Densely Fried Product

Abstract

Sintered product - having a relative density greater than 90%, - consisting of more than 80% of its volume of a stack of flat ceramic plates (10), the whole of said plates having an average thickness of less than 3 µm, - having a width (l) greater than 50 mm, and - comprising more than 20% alumina, as a percentage based on the mass of the product,

Description

Technical field The invention relates to a method for manufacturing a dense, wide-width sintered product. The invention also relates to such a product. State of the art WO2015189659 describes a process for manufacturing a dense product obtained by a process comprising a directed freezing step of a slip containing ceramic wafers, followed by a compression step. More specifically, the freezing results from the presence of two temperature gradients F and F' (see Figure 2) oriented perpendicular to the surface of a slip layer B, poured onto a horizontal surface. This progression orients the wafers P parallel to each other and substantially perpendicular to the horizontal surface. The removal of ice crystals leads to a macroporous preform M. This preform is then compressed in a direction perpendicular to the general plane of the wafers before being sintered. This sintered product is dense and exhibits good mechanical properties, notably good toughness.Its smallest dimension, that is to say its thickness e, is conventionally measured along the direction of compression. However, the process implemented in WO2015189659 does not allow for products with a width greater than 50 mm. Indeed, freezing requires that the slip layer extending horizontally be thin, and in particular less than 50 mm. The compression therefore occurs in a direction parallel to the general plane of this layer. The width of the resulting product, measured (like the length) in a plane parallel to the plane of the plates, is thus approximately equal to the thickness of the slip layer and is therefore limited. Dimension 1' shown in Figure 2 illustrates this problem. There is a need for a sintered product that does not exhibit brittle behavior, i.e. such that the KjC toughness is greater than the Kic toughness, said toughnesses being determined by the SENB method (“Single-Edge Notched Beam” in English), preferably with a toughness similar to, or even greater than, that of the products of WO2015189659, but with a width greater than 50 mm. One object of the invention is to satisfy, at least partially, this need. Summary of the invention The invention relates to a method for manufacturing a sintered product, said method comprising the following steps: a) preparation of a slip comprising a set of ceramic particles suspended in a liquid phase, the set of ceramic particles representing more than 90% of the volume of the suspended particles and comprising: - a first particulate fraction consisting of platelets with a length greater than or equal to 1 pm and preferably less than 70 pm, the first particulate fraction having a median length LI50 and representing more than 80% of the ceramic particles, by volume percentage based on all the ceramic particles, more than 50% by volume of said platelets, each comprising more than 50% by mass of alumina; and - a second particulate fraction of particles having a length less than 1 pm, the second particulate fraction having a median length D50 at least ten times less than LI50 (i.e. D50 < Llso / 10) and representing more than 1% of the ceramic particles, in volume percentage on the basis of all the ceramic particles, the particles of said second particulate fraction being made up of more than 90% by mass of oxides; b) optionally, removal of air bubbles contained in the slip, c) freezing the slip so as to form a frozen slip incorporating ice crystals; d) removal of ice crystals, preferably by freeze-drying, so as to obtain an intermediate product, and possibly drying of said intermediate product; (e) if the intermediate product is not in the form of a powder whose particles pass through the square mesh of a 25 mm sieve, grinding and / or sieving said intermediate product so that the intermediate product is in the form of such a powder; f) optionally, debinding of said intermediate product; g) optionally, thermal pretreatment; (h) shaping of the intermediate product by pressing, injection molding or extrusion so as to obtain a preform; i) sintering of the preform with application of a pressure greater than 0.5 MPa so as to obtain a sintered product, steps h) and i) being able to be carried out in a single step; j) optionally, machining of said sintered product. As will be seen in more detail later in the description, the inventors discovered that a process according to the invention makes it possible in particular to manufacture a particularly dense sintered product, exhibiting non-brittle behavior in the SENB method and of which all dimensions, and in particular the width, can be large. In particular, at the end of step e), a powder of particles is obtained, consisting of fragments of the intermediate product and thus primarily composed of agglomerated wafers. Surprisingly, even though the wafers have no preferred orientation, the inventors discovered that sintering with the application of a pressure greater than 0.5 MPa is sufficient, if preceded by freezing / thawing steps, to orient these wafers so that, in the sintered product, they are substantially parallel to each other. Contrary to the teaching of WO 2015 189659, it is therefore not necessary to maintain all the wafers parallel to each other from the freezing step to the pressing step. Furthermore, even if the wafers are oriented, it is no longer necessary to impose a pressing direction. Finally, it is no longer necessary to require that the frozen slip be in the form of a thin layer. The length, width and thickness of the sintered product can advantageously be any size, and in particular greater than 50 mm or greater than 80 mm. A method according to the invention may further include one or more of the following optional features, which may be combined in any possible combination: - the first and second particulate fractions are chosen so that the sintered product obtained at the end of step i) conforms to the invention, - in step h), the shaping of the intermediate product is carried out by pressing at a pressure greater than 3 MPa, - step a), the suspended particles represent more than 1% and less than 45% of the slip volume, - in step a), the ceramic particles represent more than 95% of the volume of the suspended particles, - in step a), more than 95% by volume of the platelets in the first particulate fraction contain more than 98% by mass of alumina, - in step a), more than 99% by volume of the