The present invention relates to a method for separating graphene from the liquid forming matrix. Known methods for producing mono- or multi-layer graphene film (patents US

2011/0108609, US 2011/0033688, US 2009/0155561, US 2011/0033688) consist essentially in that a metallic substrate is saturated with carbon, with mono- or polycrystalline graphene being deposited as a result of limited, and decreasing with temperature, solubility of carbon in the metallic substrate. During the process of saturation, usually performed with CVD methods, carbon is dissolved in a metallic substrate, forming a solid solution from which, in favourable conditions, graphene is deposited as a result of cooling.

Another method for producing graphene is epitaxial growth on a substrate with properly oriented planes (patents US 2011/0033688, EP 2 392 547). All the methods consist in the production of graphene on catalytic substrates in the solid state.

Known are also methods for the production of graphene on liquid metallic substrates. For example, the method outlined in patent application US 2012/0082787 consists in that an amorphous carbon film obtained by vapour-depositing amorphous carbon on an organic film is then transferred to a surface of liquid gallium (or, alternatively, indium, tin or antimony), forming graphene film as a result of the graphitization reaction arising at the contact interface between the solid phase and the liquid phase. Another known method, presented in patent US2010/0055464 consists in that an eutectic liquid containing pure graphite and a solution based ori Ni (or Cr, Mn, Fe, Co, Ta, Pd, Pt, La, Ce or their alloys), produces graphene layers in the process of crystallization. To this aim, for example, a graphite disc is placed on a plate made of pure nickel, heated to 1500°C, vacuum annealed and then cooled down slowly. The procedure can also be performed with iron-nickel alloy or Ni and Cu. Their powders, mixed with spectrally pure graphite powder, are placed in a graphite matrix and then vacuum heated to the alloy melting temperature. Since the density of graphite is lower than the density of the alloy, graphite flakes float on the surface of the metallic liquid, forming graphene during cooling. Known is also a method for producing graphene described in patent application P.399096 which consists in that graphene crystallizes from a liquid metal matrix on a permanent metallic or ceramic substrate. The graphene-forming matrix is a layer of a metal or a metal alloy with a melting temperature ranging from 1051°C to 1150°C (e.g. Cu) on a permanent multi-layered substrate with layers 1 to 5 constituted by metals with melting temperatures ranging from 1151°C to 3410°C (i.e. Pt, Pd, Ni, Si or Si0 ₂ ). The structure thus prepared is saturated with carbon in the hydrocarbon atmosphere (mixture of ethylene and acetylene and hydrogen) additionally diluted with argon, at a temperature between 0.5°C and 50°C higher than the melting point of the forming matrix. It is then cooled in argon, at a rate of 0.1 -2°C/min.

All the methods of obtaining graphene from the liquid phase described above essentially fail to address a method for separating graphene from the liquid forming matrix (even though the problem has been noticed - see US2010/0055464), which may give rise to major problems with widespread use of graphene sheets thus produced, especially larger ones.

The essence of the method for separating graphene film according to the present invention consists in the fact that during the cooling of the forming matrix, in the temperature range between 1200°C and 1050°C, and under argon pressure between 10 ^"6 and 1100 hPa, a mould frame is slid over the surface of the liquid forming matrix, whereby the said mould frame consists of a lattice of conductive fibres, advantageously carbon fibres, appropriately stretched and arranged in a characteristic pattern, whereupon during further cooling the mould frame is lowered until contact is achieved with the liquid metal surface of the forming matrix, whereby after a layer of graphene is attached, the mould frame is lifted between 1 and 100 mm above the forming matrix. The essence of the method for separating graphene film according to the present invention consists in the fact that during the cooling of the forming matrix (4), in the temperature range between 1200°C and 1050°C, and under argon pressure between 10 ^"6 and 1100 hPa, an intercepting frame operating together with a tape composed of conductive fibres, advantageously carbon fibres, is slid over the surface of the liquid forming matrix, whereupon during further cooling the intercepting frame is lowered until contact is achieved with the liquid metal surface of the forming matrix, whereby after a layer of graphene is attached, the intercepting frame is lifted between 1 and 100 mm above the forming matrix.

Advantageously, the mould and/or intercepting frame should be lowered until it is immersed in the liquid metal of the forming matrix. It is also advantageous for the mould and/or intercepting frame to move vertically at a rate ranging between 0.001 and 10 mm/s, with the positioning accuracy of 0.001-1 mm.

Furthermore, it is advantageous for the mould and/or intercepting frame to be provided with a system of controlled vertical slide of the system of fibres. Furthermore, it is advantageous for the mould and/or intercepting frame to be formed in the shape of a circle or a polygon.

Furthermore, it is advantageous for the pattern of the conductive fibre system to be based on the geometry of a polygon measuring between 0.1 and 250 mm.

