RU2530084C2 - Method of production of graphene structures - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to nanotechnology. The graphene structures in the form of flat carbon particles with the surface of up to 5 mm² are obtained by burning in air atmosphere or inert gas of composite press material produced from micro- and nanodisperse powders of active metals such as aluminium, titanium, zirconium, nanodisperse powders of silicon or aluminium borides taken in an amount of 10-35 wt %, and fluoropolymers such as polytetrafluoroethylene or a copolymer of tetrafluoroethylene and vinylidene fluoride, taken in amount of 90-65 wt %.

EFFECT: increased yield of graphene.

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Description

The present invention relates to a technology for producing graphene, which is used in various fields of industry.

From the scientific and patent literature there are many different methods for producing graphene.

There is a method for producing graphene by mechanical exfoliation, in which a layer of graphene is torn off of graphite using an adhesive tape, and relatively large graphene samples of ~ 10 μm in size are obtained, suitable for electrical and optical measurements. After exfoliation, adhesive tape with thin films of graphite and graphene is pressed onto an oxidized silicon substrate. In this way, it is difficult to obtain a film of a certain size and shape in fixed parts of the substrate (the horizontal dimensions of the films are usually about 10 μm) (Novoselov, K. S. et al. "Electric Field Effect in Atomically Thin Carbon Films", Science v.306, p. 666, 2004; Bunch JS et. Al. "Electromechanical Resonators from Graphene Sheets". Science, v. 315, p. 490, 2007).

A method for producing graphene is described, consisting in the fact that the oxidized silicon substrate is coated with epoxy glue (a ~ 10 μm thick adhesive layer was used) and a thin plate of graphite is pressed onto the glue using a press. After removal of the graphite plate using adhesive tape, regions with graphene and graphite remain on the surface (Rollings E. et. Al. "Synthesis and characterization of atomically thin graphite films on a silicon carbide substrate" J. Phys. Chem. Solids, v. 67 , p. 2172, 2006; Hass J. et. al. Highly ordered graphene for two dimensional electronics Appl. Phys. Lett. v. 89, p. 143 106, 2006).

US patent No. 8,287,699 (IPC B01J 19/10, 2012) protects a method for producing nanographenic materials by dispersing graphite material in a liquid medium, followed by processing the suspension with ultrasound of high intensity and duration, and graphene plates are formed.

The article (Novoselov K.S. et al. "Two-dimensional gas of massless Dirac fermions in graphene", Nature v.438, p.197, 2005) describes a method for printing graphene electrical circuits. The printing process consists of sequential transfer of gold contacts, graphene and, finally, a polymethyl methacrylate (PMMA) dielectric with a metal shutter from a Si / SiO ₂ substrate onto a transparent substrate made of polyethylene terephthalate (PET), which is previously heated above its softening temperature to 170 ° C, so contacts are pressed into PET, and graphene gains good contact with the substrate material. This method is suitable for applying graphene to any substrate suitable, in particular, for optical measurements.

In (Zhang Y. et. Al. "Experimental observation of the quantum Hall effect and Berry's phase in graphene" Nature, v. 438, p.201, 2005; Sandip Niyogi, Elena Bekyarova et al. "Solution Properties of Graphite and Graphene "J. Am. Chem. Soc .; 2006; 128 (24) pp 7720; (Communication); Bunch JS et al." Coulomb Oscillations and Hall Effect in Quasi-2D Graphite Quantum Dots "Nano Lett. 5, 287, 2005) describes chemical methods for producing graphene, which are distinguished by a large percentage of material yield, but small film sizes of ~ 10-100 nm. Microcrystals of graphite are exposed to a mixture of sulfuric and hydrochloric acids. Graphite is oxidized, and carboxyl groups of graphene appear at the edges of the sample. They are converted to chlorides with thionyl chloride. Then, under the influence of octadecylamine in solutions of tetrahydrofuran, tetrachloromethane and dichloroethane, they pass into graphene layers with a thickness of 0.54 nm. A known radio-frequency plasma-chemical method for the deposition of graphene from the gas phase (Wang JJ et. Al. "Free-standing subnanometer graphite sheets" Appl. Phys. Lett, v. 85, p. 1265 (2004) and a method for growing graphene films at high pressure and temperature (Parvizi F., et. Al. "Graphene Synthesis via the High Pressure - High Temperature Growth Process" Micro Nano Lett., V.3, p.29, 2008).

