METHOD OF MANUFACTURING A CONDUCTIVE COMPOSITE, CONDUCTIVE COMPOSITE AND USES

Abstract

The present invention relates to a method for manufacturing a conductive composite comprising a substrate, which may have any geometric shape, coated with a graphene-based layer. The present invention also relates to a conductive composite obtained by this method, as well as to its uses, for example adsorbent of microwave waves, for electromagnetic shielding, for the absorption of electromagnetic waves, for the transport of signals, for the protection of equipment for stealth. The method of the invention comprises the following steps: (a) coating a substrate, preferably non-metallic, with a liquid or solid graphene coating composition comprising: graphene at a concentration of 0.2 g / L to 250 g / L, ii) at least one surfactant; (b) subjecting the coated substrate obtained in step (a) to a heat treatment; and (c) shaping or assembling the coated substrate obtained in step b). Abstract figure: Fig.1.

Description

Title of the invention: METHOD FOR MANUFACTURING A CONDUCTIVE COMPOSITE, CONDUCTIVE COMPOSITE AND USES Technical field of the invention

[0001] The present invention relates to a method for manufacturing a conductive composite comprising a substrate, which may have any geometric shape, coated with a graphene-based layer. The present invention also relates to a conductive composite obtained by this method, as well as to its uses, for example as an adsorbent of microwaves, for electromagnetic shielding, for the absorption of electromagnetic waves, for the transport of signals, for the protection of equipment for stealth.

[0002] The mentions “Ref.” followed by a number refer to the list of references at the end of the text, before the claims. Prior art

[0003] The state of the art highlights the growing interest in conductive composites, particularly those exploiting carbon materials such as graphene, recognized for their exceptional electrical properties. These materials pave the way for a significant improvement in the electrical conductivity of composites, thus making them extremely relevant for a variety of applications, including electromagnetic shielding, electromagnetic wave absorption, signal transport, equipment protection, stealth, electromagnetic discretion and many others, in sectors as diverse as electronics, transportation, medicine, communications, and aerospace.

[0004] However, traditional methods of manufacturing conductive composites generally involve the incorporation of carbonaceous materials into a polymer or ceramic matrix, which results in a homogeneous dispersion of these materials throughout the mass of the composite.

[0005] Furthermore, despite some advances, the state of the art identifies challenges associated with the application of these methods to objects of complex shapes or large sizes. Thus, there remains in particular the need for a method making it possible to obtain a conductive composite, for example with a surface layer based on multi-sheet graphene, having improved conductivity, and which can be applied to any type of object, even of complex geometric shape. Statement of the invention

[0006] In this context, the present invention addresses these challenges by providing a method for manufacturing a conductive composite, comprising the following steps: (a) coating a substrate, preferably non-metallic, with a liquid or solid graphene coating composition comprising: (i) graphene at a concentration of 0.2 g / L to 250 g / L, (ii) at least one surfactant, (iii) optionally a binder and / or a thickener, (iv) optionally a functionalizing agent or a magnetic particle; (b) subjecting the substrate coated in step (a) to a heat treatment at a temperature of 60 to 300°C, preferably 80 to 450°C, making it possible to obtain the conductive composite comprising the substrate coated with a graphene-based layer; and (c) shaping or assembling the substrate obtained in step (b).

[0007] It is to the applicant's credit to have developed this process allowing the manufacture of composites incorporating at least one layer, also called "surface layer" below, based on graphene, thus resolving the challenges identified in the state of the art. This advance is based, thanks to this process, on a careful application of graphene on a substrate, including a substrate specifically chosen because of its particular geometric shape, thus providing an ingenious solution to the problems identified. This process in fact allows a uniform application of the graphene-based layer over the entire surface of the substrate chosen to implement the process, whatever its shape, and ensures perfect adhesion and precise adaptation of the graphene-based layer to the substrate.The flexibility offered by the method of the invention on this diversity of geometric shapes, for example a ball shape, eliminates the problems of rigidity or folding commonly observed with textile substrates, thus guaranteeing homogeneous coverage.

[0008] In this method, the substrate can therefore have any geometric shape, simple or complex, for example a shape selected from powders, films, pellets, beads, monoliths, foams, extrudates, rings, aerosols, granules, gynoid or alveolar structures, or a combination of two or more of these shapes. This or these shape(s) can be independently of different sizes. The geometric shape can be carefully selected according to the intended application for the conductive composite.

