A magnetic oriented graphene / carbon composite material and a preparation method thereof

Abstract

The application discloses a kind of magnetic orientation graphene / carbon composite material and preparation method thereof, belong to composite material technical field.Magnetic orientation graphene / carbon composite material is by porous carbon matrix and the several layer magnetic orientation graphene layer inside porous carbon matrix inside alternately parallel arrangement along vertical direction jointly formed;Porous carbon matrix is formed by carbon nanoparticles connected with plant sugar precursor conversion, and carbon nanoparticles in porous carbon matrix are mutually connected to form micro-nano size closed pore;Magnetic orientation graphene layer is formed by two-dimensional reduced graphene oxide nanosheet mutual lap joint.The preparation method is as follows: preparation magnetic graphene dispersion liquid and plant sugar precursor sol, then the two are stirred and mixed, to obtain mixed sol;Magnetic graphene in mixed sol is oriented using magnetic orientation device, then initiator is added to make mixed sol solidify into gel;Gel is low-temperature pre-carbonized and high-temperature graphitized to obtain magnetic orientation graphene / carbon composite material.The preparation method is simple, graphene orientation is controllable, low in cost and can be integrated into shape preparation composite material.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a magnetically oriented graphene / carbon composite material and its preparation method. Background Technology

[0002] Graphene, as a novel material, possesses not only extremely high strength but also an in-plane thermal conductivity exceeding 5000 W / (m·K). Utilizing graphene as a thermal conductivity-enhancing filler offers a rare opportunity for the development of next-generation heat dissipation materials. However, due to its extremely small size (less than 1 nanometer in thickness, and tens of micrometers in the two-dimensional direction), graphene is difficult to manipulate at the nanoscale. Furthermore, when used as a thermal conductivity-enhancing filler, graphene is prone to agglomeration, exhibiting high disorder within the agglomerates. This agglomeration and disorder are exacerbated, especially at higher graphene concentrations. Additionally, phonons in two-dimensional materials can only propagate effectively within the in-plane lattice, and graphene exhibits high anisotropy in thermal conductivity (a difference of two orders of magnitude between in-plane and out-of-plane conductivity). Therefore, improving the thermal conductivity enhancement effect of graphene is closely related to the ordered orientation of graphene nanosheets within the matrix. In summary, ensuring the ordered orientation of graphene within the matrix is ​​both the key and the challenge in fully utilizing its high thermal conductivity. Otherwise, it will not only fail to enhance thermal conductivity but may also have adverse effects.

[0003] Currently, many researchers have attempted to control the orientation of graphene. For example, Chinese patent CN112225204A, "Method and Equipment for Controlling the Orientation of Graphene in Graphene Sponge," and Chinese patent CN112357910A, "A Method for Preparing a Macroscopic oriented Graphene Composite," both utilize the ice template method to induce the preparation of oriented graphene aerogels. Although this method can prepare graphene with ordered and controllable orientation, the process is time-consuming and costly, making it unsuitable for large-scale preparation.

[0004] For example, in the existing paper "Orientation Control of Graphene Flakes by MagneticField: Broad Device Applications of Macroscopically Aligned Graphene" (Adv. Mater. 2016, DOI: 10.1002 / adma.201604453), Lin et al. used an external constant magnetic field to deflect graphene. However, the static magnetic field used in this method can only control the degree of freedom of graphene nanosheets in one direction, and cannot achieve the parallel arrangement of two-dimensional graphene nanosheets.

