Expanded graphite-based temperature control-electromagnetic protection integrated material and preparation method thereof

Abstract

The invention relates to the technical field of composite functional materials, in particular to an expanded graphite-based temperature control-electromagnetic protection integrated material and a preparation method thereof. The preparation method comprises the following steps: carrying out in-situ growth of NiCo bimetallic magnetic nanoparticles on the surface of expanded graphite through a chemical deposition method to obtain an expanded graphite-NiCo particle composite material; then a flower-shaped TiO2 dielectric layer is constructed on the surface of the expanded graphite-NiCo particle composite material through a solvothermal method to obtain expanded graphite-NiCo-TiO2, finally, the phase change material is packaged in the expanded graphite-NiCo-TiO2, and the expanded graphite-based temperature control-electromagnetic protection integrated material is obtained. Through collaborative optimization of component design and structure regulation and control, the dual functions of wave absorption and heat storage are achieved at the same time, and the wave absorption performance of the composite material is improved through the multi-physical field synergistic effect induced by heterogeneous interfaces such as multiple scattering of electromagnetic waves, polarization relaxation loss and the magnetoelectric coupling effect.

Description

Technical Field

[0001] This invention relates to the field of composite functional materials technology, and in particular to an expanded graphite-based integrated temperature control and electromagnetic protection material and its preparation method. Background Technology

[0002] With the increasing frequency and miniaturization of electronic devices, the coupling problem of electromagnetic radiation pollution and thermal effects is becoming increasingly prominent, and the limitations of the separate design of traditional thermal management materials and electromagnetic protection systems are gradually being exposed. In existing technologies, although phase change materials can achieve precise temperature control through latent heat storage, their inherent low thermal conductivity easily leads to local overheating, and the volume expansion and liquid leakage problems during the solid-liquid phase transition process result in poor long-term stability of the materials. On the other hand, conventional electromagnetic shielding materials are mostly based on metal matrices or carbon-based composite materials, which have defects such as high density, narrow bandwidth, and single function, making it difficult to meet the requirements of lightweight electronic devices for integrated thermal-electromagnetic synergistic control.

[0003] Current research and development of composite functional materials largely focuses on optimizing single properties, lacking system design based on multi-physics coupling mechanisms. On the one hand, while encapsulation of traditional phase change composite materials with porous carriers can alleviate leakage, adding fillers can disrupt the thermal / electrical conduction network, leading to a trade-off between improved thermal conductivity and enhanced electromagnetic performance. On the other hand, the structural design of microwave absorbing materials often neglects thermal adaptability; oxidation of the absorbing agent or flow of the phase change medium at high temperatures can easily cause structural failure. How to achieve synergistic enhancement of thermal and electromagnetic functions through cross-scale heterogeneous interface engineering, and overcome the design barriers of lightweight, highly stable, and broadband integrated materials, remains a core challenge that urgently needs to be addressed in this field. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing an integrated expanded graphite-based temperature control and electromagnetic protection material and its preparation method.

[0005] The first objective of this invention is to provide a method for preparing an integrated temperature control and electromagnetic protection material based on expanded graphite. This method involves in-situ growth of NiCo bimetallic magnetic nanoparticles on the surface of expanded graphite using chemical deposition to obtain an expanded graphite-NiCo particle composite material. Then, a flower-like TiO2 dielectric layer is constructed on the surface of the expanded graphite-NiCo particle composite material using a solvothermal method to obtain expanded graphite-NiCo-TiO2. Finally, a phase change material is encapsulated within the expanded graphite-NiCo-TiO2 to obtain the integrated temperature control and electromagnetic protection material based on expanded graphite.

