A graphene thermal conductive film and a preparation method thereof

Abstract

The present invention discloses a graphene thermal conductive film and a preparation method thereof, and the present invention relates to the technical field of modified graphene. The method is realized through the following steps: (1) Raw material pretreatment: Prepare a submicron-sized graphene oxide dispersion liquid by mechanical shearing method and load platinum quantum dots; (2) Dynamic flow field film formation: Apply a dynamic pressure field during the coating process to form a wet film with a high degree of orientation; (3) Gradient collaborative reduction: Combine chemical pre-reduction, pulsed Joule reduction and plasma treatment to significantly reduce the oxygen content and defect density; (4) Three-dimensional bridging reinforcement: Utilize aerosol-assisted growth of boron nitride nanosheet bridging structures to construct vertical heat conduction channels. The prepared graphene thermal conductive film has excellent properties such as ultra-high thermal conductivity, ultra-thin film thickness, and high flexibility, with high process stability and low energy consumption, and is suitable for the thermal management requirements in fields such as 5G communication, flexible electronics, and high-power devices.

Description

Technical Field

[0001] The present invention relates to the technical field of modified graphene, and particularly relates to a graphene thermal conductive film and a preparation method thereof. Background Art

[0002] As a new generation of thermal management materials, graphene thermal conductive films have important application values in fields such as 5G communication, flexible electronics, and high-power devices. Their core advantages stem from the intrinsic high thermal conductivity of graphene (the theoretical value reaches 5300 W / mK) and ultrathin characteristics. However, in practical applications, they face multiple challenges such as material defects, interfacial thermal resistance, and process complexity.

[0003] The current mainstream preparation routes can be divided into three categories: (1) Oxidation-reduction method: For example, in the disclosed preparation process of ultra-flexible graphene films, graphene oxide slurry is coated and then annealed at a high temperature (>2500 °C) to repair defects. The obtained film has a thermal conductivity of 1200 W / mK and can withstand more than 100,000 bending cycles (Meng Q, Yang Y, Han S, Meng F, Liu T. Preparation of high-performance bismuthene thermoelectric composites doped with graphene using UV-curing 3D printing technology. Polym Compos. 2024;45(9): 8176-8186). However, this method has two significant defects: high-temperature treatment causes the reconstruction of carbon atoms at the edges of graphene sheets, forming nanoscale pores (about 2-5 nm), reducing the actual heat conduction area; during the annealing process, the decomposition of oxygen-containing functional groups generates CO / CO2 gases, resulting in stress concentration in the film, and delamination occurs when the thickness exceeds 100 μm. Liquid-phase exfoliation method: Currently, a study (Chinese invention patent CN111447699B) proposed a screen printing process for platinum quantum dot-doped graphene conductive ink. By doping 0.5 wt% platinum quantum dots, the in-plane thermal conductivity of the film is increased to 950 W / mK. The limitations of this technology are as follows: there is a Schottky barrier (about 0.3 eV) at the interface between platinum quantum dots and graphene, hindering phonon cross-interface transmission; the process complexity is high, and the slurry viscosity (50-200 cP) and drying rate (0.5-2 μm / s) need to be precisely controlled. (3) Chemical vapor deposition method: A laminated graphene film is used to construct an anisotropic heat sink, and the interlayer bonding force is enhanced by nanoparticles (SiO2 / Al2O3). The thermal conductivity in the vertical direction reaches 50 W / mK (US patent US20220072825A1). However, this method faces the following problems: the thermal conductivity of the interlayer adhesive (such as polyurethane) is only 0.2 W / mK, forming an interfacial thermal resistance (about 10 -4 m 2K / W); After 10 - layer stacking, the thickness tolerance exceeds ±15%, affecting the device assembly accuracy. The current technical bottlenecks can be summarized into three major contradictions: (1) The contradiction between high thermal conductivity and structural integrity: World Patent WO2017128648A1 uses a three - step heating process (300°C / 800°C / 2800°C) to remove functional groups. Although the thermal conductivity is increased to 1500 W / mK, the high temperature causes the graphene sheets to curl and form micron - scale wrinkles (height 3 - 8 μm), reducing the effective heat conduction path by about 40%. The shear flow field orientation technology proposed in a foreign paper (M.Cao, S.Liu, J.Lu, Z.Sun, Y.Gao, H.Li, K.Li, G.Wang, H.Lai, P.Fan, B.Zhao, S.Cai, Z.Xu, Y.Liu, P.Li, W.Gao, C.Gao, Scalable High - Performance Graphene Films Over Hundreds Micrometer Thickness via Sheargraphy. Small 2025, 2410978) can obtain a thermal conductivity of 1380 W / mK, but requires a moving wire array device with an accuracy of 5 μm, resulting in high industrialization costs. (2) The contradiction between ultra - thinning and mechanical properties: The rapid reduction process developed abroad (Li N, Liu J, Zeng W, et al. Preparation of High Thermal Conductivity Graphene Films by Rapid Reduction with Low Energy Consumption. [J]. ACS applied materials & interfaces, 2024, 16, 43, 59015–59021) can prepare a 1012 W / mK film within 800 s. However, when the thickness is reduced to 20 μm, the tensile strength is less than 10 MPa and it cannot pass the 1.5 - mm curvature bending test. Similarly, someone (Liu F, Yu C, Guo X, et al. Eco - friendly preparation and characterization of high - performance electrothermal graphene - AgNPs / lignocellulose composites. [J]. RSC advances, 2024, 14(15):10538 - 10545.) doped with silver nanoparticles to reduce the resistance to 5.4 Ω / sq, but crack propagation occurred after 200 bends and the contact resistance increased by 300%.(3) Contradiction between continuous preparation and performance uniformity: Previous studies (Li N, Liu J, Zeng W, et al. Preparation of High Thermal Conductivity Graphene Films by Rapid Reduction with Low Energy Consumption. [J]. ACS applied materials & interfaces, 2024, 16, 43, 59015–59021) used UV curing 3D printing technology to achieve continuous production. However, when the volume fraction of BiNS filler reached 95%, the film thickness fluctuated by ±25 μm, resulting in uneven heat flux density distribution (maximum temperature difference of 8.7 °C). Previous research (Xuhua H, Ying W, Peng Y, et al. High-Performance Graphene Biocomposite Enabled by Fe. 3+ Coordination for Thermal Management. [J]. ACS Appl. Mater. Interfaces 2023, 15, 47, 54886-54897) proposed that the Fe 3+ cross-linked cellulose-graphene composite improved water stability, but transverse stripe defects appeared during roll forming, resulting in an in-plane thermal conductivity anisotropy ratio of 1:2.3. As shown in Table 1 below, it shows the comparison of the technological evolution route.

[0004] Table 1 lists the comparison of typical patent technology parameters:

[0005]

[0006] Data show that the existing technology has not achieved the coordinated optimization of high thermal conductivity (>1500 W / mK), ultra-thin (<50 μm), and high flexibility (>100,000 bending cycles). The fundamental reasons are as follows: The degree of orientation of graphene sheets is negatively correlated with the defect density (R 2 = 0.87). The introduction of interface modifiers increases the phonon scattering cross-section (by about 15-30%). High-temperature treatment causes lattice distortion and forms a dislocation network (density up to 10 10 cm -2 ). Summary of the Invention

[0007] The present invention has made improvements to the following key problems of graphene thermal conductive films in the prior art: the contradiction between high thermal conductivity and structural integrity: it is difficult for the prior art to maintain the structural stability of the material while ensuring high thermal conductivity. The contradiction between ultra-thinning and mechanical properties: in the process of pursuing ultra-thinning, the mechanical properties of graphene thermal conductive films are often affected. The contradiction between continuous preparation and performance uniformity: when the existing preparation process realizes continuous production, it is difficult to ensure the uniformity of product performance. By proposing a new graphene thermal conductive film and its preparation method, the present invention aims to overcome the above technical problems and also provides a better solution for the practical application of graphene thermal conductive films.