[0009] In this method, the substrate may be made of any material known to those skilled in the art as compatible with the solid or liquid composition of graphene and with the temperature of the heat treatment step. Preferably, the substrate is not metallic. It may be, for example, a material chosen from a thermoplastic material, a thermosetting material, a ceramic, plant fibers or synthetic, biopolymers, composites, and a combination of two or more of these materials.

[0010] Advantageously, the substrate to be coated may be chosen from acetal (POM), styrene acrylonitrile butadiene (ABS) and other specialized styrenics, polyimides (PI), for example aramids, aromatic polyamides, cellulose acetate (cellulose CA), cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP) and cellulose nitrate (CN), ethylene vinyl acetate (EVA), expanded polystyrene (EPS), expanded polypropylene (EPP), fluoroplastics PTFE (polytetrafluoroethylene) and FEP (fluorinated ethylene propylene), nylons (polyamides) PA, the family of polyaryletherketones such as polyaryletheretherketone (PEEK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK) and polyetherketoneetherketoneketone (PEKEKK), polybutene-1 (PB-1), polycarbonate (PC), polyacetals, polyoxymethylene (POM), thermoplastic polyesters such as poly(ethylene terephthalate (PETP),polybutylene terephthalate (PBT) and polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyphenylene oxide (PPO), polyphenylene sulfide PPS, polyphenylene polysulfone (PPSU), polymethylpentene PMP, polystyrene, e.g. general purpose GPPS, and high impact polystyrene HIPS, polyvinyl alcohol, polyvinyl alcohol homopolymer (PVOH), polyvinyl alcohol (PVA or PVAL), polyvinyl chloride (PVC), styrene acrylonitrile (SAN) and acrylonitrile styrene acrylate (ASA), thermoplastic elastomers (TPE), e.g. thermoplastic rubber, and thermopropylene rubber (TPR), and combinations thereof, two or more. ,

[0011] Advantageously, the substrate to be coated can also be chosen from carbon / epoxy, carbon / polyurethane, carbon / thermoplastic, thermoplastic / thermoplastic, thermoplastic / epoxy, thermoplastic / polyurethane, plant fiber / epoxy, plant fiber / polyurethane, plant fiber / thermoplastic, ceramic / epoxy, ceramic / polyurethane, ceramic / thermoplastic composites and a mixture thereof.

[0012] Whatever the material chosen for the substrate for implementing the method, and whatever its geometric shape, thanks to the method described herein, the substrate can have a very large average diameter, for example from 0.01 to 100 mm, preferably from 0.1 to 10 mm, more preferably from 0.2 to 10 mm, more preferably from 0.2 to 10 mm.

[0013] As an advantageous example, the substrate may be, for example, a polystyrene substrate, for example expanded or unexpanded polystyrene, dense, rigid, transparent and thin, but also other forms of expanded or mixed with other plastics and additives. This may be, for example, polystyrene, expanded or unexpanded, and for example in the form of beads. In this example, when the substrate is in the form of polystyrene beads, they may, for example, have a diameter of 0.5 to 10 mm, preferably 1 to 6 mm. These beads may have varying diameters and densities, for example, diameters of 1 mm, 2 mm, 3 mm, 4 mm or 6 mm with respective densities of 28 kg / m3, 19 kg / m3, 16 kg / m3, 11 kg / m3 and 6 kg / m3. Advantageously, the use of a polystyrene substrate, in particular polystyrene beads or with polystyrene incorporation, offers a solution to the weight problem, since polystyrene has a density of between 15 and 40 kg / m3.The method provided by the inventors advantageously makes it possible to benefit from the fact that polystyrene is an economical and easy-to-obtain material, having already been widely used for many years in insulating applications, which guarantees safe, economical and accessible use for the manufacture of the conductive material according to the method described herein. Advantageously, the substrate may be made exclusively of polystyrene beads, i.e. comprising only this material.

[0014] In this method, favorably, step (a) of coating the substrate can be carried out by means of a liquid or solid graphene coating composition.

