Knitted support intended for the manufacture of a CMC

Abstract

knitted support at least partly ceramic intended for the manufacture of a CMC, comprising a ceramic knit having a repetition of elementary cells, at least part of said elementary cells being at least partially sealed by at least one sealing thread, an elementary cell being defined as the smallest rectangular motif, which by its repetition forms 70%, or more, of the surface of the knit, process of manufacturing a CMC from an impregnated preform comprising at least a knitted support and CMC thus obtained.

Description

Title of the invention: Knitted support intended for the manufacture of a CMC

[0001] A Ceramic Matrix Composite, or "CMC", is a sintered product consisting of a support composed of ceramic fibers, for example a "ceramic" knit, and a ceramic matrix binding said fibers. A knit can advantageously be formed into a complex shape before introducing a slip constituting a precursor of the ceramic matrix, which makes it possible to manufacture CMCs of very diverse shapes.

[0002] A CMC generally exhibits high mechanical properties, including at high temperatures. To promote mechanical properties with a knitted support, it is preferable that the stitches, or "loops," of the knit are substantially filled with slip before the sintering operation.

[0003] The specific nature of ceramic knitting, the ceramic threads of which do not have sufficient deformation capacity to be able to be bent sufficiently to make small-sized meshes, combined with the specific nature of ceramic slip, however makes this filling difficult, in particular when the impregnated knitting constituting the preform is moved or deformed to adopt a complex shape.

[0004] There is therefore a need for a support at least partly composed of a knit, better suited to the manufacture of a CMC.

[0005] The present invention aims to at least partially satisfy this need.

[0006] The invention provides an at least partly ceramic knitted support intended for the manufacture of a CMC, comprising a ceramic knit comprising a repetition of elementary cells, at least a part of said elementary cells being at least partially closed by at least one so-called closing thread, an elementary cell being defined as being the smallest rectangular pattern, which by its repetition forms 70%, or more, of the surface of the knit.

[0007] According to preferred but non-limiting embodiments of the present invention, which may, where appropriate, be combined with each other: - more than 30% on average of the total surface area of ​​said elementary cells is closed by said at least one closing wire; - more than 40%, preferably more than 90%, in number of elementary cells are at least partially closed by a closing wire, preferably by a set of closing wires, said closing wire or all of said closing wires together closing more than 30% of the total surface area of ​​said elementary cells at least partially closed; more than 30%, in number of elementary cells are at least partially closed by a closing wire, preferably by a set of closing wires, said closing wire or all of said closing wires together closing more than 50%, preferably more than 70% of the total surface area of ​​said elementary cells at least partially closed; more than 90%, in number of elementary cells are at least partially closed by a closing wire, preferably by a set of closing wires, said closing wire or all of said closing wires together closing more than 70% of the total surface area of ​​said elementary cells at least partially closed; the ceramic knit comprises, preferably is made of mesh yarn(s) chosen from: - one or more mesh wires comprising more than 95% by mass of oxides, - one or more mesh threads comprising more than 95% by mass of carbides, - one or more mesh threads containing more than 95% by mass of borides, - one or more mesh threads comprising more than 95% by mass of nitrides, - one or more mesh threads comprising more than 95% carbon by mass, - and a mixture of said mesh yarns; the repetition of the elementary cell makes it possible to cover more than 85%, preferably more than 97% of the surface of the knit; the ceramic knit represents more than 5% and less than 25% of the mass of said knitted support; the sealing wires are oriented parallel to each other; a sealing wire, preferably each sealing wire is made of a material selected from a ceramic, an organic product, and mixtures thereof; a sealing wire, preferably each sealing wire is chosen from: - a wire comprising more than 95% by mass of oxides, - a wire containing more than 95% by mass of carbides, - a wire containing more than 95% borides by mass, - a wire comprising more than 95% by mass of nitrides, - a wire containing more than 95% carbon by mass, - and a mixture of said yarns; a sealing wire, preferably each sealing wire, comprises, preferably is made of, a semi-permanent material, present until the sintering of the CMC, and extracted during the sintering of said CMC.

[0008] The invention also relates to a knitted support according to the invention impregnated on at least part of the surface with a slip capable of forming a ceramic matrix after sintering.

[0009] The invention also relates to a knitted preform comprising at least one knitted support, and preferably a plurality of knitted supports, according to the invention.

[0010] Preferably, the knitted preform according to the invention is in the form of a three-dimensional object.

[0011] The invention also relates to a knitted preform according to the invention impregnated on at least part of the surface with a slip capable of forming a ceramic matrix after sintering.

[0012] The invention also relates to a method of manufacturing a ceramic matrix composite using a knitted support according to the invention or a knitted preform according to the invention.

[0013] The invention also proposes a method for manufacturing a ceramic matrix composite according to the invention comprising the following steps:

[0014] a) impregnation, on at least a portion of its surface, of a knitted preform according to the invention (said preform possibly consisting of a knitted support according to the invention), with a slip capable of forming a ceramic matrix after sintering, so as to obtain an impregnated preform;

[0015] b) optionally, consolidation of the impregnated preform, preferably by drying;

[0016] c) sintering the impregnated preform, optionally consolidated, so as to obtain a CMC.

[0017] According to the invention, at least one sealing thread seals at least part of the elementary cells of the knit, called “sealed elementary cells”.

[0018] Surprisingly, the inventors have found that the partial sealing of at least a portion of the elementary cells of the knit by at least one sealing thread allows the slip not to separate from the knit after impregnation, in particular during handling of the impregnated preform thus obtained. This results in a significant improvement in the mechanical properties of the CMC, even when said at least one sealing thread does not contribute significantly, in itself, to the mechanical properties of said CMC.

