WO2020094929A1

WO2020094929A1 - Process for manufacturing fibres that are thermostable at high temperatures

Info

Publication number: WO2020094929A1
Application number: PCT/FR2019/000139
Authority: WO
Inventors: Max Sardou; Patricia SARDOU
Original assignee: Max Sardou; Sardou Patricia
Priority date: 2018-11-08
Filing date: 2019-08-26
Publication date: 2020-05-14
Also published as: FR3088345A1; WO2020094929A4; FR3088345B1

Abstract

The invention relates to an optimised process for making high-performance thermostable fibres. These fibres are designed to form a composite with a ceramic or metal matrix. A composite having this structure is aimed at producing hot parts and hot structures such as hypersonic aircraft, components of aircraft reactors, components of nuclear reactors, rocket nozzles, exhaust pipes, and gas turbines. It consists in using carbon fibres coated with an innovative refractory envelope impregnated with a matrix in a PVD process.

Description

HIGH TEMPERATURE TERMOSTABLE FIBER MANUFACTURING PROCESS

Field of the invention:

The present invention relates to an innovative process optimized for producing high performance thermostable fibers. These fibers being intended to constitute a ceramic or metallic matrix composite. The composite thus formed having the objective of producing hot parts and structures such as hypersonic airplanes, aircraft reactor components, nuclear reactor components, rocket nozzles, exhaust pipes, gas turbines

Previous State of Share:

The materials used for the matrix in technical applications are currently mainly alumina, mullite, carbon and silicon carbide. The development of these ceramics was the solution to serious mechanical resistance problems encountered when using conventional technical ceramics, such as alumina, silicon carbide often used in sintered form, aluminum nitride (AIN ), silicon nitride (S13N4), oxide of

zirconium (IV) or zirconia (Zr02), indeed, all these materials break easily under mechanical or thermal stresses, because even small imperfections or scratches on the surface can become the starting point of a crack. The massive material, opposes the propagation of the crack only a weak resistance, like glass, contrary to the more ductile metals. This gives a

characteristic brittle behavior, which complicates or even prevents many uses.

It was only with the use of long fibers for the reinforcement of ceramic, known as ceramic matrix composites (CMC), that we could drastically improve the breaking strength, as well as other properties such as the possibility of elongation, resistance to thermal shock, which opened up new fields of application. In the development and applications of ceramic matrix composites (CMC), carbon fibers (C) and silicon carbide (SiC) are mainly used, and sometimes aluminum oxide or alumina (AI2O3) fibers, or mixed crystals of alumina and silicon oxide or silica (S1O2) called mullite (3AI2O3, 2S1O2). CMCs are described as "fiber type / matrix type". Thus "C / C" describes carbon reinforced with carbon fibers, "C / SiC" describes silicon carbide reinforced with carbon fibers.

The main CMCs, currently commercially available, are C / C, C / SiC, SiC / SiC, and AI2O3 / AI2O3. They differ from conventional technical ceramics mainly by the following properties:

• Elongation before breakage enlarged up to 1%

• Significantly better resistance to breakage

• Extreme resistance to thermal shock

• Better resistance to dynamic loads

• Anisotropic properties defined by the orientation of the fibers

In US patent 5021367 of June 4, 1991 the inventor uses a chemical gas deposition (CVD) to impregnate fibers in direct rovings or fabrics: CVD is difficult to control and the fact of using fabrics or rovings direct (carbon fibers, made up of a bundle of fibrils, the number of fibrils of which typically varies from 1,000 to 50,000!) in no way guarantees the perfect coating of elementary fibrils. In addition, a single protective layer is deposited, which is not optimal for withstanding thermal fatigue cycles. In addition, CVD deposition is carried out on fibers carried between 1400 ° C and 1650 ° C, many microcracks appear on the coating during cooling. Conclusion = No relation with the present patent In the patent US 4962070 of October 9, 1990 the inventor uses a chemical deposition in gas phase (CVD) to impregnate fibers in direct rovet: as explained previously the CVD is delicate to control and using direct rovings in no way guarantees the perfect covering of elementary fibrils. In addition, a single protective layer is deposited, which is not optimal for withstanding thermal fatigue cycles. In addition, the CVD deposit being made on fibers carried between 1400 ° C and 1650 ° C, many microcracks appear on the coating during cooling. Conclusion = No relation to this patent

In US patent 4,376,803 of March 15, 1983, the inventor uses a chemical deposit obtained by passing a roving (direct from graphite fibers) in an organometallic bath suspended in a solvent, then passing through pyrolysis. in order to obtain a coating of metal oxides. The use of direct rovings in no way guarantees the perfect covering of the fibrils

elementary this technology leads to the obligation to lead to metal oxides. Conclusion = No relation to this patent

In US patent 4,376,804 of March 15, 1983, the inventor uses a chemical deposit obtained by passing a direct roving (of graphite fibers) in a toluene bath, then passing through pyrolysis and again passing through an organo-bath. metals in suspension in a solvent, then re pyrolysis to obtain a coating of metal oxides. The fact of using direct rovings does not in any way guarantee the perfect coating of the elementary fibrils this technology leads to the obligation to lead to metal oxides.

