PRE-IMPREGNATED FOR CERAMIC MATRIX COMPOSITE

Abstract

The invention relates to a prepreg intended particularly for the manufacture of a ceramic matrix part, in particular a ceramic matrix composite, or CMC. The invention also relates to a method for manufacturing such a prepreg and a method for manufacturing a ceramic matrix part, in particular a CMC, from said prepreg.

Description

Title of the invention: PRE-IMPREGNATED FOR CERAMIC MATRIX COMPOSITE technical field

[0001] The invention relates to a prepreg intended particularly for the manufacture of a ceramic matrix part, in particular a ceramic matrix composite, or CMC. The invention also relates to a method for manufacturing such a prepreg and a method for manufacturing a ceramic matrix part, in particular a CMC, from said prepreg. Previous art

[0002] A ceramic matrix part is a product essentially composed of ceramic fibers bonded together by a ceramic matrix. When sintered, it is called a "CMC". A CMC exhibits high mechanical properties, even at high temperatures.

[0003] A ceramic matrix part can be manufactured by layering pre-impregnated materials, each consisting of a textile impregnated with a slip of ceramic particles. The pre-impregnated materials are flexible, so as to be able to take the desired shape. They can then be dried, and preferably sintered to form a CMC.

[0004] A ceramic matrix part, and in particular a CMC, manufactured from pre-impregnated materials that have been stored for a long time or under poor conditions, however, exhibits degraded mechanical properties.

[0005] WO2020157632A1 proposes, for example, a "dry" pre-impregnated composition which reduces the stability problem. However, the compositions considered lead to more porous sintered composites. The coating quality, which can still be improved, requires a high organic binder fraction. Furthermore, the binders used necessarily have a glass transition temperature well above 20°C to prevent unwanted sticking during the handling of the prepregs in a robotic forming line. Conversely, on a manual assembly line, the prepreg with this composition is not easily repositionable at ambient temperature (20°C) during the assembly step. It is necessary to use a specific device (for example, a removable mechanical fastener or a vacuum bag).

[0006] WO2021151899Al suggests using a prepreg formulation comprising A liquefiable gel, which retains its deformability and adhesive properties even after prolonged storage. However, it remains brittle if the pre impregnated dryness, particularly due to an extended assembly sequence, for example during major cutting operations or because of an unexpected interruption in composite production, does not allow storage in a controlled atmosphere.

[0007] There is therefore a permanent need for a pre-impregnated product:

[0008] - exhibiting good storage properties, good deformability, repositioning capability during assembly at room temperature, and

[0009] -allowing for a less porous composite with very good mechanical resistance to bending at room temperature.

[0010] The present invention aims to satisfy at least partially this need. Summary of the invention

[0011] According to the invention, this goal is achieved by means of a prepreg comprising a support consisting, for more than 25% of its mass, of a fibrous reinforcement comprising ceramic fibers, and a pre-ceramic matrix covering, at least in part, at least a portion of said ceramic fibers, said matrix comprising, as a percentage by volume based on said matrix:

[0012] - 55% to 95% of a fraction of inorganic particles;

[0013] - 5% to 40% of a binding fraction comprising a compound selected from:

[0014] -a complex comprising polyelectrolytes of opposite charges,

[0015] -coalesced particles of a polymer selected from polyvinyl butyral, polyacrylic, polystyrene acrylate, polyisoprene, polystyrene-acrylonitrile, polyurethane, polyvinyl acetate, silicone, and their derivatives, or mixtures thereof,

[0016] -or a mixture of said complex and said coalesced particles; and

[0017] - less than 10% of one or more other constituents other than residual solvent. The residual mass content of said pre-impregnated solvent, preferably polar, preferably water, is less than 5%, preferably less than 3%, or even less than 2%, or even less than 1%.

[0018] Inorganic particles can be replaced partially or completely by precursors of inorganic particles, capable of forming inorganic particles by heat treatment at a temperature above 200°C, preferably above 300°C, preferably above 400°C.

[0019] As will be seen in more detail later in the description, the inventors discovered that such a prepreg exhibits very good deformability properties without any risk of dry brittleness. This makes them less sensitive to storage conditions since the prepreg retains its integrity.

[0020] Without being bound by this theory, the inventors consider that the composition of the prepreg according to the present invention allows, at equal volumetric rate of binder fraction, optimal coating of the ceramic fibers of the support and / or on the support while reducing the stresses during debinding and formation of the ceramic matrix of the composite.

[0021] This composition has the advantage of significantly reducing the volumetric rate of the organic binder fraction, which makes it possible to obtain a composite with an open porosity of less than 40%, or even less than 35% by volume, and very good mechanical resistance to bending, in particular at room temperature, typically at 20°C.

[0022] Finally, this composition after drying, in order to promote the preservation of the prepregs, is easily re-hydrated, which allows assembly and manufacturing of the composite under industrial conditions without having to resort to significant investments.

[0023] The prepreg thus remains well suited to the manufacture of a ceramic matrix part, in particular a CMC.

[0024] A prepreg according to the invention may further comprise one or more of the following optional and preferred features: • the inorganic particles are chosen from ceramic particles and / or metallic particles (said ceramic particles preferably being present in a quantity greater than 60%, preferably greater than 65%, or even greater than 70% and / or less than 90%, preferably less than 87% in volume percentage on the basis of said matrix, and / or metallic particles preferably being present in a quantity greater than 0.5% and less than 9%, in volume percentage on the basis of said matrix); • more than 95%, by mass, of the ceramic particles are made up of oxide(s) for more than 99%, by mass, and have a chemical analysis such as A12O3 + SiO2 + ZrO2 > 95%, by mass percentage on the basis of the oxides; • the ceramic particles are chosen from particles consisting of oxide(s) for more than 90% of their mass, particles consisting of nitride(s) for more than 90% of their mass, particles consisting of silicide(s) for more than 90% of their mass, particles consisting of carbide(s) for more than 90% of their mass, particles consisting of boride(s) for more than 90% of their mass, and mixtures of these particles; the set of said ceramic particles having, by volume, a median size D50 less than 5 micrometers and greater than 50 nanometers, and a 99th percentile, D99, less than 50 micrometers; the binder fraction of said preceramic matrix has a glass transition temperature below 0°C, preferably less than or equal to -5°C, preferably less than -10°C, or even less than -20°C or even less than -30°C, and / or a film formation temperature (TFFT) below 20°C, preferably less than 15°C, preferably less than 10°C, preferably greater than 0°C; the binding fraction of said pre-ceramic matrix comprises a polymer complex including electrostatic bonds; the binding fraction comprises a film-forming agent, preferably an acrylate polymer which has a glass transition temperature below 0°, preferably below -10°C, preferably below -30°C; the median size of the coalesced polymer particles of the binding fraction is between 1 nanometer and 1 micrometer (generally determined by dynamic diffraction of light); the glass transition temperature of the binding fraction is less than 0°, preferably less than -10°C, preferably less than -30°C; the other constituents of said pre-ceramic matrix is / are organic(s) and / or selected from among dispersants, surfactants, biocidal agents, anti-foaming agents, thickeners, plasticizers, drying regulators and mixtures thereof; the ceramic fibers of said fibrous reinforcement (e.g. natural or synthetic ceramic fibers) are chosen from glass and / or glass-ceramic fibers, amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, zirconia fibers and mixtures thereof; more than 90% by number of the ceramic fibers of the fibrous reinforcement, possibly assembled in the form of threads, have a length greater than 4 mm, and an equivalent diameter, measured at mid-length, greater than 2 pm and less than 50 pm; - the ceramic fibers of the fibrous reinforcement are made up, for more than 90% of their mass, of oxide(s) and / or nitride(s) and / or carbide(s) and / or silicide(s) and / or boride(s) and / or carbon; - the fibrous reinforcement is a single yarn, or a textile comprising a plurality of yarns, in particular a sheet of unidirectional yarns, a braid, a knit, a fabric, or an entanglement of fibers, for example a veil or a felt, where said yarn or more than 50% of said yarns or ceramic fibers, by percentage by number, is / are coated, for more than 50% of their external surfaces, by said matrix; • the ceramic fibers of the fibrous reinforcement, possibly assembled in the form of threads, are made up of oxide(s) for more than 95% of their mass, and have a chemical analysis such as A12O3+ SiO2 + ZrO2 > 95%, as a percentage by mass on the basis of the oxides; • the ceramic fibers of the fibrous reinforcement, possibly assembled in the form of threads, are chosen from glass and / or glass-ceramic fibers, amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, zirconia fibers and their mixtures; • said fibrous reinforcement consists of a plurality of superimposed layers, preferably more than 2 layers and less than 10 layers; • Said pre-impregnated is such that its residual mass content of solvent, preferably polar, preferably water, measured at 20°C at 0.1 MPa, is less than 5%, preferably less than 3%, or even less than 2%, or even less than 1%; • The said pre-impregnated material is such that, as a percentage by volume of said matrix: - said inorganic particles of said matrix, preferably ceramic, are in a quantity greater than 70%, preferably greater than 75% and / or less than 95%, preferably less than 90%, or even less than 85%; and

[0025] - said binding fraction of said matrix represents at least 2%, preferably to less than 5%, preferably at least 10%, and less than 25%, preferably less than 20%; and

[0026] - said other constituents of said matrix preferably represent more than 0.5%, or even more than 1%, and less than 10%, preferably less than 5%;

[0027] -the residual mass content of said pre-impregnated solvent, preferably polar, preferably water, is less than 5%, preferably less than 3%, or even less than 2%, or even less than 1% by mass of said pre-impregnated.

[0028] The prepreg comprises a support consisting, for more than 25% of its mass, preferably for more than 35% of its mass, or even more than 45% of its mass (and in general, less than 75% of its mass, for example less than 65% of its mass) of a fibrous reinforcement comprising ceramic fibers.

