EP3502310B1 - Method for metallising a porous structure made of a carbon material - Google Patents

Method for metallising a porous structure made of a carbon material Download PDF

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EP3502310B1
EP3502310B1 EP18213736.4A EP18213736A EP3502310B1 EP 3502310 B1 EP3502310 B1 EP 3502310B1 EP 18213736 A EP18213736 A EP 18213736A EP 3502310 B1 EP3502310 B1 EP 3502310B1
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porous structure
carbon nanotubes
nanotubes
carbon
substrate
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German (de)
French (fr)
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EP3502310A1 (en
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Paul-Henri Haumesser
Jean Dijon
Raphael RAMOS
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/38—Coating with copper
    • C23C18/40—Coating with copper using reducing agents
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1633—Process of electroless plating
    • C23C18/1635—Composition of the substrate
    • C23C18/1639—Substrates other than metallic, e.g. inorganic or organic or non-conductive
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1633—Process of electroless plating
    • C23C18/1635—Composition of the substrate
    • C23C18/1644—Composition of the substrate porous substrates
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/1601—Process or apparatus
    • C23C18/1633—Process of electroless plating
    • C23C18/1675—Process conditions
    • C23C18/1682—Control of atmosphere
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron
    • C23C18/34—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron using reducing agents
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/42—Coating with noble metals
    • C23C18/44—Coating with noble metals using reducing agents
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/52—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating using reducing agents for coating with metallic material not provided for in a single one of groups C23C18/32 - C23C18/50