[0006] Furthermore, the specific steps include: S1. Weigh out expanded graphite, hexadecyltrimethylammonium bromide, NaOH, cobalt acetate tetrahydrate and nickel acetate tetrahydrate, add them to ethylene glycol solution, stir and sonicate to obtain a mixed suspension for hydrothermal synthesis. After the reaction is completed, collect the black powder product, wash and dry to obtain expanded graphite-NiCo particle composite material. S2. Weigh out the expanded graphite-NiCo particle composite material and place it in isopropanol solution. Slowly add diethylenetriamine solution, stir and sonicate thoroughly, add isopropyl titanate solution, and gently stir with a glass rod to obtain a mixed suspension for hydrothermal synthesis. After the hydrothermal synthesis reaction is completed, collect the black powder product, wash and dry it to obtain expanded graphite-NiCo-TiO2. S3. Vacuum impregnation of expanded graphite-NiCo-TiO2 with phase change material yields an integrated expanded graphite-based temperature control-electromagnetic protection material.

[0007] Furthermore, expanded graphite is obtained by thermally activating and modifying expandable graphite.

[0008] Furthermore, the calcination temperature for thermal activation modification is 800~1000 ℃, the calcination time is 10~60 s, and the calcination atmosphere is air.

[0009] Further, in step S1, the expanded graphite, hexadecyltrimethylammonium bromide, NaOH, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, and ethylene glycol are in the following weight parts: expanded graphite: 0.01~0.1 parts, hexadecyltrimethylammonium bromide: 2~6 parts, NaOH: 1~4 parts, cobalt acetate tetrahydrate: 0.2~0.5 parts, nickel acetate tetrahydrate: 0.5~3 parts, and ethylene glycol: 30~50 parts.

[0010] Furthermore, in step S1, the stirring speed is 500-1000 r / min, the stirring time is 30-60 min, the ultrasonic treatment time is 30-60 min, the hydrothermal synthesis temperature is 180-200 ℃, and the hydrothermal synthesis time is 6-12 h.

[0011] Further, in step S2, the expanded graphite-NiCo particle composite material, isopropanol, diethylenetriamine, and isopropyl titanate are in the following weight parts: expanded graphite-NiCo particle composite material: 0.05~1 part, isopropanol: 30~80 parts, diethylenetriamine: 0.02~0.1 part, and isopropyl titanate: 0.5~2 parts.

[0012] Furthermore, in step S2, the stirring speed is 500-1000 r / min, the stirring time is 30-60 min, the hydrothermal synthesis temperature is 180-200 ℃, and the hydrothermal synthesis time is 12-36 h.

[0013] Furthermore, in step S3, the mass ratio of the expanded graphite-NiCo-TiO2 composite material to the phase change material in the obtained expanded graphite-based temperature control-electromagnetic protection integrated material is 40~60:40~60.

[0014] Furthermore, in step S3, step S3 also includes hot filtration of the vacuum-impregnated expanded graphite-NiCo-TiO2; the vacuum impregnation is first carried out at room temperature for 10~50 min, and then at 40~90 °C for 10~50 min; hot filtration is carried out in a programmed temperature-controlled vacuum drying device for 12~36 h.

[0015] The second objective of this invention is to provide an expanded graphite-based integrated temperature control and electromagnetic protection material prepared by the method described above.

[0016] This invention constructs an impedance matching system through multi-scale structural design and synergistic construction of multiple heterogeneous components. A three-dimensional porous expanded graphite framework is prepared using a high-temperature intercalation-expansion process. NiCo bimetallic magnetic nanoparticles are then grown in situ on its surface via chemical deposition. A flower-like TiO2 dielectric layer is constructed on the composite surface using a solvothermal method. Finally, the phase change material (PCM) is encapsulated within a hierarchical porous structure. The high specific surface area and three-dimensional interpenetrating network structure of expanded graphite not only provide high loading rate and anti-leakage stability for the PCM, achieving efficient encapsulation and solving the leakage problem in solid-liquid phase change processes, but also establish a primary dielectric loss pathway through its intrinsic conductive network, enhancing dielectric loss through interfacial polarization. Furthermore, the in-situ growth of NiCo bimetallic magnetic particles on the expanded graphite surface utilizes the electronic coupling effect between the bimetallic components to enhance the magnetocrystalline anisotropy field. The matching between eddy current loss and natural resonant frequency can be optimized through size control, and the NiCo composite structure can be further optimized through size control. The magnetocrystalline anisotropy and eddy current loss characteristics of gold enable precise control of magnetic loss parameters. Subsequently, the flower-like TiO2 dielectric shell, with its hierarchical sheet structure, generates multiple reflection-scattering effects, which extend the electromagnetic wave propagation path through multiple scattering effects. The core-shell heterostructure formed by the TiO2 shell and the expanded graphite matrix can induce significant space charge polarization, forming a strong interfacial polarization center and enhancing dielectric loss performance. Finally, through the synergy of porous structure parameter optimization and multi-element loss mechanism, the composite material exhibits a gradient distribution of intrinsic impedance, achieving good matching with free space impedance.

