A method for preparing graphene by solid-liquid in-situ reaction and graphene prepared thereby

Abstract

The application relates to a method for preparing graphene by solid-liquid in-situ reaction and graphene prepared by the method. The method comprises the following steps: heating and melting magnesium or a magnesium alloy in a crucible to obtain a melt; adding solid hexachloroethane into the melt at a speed of 1 g / min to 20 g / min and performing mechanical stirring, and then standing to obtain a mixture containing graphene above the melt; the mass amount of the solid hexachloroethane is 2% to 5% of the mass of the melt; separating the obtained mixture containing graphene from the melt; and performing post-treatment on the mixture containing graphene separated from the melt to obtain graphene. The application provides a method for preparing graphene in large quantities at low cost, with high production efficiency and high quality; the method has the advantages of simple operation, simple production equipment, low production cost, high yield, high graphene quality, fewer defects and impurities, excellent product performance and the like.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a method for preparing graphene by solid-liquid in-situ reaction and the graphene obtained therefrom. Background Technology

[0002] Graphene is a two-dimensional layered material, representing another significant discovery in the field of carbon nanomaterials after carbon nanotubes and fullerenes. Graphene possesses a large specific surface area, high mechanical strength, excellent thermal conductivity, and high carrier mobility, making it a promising candidate for applications in electrochemistry, materials science, biomedicine, and optics. While the central part of graphene is a perfect six-membered ring, the edges are often disrupted, resulting in pentagonal or heptagonal rings. This means that graphene is not truly complete; these deformed rings are not only distributed at the edges but also exist within each sheet of graphene produced in this way, becoming structural weaknesses and prone to breakage. Therefore, traditional methods struggle to ensure the structural and property stability of graphene. Traditional methods still have the following problems: Mechanical exfoliation can produce large quantities of graphene in recent years through continuous improvements, but the number and quality of graphene layers are difficult to control; Chemical vapor deposition can grow large areas of single-layer or few-layer graphene on metal substrates, but it requires high-temperature and high-pressure reaction conditions, placing high demands on equipment, and the issues of substrate transfer and removal need to be addressed; Liquid phase exfoliation can disperse graphite into single-layer or few-layer graphene in solvents through chemical or physical methods, but it introduces impurities and defects, reducing the quality and performance of graphene. Therefore, developing low-cost, high-efficiency, and environmentally friendly preparation technologies is key to the industrialization of graphene.

[0003] Research has revealed that introducing in-situ self-generated reactions to prepare graphene can effectively overcome the shortcomings of traditional methods. The in-situ self-generated method refers to the direct synthesis of graphene in a metal matrix through chemical reactions between elements or between elements and compounds, using appropriate reactants, followed by a simpler extraction process. This method ensures the stability of graphene's structure and properties while reducing production costs, increasing efficiency, and simplifying production compared to traditional methods. Current research has shown that in-situ reactions of CO2, CO, and magnesium have successfully prepared graphene. However, the high magnesium oxide content generated during these reactions significantly inhibits graphene yield. Furthermore, graphene extraction requires additional steps, increasing time and cost. Additionally, graphene prepared using existing technologies exhibits low electromagnetic shielding effectiveness. Therefore, further optimization of the in-situ self-generated graphene preparation method is essential to improve graphene yield and performance while reducing extraction difficulty.

[0004] In summary, it is essential to provide a method for preparing graphene through solid-liquid in-situ reaction and the resulting graphene. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the mass production of graphene that solves the problems of high cost, time and labor consumption, easy pollution and damage, generally low quality of graphene, low electromagnetic shielding effectiveness, defects, impurities, lack of crystallization, etc. of traditional graphene preparation methods. The invention proposes a low-cost method for mass production of graphene that balances production efficiency and quality, as well as the graphene obtained therefrom.

[0006] In a first aspect, this invention provides a method for preparing graphene via solid-liquid in-situ reaction, the method comprising the following steps:

[0007] (1) Heat and melt magnesium and / or magnesium alloys in a crucible to obtain a melt;

[0008] (2) Solid hexachloroethane is added to the melt at a rate of 1 g / min to 20 g / min and mechanically stirred, and then allowed to stand to obtain a mixture containing graphene above the melt; the mass of the solid hexachloroethane is 2 to 5% of the mass of the melt.

[0009] (3) Separate the resulting graphene-containing mixture from the melt;

[0010] (4) The graphene-containing mixture separated from the melt is post-processed to obtain graphene.

[0011] Preferably, steps (2) and (3) are repeated multiple times before step (4) to achieve continuous synthesis of graphene.

[0012] Preferably, in step (1): magnesium or magnesium alloy is heated and melted under the condition of passing a mixture of CO2 and SF6, preferably, the volume ratio of CO2 to SF6 is 40:1; the heating and melting temperature is 10 to 200°C higher than the melting point temperature of magnesium or magnesium alloy; and / or the liquid level of the melt is 0.25 to 0.6 times the height of the crucible.

