Process for producing graphene foam-based sealing materials
Provided is a process for producing a solid graphene foam-based sealing material. The process comprises: (a) preparing a graphene dispersion having a graphene material dispersed in a liquid medium, which contains an optional blowing agent; (b) dispensing and depositing the graphene dispersion into desired shapes and partially or completely removing the liquid medium from these shapes to form dried graphene shapes; (c) heat treating the dried graphene shapes at a first heat treatment temperature from 50° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from the non-carbon elements or to activate the blowing agent for producing the graphene foam; and (d) coating or impregnating the graphene foam with a permeation-resistant binder or matrix material to form the sealing material.
1. A process for producing a graphene foam-based sealing material from graphene sheets, said process comprising:
(a) preparing a graphene dispersion having multiple sheets of a graphene material dispersed in a liquid medium, wherein said graphene material is selected from the group consisting of pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, and combinations thereof, having a non-carbon element content of substantially 0% to 50% by weight, and wherein said dispersion contains a blowing agent having a blowing agent-to-graphene material weight ratio from 0/1.0 to 1.0/1.0;
(b) dispensing and depositing said graphene dispersion to form one or a plurality of elongated shapes and partially or completely removing said liquid medium from said shapes to form one or a plurality of dried elongated graphene shapes;
(c) heat treating the one or a plurality of dried elongated graphene shapes at a first heat treatment temperature from 50° C. to 3,200° C. at a desired heating rate sufficient to induce volatile gas molecules from said non-carbon elements or to activate said blowing agent for producing one or a plurality of solid graphene foam shapes having a density from 0.01 to 1.7 g/cm 3 or a specific surface area from 50 to 2,600 m 2 /g; and
(d) coating or impregnating said one or a plurality of solid graphene foam shapes with a binder or matrix material to form one or a plurality of said sealing materials, wherein said binder or matrix material comprises a polymer material, wherein said polymer is selected from the group consisting of thermoplastic resin, thermoset resin, rubber, thermoplastic elastomer, simultaneous penetrating network, and combinations thereof, wherein said rubber or thermoplastic elastomer is selected from the group consisting of butadiene rubber (BR), butyl rubber (IIR), chlorosulfonated polyethylene (CSM), epichlorohydrin rubber (ECH, ECO), ethylene propylene diene monomer (EPDM), ethylene propylene rubber (EPR), fluoroelastomer (FKM), nitrile rubber (NBR, HNBR, HSN, Buna-N), perfluoroelastomer (FFKM), polyacrylate rubber(ACM), polychloroprene (neoprene) (CR), polyisoprene (IR), polysulfide rubber (PSR), polytetrafluoroethylene (PTFE), sanifluor (FEPM), styrene-butadiene rubber (SBR), thermoplastic elastomer (TPE) styrenics, thermoplastic polyolefin (TPO), thermoplastic polyurethane (TPU), thermoplastic ether ester elastomers (TEEEs) copolyester, thermoplastic polyamide (PEBA), melt processible rubber (MPR), thermoplastic vulcanizate (TPV), and combinations thereof.
2. The process of claim 1 , further including a step of heat-treating the solid graphene foam at a second heat treatment temperature higher than said first heat treatment temperature for a length of time sufficient for obtaining a graphene foam wherein said pore walls contain stacked graphene planes having an inter-plane spacing d 002 from 0.3354 nm to 0.36 nm and a content of non-carbon elements less than 2% by weight.
3. The process of claim 2 , wherein said first or second heat treatment temperature includes at least a temperature selected from (A) 300-1,500° C., (B) 1,500-2,100° C., and/or (C) 2,100-3,200° C.
4. The process of claim 1 , wherein said dispersion contains a blowing agent having a blowing agent-to-graphene weight ratio from 0.01/1.0 to 1.0/1.0.
5. The process of claim 1 , wherein said binder or matrix material occupies from 10% to 98% of a pore volume of said solid graphene foam shapes.
6. The process of claim 5 , wherein said binder or matrix material occupies only an outer portion of a solid graphene foam shape, leaving behind a core portion free from said binder or matrix material.
7. The process of claim 1 , wherein said graphene-based sealing material is an O-ring.
8. The process of claim 1 , wherein said non-carbon elements include an element selected from oxygen, fluorine, chlorine, bromine, iodine, nitrogen, hydrogen, or boron.
9. The process of claim 1 , wherein said graphene material is selected from the group of non-pristine graphene materials consisting of graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, and combinations thereof, and wherein said first heat treatment temperature is less than 2,500° C. and said solid graphene foam contains a content of non-carbon elements in the range of 0.01% to 2.0% by weight.
10. The process of claim 1 , wherein said liquid medium consists of water, an alcohol, an organic solvent, or a combination thereof.
11. The process of claim 1 , which is a roll-to-roll process wherein said steps (b) and (c) include feeding said supporting substrate from a feeder roller to a deposition zone, continuously or intermittently depositing said graphene dispersion onto a surface of said supporting substrate to form said wet layer of graphene material thereon, drying said wet layer of graphene material to form the dried layer of graphene material, and collecting said dried layer of graphene material deposited on said supporting substrate on a collector roller.
12. The process of claim 1 , wherein said sheet of solid graphene foam has a density from 0.1 to 1.5 g/cm 3 .
13. The process of claim 1 , wherein said graphene foam has an oxygen content or non-carbon content less than 0.01%, pore walls having an inter-graphene spacing less than 0.34 nm, a thermal conductivity from 150 W/mK to 500 W/mK per unit of specific gravity, and/or an electrical conductivity from 2,000 S/cm to 4,000 S/cm per unit of specific gravity.
14. The process of claim 1 , wherein the pore walls comprises stacked graphene planes having an inter-graphene spacing less than 0.337 nm and a mosaic spread value less than 1.0 or wherein the solid graphene foam exhibits a degree of graphitization no less than 80% and/or a mosaic spread value less than 0.4.
15. The process of claim 1 , wherein pore walls of said solid graphene foam contain a 3D network of interconnected graphene planes.
16. The process of claim 1 , wherein said solid graphene foam comprises mesoscaled pores having a pore size from 2 nm to 50 nm.