GRAPHENE-BASED CONDUCTIVE INK AND PREPARATION THEREOF

Abstract

Graphene-based conductive ink and a preparation thereof. The graphene-based conductive ink includes a modified graphene nanomaterial, a first solvent and an ink binder. The modified graphene nanomaterial is prepared by subjecting a mixture of sodium sulfanilate, a natural flake graphite and a second solvent to liquid phase exfoliation. The second solvent is a mixture of water and a second alcohol.

Claims

1. A graphene-based conductive ink, comprising: a modified graphene nanomaterial; a first solvent; and an ink binder; wherein a weight ratio of the modified graphene nanomaterial to the first solvent to the ink binder is (2-4):(50-100):(1-2); and the first solvent is a mixture of water and a first alcohol; the modified graphene nanomaterial is prepared by subjecting a mixture of sodium sulfanilate, a natural flake graphite and a second solvent to liquid phase exfoliation; and the second solvent is a mixture of water and a second alcohol.

2. The graphene-based conductive ink of claim 1, wherein a particle size of the natural flake graphite is 4000-10000 mesh.

3. The graphene-based conductive ink of claim 1, wherein the particle size of the natural flake graphite is 8000 mesh.

4. The graphene-based conductive ink of claim 1, wherein a weight ratio of the natural flake graphite to the sodium sulfanilate is 1:(0.2-10).

5. The graphene-based conductive ink of claim 1, wherein the weight ratio of the natural flake graphite to the sodium sulfanilate is 1:(0.5-2).

6. The graphene-based conductive ink of claim 1, wherein a volume ratio of the water to the first alcohol in the first solvent is 1:(0.5-2).

7. The graphene-based conductive ink of claim 1, wherein the volume ratio of the water to the first alcohol in the first solvent is 2:3.

8. The graphene-based conductive ink of claim 1, wherein a volume ratio of the water to the second alcohol in the second solvent is 1:(0.5-2).

9. The graphene-based conductive ink of claim 1, wherein the volume ratio of the water to the second alcohol in the second solvent is 2:3.

10. The graphene-based conductive ink of claim 1, wherein the first alcohol and the second alcohol are independently a lower alcohol.

11. The graphene-based conductive ink of claim 10, wherein the lower alcohol is selected from the group consisting of: ethanol, ethylene glycol, glycerol, isopropanol, n-butanol and a combination thereof.

12. The graphene-based conductive ink of claim 10, wherein the lower alcohol is preferably isopropanol.

13. The graphene-based conductive ink of claim 1, wherein the ink binder is selected from the group consisting of: polyvinyl alcohol, polyethylene glycol, acrylic resin, epoxy resin, polyurethane resin, hydroxypropyl methylcellulose, nitrocellulose and a combination thereof.

14. A method of preparing the graphene-based conductive ink of claim 1, comprising: (1) mixing the natural flake graphite, the second solvent and the sodium sulfanilate followed by ultrasonication to obtain a graphite dispersion; (2) grinding the graphite dispersion obtained in step (1) to obtain a ground slurry; (3) subjecting the ground slurry obtained in step (2) to centrifugal washing with a third solvent to obtain the modified graphene nanomaterial; and (4) mixing the modified graphene nanomaterial obtained in step (3), the ink binder and the first solvent followed by ultrasonication and grinding to obtain the graphene-based conductive ink.

15. The method of claim 14, wherein in step (1), the ultrasonication is performed at an ultrasonic frequency of 5000 Hz for 60 s.

16. The method of claim 14, wherein in step (2), the grinding is performed in a medium of zirconia beads with a particle size of 2-3 mm for 12-24 h.

17. The method of claim 14, wherein in step (2), the grinding is performed at a rotation rate of 1000-2000 rpm.

18. The method of claim 14, wherein in step (3), the third solvent is a mixture of water and isopropanol.

19. The method of claim 18, wherein a volume ratio of the isopropanol to the water is 3:2.

20. The method of claim 14, wherein in step (4), the grinding is performed in a medium of zirconia beads with a particle size of 1-3 mm at a rotation rate of 100-500 rpm for is 1-2 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 schematically shows a preparation of a modified graphene nanomaterial according to Example 1 of the present disclosure.