[0019] The introduction of at least one sealing thread into the elementary cells of a knitted fabric can advantageously be carried out with conventional knitting machines. The manufacturing cost of the CMC is advantageously limited.

[0020] According to preferred but non-limiting embodiments of the present invention, which may, where appropriate, be combined with each other: - the ratio of the median surface area of ​​the meshes of the knitted fabric of the support(s) knitted contained in the knitted preform according to the invention, expressed in cm2 and the maximum size of the particles of the slip, expressed in cm, is greater than 27.84 cm, and preferably less than 696 cm; - the ratio of the median surface area of ​​the meshes of the knitted fabric of the knitted support(s) contained in the knitted preform according to the invention, expressed in cm2 and the median size of the particles of the slip, expressed in cm, is greater than 278.4 cm and less than 13920 cm; - the quantity of ceramic particles and / or ceramic precursors in the slip is greater than 25% and less than 65%, as a percentage by volume based on the volume of said slip.

[0021] The invention also relates to an impregnated preform obtained at the end of step a) of a method according to the invention.

[0022] The invention also relates to an impregnated preform obtained at the end of step b) of a method according to the invention.

[0023] The invention finally relates to a CMC obtained or capable of having been obtained by a method according to the invention.

[0024] According to preferred but non-limiting embodiments of the present invention, which may, where appropriate, be combined with each other: - the CMC presents the imprint of the sealing wires in a semi-permanent material having been extracted during sintering; - CMC is made up of oxides for more than 90% of its mass; - the CMC is made up of more than 90% of its mass from a chosen material among a carbide, a boride, a nitride, carbon and their mixtures; - the CMC comprises a knitted preform according to the invention composed for more than 90% by mass of a material chosen from: - a carbide, - a boride, - a nitride, - carbon, - and their mixtures, and

[0025] a matrix composed of oxides for more than 90% by mass; - the CMC comprises a knitted preform according to the invention composed of oxides for more than 90% of its mass, and a matrix composed for more than 90%, by mass, of a material chosen from carbon, carbides, borides, nitrides, and their mixtures. Definitions

[0026] A “fiber” is a filament whose length is greater than 5 times its equivalent diameter.

[0027] The “equivalent diameter” of a fiber is the diameter of a disk of the same surface area as its cross-section at mid-length.

[0028] A “single yarn” is an assembly of fibers which, in cross-section, comprises more than 10 and preferably less than 500,000 fibers, and whose length is greater than 5 times the diameter.

[0029] An “assembled yarn” is an assembly of single yarns which, in cross-section, preferably comprises more than 2 and preferably less than 500 single yarns.

[0030] A “thread” means a single thread or an assembled thread.

[0031] A “stitch” is classically a loop of thread interlaced at the top and bottom.

[0032] A “knit” is classically a textile composed of a plurality of linked stitches between them.

[0033] A “knit yarn” is the yarn forming all or part of the stitches of the knitted fabric. A knitted fabric may comprise a single knit yarn, in particular when said knitted fabric is manufactured using a weft knitting method. A knitted fabric may also comprise several knit yarns, in particular when said knitted fabric is manufactured using a warp knitting technique.

[0034] A “ceramic” material is a material that is neither metallic nor organic. For the purposes of the present invention, carbon, glasses and amorphous silica are considered to be ceramic materials.

[0035] A set of sealing wires oriented in substantially the same direction is a set of unidirectional wires.

[0036] The 50th (D50) and 99.5th (D99>5) percentiles or "percentiles" of a powder are the particle sizes corresponding to the percentages, by volume, of 50% and 99.5% respectively, on the cumulative particle size distribution curve of the powder particles, the particle sizes being classified in ascending order. For example, 50%, by volume, of the particles of the powder have a size less than D50 and 50% of the particles by volume have a size greater than D50. The percentiles can be determined using a particle size distribution carried out using a laser particle size analyzer.

[0037] The "median size" of the particles of a powder is called the 50th percentile, or D50 of said powder.

[0038] The “maximum size” of the particles of a powder is called the 99.5 percentile, or D995 of said powder. Detailed description Knitted support

[0039] Preferably, more than 40%, preferably more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, of preferably more than 95%, preferably substantially 100% in number of the elementary cells of the knitted fabric of the knitted support are at least partially closed by a closing thread, preferably by a set of closing threads, preferably unidirectional.

[0040] More preferably, said sealing wire or all of said sealing wires together seal(s) more than 30% of the total surface area of ​​said at least partially sealed elementary cells.

[0041] In particular, said sealing wire or all of said sealing wires together seal(s) more than 40%, preferably more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80% of the total surface area of ​​said at least partially sealed elementary cells.

[0042] Preferably, more than 40%, preferably more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably substantially 100% in number of the elementary cells of the knit are at least partially closed by a closing thread, preferably by a set of closing threads, preferably unidirectional, said closing thread or all of said closing threads together closing more than 30%, preferably more than 40%, preferably more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80% of the total surface area of ​​said at least partially closed elementary cells.

[0043] The ceramic knit comprises, preferably consists of, mesh yarn(s) chosen from: - One or more mesh threads comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides, - One or more mesh threads comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbides, - One or more mesh threads comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of borides, - One or more mesh threads comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of nitrides, - One or more mesh threads comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbon, - And a mixture of said mesh threads.

