Graphene heat dissipation structure and its preparation method

Abstract

This application relates to the field of thermal management materials and discloses a graphene heat dissipation structure and its preparation method. The structure comprises an alternating layer of graphene and boron nitride nanosheets forming a composite thermally conductive layer. A polymer matrix layer is disposed on its outer side and connected to it. A thermoelectric functional layer is located between the composite thermally conductive layer and the polymer matrix layer. All layers are integrally formed into the heat dissipation structure through hot pressing. The method includes preparing graphene oxide and reducing it to obtain reduced graphene, preparing boron nitride nanosheets, mixing and ultrasonically treating graphene and boron nitride nanosheets, then mixing them with a polymer matrix and a surface modifier, and finally obtaining the graphene heat dissipation structure through hot pressing. This invention constructs a thermally conductive structure by alternating layers of graphene and boron nitride nanosheets, introduces a thermoelectric functional layer to achieve temperature difference energy conversion, uses hot pressing technology to ensure tight bonding of each layer, and introduces a flexible, highly insulating polymer matrix, thereby improving the thermal conductivity, stability, and device compatibility of the heat dissipation structure.

Description

Technical Field

[0001] This invention relates to the field of thermal management materials, specifically to graphene heat dissipation structures and their preparation methods. Background Technology

[0002] As the integration of electronic devices continues to increase, the heat generated under high power density operation increases rapidly, severely limiting system stability, response speed, and lifespan. Therefore, efficient, thin, flexible thermal management materials with electrical insulation properties have become a key research focus in the field of thermal interface materials. Among these, two-dimensional carbon materials, represented by graphene, are widely used to construct thermally conductive layers due to their excellent thermal conductivity. However, graphene is prone to aggregation and agglomeration in practical applications, preventing the in-plane structure from fully unfolding and thus interrupting thermal channels, limiting its overall thermal conductivity. Furthermore, graphene's inherent high electrical conductivity also restricts its application in high-frequency circuits and scenarios requiring insulation.

[0003] To address these issues, some studies have attempted to combine graphene with inorganic insulating materials (such as boron nitride) to guide the alignment of its layers and block electron pathways. However, these structures are generally achieved through physical stacking or simple mixing processes, lacking effective interfacial coupling design. The composite process easily generates voids or interlayer slip, leading to increased interfacial thermal resistance and low heat transfer efficiency. Furthermore, due to differences in polarity and affinity between materials, the composite filler is prone to phase separation or deposition, resulting in a lack of overall structural stability and repeatability, thus limiting its long-term application performance.

[0004] On the other hand, most existing thermal interface materials are passive thermally conductive structures, unable to realize the functional utilization of thermal energy, such as thermoelectric conversion or self-driven response. Some studies have proposed introducing thermoelectric materials into thermal interface composites, but these generally suffer from problems such as uneven distribution of functional layers, complex structures that are difficult to mold, and interface mismatch. In addition, the particle size distribution and dispersion state of thermoelectric materials are difficult to control, affecting their thermal response speed and stability, making it difficult to work stably in flexible, conformable practical devices. Therefore, this invention proposes a graphene heat dissipation structure and its preparation method to address the shortcomings of existing technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a graphene heat dissipation structure and its preparation method. A stable heat-conducting network is constructed by alternating layers of graphene and boron nitride nanosheets, and a thermoelectric functional layer is introduced to realize the utilization of thermal energy. At the same time, the hot-pressing integrated molding process effectively improves the bonding strength between the layers, solving the technical bottlenecks of discontinuous heat conduction paths, poor structural stability, and lack of multifunctional integration capabilities in existing materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a graphene heat dissipation structure comprising a graphene layer, a boron nitride nanosheet layer, a polymer matrix layer, and a thermoelectric functional layer. The graphene layer and the boron nitride nanosheet layer are alternately stacked to form a composite thermally conductive layer. The polymer matrix layer is disposed on the outside of and connected to the composite thermally conductive layer. The thermoelectric functional layer is disposed between the composite thermally conductive layer and the polymer matrix layer. The graphene layer, the boron nitride nanosheet layer, the polymer matrix layer, and the thermoelectric functional layer are combined by hot-pressing to form an integrated graphene heat dissipation structure.

