A thermally conductive composite material based on laser-induced graphene and its preparation method

Abstract

This invention discloses a laser-induced graphene-based thermally conductive composite material and its preparation method. The laser-induced graphene-based thermally conductive composite material includes a resin support layer and a graphene layer. The resin support layer is a polybenzoxazine film. The graphene layer includes forest-like graphene regions and mesophyll-like graphene regions, with an area ratio of 1:3 between the forest-like and mesophyll-like graphene regions. The graphene layer is filled with a phase change material, namely PEG. Furthermore, this invention also proposes a method for preparing the laser-induced graphene-based thermally conductive composite material. The laser-induced graphene-based thermally conductive composite material and its preparation method proposed in this invention solve the problems of current laser-induced graphene-based thermally conductive composite materials failing to simultaneously possess ultra-high light absorption and photothermal conversion efficiency, as well as low energy storage efficiency.

Description

Technical Field

[0001] This invention relates to the field of graphene preparation and application, and in particular to a thermally conductive composite material based on laser-induced graphene and its preparation method. Background Technology

[0002] With the continuous advancement of science and technology and the improvement of people's living standards, electronic devices are becoming increasingly miniaturized, highly integrated, and high-performance, making thermal management issues increasingly prominent. Developing new high-performance photothermal devices has become an urgent task.

[0003] Existing thermally conductive materials based on laser-induced graphene mainly fall into the following structural categories: First, planar structures, where laser-induced graphene is directly formed on a polyimide substrate, typically forming a two-dimensional honeycomb structure. These structures possess high light absorption capacity and can effectively exchange heat with the surrounding environment, resulting in relatively high photothermal conversion efficiency. However, rapid temperature fluctuations can significantly impact the lifespan of components. Second, composite three-dimensional structures, where laser-induced graphene is composited with other materials such as metals using methods like physical mixing and chemical deposition. While this improves photothermal performance perpendicular to the film direction compared to two-dimensional planar structures, the fabrication process is complex and costly, and its mechanical stability needs improvement. In summary, existing thermally conductive composite materials based on laser-induced graphene cannot simultaneously possess excellent light absorption and photothermal conversion efficiency. Furthermore, they suffer from insufficient energy storage and utilization efficiency, lack effective protection for components, and exhibit inadequate mechanical stability.

[0004] Literature indicates that the topological distribution of leaves, plants, and branches within forest communities results in extremely high light energy utilization. Inspired by the natural photothermal conversion principle and thermal energy storage structure in leaves, the veins provide rapid energy harvesting and heat transport, while the loose structure of the mesophyll enables excellent heat storage. Furthermore, phase change materials maintain the temperature stability of surrounding devices during phase transitions at different temperatures. This provides inspiration for further developing thermally conductive composite materials to address existing problems. Summary of the Invention

[0005] To address the aforementioned shortcomings, the present invention aims to propose a thermally conductive composite material based on laser-induced graphene, thereby solving the problems that current thermally conductive composite materials based on laser-induced graphene cannot simultaneously possess ultra-high light absorption rate and photothermal conversion rate, as well as low energy storage efficiency.

[0006] Another objective of this invention is to propose a method for preparing a thermally conductive composite material based on laser-induced graphene, which reduces the complexity of the preparation process, ensures that the obtained thermally conductive composite material has the desired effect, and solves the problem of complex preparation processes in the prior art.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] A thermally conductive composite material based on laser-induced graphene includes a resin support layer and a graphene layer, wherein the resin support layer is a polybenzoxazine film.

[0009] The graphene layer is obtained by laser-induced processing on the resin support layer. The graphene layer includes forest-like graphene regions and mesophyll-like graphene regions, and the area ratio of the forest-like graphene regions to the mesophyll-like graphene regions is 1:3.

[0010] The forest-like graphene region and the mesophyll-like graphene region are each composed of several wedge-shaped partitions, and the wedge-shaped partitions of the forest-like graphene region and the wedge-shaped partitions of the mesophyll-like graphene region are distributed alternately.

[0011] The graphene layer is filled with a phase change material, which is PEG.

[0012] Furthermore, the forest-like graphene region and the mesophyll-like graphene region form a ring; the wedge angle A of the wedge-shaped partition of the forest-like graphene region is 11.25°.

[0013] Preferably, the thickness ratio of the resin support layer to the graphene layer is 7:3.

[0014] A method for preparing a thermally conductive composite material based on laser-induced graphene, comprising the following steps:

[0015] S1. Preparation of benzoxazine monomer: Using phenolic source, amine source and paraformaldehyde as raw materials, and xylene as solvent, the benzoxazine monomer structure is synthesized by heating and stirring. Then, an organic solvent is used to help precipitate the benzoxazine monomer structure, and the benzoxazine monomer is obtained after purification. The phenolic source is one of bisphenol A and phenol, the amine source is 4,4'-diaminodiphenylmethane, and the organic solvent is one of petroleum ether, n-hexane and cyclohexane.