[0015] Graphene is known as a crystalline two-dimensional material, an allotropic form of carbon whose stacking constitutes graphite. For the implementation of the method provided by the inventors, the graphene may be exfoliated graphene, for example by ultrasound, epitaxial graphene, graphene produced by high-temperature catalytic decomposition of a carbon gas, for example methane or ethylene, on a metal, for example copper, nickel or iridium. It may also be graphene produced chemically by oxidation of graphite in an acid medium, for example sulfuric acid and potassium permanganate, purified by hydrazine, or graphene obtained by injection of a graphene solution into degassed water, or graphene produced by flash heating of carbon waste at a temperature of 2727°C.Examples of commercial references that can be used for implementing the method of the invention are, for example, multi-sheet graphene (commercial reference: BLF ink, supplier: BLACKLEAF), graphene nanoplatelets (commercial reference: G-Leaf Coating), multi-sheet graphene (commercial reference: GrapheneBlack, supplier: nanoxplore), (commercial reference: graphene GUP, suppliers: GrapheneUP), multi-sheet graphene (commercial reference: G3 graphene, supplier: Levidian).

[0016] For the preparation of the deposition composition for the implementation of step (a) of the method, the graphene is mixed with at least one surfactant, optionally with a binder and / or a thickener, optionally with a functionalizing agent.

[0017] Preferably, in the deposition composition, the graphene is at a concentration of 0.2 g / L to 250 g / L. One of the advantages related to the present invention is also manifested by the possible modulation of the graphene charges used to coat the substrate, adapted to each specific application. This capacity of the process makes it possible to adjust the levels of thermal or electrical conductivity and gives remarkable versatility to the invention, optimally meeting the requirements specific to each intended use.

[0018] When the deposition composition for implementing step (a) of the method is liquid, the solvent may be chosen from water, organic solvent, oil and superplasticizer, or a mixture of two or more of these solvents. The quantity of solvent is adapted according to the coating or application technique chosen and also according to the deposition composition itself, that is to say according to the ingredients which constitute it. A person skilled in the art will know how to adapt this quantity of solvent according to the composition and the quality of the result sought in the implementation of the method.

[0019] If there is a surfactant, it can be chosen from anionic, cationic, non-ionic and amphoteric, polymeric, bio-sourced or a mixture of two or more of these surfactants. Examples of products that can be used are Sodium cocoyl isethionate, (commercial reference: SCI + suppliers: arcane industrie), Polyoxyethylene-polyoxypropylene block copolymer (commercial references: Pluronic F68, suppliers: Sigma Aldrich), carboxymethyl cellulose (commercial references: CMC, supplier: Sigma Aldrich).

[0020] According to the method described herein, the deposition composition for implementing step (a) of the method may comprise a binder. This binder ensures good adhesion between the functional graphene layer and the host substrate. The binder may be chosen from organic, inorganic, bio-sourced, polymeric binders, etc., or a mixture of two or more of these binders. Examples of products that can be used are styrene butadiene rubber (commercial references: Styrofan, supplier: BASF), acrylic binder (commercial reference: acrylic DALBE, supplier: DALBE), cellulose binder (commercial reference: SUNROSE DALBE, supplier: Nippon paper group). The binder may, for example, be at a concentration in the deposition composition of 0.1% to 50%, preferably 1 to 25%.

[0021] According to the method described herein, the deposition composition for carrying out step (a) of the method may comprise a thickener. This thickener allows to obtain a viscosity adapted to the coating technique or application of the deposition composition on the chosen substrate. The thickener can for example be chosen from Polysaccharides (for example starches, vegetable gums and pectin), proteins (for example eggs, collagen, gelatin, albumin) and mineral or vegetable fats (for example butter, oil) or a mixture of two or more of these thickeners. Examples of products which can be used are Xanthan gum (commercial reference: Xanthan gum, supplier: Xanthomonas campestris), carboxymethyl cellulose (commercial reference: CMC, supplier: Sigma Aldrich). The thickening can be for example at a concentration in the deposition composition of 0.01 to 50%, preferably of 1% to 20%

[0022] Furthermore, favorably, whatever the coating or application technique of the composition chosen for step (a) of the method provided by the inventors, the method can be implemented with pure graphene or graphene functionalized and / or doped by means of a functionalizing agent and / or a doping agent respectively.

[0023] Thus, according to the method described herein, the deposition composition for implementing step (a) of the method may comprise a graphene functionalization agent. These may be, for example, functional groups, for example hydroxyl, amine, ester, amide, atoms, for example oxygen, nitrogen, sulfur, molecules, for example CO2, H2O, H2, proteins, for example bovine serum albumin, L-arginine, polylysine, polysaccharides, for example dextrose, starch, sucrose, as well as combinations thereof. Examples of products that can be used are bovine serum albumin (commercial reference: BSA, supplier: Sigma Aldrich), dextrose (commercial reference: D-glucose, supplier: Roquette). Typically, the concentration of functionalization agent in the deposition composition is from 10 ppm to 20%, preferably from 0.01 to 10%.

