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. The graphene thermal conductive film is a composite film of graphene intercalated with metal nanoparticles. By doping with metal nanoparticles, the normal thermal conductivity of graphene is significantly improved, thereby effectively improving the comprehensive heat dissipation characteristics of graphene. The graphene thermal conductive film can be rapidly mass-produced and manufactured in terms of heat dissipation and heat spreading film materials, thermal interface materials, electrochemical energy storage materials or electromagnetic shielding materials for electronic packaging systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of high thermal conductivity thin film materials, and relates to a graphene thermal conductive film and a preparation method thereof. Background Art

[0002] Thin film heat dissipation materials with high thermal conductivity coefficients play an important role in the heat dissipation of electronic packaging systems with increasing integration levels. Efficient heat dissipation materials and heat dissipation structures can significantly improve the stability and reliability of integrated circuit systems. Graphene heat dissipation films have high in-plane thermal conductivity coefficients (3000 - 5000 W / mK), and can quickly conduct the heat at the heat source to the low-temperature region to avoid thermal failure accidents caused by overheating.

[0003] However, at present, the heat dissipation of graphene thermal conductive films mainly utilizes the high in-plane thermal conductivity coefficient of graphene to quickly conduct the heat at the heat source to the low-temperature region, and then transfers it to the air through radiation heat dissipation. In this process, the heat flux of graphene is severely limited by the limited cross-sectional area of the thin film, resulting in the inability to effectively exert the heat dissipation capacity of graphene. The contact surface between the graphene film and the heat source has a large heat dissipation area. However, the normal thermal conductivity coefficient of the graphene film is relatively low (~5 W / mK), which severely limits the ability of the heat at the heat source to quickly transfer from the inside of the integrated system to the outside, and thus weakens the rapid heat dissipation ability of the graphene heat dissipation film. The main reason is the two-dimensional structure formed by the sp2 hybrid orbitals of carbon atoms in the graphene heat dissipation film, and the adjacent layers of graphene are interacted by weak hydrogen bonds (van der Waals forces). The above structure and bonding characteristics severely restrict the improvement of the normal thermal conductivity coefficient of the graphene thermal conductive film, and thus limit the significant improvement of the heat dissipation performance of the graphene thermal conductive film.

[0004] Therefore, in order to effectively improve the heat dissipation capacity and heat dissipation efficiency of the graphene heat dissipation film, it is of great value to improve the normal thermal conductivity coefficient of the graphene film and utilize the advantage of the contact area to improve the normal heat dissipation capacity of the graphene film.

[0005] In view of the above problems, the present invention is specifically proposed. The above information disclosed in the background art is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] In order to overcome the above problems, the present inventors have conducted intensive research and developed a graphene thermal conductive film and a preparation method thereof. The graphene thermal conductive film is a composite film of graphene intercalated with metal nanoparticles. By doping metal nanoparticles, the normal thermal conductivity of graphene is significantly improved, thereby effectively improving the comprehensive heat dissipation characteristics of graphene. During preparation, expanded graphene is first prepared; then metal nanoparticles are doped between the graphene layers of the expanded graphene film to obtain a graphene preform film; and the graphene thermal conductive film is prepared by densifying the graphene preform film. The preparation method is simple and has a high normal thermal conductivity, and it can be quickly mass-produced and manufactured in the fields of heat dissipation and heat equalization film materials, thermal interface materials, electrochemical energy storage materials or electromagnetic shielding materials for electronic packaging systems, thus completing the present invention.

[0007] Specifically, the objectives of the present invention are as follows:

[0008] In the first aspect, a graphene thermal conductive film is provided, which is a composite film of graphene intercalated with metal nanoparticles, and the metal nanoparticles include any one or several of silver, aluminum, cobalt, nickel, gold, titanium, and chromium.

[0009] In the second aspect, a preparation method of a graphene thermal conductive film is provided, and the method includes:

[0010] Step 1, preparing an expanded graphene film;

[0011] Step 2, doping metal nanoparticles between the graphene layers of the expanded graphene film to obtain a graphene preform film;

[0012] Step 3, densifying the graphene preform film to prepare the graphene thermal conductive film.

[0013] In the third aspect, an application of the graphene thermal conductive film according to the first aspect in the fields of heat dissipation and heat equalization film materials, thermal interface materials, electrochemical energy storage materials or electromagnetic shielding materials for electronic packaging systems is provided.

[0014] The beneficial effects of the present invention include:

[0015] (1) The graphene thermal conductive film provided by the present invention dopes metal nanoparticles between the graphene layers, so that the normal thermal conductivity of graphene is significantly improved, thereby effectively improving the comprehensive heat dissipation characteristics of graphene, and the normal thermal conductivity reaches 175 - 400 W / mK.