[0044] Preferably, said mesh thread(s) comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides are chosen from: - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 + A12O3 + ZrO2 > 50%, preferably SiO2 + A12O3 + ZrO2 > 60%, or even SiO2 + A12O3 + ZrO2 > 70%, or even SiO2 + A12O3 + ZrO2 > 80%, or even SiO2 + A12O3 + ZrO2 > 90%, in percentage by mass, - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 > 70%, preferably SiO2 > 80%, preferably SiO2 > 90%, or even SiO2 > 99%, as a percentage by mass, - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that A12O3 > 65%, preferably Al2 O3 > 70%, or even A12O3 > 80%, or even A12O3 > 90%, or even A12O3 > 95%, as a percentage by mass, - and mixtures thereof.

[0045] More preferably, at least a portion, preferably said yarn or said mesh yarns are: - one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of alumina, and / or - one or more threads composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and / or

[0046] - one or more threads composed of more than 95%, preferably more than 98%, of preferably more than 99%, preferably substantially 100% by mass of mullite, and / or - one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of mullite and corundum, and / or - one or more threads composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of glass, preferably washed.

[0047] Preferably, said mesh wire(s) comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbides are: - one or more threads composed of more than 95%, preferably more than 98%, of preferably more than 99%, preferably substantially 100% by mass of silicon carbide,

[0048] - one or more threads composed of more than 95%, preferably more than 98%, of preferably more than 99%, preferably substantially 100% by mass of boron carbide,

[0049] - and mixtures thereof.

[0050] Preferably, said mesh wire(s) comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of nitrides are one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silicon nitride.

[0051] Preferably, the mesh yarn(s) have a linear mass greater than 20 g / km, preferably greater than 25 g / km, preferably greater than 30 g / km and preferably less than 300 g / km, preferably less than 250 g / km, preferably less than 200 g / km. The linear mass in g / km is conventionally called “tex”.

[0052] Preferably, the knit has a surface mass greater than 50 g / m2, preferably greater than 100 g / m2, and preferably less than 300 g / m2, preferably less than 200 g / m2.

[0053] Preferably, the knit has a row density of 2 to 5 rows per centimeter and a column density of 1 to 3 columns per centimeter.

[0054] Preferably, the repetition of the elementary cell makes it possible to cover more than 80%, preferably more than 85%, preferably more than 90%, preferably more than 92%, preferably more than 94%, preferably more than 95%, preferably more than 97%, preferably more than 99% of the surface of the knit, the remainder being occupied by singular points, which can conventionally exist in a knit, such as for example increases (simple or baguettes), decreases (simple or baguettes), arrows, selvedges, networks or chains.

[0055] Preferably, the ceramic knit represents more than 5% and / or less than 25% of the mass of the knitted support.

[0056] The knit is preferably chosen from a jersey knit, an interlock knit, a garter stitch knit, a rice stitch knit, an English rib knit, a 1x1 rib stitch knit, a satin knit, a charmeuse knit.

[0057] A knitted support according to the present invention may comprise several different knits linked together, that is to say having different elementary cells, said knits being able in particular to be chosen from the preceding list, each knit defining a zone of said knitted support. It is understood that the present invention also relates to such a knitted support, provided that at least one of said zones is constituted by a knit as previously described of which at least a part of its elementary cells is at least partially sealed by at least one sealing wire as previously described.

[0058] Preferably, said zone conforms to the preferred characteristics previously described in relation to the knitted support. Sealing wires

[0059] Preferably, a sealing wire, preferably each sealing wire is a single wire or an assembled wire.

[0060] The sealing thread may be a filler, a float, a unidirectional thread, preferably a unidirectional thread.

[0061] Preferably, the sealing wire, preferably each sealing wire, is a unidirectional wire.

[0062] Preferably, the sealing wire, preferably each sealing wire, is distinct from a mesh wire.

[0063] Preferably the sealing thread, preferably each sealing thread, has a linear mass greater than 100 tex, preferably greater than 300 tex, preferably greater than 500 tex, preferably greater than 600 tex, and preferably less than 3000 tex, preferably less than 2000 tex, preferably less than 1500 tex.

[0064] Preferably, a sealing thread, preferably each sealing thread, is inserted into the stitches of the sealed elementary cells of the knit, preferably by depositing and trapping in the stitches, without being taken up by the stitches.

[0065] The number of sealing thread(s) sealing the elementary cells is a function of the surface area of ​​said elementary cell and the linear mass of the sealing thread(s). Preferably, the sealing threads are oriented parallel to each other and preferably in the direction of the rows or columns of mesh.

[0066] In one embodiment, a sealing thread, preferably each sealing thread, is made of a material identical to the material of the mesh threads of the knit.

[0067] In a preferred embodiment, a sealing yarn, preferably each sealing yarn, is made of a material different from the material of the mesh yarns of the knit.

[0068] A sealing wire, preferably each sealing wire, is made of a material selected from a ceramic, an organic product, and mixtures thereof. Preferably, a sealing wire, preferably each sealing wire, is made of a ceramic material.

[0069] In one embodiment, a sealing wire, preferably each sealing wire, comprises, preferably is made of, a semi-permanent material, i.e. present until the sintering of the CMC, and extracted during the sintering of said CMC, preferably chosen from a polyvinyl alcohol insoluble in the solvent of the slip, xanthan, polyethylene glycol, nylon, cotton, aramid, kevlar and mixtures thereof.

[0070] When extracted, the sealing wire, preferably each sealing wire, leaves at least some of their footprints in the CMC.

[0071] In a preferred embodiment, a sealing wire, preferably each sealing wire, is selected from: - a wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides, - a wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbides, - a wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of borides, - a wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of nitrides, - a wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbon, - and a mixture of said threads.