[0013] Preferably, a gas treatment device is connected to the top of the crucible, and the air inlet of the gas treatment device is located 40-60 mm above the crucible; preferably, the gas treatment device includes a catalyst, a purifier and an exhaust pipe connected in sequence.

[0014] Preferably, in step (2): the mechanical stirring speed is 10 r / min to 3000 r / min, preferably 1000 to 3000 r / min; the mechanical stirring time is 30 to 150 min; the mechanical stirring temperature is 580 to 800 °C; and / or the settling time is 10 to 30 min.

[0015] Preferably, in step (2): the mixture containing graphene, magnesium oxide and magnesium chloride is left to stand above the melt.

[0016] Preferably, in step (4): the post-processing involves soaking the graphene-containing mixture separated from the melt in water, filtering it, and then treating it with a dilute acid solution.

[0017] Preferably, the solid hexachloroethane is in particulate form, and the particle size of the solid hexachloroethane is 5–20 μm.

[0018] Preferably, the obtained graphene is a multilayer graphene with 10 to 15 layers; and / or the thickness of the obtained graphene is less than 4 nm.

[0019] In a second aspect, the present invention provides a graphene prepared using the method described in the first aspect of the present invention.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] (1) This invention utilizes the in-situ solid-liquid reaction of C2Cl6 solid with a melt formed of magnesium or magnesium alloy to prepare large quantities of graphene. This yields multilayer graphene with suitable grain size, good crystallinity, few defects, good electrical and thermal conductivity, good mechanical strength, and good electromagnetic shielding effectiveness. It has significant application value in fields such as electronic devices, electromagnetic shielding, energy conservation and environmental protection, biomedicine, and composite materials. Because the graphene produced in the in-situ reaction is generated piece by piece, the stability of the graphene structure and properties is ensured. Furthermore, the mechanical stirring during the in-situ reaction further improves the reaction efficiency and graphene yield.

[0022] (2) The principle of the solid-liquid in-situ reaction preparation of graphene in this invention is simple. This invention discovers that only the addition of solid reactant C2Cl6 is needed to achieve the controllable generation of graphene in the system. C2Cl6, as a solid-phase reactant, is a high-content carbon source and does not contain other elements such as O, H, and N that react with the magnesium matrix, thus reducing by-products and increasing the growth rate of graphene. Magnesium, as a liquid-phase reactant, provides a stable and controllable reaction environment. The stable temperature and properties of the reaction system make the preparation of graphene more efficient and stable. This invention achieves the in-situ reaction... During the reaction process, MgCl2 is generated. As is well known, MgCl2 is usually used as a refining agent in the smelting of magnesium matrix. The principle is that it reacts with O2, H2O, etc. at high temperature to generate HCl and / or H2 gas. The gas forms a protective layer on the surface of the magnesium liquid, which slows down the oxidation of the magnesium liquid and has a good covering effect. At high temperature, liquid MgCl2 has a good wetting ability for inclusions such as MgO and Mg3N2, and can form MgCl2·5MgO composite compounds with MgO, thus having a strong ability to remove oxidized inclusions. This invention finds that the MgCl2 generated in this invention can be regarded as an in-situ generated refining agent. The generated graphene will precipitate on the surface of the melt along with the rising gas. The mixture of MgCl2 and MgO covers the surface of graphene, preventing graphene from being oxidized and playing a protective and modifying role. This makes the extraction of graphene prepared by this invention simpler, eliminating the time-consuming and energy-intensive extraction steps of traditional graphene preparation.

[0023] (3) Solid-liquid in-situ reaction for graphene preparation has the industrial advantages of low cost and high yield. C2Cl6, as a solid carbon source, is inexpensive, with a market price of less than 100 yuan per 500g. Magnesium, as a liquid-phase reaction system, is abundant in my country, which has the world's largest primary magnesium production. Magnesium and magnesium alloys are recyclable, hence they are called "inexhaustible" metal materials. In particular, high-quality graphene powder and other nano-reinforcements are very expensive, so effectively reducing the preparation cost of graphene is crucial for the preparation of graphene and the development of related fields. At the same time, the production equipment is simple and does not require additional imports or modifications, significantly reducing the operating and maintenance costs of the equipment. In addition, solid-liquid reactions have more advantages in terms of yield compared to gas-liquid reactions: the conversion ratio of raw materials to products is higher, and there is no overflow or waste of gaseous raw materials. Theoretically, adding 1 mol of C2Cl6 can stably generate 2 mol of C, saving raw materials and making it easier to control the yield. The magnesium matrix, as a reducing agent, is itself active and efficient, greatly shortening the reaction time. The present invention provides a method for preparing graphene by solid-liquid in-situ reaction, which changes the traditional method of graphene preparation, which is difficult to extract and consumes a lot of resources. At the same time, it can be produced continuously. The added magnesium and / or magnesium alloy can be reused. After the produced graphene is transferred out, magnesium and / or magnesium alloy can be heated again, and new C2Cl6 solid can be added to carry out in-situ autogenous reaction, which reduces production costs and shortens the process flow.