[0029] The support further comprises a pre-ceramic matrix, preferably representing at least 25%, for example at least 35% (and generally at most 75%, for example at most 65%, or even at most 55%) of the mass of the support.

[0030] According to one possible embodiment, said pre-impregnated material according to the invention comprises, on at least one of its faces, an adhesive surface layer, preferably of thickness between 10 and 100 micrometers, comprising by volume relative to the volume of said adhesive layer, excluding residual solvent:

[0031] - at least 50% of a binding fraction comprising a compound selected from:

[0032] -a polymer complex comprising oppositely charged polyelectrolytes,

[0033] -coalesced particles of a polymer selected from polyvinyl butyral, polyacrylic, polystyrene acrylate, polyisoprene, polystyrene-acrylonitrile, polyurethane, polyvinyl acetate, silicone, and their derivatives, or mixtures thereof,

[0034] -or a mixture of said complex and said coalesced particles;

[0035] - less than 10% of one or more other constituents; and

[0036] - the complement to 100% of a charge comprising inorganic particles and / or ceramic fibers, preferably of the same chemical composition respectively as that of the fibrous reinforcement and / or that of the inorganic particles of the pre-ceramic matrix of said support.

[0037] The invention also relates to a method for manufacturing a prepreg, in particular a prepreg according to the invention, intended for the manufacture of a ceramic matrix part, in particular a CMC, said method comprising the following steps: 1) preparation of a first slip having the following composition in percentage by volume:

[0038] - 25% to 95% inorganic particles, which can be partially replaced or completely, by precursors of inorganic particles, capable of forming, by heat treatment at a temperature above 200°C, inorganic particles; - 1% to 25% of a binding fraction comprising a compound chosen from:

[0039] - oppositely charged polyelectrolytes,

[0040] -a colloidal dispersion of polymer particles selected from

[0041] polyvinyl butyral, polyacrylic, polystyrene acrylate, polyisoprene, polystyrene-acrylonitrile, polyurethane, polyvinyl acetate, silicone, and their derivatives, or mixtures thereof,

[0042] -or a mixture of said polyelectrolytes and said particle dispersion;

[0043] - less than 10%, preferably 0.5% to 10%, of one or more other constituents apart from the solvent; and

[0044] - 10% to 40% of a solvent, preferably polar, preferably water.

[0045] 2) application of said first slurry onto ceramic fibers of a reinforcement fibrous from a support, in order to form an impregnated support;

[0046] 3) preferably drying said impregnated support at a temperature between 10 and 70°C,

[0047] 4) preferably, storage of the pre-impregnated.

[0048] Preferably, in the manufacturing process of a prepreg described above, after drying in step 3), and preferably before step 4), storage, in order to form an adhesive surface layer, preferably with a thickness between 10 and 100 micrometers, a second slurry is applied to said prepreg, said slurry comprising, in volume percentage:

[0049] - 1% to 70%, preferably 5% to 50%, of ceramic fibers and / or particles inorganic particles that can be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C;

[0050] - 10% to 80%, preferably 30% to 80%, of a binding fraction comprising a composed chosen from:

[0051] -oppositely charged polyelectrolytes,

[0052] -a colloidal dispersion of polymer particles selected from polyvinyl butyral, polyacrylic, polystyrene acrylate, polyisoprene, polystyrene-acrylonitrile, polyurethane, polyvinyl acetate, silicone, and their derivatives, or mixtures thereof,

[0053] -or a mixture of said polyelectrolytes and said particle dispersion;

[0054] - less than 10% of one or more other constituents other than the solvent;

[0055] - 5% to 40% of a solvent, preferably polar, preferably water.

[0056] Preferably, particularly when oppositely charged polyelectrolytes are used to form a coacervate, the slurry comprises a complexation inhibitor, which is preferably a compound comprising ammonia or an amine group, preferably an amino alcohol comprising fewer than 10 carbon atoms. Such a low molecular weight compound has the advantage of triggering complexation of the polymer compound under conditions compatible with the use of a prepreg and assembly to produce a ceramic matrix composite;

[0057] The invention also relates to a method for manufacturing a ceramic matrix part, and in particular a ceramic matrix composite, said method comprising the following steps: 5) making available at least one prepreg described above, 6) shaping said prepreg, for example by pressing it onto a mold, so as to obtain a raw preform of a ceramic matrix part, 7) heat treatment for consolidation and / or crosslinking of said preform; 8) Optionally, sintering of said ceramic matrix part from step 7).

[0058] Preferably in step 6) to increase their adhesion, particularly in the case of stacking several prepregs, a solvent spray is applied to at least a portion of the surface, preferably at least one large face, of the prepreg to be assembled in such a way as to increase the residual solvent content, preferably water, of said prepreg. Preferably, the water content of the re-moistened prepreg is at least 10% measured at a temperature of 20°C under 0.1 MPa. Preferably, it does not exceed 20% in order to control any potential repositioning.

[0059] When the part to be formed comprises several prepregs stacked one on top of the other. Preferably, to promote adhesion between a first and a second prepreg stacked successively, solvent is sprayed onto at least a portion of the surface, preferably on at least one large face, of a first prepreg before the placement of the second prepreg. Alternatively or in addition, solvent is deposited onto at least a portion of the surface of the second prepreg intended to be in contact with that of the first prepreg.

[0060] A method for manufacturing a ceramic matrix part according to the invention comprises, before step 5), steps 1) to 3) of a method for manufacturing a prepreg according to the invention, and, in one embodiment, a step 4) of storing this prepreg for a period of more than 1 week, more than 1 month, more than 2 months, more than 6 months, more than 12 months.

[0061] The invention also relates to an intermediate product from step 5) and a preform from step 6) or 7).

[0062] The invention also relates to a ceramic matrix composite from step 8). Detailed description

[0063] Definitions • According to the invention, "prepreg" means a support essentially made of ceramic fibers, at least partially impregnated with a preceramic matrix comprising a preferably organic fraction binding inorganic particles and / or precursors of inorganic particles.

[0064] The support may, for example, be in the form of a yarn, a textile, for example a web of unidirectional yarns, a fabric, a felt, a veil, a braid, a knit, or an assembly of these elements. A ceramic matrix part, and in particular a CMC, may be manufactured with a single prepreg or by layering several prepregs. • By "inorganic" we mean a material that is not organic. This can therefore be a ceramic material, a metal or a cermet. • By “organic” we mean a component or material which includes molecules made up essentially of H and C atoms possibly with O, N or even S atoms. "Ceramic" refers to a material that is neither metallic nor organic. For the purposes of this invention, carbon, glasses, and amorphous silica are considered ceramic materials. In particular, the term "ceramic" may refer to an oxide, nitride, silicide, or carbide of a metal (e.g., Al, Ti, Zr, Mg) or metalloid (e.g., Si, B). Coalesced particles are particles originating from a suspension of polymers in colloidal form from which the solvent has been removed, for example by drying. By complexation inhibitor, we mean an additive that allows at least partially the formation of a complex between two polymers, more particularly polyelectrolytes, for example by adjusting the pH or by at least partially screening the opposite charges of the two polymers. The "other constituents" are the constituents other than inorganic particles and their precursors, the components of the binding fraction and water. The binding fraction is the set of components that directly contribute to binding inorganic particles and / or their precursors and to the adhesion of the pre-ceramic matrix to the reinforcement. A "fiber" is a filament whose length is greater than 5 times its equivalent diameter. The "equivalent diameter" of a fiber is the diameter of a disk with the same surface area as its cross-section at mid-length. A "thread" is an assembly of fibers which, in cross-section, has more than 10 and preferably less than 500,000 fibers, and whose length is greater than 5 times the diameter. A "long fiber" is a fiber whose length is greater than 1 mm. A "long yarn" is a yarn made up of long fibers. A "continuous fiber" is a fiber with a length greater than 10 mm. A "continuous yarn" is a yarn with a length greater than 10 mm, made up of continuous fibers or an aligned assembly of short and / or long fibers (or "staple yam"). In the context of this description, "sintering" refers to the consolidation by heat treatment at over 700°C of a preform, possibly with partial or total melting of some of its constituents (but not all of its constituents). The particle sizes corresponding to the percentages equal to 50% and 99%, respectively, by volume, on the particle size distribution curve are called "percentiles" 50 (noted D50 or median size) and 99 (noted D99). The cumulative size of the particles in a set of particles, with these particle sizes ranked in ascending order. According to this definition, 99% by volume of the particles in the set have a size smaller than D99, and 1% by volume have a size greater than or equal to D99. In a powder, percentiles can be determined by laser diffraction, for example, using a particle size distribution obtained with a Camsizer® XT, marketed by Horiba, for micron-sized powders. For submicron-sized powders, a Zetasizer Nanoseries particle size analyzer from Malvem is used.

[0065] The "median size" of a set of particles is called the 50th percentile. The median size therefore divides the particles of said set of particles into first and second populations equal in volume, these first and second populations comprising only particles having a size greater than or equal to, or less than respectively, the median size.

[0066] The particles can be the individual elements of a powder but also, by extension, these elements within a matrix • Unless otherwise stated, all oxide contents are mass percentages based on the oxides. A mass content of an oxide of a metallic element refers to the total content of that element expressed in the form of the most stable oxide, according to the usual industry convention. • A sum of oxide contents does not imply the presence of all of these oxides. For example, "Al₂O₃ + SiO₂" is the sum of the contents of Al₂O₃ and SiO₂, but does not exclude the absence of one of these oxides. • By rare earth, we mean the lanthanide group (elements with atomic numbers between 57 and 71, from lanthanum to lutetium) to which we add, due to similar chemical properties (same column of the periodic table), yttrium (Y) and scandium (Sc). • Debinding is understood to mean a heat treatment consisting of removing all or part of the organic components of the binding fraction of a prepreg or more generally of a part or preform comprising inorganic particles bonded with organic components. • “Contain” or “understand” or “present” must be interpreted in a non-exhaustive manner. • Unless otherwise stated, all averages are arithmetic means.