[0017] This invention achieves dynamic control of electromagnetic parameters through structure-component synergistic optimization. It utilizes the conductive network of porous expanded graphite to establish the main dielectric loss pathway, the high permeability of NiCo alloy to provide the magnetic loss substrate, and the TiO2 dielectric shell to introduce relaxation polarization loss, forming a multi-mechanism synergistic loss system of "electromagnetic-relaxation". Based on the equivalent transmission line theory, by adjusting the pore size, TiO2 shell thickness, and NiCo loading, the surface impedance of the composite can exhibit a gradient distribution, achieving high absorption over a wide frequency range. The phase change energy storage unit and the microwave absorption structure are integrated into a single design, maintaining a high enthalpy while suppressing the destructive effects of paraffin flow on the electromagnetic structure at high temperatures through porous confinement.

[0018] This invention employs a vacuum-assisted impregnation process to load paraffin, a phase change energy storage medium, into an expanded graphite-NiCo-TiO2 composite material with a core-shell hierarchical structure, successfully constructing a dual-functional integrated material system for thermal management and electromagnetic protection. The composite microspheres achieve highly efficient confined encapsulation of paraffin through the synergistic effect of a three-dimensional interpenetrating network structure and surface nanoscale pores, achieving a mass loading rate of 50.3%. The latent heat of phase change in the composite material reaches 110.4 J / g and 107.7 J / g, respectively, with melt-solidification phase transition temperatures of 38.2℃ and 34.2℃, respectively. This temperature range highly matches the conventional operating temperature range of electronic devices, effectively enabling rapid absorption and release regulation of overheated energy during device operation.

[0019] This invention enhances the microwave absorption performance of composite materials through the synergistic effects of multiple physics fields induced by heterogeneous interfaces, such as electromagnetic wave multiple scattering, polarization relaxation loss, and magnetoelectric coupling. The microwave absorption and heat storage integrated material constructed by this invention achieves an effective absorption bandwidth of 4.7 GHz in the 2-18 GHz range with a thickness of only 1.43 mm, demonstrating superior microwave absorption performance. Therefore, this invention, through the synergistic optimization of component design and structural control, simultaneously achieves both microwave absorption and heat storage functions, providing a theoretical basis and technical path for the development of novel lightweight electromagnetic functional materials. This is of great significance for the simultaneous realization of microwave absorption and thermal management in high-end electronic devices. Attached Figure Description

[0020] Figure 1 These are scanning electron microscope images of the expandable graphite before and after modification in Example 1; Figure 2 These are scanning electron microscope images of the expanded graphite-NiCo composite material prepared in Example 1; Figure 3 These are scanning electron microscope images of the expanded graphite-NiCo-TiO2 composite material prepared in Example 1; Figure 4These are (a) nitrogen adsorption-desorption isotherms and (b) BJH pore size distribution diagrams of the expanded graphite-NiCo-TiO2 composite material prepared in Example 1. Figure 5 The DSC curve of the expanded graphite-based integrated temperature control and electromagnetic protection material prepared in Example 1 is shown. Figure 6 Thermogravimetric analysis curve of the expanded graphite-based temperature control-electromagnetic protection integrated material prepared in Example 1; Figure 7 and 8 The electromagnetic wave absorption characteristics are those of the expanded graphite-based integrated temperature control and electromagnetic protection material prepared in Example 1. Detailed Implementation