Conclusion = No relation to this patent

In US patent 5562966 of October 8, 1996 the inventor uses a cold surfactant obtained by passing a direct roving (carbon fibers) in a solvent bath (for example polyvinyl alcohol) in which nano are diluted particles (from 46 to 76 nanometers in size) of oxidation inhibiting agents such as, for example, oxides such as zirconium oxide, carbides such as: silicon carbide, boron carbide, aluminum carbide , chromium carbide etc. the fact of using direct rovings does not in any way guarantee the perfect coating of the elementary fibrils, we use here nanoparticles supposed to be deposited on the fibers ... it is a question of trying to coat the rovet with a sizing agent (blowing agent) there is therefore a rovet of for example 1 mm in diameter containing for example 1 1000 fibrils of 10 microns in diameter, on which it is hoped to apply a uniform deposit of particles 0.05

microns ... it's unrealistic, there will be untreated areas and even on the areas to treat granules, even nanometric, will leave areas between them unprotected. Conclusion = No relation to this patent

In the patent FR 7500882 of January 13, 1975 the inventor uses a carbon rovet of for example 1 mm in diameter containing for example 1 1000 fibrils of 10 microns in diameter, the inventor claims to succeed in uniformly covering the fibrils with a wetting agent, boride type, using a chemical vapor deposition (CVD) of 10 nanometers to 1 micron at temperatures from 550 to 900 ° C. A 30-minute treatment is required to obtain a deposit of 20 microns. The fibers are then embedded in a metal which acts as a matrix. Conclusion = No relation to this patent

In UK patent 2279667 of January 1, 1995 the inventor uses a thick deposit of metal on bundles of carbon fibers. This deposit is obtained by the large circulation of a current in the cathode of the metal to be deposited.

The metal fiber composite and then compressed under vacuum to distribute the deposit relative to the fibers. Such a treatment does not consist in coating the fibers, but in drowning them in a thick metallic deposit. It results in a composite with a metallic matrix (and not a ceramic matrix, which we also wish to obtain.) This process having to deposit a large quantity of metal is necessarily slow and expensive. Conclusion = No relation to this patent

In US Patent 5,244,748 of September 14, 1993 the inventor describes a

composite metal matrix fiber, said fibers being infiltrated by the metal matrix (the method of infiltration not being described) we end up with a composite with a metal matrix (and not a ceramic matrix, which we also wish to obtain). a large amount of metal is necessarily slow and expensive. Conclusion = No relation to this patent

TECHNICAL PROBLEM TO BE SOLVED:

In order to be able to obtain a wire capable of withstanding hot oxidation:

The objective of the invention is to deposit, in a perfectly homogeneous and controlled manner, an oxygen barrier coating on all the fibrils of a carbon thread. In order not to damage the properties of the said wire, the coating must be extremely thin.

Composite matrices made up of layers containing unidirectional fibers (woven, felt, or mat) of reinforcement and matrix:

organic, mineral, metallic or ceramic, are increasingly used to produce light structures as described in the field of the invention.

When placed under significant stress, or during impacts, these composite structures are subject to deformations. We have previously seen that conventional ceramic matrices are extremely fragile and do not tolerate significant deformation. The objective of CMCs is to behave well mechanically and to be implemented as organic matrices, while having a range

more extensive thermal use, and a significantly lower cost of ownership. The present invention relates to a solution, developed for producing a thermostable ceramic composite. The serious problem encountered by CMCs at high temperature is the poor resistance to oxidation of the fibers that compose them.

The table above shows that compared to the best ceramic fibers (Nextel 720) carbon fibers are very efficient. In a protective atmosphere, the carbon fibers are treated between 2000 and 3000 ° C during their production; but they oxidize from 500 ° C in an oxidizing atmosphere (in other words, they burn)! a means of confining and protecting carbon fibers must therefore be found. Note here that the carbon fibers are made up of a bundle of fibrils with a diameter of 4 to 12 micrometers.

In addition, the table confirms that it is impossible to use ceramic fibers above 1400 ° C

CONTRIBUTION OF THE INVENTION:

The invention consists in creating a protective environment, a confinement, around the carbon fibrils so that they do not oxidize.

The best solution is to cover the fibrils with a thin, tight and refractory layer, perfectly uniform, which envelops them completely and whose radial thickness is between 0.5 and 900 nanometers. Preferably, this layer is formed by a stack of concentric layers of different nature, namely of different metals or alloys, of different ceramics, of combination of metals (or alloys) with ceramics: • The metallic type refractory lining can be made from a combination of at least one of the following metals, or their alloy:

Niobium, Molybdenum, Tantalum, Tungsten, Rhenium, Nickel, Chromium, Titanium, Zirconium, Hafnium,

• The refractory coating, of ceramic type, can be made from at least one of the following metals: Niobium, Molybdenum, Tantalum, Tungsten, Rhenium, Nickel, Chromium, Titanium, Zirconium, Hafnium, combined

chemically with a metalloid such as boron and silicon or a non-metal such as carbon, sulfur, nitrogen, phosphorus, lanthanum and oxygen in order to form, for example and in ascending order of interests:

o Zirconium Diboride (ZrB2)

o Titanium Diboride (T1B2)

o Hafnium Diboride (HfB2.)

o Tungsten Carbide (WC)

o Lanthanum hexaborure (LaB6)

Said "refractory layer" can be made up of a complex coating of several layers:

o Different metallic types

o Different ceramic types

o A combination of metallic type layers and ceramic layers The application of this coating can, preferably, be carried out in the factory producing carbon fibers during their production, ultimately.