[0024] (4) The graphene prepared by the solid-liquid reaction of this invention has higher quality. Because the reaction system has a stable temperature, the reaction can proceed in an orderly manner at a certain rate and time. Moreover, the reaction is carried out from bottom to top, which is the reaction between chlorine in C2Cl6 and magnesium matrix, and the carbon atoms rearrange to form graphene. The magnesium oxide generated on the surface when left to stand can serve as a template for graphene attachment, similar to the principle of chemical vapor deposition. The process of this invention for mass production of graphene has higher utilization and production efficiency: the reaction between C2Cl6 solid and magnesium matrix or magnesium alloy does not produce insoluble impurities, thus optimizing the graphene extraction process. Compared with mechanical exfoliation, this method improves production efficiency to achieve higher yields; compared with traditional chemical vapor deposition, it solves the problems of substrate transfer and removal; and compared with liquid phase exfoliation, it improves the production quality of graphene. The in-situ self-generation method achieves controllable and predictable results in graphene production. Furthermore, this invention discovers that the solid-liquid in-situ reaction of this invention can further control the growth of graphene by adjusting the particle size and morphology of the raw materials. The reactants can act as templates, and the morphologies of graphene generated from different C2Cl6, such as micron-sized, nano-sized, meter-sized, powdered, granular, and sheet-like forms, are all different. Attached Figure Description

[0025] Figure 1 This is a flowchart of the graphene preparation process according to the present invention;

[0026] Figure 2 This is the XRD pattern of the graphene-containing mixture obtained in Example 1 of the present invention; in the figure, Graphene represents graphene.

[0027] Figure 3 This is the SEM scan energy spectrum of the graphene-containing mixture obtained in Example 1 of the present invention;

[0028] Figure 4 These are morphological images of the graphene obtained in Example 1 of this invention; in the figures, (a) is a physical image and (b) is a SEM image.

[0029] Figure 5 This is the XRD pattern of graphene obtained in Example 1 of this invention;

[0030] Figure 6 This is a Raman spectrum test result of the graphene prepared in Example 1 of the present invention;

[0031] Figure 7 These are AFM images of graphene prepared in Comparative Examples 1, 2 and 1 of the present invention; in the figures, (a) is a structural diagram of graphene in Comparative Example 1; (b) is a structural diagram of graphene in Comparative Example 2; (c) is a structural diagram of graphene in Example 1; and (d) is a total thickness distribution of graphene in Comparative Examples 1, 2 and 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] In a first aspect, this invention provides a method for preparing graphene via solid-liquid in-situ reaction, the method comprising the following steps:

[0034] (1) Magnesium (pure magnesium) and / or magnesium alloys are heated and melted in a crucible to obtain a melt; in this invention, the magnesium alloy can be, for example, a magnesium-zinc alloy, a magnesium-calcium alloy or a magnesium-copper alloy; this invention does not have any particular limitation on magnesium-zinc alloys, magnesium-calcium alloys or magnesium-copper alloys, and those skilled in the art can make conventional choices;

[0035] (2) Solid hexachloroethane (C2Cl6) is added to the melt at a rate of 1 g / min to 20 g / min (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 g / min), preferably 2 g / min to 5 g / min (e.g., 2, 3, 4 or 5 g / min), and mechanically stirred. The mixture is then allowed to stand to obtain a graphene-containing mixture above the melt. The mass percentage of the solid hexachloroethane is 2 to 5% (e.g., 2%, 3%, 4% or 5%) of the mass of the melt. In this invention, the graphene-containing mixture is, for example, a mixture containing graphene, magnesium oxide, and chlorine. A mixture of magnesium oxide; in some specific embodiments of the present invention, the solid-liquid in-situ reaction is as follows: first, pure magnesium or magnesium alloy is placed in a crucible and heated to its melting point to melt it. SF6 / CO2 protective gas is continuously introduced into the surface of the melt to prevent oxidation of pure magnesium or magnesium alloy. Then, at a temperature 10°C-200°C higher than the melting point, a certain amount of C2Cl6 is continuously and slowly added to the crucible at a rate of 1g / min-20g / min. The mixture is continuously mechanically stirred at a speed of 10r / min-3000r / min. Finally, the reaction system is allowed to stand for 10min-30min. Under the action of gravity and MgCl2 precipitation, a large amount of a mixture containing graphene, magnesium oxide and magnesium chloride will precipitate on the surface of the melt.

[0036] (3) Separate the resulting graphene-containing mixture from the melt;

[0037] (4) The graphene-containing mixture separated from the melt is post-processed to obtain graphene.

[0038] This invention utilizes the solid-liquid in-situ preparation principle of graphene using C2Cl6 and a magnesium matrix (pure magnesium and / or magnesium alloy). The preparation principle is simple, the product cost is low, the yield is high, the quality is high, and the reaction system is stable. By reasonably controlling the preparation process of the solid-liquid reaction, this invention can obtain large quantities of multilayer graphene with suitable grain size, good crystallinity, few defects, good electrical conductivity, good thermal conductivity, and good electromagnetic shielding effectiveness. It has novel application prospects and excellent future prospects.