[0016] S2. Preparation of polybenzoxazine film: The benzoxazine monomer is melted and degassed to obtain polybenzoxazine fluid. The polybenzoxazine fluid is poured into a glass mold, cured at high temperature, and demolded after cooling to obtain polybenzoxazine film.

[0017] S3. Laser-induced processing: The polybenzoxazine film is fixed on the processing platform. Using an ultraviolet laser, the corresponding processing area on the polybenzoxazine film is laser-induced according to the preset pattern to obtain the processed three-dimensional laser-induced graphene.

[0018] The graph includes a forest-like region, a mesophyll-like region, and a heat-collecting region; the forest-like graphene region corresponds to the forest-like region, and the mesophyll-like graphene region corresponds to the mesophyll-like region;

[0019] For the forest-like area, the laser power was set to 4W, the laser scanning speed to 96mm / s, and the laser scanning interval to 0.01mm; for the mesophyll-like area 2, the laser power was set to 5W, the laser scanning speed to 77mm / s, and the laser scanning interval to 0.01mm.

[0020] S4. Filling with PEG: The processed three-dimensional laser-induced graphene is immersed in molten PEG. After vacuum treatment, excess PEG on the surface is removed to obtain a thermally conductive composite material based on laser-induced graphene.

[0021] Furthermore, in step S3, the polybenzoxazine film is laser-induced, with the laser wavelength set to 280-3500 nm and the defocusing amount to 6 mm.

[0022] Preferably, in step S1, the phenol source is bisphenol A, and the molar mass ratio of bisphenol A: 4,4'-diaminodiphenylmethane: paraformaldehyde is (1-1.2): (0.8-1.2): (1-1.5).

[0023] The heating temperature is 120℃ and the stirring time is 6 hours.

[0024] Preferably, in step S2, the heating temperature for melting the benzoxazine monomer is 110°C, and the degassing time is 30 min.

[0025] Preferably, in step S2, the high-temperature curing of the polybenzoxazine fluid is first cured at 180°C for 2 hours, then cured at 200°C for 2 hours, and finally cured at 220°C for 2 hours.

[0026] Preferably, in step S1, the step of purifying to obtain the benzoxazine monomer is as follows:

[0027] A. Dissolution: The precipitated benzoxazine monomer structure is dissolved in a solvent to obtain a solution containing the benzoxazine monomer; the solvent is one of ethyl acetate, dichloromethane, and trichloromethane;

[0028] B. Washing: Wash the solution containing benzoxazine monomer three times with deionized water;

[0029] C. Drying: After drying the solution containing benzoxazine monomer with anhydrous sodium sulfate or anhydrous magnesium sulfate, the benzoxazine monomer is obtained by rotary evaporation.

[0030] Preferably, in step S4, the processed three-dimensional laser-induced graphene is immersed in molten PEG for 2 hours at a temperature of 90°C.

[0031] The technical solution provided by this invention may include the following beneficial effects:

[0032] 1. By using different laser parameters for processing, graphene can have two microstructures: forest-like and plant leaf-like mesophyll-like. Forest-like graphene has a better light absorption rate. At the same time, mesophyll-like graphene is added and filled with phase change material PEG. The area ratio of PEG to forest-like graphene is 3:1. Together, they enable the thermally conductive composite material to have a good photothermal conversion rate while maintaining a high light absorption rate, and at the same time ensure temperature stability, effectively protecting the components that need heat collection.

[0033] 2. The complexity of the preparation process is reduced by preparing benzoxazine monomers, preparing polybenzoxazine films, laser-induced processing, and filling with phase change materials to prepare thermally conductive composite materials. Attached Figure Description

[0034] Figure 1 This is a structural schematic diagram of an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the overall structure of one embodiment of the present invention.

[0036] The structure consists of: forest-like region 1, mesophyll-like region 2, heat collection zone 3, resin support layer 4, and graphene layer 5. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0038] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0039] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0040] This solution proposes a thermally conductive composite material based on laser-induced graphene, comprising a resin support layer 4 and a graphene layer 5, wherein the resin support layer 4 is a polybenzoxazine film.

[0041] The graphene layer 5 is obtained by laser-induced processing on the resin support layer 4. The graphene layer 5 includes forest-like graphene regions and mesophyll-like graphene regions, and the area ratio of the forest-like graphene regions to the mesophyll-like graphene regions is 1:3.

[0042] The forest-like graphene region and the mesophyll-like graphene region are each composed of several wedge-shaped partitions, and the wedge-shaped partitions of the forest-like graphene region and the wedge-shaped partitions of the mesophyll-like graphene region are distributed alternately.

[0043] The graphene layer 5 is filled with a phase change material, which is PEG.

