Prepreg for ceramic matrix composite

Abstract

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

Description

[0001] PRE-IMPREGNATED FOR CERAMIC MATRIX COMPOSITE

[0002] technical field

[0003] 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.

[0004] Previous art

[0005] 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.

[0006] 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, allowing them to be molded into the desired shape. They can then be dried and, preferably, sintered to form a ceramic matrix.

[0007] However, a ceramic matrix part, and in particular a CMC, manufactured from prepregs that have been stored for a long time or under poor conditions, exhibits degraded mechanical properties.

[0008] WO2020157632A1, for example, proposes a "dry" prepreg composition that reduces the stability problem. However, the compositions considered lead to more porous sintered composites. The coating quality, which remains improvable, 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. A specific device is required (for example, a removable mechanical fastener or the use of a vacuum bag).WO2021151899A1 suggests using a prepreg formulation containing a liquefiable gel, which allows it to retain its deformability and bonding properties even after prolonged storage. However, the surface remains brittle if the prepreg dries out, particularly due to an extended assembly sequence, for example during large cutting operations, or because of an unexpected interruption in composite production, preventing storage in a controlled atmosphere.

[0009] Therefore, there is a permanent need for a pre-impregnated product:

[0010] -exhibiting good storage properties, good deformability, and the ability to reposition during assembly at room temperature, and

[0011] -allowing for a less porous composite with very good mechanical resistance to bending at room temperature.

[0012] The present invention aims to satisfy at least partially this need.

[0013] Summary of the invention

[0014] 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, in volume percentages based on said matrix:

[0015] - 55% to 95% (for example 60% to 95%, or even 65% to 95%) of a fraction of inorganic particles;

[0016] - 5% to 40% (for example 5% to 35%, or even 5% to 30%) of a binding fraction comprising a compound chosen from:

[0017] -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,

[0018] -or a mixture of said complex and said coalesced particles; and

[0019] - less than 10% of one or more other constituents besides residual solvent. Typically, these volume percentages are given on the basis of the dry matrix (i.e., without residual solvent). Preferably, the total volume of these inorganic particles has a median size D50 of less than 6 micrometers and greater than 0.1 micrometer.

[0020] 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%.

[0021] Inorganic particles can be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C, preferably above 300°C, preferably above 400°C.

[0022] As will be explained 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, as the prepreg retains its integrity.

[0023] Without being bound by this theory, the inventors consider that the composition of the prepreg according to the present invention allows, at equal volumetric rates of binder fraction, optimal coating of the ceramic fibers of the support and / or on the support while reducing stresses during debinding and formation of the ceramic matrix of the composite.

[0024] This composition has the advantage of significantly reducing the volumetric rate of 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, particularly at room temperature, typically at 20°C.

[0025] Finally, this composition, after drying, is easily re-hydrated to promote the preservation of the prepregs, allowing assembly and manufacturing of the composite under industrial conditions without the need for significant investments.

[0026] The prepreg thus remains well suited to the manufacture of a ceramic matrix part, in particular a CMC.

[0027] A prepreg according to the invention may further comprise one or more of the following optional and preferred characteristics: - 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%, or even greater than 73%, or even greater than 75% and / or less than 90%, preferably less than 87% in volume percentage on the basis of said matrix, and / or the 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);

[0028] - more than 95%, by mass, of ceramic particles are made up of oxide(s) for more than 99%, by mass, and have a chemical analysis such as Al2O3 + SiC>2 + ZrC>2 s 95%, by mass percentage on the basis of oxides;

[0029] - the ceramic particles are chosen from particles made up of oxide(s) for more than 90% of their mass, particles made up of nitride(s) for more than 90% of their mass, particles made up of silicon(s) for more than 90% of their mass, particles made up of carbide(s) for more than 90% of their mass, particles made up 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, 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, less than 70 pm, preferably less than 60 pm, preferably less than 50 micrometers, preferably less than 40 pm, preferably less than 30 pm, and / or a 10th percentile, D10, preferably less than 0.5 micrometers, preferably less than 0.3 micrometers, preferably less than 0.2 micrometers.;

[0030] - the binding 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;

[0031] - the binding fraction of said preceramic matrix comprises a polymer complex including electrostatic bonds; - the median size of the coalesced polymer particles of the binding fraction is between 1 nanometer and 1 micrometer (generally determined by dynamic light diffraction);

[0032] - the glass transition temperature of the binding fraction is less than 0°, preferably less than -10°C, preferably less than -30°C;

[0033] - the other constituents of said pre-ceramic matrix is / are organic(s) and / or chosen from among dispersants, surfactants, biocidal agents, anti-foaming agents, thickeners, plasticizers, drying regulators and mixtures thereof;

[0034] - 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 their mixtures;

[0035] - 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;

[0036] - 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;

[0037] - 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;

[0038] - the ceramic fibers of the fibrous reinforcement, possibly assembled in the form of wires, are made up of oxide(s) for more than 95% of their mass, and have a chemical analysis such as Al2O3+ SiU2 + ZrC>2 s 95%, in mass percentage on the basis of the oxides;

[0039] - 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 plies, preferably more than 2 plies and less than 10 plies;

[0040] - 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%;

[0041] - The said pre-impregnated material is such that, as a percentage by volume of said matrix:

[0042] - said inorganic particles of said matrix, preferably ceramic, are in a quantity greater than 70%, preferably greater than 75%, or even greater than 80%, and / or less than 95%, preferably less than 90%, or even less than 85%; and

[0043] - said binding fraction of said matrix represents at least 2%, preferably at least 5%, preferably at least 10%, and less than 35%, preferably less than 25%, preferably less than 20%; and

[0044] - the other constituents of the matrix preferably represent more than 0.5%, or even more than 1%, and less than 10%, preferably less than 5%;

[0045] -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.

[0046] 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.

[0047] 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.

[0048] 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:

[0049] - at least 50% of a binding fraction comprising a compound selected from: - a polymer complex comprising oppositely charged polyelectrolytes,

[0050] -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,

[0051] -or a mixture of said complex and said coalesced particles;

[0052] - less than 10% of one or more other constituents; and

[0053] - 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.

