Method for manufacturing a conductive composite comprising at least one surface layer comprising multilayer graphene

Abstract

The present invention belongs to the technical field of conductive composites, and also to the processes and methods for manufacturing same. In particular, the present invention relates to a process or a method for manufacturing a conductive composite comprising at least one surface layer comprising multilayer graphene and to the conductive composites obtained by said process or said method. The invention also relates to a device comprising a conductive composite according to the invention or else to the use of an aqueous deposition composition comprising multilayer graphene and at least one surfactant in order to form a surface layer comprising multilayer graphene on a substrate.

Description

technical field

[0001] The present invention relates to the technical field of conductive composites, as well as their manufacturing processes and methods. In particular, the present invention relates to a process or method for manufacturing a conductive composite comprising at least one surface layer of multi-layered graphene, and to the conductive composites obtained by said process or method. The invention also relates to a device comprising a conductive composite according to the invention, or to the use of an aqueous deposition composition comprising multi-layered graphene and at least one surfactant to form a surface layer of multi-layered graphene on a substrate.

[0002] In the description below, references in brackets ( [] ) refer to the list of references presented at the end of the examples. State of the art

[0003] Conductive composites, particularly those using carbon materials as conductive fillers, are attracting increasing scientific interest for numerous industrial applications. [1-6]. Among these different carbon materials, materials similar to graphene, graphite, activated carbon, or even carbon nanotubes / nanofibers are generally included.

[0004] Graphene is of growing scientific and industrial interest for the production of conductive composites, thanks in particular to its first-rate thermoelectric properties. [7-10].Thanks to the use of these carbon-based materials, the electrical conductivity of these composites can be significantly improved by introducing a small amount of conductive nanofillers within a matrix. Such composites can then be used as lightweight heating devices for various industrial sectors, including electronics, transportation, aerospace, and smart buildings, or as sensor components in a variety of everyday applications.

[0005] However, it should be noted that for most prior art conductive composites, the manufacture of these composite materials is generally based on the inclusion of carbon materials within a polymer matrix; that is, the carbon material is mixed throughout the volume of the host polymer matrix, thus resulting in the formation of the conductive composite. Other conventional preparation methods involve depositing the mixture containing the carbon material dispersed within the polymer matrix or host resin onto a substrate, such as a polymer, glass, ceramic, or fabric, to form a composite. The carbon material can also be incorporated into the fiber during its production before the fibers are woven into fabric. For ceramics, the carbon material can be mixed with a ceramic slip before casting and firing, or with ceramic powder before sintering, depending on the nature of the ceramic and its production method.

[0006] These conventional manufacturing methods therefore exclude the approach of simply coating a substrate with a functional layer, i.e., the deposition of multi-sheet graphene (MLG) only on the surface. Most syntheses leading to these conductive composite materials are thus based on the inclusion of carbon-based materials, which may include resins, within a polymer or ceramic matrix. The polymer-based conductive composite is therefore always an intimate mixture of matrix and LLG, for example, polymer / resin and LLG.

[0007] These conventional synthesis methods or processes do not allow for the creation of coatings on the surface of the conductive composite with an electrically conductive material, but rather a dispersion of this conductive material throughout the mass of the final composite.

[0008] These conventional synthesis methods or processes lead to a dispersion of this conductive material in the mass of the composite but do not allow obtaining a continuous coating of electrically conductive material on the surface of said composite.

[0009] In a manufacturing process using a blend of blends, the blending is achieved with nanofillers inserted into the polymer substrate or other insulating substrates. The main problem generated by this type of process or method is the presence of numerous conductive / insulating interfaces, which significantly reduce the electrical performance of the final conductive composites. These interfaces also exhibit local overheating points and poor conductivity between two conductive materials, which can damage the composite over time. Furthermore, for some applications requiring a composite with high electrical conductivity, it is difficult or even impossible to increase the carbon content due to final viscosity issues that hinder the dispersion of conductive fillers within the blend and also impede the blend's infiltration into the substrate matrix.

[0010] For example, commercially available polyurethane (PU) foam is one of the foams used in many industrial applications ranging from oil absorption [11-13] to the reduction of noise levels or thermal insulation [14,15], including the production of support plates for chemical reactors

[16] or even the synthesis of ceramic foams [17,18].Due to their high elasticity under compression, foams can be used effectively as compression sensors for various applications. One of the major disadvantages of foams, and particularly PU foam, is their often low electrical conductivity. Improving this conductivity could lead to the development of new industrial devices such as piezoelectric devices or low-temperature catalyst support plates for liquid-phase reactions. Additive manufacturing of structured composites has expanded significantly in recent years across diverse industrial applications and sectors. For example, it enables the production of support plates for catalysis, as well as materials for construction and transportation.

[19] .Additive manufacturing enables the production of complex devices with shapes and sometimes properties inaccessible to traditional molding or injection molding methods. Indeed, it allows the fabrication of complex parts with varying thicknesses and interconnection structures. The advantage of polymer additive manufacturing also lies in its ability to directly incorporate conductive fillers into the polymer matrix. [20,21].

[0011] However, the direct incorporation of conductive charges within the polymer matrix presents two major disadvantages: the low percolation state of the charges within said polymer matrix, which leads to poor use of electrical energy, and the low heating efficiency during the on / off process due to inertia problems.

[0012] Furthermore, conventionally, in order to increase the conductivity of the final material, a relatively high concentration of charge is required, which can significantly alter the intrinsic properties of the virgin polymer host matrix.

[22] . The high concentration of the material ensuring the electrical conductivity of the final composite also leads to problems with dispersion and homogeneity. It should also be noted that the presence of insulating / conductive interfaces generated by the synthesis method raises the issues of heating power and composite embrittlement again, as discussed previously. Finally, the increased filler content induces a viscosity variation that can become incompatible with the shaping methods.

[0013] US patent 2013 / 0065034 discloses a coating method in Examples 6 and 8 in which a PET substrate is dipped in an aqueous solution comprising a surfactant (sodium lauryl sulfate) and multi-sheet graphene (0.1 wt%) at a temperature of 40, 60, or 80°C. The test at the highest temperature (80°C) is considered a failure by the authors, thus demonstrating that this type of process does not appear to produce a satisfactory composite.

[0014] There is therefore a real need for a process or method for manufacturing conductive composites, overcoming these defects, disadvantages and obstacles of the prior art, in particular a process or method for obtaining a conductive composite comprising at least one surface layer comprising multi-layered graphene exhibiting improved conductivity and / or resistance. Description of the invention

[0015] It is to the applicant's credit that they have developed a new process or method for manufacturing a composite comprising at least one surface layer made of multi-layered graphene, which totally or partially remedies the problems encountered with prior art composites.

[0016] The process or method according to the invention makes it possible to produce a homogeneous and continuous layer of conductive material on a substrate, significantly reducing the problems associated with the presence of insulating / conductive interfaces in the composite. The process or method according to the invention is easy to implement to meet market demand. Furthermore, the process or method according to the invention has the advantage of being able to be implemented on host substrates using a solution comprising multi-layered graphene. The process or method according to the invention thus allows the use of non-harmful materials as a replacement for potentially toxic or hazardous chemical compounds (resins, polymers) that can pose problems in waste recovery and cumbersome post-synthesis processing.

[0017] The surface coating also significantly reduces the loss of electrical conductivity typically encountered with composites constructed from a mixture of graphene and polymer where the graphene is embedded in an insulating polymer layer.