[0044] To address the problems existing in current technologies, and inspired by the distribution of leaves and plants in natural forest communities, as well as the natural photothermal conversion principles and thermal energy storage structures in leaves, this technical solution proposes a thermally conductive composite material based on laser-induced graphene. The composite material includes a resin support layer 4 and a graphene layer 5. The resin support layer 4 is a polybenzoxazine film. Due to the high char residue, excellent chemical stability, and good mechanical properties of benzoxazine resin, three-dimensional porous graphene can be obtained through laser induction, offering advantages such as easy processing and low cost. The graphene layer 5 is obtained by laser-induced processing on the resin support layer 4, and includes forest-like graphene regions and mesophyll-like graphene regions. This mimics the photosynthetic process of plant leaves. Plant leaves generally consist of two parts: veins and non-vein areas. The veins primarily transport nutrients, while the non-vein areas utilize and store nutrients. These two parts work together to maximize the efficiency of photosynthesis. Based on this design, the forest-like graphene region is equivalent to leaf veins, and its microstructure resembles the distribution of forest plants. In nature, in forest communities, incident light undergoes multiple reflections between trees and branches. Applying this principle to graphene increases the light path and reflection opportunities, reduces direct light reflection, and enhances light absorption and transport, thereby improving the light absorption rate of graphene. The mesophyll-like graphene region has a microstructure similar to the mesophyll of plant leaves, possessing a large storage space. Working together with the forest-like graphene, it increases the surface area. Furthermore, graphene itself inherently possesses excellent photothermal conversion properties, achieving the goal of further improving the photothermal conversion rate while maintaining a high light absorption rate.

[0045] Meanwhile, the graphene layer 5 is filled with a phase change material (PCM). The energy storage and regulation of the thermally conductive composite material are mainly determined by the PCM. During the phase change process, the PCM absorbs or releases a large amount of latent heat, which can maintain a relatively stable temperature for a certain period of time. When the ambient temperature rises, the PCM begins to absorb heat and undergoes a phase change, such as from a solid to a liquid state. The latent heat absorbed during this process can slow down the rate of temperature rise. When the ambient temperature drops, the PCM releases latent heat and changes back from a liquid to a solid state, thereby delaying the temperature decrease and maintaining a relatively stable temperature. In addition, latent heat storage is a key mechanism for the use of PCM for energy storage. During the phase change process, the latent heat absorbed or released by the PCM can be regarded as a process of energy storage and release. Because PCM can absorb or release a large amount of heat per unit mass during the phase change, it has a high energy density in energy storage systems. The graphene in the mesophyll-like graphene region transfers the converted heat energy back to the forest-like graphene region, while storing another part of the converted heat energy in the phase change material, which facilitates subsequent energy utilization and effectively promotes photothermal conversion. This solves the problem in existing technologies where thermally conductive composite materials based on laser-induced graphene cannot simultaneously possess excellent light absorption rate and photothermal conversion rate, as well as low energy storage efficiency.

[0046] In addition, the thermally conductive composite material obtained will be used for heat collection in photothermal elements. Phase change materials play a role in controlling the temperature balance of photothermal elements. Photothermal elements, especially heat-collecting devices, need to convert the collected light into heat as much as possible, resulting in drastic temperature changes and large temperature differences, which have a significant impact on the lifespan of the components. After filling with phase change materials, the phase change materials will undergo phase changes at different temperatures, absorbing or releasing heat, thus playing a role in balancing and stabilizing the temperature of the components. Furthermore, the mesophyll-like graphene region has a large storage space, which is compatible with the requirements of filling with phase change materials. The two types of graphene work together to solve the problems of low energy storage efficiency and impact on the lifespan of components in current laser-induced graphene-based thermally conductive composite materials.

[0047] Furthermore, the area ratio of the forest-like graphene region to the mesophyll-like graphene region is 1:3. This ratio ensures that the resulting thermally conductive composite material has both high light absorption and good photothermal conversion efficiency. Both the forest-like and mesophyll-like graphene regions are divided into several wedge-shaped sections. The thermal conductivity of the forest-like graphene is much higher than that of the mesophyll-like graphene, making it more suitable for heat transfer. The slender wedge shape is suitable for concentrating the heat converted from the mesophyll-like graphene region and transferring it to the desired location. Furthermore, the wedge-shaped partitions of the forest-like graphene region and the wedge-shaped partitions of the mesophyll-like graphene region are distributed alternately. The graphene with different thermal conductivity arranged at intervals guides heat to the middle region. Due to the different thermal conductivity, thermal resistance is formed, thereby achieving the result of heat flux flowing to a specific area, playing a role in heat flow manipulation. This further ensures that the thermally conductive composite material based on laser-induced graphene of this technical solution has a high light absorption rate and an excellent photothermal conversion rate, and can effectively protect components and improve energy storage efficiency.

[0048] In addition, the phase change material is PEG, or polyethylene glycol, which has a much larger latent heat of phase change than other phase change materials, generally around 160 J / g. The larger the latent heat, the more energy can be stored or released for the same mass of material, and the better its energy storage effect. Therefore, materials with a large latent heat of phase change should be selected as much as possible to improve the energy storage and utilization efficiency. Considering factors such as cost-effectiveness and output, PEG can meet production requirements while having a large latent heat, and has a high cost-effectiveness.

[0049] Furthermore, the forest-like graphene region and the mesophyll-like graphene region form a ring, and the wedge angle A of the wedge-shaped partition of the forest-like graphene region is 11.25°.

