A method for preparing high conductivity laser-induced graphene material

Abstract

The present invention discloses a method for preparing a high-conductivity laser-induced graphene material, comprising the following steps: (1) adding a high-conductivity material into a polyimide thermoplastic liquid to form a mixed solution, coating the mixed solution on a silicon oxide substrate, and obtaining a composite film after heat treatment and curing; (2) irradiating the composite film obtained in step (1) with a laser to obtain a high-conductivity laser-induced graphene material. The present invention generates laser-induced graphene on a polyimide composite film by the action of a laser, and the added high-conductivity material will be embedded in the laser-induced graphene material during the process of converting polyimide into laser-induced graphene, thereby greatly improving the conductivity of the prepared laser-induced graphene and the adhesion between the laser-induced graphene and the high-conductivity material.

Description

Technical Field

[0001] The invention belongs to the technical field of graphene, and in particular relates to a method for preparing a conductive graphene material. Background Art

[0002] Since the discovery of laser-induced graphene (LIG) in 2014, researchers have elaborated on the synthesis mechanism of LIG from multiple aspects such as laser parameters, precursor materials, and gas atmosphere, and have effectively improved the quality of LIG, achieving effective regulation of the morphology and performance of LIG. The excellent electrical, mechanical, chemical, and thermal properties of LIG have aroused great interest. Various flexible devices based on LIG, including physical, electrochemical, and biological sensors, as well as energy storage devices such as batteries, super microcapacitors, and friction nanogenerators, have been widely used in human motion, environmental monitoring, medical health, and energy storage. Currently, the manufacture of LIG mostly uses traditional polyimide films. There is a big gap between the conductivity of the prepared LIG and that of metal wires, making it difficult to use in large-scale flexible devices or circuit interconnections.

[0003] The conventional method to improve the conductivity of LIG is to coat the surface of LIG with a conductive material, or to coat the surface of LIG with a thin layer of metal by evaporation or electrochemical plating. The method of coating the surface with a conductive material faces the problem of poor adhesion between the surface layer and LIG, and the coated surface layer is easily damaged. The evaporation or electrochemical plating method can combine metal particles on the porous inner wall of LIG, but it requires additional steps, which increases the production cost and complexity of LIG. Therefore, a simple and stable method is needed to improve the conductivity of LIG. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a high-conductivity laser-induced graphene material to improve the conductivity of the laser-induced graphene material.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing high conductivity laser-induced graphene material, comprising the following steps:

[0007] (1) adding a high conductivity material into a polyimide thermoplastic liquid to form a mixed solution, coating the mixed solution on a silicon oxide substrate, and obtaining a composite film after heat treatment and curing;

[0008] (2) Using laser to irradiate the composite film obtained in step (1) to obtain a high conductivity laser induced graphene material.

[0009] In the step (1), the high conductivity material is at least one of a silver nanowire solution, pure indium oxide powder, and pure indium tin oxide powder.

[0010] The solid content of the polyimide thermoplastic liquid is 20%.

[0011] In the silver nanowire solution, the solvent is ethanol, the concentration of the silver nanowire solution is 5 mg / mL, the length of the silver nanowire is 20 μm, and the diameter is 30 nm; the particle size of the indium oxide powder particles is 50 nm; and the particle size of the indium tin oxide powder particles is 30 nm.

[0012] The mass ratio of the polyimide thermoplastic solution to the silver nanowire solution is 1:0.5-5; the mass ratio of the polyimide thermoplastic solution to the indium oxide powder is 5:1; and the mass ratio of the polyimide thermoplastic solution to the indium tin oxide powder is 5:1.

[0013] In step (1), the mixed solution is placed in a vacuum chamber and the vacuum is drawn to 10 -1 Pa, let it stand for 1 hour, remove bubbles, and then use a coating machine to evenly coat it on a clean silicon oxide substrate.

[0014] In the step (1), heat treatment curing is performed on a heating table in an atmospheric environment, and the heat treatment curing process is as follows: heating to 100°C at a heating rate of 1-3°C / min and maintaining for 30-40min; heating to 150°C at a heating rate of 1-3°C / min and maintaining for 40-60min; heating to 170°C at a heating rate of 1-3°C / min and maintaining for 1-2h depending on the thickness.

[0015] In the step (1), the thickness of the composite film is controlled to be 50-500 μm.

[0016] In the step (2), the composite film is etched directly in the air by using a Nd:YAG laser.

[0017] The parameters of the Nd:YAG laser are set as follows: the laser wavelength is 330 nm; the laser pulse frequency is 150 kHz; the laser Q parameter is 0.2-2; and the laser scanning speed is 1 mm / s-120 mm / s.