If the application of this coating is carried out a posteriori, it is necessary to pyrolyze the surfactant which covers the fibers, for example by passing the fibers over two rollers, on which they rest (slight change in orientation of the fibers) and, by establishing a difference in electric voltage between said rollers, an electric current then travels through the fibrils of the carbon fibers and burns the size.

It is then possible to cover them with the refractory layer mentioned above, by any process known to those skilled in the art:

• Such as electroplating or electrodeposition

• Like vapor phase deposition: PVD physical deposition and CVD chemical deposition At the end of the refractory layer deposition, the deposition surface must be functionalized to decouple it from its future matrix. This consists in coating said surface with a surfactant which will allow the fiber to be isolated from the matrix in order to allow blocking. cracks coming from the latter's service. To do this, at least one of the following surfactants is used:

• Boron nitride,

• Carbon (graphite),

• Molybdenum disulfide (M0S2),

• Preferably hydrophobic silane,

• Boron

• Glass fries

The matrix can be any metal known to a person skilled in the art (for example, copper, aluminum, aluminum, zinc, tin, steel, and alloys of said metals)

The matrix can be any ceramic known to those skilled in the art (for example alumina, mullite, carbon, silicon carbide, alumina, silicon carbide often used in sintered form, nitride d aluminum (AIN), silicon nitride (S13N4), zirconium oxide (IV) or zirconia (ZrÜ2)) and, preferably the TOUGHCERAM ® ceramic matrix which is the subject of Dr SARDOU's patents:

• Patent Fr14 / 02994

• Patent Fr 16/00826

• PCT / FR 16/000140

The ceramic which is the subject of the Dr SARDOU patents mentioned above makes it possible to impregnate the reinforcing fibers (coated with their refractory layer described above) so as to obtain a ceramic composite, this polycrystallized ceramic between 60 and 180 ° C. under modest pressures. ranging from 0 to 3 bars. Said ceramic is flexible, tolerant to damage, for low temperature applications only, it can be divided into micro ceramic domains (MDC). Ceramic is produced by the polycrystallization reaction of a material called resin which is an aluminosilicate poly (silico-oxo-aluminate) i.e. (-Si-O-AI-O-) n, which can be Meta Kaolin (S12O5, AI2O2 said resin can optionally be supplemented by a material called additive which can be micronized aluminum (Al), micronized alumina (AI2O3), micronized magnesia (MgO), dioxide of micronized Zirconium (Zr02), before being mixed with a material called hardener which is a hydroxide chosen from the following hydroxides: a silica hydroxide (Si), an aluminum hydroxide (Al), a magnesium hydroxide (Mg ), Zirconium hydroxide (Zr), calcium hydroxide (Ca), complex aluminum hydroxide and silicon (Kaolin hydroxide), the Hydroxide being produced by one of the following solutions: either by attacking a strong base such as KOH (potassium hydroxide), NaOH (sodium hydroxide), CsOH (cesium hydroxide), either by one of the following acids: HCl, H2SO4, HF.

The micro ceramic domains (MDC), for low temperature applications only, are linked together by a dense network of micro elements

elastic, the said elastic network polymerizing during the polycrystallization of micro ceramic domains and binding by covalent bond with said micro ceramic domains. The network of elastic microelements (MEE) is made up of linear elastic molecular chains, terminated at their ends by functions capable of chemically binding to micro domains of solid ceramic. Said elastic network is preferably chosen from molecular chains belonging to the family of fluid silicone homopolymers

(Polysiloxanes) with active endings preferably chosen either from the OH types or from the alcohol types. The mass percentage of MEE compared to the matrix is between 0 and 60% = [MEE / (MEE + MDC)]

DESCRIPTION OF THE FIGURES AND GUIDING PRINCIPLE OF THE INVENTION:

PVD = sputtering is a thin film deposition method. It is a technique that allows the synthesis of several materials (alloy) from the condensation of a metallic or ceramic vapor, coming from a solid source (target) (16) on a substrate (fibers) (4f).

