A two-step method for making large-area graphene heat dissipation film

Abstract

The present application relates to a kind of two-step method of making large-area graphene heat dissipation film, including the preparation of graphene oxide film and the two successive steps of laser treatment reduction graphene oxide.The method uses graphene oxide solution as starting material, then it is placed on template film formation, using liquid nitrogen is carried out nondestructive demolding, finally the obtained graphene oxide film is selectively laser treated, that is, ultra-thin micron level large-area and good flexible graphene film can be obtained, which shows great application prospect in transparent conductive film, flexible device, heat dissipation film and electromagnetic shielding.The two-step method for preparing graphene film provided by the present application is simple in operation, low in cost, strong in operability, good in repeatability, and the calculated thermal conductivity is much higher than that of common metals copper, aluminum and silver, which can be used for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to a simple two-step method for preparing ultrathin, flexible, large-area graphene films, belonging to the field of thin film materials technology. Background Technology

[0002] With the rapid development of technology, electronic and electrical devices are gradually becoming thinner, smaller, and more flexible. The power density of their internal integrated circuit chips and electronic components is increasing rapidly. This inevitably leads to a large accumulation of heat in small spaces and with high power, severely affecting the performance and lifespan of electronic and electrical devices and posing safety hazards. Therefore, finding a low-density heat dissipation material with high thermal conductivity is particularly important. Graphene, a two-dimensional carbon allotrope, is composed of a single layer of sp... 2 The hexagonal lattice honeycomb two-dimensional structure composed of hybrid carbon atoms endows graphene with many excellent properties due to its unique stable structure. Among them, graphene has a high thermal conductivity (~5300 W·m). -1 ·K -1 This makes it a promising candidate for thermal management in electronic devices. In particular, large-size graphene sheets, intact interlayer structures, and ordered interlayer arrangements all positively impact the thermal conductivity of graphene-based heat dissipation materials. Although many methods exist for preparing graphene heat dissipation films, they suffer from problems such as long preparation times, low efficiency, size limitations, and stringent process parameter requirements, hindering industrial application and limiting the commercialization of graphene heat dissipation films. Therefore, developing an environmentally friendly, low-cost method for large-area, low-defect graphene-based films is crucial. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a two-step method for preparing large-area graphene heat dissipation films. The method mainly consists of two steps: the preparation of a graphene oxide film and laser treatment to obtain the graphene film. First, a simple and pollution-free graphene oxide film is prepared using a method followed by low-temperature demolding. Then, the graphene oxide film is subjected to laser reduction treatment to remove oxygen-containing functional groups and repair structural defects, resulting in a large-area, low-defect graphene functional film that can be widely used in fields such as device heat dissipation, electromagnetic shielding, and flexible electronic products.

[0004] The technical solution of this invention is as follows:

[0005] A two-step method for fabricating large-area graphene heat dissipation films includes:

[0006] Preparation of graphene oxide film: Prepare graphene oxide dispersion, place the prepared graphene oxide dispersion in a mold, and demold using low temperature.

[0007] Preparation of graphene films: The graphene oxide film is pre-annealed; and the pre-annealed graphene oxide film is further processed by laser scanning to remove oxygen-containing groups, restore the conjugated structure of graphene, and obtain a low-defect graphene film.

[0008] The obtained graphene film is pressed to obtain a large-area graphene heat dissipation film.

[0009] According to a preferred embodiment of the present invention, a low-temperature demolding process is used; comprising:

[0010] The mold containing the graphene oxide dispersion was dried in an electric furnace to form a film. Then, liquid nitrogen was slowly poured into the mold to detach the graphene oxide film from the substrate.

[0011] According to a preferred embodiment of the present invention, the heating temperature of the electric furnace is 50-100°C.

[0012] According to a preferred embodiment of the present invention, after the graphene oxide film is prepared, the substrate is cleaned with isopropanol and ethanol and then dried.

[0013] According to a preferred embodiment of the present invention, the temperature for pre-annealing the graphene oxide film is 1000°C.