[0067] Method for manufacturing a prepreg

[0068] A method for manufacturing a prepreg according to the invention comprises steps 1) to 3), and preferably step 4), above.

[0069] In step 1), a first slip (or equivalently "suspension") is prepared comprising a binding fraction and inorganic particles and / or precursors of inorganic particles.

[0070] The slip can be manufactured by mixing, in a solvent, preferably polar, preferably water, inorganic particles and / or precursors of inorganic particles, and the other constituent(s), preferably organic. All conventional mixing techniques can be used.

[0071] Inorganic particles, preferably ceramic, are intended for the constitution of the binding matrix of the ceramic matrix part, in particular of the CMC.

[0072] Preferably, the quantity of inorganic particles, preferably ceramic, is greater than 25%, preferably greater than 30%, and / or less than 55%, preferably less than 50%, as a percentage by volume based on the volume of said first slip.

[0073] Preferably, the inorganic particles, preferably ceramic, are chosen from particles consisting of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, of oxide(s), of nitride(s) of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, of carbide(s) of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, of silicide(s) of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, of boride(s) of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass,and mixtures of these particles. In particular, it may be a mixture of said oxide, nitride, or carbide, silicide, or boride particles.

[0074] Preferably, when the inorganic particles comprise an oxide, they comprise an oxide selected from Al₂O₃, SiO₂, ZrO₂, CaO, MgO, SrO, BaO, K₂O, rare earth oxides, TiO₂, Na₂O, Cr₂O₃ and mixtures thereof. Preferably the oxide is selected from Al₂O₃, SiO₂, ZrO₂, TiO₂, Cr₂O₃, rare earth oxides, and mixtures thereof.

[0075] Preferably, when the inorganic particles comprise a nitride, they comprise a nitride selected from AIN, BN, TiN, Si3N4 and their mixtures.

[0076] Preferably, when the inorganic particles comprise a carbide, they comprise a carbide selected from SiC, B4C, TiC, TaC, HfC, ZrC and their mixtures.

[0077] Preferably, when the inorganic particles contain a boride, they preferably contain HfB2, TiB2, ZrB2.

[0078] Preferably, when the inorganic particles comprise a silicide, they preferably comprise MoSi2, TaSi2; WSi2, TiSi2.

[0079] Preferably more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100%, by volume, of inorganic particles, preferably ceramic, are made up of oxide(s) for more than 90%, preferably for more than 95%, preferably for more than 99%, preferably substantially 100% of their mass.

[0080] Preferably, more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100%, by volume, of inorganic particles, preferably ceramic, are composed of oxide(s) for more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, and have a chemical analysis such as Al₂O₃ + SiO₂ + ZrO₂ + CaO + MgO + SrO + BaO + K₂O + rare earth oxides + TiO₂ + Na₂O + Cr₂O₃ > 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides. Preferably, this sum of oxide(s) contents is approximately 100%, as a percentage by mass on the basis of the oxides.

[0081] Preferably, more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100%, by volume, of inorganic particles, preferably ceramic, are composed of oxide(s) for more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, and have a chemical analysis such that Al₂O₃ + SiO₂ > 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides. Preferably, this sum of oxide(s) contents is approximately equal to 100%, as a percentage by mass on the basis of the oxides.

[0082] In one embodiment, more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100%, by volume, of inorganic particles, preferably ceramic, are made up of oxide(s) for more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, and have a chemical analysis such that SiO2 > 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides.

[0083] In one embodiment, more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100%, by volume, of the particles inorganic, preferably ceramic, are made up of oxide(s) for more than 90%, preferably for more than 95%, preferably for more than 99%, preferably for substantially 100% of their mass, and have a chemical analysis such that A12O3 > 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides.

[0084] Inorganic particles, preferably ceramic, can be replaced, partially or completely, by precursors of inorganic particles, preferably ceramic, that is to say, by constituents which, during the manufacture of the prepreg or more generally during the manufacture or use of the ceramic matrix part, in particular the CMC, lead to inorganic particles, preferably ceramic, or to an inorganic matrix, preferably ceramic, respectively. Boehmite, alumina trihydrate, tetraethyl orthosilicate or TEOS, and orthosilicic acid are examples of known precursors of alumina, alumina, silica, and silica, respectively.

[0085] In one embodiment, the slip comprises metallic particles, preferably in an amount greater than 0.5%, or even greater than 1% and / or preferably less than 9%, or even less than 8%, or even less than 5%, as a percentage by volume based on the volume of said slip.

[0086] Metallic particles, i.e., particles made of a metal or a metallic alloy, are intended to be incorporated within the ceramic matrix of the ceramic matrix part, in particular the CMC. They can modify its properties, for example, thermal and / or electrical conductivity. Since metallic particles are precursors of ceramic particles, and in particular are transformed into ceramic particles during sintering, preferably during reactive sintering, they are exclusively counted as precursors of ceramic particles.

[0087] Reactive sintering can in particular be adapted to transform, by combination with an element of the gaseous environment, in particular nitrogen and / or oxygen, metallic particles into ceramic particles.

[0088] Preferably, all or part of the metallic particles comprise, preferably is made of, a material chosen from silicon, aluminum, iron and their mixtures, in particular their alloys.

[0089] The set of metallic particles can consist of particles all having the same composition or of a mixture of particles having different compositions.

[0090] Metallic particles can be replaced, partially or completely, by metallic particle precursors, that is to say, by constituents which, during the manufacture of the prepreg or more generally during the manufacture or The use of the ceramic matrix part, particularly CMC, leads to a metallic phase. A metal sulfate, such as aluminum sulfate, a metal chlorohydrate, such as aluminum chlorohydrate, and a metal bromohydrate, such as aluminum bromohydrate, are examples of metal precursors.

[0091] Preferably, the first slip does not contain precursors of metallic particles.

[0092] In a preferred embodiment, the first slip does not contain metallic particles, nor precursors of such particles.

[0093] Preferably, the entire ceramic and metallic particle set has, by volume, a median size D50 of less than 10 pm, preferably less than 8 pm, preferably less than 6 pm, preferably less than 5 pm, preferably less than 4 pm, preferably less than 3 pm and preferably greater than 0.1 pm, preferably greater than 0.2 pm and / or a 99th percentile, D99, of less than 70 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 30 pm. The entire ceramic and metallic particle set in the slip may have a unimodal size distribution, but also a multimodal one.

[0094] The set of ceramic and metallic particles may exhibit a bimodal distribution, preferably with a "first peak" centered on a size between 0.1 and 0.3 pm and a "second peak" centered on a size between 0.5 pm and 5 pm. Preferably, the two peaks do not overlap, even partially. Preferably still, the particle population exhibiting a distribution centered on the first peak represents less than 50% by volume of the total ceramic and metallic particles.

[0095] The binding fraction comprises a compound (which may be referred to hereafter as the "polymer compound of the binding fraction") selected from:

[0096] - oppositely charged polyelectrolytes,

[0097] -a colloidal dispersion, preferably aqueous, of a polymer selected from

[0098] vinyl polybutyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, and their derivatives, or mixtures thereof;

[0099] Advantageously, the polymer compound of the binding fraction is a suspension or emulsion of polymer particles selected from vinyl polybutyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a silicone, and their derivatives, or their mixture;

[0100] More particularly, the polymer compound of the binding fraction of the preceramic matrix can be chosen from polyelectrolytes with opposite charges.

[0101] Oppositely charged polyelectrolytes are typically made up of a cationic polyelectrolyte and an anionic polyelectrolyte.

[0102] It is known that when an aqueous solution of an anionic polyelectrolyte (hereafter referred to as the "polyanion") and an aqueous solution of a cationic polyelectrolyte (hereafter referred to as the "polycation") are mixed at a pH where the anionic polyelectrolyte has a net negative charge and the cationic polyelectrolyte has a net positive charge, the polyelectrolytes will immediately associate and form a solid complex (polyelectrolyte complex) which will separate from the aqueous phase. When the aqueous polymer solutions contain water-soluble mineral salts in sufficient quantity to at least partially screen the opposite charges of the polymers, the attraction between the polyanion and the polycation will be reduced and the formation of a solid complex will be prevented.When such solutions are mixed, a phase separation will occur, with a polymer-rich concentrated phase, called the "coacervate," and a polymer-depleted supernatant phase. A detailed description of this phenomenon can be found, for example, in Wang et al., "The Polyelectrolyte Complex / Coacervate Continuum," Macromolecules, 2014, 47, 3108-3116. Alternatively, such a "coacervate" state can be achieved when the pH of the mixture is such that at least one of the anionic and cationic polyelectrolytes has a net charge of zero. In this case, it is therefore unnecessary to add salts to partially screen the charges.

[0103] The term "cationic polyelectrolyte" encompasses a cationic polyelectrolyte but also mixtures of two or more cationic polyelectrolytes. The term "anionic polyelectrolyte" encompasses an anionic polyelectrolyte but also mixtures of two or more anionic polyelectrolytes.

[0104] The ratio of the number of positive charges of the cationic polyelectrolyte to the number of negative charges of the anionic polyelectrolyte is advantageously between 0.5 and 2.0, preferably between 0.6 and 1.8, more preferably between 0.7 and 1.6 and even more preferably between 0.8 and 1.4, or even between 0.9 and 1.2.

