KR20220059491A - Graphene Based Elastic Heat Spreader Film - Google Patents

Abstract

(a) an elastomer or rubber as a binder material or matrix material; and (b) an elastic heat spreader film (and a manufacturing process for manufacturing the same) comprising a plurality of graphene sheets dispersed in a matrix material or bonded by a binder material, wherein the plurality of graphene sheets are substantially parallel to each other. and the elastomer or rubber is present in an amount of 0.001 wt % to 20 wt % based on the total weight of the heat spreader film, and the plurality of graphene sheets are pure graphene. Graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene , or a combination thereof, wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and an in-plane thermal conductivity of 200 W/mK to 1,750 W/mK. .

Description

Graphene Based Elastic Heat Spreader Film

This application claims priority to U.S. Patent Application Serial No. 16/559,000, filed September 3, 2019, and U.S. Patent Application Serial No. 16/559,004, filed September 3, 2019, the content of each is incorporated herein by reference for all purposes.

The present invention relates generally to the field of heat films or heat spreaders, and more particularly to graphene-based high modulus heat spreader films and manufacturing processes thereof.

Advanced thermal management materials are becoming increasingly important in today's microelectronic systems, photonic systems, and photovoltaic systems. As new and more powerful chip designs and light emitting diode (LED) systems are introduced, they consume more power and generate more heat. This makes thermal management an important issue in today's high-performance systems. Systems ranging from active electronic scanning radar arrays, web servers, large battery packs for personal appliances, widescreen displays and solid-state lighting devices all have high thermal conductivity to dissipate heat more efficiently. material is needed In addition, many microelectronic devices (eg, smartphones, flat screen TVs, tablets, and laptop computers) are designed and manufactured to get smaller, thinner, lighter, and more rigid. This further increases the difficulty of heat dissipation. Indeed, thermal management issues are now widely recognized as a major obstacle to the industry's ability to continuously improve device and system performance.

A heat sink is a component that facilitates heat dissipation from a heat source surface, such as a CPU or battery, of a computing device to a cooler environment, such as the atmosphere. In general, the heat generated by a heat source must be transferred to a heat sink or atmosphere through a heat spreader. Heat sinks are primarily designed to improve heat transfer efficiency between air and heat sources through increased heat sink surface area in direct contact with air. This design allows for faster heat dissipation, lowering the device operating temperature. In microelectronic devices, the high thermal conductivity of a heat spreader is essential for rapid heat transfer from a heat source to a heat sink or atmosphere.

Graphene sheet, also referred to as nano graphene platelet (NGP), is essentially a pristine graphene material containing 0% non-carbon elements, or 0.001% by weight to 0.001% by weight of non-carbon elements. It means a single-layer or few-layer graphene sheet selected from impure graphene materials containing 25 wt %, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide , graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof. A few-layer graphene sheet contains 2 to 10 graphene planes (one atom thick hexagonal planes of carbon atoms).

The heat-spreading application of graphene-based films was first developed by our research group already in 2007: "Nanoscale Graphene Plate Films and Articles" by Bor Z. Jang et al., U.S. Patent Application Serial No. 11/784,606 (April 9, 2007); Current U.S. Patent No. 9,233,850 (January 12, 2016). Foldable portable devices (eg, foldable or bendable smart phones) are becoming more and more popular. A foldable smartphone can be folded and unfolded over 10,000 times during the useful life of the phone. Individual components such as heat spreaders must also be collapsible in these devices. However, it is not known that graphene-based thermal films (or thermal films of any type) can withstand repeated bending deformation without significantly compromising desirable properties such as thermal conductivity and structural integrity.

The present invention was made to overcome the limitations of the prior art heat spreader films described above.

In certain embodiments, the present invention provides a composition comprising: A) an elastomer or rubber as a binder material or matrix material; and B) providing an elastic heat spreader film comprising a plurality of graphene sheets bonded by a binder material or dispersed in a matrix material, wherein the plurality of graphene sheets are aligned to be substantially parallel to each other, and wherein the elastomer or rubber is disposed on the heat spreader. present in an amount of 0.001 wt % to 20 wt % based on the total weight of the film, wherein the plurality of graphene sheets is a pure graphene material comprising essentially 0 % non-carbon element or 0.001 wt % to 25 wt % non-carbon A single-layer or few-layer graphene sheet selected from impure graphene materials containing elements, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene selected from pin iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof (preferably, the chemically functionalized graphene is not graphene oxide) and the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and an in-plane thermal conductivity of 200 W/mK to 1,750 W/mK (preferably and generally greater than 500 W/mK). The heat spreader film generally has a thickness of 10 nm to 500 μm.

The elastomer or rubber should have a high elasticity - a high tensile elastic deformation value (2% to 1,000%) that is fully recoverable. By definition, "elastic deformation" is a deformation that is fully recoverable upon release of a mechanical load, and it is well known in materials science and engineering that the recovery process is intrinsically instantaneous (without significant time delay). Elastomers, such as vulcanized natural rubber, contain from 2% to up to 1,000% (10 times their original length), more typically from 10% to 800%, even more typically from 50% to 500%, most typically and preferably from 100% to 300%. % of tensile elastic strain. If you use two hands to stretch the rubber band from 5 cm to 40 cm, then release the rubber band from one hand, the rubber band will return to its original length virtually immediately. Such deformations (800% in this example) are fully recoverable and virtually no plastic deformation (permanent deformation). Materials other than elastomers or rubbers do not exhibit such elastic behavior.

For example, although metals generally have high tensile ductility (i.e., they can expand to a large extent without breakage, e.g., from 10% to 200%), most strains are plastic (non-recoverable) and small amounts of Only strain is elastic strain (ie recoverable strain typically < 1 %, more typically < 0.2 %). Likewise, non-elastomeric polymers or plastics (thermoplastics or thermosets) can be stretched to a large extent, but most strains are plastic strain, a permanent strain that cannot be recovered upon release of stress/strain. For example, polyethylene (PE) can stretch up to 200% under tensile loading, but the majority of such strains (>98%) are permanent irrecoverable strains commonly referred to as plastic strains.

In some embodiments, the elastomer or rubber is a natural polyisoprene (eg, cis-1,4-polyisoprene natural rubber (NR) and trans-1,4-polyisoprene guttaperca), synthetic polyisoprene (isoprene high Non-IR), polybutadiene (BR for butadiene rubber), chloroprene rubber (CR), polychloroprene (eg neoprene, vaperene, etc.), halogenated butyl rubber (chlorobutyl rubber (CIIR) and bromobutyl rubber (BIIR) ) containing butyl rubber (copolymer of isobutylene and isoprene, IIR), styrene-butadiene rubber (copolymer of styrene and butadiene, SBR), nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), EPM (ethylene propylene rubber, copolymer of ethylene and propylene), EPDM rubber (ethylene propylene diene rubber, terpolymer of ethylene, propylene and diene components), epichlorohydrin rubber (ECO), polyacrylic rubber (ACM, ABR) , silicone rubber (SI, Q, VMQ), fluorosilicone rubber (FVMQ), fluoroelastomer (FKM and FEPM; Viton, Technoflon, Florel, Aplace and Dai-EI, etc.), perfluoroelastomer (FFKM) : Technoflon PFR, Callez, Chemraz, Perlast), polyether block amides (PEBA), chlorosulfonated polyethylene (CSM; e.g. Hypalon, and ethylene-vinyl acetate (EVA), thermoplastic elastomers (TPE) ), protein resillin, protein elastin, ethylene oxide-epichlorohydrin copolymer, polyurethane, urethane-urea copolymer, and combinations thereof.

The resulting heat spreader film comprising an elastomer or rubber suitably selected as a binder or matrix material for holding the aligned graphene sheets together is surprisingly >2%, more typically >5%, even more typically >10%, It can be stretched even more commonly to tensile-elastic strains of > 20 %, and often > 50 % (eg up to 100 %).

It can be seen that, due to such high elastic properties, the heat spreader film can be bent or folded back and forth tens of thousands of times without significantly lowering the thermal conductivity. The thermal conductivity before the first bend, which is typically between 500 W/mK and 1,750 W/mK, can maintain >80% (typically >90%) of the original thermal conductivity after repeated 10000 bends.

Preferably, in the foregoing embodiments, the elastomer or rubber is present in an amount of 0.001% to 20% by weight, more preferably 0.01% to 10% by weight, even more preferably 0.1% to 1% by weight.

In certain preferred embodiments, the graphene sheet mainly comprises monolayer graphene (90% to 100%) having an average number of layers of 1 to 2. In a specific embodiment, the graphene sheet comprises single-layer graphene and a few-layer graphene sheet having an average number of layers of less than 5. Few-layer graphene is generally defined as a graphene sheet having 2 to 10 graphene planes.

In some very useful embodiments, the heat spreader film is in the form of a thin film having a thickness of 5 nm to 500 μm, and the graphene sheet is aligned substantially parallel to the plane of the thin film. In some preferred embodiments, the heat spreader is in the form of a thin film having a thickness of 10 nm to 100 μm, and the graphene sheet is aligned substantially parallel to the plane of the thin film.

In general, the disclosed heat spreader films all have a tensile strength of 100 MPa or more, a tensile modulus of 25 GPa or more, a thermal conductivity of 500 W/mK or more, and/or an electrical conductivity of 5,000 S/cm or more, all measured along the thin film plane direction. have Generally and preferably, the metal matrix nanocomposite has a tensile strength of at least 300 MPa, a tensile modulus of at least 50 GPa, a thermal conductivity of at least 800 W/mK, and/or at least 8,000 S/cm, all measured along the thin film plane direction. have electrical conductivity. In many cases, the elastic heat spreader film has a tensile strength of 400 MPa or more, a tensile modulus of 150 GPa or more, a thermal conductivity of 1,200 W/mK or more, and/or an electrical conductivity of 12,000 S/cm or more, all measured along the thin film plane direction. have Some of the disclosed heat spreader films all have a tensile strength of 500 MPa or more, a tensile modulus of 250 GPa or more, a thermal conductivity of 1,500 W/mK or more, and/or an electrical conductivity of 20,000 S/cm or more, measured along the thin film plane direction.

In some embodiments, the elastic heat spreader film has a thickness t, front and back, and the elastomer/rubber is impregnated from two major surfaces (front and back). The elastomer or rubber may penetrate a distance 1/3 t into the film region from the front side and/or penetrate at least a distance 1/3 t into the film region from the back side, and there is an elastomer-free core (i.e., the elastomer or rubber does not reach the center or core region of the film). The size of these elastomer-free cores is generally 1/10t to 4/5t.