Definitions

  • the present invention relates to a method of metallizing a porous structure into a carbonaceous material, such as a structure of carbon nanotubes.
  • NTCs or CNTs carbon nanotubes
  • the metallization, partial or complete, internal or external, of the nanotubes makes it possible to modify the physicochemical properties of the nanotubes (for example via doping by charge transfer or grafting of metal clusters or nanoparticles) and is of interest for a certain number of 'applications such as heterogeneous catalysis or energy conversion in fuel cells or the production of conductive materials based on nanotubes.
  • the complete metallization of a network of nanotubes can result in the formation of a composite metal / nanotubes material.
  • These metal / nanotube composites are particularly interesting for making interconnections in microelectronics (conductive material with high ampacity), or thermal interface materials for packaging integrated circuits and thermal management in power electronics.
  • the CNTs can be in dispersed form, in the form of a cable of braided CNTs or else fixed to a substrate. In the latter case, they can be attached to the substrate, in a vertical or horizontal position, for example to make interconnection structures.
  • the patent US7538062 describes for example a method in which the CNTs are fixed on a metallic substrate chosen from copper, aluminum and zinc.
  • Metallization is carried out by immersing the CNTs in a solution containing a metal salt or an organometallic complex, which is then reduced chemically or electrochemically.
  • the electrochemical method offers better control over the quality and morphology of the metal deposit, but requires the ability to electrically connect the CNTs to an external generator, for example via an electrically conductive substrate, which limits its field of application.
  • the main difficulty is linked to the hydrophobic nature of the CNTs. It is difficult to suspend them in aqueous media and / or to thoroughly wet the carpet or braid of CNTs.
  • Nanoscale, planar and multi-tiered current pathways from a carbon nanotube-copper composite with high conductivity, ampacity and stability consists of electrolytically depositing copper on the carbon nanotubes.
  • an electrolyte based on acetonitrile and containing Cu (CH 3 COO) 2 is used, in order to best wet the CNTs.
  • a thermal reduction at 250 ° C, under a flow of H 2 is then carried out.
  • the invention is fundamentally distinguished from the prior art by the use of a solution comprising an ionic liquid as the reaction medium and by the vacuuming of the porous structure immersed in this solution.
  • Ionic liquids have a low saturation vapor pressure, and can therefore easily be evacuated without evaporating.
  • the vacuum allows the ionic liquid to penetrate to the heart of the structure, and therefore to metallize the structure up to the parts of the porosity furthest from the external surface of the structure.
  • the structure is metallized, not only on the surface but also in the volume of the pores. Even small pores (typically having diameters less than 10nm and even less than 5nm or even less than 2nm) are metallized.
  • the metal precursor is a precursor of copper, platinum, palladium, iron, iridium, rhodium, ruthenium, nickel, cobalt, tantalum and / or silver.
  • the metal precursor is a metal salt or an organometallic complex.
  • the reducing agent makes it possible to hydrogenate the ligands of the organometallic complex, to make them more volatile, and to eliminate them more easily, and / or to reduce the metal when that is not at a degree of oxidation (0).
  • the metal precursor is mesitylene copper.
  • the reducing hydrogenating agent is chosen from alcohols, gaseous dihydrogen, hydrazine, sodium tetrahydruroborate and triethylsilane.
  • the evacuation is carried out at a pressure ranging from 10 -7 bar to 10mbar.
  • the evacuation is carried out for a period ranging from 5 min to 4 h, preferably from 10 min to 30 min.
  • step d) is carried out at a temperature ranging from 0 ° C to 300 ° C, and preferably at a temperature ranging from 50 ° C to 100 ° C.
  • the choice of temperature will depend on the metal precursor and / or the ionic liquid.
  • the carbon material is chosen from carbon black, carbon nanofibers and a mixture of carbon nanotubes and fullerenes.
  • the carbonaceous material comprises and preferably consists of carbon nanotubes.
  • the carbon nanotubes are at least partially open. It is possible to metallize the internal surface of carbon nanotubes.
  • the carbon nanotubes are in the form of a braid.
  • the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned perpendicular to the substrate.
  • the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned parallel to the substrate.
  • metallization could relate to any type of carbon material, such as graphene, carbon black, carbon fibers or materials comprising a mixture of carbon nanotubes and fullerenes in which the fullerenes are covalently bonded to carbon nanotubes (materials also called “nanobuds").
  • carbonaceous materials find applications, for example, for fuel cells, or to form thin transparent conductive layers.
  • Metallization makes it possible to cover at least locally, and possibly completely the CNTs with a metal.
  • Metallization can make it possible to carry out doping by charge transfer of CNTs, or even the synthesis of metallic nanoparticles supported on CNTs, for fuel cell applications, for example with a view to oxygen reduction reaction, heterogeneous catalysis , energy conversion in fuel cells or the production of conductive materials based on nanotubes, such as cables based on nanotubes.
  • the complete metallization of a network of nanotubes can result in the formation of a composite metal / nanotubes material, particularly advantageous for the realization of interconnections in microelectronics (conductive material with high ampacity), or of thermal interface material for the packaging of integrated circuits and thermal management in power electronics.
  • the porous structure preferably has a porosity ranging from 10% to 80%, for example a porosity of 50%.
  • the pores of the structure are of small dimensions (typically pore diameters less than 10 nm, preferably less than 5 nm and even more preferably less than 2 nm).
  • the pore size of the carbon nanotube structure ranges, for example, from 0.5nm to 10nm.
  • the pores of the structure form an interconnected network.
  • the pores are open on at least one of the exterior surfaces of the structure.
  • the mass density of the structure ranges, for example, from 0.05 to 2 g / cm 3 .
  • the structure can be composed of several unitary elements assembled together.
  • the porous structure is preferably made of carbon nano-objects.
  • nano-object is meant, for example, nanotubes, nanofibers or nanowires. Preferably, they are nanotubes.
  • Nanotubes have a one-dimensional shape: they advantageously have a form factor greater than or equal to 100, for example from 100 to 10,000.
  • the form factor corresponds to the length / diameter ratio.
  • Nanotubes are, in general, structures having a diameter of a few nanometers to a few tens of nanometers, and a length of a few hundred nanometers to a few hundred micrometers.
  • the diameter of the nanotubes advantageously ranges from 1 nm to 15 nm, preferably from 3 nm to 10 nm.
  • the average length of the nanotubes advantageously ranges from 0.1 ⁇ m to 1000 ⁇ m, and preferably from 5 ⁇ m to 300 ⁇ m.
  • Nanotubes can be closed at their ends. They can also be opened at one or both ends, allowing metal to be inserted inside.
  • Nanotubes can also be defective, i.e. they have at least one surface defect. This defect could serve as a nucleation site for the metal. It may possibly allow the ionic solution to access the interior of the nanotube and thus proceed to the internal metallization of the nanotube.
  • Nanotubes can be supported on a substrate ( Figures 1 and 2 ).
  • the nanotubes are arranged in the form of a mat of nanotubes, fixed to a substrate, in a vertical position ( figure 1 ).
  • the nanotubes have a preferential orientation: they are aligned perpendicular to the substrate.
  • the thickness of the nanotube mat corresponds to the length of the nanotubes.
  • the density of nanotubes ranges, for example, from 10 9 to 10 13 nanotubes / cm 2 , advantageously, it is greater than or equal to 10 11 nanotubes / cm 2 .
  • Nanotubes can also be coated on the substrate, i.e. they are parallel to the substrate, in a horizontal position ( figure 2 ).
  • Obtaining coated nanotubes can be carried out by coating the nanotubes with a mat of nanotubes, for example with a roller. They are preferably lying in a given direction which will be that of least electrical resistance.
  • the use of coated nanotubes is particularly advantageous for forming microelectronic interconnection structures.
  • Nanotubes can be formed directly on the substrate. According to a variant, they can also be transferred to a substrate, after their manufacture. They can adhere weakly to the substrate. Nanotubes can be aligned using, for example, the method described in the article Adv. Funct. Mater. 2010, 20, 885-891 . They can be applied by spray.
  • the substrate is advantageously inert with respect to the solution. It is, for example, made of silicon, or of a polymer, such as polycarbonate.
  • Nanotubes may also not be supported by a substrate.
  • the nanotubes can be arranged in the form of a cable, obtained for example by braiding the nanotubes. This embodiment is interesting for producing electrical wires based on carbon nanotubes.
  • the porous structure is immersed, at least partially, and preferably completely, in the solution.
  • the solution has a low viscosity. It can have good ionic conductivity.
  • the solution comprises at least one ionic liquid.
  • the solution can as well comprise a single ionic liquid as a mixture of several (two, three, ...) ionic liquids.
  • Ionic liquid is understood to mean the association of at least one cation and an anion which generates a liquid with a melting point lower or close to 100 ° C.
  • solution is meant the presence of at least one ionic liquid. It can also be a mixture of several ionic liquids (two, three, ).
  • Ionic liquids have high thermal stability, almost zero vapor pressure (they do not evaporate, even under secondary vacuum), very low volatility, very low flammability and low surface tensions (they are good agents wetting agents). They have a very low melting point, often below room temperature.
  • the ionic liquids are not degraded during the process, which limits the cost of the process avoids the treatment of the solution after metallization. They can be recycled at the end of the reaction.
  • the ionic liquid is formed of an anion and a cation.
  • the cation is chosen from ammonium, imidazolium, pyrrolidinium, phosphonium, sulfonium and piperidinium.
  • the imidazolium is, for example, 1-octyl-3-methyl-imidazolium also noted C1C8lm, or 1-butyl-3-methyl-imidazolium also noted C1C41m.
  • the ionic liquids with imidazolium cation are the least viscous.
  • the anion is chosen from halide anions, such as Cl - , Br - , I - , amines, such as dicyanamides N (CN) 2 - denoted DCA - , tetrafluoroborate BF 4 - , hexafluorophosphate PF 6 - and sulfur ligands such as thiocyanates SCN - , bis (trifluoromethanesulfonyl) imide noted NTf2 - , bis (fluorosulfonyl) imide (FSO 2 ) 2 N - noted FSI - , trifluoromethanesulfonate or triflate CF 3 SO 3 - , tris (pentafluoroethyl ) trifluorophosphate noted FAP and bis (oxalato) borate noted BOB - .
  • halide anions such as Cl - , Br - , I -
  • amines such
  • the solution also includes a metal precursor.
  • the metal precursor can be a precursor of copper, platinum, palladium, ruthenium, nickel, cobalt, iron, tantalum, iridium, rhodium and / or silver.
  • It may be one or more metal salts and / or one or more metal complexes.
  • organometallic complex is meant a polyatomic structure in which a metallic element is linked to one or more (two, three, or four, for example) organic ligands via so-called coordination bonds.
  • the metallic element is, for example, a transition metal. According to a variant, it could be a noble or non-noble metal, a lanthanide or a rare earth element.
  • the organometallic complex can include the metallic element under an oxidation state equal to 0 or different from 0, for example (I), (II), (III), (IV) or (V).
  • the ligand (s) can be, for example, chosen from cyclooctadiene, cyclooctatriene, and ⁇ -diketones such as acetylacetone (AA), trifluoroacetyl acetone (TAA), hexafluoroacetylacetone (HFA), thenoyltrifluoroacetone ( TTA), 4,4-trifluoro-1- (2-thienyl) -1,3-butanedione (HTTA) and 1,5-cyclooctadiene-hexafluoroacetylacetone (COD-HFA).
  • the ligand (s) can also be chosen from dibenzylideneacetone, mesitylene, neopentyl, and Schrock carbene (for example, CHCMe 3 ).
  • the metal and the ligands are chosen such that the ligands facilitate the solubility of the metal in the ionic liquid.
  • the ligands are also selected so that their hydrogenation products do not contaminate the substrates and to be easily evaporated from the ionic liquid.
  • the metal precursor is, for example, copper mesitylene (CAS number 75732-01-3) or copper (II) Bis (trifluoromethanesulfonyl) imide Cu (NTf 2 ) 2 .
  • the concentration of metal precursor will be chosen by a person skilled in the art according to the surface of carbonaceous material to be covered and its limit of solubility in ionic liquid.
  • the dissolution of the metal precursor can be facilitated by the addition of a co-solvent (for example, pentane).
  • the co-solvent can then be removed by evaporation, for example during evacuation.
  • an agent can be optionally added to this mixture to make the reaction medium more fluid, by reducing the viscosity. It may be a salt or a combination of an additional ionic liquid.
  • step c the porous structure is placed under vacuum. Vacuuming leads the ionic liquid to penetrate the thickness of the porous structure. Ionic liquids, unlike an aqueous solution or a solution containing conventional organic solvents, make it possible to carry out such a step.
  • the vacuum ranges, for example, from 10 -10 bar to 10mbar and, preferably, from 10 -7 bar to 10mbar, and even more preferably from 10 -5 bar to 1mbar. It is, for example, 0, lmbar or about 10Pa.
  • the duration of the vacuuming step can range from a few minutes to a few hours, for example from 2 min to 4 h, preferably from 5 min to 4 h, for example from 5 min to 15 min, or even more preferably from 10 min to 30 min.
  • a person skilled in the art will be able to adapt the vacuum and / or the duration of the evacuation according to the different concentrations of reagents, the viscosity of the solution, the interface voltage between the ionic liquid. and the porous structure, the temperature of the process (the viscosity of the ionic liquid decreases when the temperature increases) which can be brought up to 250 ° C (depending on the stability of the ionic liquid and the metal precursor), and the thickness of the porous structure to be impregnated.
  • the porous structure impregnated with the solution is brought into contact with a hydrogenated reducing agent.
  • a hydrogenated reducing agent can be gaseous dihydrogen, hydrazine, an alcohol, sodium tetrahydruroborate (also called sodium borohydride) or a trialkylsilane, for example with a C1-C6 carbon chain, such as triethylsilane .
  • it is gaseous hydrogen. It may be pure dihydrogen or a mixture of hydrogen / neutral gas, such as H 2 / Ar.
  • the alcohols can advantageously be used to reduce the noblest metals, such as platinum or palladium, or also to reduce copper.
  • the hydrogenated reducing agent makes it possible to hydrogenate the ligands of the metal complex to release the metal, and optionally to reduce the latter when it is at an oxidation state greater than 0.
  • the hydrogenation of the ligands also makes it possible to eliminate them. easily.
  • the dihydrogen is, for example, at a pressure ranging from 1 to 10 bars or from 1 to 5 bars. For example, use a pressure of 3 bars.
  • this step is carried out at a temperature ranging from 0 ° C to 300 ° C, and preferably of the order of 20 ° C to 300 ° C, for example from 20 ° C to 250 ° C, been even more preferably from 50 ° C to 100 ° C.
  • lower temperatures can be used, for example it is possible to choose to work at room temperature (20-25 ° C). A temperature lower than the decomposition temperature of the ligands will be chosen.
  • the ionic liquid can be regenerated.
  • the solution can be reused, which reduces the consumption of reagents.
  • the porous structure is extracted from the bath and it is possible to carry out a new treatment cycle with a new porous structure to be metallized.
  • ionic liquid it is possible to deposit a film of liquid on the substrate, then heat it under vacuum. The liquid film can then be washed with a solvent at the end of the reaction and the ionic liquid can be recovered by a subsequent distillation step.
  • the method can also include a subsequent step in which the deposited metal is oxidized to form one or more metal oxides, for example with an oxidizing annealing step.
  • a mat of CNTs carbon nanotubes is fixed on a silicon substrate.
  • the CNTs are, initially, aligned perpendicular to the substrate ( figure 1 ).
  • the CNTs are coated using a metal roller ( Figure 2 ).
  • the sample is covered with a solution containing a copper precursor, copper mesitylene (CuMes, 0.05M), and an ionic liquid, [C1C4lm] [NTf2], then placed under primary vacuum (0.1mbar) for 2 hours. . During this stage, the ionic liquid does not evaporate. Then, the sample is placed under H 2 (3 bars) at 100 ° C for 1 hour to reduce the copper which is at a degree of oxidation (I) to metallic copper. At the end of the reaction, the ionic liquid is washed several times with dichloromethane.
  • a copper precursor copper mesitylene (CuMes, 0.05M)
  • an ionic liquid [C1C4lm] [NTf2]