[0050] Specifically, the forest-like graphene region and the mesophyll-like graphene region form a ring, and the device that needs to collect heat is placed in the middle of the ring, which is conducive to the transfer of the converted heat energy to the central position.

[0051] The wedge angle A of the wedge-shaped partitions of the forest-like graphene region is 11.25°, which corresponds to the area ratio of the forest-like graphene region to the mesophyll-like graphene region, i.e., the forest-like graphene region is divided into eight parts, such as... Figure 1 As shown, there are interspersed mesophyll-like graphene regions, which further ensures that heat is better directed to the central components.

[0052] Preferably, the thickness ratio of the resin support layer 4 to the graphene layer 5 is 7:3.

[0053] Specifically, the thickness ratio of the resin support layer 4 to the graphene layer 5 is 7:3. Due to the large difference in thermal conductivity between the resin support layer 4 and the graphene structure layer, thermal resistance will be formed at this ratio, effectively reducing heat loss. Furthermore, the resin support layer 4 at this thickness ratio can provide additional mechanical support and fire protection functions.

[0054] A method for preparing a thermally conductive composite material based on laser-induced graphene, comprising the following steps:

[0055] S1. Preparation of benzoxazine monomer: Using phenolic source, amine source and paraformaldehyde as raw materials, and xylene as solvent, the benzoxazine monomer structure is synthesized by heating and stirring. Then, an organic solvent is used to help precipitate the benzoxazine monomer structure, and the benzoxazine monomer is obtained after purification. The phenolic source is one of bisphenol A and phenol, the amine source is 4,4'-diaminodiphenylmethane, and the organic solvent is one of petroleum ether, n-hexane and cyclohexane.

[0056] S2. Preparation of polybenzoxazine film: The benzoxazine monomer is melted and degassed to obtain polybenzoxazine fluid. The polybenzoxazine fluid is poured into a glass mold, cured at high temperature, and demolded after cooling to obtain polybenzoxazine film.

[0057] S3. Laser-induced processing: The polybenzoxazine film is fixed on the processing platform. Using an ultraviolet laser, the corresponding processing area on the polybenzoxazine film is laser-induced according to the preset pattern to obtain the processed three-dimensional laser-induced graphene.

[0058] The graph includes a forest-like region 1, a mesophyll-like region 2, and a heat-collecting region 3; the forest-like graphene region corresponds to the forest-like region, and the mesophyll-like graphene region corresponds to the mesophyll-like region;

[0059] For forest-like region 1, the laser power was set to 4W, the laser scanning speed to 96mm / s, and the laser scanning interval to 0.01mm; for mesophyll-like region 2, the laser power was set to 5W, the laser scanning speed to 77mm / s, and the laser scanning interval to 0.01mm.

[0060] S4. Filling with PEG: The processed three-dimensional laser-induced graphene is immersed in molten PEG. After vacuum treatment, excess PEG on the surface is removed to obtain a thermally conductive composite material based on laser-induced graphene.

[0061] It is worth noting that the forest-like graphene region is located in the forest-like region 1, the mesophyll-like graphene region is located in the mesophyll-like region 2, and the heat collection region 3 houses the components. The forest-like graphene region collects light energy and works synergistically with the mesophyll-like graphene region to convert the collected light energy into heat energy. During the photothermal conversion process, the temperature around the entire component does not change drastically. The forest-like graphene region and the mesophyll-like graphene region then work synergistically to transfer the heat energy to the heat collection region 3 for thermoelectric conversion and other energy utilization. This distribution of functional regions allows for the effective hierarchical utilization of energy, and the temperature field only changes in the heat collection region 3, while the temperature is evenly distributed in the forest-like region 1 and the mesophyll-like region 2, achieving the initial design requirements.

[0062] For the forest-like region 1, the laser power was set to 4W, the laser scanning speed to 96mm / s, and the laser scanning spacing to 0.01mm; for the mesophyll-like region 2, the laser power was set to 5W, the laser scanning speed to 77mm / s, and the laser scanning spacing to 0.01mm. The laser power, scanning speed, and scanning spacing are closely related to the energy density. Too low an energy density results in incomplete graphene formation, failing to create an effective three-dimensional graphene structure; too high an energy density causes graphene to be knocked away or damaged. The shape of the graphene is directly related to the energy density; too low an energy density results in insufficient laser etching depth, preventing the formation of effective graphene; too high an energy density causes excessive etching, leading to graphene knock-away. Setting the above processing parameters ensures that the microstructure of the graphene achieves the structural state required by this technical solution while maintaining the best quality.

[0063] In step S1, an organic solvent is used to help precipitate the benzoxazine monomer structure. The organic solvent is one of petroleum ether, n-hexane, and cyclohexane. When the organic solvent is added to the solution after the reaction, the polarity and dissolution environment of the solution are changed due to the difference in solubility between the organic solvent and xylene, as well as the interaction with the benzoxazine monomer. The solubility of the benzoxazine monomer in this new mixed solvent system decreases, thereby precipitating out as a precipitate.