[0072] Preferably, a sealing wire, preferably each sealing wire comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides are: - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 + A12O3 + ZrO2 > 50%, preferably SiO2 + A12O3 + ZrO2 > 60%, or even SiO2 + A12O3 + ZrO2 > 70%, or even SiO2 + A12O3 + ZrO2 > 80%, or even SiO2 + A12O3 + ZrO2 > 90%, as a percentage by mass, and / or - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 > 70%, preferably SiO2 > 80%, preferably SiO2 > 90%, or even SiO2 > 99%, as a percentage by mass, and / or - one or more wires comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that A12O3 > 65%, preferably Al2 O3 > 70%, or even A12O3 > 80%, or even A12O3 > 90%, or even A12O3 > 95%, as a percentage by mass.

[0073] More preferably, at least a portion, preferably said thread or threads shutters are: - one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of alumina, and / or - one or more threads composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and / or

[0074] - one or more threads composed of more than 95%, preferably more than 98%, of preferably more than 99%, preferably substantially 100% by mass of mullite, and / or - one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of mullite and corundum, and / or - one or more threads composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of glass, preferably washed.

[0075] Preferably, said sealing wire(s) comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of carbides are: - one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silicon carbide,

[0076] - one or more threads composed of more than 95%, preferably more than 98%, of preferably more than 99%, preferably substantially 100% by mass of boron carbide,

[0077] - and mixtures thereof.

[0078] Preferably, said sealing wire(s) comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of nitrides are one or more wires composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silicon nitride.

[0079] In a first embodiment, said mesh yarn(s) of the knit are made of a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and one, preferably each, sealing yarn is a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides.

[0080] Preferably in this first embodiment: - the said mesh yarn(s) of the knit are composed for more than 90% of preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and one, preferably each sealing wire is composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98% of amorphous silica; - said mesh yarn(s) of the knit are composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and one, preferably each, sealing yarn is composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of glass, preferably washed; - said mesh yarn(s) of the knit are composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and one, preferably each, sealing yarn is composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of alumina; - said mesh yarn(s) of the knit are composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and one, preferably each, sealing yarn is composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of mullite.

[0081] In a second embodiment, said mesh yarn(s) of the knit are made of a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a carbide and one, preferably each, sealing yarn is a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a carbide.

[0082] Preferably in this second embodiment, the said mesh yarn(s) of the knit are composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silicon carbide, and one, preferably each, sealing yarn is composed of more than 95%, preferably more of 98%, preferably more than 99%, preferably substantially 100% by mass of silicon carbide.

[0083] In a third embodiment, said mesh yarn(s) of the knit are made of a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides, and one, preferably each, sealing yarn is a material comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a carbide.

[0084] Preferably in this third embodiment, the said mesh yarn(s) of the knit are composed of more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 90%, preferably more than 95%, preferably more than 98%, of amorphous silica, and one, preferably each, sealing yarn is composed of more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silicon carbide.

[0085] The knitted support according to the invention can be manufactured according to techniques known from the state of the art. In particular, the knitted support according to the invention can be manufactured by simultaneously knitting a plurality of mesh yarns and / or a plurality of closure yarns. The stitches of the knitted fabric can thus be formed from a plurality of mesh yarns. Similarly, a plurality of closure yarns can be introduced into the knitted fabric. All combinations are possible, for example a plurality of mesh yarns with a single closure yarn, but also a plurality of closure yarns with a single mesh yarn, or a plurality of mesh yarns with a plurality of closure yarns. Knitted preform

[0086] A knitted preform according to the invention comprises at least one knitted support according to the invention.

[0087] Preferably, the knitted preform according to the invention comprises several layers of knitting, preferably consists of several layers of knitting, at least one of which is a knitted support according to the invention.

[0088] More preferably, the knitted preform according to the invention consists of several knitted supports according to the invention, preferably arranged in layers.

[0089] In one possible embodiment, however, the knitted preform according to the invention is the knitted support according to the invention as described previously.

[0090] The set of sealing threads is preferably a set of unidirectional threads when the knitted preform according to the invention comprises several knitted supports according to the invention, preferably arranged in layers, preferably consists of several knitted supports according to the invention, preferably arranged in layers.

[0091] The knitted preform according to the invention can be manufactured according to techniques known in the state of the art.

[0092] The knitted preform according to the invention is preferably put into a three-dimensional form before or after impregnation, preferably before impregnation, for example by being pressed onto a mold, and is in the form of a three-dimensional object. Slush

[0093] The slip is distinguished in particular from the organic compositions used to manufacture a polymer matrix composite, such as those described in WO2018189497 or DE102014000153, said organic compositions having a viscosity generally higher than that of the slip, which promotes the retention of said organic composition inside the meshes of the knit.

[0094] Furthermore, when the polymer matrix is ​​created, for example by crosslinking the organic composition, the integrity of said polymer matrix and the bond between said polymer matrix and the meshes of the knit are stronger than for a ceramic matrix precursor slip.

[0095] Preferably, the ratio of the median surface area of ​​the meshes of the knitted support(s) that the knitted preform comprises, expressed in cm2 and the maximum particle size of the slip, expressed in cm, is greater than 27.84 cm, preferably greater than 34.8 cm, preferably greater than 46.4 cm, preferably greater than 69.6 cm, preferably greater than 92.8 cm, and preferably less than 696 cm, preferably less than 464 cm.