[0105] Polyelectrolytes can be strong or weak. A strong polyelectrolyte is a polymer having a net positive or negative charge that is essentially independent of pH. In particular, the zeta potential of a strong cationic polyelectrolyte is positive for any pH between 1 and 14, and the zeta potential of a strong anionic polyelectrolyte is negative for any pH between 1 and 14. The zeta potential can be measured using a zeta potential analyzer (e.g., a "zetasizer") at a suitable concentration (generally greater than 0.01%, e.g., 1% by weight of polyelectrolyte relative to the volume of solution analyzed) and generally at 20°C.

[0106] In contrast, a weak polyelectrolyte is a polymer having a net positive or negative charge that depends on the pH. Typically, the zeta potential of a weak polyelectrolyte measured at pH 1 and that measured at pH 14 are at least 10% different. Usually, a weak polyelectrolyte has a ρ between 1 and 14. More specifically, a weak cationic polyelectrolyte generally has a ρ greater than 7 (e.g., between 7.5 and 14), and a weak anionic polyelectrolyte generally has a ρ less than 7 (e.g., between 1 and 6.5). In the present application, the ρs are determined in water, at a temperature of 25°C and in 0.01 M NaCl.

[0107] In the present invention, an anionic polyelectrolyte is a polymer with a net negative charge at pH 7, and a cationic polyelectrolyte is a polymer with a net positive charge at pH 7. This does not mean that an anionic polyelectrolyte comprises only negative charges and is free of positive charges. By analogy, cationic polyelectrolytes can comprise both cationic and anionic charges as long as, at pH 7, the overall net charge is positive.

[0108] Therefore, the definition of anionic polyelectrolytes encompasses zwitterionic polyelectrolytes having an isoelectric point (pi) < 7, preferably < 6, and the definition of cationic polyelectrolytes encompasses zwitterionic polyelectrolytes having an isoelectric point (pi) > 7, preferably > 8. Most commonly known zwitterionic polyelectrolytes are proteins or peptides comprising both standby carboxyl groups (-COOH) and standby amino groups (-NH2).

[0109] In a preferred embodiment, the anionic polyelectrolyte comprises only negative charges and is free of positive charges, and the cationic polyelectrolyte comprises only positive charges and is free of negative charges.

[0110] The anionic polyelectrolyte and the cationic polyelectrolyte can be linear or branched polymers.

[0111] The cationic groups of the cationic polyelectrolyte are, for example, primary, secondary or tertiary amino groups or quaternized amine groups, located in the main chain of the polymer or on pendant groups.

[0112] The anionic groups of the anionic polyelectrolyte are, for example, chosen from the group consisting of carboxylate, sulfonate, phosphonate, boronate, sulfate, borate and phosphate groups, located in the main chain of the polymer or on pendant groups thereof.

[0113] The cationic polyelectrolyte may in particular be chosen from:

[0114] - poly(diallyldimethylammonium chloride) (PDADMAC), - poly [(2-hydroxypropyl)dimethylammonium chloride], - polyamidoamine-epichlorohydrin (PAAE), - polyethylene imine, - poly(acrylamide-co-diallyldimethylammonium chloride),

[0115] - poly(acrylic acid-co-diallyldimethylammonium chloride),

[0116] - copolymer of hydroxyethylcellulose and poly(chlorure de diallyldimethy lammonium) (Poly quaternium-4),

[0117] - copolymere d’acrylamide and dimethylaminoethylmethacrylate quaternarisé avec le sulfate de dimethyle (Polyquaternium-5, CAS 26006-22-4),

[0118] - copolymere de dimethylaminomethyl méthacrylate et alkyl méthacrylate,

[0119] - copolymere de methyl and stearyl dimethylaminoethyl ester d’acide methacrylique,

[0120] - homopolymere de N,N-(dimethylamino)ethyl ester d’acide methacrylique quaternarisé avec le bromomethane,

[0121] - poly(N,N-(dimethylamino)ethyle méthacrylate quaternarisé), - chlorure de guar hydroxypropyltrimonium,

[0122] - poly(2-(dimethylamino)ethyl méthacrylate),

[0123] - poly(chlorure de N,N-dimethyl-3,5-dimethylene piperidinium), - poly(vinylbenzyltrimethylammonium chloride), - poly[3-(methacryloylamino)propyl-trimethylammonium chloride], - poly([2-(methacryloloxy)ethyl]-trimethylammonium chloride), - polyvinylamine (PVA), - poly(N,N-dimethyl-3,5-dimethylene piperidinium chloride) (PDDPC), - poly(vinylbenzyltrimethylammonium chloride), vinylbenzyltrimethylammonium) (PVBTAC), - poly(allylamine hydrochloride) (PAH), - poly[3-(methacryloylamino)propyltrimethylammonium chloride] (PMAPTAC),

[0124] - cationic dextran,

[0125] - poly(aniline),

[0126] - poly(2-vinylpyridine),

[0127] - poly(L-lysine),

[0128] and

[0129] - their mixtures.

[0130] Preferably, the cationic polyelectrolyte is chosen from polyethylene imine, poly(allylamine hydrochloride), poly(aniline), poly(2-vinylpyridine), poly(2-(dimethylamino)ethyl methacrylate), poly(L-lysine), and mixtures thereof.

[0131] The anionic polyelectrolyte may in particular be selected from the group consisting of poly(acrylic acid), poly(acrylic-co-acrylamido acid), poly(4-styrene-sulfonic acid), lignosulfonic acid, humic acid, poly(2-acrylamido-2-methyl-l-propanesulfonic acid), hyaluronic acid, poly(vinylsulfonic acid), poly(glutamic acid), dextran sulfate, their salts (e.g. sodium salts), and mixtures thereof.

[0132] Preferably, the anionic polyelectrolyte is chosen from polyacrylic acid, poly(methacrylic acid), poly(glutamic acid), hyaluronic acid, their salts (e.g. sodium salts) and mixtures thereof.

[0133] The average molecular mass by weight (determined by light scattering) of the anionic and cationic polyelectrolytes is typically between 5,000 and 2,000,000 Da, preferably between 10,000 and 1,500,000 Da, more preferably between 20,000 and 1,000,000 Da, or even more preferably between 50,000 and 700,000 Da, for example between 100,000 and 500,000 Da. The anionic polyelectrolyte and the cationic polyelectrolyte preferably have similar molecular weights.

[0134] In a preferred embodiment, at least one of the anionic polyelectrolyte and the cationic polyelectrolyte is a weak polyelectrolyte.

[0135] In one embodiment, the cationic polyelectrolyte is a weak polyelectrolyte (preferably branched). In such an embodiment, the anionic polyelectrolyte may be a strong or weak polyelectrolyte (for example, a strong polyelectrolyte). In such an embodiment, the pH is advantageously greater than the ρ of the weak cationic polyelectrolyte. The ρ of a weak cationic polyelectrolyte is generally greater than 7, for example, between 7.5 and 14.

[0136] In another embodiment, the anionic polyelectrolyte is a weak polyelectrolyte. In such an embodiment, the cationic polyelectrolyte may be a strong or weak polyelectrolyte (for example, a strong polyelectrolyte). In such an embodiment, the pH is advantageously lower than the ρ of the weak anionic polyelectrolyte. The ρ of a weak anionic polyelectrolyte is generally less than 7, for example, between 1 and 6.5.

[0137] In a more preferred embodiment, the cationic polyelectrolyte and the anionic polyelectrolyte are both weak polyelectrolytes. In such an embodiment, the pH is advantageously such that:

[0138] -pH>pI+, or

[0139] -pH <pL,

[0140] in which pl+ refers to the pi of the weak cationic polyelectrolyte and pL refers to the pi of the weak anionic polyelectrolyte, with pl+ > pL.

[0141] In this application, pH refers to the pH of the liquid phase of the preceramic matrix which includes the binder fraction.

[0142] The polymer compound of the binding fraction of the preceramic matrix represents, by volume, generally more than 25%, preferably more than 40%, or even more than 50%, or even more than 65%, or even more than 80%, or even more than 90%, or even more than 95%, or even substantially 100% of the total volume of said binding fraction.

[0143] The so-called "other constituent(s)" do not participate in the temporary binding property of the first slip. In other words, they are not temporary binders. Preferably, the "other constituent(s)" are organic.

[0144] The quantity of other constituent(s) is preferably greater than 0.1%, preferably greater than 0.5% and / or preferably less than 6%, preferably less than 5%, as a percentage by volume based on the volume of said slip.

[0145] Preferably, the said “other constituent(s)” are chosen from dispersants, surfactants, biocidal agents, antifoaming agents, thickeners, plasticizers, drying regulators and mixtures thereof.

[0146] Preferably, the first slip contains a biocidal agent, preferably in an amount greater than 0.1% and / or less than 1%, preferably less than 0.5%, by volume based on the volume of said slip. PREVENTOL® P301, marketed by Lanxess, is, for example, a known biocidal agent.

[0147] The first slip may contain a dispersant. A dispersant of the type Dolapix CE 64 marketed by the company Zschimmer & Schwarz may be suitable.

[0148] The first slip may contain an antifoaming agent, preferably in an amount greater than 0.01%, preferably greater than 0.02% and / or less than 1%, preferably less than 0.5%, by volume based on the volume of said slip. The antifoaming agents in the CONTRASPUM range marketed by Zschimmer & Schwarz are well known.

[0149] In one embodiment, particularly when a ceramic particle precursor in colloidal form is used, the pH of the first slip can be adjusted, for example by adding a base or an acid, so as to improve deflocculation and / or stabilize the organic binding solution.

[0150] When a ceramic particle precursor in colloidal form is used, it is preferably added in the water, with the thermoreversible hydrocolloid, before the other constituents of the first slip.

[0151] Preferably, the water is demineralized water.

[0152] In step 2), the first slurry is applied to the ceramic fibers of the fibrous reinforcement of the support.

[0153] Preferably, the ceramic fibres, possibly assembled in the form of yarns, represent more than 90%, more than 95%, preferably 100% of the mass of the fibrous reinforcement.