The patents (US No. 2012/0082787, IPC B05D 3/02, C23C 16/28, 2012 and US No. 8.227.069, IPC B32B 3/00, B32B 5/00, 2012) describe the production of graphene by growing on substrates from silicon carbide SiC. A graphite film is formed by thermal decomposition of the surface of a SiC substrate at temperatures up to 1350 ° C in a vacuum of 1-10 ^-4 mm Hg. or in a stream of inert gas.

As follows from an analysis of the scientific literature and patent data, the described methods for producing graphene are technologically quite complex, highly labor intensive, and the area of graphene particles formed is small and is measured by square microns.

The objective of the invention is the development of a new method for producing graphene structures, providing the formation of graphene particles with a surface of up to 5 mm ² , a large yield and allowing to produce graphene in significant quantities (up to 50 g / day in a plant with a reactor reactor volume of 10 l).

The problem is solved in that a new method for producing graphene structures in the form of flat carbon particles with a surface of up to 5 mm ^{2 has} been developed, which consists in the fact that graphene is obtained by burning a composite press material obtained from fluoropolymer powders such as polytetrafluoroethylene and a copolymer of tetrafluoroethylene and vinylidene fluoride and micro- and nanodispersed powders of active metals such as aluminum, titanium, zirconium, nanodispersed powders of silicon and aluminum borides with a ratio of metal: fluoropolymer = 10-35: 90-65%.

In the course of scientific research it was found that the interaction of nanodispersed aluminum powder with fluoroplasts along with aluminum trifluoride forms flat carbon flakes with a surface of up to 5 mm ² .

4Al + 3 (-C ₂ F ₄ -) _n → 6C + 4AlF ₃ , ΔH ⁰ = -3612.76 kJ

When a powdery stoichiometric mixture of nanodispersed aluminum and a copolymer of tetrafluoroethylene and vinylidene fluoride is ignited by a gas burner flame, the mixture ignites and burns immediately, accompanied by the sound of cotton and the formation of smoke with small particles of carbon.

When the pressed composite is ignited by a gas burner with air injection (flame temperature of about 900-1000 ° C), violent combustion begins with two to three seconds with the combustion of the sample for 2-4 s. In this case, a large number of flat large flocculent soot particles are formed, which are easily agglomerated. In addition, the formation of filamentary and elongated funnel-shaped soot formations up to 5 mm long is also observed.

This reaction proceeds similarly in an argon atmosphere when a pressed composite is ignited by a hot nichrome wire with the formation of the same flat particles.

The study of flat carbon particles by scanning electron microscopy and X-ray diffractometry showed that they consist of two-dimensional structures characteristic of graphene (hexagonal crystalline phase, maximum in the X-ray diffraction pattern at 2Θ = 20.61 °).

Similar graphene formations are obtained by the interaction of composite materials based on micron and nanoscale powders of active metals, such as aluminum, titanium, zirconium, nanoscale powders of silicon and aluminum borides and fluoropolymers such as polytetrafluoroethylene and a copolymer of tetrafluoroethylene and vinylidene fluoride.

Composites are prepared by mixing powders of metals and fluoropolymers at a ratio of metal: fluoropolymer = 10-35: 90-65%, followed by pressing the mixture into a mold at a pressure of 150-180 kg / cm ² and a temperature of 150-190 ° C. To increase the contact efficiency of the reagents in composite materials, mixtures are prepared by mixing the components in a planetary mill. In the case of solvent-soluble fluoropolymers, a composite material is prepared by mixing the metal powder with a fluoropolymer solution with vigorous stirring, followed by evaporation of the solvent and grinding of the residue.

The invention is illustrated by the following examples.