Note: it is known that carbon fibers (or equivalent) are conductive. The strategy of the invention is to make several known physical principles cooperate to achieve, thanks to their interaction, an innovative result:

Principle # 1 = use of a vacuum enclosure (1 1 ') in order not to hinder the average free path of the vapors from the target (16), note that one can imagine putting in line leu leu several enclosures type (11 ') to apply several deposits in a row. We table here for vacuum levels between 10 ^-2 and 10 ⁸

Principle # 2 = use of a PVD method to create, under vacuum, vapors from the target (16); by PVD we mean indifferently: EV, EBPVD, PVD, PLD, MBE, Arc-PVD, PC, PCM, PCT, HiTUS. Principle # 3 = use of static electricity [either by electrostatically charging the coils (1) & (1 ') or by charging the wires (13) & (14) at the level of the guide means (8) & (8 ')] to separate the fibrils from a carbon conductive wire (13) & (14), said wire consisting of a bundle of fibrils (4f) and being charged, for example positively. The fibrils are all at the same potential, will strongly repel and adopt a balloon arrangement (4) in the chamber (11 '). All the fibrils (4f) will be distributed statistically at equal distance and all on the outer surface of said balloon (4). The table below, given as an example, shows that the inter-fibrillary distance (4f), even for a bundle of 10,000 fibrils, perhaps 14.7 times greater than the diameter of a so-called fibril, the vapors can therefore pass easily between the fibrils (4f); Example of inter-fibrillum distance calculation:

Principle # 4 = use of an electrostatic field, established between the target (16) and the fibrils (4f) the vapors, charged at the potential of the target (16) and coming from this one will cross the field lines (18 ) as shown in Figure 3.

The vapors will therefore be able to condense on all the faces of the fibrils (4f), which makes it possible to treat them uniformly, it should be noted that the targets (16) are uniformly arranged around the balloon (4) in order to facilitate

homogeneity.

^ Principle # 5 = use of an electric current [either by charging the coils (1) & (T) or by charging the wires (13) & (14) at the level of the guide means (8) & (8 ') ]; this current makes it possible to adjust the temperature of the fibrils (4f) so that the vapor, when it condenses on the fibrils (4f), is at an optimum temperature. It should be noted that, thanks to the vacuum, said temperature can be between ambient and for example 2000 ° C. without risk of degradation of the fibrils. Principle # 6 = use of the wire speed (13) & (14) in order to control the thickness of the deposit and be able to obtain extremely thin layers with particularly high productivity. It is important to deposit thin layers so as not to modify the mechanical properties of the wire.

Figure 1 shows a summary of the process which is the subject of the invention:

(1) & (1 ’) = coils of carbon fibers (carbon fibers = substrate) (2) & (2’) = PVD generators preferably having a hollow cylinder shape

(3) = PVD enclosure housing

(4f) = fibrils separated by the electrostatic field (fibril balloon) (4) = balloon formed by the fibrils (dashed line, in Figure 3) (5) & (5 ’) = anti plasma screen

(6) = gaseous plasma of revolution around the ball of fibrils

(7) = electromagnets for plasma confinement

(8) & (8 ') = means for guiding the carbon fibers, it can be either guide eyes (for example ceramic, known to those skilled in the art) or any other means of guiding and controlling the tension of said fibers, (in particular it can be capstans) '(9) & (9') = access hatches

(10) & (10 ’) = PVD generator cooling system (2) & (2’) · / (11) & (11 ”) = vacuum chambers containing the coils

(1 1 ’) = vacuum chambers corresponding to the PVD treatment zone (12) & (12’) = vacuum systems

(13) = carbon fibers from PVD treatment

(14) = carbon fibers going to PVD treatment

(15) & (15 ’) = anti electrostatic field screen

(16) = (solid source) sputtering targets preferably mounted in polyhedron around the plasma (6)

(17) electrostatic housing

Figure 2 is a simplified sectional view of the area of the vacuum chambers (11 ') corresponding to the PVD treatment area. This view briefly represents the process which is the subject of the invention. We can see the sputtering targets (16), the balloon formed by the fibrils (4) as well as the fibrils (4f) Figure 3 is a close-up view of a simplified section of the balloon (4), the latter being here shown in phantom. We can see the fibrils (4f) and a target (16); a difference in electrostatic potential is created between the fibrils (4f) and the target (16); the electrostatically charged vapors from the target therefore follow the field lines represented schematically by the dotted lines of type (18). To condense on all sides of the fibrils.

Solution A: The coils (1) and (1 ’) of carbon fibers (13), (14) are brought to an electrostatic potential with respect to the electrostatic casing (17).

Preferable solution B: the guide means (8) and (8 ’) of the carbon fibers (13), (14), are brought to an electrostatic potential with respect to the electrostatic casing (17).

The electrostatic field causes the attraction of carbon fibrils to the electrostatic housing (17) and to the targets (16) which are also charged with the same sign and substantially the same potential as the housing (17) (there are several thousand such fibrils (4f) in a carbon fiber), the fibrils then take a balloon shape (4). This balloon shape and hollow, all the fibrils (4f) being approximately all side by side on the outside diameter of said balloon (4).

The distance between fibrils can reach several times, several hundred times the diameter of said fibrils (the distance can be between 10 microns and 10 mm). The metallic vapors (or oxide or ceramic) come from targets (6) having an electrostatic charge opposite to those of the fibrils (4f); said vapors to be deposited are attracted electro-statically by the fibrils. Since the fibrils are very widely spaced, the vapors can therefore easily miss the fibrils and pass between said fibrils, however, being attracted by the electrostatic field, the vapors can follow the electrostatic field lines (18) and deposit on the entire surface of each fibril, said surface is oriented towards the housing (17) or towards the center of the balloon (4).