[0039] This invention selects solid C2Cl6 as the reactant. It has been discovered that C2Cl6 is an oxygen-free reactant that reacts more readily with a magnesium matrix. This invention utilizes an in-situ solid-liquid reaction between C2Cl6 and a magnesium matrix. Compared to using gaseous or liquid reactants, this method allows for easier control of the reaction volume and minimizes waste. Furthermore, it facilitates temperature control, avoiding the problems of violent or slow reactions caused by uncontrollable temperature. This results in a stable and controllable reaction, enabling precise regulation of graphene yield and morphology, leading to graphene with suitable grain size, good crystallinity, few defects, and good conductivity.

[0040] Mass-produced multilayer graphene with good thermal conductivity and better electromagnetic shielding performance.

[0041] This invention involves a solid-liquid in-situ reaction of solid C2Cl6 with magnesium and / or magnesium alloys. During the solid-liquid reaction, the generated graphene floats above the melt, making it easy to extract. This method of preparing graphene through solid-liquid in-situ reaction overcomes the difficulties and high consumption associated with traditional graphene preparation, while enabling continuous production. Unlike traditional methods that use gaseous or liquid reactants added according to a reaction ratio, this invention uses a much higher amount of magnesium or magnesium alloy than solid C2Cl6. Specifically, the mass of solid hexachloroethane used in this invention is only 2-5% of the mass of the melt. This allows for the reuse of magnesium and / or magnesium alloys. After the produced graphene is transferred out, the magnesium and / or magnesium alloy can be heated further, and new solid C2Cl6 can be added to continue the in-situ autogenous reaction. This significantly reduces production costs and shortens the process flow.

[0042] This invention discovers that adding solid hexachloroethane (C2Cl6) to the melt at a rate of 1 g / min to 20 g / min helps to form graphene grains of moderate size, promotes the formation of more ordered and highly crystalline graphene structures, and contributes to obtaining graphene with good electrical conductivity, thermal conductivity, and electromagnetic shielding effectiveness. Furthermore, it can reduce defects in graphene, improving product quality. Graphene with fewer defects typically exhibits better electron transport properties. In other words, it not only helps improve the electromagnetic shielding and thermal properties of graphene but also has the potential to reduce defects during the preparation process, thereby improving the quality and application potential of graphene. Conversely, excessively slow or fast addition rates will adversely affect the size, crystallinity, layer number control, and defect quantity of graphene grains.

[0043] According to some preferred embodiments, steps (2) and (3) are repeated multiple times before step (4) to achieve continuous synthesis of graphene.

[0044] According to some preferred embodiments, in step (1): magnesium or magnesium alloy is heated and melted under the condition of introducing a mixture of CO2 and SF6, preferably, the volume ratio of CO2 to SF6 is 40:1; the heating and melting temperature is 10 to 200°C higher than the melting point temperature of magnesium or magnesium alloy; and / or the liquid level of the melt is 0.25 to 0.6 of the height of the crucible. In this invention, controlling the liquid level of the melt to be 0.25 to 0.6 of the height of the crucible is beneficial for collecting the graphene-containing mixture precipitated above the melt.

[0045] According to some preferred embodiments, a gas treatment device is connected to the top of the crucible. The inlet of the gas treatment device is located 40-60 mm (e.g., 40, 45, 50, 55, or 60 mm) above the crucible, which is beneficial for maximizing the collection of chloride gas generated during processing and avoiding air pollution. Preferably, the gas treatment device includes a catalyst, a purifier, and an exhaust pipe connected in sequence. The production equipment in this invention is simple and requires no additional improvement or modification, significantly reducing the operating and maintenance costs. However, it is preferable to introduce a gas treatment device (tail gas treatment device) into the existing stirred casting equipment to construct a solid-liquid reaction system including the gas treatment device, so as to effectively solve the problem of high costs caused by pollution and loss in traditional graphene preparation.

[0046] According to some specific embodiments, the top of the crucible is connected to a gas processing device, the gas inlet of which is located 50mm above the crucible, and a catalyst, a purifier, and an exhaust pipe are connected in sequence. The catalyst is used to catalyze the collected chloride gas into a more environmentally friendly gas, and the purifier is used to further purify the catalytic gas, collect the generated chloride gas to the maximum extent, and avoid air pollution and harm to the body.

[0047] According to some preferred embodiments, in step (2): the rotational speed of the mechanical stirring is 10 r / min to 3000 r / min (e.g., 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500 or 3000 r / min), preferably 1000 to 3000 r / min (e.g., 1000, 1200, 1500, 1800, 2000, 2200, 2500 or 3000 r / min); the mechanical stirring time is 30 to 150 min (e.g., 30, 40, 50, 60, 70, 80, 90). The temperature of the mechanical stirring is 580-800℃ (e.g., 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃), preferably 600-800℃; and / or the settling time is 10-30 min (e.g., 10, 15, 20, 25 or 30 min).

[0048] According to some preferred embodiments, in step (2): the mixture containing graphene, magnesium oxide and magnesium chloride is left to stand above the melt.