Furthermore, it is advantageous that, upon completion of the stage of heating the forming matrix via the induction coil of the induction heating system, and upon completion of the process of adding the hydrocarbon mixture via a system of carbonization nozzles, during the stage of cooling of the liquid forming matrix, at a temperature of 1085°C and under argon pressure of 1063 hPa, a mould frame with a diameter of 50 mm is slid, using a lever mechanism, over the surface of the liquid forming matrix, whereby the said mould frame consists of appropriately stretched carbon fibres arranged in a characteristic pattern of honeycomb lattice with a cell size of 1 mm, whereby the said mould frame is slid in such a manner that it is 5 mm above the surface of the liquid forming matrix and during further cooling it is lowered until contact is achieved with the liquid metal surface, at a rate of 1 mm/s and with the positioning accuracy of 0.01 mm, whereby after a layer of graphene is attached, the mould frame is lifted between 1 and 100 mm above the forming matrix.

Furthermore, it is advantageous that, upon completion of the stage of heating of the forming matrix (4) via the resistance heating system, and upon completion of the process of adding of the hydrocarbon mixture via a system of carbonization nozzles, during the stage of cooling of the liquid forming matrix, at a temperature of 1088°C and under argon pressure of 1100 hPa, an intercepting frame measuring 50x25 mm is slid over the surface of the liquid forming matrix, using a lever mechanism, in order to fasten and stabilize the roll tape consisting of appropriately stretched carbon fibres arranged in a pattern of rectangular mesh with a cell size measuring 0.5x1 mm, whereby during the cooling of the forming matrix the said frame is lowered at a rate of 0.5 mm/s and with the positioning accuracy of 0.005 mm until contact is achieved with the liquid metal surface, whereby after a layer of graphene is attached the frame is lifted between 1 and 100 mm above the forming matrix. The invention will be described in more detail below in conjunction with embodiments and drawings in which individual figures illustrate:

Fig. 1 - schematic diagram of the equipment for producing graphene,

Fig. 2 - sample patterns of the conductive fibres,

Fig. 3 - schematic diagram of the frame system of conductive fibres designed for cyclic or continuous operation,

whereby the said figures are provided with symbols having the following meanings:

1. induction or resistance heating system

2a. mould frame with a system of conductive fibres

2b. frame intercepting a tape of conductive fibres

3. metallic substrate

4. liquid graphene-forming matrix

5. cooling system

6. thermocouple

7. system of carbonization nozzles

8. tape composed of electrically conductive fibres

9. system of guide rolls for the tape composed of conductive fibres

Example 1

Upon completion of the stage of heating of the liquid forming matrix 4 on the metallic substrate 3 via the induction coil of the heating system I with the thermocouple 6, and upon completion of the process of adding the hydrocarbon mixture via the system of carbonization nozzles 7, during the stage of cooling of the forming matrix 4 via the cooling system 5, at a temperature of 1085°C and under argon pressure of 1063 hPa, the mould frame 2a with a system of appropriately stretched conductive carbon fibres arranged in a characteristic pattern of honeycomb mesh was slid over the surface of the forming matrix 4 using a lever system. The cell size of the mesh was 1 mm, while the diameter of the mould frame 2a was 50 mm, whereby the distance to the surface of the forming matrix 4 was 5 mm. During further cooling the mould frame 2a was lowered at a rate of 1 mm/s and with the positioning accuracy of 0.01 mm until contact was achieved with the liquid metal surface. As a result of interactions between the fibres and the graphene film, and crystallization of the liquid forming matrix 4, a monolayer of graphene was attached to and deposited on the lattice of carbon fibres on the mould frame 2a.

Example 2

Upon completion of the stage of heating of the liquid forming matrix 4 on the metallic substrate 3 via the heating system I with the thermocouple 6, and upon completion of the process of adding the hydrocarbon mixture via a system of carbonization nozzles 7, during the stage of cooling of the forming matrix 4 via the cooling system 5, at a temperature of 1088°C and under argon pressure of 1100 hPa, the intercepting frame 2b measuring 50x25 mm was slid over the surface of the liquid forming matrix 4, using a lever mechanism, in order to fasten and stabilize the tape 8 consisting of appropriately stretched conductive carbon fibres arranged in a pattern of rectangular mesh with a cell size measuring 0.5x1 mm, driven by the system of guide rolls 9. During further cooling, the intercepting frame 2b was lowered at a rate of 0.5 mm/s with the positioning accuracy of 0.005 mm until contact was achieved with the liquid metal surface. As a result of interactions occurring between the fibres and the graphene film, and crystallization of the liquid forming matrix 4, a monolayer of graphene was attached to and deposited on the tape 8.