[0007] Preferably, the graphene heat dissipation structure comprises the following components in parts by mass: Graphene: 20-60 parts; Boron nitride nanosheets: 10–40 parts; Polymer matrix material: 20-40 parts; Thermoelectric functional materials: 1-5 parts; Surface modifier: 1-3 parts.

[0008] The graphene used is reduced graphene oxide obtained by oxidation and reduction with hydrazine hydrate. It has a multilayer sheet structure with 1 to 10 layers, a single layer thickness of 0.5 to 5 nanometers, and a lateral dimension of 0.1 to 10 micrometers. The graphene is uniformly dispersed by ultrasound and then used together with boron nitride nanosheets to construct alternating stacked thermally conductive channels.

[0009] Graphene possesses high in-plane thermal conductivity (theoretically up to 5300 W / m·K), and its two-dimensional conjugated structure facilitates efficient phonon propagation. In its layer-by-layer stacked structure, graphene can construct continuous in-plane heat conduction paths, significantly improving the overall thermal conductivity of the composite structure and reducing heat loss. Furthermore, its high specific surface area also facilitates the formation of dense interfaces with other components, improving overall thermal coupling efficiency.

[0010] Boron nitride nanosheets were prepared by liquid-phase exfoliation, with a thickness of 1–20 nm and a lateral dimension of 0.2–5 μm. They were mixed with graphene at a mass ratio of 20:1 to 1:1 and then subjected to ultrasonic treatment to form a uniformly distributed two-dimensional composite phase.

[0011] Boron nitride nanosheets are two-dimensional materials that are electrically insulating but have high thermal conductivity (approximately 300 W / m·K). Their insertion into the graphene layers prevents the overlapping and collapse of the graphene sheets, maintaining their dispersed state and thus preserving the integrity of the high thermal conductivity pathways. Furthermore, the electrical insulation properties of the boron nitride nanosheets can block current pathways between graphene layers, avoiding short-circuit risks and ensuring the electrical stability of the thermoelectric layer.

[0012] The polymer matrix uses polytetrafluoroethylene or polyimide as the supporting material, with a mass fraction of 20 to 40 parts. It is combined with the graphene-boron nitride composite layer through a hot pressing process to form a flexible supporting layer.

[0013] The polymer matrix provides structural flexibility and processability, effectively coating the thermally conductive composite layer and enhancing overall mechanical strength. Simultaneously, the polymer matrix coating of the thermally conductive phase reduces microcrack formation, improves thermal stress release, and further optimizes thermal conductivity by controlling interfacial compatibility to adjust the interfacial thermal resistance of the composite layer.

[0014] The thermoelectric functional material uses antimony tritelluride (Sb2Te3) or bismuth tritelluride (Bi2Te3) nanoparticles with a particle size controlled between 10 and 100 nanometers. These nanoparticles are physically mixed and uniformly distributed within the thermally conductive composite layer to construct a thermoelectric conversion module.

[0015] Thermoelectric materials utilize the Seebeck effect (temperature difference-driven potential generation). In graphene-boron nitride high thermal conductivity composite networks, temperature gradients can be precisely sensed to achieve the conversion of thermal energy into electrical energy. The high thermal conductivity network of graphene and boron nitride nanosheets facilitates the rapid establishment and maintenance of temperature differences, improving the effective working efficiency of thermoelectric materials, while nanoscale thermoelectric particles enhance the thermoelectric figure of merit (ZT value) due to their size quantization effect.

[0016] The surface modifier is an aminosilane or a functionalized small molecule with a carboxyl group, which is modified on the surface of the graphene sheet through covalent bonding or electrostatic interaction, and the amount used is controlled at 1 to 3 parts by mass.

[0017] Surface modifiers act as bridges at the interface, adjusting the interfacial affinity between graphene and the polymer matrix or boron nitride sheets, enhancing interfacial bonding, and reducing interfacial thermal resistance (ITR). Furthermore, the introduction of functional groups can regulate dispersibility, preventing graphene agglomeration in the system and facilitating the formation of uniform and stable thermally conductive pathways.

[0018] Preferably, the graphene is reduced graphene oxide obtained by chemical reduction treatment, having a sheet structure with 1 to 10 layers, a single layer thickness of 0.5 to 5 nanometers, and a lateral dimension of 0.1 to 10 micrometers; the boron nitride nanosheets are two-dimensional nanosheets prepared by liquid phase exfoliation, with a thickness of 1 to 20 nanometers and a lateral dimension of 0.2 to 5 micrometers; the polymer matrix material is polytetrafluoroethylene or polyimide, and the polymer matrix layer is bonded to the composite thermally conductive layer by hot pressing.

