Highly conducting graphitic films from graphene liquid crystals
View Patent ↗A process for producing a highly oriented graphitic film, consisting of (a) preparing a dispersion having graphene oxide (GO) or chemically functionalized graphene (CFG) dispersed in a liquid to form a liquid crystal phase (but not in a GO gel state); (b) depositing the dispersion onto a supporting substrate to form a layer of GO or CFG under an orientation-inducing stress; (c) removing the liquid to form a dried GO or CFG layer having an inter-plane spacing d 002 of 0.4 nm to 1.2 nm; (d) thermally reducing the dried layer at a first temperature higher than 100° C. to produce a porous layer of reduced GO or CFG; (e) further heat-treating the porous layer at a second temperature to produce a porous graphitic film having an inter-plane spacing d 002 less than 0.4 nm; and (f) compressing the porous graphitic film to produce the highly oriented graphitic film.
1. A highly oriented graphitic film comprising a graphitic material, chemically functionalized graphitic material, or a combination thereof, wherein said film contains chemically bonded graphene planes that are parallel to one another and said film has a thickness from 100 nm to 0.1 mm, a physical density from 1.8 g/cm 3 to 2.15 g/cm 3 , an inter-plane spacing d 002 from 0.3354 nm to 0.4 nm, an oxygen content or non-carbon element content less than 1% by weight, and an electrical conductivity from 3,000 S/cm to 20,000 S/cm.
2. The highly oriented graphitic film of claim 1 , wherein said chemically functionalized graphitic material contains a chemical functional group selected from a polymer, SO 3 H, COOH, NH 2 , OH, R′CHOH, CHO, CN, COCI, halide, COSH, SH, COOR′, SR′, SiR′ 3 , Si(—OR′—)yR′ 3 -y, Si(—O—SiR′ 2 —)OR′, R″, Li, AlR′ 2 , Hg—X, TlZ 2 and Mg—X; wherein y is an integer equal to or less than 3, R′ is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly(alkylether), R″ is fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, X is halide, and Z is carboxylate or trifluoroacetate, or a combination thereof.
3. The highly oriented graphitic film of claim 1 , wherein said film further comprises a polymer dispersed in or attached to the graphitic material, chemically functionalized graphitic material, or a combination thereof.
4. The highly oriented graphitic film of claim 1 , wherein said film thickness is from 100 nm to 50 μm.
5. The highly oriented graphitic film of claim 1 , wherein said film contains both pristine graphene planes and non-pristine graphene planes, and the weight ratio between said pristine graphene planes and said non-pristine graphene planes is from 1/10 to 10/1.
6. The highly oriented graphitic film of claim 1 , wherein said inter-plane spacing d 002 is from 0.3354 nm to 0.36 nm and said oxygen content or non-carbon element content is from 0.001% to 0.1% by weight.
7. The highly oriented graphitic film of claim 1 , wherein said oxygen content is less than 0.01%, and said an inter-graphene spacing is from 0.3354 nm to 0.345 nm.
8. The highly oriented graphitic film of claim 1 wherein said film has an oxygen content no greater than 0.001%, an inter-graphene spacing from 0.3354 nm to 0.336 nm, a mosaic spread value from 0.7 to 1.0, a thermal conductivity from 1,500 W/mK to 1,745 W/mK, and/or an electrical conductivity from 10,000 S/cm to 20,000 S/cm.
9. The highly oriented graphitic film of claim 1 wherein said film has an oxygen content no greater than 0.001%, an inter-graphene spacing from 0.3354 nm to 0.336 nm, a mosaic spread value from 0.2 to 0.4, a thermal conductivity from 1,600 W/mK to 1,745 W/mK, and/or an electrical conductivity from 10,000 S/cm to 20,000 S/cm.
10. The highly oriented graphitic film of claim 1 wherein said film exhibits an inter-graphene spacing from 0.3354 nm to 0.337 nm and a mosaic spread value from 0.4 to 1.0.
11. The highly oriented graphitic film of claim 1 wherein said film exhibits a degree of graphitization from 80% to essentially 100% and/or a mosaic spread value from 0.2 to 0.4.
12. The highly oriented graphitic film of claim 1 wherein said film exhibits a degree of graphitization from 90% to essentially 100% and/or a mosaic spread value from 0.2 to 0.4.
13. The highly oriented graphitic film of claim 1 wherein said film contains chemically bonded graphene planes having a maximum original graphite grain size and said highly oriented graphene film is a poly-crystal graphene structure having a grain size larger than said maximum original grain size.
14. The highly oriented graphitic film of claim 1 wherein said highly oriented graphene film is a poly-crystal graphene structure having a preferred crystalline orientation as determined by said X-ray diffraction method.
15. The highly oriented graphitic film of claim 1 , wherein said film exhibits a thickness from 100 nm to 20 μm and a thermal conductivity from 1,000 W/mK to 1,745 W/mK.