[0016] (2) The preparation method of the graphene thermal conductive film provided by the present invention is simple in operation and remarkable in strengthening effect. By means of suction filtration doping with metal ions and high-temperature pyrolysis reduction, metal nanoparticles can enter the interlayer of graphene to form a stable chemical bonding structure; the metal nanoparticles form a tight bonding structure with carbon atoms in the interlayer of graphene, providing a fast channel for the transmission of thermal phonons along the interlayer; in addition, the doping of metal nanoparticles does not affect the original flexible and deformable characteristics of the graphene thermal conductive film.

[0017] (3) The graphene thermal conductive film provided by the present invention is conducive to maintaining high-efficiency and stable heat dissipation capacity under high-temperature and thermal stress conditions in the integrated circuit packaging system, and can be quickly mass-produced and manufactured in terms of heat dissipation and heat equalization film materials, thermal interface materials, electrochemical energy storage materials or electromagnetic shielding materials in the electronic packaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By reading the following detailed description of the preferred specific embodiments, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the following described drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0019] In the drawings:

[0020] Figure 1 shows a schematic structural diagram of a suction filtration device according to a preferred embodiment of the present invention;

[0021] Figure 2 shows a cross-sectional SEM characterization diagram of the graphene thermal conductive film prepared in Example 1;

[0022] Figure 3 shows a comparison diagram of the normal thermal conductivity coefficients of the graphene thermal conductive films prepared in Examples 1 to 3 and Comparative Example 1.

[0023] Description of the reference numerals in the drawings:

[0024] 1 - open container;

[0025] 2 - graphene thermal conductive film;

[0026] 3 - fixture;

[0027] 4 - flange;

[0028] 5 - interface;

[0029] 6 - storage bottle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following will refer to the attachedFigures 1 to 3 Specific embodiments of the present invention will be described in more detail. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0031] It should be noted that in the description of the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. The specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of components as the criterion for distinction. For example, the terms "comprising" or "including" mentioned throughout the specification and claims are open-ended terms, so they should be interpreted as "including but not limited to". The subsequent description of the specification is for the purpose of implementing the preferred embodiments of the present invention, but the description is for the general principles of the specification and is not used to limit the scope of the present invention. The protection scope of the present invention shall be subject to what is defined by the appended claims.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "front", "rear", etc. is based on the orientation or positional relationship in the working state of the present invention. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0033] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific embodiments as examples in conjunction with the drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

[0034] On the one hand, a graphene thermal conductive film provided by the present invention is a graphene interlayer doped with metal nanoparticles composite film, that is, the metal nanoparticles are compounded into the graphene interlayer. The metal nanoparticles include any one or several of silver, aluminum, cobalt, nickel, gold, titanium, and chromium, preferably cobalt, nickel or aluminum, and more preferably aluminum.

[0035] Taking the doping of cobalt, nickel or aluminum as an example, the present invention provides corresponding data of the normal thermal conductivity, which proves that the normal thermal conductivity of the graphene thermal conductive film doped with the corresponding metal nanoparticles is increased by 16-160% compared with that of the graphene thermal conductive film without doped metal nanoparticles; Since silver, aluminum, cobalt, nickel, gold, titanium, and chromium metal nanoparticles all have high specific heat, therefore, the present invention can be doped with any one or any combination of silver, aluminum, cobalt, nickel, gold, titanium, and chromium, so that the obtained graphene product after doping thus has good heat exchange capacity; In addition, the metal nanoparticles may also play a role in lubricating the interlayer flow channels of graphene.

[0036] Since there is no in-depth theoretical research on this in the prior art, according to the inventor's practice, the inventor believes that this may be because some metal nanoparticles that have passed practical tests can have good synergy and matching characteristics with graphene in terms of heat conduction, so that these metal nanoparticles become efficient heat transfer media for graphene. In fact, the inventor further studied metal nanoparticles represented by silver, aluminum, cobalt, nickel, gold, titanium, and chromium, and found that: any one or any combination of them can enable the metal nanoparticles to form a tight bonding structure with carbon atoms between graphene layers, and the metal nanoparticles and the graphene layers construct a thermal conduction phonon channel, further increasing the normal thermal conductivity of the graphene thermal conductive film.

[0037] Regarding the size of the metal nanoparticles, further research found that if the particle size of the metal particles is too large, they are prone to sedimentation and even agglomeration, and it is difficult to be applied industrially. When the particle size of the metal particles is in the nanometer size, the metal nanoparticles are not easy to sediment, which is conducive to uniform attachment between graphene layers. Therefore, this limits the upper and lower limits of the size of the metal nanoparticles.

[0038] Furthermore, the particle size distribution of the metal nanoparticles ranges from 10 to 90 nm.

[0039] According to the present invention, the doping content of the metal nanoparticles is 1-5 wt.% in the composite film. For example, the nickel doping amount is 1-5 wt.% of the graphene thermal conductive film, the cobalt doping amount is 1.2-4.6 wt.% of the graphene thermal conductive film, and the aluminum doping amount is 1-3.9 wt.% of the graphene thermal conductive film. Especially for aluminum, even if its doping amount is only 1 wt.% of the graphene thermal conductive film, the normal thermal conductivity of the prepared graphene thermal conductive film reaches ~400 W / mK.