In certain embodiments, the graphene sheet includes functional groups attached thereto to make the graphene sheet exhibit a negative zeta potential with a value of -55 mV to -0.1 mV.

The graphene sheet is an alkyl or aryl silane, an alkyl or aralkyl group, a hydroxyl group, a carboxyl group, an epoxide, a carbonyl group, an amine group, a sulfonate group (-SO ₃ H), an aldehyde group, a quinoidal, a fluorocarbon, or a combination thereof. selected chemical functional groups.

In a specific embodiment, the graphene sheet is made of amidoamine, polyamide, aliphatic amine, modified aliphatic amine, cycloaliphatic amine, aromatic amine, anhydride, ketimine, diethylenetriamine (DETA), triethylene-tetramine ( TETA), tetraethylene-pentamine (TEPA), polyethylene polyamine, polyamine epoxy adduct, phenolic curing agent, non-brominated curing agent, non-amine curing agent, and combinations thereof chemically functionalized graphene Includes sheet.

Graphene sheet is OY, NHY, O=C--OY, P=C--NR'Y, O=C--SY, O=C--Y, --CR'1--OY, N'Y or a chemical functional group selected from C'Y, wherein Y is a functional group of a protein, peptide, amino acid, enzyme, antibody, nucleotide, oligonucleotide, antigen, or enzyme substrate, wherein the enzyme inhibitor or transition state analog of the enzyme substrate is R'--OH, R'--NR' ₂ , R'SH, R'CHO, R'CN, R'X, R'N ⁺ (R') ₃ X ^- , R'SiR' ₃ , R'Si(--OR'--) _y R' _3-y , R'Si(--O--SiR' ₂ --)OR', R'--R", R'--N--CO, (C ₂ H ₄ O--) _w H, (--C ₃ H ₆ O--) _w H, (--C ₂ H ₄ O) _w --R', (C ₃ H ₆ O) _w - -R', R', and w is an integer greater than 1 and less than 200.

The present invention also provides an electronic device comprising the aforementioned heat spreader film as a component (eg, thermal management element).

The present invention also provides structural members comprising a heat spreader film disclosed as a load-bearing and thermal management element.

Also disclosed herein is a process for making an elastic heat spreader film. In some embodiments, the process comprises (a) forming a layer of aggregates or clusters of a plurality of oriented/aligned graphene sheets that are substantially parallel to each other and (b) rubber or elastomeric chains forming gaps between the graphene sheets. or elastomeric/rubber-impregnated aggregates/clusters of a plurality of oriented/aligned graphene sheets in such a way as to fill defects and/or chemically bond to the graphene sheets or the graphene sheets are dispersed in a matrix comprising an elastomer or rubber. a procedure of bonding a rubber or elastomer and a graphene sheet to form, wherein the elastomer or rubber is present in an amount of 0.001 wt % to 20 wt % based on the total weight of the heat spreader film, wherein the elastic heat spreader film comprises 2 It has a fully recoverable tensile elastic strain of % to 100% and an in-plane thermal conductivity of 200 W/mK to 1,750 W/mK.

The plurality of graphene sheets is preferably a pure graphene material (defined as essentially graphene having 0 % (< 0.001 wt %) non-carbon elements) or (0.001 wt % to 25 wt % non-carbon elements) defined as graphene material) comprising a single or few-layer graphene sheet selected from an impure graphene material, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromine and graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or combinations thereof.

In certain embodiments, the process

(A) providing a layer of aggregates or clusters of a plurality of graphene sheets; and

(B) impregnating the aggregate or cluster with an elastomer or rubber as a binder material or matrix material to prepare an impregnated aggregate or cluster, wherein the plurality of graphene sheets are bonded by the binder material or dispersed in the matrix material; , the elastomer or rubber is present in an amount of 0.001% to 20% by weight, based on the total weight of the heat spreader film, wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and 200 W/mK to 1,750 It has an in-plane thermal conductivity of W/mK.

The process may further comprise (C) compressing the impregnated aggregates or clusters to produce a heat spreader film, wherein the plurality of graphene sheets are aligned substantially parallel to each other.

In certain embodiments, the elastomer or rubber is based on natural polyisoprene, synthetic polyisoprene, polybutadiene, chloroprene rubber, polychloroprene, butyl rubber, styrene-butadiene rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, metallocene. Poly(ethylene-co-octene) elastomer, poly(ethylene-co-butene) elastomer, styrene-ethylene-butadiene-styrene elastomer, epichlorohydrin rubber, polyacrylic rubber, silicone rubber, fluorosilicone rubber, perfluoro Elastomers, polyether block amides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, protein resillin, protein elastin, ethylene oxide-epichlorohydrin copolymer, polyurethane, urethane-urea copolymer, sulfonated thereof versions, precursors thereof, or combinations thereof.

In the disclosed process, in some embodiments, step (A) of providing a layer of an aggregate or cluster of a plurality of graphene sheets is selected from coating, casting, air assisted clustering, liquid assisted clustering, spraying, printing, or a combination thereof. includes procedures. The coating procedure may be selected from vapor deposition, chemical coating, electrochemical coating or plating, spray coating, painting, brushing, roll-to-roll coating, physical coating, or combinations thereof.

Preferably, the roll-to-roll coating is air knife coating, anilox coating, flexo coating, gap coating or knife-over-roll coating, gravure coating, hot melt coating, dip dip coating, kiss coating, metering rod or Meyer bar coating, roller coating, silk screen coating or rotary screen coating, slot-die coating, extrusion coating, inkjet printing, or a combination thereof.

In some embodiments, step (A) comprises (i) dispersing a plurality of graphene sheets in a liquid medium to form a suspension (also referred to herein as a dispersion or slurry), (ii) wetting the graphene sheets dispensing or depositing the suspension on the substrate surface to form aggregates or clusters, and (iii) partially or completely removing the liquid medium from the wet aggregates or clusters to form aggregates or clusters of a plurality of graphene sheets. includes In some embodiments, the process further comprises compressing or consolidating the aggregates or clusters to align the plurality of graphene sheets and/or to reduce the porosity of the aggregates or clusters. It can be seen that this compression procedure is an addition to the compression procedure of step (C) in the disclosed process.

In some embodiments, step (A) comprises spraying the plurality of graphene sheets, with or without the use of a dispersion liquid medium, onto the surface of the solid substrate to form an aggregate or cluster of the plurality of graphene sheets. . In some preferred embodiments, the process further comprises, after step (A), a procedure for heat-treating the layer of aggregates or clusters of the plurality of graphene sheets at a temperature selected from 50° C. to 3,200° C. or at a plurality of different temperatures.

In some embodiments, the process may further comprise (after step (A)) compressing or consolidating the aggregates or clusters to align the plurality of graphene sheets and/or to reduce the porosity of the aggregates or clusters. . In some embodiments, the process further comprises a procedure for heat-treating the layer of aggregates or clusters of the plurality of graphene sheets at a temperature selected from 50° C. to 3,200° C. or a plurality of different temperatures after the compressing or consolidating procedure.

In some preferred embodiments, the heat treatment procedure comprises heat-treating (e.g., heating at 100° C. for 2 hours) a layer of aggregates or clusters of a plurality of graphene sheets at a temperature selected from 50° C. After heating at 1,200° C. for 3 hours, heating at 2,800° C. for 1 hour). The heat treatment procedure is performed before or after the compression/consolidation procedure, but prior to impregnation of the elastomer or rubber.

In a specific embodiment, step (A) comprises the steps of (i) preparing a graphene dispersion comprising a plurality of individual graphene sheets dispersed in a liquid adhesive resin; and (ii) bringing the graphene dispersion into physical contact with the solid substrate surface, and aligning the graphene sheet along the planar direction of the substrate surface supported by and bonded to the substrate surface. In some embodiments, step (B) comprises performing a procedure selected from the following procedures: spraying, painting, coating, casting, or printing a layer of graphene dispersion on the substrate surface and the graphene sheets are substantially parallel to each other and bonded to the substrate surface and aligning the graphene sheet along the planar direction of the substrate surface to be supported thereby. The solid substrate may include a polymer film having a thickness of 5 μm to 200 μm.

In a specific embodiment, step (A) comprises feeding a continuous polymer film as a solid substrate from a polymer film feeder to a graphene deposition chamber containing a graphene dispersion. Step (B) is a binder/matrix elastomer/rubber (or its uncured rubber or unsolidified thermoplastic elastomer, precursor) and operating the graphene deposition chamber to deposit the graphene sheet. In some embodiments, step (C) comprises an elastomer with the substrate polymer film into an integrated region (eg, comprising a pair of rollers) that acts to align the graphene sheets parallel to the substrate plane and substantially parallel to each other. /moving the rubber-impregnated graphene cluster. The integration area may include a device (eg, a heater) for curing the rubber or incorporating the elastomer. The process may further comprise stopping to operate a winding roller to collect the layer of rubber/elastomer-impregnated graphene clusters/aggregates supported on the substrate polymer film. This is a roll-to-roll or reel-to-reel process capable of mass production.

Step (A) is generally a graphene sheet separated through chemical oxidation/intercalation of graphite, liquid exfoliation of graphite, electrochemical exfoliation of graphite, supercritical fluid exfoliation of graphite, or high shear exfoliation of graphite, etc. It begins with the manufacturing step. By these processes, lateral dimensions of 5 nm to 100 μm and thicknesses of 1 atom carbon planes of hexagonal carbon atoms (single layer graphene as small as 0.34 nm) to 10 hexagonal planes (2 to 10 planes or few layers of graphene) Separated individual graphene sheets with

In certain embodiments, step (A) of providing a layer of aggregates or clusters of a plurality of graphene sheets comprises a procedure selected from coating, casting, air assisted clustering, liquid assisted clustering, spraying, printing, or a combination thereof. . The coating procedure is preferably selected from vapor deposition, chemical coating, electrochemical coating or plating, spray coating, painting, brushing, roll-to-roll coating, physical coating, or a combination thereof. Examples of physical coating processes include spin coating, dip coating, solution coating, and the like.

Common roll-to-roll coating processes that can be used in the disclosed process include air knife coating, Anilox coating, Flexo coating, gap coating (knife-over-roll coating), gravure coating, hot melt coating, dip dip coating , kiss coating, metering rod (Meyer bar) coating, roller coating (eg forward roller coating and reverse roller coating), silk screen coating (rotary screen coating), slot-die coating, extrusion coating (curtain) coating, slide coating based coating, slot-die bead coating, tension-web slot-die coating), inkjet printing, or combinations thereof.

Preferably, the process is performed so that the graphene sheet exhibits a negative zeta potential of preferably -55 mV to -0.1 mV in the desired solution (pure graphene, graphene oxide, reduced graphene oxide, graphene). and chemically functionalizing fin fluoride, nitrogenated graphene, etc.). This zeta potential can promote attraction of specific rubber functional groups to the graphene surface.