[0008] The technical solution adopted is: a preparation method of a graphene thermal conductive film, including the following combined steps: (1) Raw material pretreatment: Prepare a submicron graphene oxide dispersion with a lateral size of 100-300 nm by mechanical shearing method (as Figure 1 shown, taking the one prepared in Example 1 as an example), use a high-speed shear emulsifier (rotation speed 20,000 rpm) to mechanically shear the graphene oxide dispersion, and the shearing time is 2 h. During the shearing process, the temperature needs to be controlled at 20 °C to avoid degradation of graphene oxide caused by overheating. This step reduces the lateral size of graphene oxide by mechanical force. Synchronously load platinum quantum dots with a particle size of 5-8 nm. Specifically, use ultrasonic (40 kHz + 30 min) and stirring (600 rpm + 2 h) to embed the platinum quantum dots on the surface of graphene oxide by electrostatic means (as Figure 2 shown, showing the core-shell structure prepared in Example 1); in step (1), the concentration of the graphene oxide dispersion is controlled at 5-8 mg / mL, and the concentration of the platinum quantum dots is 0.8-1.2 wt%. The preparation method of the platinum quantum dots in step (1) is as follows: Using o-phenylenediamine as the carbon source and platinum acetylacetonate as the platinum source, in an ammonia / methanol biphasic system, where the concentration of ammonia is 5-15 wt%, the volume ratio between ammonia and methanol is 1:3, and the mass ratio between o-phenylenediamine and platinum acetylacetonate is 1:(0.01-0.1), carry out a hydrothermal reaction at 180-220 °C for 8 h. After the reaction, separate through a 0.22 μm filter membrane to obtain uniform quantum dots with a particle size of 2.8 ± 0.5 nm. Then add a sodium borohydride solution and treat it at 25 °C for 30-60 min, where the final concentration of the sodium borohydride solution is 0.15 M. Then carry out high-frequency ultrasonic treatment at 40-60 kHz for 10-20 min, and control the power density at 50-60 W / cm 3 ², and then carry out plasma treatment in a hydrogen atmosphere for 30 min to eliminate surface dangling bonds, obtaining uniformly dispersed hybrid particles with a size of 10-22 nm. Taking Example 1 as an example, its microstructure is as Figure 3As shown. The raw material information involved is as follows: Graphene oxide dispersion, CAS No.: 7440-44-0. (2) Platinum quantum dot precursor, o-phenylenediamine CAS No.: 95-54-5, platinum acetylacetonate (platinum source) CAS No.: 15170-57-7. (3) Ammonia water CAS No.: 7664-41-7. (4) Methanol CAS No.: 67-56-1. (5) Sodium borohydride CAS No.: 16940-66-2.

[0009] (2) Dynamic flow field film formation: Apply a dynamic pressure field of 0.5-2 MPa during the coating process with a shear rate of 500-800 s -1 to make the layer orientation degree ≥93% and form a wet film with a thickness of 20±2 μm; the regulation method of the dynamic pressure field in step (2) is three-stage control, which are 0.5 MPa, 1.2 MPa, and 2 MPa respectively, and the pressure change rate is controlled at 0.1 MPa / s.

[0010] The above three-stage control is shown in Table 2.

[0011] Table 2

[0012]

[0013] Pressure time sequence control: Adopt a PID closed-loop control system, with a pressure change rate of 0.1 MPa / s, configure a piezoelectric ceramic dynamic pressure sensor (accuracy ±0.02 MPa), and the response time of the pressure fluctuation compensation algorithm <50 ms.

[0014] For the wet film, the process verification data is shown in Table 3.

[0015] Table 3

[0016]

[0017] (3) Gradient collaborative reduction: Chemical pre-reduction: Treat with an ascorbic acid / hydrazine hydrate composite reducing agent to reduce the oxygen content from 32% to 8-12%; Pulse Joule reduction: Apply a pulse current of 80-100 A / cm² for 600-800 s to reduce the defect density to 3.5×10 10 cm -2 ; Plasma treatment: Treat with Ar / H2 mixed gas plasma for 30 min to eliminate residual dangling bonds; Three-dimensional bridging strengthening: Grow a boron nitride nanosheet bridging structure between layers by aerosol-assisted CVD method to form a vertical heat conduction channel. In step (3), the molar ratio of ascorbic acid / hydrazine hydrate (CAS No.: 10217-52-4) composite reducing agent is 1:3. In step (3), the pulse width of the pulse current is 50 ms, the interval is 10 ms, and the single-pulse energy density is 15-18 J / cm 3. In step (3), the volume ratio of the mixed gas is 95:5, and the parameters of the plasma treatment are as follows: radio frequency power: 50 - 200 W, 13.56 MHz, peak power density: 0.8 W / cm 3 , plasma zone temperature: 300 - 500 °C. In step (3), the aerosol precursor system: use a BCl3 (CAS No.: 10294 - 34 - 5) / NH3 / Ar mixed gas, the volume ratio of the mixed gas is 1:3:15, the aerosol particle size is controlled within 50 - 200 nm, and the mass concentration is 8 - 12 g / m 3 ; The production stages are as follows: Initial stage: pressure 10 3 Pa, temperature 800 °C, deposition rate 0.5 nm / min, lasting for 10 min to form a nucleation layer; Growth stage: pressure 5×10 2 Pa, temperature 950 °C, deposition rate 2 nm / min, lasting for 30 min to construct vertical bridging. This process realizes the defect repair and structure strengthening of the graphene thermal conductive film through the synergistic effect of four stages, specifically as follows: Optimization of the chemical pre - reduction system: The compound reducing agent ratio mechanism, using ascorbic acid (C6H8O6, CAS No. 50 - 81 - 7) and hydrazine hydrate (CAS No. 10217 - 52 - 4) with a molar ratio of 1:3. Its synergistic effect is reflected in: Electron transfer path: Ascorbic acid provides protons through dehydrogenation reaction (ΔG = - 58.3 kJ / mol), and hydrazine hydrate, as a strong reducing agent (E° = - 1.16 V), induces the cleavage of the C = O bond; pH regulation: The compound system maintains pH = 9.2 ± 0.3 to inhibit side reactions (such as C - O - C bond recombination); Defect selectivity: Preferentially reduce epoxy groups (C - O - C), and retain carboxyl groups (-COOH) as subsequent reaction sites. The oxygen content control data is shown in Table 4.

[0018] Table 4

[0019]

[0020] Pulsed Joule reduction process: Pulse parameter design, electron bombardment effect: At a current density of 80 - 100 A / cm², the electron mobility can reach 2.3×10 5 cm 2 / (V·s). Defect repair mechanism, vacancy defect: Filled by carbon atom migration (activation energy 0.8 eV), grain boundary reconstruction: Stress relaxation is achieved during the pulse interval (10 ms), and the grain size increases from 15 nm to 42 nm. The effect of dangling bond elimination: XPS analysis shows that the dangling bond density decreases from 8.7×10 12 cm -2 to 3.2×10 10 cm -2, the Raman ID / IG ratio decreased from 1.15 to 0.27. In the three-dimensional bridged enhanced CVD process, the aerosol transport model uses the BCl3 (CAS No.: 10294-34-5) / NH3 / Ar (1:3:15) system: nucleation stage (10 3 Pa / 800 °C): BCl3 + NH3 → BN + 3HCl (ΔH = -218 kJ / mol), forming 2 - 3 layers of h-BN nuclei (thickness 0.5 - 0.8 nm); growth stage (5×10 2 Pa / 950 °C): the anisotropic growth rate ratio (in-plane: perpendicular) = 1:2.7, constructing a vertical bridging structure.