[0005] The traditional preparation route for graphene thermally conductive reinforced composite materials is as follows: first, a thermally conductive framework preform is prepared, and then the bulk density of the composite material is increased through repeated impregnation of the matrix or repeated CVI densification processes, ultimately obtaining a high-strength, high-thermal-conductivity composite material. For example, Chinese patents CN110452414A ("A Preparation Method of Highly Oriented Graphene Reinforced Bismaleimide Resin-Based Composite Material") and CN109705817A ("A High Thermal Conductivity Fast Response Phase Change Energy Storage Composite Material and Its Preparation Method") both first use freeze-drying to prepare a graphene preform framework, and then use vacuum impregnation for framework backfilling. The bulk material prepared by this process has high strength and excellent thermal properties, but this preparation process requires repeated densification, which is cumbersome and results in a long product preparation cycle, making it unsuitable for large-scale production. For example, in the existing paper "Magnetic Field-Induced Aligned Graphene / Cellulose Conductive Composites for Electroluminescent Devices" (ACS Appl. Nano Mater. 2023, DOI: 10.1021 / acsanm.3c03678), Zhi et al. used an external single static magnetic field to prepare graphene / cellulose composite materials in an integrated manner. Although this method can achieve the ordered orientation of graphene in the composite material, it can only prepare thin film materials. The films need to be stacked to obtain bulk materials, which is not conducive to large-scale preparation.

[0006] In summary, existing methods for preparing oriented graphene thermally conductive reinforced composite materials lack a method that is simple to prepare, allows for controllable graphene orientation, is low in cost, and can be integrally molded to prepare the composite material. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention aims to provide a magnetically oriented graphene / carbon composite material and its preparation method. The preparation method is simple, the graphene orientation is controllable, the cost is low, and the composite material can be prepared by integral molding.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] This invention provides a magnetically oriented graphene / carbon composite material, which is composed of a porous carbon matrix and several layers of magnetically oriented graphene layers arranged alternately in parallel along the vertical direction inside the porous carbon matrix.

[0010] The porous carbon matrix is ​​formed by connecting carbon nanoparticles converted from plant sugar precursors, and the carbon nanoparticles in the porous carbon matrix are interconnected to form micro- and nano-sized closed pores.

[0011] The magnetically oriented graphene layer is formed by overlapping two-dimensional reduced graphene oxide nanosheets.

[0012] In one embodiment, the magnetically oriented graphene / carbon composite material is anisotropic, with a thermal conductivity of 10–20 W / mK in the horizontal direction parallel to the magnetically oriented graphene layer and a thermal conductivity of 0.35–0.65 W / mK in the vertical direction perpendicular to the magnetically oriented graphene layer.

[0013] This invention also provides a method for preparing the aforementioned magnetically oriented graphene / carbon composite material, comprising the following steps:

[0014] S1: Prepare magnetic graphene dispersion and plant sugar precursor sol, then stir and mix the two to obtain a mixed sol;

[0015] S2: The magnetic graphene in the mixed sol is oriented using a magnetic orientation device, and then an initiator is added to solidify the mixed sol into a gel;

[0016] S3: The gel is pre-carbonized at low temperature and graphitized at high temperature to obtain a magnetically oriented graphene / carbon composite material.

[0017] In one embodiment, the preparation method of the magnetic graphene dispersion in step S1 is as follows:

[0018] A magnetic graphene dispersion was prepared by mixing graphene oxide, ferrofluid, and water in a mass ratio of (1-20):(3-50):(10-40).

[0019] The graphene oxide is a single-layer graphene oxide or a multi-layer graphene oxide; the magnetic graphene is graphene oxide with iron oxide nanoparticles attached to it in a ferrofluid.

[0020] In one embodiment, the method for preparing the plant sugar precursor sol in S1 is as follows:

[0021] Plant sugar, acrylamide, methylenebisacrylamide and water were mixed in a mass ratio of (10-100):(1-100):(0.1-10):(50-200) to prepare plant sugar precursor sol;

[0022] The plant sugar is one or more of glucose, sucrose, starch, fructose, maltose, and xylose.

[0023] In one embodiment, the magnetic graphene in the mixed sol accounts for 2% to 20% by mass.

[0024] In one embodiment, in S2, the magnetic orientation device includes a neodymium iron boron magnet, a motor, a loading tray, and a suspendable glass container;

[0025] The motor shaft is connected to the center of the loading tray. The suspendable glass container is placed above the loading tray. Two neodymium iron boron magnets are arranged parallel to each other on the loading tray, and the neodymium iron boron magnets are symmetrically arranged on both sides of the suspendable glass container.

