Super-flexible high thermal conductive grapheme film and preparation method thereof

Patent metadata

Field	Value
Publication number	US-11679983-B2
Application number	US-201616070449-A
Country	US
Kind code	B2
Filing date	Jul 20, 2016
Priority date	Jan 25, 2016
Publication date	Jun 20, 2023
Grant date	Jun 20, 2023

Abstract

A super-flexible high thermal conductive graphene film and a preparation method thereof are provided. The graphene film is obtained from ultra large homogeneous graphene sheets through processes of solution film-forming, chemical reduction, high temperature reduction, high pressure suppression and so on. The graphene film has a density in a range of 1.93 to 2.11 g/cm 3 , is formed by overlapping planar oriented graphene sheets with an average size of more than 100 μm with each other through π-π conjugate action, and comprises 1 to 4 layers of graphene sheets which have few defects. The graphene film can be repeatedly bent for 1200 times or more, with elongation at break of 12-18%, electric conductivity of 8000-10600 S/cm, thermal conductivity of 1800-2600 W/mK, and can be used as a highly flexible thermal conductive device.

First claim

What is claimed is:

1. A preparation method of a super-flexible high thermal conductive graphene film, the preparation method comprising steps of:
(1) preparing graphene oxide sheets with an average size of more than 100 μm into a graphene oxide aqueous solution with a concentration in a range of 6-30 mg/mL, adding an additive with a mass fraction of 0.1-5% into the aqueous solution, wherein the additive is inorganic salt, small organic molecule or macromolecule; pouring the aqueous solution added with the additive onto a mold plate after ultrasonic dispersion, obtaining a graphene oxide film by drying the mold plate, and performing reduction on the graphene oxide film through a reducing agent;
(2) increasing a temperature of the reduced graphene film to 500-800° C. at a speed of 0.1-1° C./min and preserving heat for 0.5-2 h under inert gas atmosphere;
(3) after the step (2), increasing the temperature of the reduced graphene to 1000-1300° C. at a speed of 1-3° C./min and preserving heat for 0.5-3 h under inert gas atmosphere;
(4) after the step (3), increasing the temperature of the reduced graphene film to 2500-3000° C. at a speed of 5-8° C./min and preserving heat for 0.5-4 h under inert gas atmosphere; and then naturally decreasing the temperature of the graphene film, and then obtaining a porous graphene film by forming graphene micro-airbags; and
(5) suppressing the graphene micro-airbags and forming wrinkles, thereby obtaining the super-flexible high thermal conductive graphene film which has a density in a range of 1.93 to 2.11 g/cm 3 and meets a condition of I D /I G <0.01, here, I D is an intensity of D-peak and I G is an intensity of G-peak,
wherein the graphene oxide sheets with the average size of more than 100 μm are prepared through following steps of:
(A) diluting a reaction solution of the graphite oxide sheets obtained by Modified-Hummer method through concentrated sulfuric acid, wherein a volume of the concentrated sulfuric acid is 1-10 times of the volume of the reaction solution, and obtaining a filtered product by filtering the reaction solution with a mesh screen;
(B) obtaining a mixture by evenly mixing the filtered product obtained in the step (A) with ice water, and dropwise adding hydrogen peroxide into the mixture till a color of the mixture no longer changes which means that potassium permanganate in the mixture is completely removed;
(C) dropwise adding concentrated hydrochloric acid into the mixture added with hydrogen peroxide obtained in the step (B) till flocculent graphite oxide disappears, and then filtering out graphite oxide crystals through the mesh screen; and
(D) peeling off the graphite oxide crystals by placing the graphite oxide crystals obtained in the step (C) into a shaking table, shocking and washing, thereby obtaining the graphene oxide sheets with the average size of more than 100 μm; and
wherein:
the graphene film comprises multiple layers of planar oriented graphene sheets overlapped with each other through π-π conjugate action, wherein each of the multiple layers of planar oriented graphene sheets has an average size of more than 100 μm, each one to four of a partial of the multiple layers of planar oriented graphene sheets form a graphene structure, wherein a debris content of the graphene sheets with the average size of more than 100 μm by mass is lower than 1%; and
the graphene film has wrinkles on a surface and within an interior thereof.

2. The preparation method of the super-flexible high thermal conductive graphene film according to claim 1 , wherein the inorganic salt is ammonium bicarbonate, urea, thiourea, or azodicarbonamide; the small organic molecule is glycerol, polyethylene glycol 200 or polyethylene glycol 400; and the macromolecule is cellulose, gelatin, chitosan, waterborne polyurethane, or acrylic emulsion.

3. The preparation method of the super-flexible high thermal conductive graphene film according to claim 1 , wherein the reducing agent is hydrazine hydrate, amines, ascorbic acid, or hydrogen iodide.

4. The preparation method of the super-flexible high thermal conductive graphene film according to claim 1 , wherein a pressure and a time in the suppressing step are in a range of 50-200 MP and 6-300 h, respectively.

5. The preparation method of the super-flexible high thermal conductive graphene film according to claim 1 , wherein in the step (A), the Modified-Hummer method comprises sufficiently dissolving potassium permanganate in concentrated sulfuric acid with a mass fraction of 98% at −10° C., adding graphite, stirring at a speed of 60 rev/min for 2 h, stopping stirring, reacting for 6-48 h at a low temperature of −10° C. to 20° C., and obtaining the reaction solution, wherein a mass volume ratio of the graphite, the potassium permanganate and the concentrated sulfuric acid is 1 g:(2-4) g:(30-40) ml, and a granularity of graphite is larger than 150 μm.

6. The preparation method of the super-flexible high thermal conductive graphene film according to claim 1 , wherein the mesh screen is titanium alloy acid-resistant mesh screen.

Assignees

• Univ Zhejiang

Inventors

• Gao Chao
• Peng Li
• Jiang Yanqiu
• Liu Yingjun

Classifications

• C01P2002/82

  by IR- or Raman-data · CPC title

• C01B32/192 Primary

  starting from graphitic oxides · CPC title

• C01B2204/26

  Mechanical properties · CPC title

• C01B2204/04

  Specific amount of layers or specific thickness · CPC title

• C01P2006/10

  Solid density · CPC title