Graphene composite material, preparation method thereof and electronic device

Abstract

The invention relates to a graphene composite material, a preparation method thereof and an electronic device. The graphene composite material comprises boron carbide and at least two graphene sheets, and adjacent graphene sheet layers are connected through boron carbide. The vertical heat conductivity coefficient of the graphene composite material is high.

Description

Technical Field

[0001] The present application relates to the technical field of materials, and particularly to a graphene composite material, a preparation method thereof, and an electronic device. Background Art

[0002] Electronic devices need to be maintained at a certain temperature to work reliably. When the temperature rises by 10°C, the reliability of the electronic device is reduced by 50%. Therefore, higher performance requirements are put forward for the heat dissipation materials in electronic devices. The theoretical thermal conductivity of copper is 400 W / (m·K), while the theoretical thermal conductivity of graphene can reach 5300 W / (m·K), which is 13 times that of copper, and the density is about 2 g / cm 3 , making it an ideal solid-state lightweight and highly thermally conductive material. Currently, the in-plane thermal conductivity of commercially available graphene films can reach more than 1000 W / (m·K), and they have been widely used in the fields of low-power electronic devices such as mobile phones and tablets.

[0003] Due to the two-dimensional characteristics of graphene materials, in the horizontal direction, carbon atoms are connected by C-C bonds, and the graphene film has a high in-plane thermal conductivity. However, in the vertical direction, only intermolecular forces exist between graphene layers, resulting in a vertical thermal conductivity generally less than 10 W / (m·K), which makes the heat flux of the graphene film not increase linearly with the increase in the thickness of the graphene film, greatly limiting the application of graphene films in the field of heat dissipation of high-power electronic devices.

[0004] Therefore, it is necessary to improve the traditional technology. Summary of the Invention

[0005] Based on this, the present application provides a graphene composite material with a relatively high vertical thermal conductivity, a preparation method thereof, and an electronic device.

[0006] The technical solution of the present application to solve the above technical problems is as follows.

[0007] In the first aspect of the present application, a graphene composite material is provided, which includes boron carbide and at least two graphene sheets, and adjacent graphene sheets are connected by the boron carbide between the layers.

[0008] In some embodiments, in the graphene composite material, the graphene sheet is a reduced graphene oxide sheet.

[0009] In some embodiments, in the graphene composite material, the mass content of the boron carbide in the graphene composite material is 1% - 20%.

[0010] In some embodiments, in the graphene composite material, the boron carbide includes boron carbide particles.

[0011] In some of these embodiments, in the graphene composite material, the particle size of the boron carbide particles is ≤200 nm; optionally, the boron carbide particles are 1 nm to 50 nm.

[0012] The second aspect of the present application provides a method for preparing a graphene composite material, comprising the following steps:

[0013] Sinter the precursor, where the precursor includes at least two graphene sheets and a boron source located between adjacent graphene sheet layers; the pressure of the sintering treatment is 35 MPa to 50 MPa, and the temperature of the sintering treatment is 2000°C to 2300°C.

[0014] In some of these embodiments, in the method for preparing a graphene composite material, the preparation of the precursor includes the following steps:

[0015] Perform a film-forming treatment on a mixed solution including graphene sheets and a boron source to prepare the precursor.

[0016] In some of these embodiments, in the method for preparing a graphene composite material, in the step of preparing the precursor, the graphene sheets are graphene oxide sheets;

[0017] And, after the film-forming treatment and before the sintering treatment step, it further includes a step of thermally reducing the film layer obtained by the film-forming treatment.

[0018] In some of these embodiments, in the method for preparing a graphene composite material, the thermal reduction treatment is carried out under vacuum conditions, and the temperature of the thermal reduction treatment is 300°C to 1500°C.

[0019] In some of these embodiments, in the method for preparing a graphene composite material, the thermal reduction treatment includes a first thermal reduction treatment and a second thermal reduction treatment carried out in sequence. The temperature of the first thermal reduction treatment is 300°C to 350°C, and the temperature of the second thermal reduction treatment is 1400°C to 1500°C.