[0021] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0022] Example 1: Preparation of expanded graphite This experiment used a high-temperature expansion method to prepare expanded graphite. First, 1.0 g of flake-like expandable graphite powder sample was accurately weighed using an analytical balance. The weighed sample was then uniformly transferred to a corundum square crucible pre-calcined at 950℃, ensuring the material was evenly distributed at the bottom of the crucible. The crucible containing the sample was then quickly transferred to the central area of ​​the working chamber of a box-type muffle furnace preheated to the target temperature. The furnace temperature was set at 950±5℃, and a PID temperature control system was used to maintain temperature fluctuations within ±2℃. Under high temperature, the intercalation compounds in the graphite layers underwent a violent decomposition reaction. This rapid expansion process lasted for 30 seconds, after which the crucible was immediately removed and placed on a refractory brick platform. Throughout the thermal expansion process, a significant expansion of the sample volume was observed, ultimately yielding an expanded graphite product with a typical worm-like porous structure. The entire experiment was conducted in an air atmosphere, and the heating rate was controlled at 10℃ / min using a preset furnace program to ensure uniform heat treatment.

[0023] Preparation of expanded graphite-NiCo composite materials First, expanded graphite substrate (0.05 g) was dispersed in a 40 mL ethylene glycol solvent system with surfactants cetyltrimethylammonium bromide (4 g) and sodium hydroxide (2.4 g). Then, cobalt acetate tetrahydrate (0.32 g) and nickel acetate tetrahydrate (1.2 g) were added sequentially as metal precursors. After magnetic stirring for 40 min and ultrasonic treatment for 30 min, the uniformly dispersed suspension was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 200 °C for 8 h. After the reaction system cooled naturally to room temperature, the black solid product was collected by vacuum filtration, washed three times alternately with deionized water and anhydrous ethanol, and finally dried in a 60 °C vacuum drying oven for 12 h to obtain the target product.

[0024] Construction of expanded graphite-NiCo-TiO2 composite material The experimental steps for preparing expanded graphite-NiCo-TiO2 composite materials using a hydrothermal method are as follows: 0.5 g of modified expanded graphite-NiCo precursor was accurately weighed and dispersed in 40 mL of isopropanol solvent. 0.05 mL of diethylenetriamine was added dropwise as a surfactant using a constant-pressure dropping funnel. After forming a homogeneous suspension by stirring continuously at 600 rpm for 40 min on a magnetic stirrer, 5 mL of isopropyl titanate was slowly injected as a titanium source. The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined reactor and placed in a temperature-controlled oven for hydrothermal reaction at 200 °C for 24 h. After the reaction system naturally cooled to room temperature, the black precipitate was collected and washed three times alternately with deionized water and anhydrous ethanol to remove unreacted substances. The final product was then treated at 60 °C for 12 h in a vacuum drying oven to obtain a ternary composite material of expanded graphite-NiCo-TiO2 with a multi-level structure. In this preparation process, hydrothermal conditions can promote the directional growth of TiO2 nanocrystals on expanded graphite-NiCo substrate, forming a stable heterostructure.

[0025] Preparation of expanded graphite-based integrated temperature control and electromagnetic protection materials This experiment employed a vacuum-assisted melt impregnation method to construct a multifunctional composite phase change material. 2.0 g of a multi-level expanded graphite-NiCo-TiO2 ternary composite carrier (Example 3) and 3.0 g of organic phase change matrix paraffin were precisely weighed and transferred to a vacuum filtration device after a solid-liquid ratio of 1:1.5. First, a gradient vacuum degassing treatment was performed at 298 K (maintained for 30 min initially to remove physically adsorbed gases). Then, vacuum treatment was continued for 30 min in a constant-temperature water bath at 363 K to ensure the molten paraffin fully impregnates the porous carrier. Subsequently, a dynamic thermal filtration process (333 K, for 24 h) was used to achieve directional transport and confined solidification of the phase change material within the porous network through precise temperature control, ultimately obtaining a dual-effect composite material with both electromagnetic wave absorption and thermal energy storage functions. This process, through multi-scale pore control and interface engineering optimization, effectively solves the phase separation and functional synergy problems existing in traditional composite phase change materials.