[0096] Preferably, the ratio of the median surface area of ​​the meshes of the knitted support(s) that the knitted preform comprises, expressed in cm2 and the median size of the particles of the slip, expressed in cm, is greater than 278.4 cm, preferably greater than 348 cm, preferably greater than 464 cm, and preferably less than 13920 cm, preferably less than 6960 cm, preferably less than 5568 cm.

[0097] The manufacture of slip is well known to those skilled in the art. Slip is conventionally a suspension, for example of an aqueous base or an organic solvent, containing

[0098] - ceramic particles and / or precursors of ceramic particles, that is, compounds that transform into ceramic particles during the manufacture of CMC, and in particular during sintering, and

[0099] - optionally dispersants, plasticizers, lubricants, gelling agents and / or temporary binders.

[0100] The composition of the slip, the size distribution of the ceramic particles or ceramic precursors and the mineral filler of the slip are adapted to the type of fibers and the shaping technique.

[0101] Preferably, the amount of ceramic particles and / or ceramic precursors in the slip is greater than 25%, preferably greater than 30%, and / or less than 65%, preferably less than 60%, as a volume percentage based on the volume of said slip.

[0102] Preferably, the solvent for the slip is water.

[0103] Preferably, more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of the ceramic particles and / or precursors of ceramic particles are oxides and / or carbides and / or nitrides and / or borides, in particular of the type described above.

[0104] Preferably, when the knitted preform is composed of oxides for more than 90%, preferably for more than 95%, preferably for more than 99%, by mass, the ceramic particles of the slip comprise more than 90%, preferably for more than 95%, preferably for more than 97%, preferably for more than 98%, preferably for more than 99%, preferably for more than 99.5% by mass of oxides.

[0105] Preferably, when the knitted preform is composed of carbides and / or nitride and / or borides for more than 90%, preferably for more than 95%, preferably for more than 99% by mass, the ceramic particles of the slip comprise more than 90%, preferably for more than 95%, preferably for more than 97%, preferably for more than 98%, preferably for more than 99%, preferably for more than 99.5% by mass of carbides and / or nitride and / or borides. Impregnation

[0106] The slip, capable of forming a ceramic matrix after sintering, can be impregnated on at least part of the surface, preferably on the entire surface of the knitted preform according to the invention or of the knitted support according to the invention, in particular by direct lamination, by infusion, injection, infiltration or deposition, under atmospheric pressure or under higher pressure or under vacuum, at room temperature or at higher temperature.

[0107] More preferably, more than 90%, or even more than 95% or even substantially the entire volume of the knitted preform according to the invention is impregnated with the slip capable of forming a ceramic matrix after sintering.

[0108] In a particular embodiment, in step a), several knitted supports according to the invention are individually impregnated, then assembled so as to obtain an impregnated preform. Consolidation of the impregnated preform

[0109] In optional step b), the impregnated preform can be consolidated according to any known technique. Preferably, the impregnated preform is consolidated by drying or by freeze-drying, preferably by drying.

[0110] The definition of the drying parameters does not pose any problem to those skilled in the art.

[0111] In one embodiment, in particular when the slip contains a thermoreversible hydrocolloid, the drying is carried out at a temperature at which said hydrocolloid is present in the form of a gel.

[0112] In one embodiment, the drying is preferably carried out at a temperature above 50°C and below 80°C, for a time greater than 1 hour and preferably less than 20 hours, preferably in an atmosphere having a relative humidity level greater than 20% and less than 70%.

[0113] Sintering of the optionally consolidated impregnated preform

[0114] In step c), the impregnated, optionally consolidated, preform is sintered.

[0115] A person skilled in the art knows how to determine the sintering conditions, in particular the holding temperature, the atmosphere, the holding time at the holding temperature, depending on the nature of the ceramic particles and the knitted support or the knitted preform.

[0116] Preferably, the sintering temperature is greater than 500°C, and preferably less than 2300°C.

[0117] In particular when the knitted support or the knitted preform is made of an oxide and the ceramic particles have a chemical analysis such that SiO2 > 90% by mass, the sintering temperature is preferably greater than 800°C and preferably less than 1000°C, the sintering preferably taking place in air and preferably at a pressure of 1 bar, the holding time being preferably greater than 1 hour and preferably less than 10 hours.

[0118] In particular when the knitted support or the knitted preform is made of an oxide and the ceramic particles have a chemical analysis such that A12O3 > 90% by mass, the sintering temperature is preferably greater than 1000°C and preferably less than 1300°C, the sintering preferably taking place in air and preferably at a pressure of 1 bar, the holding time being preferably greater than 1 hour and preferably less than 10 hours.

[0119] In particular when the knitted support or the knitted preform is 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 greater than 1400°C, and preferably less than 2300°C, the sintering taking place in 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.

[0120] In one embodiment, the sintering is carried out in situ, when using the impregnated preform, optionally consolidated. Preferably, in said embodiment, the impregnated preform is consolidated. CMC

[0121] The invention also relates to a CMC obtained or capable of having been obtained by a method according to the invention.

[0122] This CMC is remarkable in that it has a ceramic matrix and at least one ceramic knit, preferably a ceramic knitted preform according to the invention, preferably having one or more of the preferences previously described.

[0123] In one embodiment, said CMC has the imprint of the sealing wires in a semi-permanent material having been extracted during sintering.

[0124] The CMC according to the invention may also have one or more of the following optional characteristics: - the CMC preferably has an open porosity, measured by imbibition, according to the principle of Archimedes' thrust, greater than 10%, preferably greater than 15%, preferably greater than 20%, preferably greater than 25%, and preferably less than 50%, preferably less than 45%, preferably less than 40%; - the CMC has an apparent density greater than 0.8 g / cm3 and preferably less than 6.00 g / cm3.