[0020] In some of these embodiments, in the method for preparing a graphene composite material, before the second thermal reduction treatment and after the first thermal reduction treatment, it further includes a step of heating up to the temperature of the second thermal reduction treatment at a rate of 5°C / min to 10°C / min;

[0021] and / or, the time of the first thermal reduction treatment is 1 h to 5 h;

[0022] and / or, the time of the second thermal reduction treatment is 30 min to 60 min;

[0023] And / or, before the sintering treatment and after the second thermal reduction treatment, it further includes the steps of heating to the temperature of the sintering treatment at a rate of 5 °C / min to 8 °C / min and pressurizing to the pressure of the sintering treatment;

[0024] And / or, the time of the sintering treatment is 1 h to 2 h.

[0025] In some embodiments, in the method for preparing the graphene composite material, the boron source includes at least one of boric acid and ammonium borate.

[0026] In some embodiments, in the method for preparing the graphene composite material, in the mixed solution, the mass concentration of the graphene sheets is 5 g / L to 10 g / L;

[0027] And / or, the molar concentration of the boron source is 0.01 mol / L to 0.05 mol / L.

[0028] The third aspect of the present application provides an electronic device, including the graphene composite material provided in the first aspect or the graphene composite material prepared by the method for preparing the graphene composite material provided in the second aspect.

[0029] Beneficial effects:

[0030] The graphene composite material of the present application includes boron carbide and at least two graphene sheets, and adjacent graphene sheets are connected by boron carbide between the layers, connecting adjacent graphene sheets by chemical bonds, which can effectively improve the vertical thermal conductivity of the graphene composite material. Description of the drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application and more completely understand the present application and its beneficial effects, the following will briefly introduce the drawings required for use in the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.

[0032] Figure 1 SEM image of the boron carbide modified graphene film prepared by one embodiment. Detailed description of the specific embodiments

[0033] The following will further describe the present application in detail in combination with the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and not to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosed content of the present application more thorough and comprehensive.

[0034] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without departing from the connotation of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. For example, the features described or depicted as part of one embodiment can be combined in a suitable manner with another embodiment to produce a new embodiment. In addition, in the following description, a large number of specific details are given to provide a more thorough understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are for the purpose of describing embodiments and examples only and are not intended to limit this application.

[0036] Unless otherwise stated or there is a contradiction, the terms or phrases used herein have the following meanings:

[0037] In this application, when it comes to "a plurality of", "a variety of", "multiple times", etc., unless otherwise specified, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0038] As used herein, "its combination", "any combination thereof", "any combination mode thereof", etc. include all suitable combination modes of any two or more of the listed items.

[0039] In this application, the "suitable combination mode", "suitable mode", "any suitable mode", etc. mentioned herein, the "suitable" therein is subject to being able to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0040] In this application, "preferred", "better", "more preferably", "it is advisable" are only used to describe embodiments or examples with better effects. It should be understood that they do not constitute a limitation on the protection scope of this application. If there are multiple "preferred" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction relationship, each "preferred" is independent of each other.

[0041] In this application, "further", "even further", "especially", etc. are used for descriptive purposes to indicate differences in content, but should not be construed as a limitation on the protection scope of this application.

[0042] In this application, "optionally", "optional", and "option" mean having or not having, that is, either of the two parallel options of "having" or "not having". If the term "optional" appears in multiple places in a technical solution, without special instructions, and without contradictions or mutual restrictions, each "optional" is independent of each other.

[0043] In this application, in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumerative description and should be understood not to constitute a closed limitation on quantity.

[0044] In this application, for the technical features described in an open-ended manner, it includes both the closed technical solutions composed of the listed features and the open technical solutions containing the listed features.

[0045] In this application, regarding numerical intervals (i.e., numerical ranges), without special instructions, the distribution of the optional numerical values within the numerical interval is considered continuous, and it includes the two numerical endpoints of the numerical interval (i.e., the minimum value and the maximum value), as well as each numerical value between these two numerical endpoints. Without special instructions, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in the numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" allows for a broad inclusion of numerical interval types such as percentage intervals, ratio intervals, and ratio value intervals.

[0046] For the temperature parameters in this application, without special limitations, it allows both constant temperature treatment and fluctuations within a certain temperature range. It should be understood that the so-called constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0047] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, such as 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0048] In this application, for units related to data ranges, if a unit is only attached after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of both the left endpoint "3" and the right endpoint "5" are h (hours).