Description

DOMAINE TECHNIQUE ET ÉTAT DE LA TECHNIQUE ANTÉRIEURETECHNICAL AREA AND PRIOR ART

La présente invention concerne un procédé de métallisation d'une structure poreuse en un matériau carboné, telle qu'une structure de nanotubes de carbone.The present invention relates to a method of metallizing a porous structure into a carbonaceous material, such as a structure of carbon nanotubes.

Le dépôt de métal sur ou dans les nanotubes de carbone (NTCs ou CNTs) est largement étudié dans la littérature pour modifier leurs propriétés, leur ajouter de nouvelles fonctionnalités, ou encore créer des matériaux composites métal/CNT.The deposition of metal on or in carbon nanotubes (NTCs or CNTs) is widely studied in the literature to modify their properties, add new functionalities, or even create metal / CNT composite materials.

La métallisation, partielle ou complète, interne ou externe, des nanotubes permet de modifier les propriétés physicochimiques des nanotubes (par exemple via un dopage par transfert de charge ou un greffage de clusters ou de nanoparticules métalliques) et présente un intérêt pour un certain nombre d'applications comme la catalyse hétérogène ou la conversion d'énergie dans des piles à combustibles ou encore la réalisation de matériaux conducteurs à base de nanotubes.The metallization, partial or complete, internal or external, of the nanotubes makes it possible to modify the physicochemical properties of the nanotubes (for example via doping by charge transfer or grafting of metal clusters or nanoparticles) and is of interest for a certain number of 'applications such as heterogeneous catalysis or energy conversion in fuel cells or the production of conductive materials based on nanotubes.

La métallisation complète d'un réseau de nanotubes peut aboutir à la formation d'un matériau composite métal/nanotubes. Ces composites métal/nanotubes sont particulièrement intéressants pour la réalisation d'interconnexions en microélectronique (matériau conducteur à forte ampacité), ou de matériaux d'interface thermique pour le packaging de circuits intégrés et le management thermique en électronique de puissance.The complete metallization of a network of nanotubes can result in the formation of a composite metal / nanotubes material. These metal / nanotube composites are particularly interesting for making interconnections in microelectronics (conductive material with high ampacity), or thermal interface materials for packaging integrated circuits and thermal management in power electronics.

Les CNTs peuvent être sous forme dispersée, sous la forme d'un câble de CNTs tressés ou encore fixés à un substrat. Dans ce dernier cas, ils peuvent être attachés au substrat, en position verticale ou horizontale, par exemple pour réaliser des structures d'interconnexion. Le brevet US7538062 décrit par exemple une méthode dans laquelle les CNTs sont fixés sur un substrat métallique choisi parmi le cuivre, l'aluminium et le zinc.The CNTs can be in dispersed form, in the form of a cable of braided CNTs or else fixed to a substrate. In the latter case, they can be attached to the substrate, in a vertical or horizontal position, for example to make interconnection structures. The patent US7538062 describes for example a method in which the CNTs are fixed on a metallic substrate chosen from copper, aluminum and zinc.

La métallisation est réalisée en plongeant les CNTs dans une solution contenant un sel métallique ou un complexe organométallique, qui est ensuite réduit chimiquement ou électrochimiquement. La méthode électrochimique offre un meilleur contrôle sur la qualité et la morphologie du dépôt métallique, mais nécessite de pouvoir connecter électriquement les CNTs à un générateur externe, par exemple via un substrat électriquement conducteur, ce qui limite son champ d'application.Metallization is carried out by immersing the CNTs in a solution containing a metal salt or an organometallic complex, which is then reduced chemically or electrochemically. The electrochemical method offers better control over the quality and morphology of the metal deposit, but requires the ability to electrically connect the CNTs to an external generator, for example via an electrically conductive substrate, which limits its field of application.

Quelle que soit la méthode de dépôt choisie, la principale difficulté est liée au caractère hydrophobe des CNTs. Il est difficile de les mettre en suspension dans des milieux aqueux et/ou de mouiller en profondeur le tapis ou la tresse de CNTs.Whatever the deposition method chosen, the main difficulty is linked to the hydrophobic nature of the CNTs. It is difficult to suspend them in aqueous media and / or to thoroughly wet the carpet or braid of CNTs.

Pour y remédier, il est possible d'ajouter des composés chimiques possédant une forte affinité avec les CNTs. Par exemple, dans l'article de Hsu et al. (« Aniline as a Dispersant and Stabilizer for the Preparation of Pt Nanoparticles Deposited on Carbon Nanotubes », J. Phys. Chem. C, 2010, 114, 7933-7939 ), des nanotubes de carbone sont dispersés dans une solution eau/isopropanol contenant de l'aniline. Des ions Pt4+ sont ensuite ajoutés en présence de citrate de sodium, un agent réducteur. Après filtration, et chauffage à 400°C sous un flux de H2, des nanotubes de carbone recouvert de particules de platine sont obtenus. L'aniline, en plus de sa forte affinité avec les CNTs, permet également d'éviter l'agglomération du platine.To remedy this, it is possible to add chemical compounds having a strong affinity with CNTs. For example, in the article by Hsu et al. ("Aniline as a Dispersant and Stabilizer for the Preparation of Pt Nanoparticles Deposited on Carbon Nanotubes", J. Phys. Chem. C, 2010, 114, 7933-7939 ), carbon nanotubes are dispersed in a water / isopropanol solution containing aniline. Pt 4+ ions are then added in the presence of sodium citrate, a reducing agent. After filtration and heating to 400 ° C. under a flow of H 2 , carbon nanotubes covered with platinum particles are obtained. Aniline, in addition to its strong affinity with CNTs, also makes it possible to avoid agglomeration of platinum.

Cependant, cette solution nécessite d'utiliser des réactifs en plus et/ou de traiter les déchets issus de ces procédés, ce qui engendre un coût supplémentaire.However, this solution requires the use of additional reagents and / or treatment of the waste resulting from these processes, which generates an additional cost.

Une autre solution, décrite, par exemple, dans l'article de Subramaniam et al. (« Nano-scale, planar and multi-tiered current pathways from a carbon nanotube-copper composite with high conductivity, ampacity and stability », Nanoscale, DOI : 10.1039/c5nr03762j ) consiste à déposer par voie électrolytique du cuivre sur les nanotubes de carbone. Pour cela, un électrolyte à base d'acétonitrile et contenant du Cu(CH3COO)2 est utilisé, afin de mouiller au mieux les CNTs. Une réduction thermique à 250°C, sous un flux de H2, est ensuite réalisée.Another solution, described, for example, in the article by Subramaniam et al. ("Nano-scale, planar and multi-tiered current pathways from a carbon nanotube-copper composite with high conductivity, ampacity and stability", Nanoscale, DOI: 10.1039 / c5nr03762j ) consists of electrolytically depositing copper on the carbon nanotubes. For this, an electrolyte based on acetonitrile and containing Cu (CH 3 COO) 2 is used, in order to best wet the CNTs. A thermal reduction at 250 ° C, under a flow of H 2 , is then carried out.