The coils (1) and (1 ') of carbon fibers, or the guide means (8) and (8') of the fibers, can be brought to a potential difference, so as to allow the fibrils to be able to be heated ( 4f) and adjust their temperature. This optimizes the quality and surface reactions of the substrate during deposition.

The diameter of the balloon is adjusted by playing on the electrostatic field which will attract the fibrils towards the electrostatic casing (17) and on the control of the thread tension (13), (14), between the guide means (8) and (8 '). Adjustment procedure possible: without the presence of an electrostatic field and non-moving wire, the "soft strand" is adjusted so that the wire (13), (14) hangs in the metallization cavity (11 ') and has the shape from the low point of the fibril balloon (4) that one wishes to obtain; then the electrostatic field is triggered and the balloon (4) is formed; it is then possible to trigger the scrolling of the wire (13), (14); it is therefore necessary to have perfect control of the speed of travel of the wire (13), (14); this can be obtained either by controlling the speed of rotation of the coils (1) & (1 '), or more finely by controlling the speed of the wire (13), (14), at the level of the means (8) and (8 ') which can be capstans or any equivalent means known to those skilled in the art.

The average scrolling speed, combined with the power of the PVD, allows the thickness of the deposit to be adjusted. It is therefore possible to have considerable deposition powers coupled with a very high speed of travel of the wire (13), (14), so as to obtain a particularly fine homogeneous deposition.

It is possible either to pass several times in the PVD area (1 T) in order to apply several different layers, or to arrange at the tail-leu-leu several cells (11 ') of PVD such as that described above. .

It is specified that the adverbs preferentially, and optionally mean that one can preferably use a solution (for example this form is preferably ended by fixing loops) or that one can not use it (this is ie not to use said loops) while remaining within the scope of the invention.

It is also specified that FIGS. 1, 2 and 3 essentially represent an embodiment of the object, according to the invention, but that there may be other embodiments, which meet the definition of this invention.

It is further specified that, when, according to the definition of the invention, the object of the invention comprises “at least one” element having a given function, the embodiment described may comprise several of these elements. Conversely, if the embodiment of the object according to the invention, as illustrated, comprises several elements of identical function and if, in the description, it is not specified that the object according to this invention must necessarily include a particular number of these elements, the subject of the invention could be defined as comprising “at least one” of these elements. It is finally specified that when, in the present description, an expression defines alone, without any specific mention relating to it, a set of structural characteristics, these characteristics can be taken, for the definition of the subject of the protection sought, when technically possible, either separately or in total and / or partial combination.

It is likewise specified that, in the present description, if the adverb "substantially" is associated with a qualifier of a given means, this qualifier must be understood in the strict sense or approximated.

PVD TECHNOLOGIES by PVD we mean in the context of the invention all the variants described below and preferably the HiTUS process:

• Physical vapor deposition by electron beam (EBPVD) is a form of physical vapor deposition in which a target anode under high vacuum is bombarded by an electron beam emitted by a charged tungsten filament. The electron beam transforms the target molecules into the gas phase. These molecules then precipitate in solid form, covering the entire vacuum chamber (in a way) with a thin layer of the anode material.

• (PVD) vacuum evaporation is based on two basic processes: vacuum evaporation (EV) from a heated source and solid state condensation of the material evaporated on the substrate. Evaporation takes place under vacuum, that is to say in a gaseous environment, excluding deposit vapor, containing extremely few particles. Under these conditions, the particles of matter can propagate to the target without colliding with other particles. For example in a vacuum of 10 ^"4 Pa, a particle of 0.4 nm in diameter with an average free path of 60 m, that is to say that it can travel on average sixty meters before colliding with another particle. Heated objects (ie the heating filament) produce parasitic vapors which limit the quality of the vacuum in the deposition chamber.

• Pulsed laser ablation (PLD) is a layered deposition method

thin using a very high power laser. Technically, thin film deposition by pulsed laser ablation is based on the interaction between the target material that one wishes to deposit and a pulsed laser beam (pulse of the order of a nanosecond) of high energy. During the laser irradiation process, particles are ejected from the target. Initially, confined near the surface of the target, these particles constitute what is called the Knudsen layer. The same dimensions as the laser spot (1 to 2 mm ^A 2) the latter is mainly composed of ions, electrons, but also neutral atoms, diatomic particles or even droplets of molten material ... Device pulsed laser ablation. Relatively dense, the Knudsen layer is the site of a large number of collisions between particles, which generates a rise in temperature at the target material. This high rate of collisions, coupled with the absorption of the laser beam then lead to the ionization of the Knudsen layer, then to the formation of a plasma, called "feather". The expansion thereof, finally allows the release and deposition of particles on the surface of the monocrystalline substrate, positioned opposite the target. In addition, the deposition of thin layers by pulsed laser ablation can be carried out under conditions of high vacuum, but also in the presence of ambient gases, such as oxygen (oxide deposits), nitrogen, or argon (inert medium).