[0049] All documents mentioned in this application are cited herein for reference as if each document was cited individually for reference. Unless it conflicts with the inventive purpose and / or technical solution of this application, the cited documents involved in this application are cited in their entirety and for all purposes. When this application involves cited documents, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When this application involves cited documents, examples and preferred methods of the relevant technical features cited can also be incorporated as references into this application, but only to the extent that this application can be implemented. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or be amended adaptively according to the description in this application.

[0050] The mass or weight of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific content of each component, but also can represent the mass or weight ratio relationship between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is scaled up or down proportionally, it is within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass or weight mentioned in the specification of the embodiments of this application can be units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0051] Partially converting graphene into diamond can increase the thermal conductivity of the graphene film in the vertical direction (vertical thermal conductivity). However, converting graphene into diamond requires high temperature, high pressure (above 5 GPa) and long reaction time (tens of hours), especially the high-pressure environment, which is difficult to achieve mass production of large-sized materials.

[0052] Under high temperature and high pressure, graphene can be converted into graphyne, which has partial structures of both graphene and diamond and can limitedly improve the thermal conductivity of the material in the vertical direction. However, its conversion conditions are very harsh and it is difficult to achieve industrial production.

[0053] One embodiment of this application provides a graphene composite material, which includes boron carbide and at least two graphene sheets, and adjacent graphene sheets are connected by boron carbide between the layers.

[0054] In the graphene composite material of this application, adjacent graphene sheets are connected by chemical bonds, which can effectively increase the vertical thermal conductivity of the graphene composite material.

[0055] The graphene composite material provided by this application has a vertical thermal conductivity of up to more than 40 W / (m·K) and a horizontal thermal conductivity of up to more than 1200 W / (m·K), which can be used for heat dissipation in larger-power electronic devices with graphene films.

[0056] In some examples, the graphene composite material is composed of graphene sheets and boron carbide.

[0057] In some examples, the graphene sheets are reduced graphene oxide sheets.

[0058] In some examples, the graphene composite material is composed of reduced graphene oxide sheets and boron carbide.

[0059] In some examples, in the graphene composite material, the mass content of boron carbide is 1% - 20%.

[0060] It can be understood that the mass content of boron carbide in the graphene composite material includes but is not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%; in some examples, it can be within the range formed by any two of these point values as the end values, and the same applies hereinafter.

[0061] In some examples, in the graphene composite material, boron carbide includes boron carbide particles.

[0062] In some examples, in the graphene composite material, the particle size of the boron carbide particles ≤ 200 nm.

[0063] Furthermore, the boron carbide particles are 1 nm - 200 nm.

[0064] Optionally, the boron carbide particles are 1 nm - 50 nm.

[0065] It can be understood that the particle size of the boron carbide particles includes but is not limited to 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm.

[0066] In some examples, the graphene composite material is a graphene composite film.

[0067] Furthermore, the thickness of the graphene composite film is 0.02 mm - 0.1 mm.

[0068] An embodiment of this application provides a preparation method of a graphene composite material, including the following steps:

[0069] The precursor is sintered. The precursor includes at least two graphene sheets and a boron source located between adjacent graphene sheet layers; the pressure for sintering is 35 MPa to 50 MPa, and the temperature for sintering is 2000 °C to 2300 °C.

[0070] Sintering at appropriate pressure and temperature can promote the graphitization process of the precursor, promote densification, and cause the boron atoms in the boron source to react with the carbon atoms in the graphene sheets to form C-B bonds, so as to form boron carbide at some positions between the graphene sheet layers (there is a C-B bond between graphene and boron carbide), achieving interlayer chemical bonding, thereby improving the vertical thermal conductivity of the graphene composite material.

[0071] In some examples, in the method for preparing the graphene composite material, the time for sintering is 1 h to 2 h.

[0072] It can be understood that the pressure for sintering includes but is not limited to 35 MPa, 38 MPa, 40 MPa, 42 MPa, 45 MPa, 48 MPa, 50 MPa; the temperature for sintering includes but is not limited to 2000 °C, 2050 °C, 2100 °C, 2150 °C, 2200 °C, 2250 °C, 2300 °C, 2350 °C, 2400 °C, 2450 °C, 2500 °C; the time for sintering includes but is not limited to 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h.

