Method for improving orientation of graphene film based on atomic-scale accurate control of accurate coordination of magnetic ions and graphene oxide
By preparing graphene oxide with specific edge structures and coordinating it with magnetic ions, combined with the effect of a magnetic field, the problem of oriented alignment of graphene sheets was solved, achieving a significant improvement in the out-of-plane thermal conductivity of graphene films and enhancing the interlayer bonding tightness and orientation effect.
Patent Information
- Application Number
- CN202511937287.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-02-10
AI Technical Summary
Existing magnetic field induction techniques are insufficient to achieve effective directional alignment of graphene sheets, which limits the improvement of graphene's out-of-plane thermal conductivity. Furthermore, large-diameter graphene sheets are prone to curling and wrinkling during magnetic field induction, disrupting their directional alignment.
By preparing hydrophobic edges of graphene oxide containing oxygen-containing functional groups and exposing unoxidized sp² carbon structures, and combining magnetic ion solution coordination reaction, the graphene oxide is oriented and aligned under the action of a magnetic field. Then, a thermally reduced graphene film is obtained.
Atom-level precise coordination of graphene sheets was achieved, reducing wrinkles and curling, improving the out-of-plane thermal conductivity and orientation effect of graphene films, enhancing interlayer bonding tightness, and improving phonon transmission efficiency.
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Figure CN121494555A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to graphene atomic-level orientation technology, and more particularly to a method for improving the orientation of graphene films based on precise atomic-level control of the precise coordination between magnetic ions and graphene oxide. Background Technology
[0002] Graphene, as a novel carbon material with excellent physicochemical properties, has shown great application potential in the field of thermal conductivity. It has attracted widespread attention and has been applied in many technical fields such as heat dissipation of electronic devices and preparation of novel thermally conductive composite materials. Graphene materials possess excellent in-plane thermal conductivity, achieving extremely high in-plane thermal conductivity coefficients. This is attributed to its unique planar six-membered ring structure formed by the sp² hybridization of carbon atoms, enabling rapid phonon transport within the plane. However, due to graphene's typical two-dimensional layered structure, the layers are primarily connected by weak van der Waals forces. This structural characteristic significantly limits its out-of-plane (longitudinal) thermal conductivity. In practical applications, when heat is transferred longitudinally within graphene materials, interlayer phonon transport is hindered, resulting in an out-of-plane thermal conductivity far lower than its in-plane thermal conductivity. This severely restricts the application of graphene in scenarios requiring efficient longitudinal thermal conduction, such as certain high-performance heat dissipation devices and thermal interface materials. To improve the out-of-plane thermal conductivity of graphene, extensive research has been conducted in related fields. One approach involves controlling the alignment of graphene sheets to ensure they are oriented as much as possible along a predetermined direction (e.g., longitudinally), thereby reducing interlayer resistance during heat transfer. Currently, existing technologies utilize magnetic materials and magnetic fields to induce atomic-level oriented alignment of graphene. The core principle of this approach is to endow graphene with magnetic responsiveness using magnetic materials. Under the influence of an external magnetic field, the graphene sheets align in an oriented manner following the movement of the magnetic material, aiming to improve the out-of-plane thermal conductivity of graphene. However, due to the inherent layered structure of graphene, the aforementioned magnetic field-induced orientation alignment technology has significant drawbacks. On one hand, the layered structure of graphene means that the movement of its sheets under a magnetic field is interfered with by interlayer interactions. Magnetic materials struggle to drive the graphene sheets to achieve a regular and uniform orientation according to a predetermined direction, often resulting in an actual alignment effect that deviates from expectations and fails to effectively improve out-of-plane thermal conductivity. On the other hand, for large-diameter graphene sheets, which possess a certain balance between flexibility and rigidity, the magnetic forces during magnetic field induction can easily cause large-diameter graphene sheets to curl and wrinkle, further disrupting the orientation alignment and severely impacting the orientation effect. This makes it difficult to achieve the goal of improving the out-of-plane thermal conductivity of graphene through this technology. Therefore, how to overcome the limitations of existing magnetic field-induced technologies, achieve effective orientation alignment of graphene sheets, and thus improve their out-of-plane thermal conductivity has become a pressing technical problem in the field of graphene thermal conductive materials. Summary of the Invention
[0003] To address the technical problem of difficulty in achieving oriented alignment of graphene sheets using magnetic field induction, this invention provides a method for improving the orientation of graphene films based on atomically precise control of the coordination between magnetic ions and graphene oxide. This method involves atomically precise control of the coordination between magnetic ions and edge functional groups of graphene oxide, combined with magnetic field-induced orientation, to prepare highly vertically thermally conductive graphene films. The method includes the following steps: 1) Preparation of an aqueous graphene oxide slurry, wherein a portion of the graphene oxide edge contains oxygen-containing functional groups, the oxygen-containing functional groups being carboxyl groups, and other portions of the graphene oxide expose unoxidized sp groups. 2 Hydrophobic edges of carbon structures.