[0040] [[ID=1 / 15]]According to the present invention, the thickness of the graphene thermal conductive film is 10-150 μm, preferably 50-120 μm, more preferably 80-110 μm, such as 80 μm.

[0041] According to the present invention, the normal thermal conductivity of the graphene thermal conductive film is between 175 and 400 W / mK, which is 16 to 160% higher than that of the graphene thermal conductive film without doped metal nanoparticles.

[0042] On the other hand, according to a preparation method of a graphene thermal conductive film provided by the present invention, the method includes:

[0043] Step 1, preparing an expanded graphene film;

[0044] Step 2, doping metal nanoparticles between graphene layers of the expanded graphene film to obtain a graphene preform film;

[0045] Step 3, performing densification treatment on the graphene preform film to prepare the graphene thermal conductive film.

[0046] The above preparation method of the graphene thermal conductive film is described in detail below.

[0047] Step 1, preparing an expanded graphene film.

[0048] According to a preferred embodiment, the step 1 includes the following sub-steps:

[0049] Step 1-1, mixing graphene oxide with a dispersant to obtain a graphene oxide slurry;

[0050] Step 1-2, coating the graphene oxide slurry to obtain a graphene oxide film;

[0051] Step 1-3, performing graphitization treatment on the graphene oxide film to prepare the expanded graphene film.

[0052] Among them, in step 1-1, the sheet diameter of the graphene oxide is between 50 and 200 μm, preferably 100 to 160 μm, such as 150 μm.

[0053] In step 1-1, the dispersant is water or an organic solvent, and the organic solvent is preferably selected from any one or several of ethanol, methanol, acetone, ethylene glycol, dimethyl sulfoxide, tetrahydrofuran, N, N-dimethylformamide, and more preferably ethanol which is volatile and easy to remove.

[0054] Among them, graphene oxide has good dispersibility in both water and organic solvents. Graphene oxide has stronger dispersibility in dimethyl sulfoxide, tetrahydrofuran, and N, N-dimethylformamide, but it is almost impossible to remove completely subsequently. Ethanol is particularly prominent as a dispersant because of its volatility and non-toxicity.

[0055] Further, the mass of the graphene oxide is 10-40 wt.% of the mass of the dispersant, preferably 15-25 wt.%, such as 20 wt.%.

[0056] In step 1-1, after the graphene oxide and the dispersant are mixed, it is preferable to further add a foaming agent to obtain a graphene oxide slurry. The foaming agent is selected from any one or more of acids, alkali metals, and salts, preferably potassium permanganate, nitric acid, hydrogen peroxide, potassium chlorate, etc. having an oxidizing effect, and more preferably nitric acid.

[0057] According to the present invention, the foaming agent is used to generate bubbles in the graphene oxide, increase its interlayer spacing, and provide a transport channel for the intercalated elements.

[0058] Further, the dosage of the foaming agent is 2-10 vol% of the dispersant, preferably 4-8 vol%, such as 5 vol%.

[0059] In step 1-2, the coating method can be spin coating, spraying or inkjet printing, preferably spraying. Among them, the graphene oxide film prepared by spraying has a larger size, controllable thickness, a wider range of substrate selection, lower preparation cost and shorter time consumption.

[0060] Further, the thickness of the graphene oxide film is 10-500 μm, preferably 50-250 μm, more preferably 100-200 μm, such as 200 μm.

[0061] In step 1-3, the graphitization temperature is 800-3200 °C, preferably 1800-3200 °C, more preferably 2600-3200 °C, such as 3200 °C. Within the above temperature range, the carbon atoms in the graphene undergo an ordered rearrangement under high energy to improve the thermal phonon transport performance.

[0062] Further, the graphitization time is 8-20 h, preferably 10-15 h, more preferably 12 h.

[0063] Among them, as the graphitization holding time prolongs, the carbon atoms undergo an ordered rearrangement under high energy, and the efficiency of improving the thermal phonon transport performance increases accordingly. However, too long a time will not have an obvious impact on the improvement of the thermal phonon transport performance. Within the above temperature range, especially when the holding time is 12 h, it is the best.

[0064] In step 1-3, the porosity of the expanded graphene film is 5-30%. Further, the porosity of the expanded graphene film is 15-22%. For example, the porosity of the expanded graphene film is 20%.

[0065] Step 2: Dope metal nanoparticles between the graphene layers of the expanded graphene film to obtain a graphene preform film.

[0066] According to the preferred embodiment, Step 2 includes the following sub-steps:

[0067] Step 2-1: Perform suction filtration on the expanded graphene film with a metal salt solution to obtain a composite film;

[0068] Step 2-2: Perform reduction treatment on the composite film to obtain a graphene preform film.

[0069] In Step 2-1, the metal salt is selected from any one or more of silver nitrate (Ag(NO3)2), aluminum chloride hexahydrate (AlCl3·6H2O), cobalt chloride (CoCl2), nickel chloride (NiCl2), gold chloride (AuCl3), titanium tetrachloride (TiCl4), and chromium chloride hexahydrate (CrCl3·6H2O), preferably nickel chloride (NiCl2), cobalt chloride (CoCl2), or aluminum chloride hexahydrate (AlCl3·6H2O), such as aluminum chloride hexahydrate (A1Cl3·6H2O).