Example 1

2.9 g of nanodispersed aluminum powder (average particle diameter 200 nm) and a solution of 9.5 g of fluoroplastic F-42 B (n-A / FP) in 150 ml of acetone are loaded into the reactor, the mixture is intensively mixed, and a suspension is obtained, which poured into the mold, the height of the suspension layer is 6-8 mm Then acetone is evaporated and a composite film 0.5–2 mm thick is obtained, which is ground to a powder state, sieved through a sieve with a mesh size of 0.25 mm. The sifted powder is placed in the mold and heated at a temperature of 160-165 ° C for 30 minutes, after which the heated powder is pressed at a pressure of 150 kg / cm ² . Get a tablet with a diameter of 40 mm and a thickness of 5 mm, which is placed on a stand in a sealed box and set on fire with a gas burner flame with air blowing. The burning time of the tablet is no more than 2 seconds, resulting in a cloud of carbon particles. Particles settle on a pallet from which they are transferred to a container. 0.5 g of carbon particles with a graphene structure were obtained from 5 g of the pressed composite (56.8% of theory).

Example 2

3.0 g of aluminum powder grade ASD-4 (average particle size of 3-5 microns) and 9.5 g of fluoroplastic powder F-42 B are mixed in a planetary mill. Part of the obtained powder is placed in the mold and heated at a temperature of 160-165 ° C for 30 minutes, after which the heated powder is pressed at a pressure of 150 kg / cm ² . Get a tablet with a diameter of 40 mm and a thickness of 5 mm. The tablet is wrapped with nichrome wire, the ends of which are connected to an electric current source, then placed on a stand in a cabinet with a hermetically sealed door, which is purged with argon, voltage is applied to the wire, and the tablet flashes and lights up. As a result of burning a tablet, the duration of which is no more than 1 second, a cloud of carbon particles is formed. Particles settle on a pallet from which they are transferred to a container. From 5 g of the pressed composite 0.45 g of carbon particles with a graphene structure were obtained (54.8% of theory).

Example 3

3.0 g of nanosized silicon powder (average particle size 35 nm) and a solution of 12.0 g of fluoroplastic F-42 B in 150 ml of acetone are loaded into the reactor, the mixture is intensively mixed, and a suspension is obtained, which is poured into the crystallizer, the height of the suspension layer is 6-8 mm. After that, acetone is evaporated and a composite film with a thickness of 0.5-2 mm is obtained, which is ground to a powder state, sieved through a sieve with a mesh size of 0.25 mm. The sifted powder is placed in the mold and heated at a temperature of 160-165 ° C for 30 minutes, after which the heated powder is pressed at a pressure of 150 kg / cm ² . Get a tablet with a diameter of 40 mm and a thickness of 5 mm, which is placed on a stand in a box and set on fire with a gas burner flame with air blowing. The burning time of the tablet is no more than 3 seconds, resulting in a cloud of carbon particles. Particles settle on a pallet from which they are transferred to a container. From 5 g of the pressed composite 0.40 g of carbon particles with a graphene structure were obtained (45.9% of theory).

Example 4

6.6 g of titanium nanosized powder (average particle size 40 nm) and a solution of 13.4 g of F-42 B fluoroplastic in 150 ml of acetone are loaded into the reactor, the mixture is intensively mixed, and a suspension is obtained, which is poured into the crystallizer, the height of the suspension layer is 6-8 mm. After that, acetone is evaporated and a composite film with a thickness of 0.5-2 mm is obtained, which is ground to a powder state, sieved through a sieve with a mesh size of 0.25 mm. The sifted powder is placed in the mold and heated at a temperature of 160-165 ° C for 30 minutes, after which the heated powder is pressed at a pressure of 150 kg / cm ² . Get a tablet with a diameter of 40 mm and a thickness of 5 mm, which is placed on a stand in a box and set on fire with a gas burner flame with air blowing. The burning time of the tablet is no more than 3 seconds, resulting in a cloud of carbon particles. Particles settle on a pallet from which they are transferred to a container. From 5 g of the pressed composite, 0.40 g of carbon particles with a graphene structure were obtained.

Example 5

3.75 g of nanosized aluminum boride powder (average particle size 140 nm) and 11.25 g of F-42 B fluoroplastic powder are mixed in a planetary mill. Part of the obtained powder is placed in the mold and heated at a temperature of 160-165 ° C for 30 minutes, after which the heated powder is pressed at a pressure of 150 kg / cm ² . Get a tablet with a diameter of 40 mm and a thickness of 5 mm. The tablet is wrapped with nichrome wire, the ends of which are connected to an electric current source, then placed on a stand in a cabinet with a hermetically sealed door, which is purged with argon, voltage is applied to the wire, and the tablet flashes and lights up. As a result of burning a tablet, the duration of which is no more than 1 second, a cloud of carbon particles is formed. Particles settle on a pallet from which they are transferred to a container. From 5 g of the pressed composite 0.55 g of carbon particles with a graphene structure were obtained.