In step (B), via the forced assembly approach schematically shown in Figs. 3(a), 3(b), 3(c) and 3(d) (with or without elastomer/rubber resin) ) alignment of graphene sheets can be achieved. Accordingly, the present invention also provides a process for making an elastic heat spreader film, the process comprising the steps of (a) dispersing individual graphene sheets in a liquid medium to form a graphene dispersion; (b) subjecting the graphene dispersion to a forced assembling and orientation procedure that forces the graphene sheets to form layers of aggregates/clusters of aligned graphene sheets that are substantially parallel to each other; and impregnating the rubber/elastomer (or precursor thereof) into the aggregate/cluster, and incorporating a layer of rubber/elastomeric impregnated graphene sheet aligned to a desired elastic heat spreader film, wherein the graphene sheet is incorporated into the rubber/elastomeric material. bound to or dispersed therein, aligned to be substantially parallel to each other, and present in an amount of 80% to 99.999% by weight based on the total weight of the heat spreader. Although not preferred, the graphene dispersion may include an elastomer/rubber or a precursor thereof (eg, uncured resin) prior to subjecting the graphene dispersion to a forced assembly and orientation procedure.

In the disclosed process, the forced assembling and orientation procedure introduces a graphene dispersion with an initial volume (V ₁ ) into the mold cavity cell and into the mold cavity cell to reduce the graphene dispersion volume to a smaller value (V ₂ ). inserting a piston to allow excess liquid medium to flow out of the cavity cell and aligning the graphene sheet along the desired direction.

In a specific embodiment, the forced assembling and orientation procedure introduces a graphene dispersion with an initial volume (V ₁ ) into the mold cavity cell, and reduces the graphene dispersion volume to a smaller value (V ₂ ) of the mold cavity. applying suction pressure through the porous wall to cause excess liquid medium to flow out of the cavity cell through the porous wall and aligning the graphene sheet along the desired direction.

The forced assembling and orientation procedure introduces a first graphene dispersion layer to the supporting conveyor surface, reduces the thickness of the graphene dispersion layer, and follows a direction parallel to the conveyor surface to form an aligned graphene sheet layer. passing the layer of graphene dispersion supported on the conveyor past at least one pair of pressing rollers to align the graphene sheets.

The process includes introducing a second graphene dispersion layer to the layer surface of the graphene sheet to form a two-layer structure and reducing the thickness of the second graphene dispersion layer and the conveyor surface to form the graphene sheet layer The method may further include passing the two-layer structure through at least one pair of pressing rollers to align the graphene sheets along a direction parallel to the .

The process may further include compressing or roll pressing the layer of the graphene sheet to reduce the layer thickness and improve the orientation of the graphene sheet.

Accordingly, in some specific embodiments, the present invention also provides an alternative procedure for obtaining a heat spreader film comprising a rubber/elastomer-impregnated aggregate/cluster layer of aligned graphene sheets bonded to a major surface of a polymeric film. These procedures are

(a) supplying a continuous polymer film from a polymer film feeder to a graphene deposition chamber, wherein the graphene deposition chamber is liquid as a precursor to a rubber/elastomer (eg, uncured monomer and curing agent for rubber/elastomer). receiving a graphene dispersion comprising a plurality of individual graphene sheets dispersed in a resin (a precursor to an elastomer or rubber);

(b) operating a graphene deposition chamber to deposit a graphene sheet and resin on at least a major surface of the polymer film to form a resin/graphene coated polymer film;

(c) moving the graphene-coated film to an integration region that incorporates (eg, cures and compresses) the resin/graphene-coated polymer film to obtain a heat spreader film supported on the polymer film; and

(d) actuating a winding roller to collect the heat spreader film;

The plurality of graphene sheets consists essentially of monolayer or few-layer graphene sheets selected from a pure graphene material comprising 0% non-carbon elements or an impure graphene material comprising 0.001 wt % to 25 wt % non-carbon elements. Including, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof.

The process may further comprise implementing the elastic heat spreader film in the device as a thermal management element in such device.

1 is a flow diagram illustrating the most commonly used process for making graphene oxide sheets involving chemical oxidation/intercalation, rinsing, and high temperature exfoliation procedures.
2 is a schematic diagram of various routes of a process for making an elastic heat spreader comprising an elastomeric/rubber-impregnated aggregate/clusters of oriented/aligned graphene sheets, in accordance with certain embodiments of the present invention.
3(a) shows a mold cavity cell equipped with a compression and consolidation operation (piston or ram) to form a highly oriented graphene sheet layer, aligned perpendicular to the layer thickness direction or parallel to the bottom surface. It is a schematic diagram showing an example of use).
Figure 3(b) shows a compression and consolidation operation (piston or ram mounted) to form a highly oriented graphene sheet layer, aligned either parallel to the layer thickness direction (Z direction) or perpendicular to the lateral plane (XY plane). It is a schematic diagram showing another example of a molded cavity cell).
Figure 3(c) shows the compression and consolidation operation (using a mold cavity cell with vacuum assisted suction device) to form a highly oriented graphene sheet layer, aligned perpendicular to the layer thickness direction or parallel to the bottom surface. It is a schematic diagram showing another example.
Figure 3 (d) is a roll-to-roll (roll-to-roll) process for producing a graphene sheet layer well aligned to the plane of the supporting substrate.
Figure 4(a) shows two heat spreader film series, one series containing graphene sheets uniformly mixed and dispersed in the elastomer, and another series of elastomers containing the elastomeric resin penetrating from both sides of the graphene film. Thermal conductivity value as a function of weight %.
Figure 4(b) is the thermal conductivity values expressed as a function of the number of repeated bending deformations for two thermal film series, one series without elastomer and the other series with surface impregnated elastomer (0.01 wt %).
Figure 4(c) shows a simplified explanation of the bending test.
5 is a thermal conductivity value of a graphene-based heat spreader film expressed as a function of the final heat treatment temperature.

The present invention relates to: A) an elastomer or rubber as a binder material or matrix material; and B) providing an elastic heat spreader film comprising a plurality of graphene sheets bonded by a binder material or dispersed in a matrix material, wherein the plurality of graphene sheets are aligned to be substantially parallel to each other, and wherein the elastomer or rubber is disposed on the heat spreader. present in an amount of 0.001 wt % to 20 wt % based on the total weight of the film, wherein the plurality of graphene sheets is a pure graphene material comprising essentially 0 % non-carbon element or 0.001 wt % to 25 wt % non-carbon A single-layer or few-layer graphene sheet selected from impure graphene materials containing elements, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene selected from pin iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof (preferably, the chemically functionalized graphene is not graphene oxide) wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% (preferably greater than 5%, more preferably greater than 10%, and even more preferably greater than 20%) and 200 W/mK to It has an in-plane thermal conductivity of 1,750 W/mK (preferably and generally greater than 500 W/mK). The heat spreader film generally has a thickness of 10 nm to 500 μm.

The elastomeric or rubber material must have high elasticity (high elastic deformation values). Elastic deformation is a fully recoverable deformation and the recovery process is intrinsically instantaneous (no effective time delay). Elastomers, such as vulcanized natural rubber, contain from 2% to up to 1,000% (10 times their original length), more typically from 10% to 800%, even more typically from 50% to 500%, and most commonly and preferably It can exhibit an elastic deformation of 100% to 500%. Although metallic or plastic materials generally have high ductility (i.e., they can expand to a large extent without breakage), most strains are plastic strains (i.e., irreversible permanent strains) and small amounts (typically < 1% and more In general, it can be seen that only <0.2 %) is elastic deformation.

Various elastomers can be used either as pure resin alone or as matrix material for an elastomeric matrix composite to encapsulate anode active material particles or a plurality of particles. Encapsulation means that it substantially completely surrounds the particle(s) so as not to allow the particles to come into direct contact with the electrolyte of the battery. Elastomer materials include natural polyisoprene (eg, cis-1,4-polyisoprene natural rubber (NR) and trans-1,4-polyisoprene guttaperca), synthetic polyisoprene (IR for isoprene rubber), polybutadiene Butyl rubber, including (BR for butadiene rubber), chloroprene rubber (CR), polychloroprene (eg neoprene, vaperene, etc.), halogenated butyl rubber (chlorobutyl rubber (CIIR) and bromobutyl rubber (BIIR)) (Copolymer of isobutylene and isoprene, IIR), styrene-butadiene rubber (copolymer of styrene and butadiene, SBR), nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), EPM (ethylene propylene rubber, ethylene and propylene), EPDM rubber (ethylene propylene diene rubber, terpolymer of ethylene, propylene and diene components), epichlorohydrin rubber (ECO), polyacrylic rubber (ACM, ABR), silicone rubber (SI, Q, VMQ), fluorosilicone rubber (FVMQ), fluoroelastomers (FKM and FEPM; Viton, Tecnoflon, Fluorel, Aflas and Dai-EI, etc.); Perfluoroelastomers (FFKM: Tecnoflon PFR, Kalrez, Chemraz, Perlast, polyether block amide (PEBA), chlorosulfonated polyethylene (CSM; for example) , Hypalon), and ethylene-vinyl acetate (EVA), thermoplastic elastomer (TPE), protein resillin, protein elastin, ethylene oxide-epichlorohydrin copolymer, polyurethane, urethane-urea copolymer, and It may be selected from a combination of these.

Urethane-urea copolymer films are generally composed of two types of domains: soft domains and hard domains. An entangled linear backbone chain composed of poly(tetramethylene ether) glycol (PTMEG) units constitutes the soft domain, whereas repeated methylene diphenyl diisocyanate (MDI) and ethylene diamine (EDA) units constitute the hard domain. In fact, most thermoplastic elastomers have hard domains and soft domains in their structure, or hard domains dispersed in a soft matrix. The hard domains help hold the slightly crosslinked or physically entangled chains together, allowing for reversibility of modifications in the chains.

The plurality of graphene sheets are generally monolayer or few-layer graphene selected from a pure graphene material comprising essentially 0% non-carbon elements or an impure graphene material comprising from 0.001 wt % to 25 wt % non-carbon elements. a sheet, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof, wherein the chemically functionalized graphene is not graphene oxide, and the graphene sheet is formed by a matrix material having an average spacing of 1 nm to 300 nm. are spaced apart

The resulting heat spreader film comprising an elastomer or rubber appropriately selected as binder or matrix material to hold the aligned graphene sheets together is surprisingly >2%, more typically >5%, even more typically >10% , much more commonly > 20 %, and often > 50 % (eg, up to 100 %) of tensile-elastic strains.