[0073] In some examples, in the method for preparing the graphene composite material, the preparation of the precursor includes the following steps:

[0074] A mixed solution including graphene sheets and a boron source is subjected to film-forming treatment to prepare the precursor.

[0075] In some examples, in the method for preparing the graphene composite material, in the preparation step of the precursor, the graphene sheets are graphene oxide sheets;

[0076] Moreover, after the film-forming treatment and before the sintering treatment step, it further includes a step of thermally reducing the film layer obtained by the film-forming treatment.

[0077] In some examples, in the method for preparing the graphene composite material, the thermal reduction treatment is carried out under vacuum conditions, and the temperature for thermal reduction treatment is 300 °C to 1500 °C.

[0078] In some examples, in the method for preparing the graphene composite material, the thermal reduction treatment includes a first thermal reduction treatment and a second thermal reduction treatment carried out in sequence; the temperature of the first thermal reduction treatment is 300 °C to 350 °C, and the temperature of the second thermal reduction treatment is 1400 °C to 1500 °C.

[0079] In some of these examples, in the method for preparing the graphene composite material, before the second thermal reduction treatment and after the first thermal reduction treatment, there is also a step of heating to the temperature of the second thermal reduction treatment at a rate of 5°C / min to 10°C / min.

[0080] In some of these examples, in the method for preparing the graphene composite material, the time of the first thermal reduction treatment is 1 h to 5 h.

[0081] In some of these examples, in the method for preparing the graphene composite material, the time of the second thermal reduction treatment is 30 min to 60 min.

[0082] It can be understood that the temperature of the first thermal reduction treatment includes but is not limited to 300°C, 305°C, 310°C, 315°C, 320°C, 325°C, 330°C, 335°C, 340°C, 345°C, 350°C; further, the time of the first thermal reduction treatment includes but is not limited to 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h; further, the heating rate includes but is not limited to 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min; the temperature of the second thermal reduction treatment includes but is not limited to 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, 1460°C, 1470°C, 1480°C, 1490°C, 1500°C; further, the time of the second thermal reduction treatment includes but is not limited to 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min.

[0083] In the first thermal reduction treatment step, the boron source (boric acid) decomposes into boric anhydride and water, -COOH in the graphene oxide decomposes into CO2 and water, and at the same time, the free water adsorbed on the surface and inside of the membrane is removed. In the second thermal reduction treatment step, functional groups such as C-O-C and C=O in the graphene oxide further decompose into CO2 and water and are discharged under the condition of not applying pressure.

[0084] In some of these examples, in the method for preparing the graphene composite material, the vacuum degree of the thermal reduction treatment is 1×10 -3 Pa to 5×10 -3 Pa.

[0085] It can be understood that the vacuum degree of the thermal reduction treatment includes but is not limited to 1×10 -3 Pa, 2×10 -3 Pa, 3×10 -3 Pa, 4×10 -3 Pa, 5×10 -3 Pa.

[0086] When graphene oxide sheets are used as the raw material for preparation, a thermal reduction treatment is carried out before the sintering treatment to decompose the oxygen-containing functional groups in the graphene oxide into CO2 and water and discharge them, promoting the densification of the graphene composite material, and further improving the vertical thermal conductivity of the graphene composite material.

[0087] In some of these examples, in the method for preparing the graphene composite material, before the sintering treatment and after the second thermal reduction treatment, it further includes steps of heating to the temperature of the sintering treatment at a rate of 5 °C / min to 8 °C / min and pressurizing to the pressure of the sintering treatment.

[0088] It can be understood that the rate of heating to the temperature of the sintering treatment includes but is not limited to 5 °C / min, 5.5 °C / min, 6 °C / min, 6.5 °C / min, 7 °C / min, 7.5 °C / min, 8 °C / min.

[0089] In some of these examples, in the method for preparing the graphene composite material, the first thermal reduction treatment is carried out in an oven, and the second thermal reduction treatment and the sintering treatment are carried out in a hot press sintering furnace. It can be understood that the second thermal reduction treatment is not pressurized, and the sintering treatment is carried out under pressurized conditions.

[0090] Furthermore, the heating method of the hot press sintering furnace includes but is not limited to resistance heating, radiation heating or electromagnetic induction heating.