[0026] In one embodiment, the process of orienting the magnetic graphene in the mixed sol using a magnetic orientation device in step S2 is as follows:

[0027] The mixed sol is placed in a suspended glass container, and a motor drives parallel neodymium iron boron magnets to rotate around the suspended glass container to generate a rotating magnetic field to orient the magnetic graphene in the mixed sol.

[0028] The rotational speed is 1 to 50 r / s.

[0029] In one embodiment, in step S2, the initiator is one or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and hydrogen peroxide.

[0030] In one embodiment, the low-temperature pre-carbonization process in S3 is as follows: heat treatment in air at a heating rate of 5°C / h for 36 hours;

[0031] In S3, the high-temperature graphitization process is as follows: heat treatment at 1800-2800°C for 2 hours in an argon-hydrogen mixed atmosphere.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention provides a method for preparing magnetically oriented graphene / carbon composite materials. It utilizes highly crystalline carbon synthesized from plant sugars as the carbon matrix and inexpensive, readily available, and recyclable plant sugars as the carbon source, resulting in high carbon yield, low cost, and environmental friendliness. Graphene oxide is used as a graphene precursor, exhibiting high surface activity and excellent dispersibility in plant sugar sols, which is beneficial for large-scale composite material preparation. After converting graphene oxide into magnetic graphene, an external rotating magnetic field is applied to orient the magnetic graphene, enabling rapid orientation of graphene nanosheets in the precursor solution. Furthermore, high-temperature graphitization not only improves the crystallinity of the composite material but also converts the graphene oxide in the graphene layer into reduced graphene oxide, forming a magnetically oriented graphene layer. This helps reduce graphene defects and improve the composite material's performance. Compared to existing methods in graphene thermally conductive reinforced composite material research, this preparation method simplifies the process, shortens the preparation cycle, achieves oriented and ordered arrangement of graphene in the composite matrix, and facilitates low-cost, large-scale composite material preparation.

[0034] Furthermore, graphene oxide is more readily attached to magnetite nanoparticles in ferrofluids. With simple mechanical stirring, magnetite nanoparticles in ferrofluids can be attached to the surface of graphene oxide. After attaching superparamagnetic magnetite nanoparticles to the surface of graphene oxide, graphene oxide can have an extremely strong magnetic response.

[0035] This invention provides a magnetically oriented graphene / carbon composite material, which uses reduced graphene oxide as a thermal conductivity enhancer. The magnetically oriented graphene layer, formed by overlapping reduced graphene oxide nanosheets, is filled in a carbon matrix converted from plant sugar. This method can prepare anisotropic graphene / carbon composite materials with high thermal conductivity, high thermal insulation, and high strength. Reduced graphene oxide nanosheets overlap to form oriented magnetically oriented graphene layers. These two-dimensional magnetically oriented graphene layers are arranged in parallel, creating a good heat transfer pathway in the horizontal direction parallel to the layers, which facilitates rapid heat dissipation. In the vertical direction perpendicular to the layers, the magnetically oriented graphene layers act as layers of barriers to phonon diffusion, effectively blocking heat transfer. Furthermore, the presence of micro- and nano-sized closed pores in the porous carbon matrix formed by the conversion of plant sugar precursors restricts heat convection and thermal collisions of gas molecules, further reducing heat transfer in the vertical direction. This results in a material that simultaneously possesses high thermal conductivity and high thermal insulation, meeting the demand in the thermal management field for materials with excellent heat dissipation and insulation properties. Meanwhile, the magnetically oriented graphene layer also plays a role in mechanical reinforcement in the porous carbon matrix. When the material is subjected to external stress, the crack propagating in the porous carbon matrix can be deflected when it encounters the magnetically oriented graphene layer, which consumes the crack propagation fracture energy and reduces the crack propagation rate. The crack will bifurcate at the interface, change the propagation direction and prolong the crack propagation path, thus delaying the damage and failure of the material. In addition, the pull-out of the magnetically oriented graphene layer can also consume external stress, thereby further improving the mechanical properties of the composite material. Attached Figure Description

[0036] Figure 1 Figures a and b are optical photographs of the magnetically oriented graphene / carbon composite material prepared in Example 1 of the present invention;