It can be seen that, due to its high elastic properties, the heat spreader film can be bent or folded back and forth tens of thousands of times without significantly lowering the thermal conductivity. The thermal conductivity before the first bending (typically 500 W/mK to 1,750 W/mK) can retain >80% (typically >90%) of the original thermal conductivity after 10000 repeated bendings.

Preferably, in the foregoing examples, the elastomer or rubber is present in an amount of 0.001 wt % to 20 wt %, more preferably 0.01 wt % to 10 wt % and even more preferably 0.1 wt % to 1 wt %.

In some very useful embodiments, the heat spreader film is in the form of a thin film having a thickness of 5 nm to 500 μm, and the graphene sheet is aligned substantially parallel to the plane of the thin film. In some preferred embodiments, the heat spreader film is in the form of a thin film having a thickness of 10 nm to 100 μm, and the graphene sheet is aligned parallel to the thin film plane.

In general, all of the disclosed heat spreader films have a tensile strength of 100 MPa or more, a tensile modulus of 25 GPa or more, a thermal conductivity of 500 W/mK or more, and/or an electrical conductivity of 5,000 S/cm or more, measured along the thin film plane direction. Generally or preferably, the films all have a tensile strength of 300 MPa or more, a tensile modulus of 50 GPa or more, a thermal conductivity of 800 W/mK or more, and/or an electrical conductivity of 8,000 S/cm or more, all measured along the thin film plane direction. In many cases, the films all have a tensile strength of 400 MPa or more, a tensile modulus of 150 GPa or more, a thermal conductivity of 1,200 W/mK or more, and/or an electrical conductivity of 12,000 S/cm or more, all measured along the thin film plane direction. Some of the disclosed heat spreader films all have a tensile strength of 500 MPa or more, a tensile modulus of 250 GPa or more, a thermal conductivity of 1,500 W/mK or more, and/or an electrical conductivity of 20,000 S/cm or more, measured along the thin film plane direction.

In general, the invented films exhibit Vickers hardness values of 70 HV to 400 HV.

Preferably, the chemically functionalized graphene sheet is a graphene sheet exhibiting a negative zeta potential in a given dispersion, generally in the range of -55 mV to -0.1 mV. These functionalized graphene sheets generally have functional groups attached to these sheets to impart a negative zeta potential. The zeta potential is the potential difference between the dispersion medium and the fixed layer of a fluid attached to dispersed particles (eg, graphene sheets) dispersed in a dispersion medium (eg, water, organic solvent, electrolyte, etc.). Several commercially available instruments (eg, Zetasizer Nano from Malvern Panalytical and SZ-100 from Horiba Scientific) can be used to measure the zeta potential of different types of graphene sheets in different dispersion media.

A given type of graphene (eg, graphene oxide or reduced graphene oxide) can exhibit a positive or negative zeta potential, the value of which will vary depending on the dispersion medium used and the chemical functional groups attached to the graphene sheet. it can be seen that Unless otherwise specified, the zeta potential values provided are for graphene sheets dispersed in an aqueous solution having a pH value of 5.0 to 9.0 (mostly 7.0).

In some embodiments, the chemically functionalized graphene sheet is an alkyl or aryl silane, an alkyl or aralkyl group, a hydroxyl group, a carboxyl group, an amine group, a sulfonate group (—SO ₃ H), an aldehyde group, a quinoidal, a fluorocarbon, or and a chemical functional group selected from combinations thereof. Alternatively, the functional groups are 2-azidoethanol, 3-azidopropan-1-amine, 4-(2-azidoethoxy)-4-oxobutanoic acid, 2-azidoethyl-2-bromo- a derivative of an azide compound selected from the group consisting of 2-methylpropanoate, chlorocarbonate, azidocarbonate, dichlorocarbene, carbene, arine, nitrene, (R-)-oxycarbonyl nitrene, wherein R is any one of the following functional groups and combinations thereof.

In certain embodiments, the functional group is selected from the group consisting of hydroxyl groups, peroxides, ethers, ketos, and aldehydes. In certain embodiments, the functionalizing agent is SO ₃ H, COOH, NH ₂ , OH, R′CHOH, CHO, CN, COCl, halide, COSH, SH, COOR′, SR′, SiR′ ₃ , Si(-- OR'--) _y R' ₃ -y, Si(--O--SiR' ₂ --)OR', R", Li, AlR' ₂ , Hg--X, TlZ ₂ and Mg--X a functional group selected from the group consisting of, wherein y is an integer of 3 or less, R' is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly(alkylether), and R" is fluoro alkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, X is a halide, Z is a carboxylate or trifluoroacetate, and combinations thereof.

Functional groups include amidoamine, polyamide, aliphatic amine, modified aliphatic amine, cycloaliphatic amine, aromatic amine, anhydride, ketimine, diethylenetriamine (DETA), triethylene-tetramine (TETA), tetraethylene-penta TEPA, polyethylene polyamines, polyamine epoxy adducts, phenolic hardeners, non-brominated curing agents, non-amine curatives, and combinations thereof.

In some embodiments, a functional group is OY, NHY, O=C--OY, P=C--NR'Y, O=C--SY, O=C--Y, --CR'1--OY, may be selected from N'Y or C'Y, wherein Y is a functional group of a protein, peptide, amino acid, enzyme, antibody, nucleotide, oligonucleotide, antigen, or enzyme substrate, and the enzyme inhibitor or transition state analog of the enzyme substrate is R '--OH, R'--NR' ₂ , R'SH, R'CHO, R'CN, R'X, R'N ⁺ (R') ₃ X ^- , R'SiR' ₃ , R'Si (--OR'--) _y R' _3-y , R'Si(--O--SiR' ₂ --)OR', R'--R", R'--N--CO, ( C ₂ H ₄ O--) _w H, (--C ₃ H ₆ O--) _w H, (--C ₂ H ₄ O) _w --R', (C ₃ H ₆ O) _w -- It is selected from R' and R', and w is an integer greater than 1 and less than 200.

Graphene sheets and graphene dispersion preparations are described as follows, i.e., carbon is made of diamond, fullerene (0-D nanographitic material), carbon nanotubes or carbon nanofibers (1-D nanographitic material), graphene (2 It is known to have five unique crystal structures, including -D nano graphite material), and graphite (3-D graphite material). Carbon nanotubes (CNTs) refer to tubular structures grown as single-walled or multi-walled. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have diameters on the order of a few nanometers to hundreds of nanometers. Their longitudinal hollow structure imparts unique mechanical, electrical and chemical properties to the material. CNTs or CNFs are one-dimensional nano-carbon or 1-D nano-graphite materials.

Our research group has already pioneered the development of graphene materials and related manufacturing processes since 2002: (1) B. Z. Jang and W. C. Huang, "Nanoscale Graphene Plates," U.S. Patent No. 7,071,258 (July 4, 2006) ), applications filed on October 21, 2002; (2) B. Z. Jang et al., “Process for Fabricating Nanoscale Graphene Plates,” US Patent Application No. 10/858,814 (June 3, 2004) (US Patent Publication No. 2005/0271574); and (3) B. Z. Jang, A. Zhamu, and J. Guo, “Process for Making Nanoscale Platelets and Nanocomposites,” U.S. Patent Application Serial No. 11/509,424 (August 25, 2006) (U.S. Patent Publication No. 2008/0048152).

A single-layer graphene sheet is composed of carbon atoms occupying a two-dimensional hexagonal lattice. Multilayer graphene is a platelet composed of one or more graphene planes. The individual monolayer graphene sheets and multilayer graphene platelets are collectively referred to herein as nano graphene platelets (NGPs) or graphene materials. NGP is composed of pure graphene (essentially 99% carbon atoms), slightly oxidized graphene (<5% by weight oxygen), graphene oxide (≥5% by weight oxygen), slightly fluorinated graphene (<5% by weight). weight % fluorine), graphene fluoride (≧5 weight % fluorine), other halogenated graphene, and chemically functionalized graphene.

NGPs have been found to have a variety of unique physical, chemical and mechanical properties. For example, graphene has been found to exhibit the highest intrinsic strength and the highest thermal conductivity of all existing materials. Although actual electronic device applications for graphene (e.g., replacing Si with the backbone of transistors) are not expected to occur within the next decade, applications as nanofillers in composites and electrode materials in energy storage devices are is imminent The availability of mass-processable graphene sheets is essential to success in developing composites, energy and other applications for graphene.

A very useful approach (Fig. 1) is the treatment of natural graphite powder with an intercalating agent and an oxidizing agent (e.g., concentrated sulfuric acid and nitric acid, respectively) to obtain graphite intercalation compounds (GIC) or indeed graphite oxide (GO). [William S. Hummers, Jr. et al., Preparation of Graphite Oxide, Journal of the American Chemical Society, 1958, p. 1339.]. Prior to intercalation or oxidation, graphite has an interplanar spacing between graphenes of approximately 0,335 nm ( L _d = ½ d ₀₀₂ = 0.335 nm). By the intercalation and oxidation treatment, the graphene inter-graphene spacing is generally increased to a value greater than 0.6 nm. This is the first expansion step the graphite material experiences during this chemical pathway. The resulting GICs or GOs are then further expanded (often referred to as exfoliating) using either thermal shock exposure or solution-based ultrasonically assisted graphene delamination approaches.

In the thermal shock exposure approach, the GIC or GO is exfoliated or exfoliated to form exfoliated or further expanded graphite, typically in the form of a "graphite worm" composed of pieces of graphite that are still interconnected with each other. It is exposed to high temperature (typically 800° C. to 1,050° C.) for a short time (typically 15 to 60 seconds) to expand. Although this thermal shock procedure can produce some isolated graphite flakes or graphene sheets, in general, most graphite flakes remain interconnected. Typically, exfoliated graphite or graphite worms are then processed to separate pieces using air milling, mechanical shearing, or submerged sonication. Thus, Approach 1 essentially involves three distinct procedures: first expansion (oxidation or intercalation), further expansion (or "delamination"), and separation.

In the solution-based separation approach, the expanded or exfoliated GP powder is dispersed in water or an aqueous alcohol solution and sonicated. It is important to note that in these processes, sonication is used after intercalation and oxidation of graphite (ie after first expansion) and generally after thermal shock exposure of the resulting GIC or GO (after second expansion). Alternatively, GO powder dispersed in water is subjected to ion exchange or lengthy purification procedures in such a way that the repulsive forces between the ions present in the interplanar space overcome the inter-graphene van der Waals forces, resulting in graphene layer separation.