[0024] Thus, according to the method described herein, the deposition composition for implementing step (a) of the method may comprise a doping agent, for example in the form of heteroatoms such as oxygen; nitrogen, sulfur or metal particles, for example magnetic metal particles. These may be, for example, magnetic particles chosen from ferromagnets such as iron oxides (Magnetite (Fe3O4), supplier: Sigma aldrish and ferric oxide (Fe2O3), supplier: Funcmater), ferrimagnets such as Magnesium Ferrite (MgFe2O4, supplier: Nanographi), as well as alloys such as CoPt3 and FePt, as well as combinations thereof. Typically, the concentration of doping agent in the deposition composition is from 0.1 to 70%, preferably from 1 to 30%.

[0025] This coating or application can be carried out by any appropriate technique known to those skilled in the art, depending on the solid or liquid nature and the composition of the graphene coating composition. A person skilled in the art will be able to choose the appropriate technique. This may advantageously be a technique chosen from: spraying, dipping, dip-coating, impregnation, pad printing, doctor blade, slot die, layer by layer (LBL), screen printing, capillary deposition, inkjet or electrostatic deposition.).

[0026] When the graphene coating composition is applied to the substrate in liquid form, it may for example be an application by means of a graphene-based ink. The graphene coating may for example be deposited on the substrate by one of the methods described in patent applications FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

[0027] Once the substrate has been coated according to step (a) of the method, the coated substrate is subjected to the heat treatment of step (b). This heat treatment can be carried out using any suitable heating means known to those skilled in the art, chosen taking into account the graphene coating composition and the substrate, in particular the graphene itself, the solvent, the surfactant, optionally the binder and / or the thickener and / or the functionalizing agent. Neither the substrate, nor the composition, nor the conductive composite obtained must be altered by the heating means. This heating means must also make it possible to reach the temperatures necessary for the heat treatment.In the method provided by the inventors, these heating temperatures may be, for example, from 60 to 450°C, preferably from 80 to 300°C, preferably from 100 to 300°C, more preferably from 90 to 300°C, or from 80 to 280°C, with a marked preference for a range of 80 to 250°C in the context of the materials described herein. For example, the heating means may be chosen from an oven, a Joule effect oven, an infrared (IR) oven or heater, a halogen oven or heater, an electromagnetic induction oven or heater, and a microwave or a combination of these means.

[0028] The duration of the heat treatment of step b) can vary from 1 minute to 24 hours, preferably from 5 minutes to 2 hours, or from 30 minutes to 1 hour. It depends on the substrate of the graphene coating composition.

[0029] This heat treatment step ensures in particular the evaporation of the solvent and the lasting anchoring of the graphene layer to the surface of the substrate. The duration of the treatment is adapted so as to obtain a homogeneous conductive composite material, which does not crumble and is stable over time.

[0030] Following step (c) of the method, the substrate obtained in step (b) can be shaped or assembled according to any method commonly used in the state of the art for shaping conductive composite materials. For example, it can be poured into a container, self-supported using a binder, for example such as those mentioned above, or a thermal process, or even coated in a resin to create a stable geometry suitable for the desired application.

[0031] Advantageously, steps (a), (b) and optionally (c) of the method may be repeated or not, ideally from 1 to 30 times, in iterations of the sequence (a), (b) and optionally (c). An increased preference lies in the range of 1 to 20 repetitions, or even from 2 to 10, or even from 1 to 5. This repetition makes it possible to obtain a conductive composite material comprising the substrate coated with a multi-layer graphene.

[0032] Advantageously, the graphene layer or surface layer formed on the surface of the substrate preferably comprises multi-sheet graphene, each sheet having a thickness of 1 to 1000 nm, preferably 5 to 800 nm and even more preferably 10 to 500 nm. These intervals refer to the individual layers or "sheets", since the final layer, resulting from one or more iterations of the process or method according to the invention, has a thickness of up to a few micrometers or more. According to the method provided by the inventors, the graphene-based coating or layer of the conductive composite material obtained can in fact, for example, have a thickness ranging from 5 nm to 100 pm, preferably from 5 nm to 800 nm, more preferably from 10 nm to 500 nm, more preferably from 100 nm to 500 nm.Of course, the person skilled in the art will know how to adapt the total thickness from at least one surface layer comprising graphene depending on the intended application.