[0004] 2) Add a magnetic ion-containing solution to the aqueous graphene oxide slurry. The magnetic ions undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0005] 3) A wet film is obtained by coating a graphene oxide slurry loaded with magnetic ions. Before the wet film is cured and dried, a strong magnetic field perpendicular to the film surface is applied. The wet film with the applied magnetic field is dried to obtain an oriented graphene oxide film.
[0006] 4) After the oriented graphene oxide film is subjected to thermal reduction treatment, an oriented graphene thermal conductive film is obtained.
[0007] In a further technical solution, in step 1, the graphene oxide is obtained by mechanically pulverizing large-diameter graphene oxide sheets. Step 1 requires the preparation of graphene oxide with oxygen-containing functional groups at some edges. Graphene oxide prepared using the Hummers method always contains oxygen-containing functional groups at its edges, making it impossible to form graphene oxide with oxygen-containing functional groups at some edges that exposes unoxidized sp2+. 2 The unique structure of the hydrophobic edges of carbon structures. This application first prepares large-diameter graphene oxide sheets using the Hummers method, then mechanically pulverizes them into multiple smaller-diameter graphene oxide sheets. At this stage, the smaller graphene oxide sheets contain oxygen-containing functional groups at some edges, while other parts expose unoxidized sp(s) atoms. 2 The state of the hydrophobic edges of the carbon structure. Therefore, magnetic ions undergo coordination reactions with the oxygen-containing functional groups at the edges of graphene oxide, achieving precise coordination with graphene oxide. Under the action of a magnetic field, the magnetic ions rotate, causing the GO sheet to deflect and align its functionalized edges along the direction of the magnetic field.
[0008] In a further technical solution, in step 1, the large-diameter graphene oxide is selected with a median sheet size of 20-150 μm. After mechanical pulverization, the median sheet size of the resulting graphene oxide is 0.1-5 μm. Graphene oxide with a median sheet size of 0.1-5 μm has abundant oxygen-containing functional groups at its edges. Mechanical pulverization can yield more suitable small-diameter graphene oxide sheets, further improving the directional alignment effect. If the large-diameter graphene oxide is selected with a median sheet size less than 20 μm, mechanical pulverization is insufficient to obtain more small-diameter graphene oxide sheets, and the distribution of oxygen-containing functional groups at the edges will also decrease, resulting in a poorer directional alignment effect.
[0009] In a further technical solution, the mechanical crushing process includes one or more of homogenization, ball milling, and ultrasonic crushing. External mechanical force breaks the carbon-carbon covalent bonds within the large-diameter graphene oxide sheets, simultaneously disrupting the π-π stacking between the sheets, causing the large-diameter graphene oxide to split into smaller-diameter graphene oxide sheets while retaining the original oxygen-containing functional groups.
[0010] In a further technical solution, in step 2, the solution containing magnetic ions includes solutions containing Fe³⁺ and Co. 2 ⁺、Ni 2 The solution containing magnetic ions is specifically a halide AX (A: Fe³⁺, Co). 2 ⁺、Ni 2 ⁺,X: halide ions), oxoacid salts (containing Fe³⁺, Co 2 ⁺、Ni 2⁺ ions, such as ferric nitrate (Fe(NO3)3) and organic acid salts (containing Fe³⁺, Co 2 ⁺、Ni 2 One or more of the following are ⁺ ions, such as nickel acetate (Ni(CH3COO)2). A coordination reaction occurs between the magnetic ion solution and the oxygen-containing functional groups at the edge of graphene oxide, combining the magnetic ions with the graphene oxide and giving the graphene oxide magnetism. Driven by a magnetic field, the magnetic ions can deflect the graphene oxide, achieving a directional alignment.
[0011] In a further technical solution, in step 2, after preparing the graphene oxide slurry and before adding the magnetic ion solution, the pH of the slurry is adjusted to 3.5-4.5.