[0018] The invention thus relates to a process or method for manufacturing a conductive composite comprising at least one surface layer of multi-layered graphene, comprising the steps of: a) contacting a substrate, preferably non-metallic, and an aqueous deposition composition comprising: multi-sheet graphene at a concentration greater than or equal to 0.2 g / l, and at least one surfactant; b) heat treatment of the substrate obtained in step a) at a temperature ranging from 100 to 250°C; and obtaining the composite.

[0019] Advantageously, the duration of the heat treatment in step b) can be within a range of 1 minute to 5 hours, preferably from 5 minutes to 2 hours, or even from 30 minutes to 1 hour. The heat treatment in step b) can be carried out using various heating methods, such as, for example, in a Joule effect, infrared (IR) or halogen furnace, electromagnetic induction, and microwave.

[0020] Advantageously, the process or method according to the invention may further include a step (c) of low-temperature treatment, within a range of 40°C to 80°C, of ​​the composite obtained in step (b). The duration of the low-temperature treatment may range from 1 minute to 5 hours, preferably from 5 minutes to 2 hours, or even from 30 minutes to 1 hour. The low-temperature treatment may be carried out using the same heating systems described above, but at lower operating temperatures.

[0021] Low temperature is defined as a temperature within a range of 40°C to 80°C, preferably between 50°C and 70°C.

[0022] The process or method according to the invention also has the advantage of being able to be implemented successively to obtain a composite with varying thicknesses of conductive layers. This makes it possible, in particular, to precisely refine the electrical conductivity of the resulting composite and therefore the properties of the final object, such as the amount of heat it can emit. Step c), the low-temperature treatment, can be carried out between each deposition cycle a) and b) and can, in some cases, further increase the adhesion of the graphene layer to the substrate.

[0023] Advantageously, steps a), b) and optionally c) of the process or method can be repeated at least once, preferably from 1 to 30 times (1 to 30 iterations of sequence a), b) and optionally c)), even more preferably from 1 to 20 times or from 1 to 10 times or from 1 to 5 times.

[0024] Advantageously, step a) of bringing the substrate, preferably non-metallic, into contact with the aqueous deposition composition can be carried out by any method of direct application of the aqueous composition (e.g., with a brush, a paintbrush, a sprayer), impregnation of the aqueous composition onto the substrate, immersion of the substrate in the aqueous composition, or screen printing. When bringing the substrate into contact requires immersion or an excess of aqueous composition on the substrate, the process or method further includes an intermediate step a') of emulsifying the substrate from the aqueous composition or removing the excess aqueous composition from the surface of the substrate. Step a') is optional and generally depends on the type of contact. A person skilled in the art, by virtue of their general knowledge, is able to apply the appropriate step a') when it is required.

[0025] Advantageously, the duration of step a) depends essentially on the contact method but can be within a range from 1 second to several minutes, preferably from 30 seconds to 30 minutes, and even more preferably from 1 to 10 minutes. For example, in the case of immersion, the duration of step a) can be within a range from 10 seconds to 10 minutes, preferably from 20 seconds to 5 minutes, and even more preferably from 30 seconds to 2 minutes. In the case of application by means of a brush, the duration of step a) can be includedin a range of 10 seconds to 60 minutes, preferably 2 to 30 minutes, and even more preferably 5 to 20 minutes. In the case of spraying, the duration of step a) can be within a range of 10 seconds to 60 minutes, preferably 2 to 30 minutes, and even more preferably 5 to 20 minutes. It should be noted that the application time also depends on the total surface area of ​​the substrate to be covered. At the end of step a), a substrate is obtained that can be described as impregnated or soaked with the aqueous deposition composition.

[0026] Advantageously, the process or method according to the invention may further include a step (d) of applying a polymer topcoat. Step (d) may be carried out after step (b) or step (c) of the process or method according to the invention. When the implementation of the process according to the invention involves one or more iterations of steps (a), (b), and optionally (c), step (d) is carried out only once, after all steps (a), (b), and (c) have been completed. Step (d) may be carried out by any technique known to those skilled in the art for applying a polymer layer to a composite. The topcoat polymer may be among known polymers, such as polyurethane, PDMS, polystyrene, or other compounds such as commercially available glycerol paints or high-temperature paints.

[0027] Advantageously, the aqueous deposition composition of step a) comprises multi-sheet graphene (MLG) and at least one surfactant. Typically, the concentration of LG in the aqueous deposition composition may be greater than or equal to 0.2 g / L, preferably greater than or equal to 1 g / L, or even more preferably greater than or equal to 2 g / L. The concentration of LG in the aqueous deposition composition generally does not exceed 50, 60, or 70 g / L. For example, it may be in the range of 0.2 to 50 g / L, preferably 1 to 20 g / L, and even more preferably 2 to 10 g / L.

[0028] In this text, "few-layer graphene," "FLG," "GMF," or "FLG" refers to graphene containing more than one layer. Generally, within the scope of the invention, FLG has between 3 and 200 layers, and the layers have lateral dimensions between 0.5 and 10 µm, preferably between 1 and 5 µm, or even more preferably between 1 and 3 µm. FLG has a thickness between 1 and 640 nm, preferably between 5 and 320 nm, or even more preferably between 20 and 200 nm. Compared to GO (graphene oxide) and rGO (reduced graphene oxide), FLG exhibits significantly superior conductivity due to the absence of oxygen groups on the surface, and also a lower defect density.

[0029] Advantageously, the aqueous deposition composition of step a) comprises at least one surfactant. The surfactant may be one or more surfactants selected from the group comprising anionic, cationic, nonionic, and amphoteric (or zwitterionic) surfactants and mixtures thereof. Any type of surfactant, natural or synthetic, may be used within the scope of the invention.

[0030] Anionic surfactant is defined as a surfactant that releases a negative charge (anion) in aqueous solution. Anionic surfactant generally has a relatively high hydrophilic / lipophilic balance (HLB) (ranging from 8 to 18). Soaps, which are salts of fatty acids with the general formula RCOOM (where R is typically a hydrophobic aliphatic chain and M is a metal, an alkali metal, or an organic base), are an example. Examples include alkali soaps (such as salts of Na+, K+, and NH4+), metallic soaps (such as calcium salts), and organic soaps (such as triethanolamine salts, including triethanolamine stearate). Sulfated derivatives are also found (examples: sodium laureth sulfate, sodium lauryl sulfate and triethanolamine lauryl sulfate), as well as sulfonated derivatives (example: sodium dioctylsulfosuccinate). Lipoamino acids also exist.

[0031] A "canionic surfactant" is a surfactant that releases a positive charge (cation) in aqueous solution. These are generally nitrogenous compounds (containing a positively charged nitrogen atom). One can notably to cite quaternary ammonium salts such as alkyltrimethyl ammonium salts (example: alkyltrimethyl ammonium bromide), alkylbenzyldimethyl ammonium salts (example: benzalkonium chloride).

[0032] A "non-ionic surfactant" is defined as a surfactant that carries no net charge and does not ionize in water. Three main categories of non-ionic surfactants are identified: ester-linked surfactants (RC(O)-O-R', R and R' being, for example, hydrophobic aliphatic chains) among which we can mention glycol esters (for example: ethylene glycol stearate), glycerol esters (for example: glycerol stearate), polyoxyethylene glycol esters (obtained by the action of ethylene oxide on a fatty acid or a mixture of fatty acids), sorbitan esters, polyoxyethylenic sorbitan esters (more commonly called Tweens 20, 60, 80, etc. or polysorbates), sucrose esters (consisting of a hydrophilic glycosidic group and a hydrophobic fatty chain); ether-linked surfactants (RO-R', R and R' being for example hydrophobic aliphatic chains) among which we can mention fatty alcohol ethers and polyoxyethylene glycol for example; amide-linked surfactants (RC(O)-NH-R', R and R' being for example hydrophobic aliphatic chains).