[0037] Figure 2 SEM image of the magnetically oriented graphene / carbon composite material prepared in Example 1 of the present invention;

[0038] Figure 3 The Raman spectrum of the magnetically oriented graphene / carbon composite material prepared in Example 1 of the present invention;

[0039] Figure 4 Infrared thermal imaging of the magnetically oriented graphene / carbon composite material prepared in Example 1 of the present invention during the heating process on the surface of a heating stage (200°C);

[0040] Figure 5 Figure 1 shows a comparison of the compressive strength of magnetically oriented graphene / carbon composite materials with different magnetic graphene contents prepared in Examples 1, 2, and 3 of this invention; wherein, Figure 2a is a stress-strain curve, and Figure 3b is a graph showing the relationship between the amount of magnetic graphene added and the ultimate compressive strength of the composite material.

[0041] Figure 6 This is a structural design diagram of the magnetically oriented graphene / carbon composite material prepared in this invention;

[0042] Figure 7 This is a schematic diagram of the magnetic orientation device used in this invention;

[0043] Among them, 1-suspendable glass container, 2-neodymium iron boron magnet, 3-carrying tray, 4-motor, 5-rotating shaft; 6-porous carbon matrix, 7-magnetically oriented graphene layer. Detailed Implementation

[0044] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0045] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0046] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0047] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0048] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0049] It should be noted that the horizontal directions in this article are all parallel to the magnetically oriented graphene layers; the vertical directions are all perpendicular to the vertical direction of the magnetically oriented graphene layers.

[0050] This invention provides a magnetically oriented graphene / carbon composite material and its preparation method.

[0051] On the one hand, a method for preparing magnetically oriented graphene / carbon composite material is provided. The preparation method includes the following steps: preparing a magnetic graphene dispersion and a plant sugar precursor sol, thoroughly mixing the two to obtain a mixed sol; orienting the magnetic graphene in the mixed sol using a magnetic orientation device, and then adding an initiator to solidify the mixed sol into a gel; and subjecting the prepared gel to low-temperature pre-carbonization and high-temperature graphitization treatments to obtain the magnetically oriented graphene / carbon composite material.

[0052] The specific steps of the above preparation method are as follows:

[0053] Step 1) Prepare magnetic graphene dispersion and plant sugar precursor sol, and mix them thoroughly to obtain a mixed sol.

[0054] Step 2) Orient the magnetic graphene in the mixed sol prepared in Step 1 using a magnetic orientation device, and then add an initiator to solidify the mixed sol into a gel.

[0055] Step 3) The gel prepared in Step 2 is subjected to low-temperature pre-carbonization and high-temperature graphitization treatment to obtain magnetically oriented graphene / carbon composite material.

[0056] The specific dosage and process conditions are as follows:

[0057] In step 1), the magnetic graphene dispersion is prepared by mixing graphene oxide, ferrofluid, and water in a mass ratio of (1-20):(3-50):(10-40) to obtain the magnetic graphene dispersion.

[0058] Among them, graphene oxide is commercially available single-layer or multi-layer graphene oxide; magnetic graphene is graphene oxide with iron oxide nanoparticles attached to it in a ferrofluid.

[0059] The preparation method of plant sugar precursor sol is as follows: plant sugar, acrylamide, methylenebisacrylamide and water are thoroughly mixed in a mass ratio of (10-100):(1-100):(0.1-10):(50-200) to obtain plant sugar precursor sol.

[0060] The plant sugar can be one or a combination of several of glucose, sucrose, starch, fructose, maltose, and xylose.

[0061] Specifically, the magnetic graphene accounts for 2% to 20% of the mass of the mixed sol.

[0062] In step 2), such as Figure 7 As shown, the magnetic orientation device includes neodymium iron boron magnets 2, motors 4, a loading tray 3, and a suspended glass container 1; the rotating shaft 5 of the motor 4 is connected to the center of the loading tray 3, the suspended glass container 1 is placed above the loading tray 3, and two neodymium iron boron magnets 2 are arranged parallel to each other on the loading tray 3, and the neodymium iron boron magnets 2 are symmetrically arranged on both sides of the suspended glass container 1.

