JP7050667B2 - Monolith membrane of integrated highly oriented halogenated graphene - Google Patents

Description

The present invention generally relates to the field of graphene materials and is composed of a plurality of originally separated halogenated graphene sheets or molecules that are specifically oriented and chemically coalesced together to form a monolithic integrated layer. Regarding a novel form of halogenated graphene film.

Carbon has five unique crystal structures including diamond, fullerene (0D nanographite material), carbon nanotubes or carbon nanofibers (1D nanographite material), graphene (2D nanographite material) and graphite (3D graphite material). It is known. Carbon nanotubes (CNTs) mean tubular structures grown in single or multi-layered structures. Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have diameters of several nanometers to several hundred nanometers. These longitudinal hollow structures impart unique mechanical, electrical and chemical properties to the material. CNTs or CNFs are one-dimensional nanocarbon or 1D nanographite materials.

Constituent Graphene Surfaces of Graphite Microcrystals in Natural Graphite Particles or Artificial Graphite Particles Obtain individual graphene sheets of carbon atoms by exfoliation and extraction or isolation, provided that the interplane van der Waals forces can be overcome. Can be done. Graphene sheets of isolated individual carbon atoms are commonly referred to as single-layer graphene. A stack of multiple graphene surfaces coupled by van der Fars forces in the thickness direction at a graphene surface spacing of about 0.3354 nm is commonly referred to as multi-layer graphene. Multilayer graphene platelets have up to 300 layers of graphene surfaces (<100 nm thickness), more typically up to 30 graphene surfaces (<10 nm thickness), and even more typically up to 20. It has a graphene surface (<7 nm thickness), most typically up to 10 graphene surfaces (commonly referred to in science as multi-layer graphene). Sheets of single-layer graphene and multi-layer graphene or graphene oxide are collectively referred to as "nanographene platelets" (NGPs). Graphene or graphene oxide sheets / platelets (collectively NGP) are a new type of carbon nanomaterial (2D nanocarbon) that distinguishes them from 0D fullerenes, 1D CNTs and 3D graphite.

Our research group was a pioneer in the development of graphene materials and related manufacturing methods in 2002: (1) B. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates," US Pat. No. 7,071,258 (07/04/2006), filed October 21, 2002; (2) B.I. Z. Jang et al., "Process for Production Nano-scaled Graphene Plates," US Patent Application No. 10 / 858,814 (06/03/2004); and (3) B.I. Z. Jang, A. Zhamu, and J.M. Guo, "Process for Production Nano-scaled Platelets and Nanocomposites," US Patent Application No. 11/509,424 (08/25/2006).

As shown in FIGS. 5 (A) (process flow chart) and 5 (B) (schematic), the isolated or isolated graphene or graphene oxide sheet (NGP) is typically made into natural graphite particles. It is obtained by intercalating a strong acid and / or an oxidant to obtain a graphite intercalation compound (GIC) or graphite oxide (GO). The presence of species or functional groups in the intervening space between graphene planes serves to increase the graphene spacing (d ₀₀₂ , measured by X-ray diffraction), thereby otherwise in the c-axis direction. The van der Waals forces that maintain the graphene planes along each other are significantly reduced. In most cases, GIC or GO will use natural graphite powder (20 in FIG. 5 (A) and 100 in FIG. 5 (B)) with sulfuric acid, nitric acid (oxidizer) and another oxidant (eg, potassium permanganate or). Manufactured by immersion in a mixture of sodium perchlorate). The resulting GIC (22 or 102) is actually some kind of graphite oxide (GO) particles. The GIC or GO is then repeatedly washed and rinsed in water to remove excess acid, resulting in a suspension or dispersion of graphite oxide containing individual visually recognizable graphite oxide particles dispersed in the water. The body is obtained. After this rinsing step, there are two processing paths.

Path 1 comprises removing water from the suspension to obtain "expandable graphite", which is substantially a mass of dry GIC or dry graphite oxide particles. When expansive graphite is exposed to temperatures typically in the range of 800 to 1,050 ° C. for about 30 seconds to 2 minutes, the GIC undergoes a rapid volume expansion of 30 to 300 times and becomes a "graphite worm" (24 or 104) are formed, which are still aggregates of interconnected graphite flakes, each detached but largely unseparated. An SEM image of the graphite worm is shown in FIG. 6 (A).

In path 1A, these graphite worms (exfoliated graphite or "mesh structure of interconnected / unseparated graphite flakes") are recompressed, typically 0.1 mm (100 μm) to 0.5 mm (500 μm). ) Can be obtained as a flexible graphite sheet or foil (26 or 106) having a thickness within the range of). Alternatively, simply destroy the graphite worm for the purpose of producing so-called "expanded graphite flakes" (108) containing graphite flakes or platelets, mostly thicker than 100 nm (and therefore not nanomaterials by definition). You can choose to use a low-strength air mill or a shearing machine to do this.

All of the exfoliated graphite worms, expanded graphite flakes and recompressed lumps of graphite worms (commonly referred to as flexible graphite sheets or flexible graphite foils) are 1D nanocarbon materials (CNTs or CNFs) and 2D nanocarbon materials (generally referred to as flexible graphite sheets or foils). It is a 3D graphite material that is basically different from any of graphene sheets or platelets (NGP) and is clearly distinguished. Flexible graphite (FG) foils can be used as heat spreader materials, but typically have a maximum in-plane thermal conductivity of less than 500 W / mK (more typically <300 W / mK) and 1, It shows an in-plane electrical conductivity of 500 S / cm or less. These low conductivity values are many defects, wrinkled or folded graphite flakes, breaks or gaps between graphite flakes and non-parallel flakes (eg, many flakes from the desired orientation direction>. It is a direct result of FIG. 6 (B) SEM image) tilted at an angle deviating by 30 °. Many flakes are tilted relative to each other at very large angles (eg, 20-40 degrees misorientation). The mean deviation angle is greater than 10 °, more typically> 20 °, often> 30 °.

In Route 1B, separated single-layer and multi-layer graphene sheets (collectively referred to as NGP, 33 or 112) are provided as disclosed in our US Patent Application No. 10 / 858,814. High-strength mechanical shearing is applied to the exfoliated graphite to form (eg, an ultrasonic processor, high-shear mixer, high-strength air jet mill or high-energy ball mill is used). Single-layer graphene can be as thin as 0.34 nm, while multi-layer graphene can have a thickness of up to 100 nm, but more typically less than 20 nm.

Path 2 requires sonication of the graphite oxide suspension for the purpose of separating / isolating individual graphene oxide sheets from the graphite oxide particles. This increases the distance between graphene planes from 0.3354 nm in natural graphite to 0.6-1.1 nm in highly oxidized graphite and greatly enhances the van der Waals forces that maintain adjacent planes with each other. It is based on the recognition that it reduces to. The output of the ultrasonic waves may be sufficient to further separate the sheets of graphene surface to form separate, isolated or individual graphene oxide (GO) sheets. Next, these graphene oxide sheets are typically 0.001% to 10% by weight, more typically 0.01% to 5% by weight, most typically less than 2% by weight. It can be chemically or thermally reduced to obtain "reduced graphene oxide" (RGO) with an oxygen content.

For the purposes of defining the claims of the present application, graphene or NGP comprises a separate (isolated or separated) sheet / platelet of single-layer and multi-layered presting graphene, graphene oxide or reduced graphene oxide (RGO). .. Pristing graphene has substantially 0% oxygen. The RGO typically has an oxygen content of 0.001% to 5% by weight. Graphene oxide (including RGO) can have 0.001% to 50% by weight oxygen.

The isolated solid NGP (ie, a separate separated sheet / platelet of presting graphene, GO and RGO with a typical length / width of 100 nm to 10 μm) is macroscopically viewed, for example, by using a papermaking process. High thermal conductivity, typically as an example of useful physical properties, when filled into a film, membrane or paper sheet of a suitable size (34 or 114 of FIG. 5 (A) or FIG. 5 (B)). Does not show rate. This is mainly due to the idea that these sheets / platelets are typically poorly oriented and many types of defects are formed in the film / membrane / paper. In particular, paper-like structures or mats made from graphene, GO or RGO platelets (eg, paper sheets made by vacuum assisted filtration methods) have many defects, wrinkles or folded graphene sheets. , Breaks or gaps between the platelets and non-parallel platelets (eg, SEM image of FIG. 7B), thereby showing relatively inadequate thermal conductivity, low electrical conductivity, low dielectric breakdown strength and Low structural strength occurs. These paper-like structures or aggregates of individual NGP, GO or RGO plateslets alone (without resin binder) also have a tendency to shed and conductive particles are released into the air, but in the presence of the binder resin. , The decrease in conductivity of the structure is greatly reduced.

A graphene thin film (<5 nm and most typically <2 nm) can be made by catalytic chemical vapor deposition CVD of a hydrocarbon gas (eg, C ₂ H ₄ ) on the surface of Ni or Cu. By using Ni or Cu as a catalyst, carbon atoms obtained by decomposition of hydrocarbon gas molecules at 800 to 1,000 ° C. are deposited on the surface of the Ni or Cu foil, and a single layer or several layers of polycrystals are deposited. Form a sheet of graphene (in this case, 2-5 layers). These ultra-thin graphene films are optically transparent and electrically conductive and are intended for applications such as touch screens (used in place of indium tin oxide or ITO glass) or semiconductor devices (used in place of silicon Si). Ru. Ni or Cu-catalyzed CVD processes are not suitable for deposition of graphene surfaces above 5-10 (typically <5 nm, more typically <2 nm), above that number the underlying Ni. Or the Cu catalyst can no longer obtain a catalytic effect. There is no experimental evidence that CVD graphene films with thicknesses greater than 5 nm are possible. Moreover, the CVD process is known to be very expensive.

From the point of view of semiconductor physics, on the other hand, the multilayer graphene sheet is a metal or a conductor, and the single layer graphene sheet is a semimetal. Single-layer presting rafene has no energy bandgap because its valence and conduction bands are in contact with each other and is therefore classified as a metalloid (in contrast, Si in semiconductors has its electronic arrangement. Has an energy bandgap of 1.1 eV between the conduction band and the valence band). The absence of bandgap limits the use of graphene in modern electronic devices. The band structure of monolayer graphene can be modified to widen the bandgap by many methods, such as halogenation, oxidation, hydrogenation or non-covalent bonding of various molecules and species.

On the other hand, highly oxidized graphene or graphene oxide (GO) is considered an insulating material and can probably be used as a dielectric. However, this is a drawback because the GO's low thermal stability (to heat exposure) reduces its dielectric resistivity and heat treatment steps are often used during the manufacture of electronic devices. In addition, multilayer presting rafene (> 3 layers) and reduced graphene oxide (RGO) are conductors that are substantially unusable as dielectric and insulating materials. An example of this is shown in FIG. 7 (A).

Dielectric materials have received much attention for their potential applications in gated dielectrics, dynamic random access memory, artificial muscles and energy storage devices. Dielectric (ceramic) capacitors for energy storage are problematic for low processability (eg, processing temperatures typically above 1,000 ° C.), high density and low dielectric breakdown strength. Conventional high-dielectric perovskite ceramics, such as barium titanate-containing composites, cannot be used in situations where various shapes are required. Compared to inorganic ceramics, polymers are more suitable in higher electric fields. In addition, polymers have the advantages of light weight, low cost, ease of processing and self-healing over inorganic ceramics. However, the low operating temperature limits further development of polymer dielectrics. Commercially available capacitors are used only in limited applications such as mobile phones, video / audio systems and personal computers. For example, biaxially stretched polypropylene polymer capacitors can only operate at temperatures below 105 ° C. Therefore, materials with high dielectric constants, especially those that can be used in high temperature environments, have great potential for device applications.