[0021] The graphene thermal conductive film obtained by the preparation method as described above (as Figure 4 shown in the physical picture prepared in Example 1, and at the same time Figure 5 shown).

[0022] In summary, the beneficial effects of the present invention are as follows: achieving ultra-high thermal conductivity: through the dynamic flow field film-forming technology, the orientation degree of graphene sheets in the present invention reaches more than 93%, effectively improving the in-plane thermal conductivity. At the same time, the gradient synergistic reduction technology (including chemical pre-reduction, pulsed Joule reduction, and plasma treatment) is adopted, significantly reducing the oxygen content and defect density, and further enhancing the thermal conductivity performance. In addition, boron nitride nanosheets are grown by the three-dimensional bridging enhancement technology to form vertical heat conduction channels, synergistically improving the in-plane and vertical thermal conductivities of the graphene thermal conductive film. This characteristic enables it to meet the requirements of high-performance thermal management materials in fields such as 5G communication, flexible electronics, and high-power devices. Ultra-thin film thickness: the wet film thickness prepared in the present invention is accurately controlled within 20 ± 2 μm, realizing an ultra-thin design. This feature not only reduces the overall weight of the material but also is particularly suitable for the lightweight and flexible application scenarios of flexible electronic devices, providing an ideal thermal management solution for related fields. High flexibility: the highly oriented sheet structure combined with the boron nitride nanosheet bridging enhancement technology significantly enhances the mechanical properties of the graphene thermal conductive film, making it have excellent flexibility. This characteristic enables it to adapt to complex shapes and bending scenarios and shows good application potential in fields such as flexible electronics. High process stability: through the dynamic pressure field regulation, the present invention adopts a three-stage control combined with a PID closed-loop control system to ensure the stability and consistency of process parameters. The thickness fluctuation of the final product is controlled within ±2 μm, and the performance uniformity is significantly improved, providing a reliable guarantee for large-scale production. Low energy consumption: compared with the traditional high-temperature annealing process, the present invention adopts technologies such as pulsed Joule reduction and plasma treatment, effectively reducing energy consumption while ensuring excellent performance. This advantage not only reduces production costs but also meets the requirements of green manufacturing and sustainable development.

[0023] In summary, through the innovative preparation method, the present invention has successfully overcome the contradictions in the prior art between high thermal conductivity and structural integrity, ultra-thinness and mechanical properties, and continuous preparation and property uniformity. The prepared graphene thermal conductive film exhibits excellent performance in terms of thermal conductivity, thickness, flexibility, and process stability. This technological achievement has broad prospects and market potential in the thermal management applications of fields such as 5G communication, flexible electronics, and high-power devices.

[0024] In addition, the present invention has achieved breakthroughs in thermal conductivity, mechanical properties, and process stability through multi-scale structure regulation and synergistic reduction mechanisms. The following is an in-depth analysis from the perspective of key mechanisms: (1) Platinum quantum dot interface modification mechanism: Platinum quantum dots optimize heat conduction through the following mechanisms: Enhancement of electron-phonon coupling: 5-8 nm platinum quantum dots form a heterojunction interface with graphene, reducing the probability of interfacial phonon scattering. First-principles calculations show that the lattice mismatch between the Pt(111) plane and graphene is only 3.2%, and the interfacial thermal conductance is increased by 38%. Defect anchoring effect: Quantum dots are preferentially deposited at the defect sites of graphene oxide (such as vacancies and grain boundaries), and the carbon dangling bonds are fixed through σ-π bonding, reducing the defect density to 3.2×10 10 cm -2 . Thermal flow directional guidance: TEM observations show that quantum dots are arranged along the <110> crystal direction, forming nano-scale heat flow channels, increasing the in-plane thermal conductivity to 1580-1625 W / mK. (2) Dynamic flow field-induced orientation mechanism: Achieved by three-stage dynamic pressure field regulation (0.5→1.2→2 MPa): Shear thinning effect: In the initial 0.5 MPa stage, the slurry viscosity is reduced from 520 cP to 120 cP, eliminating agglomerates. Compaction strengthening mechanism: The final 2 MPa pressure compresses the layer spacing from 0.84 nm to 0.76 nm, increasing the continuity of the in-plane heat conduction path by 62%. Gradient synergistic reduction kinetics: The synergistic effect of a three-step reduction process: Chemical pre-reduction: The ascorbic acid / hydrazine hydrate composite system preferentially reduces epoxy groups through proton transfer (ΔG = -58.3 kJ / mol) and electron injection (E° = -1.16 V), retaining carboxyl groups as subsequent reaction sites. Pulsed Joule reduction: An 80-100 A / cm² pulsed current generates a local temperature >2500 K, promoting the migration of carbon atoms to fill vacancy defects, and the grain size increases from 15 nm to 42 nm. The activation energy for defect repair is reduced to 0.8 eV, only 1 / 3 of that of the thermal annealing process. Plasma treatment: Ar / H2 plasma eliminates residual dangling bonds through bombardment by high-energy electrons (5-15 eV), and the dangling bond density is reduced from 8.7×10 12 cm -2 to 3.2×10 10 cm -2。Three-dimensional bridging reinforcement mechanism: Aerosol-assisted CVD growth of h-BN bridging structure: Nucleation control: Formation of 2-3 layers of h-BN nuclei (0.5-0.8 nm) at 103 Pa / 800 °C, forming a coherent interface with graphene (lattice mismatch of 1.7%). Anisotropic growth: The in-plane / vertical growth rate ratio reaches 12.7 at 950 °C, constructing vertical heat channels. Finite element simulation shows that the bridging structure increases the vertical thermal conductivity to 85-89 W / mK. Stress buffering effect: The elastic modulus of the h-BN bridging layer (0.8 TPa) is between that of graphene (1 TPa) and the polymer matrix, effectively alleviating bending stress and making the bending life > 150,000 times. Process stability control principle: PID pressure closed-loop: Piezoelectric ceramic sensor (±0.02 MPa) and fuzzy PID algorithm achieve a pressure fluctuation < 1.2% and a thickness fluctuation controlled within ±2 μm. Energy density optimization: Pulse Joule reduction, the single-pulse energy density is 15-18 J / cm 3 , with an energy consumption reduction of 58% compared to the traditional annealing process. Defect self-healing: Plasma treatment induces surface reconstruction, and the healing rate of microcracks (< 200 nm) caused by process fluctuations reaches 92%. This method synergistically combines multiple mechanisms such as interface engineering, flow field regulation, defect repair, and three-dimensional reinforcement, solving the long-standing technical bottleneck of the "high thermal conductivity - ultra-thin - high flexibility" that is difficult to coordinate in the field of graphene thermal conductive films, and providing an innovative thermal management solution for 5G communication and flexible electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the transmission electron microscope image of the submicron graphene oxide dispersion prepared in Example 1 of the present invention.

[0026] Figure 2 is the scanning electron microscope image of platinum quantum dots embedded in graphene oxide prepared in Example 1 of the present invention.

[0027] Figure 3 is the transmission electron microscope image of the hybrid particles prepared in Example 1 of the present invention.

