Method of forming film having thickness of 10 micrometers or less by friction welding coating film formed by friction welding flake powders of soft metal to both surfaces of graphene conjugate

Abstract

To provide a technique for forming a graphene conjugate in which graphene planes are bonded together, forming a coating film in which aggregates of flake powders of soft metal are bonded together at its planes, and bonding the coating film to a surface of the graphene conjugate.SOLUTION: There is provided a method for forming a film. The method is configured as follows: first, a suspension is created in which aggregates of graphene are dispersed in methanol; next, the suspension is poured into a container and vibration acceleration in three directions is applied to the suspension so as to align the aggregates of graphene facing upward in the suspension, after this, the methanol is evaporated; further, flat plates are stacked onto the aggregates of graphene and the flat plates are compressed to form a graphene conjugate; then, a suspension is created in which aggregates of flake powders of soft metal are dispersed in alcohol with a viscosity of 2 to 10 mPa sec., and the graphene conjugate is immersed in the suspension and then taken out; and furthermore, the graphene conjugate is sandwiched between two flat plates, one of which is compressed, and coating films made of the aggregates of flake powders of soft metal are bonded to both surfaces of the graphene conjugate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention provides a graphene conjugate having a thickness of less than 0.1 μm by overlapping, face-to-face, groups of graphene produced by simultaneously breaking the interlayer bonds of graphite crystals in graphite particles and joining the overlapped graphenes by friction welding. Also, a group of flake powder made of a soft metal is overlapped, face-to-face, and the overlapped flake powders are joined by friction welding to form a coating having a thickness of less than 5 μm. Furthermore, the coating is joined to both surfaces of the graphene conjugate by friction welding. It has excellent thermal conductivity, electrical conductivity, and mechanical strength, and also has a metallic luster. This relates to a method for forming a film having a thickness of 10 μm or less. In addition, since flat powder made of soft metal is generally called flake powder, it will be referred to as flake powder in the present invention. [Background technology]

[0002] Graphene produced by simultaneously breaking the interlayer bonds of graphite crystals in graphite particles is small in size, and the size of the graphene varies from 1 to 300 μm. However, because graphite particles are used as the raw material, first, the most inexpensive graphene aggregates can be produced, second, only intrinsic graphene composed of graphite crystals can be produced, and third, a huge number of graphene aggregates can be simultaneously produced. In contrast, graphene produced by chemical vapor deposition or pyrolysis produces large graphene sizes, but the cost of producing graphene increases first, as the graphene size increases, second, to produce only intrinsic graphene, and third, as the number of graphene aggregates produced increases. Therefore, to produce the film of the present invention inexpensively, it is necessary to produce inexpensive graphene conjugates, and using expensive graphene is not appropriate. For these reasons, graphite particles are used as the raw material for graphene in the present invention. In JIS packaging terminology, a plate having a thickness of 250 μm or less is called a film, and a plate having a thickness of more than 250 μm is called a sheet, so the plate formed in the present invention is referred to as a film.

[0003] The film of the present invention is obtained by friction-welding a coating made of an aggregation of soft metal flake powder, which is then friction-welded to both surfaces of a graphene conjugate, and therefore the properties of the graphene conjugate are imparted to the film. That is, graphene is extremely thin, with a thickness of 0.332 nm, and its conductivity in the thickness direction is extremely low, while electrons move preferentially in the plane direction, resulting in high conductivity in the plane direction. Therefore, in a graphene assembly, in which a collection of graphene sheets overlapping each other are joined by friction welding, electrons are preferentially transported in the plane direction. For this reason, the conductivity of a graphene assembly is close to that of graphene. The volume resistivity of graphene is 1.3 μΩcm, while the volume resistivity of silver, which has the smallest volume resistivity of any metal, is 1.6 μΩcm. The conductivity of graphene is 7.5×10 7 S / m, the conductivity of silver, the metal with the highest conductivity, is 6.1 x 10 7 S / m. Furthermore, because graphene is extremely thin, its thermal conductivity in the thickness direction is extremely low, and heat is preferentially transferred in the plane direction, resulting in high thermal conductivity in the plane direction. Therefore, in a graphene joint, in which a group of graphene sheets are joined by friction welding, heat is preferentially transferred in the plane direction. For this reason, the thermal conductivity of a graphene joint is close to that of graphene itself. The thermal conductivity of graphene is 1880 W / (m·K), which is 4.5 times that of silver, the metal with the highest thermal conductivity. In this way, due to the anisotropy of the properties of graphene, the properties of the graphene conjugate are close to those of graphene. On the other hand, in the film of the present invention, a coating made of an assembly of flake powders joined by friction welding is bonded to both surfaces of the graphene conjugate by friction welding, so that the properties of the graphene conjugate are imparted to the film, and the electrical conductivity and thermal conductivity of the film are superior to those of flake powder made of soft metal. Furthermore, graphene is a tough material with a breaking strength of 42 N / m, more than 100 times that of steel, and a Young's modulus of 1020 GPa, which is extremely high. Meanwhile, when graphene aggregates are joined face-to-face by friction welding, the joining strength between the graphene aggregates is extremely high. Therefore, a graphene aggregate has a mechanical strength close to that of the graphene aggregate itself. Meanwhile, a coating made of an aggregate of soft metal flake powder joined by friction welding has a thickness of less than 5 μm, and its mechanical strength is significantly lower than that of a graphene aggregate. In contrast, the thickness of a graphene aggregate is less than 0.1 μm. Therefore, the thickness and weight of the film of the present invention are almost the same as those of two coatings. On the other hand, a film in which a coating is bonded to both surfaces of a graphene conjugate by friction welding is endowed with the properties of the graphene conjugate, and the mechanical strength of the film is significantly higher than that of the coating. Therefore, the film of the present invention has a thickness of 10 μm or less and exhibits the gloss of soft metal flake powder on both surfaces, but has significantly greater mechanical strength. Therefore, by taking advantage of the mechanical strength of the film, the film can be used for new applications. Furthermore, because the coating is bonded to the graphene conjugate by friction welding, there are no restrictions on the material of the soft metal flake powder that constitutes the film.

[0004] The present inventors have previously filed a patent application (Japanese Patent Application No. 2022-177729) for a method for forming a film in which foil made of a metal or alloy is joined by friction welding to both surfaces of a graphene conjugate. In contrast to this, the film of the present invention has a coating made of an aggregate of soft metal flake powder joined by friction welding to both surfaces of a graphene conjugate. Therefore, in the film of the present invention and the film of the prior application, the substances joined to the graphene conjugate are a coating made of an aggregate of soft metal flake powder on one side and a foil made of a metal or alloy on the other side. Therefore, the coating and foil joined by friction welding to the surface of the graphene conjugate are There is a difference .

[0005] In the prior art, soft metal flake powder is used as a raw material for conductive paste in which a collection of soft metal flake powder is dispersed in an organic vehicle. Examples of such prior art include Patent Documents 1 to 3. On the other hand, there is currently no technology that can be used in the present invention to form a thin coating by overlapping a collection of soft metal flake powder faces together and joining the overlapping flake powder faces together by friction welding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-079725 [Patent Document 2] Japanese Patent Application Publication No. 2015-069877 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-065139 [Patent Document 4] Patent No. 6166860 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] As described above, the purpose of bonding a coating made of an aggregation of soft metal flake powder, which is obtained by friction welding an aggregation of the flake powder, to the surface of a graphene conjugate is to impart the excellent properties of graphene to the coating. Meanwhile, the properties of graphene are anisotropic. Furthermore, soft metal flake powder has a thickness of submicrons and a flat surface size of microns, or a thickness of microns and a flat surface size of several tens of microns. Therefore, it is a fine flat powder with a large aspect ratio, which is the ratio of the flat surface size to the thickness. Therefore, to bond a coating to both surfaces of a graphene conjugate, first, the graphene faces must be bonded together; second, the bonded aggregation of graphene must be directly bonded to the aggregation of soft metal flake powder; and third, if the bonded aggregation of graphene and the aggregation of soft metal flake powder can be integrated, the excellent properties of graphene can be imparted to the aggregation of soft metal flake powder. Furthermore, if a film in which a coating made of an aggregate of soft metal flakes is bonded to both surfaces of a graphene conjugate can be produced inexpensively, the film can be used for general purposes. Therefore, it is necessary to form the film using inexpensive materials and a simple production method. Therefore, the problems that the invention aims to solve are as follows: First, we will find a technique to directly bond groups of graphene together face-to-face to form a graphene junction in which the graphene faces are bonded together. Second, we will discover a technology to directly bond together the surfaces of a collection of soft metal flakes, forming a coating in which the surfaces of the soft metal flakes are bonded together. Third, we will find a technique to bond a film directly to the surface of the graphene conjugate. Fourth, the method of forming a graphene conjugate, the method of forming a coating made of an aggregate of soft metal flake powder, and the method of directly bonding the coating to the graphene conjugate are simple processing methods, and the raw materials used are all inexpensive. The problems that the invention aims to solve are the four problems mentioned above. [Means for solving the problem]

