A kind of graphene conductive ink and preparation method thereof

Abstract

The present invention relates to a graphene conductive ink and a preparation method thereof, comprising the following steps: shearing bulk graphite in a solvent to obtain graphite flakes; placing the graphite flakes in an alkane for ultrasonic treatment to assist in exfoliation of the graphene into an oil phase; adding deionized water to the obtained mixture of graphene and alkane, ultrasonicating and shaking, and then allowing it to stand, and repeating this process multiple times to obtain the graphene conductive ink. Compared with the prior art, the present invention has a simple preparation process, significantly reduces preparation costs, and does not require the addition of additional solvents, additives, and binders for preparing the graphene conductive ink, thus being environmentally friendly. The graphene conductive ink prepared by the present invention has good conductivity, does not require high-temperature annealing, and has a wide range of applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of inks, and in particular relates to a graphene conductive ink and a preparation method thereof. Background Art

[0002] With the advancement of printed electronics technology, the printed electronics-based industry has grown rapidly. Conductive inks are key materials supporting this industry. Currently, conductive inks based on metal particles still dominate the market. Metallic inks offer high conductivity, but they are expensive, often unstable and toxic, and require high sintering temperatures.

[0003] Graphene's high conductivity, high mechanical strength, and green and non-toxic properties make it a substitute for traditional printed conductor fillers. With the development of graphene preparation technology, graphene conductive ink has been involved in various application fields.

[0004] Graphene used to prepare graphene conductive ink is usually prepared using a top-down method, which mainly includes two methods. One is the redox method, in which GO is first prepared and then the graphene oxide is reduced by heat treatment or chemical treatment after printing; the second method is to use mechanical exfoliation to prepare graphene and add stabilizers to maintain the dispersion of graphene. For example, patent application CN202010658998.X discloses a preparation of graphene conductive ink, which includes the following steps: pretreatment of expandable graphite, sinking the pretreated graphite in a solvent, ultrasonic treatment, preparation of graphene nanosheets, exfoliation of graphene nanosheets, filtration, rapid centrifugation, removal of unexpanded graphite particles, obtaining a graphene dispersion, concentrating, adding resin to form a film agent and stabilizer, concentrating again to obtain graphene conductive ink, screen printing the ink, and annealing.

[0005] Both of these methods typically require high-temperature treatment after printing, limiting the application of conductive inks. Furthermore, while redox-fabrication of graphene restores conductivity after reduction, its conductive properties are still compromised. Summary of the Invention

[0006] The purpose of the present invention is to provide a graphene conductive ink and a preparation method thereof in order to overcome the defects of the above-mentioned prior art. The graphene conductive ink is prepared by a shearing and then interfacial exfoliation method. The shearing and then interfacial exfoliation method is economical and environmentally friendly. The prepared conductive ink has good conductivity, does not contain toxic solvents, and has a wide range of applications.

[0007] The purpose of the present invention can be achieved by the following technical solution: A method for preparing graphene conductive ink, combining a shearing method and an interface peeling method, specifically comprising the following steps:

[0008] (1) Shearing bulk graphite in a solvent to obtain graphite sheets;

[0009] (2) placing graphite sheets in alkanes and subjecting them to ultrasonic treatment to assist in the exfoliation of graphene into the oil phase;

[0010] (3) Deionized water is added to the mixture of graphene and alkane obtained in step (2), and the mixture is ultrasonicated and shaken before being allowed to stand, and the process is repeated several times to obtain graphene conductive ink.

[0011] Furthermore, the shearing in step (1) is carried out in a high-speed shearing dispersing emulsifier with a rotation speed of 300 rpm-2500 rpm and a shearing time of 2-4 h.

[0012] Furthermore, the solvent used in step (1) is deionized water.

[0013] Furthermore, the alkane in step (2) is one of ethane, n-heptane, undecane or dodecane, preferably dodecane.

[0014] Furthermore, the mass volume ratio of the graphite to the alkane in step (2) is 1:(10-30) g / mL, preferably 1:25.

[0015] Furthermore, in step (3), the volume ratio of deionized water to alkane is 1:0.5-2, preferably 1:1.

[0016] Furthermore, in step (3), the number of ultrasonic and shaking times is 1 to 5 times, the ultrasonic time is 1 to 5 hours, the shaking time is 40 to 80 seconds, and the standing time after each ultrasonic and shaking is 1 to 96 hours.

[0017] Further preferably, the number of ultrasound and shaking is 4 times, wherein the first ultrasound time is 1 hour, the shaking time is 60 seconds, and the standing time is 1 hour; the second ultrasound time is 1 hour, the shaking time is 60 seconds, and the standing time is 24 hours; in step (3), the third ultrasound time is 3 hours, the shaking time is 60 seconds, and the standing time is 4 days; the fourth ultrasound time is 5 hours, the shaking time is 60 seconds, and the standing time is 1 day.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention expands upon the traditional shearing method for preparing graphene, and prepares graphene conductive ink by performing interfacial exfoliation after shearing. Using water and alkanes as the liquid phase, an oil-in-water emulsion is obtained by the interfacial exfoliation method, thereby eliminating the need for the additional addition of solvents, additives, and binders required for preparing graphene conductive ink. The resulting graphene conductive ink contains only graphene, alkanes, and deionized water, and does not contain toxic chemical reagents. Characterization results show that the graphene exfoliation degree is high, and the ink has good conductive properties, with a sheet resistance of only 10.8Ω / sq and a conductivity of up to 3.4×10 4 S / m. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the preparation process of graphene conductive ink;