[0064] Preferably, the organic solvent is petroleum ether, which can effectively reduce the generation of new impurities.

[0065] Furthermore, in step S3, the polybenzoxazine film is laser-induced, with the laser wavelength set to 280-3500 nm and the defocusing amount to 6 mm.

[0066] Specifically, when lasers of different wavelengths act on graphene, the varying degrees of defects arise due to the different interactions between photon energy and the bond energies of carbon atoms in the graphene. For example, ultraviolet lasers, with their shorter wavelengths and higher photon energy, easily break the chemical bonds between carbon atoms when interacting with graphene, damaging the crystal structure and creating more defects, thereby altering the electrical and mechanical properties of graphene. In contrast, infrared lasers, with their lower photon energy, cause relatively less damage to the graphene structure. Therefore, ultraviolet lasers are chosen to generate more defects, forming the desired mesophyll-like and forest-like microstructures of graphene.

[0067] Furthermore, the laser wavelength directly affects the processing accuracy. The shorter the wavelength, the smaller the focused spot during processing, and the higher the processing accuracy. However, if the wavelength is too long, the spot size is too large, and the graphene region that has already been laser-induced processed will be repeatedly scanned, resulting in excessive ablation of the graphene and potential structural damage. Therefore, the preferred laser wavelength range is 280-3500 nanometers. Within this range, the desired graphene structure can be effectively formed while ensuring that the processed areas are not damaged.

[0068] In addition, the laser-induced processing is set with a defocusing amount of 6mm. The defocusing amount is related to the energy density per unit area. When the defocusing amount is set to 6mm, the graphene can be completely formed, resulting in an effective three-dimensional graphene structure without damaging the graphene. The graphene obtained under this defocusing amount has better quality.

[0069] Preferably, in step S1, the phenol source is bisphenol A, and the molar mass ratio of bisphenol A: 4,4'-diaminodiphenylmethane: paraformaldehyde is (1-1.2): (0.8-1.2): (1-1.5).

[0070] The heating temperature is 120℃ and the stirring time is 6 hours.

[0071] Specifically, in step S1, the reaction of the phenolic source, amine source, and paraformaldehyde is problematic. If the temperature is too low, the thermal motion of the molecules is not vigorous enough, the effective collision frequency between reactant molecules is low, the reaction rate will be very slow, and the reaction will be difficult to proceed fully. On the other hand, if the temperature is too high, some side reactions may be triggered, such as the decomposition of the reactants or excessive polymerization, which will affect the yield and quality of the polybenzoxazine monomer. When the heating temperature is 120°C, stirring can maximize the yield of polybenzoxazine monomer.

[0072] Furthermore, insufficient stirring or a lack of stirring time can lead to uneven temperature distribution, resulting in inconsistent reaction rates and potentially triggering side reactions. For example, reactants may decompose in excessively hot areas. Stirring helps maintain a relatively uniform temperature throughout the reaction system, ensuring stable operation at the set temperature of 120°C. A stirring time of 6 hours further guarantees complete reaction.

[0073] Preferably, in step S2, the heating temperature for melting the benzoxazine monomer is 110°C, and the degassing time is 30 min.

[0074] It is worth noting that benzoxazine monomers have a certain melting point, and 110℃ is a temperature that allows them to fully melt. At this temperature, the benzoxazine monomers transform from a solid to a liquid state, completely melting and increasing their fluidity. This facilitates subsequent operations, ensures a smooth filling process, and guarantees the molding quality of the polybenzoxazine film. Simultaneously, it minimizes the possibility of monomer decomposition or premature polymerization caused by excessively high temperatures, thus ensuring the quality of the resulting thermally conductive composite material.

[0075] Meanwhile, the degassing time is limited to 30 minutes to remove all gas to the maximum extent, thereby increasing the probability of achieving the expected effect and reducing the occurrence of residual bubbles affecting the optical and mechanical properties of the film. It also avoids increasing the production cycle and cost, as well as some unnecessary changes, such as the partial oxidation of benzoxazine monomers due to excessive time. This ensures the degassing effect while taking into account both production efficiency and the quality of polybenzoxazine film.

[0076] Preferably, in step S2, the high-temperature curing of the polybenzoxazine fluid is first cured at 180°C for 2 hours, then cured at 200°C for 2 hours, and finally cured at 220°C for 2 hours.

[0077] Specifically, the condensation polymerization reaction that generates benzoxazine monomers is a thermally initiated polymerization reaction. Therefore, temperature is a crucial factor affecting the condensation polymerization reaction and the quality of the generated benzoxazine monomers. At lower temperatures, the thermal motion of monomer molecules is relatively slow, resulting in lower reactivity and making the polymerization reaction difficult to proceed effectively. Conversely, excessively high temperatures may lead to an overly rapid reaction rate, generating too many side reactions, such as monomer decomposition and excessive cross-linking, thus affecting the quality of the polybenzoxazine film. 180℃ is a temperature that can effectively initiate the polymerization reaction of benzoxazine monomers. At this temperature, the benzoxazine monomer molecules gain sufficient energy to allow the condensation reaction between the phenolic hydroxyl and amino groups to begin at an appropriate rate. At this temperature, the reaction is relatively mild, allowing for the gradual construction of polymer chains and promoting the formation of a more regular polymer structure.