[0008] A coating made by friction welding soft metal flake powder was then friction-welded to both surfaces of the graphene assembly. It has excellent thermal conductivity, electrical conductivity and mechanical strength, and has a metallic luster. 10μm or less mosquito The method for forming a film comprising: Two parallel plates Consists of electrode Plate pair One of the components parallel plate A collection of flake graphite particles or a collection of lump graphite particles is spread evenly on the surface of the electrode plate, and one of the parallel plate The electrode plate is immersed in methanol filled in the first container, and the other parallel plate The electrode plate is connected to the one of the agglomerates of the scaly graphite particles or the agglomerates of the lump graphite particles. parallel plate Place it on top of the electrode plate, parallel plate The electrode plate and the other parallel plate and electrode plates. Consists of two parallel plates The electrode pair is immersed in the methanol. Consists of two parallel plates A direct current potential difference having a predetermined magnitude is applied to the gap between the electrode pair, thereby making it possible to Consists of two parallel plates An electric field corresponding to a value obtained by dividing the value by the size of the gap between the electrode pair is applied to the collection of flake graphite particles or the collection of lump graphite particles, and by applying the electric field, all of the interlayer bonds of the basal planes made of graphite crystals that form the flake graphite particles or the lump graphite particles are simultaneously destroyed, Consists of two parallel plates A collection of graphene consisting of the basal plane is deposited in the gap between the electrode pair. Consists of two parallel plates The gap between the electrode pair is widened, and the Consists of two parallel plates The electrode pair is tilted in the methanol, and vibration acceleration is applied to the first container in three directions, left and right, front and back, and up and down, in order, to dissolve the graphene aggregates in the Consists of two parallel plates the electrode pair into the methanol, and then the first container Consists of two parallel plates a first step of removing an electrode pair and preparing a collection of graphene dispersed in the methanol in the first container; a second step of operating an ultrasonic homogenizer in the first container to repeatedly apply shock waves to the graphene aggregates through the methanol, thereby separating the graphene aggregates into individual graphene sheets in the methanol, and then removing the homogenizer from the first container to prepare a first suspension in the first container that is composed of the graphene aggregates separated into individual graphene sheets in the methanol; A weighed alcohol having a viscosity of 2-10 mPa·sec at 20°C is weighed, and the weight of the alcohol is converted based on the density of the alcohol to obtain a volume, and a weight of a collection of flake powder made of soft metal is weighed and the volume is converted based on the density of the soft metal that makes up the flake powder, and the alcohol and the collection of flake powder made of soft metal are weighed so that the volume ratio is 3:1, and the weighed alcohol and the weighed collection of flake powder made of soft metal are placed in a second container, Applicable a third step of stirring the alcohol to prepare a second suspension in which a collection of flake powder made of the soft metal is dispersed in the alcohol; a fourth step of pouring a predetermined amount of the first suspension into a third container, the inside of which corresponds to the size of a film to be produced, placing the third container on a vibration table of a vibrator, operating the vibrator, and repeatedly applying vibration accelerations in the front-to-back, left-to-right, and up-to-down directions to the first suspension in each direction in turn, and finally applying vibration acceleration in the up-to-down direction, thereby producing a collection of graphene in the first suspension, with the graphene in the first suspension randomly stacked face up in methanol, in the third container; thereafter, heating the third container to the boiling point of the methanol to evaporate the methanol from the first suspension, and forming a collection of graphene in the third container, with the graphene randomly stacked face up; a fifth step of overlapping a flat plate having the same size as the inside of the third container on the surface of the collection of graphene in the third container, and further uniformly compressing the entire surface of the flat plate, thereby bonding the overlapping graphene with the surface facing up by friction welding, and forming a graphene conjugate made up of the collection of graphene bonded by friction welding with a thickness of less than 0.1 μm; further applying impact acceleration simultaneously to a plurality of positions on the bottom surface of the third container, and peeling the graphene conjugate from the bottom surface of the third container; further applying impact acceleration having the same magnitude as the impact acceleration simultaneously to a plurality of positions on one side surface of the flat plate, and peeling the graphene conjugate from the flat plate, and removing the graphene conjugate; a sixth step of pouring the second suspension into a fourth container having an inner size larger than that of the graphene conjugate, the fourth container being placed on a vibration table of a vibrator, and operating the vibrator to repeatedly apply vibration accelerations to the second suspension in the front-to-back, left-to-right, and up-to-down directions in turn, the vibration accelerations being larger than the vibration acceleration applied in the fourth step, and finally applying a vibration acceleration in the up-to-down direction, thereby forming a third suspension in the fourth container, the third suspension being made up of a collection of flake powder made of soft metal in the second suspension, with the flake powder surface facing up in the alcohol. a seventh step of immersing the entire graphene conjugate prepared in the fifth step in the third suspension in the fourth container, then removing the graphene conjugate from the third suspension, and sandwiching the graphene conjugate between two flat plates that are larger than the graphene conjugate but have the same size and thickness as the graphene conjugate, then heating the two flat plates to the boiling point of the alcohol to evaporate the alcohol from the third suspension, and forming clusters of flake powder made of the soft metal that are randomly overlapping with their faces facing up on both surfaces of the graphene conjugate; an eighth step of uniformly compressing the entire surface of an upper plate of the two flat plates with a compressive stress of not more than one-third of the compressive stress applied to the graphene aggregation in the fifth step, thereby joining the overlapping soft metal flake powder with the faces facing up by friction welding, forming a coating made of the joined aggregation of soft metal flake powder with a thickness of less than 5 μm, and joining the coating to both surfaces of the graphene conjugate by friction welding, thereby forming a film in which the coating is joined to both surfaces of the graphene conjugate; further comprising: an eighth step of simultaneously applying, to a plurality of locations on one side surface of the upper plate of the two flat plates, an impact acceleration of the same magnitude as that applied to the plurality of locations on one side surface of the flat plates in the fifth step, to peel the upper plate from the film; and further simultaneously applying, to a plurality of locations on one side surface of the lower plate of the two flat plates, an impact acceleration of the same magnitude as the impact acceleration applied to the plurality of locations on one side surface of the lower plate, thereby peeling the lower plate from the film, and removing the film; By carrying out the above-mentioned eight steps in succession, a coating formed by friction welding soft metal flake powders was friction-welded to both surfaces of the graphene composite. It has excellent thermal conductivity, electrical conductivity and mechanical strength, and has a metallic luster. 10μm or less mosquito A method for forming a film comprising forming a film comprising the steps of:

[0009] The film of the present invention is formed by the following eight simple steps, carried out in sequence: The first step involves preparing a suspension of graphene clusters dispersed in methanol in a first container. To achieve this, a first container large enough to accommodate two parallel-plate electrode pairs is prepared. Methanol is poured into the first container in an amount sufficient to immerse the two parallel-plate electrode pairs. Next, a cluster of flake graphite particles or a cluster of lump graphite particles is placed between the two parallel-plate electrode pairs. The two parallel-plate electrode pairs are then immersed in methanol, and a direct current potential difference of a predetermined magnitude is applied between the two parallel-plate electrodes. This generates an electric field in the gap between the two parallel-plate electrodes, equivalent to the potential difference divided by the size of the gap between the two parallel-plate electrodes. This electric field simultaneously exerts a Coulomb force sufficient to destroy the interlayer bonds of the basal planes of the graphite crystals on all of the graphite particles, which simultaneously exerts a Coulomb force on all π electrons responsible for the interlayer bonds of the basal planes. This releases the π electrons from their constraints on the π orbitals, and all π electrons leave the π orbitals and become free electrons. In other words, when the Coulomb force acting on the π electrons is greater than the π orbital interaction, the π electrons are released from their constraints and become free electrons. As a result, all π electrons that form the interlayer bonds on the basal planes no longer exist on the π orbitals, and all interlayer bonds on the basal planes of the graphite crystals that make up the graphite particles are simultaneously broken for all graphite particles. This instantly creates a cluster of basal planes, i.e., a cluster of graphene, in the gap between the two parallel-plate electrodes. The created graphene is genuine graphene, consisting only of graphite crystals. Graphene is an extremely lightweight material with almost no mass. However, because the two parallel-plate electrodes are immersed in methanol, the cluster of graphene deposited in the gap between the parallel-plate electrodes does not scatter. The technique of simultaneously destroying the interlayer bonds of graphite crystals in flake graphite particles or chunky graphite particles by applying an electric field to produce an aggregate of graphene is described in Patent Document 4 by the present inventor. That is, between two parallel plate electrodes immersed in an insulating substance, methanol gapWhen a potential difference is applied to the graphite particles, an electric field is generated in the gap between the two parallel plate electrodes. This electric field simultaneously exerts a Coulomb force sufficient to destroy the interlayer bonds of the basal planes of the graphite crystals on all the graphite particles, to all the π electrons that are responsible for the interlayer bonds of the basal planes, and the π electrons are released from the constraints on the π orbitals, and all the π electrons leave the π orbitals and become free electrons. Methanol is an insulator with a resistivity of 3MΩ·cm or more and a dielectric constant of 33. Ethanol is also an insulator with a dielectric constant of 24. The electrical conductivity of ethanol is 7.5×10 -6 S / m, and the electrical conductivity of flake graphite particles is 43.9 S / m. Therefore, ethanol has an electrical conductivity of 1.7 x 10 compared to flake graphite particles, which are conductive. 7 It is a twice weaker insulator. The graphite particles are made from natural graphite crystals as a mineral, which are refined into graphite particles. There are three types of graphite particles: flake graphite particles, massive graphite particles (also called flake graphite particles), and amorphous graphite particles. The amorphous graphite particles have poorer crystallinity than the other two types of graphite particles, and therefore the amount of graphene obtained by breaking the interlayer bonds of the amorphous graphite particles is smaller than that of the other two types of graphite particles. Furthermore, the flake graphite particles are flat particles with a larger aspect ratio than the massive graphite particles. Therefore, breaking the interlayer bonds of the flake graphite particles results in graphene with a larger aspect ratio than the massive graphite particles. On the other hand, the massive graphite particles are larger than the flake graphite particles. Therefore, breaking the interlayer bonds of the massive graphite particles results in more graphene than the flake graphite particles. For this reason, flake graphite particles or massive graphite particles were used as the graphite particles. Next, the graphene aggregates are transferred from the gap between the two parallel-plate electrodes into the methanol. To do this, the gap between the two parallel-plate electrodes is expanded in the methanol and then tilted in the methanol. After this, three-directional vibration accelerations of 0.1-0.2 G, depending on the size of the container, are applied repeatedly to the first container filled with methanol. This causes the graphene aggregates to transfer from the gap between the two parallel-plate electrodes into the methanol. After this, the two parallel-plate electrodes are removed from the first container. As a result, a suspension of graphene aggregates dispersed in methanol is created in the first container. The second step is to prepare a first suspension in a first container, consisting of graphene aggregates separated into individual graphene sheets in methanol. To achieve this, a homogenizer is operated in the suspension containing the graphene aggregates dispersed in methanol. Specifically, shock waves are repeatedly applied to the graphene aggregates via methanol. Because graphene is an extremely lightweight substance with almost no mass, the graphene aggregates are separated into individual graphene sheets in the methanol, and the separated graphene aggregates are dispersed in the methanol. Specifically, when an ultrasonic homogenizer is operated in the suspension, the generation and disappearance of a huge number of extremely tiny bubbles, each one order of magnitude smaller than the flat surface of graphene, is repeated in the methanol according to the period of the ultrasonic vibration frequency (this phenomenon is called cavitation). The shock waves generated by the bubble popping are repeatedly applied to the massless graphene aggregates, causing the graphene aggregates to separate into individual graphene sheets in the methanol in a short period of time. As a result, the graphene aggregate separated into individual graphene sheets is dispersed in methanol. That is, the shock waves applied to low-viscosity, low-density methanol by the homogenizer device are consumed only to a small extent by the molecular vibration of the low-density methanol, and many of the shock waves are applied to the graphene aggregate, which has almost no mass. On the other hand, because the bonding force between overlapping graphene sheets is extremely small, when shock waves are applied to the overlapping graphene sheets, the overlapping graphene sheets are released in a short time and reliably in methanol, and the graphene sheets are separated into individual graphene sheets. This prevents a portion of the graphene joint formed by friction welding the graphene aggregates from peeling off at the overlapping portions of the graphene sheets. As a result, the graphene aggregates, in which the graphene sheets separated into individual graphene sheets are covered with methanol, become a first suspension dispersed in methanol. The third step is to prepare a second suspension in which the soft metal flake powder clusters are dispersed in alcohol. To this end, the alcohol and the soft metal flake powder clusters are weighed so that the volume ratio of the weight of the alcohol, which has a viscosity of 2-10 mPa·sec at 20°C, converted based on the density of the alcohol, to the weight of the soft metal flake powder clusters, which is converted based on the density of the metal that makes up the soft metal flake powder, is 3:1, and the weighed alcohol and the weighed soft metal flake powder clusters are placed in a second container, and the alcohol is stirred to prepare a second suspension in which the soft metal flake powder clusters are dispersed in the alcohol. In other words, the density of soft metal flake powder varies greatly depending on the metal material that constitutes the flake powder. Furthermore, the density of soft metal flake powder is greater than the density of alcohol. Furthermore, the density of alcohol is nearly the same regardless of the viscosity of the alcohol. Therefore, the weight of soft metal flake powder varies greatly depending on the density of the metal that constitutes the flake powder. Therefore, flake powder with a relatively high density is dispersed in alcohol with a relatively high viscosity, and flake powder with a relatively low density is dispersed in alcohol with a relatively low viscosity. This increases the adsorptive force between the flake powder with a relatively high density and the alcohol, and in the fourth step, the flake powder with a relatively high density, i.e., the flake powder with a relatively high weight, is adsorbed to the alcohol, and the second suspension in which clusters of flake powder are dispersed in the alcohol is adsorbed onto the surface of the graphene conjugate. For this purpose, the soft metal flake powder was dispersed in alcohol with a viscosity range of 2-10 mPa·sec at 20°C, depending on the density range of the soft metal flake powder. The fourth step is to form a randomly stacked graphene aggregate in a third container with the surface facing up. For this purpose, a third container is prepared whose inner size corresponds to the size of the film to be produced. A vibrator is also prepared. First, a predetermined amount of the first suspension is poured into the third container. toNext, the third container is placed on the vibration table of a vibrator, and the vibrator is operated to repeatedly apply vibration accelerations of 0.1-0.2 G in the front-to-back, left-to-right, and up-to-down directions to the first suspension, depending on the amount of the first suspension, in each direction, and finally apply a vibration acceleration of 0.1-0.2 G in the up-to-down direction. As a result, graphene in the first suspension is randomly stacked face up in the methanol, forming a cluster of graphene in the third container. Thereafter, the third container is heated to the boiling point of methanol, evaporating the methanol from the first suspension, and forming a cluster of graphene randomly stacked face up in the third container. Specifically, when vibrational acceleration is applied to graphene covered with methanol and separated into individual graphene sheets in the methanol, the graphene, which has almost no mass, moves in the vibrational direction along with the methanol. Graphene is extremely thin, at 0.332 nm, and has a very large aspect ratio (the ratio of area to thickness). Therefore, when graphene is subjected to vibrational acceleration in methanol, it moves face-up through the methanol, as this is the least stressed position. Therefore, when the graphene cluster is repeatedly subjected to vibrational acceleration in three directions, the individual graphene sheets randomly align face-up in the suspension. Finally, vibrational acceleration is applied in the vertical direction, ensuring that the individual graphene sheets form a cluster of randomly stacked graphene sheets face-up in the suspension. After this, the methanol is evaporated from the first suspension, and a cluster of randomly stacked graphene sheets face-up is formed in the third container. The fifth step is the step of forming a graphene conjugate. To this end, a flat plate having the same size as the inside of the third container is prepared. First, the flat plate is placed on the surface of the graphene aggregate formed in the third container. Then, the entire surface of the flat plate is uniformly compressed. At this time, a compressive load of 40 kg or more is applied evenly to the entire surface of the flat plate depending on the size of the flat plate. As a result, the entire overlapping graphene aggregate with its face up is uniformly compressed, and the overlapping graphene aggregates with their face up are joined by friction welding. A graphene conjugate consisting of the graphene aggregate joined by friction welding is formed on the bottom surface of the third container with a thickness of less than 0.1 μm. In other words, extremely small gaps are formed between the overlapping graphene aggregates with their face up. Therefore, if excessive compressive stress is applied to the graphene aggregates when joining the overlapping graphene aggregates with their face up, the overlapping graphene aggregates slide an extremely small distance to fill the extremely small gap, and the graphene aggregates directly overlap without forming any gaps. When graphene slides over an extremely small distance, frictional heat is generated between the overlapping surfaces of the graphene, causing the surfaces to instantly reach a high temperature, vaporizing all impurities from the graphene surfaces, and firmly bonding the purified graphene together through frictional heat. In other words, because the graphene is directly bonded to itself without any intervening foreign matter, the bonding strength between the graphene is extremely strong. Furthermore, graphene has almost no mass and is extremely thin. Therefore, it is difficult to peel off graphene once it has been bonded by friction welding. On the other hand, if the compressive stress applied to the overlapping graphene with the surface facing up is insufficient, the overlapping graphene will not slide over the extremely small distance to fill the extremely small gap, and the graphene will not be bonded to itself through frictional heat. Subsequently, an impact acceleration of 0.3-0.4 G, depending on the size of the third container, is simultaneously applied to multiple locations on the bottom surface of the third container, and the graphene conjugate is peeled off from the bottom surface of the third container. In other words, the flatness of the bottom surface of the third container is significantly inferior to that of the graphene conjugate. Therefore, the convex portions on the bottom surface of the third container come into contact with the graphene conjugate, which has excellent flatness, forming numerous contact points, and the graphene conjugate is bonded at these contact points by frictional heat. On the other hand, when subjected to compressive stress, the contact points formed by the bottom surface of the third container do not undergo elastic or plastic deformation, so the area of ​​the contact points is significantly small, approaching a point. Therefore, the bonding strength of the graphene conjugate at the contact points on the bottom surface of the third container is low. Therefore, when impact acceleration is applied simultaneously to multiple locations on the bottom surface of the third container, the impact acceleration is directly applied to all contact points formed by the bottom surface of the third container. Because the area of ​​each contact point is extremely small, the bond between the bottom surface of the third container and the graphene conjugate at all contact points is destroyed, and the graphene conjugate is peeled off from the bottom surface of the third container. Furthermore, an impact acceleration having the same magnitude as the impact acceleration is simultaneously applied to multiple locations on one side of the flat plate, peeling the graphene conjugate from the flat plate and removing the graphene conjugate. That is, like the bottom surface of the third container described above, the flatness of the bottom surface of the flat plate is significantly inferior to the flatness of the graphene conjugate. Therefore, the convex portions on the bottom surface of the flat plate come into contact with the graphene conjugate, which has excellent flatness, forming numerous contact points, and the graphene conjugate is bonded to the flat plate at the contact points formed by the bottom surface of the flat plate. On the other hand, when subjected to compressive stress, the contact points on the bottom surface of the flat plate do not undergo elastic or plastic deformation, so the area of ​​the contact points is significantly small, approaching a point. Therefore, the bonding strength of the graphene conjugate at the contact points on the bottom surface of the flat plate is low. Therefore, when impact acceleration is applied simultaneously to multiple locations on the side of the flat plate, the impact acceleration is applied directly to all contact points in a direction perpendicular to the compression direction. Because the area of ​​the contact points formed by the bottom surface of the flat plate is extremely small, the bond between the bottom surface of the flat plate and the graphene conjugate at the contact points is destroyed, and the graphene conjugate is peeled off from the bottom surface of the flat plate. The sixth step is to create a collection of randomly overlapping soft metal flakes in alcohol with their faces facing up in a fourth container. For this purpose, a fourth container is prepared whose inner size is larger than the size of the graphene composite. First, toThen, a second suspension having the same volume as the first suspension poured into the third container is poured into the fourth container. The fourth container is placed on the vibration table of the vibrator used in the fourth process, and the vibrator is operated. Vibration accelerations of 0.3-0.6 G, greater than the vibration acceleration applied in the fourth process, are repeatedly applied to the second suspension in the forward / backward, left / right, and up / down directions, depending on the density of the soft metal flake powder, and finally a vibration acceleration of 0.3-0.6 G is applied in the up / down direction. In other words, because the viscosity of the alcohol in the second suspension is 3-17 times that of the methanol in the first suspension, a vibration acceleration greater than the vibration acceleration applied in the fourth process is applied, causing the alcohol in the second suspension to move in the direction of the vibration acceleration. This creates a third suspension in the fourth container, in which the soft metal flake powder in the second suspension is randomly layered in the alcohol with the flake powder side up. As mentioned above, the density of the flake powder varies greatly depending on the metal material that makes up the flake powder. Therefore, flake powders with a relatively high density were dispersed in alcohol with a relatively high viscosity, while flake powders with a relatively low density were dispersed in alcohol with a relatively low viscosity. This increases the adsorption force between the alcohol and flake powders with a relatively high density, i.e., flake powders with a relatively high weight. On the other hand, when vibration acceleration is applied to soft metal flake powder dispersed in alcohol, the flake powder moves in the vibration direction along with the alcohol. On the other hand, flake powder is a thin powder with a large aspect ratio, which is the ratio of area to thickness. Therefore, when flake powder is subjected to vibration acceleration in alcohol, it moves with its surface facing up, as this is the least stress applied to the flake powder. Therefore, when a collection of powder flakes is subjected to repeated vibration acceleration in three directions, the powder flakes randomly overlap with their faces facing up in the suspension.Finally, vibration acceleration in the vertical direction is applied, ensuring that the powder flakes form a collection of powder flakes that are randomly overlapping with their faces facing up in the suspension.As mentioned above, the viscosity of alcohol is 3-17 times that of methanol, so the adsorption force between the soft metal flake powder and alcohol is greater than the adsorption force between graphene and methanol. Therefore, a relatively large vibration acceleration is applied depending on the density of the flake powder, and the flake powder moves in the vibration direction along with the alcohol. As a result, a collection of flake powder randomly stacked face up in the suspension is formed as a third suspension. The seventh step involves forming clusters of randomly overlapping soft metal flakes, face up, on both surfaces of the graphene conjugate. To achieve this, the graphene conjugate prepared in the fifth step is immersed entirely in the third suspension in a fourth container. The graphene conjugate is then removed from the third suspension. This allows the third suspension to adsorb onto the surface of the graphene conjugate to a thickness dependent on the viscosity of the alcohol. Because the viscosity of alcohol is 2–10 mPa·sec, the thickness of the third suspension adsorbed onto the surface of the graphene conjugate is 2–10 μm, depending on the viscosity of the alcohol. Furthermore, two flat plates of the same size and thickness but larger than the graphene conjugate are prepared. The graphene conjugate with the clusters of flakes adsorbed on its surface is then sandwiched between the two flat plates. The two plates are then heated to the boiling point of the alcohol, vaporizing the alcohol from the third suspension, forming a cluster of randomly stacked, face-up soft metal flakes on both surfaces of the graphene conjugate. The eighth step is a step of forming a film by friction-welding a coating composed of an aggregation of soft metal flake powder, which is formed by friction-welding the flake powder to both surfaces of the graphene conjugate. To this end, the graphene conjugate, with the surface adsorbed with randomly overlapping aggregations of flake powder, is sandwiched between two flat plates, and the entire surface of the upper flat plate is uniformly compressed with a compressive stress less than one-third of the compressive stress applied to the aggregations of graphene in the fifth step. In other words, when the soft metal is flattened, micron-level waviness is formed on the surface of the flake powder, and the surface flatness is significantly lower than that of the graphene conjugate. Therefore, the compressive stress required to friction-weld flake powder with poor flatness to a graphene conjugate is less than one-third of the compressive stress required to friction-weld overlapping aggregations of graphene with significantly higher flatness. Furthermore, the compressive stress when friction welding powder flakes with poor flatness together is even smaller. On the other hand, when a collection of randomly overlapping powder flakes is compressed face up, the convex portions on the surface of the powder flakes form numerous contact points with the surface of the graphene conjugate. Furthermore, the convex portions on the surface of the powder flakes form numerous contact points due to contact between the flakes themselves. Therefore, when the entire surface of the flat plate is compressed evenly, the graphene conjugate with the collection of powder flakes adsorbed on its surface is compressed evenly, and the collection of powder flakes that are randomly overlapping face up is compressed. At this time, the powder flakes first come into contact with each other at the convex portions on their surfaces. Next, because the powder flakes are made of a soft metal, the contact points between the powder flakes elastically deform according to the magnitude of the compressive stress. This increases the area of ​​the contact points. Furthermore, frictional heat is generated at the contact points, which causes the powder flakes to bond together, forming a film made up of the bonded powder flakes with a thickness of less than 5 μm. At the same time, the convex parts on the surface of the powder flakes come into contact with the surface of the graphene conjugate, which has excellent flatness. Furthermore, because the powder flakes are made of a soft metal, the contact points between the surface of the powder flakes and the surface of the graphene conjugate undergo elastic deformation depending on the magnitude of the compressive stress. This increases the area of ​​the contact points.Furthermore, frictional heat is generated at the contact points, and the contact points on the surfaces of the powder flakes bond to both surfaces of the graphene conjugate. As a result, a film is formed in which the coating is bonded to both surfaces of the graphene conjugate. Note that in both the bonding between the powder flakes and the bonding of the powder flakes to the surface of the graphene conjugate, the contact points formed by the convex parts on the surfaces of the powder flakes become surfaces rather than points due to the elastic deformation of the powder flakes, and therefore the area of ​​the bonded parts increases, and the bonding strength between the powder flakes and the bonding strength of the powder flakes to the surface of the graphene conjugate increases in accordance with the area of ​​the bonded parts. After this, an impact acceleration of the same magnitude as that applied to the multiple locations on one side of the upper plate of the two flat plates in the fifth step is simultaneously applied to multiple locations on one side of the upper plate, thereby peeling the film from the upper plate. Furthermore, an impact acceleration of the same magnitude as the impact acceleration applied to the multiple locations on one side of the lower plate of the two flat plates is simultaneously applied to multiple locations on one side of the lower plate of the two flat plates, thereby peeling the film from the lower plate and removing the film. In other words, the surface of the flat plate and the coating form numerous contact points depending on the flatness of the surface of the flat plate and the flatness of the powder flakes, and the surface of the flat plate and the powder flakes are bonded at the contact points by frictional heat. On the other hand, when subjected to compressive stress, the convex portions on the surface of the flat plate do not undergo elastic or plastic deformation, so the area of ​​the contact points is significantly small, approaching a point. In contrast, the contact points of the powder flakes that make up the coating elastically deform, but the convex portions on the surface of the flat plate do not, so the amount of elastic deformation is less than the amount of elastic deformation when the powder flakes are bonded together. Therefore, the bonding strength between the surface of the plate and the flake powder is smaller than the bonding strength between the flake powder particles themselves. Therefore, when impact acceleration is applied simultaneously to multiple locations on the side of the plate, the impact acceleration is applied directly to all contact points formed by the surface of the plate in a direction perpendicular to the direction of the applied compressive stress. Since the area of ​​the contact points formed by the surface of the plate is extremely small, the bonded points formed by the surface of the plate are first destroyed. This reduces the bonding strength between the surface of the plate and the coating. Next, impact acceleration is applied directly to all contact points formed by the flake powder on the surface of the plate in a direction perpendicular to the direction of the applied compressive stress. This destroys the bonded points formed by the flake powder on the surface of the plate, and the coating is peeled off from the surface of the plate. As a result, the film is peeled off from the plate.