Cependant, il est indiqué que lorsque la structure de nanotubes est dense, il est difficile de recouvrir les nanotubes jusqu'au cœur de la structure. De plus, il est nécessaire de traiter les déchets organiques issus de ce procédé, ce qui engendre un coût supplémentaire.However, it is indicated that when the structure of nanotubes is dense, it is difficult to cover the nanotubes to the heart of the structure. In addition, it is necessary to treat organic waste from this process, which generates an additional cost.

Les mêmes problématiques se retrouvent pour d'autres substrats carbonés, par exemple pour les couches de carbone poreux (noir de carbone par exemple) dans les électrodes des piles à combustible qu'il faut imprégner des nanoparticules catalytiques.The same problems are found for other carbon substrates, for example for the porous carbon layers (carbon black by example) in the electrodes of fuel cells that must be impregnated with catalytic nanoparticles.

EXPOSÉ DE L'INVENTIONSTATEMENT OF THE INVENTION

C'est, par conséquent, un but de la présente invention de proposer un procédé permettant de métalliser une structure poreuse en un matériau carboné jusqu'au cœur de la structure.It is therefore an object of the present invention to provide a method for metallizing a porous structure in a carbonaceous material up to the heart of the structure.

Ce but est atteint par un procédé de métallisation d'une structure poreuse en un matériau carboné, ledit procédé comprenant les étapes suivantes :

  1. a) fourniture d'une structure poreuse en un matériau carboné,
  2. b) immersion de la structure poreuse dans une solution comprenant un liquide ionique, formé par un cation et un anion, et un précurseur métallique,
  3. c) mise sous vide de la structure poreuse, immergée dans la solution, de manière à faire pénétrer la solution au sein de la porosité de la structure poreuse,
  4. d) ajout d'un agent hydrogéné réducteur, de manière à métalliser la structure poreuse jusqu'au sein de la porosité de la structure poreuse.
This object is achieved by a method of metallizing a porous structure into a carbonaceous material, said method comprising the following steps:
  1. a) supply of a porous structure in a carbonaceous material,
  2. b) immersion of the porous structure in a solution comprising an ionic liquid, formed by a cation and an anion, and a metallic precursor,
  3. c) placing the porous structure under vacuum, immersed in the solution, so as to cause the solution to penetrate within the porosity of the porous structure,
  4. d) addition of a reducing hydrogenating agent, so as to metallize the porous structure down to the porosity of the porous structure.

L'invention se distingue fondamentalement de l'art antérieur par l'utilisation d'une solution comprenant un liquide ionique comme milieu réactionnel et par la mise sous vide de la structure poreuse immergée dans cette solution. Les liquides ioniques présentent une faible pression de vapeur saturante, et peuvent donc facilement être mis sous vide, sans s'évaporer. La mise sous vide permet de faire pénétrer le liquide ionique jusqu'au cœur de la structure, et donc de métalliser la structure jusque dans les parties de la porosité les plus éloignées de la surface externe de la structure. A l'issue du procédé la structure est métallisée, non seulement, en surface mais aussi dans le volume des pores. Même les pores de faibles dimensions (typiquement ayant des diamètres inférieurs à 10nm et même inférieurs 5nm voire inférieurs à 2nm) sont métallisés.The invention is fundamentally distinguished from the prior art by the use of a solution comprising an ionic liquid as the reaction medium and by the vacuuming of the porous structure immersed in this solution. Ionic liquids have a low saturation vapor pressure, and can therefore easily be evacuated without evaporating. The vacuum allows the ionic liquid to penetrate to the heart of the structure, and therefore to metallize the structure up to the parts of the porosity furthest from the external surface of the structure. At the end of the process, the structure is metallized, not only on the surface but also in the volume of the pores. Even small pores (typically having diameters less than 10nm and even less than 5nm or even less than 2nm) are metallized.

Avantageusement, le précurseur métallique est un précurseur de cuivre, de platine, de palladium, de fer, d'iridium, de rhodium, de ruthénium, de nickel, de cobalt, de tantale et/ou d'argent.Advantageously, the metal precursor is a precursor of copper, platinum, palladium, iron, iridium, rhodium, ruthenium, nickel, cobalt, tantalum and / or silver.

Avantageusement, le précurseur métallique est un sel métallique ou un complexe organométallique. L'agent réducteur permet d'hydrogéner les ligands du complexe organométallique, pour les rendre plus volatils, et les éliminer plus facilement, et/ou de réduire le métal lorsque celui n'est pas à un degré d'oxydation (0).Advantageously, the metal precursor is a metal salt or an organometallic complex. The reducing agent makes it possible to hydrogenate the ligands of the organometallic complex, to make them more volatile, and to eliminate them more easily, and / or to reduce the metal when that is not at a degree of oxidation (0).

Avantageusement, le précurseur métallique est du cuivre mésitylène.Advantageously, the metal precursor is mesitylene copper.

Avantageusement, l'agent hydrogéné réducteur est choisi parmi les alcools, le dihydrogène gazeux, l'hydrazine, le tétrahydruroborate de sodium et le triéthylsilane.Advantageously, the reducing hydrogenating agent is chosen from alcohols, gaseous dihydrogen, hydrazine, sodium tetrahydruroborate and triethylsilane.

Avantageusement, la mise sous vide est réalisée à une pression allant de 10-7 bar à 10mbar.Advantageously, the evacuation is carried out at a pressure ranging from 10 -7 bar to 10mbar.

Avantageusement, la mise sous vide est réalisée pendant une durée allant de 5min à 4h, de préférence de 10min à 30min.Advantageously, the evacuation is carried out for a period ranging from 5 min to 4 h, preferably from 10 min to 30 min.

Avantageusement, l'étape d) est réalisée à une température allant de 0°C à 300°C, et de préférence à une température allant de 50°C à 100°C. Le choix de la température va dépendre du précurseur métallique et/ou du liquide ionique.Advantageously, step d) is carried out at a temperature ranging from 0 ° C to 300 ° C, and preferably at a temperature ranging from 50 ° C to 100 ° C. The choice of temperature will depend on the metal precursor and / or the ionic liquid.

Selon une première variante avantageuse, le matériau carboné est choisi parmi le noir de carbone, les nanofibres de carbone et un mélange de nanotubes de carbone et de fullerènes.According to a first advantageous variant, the carbon material is chosen from carbon black, carbon nanofibers and a mixture of carbon nanotubes and fullerenes.

Selon une deuxième variante avantageuse, le matériau carboné comprend et, de préférence, est constitué de nanotubes de carbone.According to a second advantageous variant, the carbonaceous material comprises and preferably consists of carbon nanotubes.

Avantageusement, les nanotubes de carbone sont au moins partiellement ouverts. Il est possible de métalliser la surface interne des nanotubes de carbone.Advantageously, the carbon nanotubes are at least partially open. It is possible to metallize the internal surface of carbon nanotubes.

Selon une variante avantageuse, les nanotubes de carbone sont sous la forme d'une tresse.According to an advantageous variant, the carbon nanotubes are in the form of a braid.

Selon une autre variante avantageuse, les nanotubes de carbone sont sous la forme d'un tapis, disposé sur un substrat, les nanotubes de carbone étant alignés perpendiculairement au substrat.According to another advantageous variant, the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned perpendicular to the substrate.

Selon une autre variante avantageuse, les nanotubes de carbone sont sous la forme d'un tapis, disposé sur un substrat, les nanotubes de carbone étant alignés parallèlement au substrat.According to another advantageous variant, the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned parallel to the substrate.