[0021] Figure 2 This is the atomic force microscope characterization image of graphene;

[0022] Figure 3 is the graphene thickness distribution histogram;

[0023] Figure 4 This is the IV curve of graphene conductive ink. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] A method for preparing graphene conductive ink, combining shearing and interfacial exfoliation methods, first, using a high shear dispersing emulsifier to shear bulk graphite in a solvent to obtain graphite flakes; adding the sheared graphite flakes to a reactor, followed by adding two immiscible liquids, exfoliating the graphene by interfacial exfoliation, and subjecting the mixture to ultrasonication, shaking, and standing to prepare the graphene conductive ink. Figure 1 As shown, the specific steps include:

[0027] (1) Shearing bulk graphite in a solvent (water is used as the solvent in this embodiment) at a rate of 2500 rpm for 3 h to obtain graphite sheets;

[0028] (2) 0.1 g of sheared graphite sheets were placed in a reactor, 2 mL of dodecane was added, and the system was subjected to water bath ultrasonic treatment for 2 hours (ultrasonic power 40%, frequency 37 kHz, temperature 43°C) to decompose large particles of graphite; then deionized water was added in a 1:1 volume ratio of dodecane to deionized water. Initially, the graphite particles were fixed at the water / oil interface.

[0029] (3) The reactor was ultrasonicated in a water bath for 1 hour (power 40%, frequency 37 kHz, temperature 43°C). After the ultrasonication, the vial was shaken for 60 seconds and allowed to stand for another 1 hour. The vial was ultrasonicated for a second time for 1 hour, with the same shaking time, and allowed to stand for 24 hours. The vial was ultrasonicated for a third time for 3 hours, shaken, and allowed to stand for 4 days. The vial was ultrasonicated for a fourth time under the same conditions for 5 hours, and then shaken for another 60 seconds. After the final shaking, a complete emulsion was formed in the reactor.

[0030] Figure 2 、 Figure 3 The graph shows the thickness characterization and thickness statistical histogram of the graphene obtained in Example 1 under an atomic force microscope. Figure 3It can be seen that the graphene thickness is concentrated in 5-10nm, the number of graphene layers is small, and the degree of exfoliation is good.

[0031] Figure 4 The graphene conductive ink has a conductivity of 40 Ω, a sheet resistance of 10.8 Ω / sq, and a conductivity of 3.4×10 4 S / m. Compared with graphene conductive inks prepared by other methods, the graphene conductive ink has good conductive properties.

[0032] Example 2

[0033] The shear speed was 1250 rpm.

[0034] The alkane used is undecane.

[0035] The volume ratio of deionized water to ethane is 1:0.5.

[0036] The mass volume ratio of graphite to ethane is 1:25 g / mL.

[0037] The rest is the same as Example 1.

[0038] Example 3

[0039] The shearing speed was 300 rpm.

[0040] The alkane used was undecane.

[0041] The volume ratio of deionized water to alkane is 1:1.

[0042] The mass volume ratio of graphene to alkane is 1:20 g / mL.

[0043] The rest is the same as Example 1.

[0044] The performance of each embodiment and comparative example was tested using the same method as in Example 1, and the results are as follows:

[0045] Example 1 Example 2 Example 3 Thickness nm 5-10 10-15 10-15 Resistance Ω 40 50 60 Sheet resistance Ω / sq 10.8 13.5 16.2 Conductivity S / m <![CDATA[3.4×10 4 ]]> <![CDATA[2.7×10 4 ]]> <![CDATA[2.2×10 4 ]]> Toxic substances none none none

[0046] As can be seen from the above table, the graphene conductive inks obtained in Examples 1-3 do not contain toxic chemical reagents and have a high degree of graphene exfoliation. At the same time, the ink of Example 1 has the best conductive performance.

[0047] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing graphene conductive ink, characterized in that: The following steps are involved: (1) Shearing bulk graphite in a solvent to obtain graphite flakes; the shearing is carried out in a high-speed shear dispersing emulsifier at a speed of 300 rpm to 2500 rpm for 2 to 4 hours; the solvent used is deionized water; (2) placing the graphite sheet in an alkane and performing ultrasonic treatment to assist the exfoliation of the graphene into the oil phase; the alkane is one of ethane, n-heptane, undecane or dodecane; the mass volume ratio of graphite to alkane is 1: (10-30) g / mL; (3) Deionized water is added to the mixture of graphene and alkane obtained in step (2), wherein the volume ratio of deionized water to alkane is 1:0.5-2, and the mixture is allowed to stand after ultrasonication and shaking, and repeated multiple times to obtain graphene conductive ink, wherein the number of ultrasonication and shaking is 1-5 times, the ultrasonication time is 1-5 hours, the shaking time is 40-80 seconds, and the standing time after each ultrasonication and shaking is 1-96 hours.

2. The method for preparing a graphene conductive ink according to claim 1, wherein: The first ultrasonication time was 1 h, the shaking time was 60 s, and the standing time was 1 h.

3. The method for preparing a graphene conductive ink according to claim 1, wherein: The second ultrasonic treatment lasted for 1 h, the shaking time was 60 s, and the standing time was 24 h.

4. The method for preparing a graphene conductive ink according to claim 1, wherein: The third ultrasonication time was 3 h, the shaking time was 60 s, and the standing time was 4 days; The fourth ultrasonication time was 5 h, the shaking time was 60 s, and the standing time was 1 day.

5. A graphene conductive ink, characterized in that: The method according to any one of claims 1 to 4 is adopted to prepare the present invention.

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