[0054] 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:

[0055] 1) preparation of a first slip having the following composition in percentage by volume:

[0056] - 25% to 95% (for example, 35% to 89%, or even 35% to 85% or even 35% to 55%) of 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;

[0057] - 1% to 25% of a binding fraction comprising a compound chosen from:

[0058] -Polyelectrolytes with opposite charges, -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 mixtures thereof,

[0059] -or a mixture of said polyelectrolytes and said particle dispersion;

[0060] - less than 10%, preferably 0.5% to 10%, of one or more other constituents besides the solvent; and - 10% to 40% of a solvent, preferably polar, preferably water.

[0061] 2) application of said first slip on ceramic fibers of a fibrous reinforcement of a support, in order to form an impregnated support;

[0062] 3) preferably drying of said impregnated support at a temperature between 10 and 70°C,

[0063] 4) preferably, storage of the pre-impregnated.

[0064] Preferably, in the manufacturing process of a prepreg described above, after drying in step 3), and preferably before storage step 4), 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, as a percentage by volume:

[0065] - 1% to 70%, preferably 5% to 50%, of ceramic fibers and / or inorganic particles which can be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles by heat treatment at a temperature above 200°C;

[0066] - 10% to 80%, preferably 30% to 80%, of a binding fraction comprising a compound selected from:

[0067] -polyelectrolytes with opposite charges,

[0068] -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,

[0069] -or a mixture of said polyelectrolytes and said particle dispersion;

[0070] - less than 10% of one or more other constituents besides the solvent;

[0071] - 5% to 40% of a solvent, preferably polar, preferably water.

[0072] Preferably, especially when oppositely charged polyelectrolytes are used to form a coacervate, the slurry comprises a complexation-inhibiting agent, 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;

[0073] 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:

[0074] 5) making available at least one prepreg described above,

[0075] 6) shaping said pre-impregnated material, for example by pressing it onto a mold, so as to obtain a raw preform of a ceramic matrix part,

[0076] 7) heat treatment for consolidation and / or crosslinking of said preform;

[0077] 8) Optionally, sintering of said ceramic matrix part from step 7).

[0078] Preferably in step 6) to increase adhesion, particularly when stacking several prepregs, a solvent spray is applied to at least part of the surface, preferably at least one large face, of the prepreg to be assembled in order 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.

[0079] When the part to be formed comprises several prepregs stacked one on top of the other, preferably, to promote adhesion between the first and second stacked prepregs, solvent is sprayed onto at least a portion of the surface, preferably at least one large face, of the first prepreg before the second prepreg is placed. 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.

[0080] 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.

[0081] The invention also relates to an intermediate product from step 5) and a preform from step 6) or 7). The invention also relates to a ceramic matrix composite from step 8).

[0082] Detailed description

[0083] Definitions

[0084] - By "pre-impregnated", according to the invention, we mean a support essentially made up of ceramic fibers, at least partially impregnated with a pre-ceramic matrix, comprising a preferably organic fraction binding inorganic particles and / or precursors of inorganic particles,

[0085] The support material can be, for example, a thread, a textile (such as a sheet of unidirectional threads), a fabric, a felt, a veil, a braid, a knit, or an assembly of these materials. A ceramic matrix part, and in particular a CMC, can be manufactured with a single prepreg or by layering several prepregs.

[0086] - By "inorganic" we mean a material that is not organic. It can therefore be a ceramic material, a metal or a cermet.

[0087] - 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.

[0088] - "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

[0089] "ceramic" can refer to an oxide, nitride, silicide or carbide of a metal (e.g. Al, Ti, Zr, Mg) or metalloid (e.g. Si, B).

[0090] - by coalesced particles, we mean particles originating from a suspension of polymers in colloidal form from which the solvent has been removed, for example by drying.

[0091] - 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.

[0092] - The "other constituents" are the constituents other than inorganic particles and their precursors, the components of the binding fraction and water.

[0093] - The binding fraction is the set of components that directly contribute to binding the 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.

[0094] - The "equivalent diameter" of a fiber is the diameter of a disk with the same surface area as its cross-section at mid-length.

[0095] - 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.

[0096] - A "long fiber" is a fiber whose length is greater than 1 mm. A "long yarn" is a yarn made up of long fibers.

[0097] - A "continuous fiber" is a fiber whose length is greater than 10 mm.

[0098] “Continuous yarn” is a yarn whose length is greater than 10 mm, made up of continuous fibers or an aligned assembly of short and / or long fibers (or “staple yarn” in English).

[0099] - 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).

[0100] - The 50th percentile (denoted D5 or median height) and the 99th percentile (denoted D) are called "percentiles". 99 ), the particle sizes corresponding to the percentages equal to 50% and 99%, respectively, by volume, on the cumulative particle size distribution curve of a set of particles, said particle sizes being ranked in ascending order. According to this definition, 99% by volume of the particles in the set of particles thus have a size less than D 99 and 1% of the particles, by volume, have a size greater than or equal to D 99 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 Malvern is used.

[0101] The 50th percentile, or "median size," of a set of particles is called the median size. The median size divides the particles of that set into first and second populations equal in volume, each containing only particles with a size greater than, equal to, or less than, respectively, the median size. Particles can be the individual elements of a powder, but also, by extension, these elements within a matrix.

[0102] - 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.

[0103] - A sum of oxide contents does not imply the presence of all of these oxides. For example, "Al2O3 + SiU2" is the sum of the contents of Al2O3 and SiU2, but does not exclude the absence of one of these oxides.

[0104] - 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).

[0105] - 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.

[0106] - “Contain” or “understand” or “present” should be interpreted in a non-limiting manner.

[0107] - Unless otherwise stated, all averages are arithmetic means.

[0108] Manufacturing process for a prepreg

[0109] A method for manufacturing a prepreg according to the invention comprises steps 1) to 3), and preferably step 4), above.

[0110] In step 1), a first slip is prepared (or equivalently

[0111] "suspension") comprising a binding fraction and inorganic particles and / or precursors of inorganic particles.