[0026] Example 2 Preparation of expanded graphite-based integrated temperature control and electromagnetic protection materials In the process of preparing expanded graphite-NiCo composite material, the loading of NiCo was changed, and cobalt acetate tetrahydrate (0.8 g) and nickel acetate tetrahydrate (3.0 g) were added sequentially as metal precursors. All other processes were the same as those in Example 1.

[0027] Example 3 Preparation of expanded graphite-based integrated temperature control and electromagnetic protection materials In the process of preparing expanded graphite-NiCo composite material, the loading of NiCo was changed, and cobalt acetate tetrahydrate (0.16 g) and nickel acetate tetrahydrate (0.6 g) were added sequentially as metal precursors. All other processes were the same as those in Example 1.

[0028] See appendix Figure 1 These are scanning electron microscope images of the expandable graphite before and after modification in Example 1. It can be seen that the expandable graphite is in a compact block shape with fewer pores. Figure 1 a) After high-temperature expansion, the intercalated graphite compounds undergo a violent decomposition reaction, the graphite sheets expand rapidly, and the sample volume shows a significant expansion phenomenon, ultimately yielding an expanded graphite product with a typical worm-like porous structure, with a specific surface area increasing from 2.1 m². 2 / g increased to 41.6 m 2 / g, pore volume from 0.0099 cm³ 3 / g increased to 0.1226 cm 3 The porous structure, with a density of / g, provides numerous adsorption sites for the phase change material, thus helping to increase the loading capacity of the phase change material onto the supporting material. Figure 1 b).

[0029] See appendix Figure 2 This is a scanning electron microscope image of the expanded graphite-NiCo composite material prepared in Example 1. The expanded graphite / NiCo nanocomposite material prepared by optimizing the synthesis process exhibits unique heterogeneous structural characteristics. The NiCo bimetallic magnetic particles constructed by the in-situ synthesis strategy show a monodisperse quasi-spherical morphology with good uniformity in particle size distribution (average particle size of approximately 3 µm), which is attributed to the precise control of nucleation-growth kinetics during the preparation process. The in-situ embedding of magnetic metal particles into the layered structure of expanded graphite was successfully achieved through an interface engineering strategy, forming an interlayer composite system with a three-dimensional conductive network. This special structural feature can significantly enhance the electromagnetic parameter control capability through the Maxwell-Wagner interface polarization effect.

[0030] See appendix Figure 3 This is a scanning electron microscope image of the expanded graphite-NiCo-TiO2 composite material prepared in Example 1. It can be seen that TiO2 nanounits with a significantly wrinkled topology were successfully constructed on the surface of the composite material, forming a highly developed hierarchical pore structure in three-dimensional space. This unique mesoscopic-macroscopic multi-scale porous system not only exhibits a significantly high specific surface area, but more importantly, it achieves a micron-to-submicron pore size gradient distribution through pore topology control, providing abundant interfacial active sites for the multi-level adsorption of phase change materials. Furthermore, this structure greatly enhances its microwave absorption performance through various physical mechanisms, including synergistic enhancement of multiple reflections / scattering, interfacial polarization relaxation loss, optimized impedance matching, induced conduction loss / microcurrent, and provision of defect loss.

[0031] See appendix Figure 4 This is (a) the nitrogen adsorption-desorption isotherm and (b) the BJH pore size distribution diagram of the expanded graphite-based temperature control-electromagnetic protection integrated material prepared in Example 1. As can be seen from the figure, the composite material combines type I and type IV isotherms at P / P... oA weak hysteresis loop exists in the range of 0.50–0.95, indicating the coexistence of numerous micropores and mesopores. Therefore, the composite material is a typical hierarchical porous material with diverse pore structure characteristics. The material's three-dimensional rigid framework effectively encapsulates paraffin molecules through size confinement. The microporous structure (<2 nm) restricts the thermal motion of paraffin molecules through strong capillary forces, while the mesoporous channels (2–50 nm) act as buffer spaces to mitigate volume changes during phase transitions. Analysis of nitrogen adsorption-desorption curves reveals that the specific surface areas of graphite and the composite material are 2.1 m² / g and 39.6 m² / g, respectively. The composite material exhibits a significantly increased specific surface area, effectively encapsulating paraffin within its rigid structure to prevent leakage. This leap in specific surface area is primarily attributed to the synergistic construction of the hierarchical porous structure: the microporous structure significantly increases the specific surface area by increasing surface energy, while the three-dimensional interconnected mesoporous network effectively reduces mass transfer resistance.