[0033] An amphoteric surfactant, also known as a zwitterionic surfactant, is a surfactant that contains both acidic and basic functional groups. Depending on the pH of the surrounding medium, it releases either a positive or a negative ion. Amphoteric surfactants generally have a high HLB (hydroxyl group). Examples include cocamidopropyl betaine (which contains a quaternary ammonium group and a carboxylic acid group), imidazoline derivatives, and polypeptides.

[0034] Advantageously, the anionic surfactant can be chosen from the group comprising carboxylates, sulfonates or sulfates such as, for example, sulfosuccinates, alpha olefin sulfonates, alkyl glyceryl ether sulfonates and sodium cocoyl monoglyceride sulfates, alkylbenzene sulfonates and mixtures thereof.

[0035] Advantageously, the cationic surfactant can be chosen from the group comprising quaternary ammonium salts such as, for example, alkylamidodimethyl propylamine or methyl triethanolammonium and mixtures thereof.

[0036] Advantageously, the non-ionic surfactant can be chosen from the group comprising hydrophobic aliphatic chain esters, amides or ethers such as, for example, polyglycerol alkyl ethers, glucosyl dialkyl ethers, sorbitan esters, polysorbates, polyglyceryl-3-di-isostearates and mixtures thereof.

[0037] Advantageously, the amphoteric surfactant can be chosen from the group including, for example, cocoamidopropyl betaine, cocoamidopropyl sultaine, lauroamphoglycinate, dihydroxyethyl tallow glycinate, disodium cocoamphoacetate, isostearamphopropionate and mixtures thereof.

[0038] Advantageously, the aqueous depot composition, for example when it is a commercial surfactant solution to which FLG is added, may further include, but not be limited to: preservatives, antimicrobials, stabilizers, humectants, chelating agents, viscosity regulators or any other additives, and mixtures thereof.

[0039] Advantageously, the mass concentration of the surfactant(s) in the aqueous deposition composition of step a) is within a range of 0.1 to 50%, preferably 0.5 to 10%, and even more preferably 0.5 to 3%. The mass concentration of the surfactant(s) in the aqueous deposition composition of step a) may also be within a range of 1 to 50%.

[0040] Advantageously, the aqueous deposition composition can be obtained by ultrasonication of graphite, preferably expanded, in an aqueous solution comprising one or more surfactant(s), for example, in micellar water (a liquid composed of water and micelles). The aqueous deposition solution may further comprise other compounds such as preservatives, antimicrobials, stabilizers, humectants, chelating agents, viscosity regulators, or any other additives, and mixtures thereof.

[0041] Advantageously, the substrate (or host substrate) can be any type of material, preferably non-metallic, that does not possess intrinsic electrical conductivity, such as polymers, fabrics, ceramics, or glasses. For example, the substrate can be chosen from the group including thermoplastic polymers (such as alkyl (methyl) methacrylate, polystyrene, polyethylene, polypropylene, polyamides, polycarbonate, polydimethylsiloxane), thermosetting polymers (such as epoxies, polyimides, polyurethane), fabrics based on natural fibers (such as cotton, linen, bamboo, silk, hemp, jute), fabrics based on synthetic fibers (such as polyamides or polyesters, aramids, acrylics, carbon fibers, glass fibers, or ceramic fibers), ceramics (such as SiC, Al2O3), glasses, and their mixtures (for example, a mixture of several polymers or a fabric based on natural and synthetic fibers).Preferably, the substrate is a thermoplastic polymer, a thermosetting polymer, a fabric based on natural fibers or a synthetic fabric or a mixture of the materials mentioned above.

[0042] The invention also relates to conductive composites obtained according to the process or method of the invention. The conductive composites according to the invention exhibit high or improved percolation performance and / or a lower filler concentration compared to conductive composites known in the prior art.

[0043] Advantageously, the conductive composites according to the invention comprise at least one surface layer comprising multi-layered graphene (on the surface of the substrate). The heat treatment step permanently bonds the graphene layer to the surface of the substrate.

[0044] Advantageously, the surface layer comprising multi-layered graphene has a thickness ranging from 1 to 1000 nm, preferably from 5 to 800 nm, and even more preferably from 10 to 500 nm. These ranges refer to the individual layers, as the final layer (resulting from one or more iterations of the process or method according to the invention) can be several micrometers thick or even more. The thickness of the final layer can be between 1 and 100 µm, preferably between 3 and 50 µm, and preferably between 4 and 30 µm. Naturally, those skilled in the art will adapt the total thickness of at least one surface layer comprising graphene according to the intended application.

[0045] The invention also relates to a conductive composite comprising a substrate as defined above, said substrate comprising at least one surface layer comprising multi-sheet graphene, preferably each of the at least one surface layer has a thickness ranging from 1 to 1000 nm, preferably from 5 to 800 nm and even more preferably from 10 to 500 nm.

[0046] Synthesized composites can be used in various fields of application such as: heating systems for domestic uses where rapid exchanges between the surface heating element and the ambient air are improved, freeze protection systems for tubing carrying fluids, defrosting systems for polymer-based materials in various fields, stress detection systems or for controlled opening / closing, metal-free thermal signaling systems, flexible systems for applications in the field of electronics, and electromagnetic radiation protection systems.

[0047] Advantageously, the surface layer comprising multi-layered graphene can have a thickness that varies from one part of the composite to another, and consequently, a different local electrical conductivity. For example, on two specific areas of the substrate, the implementation of the process or method according to the invention can differ in the number of iterations or in the concentration in the deposition solution. The number of iterations and / or the charge concentration of the initial solution (step a)) of the process or method can vary from one area of ​​the substrate to another, thus obtaining a composite having a surface layer comprising multi-layered graphene with varying thickness and / or properties.

[0048] Advantageously, the composite according to the invention can have a variable local electrical conductivity. The difference in thickness of the surface layer comprising multi-layered graphene on the substrate thus generates differences in electrical conductivity which can be used for certain applications such as de-icing or in preventing the freezing of pipes carrying different fluids, for example, at the junction of a fluid mixer with different inlet temperatures.

[0049] Advantageously, the surface layer comprising multi-layered graphene is essentially free of surfactant(s) or other elements initially present in the aqueous deposition composition. Preferably, the surface layer consists of multi-layered graphene and possibly traces of surfactant(s) or other elements initially present in the aqueous deposition composition. The surface layer generally comprises less than 1%, preferably less than 0.1%, of surfactant(s) or other elements initially present in the aqueous deposition composition.

[0050] Advantageously, the surface layer comprising multi-sheet graphene does not include polymer or resin.

[0051] Advantageously, the surface layer can consist of multi-layered graphene or of multi-layered graphene and the substrate itself, where the latter is superficially mixed with the multi-layered graphene at the interface during the implementation of the process or method according to the invention. In this embodiment, the surface layer comprises a lower portion, in contact with the substrate, slightly intermingled at the interface with the substrate, and a continuous upper portion of multi-layered graphene. This is not a mixture as observed in the prior art, where the graphene is mixed throughout the substrate, nor is it a coating consisting of a mixture of multi-layered graphene and a polymer or resin subsequently applied to the surface of the substrate as described in the prior art.Indeed, in such cases the carbon material (the filler), being a minority in mass and volume, is then dispersed more or less homogeneously in the polymer / resin matrix.

