Method for modifying the surface of a carbon nanocomposite, and watch regulator with flexible part incorporating the modified nanocomposite.

Abstract

The invention relates to a method for functionalizing and passivating a carbon surface (20a) of a carbon nanocomposite (20) configured to form a flexible part of a regulating member for a watch movement, such a flexible part, such a regulating member incorporating this flexible part and a balance which cooperates therewith, and a use of a complex for functionalizing and passivating a carbon surface (20a) of such a carbon nanocomposite (20). The method according to the invention comprises a chemical reaction of the carbon surface (20a) with a complex which comprises:- a carbon chain which is hydrocarbon or fluorocarbon, and- at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, for a covalent grafting of the reactive carbon end onto the carbon surface (20a), and a passivation of the carbon surface (20a) making it hydrophobic. Fig. 5

Description

Title of the invention: Method for modifying the surface of a carbon nanocomposite, and watch regulator with flexible part incorporating the modified nanocomposite. Technical field

[0001] The invention relates to a method for functionalizing and passivating a carbon surface of a carbon nanocomposite (i.e. of a nanostructured carbon) configured to form a flexible part of a regulating member for a watch movement, such a flexible part, such a regulating member incorporating this flexible part and a balance which cooperates therewith, and a use of a complex for functionalizing and passivating a carbon surface of such a carbon nanocomposite. The invention also relates to a method for (pre)treating said carbon surface of the carbon nanocomposite which can optionally (following the pretreatment) be functionalized and passivated by this functionalization and passivation method, it being specified that the invention may relate to this treatment method alone independently of any subsequent functionalization and passivation method.The invention applies in particular to a flexible part of the spiral spring type, for example for a mechanical watch, which may be based on a forest of carbon nanotubes infiltrated with pyrolytic carbon, without limitation. Prior art

[0002] Conventionally, watch movements include a regulator, a mechanical oscillator that determines the time base of the watch movement. This regulator includes a spiral spring associated with an oscillating mass called a balance wheel. This spiral spring requires extreme dimensional precision which determines the time accuracy of the watch movement.

[0003] The time base of a timepiece uses an oscillator with a given frequency whose oscillations must be maintained. Oscillators are known, in particular, such as the pendulum (which uses gravity), quartz (which uses piezoelectricity), the tuning fork (which uses elastic deformation) or even springs of various shapes (which also use elastic deformation to exert a return), depending on whether they are designed to oscillate over large or small amplitudes.

[0004] In particular, in most mechanical watches, the regulating organ comprises a balance-spring assembly, namely an assembly comprising a balance which is a flywheel, and a spiral-shaped spring, called a balance spring, spiral spring or spiral spring, fixed by one end to the balance shaft and by the other end to a bridge, in which the balance wheel's axis pivots. The balance-spring assembly oscillates at a given frequency around its equilibrium position. When the balance wheel leaves this position, it winds the balance spring. This creates a restoring torque which, when the balance wheel is released, makes it return to its equilibrium position. As the balance wheel has acquired a certain speed, and therefore kinetic energy, it exceeds its equilibrium position until the resistive torque of the balance spring stops it and forces it to rotate in the other direction. Following a sustained mode, the oscillations are repeated. Thus, the balance spring regulates the oscillation period of the balance wheel. Hairsprings are mainly made from a sheet wound on itself, notably in the form of an Archimedean spiral.

[0005] WO 2017 / 220672 A1 and WO 2020 / 144587 A1 each present a part for a watch movement, such as a hairspring, made of a composite material comprising a rigid matrix and a forest of nanotubes contained in the matrix.

[0006] WO 2013 / 079939 A2 discloses an oscillator spring consisting of a spring material consisting of carbon, a ceramic, a polymer, a polymer precursor, a composite and combinations of these materials, and a barrier material for modifying the number of available binding sites on the surface of the spring material, wherein the barrier material consists of one or more hydrophobic silicone or hydrophobic silane compounds. The barrier material may provide a barrier to the adsorption of water vapor in the ambient atmosphere. The barrier may thus be able to regulate the elasticity of the spring.

[0007] A major drawback of the spring presented in the latter document is that it requires the incorporation of a crystalline phase transformation additive such as silicon dioxide, into the carbon material of the spring, in order to control the modulus of elasticity of the spring, and further so that the silicone or silane compound barrier with which the carbon material incorporating this additive is provided ultimately modifies the mechanical properties of the resulting spring.

[0008] The Applicant sought to passivate the surface of a carbon nanocomposite (i.e. a nanostructured carbon), such as those used to form spiral springs for mechanical watches based on carbon nanotubes infiltrated with pyrolytic carbon, in order to oppose structural modifications observed during the application of current spiral springs based on these nanotubes, and thus to improve the performance of these springs. Statement of the invention

[0009] An aim of the invention is to propose a method for treating a carbon surface of a carbon nanocomposite (i.e. of a nanostructured carbon) capable of forming such a spiral spring for a watch movement, this nanocomposite to be treated being able to be predominantly or exclusively made of carbon, a treatment process which in particular overcomes the aforementioned drawbacks of the prior art (e.g. by not requiring any additive to be incorporated into the mass of the spring other than carbon) and which reduces the sensitivity of the spiral spring to the environment (in particular to ambient humidity, as well as possibly to other volatile constituents present in the timepiece, such as a mechanical watch, or in the ambient air, such as the oils and / or greases used in said article).

[0010] This aim is achieved in that the Applicant has verified that if the carbon surface of such a carbon nanocomposite is chemically reacted with a complex essentially comprising a carbon chain and a salt of a diazonium group at a reactive end of the chain, then it is possible to obtain a covalent grafting of the reactive carbon end onto the carbon surface and at the same time a passivation of this surface making it very hydrophobic (according to a water contact angle significantly greater than 90°) and giving it a significantly reduced surface energy in comparison with an identical carbon surface that is untreated or treated without reactive group(s) specific to the carbon surface (e.g. by a halogenated silane compound, or an Epilame® solution of the prior art), which in particular makes it possible to very effectively and durably passivate (by functionalizing it with covalent bonds) the carbon surface thus treated according to the invention.

[0011] More specifically, a method according to the invention for functionalizing and passivating a carbon surface of a carbon nanocomposite, configured to form a flexible part of a regulating organ for a watch movement, comprises a chemical reaction of the carbon surface with a complex which comprises: - a carbon chain which is hydrocarbon or fluorocarbon, and - at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, for covalent grafting of the reactive carbon end onto the carbon surface, and passivation of the carbon surface making it hydrophobic.

[0012] It will be noted that this covalent grafting coupled with the passivation of the carbon surface makes it possible to ensure the performance of the nanocomposite, such as a spiral spring for a mechanical watch, by reducing the reactivity of the nanocomposite to the environment, in particular to variations in ambient humidity and / or the content of other volatile constituents, for example present in the timepiece, such as oils and / or greases.

[0013] It will also be noted that the carbon chain of the complex adheres (i.e. clings) satisfactorily to the carbon surface thanks to its reactive end forming a “head” based on a diazonium salt for the complex which grafts onto the carbon surface by a covalent CC bond.

[0014] It will further be noted that the functionalization and passivation process according to the invention can advantageously be implemented by a purely chemical route, i.e. not by an electrochemical route in particular.

[0015] According to another characteristic of the invention, the salt of a diazonium group can be formed in situ from said precursor which is for example a fluorocarbon derivative of aniline or a triazene, or be preformed prior to the chemical reaction, the diazonium salt being able to correspond to the formula [Chem. 1]: [Chem. 1] R-feN X where R is a substituted or unsubstituted hydrocarbon group, preferably an aryl group, for example substituted phenyl, and X is an inorganic or organic anion, preferably a halogenated anion or a triflate anion, for example a chlorinated or fluorinated anion, and the reactive carbon end can be grafted onto the carbon surface by a CC covalent bond between the R group and a carbon atom of the carbon surface.

[0016] As an anion for the diazonium salt, one can for example choose an anion from Cf, BF4 (tetrafluoroborate), TFA (trifluoroacetate), Ts (tosylate), Tf (triflate), PF6 (hexafluorophosphate), heavy metal anions (for example FeCl4, AuC14, SbF6), anionic polymeric resins (for example called “Amberlyst” or “sulforesin”), without limitation.

[0017] Preferably, the carbon chain of said complex is aliphatic and fluorocarbon, being even more preferably a perfluorinated hydrocarbon chain.