[0091] It can be understood that during the sintering treatment, the flatness of the hot press platen used needs to be ≤ 5 μm to ensure the flatness and performance consistency of the film after sintering.

[0092] In some of these examples, in the method for preparing the graphene composite material, in the mixed solution, the boron source includes at least one of boric acid and ammonium borate.

[0093] In some of these examples, in the method for preparing the graphene composite material, the mass concentration of graphene in the mixed solution is 5 g / L to 10 g / L.

[0094] It can be understood that in the mixed solution, the mass concentration of graphene includes but is not limited to 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, 10 g / L.

[0095] In some of these examples, in the method for preparing the graphene composite material, the molar concentration of the boron source in the mixed solution is 0.01 mol / L to 0.05 mol / L.

[0096] It can be understood that in the mixed solution, the molar concentration of the boron source includes but is not limited to 0.01 mol / L, 0.015 mol / L, 0.02 mol / L, 0.025 mol / L, 0.03 mol / L, 0.035 mol / L, 0.04 mol / L, 0.045 mol / L, 0.05 mol / L.

[0097] In some of these examples, in the method for preparing the graphene composite material, the solvent of the mixed solution is water.

[0098] In some of these examples, in the method for preparing the graphene composite material, the oxygen content of the graphene oxide sheets is 30 a.u.% to 35 a.u.%.

[0099] In some of these examples, in the method for preparing the graphene composite material, the carbon content of the graphene oxide sheets is 65 a.u.% to 70 a.u.%.

[0100] It can be understood that compared with graphene, graphene oxide has better dispersibility in water, effectively improving the uniformity of the generated boron carbide, thereby improving the vertical heat conduction uniformity of the graphene composite material.

[0101] It can be understood that in some of these examples, the preparation of the mixed solution includes: adding boron source (boric acid) powder or boron source (boric acid) solution to the graphene solution, and the boron source and graphene in the finally prepared mixed solution only need to meet the above concentration requirements; it can also be to mix a graphene solution with a lower concentration and a boron source (boric acid) solution with a lower concentration evenly, and then remove part of the solvent to make the boron source and graphene in the finally prepared mixed solution meet the above concentration requirements.

[0102] In some of these examples, in the method for preparing the graphene composite material, the preparation of the mixed solution includes the following steps:

[0103] Mix and stir a graphene oxide solution with a mass concentration of 1 g / L to 2 g / L and a boric acid solution with a molar concentration of 0.2 mol / L to 1 mol / L, so that boric acid and graphene oxide are evenly dispersed, and then heat to remove part of the solvent, so that the mass concentration of graphene oxide in the mixed solution is 5 g / L to 10 g / L, and the molar concentration of the boron source is 0.01 mol / L to 0.05 mol / L.

[0104] Furthermore, the heating temperature is 60°C to 80°C. It can be understood that the step of heating to remove the solvent can be to evacuate to accelerate the volatilization of the solvent.

[0105] In some of these examples, in the method for preparing the graphene composite material, the film-forming treatment of the mixed solution includes:

[0106] Form a wet film from the mixed solution and form a film layer after drying.

[0107] In some of these examples, the thickness of the film layer is 0.04 mm to 0.2 mm.

[0108] In some of these examples, the drying temperature is 100°C to 120°C.

[0109] In some of these examples, the step of forming a wet film from the mixed solution includes:

[0110] Place the mixed solution on a substrate to form a wet film on the substrate.

[0111] In some of these examples, in the preparation method of the graphene composite material, the substrate and the film layer on the substrate are subjected to a first thermal reduction treatment together, and then the substrate is removed for a second thermal reduction treatment.

[0112] In some of these examples, in the preparation method of the graphene composite material, the substrate includes but is not limited to at least one of polyimide and polytetrafluoroethylene (PTFE).

[0113] It can be understood that the melting point of the substrate needs to be lower than the temperature of the first thermal reduction treatment.

[0114] In some of these examples, in the preparation method of the graphene composite material, after the sintering treatment, the temperature and pressure are reduced, and it is cooled with the furnace.

