METHOD FOR 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 its uses, for example, as a microwave adsorbent, for electromagnetic shielding, for electromagnetic wave absorption, for signal transmission, and for protecting 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: (ii) graphene at a concentration of 0.2 g / L to 250 g / L, and (ii) at least one surfactant; (b) subjecting the coated substrate obtained in step (a) to heat treatment; and (c) shaping or assembling the coated substrate obtained in step (b). (Short 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 a microwave adsorbent, for electromagnetic shielding, for electromagnetic wave absorption, for signal transmission, and 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. Previous art

[0003] The state of the art highlights the growing interest in conductive composites, particularly those utilizing carbon materials such as graphene, known 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 transmission, 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 carbon materials into a polymer or ceramic matrix, resulting in a homogeneous dispersion of these materials throughout the mass of the composite.

[0005] Furthermore, despite some progress, the state of the art identifies challenges associated with applying these methods to objects with complex shapes or large sizes. In particular, the need remains for a process to obtain a conductive composite, for example with a surface layer based on multi-layered graphene, exhibiting improved conductivity, and applicable to any type of object, even one with a complex geometric shape. Description 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 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 assembly of the substrate obtained in step (b).

[0007] The applicant deserves credit for developing this process for manufacturing composites incorporating at least one graphene-based layer, also referred to below as the "surface layer," thereby resolving the challenges encountered in the prior art. This advancement relies, thanks to this process, on the meticulous application of graphene to a substrate, including a substrate specifically chosen for its particular geometric shape, thus providing an ingenious solution to the identified problems. This process allows for the uniform application of the graphene-based layer over the entire surface of the substrate chosen for implementing the process, regardless of its shape, and ensures perfect adhesion and precise adaptation of the graphene-based layer to the substrate.The flexibility offered by the process of the invention on this diversity of geometric shapes, for example a bead shape, eliminates the problems of rigidity or folding commonly observed with textile substrates, thus guaranteeing homogeneous coverage.

[0008] In this process, 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 shape or these shapes can be independently of different sizes. The geometric shape can be carefully selected according to the intended application of the conductive composite.

[0009] In this process, the substrate can be made of any material known to those skilled in the art to be compatible with the solid or liquid composition of graphene and with the temperature of the heat treatment step. Preferably, the substrate is non-metallic. It can be, for example, a material selected from among a thermoplastic material, a thermosetting material, a ceramic, or plant fibers. or synthetic, biopolymers, composites, and a combination of two or more of these materials.

[0010] Advantageously, the substrate to be coated can 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), PTFE (polytetrafluoroethylene) and FEP (fluoroethylene propylene) fluoroplastics, PA nylons (polyamides), the polyaryletherketone family such as polyaryletheretherketone (PEEK), polyetherketone (PEK), polyetheretherketoneketone (PEEKK) and the polyetherketone (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, for example general-purpose polystyrene (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 (TPEs), for example thermoplastic rubber, and thermopropylene rubber (TPR), as well as their combinations, in pairs or several. ,

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

[0012] Whatever the material chosen for the substrate for the implementation of the process, and whatever its geometric shape, thanks to the process described herein, the substrate can have a very wide average diameter, for example from 0.01 to 100 mm, preferably from 0.1 to 10 mm, preferably still from 0.2 to 10 mm, preferably still from 0.2 to 10 mm.

[0013] By way of advantageous example, the substrate may be, for example, a polystyrene substrate, for example, expanded or non-expanded polystyrene, dense, rigid, transparent and thin, but also other forms of expanded polystyrene or mixed with other Plastics and additives. These can include, for example, polystyrene, expanded or unexpanded, and in the form of beads. In this example, when the substrate is in the form of polystyrene beads, they can have a diameter of 0.5 to 10 mm, preferably 1 to 6 mm. These beads can 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, particularly polystyrene beads or beads incorporating polystyrene, offers a solution to the weight problem, as polystyrene has a density between 15 and 40 kg / m³.The process provided by the inventors advantageously takes advantage of the fact that polystyrene is an economical and readily available material, having already been widely used for many years in insulating applications. This ensures safe, economical, and accessible use for manufacturing the conductive material according to the process described herein. Advantageously, the substrate can consist exclusively of polystyrene beads, that is, comprising only this material.