Considering these shortcomings of current dielectric materials, we have investigated the possibility of using graphene-derived materials for dielectric applications. After a thorough and extensive study, we have surprisingly found that halogenated graphene materials with thicknesses above 10 nm are good dielectric materials. Halogenated graphene is a group of graphene derivatives in which some carbon atoms are covalently bonded to halogen atoms. The carbon atom bonded to the halogen has a sp ³ hybrid, and the other carbon atoms have an sp ² hybrid. This indicates that halogenated graphene (also called halogenated graphene) can optionally be an insulating material. For this reason, a thicker halogenated graphene film (> 10 nm, preferably> 100 nm, more preferably> 1 μm, more preferably> 10 μm) is desirable. However, an ultrathin film of graphene fluoride (eg, << 10 nm), which is produced by fluorination after catalytic CVD preparation of Pristingrafene, has a combination of desirable physical and chemical properties. Thicker graphene fluoride films are not available. While most current devices are required to have thicker dielectric components, it is known in the art that thicker dielectric materials (thicker than 5-10 nm) tend to have lower breakdown strength. Has been done.

U.S. Pat. No. 7,071,258 U.S. Patent Application No. 10 / 858,814 U.S. Patent Application No. 11 / 509,424

Therefore, an object of the present invention is the cost of producing a thicker film of graphene-derived material exhibiting high dielectric breakdown strength, high dielectric constant, sufficient mechanical strength, good thermal stability and good chemical stability. It is to provide a highly effective method.

The present invention provides a method for producing a highly oriented halogenated graphene sheet or an integral layer of molecules, the film having a thickness of 10 nm to 500 μm. This method is a step of preparing either (a) a graphene oxide dispersion having a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel having graphene oxide molecules dissolved in a flow medium. The graphene oxide sheet or graphene oxide molecule contains an oxygen content of more than 5% by weight, with the step; (b) supplying a layer of graphene oxide dispersion or graphene gel oxide on the surface of the supporting substrate under shear stress conditions and The step of deposition, the feeding and deposition procedure, is the thinning induced by shearing of the graphene oxide dispersion or gel to form a wet layer of graphene oxide on the supporting substrate, and the graphene oxide sheet or molecule. Steps and; (c) in the chemical formula of C ₆ Z _{x Oy} (where Z is a halogen element selected from F, Cl, Br, I or a combination thereof), including orientation induced by shearing. In order to form a dry integrated layer of graphene halide having (i) x = 0.01-6.0, y = 0-5.0 and x + y≤6.0), of (i) graphene oxide. A halogenating agent is introduced into the wet layer and a chemical reaction is caused between the halogenating agent and the graphene oxide sheet or molecule to form a wet layer of graphene halide, and flow from the wet layer of graphene halide. The medium is removed or (ii) the flow medium is removed from the wet layer of graphene oxide to form a dry layer of graphene oxide, and a halogenating agent is introduced into the dry layer of graphene oxide and a halogenating agent. And either step of causing a chemical reaction between the graphene oxide sheet or the molecule; (d) 0 when the flow medium is removed from the wet layer of graphene halide and measured by X-ray diffraction. A step of forming an integrated layer of graphene halide having a plane spacing _d002 of .35 nm to 1.2 nm (preferably 0.40 to 1.0 nm, more preferably 0.40 nm to 0.90 nm). And include. In contrast to the original natural graphite, which is typically 0.3359 nm, interplanar spacing in the range of 0.350 to 1.0 nm is a halogen element or halogen-containing chemical group that spreads adjacent surfaces. In the case of the portion, it can be noted that in addition to this, some residual O or O-containing group) is present on the graphene surface.

Regarding the timing sequence, it can be noted that the halogenating agent can be introduced before, during or after the removal of the liquid medium from the wet layer of GO.
In a preferred embodiment, the integrated layer of oriented halogenated graphene has the chemical formula C ₆ Z _x Oy with _y = 0 and x = 0.01-6.0 (oxygen is completely removed). In another preferred embodiment, the integrated layer of oriented halogenated graphene is y = 0.1 and x = 0.1-5.0 (having a low oxygen content) of formula C ₆ Z _{x Oy} . Has.

The halogenated graphene sheets in the dry integrated layer of halogenated graphene are substantially parallel to each other along one direction, and the average deviation angle of these sheets is less than 10 degrees. It should be noted that in conventional GO or RGO sheet-based paper, the graphene sheets or platelets are tilted relative to each other at very large angles (eg, misalignment of 20-40 degrees). can. The average deviation angle from the desired orientation angle is greater than 10 °, more typically> 20 °, often> 30 °.

The present inventors have discovered that the electrical and dielectric properties of GO films deteriorate rapidly when the temperature of aging or heat treatment exceeds 100 ° C. For example, if a GO film is exposed to heat at 200 ° C. for several hours, the resistivity may drop from ^10-6 Ω-cm to 10 ^{+ 2} Ω-cm, which is eight orders of magnitude higher in resistivity. GO becomes a completely useless dielectric material. In contrast, the integrated film _{C6Z xOy} of highly oriented halogenated _graphene according to the present invention can be thermally stable up to 1,000 to 2,500 ° C. depending on the chemical composition. Higher maximum useful temperatures are obtained with larger x values or higher x / (y + x) ratios. When x = 1, the thermal stability temperature can be as high as 2,000 to 2,500 ° C.

It is known that the tensile strength of the integrated film according to the present invention is typically 60 MPa to 140 MPa, and the tensile elastic modulus is 3.0 to 12 GPa. Surprisingly, they have a high degree of structural integrity.

In certain embodiments, with respect to timing, step (b) can be performed during or after step (b). Therefore, the present invention is (a) a step of preparing either a graphene oxide dispersion having a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel having graphene oxide molecules dissolved in a flow medium. The graphene oxide sheet or graphene oxide molecule contains an oxygen content of more than 5% by weight; (b) a halogenating agent is introduced into the graphene oxide dispersion or gel, and the halogenating agent A step of causing a chemical reaction with the graphene oxide sheet or molecule to form a dispersion of the graphene halide sheet or a gel of the graphene halide molecule, wherein the graphene halide sheet is C _{6Z x} O. Chemical formula of _y (in the formula, Z is a halogen element selected from F, Cl, Br, I or a combination thereof, x = 0.01 to 6.0, y = 0 to 5.0 and x + y ≦. 6. A step of supplying and depositing a layer of the graphene halide dispersion or gel on the surface of the supporting substrate under shear stress conditions; the supply and deposit. The procedure for deposition is induced by shearing of the graphene halide sheet or molecule, with thinning induced by shearing of the graphene dispersion or gel to form a wet layer of graphene halide on the supporting substrate. Steps and; (d) the flow medium is removed from the wet layer of graphene halide to provide a plane spacing d ₀₀₂ of 0.35 nm to 1.2 nm as measured by X-ray diffraction. Also provided is a method comprising the step of forming an integral layer of said graphene halide having.

Further, the halogenated graphene sheets in the dry integrated layer of halogenated graphene are substantially parallel to each other along one direction, and the average deviation angle of these sheets is less than 10 degrees. After some aging, the integral layer is a plurality of constituent halogenated graphene surfaces that are substantially parallel to each other along one direction and are less than 10 degrees (more typically less than 5 degrees). It has a plurality of constitutional halogenated graphene surfaces having an average deviation angle of the halogenated graphene surfaces.

In various embodiments, the starting graphene oxide sheet contains a single-layer graphene oxide or multi-layer graphene oxide sheet, each having 2-10 graphene oxide surfaces. The fluid medium may be water, alcohol, a mixture of water and alcohol, or an organic solvent.

The fluorinating agent preferably contains a liquid, gaseous or plasma species containing a halogen element selected from F, Cl, Br, I or a combination thereof. In certain embodiments, the fluorinating agent contains a liquid, gaseous or plasma species containing a halogen element selected from F, Cl, Br, I or a combination thereof. In a particularly preferred embodiment, the fluorinating agent is hydrofluoric acid, hexafluorophosphoric acid or HPF ₆ , XeF ₂ , F ₂ gas, F ₂ / Ar plasma, CF ₄ plasma, SF ₆ plasma, HCl, HPCl ₆ , XeCl ₂ , Cl ₂ gas, Cl ₂ / Ar plasma, CCl ₄ plasma, SCl ₆ plasma, HBr, XeBr ₂ , Br ₂ gas, Br ₂ / Ar plasma, CBr ₄ plasma, SBr ₆ plasma, HI, XeI ₂ , I ₂ , I ₂ / Ar plasma, CI ₄ plasma, SI ₆ plasma or a combination thereof is selected.

Feeding and deposition steps can include printing, spraying, coating and / or casting procedures combined with shear stress procedures. The coating method can include slot die coating or comma coating procedures. More preferably, the feeding and deposition steps include a reverse roll transfer coating procedure.

In one preferred variant of the reverse roll transfer coating process, the feeding and deposition steps are carried out by rolling a layer of graphene oxide dispersion or graphene oxide gel in a first direction onto the surface of a coating roller that rotates at a first linear velocity. A support film comprising feeding to form an applicator layer of graphene oxide, in which a coating roller drives the graphene oxide applicator layer in a second direction opposite to the first direction at a second linear velocity. Transfers to the surface of the graphene to form a wet layer of graphene oxide on the support film. The support film can be located at a working distance from the coating roller and driven by a reverse support roller that rotates in a second direction opposite to the first direction.

The velocity ratio defined as (the second linear velocity) / (the first linear velocity) is preferably 1/5 to 5/1, more preferably greater than 1/1 and less than 5/1. Is. When the outer surface of the coating roller moves at the same speed as the linear movement speed of the support film, the speed ratio is 1/1 or 1. As an example, when the outer surface of the coating roller moves at a speed three times the linear movement speed of the support film, the speed ratio is 3/1. In some embodiments, the velocity ratio is greater than 1/1 and less than 5/1. Preferably, the velocity ratio is greater than 1/1 and less than or equal to 3/1.

In one embodiment, the step of feeding the graphene oxide dispersion or graphene oxide gel onto the surface of the coating roller is a step of feeding the graphene oxide of the desired thickness onto the surface of the coating roller using a metering roller and / or a doctor blade. Includes steps to form an applicator layer. The method can include stepping on a few or four rollers.

In a preferred embodiment, the support film is located at a working distance from the coating roller and is driven by a reverse support roller that rotates in a second direction opposite to the first direction. The velocity on the outer surface of this support roller determines the second linear velocity (of the support film). Preferably, the support film is fed from a feed roller, and the dry layer of halogenated graphene supported by the support film is wound onto a take-up roller, and this method is performed in a roll-to-roll manner.

Preferably, the method according to the invention wets graphene oxide after step (b) over an aging time of 1 hour to 7 days in an aging chamber with an aging temperature of 25 ° C to 100 ° C and a humidity level of 20% to 99%. It further comprises aging the layer, aging the wet layer of graphene halogenated after step (c), or aging the integral layer of graphene halogenated after step (d). This method can further include a compression step during or after the step (d) to reduce the thickness of the integral layer.

In the method of the present invention, the integrated layer of oriented halogenated graphene is heat-treated at a first heat treatment temperature of more than 100 ° C. but not more than 3,200 ° C. for a time of a desired length, and the surface having a surface of less than 0.4 nm. The step (e) for producing a graphite film having an interval d ₀₀₂ and a total oxygen / halogen content of less than 1% by weight can be further included. This method can further include a compression step during or after the heat treatment step to reduce the thickness of the graphite film.