[0070] In Step 2-1, first prepare a metal salt solution from the metal salt, and then perform vacuum suction filtration along the cross-sectional direction of the expanded graphene film to form a composite film with metal cations doped between the graphene layers. During this process, metal ions are uniformly loaded between the graphene layers along the cross-sectional direction of the expanded graphene film.

[0071] Among them, the metal ion concentration in the metal salt solution is 5-30 wt.%, preferably 15-25 wt.%, and more preferably 20 wt.%.

[0072] In the present invention, the lower the metal ion concentration, the lower the content of metal nanoparticles attached to the graphene thermal conductive film, and the phase thermal conductivity will not be significantly improved. When the metal ion concentration in the metal salt solution is 5-30 wt.%, especially 20 wt.%, the phase thermal conductivity is significantly improved, and there is no negative impact on the structure and properties of graphene.

[0073] In Step 2-1, the vacuum degree of the vacuum suction filtration is 50-100 kPa, such as 50 kPa.

[0074] According to the preferred embodiment, use as Figure 1Vacuum filtration is carried out using the shown suction filtration device. The suction filtration device includes an open container 1, a clamp 3, a flange 4, an interface 5, and a storage bottle 6. The expanded graphene film 2 is clamped by the clamp 3, and the expanded graphene film 2 is fixed using the flange 4. The open container 1 is used to hold the metal salt solution. The bottom of the clamp 3 is connected to the storage bottle 6, and the storage bottle 6 is provided with an interface 5 for connecting to a vacuum pump.

[0075] During use, first, the metal salt solution is placed in the open container 1 in advance; then, the expanded graphene film 2 is clamped by the clamp 3, and the expanded graphene film 2 is fixed using the flange 4; after that, a vacuum pump is connected at the interface 5 for vacuum filtration. At this time, the metal salt solution is transmitted along the cross-sectional direction of the expanded graphene film 2 to achieve doping of metal ions, and the generated filtrate is collected through the storage bottle 6.

[0076] In step 2-2, reduction is achieved through high-temperature pyrolysis, which is beneficial to the tight bonding of metal ions and graphene carbon atoms to form a phonon transport channel for heat conduction between graphene layers. At the same time, it is also beneficial to further improve the stability of graphene. The inventors of the present invention have found that both the high-temperature pyrolysis temperature and time have important effects on the morphology and particle size of metal nanoparticles. Excessive temperature and / or too long time are likely to cause coarsening of metal particles, thereby affecting the subsequent densification degree.

[0077] In step 2-2, the temperature of high-temperature pyrolysis is 600-1500 °C, preferably 650-900 °C, more preferably 700 °C; the time of high-temperature pyrolysis is 1-30 min, preferably 3-110 min, more preferably 5 min.

[0078] In step 2-2, the protective gas for high-temperature pyrolysis is a reducing gas such as a hydrogen-argon mixture, carbon monoxide gas, hydrogen gas, etc., an inert gas such as helium gas, argon gas, a helium-argon mixture, or other protective gases such as nitrogen gas; preferably a reducing gas, for example, a hydrogen-argon mixture is used. The protective gas during high-temperature pyrolysis can effectively prevent metal nanoparticles from being oxidized.

[0079] Furthermore, the gas flow rate of the protective gas used is 2-50 mL / min, preferably 10-30 mL / min, more preferably 20 mL / min.

[0080] In step 2-2, the methods of high-temperature pyrolysis include but are not limited to induction heating, plasma heating, vacuum resistance heating, etc.

[0081] In step 2, the thickness of the graphene prefabricated film is 100-300 μm. Further, the thickness of the graphene prefabricated film is 150-200 μm. For example, the thickness of the graphene prefabricated film is 200 μm.

[0082] In step 2, metal nanoparticles enter the interlayer of graphene through suction filtration doping of metal ions and high-temperature pyrolysis reduction to form a stable chemical bonding structure. The metal nanoparticles form a tight bonding structure with carbon atoms in the interlayer of graphene, providing a fast channel for the transmission of heat-conducting phonons along the interlayer. In particular, the graphene thermal conductive film finally prepared by suction filtration doping of metal ions and high-temperature pyrolysis reduction has excellent in-plane thermal conductivity, which is beneficial for the graphene thermal conductive film to maintain high-efficiency and stable heat dissipation under high-temperature and thermal stress conditions in the integrated circuit packaging system. In addition, the doping of metal nanoparticles does not affect the original flexible and deformable characteristics of the graphene thermal conductive film.

[0083] Step 3: Densify the graphene prefabricated film to obtain the graphene thermal conductive film.

[0084] In step 3, the densification treatment method is vacuum calendering treatment to increase the plasticity of the graphene thermal conductive film and extend it into a dense film product.