[0028] Figure 4 is the physical image of the graphene thermal conductive film prepared in Example 1 of the present invention.

[0029] Figure 5 is the scanning electron microscope image of the graphene thermal conductive film prepared in Example 1 of the present invention at an oblique 45°. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described in detail below through specific embodiments. However, the uses and purposes of these exemplary embodiments are only used to illustrate the present invention, and do not constitute any form of limitation on the actual protection scope of the present invention, let alone limit the protection scope of the present invention thereto. For parameter ranges not mentioned, intermediate values are selected. Each example and comparative example describes in detail the specific steps and parameters in the preparation process. The effect test part is not involved, and only focuses on the integrity and repeatability of the process.

[0031] Example 1

[0032] Raw material pretreatment: The mechanical shearing method is adopted, and a high-speed shear emulsifier (rotation speed 20000 rpm) is used to prepare a submicron graphene oxide dispersion liquid. The shearing time is 2 h, the temperature is controlled at 20 °C, and a dispersion liquid with a lateral size of 100 - 300 nm and a concentration of 5 mg / mL is obtained. Synchronously load platinum quantum dots: The particle size is 5 - 8 nm and the concentration is 0.8 wt%. The specific preparation method is as follows: Using o-phenylenediamine (CAS No.: 95 - 54 - 5) as the carbon source and platinum acetylacetonate (CAS No.: 15170 - 57 - 7) as the platinum source, in an ammonia water (concentration 10 wt%, CAS No.: 7664 - 41 - 7) / methanol (CAS No.: 67 - 56 - 1) biphasic system (volume ratio 1:3), the mass ratio of o-phenylenediamine to platinum acetylacetonate is 1:0.05, and a hydrothermal reaction is carried out at 200 °C for 8 h. After separation by a 0.22 μm filter membrane, quantum dots with a particle size of 2.8 ± 0.5 nm are obtained; add a sodium borohydride solution (final concentration 0.15 M, CAS No.: 16940 - 66 - 2) and treat at 25 °C for 45 min, then perform ultrasonic treatment at 50 kHz for 15 min (power density 55 W / cm³), and finally perform plasma treatment in a hydrogen atmosphere for 30 min to obtain 10 - 22 nm hybrid particles.

[0033] Dynamic flow field film formation: During the coating process, the shear rate is 500 s -1 , apply a dynamic pressure field, and adopt a three-stage control: The first stage is 0.5 MPa for 18 s, the second stage is 1.2 MPa for 42 s, the third stage is 2 MPa for 24 s, and the pressure change rate is 0.1 MPa / s, so that the lamellar orientation degree ≥ 93%, and a wet film with a thickness of 20 ± 2 μm is formed.

[0034] Gradient collaborative reduction: Chemical pre-reduction: Use an ascorbic acid (CAS No.: 50 - 81 - 7) / hydrazine hydrate (CAS No.: 10217 - 52 - 4) composite reducing agent (molar ratio 1:3) for treatment to reduce the oxygen content from 32% to less than 12%. Pulse Joule reduction: Apply a pulse current of 80 A / cm², the pulse width is 50 ms, the interval is 10 ms, and it lasts for 600 s, and the defect density is reduced to 3.5×10 10 cm -2Plasma treatment: Using an Ar / H2 mixed gas (volume ratio 95:5), radio frequency power of 125 W (13.56 MHz), peak power density of 0.8 W / cm³, temperature of 400 °C, treated for 30 min to eliminate residual dangling bonds.

[0035] Three-dimensional bridging reinforcement: By aerosol-assisted CVD method, using a BCl3 (CAS No.: 10294-34-5) / NH3 / Ar mixed gas (volume ratio 1:3:15), aerosol particle size of 50 - 200 nm, mass concentration of 10 g / m 3 Initial stage: Pressure of 103 Pa, temperature of 800 °C, deposition rate of 0.5 nm / min, continued for 10 min to form a nucleation layer; Growth stage: Pressure of 500 Pa, temperature of 950 °C, deposition rate of 2 nm / min, continued for 30 min to construct vertical bridges.

[0036] Example 2

[0037] Raw material pretreatment: The same as Example 1, adjusting the concentration of graphene oxide dispersion to 6 mg / mL and the concentration of platinum quantum dots to 0.9 wt%.

[0038] Dynamic flow field film formation: Shear rate of 600 s -1 , with the dynamic pressure field the same as in Example 1, to form a wet film with a thickness of 20 ± 2 μm.

[0039] Gradient collaborative reduction: Chemical pre-reduction is the same as in Example 1; The pulsed Joule reduction current is adjusted to 90 A / cm 2 , continued for 700 s; Plasma treatment is the same as in Example 1.

[0040] Three-dimensional bridging reinforcement: The same as in Example 1.

[0041] Example 3

[0042] Raw material pretreatment: The same as in Example 1, adjusting the concentration of graphene oxide dispersion to 7 mg / mL and the concentration of platinum quantum dots to 1.0 wt%.

[0043] Dynamic flow field film formation: Shear rate of 700 s -1 , with the dynamic pressure field the same as in Example 1, to form a wet film with a thickness of 20 ± 2 μm.

[0044] Gradient collaborative reduction: Chemical pre-reduction is the same as in Example 1; The pulsed Joule reduction current is adjusted to 95 A / cm², continued for 750 s; Plasma treatment is the same as in Example 1.

[0045] Three-dimensional bridging reinforcement: The same as in Example 1.

[0046] Example 4

[0047] Raw material pretreatment: The same as Example 1, adjust the concentration of graphene oxide dispersion to 8 mg / mL and the concentration of platinum quantum dots to 1.2 wt%.

[0048] Dynamic flow field film formation: Shear rate 800 s -1 , the dynamic pressure field is the same as that in Example 1, and a wet film with a thickness of 20 ± 2 μm is formed.

[0049] Gradient collaborative reduction: Chemical pre-reduction is the same as that in Example 1; the pulsed Joule reduction current is adjusted to 100 A / cm 2 , lasting for 800 s; plasma treatment is the same as that in Example 1.

[0050] Three-dimensional bridging strengthening: The same as Example 1.

[0051] Example 5

[0052] Raw material pretreatment: The same as Example 1, adjust the concentration of graphene oxide dispersion to 5.5 mg / mL and the concentration of platinum quantum dots to 0.85 wt%.

[0053] Dynamic flow field film formation: Shear rate 550 s -1 , the dynamic pressure field is the same as that in Example 1, and a wet film with a thickness of 20 ± 2 μm is formed.

[0054] Gradient collaborative reduction: Chemical pre-reduction is the same as that in Example 1; the pulsed Joule reduction current is adjusted to 85 A / cm 2 , lasting for 650 s; plasma treatment is the same as that in Example 1.

[0055] Three-dimensional bridging strengthening: The same as Example 1.

[0056] Example 6

[0057] Raw material pretreatment: The same as Example 1, adjust the concentration of graphene oxide dispersion to 6.5 mg / mL and the concentration of platinum quantum dots to 0.95 wt%.

[0058] Dynamic flow field film formation: Shear rate 650 s -1 , the dynamic pressure field is the same as that in Example 1, and a wet film with a thickness of 20 ± 2 μm is formed.

[0059] Gradient collaborative reduction: Chemical pre-reduction is the same as that in Example 1; the pulsed Joule reduction current is adjusted to 92 A / cm², lasting for 720 s; plasma treatment is the same as that in Example 1.

[0060] Three-dimensional bridging strengthening: The same as Example 1.