[0018] It will be noted that the fluorocarbon chain (which may be, for example, a partially or totally fluorinated C1-C20 chain) is advantageously a perfluorinated C5-C10 hydrocarbon chain, which makes it possible to further improve the passivation of the carbon surface, in comparison with a hydrocarbon chain (eg an alkyl chain).

[0019] It will further be noted that it is possible to use as an alternative a fluorocarbon chain comprising an ether functional group, such as a perfluoroalkoxy alkane.

[0020] Advantageously, said chemical reaction according to the invention forms for said grafting a functionalized and passivated carbon surface which can have: - a water contact angle, measured according to the method specified in the description, which is equal to or greater than 90°, preferably equal to or greater than 100° and for example between 105° and 130°; and / or - an atomic concentration of fluorine, measured as specified in the description, which is between 5% and 70%, preferably between 10 and 60%; and / or - a total surface energy, defined as the sum of the dispersive energy and the specific energy in mJ / m2 and measured as specified in the description, which is reduced by at least 20% and preferably by at least 25%, relative to the total surface energy of the carbon surface (20a) before functionalization and passivation.

[0021] According to a first aspect of the invention, the chemical reaction can form for said grafting a hydrophobic monolayer film which covers the carbon surface by functionalizing and passivating it and which is formed concomitantly or after the formation of said complex, the hydrophobic monolayer film having a water contact angle, measured according to the method specified in the description, which can be equal to or greater than 90°, advantageously equal to or greater than 100° and for example between 105° and 130°.

[0022] It will be noted that this monolayer film which is clearly hydrophobic is covalently grafted to the carbon surface, via the attachment of the reactive carbon end of the chain of the complex on this carbon surface.

[0023] It will also be noted that the aforementioned very high values ​​for the contact angle of water on the hydrophobic monolayer film demonstrate the ability of this film to effectively passivate the carbon surface, in addition to providing a covalent attachment to the carbon surface.

[0024] The water contact angle was measured on a flat substrate (silicon wafer) covered with a carbon layer which is similar to that constituting the carbon nanocomposite and which was cleaned by ultrasonication in an organic solvent after passivation to ensure the covalent attachment of the monolayer. To measure this contact angle, a 3 μL drop of distilled water was placed on the surface, then this angle was measured with a “KRUSS” contact angle analyzer, the analysis of the drop being carried out with Advance software using the Young-Laplace model by taking the average of three angle measurements at three different locations on the surface.

[0025] According to a second aspect of the invention which can supplement said first aspect, the total surface energy of the carbon surface covered with the hydrophobic monolayer film, defined as being the sum of the dispersive energy and the specific energy in mJ / m2 and measured as specified in the description below by inverse gas chromatography "iGC" or by the "OWRK" method, can be reduced by at least 20% and advantageously by at least 25%, for example by at least 50% when measured by the "OWRK" method, relative to the total surface energy of the carbon surface before deposition of the hydrophobic monolayer film.

[0026] It will be noted that this significant drop in the total surface energy after the deposition of the hydrophobic monolayer film clearly attests to the high degree of passivation obtained for the carbon surface.

[0027] The total surface energy of the carbon surface covered with the hydrophobic monolayer film was measured by inverse gas chromatography ("iGC » for short) on carbon hairsprings. The adsorbent studied is placed in a column, while a known adsorbate is used in the gas phase. The retention time is obtained as a fundamental measured parameter, which can be converted into a retention volume directly related to several physicochemical properties of the solid (adsorbent). The surface energy of the adsorbent was investigated here. Specifically, an “iGC” surface energy analyzer was used, and a portion of the nanocomposite was placed in an individual “iGC” silanized glass column, then surface coverage measurements were carried out with alkanes and polar probe molecules (adsorbates) to determine the dispersive surface energy and the specific surface energy.

[0028] As will be explained in the remainder of this description, the total surface energy of the carbon surface covered with the hydrophobic monolayer film was also measured by another method called “OWRK”, which uses contact angle measurements on flat sample substrates.

[0029] According to a third aspect of the invention which can supplement said first aspect and / or said second aspect, the atomic concentration of fluorine in an outermost surface zone of the hydrophobic monolayer film, a zone with a thickness of between approximately 2 nm and 10 nm, measured as specified in the description, can be between 5% and 70%, preferably between 10 and 60%.

[0030] It will be noted that the atomic concentration of fluorine, which makes it possible to compare the effectiveness of the reaction conditions for the deposition of the hydrophobic monolayer film, further attests to the effectiveness of the concomitant formation of the complex (incorporating the salt of a diazonium group) in the aforementioned case where this complex is formed in situ.

[0031] According to a fourth aspect of the invention which can supplement said first aspect and / or said second aspect and / or said third aspect, the hydrophobic monolayer film can comprise a product of the reaction between the carbon surface and the diazonium functional group, which corresponds to the formula [Chem. 2]: [Chem. 2] RN”N where R is a substituted or unsubstituted hydrocarbon group, where preferably: R is an aryl group, for example a substituted phenyl, and the functional group is an aryl diazonium group, for example benzenediazonium having the formula [Chem. 3]: [Chem. 3] / \ ® • CJ)--N=N

[0032] According to this fourth aspect of the invention, the monolayer film obtained comprises said R group which is functionalized with said carbon chain (preferably a fluorocarbon chain, even more preferably a perfluorinated hydrocarbon).

[0033] It will be noted that the diazonium functional group reacts with the carbon surface by releasing nitrogen in gaseous form, and thus creates the monolayer by a covalent bond between the R group and the carbon surface.

[0034] It will also be noted that the selection of an aryl type R group (for example substituted phenyl) for the diazonium salt of the formula [Chem. 1] and for the diazonium groups of the formula [Chem. 2] makes it possible to further improve the functionalization and passivation of the carbon surface.

[0035] According to another characteristic of the invention which may be common to at least one of the aforementioned characteristics and aspects, the carbon surface may optionally be immersed in a reducing solution comprising a reducing agent, for example ascorbic acid, then the chemical reaction may be carried out (with or without said reducing solution) in a reaction medium comprising said complex in solution.

[0036] According to another characteristic of the invention which may be common to at least one of the aforementioned characteristics and aspects, the carbon nanocomposite (i.e. the nanostructured carbon) may comprise carbon nanotubes and pyrolytic carbon infiltrated into a forest of nanotubes, and the carbon surface may be made up of carbon atoms, the carbon nanocomposite preferably being made up of carbon nanotubes and pyrolytic carbon, and preferably the hydrophobic monolayer film directly covers the surface of the pyrolytic carbon and the carbon nanotubes (or at least the surface of the nanotubes which are accessible).

[0037] It will be noted that the carbon nanocomposite which is the subject of the functionalization and passivation process according to the invention is preferably made up of carbon nanotubes and pyrolytic carbon infiltrated into the forest of nanotubes (i.e. without non-carbon additive in the nanocomposite), the carbon surface to be treated thus being mainly or exclusively made up of carbon atoms (it will be noted that there could be hydrogen and / or oxygen atoms present in a minority on the surface and / or in the structure of said carbon nanocomposite).

[0038] It will be noted that the carbon nanocomposite and the carbon surface to be treated according to the invention could thus be predominantly or exclusively made up of any allotropic form of carbon, including amorphous carbon, tetrahedral carbon, diamond-like carbon ("DLC"), diamond, graphite, graphene, fullerenes and single-walled nanotubes ("SWNT"), double-walled nanotubes ("DWNT") or multi-walled nanotubes ("MWNT"), without limitation.

[0039] According to another general characteristic of the method of the invention, said flexible part can be adapted to flex in a plane perpendicular to a Y axis, the carbon nanocomposite being configured to form a spiral spring adapted to oscillate around the Y axis, the carbon nanocomposite being made up of a matrix formed by the pyrolytic carbon and a forest of juxtaposed carbon nanotubes held by the matrix which infiltrates them, the nanotubes (e.g. multi-sheets) being able to be arranged globally parallel to the Y axis or not (for example when the nanotubes are not straight, but wavy in a manner not parallel to the Y axis).

[0040] Another object of the invention is to propose a flexible part of a regulating member for a watch movement, the flexible part, in particular a spiral spring (e.g. in the form of an Archimedean spiral), being adapted to flex in a plane perpendicular to a Y axis, the flexible part comprising a carbon nanocomposite (i.e. a nanostructured carbon) having a functionalized and passivated carbon surface, which overcomes the aforementioned drawbacks of the prior art and makes it possible to reduce the reactivity to the environment of the flexible part by passivating its carbon surface independently of variations in environmental conditions, in particular variations in ambient humidity and / or in the content of other volatile constituents, for example present in the timepiece, such as oils and / or greases.