[0085] In step 3, the pressure of vacuum calendering is 100 - 500 MPa, preferably 150 - 300 MPa, more preferably 200 MPa; the vacuum degree is 1 - 6 Pa, preferably 1 Pa.

[0086] Among them, with the increase of pressure or vacuum degree, the plasticity of the graphene thermal conductive film increases accordingly, but excessive pressure or vacuum degree may cause the graphene thermal conductive film to rupture. Within the above parameter range, the plasticity of the prepared graphene thermal conductive film is relatively good.

[0087] In step 3, the thickness of the graphene thermal conductive film obtained by vacuum calendering is 10 - 150 μm, preferably 50 - 120 μm, more preferably 80 - 110 μm, such as 80 μm; the content of doped metal nanoparticles is 1 - 5 wt.% of the graphene thermal conductive film.

[0088] In the present invention, the method for testing the normal thermal conductivity includes but is not limited to steady-state methods such as HotDisk, transient methods such as laser flash method, 3ω and transient thermoreflectance method (TDTR), etc.; preferably, the normal thermal conductivity of the graphene thermal conductive film is measured from the micro-nano scale by using the time-domain thermoreflectance method to accurately measure the normal thermal conductivity of the graphene thermal conductive film under the condition that both the sample plane size and thickness size are small.

[0089] In the third aspect, there is provided an application of the graphene thermal conductive film described in the first aspect or the graphene thermal conductive film prepared by the method described in the second aspect in the materials for heat dissipation and heat spreading film, thermal interface material, electrochemical energy storage material or electromagnetic shielding material in the electronic packaging system.

[0090] Examples

[0091] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not impose any limitation on the protection scope of the present invention.

[0092] Example 1

[0093] (1) Graphene oxide with a sheet diameter of ~150 μm was ultrasonically dispersed in absolute ethanol. The mass of the graphene oxide was 20 wt.% of the mass of the dispersant. Then, nitric acid was added and stirred evenly. The dosage of the nitric acid was 5 vol% of the dispersant, obtaining a graphene oxide slurry.

[0094] The graphene oxide slurry was electrostatically sprayed, dried, and peeled to obtain a graphene oxide film with a thickness of 200 μm.

[0095] The graphene oxide film was graphitized at 3200 °C for 12 h to prepare an expanded graphene film with a porosity of 20%.

[0096] (2) As Figure 1 shown, a nickel chloride solution with a nickel ion concentration of 20 wt.% was placed in an open container 1. The expanded graphene film 2 prepared in step (1) was clamped by a fixture 3, and the expanded graphene film 2 was fixed using a flange 4. Then, a vacuum pump was connected at the interface 5 for vacuum filtration. At this time, the nickel chloride solution was transmitted along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate was collected by a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with nickel ions intercalated between graphene layers was obtained. The composite film was pyrolyzed at a high temperature of 700 °C in an argon-hydrogen mixture (gas flow rate of 20 mL / min) for 10 min using an induction heating device to obtain a graphene preform film with a thickness of 150 μm.

[0097] (3) The graphene preform film obtained in step (2) was subjected to vacuum rolling at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film. The prepared graphene thermal conductive film had a thickness of 80 μm. A partial cross-section SEM is as Figure 2 shown. It can be seen that nickel nanoparticles were uniformly loaded between the graphene layers. The tight bonding structure between the nickel nanoparticles and carbon atoms constructed a thermal conductive phonon channel between the graphene layers, which was beneficial to the improvement of the normal thermal conductivity coefficient of graphene. The particle size of the nickel nanoparticles was 10 - 40 nm, and the average particle size was 32 nm. After detection, the nickel doping amount was 3 wt.% of the graphene thermal conductive film.

[0098] The normal thermal conductivity coefficient of the prepared graphene thermal conductive film was tested by the time-domain thermoreflectance method, and the results are as Figure 3 shown ( Figure 3In the case of GN@Ni, it can be seen that the normal thermal conductivity coefficient of the graphene thermal conductive film with nickel nanoparticles added reaches ~175 W / mK.

[0099] Example 2

[0100] (1) Graphene oxide with a sheet diameter of ~150 μm was ultrasonically dispersed in absolute ethanol. The mass of the graphene oxide was 20 wt.% of the mass of the dispersant. Then, nitric acid was added and stirred evenly. The dosage of the nitric acid was 5 vol% of the dispersant to obtain a graphene oxide slurry.

[0101] The graphene oxide slurry was electrostatically sprayed, dried, and peeled to obtain a graphene oxide film with a thickness of 200 μm.

[0102] The graphene oxide film was graphitized at 3200 °C for 12 h to obtain an expanded graphene film with a porosity of 20%.