In the method according to the present invention, the graphene oxide sheet in the graphene oxide dispersion preferably occupies a weight fraction of 0.1% to 25% based on the total weight of the graphene oxide sheet and the liquid medium combined. More preferably, the graphene oxide sheet in the graphene oxide dispersion occupies a weight fraction of 0.5% to 15%. In one embodiment, the graphene oxide sheet occupies a weight ratio of 3% to 15% based on the total weight of the graphene oxide sheet and the liquid medium. In certain embodiments, the graphene oxide dispersion or graphene oxide gel has more than 3% by weight of graphene oxide dispersed in a fluid medium to form a liquid crystal phase.

The graphene oxide dispersion or graphene oxide gel of the present invention is a reaction vessel of a graphite material in the form of powder or fiber at a reaction temperature for a time long enough to obtain the graphene oxide dispersion or the graphene oxide gel. The graphite material can be prepared by immersing in an oxidizing liquid inside, and the graphite material is natural graphite, artificial graphite, intermediate phase carbon, intermediate phase pitch, mesocarbon microbeads, soft carbon, hard carbon, coke, carbon fiber. , Carbon nanofibers, carbon nanotubes or combinations thereof.

The graphene oxide dispersion or graphene oxide gel of the present invention can be obtained from a graphite material having the maximum original graphite crystal grain size, and the resulting halogenated graphene film is larger than this maximum original crystal grain size. It is a polycrystalline graphene structure with a large crystal grain size. This larger crystal grain size allows the heat treatment of GO sheets, GO molecules, halogenated molecules or halogenated sheets to chemically link and coalesce graphene oxide / graphene halide sheets or graphene oxide / graphene halide molecules in an edge-to-edge manner. Or it is due to the idea of inducing a chemical bond. It can be noted that such connection between the edges significantly increases the length or width of the graphene sheet or molecule. For example, when a halogenated graphene sheet having a length of 300 nm is combined with a halogenated graphene sheet having a length of 400 nm, a sheet having a length of about 700 nm can be obtained as a result. The coalescence between the edges of a plurality of halogenated graphene sheets makes it possible to produce graphene films having a huge crystal grain size, which could not be obtained by other methods.

In one embodiment, the graphene oxide dispersion or graphene oxide gel is obtained from a graphite material having multiple graphite microcrystals that do not exhibit the preferred crystal orientation when measured by X-ray or electron diffraction, and results. The halogenated graphene film obtained as above has a single crystal or polycrystal graphene structure having a preferable crystal orientation when measured by the X-ray diffraction method or the electron diffraction method.

Any coating procedure capable of generating shear stress on a GO sheet or halogenated GO sheet can be performed by the method according to the invention, for example slot die coating, comma coating and reverse roll transfer coating. .. The reverse roll procedure arranges the GO sheet or the GO molecule itself along a specific direction (eg, X or length direction) or two specific directions (eg, X and Y direction or length and width direction). It is particularly effective to enable the formation of a favorable orientation. Even more surprisingly, during the subsequent heat treatment of the GO layer, these favorable orientations are maintained and often further improved. Most surprisingly, such a favorable orientation is a very high degree of insulation along the desired direction of the resulting halogenated graphene film (even for thick films, for example 10 nm to> 500 μm). It is important to finally obtain the breaking strength, dielectric constant, elastic modulus and tensile strength. During the coating or casting process, the thickness of the coated or cast film (layer) will not be too thick (eg, greater than 50 μm) except by the method based on the reverse roll procedure according to the invention, otherwise it will be advanced. GO or halogenated sheet orientation cannot be achieved. Generally, conventional casting or comma coating processes form a dry layer of graphene oxide with a thickness of 50 μm or less, more typically 20 μm or less, and most typically 10 μm or less when dried. The coated or cast film (wet layer) needs to be thin enough. Extensive and thorough experimental studies, we anticipate that the reverse roll procedure will be thus effective in achieving and maintaining highly favorable orientations even for very thick films. I came to recognize it without doing it.

The integrated layer of oriented halogenated graphene produced according to the present invention typically exceeds 4.0 (more typically greater than 5.0, many, when measured at a layer thickness of 100 nm. Dielectric constants greater than 10 or even greater than 15, typically ¹⁰⁸ Ω-cm to 10 ¹⁵ Ω-cm electrical resistivity and / or greater than 5 MV / cm (more typically 10 MV). It has a dielectric breakdown strength of more than / cm, sometimes more than 12 MV / cm, and in other cases more than 15 MV / cm).

The present invention also provides a microelectronic device containing an integrated layer of graphene halide as a dielectric component.

This new class of material (ie, highly oriented GO-derived halogenated graphene film GOGH) has the following properties that distinguish it from individual graphene / GO / RGO / GH sheets / platelet paper / film / membrane layers: Have:
(1) This GOGH film is an integrated halogenated graphene (GH) element having a polycrystalline structure composed of a plurality of well-arranged and interconnected crystal grains having a very large grain size. In HOGH, all graphene planes in all crystal grains are oriented substantially parallel to each other (that is, the crystallographic c-axis of all crystal grains is oriented in substantially the same direction).

(2) The reverse roll procedure can be used to achieve a very high degree of orientation of the GH platelet, not only for thin films but also for thick films (> 10 nm). For the same thickness, the reverse roll procedure allows for higher orientations and higher crystal integrity.

(3) GOGH is not a simple aggregate or laminate of multiple individual plateslets of graphene / GO / RGO / GH (halogenated graphene), but identifiable or individual flakes obtained from the original GO sheet. / An integrated graphene element that does not contain platelets. These original individual flakes or platelets are chemically bonded or linked to each other to form larger grains (grain size is larger than the original platelet / flake size).

(4) This GOGH is not manufactured by adhering individual flakes or platelets to each other using a binder or adhesive. Instead, under selected aging or heat treatment conditions, well-arranged GO / GH sheets or GO / GH molecules chemically coalesce with each other, predominantly in an edge-to-edge manner, to form giant 2D graphene grains. It can, but optionally, be combined with an adjacent GO / GH sheet above or below to form a 3D network structure of graphene chains. The formation of interconnected or covalent bonds gives graphene elements to which GO / GH sheets are adhered and integrated without the use of externally added linker or binder molecules or polymers.

(5) This GOGH, which is a polycrystal in which substantially all graphene planes have the same crystallographic c-axis, is obtained from GO, and this GO originally contains a plurality of irregularly oriented graphite microcrystals. Obtained by moderate or intense oxidation of natural or man-made graphite crystals, respectively. With a sufficiently long oxidation time to chemically oxidize to a GO dispersion (moderate to intense oxidation of graphite) or GO gel (completely separated GO molecules dissolved in water or another polar liquid). Prior to the intense oxidation of these starting or original graphite microcrystals, the initial length (La in the crystallographic a-axis), initial width (L _b in the _b -axis) and thickness (c). It has L _c ) in the axial direction. The resulting GOGH typically has _a much larger length or width than the original graphite crystallites La and _Lb.

(6) This method of manufacturing a highly oriented GH monolith integrated layer can be performed on the basis of continuous roll-to-roll and is therefore an expandable and cost-effective method.

It is a schematic diagram of the GO / GH layer transfer apparatus based on the reverse roll for producing a highly oriented GO / GH film. It is a schematic diagram of the GO / GH layer transfer apparatus based on another reverse roll for producing a highly oriented GO / GH film. It is a schematic diagram of the GO / GH layer transfer apparatus based on still another reverse roll for producing a highly oriented GO / GH film. It is a schematic diagram of the GO / GH layer transfer apparatus based on still another reverse roll for producing a highly oriented GO / GH film. (A) is a graphene oxide gel or GO dispersion produced by various prior art methods for producing exfoliated graphite products (flexible graphite foil and flexible graphite composite material) and pyrolyzed graphite (lower portion). It is a flowchart which shows together with the method. (B) is a schematic diagram showing a method for producing conventional papers, mats, films and films of simply aggregated graphite or NGP flakes / platelets. All methods begin with intercalation and / or oxidation treatment of graphite material (eg, natural graphite particles). (A) is an SEM image of a graphite worm sample after thermal exfoliation of a graphite intercalation compound (GIC) or graphite oxide powder. (B) is an SEM image of a cross section of the flexible graphite foil, showing many graphite flakes with orientations not parallel to the surface of the flexible graphite foil, with many defects, twisted or folded. Flakes are also shown. (A) is an SEM image of a film derived from GO, in which a plurality of graphene surfaces (having an initial length / width of 30 nm to 300 nm in the original graphite particles) are oxidized, peeled, reoriented, and seamlessly. Combined into a continuous length graphene sheet or layer that can be continued with a width or length of tens of centimeters (only 50 μm wide of a 10 cm wide graphite film is shown in this SEM image). .. (B) is an SEM image of a cross section of a conventional graphene paper / film made from individual graphene sheets / plateslets using a papermaking process (eg, vacuum assisted filtration). This image shows that many individual graphene sheets are folded or interrupted (not integrated), the orientation is not parallel to the film / paper surface, and there are many defects or imperfections. Has a complete part. (C) is a schematic diagram showing a method of forming HOGF which is parallel to each other and is composed of a plurality of graphene planes chemically bonded in the thickness direction or the crystallographic c-axis direction, and an accompanying SEM image. (D) is one of the possible chemical linkage mechanisms (only two GO molecules are shown as an example, and many GO molecules can be chemically linked to each other to form a graphene layer. can). Dielectric breakdown strength of GO film plotted as a function of film thickness, graphene fluoride film derived from GO (produced by reverse roll transfer coating method) and polyimide film. GO-derived fluorinated graphene film and chlorinated graphene film (both reverse roll transfer procedures) plotted as a function of degree of fluorination (atomic ratio F / (F + O)) or degree of chlorination (atomic ratio Cl / (Cl + O)) And the insulation failure strength of (produced by the casting procedure). GO-derived fluorinated graphene film (produced by reverse roll transfer procedure) and GO-derived fluorinated film produced by conventional papermaking procedure (vacuum-assisted filtration) plotted as a function of the degree of fluorination with respect to atomic ratio F / (F + O). Dielectric breakdown strength of graphene paper. The permittivity of the GO-derived fluorinated graphene film and the brominated graphene film plotted as a function of the degree of fluorination (atomic ratio F / (F + O)) or the degree of bromination (atomic ratio Br / (Br + O)).

A method of making a highly oriented halogenated graphene sheet or an integral layer of a molecular monolith (single material or single phase) is provided in which the film has a thickness of 10 nm to 500 μm. This halogenated graphene is a halogen element selected from the chemical formula of C ₆ Z _{x Oy} (in the formula, Z is F, Cl, Br, I or a combination thereof, and x = 0.01 to 6.0. , Y = 0 to 5.0 and x + y ≦ 6.0). Preparation of this integral layer begins with graphene oxide (GO) in the form of a suspension (dispersion) or gel. In particular, this method prepares either (a) a graphene oxide (GO) dispersion with a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel with graphene oxide molecules dissolved in a flow medium. In the step, the graphene oxide sheet or graphene oxide molecule exceeds 5% by weight (typically 5% to 46%, but preferably 10% to 46%, more preferably 20% to 46%) oxygen. Start with the step, which contains the amount.

Following this is a step of supplying and depositing a layer of graphene oxide dispersion or graphene oxide gel on the surface of the supporting substrate under shear stress conditions, the procedure of supplying and depositing is oxidizing on the supporting substrate. Step (b) includes shearing-induced thinning of the graphene oxide dispersion or gel to form a wet layer of graphene and shearing-induced orientation of the graphene oxide sheet or molecule. This step involves spraying, printing, extruding the wet phase of GO onto a solid substrate surface (eg, PET film, Al foil, glass surface, etc.), which comprises a shearing procedure or where the shearing procedure is next performed. Includes molding, casting and / or coating. The presence of shear stress is important for arranging GO sheets or molecules along the desired direction.

