METHOD OF ASSEMBLING NANOMATERIALS MADE FROM GRAPHENE

Abstract

The invention relates to the field of producing carbon nanomaterials, and can be used in the manufacture of electrodes in supercapacitors. The nanomaterials are produced from graphene by means of graphene sheet assembly using a method characterised in that, for said assembly, the graphene sheets undergo an electrodynamic fluidisation in which the chemically active edges of the graphene sheets connect during counter-collisions between oppositely charged sheets, resulting in the formation of covalent bonds and in the subsequent formation of aggregates and macrostructures. The series-connection of sheets in such collisions leads to strong, developed macro structures that have high electrical conductivity and a large surface, and can be used as a material for manufacturing supercapacitor electrodes. This method makes it possible to produce nanomaterials for the manufacture of supercapacitor electrodes which have high electrical conductivity and a large surface, and provides for high productivity and cost-effectiveness when producing the product.

Claims

1. A method of producing a nano-material from graphene for producing electrodes of a supercapacitor, characterized in that, as a starting material graphene sheets are used, which are subjected to electro-dynamic liquefaction, at the opposite collisions of the sheets of the graphene with the charges of the opposite sign there is a connection of their edges with formation of covalent bonds with consequent formation of aggregates and macrostructures, which are used as material for making electrodes.

2. The method according to claim 1, characterized in that the macrostructure is immersed in the electrolyte in a charged state in order to prevent sticking of the graphene sheets;

3. The method according to claim 1, characterized in that the process is carried out under a helium atmosphere to prevent the adsorption of gases in the product obtained.

Description

[0012] The attached FIGURE shows a scheme of the device for the implementation of the proposed method.

[0013] The method consists in the following.

[0014] As a source for obtaining the material, graphene sheets are used. Graphene sheets are placed in an electric field between two electrodes, with a potential difference sufficient for fluidization, when the force acting on the particle from the electric field F.sub.e=qU/d is greater than gravity F.sub.g=mg, where q is the charge of the particle, U is the potential difference of the electrodes, d is the interelectrode distance, m is the mass of the particle, and g is the acceleration due to gravity.

[0015] A two-dimensional lattice consists of graphene regular hexagons with sides d1=0, 1418 nm and an area of 5, 3510.sup.20 m.sup.2 by two carbon atoms per cell. (Eletskii A V, Iskandarov I M, Knizhnik A A and etc. Graphene: production methods and thermophysical properties. Uspekhi fizicheskikh nauk, ISSN 0042-1294, 2011, v. 181, No 3, 233-250.).

[0016] The specific gravity of graphene per unit area with a mass of one atom of carbon of 1.993.Math.10.sup.26 kg is .sub.gr=2.Math.1.993.Math.10.sup.26 kg/5.35.Math.10.sup.20 m.sup.2=7.45.Math.10.sup.7 kg/m.sup.2. For a graphene sheet with an area S, lying on the electrode, the charge density equals the electrode charge density =.sub.0U/d, where .sub.0=8.85.Math.10.sup.12 F/mthe permittivity . Then the charge of a graphene sheet is q=S=S.sub.0U/d. The mass of a graphene sheet is m=S.Math..sub.gr. The condition of fluidization of graphene sheets F.sub.e>F.sub.g gives the value of the required electric field strength U/d:

(U/d).sup.2>(.sub.gr.Math.g)/.sub.0, U/d>0, 9.Math.10.sup.3V/m,

which does not depend on the size of the graphene sheet.

[0017] This value is relatively small for ordinary values of the electric field strength at electrodynamic fluidization of about 10.sup.6 V/m, which indicates a large range of process control.

[0018] The speed of movement of particles during electrodynamic fluidization depends on the medium filling the interelectrode space. For a gas environment at atmospheric pressure with a small Reynolds number, the resistance of the environment to the movement of microparticles is determined by friction resistance, not form resistance, wherein with particles moving at a constant speed (Myazdrikov O. A. Electrodynamic fluidization of disperse systems. L: Chemistry, 1984.). According to Newton, the resistance force is F.sub.c=.Math.(V/h).Math.S, where is the kinematic viscosity of the environment, V is the velocity of the particle, h is the thickness of the boundary layer, and S is the surface area of the particle.