[0012] In a further technical solution, the pH of the slurry is adjusted using an aqueous solution of HCl and / or an aqueous solution of NaOH with a molar concentration of 0.1M.
[0013] In a further technical solution, in step 3, the thickness of the wet film is 100-200μm.
[0014] In a further technical solution, in step 3, the magnetic field strength is set to 1-2 Tesla.
[0015] Another objective of this invention is to provide an oriented graphene thermal conductive film, which is prepared by precisely controlling the coordination of magnetic ions with the edge functional groups of graphene oxide.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This application first prepares sp24 nanoparticles with oxygen-containing functional groups on some edges and partially exposed unoxidized sp24 nanoparticles. 2 Graphene oxide with hydrophobic edges in a carbon structure is then subjected to a coordination reaction with a solution containing magnetic ions. Under the influence of a magnetic field, the magnetic ions rotate, causing the GO sheet to deflect and align its functionalized edges along the magnetic field direction. This method achieves precise coordination between magnetic ions and graphene oxide. Compared to methods that directly add magnetic materials, this invention allows magnetic ions to be inserted into specific edge positions of graphene oxide through atomic-level precise coordination, thereby achieving directional alignment under the influence of a magnetic field. This reduces the occurrence of wrinkles and curling in the graphene oxide, resulting in a more long-range ordered self-assembly process. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a cross-sectional SEM image of the graphene thermal conductive film sample obtained in Example 1. Figure 2 Thermal diffusion test curve of the membrane material obtained in Example 1; Figure 3 The image shows a surface SEM image of the graphene thermal conductive film sample obtained in Example 1. Figure 4 Here is a high-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Example 2; Figure 5 Here is a high-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Example 3; Figure 6 Here is a high-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Example 4; Figure 7 Here is a high-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Example 5; Figure 8 High-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Comparative Example 1; Figure 9 This is a high-magnification SEM image of the surface of the graphene thermal conductive film sample obtained in Comparative Example 2. Detailed Implementation
[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1
[0020] A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide includes the following steps: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 109 μm diameter flake graphite as raw material, uniformly sized and intact D-type graphite was prepared by the Hummers method. 50A water-based slurry of large-diameter graphene oxide with a flake diameter of 98 μm was obtained. The slurry was subjected to high-pressure homogenization at 100 MPa for 1 hour to obtain D... 50 Aqueous graphene oxide slurry with a sheet diameter of 2.1 μm and a solid content of 6.2% was prepared. After homogenization, the graphene oxide contained oxygen-containing functional groups at some edges and exposed unoxidized sps. 2 Hydrophobic edge structure state of carbon structure.
[0021] 2) Prepare a 5 wt% ferric chloride solution (magnetic ion solution). Add the ferric chloride solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0022] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0023] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain an oriented graphene thermally conductive film. Example 2
[0024] A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide includes the following steps: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 109 μm diameter flake graphite as raw material, uniformly sized and intact D-type graphite was prepared by the Hummers method. 50 A water-based slurry of large-diameter graphene oxide with a flake diameter of 96 μm was obtained. The slurry was subjected to high-pressure homogenization at 100 MPa for 1 hour to obtain D... 50An aqueous graphene oxide slurry with a sheet diameter of 1.8 μm and a solid content of 6.1% was prepared. After homogenization, the graphene oxide contained oxygen-containing functional groups at some edges and exposed unoxidized sps. 2 Hydrophobic edge structure state of carbon structure.
[0025] 2) Prepare a nickel acetate solution (magnetic ion solution) with a mass percentage of 5 wt%. Add the nickel acetate solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of graphene oxide aqueous slurry to ferric chloride solution of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0026] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0027] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain an oriented graphene thermally conductive film. Example 3
[0028] A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide includes the following steps: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 105 μm diameter flake graphite as raw material, uniformly sized and intact D-type graphite was prepared by the Hummers method. 50 A water-based slurry of large-diameter graphene oxide with a flake diameter of 96 μm was obtained. The slurry was subjected to high-pressure homogenization at 100 MPa for 1 hour to obtain D... 50 An aqueous graphene oxide slurry with a sheet diameter of 2.3 μm and a solid content of 6% was prepared. After homogenization, the graphene oxide contained oxygen-containing functional groups at some edges and exposed unoxidized sps. 2 Hydrophobic edge structure state of carbon structure.