[0112] Slip can be manufactured by mixing, in a solvent, preferably polar, preferably water, inorganic particles and / or precursors of inorganic particles, and other constituent(s), preferably organic.

[0113] All conventional mixing techniques can be used. Inorganic particles, preferably ceramic, are intended to form the binding matrix of the ceramic matrix part, in particular the CMC.

[0114] Preferably, the quantity of inorganic particles, preferably ceramic, is greater than 25%, preferably greater than 30%, preferably greater than 35%, preferably greater than 40% and / or less than 55%, preferably less than 50%, as a percentage by volume based on the volume of said first slip.

[0115] Preferably, the inorganic particles, preferably ceramic, are selected from particles consisting of more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, of oxide(s), preferably more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, of nitride(s) more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, of carbide(s) more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, of silicide(s) more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, of boride(s) 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.

[0116] Preferably, when the inorganic particles contain an oxide, they contain an oxide selected from Al₂O₃, SiC₂, ZrC₂, CaO, MgO, SrO, BaO, K₂O, rare earth oxides, TiC₂, Na₂O, C₆O₁₂, and mixtures thereof.

[0117] Preferably, when inorganic particles contain a nitride, they contain a nitride selected from AIN, BN, TiN, SisN4 and their mixtures.

[0118] Preferably, when inorganic particles include a carbide, they include a carbide selected from SiC, B4C, TiC, TaC, HfC, ZrC and their mixtures.

[0119] Preferably, when the inorganic particles contain a boride, they preferably contain HfB2, TiB2, ZrB2. Preferably, when the inorganic particles contain a silicide, they preferably contain MoSi2, TaSi2; WSi2, TiSi2.

[0120] 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 more than 95%, preferably more than 99%, preferably substantially 100% of their mass.

[0121] 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 + Si₂ + Zr₂ + CaO + MgO + SrO + BaO + K₂O + rare earth oxides + TiCl₂ + Na₂O + Cr₂O₃ s 90%, preferably > 95%, preferably > 99%, as a mass percentage on the oxide basis. Preferably, this sum of oxide(s) contents is approximately 100%, as a mass percentage on the oxide basis.

[0122] 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 + SiC > 2 s 90%, preferably > 95%, preferably > 99%, as a mass percentage based on the oxides. Preferably, this sum of oxide(s) contents is approximately 100%, as a mass percentage based on the oxides.

[0123] 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 SiC>2 s 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides.

[0124] 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 Al2O3 s 90%, preferably > 95%, preferably > 99%, as a percentage by mass on the basis of the oxides.

[0125] Inorganic particles, preferably ceramic, can be replaced, partially or completely, by precursors of inorganic particles, preferably ceramic; that is, by constituents which, during the manufacture of the prepreg or more generally during the manufacture or use of the ceramic matrix part, particularly the CMC, lead to inorganic particles, preferably ceramic, or to an inorganic matrix, preferably ceramic, respectively. Boehmite, alumina trihydrate, tetraethyl orthosilicate (TEOS), and orthosilicic acid are examples of known precursors of alumina, alumina, silica, and silica, respectively.

[0126] 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.

[0127] Metallic particles, meaning particles made of a metal or a metallic alloy, are intended to be incorporated into the ceramic matrix of the ceramic matrix part, particularly the CMC. They can modify its properties, such as thermal and / or electrical conductivity. If metallic particles are precursors to ceramic particles, and in particular if they are transformed into ceramic particles during sintering, preferably reactive sintering, they are counted exclusively as ceramic particle precursors.

[0128] 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.

[0129] Preferably, all or part of the metallic particles comprise, and preferably are made of, a material selected from silicon, aluminum, iron, and mixtures thereof, particularly their alloys. The set of metallic particles may consist of particles all having the same composition or of a mixture of particles having different compositions.

[0130] Metallic particles can be replaced, partially or completely, by metallic particle precursors, that is, by constituents which, during the manufacture of the prepreg or more generally during the manufacture or use of the ceramic matrix part, particularly the CMC, lead 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.

[0131] Preferably, the first slip does not contain precursors of metallic particles.

[0132] In a preferred embodiment, the first slip does not contain metallic particles, nor precursors of such particles.

[0133] Preferably, the set of ceramic and metallic particles has, by volume,

[0134] -a median D50 size 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

[0135] -a 99th percentile, D 99 less than 70 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 30 pm, and / or

[0136] -a 10th percentile, D, preferably less than 0.5 micrometers, preferably less than 0.3 micrometers, preferably less than 0.2 micrometers.

[0137] The set of ceramic and metallic particles in the slip can exhibit a unimodal size distribution, but also a multimodal one, in particular bi- or tri-modal.

[0138] The entire ceramic and metallic particle population can 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. Even more preferably, the particle population with a distribution centered on the first peak represents less than 50% by volume of the entire ceramic and metallic particle population.

[0139] The binder fraction comprises a compound (which may be referred to hereafter as the "polymer compound of the binder fraction") selected from:

[0140] -polyelectrolytes with opposite charges,

[0141] -a colloidal dispersion, preferably aqueous, of a polymer selected from 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;

[0142] 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 mixtures thereof;

[0143] More specifically, the polymer compound of the binding fraction of the preceramic matrix can be chosen from polyelectrolytes with opposite charges.

[0144] Opposite-charged polyelectrolytes typically consist of a cationic polyelectrolyte and an anionic polyelectrolyte.

[0145] It is known that when an aqueous solution of an anionic polyelectrolyte (also referred to hereafter as a "polyanion") and an aqueous solution of a cationic polyelectrolyte (also referred to hereafter as a "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) that will separate from the aqueous phase. When 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, phase separation occurs, resulting in 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.

[0146] The term "cationic polyelectrolyte" encompasses a single cationic polyelectrolyte as well as mixtures of two or more cationic polyelectrolytes. The term "anionic polyelectrolyte" encompasses an anionic polyelectrolyte as well as mixtures of two or more anionic polyelectrolytes.

[0147] 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.

[0148] Polyelectrolytes can be strong or weak. A strong polyelectrolyte is a polymer with 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 (usually greater than 0.01%, e.g., 1% by weight of polyelectrolyte relative to the volume of solution analyzed) and typically at 20°C.