In the above example, the starting material for preparing the graphene sheet or NGP is natural graphite, artificial graphite, graphite oxide, graphite fluoride, graphite fiber, carbon fiber, carbon nanofiber, carbon nanotube, mesophase carbon microbead (MCMB) or a graphite material that may be selected from the group consisting of carbonaceous microspheres (CMS), soft carbon, hard carbon, and combinations thereof.

Graphite oxide can be mixed with an oxidizing agent, usually an intercalating agent (e.g., concentrated sulfuric acid) and an oxidizing agent (e.g., , nitric acid, hydrogen peroxide, sodium perchlorate, potassium permanganate) by dispersing or soaking a laminar graphite material (eg, a powder of natural flake graphite or synthetic graphite) in a mixture. Thereafter, the resulting graphite oxide particles are rinsed with water several times to adjust the pH value to generally between 2 and 5. The resulting suspension of graphite oxide particles dispersed in water is sonicated to prepare a separate dispersion of graphene oxide sheets dispersed in water. A small amount of a reducing agent (eg, Na ₄ B) may be added to obtain a reduced graphene oxide (RDO) sheet.

In order to reduce the time required to prepare the precursor solution or suspension, a method may be chosen that oxidizes the graphite to some extent in a shorter time (e.g., 30 minutes to 4 hours) to obtain the graphite intercalation compound (GIC). there is. Thereafter, the GIC particles are exposed to thermal shock in a temperature range preferably from 600° C. to 1,100° C. for generally 15 seconds to 60 seconds to obtain exfoliated graphite or graphite worms, which optionally (but preferably) heat the graphite worms. It is subjected to mechanical shearing (eg, using an ultrasonic generator or mechanical shear) to break up the constituent graphite pieces. The already separated graphene sheets or unbroken graphite worms or individual graphite pieces (after mechanical shearing) are then re-dispersed and sonicated in water, acid or organic solvent to obtain a graphene dispersion.

The pure graphene material is preferably prepared by the following three processes: (A) a process of thermal or chemical exfoliation in a non-oxidizing environment after intercalating a non-oxidizing agent into the graphite material; (B) exposing the graphite material to a supercritical fluid environment for inter-graphene penetration and exfoliation; or (C) dispersing the graphite material in powder form in an aqueous solution containing a surfactant or dispersing agent to obtain a suspension, and sonication directly into the suspension to obtain a graphene dispersion.

In procedure (A), a particularly preferred step is (i) a non-oxidizing agent selected from an alkali metal (eg potassium, sodium, lithium, or cesium), an alkaline earth metal, or an alloy, mixture, or eutectic mixture of an alkali or alkali metal. intercalating the graphite material; and (ii) chemical exfoliation (eg, by dipping the potassium intercalated graphite in an ethanol solution).

In procedure (B), the preferred step is to incubate the graphitic material with carbon dioxide (e.g., at temperature T > 31 °C and pressure P > 7.4 MPa) and water (e.g. , at a temperature of 374 °C and a pressure P > 22.1 MPa) in a supercritical fluid. After this step, a step of rapidly depressurizing the individual graphene layers to exfoliate is performed. Other suitable supercritical fluids include methane, ethane, ethylene, hydrogen peroxide, ozone, water oxidation (water containing high concentrations of dissolved oxygen), or mixtures thereof.

In procedure (C), the preferred steps include (a) dispersing particles of graphite material in a liquid medium comprising a surfactant or dispersant to obtain a suspension or slurry; and (b) stirring the suspension or slurry at an energy level for a time sufficient to prepare a graphene dispersion of isolated graphene sheets (non-oxidized NGP) dispersed in a liquid medium (eg, water, alcohol, or organic solvent). exposure to ultrasound (a process commonly referred to as sonication).

The NGP can be prepared with an oxygen content of 25 wt % or less, preferably 20 wt % or less, more preferably 5 wt % or less. In general, the oxygen content is between 5% and 20% by weight. The oxygen content may be determined using chemical elemental analysis and/or X-ray photoelectron spectroscopy (XPS).

The layered graphite material used in the prior art processes for the production of GIC, graphite oxide and subsequently produced exfoliated graphite, flexible graphite sheets and graphene platelets is in most cases natural graphite. However, the present invention is not limited to natural graphite. The starting material may be natural graphite, artificial graphite (e.g., highly oriented pyrolytic graphite, HOPG), graphite oxide, graphite fluoride, graphite fibers, carbon fibers, carbon nanofibers, carbon nanotubes, mesophase carbon microbeads (MCMB) or carbonaceous microspheres (CMS), soft carbon, hard carbon, and combinations thereof. All of these materials contain graphite microcrystals, which are composed of layers of graphene planar stacked or bonded together via van der Waals forces. In natural graphite, multiple stacks of graphene planes with different graphene plane orientations from stack to stack are clustered together. In carbon fibers, the graphene planes are generally oriented along a preferred direction. Generally speaking, soft carbon is a carbonaceous material obtained by carbonization of liquid aromatic molecules. Their aromatic rings or graphene structures are somewhat parallel to each other, allowing further graphitization. Hard carbon is a carbonaceous material obtained from an aromatic solid material (eg, a polymer such as phenolic resin and polyfurfuryl alcohol). Because their graphene structures are relatively randomly oriented, it is difficult to achieve further graphitization even at temperatures higher than 2,500 °C. However, graphene sheets are present on these carbons.

In the present specification, fluorinated graphene or graphene fluoride is used as an example of the halogenated graphene material group. Two different approaches are carried out to prepare fluorinated graphene: (1) fluorination of pre-synthesized graphene: these approaches involve CVD growth using a fluorination agent such as XeF ₂ or F based plasma. entails processing the graphene prepared by or by mechanical exfoliation; (2) Stripping of multilayer graphite fluoride: Both mechanical peeling and liquid peeling of graphite fluoride can be easily achieved [F. Karlicky, et al. " Halogenated Graphenes: Rapidly Growing Family of Graphene Derivatives " ACS Nano, 2013, 7 (8), pp 6434-6464].

The interaction of F ₂ with graphite at high temperature is covalent graphite fluoride (CF) _n or (C ₂ F) _n , whereas at low temperatures it leads to the graphene intercalation compound (GIC) C _x F (2≤x≤24) form. At (CF) _n , the fluorocarbon layer is corrugated consisting of trans-linked cyclohexane chains because the carbon atoms are sp3 hybridized. In (C ₂ F) _n , only half of the C atoms are fluorinated and all pairs of adjacent carbon sheets are linked together by covalent C-C bonds. A systematic study of fluorination reactions has shown that the resulting F/C ratio is dependent on the fluorination temperature, the partial pressure of fluorine in the fluorination gas, and the physical properties of the graphite precursor, including the degree of graphitization, particle size and specific surface area. highly dependent on Most available literature covers fluorination using F ₂ gas, sometimes in the presence of fluoride, although other fluorination agents may be used in addition to fluorine (F ₂ ).

In order to exfoliate individual single graphene layers or precursor materials stacked in a few-layer state, it is necessary to overcome the attractive force between adjacent layers and further stabilize the layers. This can be achieved by non-covalent modification using specific solvents, surfactants, polymers, or donor-acceptor aromatic molecules, or by covalent modification of the graphene surface with functional groups. The liquid exfoliation process includes sonicating graphene fluoride in a liquid medium to produce graphene fluoride sheets dispersed in the liquid medium. The resulting dispersion can be used directly for graphene deposition on the surface of polymeric components.

Nitrogenation of graphene can be performed by exposing a graphene material such as graphene oxide to ammonia at a high temperature (200° C. to 400° C.). Nitrogenized graphene can also be formed at lower temperatures by hydrothermal methods, for example, by sealing GO and ammonia in an autoclave and then increasing the temperature to 150 °C to 250 °C. . Other methods for synthesizing nitrogen-doped graphene include nitrogen plasma treatment on graphene, arc discharge between graphite electrodes in the presence of ammonia, ammonolysis of graphene oxide under CVD conditions, and graphene at different temperatures. including hydrothermal treatment of oxides and urea.

For the purpose of defining the claims of this application, NGPs or graphene materials are single-layered and multi-layered (generally less than 10, few-layered graphene) of pure graphene, graphene oxide, reduced graphene oxide (RGO). , graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, doped graphene (e.g. doped with B or N) of individual sheets/platelets. Pure graphene has essentially 0% oxygen. RGO generally has an oxygen content of 0.001% to 5% by weight. Graphene oxide (including RGO) may have 0.001 wt % to 50 wt % oxygen. Besides pure graphene, all graphene materials have from 0.001% to 50% by weight of non-carbon elements (eg, O, H, N, B, F, Cl, Br, I, etc.). These materials are referred to herein as impure graphene materials. Presently invented graphene can include pure or impure graphene and the invented method allows for this flexibility. All of these graphene sheets can be chemically functionalized.

The graphene sheet has a significant portion of the edge corresponding to the edge face of the graphite crystal. The carbon atoms on the edge face are reactive and must contain some heteroatoms or functional groups to satisfy the carbon valences. In addition, there are many types of functional groups (eg, hydroxyl groups and carboxyl groups) naturally present on the edge or surface of graphene sheets prepared through chemical or electrochemical methods. Many chemical functional groups (eg, —NH ₂ , etc.) can be readily attached to graphene edges and/or surfaces using methods well known in the art.

The functionalized NGPs of the present invention can be prepared directly by electrophilic addition to the surface of sulfonated, deoxygenated graphene platelets, or metallization. The graphene platelets may be treated prior to contacting with the functionalizing agent. Such treatment may include dispersing the graphene platelets in a solvent. In some cases, the platelets may be filtered and dried prior to contacting. One particularly useful type of functional group is the carboxylic acid moiety, which is naturally present on the NGP surface when prepared from the acid intercalation pathway described above. If carboxylic acid functionalization is desired, the NGP can be subjected to oxidation with chlorate, nitric acid, or ammonium persulfate.

Carboxylic acid functionalized graphene sheets or platelets are particularly useful because they can serve as a starting point for preparing other types of functionalized NGPs. For example, an alcohol or amide can be readily linked to an acid to give a stable ester or amide. When the alcohol or amine is part of a difunctional or polyfunctional molecule, the linkage via O- or NH- leaves the other function as a pendant group. These reactions can be carried out using any one of the methods developed for the esterification or amination of carboxylic acids with alcohols or amines as known in the art. Examples of these methods are described in G. W. Anderson, et al., J. Amer. Chem. Soc. 96, 1839 (1965). Amino groups can be introduced directly into the graphite platelets by treating the platelets with nitric acid and sulfuric acid to obtain nitrided platelets and then chemically reducing the nitrided form with a reducing agent such as sodium dithionate to obtain amino functionalized plates.