[0078] Next, raising the temperature to 200℃ can further accelerate the polymerization rate. At this temperature, the activity of the benzoxazine monomer is higher, the collision frequency between molecules increases, and more phenolic hydroxyl and amino groups can react, promoting the growth and cross-linking of polymer chains. This helps to improve the mechanical properties of the polybenzoxazine film, making it more dense and stable.

[0079] Finally, curing was performed at 220℃. Further optimization of the polybenzoxazine film's properties was achieved at this higher temperature. At this temperature, the polymerization reaction is more complete, resulting in a higher crosslinking density and thus enhancing the film's toughness, abrasion resistance, and other properties. Simultaneously, the higher temperature helps remove any small molecules that may remain within the polybenzoxazine film, such as unreacted monomers and small molecule byproducts generated during the reaction, improving the film's purity and quality.

[0080] Meanwhile, the 2-hour curing time at each temperature ensures that the polymerization reaction is sufficient at the corresponding temperature, achieving the expected performance improvement effect, without increasing production costs or production cycle.

[0081] Preferably, in step S1, the step of purifying to obtain the benzoxazine monomer is as follows:

[0082] A. Dissolution: The precipitated benzoxazine monomer structure is dissolved in a solvent to obtain a solution containing the benzoxazine monomer; the solvent is one of ethyl acetate, dichloromethane, and trichloromethane;

[0083] B. Washing: Wash the solution containing benzoxazine monomer three times with deionized water;

[0084] C. Drying: After drying the solution containing benzoxazine monomer with anhydrous sodium sulfate or anhydrous magnesium sulfate, the benzoxazine monomer is obtained by rotary evaporation.

[0085] This purification step ensures a 90% yield of the purified benzoxazine monomer while minimizing losses. Since washing with deionized water is required after purification, anhydrous sodium sulfate or anhydrous magnesium sulfate is used to adsorb the deionized water. The rotary evaporator provides efficient evaporation and gentle heating, effectively separating the solvent and improving the purity of the obtained benzoxazine monomer.

[0086] Preferably, in step S4, the processed three-dimensional laser-induced graphene is immersed in molten PEG for 2 hours at a temperature of 90°C.

[0087] It's worth noting that while the goal of this step is to fill the mesophyll-like graphene regions with PEG, the liquid PEG, under the influence of the internal and external pressure difference in a vacuum environment, will penetrate as much as possible into all accessible spaces, including the forest-like graphene regions. This further enhances the performance of the resulting thermally conductive composite material. First, PEG acts as a binder. After the PEG fills the pores and gaps between the two types of graphene with different microstructures, the internal spatial structure of the graphene becomes more compact. From a microscopic perspective, filling the gaps in the graphene in the forest-like regions—specifically, filling the spaces between the roots of a forest community—makes the connections between the originally relatively independent structural units much tighter, further improving thermal conductivity. Second, the morphology of the graphene in the forest-like regions is similar to the forest community structure of northern coniferous forests, such as pine forests. Light absorption and light energy conversion occur in the branches and leaves with their topological structure. Therefore, the gaps in the branches and leaves are relatively smaller than those in the roots of a forest community. Even filling with a small amount of PEG will not significantly affect light absorption and photothermal conversion. Finally, the PEG filling the forest-like graphene regions helps maintain temperature balance, ensuring that the graphene structure does not change due to temperature variations.

[0088] In summary, in step S4, the processed three-dimensional laser-induced graphene is immersed in molten PEG for 2 hours at a temperature of 90°C. This ensures that the PEG effectively fills the mesophyll-like graphene region without affecting the function of the forest-like graphene region, and even further improves the performance.

[0089] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0090] Example group

[0091] Example 1

[0092] S1. Preparation of benzoxazine monomer: 0.525 mol of bisphenol A, 0.477 mol of 4,4'-diaminodiphenylmethane, 0.716 mol of paraformaldehyde and 500 ml of xylene were mixed, heated to 120 °C and stirred for 6 hours. After the solution cooled, 2000 ml of petroleum ether was added dropwise to precipitate the precipitate. The precipitate was then dissolved in 400 ml of ethyl acetate, washed three times with deionized water, filtered with anhydrous sodium sulfate and dried. The benzoxazine monomer was obtained by rotary evaporation.

[0093] S2. Preparation of polybenzoxazine film: Melt and degas the benzoxazine monomer for 30 min, set the temperature to 110℃ to obtain PH-ddm fluid, pour the PH-ddm fluid into a glass mold, and cure it at 180℃, 200℃ and 220℃ for 2 hours respectively. After cooling, demold to obtain polybenzoxazine film.