[0149] Conversely, a weak polyelectrolyte is a polymer with 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 differ by at least 10%. Usually, a weak polyelectrolyte has a zeta potential (pl) between 1 and 14. More specifically, a weak cationic polyelectrolyte generally has a pl greater than 7 (e.g., between 7.5 and 14), and a weak anionic polyelectrolyte generally has a pl less than 7 (e.g., between 1 and 6.5). In the present application, the pls are determined in water at a temperature of 25°C and in 0.01 M NaCl. 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 contains only negative charges and is free of positive charges. By analogy, cationic polyelectrolytes can contain both cationic and anionic charges as long as, at pH 7, the overall net charge is positive.

[0150] Therefore, the definition of anionic polyelectrolytes encompasses zwitterionic polyelectrolytes having an isoelectric point (pl) < 7, preferably < 6, and the definition of cationic polyelectrolytes encompasses zwitterionic polyelectrolytes having an isoelectric point (pl) > 7, preferably > 8. Most commonly known zwitterionic polyelectrolytes are proteins or peptides comprising both standby carboxyl groups (-COOH) and standby amino groups (-NH2).

[0151] 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.

[0152] Anionic polyelectrolyte and cationic polyelectrolyte can be linear or branched polymers.

[0153] 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.

[0154] 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 of it.

[0155] Le polyélectrolyte cationique peut notamment être choisi parmi :

[0156] - poly(chlorure de diallyldimethylammonium) (PDADMAC),

[0157] - poly[chlorure de (2-hydroxypropyl)dimethylammonium],

[0158] - polyamidoamine-epichlorhydrine (PAAE),

[0159] - polyethylene imine,

[0160] - poly(chlorure d’acrylamide-co-diallyldimethylammonium),

[0161] - poly(acide acrylique-co-diallyldimethylammonium chlorure), - copolymer of hydroxyethylcellulose and poly(chlorure de diallyldimethylammonium) (Polyquaternium-4),

[0162] - copolymere d’acrylamide and dimethylaminoethylmethacrylate quaternarisé avec le sulfate de dimethyle (Polyquaternium-5, CAS 26006-22-4),

[0163] - copolymere de dimethylaminomethyl methacrylate et alkyl methacrylate,

[0164] - copolymere de methyl and stearyl dimethylaminoethyl ester d’acide methacrylique,

[0165] - homopolymere de N,N-(dimethylamino)ethyl ester d’acide methacrylique quaternarisé avec le bromomethane,

[0166] - poly(N,N-(dimethylamino)ethyle methacrylate quaternarisé),

[0167] - chlorure de guar hydroxypropyltrimonium,

[0168] - poly(2-(dimethylamino)ethyl methacrylate),

[0169] - poly(chlorure de N,N-dimethyl-3,5-dimethylene piperidinium),

[0170] - poly(chlorure de vinylbenzyltrimethylammonium),

[0171] - poly[chlorure de 3-(methacryloylamino)propyl-trimethylammonium],

[0172] - poly(chlorure de [2-(methacryloloxy)ethyl]-trimethylammonium),

[0173] - polyvinylamine (PVA),

[0174] - poly(chlorure de N,N-dimethyl-3,5-dimethylene piperidinium) (PDDPC),

[0175] - poly(chlorure de vinylbenzyltrimethylammonium) (PVBTAC),

[0176] - poly(chlorhydrate d’allylamine) (PAH),

[0177] - poly[3-(methacryloylamino)propyltrimethylammonium chloride] (PMAPTAC),

[0178] - cationic dextran,

[0179] - poly(aniline),

[0180] - poly(2-vinylpyridine),

[0181] - poly(L-lysine), and

[0182] - their mixtures.

[0183] 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.

[0184] The anionic polyelectrolyte may 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-1-propanesulfonic acid), hyaluronic acid, poly(vinylsulfonic acid), poly(glutamic acid), dextran sulfate, their salts (e.g., sodium salts), and mixtures thereof. Preferably, the anionic polyelectrolyte is selected from polyacrylic acid, poly(methacrylic acid), poly(glutamic acid), hyaluronic acid, their salts (e.g., sodium salts), and mixtures thereof.

[0185] The average molecular weight (determined by light scattering) of 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 and cationic polyelectrolytes preferably have similar molecular weights.

[0186] In a preferred embodiment, at least one of the anionic polyelectrolyte and the cationic polyelectrolyte is a weak polyelectrolyte.

[0187] In one embodiment, the cationic polyelectrolyte is a weak polyelectrolyte (preferably branched). In such an embodiment, the anionic polyelectrolyte may be either a strong or weak polyelectrolyte (for example, a strong polyelectrolyte). In such an embodiment, the pH is advantageously higher than the pI of the weak cationic polyelectrolyte. The pI of a weak cationic polyelectrolyte is generally greater than 7, for example, between 7.5 and 14.

[0188] In another embodiment, the anionic polyelectrolyte is a weak polyelectrolyte. In such an embodiment, the cationic polyelectrolyte can be either a strong or weak polyelectrolyte (for example, a strong polyelectrolyte). In such an embodiment, the pH is advantageously lower than the pI of the weak anionic polyelectrolyte. The pI of a weak anionic polyelectrolyte is generally less than 7, for example, between 1 and 6.5.

[0189] In a more preferred embodiment, both the cationic polyelectrolyte and the anionic polyelectrolyte are weak polyelectrolytes. In such an embodiment, the pH is advantageously such that:

[0190] - pH > pl+, or

[0191] - pH < pl-, in which pl+ refers to the pl of the weak cationic polyelectrolyte and pl- refers to the pl of the weak anionic polyelectrolyte, with pl+ > pl-.

[0192] In this application, pH refers to the pH of the liquid phase of the preceramic matrix which comprises the binder fraction. The polymer compound of the binder fraction of the preceramic matrix represents, by volume, generally more than 25%, preferably more than 40%, or even more than 50%, or more than 65%, or even more than 80%, or even more than 90%, or more than 95%, or even substantially 100% of the total volume of said binder fraction.