Also disclosed herein is a process for making an elastic heat spreader film, as schematically shown in FIG. 2 . The process generally involves (a) forming an aggregate (or cluster) layer of oriented/aligned graphene sheets that are substantially parallel to each other and (b) rubber/elastomer chains fill the gaps between the graphene sheets and/or or bonding the graphene sheet with a rubber or elastomer in which the graphene sheet is chemically bonded or the graphene sheet is dispersed in a rubber/elastomer matrix. Procedure (a) and procedure (b) may occur simultaneously or sequentially (eg, procedure (a) followed by (b), or (b) followed by (a)). As shown in Figure 2, a rubber or elastomer (or its precursor, such as a monomer, oligomer, uncured rubber chain, etc.) is brought into contact with the graphene sheet during any one of the different steps of the graphene sheet cluster formation and alignment procedure. can be

In some embodiments, the procedure for forming an aggregate or cluster layer of a plurality of oriented/aligned graphene sheets (eg, as shown in FIG. 3(D)) is performed by air assisted or Includes procedures selected from liquid assisted spraying.

In some embodiments, procedure (a) of providing an aggregate or cluster layer of a plurality of graphene sheets comprises a procedure selected from coating, casting, air assisted clustering, liquid assisted clustering, spraying, printing, or a combination thereof. The coating procedure may be selected from vapor deposition, chemical coating, electrochemical coating or plating, spray coating, painting, brushing, roll-to-roll coating, physical coating, or combinations thereof.

In certain embodiments, the procedure for forming an aggregate or cluster layer of a plurality of oriented/aligned graphene sheets forms a graphene dispersion comprising a plurality of graphene sheets dispersed in a liquid medium, followed by use of the dispersion. to perform a procedure selected from coating, casting, spraying, printing, forced assembling and orienting procedures, or combinations thereof. Such procedures generally involve liquid medium removal.

Preferably, the coating procedure is air knife coating, Anilox coating, Flexo coating, gap coating or knife-over-roll coating, gravure coating, hot melt coating, dip dip coating, kiss coating, metering rod or and a roll-to-roll coating process selected from Meyer bar coating, roller coating, silk screen coating or rotary screen coating, slot-die coating, comma coating, extrusion coating, inkjet printing, or a combination thereof. A pair of counter-rotating rollers can be used to roll press aggregates or clusters of graphene sheets, which helps to align/orient the graphene sheets parallel to each other. Coating processes are well known in the art.

In some preferred embodiments, the process further comprises a procedure for heat-treating the aggregate or cluster layer of the plurality of graphene sheets at a temperature selected from 50° C. to 3,200° C. or a plurality of different temperatures after step (a). For example, an aggregate layer of an oriented graphene sheet (eg, a graphene oxide sheet or a graphene fluoride sheet) is first heat treated at a temperature selected from 300° C. to 1,500° C. for 1 hour to 3 hours, and then from 2,500° C. to 2,500° C. It may be heat treated at a selected temperature at 3,400° C. for 0.5 to 2 hours.

A precursor to a rubber/elastomer (e.g., a liquid monomer/hardener mixture, an oligomer, or an uncured resin dissolved in a solvent, etc.) is distributed and deposited on the surface(s) of the graphene sheet layer after heat treatment or is somehow graphed It may be impregnated or penetrated into the pores of the pin cluster layer.

After the heat treatment procedure (before or after rubber/elastomer impregnation), the resulting aggregates of graphene sheets may be subjected to further compression (e.g., roll pressing) treatment to align/orient the graphene sheets parallel to each other. .

In certain embodiments, the process comprises (A) providing an aggregate or cluster layer of a plurality of graphene sheets; and (B) impregnating the aggregates or clusters with an elastomer or rubber as a matrix material or as a binder material to produce impregnated aggregates or clusters, wherein the plurality of graphene sheets are bonded by the binder material or attached to the matrix material. dispersed, wherein the elastomer or rubber is present in an amount of 0.001% to 20% by weight, based on the total weight of the heat spreader film, wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and 200 W/mK to 200 W/mK It has an in-plane thermal conductivity of 1,750 W/mK.

The process may further comprise (C) compressing the impregnated aggregates or clusters to produce a heat spreader film, wherein the plurality of graphene sheets are aligned substantially parallel to each other.

In step (a), the alignment of the graphene sheets can be achieved through a forced assembly approach schematically shown in Figs. 3(a), 3(b), 3(C) and 3(d). .

In some preferred embodiments, the forced assembly procedure introduces a graphene sheet dispersion (also called graphene dispersion) having an initial volume (V ₁ ) into the mold cavity cell and increases the graphene dispersion volume to a smaller value (V ₂ ). To reduce the piston is inserted into the mold cavity cell so that most of the remaining dispersion flows out of the cavity cell (e.g., through a hole in the mold cavity cell or through the piston), 0 degrees to the direction of movement of the piston and aligning the plurality of graphene sheets along the direction at an angle of to 90 degrees.

3( a ) shows an example of a compression and consolidation operation (using a mold cavity cell 302 equipped with a piston or ram 308 ) to form a layer of highly compressed and oriented graphene sheet 314 . A schematic drawing is provided. Contained in the chamber (mold cavity cell 302) is a dispersion (e.g., a suspension or slurry composed of graphene sheets 304 randomly dispersed in a liquid 306, optionally containing a rubber/elastomer precursor) am. As the piston 308 passes downward, the volume of the dispersion is reduced as the liquid is forced to flow either through the small channels 310 of the piston or through the microchannels 312 in the mold wall. These small channels may be present in some or all walls of the mold cavity, and the channel size is designed to allow penetration of liquid but not penetration of solid graphene sheets (typically between 0.05 μm and 100 μm in length or width). can be Liquids are shown as 316a and 316b in the diagram on the right of FIG. 3( a ). As a result of this compression and consolidation operation, the graphene sheet 314 is aligned perpendicular to the layer thickness direction or parallel to the bottom surface.

Shown in FIG. 3( b ) is a schematic diagram illustrating another example of a compression and consolidation operation (using a mold cavity cell 302 mounted with a piston or ram) to form a layer of highly oriented graphene sheet 320 . . The piston passes downward along the Y direction. The graphene sheet is aligned in the X-Z plane (along the Z-direction or thickness direction) and perpendicular to the X-Y plane. This oriented graphene sheet layer can be attached to a support substrate, which is essentially represented by an X-Y plane. In the resulting electrode, graphene sheets are aligned perpendicular to the substrate. Uncured rubber or elastomer may be incorporated before or after compression and consolidation operations.

3( c ) is a schematic diagram illustrating another example of a compression and consolidation operation (using a mold cavity cell with vacuum assisted suction facility) to form a layer of highly oriented graphene sheet 326 . The process begins with dispersing the separated graphene sheet 322 and optional elastomer/rubber or precursor thereof in liquid 324 to form a dispersion. Next, a step of creating a negative pressure through the vacuum system sucking the liquid 332 through the channel 330 is performed. This compression and consolidation operation reduces the dispersion volume and serves to align all of the separated graphene sheets on the bottom surface of the mold cavity cell. The compressed graphene sheets are aligned parallel to the bottom surface or perpendicular to the layer thickness direction. Preferably, the resulting graphene sheet structure layer is further compressed to achieve a much higher tap density. Uncured rubber or elastomer may be incorporated before or after compression and consolidation operations.

Thus, in some preferred embodiments, the forced assembly procedure introduces the graphene sheet dispersion into a mold cavity cell with an initial volume (V ₁ ) and reduces the graphene dispersion volume to a smaller value (V ₂ ) in the mold cavity. applying suction pressure through the porous wall of Including, this angle depends on the inclination of the floor surface with respect to the suction direction.

Fig. 3(d) shows a roll-to-roll process for manufacturing an aligned graphene sheet and a thick heat spreader layer comprising an elastomer or rubber. The process begins by feeding a continuous solid substrate 332 (eg, PET film or stainless steel sheet) from a feeder roller 331 . The dispenser 334 is a graphene sheet separated on the substrate surface to form a deposited dispersion layer that feeds it through the gap between the two compression rollers 340a and 240b to form a highly oriented graphene sheet layer and operated to dispense a dispersion 336 comprising an optional elastomeric/rubber resin precursor. The graphene sheet is well aligned to the plane of the supporting substrate. Then, if desired, the second dispenser 344 is operated to dispense another dispersion layer 348 to the previously integrated dispersion layer surface. The two-layer structure is passed through the gap between the two roll press rollers 350a and 350b to form a thicker graphene sheet layer 352 that is taken up by a winding roller 354 . The precursor to the rubber/elastomer can be sprayed onto the graphene sheet at any point in the process.

Thus, in some preferred embodiments, the forced assembly procedure includes introducing a first layer of graphene sheet dispersion (with or without rubber/elastomeric resin) onto a supporting conveyor surface and varying the thickness of the graphene sheet dispersion layer. passing the graphene sheet suspension layer supported on the conveyor through at least a pair of pressing rollers to reduce and align the plurality of graphene sheets along a direction parallel to the conveyor surface to form the graphene sheet layer; include

The process introduces a second graphene sheet dispersion layer (with or without rubber/elastomeric resin) over the surface of the graphene sheet structure layer (with or without rubber/elastomeric resin) to form a bilayer structure and at least one pair of pressing rollers to align the plurality of graphene sheets along a direction parallel to the conveyor surface to reduce the thickness of the second graphene sheet layer and form an oriented graphene sheet layer. The step of allowing the layer structure to pass may be further included. Allowing the conveyor to move towards a third set of pressing rollers, depositing an additional (third) graphene sheet dispersion layer over the two-layer structure, and depositing an additional (third) layer of graphene sheet dispersion over the resulting 3 The same procedure can be repeated by allowing the layer structure to pass through the gap between the two rollers of the third set. In other words, the elastomer/rubber resin or its precursor may be added during any step of this process.

The paragraphs above for Figures 3(a)-3(d) are used to produce thermal film structures comprising highly oriented and closely packed graphene sheets bonded by or dispersed in rubber/elastomer. These are just four of the many examples of possible devices or processes that could be used.

The following examples are used to illustrate some specific details of the best mode of carrying out the invention and should not be construed as limiting the scope of the invention. The tensile properties, thermal conductivity and cell conductivity of the films were measured according to well-known standard procedures.