[0125] In a first embodiment, the CMC consists of oxides for more than 90% of its mass, preferably for more than 95% of its mass, preferably for more than 98% of its mass, preferably for more than 99% of its mass, preferably for more than 99.5% of its mass.

[0126] In said first embodiment, the CMC has one or more of the following optional and preferred features: - the knitted preform of the CMC is composed of oxides for more than 90%, preferably for more than 95%, preferably for more than 97%, preferably for more than 98%, preferably for more than 99%, preferably for more than 99.5% of its mass; - at least a part, preferably all of the sealing wires of the sealed preform are:

[0127] - yarns comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 + A12O3 + ZrO2 > 50%, preferably SiO2 + A12O3 + ZrO2 > 60%, or even SiO2 + A12O3 + ZrO2 > 70%, or even SiO2 + A12O3 + ZrO2 > 80%, or even SiO2 + A12O3 + ZrO2 > 90%, in percentage by mass, and / or

[0128] - yarns comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such as SiO2 > 70%, preferably SiO2 > 80%, preferably SiO2 > 90%, or even SiO2 > 99%, in percentage by mass, and / or

[0129] - yarns comprising more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of oxides and having a chemical analysis such that A12O3 > 65%, preferably A12O3 > 70%, or even A12O3 > 80%, or even A12O3 > 90%, or even A12O3 > 95%, as a percentage by mass. - at least a portion, preferably all of the sealing wires of the sealed preform are: - wires comprising more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of alumina, and / or - yarns comprising more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of silica, preferably composed of more than 95%, preferably more than 98%, of amorphous silica, and / or - wires comprising more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of mullite and corundum, and / or - yarns comprising more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by mass of glass, preferably washed, and / or - a mixture of said threads. - the matrix of said CMC is composed of oxides for more than 90%, preferably for more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass, preferably, the matrix of the CMC is substantially composed of oxides; - the CMC matrix comprises A12O3 and / or SiO2 and / or ZrO2 and / or Cr2O3, preferably the CMC matrix comprises A12O3 and SiO2; - in one embodiment, the content of A12O3 in the CMC matrix, in percentage by mass based on the mass of the matrix, is greater than 65%, preferably greater than 70%; - in one embodiment, the SiO2 content in the CMC matrix, as a percentage by mass based on the mass of the matrix, is greater than 15%, preferably greater than 20% and / or less than 35%, preferably less than 30%; - in one embodiment, the SiO2 content in the CMC matrix, as a percentage by mass based on the mass of the matrix, is greater than 60%, preferably greater than 70%, preferably greater than 80%; - in one embodiment, the content of oxides other than Al2O3 and SiO2 in the CMC matrix, as a percentage by mass based on the mass of the matrix, is less than 3%, preferably less than 2%, preferably less than 1%; - in one embodiment, the total content of Al2O3 and SiO2 in the CMC matrix is ​​greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, as a percentage by mass based on the mass of the matrix; - in one embodiment, the silica of the CMC matrix is ​​amorphous; - preferably, the CMC has a total mass content of SiO2+Al2O3+ZrO2 +Cr2O3 greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, preferably greater than 97%, preferably greater than 97%. More preferably, the CMC has a total mass content of SiO2+Al2O3 greater than 80%, preferably greater than 85%, preferably greater than 90%, preferably greater than 95%, preferably greater than 97%, preferably greater than 97%.

[0130] In a second embodiment, the CMC consists of more than 90% of its mass, preferably more than 95% of its mass, preferably more than 98% of its mass, preferably more than 99% of its mass, preferably more than 99.5% of its mass of a material chosen from a carbide, a boride, a nitride, carbon and their mixtures.

[0131] In said second embodiment, the CMC has one or more of the following optional and preferred features: - the knitted preform of the CMC is composed of more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a material chosen from: - a carbide, preferably silicon carbide, boron carbide and mixtures thereof, - a boride, - a nitride, preferably a silicon nitride, - carbon, - and their mixtures; - the matrix of said CMC is composed of more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a material chosen from carbides, borides, nitrides and their mixtures; - preferably, the CMC matrix comprises, or is made of, silicon carbide, silicon nitride, or a mixture thereof.

[0132] In a third embodiment, the CMC comprises a knitted preform composed of more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a material chosen from: - a carbide, preferably silicon carbide, boron carbide and mixtures thereof, - a boride, - a nitride, preferably a silicon nitride, - carbon, - and their mixtures, and

[0133] a matrix composed of oxides for more than 90%, preferably for more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass, preferably comprising, or even consisting of Al2 O3 and / or SiO2 and / or ZrO2 and / or Cr2O3, preferably comprising or even consisting of Al2O3 and SiO2.

[0134] In a fourth embodiment, the CMC comprises a knitted preform composed of oxides for more than 90%, preferably for more than 95%, preferably for more than 97%, preferably for more than 98%, preferably for more than 99%, preferably for more than 99.5% of its mass, and a matrix composed for more than 90%, preferably for more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5% by mass of a material chosen from carbon, carbides, borides, nitrides, and mixtures thereof. Examples

[0135] The following non-limiting examples are given for the purpose of illustrating the invention.