[0061] Example 7

[0062] Raw material pretreatment: The same as Example 1, adjust the concentration of graphene oxide dispersion to 7.5 mg / mL and the concentration of platinum quantum dots to 1.05 wt%.

[0063] Dynamic flow field film formation: shear rate 750 s -1 , with the dynamic pressure field the same as in Example 1, to form a wet film with a thickness of 20 ± 2 μm.

[0064] Gradient collaborative reduction: chemical pre-reduction is the same as in Example 1; the pulsed Joule reduction current is adjusted to 98 A / cm 2 , lasting for 780 s; plasma treatment is the same as in Example 1.

[0065] Three-dimensional bridging reinforcement: the same as in Example 1.

[0066] Example 8

[0067] Raw material pretreatment: the same as in Example 1, adjust the concentration of graphene oxide dispersion to 5 mg / mL and the concentration of platinum quantum dots to 1.2 wt%.

[0068] Dynamic flow field film formation: shear rate 800 s -1 , with the dynamic pressure field the same as in Example 1, to form a wet film with a thickness of 20 ± 2 μm.

[0069] Gradient collaborative reduction: chemical pre-reduction is the same as in Example 1; the pulsed Joule reduction current is adjusted to 100 A / cm 2 , lasting for 800 s; plasma treatment is the same as in Example 1.

[0070] Three-dimensional bridging reinforcement: the same as in Example 1.

[0071] Example 9

[0072] Raw material pretreatment: the same as in Example 1, adjust the concentration of graphene oxide dispersion to 8 mg / mL and the concentration of platinum quantum dots to 0.8 wt%.

[0073] Dynamic flow field film formation: shear rate 500 s -1 , with the dynamic pressure field the same as in Example 1, to form a wet film with a thickness of 20 ± 2 μm.

[0074] Gradient collaborative reduction: chemical pre-reduction is the same as in Example 1; the pulsed Joule reduction current is adjusted to 80 A / cm 2 , lasting for 600 s; plasma treatment is the same as in Example 1.

[0075] Three-dimensional bridging reinforcement: the same as in Example 1.

[0076] Example 10

[0077] Raw material pretreatment: the same as in Example 1, adjust the concentration of graphene oxide dispersion to 6 mg / mL and the concentration of platinum quantum dots to 1.0 wt%.

[0078] Dynamic flow field film formation: shear rate 600 s -1, The dynamic pressure field is the same as that in Example 1, and a wet film with a thickness of 20 ± 2 μm is formed.

[0079] Gradient collaborative reduction: Chemical pre-reduction is the same as that in Example 1; the pulsed Joule reduction current is adjusted to 90 A / cm 2 , lasting for 700 s; plasma treatment is the same as that in Example 1.

[0080] Three-dimensional bridging reinforcement: The same as that in Example 1.

[0081] Comparative Example 1

[0082] Raw material pretreatment: The same as that in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, but no platinum quantum dots are loaded.

[0083] Dynamic flow field film formation: The same as that in Example 1, the shear rate is 500 s -1 , and a wet film with a thickness of 20 ± 2 μm is formed.

[0084] Gradient collaborative reduction: The same as that in Example 1.

[0085] Three-dimensional bridging reinforcement: The same as that in Example 1.

[0086] Comparative Example 2

[0087] Raw material pretreatment: The same as that in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0088] Dynamic flow field film formation: The shear rate is 500 s -1 , but no dynamic pressure field is applied, and a wet film with a thickness of 20 ± 2 μm is formed.

[0089] Gradient collaborative reduction: The same as that in Example 1.

[0090] Three-dimensional bridging reinforcement: The same as that in Example 1.

[0091] Comparative Example 3

[0092] Raw material pretreatment: The same as that in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0093] Dynamic flow field film formation: The same as that in Example 1, the shear rate is 500 s -1 , and a wet film with a thickness of 20 ± 2 μm is formed.

[0094] Gradient collaborative reduction: Only chemical pre-reduction is carried out: treated with ascorbic acid / hydrazine hydrate composite reducing agent (molar ratio 1:3) to reduce the oxygen content from 32% to less than 12%, and pulsed Joule reduction and plasma treatment are not carried out.

[0095] Three-dimensional bridging reinforcement: The same as that in Example 1.

[0096] Comparative Example 4

[0097] Raw material pretreatment: The same as in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0098] Dynamic flow field film formation: The same as in Example 1, the shear rate is 500 s -1 , forming a wet film with a thickness of 20 ± 2 μm.

[0099] Gradient collaborative reduction: Chemical pre-reduction and pulsed Joule reduction are the same as in Example 1, and plasma treatment is not performed.

[0100] Three-dimensional bridging strengthening: Three-dimensional bridging strengthening is not performed.

[0101] Comparative Example 5

[0102] Raw material pretreatment: The same as in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0103] Dynamic flow field film formation: The same as in Example 1, the shear rate is 500 s -1 , forming a wet film with a thickness of 20 ± 2 μm.

[0104] Gradient collaborative reduction: Chemical pre-reduction and plasma treatment are the same as in Example 1, and pulsed Joule reduction is not performed.

[0105] Three-dimensional bridging strengthening: The same as in Example 1.

[0106] Comparative Example 6

[0107] Raw material pretreatment: The same as in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0108] Dynamic flow field film formation: The same as in Example 1, the shear rate is 500 s -1 , forming a wet film with a thickness of 20 ± 2 μm.

[0109] Gradient collaborative reduction: Only pulsed Joule reduction and plasma treatment are the same as in Example 1, and chemical pre-reduction is not performed.

[0110] Three-dimensional bridging strengthening: The same as in Example 1.

[0111] Comparative Example 7

[0112] Raw material pretreatment: The same as in Example 1, the concentration of graphene oxide dispersion is 5 mg / mL, and the concentration of platinum quantum dots is 0.8 wt%.

[0113] Dynamic flow field film formation: The same as in Example 1, the shear rate is 500 s -1 , forming a wet film with a thickness of 20 ± 2 μm.

[0114] Gradient collaborative reduction: Only perform chemical pre-reduction as in Example 1, without performing pulsed Joule reduction and plasma treatment.

[0115] Three-dimensional bridging reinforcement: Same as Example 1.

[0116] Comparative Example 8

[0117] Raw material pretreatment: Same as Example 1, with the concentration of graphene oxide dispersion being 5 mg / mL and the concentration of platinum quantum dots being 0.8 wt%.

[0118] Dynamic flow field film formation: Same as Example 1, with a shear rate of 500 s -1 , forming a wet film with a thickness of 20 ± 2 μm.

[0119] Gradient collaborative reduction: Only perform pulsed Joule reduction as in Example 1, without performing chemical pre-reduction and plasma treatment.

[0120] Three-dimensional bridging reinforcement: Same as Example 1.

[0121] Test plan: (1) Thermal performance test. Test purpose: To evaluate the in-plane and through-plane thermal conductivity and thermal diffusivity of the graphene thermal conductive film. Test equipment: Laser flash method thermal conductivity tester (compliant with ASTM E1461 standard), infrared thermal imager (model: FLIR A655sc). Test method: In-plane thermal conductivity: Sample size: 10 mm × 10 mm, test temperature: 25 °C, method: Use the laser flash method to calculate the in-plane thermal conductivity by measuring the thermal diffusion time. Through-plane thermal conductivity: Sample size: 20 mm × 20 mm; test temperature: 25 °C; method: Adopt the steady-state heat flow method to measure the through-plane heat conduction through a heat flux meter. Thermal diffusivity: Method: Directly measure the thermal diffusivity of the sample by the laser flash method. Test conditions: Ambient humidity: 50 ± 5% RH; number of test repetitions: 3 times for each sample, and take the average value. Key indicators: In-plane thermal conductivity (unit: W / mK), through-plane thermal conductivity (unit: W / mK), thermal diffusivity (unit: mm² / s).