[0193] The aforementioned "other constituent(s)" do not contribute to the temporary binding properties of the first slip. In other words, they are not temporary binders. Preferably, the "other constituent(s)" are organic.

[0194] 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.

[0195] Preferably, the so-called "other constituents" are chosen from among dispersants, surfactants, biocidal agents, antifoaming agents, thickeners, plasticizers, drying regulators and mixtures thereof.

[0196] Preferably, the first slurry contains a biocidal agent, preferably in a quantity greater than 0.1% and / or less than 1%, preferably less than 0.5%, by volume based on the volume of said slurry. PREVENTOL® P301, marketed by Lanxess, is, for example, a known biocidal agent.

[0197] The first slip may contain a dispersant. A dispersant of the Dolapix CE 64 type, marketed by the company Zschimmer & Schwarz, may be suitable.

[0198] The first slip may contain an antifoaming agent, preferably in a quantity 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.

[0199] 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.

[0200] When a ceramic particle precursor in colloidal form is used, it is preferably added to the water, along with the thermoreversible hydrocolloid, before the other constituents of the first slip.

[0201] Preferably, the water is demineralized water. In step 2), the first slurry is applied to the ceramic fibers of the fibrous reinforcement of the support.

[0202] Preferably, ceramic fibers, possibly assembled in the form of threads, represent more than 90%, more than 95%, preferably 100% of the mass of the fibrous reinforcement.

[0203] Preferably, more than 50%, 70%, 90% by number of ceramic fibers, preferably 100% of the ceramic fibers, possibly assembled in the form of yarns, have:

[0204] - a length greater than 10 mm; and

[0205] - 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.

[0206] Ceramic fibers may have a sizing and / or ceramic yarns may have an organic surface coating (finishing), said sizing and / or 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.

[0207] Preferably, the ceramic fibers, possibly assembled in the form of yarns, 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 chosen from Al2O3, SiC>2, ZrC>2, CaO, MgO, an iron oxide, rare earth oxides, TiU2, Na2U, Cr2Os and their mixtures, or of SiC.

[0208] Preferably, the ceramic fibers, possibly assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass. Preferably, the ceramic fibers, possibly assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% of their mass, and exhibit a chemical analysis such as Al₂O₃ + Si₂ + ZrCl₂ + CaO + MgO + Fe₂O₃ + rare earth oxides + TiCl₂ + Na₂<D + C^Os s 90%, de préférence > 95%, preferably > 99%, preferably approximately equal to 100%, as a percentage by mass on the basis of oxides.

[0209] Preferably, the ceramic fibers, possibly assembled into yarns, consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% by mass, and have a chemical analysis such as Al₂O₃ + SiU₂ → 90%, preferably > 95%, preferably > 99%, preferably approximately 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.

[0210] 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% of their mass, and exhibit a chemical analysis such that SiC > 2s 90%, preferably

[0211] > 95%, preferably > 99%, as a percentage by mass based on oxides. Preferably, in this embodiment, the ceramic fibers, possibly assembled in the form of yarns, are selected from glass fibers, amorphous silica fibers and mixtures thereof.

[0212] In one embodiment, the ceramic fibers, optionally assembled in the form of threads, consist 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 as Al2O3 s 90%, preferably

[0213] > 95%, preferably > 99%, as a mass percentage based on oxides. Preferably, in this embodiment, the ceramic fibers, optionally assembled into yarns, are corundum fibers. In one embodiment, the ceramic fibers, optionally assembled into yarns, consist 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 Al₂O₃ s 50%, preferably > 60%, preferably > 70% and < 90%, as a mass percentage based on oxides. Preferably, in this embodiment, the ceramic fibers, optionally assembled into yarns, are selected from mullite fibers, mullite-corundum fibers, and mixtures thereof.

[0214] The material of the inorganic particles, preferably ceramic, and the material of the ceramic fibers, possibly in the form of threads, may be identical or different.

[0215] Preferably, the ceramic fibers, possibly assembled into yarns, are selected from glass fibers, amorphous silica fibers, corundum fibers, mullite fibers, mullite-corundum fibers, and mixtures thereof. The ceramic particles consist of oxide(s) comprising more than 90%, preferably more than 95%, preferably more than 99%, preferably approximately 100% by mass, and exhibit a chemical analysis such that Al₂O₃ + SiU₂ + ZrC > 2 s 90%, preferably > 95%, preferably > 99%, as a mass percentage based on the oxides. Preferably, this sum of oxide contents is approximately 100%, as a mass percentage based on the oxides.

[0216] The fibrous reinforcement may be in the form of a sheet, preferably in the form of a fabric having weft and warp threads, a knit or a braid, or in the form of a felt in the form of a layer.

[0217] The layer, preferably a 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.

[0218] Preferably, the web consists of ceramic yarns made up of assembled ceramic fibers, preferably ceramic fibers exhibiting one or more of the fiber characteristics described above. Such a ceramic yarn typically comprises several hundred to several thousand ceramic fibers. At least one yarn, preferably representing more than 90% by number of the ceramic yarns, preferably each ceramic yarn in 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.

[0219] In one embodiment, the fibrous reinforcement consists of a single layer.

[0220] In one 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 yarns.

[0221] 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°.

[0222] In one embodiment, the fibrous reinforcement has the form of a single wire, that is to say not assembled with other wires.

[0223] 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.

[0224] 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 layering of sheets. Impregnation is also possible when the substrate is in the form of a wire. The first slip then penetrates the substrate.

[0225] Impregnation can be carried out using any technique known to those skilled in the art, in particular by scraping (or the "doctor blade" process), tape casting (or the "tape casting" process), immersion (for example, using the "dip coating" process), spraying, brushing, or screen printing. When the fibrous reinforcement consists of several superimposed layers, each layer can be impregnated before being layered on top of the others. Alternatively, the layers can be layered without being impregnated, with all the superimposed layers then being impregnated simultaneously. Preferably, when the fibrous reinforcement consists of several superimposed layers, each layer is impregnated before being layered on top of the others.

[0226] The first slip impregnates all or part of the fibrous reinforcement, preferably all of the fibrous reinforcement.

