Heat dissipation system comprising a unitary graphene monolith
A unitary graphene layer or graphene single crystal containing closely packed and chemically bonded parallel graphene planes having an inter-graphene plane spacing of 0.335 to 0.40 nm and an oxygen content of 0.01% to 10% by weight, which unitary graphene layer or graphene single crystal is obtained from heat-treating a graphene oxide gel at a temperature higher than 100° C., wherein the average mis-orientation angle between two graphene planes is less than 10 degrees, more typically less than 5 degrees. The molecules in the graphene oxide gel, upon drying and heat-treating, are chemically interconnected and integrated into a unitary graphene entity containing no discrete graphite flake or graphene platelet. This graphene monolith exhibits a combination of exceptional thermal conductivity, electrical conductivity, mechanical strength, surface smoothness, surface hardness, and scratch resistance unmatched by any thin-film material of comparable thickness range.
1. A heat dissipation system comprising a heat spreader comprising a unitary grapheme monolith comprising closely packed and chemically bonded parallel graphene oxide planes having an inter plane spacing of 0.335 to 0.50 nm, a thickness greater than 10 nm, an electrical conductivity from 1,500 S/cm to 15,000 S/cm, a thermal conductivity from 600 W/mK to 1807 W/mk, and a physical density greater than 1.8 g/cm 3 , and an oxygen content of 0.01% to 10% by weight, wherein an average mis-orientation angle between two graphene oxide planes is less than 10 degrees.
2. The heat dissipation system of claim 1 , wherein the heat spreader has a thickness from 10 nm to 200 μm.
3. The heat dissipation system of claim 1 , wherein the heat spreader has a density from 1.8 g/cm 3 to 2.1 g/cm 3 .
4. The heat dissipation system of claim 1 , wherein the heat spreader has a tensile strength from 40 MPa to 121 MPa.
5. The heat dissipation system of claim 1 , wherein the heat spreader has a Rockwell hardness from 34 to 88.
6. The heat dissipation system of claim 1 , wherein the heat spreader contains a poly-crystal having an incomplete grain boundary, and contains no discrete graphite flake or grapheme platelet dispersed therein.
7. The heat dissipation system of claim 1 , wherein the heat spreader contains no complete grain boundary therein.
8. The heat dissipation system of claim 1 , wherein the chemically bonded parallel grapheme planes contain a combination of sp2 and sp3 electronic configurations.
9. The heat dissipation system of claim 1 , wherein the heat spreader contains grains from 100 μm to 1 cm in size.
10. The heat dissipation system of claim 1 , wherein the heat spreader further comprises a protective layer.
11. The heat dissipation system of claim 10 , wherein the protective layer is selected from electrically insulating including PET film and resin.
12. The heat dissipation system of claim 1 , wherein the unitary graphene monolith further comprises nano graphene platelets (NGP) at 1% to 50% by weight.
13. The heat dissipation system of claim 1 , wherein the heat spreader further comprises a graphitic substrate.
14. The heat dissipation system of claim 13 , wherein the graphitic substrate comprises a material selected from pristine graphene paper, carbon nanotube paper, carbon nanofiber mat, flexible graphite foil, graphite-epoxy composite film, carbon-carbon composite layer, carbon paper, and combinations thereof.
15. The heat dissipation system of claim 1 , comprising a unitary graphene monolith coated onto one or two primary surfaces of a graphitic substrate, wherein the coating has a thickness of 10 μm to 80 μm.
16. The heat dissipation system of claim 1 , wherein the heat spreader further comprises a graphitic core.
17. The heat dissipation system of claim 16 , wherein the graphitic core comprises a material selected from pristine graphene paper, carbon nanotube paper, carbon nanofiber mat, flexible graphite foil, graphite-epoxy composite film, carbon-carbon composite layer, carbon paper, and combinations thereof.
18. The heat dissipation system of claim 17 , wherein the graphitic core has a thickness from 100 μm to 268 μm.
19. The heat dissipation system of claim 1 , comprising a unitary graphene monolith coated onto two primary surfaces of a graphitic core layer, wherein the coating has a thickness of 10 μm to 80 μm per layer.
20. The heat dissipation system of claim 1 , configured for use in a power tool; a microelectronic or telecommunication device including mobile phone, tablet, laptop computer and LCD display; or a light-emitting diode (LED) lighting device or system.