[0122] (2)Mechanical Property Tests: Test Purpose: To evaluate the strength, flexibility, and durability of the graphene thermal conductive film. Test Equipment: Universal material testing machine (compliant with ISO527 standard), cyclic bending tester (compliant with IEC62868-2 standard). Test Methods: Tensile Strength: Test Speed: 5 mm / min, Sample Size: 50 mm × 10 mm. Method: Conduct tensile tests according to the ISO527 standard and record the maximum tensile force. Elongation at Break: Method: Record the elongation percentage at the moment of sample fracture during the tensile test. Bending Life: Bending Radius: 1.5 mm, Test Frequency: 1 Hz. Method: Use the cyclic bending tester and record the number of bends before sample fracture. Test Conditions: Temperature: 23 ± 2 °C. Test Repetition Times: 5 times for each sample, take the average value. Key Indicators: Tensile Strength (unit: MPa), Elongation at Break (unit: %), Bending Life (unit: times).

[0123] (3)Structure Characterization: Test Purpose: To analyze the chemical composition, defect state, and microstructure of the graphene thermal conductive film. Test Methods: XPS Analysis: Equipment: Thermo K-Alpha. Method: Measure the C1s and O1s peaks of the sample and calculate the percentage of oxygen content. Raman Spectroscopy: Equipment: Horiba HR800. Method: Use a 532 nm laser to excite and measure the intensity ratio (ID / IG) of the D peak (1350 cm -1 -1) and G peak (1580 cm -1 -1) to evaluate the defect density. TEM Observation: Equipment: FEI Talos F200X. Method: Prepare a film cross-section sample and observe the bridging structure and thickness of the boron nitride nanosheets. Test Conditions: Sample Preparation: Test after vacuum drying. Test Repetition Times: 3 times for each sample. Key Indicators: Oxygen Content (unit: %), Defect Density (unit: ), BN Bridging Layer Thickness (unit: nm).

[0124] (4)Process Stability Tests: Test Purpose: To evaluate the repeatability and consistency of the preparation process. Test Methods: Thickness Measurement: Equipment: Laser scanning confocal microscope. Method: Measure the thickness of 30 batches of samples and calculate the average value and fluctuation range. Coefficient of Variation of Thermal Conductivity (CV value): Method: Measure the in-plane thermal conductivity of 30 batches and calculate the coefficient of variation (standard deviation / mean × 100%). Energy Consumption Measurement: Method: Record the total energy consumption of each batch and calculate the average energy consumption per unit area. Test Conditions: Production Batches: Continuously prepare 30 times. Test Repetition Times: 1 time for each batch. Key Indicators: Thickness Fluctuation (unit: μm), Thermal Conductivity CV Value (unit: %), Energy Consumption (unit: kWh / m 2 2).

[0125] The test results of the examples are as follows. Example 1: Thermal properties: In-plane thermal conductivity: 1580±25 W / mK, through-thickness thermal conductivity: 85±3 W / mK, thermal diffusivity: 412±15 mm 2 / s. Mechanical properties: Tensile strength: 86±3 MPa, elongation at break: 12.5±0.8%, flexural life: >150000 cycles. Structural characterization: Oxygen content: 8.3%, defect density: 3.2×10 10 cm -2 、BN bridging layer thickness: 0.8 - 1.2 nm. Process stability: Thickness fluctuation: ±1.8 μm, thermal conductivity CV value: 2.1%, energy consumption: 8.7 kWh / m 2 .

[0126] Example 2: Thermal properties: In-plane thermal conductivity: 1590±28 W / mK, through-thickness thermal conductivity: 86±3 W / mK, thermal diffusivity: 415±16 mm² / s. Mechanical properties: Tensile strength: 88±3 MPa, elongation at break: 12.8±0.9%, flexural life: >150000 cycles. Structural characterization: Oxygen content: 8.5%, defect density: 3.3×10 10 cm -2 、BN bridging layer thickness: 0.9 - 1.3 nm. Process stability: Thickness fluctuation: ±1.9 μm, thermal conductivity CV value: 2.2%, energy consumption: 8.8 kWh / m².

[0127] Example 3: Thermal properties: In-plane thermal conductivity: 1600±30 W / mK, through-thickness thermal conductivity: 87±4 W / mK, thermal diffusivity: 420±17 mm² / s. Mechanical properties: Tensile strength: 92±4 MPa, elongation at break: 13.2±1.1%, flexural life: >150000 cycles. Structural characterization: Oxygen content: 8.2%, defect density: 3.1×10 10 cm -2 、BN bridging layer thickness: 0.8 - 1.2 nm. Process stability: Thickness fluctuation: ±1.7 μm, thermal conductivity CV value: 2.0%, energy consumption: 8.6 kWh / m².

[0128] Example 4: Thermal properties: In-plane thermal conductivity: 1625±30 W / mK, through-thickness thermal conductivity: 89±4 W / mK, thermal diffusivity: 428±18 mm² / s. Mechanical properties: Tensile strength: 94±4 MPa, elongation at break: 13.5±1.2%, flexural life: >150000 cycles. Structural characterization: Oxygen content: 8.0%, defect density: 3.0×10 10 cm -2, BN bridging layer thickness: 0.7 - 1.1 nm. Process stability: thickness fluctuation: ±1.6 μm, thermal conductivity CV value: 1.9%, energy consumption: 8.5 kWh / m².

[0129] Example 5: Thermal properties: in-plane thermal conductivity: 1575 ± 26 W / mK, through-plane thermal conductivity: 84 ± 3 W / mK, thermal diffusivity: 410 ± 14 mm² / s. Mechanical properties: tensile strength: 85 ± 3 MPa, elongation at break: 12.3 ± 0.7%, flexural life: >150000 cycles. Structural characterization: oxygen content: 8.4%, defect density: 3.4×10 10 cm -2 , BN bridging layer thickness: 0.9 - 1.3 nm. Process stability: thickness fluctuation: ±2.0 μm, thermal conductivity CV value: 2.3%, energy consumption: 8.9 kWh / m².

[0130] Example 6: Thermal properties: in-plane thermal conductivity: 1595 ± 29 W / mK, through-plane thermal conductivity: 86 ± 4 W / mK, thermal diffusivity: 416 ± 16 mm² / s. Mechanical properties: tensile strength: 89 ± 3 MPa, elongation at break: 12.9 ± 0.9%, flexural life: >150000 cycles. Structural characterization: oxygen content: 8.3%, defect density: 3.2×10 10 cm -2 , BN bridging layer thickness: 0.8 - 1.2 nm. Process stability: thickness fluctuation: ±1.8 μm, thermal conductivity CV value: 2.1%, energy consumption: 8.7 kWh / m².

[0131] Example 7: Thermal properties: in-plane thermal conductivity: 1610 ± 31 W / mK, through-plane thermal conductivity: 88 ± 4 W / mK, thermal diffusivity: 422 ± 17 mm² / s. Mechanical properties: tensile strength: 93 ± 4 MPa, elongation at break: 13.3 ± 1.1%, flexural life: >150000 cycles. Structural characterization: oxygen content: 8.1%, defect density: 3.1×10 10 cm -2 , BN bridging layer thickness: 0.7 - 1.1 nm. Process stability: thickness fluctuation: ±1.7 μm, thermal conductivity CV value: 2.0%, energy consumption: 8.6 kWh / m².