[0032] See appendix Figure 5 This is the DSC curve of the expanded graphite-based temperature control-electromagnetic protection integrated material prepared in Example 1. The constructed heat storage and electromagnetic interference absorption integrated composite material exhibits significant thermal energy storage characteristics. The enthalpy of the material reaches 110.4 J / g during the melting phase transition and 107.7 J / g during the solidification phase transition. The critical phase transition temperature of the phase change material was precisely controlled to 38.2℃ (melting) and 34.2℃ (solidification), and this temperature window forms an ideal coupling with the operating temperature range of typical electronic devices. When the device temperature exceeds the phase transition temperature, the phase transition heat absorption mechanism can effectively suppress thermal failure; while in the standby state, the solidification heat release behavior is beneficial to maintaining the stability of the device's operating temperature. This temperature-adaptive latent heat storage system provides an innovative path to solve the problems of thermally induced performance degradation and electromagnetic interference coupling in high-power electronic devices.

[0033] See appendix Figure 6 The figure shows the thermogravimetric analysis curve of the expanded graphite-based temperature control-electromagnetic protection integrated material prepared in Example 1. Thermal decomposition kinetics analysis indicates that the composite material achieves a high loading rate of 50.3% for the paraffin phase change medium. Microstructural characterization confirms that the three-dimensional porous network structure and the hierarchical pore system constructed from wrinkled TiO2 nanosheets produce a significant mesoporous confinement effect. The capillary forces induced by the surface energy gradient, combined with chemisorption, allow paraffin molecules to be stably anchored within the rigid framework through physical wetting and interfacial bonding.

[0034] See appendix Figure 7 and 8This study describes the electromagnetic wave absorption characteristics of the expanded graphite-based temperature control and electromagnetic protection integrated material prepared in Example 1. Based on the relative complex permittivity and permeability under different given absorber thicknesses, and combined with transmission line theory, the reflection loss value of the sample was simulated and calculated, and the corresponding two-dimensional curves and three-dimensional surface plots were plotted. In the 2-18 GHz range, the composite microspheres, with a thickness of only 1.43 mm, can achieve an effective absorption bandwidth of 4.7 GHz. The introduction of NiCo alloy particles constructs a multiple magnetic loss mechanism. The natural resonance effect generated by their high saturation magnetization can effectively broaden the absorption bandwidth, while the uniform submicron particle size distribution significantly reduces the material thickness and electromagnetic matching characteristics through the synergistic effect of optimized eddy current loss and skin effect. Furthermore, the heterogeneous interface formed between the expanded graphite matrix and the magnetic particles not only promotes interfacial polarization loss, but its three-dimensional conductive network also generates conduction loss by constructing microcurrent loops. This synergistic effect of the dielectric-magnetic dual loss mechanism enables the composite material to exhibit excellent impedance matching characteristics and broadband absorption performance in the 2-18 GHz microwave band. Furthermore, a strong interfacial coupling effect is formed between expanded graphite-NiCo and TiO2 nanostructures. This unique interfacial structure not only significantly improves the dielectric loss capability of the material through multiple polarization relaxation mechanisms (including interfacial polarization, dipole polarization, and defect polarization), but also achieves gradient matching of electromagnetic parameters thanks to the magnetic anisotropy modulation of the NiCo alloy. The improved microwave absorption performance of the composite material can be attributed to the synergistic effect of multiple physics fields induced by the heterogeneous interface, including multiple scattering of electromagnetic waves, polarization relaxation loss, and magnetoelectric coupling. Therefore, this study provides a theoretical basis and technical path for the development of novel lightweight electromagnetic functional materials through the synergistic optimization of component design and structural control.