Next, step (c) of the third step is performed to chemically replace the O or oxygen-containing functional group with a halogen element or a halogen-containing group. As used herein, halogen means F, Cl, Br, I or a combination thereof. Therefore, in this step (c), a halogenating agent is introduced into the wet layer of graphene oxide, and a chemical reaction is caused between the halogenating agent and the graphene oxide sheet or molecule to cause C _{6Z x Oy} . (In the formula, Z is a halogen element selected from F, Cl, Br, I or a combination thereof, and x = 0.01 to 6.0, y = 0 to 5.0 and x + y≤6. Accompanied by forming a wet layer of halogenated graphene with (.0). The fluorinating agent can contain a liquid, gas or plasma species containing a halogen element selected from F, Cl, Br, I or a combination thereof. Halogenated graphene is a group of graphene derivatives in which some carbon atoms are covalently bonded to halogen atoms. The carbon atom bonded to the halogen has a sp ³ hybrid, and the other carbon atoms have an sp ² hybrid. The physical and chemical properties of halogenated graphene (also referred to as halogenated graphene) are highly dependent on the degree of halogenation.

Next, following step (c), the flow medium is removed from the wet layer of graphene halogenated and halogenated with a plane spacing d ₀₀₂ of 0.35 nm to 1.2 nm as measured by X-ray diffraction. Step (d) of forming an integral layer of graphene is performed. Removal of the liquid fluid can be performed before, during or after the halogenation reaction.

To carry out the halogenation reaction, for example, a hydrofluoric acid or hexafluorophosphoric acid (HPF ₆ ) liquid may be injected into the GO suspension or GO gel stream before, during or after the feed / deposition step. can. Alternatively, F ₂ gas, Cl ₂ gas, Br ₂ gas and / or I ₂ gas (vapor) are introduced into the chamber containing the wet GO layer to allow halogen gas molecules to permeate into the wet GO layer. Can react with internal and above GO. Yet another option is to remove the liquid medium from the wet layer of the GO to form a dry layer of the GO and then introduce a halogenating agent to react with the GO. The GO dry layer can preferably be treated with a halogen-containing gas or plasma.

In particular, the fluorinating agents are hydrofluoric acid, hexafluorophosphoric acid or HPF ₆ , XeF ₂ , F ₂ gas, F ₂ / Ar plasma, CF ₄ plasma, SF ₆ plasma, HCl, HPCl ₆ , XeCl ₂ , Cl. ₂ gas, Cl ₂ / Ar plasma, CCl ₄ plasma, SCl ₆ plasma, HBr, XeBr ₂ , Br ₂ gas, Br ₂ / Ar plasma, CBr ₄ plasma, SBr ₆ plasma, HI, XeI ₂ , I ₂ , I ₂ You can choose from / Ar plasma, CI ₄ plasma, SI ₆ plasma or a combination thereof.

A highly preferred supply and deposition procedure is a reverse roll transfer coating that essentially induces high shear stress in the suspension or gel coated on the rollers. As schematically shown in FIG. 1 as a preferred embodiment, a method for producing a monolithic integrated layer of highly oriented halogenated graphene (HOGH) is a graphene oxide dispersion (GO dispersion) supplied to trough 208. ) Or graphene oxide gel (GO gel). The rotational movement of the coating roller 204 in the first direction allows the GO dispersion or gel continuous layer 210 to be supplied onto the outer surface of the coating roller 204. An optional doctor blade 212 is used to adjust the thickness (amount) of the graphene oxide (GO) applicator layer 214. This applicator layer is continuously fed to the surface of the support film 216 moving in a second direction (eg, driven by a reversing roller 206 rotating in the direction opposite to the first direction) to provide graphene oxide. A wet layer 218 is formed. The wet layer of this GO is then subjected to a liquid removal treatment (eg, in a heated environment and / or using a vacuum pump).

In summary, this method begins with the preparation of either a graphene oxide dispersion with a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel with graphene oxide molecules dissolved in a flow medium, starting with graphene oxide. The sheet or graphene oxide molecule has an oxygen content of greater than 5% by weight. The graphene oxide dispersion or graphene oxide gel is then dispensed and fed onto the surface of the coating roller, which rotates in a first direction at a first linear velocity (the linear velocity of the outer surface of the coating roller). A layer is formed and the graphene oxide applicator layer is transferred onto the surface of the support film driven at a second linear velocity in a second direction opposite to the first direction and oxidized onto the support film. Form a wet layer of graphene.

In a preferred embodiment, the support film is driven by a reversing support roller (eg, 206 in FIG. 1) that is located at a working distance from the coating roller and rotates in a second direction opposite to the first direction. The velocity on the outer surface of this support roller determines the second linear velocity (of the support film). Preferably, the support film is fed from a feed roller, and the dry layer of graphene oxide supported by the support film is wound onto a take-up roller, and this method is performed in a roll-to-roll manner.

This method is further shown in FIGS. 2, 3 and 4. In a preferred embodiment, a GO dispersion / gel trough 228 is naturally formed between the coating roller 224 and the weighing roller 222 (also referred to as a doctor roller), as shown in FIG. The relative motion or rotation of the coating roller 224 with respect to the weighing roller 222 at a desired speed forms the GO applicator layer 230 on the outer surface of the coating roller 224. The GO applicator layer is then transferred to place the GO wet layer 232 on the surface of the support film 234, driven by a support roller 226 that rotates in the direction opposite to the direction of rotation of the applicator roller 224. Form. The wet layer can then be halogenated and dried.

In another preferred embodiment, a GO dispersion / gel trough 244 is naturally formed between the coating roller 238 and the weighing roller 236, as shown in FIG. The relative motion or rotation of the coating roller 238 with respect to the weighing roller 236 at a desired speed forms the GO applicator layer 248 on the outer surface of the coating roller 238. A doctor blade 242 can be used to scrape off the GO gel / dispersion on the outer surface of the weighing roller 236. The GO applicator layer 248 is then transferred onto the surface of the support film 246 (driven by a support roller 240 that rotates in the opposite direction of the applicator roller 238) to the GO wet layer 250. To form. The wet layer can then be halogenated and dried.

In yet another preferred embodiment, the GO dispersion / gel trough 256 is naturally formed between the coating roller 254 and the weighing roller 252, as shown in FIG. The relative motion or rotation of the coating roller 254 with respect to the weighing roller 252 at a desired speed forms the GO applicator layer 260 on the outer surface of the coating roller 254. The GO applicator layer 260 is then transferred to form a GO wet layer 262 on the surface of the support film 258 driven to move in a direction opposite to the tangential rotation direction of the applicator roller 254. The support film 258 can be supplied from a feed roller (not shown) and can be taken up (wound) onto a take-up roller (not shown) which may be a drive roller. In this example there are at least 4 rollers. The wet layer can then be halogenated and dried. In the case of liquid medium removal, there is a heating zone after the GO wet layer is formed in order to at least partially remove the liquid medium (eg, water) from the wet layer to form a GO dry layer. Can be done.

In one embodiment, the step of feeding the graphene oxide dispersion or graphene oxide gel onto the surface of the coating roller is an applicator of graphene oxide of the desired thickness on the surface of the coating roller using a metering roller and / or a doctor blade. Includes steps to form layers. In general, the method of the invention comprises the steps of manipulating a few or four rollers. Preferably, the method of the invention comprises a reverse roll coating procedure.

It can be noted that the velocity ratio defined as (second linear velocity) / (first linear velocity) is 1/5 to 5/1. When the outer surface of the coating roller moves at the same speed as the linear movement speed of the support film, the speed ratio is 1/1 or 1. As an example, when the outer surface of the coating roller moves at a speed three times the linear movement speed of the support film, the speed ratio is 3/1. As a result, the transferred GO wet layer is about three times thicker than the GO applicator layer. Quite unexpectedly, this allows the production of much thicker layers and still maintains a high degree of GO orientation in the wet and dry layers. This is very important and desirable as it has not been possible to achieve high GO sheet orientation on thick films (eg> 50 μm thickness) by using casting or other coating techniques such as comma coating and slot die coating. It is a result. In some embodiments, the velocity ratio is greater than 1/1 and less than 5/1. Preferably, the velocity ratio is greater than 1/1 and less than or equal to 3/1. The slot die coating or comma coating can also apply shear forces to induce the required orientation of the GO or GH sheet or molecule.

Preferably, the method of the invention is in an aging chamber at an aging temperature of 25 ° C to 200 ° C (preferably 25 ° C to 100 ° C, more preferably 25 ° C to 55 ° C) and a humidity level of 20% to 99% for 1 hour. It further comprises the step of aging the wet or dry layer of graphene oxide over an aging time of ~ 7 days to form an aged layer of graphene oxide. Microscopic observation revealed that the average length / width of the GO sheet increased significantly (2-3 times) after aging, and we were surprised by this aging procedure in an edge-to-edge manner. It has been confirmed that the GO sheet or a part of the molecule can be chemically linked or coalesced. This allows the sheet orientation to be maintained and later edge-to-edge connections to large grain or crystal regions to be facilitated.

In certain embodiments, the method of the invention is a dry layer of graphene oxide over a desired length of time at a first heat treatment temperature above 100 ° C. but below 3,200 ° C. (preferably below 2,500 ° C.). Alternatively, it further comprises the step of heat treating the dried and aged layer to form a film having an interplanar _spacing of less than 0.4 nm and an oxygen and / or halogen content of less than 5% by weight. The method of the present invention can further include a compression step for reducing the thickness of the graphene film during or after this heat treatment step.

In the method according to the invention, the graphene oxide sheet in the graphene oxide dispersion preferably occupies a weight fraction of 0.1% to 25% based on the total weight of the graphene oxide sheet and the liquid medium combined. More preferably, the graphene oxide sheet in the graphene oxide dispersion occupies a weight fraction of 0.5% to 15%. In one embodiment, the graphene oxide sheet occupies a weight ratio of 3% to 15% based on the total weight of the graphene oxide sheet and the liquid medium combined. In certain embodiments, the graphene oxide dispersion or graphene oxide gel has more than 3% by weight of graphene oxide dispersed in a fluid medium to form a liquid crystal phase.

The monolithic integrated halogenated graphene film contains chemically bonded and coalesced graphene surfaces. These planar aromatic molecules or graphene planes (hexagonal carbon atoms with the desired amount of oxygen-containing and / or halogen-containing groups) are parallel to each other. The lateral dimensions (length or width) of these surfaces are enormous, typically several times or even orders of magnitude larger than the maximum microcrystalline dimensions (or maximum constituent graphene surface dimensions) of the starting graphite particles. The halogenated graphene film according to the present invention is a "giant graphene crystal" or "giant planar graphene particle" in which all constituent graphene planes are substantially parallel to each other. This is a unique new class of material that has never been previously discovered, developed, or suggested to exist.

The dry halogenated graphene (GH) layer has a high birefringence between the in-plane direction and the direction perpendicular to the plane. The layer itself of oriented graphene oxide and / or halogenated graphene is, surprisingly, a very unique and new class of material with very strong cohesive forces (self-bonding, self-polymerizing and self-crosslinking properties). These properties have not been taught or suggested in the prior art. GO is obtained by immersing the powder or filament of the starting graphite material in an oxidizing liquid medium (eg, a mixture of sulfuric acid, nitric acid and potassium permanganate) in a reaction vessel. The starting graphite material can be selected from natural graphite, artificial graphite, intermediate phase carbon, intermediate phase pitch, mesocarbon microbeads, soft carbon, hard carbon, coke, carbon fiber, carbon nanofibers, carbon nanotubes or a combination thereof. can.