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

[0015] Graphene is known as a two-dimensional crystalline material, an allotropic form of carbon, the stacking of which constitutes graphite. For the implementation of the process 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 carbonaceous 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 acidic medium, for example sulfuric acid and potassium permanganate, purified with hydrazine, or graphene obtained by injecting a graphene solution into degassed water, or graphene produced by flash heating of carbonaceous waste at a temperature of 2727°C.Examples of commercial references that can be used for implementing the process of the invention include, for example, multi-sheet graphene (commercial reference: BLF ink, supplier: BLACKLEAF), graphene nano-platelets (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 process, 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 coating composition, the graphene is present at a concentration of 0.2 g / L to 250 g / L. One of the advantages of the present invention is also manifested by the possibility of modulating the graphene charges used to coat the substrate, adapted to each specific application. This capability of the process makes it possible to adjust the levels of thermal or electrical conductivity and gives the invention remarkable versatility, optimally meeting the specific requirements of each intended use.

[0018] When the deposition composition for carrying out step (a) of the process 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 adjusted according to the coating or application technique chosen and also according to the deposition composition itself, i.e., according to its constituent ingredients. A person skilled in the art will be able to adjust this quantity of solvent according to the composition and the quality of the result sought in carrying out the process.

[0019] If a surfactant is present, it may be chosen from anionic, cationic, nonionic and amphoteric, polymeric, bio-based, or a mixture of two or more of these surfactants. Examples of usable products are Sodium cocoyl isethionate (trade reference: SCI + supplier: arcane industrie), Polyoxyethylene-polyoxypropylene block copolymer (trade references: Pluronic F68, supplier: Sigma Aldrich), and carboxymethyl cellulose (trade reference: CMC, supplier: Sigma Aldrich).

[0020] According to the process described herein, the deposition composition for carrying out step (a) of the process may include a binder. This binder ensures good adhesion between the graphene functional layer and the host substrate. The binder may be chosen from organic, inorganic, bio-based, polymeric, etc. binders, or a mixture of two or more of these binders. Examples of usable products are styrene butadiene rubber (trade names: Styrofan, supplier: BASF), acrylic binder (trade name: DALBE acrylic, supplier: DALBE), and cellulosic binder (trade name: 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 from 1% to 25%.

[0021] According to the process described herein, the deposition composition for carrying out step (a) of the process may include a thickener. This thickener This allows for achieving a viscosity suitable for the coating technique or application of the deposition composition onto the chosen substrate. The thickener can be selected from polysaccharides (e.g., starches, vegetable gums, and pectin), proteins (e.g., egg, collagen, gelatin, albumin), and mineral or vegetable fats (e.g., butter, oil), or a mixture of two or more of these thickeners. Examples of suitable products include xanthan gum (trade name: Xanthan gum, supplier: Xanthomonas campestris) and carboxymethyl cellulose (trade name: CMC, supplier: Sigma Aldrich). The thickener can be present at a concentration of 0.01% to 50% in the deposition composition, preferably from 1% to 20%.

[0022] Furthermore, favorably, regardless of the coating or application technique of the composition chosen for step (a) of the process provided by the inventors, the process can be carried out 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 process described herein, the deposition composition for carrying out step (a) of the process may include a graphene functionalizing agent. This may include, for example, functional groups, e.g., hydroxyl, amine, ester, amide; atoms, e.g., oxygen, nitrogen, sulfur; molecules, e.g., CO2, H2O, H2; proteins, e.g., bovine serum albumin, L-arginine, polylisine; polysaccharides, e.g., dextrose, starch, sucrose; and combinations thereof. Examples of usable products are bovine serum albumin (trade name: BSA, supplier: Sigma Aldrich) and dextrose (trade name: D-glucose, supplier: Roquette). Typically, the concentration of the functionalizing agent in the deposition composition is 10 ppm to 20%, preferably 0.01 to 10%.