[0041] For this purpose, the flexible part according to the invention is such that the functionalized and passivated carbon surface comprises the product of a chemical reaction between an original carbon surface of the carbon nanocomposite and a complex, which comprises: a carbon chain which is hydrocarbon or fluorocarbon, and at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, the reactive carbon end of the chain being grafted by a covalent bond onto the original carbon surface, and the functionalized and passivated carbon surface being hydrophobic.

[0042] Generally speaking, it will be noted that the flexible part can be advantageously obtained by the method according to the invention for functionalizing and passivating a carbon surface of a carbon nanocomposite, as presented in the characteristics and aspects set out above, with the aforementioned advantages for the method which also relate to the flexible part obtained (these advantages including in particular an effective passivation of the carbon surface of the nanocomposite, such as a spiral spring for a mechanical watch, by reducing the reactivity of the nanocomposite to the environment, in particular to variations in ambient humidity and / or to the content of other volatile constituents for example present in the watch, such as oils and / or greases).

[0043] Advantageously, the functionalized and passivated carbon surface can optionally form a hydrophobic monolayer film which covers the original carbon surface, said functionalized and passivated carbon surface being able to have at least one of the following characteristics: - a water contact angle, measured according to the method specified in the description, which is equal to or greater than 90°, preferably equal to or greater than 100° and for example between 105° and 130°, - a total surface energy, defined as the sum of the dispersive energy and the specific energy in mJ / m2 and measured as specified in the description, by inverse gas chromatography "iGC" or by the "OWRK" method, which is reduced by at least 20% and preferably by at least 25%, for example by at least 50% when measured by the "OWRK" method, compared to the total surface energy of the original carbon surface, - an atomic concentration of fluorine in an outermost surface area of ​​the hydrophobic monolayer film, measured as specified in the description, which is between 5% and 70%, preferably between 10 and 60%, and - a hydrocarbon group R (preferably an aryl group, for example substituted phenyl), functionalized with said carbon chain (preferably a fluorocarbon chain, even more preferably a perfluorinated hydrocarbon).

[0044] Advantageously, said original carbon surface may be predominantly or exclusively made up of carbon atoms and the nanocomposite may comprise a forest of carbon nanotubes and a matrix of pyrolytic carbon infiltrated into the forest of nanotubes, which are juxtaposed and held by the matrix, the nanotubes (for example of the multi-layer type) being arranged generally parallel to the Y axis or not (for example when the nanotubes are not straight, but wavy in a manner not parallel to the Y axis).

[0045] It will be noted again that the nanocomposite is preferably made of the carbon nanotubes and the pyrolytic carbon infiltrated into the nanotube forest (i.e. without any non-carbon additive in the nanocomposite or alternatively with traces of hydrogen and / or oxygen in the pyrolytic carbon), but that the nanocomposite and its original carbonaceous surface could be predominantly or exclusively made of any allotropic form of carbon, including amorphous carbon, tetrahedral carbon, diamond-like carbon ("DLC"), diamond, graphite, graphene, fullerenes and single-walled, two-walled or multi-walled nanotubes, without limitation.

[0046] Another object of the invention is to propose a regulating organ for a watch movement, the regulating organ comprising: - a flexible part adapted to flex in a plane perpendicular to a Y axis, in particular a spiral spring adapted to oscillate around the Y axis, and - a balance cooperating with the flexible part, which overcomes the aforementioned drawbacks of the prior art and makes it possible to reduce the reactivity to the environment of the flexible part by passivating its carbon surface independently of variations in environmental conditions, in particular variations in ambient humidity and / or in the content of other volatile constituents, for example present in the timepiece, such as oils and / or greases.

[0047] For this purpose, this flexible part is as defined above in relation to the aforementioned characteristics and aspects of the invention.

[0048] Another aim of the invention is to propose a use of a complex comprising - a carbon chain which is hydrocarbon or fluorocarbon, and - at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, to functionalize and passivate by chemical reaction a carbon surface of a carbon nanocomposite (i.e. of a nanostructured carbon) configured to form a flexible part of a regulating organ for a watch movement, via covalent grafting of the reactive carbon end of the chain onto the carbon surface and passivation of the carbon surface making it hydrophobic.

[0049] Advantageously, this use according to the invention of said complex can be further defined by all or part of the characteristics and aspects of the functionalization and passivation process as defined above.

[0050] According to yet another aspect of the invention relating to a step that can be implemented prior to the functionalization and passivation of the carbon surface of said carbon nanocomposite (another aspect which is hereinafter called "preliminary aspect of the invention" and which can be optionally combined with all or part of the characteristics and aspects of the subsequent functionalization and passivation process as defined above), an objective of the Applicant has also been to remedy drawbacks encountered in the prior art of chemical vapor deposition ("CVD") carried out to obtain forests of carbon nanotubes infiltrated by pyrolytic carbon, drawbacks which are in particular that: - the carbon nanocomposite thus obtained is relatively porous with an open porosity favoring the subsequent adsorption of molecules in the pores; and that - the free external face of the carbon nanocomposite with infiltrated nanotubes has a specific surface area and a surface energy that are both relatively high.

[0051] This objective is achieved in that the Applicant has just discovered that if a controlled deposition by “CVD” of a sufficiently thin and conforming carbon coating is carried out on the carbon surface (non-functionalized and passivated) of the carbon nanocomposite, under an inert atmosphere, with conditions of duration, temperature and nature of the precursors favoring the deposition of pyrolytic carbon at the entrance of the pores of the carbon surface, using for this deposition reagents all in gas phase, then this treatment of the carbon surface makes it possible to effectively close the open porosity of said carbon material formed from forests of carbon nanotubes and the pyrolytic carbon infiltrating them, while significantly reducing the specific surface area and the surface energy of the external face of said carbon nanocomposite.

[0052] More specifically, a method of (pre)treatment according to said preliminary aspect of the invention of a carbon surface of a carbon nanocomposite, the nanocomposite being configured to form a flexible part of a regulating member for a watch movement and the (pre)treated carbon surface being optionally subsequently functionalized and passivated by the aforementioned functionalization and passivation method according to the invention, essentially comprises exposing the carbon nanocomposite, which has open porosity and comprises a forest of carbon nanotubes infiltrated by pyrolytic carbon, in a "CVD" reactor at a temperature between 500°C and 1200°C, to gaseous reagents comprising a hydrocarbon source of carbon and an agent inhibiting the carbon deposition reaction in the reactor,for a controlled deposition of a carbon coating with an average thickness between 50 nm and 500 nm which covers the carbon surface.

[0053] Even more precisely, this (pre)treatment method may comprise: - an introduction into the “CVD” reactor, which contains the carbon nanocomposite having open porosity and which is heated to a temperature between 500°C and 1200°C, of ​​reactants comprising: the hydrocarbon source of carbon in gaseous phase, and the inhibiting agent, also in gaseous phase, capable of inhibiting the pyrolytic carbon deposition reaction and thus limiting the quantity (i.e. the thickness) of the carbon coating to be deposited on said carbon surface, optionally by means of an inert gas transporting the reactants and reaction products inside the reactor while controlling the volume fractions of the reactants; and concomitantly with said introduction of the reactants and, where appropriate, the inert gas - exposure of the carbon nanocomposite to said reagents at said temperature between 500°C and 1200°C for a duration between 1 min. and 1 h 30 min., for controlled deposition of the carbon coating.

[0054] It will be noted that said temperature of exposure of the nanocomposite to the reagents is preferably between 800°C and 1000°C, when said hydrocarbon source of carbon is ethylene.

[0055] According to an exemplary embodiment of said preliminary aspect of the invention, the carbon nanocomposite, (i) before its (pre)treatment: - comprises a forest of carbon nanotubes infiltrated with pyrolytic carbon and having open porosity, the nanotubes covering support elements deposited on a semiconductor substrate, and - presents said carbon surface (i.e. the external surface of the nanocomposite, surface which externally delimits the infiltrated forest of nanotubes) which comprises: summit surfaces, basal surfaces, which are at the base of the infiltrated carbon nanotube forest (i.e. lower surfaces of said infiltrated forest, in contact with the layer formed by the support elements covering the substrate) and which are opposite the summit surfaces, and lateral surfaces that connect the summit surfaces to the basal surfaces; and (ii) after its (pre)treatment: comprises said carbon coating deposited on said top surfaces, said basal surfaces and said lateral surfaces of the carbon nanocomposite, the carbon coating thus continuously covering said carbon surface in this exemplary embodiment, making it possible to reduce or even eliminate the open porosity of the carbon nanocomposite.