[0019] Preferably, the thermoelectric functional material is bismuth tritelluride or antimony tritelluride, with a particle size of 10-100 nanometers, and is distributed inside the composite thermally conductive layer; the surface modifier includes aminosilane compounds or carboxyl functional group molecules, which are attached to the surface of the graphene sheet by covalent grafting or electrostatic adsorption.

[0020] This invention also provides a method for preparing a graphene heat dissipation structure, comprising the following steps: S1. Preparation of graphene: Natural graphite powder is mixed with concentrated sulfuric acid and hydrogen peroxide and stirred to obtain graphene oxide. S2. Graphene oxide reduction treatment: Graphene oxide is mixed with hydrazine hydrate reducing agent, stirred, and cooled to room temperature to obtain reduced graphene. S3. Preparation of boron nitride nanosheets: Boron nitride powder is mixed with N-methylpyrrolidone solvent and stirred to obtain boron nitride nanosheets; S4. Mixing graphene and boron nitride nanosheets: Mix graphene and boron nitride nanosheets and then perform ultrasonic treatment to obtain a graphene-boron nitride composite. S5. Hot pressing: The composite is mixed with the polymer matrix material and surface modifier, hot pressed, and cooled to room temperature to obtain a graphene heat dissipation structure.

[0021] Preferably, in step S1, graphene oxide is prepared by mixing natural graphite powder with concentrated sulfuric acid with a mass concentration of 98% and hydrogen peroxide with a mass concentration of 30%, controlling the reaction temperature at 20-30°C, and reacting for 2-4 hours under stirring at 500-800 rpm until graphene oxide is obtained.

[0022] Preferably, in step S2, the reduction treatment of graphene oxide uses hydrazine hydrate reducing agent with a mass concentration of 80%, the reaction temperature is 150-200℃, and the reaction is carried out for 4-6 hours under stirring conditions of 400-600 rpm. After the reaction is completed, the mixture is cooled to room temperature to obtain reduced graphene.

[0023] Preferably, in step S3, the boron nitride nanosheets are formed by mixing boron nitride powder with N-methylpyrrolidone solvent, stirring at 1000 rpm at 50-60°C, and reacting for 2-3 hours until the boron nitride nanosheets are completely dispersed.

[0024] Preferably, in step S4, graphene and boron nitride nanosheets are mixed at a mass ratio of 20:1 to 1:1 and then subjected to ultrasonic treatment for 30 to 60 minutes to obtain a graphene-boron nitride composite.

[0025] Preferably, in step S5, after the composite is mixed evenly with the polymer matrix material and the surface modifier, it is pressed by a hot pressing process at a temperature of 150-250°C, a pressure of 2-5 MPa, a holding time of 10-30 minutes, and then cooled to room temperature to obtain a graphene heat dissipation structure.

[0026] This invention provides a graphene heat dissipation structure and its preparation method. It has the following beneficial effects: 1. This invention employs a technical solution of alternating stacking of graphene and boron nitride nanosheets to construct a thermally conductive structure, achieving the dual effects of improving in-plane thermal conductivity and suppressing electron leakage. Compared to the existing technology's single graphene filler thermal interface structure, this solution solves the problems of interrupted thermal channels and poor insulation caused by agglomeration and collapse.

[0027] 2. This invention employs a composite design that embeds a thermoelectric functional layer between the thermally conductive layer and the substrate layer, achieving the effect of utilizing temperature difference energy while maintaining the stability of the heat dissipation structure. Unlike traditional heat dissipation materials that only passively conduct heat, this invention effectively solves the problems of single functional structure and low energy conversion efficiency.

[0028] 3. This invention uses a hot-pressing process to integrally press each functional layer together, achieving the technical goal of tightly bonded multilayer structures and significantly reduced interfacial thermal resistance. In contrast, existing multilayer composite films generally employ physical lamination, resulting in defects such as interlayer gaps and weak bonding, which cannot guarantee performance stability under high-temperature operating environments.

[0029] 4. This invention achieves the technical advantage of improving device compatibility and application versatility by introducing a flexible, highly insulating polymer material into the polymer matrix for encapsulation. Compared with existing thermal interface materials, which are generally rigid and prone to warping, this invention significantly improves problems such as poor adhesion and difficulties in actual assembly. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the graphene heat dissipation structure of the present invention; Figure 2 This is a flowchart of the preparation method of the present invention.