[0136] The following raw materials are used:

[0137] - a solution of LUDOX AS40 colloidal silica,

[0138] - a powder of amorphous silica particles, having a mass purity of greater than 99.5%, a median size equal to 1.3 pm and a 99.5 percentile equal to 4 pm,

[0139] - polyethylene glycol PEG 4000 in liquid form and whose PEG 4000 concentration is equal to 50% by mass, the remainder being water,

[0140] - KELZAN® xanthan gum marketed by the company CP Kelco,

[0141] - for example 1, two Tl knits in jersey-type gathered stitch in yarns of Quartzel® with a grammage equal to 120 g / m2, a row density equal to 3.43 rows per centimeter and a column density equal to 2.1 columns per centimeter, rectangular in shape with a length equal to 300 mm and a width equal to 300 mm, manufactured by the company Saint-Gobain Performance Plastics, said Quartzel® threads bearing the reference C9 33 Z20 QS1318 and being marketed by the company Saint-Gobain Quartz. The texture of this knit is described in [Fig.l]. [Fig.2] is a representation of a knit Tl in which the reference 1 represents the Quartzel® threads and in which the elementary cell of this knit is illustrated by the dotted rectangle SL The repetition of this elementary cell makes it possible to cover 100% of the total surface of the knit.

[0142] - for example 2, two knitted supports ST each composed of a T2 knit identical to the Tl knit and of sealing threads represented in [Fig.3] by gray lines 2, said sealing threads being Quartzel® threads of reference C14 640 QS1318 marketed by the company Saint-Gobain Quartz, deposited in the direction of the rows of stitches, without support in the stitches, said threads being trapped in said stitches.

[0143] The total weight of each knitted support is equal to 1000g / m2 for a mesh density equivalent to that of the T1 knit, said yarns being oriented substantially all in the same direction (that of the rows of stitches), as illustrated in [Fig.3]. The texture of this knitted support is described in [Fig.4].

[0144] The sealing rate is the ratio between the surface S2 occupied by all the Quartzel® sealing wires and the surface SI of the elementary cell previously described, as illustrated in [Fig.5]. According to example 2, it is thus calculated that 59% of the total surface of the elementary cells is sealed by the sealing wires. In this example, 100% of the elementary cells are sealed by said wires.

[0145] Example 1, comparative, is carried out according to the following method.

[0146] In step a), a slip is prepared in the following manner.

[0147] In a jar with a volume equal to 5 liters, 825 g of LUDOX AS40 are placed, then 950 g of water, then 44 g of PEG 4000, then 4.4 g of xanthan gum, then 1870 g of amorphous silica powder, and finally 2860 g of a powder of alumina beads with a median size equal to 6 mm. The jar is closed, then it is rotated on a jar turner at a rotation speed equal to 50 rpm for 12 hours.

[0148] The beads are then extracted and the slip is filtered through a sieve with an opening of 190 microns. The slip thus produced is then placed in a tank.

[0149] Each knitted fabric T1 is fully immersed, first on the front and then on the back, in the slip tank for 10 seconds, then the knitted fabric T1 impregnated with slip is removed from the tank and placed on a plastic sheet. A second plastic sheet is then placed on the impregnated knitted fabric, and the upper surface of this second plastic sheet is scraped using a scraper so as to evenly distribute the slip within the knitted fabric T1 and to remove the excess slip.

[0150] Then each impregnated Tl knit is stripped of its plastic sheets.

[0151] Next, an impregnated T1 knit is placed on the surface of a support for giving the knit a shape, said support being covered with a plastic. Then, the second impregnated T1 knit is placed on the first impregnated T1 knit. Then a plastic sheet is placed and the upper surface of this second plastic sheet is scraped using a scraper.

[0152] Immediately after scraping, the assembly of the two impregnated Tl knits forming the impregnated preform is stripped of the upper plastic sheet.

[0153] In step b), the impregnated preform placed on its support is placed in an electric oven and dried for 12 hours at 50°C in air having a relative humidity equal to 30%.

[0154] After drying, when handling the consolidated preform, the dried matrix separates from the consolidated preform, creating matrix-free areas, which is detrimental to the final properties of the CMC.

[0155] Example 2, according to the invention, is carried out according to the following method.

[0156] Steps a), b) and the slip are identical to those of example 1) at difference that two ST knitted supports were used in place of the two TL knits

[0157] At the end of step b), after drying, and contrary to what was observed for example 1, the dried matrix does not separate from the consolidated preform obtained with the two knitted supports ST during its handling.

[0158] In step c), the consolidated impregnated preform is placed on a cordierite plate and sintered in air using the following cycle so as to obtain a CMC:

[0159] - rise from 20°C to 850°C at a speed equal to 100°C / h

[0160] - maintain at 850°C for 6 hours

[0161] - descent at a speed equal to 100°C / h.

[0162] The method of example 2 according to the invention is remarkable in that it allows the production of a CMC from a knitted support according to the invention allowing good retention of the ceramic matrix.

Claims

Claims

1. Knitted support at least partly ceramic intended for the manufacture of a CMC, comprising a ceramic knit comprising a repetition of elementary cells, at least a part of said elementary cells being at least partially closed by at least one closing wire, an elementary cell being defined as being the smallest rectangular pattern, which by its repetition forms 70%, or more, of the surface of the knit.

2. Knitted support according to the preceding claim, in which more than 30% on average of the total surface area of ​​said elementary cells is closed by said at least one closing thread,

3. Knitted support according to the preceding claim, in which more than 40% in number of elementary cells are at least partially closed by a closing thread, preferably by a set of closing threads, said closing thread or all of said closing threads together closing more than 30% of the total surface area of ​​said at least partially closed elementary cells.

4. Knitted support according to the preceding claim, in which more than 90% by number of elementary cells are at least partially closed by a closing thread, preferably by a set of closing threads, said closing thread or all of said closing threads together closing more than 30% of the total surface area of ​​said at least partially closed elementary cells.