[0115] In some specific examples, the preparation method of the graphene composite material includes the following steps:

[0116] Mix and stir an aqueous solution of graphene oxide with a mass concentration of 1 g / L to 2 g / L and an aqueous solution of boric acid with a molar concentration of 0.2 mol / L to 1 mol / L. After the boric acid and graphene oxide are uniformly dispersed, heat to remove part of the water to obtain a mixed solution; the mass concentration of graphene oxide in the mixed solution is 5 g / L to 10 g / L, and the molar concentration of the boron source is 0.01 mol / L to 0.05 mol / L;

[0117] Place the mixed solution on a substrate to form a wet film on the substrate, and form a film layer after drying;

[0118] After the substrate and the film layer on the substrate are subjected to a first thermal reduction treatment together, the substrate is removed for a second thermal reduction treatment to prepare a precursor; the temperature of the first thermal reduction treatment is 300°C to 350°C, and the temperature of the second thermal reduction treatment is 1400°C to 1500°C;

[0119] Sinter the precursor, the pressure of the sintering treatment is 35 MPa to 50 MPa, and the temperature of the sintering treatment is 2000°C to 2500°C.

[0120] It can be understood that the method for preparing the graphene composite material provided by the present application can prepare the graphene composite material provided above, which has high vertical thermal conductivity; in other words, the graphene composite material provided by the present application can be prepared under relatively mild conditions.

[0121] An embodiment of the present application provides an electronic device, including the above graphene composite material or the graphene composite material prepared by the above method for preparing the graphene composite material.

[0122] It can be understood that the electrical device provided by the present application, including the above graphene composite material or the graphene composite material prepared by the above method for preparing the graphene composite material, can endow the electrical device with good thermal conductivity.

[0123] The following further describes the present application in detail in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0124] The solutions used in the following examples and comparative examples are all aqueous solutions.

[0125] Example 1

[0126] (1) At room temperature, take 1 L of a 2 g / L graphene oxide solution, where the carbon content of the graphene oxide is 65 - 70 a.u.%, and the oxygen content is 30 - 35 a.u.%; then add 10 mL of a 1 mol / L boric acid solution and stir for 4 h to uniformly disperse the boric acid and graphene oxide, obtaining a graphene oxide boric acid solution.

[0127] (2) Heat the graphene oxide boric acid solution prepared in step (1) to 80 °C, evacuate, and continuously stir to obtain a mixed solution. The mass concentration of graphene oxide in the mixed solution is 10 g / L, and the molar concentration of boric acid in the mixed solution is 0.05 mol / L.

[0128] (3) Place the mixed solution prepared in step (2) on a coater, use a 0.1 mm thick polyimide film as the substrate, coat a wet film, and then dry it at 120 °C for 2 h to obtain a graphene oxide boric acid film with a thickness of about 0.2 mm.

[0129] (4) Put the graphene oxide boric acid film prepared in step (3) and the polyimide substrate together into a vacuum oven and bake at 300 °C for 5 h under vacuum (the first thermal reduction treatment) to prepare boric acid-modified graphene oxide.

[0130] (5) Peel the boric acid-modified graphene oxide prepared in step (4) from the polyimide substrate and place it in a hot press sintering furnace. The flatness of the hot press punch used is ≤5 μm; at 10 -3Under a Pa vacuum, the temperature was raised to 1500 °C at a rate of 10 °C / min for the second thermal reduction treatment for 30 min; then the temperature was raised to 2200 °C at a rate of 5 °C / min. During this process, the pressure was gradually increased to 35 MPa, and sintering treatment was carried out under isothermal and isobaric conditions for 1 h; then the pressure was unloaded, and the temperature was cooled to below 200 °C with the furnace to obtain a boron carbide modified graphene film (graphene composite material). The SEM image is as shown in Figure 1 shown; the mass content of boron carbide in the graphene composite material is 10%, the thickness is 0.1 mm, the vertical thermal conductivity is 40 W / (m·K), and the horizontal thermal conductivity is 1200 W / (m·K).

[0131] Among them, Figure 1 the particles in are boron carbide nanoparticles, and the graphene sheets are connected by boron carbide nanoparticles.