BRÈVE DESCRIPTION DES DESSINSBRIEF DESCRIPTION OF THE DRAWINGS

La présente invention sera mieux comprise sur la base de la description qui va suivre et des dessins en annexe sur lesquels :

  • la figure 1 est un cliché obtenu par microscopie électronique à balayage, d'une structure poreuse de nanotubes de carbone alignés verticalement sur un substrat, selon un mode de réalisation particulier de l'invention,
  • la figure 2 est un cliché obtenu par microscopie électronique à balayage, d'une structure poreuse de nanotubes de carbone alignés horizontalement sur un substrat, selon un mode de réalisation particulier de l'invention,
  • la figure 3 est un cliché obtenu par microscopie électronique à balayage, d'une vue de dessus d'une structure poreuse de nanotubes de carbone alignés horizontalement sur un substrat, après métallisation, selon un mode de réalisation du procédé de l'invention,
  • les figures 4A et 4B sont des clichés obtenus par microscopie électronique à balayage, d'une vue en coupe, d'une structure poreuse de nanotubes de carbone alignés horizontalement sur un substrat, après métallisation, selon un mode de réalisation du procédé de l'invention, respectivement à faible grossissement et à fort grossissement.
The present invention will be better understood on the basis of the description which follows and of the appended drawings in which:
  • the figure 1 is a photograph obtained by scanning electron microscopy, of a porous structure of carbon nanotubes vertically aligned on a substrate, according to a particular embodiment of the invention,
  • the figure 2 is a photograph obtained by scanning electron microscopy, of a porous structure of carbon nanotubes aligned horizontally on a substrate, according to a particular embodiment of the invention,
  • the figure 3 is a photograph obtained by scanning electron microscopy, of a top view of a porous structure of carbon nanotubes aligned horizontally on a substrate, after metallization, according to an embodiment of the method of the invention,
  • the Figures 4A and 4B are photographs obtained by scanning electron microscopy, of a sectional view, of a porous structure of carbon nanotubes aligned horizontally on a substrate, after metallization, according to an embodiment of the process of the invention, respectively at low magnification and high magnification.

EXPOSÉ DÉTAILLÉ DE MODES DE RÉALISATION PARTICULIERSDETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

Par la suite, la métallisation de nanotubes de carbone (CNTs) est décrite. Cependant, la métallisation pourrait concerner tout type de matériau carboné, tel que du graphène, du noir de carbone, des fibres de carbone ou encore des matériaux comprenant un mélange de nanotubes de carbone et de fullerènes dans lequel les fullerènes sont liés de manière covalentes aux nanotubes de carbone (matériaux aussi appelés « nanobuds »). Ces matériaux carbonés trouvent des applications, par exemple, pour des piles à combustible, ou pour former des couches minces transparentes conductrices.Next, the metallization of carbon nanotubes (CNTs) is described. However, metallization could relate to any type of carbon material, such as graphene, carbon black, carbon fibers or materials comprising a mixture of carbon nanotubes and fullerenes in which the fullerenes are covalently bonded to carbon nanotubes (materials also called "nanobuds"). These carbonaceous materials find applications, for example, for fuel cells, or to form thin transparent conductive layers.

La métallisation permet de recouvrir au moins localement, et éventuellement totalement les CNTs par un métal.Metallization makes it possible to cover at least locally, and possibly completely the CNTs with a metal.

La métallisation peut permettre de réaliser le dopage par transfert de charge des CNTs, ou encore la synthèse de nanoparticules métalliques supportées sur des CNTs, pour des applications piles à combustibles, par exemple en vue de réaction de réduction de l'oxygène, la catalyse hétérogène, la conversion d'énergie dans des piles à combustibles ou la réalisation de matériaux conducteurs à base de nanotubes, tels que des câbles à base de nanotubes.Metallization can make it possible to carry out doping by charge transfer of CNTs, or even the synthesis of metallic nanoparticles supported on CNTs, for fuel cell applications, for example with a view to oxygen reduction reaction, heterogeneous catalysis , energy conversion in fuel cells or the production of conductive materials based on nanotubes, such as cables based on nanotubes.

La métallisation complète d'un réseau de nanotubes peut aboutir à la formation d'un matériau composite métal/nanotubes, particulièrement intéressants pour la réalisation d'interconnexions en microélectronique (matériau conducteur à forte ampacité), ou de matériau d'interface thermique pour le packaging de circuits intégrés et le management thermique en électronique de puissance.The complete metallization of a network of nanotubes can result in the formation of a composite metal / nanotubes material, particularly advantageous for the realization of interconnections in microelectronics (conductive material with high ampacity), or of thermal interface material for the packaging of integrated circuits and thermal management in power electronics.

Structure poreuse :Porous structure:

La structure poreuse a, de préférence, une porosité allant de 10% à 80%, par exemple de une porosité de 50%.The porous structure preferably has a porosity ranging from 10% to 80%, for example a porosity of 50%.

Les pores de la structure sont de faibles dimensions (typiquement des diamètres de pores inférieurs à 10nm, de préférence inférieurs à 5nm et encore plus préférentiellement inférieurs à 2nm). La taille des pores de la structure de nanotubes de carbone va, par exemple, de 0,5nm à 10nm.The pores of the structure are of small dimensions (typically pore diameters less than 10 nm, preferably less than 5 nm and even more preferably less than 2 nm). The pore size of the carbon nanotube structure ranges, for example, from 0.5nm to 10nm.

Les pores de la structure forment un réseau interconnecté. Les pores sont ouverts sur au moins l'une des surfaces extérieures de la structure.The pores of the structure form an interconnected network. The pores are open on at least one of the exterior surfaces of the structure.

La densité massique de la structure va, par exemple, de 0,05 à 2g/cm3.The mass density of the structure ranges, for example, from 0.05 to 2 g / cm 3 .

La structure peut être composée de plusieurs éléments unitaires assemblés ensemble.The structure can be composed of several unitary elements assembled together.

La structure poreuse est, de préférence, en nano-objets de carbone.The porous structure is preferably made of carbon nano-objects.

Par nano-objet, on entend, par exemple, des nanotubes, des nanofibres ou des nanofils. De préférence, il s'agit de nanotubes.By nano-object is meant, for example, nanotubes, nanofibers or nanowires. Preferably, they are nanotubes.

Les nanotubes ont une forme unidimensionnelle : ils présentent, avantageusement, un facteur de forme supérieur ou égal à 100, par exemple de 100 à 10000. Le facteur de forme correspond au rapport longueur/diamètre.Nanotubes have a one-dimensional shape: they advantageously have a form factor greater than or equal to 100, for example from 100 to 10,000. The form factor corresponds to the length / diameter ratio.

Les nanotubes sont, de manière générale, des structures présentant un diamètre de quelques nanomètres à quelques dizaines de nanomètres, et une longueur de quelques centaines de nanomètres à quelques centaines de micromètres.Nanotubes are, in general, structures having a diameter of a few nanometers to a few tens of nanometers, and a length of a few hundred nanometers to a few hundred micrometers.

Le diamètre des nanotubes va, avantageusement, de 1nm à 15nm, de préférence de 3nm à 10nm.The diameter of the nanotubes advantageously ranges from 1 nm to 15 nm, preferably from 3 nm to 10 nm.

La longueur moyenne des nanotubes va, avantageusement, de 0,1µm à 1000µm, et de préférence de 5µm à 300µm.The average length of the nanotubes advantageously ranges from 0.1 μm to 1000 μm, and preferably from 5 μm to 300 μm.

Les nanotubes peuvent être fermés à leurs extrémités. Ils peuvent également être ouverts à l'une de leur extrémité ou à leurs deux extrémités, ce qui permet d'insérer un métal à l'intérieur.Nanotubes can be closed at their ends. They can also be opened at one or both ends, allowing metal to be inserted inside.

Les nanotubes peuvent également être défectueux, c'est-à-dire qu'ils présentent au moins un défaut en surface. Ce défaut pourra servir de site de nucléation pour le métal. Il pourra éventuellement permettre à la solution ionique d'accéder à l'intérieur du nanotube et ainsi procéder à la métallisation interne du nanotube.Nanotubes can also be defective, i.e. they have at least one surface defect. This defect could serve as a nucleation site for the metal. It may possibly allow the ionic solution to access the interior of the nanotube and thus proceed to the internal metallization of the nanotube.

Les nanotubes peuvent être supportés sur un substrat (figures 1 et 2).Nanotubes can be supported on a substrate ( Figures 1 and 2 ).

Par exemple, les nanotubes sont agencés sous la forme d'un tapis de nanotubes, fixés à un substrat, en position verticale (figure 1). Les nanotubes présentent une orientation préférentielle : ils sont alignés perpendiculairement au substrat. L'épaisseur du tapis de nanotubes correspond à la longueur des nanotubes. La densité de nanotubes va, par exemple, de 109 à 1013 nanotubes/cm2, avantageusement, elle est supérieure ou égale à 1011 nanotubes/cm2.For example, the nanotubes are arranged in the form of a mat of nanotubes, fixed to a substrate, in a vertical position ( figure 1 ). The nanotubes have a preferential orientation: they are aligned perpendicular to the substrate. The thickness of the nanotube mat corresponds to the length of the nanotubes. The density of nanotubes ranges, for example, from 10 9 to 10 13 nanotubes / cm 2 , advantageously, it is greater than or equal to 10 11 nanotubes / cm 2 .