[0056] According to this exemplary embodiment of the (pre)treatment method according to the invention, a turning of the nanocomposite is carried out to deposit the carbon coating on the basal surfaces, after having deposited it on the summit surfaces and on the lateral surfaces, so that the carbon surface to be (pre)treated can be made up of carbon atoms (the carbon nanocomposite preferably being made up of carbon nanotubes and pyrolytic carbon). It will be noted that the carbon nanocomposite and the carbon surface to be (pre)treated according to the invention could thus be predominantly or exclusively made up of any allotropic form of carbon, including amorphous carbon, tetrahedral carbon, diamond-like carbon ("DLC"), diamond, graphite, graphene, fullerenes and single-walled nanotubes ("SWNT"), double-walled nanotubes ("DWNT") or multi-walled nanotubes ("MWNT"), without limitation.

[0057] The (pre)treatment method according to said preliminary aspect of the invention (including said exemplary embodiment with infiltrated nanotubes) may be such that the controlled deposition of the carbon coating is carried out at an internal pressure P in the reactor which is for example less than or equal to atmospheric pressure (i.e. at a pressure P < 1,013.105 Pa approximately).

[0058] Advantageously, the (pre)treatment method according to said preliminary aspect of the invention (including said exemplary embodiment with infiltrated nanotubes) may be such that one uses: - as a hydrocarbon source of carbon, an unsaturated aliphatic or aromatic hydrocarbon, for example chosen from ethylene, acetylene or xylene, and / or - as a reducing agent for the thickness of the carbon coating, a hydrogenated gas, for example hydrogen (H2) or ammonia (NH3); and / or - as inert gas, nitrogen (N2) or argon (Ar).

[0059] Preferably, the (pre)treatment method according to said preliminary aspect of the invention (including said example with infiltrated nanotubes) is such that the following is used: - as hydrocarbon source of carbon, ethylene (C2H4) according to a volume fraction XC2H4 of between 0.05 and 0.50 (i.e. XC2h4 =5-50%), and / or - as a reducing agent, hydrogen (H2) according to a volume fraction XH2 of between 0.30 and 0.65 (i.e. XH2 30-65%), and / or - as an inert gas, argon (Ar) with a volume fraction XAr between 0 and 0.50 (i.e. Xat 3-50%).

[0060] It will be noted that the volume fraction X; of each gaseous species is defined as being the ratio of the volume flow rate Q; of each species to the sum of the volume flow rates of the gaseous species (X; = Qi / EQ0, each volume flow rate being for example expressed in cm3 / min. or in sccm (for “Standard Cubic Centimeters per Minute” in English, i.e. at a density defined by standard conditions of temperature and pressure).

[0061] Also preferably, the (pre)treatment method according to said preliminary aspect of the invention (including said example with infiltrated nanotubes) is such that, for the controlled deposition of the carbon coating, the following is used: - a reaction time of between 10 min. and 50 min., and / or - a temperature between 850°C and 900°C, and / or - a pressure P in the reactor equal to atmospheric pressure (1,013.105 Pa), to obtain an average thickness of the carbon coating, for example, between 90 nm and 200 nm.

[0062] According to other characteristics of the (pre)treatment method according to said preliminary aspect of the invention (including said exemplary embodiment with infiltrated nanotubes), this method may further comprise the following steps: - before the introduction of the reagents and the inert gas into the reactor containing the nanocomposite and the concomitant exposure of the latter to the reagents at a temperature between 500°C and 1200°C: a step a) purging the reactor under an inert atmosphere to evacuate the reagents and reaction products previously used for the deposition of pyrolytic carbon (eg the reagents and reaction products relating to the infiltration of nanotubes), and adjusting the temperature under said inert atmosphere for the purpose of controlled deposition (the temperature being able to remain constant or vary relative to the temperature used for the infiltration of nanotubes in said exemplary embodiment); - a step b) of controlled deposition of the carbon coating with continuous introduction of the precursors; - a step c) comprising purging the reactor followed by cooling said reactor under an inert atmosphere (for example under argon or nitrogen); - a step d) of removing from the reactor the substrate support elements and the carbon nanocomposites which surmount them and comprise the forests of nanotubes infiltrated at least partially (pre)treated (i.e. covered at least in part by the carbon coating); - a step e) of cleaning the reactor (for example by adding air at a temperature between 800 and 1000°C); and - optionally a step f) of reintroduction into the reactor of only the carbon nanocomposites partially (pre)treated and detached from the support elements of the substrate, the nanocomposites being turned 180° relative to the axis included in the main plane, to repeat steps a) to d) by completing the deposition of the carbon coating (in said example with infiltrated nanotubes, to deposit this coating on said basal surfaces of the nanocomposite).

[0063] According to said preliminary aspect of the invention relating to the aforementioned treatment method, there is also disclosed a flexible part of a regulating member for a watch movement, the flexible part, in particular a spiral spring, being adapted to flex in a plane perpendicular to an axis. The flexible part comprises a carbon nanocomposite having a carbonaceous surface treated as indicated above, the carbon nanocomposite comprising a forest of carbon nanotubes infiltrated by pyrolytic carbon, and said carbonaceous surface is covered with said carbon coating of average thickness between 50 nm and 500 nm, for example between 90 nm and 200 nm.

[0064] A flexible portion according to said preliminary aspect of the invention may be such that the carbon coating covers said top surfaces, said basal surfaces and said lateral surfaces of the carbon nanocomposite.

[0065] Advantageously, said carbon surface may present after said treatment according to the invention: - a total surface energy, defined as the sum of the dispersive energy and the specific energy in mJ / m2 and measured as specified in the description by inverse gas chromatography "iGC", which is reduced by at least 20%, for example at least 50%, compared to the total surface energy of the original carbon surface, and / or - a specific surface area, measured as specified in the description by inverse gas chromatography “iGC”, which is less than or equal to 1.5 m2 / g.

[0066] According to said preliminary aspect of the invention relating to the aforementioned treatment method, there is also disclosed a regulating organ for a watch movement, the regulating organ comprising: - a flexible part as defined above, in particular a spiral spring adapted to oscillate around said axis, and - a balance lever cooperating with the flexible part.

[0067] By the expression "based on", it is meant in the present description that the material or element considered comprises predominantly by weight the constituent concerned, i.e. according to a mass fraction greater than 50%, preferably greater than 75% and possibly up to 100% (if the material is made up of this constituent). Brief description of the drawings

[0068] Other characteristics, advantages and details of the present invention will emerge on reading the following description of several exemplary embodiments of the invention, given for illustrative and non-limiting purposes in relation to the attached drawings, among which: Fig.l

[0069] [Fig.l] is a schematic view of an example of a timepiece that may comprise a flexible part according to the invention, such as a spiral spring. Fig. 2

[0070] [Fig.2] is a top view of an embodiment of a spiral spring of a member regulator of the article of [Fig.l], according to an exemplary embodiment of the invention. Fig. 3

[0071] [Fig.3] schematically illustrates an example of the constitution of the material of the spiral spring of [Fig.2] in the form of a forest of nanotubes, the nanotubes being intentionally enlarged for clarity and therefore not shown to scale. Fig. 4

[0072] [Fig.4] is a perspective view of an example of a regulating member according to the invention comprising the spiral spring of [Fig.2]. Fig. 5

[0073] [Fig.5] is a simplified reaction scheme showing the main steps for implementing the functionalization and passivation process according to an example of the invention, starting from a precursor of the diazonium salt complex (fluorocarbon derivative of aniline). Fig. 6

[0074] [Fig.6] is a graph comparing the contact angles of distilled water on the same silicon substrate coated with a layer of pyrolytic carbon: - without treatment (reference sample), - with surface treatment by a solution containing a halogenated silane (silane sample), - with surface treatment by an Epilame® solution (Epilame® sample), - with functionalization and passivation by a hydrophobic monolayer film according to example 1 of the invention, and - with functionalization and passivation by a hydrophobic monolayer film according to example 4 of the invention, and - with functionalization and passivation by a hydrophobic monolayer film according to example 6 of the invention. Fig. 7