[0031] The structure consists of: 1. Graphene layer; 2. Boron nitride nanosheet layer; 3. Polymer matrix layer; and 4. Thermoelectric functional layer. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figure 1This invention provides a graphene heat dissipation structure, including a graphene layer 1, a boron nitride nanosheet layer 2, a polymer matrix layer 3, and a thermoelectric functional layer 4. The graphene layer 1 and the boron nitride nanosheet layer 2 are stacked alternately to form a composite thermally conductive layer, forming a two-dimensional thermally conductive network with in-plane orientation. The polymer matrix layer 3 covers and is disposed on the outside of the composite thermally conductive layer to provide structural support and flexible encapsulation. The thermoelectric functional layer 4 is sandwiched between the composite thermally conductive layer and the polymer matrix layer 3 to construct a functional interface with thermoelectric conversion capability.

[0034] Graphene layer 1 is composed of sheet-like reduced graphene oxide with a thickness of 0.5–5 nanometers and a lateral dimension of 0.1–10 micrometers, exhibiting high thermal conductivity and in-plane heat transfer advantages. Boron nitride nanosheet layer 2 is composed of two-dimensional boron nitride obtained through liquid phase exfoliation with a thickness of 1–20 nanometers. It is used to adjust the interlayer spacing of graphene, block electron conduction paths, and at the same time help maintain the stability of the sheet structure, improve insulation and the integrity of the thermal channels between composite layers.

[0035] The polymer matrix layer 3 is selected from high-temperature resistant and highly insulating polymer materials such as polyimide and polytetrafluoroethylene, which have good flexibility and encapsulation adaptability, and can achieve bonding treatment on the surfaces of different devices. The thermoelectric functional layer 4 is filled with thermoelectric functional materials such as antimony tritelluride (Sb2Te3) and bismuth tritelluride (Bi2Te3), with a particle size controlled at 10-100 nanometers, and uniformly dispersed in the composite thermally conductive layer, utilizing the temperature difference to realize the conversion of thermal energy into electrical energy.

[0036] The above-mentioned layers are combined by hot pressing to form an integrated heat dissipation structure. The hot pressing temperature is controlled at 150-250℃, the pressure is 2-5MPa, and the pressure is held for 10-30 minutes.

[0037] Please see Figure 2 : Example 1: Preparation of Flexible High Thermal Conductivity Composite Graphene Heat Dissipation Film Graphene preparation: Take 40 parts of graphene raw material (obtained from natural graphite through oxidation-reduction), react with concentrated sulfuric acid and 30% hydrogen peroxide, control the temperature at 25℃, stir at 600 rpm, and react for 3 hours to obtain reduced graphene dispersion.

[0038] Preparation of boron nitride nanosheets: 20 parts of boron nitride nanosheet raw material were added to N-methylpyrrolidone and stirred at 55°C for 2 hours at a stirring rate of 1000 rpm to obtain a stable dispersed nanosheet liquid.

[0039] Composite mixing treatment: Graphene and boron nitride nanosheets were mixed at a mass ratio of 2:1, ultrasonically treated for 40 minutes, and then 2 parts of surface modifier (aminosilane) were added. After stirring for another 20 minutes, a uniform thermally conductive composite was formed.

[0040] Hot pressing: Add 30 parts of polymer matrix material (polyimide) and 2 parts of thermoelectric functional material (antimony tritelluride), and hot press in a mold at 200°C and 3MPa for 15 minutes, then allow to cool naturally to form a film.

[0041] Example 2: Preparation of an enhanced electrically insulating graphene-boron nitride heat dissipation composite sheet Graphene preparation: Take 30 parts of graphene raw material and prepare it according to the standard oxidation-reduction method. The reduction temperature is set at 150℃ and the mixture is stirred continuously for 6 hours to obtain reduced graphene.

[0042] Preparation of boron nitride nanosheets: Take 30 parts of boron nitride nanosheets, disperse them with NMP, and stir at high speed at 60℃ for 2.5 hours to form a uniform sheet-like dispersion.