[0132] Example 2

[0133] It is basically the same as Example 1, the difference is that the step of the second thermal reduction treatment is omitted. The step (5) of Example 2 is as follows:

[0134] (5) Peel the boric acid modified graphene oxide prepared in step (4) from the polyimide substrate and place it in a hot pressing sintering furnace. The flatness of the hot pressing punch used is ≤5 μm; the temperature is raised to 2200 °C at a rate of 5 °C / min. During this process, the pressure is gradually increased to 35 MPa, and sintering treatment is carried out under isothermal and isobaric conditions for 1 h; then the pressure is unloaded, and the temperature is cooled to below 200 °C with the furnace to obtain a boron carbide modified graphene film (graphene composite material). The vertical thermal conductivity is 32 W / (m·K), and the horizontal thermal conductivity is 950 W / (m·K).

[0135] Comparative Example 1

[0136] It is basically the same as Example 1, the difference is that the sintering treatment step is omitted; the step (5) of Comparative Example 1 is as follows:

[0137] (5) Peel the boric acid modified graphene oxide prepared in step (4) from the polyimide substrate and place it in a hot pressing sintering furnace. The flatness of the hot pressing punch used is ≤5 μm; under a 10 -3 Pa vacuum, the temperature was raised to 1500 °C at a rate of 10 °C / min for the second thermal reduction treatment for 30 min; then the temperature was cooled to below 200 °C with the furnace to obtain a boron-doped graphene film. The vertical thermal conductivity is 8 W / (m·K), and the horizontal thermal conductivity is 470 W / (m·K).

[0138] Comparative Example 2

[0139] (1)At room temperature, take 1 L of a 2 g / L graphene oxide solution, where the carbon content of the graphene oxide is 65 - 70 a.u.% and the oxygen content is 30 - 35 a.u.%; then add 2.5 mmol of boron carbide powder and stir for 4 h to obtain a graphene oxide - boron carbide solution.

[0140] (2)Heat the graphene oxide - boron carbide solution prepared in step (1) to 80 °C, evacuate to vacuum, and stir continuously to obtain a mixed solution, where the mass concentration of graphene oxide in the mixed solution is 10 g / L.

[0141] (3)Place the mixed solution prepared in step (2) on a coater, use a 0.1 - mm - thick polyimide film as the substrate, coat a wet film, and then dry at 120 °C for 2 h to obtain a graphene oxide - boron carbide film with a thickness of about 0.2 mm.

[0142] (4)Put the graphene oxide - boron carbide film prepared in step (3) and the polyimide substrate together into a vacuum oven, and bake at 300 °C for 5 h under vacuum (the first thermal reduction treatment) to prepare boron carbide - modified graphene oxide.

[0143] (5)Peel off the boron carbide - modified graphene oxide prepared in step (4) from the polyimide substrate and place it in a hot - pressing sintering furnace. The flatness of the hot - pressing punch used is ≤5 μm; under a vacuum of 10 -3 Pa, heat it at a rate of 10 °C / min to 1500 °C for the second thermal reduction treatment for 30 min; then heat it at a rate of 5 °C / min to 2200 °C. During this process, gradually increase the pressure to 35 MPa, and keep it at a constant temperature and pressure for sintering for 1 h; then unload the pressure and cool it in the furnace to below 200 °C to obtain a boron carbide - modified graphene film with a vertical thermal conductivity of 12 W / (m·K) and a horizontal thermal conductivity of 1100 W / (m·K).

[0144] Comparative Example 3

[0145] (1)At room temperature, take 1 L of a 2 g / L graphene oxide solution, where the carbon content of the graphene oxide is 65 - 70 a.u.% and the oxygen content is 30 - 35 a.u.%; then add 2.5 mmol of silicon dioxide powder and stir for 4 h to obtain a graphene oxide - silicon dioxide solution.

[0146] (2)Heat the graphene oxide - silicon dioxide solution prepared in step (1) to 80 °C, evacuate to vacuum, and stir continuously to obtain a mixed solution, where the mass concentration of graphene oxide in the mixed solution is 10 g / L.

[0147] (3) Place the mixed solution prepared in step (2) on a coater, coat a wet film with a 0.1 mm thick polyimide film as the substrate, and then dry it at 120 °C for 2 h to obtain a graphene oxide-silica film with a thickness of about 0.2 mm.

[0148] (4) Put the graphene oxide-silica film prepared in step (3) and the polyimide substrate together into a vacuum oven, and bake at 300 °C for 5 h under vacuum (the first thermal reduction treatment) to prepare silica-modified graphene oxide.