[0052] Advantageously, the electrical conductivity of the surface layer comprising multi-sheet graphene, measured by the four-point method, can be greater than 200 S / m, preferably greater than 2000 S / m and even more preferably greater than 5000 S / m.

[0053] Advantageously, the structure of the FLG sheets is not altered during the implementation of the process or method. The FLG sheets contained in the surface layer of the composite, generally parallel to the substrate surface, according to the invention, have a structure similar to that which they have in the aqueous deposition solution.

[0054] Advantageously, the surface layer comprising multi-layered graphene has a resistance in the range of 1 Ω to 2 kΩ, preferably from 10 Ω to 1000 Ω, and more preferably from 80 Ω to 500 Ω. This resistance value can be measured by applying two copper bars across the surface of the composite, the resistance then being measured with an ohmmeter between these two terminals.

[0055] Advantageously, the multi-layered graphene surface layer can act as a protective layer to reduce scratch formation on the device. After the process is implemented, the multi-layered graphene surface layer can be treated by additional heating (step c')), preferably with a laser pulse, to remove residual oxygen attached to its surface, which increases its hydrophobicity. This hydrophobicity reduces the deposition of other substances on the composite surface. For example, it reduces the formation of hydrate nuclei in gas or fluid transport pipes that can gradually clog the conduit.

[0056] Advantageously, the composite according to the invention may further comprise a finishing polymer layer. In this embodiment of the invention, the layer comprising multi-layered graphene is covered wholly or partially by the finishing polymer layer. In such a composite, scratches generated on the surface of the polymer layer can be eliminated by heating the graphene / substrate composite beneath it to the required temperature in order to slightly soften the surface polymer layer and thus eliminate the scratches by flattening the surface. This application is particularly relevant in scratch-resistant devices.

[0057] The conductive composites according to the invention can find applications in numerous fields. In particular, conductive composites for heating can enable better heat dissipation management, thus significantly reducing the load concentration and increasing heating efficiency. Indeed, the surface layer comprising the multi-layered graphene that provides the heating element has the advantage of being continuous. This allows for a better response to the applied current with a significantly lower thermal inertia than that of prior art composites, where the conductive material is dispersed discontinuously throughout the matrix.

[0058] The composites according to the invention can find application, without limitation, in fields such as low-temperature heating (domestic or fluid ducts in aircraft or other devices), force or medium detectors (via a change in conductivity or resistance when a force is applied or in the presence of compounds that adsorb onto the surface), de-icing of polymer-based composites, repulsive surfaces (for example, to accelerate vapor evacuation), flexible electrical circuits, or temperature detectors by changing the overall resistance as a function of the temperature of the exposed medium, the reduction of deposits from solids that may be present in fluids, on the surface in contact with gas or oil in transport pipes, and which, through progressive growth,can clog the tubing (for example, hydrate deposits in the gas or oil production sector).

[0059] Advantageously, the applied current / emitted energy efficiencies for the same type of substrate are within a range of 50 W / m² to 5000 W / m², preferably between 500 W / m² and 3000 W / m², and even more preferably between 1000 W / m² and 3000 W / m². These efficiencies are generally observed for applied voltages below 40 V. Higher power outputs can be obtained by applying higher voltages; for example, for an applied voltage of 20 V, a power output of 2000 W / m² is obtained, while for an applied voltage of 220 V, the generated power will be on the order of 22,000 W / m².

[0060] The conductive composites according to the invention comprise a surface layer of multi-layered graphene. Advantageously, said surface layer of multi-layered graphene is uniformly distributed and comprises a thin surface layer of graphene. This results in the use of a small amount of graphene and a low heating voltage, thus enabling a higher switching frequency (start / stop) than with known composites.

[0061] These characteristics and performance allow, in particular, the use of these conductive composites according to the invention in intelligent heating devices or in mechanical sensors to control stress and deformation phenomena.

[0062] Advantageously, the conductive composite according to the invention has a very high heating switching frequency of between 30 seconds and 60 minutes, preferably between 60 seconds and 30 minutes, and preferably between 120 seconds and 15 minutes, depending on the applied voltage.

[0063] The invention further relates to a device, for example a heating device or a mechanical sensor, comprising a conductive composite according to the invention.

[0064] The invention also relates to the use of an aqueous deposition composition comprising multi-sheet graphene at a concentration greater than or equal to 0.2 g / l, preferably greater than or equal to 1 g / l or even more preferably greater than or equal to 2 g / l, and at least one surfactant, to form a surface layer made of multi-sheet graphene on a substrate, preferably non-metallic, according to the method according to any one of claims 1 to 8. Brief description of the figures

[0065] There figure 1represents (A) digital photographs of an ABS (acrylonitrile butadiene styrene) polymer-based structure produced by 3D printing before and after four brush-coating cycles of a paint based on a multi-layer aqueous graphene solution (10 g / l), each time followed by a heat treatment at 110°C (composite no. 1); (B) the result of an ultrasonication process of composite no. 1 highlighting the mechanical strength of the composite according to the invention and the strong adhesion of the graphene matrix (GMF) to the polymer surface: left image: composite no. 1 before ultrasonication; right image: the composite after ultrasonication showing the total absence of residue in the solution, thus confirming the strong adhesion of the graphene layer to the substrate surface. figure 2represents SEM (scanning electron micrographs) of the polymer (ABS) as printed (A) and after four coating cycles (B) (composite no. 1), showing a highly homogeneous surface coating of the polymer host matrix with a FLG layer and a high-resolution SEM micrograph showing the smooth coating layer covering the polymer surface after heat treatment at 110°C (C). figure 3 represents (A) optical images of a PMMA (Polymethyl Methacrylate) plate before and after coating with a layer of FLG with a weight content of approximately 0.8 wt%, (B) SEM micrographs with a cross-sectional view of composite No. 7 FLG@PMMA showing the thickness of the FLG layer on the order of 4 µm, and (C) a measurement of electrical conductivity (S.m⁻¹) as a function of the weight content of FLG (%) recorded on a series of FLG@PMMA composites (Nos. 2 to 7). figure 4Figure (A1) represents an optical image of the FLG@PMMA composite (composite no. 8) with a FLG weight content of 0.23%. Figure (B1) is the thermal image showing the temperature recorded at the surface of the composite after application of a 20 V voltage. Figures (A2 and B2) represent the same composite (A) coated with a polyurethane topcoat and its corresponding thermal properties. Figures (A3 and B3) represent the same composite (A2) coated with a white glycerol-based paint topcoat and its corresponding thermal properties. figure 5 Figures (A, B) represent photos of a 3D-printed ABS airplane covered with a surface layer of FLG (composite #9) and the corresponding resistance values. Figures (C, D) show digital and thermal images of the ABS airplane generated with a 24V power supply and acquired using an IR thermal camera. figure 6Figure (A) shows a FLG (Flammable Liquid Gum) coating on an aircraft manufactured by 3D printing in ABS (composite #10). The aircraft rests on a container of liquid nitrogen to create a thin layer of ice on its surface. (B to D) The thermal images show the different surface temperatures of the aircraft over time with a 24V power supply. The highest temperature reached after 120 seconds of power supply is over 40°C – in the presence of liquid nitrogen under the aircraft. These results illustrate the effectiveness of the deposited FLG layer for de-icing applications in cold environments. figure 7Figures (A, D) represent the optical and thermal images of an ABS aircraft coated with a layer of FLG (composite #11) after being placed in a freezer for 30 minutes to produce a thick layer of ice over its entire surface. Figures (B, E, C, F) show the optical and thermal photographs of the melting of the ice layer and the temperatures recorded on the aircraft with an applied voltage of 24 V – as a function of the heating time. figure 8 Figures (A, B) represent SEM images of the cotton-based fabric at different magnifications. Figures (C, D) represent SEM images of the cotton-based fabric coated with a multi-layer graphene (composite no. 12), after heat treatment in air at 130 °C in an oven, at different magnifications. figure 9represents (A, B) the electrical conductivity (in Siemens / m) of the graphene@fabric composites (No. 13-22), after synthesis and after heat treatment at 200°C under air in a furnace, as a function of the graphene load and the number of deposits. Figure 10 Figure (A) Digital photographs of an electric radiator and a graphene@tissu composite (No. 22) measuring 16 x 16 cm² covered with a layer of resin to insulate the conductive surface. (B) Thermal image of the temperature taken at the center of the radiator powered by a voltage of 230V. (C) (Top left) Digital image of the composite with electrical connections. (Top center and right, and bottom left to right) Thermal images of the graphene@tissu composite with applied voltages ranging from 5V to 24V, showing the temperature increase with the applied voltage. figure 11Figure (A) represents optical images illustrating the synthesis process of graphene and multi-sheet graphene by sonication from a water-based solution and Garnier micellar water (surfactant: Disodium cocoamphodiacetate). (B1) micro-Raman image of the analyzed area, (B2) Raman spectra corresponding to each dilution, and (B3) high-resolution spectra of the 2D band. figure 12 This represents scanning and transmission electron microscopy images of graphene and multi-sheet graphene synthesized by sonication using Garnier micellar water as an exfoliating agent (surfactant: Disodium cocoamphodiacetate). figure 13represents (A) an uncoated PEEK tube of the following dimensions: external diameter, 24 mm, internal diameter, 22 mm, length 61 mm, (B) the same PEEK tube covered by a FLG film, (C) surface temperature measured on the PEEK tube covered by the FLG film without any voltage applied and (D) the surface temperature of the PEEK-FLG tube measured after application of a voltage of 14 V for two minutes. EXAMPLES Example 1: METHOD FOR MANUFACTURING CONDUCTIVE COMPOSITES FLG@SUBSTRAT