[0043] Composite and modified: Graphene and boron nitride were mixed at a mass ratio of 1:1, and 1.5 parts of surface modifier (small molecule with carboxyl functional group) were added. The mixture was ultrasonically treated for 45 minutes to enhance the interfacial bonding ability.

[0044] Molding and filling: Add 25 parts of polymer matrix material (polytetrafluoroethylene) and 1 part of thermoelectric functional material (bismuth tritelluride), stir evenly, press in a hot press, set temperature 250℃, pressure 5MPa, hold pressure for 20 minutes, and cool to form.

[0045] Example 3: Preparation of a high thermoelectric efficiency integrated composite structure Graphene preparation: Take 50 parts of graphene and prepare it by oxidation-reduction method. During the reduction stage, the temperature is controlled at 200℃, the stirring rate is 600rpm, and the reaction time is 4 hours.

[0046] Preparation of boron nitride nanosheets: Take 30 parts of boron nitride nanosheets, add them to NMP and stir for 1.5 hours, with the temperature controlled at 50℃, to obtain a uniform dispersion.

[0047] Composite and functionalization: Graphene and boron nitride are mixed in a 1:1 ratio, 2 parts of surface modifier (silane coupling agent KH792) are added, and 4 parts of thermoelectric functional material (antimony tritelluride and bismuth tritelluride mixed in equal mass) are added, and ultrasonic treatment is carried out for 30 minutes.

[0048] Hot pressing: Add 20 parts of polymer matrix material (polyimide), mix evenly and then hot press at 180℃ and 2MPa for 10 minutes to obtain a multifunctional graphene heat dissipation structure with a thickness of about 120μm.

[0049] Comparative Example 1 The difference from Example 1 is that boron nitride nanosheets were not added; otherwise, they are the same.

[0050] Comparative Example 2 Compared with Example 1, the difference is that no pressure was applied during the hot pressing process, and the temperature was only heated to 200°C, while the rest were the same.

[0051] Comparative Example 3 The difference between Example 2 and Example 3 is that no surface modifier was added; otherwise, they are the same.

[0052] Comparative Example 4 Compared with Example 2, the difference is that the mass fraction of boron nitride nanosheets used is 50, which exceeds the scope of the claims, but all other aspects are the same.

[0053] Comparative Example 5 Compared with Example 3, the difference is that no thermoelectric functional material was added, but everything else is the same.

[0054] Comparative Example 6 Compared with Example 3, the difference is that ultrasonic treatment was not performed, only mechanical stirring and mixing was performed, and the rest are the same.

[0055] Test Example 1: Thermal Conductivity Comparison Test (Experimental Description) I. Experimental Objective: To evaluate the composite thermally conductive network structure constructed from graphene and boron nitride nanosheets, and the effect of hot pressing conditions on the thermal conductivity performance of the heat dissipation structure.

[0056] II. Experimental Subjects: Example 1: Complete structure, containing graphene + boron nitride + surface modifier + thermoelectric material, hot-pressed.

[0057] Comparative Example 1: Boron nitride nanosheets were removed, and the rest remained the same.

[0058] Comparative Example 2: The pressure input during the hot pressing process is cancelled, and the rest is the same.

[0059] III. Experimental Equipment and Materials: Laser flash thermal conductivity meter (LFA-467); Constant temperature vacuum drying oven; Hot pressing mold (graphite mold); Graphene, boron nitride nanosheets, polyimide, surface modifier, thermoelectric functional materials (consistent with the examples).

[0060] IV. Experimental Procedure: Sample preparation: Samples were prepared according to the process parameters of Example 1, Comparative Example 1 and Comparative Example 2 to form heat dissipation structure sheets with a thickness of approximately 150 μm.

[0061] Three parallel samples were prepared for each structure to ensure test accuracy.

[0062] Preprocessing: All samples were dried in a vacuum oven at 80°C for 2 hours to remove residual solvents and moisture.

[0063] Thermal conductivity test: The transverse thermal conductivity was tested using the laser scintillation method at room temperature (approximately 25°C). The in-plane thermal diffusivity of the sample was measured, and the thermal conductivity was calculated by combining the density and specific heat capacity.