[0018] Beneficial effects: The present invention generates laser-induced graphene on a polyimide composite film by the action of a laser. The doped high-conductivity material will be embedded in the laser-induced graphene material during the process of converting polyimide into laser-induced graphene, thereby greatly improving the conductivity of the prepared laser-induced graphene and its adhesion with the high-conductivity material. Compared with the prior art, the present invention has the following advantages: (1) The present invention directly dopes the polyimide film with silver nanowires, indium oxide and indium tin oxide. Compared with the laser-induced graphene formed on the undoped polyimide film under the same laser power, its conductivity is increased by about 400%, and it can be directly used for circuit interconnection; (2) The high-conductivity material can be in-situ embedded in the internal structure of the laser-induced graphene during the process of laser-induced generation of graphene, and has excellent stability; (3) The conductivity of the laser-induced graphene can be controlled by doping different amounts of high-conductivity materials in the composite film. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process steps of the present invention;

[0020] Figure 2 A composite film formed of polyimide and silver nanowires on a silicon oxide substrate;

[0021] Figure 3 This is an optical microscope image of a polyimide and silver nanowire composite film;

[0022] Figure 4 This is a picture of laser-induced graphene formed on a composite film of polyimide and silver nanowires;

[0023] Figure 5 Raman characterization results of laser-induced graphene formed on polyimide and indium oxide composite films. DETAILED DESCRIPTION

[0024] The present invention will be further explained below in conjunction with the embodiments.

[0025] like Figure 1 As shown, a method for preparing a high-conductivity laser-induced graphene material of the present invention comprises the following steps:

[0026] (1) The high conductivity material is mixed into the polyimide thermoplastic liquid to form a mixed solution, the mixed solution is placed in a vacuum chamber, and the vacuum is drawn to 10 -1Pa, stand for 1 hour, remove bubbles, and evenly coat on a clean silicon oxide substrate using a coating machine. Heat treatment and curing are performed on a heating table in an atmospheric environment to obtain a composite film. The heat treatment and curing process is as follows: heating to 100°C at a heating rate of 1-3°C / min and maintaining for 30-40min; heating to 150°C at a heating rate of 1-3°C / min and maintaining for 40-60min; heating to 170°C at a heating rate of 1-3°C / min and maintaining for 1-2h depending on the thickness; the thickness of the composite film is controlled at 50-500μm;

[0027] The high conductivity material is at least one of a silver nanowire solution, pure indium oxide powder, and pure indium tin oxide powder; the solid content of the polyimide thermoplastic solution is 20%; in the silver nanowire solution, the solvent is ethanol, the concentration of the silver nanowire solution is 5 mg / mL, the length of the silver nanowire is 20 μm, and the diameter is 30 nm; the particle size of the indium oxide powder is 50 nm; the particle size of the indium tin oxide powder is 30 nm; the mass ratio of the polyimide thermoplastic solution to the silver nanowire solution is 1:0.5-5; the mass ratio of the polyimide thermoplastic solution to the indium oxide powder is 5:1; the mass ratio of the polyimide thermoplastic solution to the indium tin oxide powder is 5:1;

[0028] (2) Using a Nd:YAG laser to directly etch the composite film obtained in step (1) in air, a high conductivity laser-induced graphene material is obtained.

[0029] The power of the Nd:YAG laser is determined by multiple factors including laser wavelength, laser pulse frequency, laser Q parameter, laser scanning speed, etc. The laser scanning path is controlled by computer-aided design (CDR) software. The parameters of the Nd:YAG laser are set as follows: laser wavelength is 330nm; laser pulse frequency is 150kHz; laser Q parameter is 0.2-2; laser scanning speed is 1mm / s-120mm / s.

[0030] The present invention will be further described below in conjunction with the embodiments.

[0031] Embodiment 1:

[0032] A 6-inch silicon oxide wafer was used as a substrate, cleaned with alcohol and deionized water, and the surface of the wafer was dried with nitrogen.

[0033] The polyimide thermoplastic solution and the silver nanowire solution were mixed in an effective mass ratio of 1:2, and after the bubbles were removed by vacuum, the mixture was spin-coated on a silicon oxide substrate at a speed of 1000 r / min.

[0034] The specific steps of heating treatment in atmospheric environment are as follows: (1) heating to 100°C at a heating rate of 2°C / min and maintaining for 30 min; (2) heating to 150°C at a heating rate of 2°C / min and maintaining for 40 min; (3) heating to 170°C at a heating rate of 2°C / min and maintaining the thickness for 1.5 h; (4) after cooling, a polyimide and silver nanowire composite film with a smooth surface, no bubbles and wrinkles is obtained, such as Figure 2 .

[0035] The composite film was placed under an optical microscope to observe the surface morphology of the film. Figure 3 It can be seen that the composite film is mixed evenly, and no large clusters or aggregations of silver nanowires are observed.