[0010] The effects of the film produced by the method described above will now be described. The film is a 10 μm thick film or less, made by friction welding a coating consisting of a collection of soft metal flake powder and less than 5 μm thick to both surfaces of a graphene conjugate that is less than 0.1 μm thick. This film has a material composition and structure that have never existed before. Therefore, the film exhibits effects that have not been achieved with previous films. First, the effects of the film will be explained based on the material composition and structure of the film. A film made of an aggregate of soft metal flake powder has electrical conductivity and thermal conductivity according to the metal material. In addition, the appearance of the film has a metallic luster. On the other hand, graphene conjugates reflect the properties of graphene and have superior electrical conductivity and thermal conductivity than soft metal flake powder. Therefore, a film made of an aggregate of soft metal flake powder forms a path for electron movement in the film, and the graphene conjugate also forms a path for electron movement in the film. Therefore, three paths for electron movement are formed in the film. On the other hand, since the graphene conjugate has superior electrical conductivity than a film made of an aggregate of soft metal flake powder, the conductivity of the graphene conjugate is dominant in the conductivity of the film. In addition, with regard to thermal conductivity, three paths for heat conduction are formed in the film. On the other hand, since the graphene conjugate has superior thermal conductivity than a film made of an aggregate of soft metal flake powder, the thermal conductivity of the film is higher than that of the graphene conjugate. Heat conduction Sex becomes dominant. Furthermore, the film, in which a coating made of an aggregate of soft metal flake powder is friction-welded to both surfaces of the graphene conjugate, is less than 10 μm thick, but the mechanical strength of the film is significantly higher than that of a coating made of an aggregate of soft metal flake powder, due to the properties of the graphene conjugate. Therefore, although the film has a thin appearance with a metallic luster, its mechanical strength can be utilized to make parts or substrates. Next, the effects of the film will be explained based on the inherent properties of the graphene composite and the inherent properties of the soft metal flake powder. First, the film is endowed with the thermal conductivity of graphene conjugates, which have superior thermal conductivity compared to films made of aggregates of soft metal flake powder. Specifically, the thermal conductivity of graphene is 1880 W / (m·K), which is 4.5 times that of silver, the metal with the highest thermal conductivity. Furthermore, because the graphene is extremely thin (0.332 nm), its thermal conductivity in the thickness direction is extremely low. Heat is preferentially transferred in the plane direction, resulting in high thermal conductivity in the plane direction. Therefore, a graphene conjugate in which all graphene particles are bonded face-to-face has a thermal conductivity close to that of graphene. Meanwhile, soft metal flake powder is also thermally conductive. Therefore, the film of the present invention has three heat conduction paths: two paths for heat conduction in the film made of aggregates of soft metal flake powder and one path for heat conduction in the graphene conjugate. These three paths simultaneously function as heat conduction paths in the film. On the other hand, because the thermal conductivity of graphene composites is higher than that of films made of an aggregate of soft metal flake powder, heat conduction in the film is dominated by heat conduction in the graphene composites. Therefore, the film of the present invention has superior thermal conductivity to films made of an aggregate of soft metal flake powder. For example, when the film of the present invention is formed using flake powder made of a metal with relatively low thermal conductivity, the film has the effect of having the thermal conductivity of a metal with relatively high thermal conductivity. As a result, the film of the present invention can be used as a heat-dissipating film, taking advantage of its excellent thermal conductivity. Second, the graphene composite provides the film with better conductivity than a film made of a collection of soft metal flakes. The volume resistivity of graphene is 1.3 μΩcm, which is lower than the 1.6 μΩcm of silver, the lowest volume resistivity of any metal. The conductivity of graphene is also 7.5×10 7 S / m, the conductivity of silver, the metal with the highest conductivity, is 6.1 x 10 7S / m. On the other hand, because the thickness of graphene is extremely thin at 0.332 nm, the conductivity in the thickness direction of graphene is extremely low, and electrons preferentially move in the plane direction, resulting in high conductivity in the plane direction. Therefore, a graphene conjugate in which all graphene particles are bonded face-to-face has conductivity close to that of graphene. On the other hand, a film made of an aggregate of soft metal flake powder is also conductive. Therefore, three paths for electron movement in the film of the present invention are formed: two paths for electron movement in the film made of an aggregate of soft metal flake powder and a path for electron movement in the graphene conjugate, which has conductivity superior to that of silver, and these three paths simultaneously function as electron movement paths in the film. On the other hand, because the conductivity of the graphene conjugate is higher than that of the film made of an aggregate of soft metal flake powder, electron movement in the graphene conjugate is dominant in the film. Therefore, the film of the present invention has conductivity superior to that of the metal constituting the flake powder. For example, when the film of the present invention is formed using a flake powder made of a metal having a relatively low conductivity, the film has the effect of having the conductivity of a metal having a relatively high conductivity. Taking advantage of the excellent conductivity of the film, the film of the present invention can be used as wiring for electric circuits, electrodes, electromagnetic wave shielding films, and antistatic films. Third, the extremely strong properties of graphene are imparted to the film. Graphene is a tough material with a breaking strength of 42 N / m, more than 100 times stronger than steel, and a Young's modulus of 1020 GPa. Therefore, the graphene composite, in which all the graphene particles are joined face-to-face by friction welding, is endowed with the properties of graphene's faces, giving the composite a strength close to that of graphene. For this reasonWhen overlapping graphene particles are joined by friction welding, the graphene does not break. Meanwhile, the entire surface of a coating made of an aggregate of soft metal flake powder thinner than 5 μm is joined to the graphene conjugate by friction welding. Therefore, the coating is reinforced by the graphene conjugate, and although the coating has a thin thickness and an appearance that has a metallic luster, it has significantly greater impact strength and bending strength than the coating. Therefore, although the film of the present invention has a thickness of 10 μm or less and has a metallic luster, it can be used as a high-strength component or substrate. Fourth, the bonding strength between the graphene conjugate and the coating made of soft metal flakes is strong. The bonding strength between the soft metal flakes themselves is also strong. Therefore, the thin film with a metallic luster can be used as a high-strength component or substrate. In other words, the surface of graphene stacked face-up forms steps due to the thickness of the graphene, but because the graphene is extremely thin at 0.332 nm, the surface is extremely flat. Therefore, to bond highly flat graphene together, excessive compressive stress must be applied to the graphene clusters. In other words, when excessive compressive stress is applied to the graphene clusters, the stacked graphene clusters slide a very short distance to fill the extremely small gap, resulting in a direct overlap of the graphene clusters without forming any gaps. During this process, frictional heat is generated between the stacked graphene clusters, which instantly heat up the stacked graphene clusters. This vaporizes all impurities from the graphene clusters, and the purified graphene clusters are firmly bonded together by the frictional heat. In other words, because graphene is so thin, unless excessive compressive stress is applied to the stacked graphene, the stacked graphene does not slide over the small distance to fill the extremely small gap, and the graphene does not bond due to frictional heat. The graphene surfaces are bonded directly to each other without any intervening foreign matter, resulting in an extremely strong bonding force. Therefore, even when compressive stress or bending stress is applied to the graphene assembly, the graphene assembly does not break and has mechanical strength close to that of graphene. Furthermore, when soft metal flake powder is flattened, micron-sized undulations are formed on the surface, making the surface of the flake powder uneven. Therefore, when the entire surface of a collection of soft metal flake powders facing up is evenly compressed, the convex portions on the surface of the flake powder first come into contact with the surface of the graphene conjugate, which has excellent flatness. Furthermore, the convex portions on the surface of the flake powder undergo elastic deformation, and immediately after this, frictional heat is generated at the contact points, where the contact area has increased due to the elastic deformation. At this time, impurities present at the contact points are instantaneously vaporized, and the contact points are cleaned. Since the numerous cleaned contact points are bonded to the graphene conjugate by friction welding, the bonding strength between the surface of the soft metal flake powder and the graphene conjugate is strong. Furthermore, when compressive stress is applied to soft metal flake powders stacked face up, the convex portions formed on the surface of the flake powder come into contact with the surface of the flake powder. Furthermore, the convex portions on the surface of the powder flakes elastically deform, and immediately after this, frictional heat is generated at the contact points where the contact area has increased due to the elastic deformation. At this time, impurities present at the contact points are instantaneously vaporized, cleaning the contact points. Because numerous cleaned contact points are bonded to the surface of the powder flakes by friction welding, the bonding strength between the soft metal powder flakes is also strong. The bonding strength at the contact points increases with the area of ​​the contact points. Therefore, the bonding strength between the powder flakes is greater than the bonding strength between the powder flakes and the graphene conjugate. As a result, even when an impact force or bending stress is applied to the film, the bonding between the powder flakes is not destroyed, and the coating consisting of the aggregate of the soft metal powder flakes is not peeled off from the surface of the graphene conjugate. Therefore, the film of the present invention is a thin film that emits a metallic luster, but can be used as a high-strength part or substrate. Fifth, because a coating consisting of an aggregate of soft metal flake powder and having a thickness of less than 5 μm is friction-welded to both surfaces of a graphene conjugate having a thickness of less than 0.1 μm, the weight and thickness of the resulting film are almost the same as those of the two coatings. Meanwhile, the film has mechanical strength similar to that of a graphene conjugate. Therefore, the film of the present invention, which has a metallic luster and a thickness of 10 μm or less, can be used as a high-strength component or substrate. Sixth, because a coating made of an aggregate of soft metal flake powder and having a thickness of less than 5 μm is friction-welded to both surfaces of a graphene conjugate having a thickness of less than 0.1 μm, the coating is not destroyed by impact or bending stress. In other words, the thinner the coating made of an aggregate of soft metal flake powder, the greater the aspect ratio of the surface area to the thickness formed by the coating. The greater the aspect ratio, the greater the bonding strength between the coating and the graphene conjugate. Therefore, even if the coating is thinner than 5 μm, when an impact is applied to the film, the impact is transmitted to the graphene conjugate via the coating, and the coating is not destroyed. Furthermore, when bending stress is applied to the formed film, the bending stress is transmitted to the graphene conjugate via the coating, and the coating is not destroyed. Therefore, although the film has a metallic luster in appearance, it can be used as a high-strength component or substrate. Seventh, because a coating made of an aggregate of soft metal flake powder and having a thickness of less than 5 μm is friction-welded to both surfaces of a graphene conjugate having a thickness of less than 0.1 μm, the coating can be friction-welded to the graphene conjugate regardless of the material of the flake powder. As a result, the surface of the film of the present invention exhibits the luster of various metals and exhibits the properties of various flake powders. Eighth, the eight steps for forming the film are all extremely simple. Furthermore, the raw materials used are all general-purpose materials. That is, graphite particles are a general-purpose industrial material, and methanol and alcohols with a viscosity of 2-10 mPa·sec are general-purpose alcohols. Furthermore, soft metal flake powder is a general-purpose industrial substrate. Therefore, the film of the present invention provides a variety of groundbreaking effects and can be produced inexpensively. As described above, the film of the present invention has a different composition and structure from conventional films. Therefore, unlike conventional films made of metals or alloys or synthetic resins, the film exhibits a synergistic effect inherent to the flake powder and graphene conjugates. This solves all of the problems described in paragraph 7.