Les nanotubes peuvent également être couchés sur le substrat, c'est-à-dire qu'ils sont parallèles au substrat, en position horizontale (figure 2). L'obtention de nanotubes couchés peut être réalisée en couchant les nanotubes d'un tapis de nanotubes, par exemple avec un rouleau. Ils sont, de préférence, couchés dans une direction donnée qui sera celle de moindre résistance électrique. L'utilisation de nanotubes couchés est particulièrement intéressante pour former des structures d'interconnexions microélectroniques.Nanotubes can also be coated on the substrate, i.e. they are parallel to the substrate, in a horizontal position ( figure 2 ). Obtaining coated nanotubes can be carried out by coating the nanotubes with a mat of nanotubes, for example with a roller. They are preferably lying in a given direction which will be that of least electrical resistance. The use of coated nanotubes is particularly advantageous for forming microelectronic interconnection structures.

Les nanotubes peuvent être formés directement sur le substrat. Selon une variante, ils peuvent également être transférés sur un substrat, après leur fabrication. Ils peuvent adhérer faiblement sur le substrat. Les nanotubes peuvent être alignés en utilisant, par exemple, la méthode décrite dans l'article Adv. Funct. Mater. 2010, 20, 885-891 . Ils peuvent être déposés par spray.Nanotubes can be formed directly on the substrate. According to a variant, they can also be transferred to a substrate, after their manufacture. They can adhere weakly to the substrate. Nanotubes can be aligned using, for example, the method described in the article Adv. Funct. Mater. 2010, 20, 885-891 . They can be applied by spray.

Le substrat est, avantageusement, inerte vis-à-vis de la solution. Il est, par exemple, en silicium, ou en un polymère, tel du polycarbonate.The substrate is advantageously inert with respect to the solution. It is, for example, made of silicon, or of a polymer, such as polycarbonate.

Les nanotubes peuvent également ne pas être supportés par un substrat. Les nanotubes peuvent être agencés sous la forme d'un câble, obtenu par exemple en tressant les nanotubes. Ce mode de réalisation est intéressant pour réaliser des fils électriques à base de nanotubes de carbone.Nanotubes may also not be supported by a substrate. The nanotubes can be arranged in the form of a cable, obtained for example by braiding the nanotubes. This embodiment is interesting for producing electrical wires based on carbon nanotubes.

Le procédé de métallisation :The metallization process:

Le procédé de métallisation de nanotubes de carbone comprend les étapes suivantes :

  1. a) fourniture d'une structure poreuse de nanotubes de carbone,
  2. b) immersion de la structure poreuse dans une solution comprenant un liquide ionique, formé par un cation et un anion, et un précurseur métallique, tel qu'un sel métallique ou un complexe métallique,
  3. c) mise sous vide de la structure poreuse, immergée dans la solution, de manière à faire pénétrer la solution au cœur de la structure poreuse,
  4. d) ajout d'un agent réducteur hydrogéné, de manière à réduire le précurseur métallique et à métalliser les nanotubes de carbone.
The metallization process for carbon nanotubes includes the following steps:
  1. a) supply of a porous structure of carbon nanotubes,
  2. b) immersion of the porous structure in a solution comprising an ionic liquid, formed by a cation and an anion, and a metal precursor, such as a metal salt or a metal complex,
  3. c) placing the porous structure under vacuum, immersed in the solution, so as to make the solution penetrate the heart of the porous structure,
  4. d) addition of a hydrogenated reducing agent, so as to reduce the metal precursor and to metallize the carbon nanotubes.

Lors de l'étape b), la structure poreuse est plongée, au moins partiellement, et préférence totalement, dans la solution.During step b), the porous structure is immersed, at least partially, and preferably completely, in the solution.

La solution présente une faible viscosité. Elle peut présenter une bonne conductivité ionique.The solution has a low viscosity. It can have good ionic conductivity.

La solution comprend au moins un liquide ionique. La solution peut aussi bien comprendre un seul liquide ionique qu'un mélange de plusieurs (deux, trois,...) liquides ioniques.The solution comprises at least one ionic liquid. The solution can as well comprise a single ionic liquid as a mixture of several (two, three, ...) ionic liquids.

On entend par liquide ionique l'association d'au moins un cation et un anion qui génère un liquide avec une température de fusion inférieure ou voisine de 100°C. Par solution, on entend la présence au minimum d'un liquide ionique. Il peut également s'agir d'un mélange de plusieurs liquides ioniques (deux, trois,...).Ionic liquid is understood to mean the association of at least one cation and an anion which generates a liquid with a melting point lower or close to 100 ° C. By solution is meant the presence of at least one ionic liquid. It can also be a mixture of several ionic liquids (two, three, ...).

L'utilisation de liquide présente de nombreux avantages en termes de chimie, de coût ou de procédé. Les liquides ioniques présentent une grande stabilité thermique, une tension de vapeur quasi nulle (ils ne s'évaporent pas, même sous vide secondaire), une très faible volatilité, une très faible inflammabilité et des tensions de surface faibles (ce sont de bons agents mouillants). Ils ont un point de fusion très bas, souvent inférieur à la température ambiante.The use of liquid has many advantages in terms of chemistry, cost or process. Ionic liquids have high thermal stability, almost zero vapor pressure (they do not evaporate, even under secondary vacuum), very low volatility, very low flammability and low surface tensions (they are good agents wetting agents). They have a very low melting point, often below room temperature.

Les liquides ioniques ne sont pas dégradés pendant le procédé, ce qui limite le coût du procédé évite le traitement de la solution après la métallisation. Ils peuvent être recyclés à l'issue de la réaction.The ionic liquids are not degraded during the process, which limits the cost of the process avoids the treatment of the solution after metallization. They can be recycled at the end of the reaction.

Le liquide ionique est formé d'un anion et d'un cation.The ionic liquid is formed of an anion and a cation.

Avantageusement, le cation est choisi parmi un ammonium, un imidazolium, un pyrrolidinium, un phosphonium, un sulfonium et un pipéridinium.Advantageously, the cation is chosen from ammonium, imidazolium, pyrrolidinium, phosphonium, sulfonium and piperidinium.

L'imidazolium est, par exemple, le 1-octyl-3-méthyl-imidazolium aussi noté C1C8lm, ou le 1-butyl-3-méthyl-imidazolium aussi noté C1C41m. Les liquides ioniques à cation imidazolium sont les moins visqueux.The imidazolium is, for example, 1-octyl-3-methyl-imidazolium also noted C1C8lm, or 1-butyl-3-methyl-imidazolium also noted C1C41m. The ionic liquids with imidazolium cation are the least viscous.

Avantageusement, l'anion est choisi parmi les anions halogénures, tels que Cl-, Br-, I-, les amines, comme les dicyanamides N(CN)2 - notés DCA-, le tétrafluoroborate BF4 -, l'hexafluorophosphate PF6 - et les ligands soufrés tels que les thiocyanates SCN-, le bis(trifluoromethanesulfonyl)imide noté NTf2-, bis(fluorosulfonyl)imide (FSO2)2N- noté FSI-, trifluorométhanesulfonate ou triflate CF3SO3 -, tris(pentafluoroéthyl)trifluorophosphate noté FAP et bis(oxalato)borate noté BOB-.Advantageously, the anion is chosen from halide anions, such as Cl - , Br - , I - , amines, such as dicyanamides N (CN) 2 - denoted DCA - , tetrafluoroborate BF 4 - , hexafluorophosphate PF 6 - and sulfur ligands such as thiocyanates SCN - , bis (trifluoromethanesulfonyl) imide noted NTf2 - , bis (fluorosulfonyl) imide (FSO 2 ) 2 N - noted FSI - , trifluoromethanesulfonate or triflate CF 3 SO 3 - , tris (pentafluoroethyl ) trifluorophosphate noted FAP and bis (oxalato) borate noted BOB - .

La solution comprend en outre un précurseur métallique.The solution also includes a metal precursor.