[0036] FIGS. 2A-2J show test results of conductivity of a graphene conductive film according to Example 1 of the present disclosure on different substrates, where 2A-C: polyethylene terephthalate (PET) substrate; 2D-E: glass substrate; 2F-G: nylon fiber; 2H: wire; 21: plant; and 2J: paper substrate.

[0037] FIG. 3 shows test results of dispersity of the modified graphene nanomaterial (20 mg/mL) prepared in Example 1 of the present disclosure.

[0038] FIGS. 4A-4C show performance of the graphene conductive film according to Example 1 of the present disclosure, where 4A: change curve of conductivity of a modified graphene nanomaterial sheet versus pressure; 4B: effect of polishing treatment on resistance of the graphene conductive film (1 cm×1 cm) under different dip coating cycles; and 4C: comparison between the graphene conductive film and a commercial carbon black conductive film in terms of flexibility.

DETAILED DESCRIPTION OF EMBODIMENTS

[0039] Technical solutions of this application will be further described in detail below with reference to the embodiments and accompanying drawings.

EXAMPLE 1

[0040] This embodiment provides a method of preparing a modified graphene nanomaterial, including the following steps.

[0041] (1) 10 g of a natural flake graphite with a particle size of 8000 mesh, 10 g of sodium sulfanilate (SAS), 240 mL of isopropanol and 160 mL of distilled water were mixed and subjected to ultrasonication at 5,000 Hz for 60 s to obtain a graphite dispersion.

[0042] (2) The graphite dispersion was poured into a basket grinder and subjected to ball milling by zirconia beads (a particle size of 2.5 mm) at 2,000 rpm for 24 h, where during the ball milling process, cooling water was introduced for circulating cooling.

[0043] (3) Upper material in the charging basket of the basket grinder was collected and subjected to centrifugal washing 5 times with a mixed solution of isopropanol and water (V.sub.isopropanol/V.sub.water=3:2) to obtain the modified graphene nanomaterial (G-SAS). In the G-SAS, the sodium sulfanilate adhered to the grapheme surface through π-π conjugation, physical adsorption and chemical grafting. The specific preparation process was shown in FIG. 1.

[0044] This embodiment further provides a method of preparing a graphene-based conductive ink, including the following steps.

[0045] (1) 5 g of the above-mentioned modified graphene nanomaterial, 1.5 g of an aqueous acrylic resin emulsion, 60 mL of isopropanol and 40 mL of distilled water were mixed and subjected to ultrasonication to obtain an ink dispersion.

[0046] (2) The ink dispersion was poured into the basket grinder and subjected to ball milling by zirconia beads (a particle size of 2.5 mm) at 500 rpm for 2 h to obtain a ground slurry as the graphene-based conductive ink, where during the ball milling process, cooling water was introduced for circulating cooling.

[0047] The graphene-based conductive ink was respectively dip-coated on a PET substrate (FIGS. 2A-C), a glass substrate (FIGS. 2D-E), a nylon fiber substrate (FIGS. 2F-G), a wire substrate (FIG. 2H), a plant substrate (FIG. 21) and a paper substrate (FIG. 2J) and then dried at 80° C. in a constant temperature blast oven to obtain a graphene conductive film. These graphene conductive films were respectively connected to a conductive path to test the conductivity, and test results were shown in FIGS. 2A-J. As a result, the light-emitting diodes in FIGS. 2E, G, I and J can emit light, which verified that the modified graphene nanomaterial prepared herein had excellent electrical conductivity.

[0048] The dispersity of the modified graphene nanomaterial was tested, and the results were shown in FIG. 3. The conductivity of the graphene conductive film was tested by four-point probe method, and the results were shows in FIGS. 4A-C. It can be seen from FIG. 3 that the modified graphene nanomaterial provided herein can experience a two-month stable dispersion in water, ethanol, ethylene glycol, glycerol, n-butanol, isopropanol, dimethylformamide (DMF) and N-methyl pyrrolidone (NMP) as a conductive filler, indicating good dispersion adaptability. As shown in FIG. 4A, the graphene conductive film provided herein had an electrical conductivity of 2.60×10.sup.4 S/m at a pressure of 25 kPa; as shown in FIG. 4B, the polishing treatment cano greatly improve the conductivity of the graphene conductive film obtained by a simple dip coating process, and at the same time, the polished graphene nanosheet had superior density, uniformity and continuity with respect to the unpolished graphene nanosheet; and as shown in FIG. 4C, the graphene conductive film had a conductivity retention of 79% after thousands of bends, while an ordinary carbon black conductive film almost lost its conductivity after 200 bends due to the destruction of the conductive pathway.