[0227] 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 felt or 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 outer surfaces, with the first slip.

[0228] In 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.

[0229] 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.

[0230] Preferably, the pre-impregnated product should be dry to the touch.

[0231] 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 material.

[0232] In step 4), which is optional, the pre-impregnated material according to the invention is stored.

[0233] The prepreg 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. If several prepregs are stored together, an interlayer made of a material that prevents sticking between them, such as a polymer, is preferably used. For example, a polyester, polyethylene, or polyethylene terephthalate film, such as Mylar, can be used to separate stacked prepregs.

[0234] 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.

[0235] Advantageously, a pre-impregnated material according to the invention can be stored at room temperature for a long time, substantially without degradation.

[0236] Adhesive surface layer:

[0237] According to a preferred method, 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.

[0238] This layer is preferably continuous but, according to one possible mode, it can be discontinuous.

[0239] This layer is formed by depositing a second slip comprising, in volume percentage:

[0240] - 10% to 60% of ceramic fibers and / or inorganic particles that can be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles through heat treatment at a temperature above 200°C.

[0241] - 10% to 60% of a binding fraction comprising a compound chosen from:

[0242] -polyelectrolytes with opposite charges,

[0243] -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 their mixtures;

[0244] - less than 10% of one or more other constituents;

[0245] -10% to 40% of a solvent, preferably polar, preferably water. In one possible manner, the formulation of said second slip is the same as that of the first slip used for the manufacture of the prepreg.

[0246] According to a preferred mode, the polymer compound of the binder 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.

[0247] The polymer compound of the binding fraction of the adhesive surface layer represents, by volume, generally more than 25%, preferably more than 40%, or even more than 50%, or 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 of said surface layer.

[0248] 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%.

[0249] Manufacturing process for a ceramic matrix part

[0250] A method for manufacturing a ceramic matrix part according to the invention comprises steps 5) to 8) described above, step 8) being optional.

[0251] 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°.

[0252] In one possible method, at least a portion of the surface, preferably at least one large face, of the 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 the prepreg is measured at a temperature of 20°C under 0.1 MPa. The solvent is preferably water.

[0253] Remarkably, temporary storage of the prepreg at room temperature does not significantly degrade it. In step 6), the prepreg is shaped according to the desired geometry, using any technique known to those skilled in the art, so as to obtain a deformable preform.

[0254] Preferably, the pre-impregnated material is shaped by being pressed onto a mold.

[0255] 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.

[0256] Typically, several prepregs prepared in step 5 are formed simultaneously, for example, after being stacked on top of each 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 single sheet or several overlapping sheets.

[0257] 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.

[0258] A prepreg in the form of a wire can be wound around a base, temporarily or permanently, for example around a mandrel, for example with a circular, oval or polyhedral cross-section. This operation is called filament winding.

[0259] The base can be temporary or permanent, depending on whether it is subsequently separated from the wound wire. The number of turns around the base can be greater than 5, 50, 500, or 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, unwound to obtain a flat shape.

[0260] The shaping of a prepreg into a filament can alternatively result from localized preparation of the prepreg, deposition onto a surface, and then the application of pressure; the deposition and / or the application of pressure can be simultaneous. A prepreg in filament form can, in particular, 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.

[0261] Steps 5) and 6) can be simultaneous, as described in particular in the example below.

[0262] 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 it. This heat treatment may, for example, allow cross-linking of at least a portion of the binder fraction to enable handling of the preform.

[0263] 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, better still less than or equal to 150°C.

[0264] Any technique known to a person skilled in the art can be used.

[0265] The heat treatment in step 7) drying results in a raw ceramic matrix part. Preferably, the process does not include step 7).

[0266] 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.

[0267] A person skilled in the art knows how to determine the sintering conditions based on the nature of the ceramic particles, optional metallic particles, and ceramic fibers.

[0268] In particular, when the ceramic fibers are in an oxide form and the ceramic particles have a chemical analysis such as SiC > 2 s 90%, the sintering temperature is preferably above 800°C and preferably below 1000°C, with sintering preferably taking place under air and preferably at a pressure of 1 bar, and the holding time preferably exceeding 1 hour and preferably less than 10 hours. Similarly, when the ceramic fibers are in an oxide form and the ceramic particles have a chemical analysis such as Al₂O₃ s 90%, the sintering temperature is preferably above 800°C and preferably below 1500°C, with sintering preferably taking place under air and preferably at a pressure of 1 bar, and the holding time preferably exceeding 1 hour and preferably less than 10 hours.

[0269] 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.

[0270] The resulting CMC exhibits 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.

[0271] CMC can be used in the following applications: hot gas exhaust part, cooking support, thermal insulation, hot drive rollers for hot glass parts.

[0272] A prepreg according to the invention is not 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, i.e., one that can adapt to the shape of the object to be thermally protected.

[0273] Pre-impregnated

[0274] The characteristics, and in particular the preferred characteristics, of a prepreg according to the invention derive directly from the preceding description of the process.

[0275] Especially,

[0276] - quantities, and in particular preferred quantities,

[0277] - the compositions, and in particular the favorite compositions,

[0278] - median sizes, and in particular preferred median sizes,

[0279] - the 99th percentiles (D 99), and in particular the preferred 99th percentiles, - the particle size distributions, and in particular the preferred particle size distributions, of ceramic particles, metallic particles, ceramic particle precursors, and metallic particle precursors in the slip are identical to those described above for the slip;

[0280] - quantities, and in particular preferred quantities,

[0281] - the compositions, and in particular the preferred compositions, of the "other constituents" are identical to those described above for the slip;

[0282] - quantities, and in particular preferred quantities,

[0283] - the compositions, and in particular the favorite compositions,

[0284] - the dimensions, and in particular the preferred dimensions, of the fibers and yarns of the fibrous reinforcement are identical to those described above for the manufacturing process of the ceramic matrix part; the portions of the outer surface of the fibers and yarns of the fibrous reinforcement covered by the pre-ceramic matrix are identical to those described above for the portions of the outer surface of the fibers and yarns of the fibrous reinforcement covered by the slip;

[0285] - shapes, and in particular preferred shapes,

[0286] - the structures, for example the orientation of the wires of different superimposed layers as well as the number of layers, and in particular the preferred structures,

[0287] - the dimensions, and in particular the preferred dimensions, of the fibrous reinforcement are identical to those described above for the manufacturing process of the ceramic matrix part; 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.