[0014] According to a preferred embodiment of the present invention, a laser light source with a laser aperture of 50 micrometers is used to perform laser scanning processing on the obtained graphene oxide film, the laser power density is 1-20W, and the laser scanning speed is 0.8-2.0m / s.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. The method for preparing graphene films provided by this invention is simple to operate and mainly consists of two steps: the preparation of graphene oxide films and laser reduction treatment. This operation is low-cost, highly operable, and has good repeatability. It is also very suitable for the preparation of large-area graphene-based films of different thicknesses. The prepared graphene-based films have excellent flexibility and can be applied to industrial production.

[0017] 2. In the preparation of graphene oxide films, this invention changes the traditional film preparation process. The graphene-based dispersion is poured into a mold and dried to form a film. Liquid nitrogen is used to achieve non-destructive demolding of the graphene oxide film. After the film is removed from the substrate, the mold can be recycled, greatly reducing costs. Furthermore, different templates with different properties can be selected as needed, which is beneficial for further functionalization of the film.

[0018] 3. This invention utilizes lasers to process graphene oxide films, offering advantages such as higher selectivity, higher efficiency, and lower cost. The laser not only removes a large number of oxygen-containing groups from the surface of graphene oxide through high temperature and chemical reaction, but also breaks chemical bonds, leading to recombination and the formation of sp...2 The conjugated graphene planar hexagonal structure further reduces impurities and defects within the film, effectively improving the quality and performance of the graphene film. The 10 μm graphene heat dissipation film obtained by this invention has a thermal conductivity of 1801.07 W / (m·K). This thermal conductivity is significantly higher than that of common metals such as Cu (400 W / (m·K)), Al (237 W / (m·K)), and Ag (429 W / (m·K)). It has excellent commercialization prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a graphene oxide film.

[0020] Figure 2 This is a schematic diagram of a graphene film after laser processing and pressing. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0022] Example 1

[0023] A two-step method for fabricating large-area graphene heat dissipation films includes:

[0024] Preparation of graphene oxide film: Prepare graphene oxide dispersion, place the prepared graphene oxide dispersion in a mold of a certain shape, and perform demolding treatment at low temperature.

[0025] Preparation of graphene films: The graphene oxide film is pre-annealed; and the pre-annealed graphene oxide film is further processed by laser scanning to remove oxygen-containing groups, restore the conjugated structure of graphene, and obtain a low-defect graphene film.

[0026] The obtained graphene film is pressed to obtain a large-area graphene heat dissipation film.

[0027] Example 2

[0028] The method for fabricating a large-area graphene heat dissipation film using a two-step process as described in Example 1 differs in that:

[0029] The preparation of graphene oxide solution includes: adding a certain volume of concentrated sulfuric acid to a beaker, cooling it in an ice-water bath, then adding graphite, sodium nitrate and potassium permanganate in sequence, controlling the reaction temperature, and finally adding 30% hydrogen peroxide to terminate the reaction. After precipitation, washing and other operations, a graphene oxide colloidal solution is obtained.

[0030] In this embodiment, a certain volume of concentrated sulfuric acid was poured into a beaker, which was then cooled in an ice-water bath. Expanded graphite and sodium nitrate were then added, and after stirring for a period of time, potassium permanganate was added. The temperature was controlled at 0-8°C, and the reaction time was 1 hour. Specifically, the amount of concentrated sulfuric acid used was 400 mL, the mass of graphite was 10 g, the mass of sodium nitrate was 7.5 g, and the mass of potassium permanganate was 30 g. Subsequently, the mixture was heated at 30-45°C for 1 hour. Then, 600-1200 mL of 5% dilute sulfuric acid was added to the solution, and the reaction was continued at 90-99°C for 1 hour. Finally, 20-50 mL of 30% hydrogen peroxide was added to terminate the reaction. The solution was allowed to settle at room temperature and washed with deionized water until neutral to obtain a graphene oxide colloidal solution.

[0031] The preparation of graphene oxide dispersion includes: dispersing graphene oxide colloidal solution into deionized water, and then treating it with ultrasound to obtain a uniform large-sheet graphene oxide solution.