Other examples are given in the table. Designations in the table:

n-Al - nanodispersed aluminum (S _beats = 8-11 m ² / g),

ASD-4 - aluminum powder with spherical particles 5-8 microns in size,

n-BA - nano-boride aluminum, obtained by the joint plasma recondensation of aluminum and boron powders (S _beats = 15-35 m ² / g),

n-Si - nanosized silicon powder (S _beats = 50-80 m ² / g),

n-Al / n-B-60/40 - a mechanical mixture of nanodispersed powders of nano-aluminum and nanoboron in a% ratio of 60/40,

n-Zr - nanodispersed zirconium powder (S _beats = 50-70 m ² / g),

n-Ti - nanodispersed titanium powder (S _beats = 40-60 m ² / g),

PTFE - polyethylene tetrafluoride powder,

PTFE / F-42 B 85/15 - a mechanical mixture of PTFE and F-42 B powders in a 85% -15% ratio,

n-Al / n-B 60/40 - a mechanical mixture of powders of nano-aluminum and nanoboron in a% ratio of 60:40.

Table 1 Example Metal Fluoropolymer The ratio of components,%, Me: FP * Mixing method Press temperature ° C Atmosphere
burning one. n-Al F-42b 23.4: 76.6 in acetone 160-165 air 2. n-Al F-42b 23.4: 76.6 in acetone 160-165 argon 3. n-Al F-42b 23.4: 76.6 mill 160-165 air four. n-Al F-42b 10.0: 90.0 mill 160-165 argon 5. ASD-4 F-42b 26.5: 73.5 in acetone 165-170 air 6. ASD-4 F-42b 26.5: 73.5 in acetone 165-170 argon 7. ASD-4 F-42b 26.5: 73.5 mill 165-170 air 8. ASD-4 PTFE / F-42B 85/15 35.0: 65.0 mill 175-180 argon 9. n-BA F-42b 25.0: 75.0 in acetone 165-170 air 10. n-Si F-42b 20.0: 80.0 in acetone 165-170 argon eleven. n-Si F-42b 20.0: 80.0 mill 165-175 air 12. n-Si PTFE / F-42B 85/15 25.0: 75.0 mill 175-180 argon 13. n-Al / n-B 60/40 F-42b 25.0: 75.0 in acetone 165-170 air fourteen. n-Zr F-42b 47: 53 in acetone 165-170 air fifteen. n-Ti F-42b 33: 67 in acetone 165-170 air

* - Me - metals or their mixture, FP - fluoropolymers

The structure of the obtained particles was studied using electron scanning microscopy (SEM) and X-ray diffractometry. Electron micrographs (Fig. 1-3) of carbon particles show that they consist of thin two-dimensional structures. The thickness of the observed carbon planes is much lower than the resolution of the Philips SEM505 electron microscope that we used, equipped with the Micro Capture SEM3.0 M image capture system, and EDAX elemental microanalysis system with an energy dispersive detector SAPHIRE Si (Li) type SEM10. The resolution of the microscope is about 30Ǻ.

The crystal structure of the carbon powder was studied on a STOE IPDS X-ray diffractometer. MoC radiation wavelength _α = 0.709 Ǻ. The device allowed measurements with a thin x-ray beam with a cross-sectional diameter of 500 μm, the beam displacement step was 10 μm. The studied powder was placed between X-ray transparent micron polymer films in a special holder. The analysis of experimental results was carried out taking into account the base of the international center for diffraction data ICDD.