[0132] Example 8: Thermal properties: in-plane thermal conductivity: 1620 ± 32 W / mK, through-plane thermal conductivity: 89 ± 4 W / mK, thermal diffusivity: 425 ± 18 mm² / s. Mechanical properties: tensile strength: 95 ± 4 MPa, elongation at break: 13.6 ± 1.2%, flexural life: >150000 cycles. Structural characterization: oxygen content: 8.0%, defect density: 3.0×10 10 cm -2, BN bridging layer thickness: 0.7 - 1.1 nm. Process stability: thickness fluctuation: ±1.6 μm, CV value of thermal conductivity: 1.9%, energy consumption: 8.5 kWh / m².

[0133] Example 9: Thermal properties: in-plane thermal conductivity: 1585 ± 27 W / mK, vertical thermal conductivity: 85 ± 3 W / mK, thermal diffusivity: 413 ± 15 mm² / s. Mechanical properties: tensile strength: 87 ± 3 MPa, elongation at break: 12.6 ± 0.8%, flexural life: >150000 times. Structure characterization: oxygen content: 8.3%, defect density: 3.2×10 10 cm -2 , BN bridging layer thickness: 0.8 - 1.2 nm. Process stability: thickness fluctuation: ±1.8 μm, CV value of thermal conductivity: 2.1%, energy consumption: 8.7 kWh / m².

[0134] Example 10: Thermal properties: in-plane thermal conductivity: 1590 ± 28 W / mK, vertical thermal conductivity: 86 ± 3 W / mK, thermal diffusivity: 415 ± 16 mm² / s. Mechanical properties: tensile strength: 88 ± 3 MPa, elongation at break: 12.8 ± 0.9%, flexural life: >150000 times. Structure characterization: oxygen content: 8.2%, defect density: 3.1×10 10 cm -2 , BN bridging layer thickness: 0.8 - 1.2 nm. Process stability: thickness fluctuation: ±1.7 μm, CV value of thermal conductivity: 2.0%, energy consumption: 8.6 kWh / m².

[0135] The test results of the comparative examples are shown as follows. Comparative example 1: Thermal properties: in-plane thermal conductivity: 1120 ± 40 W / mK, vertical thermal conductivity: 32 ± 2 W / mK, thermal diffusivity: 298 ± 20 mm² / s. Mechanical properties: tensile strength: 65 ± 3 MPa, elongation at break: 8.5 ± 0.6%, flexural life: 80000 times. Structure characterization: oxygen content: 12.5%, defect density: 5.5×10 10 cm -2 , BN bridging layer thickness: 0.5 - 0.9 nm. Process stability: thickness fluctuation: ±3.5 μm, CV value of thermal conductivity: 4.5%, energy consumption: 10.2 kWh / m².

[0136] Comparative example 2: Thermal properties: in-plane thermal conductivity: 980 ± 35 W / mK, vertical thermal conductivity: 29 ± 2 W / mK, thermal diffusivity: 285 ± 18 mm² / s. Mechanical properties: tensile strength: 48 ± 2 MPa, elongation at break: 5.3 ± 0.6%, flexural life: 3,200 times. Structure characterization: oxygen content: 15.2%, defect density: 6.8×10 10 cm-2 , BN bridging layer thickness: 0.4 - 0.8 nm. Process stability: thickness fluctuation: ±23 μm, CV value of thermal conductivity: 6.8%, energy consumption: 12.5 kWh / m².

[0137] Comparative Example 3: Thermal properties: in-plane thermal conductivity: 1250 ± 38 W / mK, vertical thermal conductivity: 45 ± 3 W / mK, thermal diffusivity: 320 ± 22 mm² / s. Mechanical properties: tensile strength: 70 ± 3 MPa, elongation at break: 9.2 ± 0.7%, flexural life: 50000 times. Structural characterization: oxygen content: 19.7%, defect density: 4.8×10 10 cm -2 , BN bridging layer thickness: 0.6 - 1.0 nm. Process stability: thickness fluctuation: ±4.2 μm, CV value of thermal conductivity: 5.2%, energy consumption: 11.0 kWh / m².

[0138] Comparative Example 4: Thermal properties: in-plane thermal conductivity: 1450 ± 35 W / mK, vertical thermal conductivity: 41 ± 3 W / mK, thermal diffusivity: 385 ± 22 mm² / s, mechanical properties: tensile strength: 78 ± 3 MPa, elongation at break: 10.5 ± 0.8%, flexural life: 82,000 times. Structural characterization: oxygen content: 9.5%, defect density: 4.2×10 10 cm -2 , BN bridging layer thickness: none. Process stability: thickness fluctuation: ±5.6 μm, CV value of thermal conductivity: 3.8%, energy consumption: 9.8 kWh / m².

[0139] Comparative Example 5: Thermal properties: in-plane thermal conductivity: 1350 ± 32 W / mK, vertical thermal conductivity: 50 ± 3 W / mK, thermal diffusivity: 350 ± 20 mm² / s. Mechanical properties: tensile strength: 72 ± 3 MPa, elongation at break: 9.8 ± 0.7%, flexural life: 82,000 times. Structural characterization: oxygen content: 10.2%, defect density: 4.5×10 10 cm -2 , BN bridging layer thickness: 0.7 - 1.1 nm. Process stability: thickness fluctuation: ±3.0 μm, CV value of thermal conductivity: 3.5%, energy consumption: 9.5 kWh / m².

[0140] Comparative Example 6: Thermal properties: in-plane thermal conductivity: 1280 ± 34 W / mK, vertical thermal conductivity: 48 ± 3 W / mK, thermal diffusivity: 330 ± 21 mm² / s. Mechanical properties: tensile strength: 75 ± 3 MPa, elongation at break: 10.0 ± 0.8%, flexural life: 60000 times. Structural characterization: oxygen content: 18.5%, defect density: 5.0×10 10 cm -2, BN bridging layer thickness: 0.6 - 1.0 nm. Process stability: thickness fluctuation: ±4.0 μm, CV value of thermal conductivity: 4.8%, energy consumption: 10.5 kWh / m².

[0141] Comparative Example 7: Thermal properties: in-plane thermal conductivity: 1200 ± 36 W / mK, vertical thermal conductivity: 40 ± 2 W / mK, thermal diffusivity: 310 ± 19 mm² / s. Mechanical properties: tensile strength: 68 ± 3 MPa, elongation at break: 8.8 ± 0.6%, flexural life: 40000 times. Structural characterization: oxygen content: 20.0%, defect density: 5.2×10 10 cm -2 , BN bridging layer thickness: 0.5 - 0.9 nm. Process stability: thickness fluctuation: ±4.5 μm, CV value of thermal conductivity: 5.5%, energy consumption: 11.2 kWh / m².

[0142] Comparative Example 8: Thermal properties: in-plane thermal conductivity: 1300 ± 33 W / mK, vertical thermal conductivity: 45 ± 3 W / mK, thermal diffusivity: 340 ± 20 mm² / s. Mechanical properties: tensile strength: 70 ± 3 MPa, elongation at break: 9.5 ± 0.7%, flexural life: 50000 times. Structural characterization: oxygen content: 15.0%, defect density: 1.1×10 11 cm -2 , BN bridging layer thickness: 0.6 - 1.0 nm. Process stability: thickness fluctuation: ±3.8 μm, CV value of thermal conductivity: 4.2%, energy consumption: 10.0 kWh / m².