[0049] According to some preferred embodiments, in step (4): the post-processing involves soaking the graphene-containing mixture separated from the melt in water, filtering it, and then treating it with a dilute acid solution.

[0050] According to some preferred embodiments, the solid hexachloroethane is in particulate form with a particle size of 5–20 μm. This facilitates precise control over the crystal structure of multilayer graphene, resulting in high-quality multilayer graphene with moderate grain size, high crystallinity, few defects, good electrical conductivity, good electromagnetic shielding effectiveness, good thermal conductivity, and high mechanical strength. This invention has found that using particulate solid hexachloroethane with a particle size of 5–20 μm helps form a uniform reaction mixture, and appropriately sized particles can act as catalytic nuclei, helping to control the grain size of graphene. Furthermore, this invention... Using granular solid hexachloroethane with a particle size of 5–20 μm can provide more nucleation sites in the growth of graphene, promoting more ordered crystal growth, increasing the crystallinity of graphene, and thus improving its electrical conductivity, electromagnetic shielding effectiveness, and thermal conductivity. Furthermore, granular solid hexachloroethane with a particle size of 5–20 μm is more conducive to uniform distribution in the reaction system, which can reduce the formation of defects and improve the quality of graphene. The use of granular solid hexachloroethane with a particle size of 5–20 μm in this invention also helps to improve the mechanical strength of multilayer graphene, making it more suitable for applications requiring strength and durability. This invention reveals that if the particle size of granular hexachloroethane is too large, the large solid hexachloroethane particles are difficult to disperse uniformly in the melt, resulting in a non-uniform distribution in the reaction system. This affects the uniformity of graphene growth and leads to excessively large graphene grains, which reduces electron mobility and conductivity. Furthermore, large solid hexachloroethane particles introduce more defects into the graphene structure, thereby reducing its overall mechanical stability. Conversely, if the particle size of granular hexachloroethane is too small, the growth points of graphene will be unevenly dispersed, making it difficult to form appropriately sized grains. Small particles also fail to promote highly ordered crystalline growth, leading to reduced crystallinity of graphene and consequently reduced electrical and thermal conductivity. In addition, small particles weaken the bonding between graphene layers, affecting the overall mechanical properties of multilayer graphene and making it more prone to interlayer slippage and fracture. This increases the brittleness of the graphene structure, making it more susceptible to fracture under stress.

[0051] According to some preferred embodiments, the obtained graphene is a multilayer graphene with 10 to 15 layers; and / or the thickness of the obtained graphene is less than 4 nm. In this invention, it is preferred to prepare a multilayer graphene with about 10 layers and a total thickness of less than 4 nm. The multilayer graphene obtained by this invention has a total thickness of less than 4 nm, making it thinner and thus more flexible. This is very suitable for applications that require flexibility and thinness, such as wearable electronic devices and flexible electronic devices. Furthermore, due to the small total thickness of the multilayer graphene, the prepared multilayer graphene is suitable for the fabrication of some nanoscale devices. In the fields of nanoelectronics and nanooptics, this nanoscale multilayer graphene can exhibit unique properties. Moreover, the surface effect of the thin multilayer graphene of this invention is more significant, which allows the enhanced surface effect to improve the material's performance in some sensor and catalytic applications.

[0052] According to some specific embodiments, the solid-liquid in-situ reaction preparation of graphene according to the present invention includes the following steps:

[0053] ① Pure magnesium or magnesium alloy of mass M grams is heated and melted in a crucible at a temperature 10-200°C above its melting point. A mixture of CO2 and SF6 is introduced to prevent the magnesium alloy or magnesium from burning, wherein the volume ratio of CO2 to SF6 is 40:1. The liquid level after melting occupies 1 / 4-1 / 2 of the crucible to collect the precipitated mixture containing graphene, magnesium oxide, and magnesium chloride. In some more specific embodiments, for example, pure magnesium is heated and melted in a crucible at a temperature 100°C above its melting point. Magnesium ingots are added to the crucible, the furnace temperature is set to 750°C, and a mixture of CO2 and SF6 is introduced to prevent the magnesium from burning, wherein the volume ratio of CO2 to SF6 is 40:1.

[0054] ② The top of the crucible is connected to the gas treatment device, and the gas inlet is located 50mm above the crucible to collect the chloride gas generated during treatment to the greatest extent and avoid air pollution.

[0055] ③ Select C2Cl6 powder. The C2Cl6 powder should be in granular form with a powder size of 5-20 micrometers. The selected liquid stirring temperature is 580-600℃, the stirring speed is 10 r / min-3000 r / min, and the C2Cl6 solid addition rate is 1 g / min-20 g / min, with a total added mass of 2%M-5%M (M is the mass of pure magnesium or magnesium alloy). After the magnesium melt is completely melted, slowly and continuously add C2Cl6 to the melt while mechanically stirring for 30-150 minutes. Stirring accelerates the reaction, maintains a uniform and stable temperature, and ensures efficient and stable graphene preparation. In some more specific embodiments, for example, after the magnesium ingot melts, the selected mechanical stirring temperature is 720℃. A certain amount of C2Cl6 solid is continuously added to the magnesium melt while mechanically stirring at a speed of 2000 r / min. After adding C2Cl6 in small amounts to the magnesium melt multiple times, continue stirring for 60 minutes to allow for sufficient reaction.