• Molecular jet epitaxy (MBE) is a technique consisting in sending one or more molecular jets to a substrate

previously chosen to achieve epitaxial growth. It allows nanostructured samples of several cm2 to grow at a speed of around one atomic monolayer per second.

• Deposition by electric arc (Arc-PVD): atoms and ions are vaporized

under the action of a strong current, caused by electric discharge between two electrodes with a strong potential difference, which detaches metal particles and makes them pass into the gas phase.

• Sputtering is a thin layer deposition method. It is a technique that allows the synthesis of several materials from the condensation of a metallic vapor from a solid source (target) on a substrate. Applying a potential difference between the target and the walls of the reactor in a rarefied atmosphere allows the creation of a cold plasma, composed of electrons, ions, photons and neutrons in a ground or excited state. Under the effect of the electric field, positive plasma species are attracted to and collide with the cathode (target). They then communicate their momentum, thus causing the atomization of atoms in the form of neutral particles which condense on the substrate. The film is formed according to several mechanisms which depend on the interaction forces between the substrate and the film. The discharge is self-sustaining by the secondary electrons emitted from the target. Indeed, these, in inelastic collisions, transfer part of their kinetic energy into potential energy to the atoms of the gas present in the enclosure which can be ionized. The PVD has the following variants:

Magnetron sputtering (PCM): Sputtering sources are usually magnetrons which use strong electric and magnetic fields to trap electrons near the surface of the magnetron, which is known as the target.

Triode cathode sputtering (PCT): To facilitate the supply of additional electrons to the plasma, you can add a hot filament acting as a cathode (3rd electrode for the plasma). By applying a negative bias to the wire with respect to the plasma, the electrons emitted thermally by it are ejected. This tension should be kept as low as possible to limit spraying of the filament. This technique called triode sputtering or PCT sputtering makes it possible to obtain high deposition rates, therefore thin coatings but also with relatively large thicknesses.

HiTUS (High use of sputtering targets). HiTUS is the process we favor. HiTUS is a major evolution of the traditional magnetron thin film deposition technology widely used in industry and research. HiTUS is based on the remote generation of a plasma high density. The plasma is generated in a side chamber opening onto the main chamber containing the target and the substrate to be coated. HiTUS offers a multitude of advantages compared to traditional spraying techniques such as:

^■ Better precision of deposits;

^■ Better control of the characteristics of the film with properties close to those of the material deposited in the mass;

^■ Better control of the surface condition: smoothing;

^■ High levels of reproducibility and repeatability;

^■ Higher production speed;

^» Possibility of online production or winding process with the possibility of multilayers;

^■ Constraint in the easily controllable deposit, compression at tension, or zero between these two possibilities;

^■ Low temperature process authorizing deposition on

organic substrates

IN SUMMARY

We claim a process intended to produce fibers with high

performance, thermostable up to 2000 ° C in an oxidizing atmosphere, the basic principle being to cover in a homogeneous and perfectly controlled manner all the fibrils (4f) of a wire (13) & (14) of one to several concentric refractory layers extremely fine with barrier properties against oxidation, the said process is characterized by the simultaneous implementation of at least one or a combination of the physical principles described below, namely:

Principle 1: vacuum of at least one treatment enclosure (11 '), the vacuum levels being between 10 ^{' 2} and 10 ⁸ mbar

Principle 2: to evaporate the target material, use of a PVD process, ie at least one of the following treatments: EV, EBPVD, PVD, PLD, MBE, Arc-PVD, PC, PCM, PCT , HiTUS [Vacuum evaporation of the substrate to be deposited (EV), Physical vapor deposition by electron beam (EBPVD), Cathode sputtering (PVD and PC), Pulsed laser ablation (PLD), Molecular jet epitaxy (MBE) Electric arc deposit (Arc PVD), Magnetron cathode sputtering (PCM), Cathode sputtering triode (PCT). Advanced magnetron deposit says "High use of sputtering targets" (HiTUS)]

Principle 3: use of static electricity, to spread the fibrils (4f) of the wires (13) & (14) evenly

Principle 4: use of an electrostatic field, established between the target (16) and the fibrils (4f) to guide the vapors from the targets (6) to the substrate = fibrils (4f)

v 'Principle 5: use of an electric current to heat the fibrils (4f) Principle 6 = use of the thread speed (13) & (14) in order to control the thickness of the deposit on the fibrils (4f)

. We are claiming thermostable fibers protected against oxidation and combustion, to be incorporated into a high performance ceramic or metallic matrix, intended to produce so-called hot parts and structures such as hypersonic planes, aircraft reactor components, components of nuclear reactors, rocket nozzles, solid or hybrid fuel rocket bodies, exhaust pipes, gas turbines, said thermostable fibers are carbon fibers, said carbon fibers being

made up of a bundle of fibrils with a diameter of 4 to 12 micrometers, each elementary fibril being coated, by means of a PVD process (physical vapor deposition), with at least one tight and refractory layer, perfectly uniform , which envelops it entirely and whose radial thickness is between 0.5 and 900 nanometers, PVD is a generic term which designates one, or one

combination of the following techniques: Vacuum evaporation of the substrate to be deposited, Physical vapor deposition by electron beam (EBPVD), Cathode sputtering, Pulsed laser ablation (PLD), Epitaxy by jets

molecular (MBE) .Deposition by electric arc (Arc-PVD), Magnetron deposit

improved said to "High use of spray targets" (HiTUS), this latter process offers high productivity, perfect control of the thickness of the deposit, its homogeneity and the possibility of depositing on organic fibers at temperatures between 20 and 1500 °, depending on the desired surface chemical reactions.