[0154] Preferably, more than 50%, 70%, 90% by number of the ceramic fibers, preferably 100% of the ceramic fibers, optionally assembled in the form of yarns, have: • a length greater than 10 mm; and • an equivalent diameter, measured at mid-length, greater than 2 pm, preferably greater than 4 pm, preferably greater than 6 pm and / or preferably less than 50 pm, preferably less than 30 pm, preferably less than 20 pm.

[0155] The ceramic fibers may have a sizing and / or the ceramic yarns may have an organic surface coating (finishing), said sizing and / or said coating may be removed, at least partially, chemically and / or thermally, before application of the slurry, said sizing classically representing less than 1% of the mass of the ceramic fiber that it at least partially covers, and said coating classically representing less than 4% of the mass of the ceramic yarn that it at least partially covers.

[0156] Preferably, the ceramic fibres, possibly assembled in the form of wires, are made up of more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% of their mass, of oxide(s) and / or nitride(s) and / or carbide(s) and / or boride(s) and / or silicide and / or carbon, preferably of oxide(s) and / or carbide(s) and / or carbon, preferably of an oxide selected from Al2O3, SiO2, ZrO2, CaO, MgO, an iron oxide, rare earth oxides, TiO2, Na2O, Cr2O3 and their mixtures, or of SiC.

[0157] Preferably, the ceramic fibres, possibly assembled in the form of wires, are made up of oxide(s) for more than 90%, preferably for more than 95%, preferably for more than 99%, preferably for substantially 100% of their mass.

[0158] Preferably, the ceramic fibers, possibly assembled in the form of yarns, are made up of oxide(s) for more than 90%, preferably for more than 95%, preferably for more than 99%, preferably for substantially 100% of their mass, and have a chemical analysis such as A12O3+ SiO2 + ZrO2 + CaO + MgO + Fe2O3 + rare earth oxides + TiO2+Na2O + Cr2O3 > 90%, preferably > 95%, preferably > 99%, preferably substantially equal to 100%, as a percentage by mass on the basis of the oxides.

[0159] Preferably, the ceramic fibers, possibly assembled into yarns, are composed of oxide(s) for more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% by mass, and have a chemical analysis such that Al₂O₃ + SiO₂ > 90%, preferably > 95%, preferably > 99%, preferably substantially equal to 100%, as a mass percentage based on the oxides. Preferably, the ceramic fibers, possibly assembled into yarns, are selected from natural or synthetic ceramic fibers, preferably from glass and / or glass-ceramic fibers. amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, zirconia fibers and mixtures thereof.

[0160] In one embodiment, the ceramic fibers, optionally assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% by mass, and have a chemical analysis such that SiO2 > 90%, preferably > 95%, preferably > 99%, as a mass percentage based on the oxides. Preferably, in this embodiment, the ceramic fibers, optionally assembled into yarns, are selected from glass fibers, amorphous silica fibers, and mixtures thereof.

[0161] In one embodiment, the ceramic fibers, optionally assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% by mass, and have a chemical analysis such that Al₂O₃ > 90%, preferably > 95%, preferably > 99%, as a mass percentage based on the oxides. Preferably, in this embodiment, the ceramic fibers, optionally assembled into yarns, are corundum fibers.

[0162] In one embodiment, the ceramic fibers, optionally assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% by mass, and have a chemical analysis such that Al₂O₃ > 50%, preferably > 60%, preferably > 70% and < 90%, as a mass percentage based on the oxides. Preferably, in this embodiment, the ceramic fibers, optionally assembled into yarns, are selected from mullite fibers, mullite-corundum fibers, and mixtures thereof.

[0163] The material of the inorganic particles, preferably ceramic, and the material of the ceramic fibers, possibly in the form of wires, may be identical or different.

[0164] Preferably, the ceramic fibers, optionally assembled in the form of yarns, are selected from glass fibers, amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, and mixtures thereof, and the ceramic particles consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably substantially 100% by mass, and have a chemical analysis such that Al₂O₃ + SiO₂ + ZrO₂ > 90%, preferably > 95%, preferably > 99%, as a mass percentage based on the oxides. Preferably, this sum of oxide contents is substantially equal to 100%, as a mass percentage based on the oxides.

[0165] The fibrous reinforcement may be in the form of a sheet, preferably in the form of a fabric having weft and warp yarns, a knit or a braid, or in the form of a felt in the form of a layer.

[0166] The layer, preferably the fabric, may in particular have a thickness of less than 5 mm, 2 mm, or 1 mm. It may consist of a set of ceramic threads oriented randomly or in an ordered manner, for example parallel to each other. It may consist of a set of ceramic fibers, preferably ceramic, or ceramic threads entangled or preferentially oriented, for example in a plane or parallel to the same direction or to several preferred directions of orientation.

[0167] Preferably, the web is made of ceramic yarns consisting of assembled ceramic fibers, preferably ceramic fibers having one or more of the characteristics of the fibers described above. Such a ceramic yarn typically comprises several hundred to several thousand ceramic fibers.

[0168] At least one wire, preferably more than 90% by number of the ceramic wires, preferably each ceramic wire of a web, preferably has a length greater than 10 mm, 5 cm, 10 cm, 30 cm, or 1 m, and / or preferably less than 10,000 m, 5,000 m, 1,000 m, 100 m, 50 m or 10 m.

[0169] In one embodiment, the fibrous reinforcement consists of a single layer. In another embodiment, the fibrous reinforcement may consist of a plurality of layers, preferably more than 2 layers and / or preferably fewer than 10 layers, preferably fewer than 8 layers, of identical or different structures, superimposed one on top of the other. Preferably, each layer is made up of said fibers.

[0170] In one embodiment, the fibrous reinforcement comprises a lower layer, preferably non-woven, and an upper layer, preferably non-woven, extending over the lower layer, each lower and upper layer comprising a plurality of yarns, preferably said yarns, oriented parallel to the directions of the lower and upper layers, respectively, the directions of the lower and upper layers forming an angle between them preferably greater than 15°, 30°, 50°, for example about 90°.

[0171] In one embodiment, the fibrous reinforcement has the form of a single wire, i.e. not assembled with other wires.

[0172] In one embodiment, particularly when the fibrous reinforcement is an amorphous silica yarn, the ceramic particles are chosen so as to have a Na2O+K2O content preferably less than 0.5%, preferably less than 0.1% and / or the other constituents, in particular the dispersants, do not contain substantially sodium and / or potassium.

[0173] The application of the first slip to the ceramic fibers of the fibrous reinforcement can be carried out by impregnation, particularly when the substrate is in the form of a sheet or a superposition of sheets. Impregnation is also possible when the substrate is in the form of a wire. The first slip then penetrates the substrate.

[0174] Impregnation can be carried out using any technique known to those skilled in the art, in particular by scraping (or the "doctor blade" process), by tape casting (or the "tape casting" process), by immersion (for example, using the "dip coating" process), by spray gun, by brush, or by screen printing.

[0175] When the fibrous reinforcement comprises several superimposed layers, each layer can be impregnated before being superimposed on the others. Alternatively, the layers can be superimposed on one another without having been impregnated, with all the superimposed layers then being impregnated simultaneously. Preferably, when the fibrous reinforcement comprises several superimposed layers, each layer is impregnated before being superimposed on the others.

[0176] The first slip impregnates all or part of the fibrous reinforcement, preferably all of the fibrous reinforcement.

[0177] Preferably, the fibrous reinforcement is a single yarn, a web of yarns, a braid of yarns, a fabric, a knit of yarns or an entanglement of fibers, such as a felt or a veil, said yarn or more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably 100% of the yarns or fibers, in percentage by number, is / are preferably coated, for more than 20%, preferably more than 50%, preferably more than 60%, preferably more than 70%, more than 80%, more than 90%, more than 95%, preferably 100% of their external surfaces, with the first slip.

[0178] At step 3), the fibrous reinforcement impregnated with the first slip is dried to evaporate the solvent such that its residual solvent content, preferably polar, preferably water, measured at 0.1 MPa at 20°C is less than 5%, preferably less than 3%, or even less than 2%, or even less than 1% by mass on the basis of the mass of the prepreg.

[0179] Preferably, the fibrous reinforcement impregnated with the first slip is dried at a temperature above 10°C, preferably above 20°C, preferably above 30°C, and preferably below 150°C, preferably below 120°C, preferably below 110°C, preferably below 100°C, preferably below 80°C.

[0180] Preferably, the pre-impregnated material is dry to the touch.

[0181] After drying, the inorganic particles of the pre-ceramic matrix generally represent, by volume, more than 25%, preferably more than 30%, preferably more than 35%, and / or less than 80%, or even less than 60%, of the volume of the dry pre-impregnated.

[0182] In step 4), optional, the pre-impregnated according to the invention is stored.

[0183] The pre-impregnated material can be stored for example for more than 1 month, 2 months, 3 months, 6 months or 1 year and / or preferably less than 5 years.

[0184] If several prepregs are stored together, preferably an interlayer made of a material preventing any sticking between the different prepregs, for example a polymer, is provided. For example, a polyester, polyethylene, or polyethylene terephthalate film, for example Mylar, can be used to separate stacked prepregs.

[0185] Preferably, such an interlayer is also interposed between each layer of the same prepreg, or between two layers of the same prepreg which, without this interlayer, would be in contact, in particular if the prepreg is folded over itself or rolled up in the form of a roll.

[0186] Advantageously, a pre-impregnated material according to the invention can be stored at room temperature for a long time, substantially without degradation.

[0187] Adhesive surface layer:

[0188] According to a preferred embodiment, an adhesive surface layer is formed on the prepreg according to the invention. The thickness of this layer is preferably greater than 10 micrometers and / or less than 100 micrometers.

[0189] This layer is preferably continuous but, according to one possible mode, it can be discontinuous.