[0033] Also, the present invention also relates to a conductive composite material obtained by the method of the invention. The substrate, the graphene, the surfactant, the binder, the thickener, the functionalizing agent are described above.

[0034] In a preferred configuration, the conductive composites obtained by the method described herein incorporate at least one graphene-based layer or "surface layer", preferably several, thus forming a multi-sheet graphene layer, applied to the surface of the substrate, the substrate being able to have a very varied geometric shape, for example selected from powders, films, pellets, beads, monoliths, foams, extrudates, aerosols of different sizes, rings, granules, gynoid or alveolar structures and a combination of two or more of these shapes, preferably in the form of beads, preferably polystyrene or with incorporation of polystyrene as described above.

[0035] The composite obtained by the method described herein can be configured either by filling it in a container, for example thermoplastic, thermosetting, composites, synthetic or vegetable fibers, ceramic, or by self-supporting it using a binder or a thermal process, or by coating it in a coating material, for example a polymer resin, for example polyurethane (reference commercial reference: X970 ISO, supplier: SAMARO specialty Chemicals), polyester (commercial reference: Resion Polyester Laminating Resin, supplier: Resion resin technology), epoxy (commercial reference: RENGEL SW 56 / REN HY 2404, supplier: SAMARO specialty Chemicals), silicone (commercial reference: SILASTIC RTV-4234-T4, supplier: SAMARO specialty Chemicals) as well as their combinations, to generate a stable geometry in accordance with the desired application. Advantageously, the coating material can be a polymer of natural or synthetic origin in powder or liquid form. It can be chosen from polyurethane, polyester, epoxy resins, as well as their combinations. It can be a thermo- and / or photo-cured, thermo- and / or photo-polymerizable polymer (commercial reference: SUNLU Standard resin, supplier: SAMARO specialty Chemicals.The person skilled in the art will know how to choose the coating and adapt the shape of the container according to their specificities and needs.

[0036] Advantageously, the method described herein makes it possible to adjust the coating rate of the substrate, i.e. the graphene load which can vary from a few milligrams up to a hundred grams, in particular depending on the geometry and the material of the substrate chosen, aiming to achieve the desired characteristics of electrical conductivity and percolation rate. A person skilled in the art can easily adapt this coating rate to obtain the desired result, based on his general knowledge.

[0037] The present invention also relates to the use of a conductive composite obtained by the method described herein as a microwave adsorbent, as well as to the use of a conductive composite obtained by the method described herein for electromagnetic shielding, for the absorption of electromagnetic waves, for the transport of signals, for the protection of equipment, stealth, electromagnetic discretion and many others, in sectors as diverse as electronics, transportation, medicine, communications, and aerospace. The composite material of the present invention can be used in the applications described for example in the documents Yao Chen, Jinzhe Li, Tian Li, Likui Zhang, Fanbin Meng, Recent advances in graphene-based films for electromagnetic interference shielding: Review and future prospects,Carbon, Volume 180, 2021, Pages 163-184 (Ref. 3); Papari Das, Ashish B.Deoghare, Saikat Ranjan Maity, Exploring the Potential of Graphene as an EMI Shielding Material - An OverView, Materials Today: Proceedings, Volume 22, Part 4, 2020, Pages 1737-1744 (Réf. 4) ; et Samira Naghdi, Babak Jaleh, Mahtab Eslamipanah, Aida Moradi, Mahsa Abdollahi, Naeemeh Einali, Kyong Yop Rhee, Graphene family, and their hybrid structures for electromagnetic interférence shielding applications: Recent trends and prospects, Journal of Alloys and Compounds,Volume 900, 2022, 163176 (Réf. 5). .

[0038] The method described herein, the conductive composite obtained by this method, as well as the uses of the conductive composite described herein assert themselves as a significant advance, successfully overcoming the limitations of the methods of the prior art, by presenting a different and flexible approach for the application of surface layers of graphene, including multi-sheets, on substrates having a wide variety of material and geometric shapes.

[0039] Furthermore, the method described herein proves to be particularly advantageous for objects of complex shapes, such as vehicles, while avoiding significant overload. Thus, this method effectively and versatilely meets the unmet needs identified in the state of the art, opening up new perspectives for the aforementioned applications requiring controlled conductivity. Brief description of the figures

[0040] [Fig-1] represents on the left the substrate in the form of polystyrene beads before the coating according to the method provided by the inventors and the same substrate after applying the coating method with graphene.