[0029] 2) Prepare a 5 wt% ferric nitrate solution (magnetic ion solution). Add the ferric nitrate solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0030] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0031] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain an oriented graphene thermally conductive film. Example 4
[0032] Compared with Example 1, this embodiment sets the magnetic field strength to 2T to explore the effect of different magnetic field strengths on the directional alignment effect.
[0033] A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide includes the following steps: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 109 μm diameter flake graphite as raw material, uniformly sized and intact D-type graphite was prepared by the Hummers method. 50 A water-based slurry of large-diameter graphene oxide with a flake diameter of 98 μm was obtained. The slurry was subjected to high-pressure homogenization at 100 MPa for 1 hour to obtain D... 50 An aqueous slurry of graphene oxide with a sheet diameter of 2.1 μm and a solid content of 6% was prepared. After homogenization, the graphene oxide contained oxygen-containing functional groups at some edges and exposed unoxidized sps. 2 Hydrophobic edge structure state of carbon structure.
[0034] 2) Prepare a 5 wt% ferric chloride solution (magnetic ion solution), add the ferric chloride solution (magnetic ion solution) to the graphene oxide aqueous slurry, adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution, stir evenly, and the magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0035] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 2T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0036] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain an oriented graphene thermally conductive film. Example 5
[0037] Compared with Example 1, this embodiment prepares graphene oxide with a median sheet diameter of about 20 μm as large-diameter graphene to explore the effect of different large-diameter graphene sheet diameters on the orientation alignment effect.
[0038] A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide includes the following steps: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 51 μm diameter flake graphite as raw material, uniformly sized and intact D-type graphite flakes were prepared by the Hummers method. 50 A water-based slurry of large-diameter graphene oxide flakes with a diameter of 23 μm was obtained. The slurry was subjected to high-pressure homogenization at 100 MPa for 2 hours to obtain D... 50 An aqueous graphene oxide slurry with a sheet diameter of 0.8 μm and a solid content of 6.1% was prepared. After homogenization, the graphene oxide contained oxygen-containing functional groups at some edges and exposed unoxidized sps. 2 Hydrophobic edge structure state of carbon structure.
[0039] 2) Prepare a 5 wt% ferric chloride solution (magnetic ion solution). Add the ferric chloride solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0040] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0041] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain an oriented graphene thermally conductive film. Comparative Example 1
[0042] Compared with Example 1, Comparative Example 1 did not undergo pulverization and magnetic solution was added directly.
[0043] The specific steps are as follows: 1) Use grading equipment to classify 50-200 mesh flake graphite raw materials and screen the obtained D 50 Using 112 μm diameter flake graphite as raw material, uniformly sized and complete D-type graphite flakes were prepared by the Hummers method. 50 Large-diameter graphene oxide aqueous slurry with a sheet diameter of 96μm.
[0044] 2) Prepare a 5 wt% ferric chloride solution (magnetic ion solution). Add the ferric chloride solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0045] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0046] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and the temperature is held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain the graphene thermal conductive film. Comparative Example 2
[0047] Compared to Example 1, Comparative Example 2 showed that the flake graphene was not screened by a grading device, and the D of the graphene oxide before mechanical crushing was... 50 The film diameter is 29 μm.
[0048] 1) D-type materials with uniform and complete dimensions were prepared using the Hummers method. 50 Aqueous slurry of graphene oxide with a sheet diameter of 29 μm.
[0049] 2) Prepare a 5 wt% ferric chloride solution (magnetic ion solution). Add the ferric chloride solution (magnetic ion solution) to the graphene oxide aqueous slurry at a mass ratio of 100:1. Adjust the pH of the slurry to 4.0 using a 0.1 M HCl aqueous solution and / or NaOH aqueous solution. Stir until homogeneous. The magnetic ions will undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions.
[0050] 3) The slurry from step 2) is coated onto the PET film using a doctor blade coating method. Then, a magnetic field with a strength of 1T is applied perpendicular to the film surface. After drying at 80℃ for 75 minutes, the graphene oxide film is directly peeled off and wound up. The coating thickness is 200μm and the coating speed is 1.5m / min.