[0011] The method of forming the film described in paragraph 8 is The soft metal flake powder described in paragraph 8 is made of gold, silver, copper or aluminum. Either one of the following It is a flake powder, Either one of the following The flake powder is used as the flake powder made of the soft metal described in paragraph 8, and the film is formed according to the method described in paragraph 8. centre 9. The method of forming a film of paragraph 8, comprising forming a film.

[0012] Specifically, soft metal flake powder is produced by flattening soft metal powder (except aluminum, gold, silver, copper, tin, or zinc) using a stamp mill. This flake powder has a smooth surface, resulting in a low coefficient of friction of 0.20–0.25. Therefore, soft metal flake powder has a lubricating surface and possesses both electrical and thermal conductivity due to the soft metal's properties. Furthermore, it has a high aspect ratio, which is the ratio of the powder's surface area to its thickness. Therefore, by stacking flake powders face up, a small amount of flake powder can be used to form a coating that combines lubricity, electrical conductivity, and thermal conductivity. Aluminum flake powder, due to the high activity of aluminum particles, is produced by atomization and then flattened using a wet ball mill. On the other hand, flake powders made from soft metals are characterized by their superiority in five properties: heat resistance, cold resistance, load-bearing capacity, thermal conductivity, and electrical conductivity, compared to lubricating flat powders made from metal oxides such as glass, mica, alumina, silica, and iron oxide, inorganic compounds such as molybdenum disulfide, tungsten disulfide, boron nitride, and graphite fluoride, and graphite particles known as scaly graphite or flake graphite. In other words, most flat powders made from metal oxides and inorganic compounds have excellent heat resistance, but are electrically insulating. Graphite particles, on the other hand, are inferior to soft metals in terms of heat resistance, thermal conductivity, and electrical conductivity. In other words, the thermal conductivity and electrical conductivity of metals are best in the order of silver, copper, gold, and aluminum. The thermal conductivity and electrical conductivity of these metals are better than those of alloys. On the other hand, metals made of soft metals have significantly different densities. For example, the density of gold is 19.32 g / cm 3 The density of silver is 10.49 g / cm 3 The density of copper is 8.96 g / cm 3 The density of aluminum is 2.70 g / cm 3 Therefore, the density of gold is 7.2 times greater than that of aluminum. In contrast, the density of alcohol remains nearly constant regardless of the viscosity of the alcohol. Therefore, the weight of soft metal flake powder varies significantly depending on the density of the metal that makes up the flake powder. Therefore, in the third step described in paragraph 8, flake powder with a relatively high density is dispersed in a relatively high-viscosity alcohol, while flake powder with a relatively low density is dispersed in a relatively low-viscosity alcohol. This increases the adsorption force between the flake powder with a relatively high density and the alcohol. In the fourth step, the second suspension, in which the flake powder with a relatively high density (i.e., the flake powder with a relatively high weight) is dispersed in alcohol, can adsorb to the surface of the graphene conjugate. Therefore, soft metal flake powder was dispersed in alcohols with viscosities ranging from 2 to 10 mPa·sec at 20°C, depending on the density range of the soft metal flake powder. On the other hand, the melting point of tin is 232°C, and it becomes brittle at low temperatures from around -40°C. For this reason, tin flake powder is not suitable as flake powder to form a film that is both heat-resistant and cold-resistant. Zinc also has a melting point of 420°C, and like tin, it becomes brittle at low temperatures. For this reason, zinc flake powder is not suitable as flake powder to form a cold-resistant film. The melting points of aluminum, silver, copper, and gold are all high at 660°C, 962°C, 1085°C, and 1064°C, respectively, and these four metals do not become brittle at low temperatures. Therefore, films bonded with coatings made from an aggregate of flake powder made from soft metals other than tin and zinc can be used in harsh environments where oil lubrication is not possible, such as high temperatures, extremely low temperatures, ultra-vacuum, and ultra-high pressure. Furthermore, soft metals other than tin have a high load-bearing capacity of 600 MPa. Therefore, when forming a film, the aggregate of flake powder is compressed, but the flat surfaces of the flake powder can withstand the compressive stress. Furthermore, flake powder made from soft metals has a smooth surface, but the surface is not flat; the inherent surface roughness is formed when the raw powder is flattened. In contrast, the graphene that makes up the graphene junction is a single-crystal material with a melting point exceeding 3000°C, making it highly heat-resistant. Furthermore, it is a tough material with a breaking strength of 42 N / m, more than 100 times stronger than steel, and a Young's modulus of 1020 GPa. It is also an extremely stable substance that does not react with any acid or alkali. Therefore, a film in which a coating made of an aggregate of gold, silver, copper, or aluminum flake powder is friction-welded to both surfaces of a graphene conjugate can be used in harsh environments such as high temperatures, extremely low temperatures, ultra-vacuums, and ultra-high pressures. Furthermore, soft metals can be combined with metals with low mutual solubility between them, and when the film of the present invention is used as a sliding member, the amount of wear on the sliding surface is drastically reduced. For example, silver-coated copper flake powder, in which the surface of copper flake powder is coated with silver by plating, or silver flake powder, has a mutual solubility between iron, nickel, cobalt, or chromium and silver, which is close to zero. Therefore, when a sliding member made of these metals and a film made of silver-coated copper flake powder or silver flake powder are used as the sliding surface of a film, the sliding properties at the sliding surface are further improved and the amount of wear on the sliding surface is reduced. Also, when a sliding member made of these metals and a film made of copper flake powder have a low mutual solubility with chromium, molybdenum, tungsten, or niobium, and copper, the sliding properties at the sliding surface are improved and the amount of wear on the film is reduced. Furthermore, soft metals have excellent electromagnetic wave shielding properties, allowing the film of the present invention to be used as an electromagnetic wave shielding film. Specifically, if the electrical conductivity of copper is taken as 1, and the relative electrical conductivity is taken as a, and the magnetic permeability of copper is taken as 1, and the relative magnetic permeability is taken as b, then a / b indicates the degree of electromagnetic wave reflection loss, and a·b indicates the degree of electromagnetic wave absorption loss. Metals with a high degree of electromagnetic wave reflection loss include silver (a / b = 1.06), copper (a / b = 1.00), gold (a / b = 0.78), and aluminum (a / b = 0.63). Nickel has a low a / b ratio of 0.23, and iron has an even lower a / b ratio of 0.0017. Metals with a high degree of electromagnetic wave absorption loss include silver, with an a·b ratio of 1.06; copper, with an a·b ratio of 1.00; gold, with an a·b ratio of 0.78; and aluminum, with an a·b ratio of 0.63. Nickel has a low a·b ratio of 0.23, while iron has a high a·b ratio of 17. Therefore, flake powder made from soft metals consisting of silver, copper, gold, and aluminum has high electromagnetic wave shielding performance. Therefore, films bonded with a coating made from an aggregate of flake powder made from soft metals other than zinc and tin function as electromagnetic wave shielding films. Furthermore, because soft metals made from silver, copper, gold, and aluminum have excellent conductivity, films bonded with a coating made from an aggregate of soft metal flake powder can be used as antistatic films. As explained above, flake powders made of gold, silver, copper, or aluminum are suitable for use in forming films that combine electrical conductivity, thermal conductivity, lubricity, electromagnetic wave shielding properties, antistatic properties, heat resistance, and cold resistance. Therefore, by selecting the soft metal material according to the specifications required of the film, the film of the present invention has versatility.

[0013] The method of forming the film described in paragraph 8 is The alcohol having the property of a viscosity of 2-10 mPa·sec at 20°C as described in paragraph 8 is 1-propanol, 2-propanol, 1-butanol, 1-pentanol, tertiary butyl alcohol, 2-pentanol, 3-methyl-1-butanol, tertiary amyl alcohol, 21-methyl-2-butanol, 2-butanol, 2-methyl-1-butanol, 2-heptanol, isobutyl alcohol, 4-methyl-2-pentanol, 1-hexanol, 3-pentanol, 2-octanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, or isooctyl alcohol, Either one of the following The method of forming a film described in paragraph 8, wherein the alcohol has a viscosity of 2-10 mPa·sec at 20°C as described in paragraph 8, and a film is formed according to the method of forming a film described in paragraph 8.