When the starting graphite powder or filament is mixed in an oxidizing liquid medium, the resulting slurry is a heterogeneous suspension and appears dark and opaque. If the oxidation of graphite proceeds for a sufficient period of time at the reaction temperature, the reaction mass can eventually become a pale green, yellowish-looking suspension, but it remains opaque. The degree of oxidation is sufficiently high (eg, having an oxygen content of 20% to 50% by weight, preferably 30% to 50%), and all the original graphene surfaces are completely oxidized and exfoliated to oxidize each. Separation of the graphene surface (here, graphene oxide sheet or molecule) to the extent that it is surrounded by molecules in the liquid medium gives a GO gel. This GO gel is an optically translucent, substantially homogeneous solution, in contrast to non-uniform suspensions.

This GO suspension or GO gel typically contains some excess of acid and is advantageously subjected to some acid dilution treatment to advantageously increase the pH value (preferably> 4.0). be able to. The GO suspension (dispersion) preferably contains at least 1% by weight of the GO sheet dispersed in the liquid medium, more preferably at least 3% by weight, and most preferably at least 5% by weight. It is advantageous to have a sufficient amount of GO sheets to form the liquid crystal phase. We have surprisingly found that liquid crystal GO sheets are most likely to be easily oriented under the influence of shear stresses generated by commonly used casting or coating processes.

The graphene oxide suspension oxidizes the graphite material (in powder or fiber form) over a period of time sufficient to obtain a GO sheet dispersed in the remaining liquid at the reaction temperature in the reaction vessel. It can be prepared by immersing in a reactive slurry to form a reactive slurry. Typically, this residual liquid is a mixture of an acid (eg, sulfuric acid) and an oxidant (eg, potassium permanganate or hydrogen peroxide). The residual liquid is then washed and replaced with water and / or alcohol to form a GO dispersion in which the individual GO sheets (single-layer or multilayer GO) are dispersed in the fluid. This dispersion is a heterogeneous suspension of individual GO sheets suspended in a liquid medium, optically opaque, dark (relatively low oxidation) or pale green and yellowish (oxidation). It looks like (when the degree is high).

Here, the GO sheet contains a sufficient amount of oxygen-containing functional groups and the resulting dispersion (suspension or slurry) is mechanically sheared or ultrasonically treated with water and / or alcohol or the like. When individual GO sheets or molecules dissolved (not just dispersions) are formed in a protic solvent, all individual GO molecules reach a material state called a "GO gel" surrounded by liquid medium molecules. can do. The GO gel is translucent and appears to be a uniform solution in which recognizable individual GOs or graphene sheets are visually indistinguishable. Useful starting graphite materials include natural graphite, artificial graphite, intermediate phase carbon, intermediate phase pitch, mesocarbon microbeads, soft carbon, hard carbon, coke, carbon fiber, carbon nanofibers, carbon nanotubes or combinations thereof. Be done. When the oxidation reaction proceeds to the required extent and the individual GO sheets are completely separated (at this stage the graphene surface and edges are heavily modified with oxygen-containing groups), an optically clear or translucent solution is formed. And this is GO gel.

Preferably, the GO sheet in such a GO dispersion or the GO molecule in such a GO gel is present in an amount of 1% to 15% by weight, but may be higher or lower. More preferably, the GO sheet is 2% to 10% by weight in suspension. Most preferably, the amount of GO sheet is sufficient to form a liquid crystal phase in the dispersion liquid. GO sheets typically have an oxygen content in the range of 5% to 50% by weight, more typically 10% to 50% by weight, and most typically 20% to 46% by weight. ..

The above features are further described and described in detail below. As shown in FIG. 5B, graphite particles (eg, 100) are typically composed of a plurality of graphite microcrystals or crystal grains. Graphite crystallites are composed of layers of hexagonal network of carbon atoms. The faces of these layers of hexagonally arranged carbon atoms are substantially flat and oriented or arranged so that they are substantially parallel and equidistant to each other in the individual crystallites. These layers of hexagonal carbon atoms, commonly referred to as graphene layers or bottom surfaces, are weakly bonded to each other in their thickness direction (crystallographic c-axis direction) by weak van der Waals forces, and these graphene layers. Groups are arranged in microcrystals. Graphite crystallite structures are usually characterized with respect to the c-axis direction and the a-axis (or b-axis) direction of the two axes or directions. The c-axis is in the direction perpendicular to the bottom surface. The a-axis or b-axis is a direction parallel to the bottom surface (perpendicular to the c-axis direction).

Highly ordered graphite particles have a length of La along the crystallographic a-axis direction, a width of L _b along the crystallographic _b -axis direction, and a thickness L _c along the crystallographic c-axis direction. It can consist of crystallography of considerable size. Composition of crystallites Graphene planes are highly aligned or oriented with respect to each other, and therefore these anisotropic structures give rise to many highly directional properties. For example, the thermal and electrical conductivity of a crystallite is high along the plane direction (a-axis or b-axis direction) but relatively low in the vertical direction (c-axis). As shown in the upper left portion of FIG. 5 (B), the different microcrystals in the graphite particles are typically oriented in different directions, and therefore the specific properties of the polycrystalline particles of polycrystals are all. It is the average value in the direction of the constituent microcrystals.

Due to the weak van der Waals force that maintains the parallel graphene layers, treatment with natural graphite can increase the spacing of the graphene layers to a large extent so that they expand significantly along the c-axis. It is possible to form an expanded graphite structure in which the layered properties of the carbon layer are substantially maintained. Methods for producing flexible graphite are well known in the art. In general, natural graphite flakes (eg, 100 in FIG. 5B) are intercalated in an acid solution to produce a graphite intercalation compound (GIC, 102). The GIC is washed, dried and then stripped by short exposure to high temperatures. This causes the flakes to expand or exfoliate in the c-axis direction of graphite up to 80-300 times the original dimensions. The exfoliated graphite flakes are worm-like in appearance and are therefore commonly referred to as the worm 104. From these highly expanded graphite flake worms, the aggregate or integration of expanded graphite with a typical density of about 0.04 to 2.0 g / cm ³ for most applications without the use of a binder. Sheets such as webs, papers, strips, tapes, foils, mats and the like (typically referred to as "flexible graphite" 106) can be formed.

The upper left portion of FIG. 5A shows a flow chart showing a prior art method used in the manufacture of a flexible graphite foil and a resin impregnated flexible graphite composite material. These methods typically intercalate graphite particles 20 (eg, natural graphite or synthetic graphite) with an intercalant (typically a strong acid or acid mixture) to give graphite intercalation compound 22 (GIC). Start by getting. After washing in water to remove excess acid, the GIC becomes "expandable graphite". The GIC or expansive graphite is then exposed to a high temperature environment (eg, in a tube furnace preset to a temperature in the range of 800-1,050 ° C.) for a short period of time (typically 15 seconds to 2 minutes). .. By this heat treatment, graphite can be expanded from 30 times to several hundred times in the c-axis direction to obtain a worm-like insect-like structure 24 (graphite worm), which has been peeled off but not separated. It contains graphite flakes and has large pores intervening between these interconnected flakes. An example of a graphite worm is shown in FIG. 6 (A).

In one of the prior art methods, the exfoliated graphite (or graphite worm mass) is recompressed using calendaring or roll press techniques to make the flexible graphite foil (26 or 5 in FIG. 5 (A)). B) 106) are obtained, which are typically 100-300 μm thick. An SEM image of a cross section of the flexible graphite foil is shown in FIG. 6B, which shows many graphite flakes with orientations that are not parallel to the surface of the flexible graphite foil, many defects and There is an incomplete part.

Due primarily to the misalignment and the presence of defects in these graphite flakes, commercially available flexible graphite foils typically have an in-plane electrical conductivity of 1,000-3,000 S / cm in the plane-penetrating direction ( The electrical conductivity in the thickness direction or the Z direction is 15 to 30 S / cm, the in-plane thermal conductivity is 140 to 300 W / mK, and the thermal conductivity in the surface penetration direction is about 10 to 30 W / mK. .. These defects and misalignments also contribute to low mechanical strength (eg, defects are potential stress concentration sites where cracks initiate preferentially). These properties are inadequate for many temperature control applications and the present invention is configured to address these issues.

In another prior art method, the exfoliated graphite worm 24 can be impregnated with resin and then compressed and cured to form the flexible graphite composite material 28, which is also usually of low strength. Furthermore, when impregnated with resin, the electrical and thermal conductivity of the graphite worm can be reduced by double orders of magnitude.

Alternatively, the exfoliated graphite is subjected to high-strength mechanical shearing / separation treatment using a high-strength air jet mill, high-strength ball mill or ultrasonic device, and all graphene platelets are thinner than 100 nm and are mostly Separated nanographene platelets 33 (NGP) can be produced that are thinner than 10 nm and are often single-layer graphene (also shown as 112 in FIG. 5 (B)). The NGP is composed of one graphene sheet or a plurality of graphene sheets, each of which is a two-dimensional hexagonal structure of carbon atoms.

Yet another, with low-strength shear, the graphite worm tends to separate into so-called expanded graphite flakes with a thickness of> 100 nm (108 in FIG. 5 (B). Using the method of making paper or matte). Graphite paper or matte 106 can be formed from these flakes. The expanded graphite paper or matte 106 is a simple aggregate or laminate of individual flakes with defects, breaks and misalignments between the individual flakes. be.

For the purpose of defining the shape and orientation of the NGP, the NGP is described as having a length (maximum dimension), width (second largest dimension) and thickness. This thickness is the minimum dimension and is less than 100 nm, preferably less than 10 nm in this application. If the platelet is approximately circular, the length and width are described as diameter. In NGP as defined herein, both length and width can be less than 1 μm, but can exceed 200 μm.

Graphene film / paper from multiple NGP masses (including individual sheets / platelets of single-layer and / or multi-layer graphene or graphene oxide, 33 in FIG. 5 (A)) using a film or paper manufacturing method. (34 of FIG. 5 (A) or 114 of FIG. 5 (B)) can be manufactured. FIG. 7B shows an SEM image of a cross section of graphene paper / film made from individual graphene sheets using a papermaking process. This image shows the presence of a large number of individual graphene sheets folded or interrupted (not integrated), with most of the platelet orientation not parallel to the film / paper surface and many defects or There are imperfections. NGP aggregates, even when tightly packed, conduct thermal conductivity above 1,000 W / mK only when the film or paper is cast and strongly pressed onto a sheet with a thickness of less than 10 μm. Shows the rate. Heat spreaders in many electronic devices are usually required to be thicker than 10 μm but thinner than 35 μm).

Another graphene-related product is graphene oxide gel 21 (FIG. 5 (A)). The GO gel is obtained by immersing the graphite material 20 in powder or fiber form in a strongly oxidizing liquid in a reaction vessel to form a suspension or slurry that is initially optically opaque and dark in color. Be done. This optical opacity is due to the individual graphite flakes at the beginning of the oxidation reaction and the individual graphene oxide flakes at a later stage that scatter and / or absorb visible wavelengths, resulting in an opaque, totally dark fluid mass. It reflects that. The reaction between the graphite powder and the oxidant can proceed at a sufficiently high reaction temperature for a sufficient length of time, and when all the resulting GO sheets are completely separated, the opaque suspension will be brown. Typically turned into a translucent or clear solution, at this stage it is a "graphene oxide gel" that does not contain distinguishable individual graphite flakes or graphite oxide platelets (21 in FIG. 5 (A)). It is a uniform fluid called. When supplied and deposited using the reverse roll coating according to the present invention, molecular orientation of the GO gel occurs to form a layer of highly oriented GO35, which can be heat treated to form a graphite film 37.