[0066] Composites according to the invention have been obtained from various substrates such as ABS, PMMA and have been synthesized according to the method described according to the invention.

[0067] The following method was implemented: a) An aqueous deposition composition comprising a concentration of 10 g / l of FLG and 0.25% (vol.%) of disodium cocoamphodiacetate (micellar water type) was deposited onto the host substrate (3D-printed ABS grid) using a brush-on coating technique. b) The substrate thus formed, saturated in step a), was then oven-dried at a temperature of 110 °C for 30 minutes.

[0068] The sequence a), b) was repeated four times. This yields the composite FLG@ABS. The Figure 1A represents the FLG@ABS composite.

[0069] The following composites were prepared in the same way: Table 1: Composites No. 1 to 11 and 23 to 24 according to the invention. Aqueous composition of deposit Composite Composite No. Substrate type Surfactant (vol. concentration%) FLG concentration (g / l) Number of layer(s) No. 1 FLG@ABS ABS Disodium cocoamphodiacetate (0.25) 10 4 No. 2 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 1 No. 3 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 2 No. 4 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 3 No. 5 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 4 No. 6 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 5 No. 7 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 6 No. 8 FLG@PMMA PMMA Disodium cocoamphodiacetate (0.25) 10 2 No. 9 FLG@ ABS ABS Disodium cocoamphodiacetate (0.1) 5 4 No. 10 FLG@ ABS ABS Disodium cocoamphodiacetate (0.1) 5 4 No. 11 FLG@ ABS ABS Disodium cocoamphodiacetate (0.1) 5 4 No. 23 FLG@PEEK PEEK Disodium cocoamphodiacetate (0.1) 3 4 No. 24 FLG@PEEK PEEK Disodium cocoamphodiacetate (0.5) 10 6 Example 2: FLG@ABS STABILITY TEST

[0070] The mechanical stability of the surface layer of composite no. 1 FLG@ABS is evaluated by subjecting the composite to ultrasound in an aqueous medium for 30 min.

[0071] The surrounding liquid remains colorless, which confirms the very high stability of the coating because if graphene had been released into the liquid, the latter should have a greyish color ( Fig. 1B ).

[0072] The corresponding scanning electron micrographs (SEM) of the FLG@ABS composite are presented on the... figures 2A to C The SEM micrograph of the figure 2A highlights the native roughness of the ABS polymer surface, which was 3D printed layer by layer. The same surface after the deposition of the FLG layer followed by heat treatment at 110°C exhibits a smoothed appearance due to the formation of a continuous and percolated graphene layer ( Fig. 2b and c ).

[0073] The extremely smooth appearance of the FLG layer ( figure 2C ) allows us to account for its continuity. Example 3: Conductivity of Flg@ABS

[0074] The optical images corresponding to composite #7 FLG@PMMA are presented on the Fig. 3A .

[0075] The surface of the composite (right) displays a dark grey color characteristic of the formation of a FLG surface layer.

[0076] There Fig. 3B The image shows SEM images of composite #7. The images demonstrate good percolation and continuity of the FLG layer with a thickness of approximately 4 µm. Electrical conductivity (S.m⁻¹) as a function of FLG loading and deposition number was measured on a series of FLG@PMMA composites #2 to #7, and is presented in the image. Fig. 3C. It is demonstrated here that the electrical conductivity increases gradually as a function of the coating cycles, in other words of the concentration of FLG, and an electrical conductivity of approximately 1.3. 10 5< S. m -1< was recorded for a mass charge of FLG 0.8 % relative to the mass of PMMA.

[0077] Composite No. 8 was made from a PMMA plate (18 x 30 x 0.1 cm) coated with a layer of FLG of approximately 0.23% by weight relative to the weight of the PMMA plate.

[0078] An external voltage of 24 V was applied to the device. The optical and thermal images recorded on the sample as a function of time are presented in the Figure 4 A1 and B1. According to the results obtained, a rapid increase in temperature is observed on the surface of the composite, going from ambient to approximately 70°C in less than 10 minutes and stabilizing under electrical voltage.

[0079] No apparent degradation was observed, namely, no formation of cracks or detachment of the interface and components of the device was observed throughout the heating process.

[0080] The same device was coated with a protective polyurethane-based resin to isolate the top layer of FLG ( Figure 4 A2) and a voltage of 24V was applied again. The optical and thermal images collected under the same heating conditions used previously are presented in the Figure 4 A2 and B2. According to the results obtained, the polyurethane film does not alter the calorific properties of the device in any way.

[0081] The final experiment was carried out by applying a layer of white glycerol paint to the surface of the polyurethane film ( Figure 4 A3) and the same heating protocol was repeated. The results presented in the Figure 4B3 clearly demonstrates that the heat capacity of the latter is significantly higher than that of systems that are either uncoated or coated only with polyurethane resin, reaching a temperature of approximately 95°C instead of 72°C for the same heating durations. This can be explained by the fact that the glycerol-based paint film acts as thermal insulation, limiting excessive heat exchange with the ambient atmosphere and thus trapping the heat produced by the conductive layer of FLG.