[0190] This layer is formed by depositing a second slip comprising, as a percentage by volume:

[0191] - 10% to 60% % of ceramic fibers and / or inorganic particles that may be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C, - 10% to 60% of a binding fraction comprising a compound selected from:

[0192] - oppositely charged polyelectrolytes,

[0193] -a suspension or emulsion of polymer particles selected from polyvinyl butyral, a polyacrylic, a polystyrene acrylate, a polyisoprene; a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, their derivatives, and mixtures thereof;

[0194] - less than 10% of one or more other constituents;

[0195] -10% to 40% of a solvent, preferably polar, preferably water.

[0196] According to one possible mode the formulation of said second slip is the same as that of the first slip used for the manufacture of the prepreg.

[0197] According to a preferred mode, the polymer compound of the binding fraction of the adhesive surface layer is a suspension or emulsion of polymer particles selected from vinyl polybutyral, polyacrylic, polystyrene acrylate, polyisoprene, polystyrene-acrylonitrile, and mixtures thereof.

[0198] The polymer compound of the binder fraction of the adhesive surface layer represents, by volume, generally more than 25%, preferably more than 40%, or even more than 50%, or even more than 65%, or even more than 80%, or even more than 90%, or even more than 95%, or even substantially 100% of the total volume of said binder fraction of said surface layer.

[0199] The mass content of solvent (preferably polar solvent, such as water) in the surface adhesive layer is typically less than 5%, preferably less than 3%, or even less than 2%, or even less than 1%.

[0200] Method for manufacturing a ceramic matrix part

[0201] A method for manufacturing a ceramic matrix part according to the invention comprises steps 5) to 8) described above, step 8) being optional.

[0202] In step 5), at least one pre-impregnated material according to the invention, preferably manufactured according to the preceding steps, is made available. Whether still wet or already dry, it is easily deformable at room temperature, preferably at 20°C, without being brittle, that is to say, without detaching when folded upon itself at an angle of 120°.

[0203] According to one possible method, at least a portion of the surface, preferably at least one large face, of said prepreg is re-moistened, for example by spraying with solvent, so as to increase the solvent content to at least 20%. The residual solvent content by mass of said prepreg is measured at a temperature of 20°C under 0.1 MPa. The solvent is preferably water.

[0204] Remarkably, temporary storage of the pre-impregnated material at room temperature does not substantially degrade it.

[0205] At step 6), the prepreg is shaped according to the desired geometry, according to any technique known to a person skilled in the art, so as to obtain a deformable preform.

[0206] Preferably, the pre-impregnated material is shaped by being pressed onto a mold.

[0207] Several pre-impregnated materials from the previous step, preferably more than 2 and preferably less than 200 pre-impregnated materials, can be shaped in step 6). Preferably, each pre-impregnated material has the shape of a sheet or several superimposed sheets.

[0208] Conventionally, several prepregs prepared in step 5) are formed simultaneously, for example after being stacked one on top of the other, or are successively applied to a mold, in overlapping layers. The forming process may include stacking several prepregs followed by lamination or stacking several prepregs followed by autoclaving, particularly when the prepregs are in the form of a sheet or several overlapping sheets.

[0209] The shaping of a prepreg into a wire can also result from a localized preparation of the prepreg followed by automated positioning, for example using a robot.

[0210] A prepreg in the form of a wire can in particular be wound around a base, temporarily or permanently, for example around a mandrel, for example of circular, oval or polyhedral cross-section. This operation is called filament winding.

[0211] The base can be temporary or permanent, depending on whether it is subsequently separated from the wound wire or not. The number of turns around the base can be greater than 5, 50, 500, 5,000 and / or preferably less than 1,000,000 or 100,000. In one embodiment, winding the wire results in a tubular shape. In another embodiment, this tubular shape can be cut, for example along a generatrix, and, for example, unfolded to obtain a flat shape.

[0212] The shaping of a prepreg into a wire can alternatively result from a localized preparation of the prepreg, a deposition on a surface, and then the application of pressure, the deposition and / or the application of pressure being able to be simultaneous.

[0213] A prepreg in the form of a filament can be deposited onto a surface that is not closed, for example, a flat surface. This operation is called filament placement. It can be carried out using a 3D printer or a robot. The unwound filament can be placed with or without overlap (juxtaposition). In one embodiment, the filament placement results in a flat shape.

[0214] Steps 5) and 6) can be simultaneous, as described in particular in the example below.

[0215] In step 7), which is optional, the deformable preform resulting from the previous step, consisting of one or more prepregs according to the invention, is heat-treated to consolidate the preform, preferably before demolding said preform. This heat treatment may, for example, allow cross-linking of at least a portion of the binder fraction to enable handling of the preform.

[0216] Preferably by heating to a temperature above 10°C, preferably above 20°C, preferably above 30°C, and preferably below 200°C, preferably less than or equal to 180°C, even better less than or equal to 150°C.

[0217] Any technique known to a person skilled in the art may be used.

[0218] The heat treatment in step 7) drying results in a raw ceramic matrix part. Preferably, the process does not include step 7).

[0219] In step 8), which is optional and preferred, the ceramic matrix part from the previous step is sintered. The ceramic matrix part is then a CMC.

[0220] A person skilled in the art can determine the sintering conditions according to the nature of the ceramic particles, optional metallic particles and ceramic fibers.

[0221] In particular when the ceramic fibers are in an oxide and the ceramic particles have a chemical analysis such as SiO2 > 90%, the sintering temperature is preferably above 800°C and preferably below 1000°C, the sintering taking place preferably under air and preferably at a pressure of 1 bar, the holding time being preferably greater than 1 hour and preferably less than 10 hours.

[0222] In particular when the ceramic fibers are in an oxide and the ceramic particles have a chemical analysis such as A12O3 > 90%, the sintering temperature is preferably above 800°C and preferably below 1500°C, the sintering taking place preferably under air and preferably at a pressure of 1 bar, the holding time being preferably greater than 1 hour and preferably less than 10 hours.

[0223] In particular when the ceramic fibers are made of a carbide and / or a boride and / or a nitride and / or carbon and the ceramic particles are made of a carbide and / or a boride and / or a nitride and / or carbon, the sintering temperature is preferably above 1400°C, and preferably below 2300°C, the sintering taking place under a neutral, reducing or reactive atmosphere, preferably at a pressure of 1 bar, the holding time being preferably greater than 1 hour and preferably less than 10 hours.

[0224] The resulting CMC has an open porosity of less than 40%, or even less than 35%, by volume. Preferably, the open porosity of the composite is measured according to ISO 18754.

[0225] The CMC can be used in particular in the following applications: hot gas exhaust part, cooking support, thermal insulation, hot drive rollers for hot glass parts.

[0226] A pre-impregnated material according to the invention is not, however, limited to the manufacture of a CMC and can, for example, be used to manufacture other ceramic matrix parts, in particular a thermal screen, especially a conformable thermal screen, that is to say, one that can adapt to the shape of the object to be thermally protected.

[0227] Pre-impregnated

[0228] The characteristics, and in particular the preferred characteristics, of a prepreg according to the invention follow directly from the preceding description of the process.

[0229] In particular, • the quantities, and in particular the preferred quantities, • compositions, and in particular favorite compositions, • median sizes, and in particular preferred median sizes, • the 99th percentiles (D99), and in particular the preferred 99th percentiles, • particle size distributions, and in particular the distributions preferred particle size distribution,

[0230] ceramic particles, metallic particles, ceramic particle precursors, and metallic particle precursors in the slip are identical to those described above for the slip; • the quantities, and in particular the preferred quantities, • the compositions, and in particular the preferred compositions,

[0231] of the "other constituents" are identical to those described above for the slip; • the quantities, and in particular the preferred quantities, • compositions, and in particular favorite compositions, • the dimensions, and in particular the preferred dimensions,

[0232] the fibers and yarns of the fibrous reinforcement are identical to those described above for the manufacturing process of the ceramic matrix part;

[0233] the outer surface portions of the fibers and wires of the fibrous reinforcement covered by the pre-ceramic matrix, are identical to those described above for the outer surface portions of the fibers and wires of the fibrous reinforcement covered by slip; • shapes, and in particular preferred shapes, • the structures, for example the orientation of the wires in different superimposed layers as well as the number of layers, and in particular the preferred structures, • the dimensions, and in particular the preferred dimensions,

[0234] of the fibrous reinforcement are identical to those described above for the manufacturing process of the ceramic matrix part;

[0235] the conditioning of the prepreg, and in particular the addition of interlayers and the packaging, is identical to that described above for the manufacturing process of the ceramic matrix part. Examples

[0236] The following non-limiting examples are given for the purpose of illustrating the invention.

[0237] The following raw materials were used according to the examples carried out:

[0238] - a gelatin (thermoreversible hydrocolloid), having a Bloom value equal to 280, passing entirely through a square mesh sieve with an opening of 0.841 mm, marketed by Weishardt International - a binder in the form of a polymer complex, on the one hand polyacrylic acid (PAA) 250 kg / mol in the form of a solution comprising 35% of this polymer acting as an anionic polymer and on the other hand Polyethylene Imine (PEI) 25 kg / mol in the form of a solution comprising 30% of this polymer acting as a cationic polymer, - a binder in the form of an acrylic polymer, latex in solution supplied by Alberdingk AC75022 (67% solid fraction in water), - binder in the form of poly(2-ethyl-2-oxazoline) of 50 kg / mol reference Aquazol50 (30% w solid in water) sold by Polymer Chemistry Innovations Inc., - a complexation inhibitor of 2-amino-2-methyl-l-propanol in solution with 5% water (AMP95) in liquid form. - a Dolapix CE64 dispersing agent - an agent for adjusting the pH, a solution of ammonium hydroxide NH4OH in water, at a concentration of 20% by mass, - as a precursor to ceramic particles, a LUDOX AS40 colloidal silica solution, - as a ceramic particle powder, an amorphous silica powder having a mass purity greater than 99.9%, a median size of 1.4 pm and a 99th percentile of 4 pm, - as ceramic particle powder, an alpha alumina powder having a mass purity greater than 99.99%, a median size equal to 0.2 pm. - as ceramic particle powder, an alpha alumina powder having a mass purity greater than 99.9%, a median size of 0.4 pm. - as a binder, polyethylene glycol PEG4000 in liquid form with a PEG 4000 concentration of 50% by mass, the remainder being water,

[0239] A first series of eight pre-impregnated pieces was impregnated with slip according to Example 1 (comparative) and the protocol disclosed by WO2021 / 151899A1 pages 43 to 46.