[0024] Thus, according to the process described herein, the deposition composition for carrying out step (a) of the process may include a doping agent, for example in the form of heteroatoms such as oxygen, nitrogen, sulfur, or metallic particles, for example, magnetic metallic particles. These may include, for example, magnetic particles selected from ferromagnetics such as iron oxides (Magnetite (Fe3O4), supplier: Sigma Aldrish, and ferric oxide (Fe2O3), supplier: Funcmater), ferrimagnetics such as Magnesium Ferrite (MgFe2O4, supplier: Nanographi), as well as alloys such as CoPt3 and FePt, and combinations thereof. Typically, the concentration of the 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 know how 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, this may be, for example, by means of a graphene-based ink. The graphene coating may, for example, be deposited on the substrate by one of the processes described in patent applications FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

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

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

[0029] This heat treatment step ensures, in particular, the evaporation of the solvent and the durable bonding of the graphene layer to the substrate surface. The duration of the treatment is adapted to obtain a homogeneous, non-friable, and stable conductive composite material over time.

[0030] Following step (c) of the process, 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 with a binder, for example such as those mentioned above, or by a thermal process, or even encased in a resin to create a stable geometry suitable for the desired application.

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

[0032] Advantageously, the graphene layer or surface layer formed on the surface of the substrate, preferably comprising 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 ranges 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 even more. According to the process provided by the inventors, the graphene-based coating or layer of the resulting conductive composite material can, for example, have a thickness ranging from 5 nm to 100 µm, preferably from 5 nm to 800 nm, preferably again from 10 nm to 500 nm, and even more preferably from 100 nm to 500 nm.Of course, a person skilled in the art will be able to adapt the total thickness, starting from at least one surface layer containing graphene, according to the intended application.

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

[0034] In a preferred configuration, the conductive composites obtained by the process described herein incorporate at least one graphene-based layer or "surface layer", preferably several, thus forming a multi-layered 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 of polystyrene or with incorporation of polystyrene as described above.

[0035] The composite obtained by the process described herein can be configured either by filling it in a container, for example thermoplastic, thermosetting, composite, synthetic or plant fiber, ceramic, or by self-supporting it using a binder or a thermal process, or by embedding 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), and their combinations, to generate a stable geometry conforming to 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, and their combinations. It can be a thermo- and / or photo-curing, thermo- and / or photo-polymerizable polymer (commercial reference: SUNLU Standard resin, supplier: SAMARO specialty Chemicals).A skilled professional will know how to choose the coating and adapt the shape of the container according to its specific characteristics and needs.

[0036] Advantageously, the process described herein allows the coating level of the substrate, i.e., the graphene charge, to be adjusted, varying from a few milligrams to about one hundred grams, depending in particular on the geometry and material of the substrate chosen, in order to achieve the desired characteristics of electrical conductivity and percolation rate. A person skilled in the art can easily adapt this coating level to obtain the desired result, based on their general knowledge.

[0037] The present invention also relates to the use of a conductive composite obtained by the process described herein as a microwave wave adsorbent, as well as to the use of a conductive composite obtained by the process described herein for electromagnetic shielding, for the absorption of electromagnetic waves, for signal transmission, for equipment protection, stealth, electromagnetic discretion, and many other applications, 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 process described herein, the conductive composite obtained by this process, and the uses of the conductive composite described herein represent a significant advance, successfully overcoming the limitations of prior art methods, by presenting a different and flexible approach for the application of surface layers of graphene, including multi-sheet, on substrates with a wide variety of materials and geometric shapes.

[0039] Furthermore, the process described herein proves particularly advantageous for objects with complex shapes, such as vehicles, while avoiding significant overloading. Thus, this process effectively and versatilely addresses unmet needs identified in the prior art, opening 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 process provided by the inventors and the same substrate after the application of the coating process 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, purposes and particular features of the present invention will become apparent from the examples that follow, given for illustrative purposes only and in no way as limiting. EXAMPLES

[0044] Example 1: METHOD FOR MANUFACTURING 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: (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) (b) the substrate soaked in step (a) thus formed was then dried in an oven at a temperature of 110 °C for a period of 1h.

[0047] This sequence (a), (b) was repeated four times, resulting in the fabrication of the few-layer graphene-on-polystyrene-particle composite (“FLG@PS” for “few-layer graphene on polystyrene particles”). The FLG@PS composite thus obtained was introduced into a PET bag and used as a microwave wave adsorbent in an anechoic chamber (measurement of reflection coefficient in dB, Frequency: 2-18 GHz, Normal incidence, Double linear polarization, Horn antenna + focusing lens, spot of max diameter 15-20 cm, Time filtering and Calibration with a measurement on a metal plate and a measurement in free space).