16. The highly oriented graphitic film of claim 7 , where said film exhibits a thermal conductivity from 1,000 W/mK to 1,745 W/mK.
17. The highly oriented graphitic film of claim 1 , wherein said film has an oxygen content less than 0.01%, an inter-graphene spacing from 0.3354 nm to 0.337 nm and an electrical conductivity from 5,000 S/cm to 20,000 S/cm.
18. The highly oriented graphitic film of claim 1 wherein said film has an electrical conductivity from 5,000 S/cm to 20,000 S/cm, a thermal conductivity from 800 W/mK to 1,745 W/mK, a physical density from 1.9 g/cm 3 to 2.15 g/cm 3 , a tensile strength from 80 MPa to 120 MPa, and/or an elastic modulus from 60 GPa to 120 GPA.
19. The highly oriented graphitic film of claim 1 wherein said film has an electrical conductivity from 8,000 S/cm to 20,000 S/cm, a thermal conductivity from 1,200 W/mK to 1,745 W/mK, a physical density from 2.0 g/cm 3 to 2.15 g/cm 3 a tensile strength from 100 MPa to 120 MPa, and/or an elastic modulus from 80 GPa to 120 GPA.
20. The highly oriented graphitic film of claim 1 wherein said film has an electrical conductivity from 12,000 S/cm to 20,000 S/cm, a thermal conductivity from 1,500 W/mK to 1,745 W/mK, a physical density from 2.1 g/cm 3 to 2.15 g/cm 3 .
21. A microelectronic device containing the highly oriented graphitic film of claim 1 as a heat-dissipating element.
22. The microelectronic device of claim 21 , wherein said microelectronic device is a smart phone, tablet computer, flat-panel display, flexible display, LED lighting device, electronic watch, a wearable electronic device, a digital camera, or a microelectronic communications device.
23. A process for producing a highly oriented graphitic film of claim 1 , wherein said film has a thickness from 100 nm to 0.1 mm and physical density from 1.8 g/cm 3 to 2.15 g/cm 3 , said process comprising:
a) preparing a dispersion of pristine graphene having pristine graphene sheets dispersed in a liquid medium, wherein said pristine graphene sheets are in an amount sufficient to form a pristine graphene liquid crystal phase in said liquid medium;
b) dispensing and depositing said dispersion onto a surface of a supporting substrate to form a layer of pristine graphene, wherein said dispensing and depositing procedure includes subjecting said liquid crystal phase to an orientation-inducing stress;
c) partially or completely removing said liquid medium from the pristine graphene layer to form a dried pristine graphene layer having a layer thickness from 100 nm to 200 μm;
d) optionally compressing said dried pristine graphene layer to reduce a thickness of said pristine graphene layer;
e) heat-treating said pristine graphene layer at a temperature from 1,500° C. to 3,250° C. for a sufficient period of time to produce a graphitic film having an inter-plane spacing d 002 from 0.3354 nm to 0.37 nm; and
f) compressing said graphitic film to produce said highly oriented graphitic film.
24. The highly oriented graphitic film of claim 1 , wherein said film exhibits a thermal conductivity from 5 W/mK to 10 W/mK along the crystallographic C-axis direction.
25. A process for producing a highly oriented graphitic film comprising a graphitic material and further comprising chemically functionalized graphitic material or graphene oxide, wherein said film contains chemically bonded graphene planes that are parallel to one another and said film has a thickness from 100 nm to 0.1 mm, a physical density from 1.8 g/cm 3 to 2.15 g/cm 3 , an inter-plane spacing d 002 from 0.3354 nm to 0.4 nm, an oxygen content or non-carbon element content less than 1% by weight, and an electrical conductivity from 3,000 S/cm to 20,000 S/cm, said process comprising:
a) preparing a dispersion of pristine graphene comprising pristine graphene sheets dispersed in a liquid medium, wherein said pristine graphene sheets are in an amount sufficient to form a pristine graphene liquid crystal phase in said liquid medium
b) adding graphene oxide sheets or chemically functionalized graphene sheets to said dispersion of pristine graphene, wherein said graphene oxide sheets or chemically functionalized graphene sheets comprise 0% to 20% by weight of the graphene sheets in said dispersion;
c) dispensing and depositing said dispersion onto a surface of a supporting substrate to form a layer of graphene material, wherein said dispensing and depositing procedure includes subjecting said liquid crystal phase to an orientation-inducing stress;
d) partially or completely removing said liquid medium from a layer of graphene material to form a dried a layer of graphene material having a layer thickness from 100 nm to 200 μm;
e) optionally compressing said a layer of graphene material to reduce a thickness of said material;
f) heat-treating said a layer of graphene material under optional compressive stress at a temperature from 1,500° C. to 3,250° C. for a sufficient period of time to produce a graphitic film having an inter-plane spacing d 002 from 0.3354 nm to 0.37 nm; and
g) optionally compressing said graphitic film to produce said highly oriented graphitic film.