[0103] (2) As Figure 1 shown, a cobalt chloride solution with a cobalt ion concentration of 20 wt.% was placed in the open container 1. The expanded graphene film 2 prepared in step (1) was clamped by the clamp 3, and the expanded graphene film 2 was fixed using the flange 4. Then, a vacuum pump was connected at the interface 5 for vacuum filtration. At this time, the cobalt chloride solution was transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate was collected through the receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with cobalt ions intercalated between the graphene layers was obtained. The composite film was pyrolyzed at high temperature for 5 min at 800 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) using an induction heating device to obtain a graphene preform film ( Figure 3 denoted as GN@Co in

[0104] (3) The graphene preform film obtained in step (2) was subjected to vacuum rolling at a pressure of 200 MPa and a vacuum degree of 1 Pa to obtain a graphene thermal conductive film. The thickness of the obtained graphene thermal conductive film was 80 μm, the particle size of the cobalt nanoparticles was 15 - 35 nm, and the average particle size was 28 nm. After detection, the cobalt doping amount was 2 wt.% of the graphene thermal conductive film.

[0105] The normal thermal conductivity coefficient of the prepared graphene thermal conductive film was tested by the time-domain thermoreflectance method. The results are as Figure 3 shown ( Figure 3 denoted as GN@Co in

[0106] Example 3

[0107] (1) Ultrasonically disperse graphene oxide with a sheet diameter of ~150 μm in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then, add nitric acid and stir evenly. The dosage of the nitric acid is 5 vol% of the dispersant to obtain a graphene oxide slurry;

[0108] Electrostatically spray the graphene oxide slurry, dry and peel it to obtain a graphene oxide film with a thickness of 200 μm;

[0109] Graphitize the graphene oxide film at 3200 °C for 12 h to obtain an expanded graphene film with a porosity of 20%.

[0110] (2) As Figure 1 shown, place an aluminum chloride solution with an aluminum ion concentration of 20 wt.% in an open container 1. Clamp the expanded graphene film 2 prepared in step (1) with a clamp 3 and fix the expanded graphene film 2 with a flange 4. Then, connect a vacuum pump at the interface 5 for vacuum filtration. At this time, the aluminum chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected through a receiving bottle 6. After vacuum filtration at 50 kPa for 5 h, a composite film with aluminum ions doped between the graphene layers is obtained. Pyrolyze the composite film at 700 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) for 5 min using an induction heating device to obtain a graphene preform film with a thickness of 200 μm.

[0111] (3) Perform vacuum rolling treatment on the graphene preform film obtained in step (2) at a pressure of 200 MPa and a vacuum degree of 1 Pa to obtain a graphene thermal conductive film ( Figure 3 represented by GN@Al in

[0112] ). The thickness of the obtained graphene thermal conductive film is 80 μm, the particle size of the aluminum nanoparticles is 20 - 90 nm, and the average particle size is 45 nm as detected. The aluminum doping amount is 1 wt.% of the graphene thermal conductive film. Figure 3 shown ( Figure 3 represented by GN@Al in

[0113] Example 4

[0114] (1) Ultrasonically disperse graphene oxide with a sheet diameter of ~150 μm in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then, add nitric acid and stir evenly. The dosage of the nitric acid is 5 vol% of the dispersant to obtain a graphene oxide slurry;

[0115] Electrostatically spray the graphene oxide slurry, dry and peel it to obtain a graphene oxide film with a thickness of 200 μm;

[0116] Graphitize the graphene oxide film at 3200 °C for 12 h to obtain an expanded graphene film.

[0117] (2) As shown in Figure 1 the figure, place a nickel chloride solution with a nickel ion concentration of 10 wt.% in the open container 1. Clamp the expanded graphene film 2 prepared in step (1) with the clamp 3 and fix the expanded graphene film 2 using the flange 4; then, connect a vacuum pump at the interface 5 for vacuum filtration. At this time, the nickel chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected by the receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with nickel ions doped between the graphene layers is obtained; heat the composite film pyrolytically at a high temperature of 700 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) for 10 min using an induction heating device to obtain a graphene preform film.

[0118] (3) Perform vacuum rolling treatment on the graphene preform film obtained in step (2) at a pressure of 200 MPa and a vacuum degree of 1 Pa to obtain a graphene thermal conductive film. After testing, the nickel doping amount is 1 wt.% of the graphene thermal conductive film.

[0119] Example 5

[0120] (1) Ultrasonically disperse graphene oxide with a particle diameter of ~150 μm in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then, add nitric acid and stir evenly. The dosage of the nitric acid is 5 vol.% of the dispersant to obtain a graphene oxide slurry;

[0121] Electrostatically spray the graphene oxide slurry, dry and peel it to obtain a graphene oxide film with a thickness of 200 μm;

[0122] Graphitize the graphene oxide film at 3200 °C for 12 h to obtain an expanded graphene film.

[0123] (2) As shown in Figure 1As shown in the figure, a nickel chloride solution with a nickel ion concentration of 40 wt.% is placed in an open container 1. The expanded graphene film 2 prepared in step (1) is clamped by a fixture 3, and the expanded graphene film 2 is fixed by a flange 4. Then, a vacuum pump is connected at the interface 5 for vacuum filtration. At this time, the nickel chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected by a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with nickel ions doped between graphene layers is obtained. The composite film is pyrolyzed at a high temperature of 700 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) for 10 min using an induction heating device to obtain a graphene preform film.