[0048] Example 2: METHOD FOR MANUFACTURING CONDUCTIVE COMPOSITES FLG@POEYSTYRENE (PS) BEADS MOLDED IN AN EPOXY RESIN

[0049] The composite according to the invention was obtained from polystyrene beads according to the method described herein by the inventors.

[0050] The following method was implemented: (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).

[0051] (b) the substrate soaked in step (a) thus formed was then oven-dried at a temperature of 110 °C for a duration of Ih.

[0052] This sequence (a), (b) was repeated four times, resulting in the manufacture of the FLG@PS composite.

[0053] The coated beads are then placed in a silicone mold, and 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 an anechoic chamber (condition: measurement of reflection coefficient in dB, Frequency: 2-18 GHz, Normal incidence, Double linear polarization, Horn antenna + focusing lens, spot of max diameter 15-20 cm, Time filtering and Calibration with a measurement on a metal plate and a measurement in free space).

[0054] Example 3: METHOD FOR MANUFACTURING FLG CONDUCTIVE COMPOSITES DOPPED WITH MAGNETIC IRON PARTICLES DEPOSITED ON POLYSTYRENE (PS) BEADS

[0055] The composite according to the invention was obtained from polystyrene beads manufactured according to the method described according to the invention.

[0056] The following method was implemented:

[0057] (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 and Fe2O3 particles (trade name: ferric oxide (Fe2O3), particle size: 70-90 nm, supplier: Funcmater with a FLG / Fe2O3 ratio: 70 / 30 was filed on the polystyrene beads by the method described in patent application FR3087432 (Ref. 1) or WO2020109380 (Ref. 2).

[0058] (b) the substrate soaked in step (a) thus formed was then oven-dried at a temperature of 110 °C for a duration of Ih.

[0059] 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 placed in a polycarbonate frame and used as a low-frequency wave adsorbent in an anechoic chamber. Conditions: reflection coefficient measurement in dB, frequency: less than 2 GHz, normal incidence, double linear polarization, horn antenna + focusing lens, spot diameter max 15-20 cm, time filtering, and calibration with a measurement on a metal plate and a measurement in free space. List of bibliographic references

[0060] Ref.l: FR3087432 (BLAKLEAF).

[0061] Ref.2: WO2020109380 (BLAKLEAF).

[0062] 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.

[0063] 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.

[0064] 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

Demands

1. A method for manufacturing a conductive composite, comprising the following steps: (a) coating a substrate made of a material selected from a ceramic, a ceramic / epoxy composite, a ceramic / polyurethane composite, a ceramic / thermoplastic composite, polyimides, aramids, aromatic polyamides, expanded polystyrene and expanded polypropylene, 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 coated substrate in step (a) to 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. A method according to claim 1, wherein the substrate has a form selected from powders, films, pellets, beads, monoliths, foams, extrudates, aerosols, rings, granules, gynoid or alveolar structures.

3. A method according to any one of the preceding claims, wherein the substrate has an average diameter of 0.01 to 100 mm, preferably 0.1 to 10 mm, preferably still 0.2 to 10 mm, preferably still 0.2 to 10 mm.

4. A method according to any one of the preceding claims, wherein the substrate is in the form of beads.

5. A method according to any one of the preceding claims, wherein steps (a), (b), and optionally (c), are repeated or not, preferably from 1 to 30 times, in iterations of the sequence (a), (b), and optionally (c)).

6. Conductive composite obtained by the process 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 graphene

8.

9.

10.

11.

12.

13.

14. functionalized, in solid or liquid form, or from a graphene-based ink. 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, preferably further from 10 nm to 500 nm, preferably further from 100 nm to 500 nm. Composite according to any one of claims 6 to 8, wherein the substrate is in a form selected 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. Composite according to any one of claims 6 to 9, wherein the substrate is in the form of beads. Composite according to any one of claims 6 to 10, wherein the graphene-based layer comprises multi-sheet graphene where each sheet has a thickness between 1 and 1000 nm. Composite according to any one of claims 6 to 11, said composite being coated in a coating material selected from a polymer of natural or synthetic origin in powder or liquid form, selected from polyurethane, polyester, epoxy resins. Use of a composite according to any one of claims 6 to 12 as a microwave wave adsorbent. 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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