[0288] Examples

[0289] The following non-limiting examples are given for the purpose of illustrating the invention.

[0290] The following raw materials were used in the examples: - a thermoreversible hydrocolloid gelatin, with a Bloom value of 280, passing completely through a square mesh sieve with an opening of 0.841 mm, marketed by Weishardt International

[0291] - 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,

[0292] - a binder in the form of an acrylic polymer, latex in solution supplied by Alberdingk AC75022 (67% solid fraction in water),

[0293] - 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.,

[0294] - a complexation inhibitor of 2-amino-2-methyl-1-propanol in solution with 5% water (AMP95) in liquid form.

[0295] - a Dolapix CE64 dispersing agent

[0296] - an agent for adjusting the pH, a solution of ammonium hydroxide NH4OH in water, at a concentration of 20% by mass,

[0297] - as a precursor of ceramic particles, a LUDOX AS40 colloidal silica solution (D50 = 22 nm),

[0298] - as a ceramic particle powder, an amorphous silica powder (FAR-11) exhibiting a mass purity greater than 99.9%, a median particle size of 1.4 pm and a 99th percentile of 4 pm,

[0299] - as ceramic particle powder, an amorphous silica powder (FMT-07) exhibiting a mass purity greater than 99.9%, a median size of 7.5 pm.

[0300] - as ceramic particle powder, an alpha alumina powder having a mass purity greater than 99.99%, a median size equal to 0.2 pm.

[0301] - as ceramic particle powder, an alpha alumina powder having a mass purity greater than 99.9%, a median size of 0.4 pm.

[0302] - as a binder, polyethylene glycol PEG4000 in liquid form with a PEG 4000 concentration of 50% by mass, the remainder being water,

[0303] An initial series of eight prepregs was impregnated with the slip according to Example 1 (comparative) and the protocol detailed in WO2021 / 151899A1, pages 43 to 46, incorporated by reference. Unlike this initial series of prepregs, further series of eight prepregs were produced for each of Examples 2 to 8, using the formulations shown in Table 1 below. Example 6 is representative of a prepreg detailed in WO2020 / 157632.

[0304] 5 [Table 1]

[0305] NA=not applicable; *as a dry extract; **taking into account the water content of the Ludox solution

[0306] AS40; compar. = comparative; Inv. = invention; dispers. = dispersing

[0307] NM not measured

[0308] For this second series of examples 2 to 5, according to step 1) with reference to method 10 according to the invention described above, as well as for examples 6 to 8

[0309] (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:

[0310] -Add the PAA polymer solution, complexation inhibitor, and water (according to the percentages given in Table 1), and mix for 3 minutes at 500 rpm.

[0311] -add the dispersant and the PEI polymer solution, mix for 5 minutes at 950 rpm.

[0312] - Add the mineral particle powder, mix for 20 min. at 4000 rpm. - Add the colloidal mineral particle solution, mix for 10 min. at 2500 rpm.

[0313] The glass transition temperature was measured by differential scanning calorimetry.

[0314] The film formation temperature (TMFF) was measured according to ISO 2115-1996.

[0315] According to step 2), with reference to the process according to the invention described above, for each example 2, 3, 4, 7 and 8, the resulting slip was then poured onto a 200 mm x 300 mm silica fibrous reinforcement, laid flat. This fibrous reinforcement is a 1 / 5 satin fabric made of Quartzel® yarns with a basis weight of 200 g / m². 2The said yarns, bearing the reference C14 80 Z0 QS1318, are marketed by the company Saint-Gobain Quartz. Prior to its coating with slip, the fabric underwent a heat treatment in an electric furnace to desensitize the yarns, said heat treatment consisting of a rise to 550°C at a speed of 100°C / min, a holding period of 1 hour at 550°C and a natural temperature decrease.

[0316] The slip was spread onto the fabric using a plastic spatula. The fabric was then turned over, and more slip was poured and spread onto the other side of the fabric in the same way.

[0317] 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. 2, being marketed by the company 3M. Prior to its use, the fabric underwent heat treatment in an electric oven to desensitize the fibers, said heat treatment consisting of heating to 700°C at a rate of 100°C / min, a holding period of 1 hour at 700°C, and a natural cooling. According to step 2) with reference to the process according to the invention described above, the impregnated fabrics, except for that of Example 1, were then dried at a temperature of 20°C for 3 hours.

[0318] For examples 3 and 5 in particular, an adhesive layer loaded with ceramic particles was deposited on both sides 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 side of the dry prepreg, typically with a thickness between 10 and 100 µm.

[0319] [Table 2]

[0320] *as a dry extract. ** takes into account the water content of the Ludox AS40 solution.

[0321] Composite manufacturing:

[0322] For each of the preceding examples, a composite was manufactured from the eight prepregs obtained previously. The composites in examples 1 to 8 were manufactured according to the following successive steps 6) to 8).

[0323] In step 6), with reference to the process steps described previously, 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.

[0324] For example 1, this assembly must be done on a hot plate at 40°C. For examples 2, 4, 7, and 8, a water spray is applied to each prepreg surface before they are placed in 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).

[0325] The prepregs according to the invention exhibit good conformability and bonding properties, particularly after a storage period between manufacturing and use. The shaping process is simplified, especially compared to comparative examples 1 and 6, as no temperature control is essential for shaping the composite.

[0326] In step 7), with reference to the process steps described previously, 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 residual water in the preforms of examples 2 to 8 to evaporate, and the preform of example 1 to consolidate.

[0327] In step 8), with reference to the process steps described previously, the preform is sintered in an electric furnace, according to the following cycle, in order to obtain a ceramic matrix composite:

[0328] Examples 1 to 4, 7 and 8 (silica tissues)

[0329] - rising from 20°C to 860°C at a rate of 10°C / min,

[0330] - maintained at 860°C for 6 hours,

[0331] - natural descent to room temperature.