[0124] (3) The graphene preform film obtained in step (2) is subjected to vacuum rolling treatment at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film. After detection, the nickel doping amount is 5 wt.% of the graphene thermal conductive film.

[0125] Example 6

[0126] (1) Graphene oxide with a sheet diameter of ~150 μm is ultrasonically dispersed in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then, nitric acid is added and stirred evenly. The dosage of the nitric acid is 5 vol% of the dispersant to obtain a graphene oxide slurry.

[0127] The graphene oxide slurry is electrostatically sprayed, dried, and peeled to obtain a graphene oxide film with a thickness of 200 μm.

[0128] The graphene oxide film is graphitized at 3200 °C for 12 h to prepare an expanded graphene film.

[0129] (2) As Figure 1 shown in the figure, a cobalt chloride solution with a cobalt ion concentration of 15 wt.% is placed in an open container 1. The expanded graphene film 2 prepared in step (1) is clamped by a fixture 3, and the expanded graphene film 2 is fixed by a flange 4. Then, a vacuum pump is connected at the interface for vacuum filtration. At this time, the cobalt chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected by a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with cobalt ions doped between graphene layers is obtained. The composite film is pyrolyzed at a high temperature of 800 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) for 5 min using an induction heating device to obtain a graphene preform film.

[0130] (3) The graphene preform film obtained in step (2) is subjected to vacuum rolling treatment at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film. After detection, the cobalt doping amount is 1.2 wt.% of the graphene thermal conductive film.

[0131] Example 7

[0132] (1) Ultrasonically disperse graphene oxide with a sheet diameter of ~150 μm in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then add nitric acid and stir evenly. The dosage of the nitric acid is 5 vol% of the dispersant to obtain a graphene oxide slurry;

[0133] Perform electrostatic spraying on the graphene oxide slurry, dry and peel it to obtain a graphene oxide film with a thickness of 200 μm;

[0134] Graphitize the graphene oxide film at 3200 °C for 12 h to obtain an expanded graphene film.

[0135] (2) As Figure 1 shown, place a cobalt chloride solution with a cobalt ion concentration of 40 wt.% in an open container 1. Clamp the expanded graphene film 2 prepared in step (1) with a fixture 3 and fix the expanded graphene film 2 using a flange 4; then, connect a vacuum pump at the interface 5 for vacuum filtration. At this time, the cobalt chloride solution is transmitted along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected through a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with cobalt ions doped between the graphene layers is obtained; heat the composite film pyrolytically at a high temperature of 800 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) for 5 min using an induction heating device to obtain a graphene preform film.

[0136] (3) Perform vacuum rolling on the graphene preform film obtained in step (2) at a pressure of 200 MPa and a vacuum degree of 1 Pa to obtain a graphene thermal conductive film. After testing, the cobalt doping amount is 4.6 wt.% of the graphene thermal conductive film.

[0137] Example 8

[0138] (1) Ultrasonically disperse graphene oxide with a sheet diameter of ~150 μm in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then add nitric acid and stir evenly. The dosage of the nitric acid is 5 vol% of the dispersant to obtain a graphene oxide slurry;

[0139] Perform electrostatic spraying on the graphene oxide slurry, dry and peel it to obtain a graphene oxide film with a thickness of 200 μm;

[0140] Graphitize the graphene oxide film at 3200 °C for 12 h to obtain an expanded graphene film.

[0141] (2) As Figure 1As shown in the figure, an aluminum chloride solution with an aluminum ion concentration of 30 wt.% is placed in an open container 1. The expanded graphene film 2 prepared in step (1) is clamped by a fixture 3, and the expanded graphene film 2 is fixed by a flange 4. Then, a vacuum pump is connected at the interface 5 for vacuum filtration. At this time, the aluminum chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected by a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with aluminum ions doped between graphene layers is obtained. The composite film is pyrolyzed at a high temperature of 700 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) using an induction heating device for 5 min to obtain a graphene preform film.

[0142] (3) The graphene preform film obtained in step (2) is subjected to vacuum rolling treatment at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film. After testing, the aluminum doping amount is 2.2 wt.% of the graphene thermal conductive film.

[0143] Example 9

[0144] (1) Graphene oxide with a particle diameter of ~150 μm is ultrasonically dispersed in absolute ethanol. The mass of the graphene oxide is 20 wt.% of the mass of the dispersant. Then, nitric acid is added and stirred evenly. The dosage of the nitric acid is 5 vol.% of the dispersant to obtain a graphene oxide slurry.

[0145] The graphene oxide slurry is electrostatically sprayed, dried, and peeled to obtain a graphene oxide film with a thickness of 200 μm.

[0146] The graphene oxide film is graphitized at 3200 °C for 12 h to prepare an expanded graphene film.