[0056] ④ After the initial settling period, the graphene in the melt is spontaneously separated using gravity and the precipitation of MgCl2. The settling time is 10-30 minutes to ensure complete separation of the product from the magnesium melt. The mixture containing graphene, magnesium oxide, and magnesium chloride precipitates onto the surface of the melt. Using a crucible spoon, the mixture is removed from the crucible. The mixture is then soaked in distilled water for 3-5 minutes and filtered. Finally, a dilute sulfuric acid solution is used to remove impurities from the graphene powder, resulting in pure graphene powder. In this invention, for example, the mixture containing graphene, magnesium oxide, and magnesium chloride is soaked in distilled water for 3-5 minutes and then filtered. Impurities are then removed with a dilute acid solution, followed by filtration and drying to obtain graphene. Alternatively, in this invention, 1000 mL of a 1-wt%–10-wt% dilute sulfuric acid solution is used to soak the mixture for 10-30 minutes to remove impurities, followed by filtration and drying to obtain graphene.

[0057] ⑤ After recovering the mixture containing graphene, magnesium oxide, and magnesium chloride, solid C2Cl6 is introduced into the crucible, and steps ③ and ④ are repeated to ensure continuous synthesis of graphene. In some specific embodiments, step ④ in this invention can also be: after stirring is completed, let it stand for 20 minutes to allow the graphene-containing mixture to precipitate from the surface of the melt, and separate the graphene-containing mixture from the melt; reheat the melt and add C2Cl6 again to achieve repeated and efficient utilization. Step ⑤ in this invention can also be: soak the mixture containing graphene, magnesium oxide, and magnesium chloride in distilled water for 3-5 minutes, filter it, remove impurities with dilute acid solution, filter and dry it to obtain graphene.

[0058] In a second aspect, the present invention provides a graphene prepared using the method described in the first aspect of the present invention.

[0059] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0060] Example 1

[0061] ① Heat 800g of pure magnesium in a crucible at 720℃ to melt it, and introduce a mixture of carbon dioxide (CO2) and sulfur hexafluoride (SF6) to prevent the magnesium from burning. The volume ratio of CO2 to SF6 is 40:1. After melting, the liquid level of the melt is 0.4 times the height of the crucible.

[0062] ② Adjust the melt temperature to 600℃ to ensure that the melt temperature is in the semi-solid range, and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 10μm to the magnesium melt at a rate of 3g / min, and after all C2Cl6 has been added, keep mechanically stirring for 60min.

[0063] ③ After mechanical stirring is complete, the mixture containing graphene, magnesium oxide, and magnesium chloride (the product) in the melt is spontaneously separated by gravity and the precipitation of MgCl2. Specifically, it is allowed to stand for 30 minutes to ensure complete separation of the product from the magnesium melt. Wait for the mixture containing graphene, magnesium oxide, and magnesium chloride to precipitate above the melt, and then use a crucible spoon to remove the mixture from the crucible.

[0064] ④ After recovering the mixture containing graphene, magnesium oxide and magnesium chloride (i.e., the mixture containing graphene), continue to introduce solid C2Cl6 into the crucible, repeat steps ② and ③ multiple times to ensure that graphene can be synthesized continuously, and obtain multiple mixtures containing graphene, magnesium oxide and magnesium chloride.

[0065] ⑤ Mix all the obtained mixture containing graphene, magnesium oxide and magnesium chloride, soak it in distilled water for 5 minutes and then filter it. Finally, soak it in 1000 mL of 5 wt% dilute sulfuric acid solution for 20 minutes to remove impurities, and then filter and dry it to obtain graphene.

[0066] In this invention, the mixture containing graphene, magnesium oxide, and magnesium chloride precipitated in the upper layer of this embodiment was ground, and the resulting powder was subjected to XRD testing. The results are as follows: Figure 2As shown; XRD analysis revealed distinct characteristic diffraction peaks of MgO, along with lower diffraction peaks of Mg3N2 and (MgCl2)(H2O)4. Characteristic diffraction peaks of the carbon products were also observed, providing preliminary evidence of their presence. In this embodiment, the mixture containing graphene, magnesium oxide, and magnesium chloride precipitated from the upper layer was subjected to SEM energy dispersive spectroscopy analysis, with results as shown below. Figure 3 As shown; from Figure 3 It can be seen that the mixture of precipitated layers contains elements such as Mg, C, O, N, and Cl. The mass percentage of C is 35.46%, and the atomic percentage of C is 46.16%, which can further prove the presence of carbon products and infer the content of carbon products.