Le précurseur métallique peut être un précurseur de cuivre, de platine, de palladium, de ruthénium, de nickel, de cobalt, de fer, de tantale, d'iridium, de rhodium et/ou d'argent.The metal precursor can be a precursor of copper, platinum, palladium, ruthenium, nickel, cobalt, iron, tantalum, iridium, rhodium and / or silver.

Il peut s'agir d'un ou de plusieurs sels métalliques et/ou d'un ou plusieurs complexes métalliques.It may be one or more metal salts and / or one or more metal complexes.

Par complexe organométallique, on entend un édifice polyatomique dans lequel un élément métallique est lié à un ou plusieurs (deux, trois, ou quatre, par exemple) ligands organiques via des liaisons dites de coordination.By organometallic complex is meant a polyatomic structure in which a metallic element is linked to one or more (two, three, or four, for example) organic ligands via so-called coordination bonds.

Il peut y avoir un élément métallique ou plus d'un élément métallique dans le complexe organométallique, par exemple deux éléments métalliques identiques (dimère). L'élément métallique est, par exemple, un métal de transition. Il pourrait s'agir, selon une variante, d'un métal noble ou non noble, d'un lanthanide ou d'un élément des terres rares.There may be one metallic element or more than one metallic element in the organometallic complex, for example two identical metallic elements (dimer). The metallic element is, for example, a transition metal. According to a variant, it could be a noble or non-noble metal, a lanthanide or a rare earth element.

Le complexe organométallique peut inclure l'élément métallique sous un degré d'oxydation égal à 0 ou différent de 0, par exemple (I), (II), (III), (IV) ou (V).The organometallic complex can include the metallic element under an oxidation state equal to 0 or different from 0, for example (I), (II), (III), (IV) or (V).

Le ou les ligands peuvent être, par exemple, choisis parmi le cyclooctadiène, le cyclooctatriène, et les β-dicétones telles que l'acétylacétone (AA), la trifluoroacétyl-acétone (TAA), l'hexafluoroacétylacétone (HFA), la thénoyltrifluoroacétone (TTA), la 4,4- trifluoro-l-(2-thiényl)-l,3-butanedione (HTTA) et la 1,5-cyclooctadiène-hexafluoroacétylacétone (COD-HFA). Le ou les ligands peuvent également être choisis parmi le dibenzylidèneacétone, le mésitylène, le néopentyl, et le Carbène de Schrock (par exemple, CHCMe3).The ligand (s) can be, for example, chosen from cyclooctadiene, cyclooctatriene, and β-diketones such as acetylacetone (AA), trifluoroacetyl acetone (TAA), hexafluoroacetylacetone (HFA), thenoyltrifluoroacetone ( TTA), 4,4-trifluoro-1- (2-thienyl) -1,3-butanedione (HTTA) and 1,5-cyclooctadiene-hexafluoroacetylacetone (COD-HFA). The ligand (s) can also be chosen from dibenzylideneacetone, mesitylene, neopentyl, and Schrock carbene (for example, CHCMe 3 ).

Le métal et les ligands sont choisis de telle sorte que les ligands facilitent la solubilité du métal dans le liquide ionique. Avantageusement, les ligands sont également sélectionnés de sorte que leurs produits d'hydrogénation ne contaminent pas les substrats et pour être facilement évaporés du liquide ionique.The metal and the ligands are chosen such that the ligands facilitate the solubility of the metal in the ionic liquid. Advantageously, the ligands are also selected so that their hydrogenation products do not contaminate the substrates and to be easily evaporated from the ionic liquid.

Le précurseur métallique est, par exemple, du cuivre mésitylène (numéro CAS 75732-01-3) ou du cuivre (II) Bis(trifluorométhanesulfonyl)imide Cu(NTf2)2.The metal precursor is, for example, copper mesitylene (CAS number 75732-01-3) or copper (II) Bis (trifluoromethanesulfonyl) imide Cu (NTf 2 ) 2 .

La concentration en précurseur métallique sera choisie par l'homme du métier en fonction de la surface de matériau carboné à recouvrir et de sa limite de solubilité dans le liquide ionique. La dissolution du précurseur métallique peut être facilitée par l'ajout d'un co-solvant (par exemple, le pentane). Le co-solvant peut être ensuite éliminé par évaporation, par exemple lors de la mise sous vide.The concentration of metal precursor will be chosen by a person skilled in the art according to the surface of carbonaceous material to be covered and its limit of solubility in ionic liquid. The dissolution of the metal precursor can be facilitated by the addition of a co-solvent (for example, pentane). The co-solvent can then be removed by evaporation, for example during evacuation.

Avantageusement, à ce mélange il peut être optionnellement ajouté un agent pour fluidifier le milieu réactionnel, en diminuant la viscosité. Il peut s'agir d'un sel ou de l'association d'un liquide ionique additionnel.Advantageously, an agent can be optionally added to this mixture to make the reaction medium more fluid, by reducing the viscosity. It may be a salt or a combination of an additional ionic liquid.

Lors de l'étape c), la structure poreuse est mise sous vide. La mise sous vide conduit le liquide ionique à pénétrer dans l'épaisseur de la structure poreuse. Les liquides ioniques, contrairement à une solution aqueuse ou à une solution contenant des solvants organiques classiques, permettent de réaliser une telle étape.During step c), the porous structure is placed under vacuum. Vacuuming leads the ionic liquid to penetrate the thickness of the porous structure. Ionic liquids, unlike an aqueous solution or a solution containing conventional organic solvents, make it possible to carry out such a step.

Le vide va, par exemple, de 10-10bar à 10mbar et, de préférence, de 10-7bar à 10mbar, et encore plus préférentiellement de 10-5bar à 1mbar. Il est, par exemple, de 0,lmbar soit environ 10Pa.The vacuum ranges, for example, from 10 -10 bar to 10mbar and, preferably, from 10 -7 bar to 10mbar, and even more preferably from 10 -5 bar to 1mbar. It is, for example, 0, lmbar or about 10Pa.

La durée de l'étape de mise sous vide peut aller de quelques minutes à quelques heures, par exemple de 2min à 4h, de préférence de 5min à 4h, par exemple de 5min à 15min, ou encore plus préférentiellement de 10min à 30min.The duration of the vacuuming step can range from a few minutes to a few hours, for example from 2 min to 4 h, preferably from 5 min to 4 h, for example from 5 min to 15 min, or even more preferably from 10 min to 30 min.

D'une manière générale, l'homme du métier pourra adapter le vide et/ou la durée de la mise sous vide en fonction des différentes concentrations de réactifs, de la viscosité de la solution, de la tension d'interface entre le liquide ionique et la structure poreuse, de la température du procédé (la viscosité du liquide ionique diminue lorsque la température augmente) qui peut être portée jusqu'à 250°C (en fonction de la stabilité du liquide ionique et du précurseur métallique), et de l'épaisseur de la structure poreuse à imprégner.In general, a person skilled in the art will be able to adapt the vacuum and / or the duration of the evacuation according to the different concentrations of reagents, the viscosity of the solution, the interface voltage between the ionic liquid. and the porous structure, the temperature of the process (the viscosity of the ionic liquid decreases when the temperature increases) which can be brought up to 250 ° C (depending on the stability of the ionic liquid and the metal precursor), and the thickness of the porous structure to be impregnated.

Lors de l'étape d), la structure poreuse imprégnée de la solution est mise en présence d'un agent réducteur hydrogéné. Il peut s'agir de dihydrogène gazeux, d'hydrazine, d'un alcool, de tétrahydruroborate de sodium (aussi appelé borohydrure de sodium) ou d'un trialkylsilane, par exemple avec une chaine carbonée en C1-C6, tel que le triéthylsilane. De préférence, il s'agit dihydrogène gazeux. Il peut s'agir de dihydrogène pur ou d'un mélange dihydrogène/gaz neutre, tel que H2/Ar.During step d), the porous structure impregnated with the solution is brought into contact with a hydrogenated reducing agent. It can be gaseous dihydrogen, hydrazine, an alcohol, sodium tetrahydruroborate (also called sodium borohydride) or a trialkylsilane, for example with a C1-C6 carbon chain, such as triethylsilane . Preferably, it is gaseous hydrogen. It may be pure dihydrogen or a mixture of hydrogen / neutral gas, such as H 2 / Ar.