[0051] 4) The graphene oxide film obtained in step 3) is subjected to thermal reduction treatment. The thermal reduction treatment includes pretreatment, carbonization treatment, and graphitization treatment. The pretreatment is carried out at 250°C for 30 minutes at a heating rate of 1°C / min; the carbonization treatment is carried out at 1400°C at a heating rate of 4°C / min, and the temperature is held at the preset temperature for 2 hours; the graphitization treatment is carried out at 3200°C for 2 hours. After the thermal reduction treatment is completed, the film is allowed to cool naturally to obtain the graphene thermal conductive film.
[0052] The graphene thermal conductive films prepared in Examples 1-5 and Comparative Examples 1 and 2 were examined under a scanning electron microscope to observe their microstructure. The microstructures of the graphene thermal conductive films in Examples 1-3 are as follows: Figure 3 , Figure 4 and Figure 5 As shown, the graphene sheets are arranged in a relatively regular manner, with some sheets even approaching parallelism, exhibiting a high degree of orientation, tight interlayer bonding, and few defects, which is beneficial for efficient phonon transport. Example 4 changed the magnetic field strength; the microstructure is as follows... Figure 6 As shown, similar to Examples 1-3, the degree of ordering is improved. The sample in Example 5 also exhibits a relatively ordered layered structure, as shown in the microstructure diagram. Figure 7 As shown, while slight wrinkles and disordered stacking regions exist locally, good continuity is still maintained. This is attributed to the smaller median sheet diameter of the large-diameter graphene and the fewer functional groups distributed at the edges. Furthermore, some of the small-diameter graphene obtained after physical disruption may not contain oxygen-containing functional groups, and therefore does not exhibit directional alignment under magnetic influence. In contrast, the microstructure diagrams of Comparative Example 1 and Comparative Example 2 are shown below. Figure 8 and Figure 9 As shown, the graphene thermal conductive film has a relatively disordered arrangement of layers, which is not conducive to improving thermal conductivity. In particular, the graphene thermal conductive film in Comparative Example 1 has large interlayer gaps in some areas, and the graphene sheets have obvious wrinkles.
[0053] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0054] The above description describes specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, characterized in that: Includes the following steps, 1) Preparation of an aqueous graphene oxide slurry, wherein a portion of the graphene oxide edge contains oxygen-containing functional groups, the oxygen-containing functional groups being carboxyl groups, and other portions of the graphene oxide expose unoxidized sp groups. 2 Hydrophobic edges of carbon structures; 2) Add a magnetic ion-containing solution to the aqueous graphene oxide slurry. The magnetic ions undergo a coordination reaction with the oxygen-containing functional groups at the edge of the graphene oxide to obtain a graphene oxide slurry loaded with magnetic ions. 3) A wet film is obtained by coating a graphene oxide slurry loaded with magnetic ions. Before the wet film is cured and dried, a strong magnetic field perpendicular to the film surface is applied. The wet film with the applied magnetic field is then dried to obtain an oriented graphene oxide film. 4) After the oriented graphene oxide film is subjected to thermal reduction treatment, an oriented graphene thermal conductive film is obtained.
2. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 1, is characterized in that: In step 1, the graphene oxide is obtained by mechanically crushing large-diameter graphene oxide sheets.
3. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 2, is characterized in that: In step 1, the large-diameter graphene oxide is selected from graphene oxide with a median sheet diameter of 20-150 μm. After mechanical crushing, the median sheet diameter of the obtained graphene oxide is 0.1-5 μm.
4. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 3, is characterized in that: The mechanical crushing process includes one or more of the following: homogenization, ball milling, and ultrasonic crushing.
5. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 1, is characterized in that: In step 2, the solution containing magnetic ions includes solutions containing Fe³⁺ and Co. 2 ⁺、Ni 2 The solution containing magnetic ions is selected from one or more of ferric chloride, ferric nitrate, and nickel acetate (Ni(CH3COO)2).
6. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 1, is characterized in that: In step 2, after preparing the graphene oxide slurry, before adding the magnetic ion solution, adjust the pH of the slurry to 3.5-4.
5.
7. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 6, is characterized in that: The pH of the slurry is adjusted using a 0.1M aqueous solution of HCl and / or an aqueous solution of NaOH.
8. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 1, is characterized in that: In step 3, the thickness of the wet film is 100-200 μm.
9. The method for improving the orientation of graphene films based on atomically precise control of the precise coordination between magnetic ions and graphene oxide, as described in claim 1, is characterized in that: In step 3, the magnetic field strength is set to 1-2 Tesla.
10. A vertically oriented graphene thermal conductive film, characterized in that: Prepared using the method described in claims 1-9.