[0075] [Fig.7] is a diagram illustrating, in a “CVD” process for obtaining a nanocomposite based on carbon nanotubes infiltrated by pyrolytic carbon, the usual result of an initial step of treatment of a catalyst layer, step applied to a substrate covered with layers ending with the catalyst layer, with a view to growing carbon nanotubes there. Fig. 8

[0076] [Fig.8] is a diagram illustrating, in this “CVD” process, the usual result of a following step of growth of carbon nanotubes on the catalyst layer treated in [Fig.7]. Fig. 9

[0077] [Fig.9] is a diagram illustrating, in this “CVD” process, the usual result of a following step of infiltration of pyrolytic carbon into and between the carbon nanotubes deposited in [Fig.8]. Fig. 10

[0078] [Fig. 10] is a diagram illustrating, in this “CVD” process, the result of a following step, according to said preliminary aspect of the invention, of depositing a coating of carbon on the top and side surfaces of the carbon nanocomposite obtained in [Fig.9]. Fig. 11

[0079] [Fig. 11] is a diagram illustrating, in this “CVD” process, the result of a following step, according to said preliminary aspect of the invention, of turning over the carbon nanocomposite provided with the coating of [Fig. 10], with a view to depositing this coating further on the basal surface of the nanocomposite. Fig. 12

[0080] [Fig. 12] is a diagram illustrating, in this “CVD” process, the result of a following step, according to said preliminary aspect of the invention, of depositing the carbon coating on the basal surface of the carbon nanocomposite returned according to [Fig.l 1]. Examples of embodiments of the invention

[0081] [Fig.l] represents a timepiece 1 such as a mechanical watch, comprising: - a case 2, - a watch movement 3 contained in the case 2, - generally, a winder 4, - a dial 5, - a glass 6 covering the dial 5, and - a time indicator 7, comprising for example two hands 7a, 7b respectively for the hours and the minutes, arranged between the glass 6 and the dial 5 and actuated by the clock movement 3.

[0082] [Fig. 2] illustrates a spiral spring 20 of a regulating member 1a according to the invention (see [Fig. 4]). This spiral spring 20 is arranged to rotate with a balance 10 (see also [Fig. 4]) around a central axis Y. The spiral 20 has a length L, and comprises several turns 22 and also a terminal portion 23 (“terminal curve”) which is fixed, generally by a stud to a bridge (reference 40 in [Fig. 4]) on which the balance 10 is pivotally mounted.

[0083] The spiral spring 20 comprises a central portion 21 which allows it to be fixed to the axis of the balance wheel 10. In the example of [Fig.2], this central portion 21 is integrated into the spiral spring 20 and made of the same material as the spiral spring 20. As visible in [Fig.2], the turns 22 have a thickness t (in the plane perpendicular to the Y axis) for example of the order of a few tens of μm, eg from 10 μm to 100 μm approximately. It will be noted that this thickness of the turns 22 may not be constant.

[0084] As visible in [Fig.3], the coils 22 also have a height h (parallel to the Y axis), and the spiral spring 20 is made of a composite material comprising carbon nanotubes 200 held by a matrix 202 of pyrolytic carbon. The nanotubes 200 form a forest of juxtaposed nanotubes all arranged substantially parallel to each other, advantageously substantially parallel to the Y axis or not (for example when the nanotubes are not straight, but wavy in a manner not parallel to the Y axis). They are generally regularly spaced from each other and present throughout the mass of the composite material.

[0085] The nanotubes may have a diameter d of between 1 nm and 30 nm, possibly between 4 nm and 18 nm, in particular of the order of 10 nm. The nanotubes may have a length of between 50 pm and 500 pm, possibly between 150 pm and 275 pm, in particular of the order of 225 pm. This length may advantageously correspond to the aforementioned thickness h of the turns 22 of the spiral spring 20.

[0086] The matrix 202 can advantageously be made of pyrolytic carbon, and it can advantageously encompass the nanotubes 200 by being present in the interstices 204 between the nanotubes 200 and in their internal spaces 206. The matrix 202 makes it possible to provide cohesion to the forest of nanotubes.

[0087] [Fig.4] illustrates a perspective view of an example of a regulating organ according to the invention, with the balance 10 which comprises a rim 12 and four arms 14, each arm 14 having a substantially triangular shape and comprising a central opening 17, which in this case has no technical functions. Alternatively, the number of arms may be other than four. In another variant, the arms have a substantially linear shape. In yet another variant, the arms are devoid of any opening. Also visible in the example of [Fig.4] is an index assembly 30 acting on the active length of the spiral spring 20 to adjust the oscillation frequency.

[0088] For example, spiral springs 20, such as that illustrated in [Fig.2], are manufactured essentially by: - a chemical vapor deposition process ("CVD") on a silicon wafer forming a substrate, then by - a cleaning process implemented in a first step using air or nitrogen, then for example by sonication in solvents, to clean the surface during a second step, then to extract the physisorbed molecules during a third step, then finally by - drying at room temperature or hot to remove traces of solvents.

[0089] The spiral springs 20 thus manufactured are then classified by listing them in specific classes, then they are stored.

[0090] According to the invention, the carbon surface 20a of the spiral spring 20 was functionalized and passivated in its cleaning cycle, preferably between said second step and said third step (see [Fig.5]).

[0091] In the examples presented below, the carbon surface 20a of the same spiral 20 formed from a carbon / carbon nanocomposite, consisting of a forest of carbon nanotubes 200 which is infiltrated by pyrolytic carbon 202 (also called “nanocrystalline carbon” or “amorphous carbon”), was functionalized and passivated. As explained below, a hydrophobic monolayer film was deposited by the method of the invention both on the pyrolytic carbon 202 and on the carbon nanotubes 200 (provided that these nanotubes 200 are accessible).

[0092] For this purpose, as visible in [Fig.5], a precursor of said complex was used, a precursor which was for example constituted by a fluorocarbon derivative of aniline, namely 4-(heptadecafluorooctyl)aniline whose developed formula is illustrated in the left part of [Fig.5]. This precursor was reacted for example at 20°C with NaNO2 in HCl and DMSO (dimethylsulfoxide), to obtain the complex with a fluorocarbon chain ending in the salt of the diazonium group, which corresponds to the formula in the center of [Fig.5] with the anion X which was Cl in this embodiment.

[0093] This precursor of the complex was reacted with the spiral 20 according to the in situ embodiment (it being specified that another precursor e.g. of the triazene type can be used as a variant), or the complex which is derived from it (according to the preformed embodiment), by adding the precursor or the complex to the reaction medium. As detailed below in examples, a first in situ protocol was followed with reducing agent applied to 50 spirals, as a variant, a second in situ protocol without reducing agent also applied to 50 spirals, and a third protocol with preformed precursor.

[0094] First experimental protocol followed with a reducing agent (example 1): The hairsprings were pre-cleaned by sonication for 10 minutes in 10 mL of isopropyl alcohol (IPA). A reducing agent solution was prepared in a first flask by diluting ascorbic acid (18 mg) first in water (1.25 mL) and then adding IPA (3.75 mL) to obtain a final concentration of 0.02 mol / L. The hairsprings were immersed in the ascorbic acid solution. In a second flask, 64 mg of 4-(heptadecafluorooctyl)aniline was dissolved in 5 mL of IPA (0.025 mol / L), to which 0.25 mL of 1 mol / L aqueous HCl was added. Then, 1.25 mL of aqueous NaNO2 (0.1 mol / L) was added to the 4-(heptadecafluorooctyl)aniline solution to induce the formation of the diazonium salt. The diazonium salt solution was then added to the reducing solution containing the spiral, to have a 1:1 volume ratio of the two solutions. The surface was allowed to react for 24 hours. The hairsprings were then removed and rinsed, possibly sonicated 1 to 3 times with acetone, then 1 to 3 times with water, and finally 1 to 3 times with IPA. The hairsprings were then allowed to dry for 1 hour in ambient air.

[0095] Second experimental protocol followed without reducing agent (example 4): The hairsprings were pre-cleaned by sonication for 10 minutes in 10 mL of isopropyl alcohol (IPA). 128 mg of 4-(heptadecafluorooctyl)aniline was then dissolved in 10 mL of dimethyl sulfoxide (DMSO) (0.025 mol / L), to which 0.5 mL of 1 mol / L aqueous HCl was added. The hairsprings were then added to the solution. 2.5 mL of NaNO2 in 0.1 mol / L DMSO was then added to the solution. The surface was allowed to react for 24 hours. The hairsprings were then removed and rinsed, optionally sonicated, with acetone 1 to 3 times, then water 1 to 3 times, and then IPA 1 to 3 times. The hairsprings were then left to dry for 1 hour in ambient air.