[0035] Any aspects not covered above are applicable to existing technologies. Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an integrated temperature control and electromagnetic protection material based on expanded graphite, characterized in that, Expanded graphite-NiCo particle composite material was obtained by in-situ growth of NiCo bimetallic magnetic nanoparticles on the surface of expanded graphite using chemical deposition; then, expanded graphite-NiCo-TiO2 was obtained by constructing a flower-like TiO2 dielectric layer on the surface of the expanded graphite-NiCo particle composite material using a solvothermal method; finally, a phase change material was encapsulated in expanded graphite-NiCo-TiO2 to obtain an integrated temperature control and electromagnetic protection material based on expanded graphite.

2. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: S1. Weigh out expanded graphite, hexadecyltrimethylammonium bromide, NaOH, cobalt acetate tetrahydrate and nickel acetate tetrahydrate, add them to ethylene glycol solution, stir and sonicate to obtain a mixed suspension for hydrothermal synthesis. After the reaction is completed, collect the black powder product, wash and dry to obtain expanded graphite-NiCo particle composite material. S2. Weigh out the expanded graphite-NiCo particle composite material and place it in isopropanol solution. Slowly add diethylenetriamine solution, stir and sonicate thoroughly, add isopropyl titanate solution, and gently stir with a glass rod to obtain a mixed suspension for hydrothermal synthesis. After the hydrothermal synthesis reaction is completed, collect the black powder product, wash and dry it to obtain expanded graphite-NiCo-TiO2. S3. Vacuum impregnation of expanded graphite-NiCo-TiO2 with phase change material yields an integrated expanded graphite-based temperature control-electromagnetic protection material.

3. The preparation method according to claim 2, characterized in that, Expanded graphite is obtained by thermally activating and modifying expandable graphite.

4. The preparation method according to claim 3, characterized in that, The calcination temperature for thermal activation modification was 800~1000℃, the calcination time was 10~60 s, and the calcination atmosphere was air.

5. The preparation method according to claim 2, characterized in that, In step S1, the expanded graphite, hexadecyltrimethylammonium bromide, NaOH, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, and ethylene glycol are in the following weight parts: expanded graphite: 0.01~0.1 parts, hexadecyltrimethylammonium bromide: 2~6 parts, NaOH: 1~4 parts, cobalt acetate tetrahydrate: 0.2~0.5 parts, nickel acetate tetrahydrate: 0.5~3 parts, and ethylene glycol: 30~50 parts.

6. The preparation method according to claim 2, characterized in that, In step S1, the stirring speed is 500-1000 r / min, the stirring time is 30-60 min, the ultrasonic treatment time is 30-60 min, the hydrothermal synthesis temperature is 180-200℃, and the hydrothermal synthesis time is 6-12 h.

7. The preparation method according to claim 2, characterized in that, In step S2, the expanded graphite-NiCo particle composite material, isopropanol, diethylenetriamine, and isopropyl titanate are in the following weight parts: expanded graphite-NiCo particle composite material: 0.05~1 part, isopropanol: 30~80 parts, diethylenetriamine: 0.02~0.1 part, and isopropyl titanate: 0.5~2 parts.

8. The preparation method according to claim 2, characterized in that, In step S2, the stirring speed was 500-1000 r / min and the stirring time was 30-60 min; the hydrothermal synthesis temperature was 180-200 ℃ and the hydrothermal synthesis time was 12-36 h.

9. The preparation method according to claim 2, characterized in that, In step S3, the mass ratio of the expanded graphite-NiCo-TiO2 composite material to the phase change material obtained is 40~60:40~60. Step S3 also includes hot filtration of the vacuum-impregnated expanded graphite-NiCo-TiO2; the vacuum impregnation is first carried out at room temperature for 10-50 min, and then at 40-90 °C for 10-50 min; hot filtration is carried out in a programmed temperature-controlled vacuum drying device for 12-36 h.

10. An expanded graphite-based integrated temperature control and electromagnetic protection material prepared by the preparation method according to any one of claims 1-9.

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