[0143] The test results are analyzed as follows: Thermal properties: Performance of the examples: The in-plane thermal conductivity of Examples 1-10 ranges from 1575 to 1625 W / mK, the through-plane thermal conductivity ranges from 84 to 89 W / mK, and the thermal diffusivity is 410-428 mm² / s, indicating excellent thermal conduction performance. Comparison with the comparative examples: Comparative Example 1 (without platinum quantum dots): The in-plane thermal conductivity drops to 1120 W / mK, a decrease of about 28.6%, indicating that platinum quantum dots are crucial for enhancing the thermal conductivity. Comparative Example 4 (without three-dimensional bridging): The through-plane thermal conductivity is only 41 W / mK, a decrease of about 117% compared to Example 1, proving that the boron nitride bridging structure significantly enhances the through-plane heat conduction. Mechanical properties: Performance of the examples: Tensile strength is 85-95 MPa, elongation at break is 12.3-13.6%, and the bending life exceeds 150,000 times, demonstrating excellent flexibility and durability. Comparison with the comparative examples: Comparative Example 2 (without dynamic pressure field): Tensile strength is only 48 MPa, a decrease of 79% compared to Example 1, and the bending life is only 3200 times, indicating the enhancing effect of the dynamic pressure field on the lamellar orientation and mechanical properties. Comparative Example 5 (without pulsed Joule reduction): The bending life is 82,000 times, a decrease of about 46% compared to Example 1, indicating the importance of defect repair for flexibility. Structural characterization: Performance of the examples: Oxygen content is stable at 8.0-8.5%, defect density is 3.0-3.4×10 10 cm -2 , the thickness of the BN bridging layer is 0.7-1.3 nm, and the structural integrity is high. Comparison with the comparative examples: Comparative Example 3 (only chemical pre-reduction): Oxygen content is 19.7%, defect density is 4.8×10 10 cm -2 , indicating the necessity of gradient synergistic reduction. Comparative Example 8 (without chemical pre-reduction and plasma treatment): The defect density is as high as 1.1×10 11 cm -2 , showing that the sole effect of pulsed Joule reduction is insufficient to optimize the structure. Process stability: Performance of the examples: Thickness fluctuation is ±1.6-2.0 μm, the CV value of thermal conductivity is 1.9-2.3%, and the energy consumption is 8.5-8.9 kWh / m², with excellent process consistency and energy efficiency. Comparison with the comparative examples: Comparative Example 2 (without dynamic pressure field): Thickness fluctuation is ±23 μm, the CV value is 6.8%, and the stability significantly decreases. The energy consumption range of Comparative Examples 1-8 is 9.5-12.5 kWh / m², about 10-45% higher than that of the examples, showing the low energy consumption advantage of the process of the present invention.

[0144] This test plan comprehensively verifies the high-performance performance of Examples 1-10 through thermal, mechanical, structural, and process stability tests. Compared with Comparative Examples 1-8, the Examples are significantly superior to the prior art in terms of thermal conductivity (31.7% increase in-plane and 70% increase perpendicular), flexibility (4-47 times improvement in bending life), and process stability (86% reduction in thickness fluctuation), providing an innovative thermal management solution for fields such as 5G communication and flexible electronics.

[0145] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation method of a graphene thermal conductive film, characterized in that, Comprising the following step combinations: (1) Raw material pretreatment: Mechanically shear to prepare a submicron graphene oxide dispersion with a lateral dimension of 100 - 300 nm, and simultaneously load platinum quantum dots with a particle size of 5 - 8 nm; (2) Dynamic flow field film formation: Apply a dynamic pressure field of 0.5 - 2 MPa during the coating process with a shear rate of 500 - 800 s -1 to make the layer orientation degree ≥ 93% and form a wet film with a thickness of 20 ± 2 μm; (3) Gradient cooperative reduction: Chemical pre-reduction: Treat with an ascorbic acid / hydrazine hydrate composite reducing agent to reduce the oxygen content from 32% to 8 - 12%; Pulse Joule reduction: Apply a pulse current of 80 - 100 A / cm² for 600 - 800 s to reduce the defect density to 3.5×10 10 cm -2 ; Plasma treatment: Treat with an Ar / H2 mixed gas plasma for 30 min to eliminate residual dangling bonds; Three-dimensional bridging strengthening: Grow a boron nitride nanosheet bridging structure between layers through aerosol-assisted CVD to form a vertical heat conduction channel.

2. The preparation method of the graphene thermal conductive film according to claim 1, wherein, In step (1), the concentration of the graphene oxide dispersion is controlled at 5 - 8 mg / mL, and the concentration of the platinum quantum dots is 0.8 - 1.2 wt%.

3. The preparation method of the graphene thermal conductive film according to claim 1, characterized in that, The preparation method of platinum quantum dots in step (1) is as follows: Using o-phenylenediamine as the carbon source and platinum acetylacetonate as the platinum source, in an ammonia / methanol biphasic system, where the concentration of ammonia water is 5-15 wt%, the volume ratio between ammonia water and methanol is 1:3, and the mass ratio between o-phenylenediamine and platinum acetylacetonate is 1:(0.01-0.1). Hydrothermal reaction is carried out at 180-220 °C for 8 h. After the reaction, it is separated by a 0.22 μm filter membrane to obtain uniform quantum dots with a particle size of 2.8±0.5 nm. Then, a sodium borohydride solution is added and treated at 25 °C for 30-60 min, where the final concentration of the sodium borohydride solution is 0.15 M. Then, high-frequency ultrasonic treatment is carried out at 40-60 kHz for 10-20 min, and the power density is controlled at 50-60 W / cm 3 , and then plasma treatment is carried out in a hydrogen atmosphere for 30 min to eliminate surface dangling bonds, obtaining hybrid particles with a uniform dispersion of 10-22 nm.

4. The preparation method of the graphene thermal conductive film according to claim 1, characterized in that, In step (2), the regulation method of the dynamic pressure field is three-stage control, which are 0.5 MPa, 1.2 MPa, and 2 MPa respectively, and the pressure change rate is controlled at 0.1 MPa / s.

5. The preparation method of the graphene thermal conductive film according to claim 1, characterized in that, In step (3), the molar ratio of ascorbic acid / hydrazine hydrate composite reducing agent is 1:

3.

6. The method for preparing the graphene thermal conductive film according to claim 1, wherein In step (3), the pulse width of the pulsed current is 50 ms, the interval is 10 ms, and the single-pulse energy density is 15 - 18 J / cm 3 .

7. The preparation method of the graphene thermal conductive film according to claim 1, wherein, In step (3), the volume ratio of the mixed gas is 95:5, and the parameters of the plasma treatment are as follows: radio frequency power: 50 - 200 W, 13.56 MHz, peak power density: 0.8 W / cm 3 , plasma zone temperature: 300 - 500 °C.

8. The preparation method of the graphene thermal conductive film according to claim 1, wherein, In step (3), the aerosol precursor system: a mixed gas of BCl3 / NH3 / Ar is used, with a volume ratio of the mixed gas of 1:3:15, the aerosol particle size is controlled at 50 - 200 nm, and the mass concentration is 8 - 12 g / m 3 ; The production stages are as follows: Initial stage: pressure 10 3 Pa, temperature 800 °C, deposition rate 0.5 nm / min, lasting for 10 min to form a nucleation layer; Growth stage: pressure 5×10 2 Pa, temperature 950 °C, deposition rate 2 nm / min, lasting for 30 min to construct vertical bridging.

9. A graphene thermal conductive film, characterized in that, The graphene thermal conductive film described is obtained by the preparation method according to any one of claims 1 - 8.

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