.

[0209] In summary, Comparative Examples 1-3 were all subjected to electrothermal treatment under low temperature conditions. Although the samples showed a certain degree of graphitization, the results showed that this graphitization may be caused by local high temperature, resulting in an uneven internal structure of the material. Combined with Raman data ( Fig.37 ) shows that the obtained graphene has a high defect density, indicating that the process cannot stably control the quality of graphene.

[0210] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0211] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing graphene by electric pulse high temperature, characterized in that: The following steps are involved: mixing a non-graphitizable carbon material and a conductive carbon material to obtain a mixture; Applying a pulse current to the mixture to heat the mixture to 2000-3000° C. to obtain an electrothermally treated mixture; Cooling the mixture subjected to the electrothermal treatment to obtain the graphene; Wherein, the carbon content in the non-graphitizable carbon material is ≥50wt%; The heating rate is 10 3 -10 4 ℃ / s.

2. The method according to claim 1, characterized in that: The cooling rate in the cooling process is 10 2 -10 4 ℃ / s.

3. The method according to claim 1, characterized in that: The mixing mass ratio of the non-graphitizable carbon material and the conductive carbon material is (1-30):

1.

4. The method according to claim 1, characterized in that: The non-graphitized carbon material comprises at least one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyimide, polyacrylonitrile, polyethylene terephthalate, waste plastics, waste rubber, asphalt, petroleum coke, coke or oil drilling sludge; Optionally, the conductive carbon material includes at least one of carbon black, graphite or activated carbon.

5. The method according to claim 1, characterized in that The pulse current is 20-5000A, preferably 100-1000A; the pulse voltage is 30-1000V, preferably 30-500V; and the pulse duration is 0.1-30s.

6. The method according to claim 1, characterized in that The electrothermal treatment is performed in an inert atmosphere.

7. The method according to claim 1, characterized in that The electrothermal treatment is carried out at 100 Pa-10 KPa.

8. The method according to claim 1, characterized in that The method further comprises: pulverizing and acid-washing the non-graphitizable carbon material to obtain non-graphitizable carbon particles, and mixing the non-graphitizable carbon particles with a conductive carbon material to obtain a mixture.

9. The method according to claim 8, characterized in that The pickling treatment includes mixing the crushed non-graphitizable carbon material with an acid solution.

10. The method according to claim 1, characterized in that The number of layers of the graphene is ≤10, and the Raman spectrum of the graphene is D / I G ≤0.5, I 2D / I G ≥0.5.

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