[0096] Third experimental protocol followed with preformed complex (example 6) A solution of t-BuONO (124 mg) and 4-(heptadecafluorooctyl)aniline (511 mg) in glacial acetic acid (4 mL) was added dropwise to a solution of triflic acid (180 mg) in glacial acetic acid (6 mL). The reaction mixture was stirred for 10–20 minutes. After the reaction was complete, diethyl ether (100–150 mL) was added. The precipitated diazonium salt was collected as a white powder by filtration and dried. This powder (134 mg) was dissolved in DMSO (10 mL) to obtain a concentration of 0.02 mol / L, to which the hairsprings pre-cleaned by sonication for 10 minutes in 10 mL of isopropyl alcohol (IPA) were added. The surface was allowed to react for 24 hours. Then the spirals were removed and rinsed, possibly subjected to sonication, with acetone 1 to 3 times, then water 1 to 3 times, then IPA 1 to 3 times.The hairsprings were then left to dry for 1 hour in ambient air.

[0097] “XPS” protocol followed to analyze the samples of spirals obtained by these treatments:

[0098] The XPS (X-ray photoelectron spectrometry) analysis was carried out in an accredited laboratory in accordance with ISO / IEC 17025:2017-11. The XPS was calibrated in accordance with ISO 15472:2010-05, and the performance was checked monthly in accordance with ISO 16129:2018-11. The preparation of the samples in accordance with ISO 18117:2009-03. Analysis and evaluation were carried out in accordance with ISO 10810:2019-08.

[0099] More specifically, the "XPS" measurements were carried out with this method, the electrons of an atom are so excited by the X-rays bombarding them that they leave their atom and eventually the surface of each sample. The energy of the photoelectrons was analyzed with a hemispherical analyzer, and their binding energy was thus calculated. This made it possible to quantitatively determine the chemical composition in the upper 5 nm to 10 nm of each sample.

[0100] This “XPS” analysis made it possible in particular to evaluate the atomic concentration of fluorine on the surface in a superficial zone of the passivated carbon surface (i.e. the outermost zone of each spiral, approximately 2-10 nm thick) deposited on each sample of spiral obtained by treatments according to the invention, as a function of reaction parameters, as indicated in Table 1 below which compares the efficiency of the deposition of this film as a function of the reaction conditions used. This atomic concentration of fluorine on the surface is the % of F measured on the surface 20a of the spiral 20, after the latter has been functionalized and passivated by the deposition of the hydrophobic monolayer film. Since the fluorine comes only from this film, this atomic concentration of F reflects an evaluation of the quantity of molecules present on the surface of the spiral (the atomic % of F = 0 for untreated spirals).

[0101] Examples 1-6 according to the invention of treatment of a spiral 20:

[0102] In the particular case of Examples 1-5 presented in Table 1 below, the in situ formation of the complex and the deposition of the monolayer film took place simultaneously. The atomic concentration of fluorine therefore reflected in this case the efficiency of the formation of the complex and that of the deposition of the monolayer film.

[0103] In Table 1 below: - the abbreviation “Na Asc” means sodium ascorbate; - conc. means the concentration of the complex (mmol / L) in the reaction medium, and - the abbreviations IPA, DMSO and TFA mean respectively isopropyl alcohol, dimethyl sulfoxide and trifluoroacetic acid (used as acid to treat the samples of Example 5 instead of HCl in Examples 1-4).

[0104] [Table 1]: Duration Temp. Reducing agent Solvent conc. atomic concentration of F on surface (XPS) Example 1 24 h 20°C Na Asc 10 mmol / L IPA 75% HCl aq (0.15 mmol / L) 25% 14% Example 2 24 h 20° C none 10 mmol / L IPA 75% HCl aq (0.15 mmol / L) 25% 23 % Example 3 24 h 20° C Na Asc 10 mmol / L DMSO 95% HCl aq (0.1 mmol / L) 5% 24% Example 4 24 h 20° C none 20 mmol / L DMSO 95% HCl aq (0.1 mmol / L) 5% 30% Example 5 24 h 20° C none 20 mmol / L IPA, TFA 1% 12% Example 6 24 h 20°C none 20 mmol / L DMSO 100% (preformed diazonium salt) 29%

[0105] Protocol followed for the measurement of water contact angles:

[0106] Since the water contact angle cannot be measured directly on the spirals 20 obtained, a flat substrate (silicon wafer) covered with a layer of pyrolytic carbon similar to that defining the carbon surface 20a of each spiral 20 was used as a reference sample.

[0107] Description of samples: - reference: standard sample without surface treatment, cleaned by ultrasonication in isopropyl alcohol (IPA), after which the water contact angle was measured; - silane: the standard sample was immersed in a chloroform solution containing 1H,1H,2H,2H-perfluorooctyl-trichlorosilane at 0.01 mol / L for 24 hours, then the sample was rinsed with chloroform and then subjected to sonication in pure chloroform to remove chemical species not bound to the carbon surface, after which the water contact angle was measured; - pilame: the sample type was immersed in a commercial solution of “Moebius FixoDrop ES / BS 8981” commonly known as “epilame” (based on a fluorinated polyester) for 24 hours, then the sample was rinsed with acetone and then subjected to ultrasonication in pure acetone to remove chemical species not bound to the surface, after which the water contact angle was measured; and - examples 1, 4 and 6 of the invention: the water contact angle was measured for each of the samples of examples 1, 4 and 6 as detailed in table 1, after rinsing each of these samples as described in the experimental protocol above-mentioned (first protocol with reducing agent for example 1, second protocol without reducing agent for example 4, third protocol with preformed complex for example 6), then after having subjected them to sonication in acetone.

[0108] The contact angle of water was measured by depositing a 3 pL drop of distilled water on the surface of each sample to be characterized. More precisely, the contact angle was measured with a contact angle analyzer, and the analysis of the drop was carried out using the Young-Laplace model. The values ​​reported in [Fig.6] were, for each sample, the average of three angle measurements at three different locations on the surface to be characterized.

[0109] As shown in the graph of [Fig.6], the carbon surface of the samples modified according to Examples 1, 4 and 6 of the invention was truly hydrophobic, i.e. it had a water contact angle well above 90°, this angle being in fact more than 100° for the treated samples of Examples 1, 4 and 6, in comparison in particular with the water contact angles around 90° for the samples treated with a silane and epilame agent, respectively. These measurements therefore clearly demonstrated that the monolayer films based on diazonium functional groups were capable of effectively passivating the carbon surface 20a of the balance spring 20, while grafting via covalent bonds onto this surface 20a.

[0110] Protocol followed to measure the surface energies of the samples: The Owens-Wendt-Rabel & Kaelble "OWRK" method (Owens DK and Wendt RC, 1969, J. Appl. Polym. Sci. 13, 1741) was used to determine the dispersive surface energy and specific surface energy of the samples to be characterized. This method uses the static contact angles of several liquids. The static contact angle of water, diiodomethane, glycerol, and ethylene glycol was measured by placing a 3 μL drop on the surface of each sample (reference and example 4) to be characterized. More precisely, the contact angle was measured with a contact angle analyzer (Kruss), and the drop analysis was performed using the Young-Laplace model. The values ​​reported in Table 2 were, for each sample, the average of three angle measurements at three different locations on the surface to be characterized.These values ​​were then used in the “OWRK” model to obtain the specific surface energy and dispersive surface energy of each sample.

[0111] Tables 2 and 3 below present the results obtained for the contact angles and for the resulting surface energies, respectively.

[0112] [Table 2]: Contact angles Solvent Contact angle on flat carbon substrate Contact angle on flat carbon substrate with monolayer film (example 4) Water 68° 112° Diiodomethane 34° 97° Glycerol 76° 108° Ethylene glycol 53° 93° [Table 3]: Surface energy calculated with the “OWRK” model Sample Specific surface energy Dispersive surface energy Total surface energy Planar carbon substrate 9 mJ / m2 27 mJ / m2 36 mJ / m2 Planar carbon substrate with monolayer film (example 4) 1 mJ / m2 9 mJ / m2 10 mJ / m2

[0113] Protocol followed to measure the surface energies of the spirals 20:

[0114] As explained in the above general description of the invention relating to said second aspect, inverse gas chromatography ("iGC") was used, with all analyses performed using an "iGC" surface energy analyzer (surface area measurement system). The data were analyzed by standard and advanced "SEA" analysis software. Approximately 32 mg to 56 mg of the material of the hairspring 20 was placed in an individual "iGC" silanized glass column.