[0063] The process of orienting magnetic graphene in a mixed sol using a magnetic orientation device is as follows:

[0064] The mixed sol is placed in a suspended glass container 1, and a motor 4 drives parallel neodymium iron boron magnets 2 to rotate around the suspended glass container 1 to generate a rotating magnetic field to orient the magnetic graphene in the mixed sol; the rotation speed is 1 to 50 r / s.

[0065] Specifically, the magnetic orientation device consists of two parallel neodymium iron boron magnets 2, a motor 4 with adjustable speed, an acrylic disc, and a suspended glass container 1; the magnetic orientation is achieved by the motor 4 driving the parallel neodymium iron boron magnets 2 to rotate around the suspended glass container 1 to generate a rotating magnetic field.

[0066] Specifically, the initiator is one or a combination of several of the following: ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and hydrogen peroxide.

[0067] In step 3), the low-temperature pre-carbonization process is as follows: heat treatment at a heating rate of 5℃ / h in air atmosphere for 36h; the high-temperature grapheneization process is as follows: heat treatment at 1800~2800℃ in an argon-hydrogen mixed atmosphere for 2h.

[0068] On the other hand, the present invention also provides a magnetically oriented graphene / carbon composite material, such as... Figure 6 As shown, the magnetically oriented graphene / carbon composite material is composed of a porous carbon matrix 6 and several layers of magnetically oriented graphene layers 7 arranged alternately in the vertical direction inside the porous carbon matrix 6. The porous carbon matrix 6 is formed by connecting carbon nanoparticles converted from plant sugar precursors, and the carbon nanoparticles in the porous carbon matrix 6 are interconnected to form micro- and nano-sized closed pores. The magnetically oriented graphene layers 7 are formed by overlapping two-dimensional reduced graphene oxide nanosheets.

[0069] like Figure 1 As shown, the magnetically oriented graphene / carbon composite material is a black three-dimensional bulk with a density of 0.15–0.35 g / cm³. 3The main components of the magnetically oriented graphene / carbon composite material are carbon and reduced graphene oxide; in the magnetically oriented graphene / carbon composite material, the two-dimensional magnetically oriented graphene layers 7 are arranged in parallel; the porous carbon matrix 6 in the magnetically oriented graphene / carbon composite material is composed of carbon nanoparticles formed by the conversion of plant sugar precursors, and the carbon nanoparticles in the porous carbon matrix 6 are interconnected to form micro- and nano-sized closed pores; the constituent element of the magnetically oriented graphene / carbon composite material is C.

[0070] The magnetically oriented graphene / carbon composite material is anisotropic, exhibiting high thermal conductivity (10–20 W / mK) in the horizontal direction and low thermal conductivity (0.35–0.65 W / mK) in the vertical direction. It also possesses excellent mechanical properties, with a maximum compressive strength of 43.59 MPa.

[0071] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0072] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0073] Example 1:

[0074] Step 1) Mix 1g of graphene oxide, 3g of ferrofluid, and 10g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 10g of glucose, 1g of acrylamide, 0.1g of methylenebisacrylamide, and 50g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 20%.

[0075] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 1 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add ammonium persulfate to solidify the mixed sol into a gel.

[0076] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2500℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0077] The prepared magnetically oriented graphene / carbon composite material has a density of 0.20 g / cm³. 3 The thermal conductivity in the horizontal direction at room temperature is 15 W / mK, and the thermal conductivity in the vertical direction is 0.42 W / mK. The compressive strength of the material is 43.59 MPa. Figure 1 As can be seen, the magnetically oriented graphene / carbon composite material appears as a black three-dimensional block.