Les alcools peuvent être, avantageusement, utilisés pour réduire les métaux les plus nobles, tels que le platine ou le palladium, ou encore pour réduire le cuivre.The alcohols can advantageously be used to reduce the noblest metals, such as platinum or palladium, or also to reduce copper.

L'agent réducteur hydrogéné permet d'hydrogéner les ligands du complexe métallique pour libérer le métal, et éventuellement de réduire ce dernier lorsqu'il est à un degré d'oxydation supérieur à 0. L'hydrogénation des ligands permet par ailleurs de les éliminer facilement.The hydrogenated reducing agent makes it possible to hydrogenate the ligands of the metal complex to release the metal, and optionally to reduce the latter when it is at an oxidation state greater than 0. The hydrogenation of the ligands also makes it possible to eliminate them. easily.

Le dihydrogène est, par exemple, à une pression allant de 1 à 10bars ou de 1 à 5 bars. On utilisera par exemple une pression de 3bars.The dihydrogen is, for example, at a pressure ranging from 1 to 10 bars or from 1 to 5 bars. For example, use a pressure of 3 bars.

Avantageusement, cette étape est réalisée à une température allant de 0°C à 300°C, et de préférence de l'ordre de 20°C à 300°C, par exemple de 20°C à 250°C, été encore plus préférentiellement de 50°C à 100°C. Lorsque que le précurseur métallique est à un degré d'oxydation 0, des températures plus faibles peuvent être utilisées, par exemple il est possible de choisir de travailler à la température ambiante (20-25°C). On choisira une température inférieure à la température de décomposition des ligands.Advantageously, this step is carried out at a temperature ranging from 0 ° C to 300 ° C, and preferably of the order of 20 ° C to 300 ° C, for example from 20 ° C to 250 ° C, been even more preferably from 50 ° C to 100 ° C. When the metal precursor is at an oxidation state 0, lower temperatures can be used, for example it is possible to choose to work at room temperature (20-25 ° C). A temperature lower than the decomposition temperature of the ligands will be chosen.

A l'issue du procédé, le liquide ionique peut être régénéré. La solution peut être réutilisée, ce qui réduit la consommation de réactifs.At the end of the process, the ionic liquid can be regenerated. The solution can be reused, which reduces the consumption of reagents.

Après la métallisation, la structure poreuse est extraite du bain et il est possible de procéder à un nouveau cycle de traitement avec une nouvelle structure poreuse à métalliser.After metallization, the porous structure is extracted from the bath and it is possible to carry out a new treatment cycle with a new porous structure to be metallized.

Selon une autre alternative, pour limiter la quantité de liquide ionique utilisée, on pourra déposer un film de liquide sur le substrat, puis le chauffer sous vide. Le film de liquide peut ensuite être lavé par un solvant à l'issue de la réaction et le liquide ionique peut être récupéré par une étape de distillation ultérieure.According to another alternative, to limit the amount of ionic liquid used, it is possible to deposit a film of liquid on the substrate, then heat it under vacuum. The liquid film can then be washed with a solvent at the end of the reaction and the ionic liquid can be recovered by a subsequent distillation step.

Le procédé peut également comprendre une étape ultérieure dans laquelle le métal déposé est oxydé pour former un ou plusieurs oxydes métalliques, par exemple avec une étape de recuit oxydant.The method can also include a subsequent step in which the deposited metal is oxidized to form one or more metal oxides, for example with an oxidizing annealing step.

Exemple illustratif et non limitatif d'un mode de réalisation :Illustrative and nonlimiting example of an embodiment:

Dans cet exemple, un tapis de nanotubes de carbone CNTs est fixé sur un substrat de silicium. Les CNTs sont, initialement, alignés perpendiculairement au substrat (figure 1). Les CNTs sont couchés à l'aide d'un rouleau métallique (Figure 2).In this example, a mat of CNTs carbon nanotubes is fixed on a silicon substrate. The CNTs are, initially, aligned perpendicular to the substrate ( figure 1 ). The CNTs are coated using a metal roller ( Figure 2 ).

L'échantillon est recouvert d'une solution contenant un précurseur du cuivre, le cuivre mésitylène (CuMes, 0.05M), et un liquide ionique, le [C1C4lm][NTf2], puis placé sous vide primaire (0,1mbar) pendant 2h. Durant cette étape, le liquide ionique ne s'évapore pas. Ensuite, l'échantillon est placée sous H2 (3 bars) à 100°C pendant 1h pour réduire le cuivre qui est à un degré d'oxydation (I) en cuivre métallique. A l'issue de la réaction, le liquide ionique est lavé plusieurs fois au dichlorométhane.The sample is covered with a solution containing a copper precursor, copper mesitylene (CuMes, 0.05M), and an ionic liquid, [C1C4lm] [NTf2], then placed under primary vacuum (0.1mbar) for 2 hours. . During this stage, the ionic liquid does not evaporate. Then, the sample is placed under H 2 (3 bars) at 100 ° C for 1 hour to reduce the copper which is at a degree of oxidation (I) to metallic copper. At the end of the reaction, the ionic liquid is washed several times with dichloromethane.

Un examen au MEB du tapis de CNTs révèle la présence de nombreux agrégats métalliques sur les CNTs à l'issue du procédé (Figure 3). Cela montre que les CNTs possèdent des sites de nucléation pour le Cu qui restent actifs en milieu liquide ionique. Ce dépôt est présent jusqu'à la base des CNTs, ce qui prouve que la solution a pu pénétrer au sein de l'épaisseur du tapis de CNTs (Figures 4A et 4B).A SEM examination of the CNT mat reveals the presence of numerous metallic aggregates on the CNTs at the end of the process ( Figure 3 ). This shows that the CNTs have nucleation sites for Cu which remain active in ionic liquid medium. This deposit is present up to the base of the CNTs, which proves that the solution was able to penetrate within the thickness of the CNTs mat ( Figures 4A and 4B ).

Claims (14)

  1. Method for metallising a porous structure made of carbon material, said method comprising the following steps:
    a) supplying a porous structure made of carbon material,
    b) immersing the porous structure in a solution comprising an ionic liquid, formed by a cation and an anion, and a metal precursor,
    c) placing the porous structure in a vacuum, immersed in the solution, in such a way as to cause the solution to penetrate into the porosity of the porous structure,
    d) adding a hydrogenated reducing agent, in such a way as to metallise the porous structure to within the porosity of the porous structure.
  2. Method according to claim 1, characterized in that the metal precursor is a copper, platinum, palladium, ruthenium, nickel, cobalt, iron, tantalum, iridium, rhodium and/or silver precursor.
  3. Method according to one of claims 1 and 2, characterized in that the metal precursor is a metal salt or an organometallic complex.
  4. Method according to one of claims 1 to 3, characterized in that the metal precursor is copper mesitylene.
  5. Method according to any one of the preceding claims, characterized in that the hydrogenated reducing agent is chosen from gaseous hydrogen, hydrazine, alcohols, sodium tetrahydridoborate and triethylsilane.
  6. Method according to any one of the preceding claims, characterized in that the placing in a vacuum is carried out at a pressure ranging from 10-7 bar to 10 mbar.
  7. Method according to any one of the preceding claims, characterized in that the placing in a vacuum is carried out for a duration ranging from 5 min to 4 h, and preferably from 10 min to 30 min.
  8. Method according to any one of the preceding claims, characterized in that the step d) is carried out at a temperature ranging from 0°C to 300°C, and preferably from 50°C to 100°C.
  9. Method according to any one of claims 1 to 8, characterized in that the carbon material is chosen from carbon black, carbon nanofibres, and a mixture of carbon nanotubes and fullerenes.
  10. Method according to any one of claims 1 to 8, characterized in that the carbon material comprises and, preferably, consists of carbon nanotubes.
  11. Method according to the preceding claim, characterized in that the carbon nanotubes are at least partially open.
  12. Method according to one of claims 10 and 11, characterized in that the carbon nanotubes are in the form of a braid.
  13. Method according to one of claims 10 and 11, characterized in that the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned perpendicularly to the substrate.
  14. Method according to one of claims 10 and 11, characterized in that the carbon nanotubes are in the form of a mat, arranged on a substrate, the carbon nanotubes being aligned parallel to the substrate.
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