X-ray powder diffraction of a carbon product shows that it consists almost entirely of a crystalline phase (Fig. 4). Diffraction patterns show maxima whose exact positions are given in Tables 2 and 3. Instead of intense maxima corresponding to reflections (002) and (100) associated with diffraction by carbon structures consisting of parallel graphite planes (for example, for graphite and multi-walled carbon nanotubes ), there is only an inflection in the region of 20-12 ° and a weak maximum at 2Θ = 20.61 °.

table 2 X-ray diffraction data for MoC _α radiation for a carbon residue sample obtained after burning an F-42B fluoroplastic tablet with nano-Al in air 2Θ, degrees D, Ǻ I, rel. units Structure Crystal system Miller Indices h k l 11.62 3,509 1000 Alf ₃ Trigon. 0 one 2 14.49 2,816 80.8 Al ₄ C ₃ Trigon. 0 one 2 16.23 2,516 47.59 Al ₄ C ₃ Trigon. 0 one 5 18.25 2,240 50.97 Al ₄ C ₃ Trigon. one 0 7 19.36 2,112 248.49 Alf ₃ Trigon. one one -3 20.61 1,985 72.51 Graphene Hexagon. 0 0 2 21.86 1,873 28.85 Al ₄ C ₃ Trigon. one 0 10 23.33 1,757 186.12 Alf ₃ Trigon. 0 2 four 24.62 1,666 51.65 Al ₄ C ₃ Trigon. one 0 fifteen 25.92 1,584 128 Alf ₃ Trigon. one one -6 28.86 1,425 36.77 Al ₄ C ₃ Trigon. 2 0 2 29.58 1,391 58.66 Al ₄ C ₃ Trigon. 2 0 5 31.7 1.3 15.9 Al ₄ C ₃ Trigon. one one 12 32.91 1,254 32 Alf ₃ Trigon. 2 0 8 35.57 1,163 30.01 Alf ₃ Trigon. one 3 -2

Table 3 X-ray diffraction data for MoC _α radiation for a carbon residue sample obtained after burning an F-42B fluoroplastic tablet with nano-Al in argon 2Θ, degrees D, Ǻ I, rel. units Structure Crystal system Miller Indices h to l 11.62 3,509 1000 A1F ₃ Trigon. 0 one 2 14.49 2,816 55.8 Al ₄ C ₃ Trigon. 0 one 2 16.23 2,516 33.27 Al ₄ C ₃ Trigon. 0 one 5 18.25 2,240 38.32 Al ₄ C ₃ Trigon. one 0 7 19.36 2,112 248.09 Alf ₃ Trigon. one one -3 20.61 1,985 103.52 Graphene Hexagon. 0 0 2 21.86 1,873 19.96 Al ₄ C ₃ Trigon. one 0 10 23.33 1,757 186.10 Alf ₃ Trigon. 0 2 four 24.62 1,666 36.11 Al ₄ C ₃ Trigon. one 0 fifteen 25.92 1,584 127.90 Alf ₃ Trigon. one one -6 28.86 1,425 25.70 Al ₄ C ₃ Trigon. 2 0 2 29.58 1,391 41.02 Al ₄ C ₃ Trigon. 2 0 5

Thus, on the basis of the results obtained, it can be concluded that under the conditions established by us during the reaction of nanodispersed or micropowders of aluminum, aluminum borides, silicon, titanium and zirconium with a copolymer of tetrafluoroethylene and vinylidene fluoride, graphene structures are formed.

Fig. 1 Electron micrographs of carbon particles in sample 1 of the residue obtained after burning an F-42B fluoroplastic tablet with nano-Al in air.

Fig. 2 Electron micrographs of carbon particles in sample 2 of the residue obtained after burning an F-42B fluoroplastic tablet with nano-Al in air.

Fig. 3 Electron micrographs of carbon particles in sample 3 of the residue obtained after burning an F-42B fluoroplastic tablet with nano-Al in argon.

Fig. 4 Diffraction pattern of sample 2 of the carbon residue obtained after burning a F-42B fluoroplastic tablet with nano-Al.

Claims (1)

A method for producing graphene structures in the form of flat carbon particles up to 5 mm in size, characterized in that graphene structures are obtained by burning in the atmosphere of air or inert gas a composite press material obtained from micro- and nanodispersed powders of active metals, such as aluminum, titanium, zirconium, nanosized powders of silicon and aluminum borides, and fluoropolymers such as polytetrafluoroethylene and a copolymer of tetrafluoroethylene and vinylidene fluoride, with a ratio of metal: fluoropolymer = 10-35: 90-65%.

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