[0014] Specifically, the alcohol described below has a viscosity of 2-10 mPa·sec at 20°C, a boiling point below 200°C, and is a commonly used alcohol. Therefore, the alcohol described in paragraph 8, which has a viscosity of 2-10 mPa·sec at 20°C, is suitable. Therefore, as described in paragraph 12, an alcohol with an appropriate viscosity is selected based on the density of the soft metal, and the second suspension is prepared in the third step described in paragraph 8. The viscosity of the second suspension is adjusted by the volume ratio between the weight of the weighed alcohol converted based on its density and the weight of the weighed flake powder converted based on its density. While the third step in paragraph 8 describes a volume ratio of 3:1, the volume ratio can vary between 2.5-3.5 and 0.5-1.5, so the viscosity of the second suspension changes depending on the volume ratio. 2-Propanol (CH3)2CH(OH) has a viscosity of 1.8 mPa·s at 20°C and a low boiling point of 82°C. 1-propanol CH3(CH2)2OH has a viscosity of 1.9 mPa·sec at 20°C and a low boiling point of 98°C. 1-butanol CH3(CH2)3OH has a viscosity of 3.0 mPa·s at 20°C and a low boiling point of 117°C. 1-Pentanol CH3(CH2)4OH has a viscosity of 3.3 mPa·s at 20°C and a boiling point of 138°C. Tertiary butyl alcohol (CH3)3C(OH) has a viscosity of 3.4 mPa·s at 30°C and a low boiling point of 82°C. 2-Pentanol CH3(CH2)CH(OH)CH3 has a viscosity of 3.5 mPa·s at 20°C and a low boiling point of 119°C. 3-Methyl-1-butanol (CH3)2CH(CH2)2OH has a viscosity of 3.7 mPa·s at 20°C and a boiling point of 131°C. Tertiary amyl alcohol CH3CH2COH(CH3)2 has a viscosity of 3.8 mPa·s at 25°C and a low boiling point of 103°C. 2-Methyl-2-butanol (CH3)2C(OH)CH2CH3 has a viscosity of 3.8 mPa·s at 25°C and a low boiling point of 103°C. 2-butanol CH3CH2CH(OH)CH3 has a viscosity of 3.9 mPa·sec at 20°C and a low boiling point of 99°C. 2-Methyl-1-butanol CH3CH2CH(CH3)CH2OH has a viscosity of 4.0 mPa·s at 20°C and a low boiling point of 108°C. 2-Heptanol CH3(CH2)4CH(OH)CH3 has a viscosity of 4.0 mPa·s at 20°C and a boiling point of 159°C. Isobutyl alcohol (CH3)2CHCH2OH has a viscosity of 4.0 mPa·s at 20°C and a low boiling point of 108°C. 4-Methyl-2-pentanol (CH3)2CHCH2CHOHCH3 has a viscosity of 4.1 mPa·s at 20°C and a boiling point of 132°C. 1-Hexanol CH3(CH2)5OH has a viscosity of 5.3 mPa·s at 20°C and a boiling point of 157°C. 3-Pentanol CH3CH2CH(OH)CH2CH3 has a viscosity of 6.4 mPa·s at 20°C and a boiling point of 116°C. 2-Octanol CH3(CH2)5CH(OH)CH3 has a viscosity of 6.2 mPa·s at 20°C and a boiling point of 178°C. 1-Heptanol CH3(CH2)6OH has a viscosity of 5.8 mPa·s at 25°C and a boiling point of 176°C. 1-Octanol CH3(CH2)7OH has a viscosity of 7.3 mPa·s at 25°C and a boiling point of 194°C. 2-Ethyl-1-hexanol, CH3(CH2)3CH(C2H5)CH2OH, has a viscosity of 9.8 mPa·s at 25°C and a boiling point of 185°C. Isooctyl alcohol CH3(CH2)7OH has a viscosity of 10.6 mPa·s at 15°C and a boiling point of 188°C.

[0015] The method of joining the film formed by the method described in paragraph 8 to the surface of a substrate or part by friction welding is as follows: 8 A method for friction welding a film formed by the method described in paragraph 8 to the surface of a substrate or part, comprising: forming a film by the method described in paragraph 8; placing the film on the surface of a substrate or part to be joined; preparing a flat plate of the same size as the film; overlapping the flat plate on the surface of the film; uniformly compressing the entire surface of the flat plate; and joining the film to the surface of the substrate or part by friction welding; thereafter, applying impact acceleration simultaneously to multiple locations on one side of the flat plate to separate the flat plate from the film; thereby forming the film joined to the surface of the substrate or part by friction welding;

[0016] In other words, the surface of the substrate or part and the surface of the flat plate have micron-sized irregularities due to processing. Therefore, when a film is placed on the surface of the substrate or part, and then a flat plate is placed on the surface of the film, and the entire surface of the flat plate is then evenly compressed, the convex portions on the surface of the substrate or part first come into contact with the flake powder on the surface of the film, and then the convex portions of the flake powder on the surface of the film come into contact with the surface of the substrate or part. At the same time, the convex portions of the flake powder on the surface of the film come into contact with the surface of the flat plate, and then the convex portions of the flat plate come into contact with the flake powder on the surface of the film. Furthermore, high-temperature frictional heat is generated, albeit for an extremely short time, between the convex portions on the surface of the substrate or part and the convex portions of the flake powder on the surface of the film, and between the convex portions on the surface of the flat plate and the convex portions of the flake powder on the surface of the film. At this time, impurities present at the contact points are instantly vaporized, and the contact points are cleaned. Numerous clean contact points are used to friction-weld the surface of a substrate or part to the surface of a film, and also to friction-weld the surface of a film to the surface of a flat plate. Because the joints are free of foreign matter, the joining strength achieved by friction welding is strong. Therefore, as long as the substrate or part can withstand compressive stress, there are no restrictions on the material or shape of the substrate or part. Next, impact acceleration is applied simultaneously to multiple locations on one side of the flat plate, separating the flat plate from the film. In other words, when subjected to compressive stress, the convex portions on the surface of the substrate or component and the convex portions on the surface of the flat plate do not undergo elastic or plastic deformation, so the bonded area formed between the convex portions on the surface of the substrate or component and the convex portions on the surface of the flat plate on the film is extremely small, approaching a point. In contrast, the contact area formed between the flake powder constituting the film surface and the surface of the substrate or component and the surface of the flat plate undergoes elastic deformation, so the bonded area formed by the flake powder between the surface of the substrate or component and the surface of the flat plate is a surface rather than a point. Therefore, the bonding strength between the convex portions on the surface of the substrate or component and the convex portions on the surface of the flat plate and the film surface is smaller than the bonding strength between the flake powder and the surface of the substrate or component and the surface of the flat plate. In other words, the magnitude of the bonding strength varies depending on the area of ​​the bonded area, so the bonding strength at a bonded area that is close to a point is smaller than the bonding strength at a bonded area that forms a surface. Therefore, when impact acceleration is applied simultaneously to multiple locations on the side of the flat plate, the impact acceleration is applied directly to all contact points formed by the surface of the flat plate in a direction perpendicular to the direction in which the compressive stress is applied, and because the area of ​​the joints formed by the surface of the flat plate is extremely small, the joints formed by the surface of the flat plate are first destroyed. This reduces the bonding strength between the surface of the flat plate and the surface of the film. Next, impact acceleration is applied directly to all joints formed by the flake powder on the surface of the flat plate in a direction perpendicular to the direction in which the compressive stress is applied, destroying the joints formed by the flake powder on the surface of the flat plate and causing the film to be peeled off from the surface of the flat plate.

[0017] By friction welding the film formed by the method described in paragraph 8 onto the surface of a substrate or part prepared by the method described above, the properties of the film can be imparted to the surface of the substrate or part. In other words, the thermal conductivity and electrical conductivity of the film described in paragraph 10, as well as the lubricity, electromagnetic shielding properties, and antistatic properties based on the properties of the flake powder on the surface of the film described in paragraph 12, are imparted to the surface of the substrate or part. [Brief explanation of the drawings]

[0018] [Figure 1]FIG. 10 is an enlarged view of a portion of the side of a film in which a coating made of an aggregate of silver flake powder is formed on both surfaces of a graphene composite. DETAILED DESCRIPTION OF THE INVENTION

[0019] Example 1 This example is an example in which a suspension consisting of an assembly of graphene separated into individual sheets in methanol is prepared in a container according to the method described in the first and second steps of paragraph 8. First, 5 liters of methanol was filled into a shallow container with a base of 2.2 m x 2.2 m. Next, two parallel plate electrodes with an effective area of ​​2m x 2m were prepared, and an electric field was generated in the gap between them. The two parallel plate electrodes were stacked with a gap of 100μm between them. Graphite particles were evenly spread in this gap and precipitated in methanol. The graphite particles were assumed to be spheres with a particle size of 25μm, and when the graphite particles were evenly spread in the 100μm gap created by the two parallel plate electrodes, the number of particles was 2.6 x 10 8 When a DC voltage of 10.6 kV or more is applied to this collection of graphite particles, the interlayer bonds on the basal planes of all the graphite particles are simultaneously destroyed. 13 A cluster of graphene particles was obtained, and the cluster of graphite particles used was only 4.72 g. 50 g of flake graphite particles (e.g., XD100 from Ito Graphite Industries Co., Ltd.) were laid on the surface of parallel plate electrodes with an effective area of ​​2 m x 2 m, generating an electric field. This parallel plate electrode was immersed in a container filled with methanol, and another parallel plate electrode was placed on top of the first parallel plate electrode. The two parallel plate electrodes were separated by a 100 μm gap, and a 12 kV DC voltage was applied between the electrodes. Next, the gap between the two parallel plate electrodes was widened, and the two parallel plate electrodes were tilted in the methanol. Vibration accelerations of 0.2 G in three directions were repeatedly applied to the container, after which the two parallel plate electrodes were removed from the container. Furthermore, ultrasonic vibrations of 20 kHz were applied to the methanol in the container for 2 minutes using an ultrasonic homogenizer (LUH300 from Yamato Scientific Co., Ltd.). The ultrasonic homogenizer was then removed from the container. After this, the graphene aggregates dispersed in the methanol in the container were stirred to create a suspension consisting of aggregates of graphene separated into individual sheets in the methanol. Next, a portion of the prepared sample was removed and observed and analyzed using an electron microscope. The electron microscope used was an ultra-low accelerating voltage SEM from JFE Techno-Research Corporation. This device is capable of surface observation at ultra-low accelerating voltages starting from 100 volts, and has the advantage of being able to directly observe the surface of a sample without forming a conductive coating on the sample. Secondary electron beams between 900-1000 volts were extracted from the electron beam reflected from the surface of the sample and image processing was performed. It was confirmed that the material dispersed in methanol was an extremely thin, flat material. Furthermore, image processing of the energy and intensity of the characteristic X-rays revealed that only carbon atoms were present. This confirmed that the material was graphene. As a result, a collection of flake graphite particles is laid in the gap between two parallel plate electrodes, and a direct current potential difference is applied between the electrodes. An electric field equivalent to this potential difference divided by the size of the gap between the two parallel plate electrodes is generated in the electrode gap where the collection of flake graphite particles is located.This electric field simultaneously applies a Coulomb force to all π electrons, which are responsible for the interlayer bonds of the basal planes of all graphite particles, sufficient to destroy the interlayer bonds of the basal planes made of graphite crystals.As a result, all interlayer bonds of the graphite crystals are simultaneously destroyed, and it was confirmed that a basal plane made of graphite crystals, i.e., a collection of graphene, can be produced.