[0115] A series of surface coverage measurements were thus carried out with alkanes and polar probe molecules (adsorbates), to determine the dispersive surface energy and the specific surface energy. For this purpose, the sample columns were pre-conditioned for 1 hour at 30°C and 0% relative humidity (RH), with 10 mL / min. of helium carrier gas. The experiments were carried out at 30°C with a total helium flow rate of 10 mL / min. and using methane for dead volume corrections.

[0116] Table 4 below presents the results obtained, before and after the treatment of the invention applied to the sample of example 1 mentioned above in table 1 (i.e. untreated reference sample, and sample treated according to the invention), at relative humidity (RH) levels of 0%, 30% and 60%, respectively. [Tables 4] Comparison of the total surface energy of the hairsprings measured by "iGC" before and after treatment at different humidity levels 0% RH 30% RH 60% RH Without treatment of the carbon surface of the hairspring 90 mJ / m2 70 mJ / m2 70 mJ / m2 After treatment of the carbon surface of the hairspring according to example 1 50 mJ / m2 50 mJ / m2 50 mJ / m2

[0117] Comparison of the reference sample (i.e. without deposited single-layer film) with the sample of example 1 demonstrates the passivation of the carbon surface 20a of the balance spring 20 in this example 1, which is attested by the significant reduction in the total surface energy, and this with a relative humidity rate varying from 0% to 60%. This table 4 thus demonstrates the insensitivity of the treated surface to variations in humidity in the environment (constant total surface energy), unlike an untreated surface whose total surface energy decreases with increasing relative humidity.

[0118] Finally, it will be noted that the functionalization and passivation treatment according to the invention does not modify the mechanical properties (i.e. the classification) of the hairspring 20 before and after this treatment, but the reactivity of the hairspring 20 to the environment. Indeed, the Applicant has verified that each of the samples of treated hairsprings 20 prepared according to examples 1-6 did not present a significant difference in class before and after the treatment of the invention, it being specified that the difference in class of a single unit sometimes observed was within the measurement error of the instrument.

[0119] [Fig.7] is a cross-section illustrating the known deposition in a “CVD” reactor, on a silicon (Si) substrate 50 covered with a layer 51 of silica (SiO2), at a temperature between 650 and 750°C in the presence of an inert gas such as argon (Ar) and hydrogen (H2), of support elements 52 (only one is shown) formed from a layer of alumina (A12O3). The support elements 52 are deposited on the layer 51, and these elements 52 incorporate a layer of iron 53 (Fe) to grow carbon nanotubes 61 ([Fig.8]).

[0120] [Fig.8] is a cross-section which illustrates the known deposition by “CVD” at a temperature between 650 and 750°C in the same reactor, of carbon nanotubes 61, via a globally axial growth (i.e. mainly in a direction globally perpendicular to the substrate 50) of the nanotubes 61 on the elements 52 thus treated in [Fig.7], via a hydrocarbon gas as a source of carbon introduced into the “CVD” reactor, always in the presence of argon as an inert gas and hydrogen. This produces a forest 60 of carbon nanotubes 61 with a length of, for example, between 100 pm and 500 pm.

[0121] [Fig.9] is a cross-section illustrating the deposit also known by “CVD”, at a temperature between 750 and 850°C in the same reactor, always with a hydrocarbon gas as a carbon source and in the presence of argon and hydrogen, pyrolytic carbon 70 infiltrated into and between the bundles 60 of nanotubes 61, in contact with the support elements 52.

[0122] [Fig. 9] further identifies the top surface 63 (horizontal in [Fig. 9]) and the opposite base surface 64 of each forest 60 of nanotubes 61, which extends substantially at a right angle by the lateral surfaces 62 (vertical in [Fig. 9]), the surfaces 62, 63, 64 defining the entire carbon external surface 80 of the carbon nanocomposite 90 to be coated.

[0123] Thus, the term carbon surface 80 of the nanocomposite 90 is understood to mean the surface 80 intended to be the subject of the (pre)treatment according to the invention, comprising all of the respective top 63, base 64 and lateral 62 surfaces of the forests 60 of carbon nanotubes 61 infiltrated by pyrolytic carbon.

[0124] [Fig. 10] is a cross-section illustrating the deposition according to the invention of the carbon coating 100 on the top 63 and lateral 62 surfaces of the forest 60 of nanotubes 61 by “CVD”, at approximately 850°C in the same reactor with, for example, ethylene (C2H4) as the carbon source and in the presence of argon as the inert gas and hydrogen as the reducing agent. [Fig. 10] shows that the carbon coating 100, with an average thickness preferably between 50 nm and 500 nm, for example between 90 nm and 200 nm, continuously covers the top surface 63 and the lateral surfaces 62 of the carbon surface 80 (the surfaces 62 and 63 are visible in [Fig. 9]).

[0125] According to an example of implementation of the method for depositing the carbon coating 100 according to the invention, the procedure was as follows, via the following successive steps: - purging the “CVD” reactor with argon, in order to evacuate all the reagents and reaction products from the previous step of the [Fig.9] infiltration of the pyrolytic carbon between and into the nanotubes 61 of each forest 60 of nanotubes 61; - adjusting the temperature in the reactor for the purpose of depositing the carbon coating 100 under an inert argon atmosphere, it being specified that the imposed temperature can remain constant (i.e. 750-850°C for infiltration and for example 850°C for the deposition of the carbon coating 100); - deposition of the carbon coating 100 (see [Fig. 10]) on the top surfaces 63 and on the lateral surfaces 62 of the forests 60 of nanotubes 61, at the pressure atmospheric and at a temperature between 850°C and 900°C for a deposition time of approximately 30 minutes (which makes this deposition rapid, in comparison with the relatively slow deposition for the infiltration obtained in [Fig.9] which lasts several hours), with the following volume fractions and flow rates for argon, ethylene and hydrogen gas in the reactor: Ar: volume fraction = 0.38 and volume flow rate = 2500 sccm; C2H4: volume fraction = 0.23 and volume flow rate = 1500 sccm; H2: volume fraction = 0.38 and volume flow rate = 2500 sccm; - purging, then cooling of the reactor under an inert argon atmosphere (nitrogen can also be used as a variant); - removal from the reactor of the entire substrate 50 provided with layers 51-52 and nanocomposite 90; - cleaning of the reactor by adding air at 900°C; - detaching the nanocomposite 90 from the layer formed by each support element 52 surmounting the substrate 50; then - reintroduction into the reactor of only the nanocomposite 90, detached from the layer of elements 52 and turned 180° relative to the axis included in the main plane (see [Fig. 11]), to carry out the deposition of the carbon coating 100 on the basal surfaces 64 (visible in [Fig. 12]), using the same reaction conditions as previously for the summit surfaces 63 and the lateral surfaces 62.

[0126] Scanning electron microscope (SEM) and transmission electron microscope (TEM) images demonstrated the compact microstructure of the carbon 100 coating obtained for each carbon 90 nanocomposite (pre)treated according to the invention (thickness of the coating 100 locally 95 nm), in comparison with the more porous microstructure of each nanocomposite 90 devoid of this coating 100. Indeed, the top surface 63, the base surface 64 and the lateral surfaces 62 of each coated nanocomposite 90 (i.e. the entire carbon surface 80 thus coated with the (pre)treated nanocomposite 90), presented a significant closed porosity, which makes it possible to limit, or even eliminate, the adsorption of molecules in the pores of the (pre)treated nanocomposite 90 according to the invention.