EXAMPLE 2

[0049] This embodiment provides a method of preparing a modified graphene nanomaterial, including the following steps.

[0050] (1) 10 g of a natural flake graphite with a particle size of 8000 mesh, 5 g of sodium sulfanilate, 240 mL of isopropanol and 160 mL of distilled water were mixed and subjected to ultrasonication at 5,000 Hz for 60 s to obtain a graphite dispersion.

[0051] (2) The graphite dispersion was poured into a basket grinder and subjected to ball milling by zirconia beads (a particle size of 2.5 mm) at 2,000 rpm for 24 h, where during the ball milling process, cooling water was introduced for circulating cooling.

[0052] (3) Upper material in the charging basket of the basket grinder was collected and subjected to centrifugal washing 5 times with a mixed solution of isopropanol and water (V.sub.isopropanol/V.sub.water=3:2) to obtain the modified graphene nanomaterial. The specific preparation process was shown in FIG. 1.

[0053] This embodiment further provides a method of preparing a graphene-based conductive ink, including the following steps.

[0054] (1) 1 g of the above-mentioned modified graphene nanomaterial, 1 g of an aqueous acrylic resin emulsion, 240 mL of isopropanol and 160 mL of distilled water were mixed and subjected to ultrasonication to obtain an ink dispersion.

[0055] (2) The ink dispersion was poured into the basket grinder and subjected to ball milling by zirconia beads (a particle size of 2.5 mm) at 500 rpm for 2 h to obtain a ground slurry as the graphene-based conductive ink, where during the ball milling process, cooling water was introduced for circulating cooling.

[0056] The graphene-based conductive ink was respectively dip-coated on a PET substrate, a glass substrate, a nylon fiber substrate, a wire substrate, a plant substrate and a paper substrate and then dried at 80° C. in a constant temperature blast oven to obtain a graphene conductive film. These graphene conductive films were respectively connected to a conductive path to test the conductivity, and test results were similar to those in FIGS. 2A-J.

[0057] The dispersity of the modified graphene nanomaterial was tested, and the results were similar to those in FIG. 3. The conductivity of the graphene conductive film was tested by four-point probe method, and the results were similar to those in FIGS. 4A-C.

[0058] This embodiment provides a modified graphene nanomaterial and a preparation thereof In the preparation method, the solvent of isopropanol and water (V.sub.isopropanol/V.sub.water=3:2)) with surface tension matching the surface energy of grapheme is used to reduce the effect of Van der Waals' force between graphite layers, and a peeling efficiency is further improved through the π-π conjugation of the SAS with conjugation effect and the graphite surface. In addition, the modified graphene nanomaterial is prepared by peeling the graphite through mechanical shearing of a circular ball mill. The modified graphene nanomaterial is able to be stably dispersed in solvents, ensuring dispersion stability of the graphene-based conductive ink.

[0059] This embodiment provides graphene-based conductive ink and a preparation thereof In the preparation method, the liquid phase exfoliation process is simple and feasible, and the graphene-based conductive ink is green and environmentally friendly and has a wide range of adaptation. The modified graphene nanomaterial provided herein can be stably dispersed in the graphene-based conductive ink, ensuring the long-term effectiveness of the graphene-based conductive ink. In addition, the graphene-based conductive ink has an excellent printing adaptability and can be stably dispersed in solvents, including water, ethanol, ethylene glycol, glycerol, isopropanol, n-butanol, DMF and NMP. At the same time, the graphene-based conductive ink has excellent conductivity and film-forming, rheological and mechanical properties as a printed conductive material. As a consequence, the graphene-based conductive ink provided herein is expected to be applied in printing flexible electronic devices.

[0060] The above are only preferred embodiments of this application, and are not intended to limit the scope of this application. Any changes and modifications made by those skilled in the art without departing from the spirit and principle of this application shall fall within the scope of this application defined by the appended claims.