[0064] V. Experimental Data The following table shows the test data (the data closest to the average value in each group is displayed): Table 1: Thermal conductivity test results of Example 1 and comparative sample (lateral direction, 25°C) Example 1 17.8 149 1.75 Good heat dissipation performance Comparative Example 1 9.4 152 1.67 The heat conduction path is interrupted, resulting in failure. Comparative Example 2 6.7 160 1.59 Insufficient compaction, high thermal resistance Experiment Summary: Experimental results show that the synergistic construction of graphene and boron nitride nanosheets plays a decisive role in the formation of the in-plane thermal conductivity network. Although graphene possesses high intrinsic thermal conductivity, it is prone to agglomeration and collapse without auxiliary filler support, leading to discontinuous thermal channels and significantly inhibiting its thermal conductivity. The introduction of boron nitride nanosheets effectively maintains the stability of the sheet structure through interlayer support, while providing additional thermal conduction paths, thereby significantly improving the overall thermal conductivity efficiency of the composite structure. This composite strategy achieves compatibility between high thermal conductivity and electrical insulation, providing structural support for efficient heat dissipation design.

[0065] Furthermore, the pressurization step in the hot pressing process is crucial for the dense forming of the material and the control of interfacial thermal resistance. Experimental comparisons revealed that samples without pressure exhibited numerous pores and microcracks, resulting in poor interfacial density and limiting effective heat transfer. In contrast, under suitable pressure conditions, a highly coupled structural interface was formed between the thermally conductive composite phase and the polymer matrix layer, reducing the cumulative effect of interfacial thermal resistance and making the heat conduction pathway more efficient and continuous. The synergy between process factors and structural design is key to achieving high thermal conductivity.

[0066] Therefore, the graphene-boron nitride laminated composite design and hot-pressing integrated molding process adopted in this invention specifically solves the technical problems of agglomeration failure, weak interfacial bonding, and low thermal diffusion efficiency in traditional graphene fillers. This mechanism is not a single-component effect, but a comprehensive result of material synergy and orderly structural construction, exhibiting superior heat dissipation performance and reliability compared to existing technologies.

[0067] Test Example 2: Interface Adaptation and Thermal Resistance Test (Experimental Description) I. Experimental Objective: The effect of the interfacial bonding between graphene and the polymer matrix on thermal resistance was tested, and the role of the mass ratio of surface modifier to boron nitride in the construction of the thermal interface was evaluated.

[0068] II. Experimental Subjects: Example 2: Complete structure, containing boron nitride, surface modifier, and polytetrafluoroethylene body.

[0069] Comparative Example 3: Removal of surface modifier.

[0070] Comparative Example 4: The mass fraction of boron nitride was 50, which exceeds the recommended range.

[0071] III. Experimental Equipment and Materials: Thermal interface resistance tester (TIMA-FP type); Heat flow meter module (for steady-state measurement); The infrared thermal imager (FLIR-E85) is used for thermal diffusion visualization; The material source remained consistent with the example, and the sample thickness was controlled to be approximately 160 μm.

[0072] IV. Experimental Procedure: Sample preparation: Samples for Example 2, Comparative Example 3, and Comparative Example 4 were prepared, and three copies of each were taken for parallel testing.

[0073] The mass fraction of polytetrafluoroethylene in the structure remains consistent, and the graphene content is fixed at 30 parts, with only the boron nitride and modifier conditions being changed.

[0074] Drying and pretreatment: The sample was treated in a vacuum drying oven at 60°C for 2 hours to remove residual solvent.

[0075] Thermal resistance testing method: A steady-state thermal resistance testing system was used, in which the sample was clamped between two isothermal platforms. The platforms were set to a high-temperature end (80°C) and a low-temperature end (30°C), respectively, and the steady-state heat flow was recorded to calculate the interfacial thermal resistance.

[0076] Simultaneously, an infrared thermal imager was used to monitor the lateral thermal diffusion area of ​​the sample to help verify the uniformity of heat flow.

[0077] V. Experimental Data Table 2: Interfacial thermal resistance test results for different samples (steady-state method) Experiment Summary: Thermal resistance testing results show that the surface modifier plays an indispensable role in interface regulation in the composite structure. In Example 2, aminosilane molecules successfully connected the graphene surface to the polymer segments, enhancing interfacial affinity and chemical stability, allowing heat energy to flow smoothly between layers and significantly reducing interfacial thermal resistance. Infrared thermography also confirms that its heat diffusion surface morphology is the most uniform, indicating that heat flow is continuous and without obvious discontinuities within the material.