Example 1 : Graphene Oxide from Sulfuric Acid Intercalation and Exfoliation of MCMB

MCMB (Mesophase-Carbon Microbeads) was supplied from China Steel Chemical Co. This material has a median particle size of about 16 μm and a density of about 2.24 g/cm 3 . MCMB (10 g) was intercalated with an acid solution (sulfuric acid, nitric acid and potassium permanganate in a ratio of 4:1:0.05) for 48 hours. After completion of the reaction, the mixture was poured into deionized water and filtered. To remove most of the sulfate ions, the intercalated MCMB was washed repeatedly with 5% HCl solution. Thereafter, the sample was washed repeatedly with deionized water until the pH of the filtrate became neutral. The slurry was dried and stored in a vacuum oven at 60° C. for 24 hours. To obtain a reduced graphene oxide (RGO) sheet, a dried powder sample was placed in a quartz tube, and inserted into a horizontal tube preset at a desired temperature of 800 °C to 1,100 °C for 30 to 90 seconds. To obtain a graphene dispersion, a certain amount of graphene sheets were mixed with water and sonicated at 60 W power for 10 minutes.

A small amount was sampled and dried, and as a result of TEM investigation, most of the NGPs were found to have 1 to 10 layers. The oxygen content of the prepared graphene powder (GO or RGO) was 0.1% to about 25% depending on the exfoliation temperature and time.

Several graphene dispersions were added separately along with various elastomeric precursor resins (eg, based on urethane/urea copolymers) for use in a slot-die coating procedure to deposit graphene on polymeric films. Separately, a thin film having a thickness of 10 μm to 100 μm was prepared with a graphene dispersion containing a resin not including an elastomer. After drying, the resulting reduced graphene oxide (RGO) thin film was spray deposited with an elastomeric precursor resin from both sides (two major surfaces of the RGO film) and then cured.

Figure 4(a) shows two heat spreader film series, one series containing graphene sheets uniformly mixed and dispersed in the elastomer, and another series containing the elastomeric resin penetrating into the graphene film from both sides of the film. The thermal conductivity plotted over a broad weight % range (0.001% to 10%) of the elastomer for As shown, the increase in the elastomer ratio rapidly decreases the thermal conductivity of the composite including the graphene sheet dispersed in the elastomeric matrix. However, a relatively small decrease in thermal conductivity was observed as the elastomer ratio increased in the case of thermal films having an elastomeric resin impregnated inward from the two major surfaces of the film (impregnation occurred after the film was made). This unexpected result is important and of great utility, given that this strategy allows to achieve high thermal conductivity while maintaining high resistance to bending-induced thermal conductivity loss thanks to elastomer impregnation (Fig. b)).

This strategy generally leads to heat spreader structures with an elastomer-free core, in which the elastomer does not reach the center by design and penetrates only a limited distance from the two major surfaces. Also, a method that allows full penetration of the graphene film by the elastomeric resin; For example, one can find a method to first form a porous film, then to perform impregnation and full compression. The elastic heat spreader film has a thickness t and two major surfaces (referred to as front and back). In the irradiated example, the elastomer or rubber is generally capable of penetrating into the film to an area at least a distance 1/3 t from the front side and at least a distance 1/3 t deep from the back side.

The thermal conductivity values as a function of the number of repeated bending deformations are shown in Fig. 4(b) for two thermal film series, one series without elastomer and the other series containing surface impregnated elastomer (0.01 wt %). . The sample without elastomer shows a decrease in thermal conductivity from 1220 W/mK to 876 W/mK after 100 bending deformations up to 180 degrees each time. The sheet broke after 110 bends. In contrast, a small amount of elastomer contained in the heat spreader film can withstand 10000 repeated bending without breakage and still maintain a relatively high thermal conductivity.

As shown in Fig. 4(c), the bending test is easy to perform. After taking the desired number of identical thermal films, bending them for the desired number of repetitions, and measuring the thermal conductivity of a specimen prepared by cutting a strip of film lengthwise across the bending area, a well-known laser flash or other method is used to measure the thermal conductivity of this piece. Thermal conductivity can be measured.

Example 2 : Oxidation and exfoliation of natural graphite

Graphite pieces were oxidized using sulfuric acid, sodium nitrate and potassium permanganate in a ratio of 4:1:0.5 at 30° C. for 48 hours according to the method of Hummers [US Pat. No. 2,798,878, Jul. 9, 1957]. The oxide was prepared. After the reaction was completed, the mixture was poured into deionized water and filtered. Thereafter, the sample was washed with 5% HCl solution to remove most of the sulfate ions and residual salts, followed by repeated rinsing with deionized water until the filtrate had a pH of about 4. The intention was to remove all sulfuric acid and nitric acid residues from the graphite crevices. The slurry was dried and stored in a vacuum oven at 60° C. for 24 hours.

In order to obtain highly exfoliated graphite, the sample was placed in a quartz tube inserted into a horizontal tube pre-set at 650° C., and the dried and intercalated (oxidized) compound was peeled off. The exfoliated graphite was dispersed in water in a flat-bottomed flask together with 1% surfactant at 45 °C, and the resulting suspension was sonicated for 15 minutes to obtain a graphene oxide (GO) sheet dispersion.

Then, the dispersion was coated on PET film using reverse-roll coating procedure to obtain GO film. After peeling from the PET substrate, the GO film was placed in a graphite mold and subjected to various heat treatments with a final heat treatment temperature of 25 °C to 2,900 °C. After heat treatment, the film was sprayed with some rubber solution (eg polyisoprene dissolved in THF) and then dried to remove the solvent. after. The rubber impregnated film was roll pressed into cured rubber.

5 shows the thermal conductivity values of the graphene/rubber film together with the thermal conductivity values of the flexible graphite sheet as a function of the final heat treatment temperature. This chart shows the importance of the final heat treatment temperature on the thermal conductivity of various heat spreader films.

Example 3 : Pure Graphene Preparation

Pure graphene sheets were prepared using direct sonication or liquid exfoliation processes. In a general procedure, 5 g of graphite pieces ground to a size of about 20 μm were dispersed in 1,000 mL of deionized water (containing 0.1 wt % of a dispersant (Zonyl® FSO, DuPont)) to obtain a suspension. For exfoliation, separation, and size reduction of the graphene sheet, an ultrasonic energy level of 85 W (Branson S450 Ultrasonicator) was used for 15 minutes to 2 hours. The resulting graphene sheets were pure graphene, which had never been oxidized, had no oxygen, and was relatively free from defects. A thermal film was prepared from pure graphene according to the procedure as described in Example 2. 5 shows the thermal conductivity values of the pure graphene/rubber films as a function of the final heat treatment temperature.

Example 4 : Preparation of Graphene Fluoride

Although we have used several processes to prepare GF, only one process is described herein as an example. In a general procedure, highly exfoliated graphite (HEG) was prepared from the intercalation compound (С ₂ F·xClF ₃ ). The HEG was further fluorinated with chlorine trifluoride vapor to produce fluorinated highly exfoliated graphite (FHEG). A precooled Teflon reactor was charged with 20 ml to 30 mL of precooled liquid ClF ₃ , then the reactor was closed and cooled to liquid nitrogen temperature. No more than 1 gram of HEG was then placed in a vessel with holes allowing ClF ₃ gas to access the reactor. After 7-10 days, a gray-beige product with the approximate formula C ₂ F was formed. The GF sheets were then dispersed in a halogenated solvent to form a suspension. Then, the suspension was coated on the surface of the PET film substrate using comma coating, dried, peeled off the substrate, and then heat treated at 500° C. for 3 hours and 2750° C. for 1 hour. After heat treatment, the film was sprayed with some rubber solution (eg, ethylene oxide-epichlorohydrin copolymer dissolved in xylene) and then dried to remove the solvent. Then, the rubber-impregnated film was roll-pressed with the cured rubber.

Example 5 : Preparation of Nitrogenated Graphene

The graphene oxide (GO) synthesized in Example 2 was finely ground with different proportions of urea and the pelletized mixture was heated in a microwave reactor (900 W) for 30 seconds. The product was washed several times with deionized water and dried in vacuo. In this method, graphene oxide is simultaneously reduced and doped with nitrogen. The products obtained with graphene/urea mass ratios of 1/0.5, 1/1 and 1/2 were designated as N-1, N-2 and N-3, respectively, and the nitrogen content of these samples was determined by elemental analysis and was 14.7, respectively. wt.%, 18. 2 wt.% and 17.5 wt.%. These nitrogenized graphene sheets remain dispersible in water. A compression/alignment procedure is performed with the resulting dispersion as shown in Fig. 3(a) to form a thermal film.

Example 6 : Functionalized Graphene Based Thermal Film

Thermal films were prepared from several functionalized graphene-elastomer dispersions comprising 5 wt % functionalized graphene sheets (minor-layer graphene) and 0.01 wt % urethane oligomers (mixtures of diisocyanates and polyols). Chemical functional groups involved in this study include azide compound (2-azidoethanol), alkyl silane, hydroxyl group, carboxyl group, amine group, sulfonate group (-SO ₃ H), and diethylenetriamine (DETA). These functionalized graphene sheets were supplied from Taiwan Graphene Co., Taipei (Taiwan). After dispersion casting, removal of liquid medium (acetone), compression with a hot press, and curing at 150° C. for 45 minutes, a thermal film in which graphene sheets were well bonded to a urethane-based elastomer was obtained. Presently invented highly oriented graphene-elastomer composites can deliver thermal conductivity as high as 1,255 W/mK. The fully recoverable tensile strain (elastic strain) of this elastomer-protected graphene film series was found to be generally between 8% and 45%. In contrast, no polymer matrix composite of any type previously exhibited thermal conductivity higher than 500 W/mK.