[0332] Examples 5 and 6 (alumina fabrics)

[0333] - rise from 20°C to 1300°C at a rate of 10°C / min, maintenance at 1300°C for 1 hour, natural descent to ambient temperature.

[0334] Table 3 below shows the mass ratios of fibrous reinforcement and pre-ceramic matrix of the pre-impregnated materials based on the pre-impregnated materials after drying and the volume percentage of the inorganic particle fraction by volume of the matrix of the pre-impregnated materials before drying.

[0335] Also reported are the following characterizations carried out on prepregs and on ceramic matrix composites made from prepregs.

[0336] Test #1: Friability of the prepreg evaluated after 3 hours of drying at 20°C:

[0337] 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: -very friable: appearance of cracks and presence of detachment of material, -acceptable: appearance of some cracks but no detachment of material, -non friable: no cracks and no detachment of material.

[0338] Test #2: Porosity on the ceramic matrix composite:

[0339] It was measured according to the ISO18754 standard.

[0340] Test #3: Mechanical resistance of the ceramic matrix composite:

[0341] The 3-point bending strength was measured in MPa according to ASTM C 1341 (2013). The setup consisted of two lower cylindrical supports and one upper support, each 10 mm in diameter. The two lower supports were spaced 68 mm apart, with the upper support centered between them. The upper support came into contact with the sample, which was centered on the two lower supports, and then descended at 0.45 mm / s until the sample failed. The tested sample had dimensions of 85 mm in length, 10 mm in width, and 1.7 mm in thickness.

[0342] The results are summarized in Table 3 below: [Table 3]

[0343] * content relative to the dry prepreg (i.e., excluding residual solvent); NM = not measured; compar. = comparative; Inv. = invention; RED = delamination failure

[0344] 5 These results show that:

[0345] 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.

[0346] 10 - The composite in 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 a CCMC (its adhesion mechanism is altered by drying). Re-wetting it does not restore its initial adhesive strength.

[0347] 15 - 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 W02020 / 157632, the dry matrix must contain between 40 and 55% by volume of organic binder, which inevitably reduces the mineral proportion.

[0348] 20 integrable into the prepreg. The activation of its adhesion mechanism by temperature necessitates the use of shaping methods such as hot press, autoclave or Automated Filament Placement for the manufacture of the OCMC part.

[0349] Examples 2, 3, 4, and 5 of the invention demonstrate very high levels of inorganic particle content in the pre-ceramic matrix of the prepreg, resulting in a ceramic matrix with reduced porosity and significantly improved mechanical properties. The adhesive strength of these prepregs is activated by surface humidification (partial release of 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 strength, 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 easily detach the misaligned prepreg and reposition it at room temperature without the need for any complex equipment.

[0350] Examples 7 and 8 show that if the set of said inorganic particles has, by volume, a median size D5o that is too small or too large compared to the claimed range, the composite after sintering shows a tendency towards delamination which results in insufficient mechanical properties.

[0351] 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.

[0352] 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, as a percentage by volume based on said matrix: - 65% to 95% of a fraction of inorganic particles, the set of said inorganic particles having, by volume, a median size D50 less than 6 micrometers and greater than 0.1 micrometer; - 5% to 40% of a binding fraction comprising a compound chosen from: - a complex comprising polyelectrolytes of opposite charges, - 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, -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 replaced partially or completely by precursors of inorganic particles, 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 a quantity greater than 60% and less than 90%, by volume percentage on the basis of said matrix; and / or - metallic particles being present in a quantity greater than 0.5% and less than 9%, as a percentage by volume on the basis of said matrix.

3. Pre-impregnated according to claim 2, wherein more than 95%, by mass, of the ceramic particles are composed of oxide(s) for more than 99%, of their mass, and present a chemical analysis such as Al2O3 + SiU2 + ZrU2 s 95%, as a percentage by mass on the basis of 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% by mass, particles consisting of nitride(s) for more than 90% by mass, particles consisting of carbide(s) for more than 90% by mass, particles consisting of boride(s) for more than 90% by mass, and mixtures of these particles; the ceramic particles as a whole having, by volume, a median size D50 of less than 5 micrometers and greater than 50 nanometers, and a 99th percentile, D 99 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 in the fibrous reinforcement, possibly assembled into threads, have a length greater than 4 mm, and an equivalent diameter, measured at mid-length, greater than 2 µm and less than 50 µm; and / or - the ceramic fibers of the fibrous reinforcement are composed, 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 sheet 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 outer 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, consist of oxide(s) for more than 95% of their mass, and have a chemical analysis such as Al2O3 + SiC>2 + ZrC>2 s 95%, as a percentage by mass 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 thickness between 10 and 100 micrometers, comprising by volume relative to the volume of said adhesive layer, excluding residual solvent: - at least 50% of a binding fraction comprising a compound chosen from: -a polymer complex comprising polyelectrolytes of opposite charges, -coalesced particles of a polymer selected from polyvinyl butyral, polyacrylic, polystyrene acrylate, 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 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.

15. A method for manufacturing a prepreg for the manufacture of a ceramic matrix composite, said prepreg preferably being as defined in any one of claims 1 to 14, said method comprising the following steps: 1) preparation of a first slip having the following composition in percentage by volume: - 35% to 89% inorganic particles, which can be partially or completely replaced by inorganic particle precursors capable of forming inorganic particles through heat treatment at a temperature above 200°C. - 1% to 25% of a binding fraction comprising a compound chosen from: -polyelectrolytes with opposite charges, -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 mixtures thereof, -or a mixture of said polyelectrolytes and said particle dispersion; - 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 on 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.

16. A method for manufacturing a prepreg according to the preceding claim, wherein, 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 impregnated material, said slurry comprising the following percentages by volume: - 1% to 70% of ceramic fibers and / or 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; - 10% to 80% of a binding fraction comprising a compound chosen from: - polyelectrolytes with opposite charges, - 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, -or a mixture of said polyelectrolytes and said particle dispersion; - less than 10% of one or more other constituents besides 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 slip comprises a complexation inhibitor agent, 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 pre-impregnated material, 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).

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