[0240] Unlike this first series of prepregs, further series of eight prepregs were prepared for each of Examples 2 to 6 from the formulations shown in Table 1 below. Example 6 is representative of a prepreg disclosed by WO2020 / 157632.

[0241] [Tables 1] Example 1 Comparison Example 2 Invention Example 3 Invention Example 4 Invention Example 5 Invention Example 6 Comparison Formulation by volume percentage of the preceramic slip Ceramic particles Silica powder FAR -11 34 43.7 43.8 42.0 0 0 LUDOX AS40 13* 9.5* 9.5* 9.1* 0 0 Alumina powder AKP 50 0 0 0 0 4.4 24.7 Alumina powder P172 HPB 0 0 0 0 41.7 0 Binder fraction Gelatin 280 Bloom 1.2 0 0 0 0 0 PEG4000 1.8 0 0 0 0 0 PAA 0 0.4 0 0.4 0.7 0 PEI 0 0.8 0 0.8 1.4 0 AMP95 0 3.5 0 3.4 4.7 0 Poly(2-ethyl-2-oxazoline) (50K MW) 0 0 0 0 0 18.4 Acrylic Latex 0 0 7.8 5.2 9.2 0 Other constituents Glycerol (plasticizer) 0 0 0 0 0 5.3 DolapixCE64 (dispersant) 0 3.2 4.0 3.0 0.9 0 HNO3 (dispersant) 0 0 0 0 0 0.2 Water (total content**) 50 38.9 34.9 36.1 37.0 51.4 Mass ratio PEI / PAA NA 2 NA 2 2 NA Tg of the binder fraction °C 56 NM -40 -7 -5 69 TMFF of the binder fraction °C NA 15 0 2 2 NA

[0242] NA=not applicable;*as a dry extract;**taking into account the water content of the Ludox AS40 solution

[0243] NM not measured

[0244] For this second series of examples 2 to 5, according to step 1) with reference to the process according to the invention described above, as well as for example 6 (comparative), a slip was prepared according to the volume proportions shown in Table 1 and according to the following process in a 1.5 L double-walled tank maintained at a temperature of 5°C, placed in a mixer equipped with a 7cm diameter deflocculating blade:

[0245] - addition of the PAA polymer solution and the complexation inhibitor and water (according to the percentage given in Table 1), and mixing for 3 minutes at 500 rpm

[0246] -addition of the dispersant and the PEI polymer solution, mixing for 5 minutes at 950 rpm.

[0247] - Addition of mineral particle powder, mixing for 20 min. at 4000 rpm.

[0248] - Addition of colloidal mineral particle solution, mixing for 10 min. at 2500 rpm.

[0249] The glass transition temperature was measured by differential scanning calorimetry.

[0250] The film formation temperature (TMFF) was measured according to ISO 2115-1996.

[0251] According to step 2) with reference to the process according to the invention described above, for each example 2, 3, and 4, the resulting slip was then poured onto a 200 mm x 300 mm silica fiber reinforcement laid flat. This fiber reinforcement is a 1 / 5 satin fabric made of Quartzel® yarns with a basis weight of 200 g / m², said yarns bearing the reference C14 80 Z0 QS1318 being marketed by Saint-Gobain Quartz. Prior to being coated with the slip, the fabric underwent heat treatment in an electric furnace to desensitize the yarns, said heat treatment consisting of heating to 550°C at a rate of 100°C / min, holding for 1 hour at 550°C, and then a natural cooling.

[0252] The slip was spread on the fabric using a plastic spatula. The fabric was then turned over, and more slip was poured and spread on the other side of the fabric in the same way.

[0253] For Examples 5 and 6, the same procedure was followed as before, but using an alumina fiber reinforcement. This fiber reinforcement is a 1 / 8 satin fabric made of Nextel® 610 alumina yarns with a basis weight of 370 g / m², marketed by 3M. Prior to its use, the fabric underwent heat treatment in an electric furnace to desiminate the yarns. This heat treatment consisted of heating to 700°C at a rate of 100°C / min, holding at 700°C for one hour, and then allowing the temperature to cool naturally.

[0254] According to step 2) with reference to the process according to the invention described above, the impregnated fabrics, except that of example 1, were then dried at a temperature of 20°C for 3 hours.

[0255] For Examples 3 and 5 in particular, an adhesive layer loaded with ceramic particles was deposited on the front and back of the dried prepreg. A second slip was prepared according to a formulation specific to each example, as detailed in Table 2 below. The slip was spread using a spatula to obtain a layer covering each layer of the dry prepreg, typically with a thickness between 10 and 100 µm.

[0256] [Tables2] slurry for the adhesive surface layer. Formulation by volume percentage. Example 3 according to the invention Example 5 according to the invention Inorganic powder Silica powder FAR-11 25 0 LUDOX AS40 5* 0 Alumina powder AKP50 0 2.2 Alumina powder P172 HPB 0 19.6 Binder fraction Acrylic latex AC75022 57 51 PAA 0 0.7 PEI 0 1.4 AMP95 0 4.4 Other components Dolapix CE64 0 0.1 Total water** 13 20.6

[0257] *as a dry extract. ** takes into account the water content of the Ludox AS40 solution. Manufacturing of composites#:

[0258] For each of the preceding examples, a composite was manufactured from the eight prepregs obtained previously.

[0259] The composites of examples 1 to 6 were manufactured according to the following successive steps A to C.

[0260] In step 6), with reference to the process steps described above, the eight layers of prepregs are assembled according to the symmetric stacking [0 / -0 / 0 / -0 / / -0 / 0 / -0 / 0] with a smearing step at each stacked layer in order to obtain for each example a preform.

[0261] For example 1, this assembly is necessarily carried out on a hot plate at 40°C. For examples 2 and 4, a water spray is applied to each prepreg surface before they are brought into contact with each other, such that the residual water content of the prepreg is 10% by mass. For examples 3 and 5, no special shaping conditions are required. Example 6 is stacked without scrimming before being placed in a vacuum bag and autoclaved (195 psi - 30 min then pressure heating at 121°C - 4 hours).

[0262] The prepregs according to the invention exhibit good conformability and good bonding properties, particularly after a storage period between manufacturing and use. The shaping process is simplified compared to comparative examples 1 and 6 because no temperature control is essential for shaping the composite.

[0263] In step 7), with reference to the process steps described above, the preform of each example is dried for 12 hours in an oven at 50°C in an atmosphere with 30% relative humidity. This step allows the evaporation of residual water from the preforms of examples 2 to 6, and the consolidation of the preform of example 1.

[0264] In step 8), with reference to the process steps described above, the preform is sintered in an electric furnace, according to the following cycle, to obtain a ceramic matrix composite:

[0265] Examples 1 to 4 (silica tissues) - rising from 20°C to 860°C at a rate of 10°C / min, - maintained at 860°C for 6 hours, - natural descent to room temperature.

[0266] Examples 5 and 6 (alumina fabrics) Heating from 20°C to 1300°C at a rate of 10°C / min, maintained at 1300°C for 1 hour. - natural descent to room temperature.

[0267] The following table 3 shows the mass ratios of fibrous reinforcement and pre-ceramic matrix of the pre-impregnated materials on the basis of said pre-impregnated materials after drying and the volume percentage of the fraction of inorganic particles by volume of said matrix of said pre-impregnated materials before drying.

[0268] Also reported are the following characterizations carried out on prepregs and on ceramic matrix composites made from prepregs.

[0269] Test no. 1: Friability of the prepreg evaluated after 3 hours of drying at 20°C:

[0270] Friability is assessed by folding the pre-impregnated fabric at an angle of 120° and observing the detachment of the matrix in the form of dust or flakes:

[0271] -very brittle: appearance of cracks and presence of detachment of material.

[0272] -acceptable: appearance of some cracks but no detachment of material.

[0273] -non-friable: no cracks and no detachment of material.

[0274] Test No. 2: Porosity on the ceramic matrix composite:

[0275] It was measured according to ISO 18754.

[0276] Test No. 3: Mechanical resistance of the ceramic matrix composite:

[0277] The 3-point bending strength was measured in MPa according to ASTM C 1341 (2013). The setup includes two lower cylindrical supports and one upper support, each 10 mm in diameter. The two lower supports are spaced 68 mm apart, and the upper support is centered between them. The upper support comes into contact with the sample, which is centered on the two lower supports, and then descends at 0.45 mm / s until the sample breaks. The dimensions of the tested sample are 85 mm long, 10 mm wide, and 1.7 mm thick.

[0278] The results are summarized in Table 3 below:

[0279] [Tables3] % Example 1 Comparative Example 2 Invention Example 3 Invention Example 4 Invention Example 5 Invention Example 6 Comparative % mass of prepreg fibers after drying* 44 55 58 59 53 53 % mass of prepreg matrix after drying* 56 45 42 41 47 47 % volume of inorganic particle fraction of preceramic matrix after drying NM 91 81 83 80 51 Test #1 Very fragile Not fragile Acceptable Not fragile Not fragile Not fragile Test #2 NMNMNMNM 31 44 Test #3 NMNM NM NM 226 59

[0280] * contents relative to the dry prepreg (i.e., excluding residual solvent); NM = no measure

[0281] These results show that:

[0282] The prepregs according to the invention exhibit acceptable, even very low, friability. Unlike comparative examples, the prepregs according to the invention could be stored for extended periods, without temperature or humidity constraints, and without substantial changes in their characteristics.