[0149] (5) Peel off the silica-modified graphene oxide prepared in step (4) from the polyimide substrate and place it in a hot press sintering furnace. The flatness of the hot press punch used is ≤5 μm; under a vacuum of 10 -3 Pa, heat it up to 1500 °C at a rate of 10 °C / min for the second thermal reduction treatment for 30 min; then heat it up to 2200 °C at a rate of 5 °C / min for sintering treatment for 1 h; then unload the pressure and cool it down to below 200 °C with the furnace to obtain a silicon carbide-modified graphene film with a vertical thermal conductivity of 18 W / (m·K) and a horizontal thermal conductivity of 1120 W / (m·K).

[0150] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0151] The above-described embodiments only represent several implementation manners of the present application, which are convenient for understanding the technical solutions of the present application specifically and in detail, but should not be construed as a limitation on the protection scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the technical solutions provided by the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the patent of the present application should be subject to the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A graphene composite material, characterized in that, It includes boron carbide and at least two graphene sheets, and adjacent graphene sheets are connected by the boron carbide between the layers.

2. The graphene composite material according to claim 1, characterized in that, The graphene sheet is a reduced graphene oxide sheet.

3. The graphene composite material according to claim 1, characterized in that, In the graphene composite material, the mass content of the boron carbide is 1% - 20%.

4. The graphene composite material according to any one of claims 1 to 3, wherein The boron carbide includes boron carbide particles.

5. The graphene composite material according to claim 4, characterized in that, The particle size of the boron carbide particles is ≤ 200 nm; optionally, the boron carbide particles are 1 nm - 50 nm.

6. A method for preparing a graphene composite material, characterized in that, It includes the following steps: Sinter the precursor, where the precursor includes at least two graphene sheets and a boron source located between the adjacent graphene sheets; the pressure of the sintering treatment is 35 MPa - 50 MPa, and the temperature of the sintering treatment is 2000°C - 2300°C.

7. The preparation method of the graphene composite material according to claim 6, wherein, The preparation of the precursor includes the following steps: Perform a film-forming treatment on a mixed solution including graphene sheets and a boron source to prepare the precursor.

8. The preparation method of the graphene composite material according to claim 7, characterized in that, In the preparation step of the precursor, the graphene sheet is a graphene oxide sheet; And, after the film-forming treatment and before the sintering treatment step, it further includes a step of thermally reducing the film layer obtained by the film-forming treatment.

9. The preparation method of the graphene composite material according to claim 8, characterized in that, The thermal reduction treatment is carried out under vacuum conditions, and the temperature of the thermal reduction treatment is 300°C - 1500°C; Optionally, the thermal reduction treatment includes a first thermal reduction treatment and a second thermal reduction treatment carried out in sequence. The temperature of the first thermal reduction treatment is 300°C - 350°C, and the temperature of the second thermal reduction treatment is 1400°C - 1500°C.

10. The preparation method of the graphene composite material according to claim 9, characterized in that, Before the second thermal reduction treatment and after the first thermal reduction treatment, it further includes a step of heating to the temperature of the second thermal reduction treatment at a rate of 5°C / min - 10°C / min; And / or, the time of the first thermal reduction treatment is 1 h - 5 h; And / or, the time of the second thermal reduction treatment is 30 min - 60 min; And / or, before the sintering treatment and after the second thermal reduction treatment, it further includes a step of heating to the temperature of the sintering treatment at a rate of 5°C / min - 8°C / min and pressurizing to the pressure of the sintering treatment; And / or, the time of the sintering treatment is 1 h - 2 h.

11. The preparation method of the graphene composite material according to any one of claims 7 to 10, characterized in that, The boron source includes at least one of boric acid and ammonium borate.

12. The preparation method of the graphene composite material according to any one of claims 7 to 10, characterized in that, In the mixed solution, the mass concentration of the graphene sheets is 5 g / L - 10 g / L; And / or, the molar concentration of the boron source is 0.01 mol / L - 0.05 mol / L.

13. An electronic device, characterized in that, It includes the graphene composite material as described in any one of claims 1 - 5 or the graphene composite material prepared by the preparation method of the graphene composite material as described in any one of claims 6 - 12.

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