[0032] Demolding is performed using low temperatures; including:

[0033] The mold containing the graphene oxide dispersion is dried in an electric furnace to form a film. Liquid nitrogen is then slowly poured into the mold to detach the graphene oxide film from the substrate. Specifically, this includes:

[0034] Assemble the mold (made of aluminum plate). Then, clean and dry the mold sequentially with isopropanol and ethanol. Add 10-50 mL of solution to the preheated mold at 50-100℃. After the solution forms a film, remove the mold from the heating stage and allow it to cool to room temperature. Then, add liquid nitrogen until the thin substrate detaches. Remove the substrate as shown in the image. Figure 1 The graphene oxide film shown is highly flexible. The metal mold not only acts as a substrate but also performs preliminary reduction of the graphene oxide film, with a noticeable metallic luster on the side in direct contact with the metal substrate.

[0035] The mold of a certain shape can be made of metal, plastic, or other materials. Metals (such as copper, zinc, and aluminum) have certain reducing properties, which can be used to initially reduce graphene oxide and dope the resulting film with certain metal ions to prepare a composite graphene film. If plastic is used, pure graphene-based films can be prepared.

[0036] The size and shape of the mold can be selected according to different application fields, thereby preparing graphene functional films of different sizes and shapes. In addition, there are no strict requirements on the thickness of the mold; for example, in metal molds, either thick aluminum plates or thin aluminum foils can be used.

[0037] After the graphene oxide film is prepared, the substrate is cleaned with isopropanol and ethanol and then dried. It can be used for the next film preparation, realizing the recycling of the substrate.

[0038] The preparation of graphene films includes:

[0039] The obtained film was pretreated by annealing at 1000℃ for 2 hours in an Ar / H2 atmosphere. Then, the graphene oxide film was laser treated using a ReniShawRenAM 500E laser with a laser power of 1-20W and a laser scanning speed of 0.8-2.0m / s. By changing the number of scans, the graphene oxide film was deoxygenated and the conjugated structure of graphene was restored, achieving deep reduction of graphene. Figure 2 This is a photograph of a graphene film that has been laser-processed and pressed.

[0040] The obtained film was subjected to hydraulic treatment to eliminate internal air bubbles. The thermal diffusivity of three films with different thicknesses was tested using the laser scintillation method, and the calculated thermal conductivity is shown in Table 1 below.

[0041] Table 1

[0042]

[0043] When the film thickness is 20 and 10 micrometers, the measured thermal conductivity is significantly higher than that of common metals such as Cu (400 W / (m·K)), Al (237 W / (m·K)), and Ag (429 W / (m·K)). Furthermore, the prepared films exhibit excellent flexibility. This method is very simple to operate, allows for the modification of substrate dimensions as needed, enables the fabrication of large-area films, and the substrates used are recyclable. It has a high degree of industrialization potential and shows great promise for applications in heat dissipation, electromagnetic shielding, and flexible electronic devices.

Claims

1. A two-step method for fabricating large-area graphene heat dissipation films, characterized in that, include: Preparation of graphene oxide films: A graphene oxide dispersion is prepared, and the prepared graphene oxide dispersion is placed in a mold and demolded using low temperature; including: The mold containing the graphene oxide dispersion was dried in an electric furnace to form a film. Then, liquid nitrogen was slowly poured into the mold to detach the graphene oxide film from the substrate. Preparation of graphene films: The graphene oxide film is pre-annealed; and the pre-annealed graphene oxide film is further processed by laser scanning to remove oxygen-containing groups, restore the conjugated structure of graphene, and obtain a low-defect graphene film. The obtained graphene film is pressed to obtain a large-area graphene heat dissipation film.

2. The method for fabricating a large-area graphene heat dissipation film using a two-step process according to claim 1, characterized in that, The heating temperature of the electric furnace is 50-100℃.

3. The method for fabricating a large-area graphene heat dissipation film using a two-step process according to claim 1, characterized in that, After the graphene oxide film is prepared, the substrate is cleaned with isopropanol and ethanol and then dried.

4. The method for fabricating a large-area graphene heat dissipation film using a two-step process according to claim 1, characterized in that, The pre-annealing temperature for the graphene oxide film is 1000 ℃.

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