[0041] [Fig.2] represents an example of a composite according to the invention, where the graphene-coated substrate is integrated into a PET container.

[0042] [Fig.3] represents another example of a composite according to the invention, where the graphene-coated substrate is molded in an epoxy resin.

[0043] Other advantages, aims and particular characteristics of the present invention will emerge from the examples which follow, given for illustrative and in no way limiting purposes. EXAMPLES

[0044] Example 1: PROCESS FOR THE PREPARATION OF CONDUCTIVE COMPOSITES FLG@POLYSTYRENE (PS) BEADS

[0045] The composite according to the invention was obtained from polystyrene beads according to the method described below.

[0046] The following method was implemented:

[0047] (a) an aqueous composition based on FLG graphene (FLG = “few layer graphene », trade name: BLK ink, supplier BLACKLEAF) with a concentration of 7 g / l was deposited on the polystyrene beads by the method described in patent application FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

[0048] (b) the soaked substrate of step (a) thus formed was then oven dried at a temperature of 110°C for a duration of 1 hour.

[0049] This sequence (a), (b) was repeated four times, resulting in the manufacture of the composite with few layers of graphene on polystyrene particles (“FLG@PS for “few layer graphene on polystyrene particles”). The FLG@PS composite as well obtained was introduced into a PET bag and used as an adsorbent of microwave waves in an anechoic chamber (measurement of reflection coefficient in dB, Frequency: 2-18 GHz, Normal incidence, Double linear polarization, Horn antenna + focusing lens, task of max diameter 15-20 cm, Temporal filtering and Calibration with a measurement on a metal plate and a measurement in free space).

[0050] Example 2: PROCESS FOR MANUFACTURING CONDUCTIVE COMPOSITES FLG@POEYSTYRENE (PS) BALLS MOULDED IN AN EPOXY RESIN

[0051] The composite according to the invention was obtained from polystyrene beads according to the method described herein by the inventors.

[0052] The following method was implemented:

[0053] (a) an aqueous composition based on FLG graphene (FLG = “few layer graphene », trade name: BLK ink, supplier BLACKLEAF) with a concentration of 7 g / l was deposited on the polystyrene beads by the method described in patent application FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

[0054] (b) the soaked substrate of step (a) thus formed was then oven dried at a temperature of 110°C for a duration of 1 hour.

[0055] This sequence (a), (b) was repeated four times, resulting in the manufacture of the FLG@PS composite.

[0056] The coated beads are then placed in a silicone mold, then the epoxy resin doped with 0.2% graphene is poured into the mold containing the beads. The mixture is left to harden for 12 hours, demolded, and the final FLG / PS@Epoxy composite, measuring 50 cm x 50 cm with a thickness of 10 mm, is used in electromagnetic wave adsorption applications in anechoic chamber (condition: measurement of reflection coefficient in dB, Frequency: 2-18 GHz, Normal incidence, Dual linear polarization, Horn antenna + focusing lens, task with max diameter 15-20 cm, Temporal filtering and Calibration with a measurement on a metal plate and a measurement in free space).

[0057] Example 3: PROCESS FOR THE MANUFACTURE OF FLG CONDUCTIVE COMPOSITES DOUPED WITH MAGNETIC IRON PARTICLES DEPOSITED ON POLYSTYRENE (PS) BEADS

[0058] The composite according to the invention was obtained from polystyrene beads and manufactured according to the method described according to the invention.

[0059] The following method was implemented:

[0060] (a) An aqueous composition based on FLG graphene (FLG = “few layer graphene », trade name: BLK ink, supplier BLACKLEAF) with a concentration of 7 g / 1 and Fe2O3 particles (trade name: ferric oxide (Fe2O3), particle size: 70-90 nm, supplier: Funcmater with a ratio FLG / Fe2O3:70 / 30 has been deposited on polystyrene beads by the method described in patent application FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

[0061] (b) the soaked substrate of step (a) thus formed was then oven dried at a temperature of 110°C for a duration of 1 hour.