Again, typically this graphene oxide gel is optically transparent or translucent, without the internally dispersed graphite, graphene or graphene oxide recognizable separate flakes / platelets. It is visually uniform. In a GO gel, GO molecules uniformly "dissolve" in an acidic liquid medium. In contrast, suspensions of individual graphene sheets or graphene oxide sheets in a fluid (eg, water, organic acid or solvent) appear dark, black or dark brown, even with the naked eye, or at low magnification optics. Individual graphene or graphene oxide sheets can be recognized or identified using a microscope (100x to 1,000x).

Graphite oxide suspensions or GO gels are obtained from graphite materials (eg, natural graphite powder) with multiple graphite microcrystals that do not exhibit the preferred crystal orientation when measured by X-ray or electron diffraction. However, the resulting graphite film exhibits a very high degree of favorable crystal orientation when measured by the same X-ray or electron diffraction method. It is composed of hexagonal carbon atoms that make up the particles of the original or starting graphite material. Chemical modification, conversion, rearrangement, rearrangement, linkage or cross-linking, coalescence and integration as well as halogenation of the graphene surface. It provides yet another piece of evidence that it has been damaged.

Example 1: Preparation of Individual Nanographene Oxide Platelets (NGPs) or GO Sheets Graphite short fibers and natural graphite particles with an average diameter of 12 μm are used separately as starting materials, and the starting materials are concentrated sulfuric acid, nitric acid and permanganate. Graphite intercalation compound (GIC) was prepared by immersion in a mixture of potassium acid (as a chemical intercalate and oxidant). The starting material was first dried in a vacuum oven at 80 ° C. for 24 hours. A mixture of concentrated sulfuric acid, fuming nitric acid and potassium permanganate (in a weight ratio of 4: 1: 0.05) is then slowly added to a three-necked flask containing a piece of fiber under appropriate cooling and stirring. rice field. After the reaction for 5-16 hours, the acid-treated graphite fibers or natural graphite particles were filtered and washed thoroughly with deionized water until the pH level of the solution reached 6. After drying overnight at 100 ° C., the resulting graphite intercalation compound (GIC) or graphite oxide fibers were redistributed in water and / or alcohol to form a slurry.

In one sample, 500 grams of graphite oxide fibers were mixed with a 2,000 ml alcohol solution consisting of a 15:85 ratio of alcohol and distilled water to give a slurry mass. Next, the mixture slurry was irradiated with ultrasonic waves having an output of 200 W for various lengths of time. After 20 minutes of sonication, the GO fibers were effectively exfoliated and separated into thin graphene oxide sheets with an oxygen content of about 23% to 31% by weight.

Next, a reverse roll transfer procedure was performed, and from the obtained suspension, a thin film and a thick film of GO (thickness of 10 nm, 100 nm, 1 to 25 μm, 100 μm and 500 μm) were applied onto a polyethylene terephthalate (PET) film. Was produced. For comparison purposes, GO layers in the same thickness range were also made by drop casting and comma coating techniques.

A number of aging and halogenation treatments, including typically 1-8 hours at an aging temperature of 30-100 ° C. and 1-24 hours at 25-250 ° C., to produce a halogenated graphene film. I went to a sheet of GO film. A typical form is shown in FIG. 7 (C).

Example 2: Preparation of a single-layer graphene oxide sheet from mesocarbon microbeads (MCMB) Mesocarbon microbeads (MCMB) are prepared from China Steel Chemical Co., Ltd. , Kaohsiung, Taiwan. This material has a density of about 2.24 g / cm ³ and a median particle size of about 16 μm. MCMB (10 grams) was intercalated with an acid solution (4: 1: 0.05 ratio of sulfuric acid, nitric acid and potassium permanganate) for 48-96 hours. After completion of the reaction, the mixture was poured into deionized water and filtered. The intercalated MCMB was repeatedly washed in a 5% solution of HCl to remove most of the sulfate ions. Next, washing of the sample with deionized water was repeated until the pH of the filtrate became 4.5 or higher. Next, this slurry was subjected to ultrasonic treatment for 10 to 100 minutes to obtain a GO suspension. In TEM and atomic force microscopy studies, most GO sheets were single-layer graphene when the oxidation treatment exceeded 72 hours, and 2- or 3-layer graphene when the oxidation time was 48-72 hours. It is shown that.

The GO sheet has a ratio of oxygen of about 35% by weight to 47% by weight for an oxidation treatment time of 48 to 96 hours. The suspension was then coated on the PET polymer surface using a reverse roll transfer coating and a separate comma coating procedure to create an oriented GO film. The obtained GO film has a thickness that can vary from about 0.5 to 500 μm after removal of the liquid. Halogenation treatments were performed before (using HF acid) and after the feeding step (eg, F ₂ and Br ₂ plasmas further discussed below).

Example 3: Preparation of Graphene (GO) Oxide Suspension and GO Gel from Natural Graphite 30 ° C. with a liquid oxidant consisting of sulfuric acid, sodium nitrate and potassium permanganate in a 4: 1: 0.05 ratio. Graphite oxide was prepared by oxidizing graphite flakes in. When natural graphite flakes (14 μm particle size) are immersed in a liquid oxidant mixture for 48 hours and dispersed, the suspension or slurry appears optically opaque and dark in color and is maintained. After 48 hours, the reaction mass was washed 3 times with water to adjust to a pH value of at least 3.0. The final amount of water was then added to prepare a series of GO-aqueous suspensions. The present inventors have confirmed that the GO sheet forms a liquid crystal phase when the GO sheet occupies a weight fraction of> 3%, typically 5% to 15%.

For comparative purposes, we also prepared GO gel samples by extending the oxidation time to about 96 hours. With continued vigorous oxidation, the dark, opaque suspension obtained after 48 hours of oxidation turns into a translucent, brown-yellowish solution after some water washing.

By feeding and coating a GO suspension or GO gel on a PET film using both reverse roll coating and slot die coating and removing the liquid medium from the coated film, we dry. A thin film of graphene oxide was obtained. Next, the GO film was subjected to various heat treatments and halogenation treatments. These heat treatments typically include an aging treatment at 45 ° C. to 150 ° C. for 1-10 hours. The halogenation treatment is discussed in Examples 4 and 5.

Photographs of lattice images of the graphene layer by scanning electron microscope (SEM) and transmission electron microscope (TEM) and images of selected area electron diffraction (SAD), bright field (BF) and dark field (DF) are also halogenated graphene materials. Used to characterize the structure of the integrated layer of. For measurement of cross-sectional views of the film, the sample was embedded in a polymer matrix, sliced using an ultramicrotome and etched with Ar plasma.

By close investigation and comparison of FIGS. 6 (A), 6 (A) and 7 (B), the graphene layers in the halogenated GO film produced according to the present invention can be oriented substantially parallel to each other. As shown, this is not the case for flexible graphite foil and GO or GH paper. The tilt angle between the two identifiable layers in the integrated film of graphene halogenated is predominantly less than 5 degrees. In contrast, due to the presence of many folded graphite flakes, twists and misalignments in flexible graphite, many of the angles between the two graphite flakes exceed 10 degrees and some are as large as 45 degrees. (Fig. 6 (B)). Although it is not a defect, the misalignment between the graphene platelets in the graphene paper (FIG. 7 (B)) is also large (>> 10 to 20 ° on average), and there are many gaps between the platelets. There are virtually no gaps in the integrated halogenated graphene film.

Example 4: Halogenation treatment of GO after deposition of GO layer Chloroform (CF) and separately chlorobenzene (CB) are used at a temperature of 50 to 100 ° C. for 1 to 10 hours to chlorinate the GO platelet. Was done. The degree of GO chlorination was assessed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). In order to investigate the effect of CF or CB treatment on the dielectric performance of the obtained chlorinated GO, a film having a thickness of about 70 nm to 2 μm was prepared.

The reduced graphene oxide sheet (single layer and multilayer) can be fluorinated in a plasma containing CF ₄ , SF ₆ , XeF ₂ , a fluoropolymer or Ar / F ₂ as a fluorinating agent. By changing the plasma treatment time and the type of fluorinating agent, the fluorine content of the obtained fluorinated graphene can be changed.

Numerous techniques were used to fluorinate graphene oxide, including exposure to F ₂ gas at intermediate temperatures (400-600 ° C.) and treatment with F-based plasma. XeF ₂ is a potent fluorinating agent for graphene oxide without etching, thus providing an easy route for graphene halogenation. By characterization of this method by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, it corresponds to a coverage of 25-50% (formulas _C4 F to C ₂ F) for single-sided exposure by fluorination at room temperature. ) And in the case of double-sided exposure, it becomes clear that it is saturated with CF. Due to its high electronegativity, fluorine causes a strong chemical shift in carbon 1s bond energy, which allows X-ray photoelectron spectroscopy (XPS) to be used to quantify composition and bond types.

Fluorination was also performed by plasma-enhanced chemical vapor deposition (PECVD). In a typical procedure, the PECVD chamber was evacuated to about 5 mTorr and the temperature was raised from room temperature to 200 ° C. CF ₄ gas was then introduced into the chamber at a controlled gas flow rate and pressure. The degree of fluorination of the GO sample was adjusted by varying the exposure time. A suitable CF4 plasma exposure time was found to be 3-7 minutes _per 1 nm of Go layer thickness. For example, when the GO layer was 10 nm thick, the exposure time was 30-70 minutes.

Go bromination and iodination were performed in a similar procedure using a gas or plasma of Br ₂ , I ₂ , BrI, CBr ₄ and / or CCl ₄ under equivalent conditions.

Example 5: Preparation of various halogenated graphene oxide sheets / molecules prior to the feeding and deposition steps by sonication in the presence of sulfolane, dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP). A graphene fluoride suspension was obtained by chemically etching (commercially available) graphite fluoride particles. During this process, solvent molecules intercalate between graphene layers, weakening the van der Waals forces between adjacent layers and promoting the formation of graphene suspensions by exfoliation of graphite fluoride. The GF suspension is applied onto the surface of the PET film under high shear conditions (eg, faster linear velocity ratios 2/1 to 5/1) using comma coating, slot die coating or preferably reverse roll transfer coating. I was able to coat it directly.

By the chemical reaction between graphene oxide and hydrofluoric acid, graphene fluoride having various fluorine contents could be easily obtained. Fluorination of graphene oxide can be carried out by exposure of graphene oxide to anhydrous HF vapor at various temperatures, or can be carried out photochemically at room temperature using HF solution. These procedures were performed on GO sheets or molecules prior to the feeding and deposition steps.

Both single-layer graphene and multi-layer graphene can be chlorinated up to 56-74% by weight by UV light irradiation in a liquid chlorinated medium. Both single-layer graphene and multi-layer graphene can be brominated under similar conditions.