[0020] Example 2 This example is a first example in which a second suspension is prepared by dispersing a collection of flake powder made of soft metal in alcohol according to the method described in the third step of paragraph 8. Silver flake powder (YFS-2 Silver Flakes from Yamamoto Precious Metals Co., Ltd.) was used as the soft metal flake powder. 1-Hexanol CH3(CH2)5OH, which has a viscosity of 5.3 mPa·s at 20°C and a boiling point of 157°C, was used as the alcohol. The silver flake powder was thin flake powder with an average major axis diameter of 3.85 μm, an average minor axis diameter of 2.72 μm, an average thickness of 0.26 μm, and an average aspect ratio of 14.76. 100 g of 1-hexanol was mixed with 430 g of silver flake powder and stirred to prepare a second suspension. 3 When converted to volume using the density of 3 Also, 430g of silver flake powder occupies a volume of 10.49g / cm 3 When converted to volume based on the density of 3 Therefore, the volume ratio of 100g of 1-hexanol to 643g of silver flake powder is 3.0 to 1.0.

[0021] Example 3 This example is a second example in which a second suspension is prepared by dispersing a collection of flake powder made of soft metal in alcohol according to the method described in the third step of paragraph 8. Copper flake powder (MS-800, product of Fukuda Metal Foil and Powder Co., Ltd.) was used as the flake powder made from soft metal. 2-heptanol CH3(CH2)4CH(OH)CH3, which has a viscosity of 4.0 mPa·s at 20°C and a boiling point of 159°C, was used as the alcohol. The particle size distribution of the copper flake powder was such that +75 μm was more than 4%, +45 μm was more than 25%, and -45 μm was less than 75%. The particle size is relatively large for flake powder. 100 g of 2-heptanol was mixed with 365 g of copper flake powder and stirred to prepare a second suspension. 3 When converted to volume using the density of 3 Also, 365g of copper flake powder occupies a volume of 8.96g / cm 3 When converted to volume using the density of 3 Therefore, the volume ratio of 100g of 1-hexanol to 365g of silver flake powder is 3.0 to 1.0.

[0022] Example 4 In this example, a collection of randomly stacked graphene is formed face up in a container according to the method described in the fourth step of paragraph 8. First, a container with an inner size of 10 cm x 10 cm x 2 cm (thickness) is prepared. A vibrator is also prepared. Next, the suspension prepared in Example 1 is poured into the container to a height of 3 mm. The container is then placed on the vibration table of the vibrator, and the vibrator is operated. Vibration accelerations of 0.1 G are applied to the suspension in the front-to-back, left-to-right, and up-to-down directions, repeated three times in each direction, and finally, a vibration acceleration of 0.1 G is applied in the up-to-down direction. The container is then heated to the boiling point of methanol, and the methanol is evaporated from the suspension, forming a cluster of randomly stacked graphene particles face up inside the container.

[0023] Example 5 This example is an example of forming a graphene conjugate according to the method described in the fifth step of paragraph 8. First, a flat plate measuring 10 cm × 10 cm × 3 cm (thickness) was prepared. The flat plate was then placed on the surface of the graphene assembly in the container prepared in Example 4. Then, cylinders with a diameter of 2 cm and a thickness of 2 cm were placed at nine locations on a diagonal line connecting the corners of the upper surface of the flat plate, including five equally spaced locations and four locations corresponding to the centers of the two locations closest to the corners on the diagonal line. A compressive load equivalent to 40 kg was simultaneously applied to the nine cylinders, producing a graphene composite. An impact acceleration of 0.3 G was then simultaneously applied to five locations on the bottom of the container, corresponding to five locations on a diagonal line connecting the corners of the surface of the plate, to peel the graphene conjugate from the bottom of the container. An impact acceleration of 0.3 G was then simultaneously applied to three locations on one side of the plate, to peel the graphene conjugate from the plate, and the graphene conjugate was extracted. The thickness of the graphene conjugate was observed using the electron microscope used in Example 1, and was found to be 600 nm.

[0024] Example 6 This example is an example in which, following the method described in the sixth step of paragraph 8, a collection of silver flake powder is created in a container in which the silver flake powder is randomly stacked on top of each other in 1-hexanol, with the silver flake powder side up, in comparison with the suspension of silver flake powder prepared in Example 2 dispersed in 1-hexanol. First, a container measuring 12 cm × 12 cm × 5 cm (thickness) was prepared. Next, the suspension prepared in Example 2 was poured into the container in a volume equal to the volume of the suspension poured into the container in Example 4. Thereafter, the container was placed on the vibration table of the vibration exciter used in Example 4, and the vibration exciter was operated to repeatedly apply a vibration acceleration of 0.3 G to the suspension in each of the forward / backward, left / right, and up / down directions three times in turn. Finally, a vibration acceleration of 0.3 G was applied in the up / down direction, creating a cluster of silver flake powder in the container, with the silver flake powder facing up and randomly overlapping in 1-hexanol.

[0025] Example 7 In this example, a cluster of randomly overlapping silver flakes is formed face up on both surfaces of a graphene conjugate according to the method described in the seventh step of paragraph 8. In Example 6, the graphene conjugate prepared in Example 5 was immersed entirely in a container containing a collection of randomly overlapping silver flake powder in 1-hexanol with the silver flake powder facing up. Thereafter, the graphene conjugate was removed from the container. Two flat plates measuring 12 cm × 12 cm × 2 cm (thickness) were then prepared. The removed graphene conjugate was then sandwiched between the two flat plates. The two flat plates were then heated to 185°C, the boiling point of 1-hexanol, to evaporate the 1-hexanol from the suspension prepared in Example 6, forming clusters of silver flake powder on both surfaces of the graphene conjugate, with the faces facing up and randomly overlapping each other.

[0026] Example 8 This example is an example in which, according to the method described in the eighth step in paragraph 8, coatings made of aggregates of silver flake powder formed by friction welding are formed on both surfaces of a graphene conjugate by friction welding. In Example 7, a graphene composite was sandwiched between two flat plates. Cylinders each having a diameter of 2 cm and a thickness of 2 cm were placed at nine locations on the surface of the upper flat plate of the two plates, including five locations equally spaced apart on a diagonal line connecting the corners of the surface of the upper flat plate and four locations corresponding to the centers of two of the five locations closest to the corners on the diagonal line, and a compressive load equivalent to 12 kg was simultaneously applied to the nine cylinders. After this, an impact acceleration of 0.3 G was simultaneously applied to three locations on one side of the upper plate of the two flat plates, and then an impact acceleration of 0.3 G was simultaneously applied to three locations on one side of the lower plate of the two flat plates, and the film formed in the gap between the two flat plates was removed. First, the side of the prepared film was observed using the electron microscope used in Example 1. A 4 μm-thick silver film was formed on both surfaces of the 600 nm-thick graphene conjugates. Figure 1 shows an enlarged schematic view of a portion of the side of the film. 1 is the film made of an aggregate of silver flake powder, and 2 is the graphene conjugates. Next, the surface resistance of the film surface was measured using a surface resistance meter (Simco Japan Co., Ltd. surface resistance meter ST-4). The surface resistance value was 1×10 3 Since the surface resistance was less than Ω / □, the film had a surface resistance close to that of silver. Furthermore, the thermal conductivity of the film was measured. The thermal conductivity of the film was measured using a cyclic heating diffusivity measurement device (FTC-1 manufactured by Advance Riko Co., Ltd.) based on the cyclic heating method, a type of unsteady state method. The thermal conductivity of the film at 20°C was 610±20 W / (m·K), a thermal conductivity superior to that of silver. Furthermore, the coefficient of friction of the film surface was repeatedly measured using a measuring device (Shimadzu Corporation's tabletop precision universal testing machine, Autograph AGS-X) to measure the static and dynamic coefficients of friction. The static coefficient of friction was 0.18±0.05, and the dynamic coefficient of friction was 0.12±0.03. Both coefficients of friction were small, close to those of silver flake powder. Therefore, the film can be used not only as a lubricating film with a low coefficient of friction, but also as a water-repellent and stain-resistant film. Furthermore, the impact strength of the film was measured by drop impact. The film was allowed to drop from a height of 2m three times, but no change was observed in the film. Furthermore, the film was allowed to drop from a height of 4m three times, but no change was observed in the film. Therefore, the film had excellent impact strength. The refractive index of the film was then measured using an Instron universal testing machine by a three-point bending test. 4 The film had a bending strength of 1020 GPa. Hot-rolled steel sheets are commercially available with a bending strength of 980 MPa. Therefore, the film had a bending strength 74 times that of hot-rolled steel sheets. The Young's modulus of silver is 83 GPa, while that of graphene is 1020 GPa.

[0027] Example 9 This example is an example in which, following the method described in the sixth step of paragraph 8, a collection of copper flake powder is created in a container in which the copper flake powder is randomly stacked on top of each other in 2-heptanol, with the copper flake powder surface facing up, in comparison with the suspension of copper flake powder prepared in Example 3 dispersed in 2-heptanol. First, a container measuring 12 cm × 12 cm × 5 cm (thickness) was prepared. Next, the suspension of copper flake powder dispersed in 2-heptanol prepared in Example 3 was poured into the container in the same volume as the suspension poured into the container in Example 4. Thereafter, the container was placed on the vibration table of the vibrator used in Example 4, and the vibrator was operated. A vibration acceleration of 0.3 G was repeatedly applied to the suspension in the front-to-back, left-to-right, and up-to-down directions three times in each direction, and finally a vibration acceleration of 0.3 G was applied in the up-to-down direction, creating a cluster of copper flake powder in the container, with the copper flake powder facing up and randomly overlapping in the 2-heptanol.

[0028] Example 10 In this example, a cluster of randomly stacked copper flakes is formed face up on both surfaces of a graphene conjugate according to the method described in the seventh step of paragraph 8. In Example 9, the graphene conjugate prepared in Example 5 was immersed entirely in a container containing copper flake powder with the copper flake powder side up, forming a mass of copper flake powder randomly overlapping each other in 2-heptanol. Thereafter, the graphene conjugate was removed from the container. Two flat plates measuring 12 cm × 12 cm × 2 cm (thickness) were prepared. The removed graphene conjugate was then sandwiched between the two flat plates. The two flat plates were then heated to 159°C, the boiling point of 2-heptanol, to evaporate the 2-heptanol from the suspension prepared in Example 9, forming clusters of copper flake powder that were randomly stacked face up on both surfaces of the graphene conjugate.