[0078] Depend on Figure 2 As can be seen, in the magnetically oriented graphene / carbon composite material, reduced graphene oxide overlaps to form parallel-arranged two-dimensional magnetically oriented graphene layers 7, and the porous carbon matrix 6 is formed by carbon nanoparticles converted from plant sugar precursors, with the carbon nanoparticles in the porous carbon matrix 6 interconnecting to form micro- and nano-sized closed pores. Figure 3 It is evident that the magnetically oriented graphene / carbon composite material, after low-temperature pre-carbonization and high-temperature graphitization treatment, exhibits fewer defects and higher crystallinity in its Raman spectrum. Highly crystalline carbon is beneficial for improving phonon transport rates, thereby enhancing the material's thermal conductivity and mechanical strength. Figure 4 It can be seen that the surface temperature of the magnetically oriented graphene / carbon composite material is still relatively low (about 60°C) after being placed on a heating stage at 200°C for 10 minutes. This proves that due to the thermal barrier effect of the magnetically oriented graphene layer 7, the prepared composite material has excellent thermal insulation performance in the direction perpendicular to the magnetically oriented graphene layer 7.

[0079] Example 2:

[0080] Step 1) Mix 1g of graphene oxide, 3g of ferrofluid, and 10g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 10g of glucose, 1g of acrylamide, 0.1g of methylenebisacrylamide, and 50g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 10%.

[0081] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 1 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add ammonium persulfate to solidify the mixed sol into a gel.

[0082] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2500℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0083] Example 3:

[0084] Step 1) Mix 1g of graphene oxide, 3g of ferrofluid, and 10g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 10g of glucose, 1g of acrylamide, 0.1g of methylenebisacrylamide, and 50g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 2%.

[0085] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 1 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add ammonium persulfate to solidify the mixed sol into a gel.

[0086] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2500℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0087] Depend on Figure 5 It can be seen that, keeping other variables constant, within the range of 2% to 20% magnetic graphene mass ratio, the ultimate compressive strength of the composite material increases with the increase of the magnetic graphene mass ratio. This shows that the magnetically oriented graphene layer effectively improves the mechanical strength of the composite material as a mechanical reinforcing phase.

[0088] Example 4:

[0089] Step 1) Mix 20g of graphene oxide, 50g of ferrofluid, and 40g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 100g of sucrose, 100g of acrylamide, 10g of methylenebisacrylamide, and 200g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 10%.

[0090] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 50 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add potassium persulfate to solidify the mixed sol into a gel.

[0091] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2200℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0092] Example 5:

[0093] Step 1) Mix 5g of graphene oxide, 20g of ferrofluid, and 40g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 50g of starch, 10g of acrylamide, 2g of methylenebisacrylamide, and 150g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 2%.

[0094] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 25 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add azobisisobutyronitrile to solidify the mixed sol into a gel.

[0095] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2000℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0096] Example 6:

[0097] Step 1) Mix 10g of graphene oxide, 3g of ferrofluid, and 10g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 50g of fructose, 1g of acrylamide, 0.1g of methylenebisacrylamide, and 50g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 15%.

[0098] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 20 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add ammonium persulfate to solidify the mixed sol into a gel.

[0099] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 1800℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0100] Example 7:

[0101] Step 1) Mix 3g of graphene oxide, 3g of ferrofluid, and 15g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 5g of maltose, 2g of acrylamide, 3g of methylenebisacrylamide, and 150g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 5%.

[0102] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 1 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add hydrogen peroxide to solidify the mixed sol into a gel.

[0103] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 2800℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0104] Example 8:

[0105] Step 1) Mix 1g of graphene oxide, 3g of ferrofluid, and 10g of water until homogeneous to obtain a magnetic graphene dispersion. Then mix 10g of xylose, 1g of acrylamide, 0.1g of methylenebisacrylamide, and 50g of water until homogeneous to obtain a plant sugar precursor sol. Finally, thoroughly mix the magnetic graphene dispersion and the plant sugar precursor sol to obtain a mixed sol, wherein the mass percentage of magnetic graphene in the mixed sol is 2%.

[0106] Step 2) Place the mixed sol prepared in Step 1 in a magnetic orientation device, adjust the speed of motor 4 to 1 r / s to generate a rotating magnetic field, and magnetically orient the magnetic graphene in the mixed sol. Then add ammonium persulfate to solidify the mixed sol into a gel.

[0107] Step 3) The gel prepared in step 2 is placed in a heating device and heat-treated in air at a heating rate of 5℃ / h for 36h for low-temperature pre-carbonization. Then, it is heat-treated at 1800℃ for 2h in an argon-hydrogen mixed atmosphere for high-temperature graphitization, thus obtaining the magnetically oriented graphene / carbon composite material.