Claims (36)

An elastic heat spreader film comprising:
A) elastomers or rubbers as binder material or matrix material; and
B) comprising a plurality of graphene sheets bonded to the binder material or dispersed in the matrix material,
the plurality of graphene sheets are aligned to be substantially parallel to each other, and the elastomer or rubber is present in an amount of 0.001 wt % to 20 wt % based on the total weight of the heat spreader film;
wherein the plurality of graphene sheets comprises essentially a graphene sheet selected from pure graphene material having 0% non-carbon element, or non-pure graphene material having 0.001 weight % to 25 weight % non-carbon element, The impure graphene includes graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped graphene, chemically functionalized graphene, or a combination thereof; and
wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and an in-plane thermal conductivity of 200 W/mK to 1,750 W/mK. According to claim 1,
The elastomer or rubber is natural polyisoprene, synthetic polyisoprene, polybutadiene, chloroprene rubber, polychloroprene, butyl rubber, styrene-butadiene rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, metallocene-based poly(ethylene-) co-octene) elastomer, poly(ethylene-co-butene) elastomer, styrene-ethylene-butadiene-styrene elastomer, epichlorohydrin rubber, polyacrylic rubber, silicone rubber, fluorosilicone rubber, perfluoroelastomer, polyether block amides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, protein resillin, protein elastin, ethylene oxide-epichlorohydrin copolymer, polyurethane, urethane-urea copolymer, sulfonated versions thereof, or these An elastic heat spreader film comprising a material selected from a combination of: According to claim 1,
The heat spreader film is an elastic heat spreader film having a thickness of 5 nm to 500 μm. According to claim 1,
The graphene sheet is an elastic heat spreader film present in an amount of 80% to 99.9% by weight. According to claim 1,
The elastic heat spreader film has a thickness t, front and back surfaces, wherein the elastomer or rubber extends from the front surface to a depth of 1/3 t into the film and/or from the back surface to a depth of 1/3 t into the film. An elastic heat spreader film with an elastomer-free core present in the region. According to claim 1,
wherein the elastic heat spreader film has a thickness t and an elastomer-free core size from 1/10t to 4/5t. According to claim 1,
An elastic heat spreader film having a tensile strength of 300 MPa or more, a tensile modulus of 75 GPa or more, a thermal conductivity of 500 W/mK or more, and/or an electrical conductivity of 5,000 S/cm or more, all measured along the thin film plane direction. According to claim 1,
An elastic heat spreader film having a tensile strength of 400 MPa or more, a tensile modulus of 150 GPa or more, a thermal conductivity of 800 W/mK or more, and/or an electrical conductivity of 8,000 S/cm or more, all measured along the thin film plane direction. According to claim 1,
An elastic heat spreader film having a tensile strength of 500 MPa or more, a tensile modulus of 250 GPa or more, a thermal conductivity of 1,200 W/mK or more, and/or an electrical conductivity of 12,000 S/cm or more, all measured along the thin film plane direction. According to claim 1,
An elastic heat spreader film having a tensile strength of 600 MPa or more, a tensile modulus of 350 GPa or more, a thermal conductivity of 1,500 W/mK or more, and/or an electrical conductivity of 20,000 S/cm or more, all measured along the thin film plane direction. According to claim 1,
The graphene sheet is an elastic heat spreader film comprising a functional group attached thereto to make the graphene sheet exhibit a negative zeta potential of -55 mV to -0.1 mV. According to claim 1,
The graphene sheet may be an alkyl or aryl silane, an alkyl or aralkyl group, a hydroxyl group, a carboxyl group, an epoxide, a carbonyl group, an amine group, a sulfonate group (—SO ₃ H), an aldehyde group, a quinoidal, a fluorocarbon, or a combination thereof. An elastic heat spreader film comprising a chemical functional group selected from According to claim 1,
The graphene sheet may include amidoamine, polyamide, aliphatic amine, modified aliphatic amine, cycloaliphatic amine, aromatic amine, anhydride, ketimine, diethylenetriamine (DETA), triethylene-tetramine (TETA), tetra Chemical functional groups selected from the group consisting of ethylene-pentamine (TEPA), polyethylene polyamines, polyamine epoxy adducts, phenolic hardeners, non-brominated curing agents, non-amine curatives, and combinations thereof An elastic heat spreader film comprising a chemically functionalized graphene sheet having a. According to claim 1,
The graphene sheet is OY, NHY, O=C--OY, P=C--NR'Y, O=C--SY, O=C--Y, --CR'1--OY, N' contains a chemical functional group selected from Y or C'Y, Y is a functional group of a protein, peptide, amino acid, enzyme, antibody, nucleotide, oligonucleotide, antigen, or enzyme substrate, and an enzyme inhibitor or a transition state analog of an enzyme substrate is R '--OH, R'--NR' ₂ , R'SH, R'CHO, R'CN, R'X, R'N ⁺ (R') ₃ X ^- , R'SiR' ₃ , R'Si (-OR'-) _y R' _3-y , R'Si(-O--SiR' ₂ -)OR', R'--R", R'--N--CO, (C ₂ H ₄ O-) _w H, (-C ₃ H ₆ O-) _w H, (-C ₂ H ₄ O) _w -R', (C ₃ H ₆ O) _w -R', R', w is an integer greater than 1 and less than 200; an elastic heat spreader film. An electronic device comprising the elastic heat spreader film of claim 1 as a thermal management element. A structure member comprising the elastic heat spreader film of claim 1 as a load-bearing and thermal management element. A process for making an elastic heat spreader film, comprising:
The process comprises (a) forming an aggregate or cluster layer of a plurality of oriented/aligned graphene sheets that are substantially parallel to each other and (b) rubber or elastomeric chains fill gaps or defects between the graphene sheets, and rubber to form elastomeric/rubber-impregnated aggregates/clusters of a plurality of oriented/aligned graphene sheets in such a way that/or chemically bonds to the graphene sheets or the graphene sheets are dispersed in a matrix comprising the elastomer or rubber. or combining the elastomer and the graphene sheet,
The elastomer or rubber is present in an amount of 0.001% to 20% by weight based on the total weight of the heat spreader film, wherein the elastic heat spreader film has a fully recoverable tensile elastic strain of 2% to 100% and 200 W/mK to 1,750 W/ A process with an in-plane thermal conductivity of mK. 18. The method of claim 17,
The plurality of graphene sheets is essentially a single-layer or few-layer graphene sheet selected from a pure graphene material having 0% non-carbon element, or an impure graphene material having 0.001% to 25% by weight non-carbon element. Including, wherein the impure graphene is graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, doped A process selected from graphene, chemically functionalized graphene, or a combination thereof. 18. The method of claim 17,
The elastomer or rubber is natural polyisoprene, synthetic polyisoprene, polybutadiene, chloroprene rubber, polychloroprene, butyl rubber, styrene-butadiene rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, metallocene-based poly(ethylene-) co-octene) elastomer, poly(ethylene-co-butene) elastomer, styrene-ethylene-butadiene-styrene elastomer, epichlorohydrin rubber, polyacrylic rubber, silicone rubber, fluorosilicone rubber, perfluoroelastomer, polyether Block amides, chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplastic elastomers, protein resillin, protein elastin, ethylene oxide-epichlorohydrin copolymers, polyurethanes, urethane-urea copolymers, sulfonated versions thereof, to these A process comprising a material selected from a precursor for, or a combination thereof. 18. The method of claim 17,
wherein the procedure of forming a layer of an aggregate or cluster of the plurality of oriented/aligned graphene sheets comprises a procedure selected from air assisted or liquid assisted spraying of the plurality of graphene sheets. 18. The method of claim 17,
The procedure of forming a layer of an aggregate or cluster of a plurality of oriented/aligned graphene sheets is performed after forming a graphene dispersion comprising a plurality of graphene sheets, followed by coating, casting, spraying, printing, forcing A process comprising performing a procedure selected from a forced assembling and orienting procedure, or a combination thereof. 22. The method of claim 21,
wherein the coating is selected from vapor deposition, chemical coating, electrochemical coating or plating, spray coating, painting, brushing, roll-to-roll coating, physical coating, or a combination thereof. 23. The method of claim 22,
The roll-to-roll coating is air knife (air knife) coating, anilox (Anilox) coating, flexo (Flexo) coating, gap (gap) coating or knife-over-roll (knife-over-roll) coating, gravure (gravure) ) coating, hot melt coating, immersion dip coating, kiss coating, metering rod or Meyer bar coating, roller coating, silk screen ) coating or rotary screen coating, slot-die coating, extrusion coating, inkjet printing, or a combination thereof. 18. The method of claim 17,
Procedure (b) comprises impregnating the aggregates or clusters with an elastomer or rubber as a binder material or as a matrix material to produce impregnated aggregates or clusters, wherein the plurality of graphene sheets are joined by the binder material. or dispersed in the matrix material. 25. The method of claim 24,
compressing the impregnated aggregates or clusters to produce the heat spreader film in which the plurality of graphene sheets are aligned substantially parallel to each other. 18. The method of claim 17,
wherein procedure (a) comprises a procedure selected from coating, casting, air assisted clustering, liquid assisted clustering, spraying, printing, or a combination thereof. 18. The method of claim 17,
The procedure (a) comprises the steps of (i) dispersing the plurality of graphene sheets in a liquid medium to form a suspension, (ii) dispensing the suspension over the substrate surface to form wet aggregates or clusters of graphene sheets. and (iii) partially or completely removing said liquid medium from said wet aggregates or clusters to form aggregates or clusters of said plurality of graphene sheets. 28. The method of claim 27,
and compressing or consolidating the aggregates or clusters to align the plurality of graphene sheets and/or reduce the porosity of the aggregates or clusters. 18. The method of claim 17,
The procedure (a) includes spraying the plurality of graphene sheets, with or without the use of a dispersion liquid medium, onto a surface of a solid substrate to form an aggregate or cluster of the plurality of graphene sheets. . 30. The method of claim 29,
and compressing or consolidating the aggregates or clusters to align the plurality of graphene sheets and/or reduce the porosity of the aggregates or clusters. 18. The method of claim 17,
The process further comprises a procedure for heat-treating the layer of the aggregate or cluster of the plurality of graphene sheets at a temperature selected from 50° C. to 3,200° C. or a plurality of different temperatures after step (a). 32. The method of claim 31,
The process further comprises a process for compressing or consolidating the aggregate or cluster of the plurality of graphene sheets after the process of heat treatment. 18. The method of claim 17,
The procedure (a) comprises the steps of (i) dispersing a plurality of individual graphene sheets in a liquid medium to form a graphene dispersion, and (ii) aligned graphene sheets substantially parallel to each other with respect to the graphene dispersion. performing a forced assembling and orientation procedure that forces them to form a layer of aggregates or clusters of pin sheets; and procedure (b) comprises impregnating the aggregate or cluster with a rubber or elastomer or a precursor thereof and incorporating the aligned rubber/elastomer impregnated graphene sheet layer into an elastic heat spreader film,
A process in which graphene sheets are bonded by or dispersed in a rubber/elastomeric material and aligned to be substantially parallel to each other. 34. The method of claim 33,
The forced assembling and orientation procedure introduces a graphene dispersion with an initial volume (V ₁ ) into the mold cavity cell, and reduces the graphene dispersion volume to a smaller value (V ₂ ) in the mold cavity cell. A process comprising pushing a piston in to cause excess liquid medium to flow out of the cavity cell and aligning the graphene sheet along a desired direction. 34. The method of claim 33,
The forced assembling and orientation procedure introduces a graphene dispersion with an initial volume (V ₁ ) into a mold cavity cell, and reduces the volume of the graphene dispersion to a smaller value (V ₂ ) of the mold cavity. A process comprising applying suction pressure through the porous wall to cause excess liquid medium to flow out of the cavity cell through the porous wall and aligning the graphene sheet along a desired direction. 18. The method of claim 17,
and implementing the resilient heat spreader film in a device as a thermal management element.

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