5. Knitted support according to claim 1, in which more than 30% by number of elementary cells are at least partially closed by a closing thread, preferably by a set of closing threads, said closing thread or all of said closing threads together closing more than 50% of the total surface area of ​​said at least partially closed elementary cells.

6. Knitted support according to the preceding claim, in which more than 30% in number of elementary cells are at least partially closed by a closing thread, preferably by a set of closing threads, said closing thread or all of said closing threads together closing more than 70% of the total surface area of ​​said at least partially closed elementary cells.

7. Knitted support according to one of the preceding claims, in which more than 90% by number of elementary cells are at least par- partially sealed by a sealing wire, preferably by a set of sealing wires, said sealing wire or all of said sealing wires together sealing more than 70% of the total surface area of ​​said elementary cells at least partially sealed.

8. Knitted support according to one of the preceding claims, in which the ceramic knit comprises, preferably consists of, mesh yarn(s) chosen from: - one or more mesh yarns comprising more than 95% by mass of oxides, - one or more mesh yarns comprising more than 95% by mass of carbides, - one or more mesh yarns comprising more than 95% by mass of borides, - one or more mesh yarns comprising more than 95% by mass of nitrides, - one or more mesh yarns comprising more than 95% by mass of carbon, - and a mixture of said mesh yarns.

9. Knitted support according to one of the preceding claims, in which the repetition of the elementary cell makes it possible to cover more than 85%.

10. Knitted support according to the preceding claim, in which the repetition of the elementary cell makes it possible to cover more than 97% of the surface of the knit.

11. Knitted support according to one of the preceding claims, in which the ceramic knit represents more than 5% and less than 25% of the mass of said knitted support.

12. Knitted support according to one of the preceding claims, in which the sealing threads are oriented parallel to each other.

13. Knitted support according to one of the preceding claims, in which a sealing thread, preferably each sealing thread is made of a material chosen from a ceramic, an organic product, and their mixtures.

14. Knitted support according to the preceding claim, in which a sealing thread, preferably each sealing thread is chosen from: - a thread comprising more than 95% by mass of oxides, - a thread comprising more than 95% by mass of carbides, - a wire comprising more than 95% by mass of borides, - a wire comprising more than 95% by mass of nitrides, - a wire comprising more than 95% by mass of carbon, - and a mixture of said wires.

15. Knitted support according to one of claims 1 to 12, in which a sealing thread, preferably each sealing thread, comprises, preferably is made of, a semi-permanent material, present until sintering of the CMC, and extracted during sintering of said CMC.

16. Knitted support according to one of the preceding claims, impregnated on at least part of the surface with a slip capable of forming a ceramic matrix after sintering.

17. A knitted preform comprising at least one knitted support, and preferably a plurality of knitted supports, according to any one of the preceding claims.

18. Knitted preform according to the preceding claim, in the form of a three-dimensional object.

19. Knitted preform according to any one of claims 17 to 18, impregnated on at least part of the surface with a slip capable of forming a ceramic matrix after sintering.

20. A method of manufacturing a ceramic matrix composite using a knitted preform according to any one of claims 17 to 19.

21. Manufacturing method according to the preceding claim, comprising the following steps: a) impregnation, on at least a portion of its surface, of a knitted preform according to one of claims 17 to 19, with a slip capable of forming a ceramic matrix after sintering, so as to obtain an impregnated preform; b) optionally, consolidation of the impregnated preform, preferably by drying; c) sintering of the impregnated preform, optionally consolidated, so as to obtain a CMC.

22. Manufacturing method according to one of claims 20 to 21, in which the ratio of the median surface area of ​​the meshes of the knitted fabric of the knitted support(s) contained in the knitted preform according to one of claims 17 to 19, expressed in cm2 and the maximum particle size of the slip, expressed in cm, is greater than 27.84 cm and preferably less than 696 cm.

23. Manufacturing method according to the preceding claim, in which the ratio of the median surface area of ​​the meshes of the knitted fabric of the knitted support(s) contained in the knitted preform according to one of claims 17 to 19, expressed in cm2 and the median size of the particles of the slip, expressed in cm, is greater than 278.4 cm and less than 13920 cm.

24. A manufacturing method according to one of the three immediately preceding claims, wherein the amount of ceramic particles and / or ceramic precursors in the slip is greater than 25% and less than 65%, as a volume percentage based on the volume of said slip.

25. Impregnated preform obtained at the end of step a) of a method according to one of the four immediately preceding claims.

26. Consolidated impregnated preform obtained at the end of step b) of a method according to one of claims 21 to 24.

27. ​​CMC obtained or capable of being obtained by a process according to one of claims 20 to 24.

28. CMC according to the preceding claim, having the imprint of the sealing wires in a semi-permanent material having been extracted during sintering.

29. CMC according to any one of the two immediately preceding claims, consisting of oxides, for more than 90% of its mass.

30. CMC according to any one of claims 27 to 28, consisting, for more than 90% of its mass, of a material chosen from a carbide, a boride, a nitride, carbon and their mixtures.

31. CMC according to any one of claims 27 to 28, comprising a knitted preform according to one of claims 17 to 19 composed for more than 90% by mass of a material chosen from: - a carbide, - a boride, - a nitride, - carbon, - and their mixtures, and a matrix composed of oxides for more than 90% by mass.

32. CMC according to any one of claims 27 to 28, comprising a knitted preform according to one of claims 17 to 19 composed of oxides for more than 90% of its mass, and a matrix composed for more than 90%, by mass, of a material chosen from carbon, carbides, borides, nitrides, and their mixtures.

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