[0029] Example 11 This example is an example in which, according to the method described in the eighth step in paragraph 8, copper flake powder is joined together by friction welding, and a film made of the flake powder is formed by friction welding on both surfaces of a graphene conjugate. In Example 10, a graphene composite was sandwiched between two flat plates. Cylinders each having a diameter of 2 cm and a thickness of 2 cm were placed at nine locations on the surface of the upper flat plate of the two plates, including five locations equally spaced apart on a diagonal line connecting the corners of the surface of the upper flat plate and four locations corresponding to the centers of two of the five locations closest to the corners on the diagonal line, and a compressive load equivalent to 12 kg was simultaneously applied to the nine cylinders. After this, an impact acceleration of 0.3 G was simultaneously applied to three locations on one side of the upper plate of the two flat plates, and then an impact acceleration of 0.3 G was simultaneously applied to three locations on one side of the lower plate of the two flat plates, and the film formed in the gap between the two flat plates was removed. First, the side surfaces of the produced film were observed with the electron microscope used in Example 1. Copper coatings each having a thickness of 3 μm were formed on both surfaces of the graphene conjugate having a thickness of 600 nm. Next, the surface resistance of the film surface was measured using a surface resistance meter (Simco Japan Co., Ltd. surface resistance meter ST-4). The surface resistance value was 1×10 3Since the surface resistance was less than Ω / □, the film had a surface resistance close to that of copper. Furthermore, the thermal conductivity of the film was measured. The thermal conductivity of the film was measured using a cyclic heating diffusivity measurement device (FTC-1 manufactured by Advance Riko Co., Ltd.) based on the cyclic heating method, a type of unsteady state method. The thermal conductivity of the film at 20°C was 550±20 W / (m·K), a thermal conductivity superior to that of silver. Furthermore, the coefficient of friction of the film surface was repeatedly measured using a measuring device (Shimadzu Corporation's tabletop precision universal testing machine, Autograph AGS-X) to measure the static and dynamic coefficients of friction. The static coefficient of friction was 0.20 ± 0.05, and the dynamic coefficient of friction was 0.15 ± 0.03. Both coefficients of friction were small, close to those of copper flake powder. Therefore, the film can be used not only as a lubricating film with a low coefficient of friction, but also as a water-repellent and stain-resistant film. Furthermore, the impact strength of the film was measured by drop impact. The film was allowed to drop from a height of 2m three times, but no change was observed in the film. Furthermore, the film was allowed to drop from a height of 4m three times, but no change was observed in the film. Therefore, the film had excellent impact strength. Next, the refractive index of the film was measured by a three-point bending test using an Instron universal testing machine. 4 MPa. Hot-rolled steel sheets with a bending strength of 980 MPa are commercially available. Therefore, the film had a bending strength 92 times that of hot-rolled steel sheets. Furthermore, the Young's modulus of copper is 117 GPa, while that of graphene is 1020 GPa.

[0030] In the examples, metal flake powder made of silver and copper was used, but the material of the metal flake powder that can be used in the present invention is not limited to the metal flake powder made of silver and copper in the examples, and flake powder made of gold and aluminum can also be used. Furthermore, the thickness of the graphene conjugate and the thickness of the coating made of an aggregate of metal flake powder are not limited to the thicknesses formed in the examples. Furthermore, the size of the graphene conjugate and the size of the coating made of an aggregate of metal flake powder are not limited to the sizes formed in the examples. In other words, the thickness and size of the graphene conjugate can be freely changed by the size of the container and the amount of the first suspension poured into the container. Furthermore, the thickness and size of the coating made of an aggregate of metal flake powder can be freely changed by the viscosity of the alcohol used, the size of the container, and the amount of the second suspension poured into the container. Therefore, because a coating made of an aggregate of metal flake powder is bonded to both surfaces of the graphene conjugate by friction welding, a film can be formed in which a coating made of an aggregate of metal flake powder is bonded to both surfaces of the graphene conjugate, regardless of the thickness and size of the graphene and the thickness and size of the coating made of an aggregate of metal flake powder. Therefore, the thickness and size of the graphene, the material of the metal flake powder, and the thickness and size of the coating made of an aggregate of metal flake powder are determined depending on the application of the film. [Explanation of symbols]

[0031] 1. A film made of an aggregate of silver flakes 2. A graphene junction

Claims

1. A method for forming a film having a thickness of 10 μm or less, which has excellent thermal conductivity, electrical conductivity, and mechanical strength and has a metallic luster, is provided by friction-welding a coating formed by friction-welding soft metal flake powders together to both surfaces of a graphene conjugate, the method comprising: A cluster of flake graphite particles or a cluster of lump graphite particles is spread evenly on the surface of one of the parallel plate electrodes constituting a pair of electrodes consisting of two parallel plates, and the one parallel plate electrode is immersed in methanol filled in a first container. The other parallel plate electrode is placed on top of the one parallel plate electrode via the cluster of flake graphite particles or the cluster of lump graphite particles, and the two parallel plate electrode pair consisting of the one parallel plate electrode and the other parallel plate electrode is immersed in the methanol. Thereafter, a direct current potential difference of a predetermined magnitude is applied to the gap between the pair of electrodes consisting of the two parallel plates. As a result, an electric field corresponding to the value obtained by dividing the magnitude of the potential difference by the size of the gap between the pair of electrodes consisting of the two parallel plates is generated between the cluster of flake graphite particles or the a first step of applying an electric field to a collection of aggregate graphite particles, wherein the application of the electric field simultaneously destroys all interlayer bonds of the basal planes of the graphite crystals forming the flake graphite particles or the aggregate graphite particles, and a collection of graphene made of the basal planes is precipitated in the gap between the electrode pair made of the two parallel plates; thereafter, the gap between the electrode pair made of the two parallel plates is enlarged, and the electrode pair made of the two parallel plates is tilted in the methanol; further, vibration accelerations are repeatedly applied to the first container in three directions, left and right, front and back, and up and down, in order, to move the collection of graphene from the gap between the electrode pair made of the two parallel plates into the methanol; thereafter, the electrode pair made of the two parallel plates is removed from the first container; a second step of operating an ultrasonic homogenizer device in the first container to repeatedly apply shock waves to the graphene aggregates through the methanol, thereby separating the graphene aggregates into individual graphene sheets in the methanol, and then removing the homogenizer device from the first container to prepare a first suspension in the first container that is composed of the graphene aggregates separated into individual graphene sheets in the methanol; a third step of weighing an alcohol having a viscosity of 2-10 mPa seconds at 20°C and converting the weight of the alcohol based on the density of the alcohol to a volume obtained by weighing a collection of flake powder made of soft metal and converting the weight of the flake powder based on the density of the soft metal that constitutes the flake powder so that the volume ratio between the alcohol and the collection of flake powder made of soft metal is 3:1, placing the weighed alcohol and the weighed collection of flake powder made of soft metal in a second container, and stirring the alcohol to create a second suspension in which the collection of flake powder made of soft metal is dispersed in the alcohol; a fourth step of pouring a predetermined amount of the first suspension into a third container, the inside of which corresponds to the size of a film to be produced, placing the third container on a vibration table of a vibrator, operating the vibrator, and repeatedly applying vibration accelerations in the front-to-back, left-to-right, and up-to-down directions to the first suspension in each direction in turn, and finally applying vibration acceleration in the up-to-down direction, thereby producing a collection of graphene in the first suspension, with the graphene in the first suspension randomly stacked face up in methanol, in the third container; thereafter, heating the third container to the boiling point of the methanol to evaporate the methanol from the first suspension, and forming a collection of graphene in the third container, with the graphene randomly stacked face up; a fifth step of overlapping a flat plate having a size equal to the inside of the third container on the surface of the collection of graphene in the third container, and further uniformly compressing the entire surface of the flat plate, thereby bonding the overlapping graphene with the surface facing up by friction welding, and forming a graphene conjugate made up of the collection of graphene bonded by friction welding with a thickness less than 0.1 μm; further applying impact acceleration simultaneously to a plurality of positions on the bottom surface of the third container, and peeling the graphene conjugate from the bottom surface of the third container; further applying impact acceleration having the same magnitude as the impact acceleration simultaneously to a plurality of positions on one side surface of the flat plate, and peeling the graphene conjugate from the flat plate, and removing the graphene conjugate; a sixth step of pouring the second suspension into a fourth container having an inner size larger than that of the graphene conjugate, the fourth container being placed on a vibration table of a vibrator, and operating the vibrator to repeatedly apply vibration accelerations to the second suspension in the front-to-back, left-to-right, and up-to-down directions in turn, the vibration accelerations being larger than the vibration acceleration applied in the fourth step, and finally applying a vibration acceleration in the up-to-down direction, thereby forming a third suspension in the fourth container, the third suspension being made up of a collection of flake powder made of soft metal in the second suspension, with the flake powder surface facing up in the alcohol. a seventh step of immersing the entire graphene conjugate prepared in the fifth step in the third suspension in the fourth container, then removing the graphene conjugate from the third suspension, and sandwiching the graphene conjugate between two flat plates that are larger than the graphene conjugate but have the same size and thickness as the graphene conjugate, then heating the two flat plates to the boiling point of the alcohol to evaporate the alcohol from the third suspension, and forming clusters of flake powder made of the soft metal that are randomly overlapping with their faces facing up on both surfaces of the graphene conjugate; an eighth step of uniformly compressing the entire surface of an upper plate of the two flat plates with a compressive stress of not more than one-third of the compressive stress applied to the graphene aggregation in the fifth step, whereby the overlapping soft metal flake powders with their faces facing up are joined by friction welding, and a coating made of the joined aggregation of soft metal flake powder is formed with a thickness of less than 5 μm, and the coating is joined to both surfaces of the graphene conjugate by friction welding, thereby forming a film in which the coating is joined to both surfaces of the graphene conjugate; further comprising: an eighth step of simultaneously applying, to a plurality of locations on one side surface of the upper plate of the two flat plates, an impact acceleration of the same magnitude as that applied to the plurality of locations on one side surface of the flat plates in the fifth step, and peeling the upper plate from the film; and further simultaneously applying, to a plurality of locations on one side surface of the lower plate of the two flat plates, an impact acceleration of the same magnitude as the impact acceleration, and peeling the lower plate from the film, and removing the film; The method for forming a film includes the steps of: successively carrying out the eight steps described above, and forming a film having a thickness of 10 μm or less; the film having excellent thermal conductivity, electrical conductivity, and mechanical strength; and having a metallic luster; and the film having a configuration in which coatings formed by friction welding of soft metal flake powders are bonded to both surfaces of a graphene conjugate by friction welding.

2. The method for forming a film according to claim 1 comprises: The method for forming a film according to claim 1, wherein the flake powder made of the soft metal according to claim 1 is any one type of flake powder made of gold, silver, copper or aluminum, and the flake powder of any one type is used as the flake powder made of the soft metal according to claim 1, and a film is formed according to the method for forming a film according to claim 1.

3. The method for forming a film according to claim 1 comprises:

2. The method for forming a film according to claim 1, wherein the alcohol having a viscosity of 2 to 10 mPa sec at 20°C according to claim 1 is any one of 1-propanol, 2-propanol, 1-butanol, 1-pentanol, tertiary butyl alcohol, 2-pentanol, 3-methyl-1-butanol, tertiary amyl alcohol, 2-methyl-2-butanol, 2-butanol, 2-methyl-1-butanol, 2-heptanol, isobutyl alcohol, 4-methyl-2-pentanol, 1-hexanol, 3-pentanol, 2-octanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, and isooctyl alcohol, and wherein the any one of the alcohols is used as the alcohol having a viscosity of 2 to 10 mPa sec at 20°C according to claim 1, and a film is formed according to the method for forming a film according to claim 1.

4. The method for joining the film formed by the method according to claim 1 to the surface of a substrate or a part by friction welding comprises the steps of:

10. A method for friction-welding a film formed by the method recited in claim 1 to the surface of a substrate or a part to be joined, comprising: forming a film by the method recited in claim 1; placing the film on the surface of a substrate or a part to be joined; preparing a flat plate of the same size as the film; overlapping the flat plate on the surface of the film; uniformly compressing the entire surface of the flat plate; and joining the film to the surface of the substrate or the part by friction welding; thereafter, simultaneously applying impact acceleration to multiple locations on one side of the flat plate to separate the flat plate from the film; thereby forming the film joined to the surface of the substrate or the part by friction welding.

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