[0019] For spherical particles, S=4r.sup.2, where r is the particle radius, h=2/3r and F.sub.c=6rV is the Stokes formula. Assuming that the graphene sheets have a shape close to a disk, we can take S=2r.sup.2, h=2/3r and then F.sub.c=3rV. When F.sub.c=F.sub.e, the constant velocity of a particle of radius r is equal to:

V=().Math.(.sub.0/).Math.r.Math.(U/d).sup.2.

Thus, the velocity of the particles is proportional to their size. This means that larger particles will have greater velocity and, consequently, a greater opportunity to attach smaller particles with further growth up to aggregates and macrostructures.

[0020] For U/d=10.sup.6 V/m and r=0.5.Math.10.sup.6 m, the velocity of particles in the air is 7.3.Math.10.sup.2 m/s. For the effective formation of macrostructures requires a sufficient concentration of particles involved in the process of electrodynamic fluidization. Mathematical simulation of this process and comparison with experimental data (Zhebelev S. I. Statistical simulation of microparticle pseudoliquefaction within electrical field. J Eng Phys, ISSN 1062-0125, 1991 t. 60, No 1, p. 64-72) showed: when the quantity of collisions of particles is maximum, the concentration of microparticles exceeds the concentration of the monolayer N=1/(S.sub.av.Math.d), where S.sub.av is the average particle area.

[0021] For S.sub.av=r.sup.2, r=0.5.Math.10.sup.6 m, d=10.sup.2 m, the concentration is N=1.27.Math.10.sup.14 m.sup.3. A sufficient concentration of particles can be obtained either by over-feeding the source material into the interelectrode space (with the formation of deposits of excess particles on the lower electrode) or by choosing special-shaped electrodes with a non-uniform electric field.

[0022] This method makes it possible to produce nanomaterials for the manufacturing of supercapacitor electrodes which have high electrical conductivity and a large surface, and provides for high productivity and cost-effectiveness when producing the product.

[0023] The ability to implement the claimed invention is shown by the following example.

EXAMPLE

[0024] The FIGURE shows the scheme of the device for produce material.

[0025] The device uses two divergent electrodes to form a stream of particles also along the electrodes. Using the loading of the source material in a narrow part of the interelectrode space and unloading the product in its wider part. As it is known (Myazdrikov O. A. Electrodynamic fluidization of disperse systems. L: Chemistry, p. 355, 1984.) with non-parallel electrodes during self-oscillatory motion, particles move along curvilinear trajectories and due to centrifugal force are thrown towards lower field strength U/d.

[0026] The centrifugal force is proportional to the square of the velocity of movement of the particles between the electrodes V.sup.2 and proportional to r.sup.4. Through environment resistance proportional to the particle size r, the velocity of movement of particles along the electrodes is proportional to r.sup.3. Thus, the larger the particle (macrostructure), the faster it leaves the interelectrode space. This property can also be used to pre-sort the source material by size, similar to chromatography for molecular substances. To prevent sticking of graphene sheets between themselves in the finished product when impregnated with electrolyte, this process should be carried out in a charged state. In the scheme of the device shown in the figure, a storage device is provided in which the product is in an electric field insufficient to fluidization the particles (less than 10.sup.3 V/m) but sufficient to charging them when the finished product is impregnated by electrolyte. It is advisable to fill the internal space of the device with helium (gas with low solubility and low adsorption capacity) to prevent the adsorption of extraneous gases on the surface of graphene and dissolving in the electrolyte.

[0027] Thus, this method makes it possible to produce nanomaterials for the manufacture of supercapacitor electrodes which have high electrical conductivity and a large surface, and provides for high productivity and cost-effectiveness when producing the product.