As an example, GO (15 mg) was mixed with 30 mL of carbon tetrachloride and sonicated for 20 minutes using a chip sonicator. The resulting suspension was transferred into a 500 mL quartz vessel equipped with a condenser maintained at 277 ° C. High-purity nitrogen was purged into the reaction chamber for 30 minutes, and chlorine gas was passed through the chamber. Gaseous chlorine condensed in a quartz vessel. A quartz container containing about 20 mL of liquid chlorine was heated to 250 ° C. and simultaneously irradiated with UV light (250 watt high pressure Hg vapor lamp) for 1.5 hours. After removing the solvent and excess chlorine, a clear film remained on the wall of the quartz vessel. The solid was dispersed in anhydrous alcohol under ultrasonic treatment, filtered and washed with distilled water and anhydrous alcohol. The filtrate was then redistributed in 40 ml of distilled water, sonicated for 2 minutes and centrifuged. The obtained black supernatant was separated and filtered using a PVDF membrane (pore diameter of 200 nm). The yield from the 15 mg GO sample was about 7-10 mg. Dispersing this chlorinated graphene sheet in a solvent (eg, CCl ₄ ) can be used to form suspensions for supply and deposition.

For bromination, 12 mg of graphene was mixed in a quartz vessel and 20 mL of liquid bromine was added to it. The mixture was sonicated for 10 minutes using an sonicator. To this, 0.5 g of carbon tetrabromide was added. Next, the quartz container was heated to 250 ° C. and irradiated with UV light at the same time as in the case of chlorination. Excess bromine was removed and the product was washed with sodium thiosulfate. The solid residue was then washed several times with water and anhydrous alcohol to remove sodium thiosulfate, then dispersed in 40 mL of distilled water and centrifuged. The obtained black supernatant was separated and filtered using a PVDF membrane (pore diameter of 200 nm). The yield from the 12 mg sample was about 5-7 mg. By dispersing this brominated graphene sheet in a solvent (eg, CBr ₄ ), suspensions for feeding and deposition can be formed.

The desired amount of halogenated GO sheet / molecule can be added to the GO suspension or GO gel prior to the feed / deposition step to form a GO / halogenated GO mixed suspension or gel. Typically, the weight ratio of halogenated GO to GO is 10/1 to 1/10 (in a selected liquid medium such as DMF and NMP), more typically 1/1 to 1/10 (liquid). If the medium is water).

Example 6: Properties of the integrated layer of graphene halide A method for measuring dielectric strength, dielectric constant, and volume resistivity (reciprocal of electrical resistivity) is well known in the art. The studies of the present invention followed standardized methods: dielectric strength (ASTM D-149-91), permittivity (ASTM D-150-92) and volume resistivity (ASTM D-257-91).

FIG. 8 shows the dielectric breakdown strength of a GO film plotted as a function of film thickness, a GO-derived integrated graphene fluoride film according to the present invention (produced by a reverse roll transfer coating method), and a polyimide film of the prior art. From these data, it can be seen that the graphene halide film according to the present invention exhibits a very high dielectric breakdown strength (> 12 MV / cm) even for a large film thickness of 25 to 125 μm (unexpectedly unexpected). Is). It was found that the dielectric breakdown strength value was relatively independent of the film thickness. In contrast, for the same thickness range, the graphene oxide film withstands a dielectric strength of 0.62 to 1.1 MV / cm and is an order of magnitude smaller in size. For comparison purposes, a commercially available polyimide film (duPont Kapton film) has a dielectric strength of 1.54 to 3.03 MV / cm.

The insulation breakdown strength of GO-derived fluorinated graphene film and chlorinated graphene film (both produced by the reverse roll transfer procedure and separately by the casting procedure) is determined by the degree of fluorination (atomic allocation F / (F + O) or degree of chlorination (atom). The ratio is plotted in FIG. 9 as a function of Cl / (Cl + O). The casting procedure did not include any significant amount of shear stress, whereas the reverse roll coating method was highly sheared in the orientation of GO and fluorinated GO films. Includes stress. These data show that for the same 100 nm thickness, the insulation strength of the GO film is from 2.6 MV / cm for a pure GO film (no fluorination or zero fluorination) to complete fluorine. It is shown that it increased to 22.2 MV / cm in the case of the chemical film. Again, it is shown that the GO film can be provided with a significantly improved insulating strength by fluorination. This is unexpected. Chlorization. The integrated film of GO film has the same tendency.

Most notably and unexpectedly, due to the fluorinated or non-fluorinated GO sheet or the orientation induced by shearing of the molecule, the integral film is the insulation of the non-oriented or less oriented equivalent made by conventional casting. It can withstand dielectric breakdown strength (2.6 to 22.2 MV / cm) much higher than breakdown strength (1.1 to 7.2 MV / cm). Similarly, highly oriented chlorinated GO sheets or integrated films of molecules can provide much higher dielectric strength compared to their casting equivalents where the sheets / molecules are not properly oriented. This is a very important finding, which provides a versatile method for achieving the extraordinary dielectric strength of graphene materials.

GO-derived fluorinated graphene film (prepared by reverse roll transfer procedure) and GO-derived fluorinated film prepared by conventional papermaking procedure (vacuum-assisted filtration) plotted as a function of the degree of fluorination with respect to atomic ratio F / (F + O). The dielectric breakdown strength of graphene paper is summarized in FIG. These data show that the dielectric strength (1.1 to 1.45 MV / cm) of the GO-based paper film prepared by the conventional method of vacuum-assisted filtration of multiple fluorinated GO sheets is relatively low, and is compared with the degree of fluorination. Show that it is irrelevant. Some orientation is achieved in this way, but the dielectric strength remains very low. Defects, voids, twists and breaks in the fluorinated GO sheet begin dielectric breakdown at these imperfections at relatively low overall (average) low voltage levels and then a concentration that propagates rapidly throughout the sample. It seems to be a local drop site of the electric field. The method according to the invention eliminates these imperfections.

The dielectric constants of the GO-derived fluorinated graphene film and the brominated graphene film plotted as a function of the degree of fluorination (atomic allocation F / (F + O) or degree of bromination (atomic ratio Br / (Br + O)) are summarized in FIG. As the degree of fluorination or bromination increases, the permittivity of the integral film of graphene halide increases to reach the maximum value, and then decreases when the degree of fluorination or bromination exceeds 0.6. The most notable thing is the partially halogenated GO film (C ₆ Z _{x Oy} (in the formula, Z is a halogen element selected from F, Cl, Br, I, x = 0.01 ~ 6.0, y = 0 to 5.0 and x + y≤6.0) can exhibit a dielectric constant of 3.9 to 22.2, and the GO integrated layer (x = 0; C ₆ O). It is a measurement result that it is in contrast to the dielectric constant value 2.3 in the case of _y ).

In summary, an integrated film of halogenated graphene (highly oriented GO-derived halogenated graphene film, GOGH) made from the original graphene oxide suspension or GO gel using shear stress-based methods to control orientation. Has the following characteristics:
(1) The integrated halogenated graphene film (thin or thick) is an integrated halogenated graphene oxide or a substantially oxygen-free halogenated graphene structure, which is typically a polycrystal with large crystal grains. Is. This film has wide or long chemically bonded graphene surfaces, all oriented substantially parallel to each other. In other words, the crystallographic c-axis directions of all constituent graphene planes in all grain grains are oriented in substantially the same direction. In other words, the integral layer is a plurality of constituent halogenated graphene surfaces that are substantially parallel to each other along one direction, these halogenations of less than 10 degrees (more typically less than 5 degrees). It has a plurality of constituent halogenated graphene surfaces having an average deviation angle of graphene surfaces.

(2) Reverse roll coating is very effective in achieving high graphene surface orientation and crystal integrity of halogenated graphene.

(3) The coexistence of halogen and oxygen in the integrated halogenated GO layer provides an unexpected synergistic effect in the production of a film having a high dielectric constant.

(4) The GOGH film is a single graphene element that is fully integrated and has virtually no voids, without the distinctive individual flakes or platelets that were present in the original GO suspension. Or a monolith. In contrast, a paper or membrane of halogenated graphene or GO platelets (each platelet <100 nm) is a simple unbound aggregate / laminate of multiple individual platelets of GO or halogenated GO. The platelets in these papers / membranes are poorly oriented and have numerous twists, curves and wrinkles. Many voids or other imperfections are present in these paper / membrane structures, resulting in low breakdown strength.

(5) In the prior art method, individual graphene or GO sheets (<< 100 nm, typically <10 nm) constituting the original structure of the graphite particles can be obtained by expansion, exfoliation and separation treatments. did it. By simply mixing these separate sheets / flakes and recompressing them into a bulk object, it was possible to attempt to orient these sheets / flakes along one direction, preferably by compression. However, with these conventional methods, the resulting aggregate-constituting flakes or sheets can be easily identified or clearly observed, even with the naked eye, or under a low-magnification light microscope (100-1000x). Remains as individual flakes / sheets / platelets that can be made.

In contrast, the fabrication of integrated films of graphene halides according to the invention involves the oxidation of virtually all original graphene surfaces to separate them from each other with highly reactive functional groups (eg, -OH,> O and-. It comprises the step of violently oxidizing the original graphite particles to the extent that they become individual graphene surfaces or molecules with COOH) on or on the edges of the graphene surface surface. These individual hydrocarbon molecules (containing elements such as O and H in addition to carbon atoms) are dispersed in a liquid medium (eg, a mixture of water and alcohol) to form a GO dispersion. Next, the dispersion is reverse-roll coated on a smooth substrate surface and then the liquid component is removed to form a dry GO layer. With slight heating or aging, these highly reactive molecules react with each other, mostly laterally along the graphene planes (in an edge-to-edge manner with increasing length and width), and possibly even between graphene planes. And chemically bond.

FIG. 7 (D) shows a possible chemical linking mechanism in which a large number of GO molecules can be chemically linked to each other to form a film, but only two arranged GO molecules are shown as an example. ing. Moreover, chemical ligation can occur not only between edges but also between faces. These ligation and coalescence reactions proceed in such a way that the molecules chemically coalesce, tie, and unite into a single material. These molecules or "sheets" are very long and wide. These molecules (GO sheets) have completely lost their original properties and are no longer separate sheets / platelets / flakes. There is only one monolayer structure, which is a substantial network structure of interconnected macromolecules with a substantially infinite molecular weight. It can also be described as a graphene polycrystal (having several grains, but typically without distinguishable, well-defined grain boundaries). All constituent graphene surfaces are very large in lateral dimensions (length and width) and are arranged parallel to each other.

By more detailed studies using a combination of SEM, TEM, selected area diffraction, X-ray diffraction, AFM, Raman spectroscopy and FTIR, the graphite film has several large graphene surfaces (typically length / width>. It is shown to be composed of> 100 μm, more typically >> 1 mm). These giant graphene surfaces are often laminated and bonded along the thickness direction (crystallographic c-axis direction) not only by van der Waals forces (like conventional graphite crystallites) but also by covalent bonds. .. In these cases, although not desired to be limited by theory, studies of Raman spectroscopy and FTIR spectroscopy show that not only conventional sp ² but also sp ² (dominant) and sp ³ (weak) in graphite. It seems to indicate the coexistence of the electron configuration of (existing).

(6) This integrated GOGH film is not made by adhering or bonding individual flakes / platelets to each other using a resin binder, linker or adhesive. Instead, the GO or halogenated GO sheet (molecule) in the dispersion or gel coalesces with each other by the formation of linkages or covalent bonds into an integrated graphene element with any linker or binder molecule added externally. No polymer is used. These GO or halogenated GO molecules are "living" molecules that can be linked to each other in a manner similar to living polymer chains where "rebinding" occurs (eg, 1,000 monomer units of living chains and 2,000). Combined or linked with another living chain of monomer units to form a polymer chain of 3,000 units). It is possible that a 3,000-unit chain may be combined with a 4,000-unit chain to form a 7,000-unit giant chain.