The fibrils (substrate) receive a refractory coating, consisting of a

combination of at least one layer of at least one of the following metals and their alloys: Niobium, Molybdenum, Tantalum, Tungsten, Rhenium, Nickel, Chromium, Titanium, Zirconium, Hafnium, Iridium, Osmium, Ruthenium, it should be noted that with the claimed PVD processes homogeneous, extremely thin and non-oxidized metal layers are obtained, allowing to benefit, in particular, from the excellent elongation properties at break of certain metals, it should be noted that thanks to PVD it is possible to produce “alloys in situ” using different metal targets placed side by side, note that thanks to PVD several layers of different metals can be deposited concentrically around the substrate, this appreciably improves the sealing and the barrier effect against the desired oxidation.

In order to optimize the deposition of the coating by refractory metals, the deposition can be carried out on fibrils heated between 250 and 1500 ° C. in order to obtain the

"Carburetion" of a sublayer of one to ten atomic thicknesses, between the first filler metal (of the first layer) and the carbon fibril, this carbureted sublayer participates in the transition between the metal and the fibril, in addition, for example, a tungsten carbide, offers barrier properties to effective oxidation, the remainder of the upper layer of the first filler metal remaining said pure filler metal.

the refractory lining, fibrils, can consist of at least one layer of at least one ceramic produced with at least one of the following metals:

Niobium, Molybdenum, Tantalum, Tungsten, Rhenium, Nickel, Chromium, Titanium,

Zirconium, Hafnium, Iridium, Osmium, Ruthenium, Chromium, Calcium, Magnesium, chemically combined with a metalloid such as boron and silicon or a non-metal such as carbon, sulfur, nitrogen, phosphorus and oxygen and thus forming ceramics such as for example and in ascending order of interest:

o Zirconium Diboride (ZrB2)

o Titanium Diboride (TiB2)

o Hafnium Diboride (HfB2)

o Rhenium Diboride (ReB2)

o Zirconium Dioxide (Zr02)

o Magnesium Oxide (MgO)

o Tungsten Carbide (WC)

Note that the fact of depositing several concentric layers of ceramics around the substrate significantly improves the sealing and the barrier effect against the desired oxidation. The coating of the fibrils consists of at least a combination of metallic coatings, and of at least one layer of ceramic coatings, as described above, the fact of depositing several concentric layers around the substrate, and in particular of combining metals and ceramics significantly improves the seal and the barrier effect against oxidation sought.

The coating of the fibrils as defined above, is coated with at least one of the following surfactants: boron nitride, carbon (graphite), molybdenum disulfide (M0S2), silane, boron, glass frit, PEG (Polyethylene glycol = Formula :

C2nH4n + 20n + 1).

The fibrils are carefully rid of any pollution and any size before PVD treatment.

The fibers are preferably placed on spools (1 and 1 ’), in the PVD chamber. Said chamber is placed under vacuum with either a neutral gas or traces of reaction gas, such as oxygen The fibrils are separated in the PVD chamber by the application of an electrostatic field between the fibrils (4) and the casing (3) of said chamber.

The PVD means or means (2) are arranged so as to allow perfect treatment of the fibrils.

The matrix used to coat the fibers and constitute a thermo structural composite is a ceramic or a metal.

NOTES:

Within the framework of an industrial production and in order to deposit several different layers arranged concentrically on the fibrils (4f), one can:

• Put in series several PVD treatment chambers (11 ’}, each

enclosure with its own PVD generator (2, 2 ’) and its own sputtering targets (16)

• Put in series in a long PVD treatment enclosure (1 1 ’),

having a long plasma (6) and a long flask (4), several different treatment zones and therefore sputtering targets (16) different placed in series along the flask (4), optionally containment electromagnets (7) preferably set at low power, placed along the plasma can make it possible to modulate the shape of the plasma so as to avoid pollution of a treatment zone by the following.