[0283] - The composite of Example 1 has acceptable fiber and mineral mass ratios, but it tends to dry out quickly and easily, becoming brittle and immediately degrading its ability to form an OCMC (its adhesion mechanism is altered by drying). Re-wetting it does not restore its initial adhesive strength.

[0284] - Comparative example 6 exhibits low friability and good long-term stability, but a mineral content significantly lower than the other examples, which is not conducive to achieving the desired mechanical properties of OCMC. Indeed, according to WO2020 / 157632, the dry matrix must contain between 40 and 55% by volume of organic binder, which inevitably reduces the proportion of minerals that can be incorporated into the prepreg. The activation of its adhesion mechanism at temperature necessitates the use of shaping methods such as hot presses, autoclaves, or Automated Filament Placement (AFP) for manufacturing the OCMC part.

[0285] - The examples according to the invention (2, 3, 4, 5) show very high levels of inorganic particle loading in the pre-ceramic matrix of the prepreg, which allows for the production of a CMC with reduced porosity and significantly improved mechanical properties. The adhesive power of these prepregs is activated by wetting the surfaces (partial release of the polyelectrolyte complexes) (examples 2 and 4), or is already integrated by an adhesive surface layer loaded with ceramic particles (examples 3 and 5). In both cases, its adhesive power, whether activated or not, does not deteriorate over time or under storage conditions. Furthermore, repositioning with these prepregs is greatly facilitated because their reversible adhesion allows the operator, during assembly, to detach the mispositioned prepreg and easily reposition it at room temperature without the need for any complex equipment.

[0286] As is now clear, the invention provides a pre-impregnated material, enabling the easy manufacture (no loss of adhesion, no shaping constraints) of a ceramic matrix part, whose porosity is reduced and whose mechanical properties can be maximized.

[0287] Of course, the invention is not limited to the examples and embodiments described above.

Claims

Demands

1. Prepreg comprising a support consisting, for more than 25% of its mass, of a fibrous reinforcement comprising ceramic fibers, and a pre-ceramic matrix covering, at least in part, at least a portion of said ceramic fibers, said matrix comprising in percentage by volume on the basis of said matrix: - 55% to 95% of a fraction of inorganic particles; - 5% to 40% of a binder fraction comprising a compound selected from: - a complex comprising polyelectrolytes of opposite charges, - coalesced particles of a polymer selected from polyvinyl butyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, and their derivatives, or mixtures thereof, - or a mixture of said complex and said coalesced particles; - less than 10% of one or more other constituents other than residual solvent;the residual mass content of said pre-impregnated solvent, preferably polar, preferably water, is less than 5%; the inorganic particles being able to be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C.

2. Pre-impregnated according to claim 1, wherein the inorganic particles are selected from ceramic particles and / or metallic particles, - said ceramic particles being present in an amount greater than 60% and less than 90%, by volume percentage on the basis of said matrix; and / or - the metallic particles being present in an amount greater than 0.5% and less than 9%, by volume percentage on the basis of said matrix.

3. Pre-impregnated according to claim 2, wherein more than 95%, by mass, of the ceramic particles are made up of oxide(s) for more than 99%, by mass, and have a chemical analysis such as A12O3 + SiO2 + ZrO2 > 95%, by mass percentage on the basis of the oxides.

4. Pre-impregnated according to any one of claims 1 to 3, wherein the ceramic particles are selected from particles consisting of oxide(s) for more than 90% of their mass, particles consisting of nitride(s) for more than 90% of their mass, particles consisting of carbide(s) for more than 90% of their mass, particles consisting of boride(s) for more than 90% of their mass, and mixtures of these particles; the set of said ceramic particles having, by volume, a median size D50 of less than 5 micrometers and greater than 50 nanometers, and a 99th percentile, D99, of less than 50 micrometers;

5. Pre-impregnated according to any one of claims 1 to 4, wherein the binder fraction has a glass transition temperature below 0°C and / or a film formation temperature below 20°C, preferably below 15°C, preferably below 10°C, preferably above 0°C.

6. Pre-impregnated according to any one of claims 1 to 5, wherein the binding fraction comprises a polymer complex including electrostatic bonds.

7. Pre-impregnated according to claim 1 to 6, wherein the binding fraction comprises a film-forming agent, preferably an acrylate polymer having a glass transition temperature below 0°, preferably below -10°C, preferably below -30°C.

8. Pre-impregnated according to any one of claims 1 to 7, wherein the other constituent(s) is / are organic(s) and / or selected from dispersants, surfactants, biocidal agents, antifoaming agents, thickeners, plasticizers, drying regulators and mixtures thereof.

9. Pre-impregnated according to any one of claims 1 to 8, wherein the ceramic fibers are selected from glass and / or glass-ceramic fibers, amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, zirconia fibers and mixtures thereof.

10. Pre-impregnated according to any one of claims 1 to 9, wherein - more than 90% by number of the ceramic fibers of the fibrous reinforcement, optionally assembled in the form of yarns, have a length greater than 4 mm, and an equivalent diameter, measured at mid-length, greater than 2 pm and less than 50 pm; and / or - the ceramic fibers of the fibrous reinforcement are made up, for more than 90% of their mass, of oxide(s) and / or nitride(s) and / or carbide(s) and / or boride(s) and / or carbon; and / or - the fibrous reinforcement is a single yarn or a textile comprising a plurality of yarns, in particular a web of undirectional yarns, a braid, a knit, a fabric, or an entanglement of fibers, for example a veil or a felt, where said yarn or more than 50% of said yarns or fibers, by percentage by number, is / are coated, for more than 50% of their external surfaces, by said matrix.

11. Pre-impregnated according to any one of claims 1 to 10, wherein the ceramic fibers of the fibrous reinforcement, optionally assembled in the form of yarns, are made up of oxide(s) for more than 95% of their mass, and have a chemical analysis such as A12O3+ SiO2 + ZrO2 > 95%, by mass percentage on the basis of the oxides.

12. Pre-impregnated according to any one of claims 1 to 11, wherein the ceramic fibers of the fibrous reinforcement are assembled in the form of threads.

13. Pre-impregnated according to any one of claims 1 to 12, wherein the fibrous reinforcement consists of a plurality of superimposed plies, preferably of more than 2 plies and less than 10 plies.

14. Pre-impregnated according to any one of claims 1 to 13, comprising on at least one of its faces, an adhesive surface layer, preferably of a thickness between 10 and 100 micrometers, comprising by mass relative to the mass of said adhesive layer, excluding residual solvent: - at least 50% of a binder fraction comprising a compound selected from: - a polymer complex comprising polyelectrolytes of opposite charges, - coalesced particles of a polymer selected from polyvinyl butyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, and their derivatives, or mixtures thereof, - or a mixture of said complex and said coalesced particles; - less than 10% of one or more other constituents; - the complement to 100% of a filler comprising inorganic particles and / or ceramic fibers, preferably of the same chemical composition respectively as that of the fibrous reinforcement and / or that of the inorganic particles of the pre-ceramic matrix of said support.

15. A method for manufacturing a prepreg for the manufacture of a ceramic matrix composite, said method comprising the following steps: 1) preparation of a first slurry having the following composition by volume percentage: - 25% to 95% inorganic particles, which may be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C, - 1% to 25% of a binder fraction comprising a compound selected from: - oppositely charged polyelectrolytes, - a colloidal dispersion of polymer particles selected from polyvinyl butyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, and their derivatives, or a mixture thereof, - or a mixture of said polyelectrolytes and said dispersion of particles;- less than 10% of one or more other constituents besides the solvent; and - 10% to 40% of a solvent, preferably polar, preferably water. 2) application of said first slip onto ceramic fibers of a fibrous reinforcement of a support, in order to form an impregnated support; 3) preferably drying of said impregnated support at a temperature between 10 and 70°C; 4) preferably, storage of the pre-impregnated material.

16. A method for manufacturing a prepreg according to the preceding claim, wherein, after drying in step 3), and preferably before step 4), storage to form an adhesive surface layer, preferably of a thickness between 10 and 100 micrometers, a second slip is applied to said impregnated material, said slip comprising in percentage by volume: - 1% to 70% of ceramic fibers and / or inorganic particles which can be partially or completely replaced by precursors of inorganic particles, capable of forming inorganic particles by heat treatment at a temperature above 200°C; - 10% to 80% of a binding fraction comprising a compound selected from: - oppositely charged polyelectrolytes, - a colloidal dispersion of polymer particles selected from polyvinyl butyral, a polyacrylic, a polystyrene acrylate, a polyisoprene, a polystyrene-acrylonitrile, a polyurethane, a polyvinyl acetate, a silicone, and their derivatives, or a mixture thereof, - or a mixture of said polyelectrolytes and said particle dispersion; - less than 10% of one or more other constituents other than the solvent;- 5% to 40% of a solvent, preferably polar, preferably water.

17. A method for manufacturing a prepreg according to claim 15 or 16, wherein said slurry comprises a complexation inhibitor, preferably a compound comprising ammonia or an amine group, preferably an amino alcohol comprising less than 10 carbon atoms.

18. A method for manufacturing a ceramic matrix part, said method comprising the following steps: 5) making available at least one prepreg according to any one of claims 1 to 14; 6) shaping said prepreg so as to obtain a raw preform of a ceramic matrix part; 7) consolidating heat treatment and / or crosslinking said preform; 8) optionally sintering said ceramic matrix part obtained from step 7).