(7) This integrated film typically has incomplete grain boundaries and typically large crystal grains in which the crystallographic c-axis in all the grains is substantially parallel to each other. It is a polycrystal composed of. This element is essentially derived from a GO suspension or GO gel obtained from particles of natural or artificial graphite with multiple graphite microcrystals. Prior to chemical oxidation, these starting graphite crystallites had an initial length (L a in the crystallographic a-axis direction), an initial width (L _b in the _b -axis direction) and a thickness (L _c in the c-axis direction). Has. Upon intense oxidation, these early individual graphite particles are chemically converted to highly aromatic graphene oxide molecules with high concentrations of edge or surface functional groups (eg, -OH, -COOH, etc.). Ru. These aromatic halogenated GO molecules in the GO suspension have lost their original property of being part of graphite particles or flakes. After removing the liquid component from the suspension and performing thermal aging, the resulting GO molecules are chemically coalesced and linked into highly oriented single or monolithic graphene elements.

The resulting single graphene element typically has _a much larger length or width than the original crystallites La and _Lb. The length / width of this graphite film is much larger than the original crystallites _La and _Lb. Even the individual grains in the polycrystalline graphite film have _a much larger length or width than the original microcrystals La and _Lb.

(8) These unique chemical compositions (including oxygen content), morphology, crystal structure (including graphene spacing) and structural features (eg, highly oriented, few defects, chemical bonds and gaps between graphene sheets). Because of the absence and no interruptions in the graphene plane), the highly oriented graphene oxide-derived halogenated GO film has a unique combination of significant dielectric constant and insulation breakdown strength.

In conclusion, we have successfully developed an integrated film of highly oriented pyrolytic graphene monolith, a completely new, novel and unexpectedly distinctly different kind of dielectric material. The chemical composition (oxygen and halogen content), structure (crystal completeness, grain size, defect population, etc.), crystal orientation, feasible thickness, morphology, manufacturing method and with high orientation of this new kind of material. The properties are fundamentally different from all well-known graphene materials and are distinctly different. These halogenated graphene films can be used as dielectric material components in a wide variety of microelectronic devices.

Claims (24)

A method of producing a sheet of halogenated graphene or an integral layer of molecules.
(A) A step of preparing either a graphene oxide dispersion having a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel having a graphene oxide molecule dissolved in a flow medium, wherein the graphene oxide sheet is used. Or with the step, wherein the graphene oxide molecule contains an oxygen content of more than 5% by weight;
(B) A step of supplying and depositing a layer of the graphene oxide dispersion or the graphene oxide gel on the surface of the supporting substrate under shear stress conditions, wherein the supply and deposition procedure is on the supporting substrate. Includes shear-induced thinning of the graphene oxide dispersion or graphene gel oxide to form a wet layer of graphene oxide and shearing-induced orientation of the graphene oxide sheet or graphene oxide molecule. , Steps and;
(C) Chemical formula of C ₆ Z _{x Oy} (in the formula, Z is a halogen element selected from F, Cl, Br, I or a combination thereof, and x = 0.01 to 6.0, y = A dry integrated layer of halogenated graphene having (0 to 5.0 and x + y ≦ 6.0) and a plane spacing d ₀₀₂ of 0.35 nm to 1.2 nm as measured by X-ray diffraction. The following steps (i) or (ii) to form
(I) A halogenating agent is introduced into the wet layer of the graphene oxide, and a chemical reaction is caused between the halogenating agent and the graphene oxide sheet or the graphene oxide molecule to form a wet layer of the halogenated graphene. The flow medium is formed and removed from the wet layer of the halogenated graphene, or (ii) the flow medium is removed from the wet layer of the graphene oxide to form a dry layer of graphene oxide, and the oxidation. A halogenating agent is introduced into the dry layer of graphene, and a halogenation treatment is carried out by either causing a chemical reaction between the halogenating agent and the graphene oxide sheet or the graphene oxide molecule.
(D) A wet layer of graphene oxide in an aging chamber at 25 ° C. to 200 ° C. and a humidity level of 20% to 99% for 1 hour to 7 days prior to the halogenation treatment at 25 ° C. to 250 ° C. for 1 to 24 hours. Alternatively, the dry layer may be aged to form an aged layer of graphene oxide, or
As an aging treatment, a dry layer of graphene oxide or a dried and aged layer is heat-treated at a first heat treatment temperature of more than 100 ° C. but not more than 3200 ° C., with a surface spacing of less than 0.4 nm _d002 and 5% by weight. A method of performing a step having an oxygen and / or halogen content of less than. A method of producing a sheet of halogenated graphene or an integral layer of molecules.
a. A step of preparing either a graphene oxide dispersion having a graphene oxide sheet dispersed in a flow medium or a graphene oxide gel having a graphene oxide molecule dissolved in a flow medium, the graphene oxide sheet or the oxidation. With steps, graphene molecules contain more than 5% by weight of oxygen;
b. A halogenating agent is introduced into the graphene oxide dispersion or the graphene oxide gel, and a chemical reaction is caused between the halogenating agent and the graphene oxide sheet or the graphene oxide molecule to disperse the halogenated graphene sheet. A step of forming a gel of a body or a halogenated graphene molecule and performing a halogenation treatment, wherein the halogenated graphene sheet has a chemical formula of C ₆ Z _{x Oy} (in the formula, Z is F, Cl, Br, I or Halogen elements selected from their combinations, with x = 0.01-6.0, y = 0-5.0 and x + y≤6.0).
c. The step of supplying and depositing a layer of the halogenated graphene dispersion or gel on the surface of the supporting substrate under shear stress conditions, wherein the supplying and depositing procedure is the wetting of graphene oxide on the supporting substrate. A wet layer of halogenated graphene by comprising shearing-induced thinning of the halogenated graphene dispersion or gel to form a layer and shearing-induced orientation of the halogenated graphene sheet or molecule. With the steps formed on the surface of the supporting substrate ;
d. The flow medium is removed from the wet layer of the halogenated graphene to form an integrated layer of the halogenated graphene having a plane spacing _d002 of 0.35 nm to 1.2 nm as measured by X-ray diffraction. Including steps
Wet or dry layer of graphene oxide in an aging chamber at 25 ° C. to 200 ° C. and 20% to 99% humidity level for 1 hour to 7 days prior to the halogenation treatment at 25 ° C. to 250 ° C. for 1 to 24 hours. Aging to form an aged layer of graphene oxide, or
As an aging treatment, a dry layer or a dried and aged layer of graphene oxide is heat-treated at a first heat treatment temperature of more than 100 ° C. but not more than 3200 ° C., with a surface spacing of less than 0.4 nm _d002 and 5% by weight. A method of performing a step having an oxygen and / or halogen content of less than. The method according to claim 1, wherein the graphene oxide sheet contains a single-layer graphene oxide or a multi-layer graphene oxide sheet having 2 to 10 graphene oxide surfaces. The method according to claim 1, wherein the halogenating agent contains a chemical species in a liquid, gas or plasma state containing a halogen element selected from F, Cl, Br, I or a combination thereof. The method according to claim 2, wherein the halogenating agent contains a chemical species in a liquid, gas or plasma state containing a halogen element selected from F, Cl, Br, I or a combination thereof. The halogenating agent is hydrofluoric acid , HPF ₆ , XeF ₂ , F ₂ gas, F ₂ / Ar plasma, CF ₄ plasma, SF ₆ plasma, HCl, HPCl ₆ , XeCl ₂ , Cl ₂ gas, Cl ₂ /. Ar plasma, CCl ₄ plasma, SCl ₆ plasma, HBr, XeBr ₂ , Br ₂ gas, Br ₂ / Ar plasma, CBr ₄ plasma, SBr ₆ plasma, HI, XeI ₂ , I ₂ , I ₂ / Ar plasma, CI ₄ The method of claim 1, selected from plasma, SI ₆ plasma or a combination thereof. The fluorinating agent is hydrofluoric acid , HPF ₆ , XeF ₂ , F ₂ gas, F ₂ / Ar plasma, CF ₄ plasma, SF ₆ plasma, HCl, HPCl ₆ , XeCl ₂ , Cl ₂ gas, Cl ₂ /. Ar plasma, CCl ₄ plasma, SCl ₆ plasma, HBr, XeBr ₂ , Br ₂ gas, Br ₂ / Ar plasma, CBr ₄ plasma, SBr ₆ plasma, HI, XeI ₂ , I ₂ , I ₂ / Ar plasma, CI ₄ The method of claim 2, selected from plasma, SI ₆ plasma or a combination thereof. The method of claim 1, wherein the feeding and depositing steps include a printing, spraying, coating and / or casting procedure combined with a shear stress procedure. The method of claim 1, wherein the feeding and depositing steps include a reverse roll transfer coating procedure. The method of claim 1, wherein the feeding and depositing step comprises a slot die coating or comma coating procedure. The feeding and depositing steps feed a layer of the graphene oxide dispersion or graphene oxide gel onto the surface of a coating roller rotating in a first direction at a first linear velocity to form an applicator layer of graphene oxide. The coating roller transfers the graphene oxide applicator layer to the surface of a support film driven at a second linear velocity in a second direction opposite to the first direction. The method according to claim 1, wherein a wet layer of the graphene oxide is formed on the support film. 11. The method of claim 11, wherein the support film is located at an operating distance from the coating roller and is driven by a reverse rotation support roller that rotates in the second direction opposite to the first direction. The step of feeding the graphene oxide dispersion or graphene gel oxide onto the surface of the coating roller is a graphene oxide of the desired thickness on the coating roller surface using a metering roller and / or a doctor blade. 11. The method of claim 11, comprising providing a step of providing an applicator layer. 11. The method of claim 11, comprising the step of operating a few or four rollers. A claim, wherein the support film is supplied from a feed roller, and a dry layer of the halogenated graphene supported by the support film is wound onto a take-up roller, and the method is performed in a roll-to-roll manner. 11. The method according to 11. The method according to claim 11, wherein the speed ratio defined as (the second linear velocity) / (the first linear velocity) is 1/5 to 5/1. 16. The method of claim 16, wherein the speed ratio is greater than 1/1 and less than 5/1. After step (b), the wet layer of graphene oxide is aged or stepped in an aging chamber with an aging temperature of 25 ° C to 100 ° C and a humidity level of 20% to 99% for an aging time of 1 hour to 7 days. The method of claim 1, further comprising (c) later aging the wet layer of the halogenated graphene, or step (d) later aging the integral layer of the halogenated graphene. The integral layer of the halogenated graphene is heat-treated at a first heat treatment temperature of more than 100 ° C. but less than 3,200 ° C. to have a surface spacing of less than 0.4 nm _d002 and less than 1% by weight oxygen / halogen. The method of claim 1, further comprising step (e) of producing a graphite film having a total content. The method according to claim 1, wherein the flow medium comprises water, alcohol, a mixture of water and alcohol, or an organic solvent. The method of claim 1, further comprising a compression step during or after step (d) to reduce the thickness of the integral layer. 19. The method of claim 19, further comprising a compression step during or after the heat treatment step to reduce the thickness of the graphite film. The graphene oxide dispersion or graphene oxide gel is prepared by immersing a graphite material in the form of powder or fiber in an oxidizing liquid in a reaction vessel at the reaction temperature, where the graphite material is natural graphite, artificial graphite, intermediate. The method according to claim 1, wherein the method is selected from phase carbon, intermediate phase pitch, mesocarbon microbeads, soft carbon, hard carbon, coke, carbon fiber, carbon nanofiber, carbon nanotube or a combination thereof. 18. The method of claim 18, wherein the aging step induces chemical ligation, coalescence or chemical bonding of the graphene oxide sheet or the graphene oxide molecule in an edge-to-edge manner.

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