[0147] (2) As Figure 1 shown in the figure, an aluminum chloride solution with an aluminum ion concentration of 40 wt.% is placed in an open container 1. The expanded graphene film 2 prepared in step (1) is clamped by a fixture 3, and the expanded graphene film 2 is fixed by a flange 4. Then, a vacuum pump is connected at the interface 5 for vacuum filtration. At this time, the aluminum chloride solution is transported along the cross-sectional direction of the expanded graphene film 2, and the generated filtrate is collected by a receiving bottle 6. After vacuum filtration at a pressure of 50 kPa for 5 h, a composite film with aluminum ions doped between graphene layers is obtained. The composite film is pyrolyzed at a high temperature of 700 °C in an argon-hydrogen mixture (gas flow rate: 20 mL / min) using an induction heating device for 5 min to obtain a graphene preform film.

[0148] (3) The graphene preform film obtained in step (2) is subjected to vacuum rolling treatment at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film. After testing, the aluminum doping amount is 3.9 wt.% of the graphene thermal conductive film.

[0149] Comparative Example

[0150] Comparative Example 1

[0151] (1) Graphene oxide with a sheet diameter of ~150 μm was ultrasonically dispersed in absolute ethanol. The mass of the graphene oxide was 20 wt.% of the mass of the dispersant. Then, nitric acid was added and stirred evenly. The dosage of the nitric acid was 5 vol% of the dispersant, obtaining a graphene oxide slurry;

[0152] The graphene oxide slurry was electrostatically sprayed, dried, and peeled to obtain a graphene oxide film with a thickness of 200 μm;

[0153] The graphene oxide film was graphitized at 3200 °C for 5 h to prepare an expanded graphene film with a porosity of 10%.

[0154] (2) The expanded graphene film obtained in step (1) was subjected to vacuum rolling treatment at a pressure of 200 MPa and a vacuum degree of 1 Pa to prepare a graphene thermal conductive film ( Figure 3 denoted as Pure GN in the text). The thickness of the prepared graphene thermal conductive film was 80 μm.

[0155] The normal thermal conductivity of the prepared graphene thermal conductive film was tested by the time-domain thermoreflectance method. The results are as Figure 3 shown. It can be seen that the normal thermal conductivity of the graphene thermal conductive film was only ~150 W / mK.

[0156] Through Figure 3 it can be clearly seen that doping with nickel nanoparticles, cobalt nanoparticles, or aluminum nanoparticles can significantly improve the normal thermal conductivity of the graphene thermal conductive film.

[0157] The present invention has been described in detail above in combination with preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are only illustrative explanations of the present invention and do not constitute any limitation to the protection scope of the present invention. Without departing from the spirit and protection scope of the present invention, various improvements, equivalent substitutions, or modifications can be made to the technical content and its implementation manners of the present invention, and these all fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A graphene thermal conductive film, characterized in that, It is a composite film of graphene intercalated with metal nanoparticles. The metal nanoparticles include any one or several of silver, aluminum, cobalt, nickel, gold, titanium, and chromium, so as to enable the metal nanoparticles to form a tight bonding structure with carbon atoms between the graphene layers. A thermal conduction phonon channel is constructed between the metal nanoparticles and the graphene layers to further increase the normal thermal conductivity of the graphene thermal conduction film. Among them, The preparation method of the graphene thermal conduction film includes: Step 1, preparing an expanded graphene film; Step 2, doping metal nanoparticles between the graphene layers of the expanded graphene film to obtain a graphene preform film; Step 3, performing densification treatment on the graphene preform film to obtain the graphene thermal conduction film; The said Step 1 includes the following sub-steps: Step 1-1, mixing graphene oxide with a dispersant to obtain a graphene oxide slurry; Step 1-2, coating the graphene oxide slurry to obtain a graphene oxide film; Step 1-3, performing graphitization treatment on the graphene oxide film to obtain the expanded graphene film; By suction filtration doping metal ions and high-temperature pyrolysis reduction, metal nanoparticles can enter between the graphene layers to form a stable chemical bonding structure; The graphene thermal conduction film is doped with metal nanoparticles between the graphene layers, so that the normal thermal conductivity of graphene is significantly increased, and thus the comprehensive heat dissipation characteristics of graphene are effectively improved. The normal thermal conductivity reaches 175-400 W / mK.

2. The graphene thermal conductive film according to claim 1, wherein The particle size distribution of the metal nanoparticles is between 10 and 90 nm.

3. The graphene thermal conductive film according to claim 1, wherein The thickness of the composite film of the graphene thermal conduction film is 10-150 μm.

4. The graphene thermal conductive film according to claim 1, characterized in that In Step 1-3, the temperature of the graphitization is 800-3200 °C.

5. The graphene thermal conductive film according to claim 4, wherein The temperature of the graphitization is 1800-3200 °C.

6. The graphene thermal conductive film according to claim 1, wherein In Step 3, the densification treatment method is vacuum rolling treatment.

7. The application of the graphene thermal conduction film according to any one of claims 1 to 3 in the heat dissipation and heat spreading film material, thermal interface material, electrochemical energy storage material or electromagnetic shielding material of an electronic packaging system.

Images