[0067] The morphology of the graphene obtained in Example 1 was tested in this invention, as follows: Figure 4 As shown, Figure 4 (a) is a picture of the actual object. Figure 4 (b) is a SEM image, from... Figure 4 (b) It can be seen that there are many wrinkles, which is a clear two-dimensional curved sheet structure, consistent with the typical two-dimensional morphological characteristics of graphene. The graphene obtained in Example 1 was subjected to XRD and Raman spectroscopy tests, as shown below. Figure 5 and Figure 6 As shown; Figure 5 The characteristic peaks produced by the (002) crystal plane of graphene can be observed as shown. Figure 6 As shown, Raman spectroscopy analysis revealed distinct D, G, and 2D peaks of graphene. These results indicate that the carbon product generated by the in-situ spontaneous reaction of solid C₂Cl₆ with magnesium melt is graphene. The present invention also subjected the graphene prepared in Example 1 and the following Comparative Examples 1 and 2 to atomic force microscopy testing, with results as follows... Figure 7 As shown; from Figure 7 As can be seen, the graphene exhibits distinct two-dimensional morphological characteristics. It can be observed that the total thickness of the multilayer graphene sheets generated in this embodiment is less than 4 nm, indicating that the graphene prepared by the solid-liquid reaction method of this invention is not single-layer graphene, but rather multilayer graphene with a layer count fluctuating around 10 layers. The total thickness of the graphene prepared in Comparative Example 1 is significantly higher than that of the graphene obtained in Example 1, with an average total thickness of approximately 5 nm. Excluding deviations from the average thickness, the total thickness of the graphene prepared in Comparative Example 2 is lower than that of the graphene prepared in Comparative Example 1, with an average total thickness of approximately 4 nm. It should be noted that… Figure 7(d) is the y-axis offset packing plot. Excluding points deviating from the average thickness, the difference between the upper and lower vertices is calculated to obtain the average total thickness. This shows that the graphene quality of Comparative Examples 1 and 2 is far inferior to that of Example 1. The C2Cl6-Mg solid-liquid in-situ reaction production process in Example 1 is superior to the separation system production process and the CO2-Mg gas-liquid in-situ reaction production process. It can also be seen that the graphene surface is not completely smooth and may contain some wrinkles. This further corroborates the two-dimensional morphological characteristics of the SEM images.

[0068] Example 2

[0069] Example 2 is basically the same as Example 1, except that:

[0070] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 10μm to the magnesium melt at a rate of 1g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0071] Example 3

[0072] Example 3 is basically the same as Example 1, except that:

[0073] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 10μm to the magnesium melt at a rate of 20g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0074] Example 4

[0075] Example 4 is basically the same as Example 1, except that:

[0076] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 10μm to the magnesium melt at a rate of 0.5g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0077] Example 5

[0078] Example 5 is basically the same as Example 1, except that:

[0079] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 10μm to the magnesium melt at a rate of 25g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0080] Example 6

[0081] Example 6 is basically the same as Example 1, except that:

[0082] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 1μm to the magnesium melt at a rate of 3g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0083] Example 7

[0084] Example 7 is basically the same as Example 1, except that:

[0085] ② Adjust the melt temperature to 600℃ and mechanically stir at a speed of 600r / min; at the same time, continuously add 33.3g of C2Cl6 solid particles with an average particle size of 1mm to the magnesium melt at a rate of 3g / min. After all the C2Cl6 has been added, keep mechanically stirring for 60min.

[0086] Comparative Example 1

[0087] Dissolve 6g of hexachloroethane with an average particle size of 10μm in 20mL of benzene, transfer to a stainless steel reactor, and add 20g of magnesium metal in a glove box. Place the reactor in a muffle furnace and rapidly heat to 700℃ within 60min, hold for 1h, then adjust to 650℃ and hold for 16h. After the reaction is complete, allow it to cool naturally to room temperature. Open the reactor, add 1000mL of acetone to the lining, and wash all the reaction product into a 2000mL beaker, stirring thoroughly for 30min. Filter. Wash the filter cake with deionized water, add 1000mL of 10wt% hydrochloric acid solution, heat to 60℃, and stir thoroughly for 30min. Filter and wash with approximately 10L of deionized water to thoroughly remove byproducts generated during the reaction. Dry the obtained product under vacuum at 80℃ for 8h, and then ultrasonically disperse for 30min to obtain the graphene product.

[0088] Comparative Example 2

[0089] 800g of magnesium ingot was melted in a crucible at 720℃, and a mixture of carbon dioxide (CO2) and sulfur hexafluoride (SF6) was introduced to prevent magnesium combustion, with a CO2:SF6 volume ratio of 40:1. The resulting melt was then cooled to a semi-solid temperature range of 625℃ and mechanically stirred at 600 rpm. Simultaneously, high-purity CO2 gas at a flow rate of 3 L / min was introduced into the alloy melt for 10 minutes. The crucible was then placed in a water bath for cooling. Finally, dilute sulfuric acid solution was used to etch away the alloy and oxide impurities to obtain a graphene solution. After continuous washing, the graphene solution was dried to prepare graphene powder.