[0127] Table 5 below presents the results obtained for total surface energy measured by the aforementioned “iGC” technique, for a variant with the deposition of the carbon coating 100 of the invention applied to the nanocomposite 90 as described with reference to Figures 10-12 (i.e. sample treated according to the invention), in comparison with a variant not in accordance with the invention without carbon coating as described with reference to [Fig.9] (i.e. untreated reference sample). [Tables 5] Comparison of the total surface energy of nanocomposites measured by “iG C” without carbon coating and with carbon coating Without carbon coating of the carbon surface of the hairspring 90 mJ / m2 After carbon coating of the carbon surface of the hairspring 42 mJ / m2

[0128] Table 6 below presents the results obtained for specific surface area measured by “iGC”, for an example with the deposition of the carbon coating 100 of the invention applied to the nanocomposite 90 as described with reference to figures 10-12 (i.e. sample treated according to the invention), in comparison with a variant without carbon coating as described with reference to [Fig.9] (i.e. untreated reference sample). [Tableauxô] Comparison of the specific surface area (BET) of nanocomposites measured by “iG C” without carbon coating and with carbon coating Without carbon coating of the carbon surface 7.5 m2 / g After carbon coating of the carbon surface 1.5 m2 / g

Claims

Claims

1. Method for functionalizing and passivating a carbon surface (20a) of a carbon nanocomposite (20) configured to form a flexible part of a regulating member (la) for a watch movement, in which the method comprises a chemical reaction of the carbon surface (20a) with a complex which comprises: - a carbon chain which is hydrocarbon or fluorocarbon, and - at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, for a covalent grafting of the reactive carbon end onto the carbon surface (20a), and a passivation of the carbon surface (20a) making it hydrophobic.

2. A method according to claim 1, wherein the salt of a diazonium group is formed in situ from said precursor which is for example a fluorocarbon derivative of aniline or a triazene, or is preformed prior to the chemical reaction, the diazonium salt having the formula [Chem. 1]: [Chem. 1] RN^NX“ where R is a substituted or unsubstituted hydrocarbon group, for example substituted phenyl, and X is an inorganic or organic anion, for example a halogenated anion or a triflate anion, and wherein the reactive carbon end is grafted onto the carbon surface (20a) by a covalent CC bond between the R group and a carbon atom of the carbon surface (20a).

3. A method according to claim 1 or 2, wherein the carbon chain of said complex is aliphatic and fluorocarbon, for example a perfluorinated hydrocarbon chain.

4. Method according to one of the preceding claims, in which the chemical reaction forms for said grafting a functionalized and passivated carbon surface having: - a water contact angle which is equal to or greater than 90°, for example between 105° and 130°; and / or - an atomic concentration of fluorine which is between 5% and 70%; and / or - a total surface energy, defined as the sum of the dispersive energy and the specific energy in mJ / m2 and measured by inverse gas chromatography “iGC” or by the “OWRK” method, which is reduced by at least 20%, for example by at least 50% when measured by the “OWRK” method, compared to the total surface energy of the carbon surface (20a) before functionalization and passivation.

5. Method according to one of the preceding claims, in which the chemical reaction forms for said grafting a hydrophobic monolayer film which covers the carbon surface (20a) by functionalizing and passivating it and which is formed concomitantly or after the formation of said complex, the hydrophobic monolayer film having a water contact angle which is equal to or greater than 90°, for example between 105° and 130°.

6. Method according to claim 5, in which: - the total surface energy of the carbon surface (20a) covered with the hydrophobic monolayer film, defined as being the sum of the dispersive energy and the specific energy in mJ / m2 and measured by inverse gas chromatography "iGC" or by the "OWRK" method, is reduced by at least 20%, for example by at least 50% when measured by the "OWRK" method, relative to the total surface energy of the carbon surface (20a) before deposition of the hydrophobic monolayer film; and / or - the atomic concentration of fluorine in an outermost surface zone of the hydrophobic monolayer film, with a thickness of between approximately 2 nm and 10 nm, is between 5% and 70%.

7. A method according to claim 5 or 6, wherein the hydrophobic monolayer film comprises a reaction product between the carbon surface and a diazonium functional group having the formula [Chem. 2]: [Chem. 2] R—N=N where R is a substituted or unsubstituted hydrocarbon group, wherein the hydrophobic monolayer film comprises said group R which is functionalized with said carbon chain, for example a perfluorinated hydrocarbon chain and preferably wherein: R is an aryl group, e.g. substituted phenyl, and the functional group is an aryl diazonium group, e.g. benzenediazonium having the formula [Chem. 3]: [Chem. 3] C y—

8. Method according to one of the preceding claims, in which the carbon surface (20a) is immersed in a reducing solution comprising a reducing agent, for example ascorbic acid, and then in which the chemical reaction is carried out in a reaction medium comprising said complex in solution.

9. The method of one of claims 5 to 7, wherein said carbon nanocomposite (20) comprises a forest of carbon nanotubes (200) infiltrated by pyrolytic carbon (202), wherein said carbon surface (20a) is made of carbon atoms, and wherein the hydrophobic monolayer film directly covers the pyrolytic carbon (202) and the accessible carbon nanotubes (200).

10. The method of claim 9, wherein the flexible portion is adapted to flex in a plane perpendicular to an axis (Y), the carbon nanocomposite (20) being configured to form a spiral spring adapted to oscillate around the axis (Y), the carbon nanocomposite (20) consisting of a matrix formed by the pyrolytic carbon (202) and the forest of carbon nanotubes (200) juxtaposed and held by the matrix which infiltrates them, the nanotubes (200) for example of the multi-sheet type being arranged generally parallel to the axis (Y) or being corrugated in a manner not parallel to the axis (Y).

11. A method according to claim 9 or 10, wherein, prior to said chemical reaction, the method comprises a step of pretreating the carbon surface (80) comprising exposing the carbon nanocomposite (90), which has open porosity, in a chemical vapor deposition reactor at a temperature between 500°C and 1200°C, to gaseous reactants comprising a hydrocarbon source of carbon and an agent inhibiting carbon deposition in the reactor, for controlled deposition of a carbon coating (100) with an average thickness of between 50 nm and 500 nm which covers the carbon surface (80).

12. Flexible part (20) of a regulating member (la) for a watch movement, the flexible part, in particular a spiral spring, being adapted to flex in a plane perpendicular to an axis (Y), the flexible part comprising a carbon nanocomposite (20) having a functionalized and passivated carbon surface, wherein said functionalized and passivated carbon surface comprises the product of a chemical reaction between an original carbon surface (20a) of the carbon nanocomposite (20) and a complex, which comprises: a carbon chain which is hydrocarbon or fluorocarbon, and at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, wherein the reactive carbon end is grafted by a covalent bond onto the original carbon surface (20a), and wherein said functionalized and passivated carbon surface is hydrophobic.

13. A flexible portion (20) according to claim 12, wherein said functionalized and passivated carbon surface forms a hydrophobic monolayer film which covers the original carbon surface (20a), said functionalized and passivated carbon surface having at least one of the following characteristics: - a water contact angle which is equal to or greater than 90°, for example between 105° and 130°, - a total surface energy, defined as the sum of the dispersive energy and the specific energy in mJ / m2 and measured by inverse gas chromatography "iGC" or by the "OWRK" method, which is reduced by at least 20%, for example by at least 50% when measured by the "OWRK" method, compared to the total surface energy of the original carbon surface, - an atomic concentration of fluorine which is between 5% and 70%, and - a substituted or unsubstituted hydrocarbon group R, for example substituted phenyl, which is functionalized with said carbon chain, which is for example a perfluorinated hydrocarbon chain.

14. A flexible portion (20) according to claim 12 or 13, wherein said original carbon surface (20a) is made of carbon atoms and the carbon nanocomposite (20) comprises a forest of carbon nanotubes (200) and a pyrolytic carbon matrix (202) infiltrated into the forest of nanotubes (200), the nanotubes being juxtaposed and held by the matrix, the nanotubes (200) for example of the multi-wall type being arranged generally parallel to the axis (Y) or being corrugated in a manner not parallel to the axis (Y).

15. Regulating member (la) for a watch movement, the regulating member comprising: - a flexible part (20) adapted to flex in a plane perpendicular to an axis (Y), in particular a spiral spring adapted to oscillate around the axis (Y), and - a balance (10) cooperating with the flexible part (20), wherein the flexible part (20) is as defined in one of claims 12 to 14.

16. Use of a complex which comprises: - a carbon chain which is hydrocarbon or fluorocarbon, and - at a reactive carbon end of the chain, a salt of a diazonium group or of a precursor of said group, to functionalize and passivate by chemical reaction a carbon surface (20a) of a carbon nanocomposite (20) configured to form a flexible part of a regulating member for a watch movement, via covalent grafting of the reactive carbon end onto the carbon surface (20a) and passivation of the carbon surface (20a) making it hydrophobic.

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