[0108] In summary, the magnetically oriented graphene / carbon composite material prepared by this invention enables the directional and ordered arrangement of magnetically oriented graphene layers within the composite matrix using a simple and rapid method. This simplifies the composite material preparation process, shortens the preparation cycle, and reduces preparation costs. The prepared composite material exhibits excellent compressive strength, as well as superior thermal conductivity and insulation properties. Furthermore, it can be mass-produced, demonstrating significant application potential in thermal management fields such as aerospace, communication base stations, and electronic equipment.

[0109] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A magnetically oriented graphene / carbon composite material, characterized in that, The magnetically oriented graphene / carbon composite material is composed of a porous carbon matrix and several layers of magnetically oriented graphene layers arranged alternately in parallel along the vertical direction inside the porous carbon matrix. The porous carbon matrix is ​​formed by connecting carbon nanoparticles converted from plant sugar precursors, and the carbon nanoparticles in the porous carbon matrix are interconnected to form micro- and nano-sized closed pores. The magnetically oriented graphene layer is formed by overlapping two-dimensional reduced graphene oxide nanosheets.

2. The magnetically oriented graphene / carbon composite material according to claim 1, characterized in that, The magnetically oriented graphene / carbon composite material is anisotropic, with a thermal conductivity of 10~20 W / mk in the horizontal direction parallel to the magnetically oriented graphene layer and a thermal conductivity of 0.35~0.65 W / mk in the vertical direction perpendicular to the magnetically oriented graphene layer.

3. A method for preparing a magnetically oriented graphene / carbon composite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1: Prepare magnetic graphene dispersion and plant sugar precursor sol, then stir and mix the two to obtain a mixed sol; S2: The magnetic graphene in the mixed sol is magnetically oriented using a magnetic orientation device, and then an initiator is added to solidify the mixed sol into a gel; the magnetic orientation device includes neodymium iron boron magnets (2), a motor (4), a loading plate (3), and a suspendable glass container (1); the shaft (5) of the motor (4) is connected to the center of the loading plate (3), the suspendable glass container (1) is set above the loading plate (3), two neodymium iron boron magnets (2) are set parallel to each other on the loading plate (3), and the neodymium iron boron magnets (2) are symmetrically set on both sides of the suspendable glass container (1); the magnetic orientation is generated by the motor (4) driving the parallel neodymium iron boron magnets (2) to rotate around the suspendable glass container (1) to generate a rotating magnetic field; S3: The gel is pre-carbonized at low temperature and graphitized at high temperature to obtain a magnetically oriented graphene / carbon composite material.

4. The method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, In step S1, the preparation method of the magnetic graphene dispersion is as follows: Magnetic graphene dispersion was prepared by mixing graphene oxide, ferrofluid and water in a mass ratio of (1~20):(3~50):(10~40). The graphene oxide is a single-layer graphene oxide or a multi-layer graphene oxide; the magnetic graphene is graphene oxide with iron oxide nanoparticles attached to it in a ferrofluid.

5. The method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, In step S1, the preparation method of the plant sugar precursor sol is as follows: Plant sugar precursor sol was prepared by mixing plant sugar, acrylamide, methylenebisacrylamide and water in a mass ratio of (10~100):(1~100):(0.1~10):(50~200).

6. The method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, The plant sugar is one or more of glucose, sucrose, starch, fructose, maltose, and xylose.

7. The method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, The mass percentage of magnetic graphene in the mixed sol is 2% to 20%.

8. The method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, In step S2, the initiator is one or more of ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and hydrogen peroxide.

9. A method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, In S3, the low-temperature pre-carbonization process is as follows: heat treatment in air at a heating rate of 5 °C / h for 36 h.

10. A method for preparing a magnetically oriented graphene / carbon composite material according to claim 3, characterized in that, In S3, the high-temperature graphitization process is as follows: heat treatment at 1800~2800 °C for 2 h in an argon-hydrogen mixed atmosphere.

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