[0090] The electromagnetic shielding performance of the graphene prepared in each embodiment and comparative example was tested using the following methods:

[0091] 30g of epoxy resin was heated to 60℃, and 15wt% of graphene prepared in each example or comparative example (based on the mass of the epoxy resin) was added. The mixture was stirred in a planetary mixer for 20 minutes to obtain a mixture. Then, 7.5g of curing agent DDM was weighed, melted by heating, and poured into the above mixture. The mixture was stirred again for 20 minutes. After thorough mixing, the mixture was vacuum degassed at 70℃ for 30 minutes. The mixture was then poured into a mold wrapped with thick tin foil and cured at 130℃ for 1 hour to obtain an epoxy resin / graphene composite material board. Electromagnetic shielding tests of the epoxy resin / graphene composite material board were conducted on a vector network analyzer in a frequency range of 2-18GHz. During the test, the mass ratio of epoxy resin / graphene composite material to paraffin was 1:3. After grinding, the composite material was pressed into a ring-shaped sample with a thickness of 2mm for testing. The test results are shown in Table 1.

[0092] Table 1

[0093] Example Electromagnetic shielding effectiveness of 2-18GHz Example 1 30dB Example 2 28.5dB Example 3 28dB Example 4 24.5dB Example 5 24dB Example 6 25dB Example 7 22dB Comparative Example 1 21dB Comparative Example 2 19.5dB

[0094] Furthermore, the electromagnetic shielding efficiency of pure epoxy resin (0 wt% graphene content) measured by this invention is 1.00 dB, indicating that pure epoxy resin hardly absorbs electromagnetic waves. With increasing graphene content, the electromagnetic shielding efficiency of the epoxy resin / graphene composite material gradually increases; when the graphene content is 15 wt%, the electromagnetic shielding efficiency of the epoxy resin / graphene composite material obtained using the graphene prepared in Example 1 increases to 30 dB. However, according to research, the highest reported electromagnetic shielding efficiency improvement when using graphene produced with existing technology in epoxy resin / graphene composite materials with a graphene content of 15 wt% is only around 25 dB, and the electromagnetic shielding efficiency when using traditionally produced graphene in epoxy resin / graphene composite materials with a graphene content of 15 wt% is generally only around 20 dB. As can be seen from the results in Table 1, the electromagnetic shielding efficiency of the graphene prepared by this invention is significantly higher. This is mainly because the two-dimensional molecular continuous network channels formed by the graphene prepared by this invention are more complex, and the graphene surface forms more wrinkles and bends, which makes electromagnetic waves repeatedly absorbed and reflected in the conductive network, thus resulting in better electromagnetic shielding performance than existing graphene.

[0095] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing graphene via solid-liquid in-situ reaction, characterized in that, The method includes the following steps: (1) Heat and melt magnesium and / or magnesium alloys in a crucible to obtain a melt; (2) Solid hexachloroethane is added to the melt at a rate of 1 g / min to 20 g / min and mechanically stirred, and then allowed to stand to obtain a mixture containing graphene above the melt; the mass of the solid hexachloroethane is 2 to 5% of the mass of the melt. (3) Separate the resulting graphene-containing mixture from the melt; (4) The graphene-containing mixture separated from the melt is post-processed to obtain graphene.

2. The method according to claim 1, characterized in that: Before proceeding to step (4), steps (2) and (3) are repeated multiple times to achieve continuous synthesis of graphene.

3. The method according to claim 1, characterized in that, In step (1): Magnesium or magnesium alloys are heated and melted under a mixture of CO2 and SF6. The heating and melting temperature is 10~200℃ higher than the melting point of the magnesium or the magnesium alloy; and / or The liquid level of the melt is 0.25 to 0.6 times the height of the crucible.

4. The method according to claim 3, characterized in that: The volume ratio of CO2 to SF6 is 40:

1.

5. The method according to claim 1, characterized in that: A gas processing device is connected to the top of the crucible, and the gas inlet of the gas processing device is located 40-60 mm above the crucible.

6. The method according to claim 5, characterized in that: The gas treatment device includes a catalyst, a purifier, and an exhaust pipe connected in sequence.

7. The method according to claim 1, characterized in that, In step (2): The mechanical stirring speed is 10 r / min to 3000 r / min; The mechanical stirring time is 30-150 minutes, and the mechanical stirring temperature is 580-800℃; and / or The settling time is 10-30 minutes.

8. The method according to claim 7, characterized in that: The mechanical stirring speed is 1000~3000 r / min.

9. The method according to claim 1, characterized in that, In step (2): After standing, a mixture containing graphene, magnesium oxide and magnesium chloride is obtained above the melt.

10. The method according to claim 1, characterized in that, In step (4): The post-processing involves soaking the graphene-containing mixture separated from the melt in water, filtering it, and then treating it with a dilute acid solution.

11. The method according to claim 1, characterized in that: The solid hexachloroethane is in particulate form, and the particle size of the solid hexachloroethane is 5~20μm.

12. The method according to any one of claims 1 to 11, characterized in that: The obtained graphene is a multilayer graphene with 10 to 15 layers; and / or The thickness of the obtained graphene is less than 4 nm.

13. A graphene, characterized in that, The graphene is prepared using the method described in any one of claims 1 to 12.

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