[0078] In Comparative Example 3, the lack of effective interfacial bridging resulted in poor compatibility between the graphene sheets and the polymer material, leading to uneven dispersion, localized aggregation, and ultimately, the formation of a "thermal bottleneck." This blocked the continuous thermal channels, causing a sharp increase in interfacial thermal resistance. The infrared image shows a clear concentration of heat areas, indicating that the internal heat flow of the material cannot diffuse uniformly, and energy accumulates locally.

[0079] Comparative Example 4 reveals the negative effects of excessive boron nitride (BN) content. Although BN exhibits good thermal conductivity, it tends to accumulate when its proportion exceeds a reasonable level, creating an isolation effect between adjacent layers and blocking the thermal coupling channels between graphene layers. Furthermore, excessive filler also reduces the polymer's encapsulation properties and increases interlayer porosity. Therefore, it is evident that the filler ratio and interface modification need to be synergistically optimized to obtain an ideal composite structure with low interfacial thermal resistance and high heat transfer efficiency.

[0080] Test Example 3: Thermoelectric Performance Test (Experimental Description) I. Experimental Objective: The contribution of thermoelectric functional materials to the thermoelectric conversion performance of composite structures is verified, and the effect of ultrasonic dispersion treatment on particle distribution uniformity is evaluated, thereby determining the advantages of this invention in terms of thermal energy utilization and functional integration.

[0081] II. Experimental Subjects: Example 3: Containing thermoelectric material (Bi2Te3 / Sb2Te3) + ultrasonic dispersion treatment; Comparative Example 5: No thermoelectric functional materials were added; Comparative Example 6: No ultrasound treatment was performed; all other aspects were the same.

[0082] III. Experimental Equipment and Materials: Thermoelectric performance analyzer (ZEM-3); Seebeck voltage test probe (differential temperature contact at both ends); Thermocouple precision control platform (temperature difference set to ΔT = 10℃); All materials and processing methods are set according to the foregoing embodiments.

[0083] IV. Experimental Procedure: Sample preparation: Examples 3 and Comparative Examples 5 and 6 were prepared according to the corresponding process parameters, with the thickness controlled at 120–140 μm.

[0084] Electrode coating and fixation: Each sample is coated with silver paste electrodes at both ends, which are then dried and brought into stable contact for differential temperature voltage acquisition.

[0085] Temperature difference loading and measurement: The sample is sandwiched between the upper and lower temperature control modules, with the upper end at 45°C and the lower end at 35°C, forming a stable temperature difference.

[0086] Measure the generated Seebeck voltage and record the output voltage change curve over time.

[0087] V. Experimental Data Table 3: Thermoelectric performance test data (temperature difference 10℃) Experiment Summary: Experimental results fully demonstrate that the introduction of thermoelectric functional materials has a decisive impact on the energy conversion capability of this composite structure. In the sample of Example 3, antimony tritelluride and bismuth tritelluride are uniformly distributed at the nanoscale in the thermally conductive network, significantly improving the Seebeck coefficient and output voltage by efficiently capturing temperature-induced carrier flow. The thermally conductive structure constructed from graphene and boron nitride provides a rapid and uniform thermal gradient environment, providing stable support for thermoelectric conversion.

[0088] In Comparative Example 5, the thermoelectric functional material was completely removed. Although the structure itself had good thermal conductivity, it lacked a carrier generation and migration mechanism, and therefore produced almost no thermoelectric output. This shows that the energy conversion function cannot be completed by the thermally conductive material alone; it must rely on the coordinated action of active thermoelectric functional units.

[0089] Although thermoelectric materials were added in Comparative Example 6, the lack of ultrasonic treatment resulted in severe particle aggregation and segregation within the structure, leading to localized thermoelectric potential concentration, significant output drift, and a markedly prolonged response time. This phenomenon confirms the impact of material dispersion uniformity on thermoelectric response efficiency, echoing the importance of surface modification and composite treatment mentioned earlier, and embodying an integrated optimization approach from microstructure control to macroscopic performance response.

[0090] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A graphene heat dissipation structure, comprising a graphene layer (1), a boron nitride nanosheet layer (2), a polymer matrix layer (3), and a thermoelectric functional layer (4), characterized in that, The graphene layer (1) and the boron nitride nanosheet layer (2) are alternately stacked to form a composite thermal conductive layer. The polymer matrix layer (3) is disposed on the outside of the composite thermal conductive layer and connected to it. The thermoelectric functional layer (4) is disposed between the composite thermal conductive layer and the polymer matrix layer (3). The graphene layer (1), the boron nitride nanosheet layer (2), the polymer matrix layer (3) and the thermoelectric functional layer (4) are combined by hot pressing to form an integrated graphene heat dissipation structure. The polymer matrix layer (3) is made of polytetrafluoroethylene or polyimide; the thermoelectric functional layer (4) is made of bismuth tritelluride or antimony tritelluride.