[0062] This sequence (a), (b) was repeated four times, resulting in the fabrication of the FLG-Fe2O3 / PS composite. The FLG-Fe2O3 / PS composite thus obtained was introduced into a polycarbonate frame and used as an adsorbent for low-frequency waves in an anechoic chamber. Conditions: measurement of reflection coefficient in dB, Frequency: less than 2 GHz, Normal incidence, Dual linear polarization, Horn antenna + focusing lens, task with a maximum diameter of 15-20 cm, Temporal filtering and Calibration with a measurement on a metal plate and a measurement in free space. List of bibliographic references

[0063] Ref.l: FR3087432 (BLAKLEAF).

[0064] Ref.2: WO2020109380 (BLAKLEAF).

[0065] Ref.3: Yao Chen, Jinzhe Li, Tian Li, Likui Zhang, Fanbin Meng, Recent advances in graphene-based films for electromagnetic interference shielding: Review and future prospects, Carbon, Volume 180, 2021, Pages 163-184.

[0066] Réf. 4 : Papari Das, Ashish B. Deoghare, Saikat Ranjan Maity, Exploring the Potential of Graphene as an EMI Shielding Material - An OverView, Materials Today: Proceedings, Volume 22, Part 4, 2020, Pages 1737-1744.

[0067] Réf. 5 : Samira Naghdi, Babak Jaleh, Mahtab Eslamipanah, Aida Moradi, Mahsa Abdollahi, Naeemeh Einali, Kyong Yop Rhee, Graphene family, and their hybrid structures for electromagnetic interférence shielding applications: Recent trends and prospects, Journal of Alloys and Compounds,Volume 900, 2022, 163176.

Claims

Claims

1. A method for manufacturing a conductive composite, comprising the following steps: (a) coating a substrate, preferably non-metallic, with a liquid or solid graphene coating composition comprising: (i) graphene at a concentration of 0.2 g / L to 250 g / L, (ii) at least one surfactant, (iii) optionally a binder and / or a thickener, (iv) optionally a functionalizing agent or a magnetic particle; (b) subjecting the substrate coated in step (a) to a heat treatment at a temperature of 60 to 300°C, preferably 80 to 450°C, to obtain the conductive composite comprising the substrate coated with a graphene-based layer; and (c) shaping or assembling the substrate obtained in step (b).

2. The method of claim 1, wherein the substrate has a shape selected from powders, films, pellets, beads, monoliths, foams, extrudates, aerosols, rings, granules, gynoid or honeycomb structures.

3. Method according to claim 2, in which the substrate is in the form of beads, preferably polystyrene.

4. A method according to any preceding claim, wherein the substrate is in the form of polystyrene beads having a diameter of 0.5 to 10 mm.

5. A method according to any preceding claim, wherein steps (a), (b), and optionally (c), are repeated, preferably 1 to 30 times, in iterations of the sequence (a), (b), and optionally (c)).

6. Conductive composite obtained by the method defined in any one of claims 1 to 5.

7. Composite according to claim 6, wherein the graphene layer is obtained from pure graphene or functionalized graphene, in solid or liquid form, or from a graphene-based ink.

8. A composite according to any one of claims 6 or 7, wherein the thickness of the graphene-based layer is from 5 nm to 100 pm, preferably from 5 nm to 800 nm, more preferably from 10 nm to 500 nm, more preferably from 100 nm to 500 nm.

9. A composite according to any one of claims 6 to 8, wherein the substrate is made of a material selected from a thermoplastic material, a thermosetting material, a ceramic, plant or synthetic fibers, biopolymers, composites and a combination of two or more of these materials.

10. Composite according to any one of claims 6 to 9, wherein the substrate is in a form chosen from powders, films, pellets, beads, monolith, foams, extrudates, aerosols, rings, granules, gynoid or alveolar structures, said substrate comprising at least one graphene-based layer or a combination of two or more of these forms.

11. Composite according to any one of claims 6 to 10, wherein the substrate is in the form of beads, preferably polystyrene.

12. A composite according to any one of claims 6 to 11, wherein the graphene-based layer comprises multi-sheet graphene where each sheet has a thickness of between 1 and 1000 nm.

13. llili. Composite according to any one of claims 6 to 12, said composite being coated in a coating material chosen from a polymer of natural or synthetic origin in powder or liquid form, chosen from polyurethane, polyester, epoxy resins.

14. Use of a composite according to any one of claims 6 to 13 as a microwave adsorbent.

15. Use of a composite according to any one of claims 6 to 13 for electromagnetic shielding, for the absorption of electromagnetic waves, for the transport of signals, for the protection of equipment for stealth.

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