[0094] S3. Laser-induced processing: The polybenzoxazine film is fixed on the processing platform. Using an ultraviolet laser, according to the preset pattern, for the forest-like region 1, the laser power is set to 4W, the laser scanning speed is 96mm / s, and the laser scanning interval is 0.01mm; for the mesophyll-like region 2, the laser power is set to 5W, the laser scanning speed is 77mm / s, and the laser scanning interval is 0.01mm; thus, the processed three-dimensional laser-induced graphene is obtained.

[0095] The graphic includes a forest-like region 1, a mesophyll-like region 2, and a heat-collecting region 3, wherein the area ratio of the forest-like region 1 to the mesophyll-like region 2 is 1:3.

[0096] S4. Filling with PEG: The processed three-dimensional laser-induced graphene is immersed in molten PEG. After vacuum treatment, excess PEG on the surface is removed to obtain a thermally conductive composite material based on laser-induced graphene.

[0097] Comparative group

[0098] Comparative Example 1

[0099] Compared with Example 1, when laser induction is performed in Comparative Example 1, the area ratio of the forest-like region 1 to the mesophyll-like region 2 in the preset pattern is 1:1, and everything else is the same.

[0100] Comparative Example 2

[0101] Compared with Example 1, when laser induction was performed in Comparative Example 2, the preset pattern did not include the mesophyll-like region 2, but everything else was the same.

[0102] Comparative Example 3

[0103] Compared with Example 1, when laser induction was performed in Comparative Example 3, the preset pattern did not include the forest-like region 1, but everything else was the same.

[0104] The thermally conductive composite materials based on laser-induced graphene prepared in the above embodiments and comparative examples were subjected to performance tests. The specific performance tests were as follows:

[0105] Light absorption rate: The light absorption rate is calculated under AM1.5 standard, simulating solar radiation, in the wavelength range of 280-2500 nm.

[0106] Temperature rise rate: Under the AM1.5 standard, simulating solar radiation, the temperature was measured after 5s, 40s and 60s at a room temperature of 25℃, and the temperature rise rate was obtained.

[0107] The specific test results are shown in Table 1:

[0108] Table 1. Test results of relevant properties of thermally conductive composite materials

[0109] Performance testing items Light absorption rate T1 / ℃ (t=5s) T2 / ℃ (t=40s) △T1 / ℃ △T2 / ℃ Example 1 97.70％ 53.8 90 65 36.2 Comparative Example 1 88.40％ 50.6 88.9 63.9 38.3 Comparative Example 2 98.80％ 49 86.8 61.8 37.8 Comparative Example 3 80.50％ 47.3 83 58 35.7

[0110] During the temperature rise rate test, the temperature after 60 seconds of irradiation was basically the same as that after 40 seconds of irradiation, indicating that the equilibrium temperature had been reached near 40 seconds. Here, ΔT1 represents the difference between the equilibrium temperature and room temperature, and ΔT2 represents the difference between the temperature at 40 seconds and the temperature at 5 seconds.

[0111] As can be seen from the test results in Table 1, the light absorption rate of Example 1 is 97.70%, which is relatively high. Furthermore, ΔT1 is 65℃, indicating a large temperature difference, while ΔT2 is relatively small. This suggests that the thermally conductive composite material obtained in Example 1 has the highest photothermal conversion efficiency and a smaller fluctuation range at high temperatures. It exhibits both high light absorption rate and high photothermal conversion efficiency.

[0112] In Comparative Example 1, the area occupied by forest-like graphene was 1:1 to that occupied by mesophyll-like graphene. Under this ratio, the light absorption rate was 88.40%, which was significantly lower than 97.70% in Example 1. Although the temperature difference was 63.9℃, which is relatively high, the temperature rise rate was slow, and ΔT2 was 38.3℃, which was higher than 36.2℃ in Example 1. The large fluctuation at high temperatures was not conducive to light absorption and had an impact on the components.

[0113] In Comparative Example 2, which does not include mesophyll-like graphene, the resulting thermally conductive composite material has a large area of ​​forest-like graphene, resulting in a high light absorption rate of 98.80%, which is greater than 97.70% in Example 1. However, the temperature difference in Comparative Example 2 is 61.8℃, which is less than 65℃ in Example 1. This indicates that Comparative Example 2 has a good light absorption rate, but insufficient photothermal conversion efficiency, and cannot have both good light absorption rate and good photothermal conversion efficiency.

[0114] Comparative Example 3, which does not include forest-like graphene, has the lowest light absorption rate of the thermally conductive composite material, at only 80.50%, which is much lower than 97.70% in Example 1. At the same time, the temperature difference between the equilibrium temperature and room temperature is the smallest, at only 58°C, which is less than 65°C in Example 1. This indicates that although the thermally conductive composite material made with only mesophyll-like graphene has better temperature stability, its light absorption rate and photothermal conversion rate are not as good as those of Example 1.