Claims

CLAIMS METHOD FOR MANUFACTURING HIGH TEMPERATURE TERMOSTABLE FIBERS

1. Process for producing high performance fibers, thermostable up to 2000 ° C in an oxidizing atmosphere, the basic principle being to cover all the fibrils (4f) in a homogeneous and perfectly controlled manner with a thread (13) & (14) of one to several extremely thin concentric refractory layers having barrier properties against oxidation, said method is characterized by the simultaneous implementation of at least one or a combination of the physical principles described below, namely:

Principle 1: vacuuming of at least one treatment enclosure (11 '), the vacuum level being between 10 ^{' 2} and 10 ⁸ mbar

Principle 2: to evaporate the target material, use of a PVD process, i.e. at least one of the following treatments: EV, EBPVD, PVD, PLD, MBE, Arc-PVD, PC, PCM, PCT , HiTUS [Vacuum evaporation of the substrate to be deposited (EV), Physical vapor deposition by electron beam (EBPVD), Cathode sputtering (PVD and PC), Pulsed laser ablation (PLD), Molecular jet epitaxy (MBE) ) .Deposition by electric arc (Arc- PVD), Magnetron cathode sputtering (PCM), Triode cathode sputtering (PCT) .Stretched magnetron deposit says "High use of sputtering targets" (HiTUS)]

Principle 3: use of static electricity, to spread the fibrils (4f) of the wires (13) & (14) evenly in order to form the balloon (4)

Principle 4: use of an electrostatic field, established between the target (16) and the fibrils (4f) to guide the ionic vapors from the targets (6) to the substrate = fibrils (4f)

Principle 5: use of an electric current to heat the fibrils (4f) 'Principle 6 = use of the thread speed (13) & (14) in order to control the thickness of the deposit on the fibrils (4f)

2. Method according to claim 1 characterized by the use of carbon fibers (13) & (14) consisting of a bundle of fibrils (4f) with a diameter of 4 to 12 micrometers, each elementary fibril being coated, at by means of a PVD (physical vapor deposition) process, of at least one oxygen barrier layer, waterproof and refractory, perfectly uniform, which completely envelops it and whose radial thickness is between 0.5 and 900 nanometers,

3. Objects of claims 1 and 2, characterized in that the coating with refractory metals, fibrils (4f), substrate, can be performed on fibrils heated between ambient and 2000 ° C in order to obtain a, carburetion, of a sublayer of one to ten atomic thicknesses, between the first filler metal, of the first layer, and the carbon fibril.

4. Processes objects of claims 1 to 3 characterized in that the fibrils (4f) are carefully rid of any pollution and any size before PVD treatment of claim 1

5. Processes, subjects of claims 1 to 4, within the framework of an industrial production, and in order to deposit several diferent layers arranged

concentrically on the fibrils (4f), said method is characterized by the simultaneous implementation of at least one of the following solutions:

• Put in series several PVD treatment chambers (1 1 ’), each chamber having its own PVD generator (2, 2’) and its own sputtering targets (16)

• Put in series in a long PVD treatment enclosure (11 '), having a long plasma (6) and a long flask (4), several different treatment zones and therefore sputtering targets (16) different placed in series along the balloon (4), optionally containment electromagnets (7) preferably set at low power, placed along the plasma can allow to modulate the shape of the plasma so as to avoid pollution of an area of treatment, by the following.

6. Fibers modified according to the methods which are the subject of claims 1 to 6, characterized in that the refractory coating, of fibrils (4f), substrate, consists of at least one layer of at least one of the following metals and of their alloys: Niobium, Molybdenum, Tantalum, Tungsten, Rhenium, Nickel, Chromium,

Titanium, Zirconium, Hafnium, Iridium, Osmium, Ruthenium

7. Fibers modified according to the methods which are the subject of claims 1 to 6, characterized in that the refractory lining of the fibrils (4f) consists of at least one concentric layer of at least one ceramic produced with at least one of the following metals: Niobium, Molybdenum, Tantalum, Tungsten, Rhenium,

Nickel, Chromium, Titanium, Zirconium, Hafnium, Iridium, Osmium, Ruthenium, Chromium, Calcium, Magnesium, chemically combined with a metalloid such as boron and silicon or a non-metal such as carbon, sulfur, nitrogen, phosphorus, lanthanum and oxygen and thus forming ceramics such as for example and in ascending order of interest:

o Zirconium Diboride (ZrB2)

o Titanium Diboride (TiB2)

o Hafnium Diboride (HfB2)

o Rhenium Diboride (ReB2)

o Zirconium Dioxide (Zr02)

o Magnesium Oxide (MgO)

o Tungsten Carbide (WC)

o Lanthanum Hexaborure (LaB6)

8. Modified fibers according to one of claims 5 and 7 and the process claim 3, characterized in that the coating of the fibrils (4f) may consist of: at least a combination of metallic coatings, as described in claim 5, at least one carburetted under layer as described in claim 3, and at least one layer of ceramic coatings, as described in claim 6.

9. Modified fibers according to one of claims 5 to 8, characterized in that the coating of the fibrils (4f) as defined above, is coated with at least one of the following surfactants: boron nitride, carbon (graphite) , molybdenum disulfide (M0S2), silane, boron, glass frit, PEG (Polyethylene glycol = Formula: C2nH4n + 20n + l).

10. Thermostructural composite having a ceramic matrix reinforced with modified fibers according to one of claims 5 to 9

11. Thermostructural composite having a metallic matrix reinforced by modified fibers according to one of claims 5 to 9