[0082] Electrical conductivity measurements of FLG@polymer composites as a function of graphene concentration are presented in Table 2, and compared to values ​​reported in the literature. Table 2: Comparison of conductivity of composites according to invention No. 2 to 7 and composites according to the prior art. Matrix Conductive charge Load / matrix mass ratio (%) Process Conductivity (σ) of the composite (S / m) Ref. Insulating Driver Epoxy wrGO 15 In-situ 10

[23] PS foam CNT 7 In-situ 0,5

[24] PMMA foam Graphene 5 In-situ 3

[25] PDMS Graphene 0,8 In-situ 108 [3] PEDOT Graphene 35 In-situ 5008

[26] PANI Graphene 30 In-situ 3900

[27] PANI SWCNT 41 In-situ 120000

[28] PMMA Nano EG 10 In-situ 78

[22] PS Graphene 2 In-situ 1.10 -2<

[29] Nylon FG 0,75 In-situ 1.10 -5<

[30] HDPE UG 5 Fusion 1.10 -10<

[31] PANI Graphene 1,5 In-situ 5

[32] PET FGS 0,47 Fusion 7,4.10 -2<

[33] Polycarbonate FGS 2 Fusion 1.10 -9<

[34] PDMS GF 5 In-situ 10 [6] PS Graphene 0,1 In-situ 0,1 [2] PMMA GMF 0,05 Surface coating 8896 Comp. (No. 2) PMMA GMF 0,2 Surface coating 14000 Comp. (No. 3) PMMA GMF 0,4 Surface coating 43000 Comp. (No. 4) PMMA GMF 0,5 Surface coating 65000 Comp. (No. 5) PMMA GMF 0,6 Surface coating 100000 Comp. (No. 6) PMMA GMF 0,8 Surface coating 130000 Comp. (No. 7) Example 4: DE-ICING OF ABS-BASED POLYMER STRUCTURES

[0083] An ABS structure in the shape of an airplane was manufactured by 3D printing and coated with a FLG layer according to the process of the invention.

[0084] There figure 5 represents the results obtained.

[0085] To conduct the experiment, two configurations were used to evaluate the resistance values ​​at different points ( Fig 5 A and B ): 1. In the first case, the entire surface of the aircraft was coated with a surface layer of FLG at a concentration of 0.23 wt.%. 2. In the second case, only the wings were coated with a surface layer of FLG at a concentration of 0.15 wt.%.

[0086] The surface temperature observed by infrared camera at different applied voltages and for various configurations is presented in the Figure 5C and D -confirms the high efficiency of the deposited layer, giving the surface both heating and homogeneous resistance values.

[0087] The temperature on the surface of the composite is homogeneous in the areas where the FLG deposit has been made, i.e. on the wings or on the entire surface - thus confirming the high efficiency of the composites according to the invention for applications or heating elements.

[0088] As part of further testing, the aircraft is held on a container filled with liquid nitrogen ( Fig. 6A ) and an electrical voltage of 24V was applied to the wings of the aircraft ( Fig. 6B to D). Thanks to IR images, we note that the temperature quickly reaches 40°C after only 120 seconds of powering - highlighting a de-icing effect on the surface of the aircraft despite the presence of a cold environment below.

[0089] Finally, the aircraft was placed in a freezer for 2 hours to generate a thick layer of ice on its surface. Temperatures recorded by IR camera show values ​​below 4°C ( Figure 7A and D Electrical voltage was applied to the wings and temperature readings were taken over time using thermal photography to demonstrate the effectiveness of such a system for de-icing ( Fig. 7B to F The results show that the ice formed on the surface of the aircraft is completely melted after 240s of 24V voltage applied. Example 5: HEATING ON GRAPHENE@TISSUE COMPOSITES

[0090] FLG@tissu composites are prepared according to the following method.

[0091] A cotton-based substrate ( Fig. 8A and B ) is coated with a layer of multi-layered graphene ( Figure 8C and D The aqueous solution composition is 10 g / l. The deposition was performed four times, and the composite was treated at 130°C in an oven for 15 minutes after each deposition. The SEM images of Figures 8A and C (as well as the insets in the figures) indicate that the morphology of the fibers constituting the fabric is preserved after graphene deposition and heat treatment. The images of Figures 8C and D confirm the presence of a graphene layer covering the entire surface of the fiber.

[0092] Similar experiments were performed with cotton fabric depending on the successive depositions, and the results are presented in Table 3. After each deposition of the graphene layer, the impregnated substrate was heat-treated at 200°C for 30 minutes. The corresponding electrical conductivities are shown in Table 3. Figure 9 depending either on the graphene load or on the number of deposits.

[0093] The following composites are obtained: Table 3: Composites No. 12 to 22 according to the invention Composite No. Substrate type Surfactant (vol. concentration%) FLG concentration (g / l) Number of layer(s) No. 12 FLG@fabric Fabric Disodium cocoamphodiacetate (0.25) 10 4 No. 13 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 1 No. 14 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 2 No. 15 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 3 No. 16 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 4 No. 17 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 5 No. 18 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 6 No. 19 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 7 No. 20 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 8 No. 21 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 9 No. 22 FLG@fabric fabric Disodium cocoamphodiacetate (0.1) 5 10

[0094] Depending on the measured electrical conductivity, the deposition can be repeated in order to increase the graphene load in the composite ( Figure 9 ).

[0095] FLG@tissu composites #13 to #22 are prepared with different graphene fillers (number of process implementations ranging from 1 to 10 iterations). As shown in the results in the Figures 9A and B the increase in the number of deposits, and consequently, the increase in the graphene load contributes to a strong increase in the electrical conductivity of the composite.

[0096] The FLG@tissu n°22 composite (dimension 16 x 16 cm²) is covered with a transparent polyurethane resin topcoat to provide electrical insulation for heating applications ( Figure 10A ).

[0097] The chosen dimensions allow for the same heating surface area as an electric radiator ( Figure 10A ) which serves as a reference. The temperature of the radiator, powered by a voltage of 230 V, measured by a thermal camera, is approximately 46°C at the center and with a maximum around 87°C ( Figure 10B ).

[0098] The graphene@fabric composite is powered with different voltages ranging from 5 to 24V and the thermal images are presented on the Figure 10C With an applied voltage of 24V, the graphene@fabric composite generates a more homogeneous temperature of around 83°C at the center and with a maximum around 86°C.

[0099] These results can be explained by the difference in heating systems: in a radiator, heating is achieved by wire resistors embedded in a block, whereas the composite according to the invention has a continuous conductive layer. This results in better temperature uniformity, while the composite's thinness also allows for rapid heating of the system. Example 6: Preparation of an aqueous deposition composition, by sonication of expanded graphite in an aqueous solution comprising a surfactant (disodium cocoamphodiacetate).

[0100] 5.4 g of expanded graphite is added to a 1 liter beaker, then 540 ml (540 g) of a mixture composed of water (450 ml) and micellar water (90 ml) is added to the beaker and subjected to the sonication process (40 watts) assisted by stirring for 2 hours ( Figure 11 The volume of the surfactant (disodium cocoamphodiacetate) is 1.35 ml, representing 0.25% of the total volume, and the graphene concentration is 10 g / l, or 1% of the solution. The resulting dispersion can be directly filtered, dried, and / or redispersed in an aqueous solution.