[0115] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A thermally conductive composite material based on laser-induced graphene, characterized in that: It includes a resin support layer and a graphene layer, wherein the resin support layer is a polybenzoxazine film; The graphene layer is obtained by laser-induced processing on the resin support layer. The graphene layer includes forest-like graphene regions and mesophyll-like graphene regions, and the area ratio of the forest-like graphene regions to the mesophyll-like graphene regions is 1:

3. The forest-like graphene region and the mesophyll-like graphene region are each composed of several wedge-shaped partitions, and the wedge-shaped partitions of the forest-like graphene region and the wedge-shaped partitions of the mesophyll-like graphene region are distributed alternately. The graphene layer is filled with a phase change material, which is PEG. The preparation method of the forest-like graphene region and the mesophyll-like graphene region is as follows: laser-induced processing, fixing the polybenzoxazine film on the processing platform, using an ultraviolet laser, according to the preset pattern, laser-induced processing is performed on the corresponding processing area on the polybenzoxazine film to obtain the processed three-dimensional laser-induced graphene. The graph includes a forest-like region, a mesophyll-like region, and a heat-collecting region; the forest-like graphene region corresponds to the forest-like region, and the mesophyll-like graphene region corresponds to the mesophyll-like region; For forest-like areas, the laser power was set to 4W, the laser scanning speed to 96mm / s, and the laser scanning interval to 0.01mm; for mesophyll-like areas, the laser power was set to 5W, the laser scanning speed to 77mm / s, and the laser scanning interval to 0.01mm.

2. The thermally conductive composite material based on laser-induced graphene according to claim 1, characterized in that: The forest-like graphene region and the mesophyll-like graphene region form a ring; The wedge angle A of the wedge-shaped partition of the forest-like graphene region is 11.25°.

3. The thermally conductive composite material based on laser-induced graphene according to claim 1, characterized in that: The thickness ratio of the resin support layer to the graphene layer is 7:

3.

4. A method for preparing a thermally conductive composite material based on laser-induced graphene, characterized in that, The method for preparing a laser-induced graphene-based thermally conductive composite material according to any one of claims 1-3 comprises the following steps: S1. Preparation of benzoxazine monomer: Using phenolic source, amine source and paraformaldehyde as raw materials, and xylene as solvent, the benzoxazine monomer structure is synthesized by heating and stirring. Then, an organic solvent is used to help precipitate the benzoxazine monomer structure, and the benzoxazine monomer is obtained after purification. The phenolic source is one of bisphenol A and phenol, the amine source is 4,4'-diaminodiphenylmethane, and the organic solvent is one of petroleum ether, n-hexane and cyclohexane. S2. Preparation of polybenzoxazine film: The benzoxazine monomer is melted and degassed to obtain polybenzoxazine fluid. The polybenzoxazine fluid is poured into a glass mold, cured at high temperature, and demolded after cooling to obtain polybenzoxazine film. S3. Laser-induced processing: The polybenzoxazine film is fixed on the processing platform. Using an ultraviolet laser, the corresponding processing area on the polybenzoxazine film is laser-induced according to the preset pattern to obtain the processed three-dimensional laser-induced graphene. The graph includes a forest-like region, a mesophyll-like region, and a heat-collecting region; the forest-like graphene region corresponds to the forest-like region, and the mesophyll-like graphene region corresponds to the mesophyll-like region; For forest-like areas, the laser power was set to 4W, the laser scanning speed to 96mm / s, and the laser scanning interval to 0.01mm; for mesophyll-like areas, the laser power was set to 5W, the laser scanning speed to 77mm / s, and the laser scanning interval to 0.01mm. S4. Filling with PEG: The processed three-dimensional laser-induced graphene is immersed in molten PEG. After vacuum treatment, excess PEG on the surface is removed to obtain a thermally conductive composite material based on laser-induced graphene.

5. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S3, the polybenzoxazine film is laser-induced, with the laser wavelength set to 280-3500 nm and the defocusing amount to 6 mm.

6. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S1, the phenol source is bisphenol A, and the molar mass ratio of bisphenol A: 4,4'-diaminodiphenylmethane: paraformaldehyde is (1-1.2): (0.8-1.2): (1-1.5). The heating temperature is 120℃ and the stirring time is 6 hours.

7. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S2, the heating temperature for melting the benzoxazine monomer is 110°C, and the degassing time is 30 min.

8. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S2, the polybenzoxazine fluid is cured at high temperature, first at 180°C for 2 hours, then at 200°C for 2 hours, and finally at 220°C for 2 hours.

9. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S1, the purification process to obtain the benzoxazine monomer is as follows: A. Dissolution: The precipitated benzoxazine monomer structure is dissolved in a solvent to obtain a solution containing the benzoxazine monomer; the solvent is one of ethyl acetate, dichloromethane, and trichloromethane; B. Washing: Wash the solution containing benzoxazine monomer three times with deionized water; C. Drying: After drying the solution containing benzoxazine monomer with anhydrous sodium sulfate or anhydrous magnesium sulfate, the benzoxazine monomer is obtained by rotary evaporation.

10. The method for preparing a thermally conductive composite material based on laser-induced graphene according to claim 4, characterized in that: In step S4, the processed three-dimensional laser-induced graphene is immersed in molten PEG for 2 hours at a temperature of 90°C.

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