[0036] Computer-aided design (CDR) was used to design a 2×10 mm 2 The laser parameters of the Nd:YAG laser were set to: laser wavelength 330nm; laser pulse frequency 150kHz; laser Q parameter 0.2; laser scanning speed 10mm / s. The laser was used to irradiate the composite film to form 5 2×10mm patterns on the composite film. 2 The structure of each laser-induced graphene is as follows Figure 4 shown.

[0037] The resistance of laser-induced graphene was measured using a digital multimeter VC890C+ and the average value was 23.56Ω.

[0038] Comparative Example 1-1:

[0039] The same as Example 1, except that the effective mass ratio of the polyimide thermoplastic solution to the silver nanowire solution is changed to 1:1.

[0040] Use digital multimeter VC890C+ to measure 5 dimensions of 2×10mm 2 The resistance of laser-induced graphene is 30.25Ω on average. As the content of silver nanowires in the composite film decreases, the resistance of laser-induced graphene generated under the same laser parameters decreases.

[0041] Comparative Example 1-2:

[0042] The same as Example 1, except that only polyimide thermoplastic liquid is used without any other materials being added.

[0043] Use digital multimeter VC890C+ to measure 5 dimensions of 2×10mm 2The resistance of laser-induced graphene is 79.86Ω on average. The polyimide film is not doped with any high-conductivity material. Compared with the composite film formed by the effective mass ratio of polyimide and silver nanowire solution of 1:2, the resistance value of laser-induced graphene generated under the same laser parameters is about 4 times that of laser-induced graphene formed on the composite film.

[0044] Embodiment 2:

[0045] The same as Example 1, except that the doping material is replaced with indium oxide powder, and the effective mass ratio of the polyimide thermoplastic liquid to the indium oxide powder is 5:1.

[0046] Use digital multimeter VC890C+ to measure 5 dimensions of 2×10mm 2 The laser-induced graphene resistor has an average resistance of 22.47Ω.

[0047] Raman spectroscopy analysis of laser-induced graphene formed on polyimide and indium oxide composite films revealed that the -1 D peak, 1577cm -1 The G peak and 2694cm -1 The 2D peaks at 127, 300, 486, and 613 cm -1 The characteristic Raman peaks of cubic indium oxide, such as Figure 5 , confirming the existence of indium oxide inside laser-induced graphene.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing high conductivity laser-induced graphene material, Features: The following steps are involved: (1) adding a high conductivity material into a polyimide thermoplastic liquid to form a mixed solution, coating the mixed solution on a silicon oxide substrate, and obtaining a composite film after heat treatment and curing; (2) irradiating the composite film obtained in step (1) with a laser to obtain a high-conductivity laser-induced graphene material; In the step (1), the high conductivity material is at least one of a silver nanowire solution, pure indium oxide powder, and pure indium tin oxide powder; In the silver nanowire solution, the solvent is ethanol, the concentration of the silver nanowire solution is 5 mg / mL, the length of the silver nanowire is 20 μm, and the diameter is 30 nm; the particle size of the indium oxide powder particles is 50 nm; and the particle size of the indium tin oxide powder particles is 30 nm.

2. The method for preparing high conductivity laser induced graphene material according to claim 1, Features: The solid content of the polyimide thermoplastic liquid is 20%.

3. The method for preparing high conductivity laser-induced graphene material according to claim 1 or 2, Features: The mass ratio of the polyimide thermoplastic solution to the silver nanowire solution is 1:0.5-5; the mass ratio of the polyimide thermoplastic solution to the indium oxide powder is 5:1; and the mass ratio of the polyimide thermoplastic solution to the indium tin oxide powder is 5:

1.

4. The method for preparing high conductivity laser-induced graphene material according to claim 1, Features: In step (1), the mixed solution is placed in a vacuum chamber and the vacuum is drawn to 10 -1 Pa, let it stand for 1 hour, remove bubbles, and then use a coating machine to evenly coat it on a clean silicon oxide substrate.

5. The method for preparing high conductivity laser-induced graphene material according to claim 1, Features: In the step (1), heat treatment curing is performed on a heating table in an atmospheric environment, and the heat treatment curing process is as follows: heating to 100°C at a heating rate of 1-3°C / min and maintaining for 30-40min; heating to 150°C at a heating rate of 1-3°C / min and maintaining for 40-60min; heating to 170°C at a heating rate of 1-3°C / min and maintaining for 1-2h depending on the thickness.

6. The method for preparing high conductivity laser induced graphene material according to claim 1, Features: In the step (1), the thickness of the composite film is controlled to be 50-500 μm.

7. The method for preparing high conductivity laser-induced graphene material according to claim 1, Features: In the step (2), the composite film is etched directly in the air by using a Nd:YAG laser.

8. The method for preparing high conductivity laser-induced graphene material according to claim 7, Features: The parameters of the Nd:YAG laser are set as follows: the laser wavelength is 330nm; the laser pulse frequency is 150kHz; The laser Q parameter is 0.2-2; the laser scanning speed is 1mm / s-120mm / s.

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