[0101] The FLG dispersion thus obtained can be separated into two phases by a sedimentation process ( Figure 11AThe first part (A) consists of the remaining exfoliating solution (400 ml) and can be reused for an additional exfoliation process. Part B, consisting of 38.5 g / l (3.85%) of graphene and multi-sheet graphene, can be used directly. According to the results of Raman analysis, the resulting graphene solution exhibits a 2D band characteristic of FLG-based materials with a number of layers less than 20 ( Figure 11 . B1, B2, B3).

[0102] The morphology and microstructures of the synthesized FLG were studied by scanning electron microscopy (SEM) and the observations revealed lateral sizes ranging from 5 nm to 25 µm ( figures 12A and B ). Example 7: METHOD FOR MANUFACTURING CONDUCTIVE POLYMER COMPOSITES FLG@PEEK.

[0103] Production of a 3g / L concentration solution of multi-sheet graphene (500 ml H 2 O, 1 ml (1.1 g) of disodium cocoamphodiacetate and 1.5g of graphite) according to the method described in example 6.

[0104] The FLG solution is sprayed onto the surface of a polyetheretherketone (PEEK) tube using an airbrush. The tube has the following dimensions: external diameter, 24 mm; internal diameter, 22 mm; length, 61 mm. The tube is then dried in an oven at 80 °C to remove excess aqueous composition from the substrate surface and evaporate any remaining water. This is followed by heat treatment at 250 °C for 15 minutes in a tubular electric furnace. This process is repeated four times to achieve a 0.1 wt% FLG deposit on the PEEK tube.

[0105] We obtain the PEEK@FLG composites (composites no. 23 and 24, see table no. 1).

[0106] FLG charge: 6.2 mg (∼0.1% of the mass of the PEEK support) Longitudinal resistance ∼9.6 Ω.

[0107] Temperature measured by IR camera > 180 °C with an applied voltage of 14 V.

[0108] The PEEK@FLG composite was heated and cooled (by alternately applying a voltage of 0 V and 14 V) six times and the maximum temperature is always above 180°C for the same applied voltage of 14 V, thus indicating excellent stability regarding the adhesion of the FLG film to the surface of the polymer. List of references

[0109] [1] S. Hooshmand, A. Soroudi, M. Skrifvars, Electro-conductive composite fibers by melt spinning of polypropylene / polyamide / carbon nanotubes, Synth. Met. 161 (2011) 1731-1737. doi:10.1016 / j.synthmet.2011.06.014. [2] S. Stankovich, D.A. Dikin, G.H.B. Dommett, K.M. Kohlhaas, E.J. Zimney, E.A. Stach, R.D. Piner, S.T. Nguyen, R.S. Ruoff, Graphene-based composite materials, Nature. 442 (2006) 282-286. doi: 1 0.1 038 / nature04969. [3] Z. Chen, C. Xu, C. Ma, W. Ren, H.-M. Cheng, Lightweight and Flexible Graphene Foam Composites for High-Performance Electromagnetic Interference Shielding, Adv. Mater. 25 (2013) 1296-1300. doi:10.1002 / adma.201204196. [4] A. Katunin, K. Krukiewicz, R. Turczyn, P. Sul, M. Bilewicz, Electrically conductive carbon fibre-reinforced composite for aircraft lightning strike protection, IOP Conf. Ser. Mater. Sci. Eng. 201 (2017) 012008. doi:10.1088 / 1757-899X1201 / 1 / 012008. [5] N.C. Das, T.K. Chaki, D. Khastgir, A.Chakraborty, Electromagnetic interference shielding effectiveness of conductive carbon black and carbon fiber-filled composites based on rubber and rubber blends, Adv. Polym. Technol. 20 (2001) 226-236. doi:10.1002 / adv.1018. [6] Z. Chen, W. Ren, L. Gao, B. Liu, S. Pei, H.-M. Cheng, Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapour deposition, Nat. Mater. 10 (2011) 424-428. doi:10.1038 / nmat3001. [7] Z.-S. Wu, W. Ren, L. Gao, J. Zhao, Z. Chen, B. Liu, D. Tang, B. Yu, C. Jiang, H.-M. Cheng, Synthesis of Graphene Sheets with High Electrical Conductivity and Good Thermal Stability by Hydrogen Arc Discharge Exfoliation, ACS Nano. 3 (2009) 411-417. doi:10.1021 / nn900020u. [8] S. Ghosh, I. Calizo, D. Teweldebrhan, E.P. Pokatilov, D.L. Nika, A.A. Balandin, W. Bao, F. Miao, C.N. Lau, Extremely high thermal conductivity of graphene: Prospects for thermal management applications in nanoelectronic circuits, Appl. Phys. Lett. 92 (2008) 151911. doi:10.1063 / 1.2907977. [9] S. Vadukumpully, J. Paul, N. Mahanta, S. Valiyaveettil, Flexible conductive graphene / poly(vinyl chloride) composite thin films with high mechanical strength and thermal stability, Carbon. 49 (2011) 198-205. doi:10.1016 / j.carbon.2010.09.004.

[10] H. Kim, Y. Miura, C.W. Macosko, Graphene / Polyurethane Nanocomposites for Improved Gas Barrier and Electrical Conductivity, Chem. Mater. 22 (2010) 3441-3450. doi:10.1021 / cm100477v.

[11] B. Li, X. Liu, X. Zhang, J. Zou, W. Chai, Y. Lou, Rapid adsorption for oil using superhydrophobic and superoleophilic polyurethane sponge, J. Chem. Technol. Biotechnol. 90 (2015) 2106-2112. doi: 1 0.1 002 / jctb.4646.

[12] H. Li, L. Liu, F. Yang, Oleophilic Polyurethane Foams for Oil Spill Cleanup, Procedia Environ. Sci. 18 (2013) 528-533. doi:10.1016 / j.proenv.2013.04.071.

[13] Z. Wang, H. Ma, B. Chu, B.S. Hsiao, Super-hydrophobic polyurethane sponges for oil absorption, Sep. Sci. Technol. 52 (2017) 221-227. doi: 1 0.1 080 / 01496395.2016.1246570.

[14] A.-E. Tiuc, H. Vermesan, T. Gabor, O. Vasile, Improved Sound Absorption Properties of Polyurethane Foam Mixed with Textile Waste, Energy Procedia. 85 (2016) 559-565. doi:10.1016 / j.egypro.2015.12.245.

[15] A.M. Papadopoulos, State of the art in thermal insulation materials and aims for future developments, Energy Build. 37 (2005) 77-86. doi:10.1016 / j.enbuild.2004.05.006.

[16] Y.-J. Lee, J.S. Lee, Y.S. Park, K.B. Yoon, Synthesis of Large Monolithic Zeolite Foams with Variable Macropore Architectures, Adv. Mater. 13 (2001) 1259-1263. doi:10.1002 / 1521-4095(200108)13:16<1259::AID-ADMA1259>3.0.CO;2-U.

[17] S.J. Powell, J.R.G. Evans, The Structure of Ceramic Foams Prepared from Polyurethane-Ceramic Suspensions, Mater. Manuf. Process. 10 (1995) 757-771. doi:10.1080 / 10426919508935063.

[18] J. Luyten, I. Thijs, W. Vandermeulen, S. Mullens, B. Wallaeys, R. Mortelmans, Strong ceramic foams from polyurethane templates, Adv. Appl. Ceram. 104 (2005) 4-8. doi:10.1179 / 174367605225010990.