2. The graphene heat dissipation structure according to claim 1, characterized in that, The graphene heat dissipation structure comprises the following components in parts by weight: Graphene: 20-60 parts; Boron nitride nanosheets: 10–40 parts; Polymer matrix material: 20-40 parts; Thermoelectric functional materials: 1-5 parts; Surface modifier: 1-3 parts.

3. The graphene heat dissipation structure according to claim 2, characterized in that, The graphene is reduced graphene oxide obtained by chemical reduction treatment, which has a sheet structure with 1 to 10 layers, a single layer thickness of 0.5 to 5 nanometers, and a lateral dimension of 0.1 to 10 micrometers; the boron nitride nanosheets are two-dimensional nanosheets prepared by liquid phase exfoliation, with a thickness of 1 to 20 nanometers and a lateral dimension of 0.2 to 5 micrometers.

4. The graphene heat dissipation structure according to claim 2, characterized in that, The thermoelectric functional material has a particle size of 10-100 nanometers and is distributed inside the composite thermally conductive layer; the surface modifier includes aminosilane compounds or carboxyl functional group molecules, which are attached to the surface of the graphene sheet by covalent grafting or electrostatic adsorption.

5. A method for preparing a graphene heat dissipation structure, applied to the graphene heat dissipation structure according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of graphene: Natural graphite powder is mixed with concentrated sulfuric acid and hydrogen peroxide and stirred to obtain graphene oxide. S2. Graphene oxide reduction treatment: Graphene oxide is mixed with hydrazine hydrate reducing agent, stirred, and cooled to room temperature to obtain reduced graphene. S3. Preparation of boron nitride nanosheets: Boron nitride powder is mixed with N-methylpyrrolidone solvent and stirred to obtain boron nitride nanosheets; S4. Mixing graphene and boron nitride nanosheets: Mix graphene and boron nitride nanosheets and then perform ultrasonic treatment to obtain a graphene-boron nitride composite. S5. Hot pressing: The composite is mixed with the polymer matrix material and surface modifier, hot pressed, and cooled to room temperature to obtain a graphene heat dissipation structure.

6. The method for preparing the graphene heat dissipation structure according to claim 5, characterized in that, In step S1, graphene oxide is prepared by mixing natural graphite powder with concentrated sulfuric acid with a mass concentration of 98% and hydrogen peroxide with a mass concentration of 30%, controlling the reaction temperature at 20-30°C, and reacting for 2-4 hours under stirring at 500-800 rpm until graphene oxide is obtained.

7. The method for preparing the graphene heat dissipation structure according to claim 5, characterized in that, In step S2, the reduction treatment of graphene oxide uses hydrazine hydrate reducing agent with a mass concentration of 80%, the reaction temperature is 150-200℃, and the reaction is carried out for 4-6 hours under stirring conditions of 400-600 rpm. After the reaction is completed, the mixture is cooled to room temperature to obtain reduced graphene.

8. The method for preparing the graphene heat dissipation structure according to claim 5, characterized in that, In step S3, boron nitride nanosheets are produced by mixing boron nitride powder with N-methylpyrrolidone solvent, stirring at 1000 rpm at 50-60°C, and reacting for 2-3 hours until the boron nitride nanosheets are completely dispersed.

9. The method for preparing the graphene heat dissipation structure according to claim 5, characterized in that, In step S4, graphene and boron nitride nanosheets are mixed at a mass ratio of 20:1 to 1:1 and then subjected to ultrasonic treatment for 30 to 60 minutes to obtain a graphene-boron nitride composite.

10. The method for preparing the graphene heat dissipation structure according to claim 5, characterized in that, In step S5, after the composite is mixed evenly with the polymer matrix material and the surface modifier, it is pressed by a hot pressing process at a temperature of 150-250°C, a pressure of 2-5 MPa, a holding time of 10-30 minutes, and then cooled to room temperature to obtain a graphene heat dissipation structure.

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