[19] H.-W. Engels, H.-G. Pirkl, R. Albers, R.W. Albach, J. Krause, A. Hoffmann, H. Casselmann, J. Dormish, Polyurethanes: Versatile Materials and Sustainable Problem Solvers for Today's Challenges, Angew. Chem. Int. Ed. 52 (2013) 9422-9441. doi:10.1002 / anie.201302766.

[20] M. Castellino, A. Chiolerio, M.I. Shahzad, P.V. Jagdale, A. Tagliaferro, Electrical conductivity phenomena in an epoxy resin-carbon-based materials composite, Compos. Part Appl. Sci. Manuf. 61 (2014) 108-114. doi:10.1016 / j.compositesa.2014.02.012.

[21] H.B. Man, K. Zhang, E. Robinson, E.K. Chow, D. Ho, Chapter 15 - Engineering Nanoparticulate Diamond for Applications in Nanomedicine and Biology, in: O.A.S.M. Gruen (Ed.), Ultananocrystalline Diam. Second Ed., William Andrew Publishing, Oxford, 2012: pp. 493-518. http: / / www.sciencedirect.com / science / article / pii / B9781437734652000 153 (accessed June 2, 2015).

[22] W. Wang, Y. Liu, X. Li, Y.You, Synthesis and characteristics of poly(methyl methacrylate) / expanded graphite nanocomposites, J. Appl. Polym. Sci. 100 (2006) 1427-1431. doi:10.1002 / app.23471.

[23] J. Liang, Y. Wang, Y. Huang, Y. Ma, Z. Liu, J. Cai, C. Zhang, H. Gao, Y. Chen, Electromagnetic interference shielding of graphene / epoxy composites, Carbon. 47 (2009) 922-925. doi:10.1016 / j.carbon.2008.12.038.

[24] Y. Yang, M.C. Gupta, K.L. Dudley, R.W. Lawrence, Novel Carbon Nanotube-Polystyrene Foam Composites for Electromagnetic Interference Shielding, Nano Lett. 5 (2005) 2131-2134. doi:10.1021 / nl051375r.

[25] H.-B. Zhang, Q. Yan, W.-G. Zheng, Z. He, Z.-Z. Yu, Tough Graphene-Polymer Microcellular Foams for Electromagnetic Interference Shielding, ACS Appl. Mater. Interfaces. 3 (2011) 918-924. doi:10.1021 / am200021v.

[26] K. Xu, G. Chen, D. Qiu, Convenient construction of poly(3,4-ethylenedioxythiophene)-graphene pie-like structure with enhanced thermoelectric performance, J. Mater. Chem. A. 1 (2013) 12395-12399. doi:10.1039 / C3TA12691A

[27] B.N. Reddy, M. Deepa, A.G. Joshi, A.K. Srivastava, Poly(3,4-Ethylenedioxypyrrole) Enwrapped by Reduced Graphene Oxide: How Conduction Behavior at Nanolevel Leads to Increased Electrochemical Activity, J. Phys. Chem. C. 115 (2011) 18354-18365. doi:10.1021 / jp205551k.

[28] Y. Lu, Y. Song, F. Wang, Thermoelectric properties of graphene nanosheets-modified polyaniline hybrid nanocomposites by an in situ chemical polymerization, Mater. Chem. Phys. 138 (2013) 238-244. doi:10.1016 / j.matchemphys.2012.11.052.

[29] W. Weng, G. Chen, D. Wu, Crystallization kinetics and melting behaviors of nylon 6 / foliated graphite nanocomposites, Polymer. 44 (2003) 8119-8132. doi:10.1016 / j.polymer.2003.10.028.

[30] W. Weng, G. Chen, D. Wu, X. Chen, J. Lu, P. Wang, Fabrication and characterization of nylon 6 / foliated graphite electrically conducting nanocomposite, J. Polym. Sci. Part B Polym. Phys. 42 (2004) 2844-2856. doi:10.1002 / polb.20140.

[31] W. Zheng, X. Lu, S.-C.Wong, Electrical and mechanical properties of expanded graphite-reinforced high-density polyethylene, J. Appl. Polym. Sci. 91 (2004) 2781-2788. doi:10.1002 / app.13460.

[32] X.S. Du, M. Xiao, Y.Z. Meng, Facile synthesis of highly conductive polyaniline / graphite nanocomposites, Eur. Polym. J. 40 (2004) 1489-1493. doi:10.1016 / j.eurpolymj.2004.02.009.

[33] H.-B. Zhang, W.-G. Zheng, Q. Yan, Y. Yang, J.-W. Wang, Z.-H. Lu, G.-Y. Ji, Z.-Z. Yu, Electrically conductive polyethylene terephthalate / graphene nanocomposites prepared by melt compounding, Polymer. 51 (2010) 1191-1196. doi: 1 0.1 016 / j.polymer.201 0.01.027.

[34] H. Kim, C.W. Macosko, Processing-property relationships of polycarbonate / graphene composites, Polymer. 50 (2009) 3797-3809. doi:10.1016 / j.polymer.2009.05.038.

Claims

1. A method of manufacturing a conductive composite comprising at least one surface layer comprising multi-layer graphene, comprising the steps of: a) bringing into contact a substrate, preferably non-metallic, and an aqueous deposition composition comprising: ∘ multi-layer graphene at a concentration of 0.2 g / l or more, preferably 1 g / l or more, or even more preferably 2 g / l or more, and ∘ at least one surfactant; b) heat treatment of the substrate obtained in step a) at a temperature ranging from 100 to 250°C; and obtaining the composite.

2. The method according to the preceding claim, further comprising a step c) of treating the composite obtained in step b) at a low temperature, within a range of 40°C to 80°C, preferably for a duration within a range of 5 minutes to 5 hours.

3. The method according to any of the preceding claims, wherein steps a), b) and optionally c) are repeated at least once, preferably from 1 to 30 times.

4. The method according to any of the preceding claims, wherein step a), comprising bringing the substrate into contact with the aqueous deposition composition, is carried out by direct application of the aqueous composition using a paintbrush, a brush or a spray, by impregnating the substrate with the aqueous composition, by immersing the substrate in the aqueous composition, or by screen printing.

5. The method according to any of the preceding claims, wherein the duration of the heat treatment of step b) is in the range of 1 minute to 5 hours.

6. The method according to any of the preceding claims, wherein the at least one surfactant is selected from the group comprising anionic, cationic, amphoteric and non-ionic surfactants and mixtures thereof.

7. The method according to any one of the preceding claims, wherein the mass concentration of surfactant(s) in the aqueous coating composition is in the range of 0.1 to 50%.

8. The method according to any one of the preceding claims, wherein the substrate is selected from the group comprising thermoplastic polymers, thermosetting polymers, fabrics based on natural and / or synthetic fibres, ceramics, glasses and mixtures thereof.

9. A conductive composite comprising at least one surface layer consisting of multi-layer graphene, obtained by the method of any of the preceding claims.

10. The composite according to the preceding claim, wherein the at least one surface layer consisting of multi-layer graphene has a thickness in the range of 1 to 1000 nm.

11. The composite according to any of claims 9 or 10 having an electrical conductivity greater than 200 S / m.

12. A device comprising a composite according to any one of claims 9 to 11.

13. Use of an aqueous deposition composition comprising multi-layer graphene at a concentration of 0.2 g / l or more, preferably 1 g / l or more, or more preferably 2 g / l or more, and at least one surfactant, to form a surface layer consisting of multi-layer graphene on a substrate, preferably a non-metallic substrate, according to of the method any one of claims 1 to 8.

Images