platelets in the first particulate fraction contain more than 99% by mass of alumina, - in step a), more than 80% by volume of the platelets in the first particulate fraction have a length of less than 70 pm, - the pressure applied during step i) is greater than 20 MPa, preferably greater than 40 MPa and less than 150 MPa, preferably less than 100 MPa, - steps h) and i) are carried out in a single step, preferably using an SPS process, - in step d), the removal of ice crystals is achieved by freeze-drying, - the second particulate fraction represents more than 3% and less than 10% of the ceramic particles, as a volume percentage based on all the ceramic particles, - more than 90% by number of particles in the second particulate fraction have a length at least 15 times less than LI50, preferably at least 25 times less than LI50. - the second particulate fraction consists, for more than 80% by volume, of alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, - the second particulate fraction comprises glass particles and / or glass-ceramic particles, the total quantity of glass particles and glass-ceramic particles being greater than 0.5%, preferably greater than 1% and less than 18%, preferably less than 5%, as a volume percentage based on all the ceramic particles in the slip, - the glass particles are chosen from the group consisting of glasses containing silica, glasses containing boron oxide, and their mixtures, preferably chosen from the group of glasses containing, preferably made up of more than 90% by mass of SiU2 on the one hand, and of CaO and / or MgO and / or Na2O and / or TiCh and / or K2O and / or Al2O3 on the other hand, the silica content being greater than 10% by mass, preferably greater than 80% by mass, preferably the molar ratio SiCh / CaO is between 2 and 4, or o of B2O3 on the one hand, and of CaO and / or Na2O and / or TiCh and / or K2O and / or Al2O3 on the other hand, the boron content being greater than 10% by mass, preferably greater than 80% by mass, - the second particulate fraction consists, for more than 80% by volume, of alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, and / or glass particles consisting for more than 90% by mass of SiCh on the one hand, and of CaO and / or MgO and / or Na2O and / or TiO2 and / or K2O and / or Al2O3 on the other hand, - the ratio of the volumetric quantity of particles that are neither glass particles nor glass-ceramic particles to the total quantity of glass particles and glass-ceramic particles is greater than 0.5, preferably greater than 1 and less than 4, preferably less than 2.5, - in the second particulate fraction, the median length of the glass particles and / or glass-ceramic particles of the second particulate fraction Dsov is at least 2 times smaller, preferably at least 5 times smaller than the median length of the particles that are not glass particles. The invention also relates to a sintered product - exhibiting a relative density greater than 90%, preferably a crack initiation toughness Kic greater than 3.5 MPa.m1 / 2, and preferably a crack initiation toughness KjC greater than 6 MPa.m1 / 2 - consisting of more than 80% of its volume of a stack of ceramic plates, all of the plates having an average thickness of less than 3 pm, - having a width greater than 50 mm, and - presenting a chemical analysis such that the alumina content is greater than 20% based on the mass of the product, the thickness (Wl) of a plate being the length of the minor axis of the ellipse (E) of minimum area in which the median cross-section of said plate can be inscribed, said median cross-section being a section in a cutting plane (A) perpendicular to the direction of the length (Ll) of said plate and cutting said plate at mid-length, said length being the largest dimension of said plate observable on a photograph taken along a direction perpendicular to the plane on which said plate rests, flat, the width ( / ) of the product being the largest dimension measured in the plane (C) in which the length of the product is measured, along a direction perpendicular to the direction of said length, the length (L) of said product being its largest dimension in a plane parallel (C) to the general plane in which the plates extend. Preferably, the product according to the invention also has one or more of the following optional features: a crack initiation tenacity Kic greater than 3.5 MPa.m1 / 2 preferably greater than 5 MPa.m1 / 2 a KjC toughness greater than 6 MPa.m1 / 2, preferably greater than 8 MPa.m1 / 2, a relative density greater than 95%, preferably greater than 98%, an average platelet thickness less than 2.0 pm, preferably less than 1.5 pm, a width greater than 60 mm, preferably greater than 85 mm, more than 70%, preferably more than 95%, by number of the sintered product wafers, comprising more than 70%, preferably more than 95%, by mass of alumina, a boron nitride content greater than 1% and less than 20% by mass based on the mass of said product, the boron nitride being present in the form of platelets, over 90% by number of the platelets of said product have a length less than 70 pm and greater than 2 pm, a chemical analysis such as, in mass percentages: or the SiCh content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the CaO + MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 0.8%, preferably the Al2O3 content is greater than 95%, preferably greater than 96.9% and less than 99.7%, preferably less than 99.5%. or such or the SiCh content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the CaO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and or the MgO content is less than 0.3%, preferably less than 0.1%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 0.8%, o preferably the Al2O3 content is greater than 95%, preferably greater than 96.8% and less than 99.7%, preferably less than 99.5%. or such or the SiCh content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and or the CaO content is less than 0.3%, preferably less than 0.1%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 0.8%, o preferably the Al2O3 content is greater than 95%, preferably greater than 96.8% and less than 99.7%, preferably less than 99.5%. or such or the ZrU2 content, possibly stabilized, is greater than 1% and less than 15%, and or the SiU2 content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the CaO+MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 1.5%, preferably less than 0.8%, or such or the SiU2 content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the CaO+MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and where the boron nitride content is greater than 1% and less than 20%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 1.5%, preferably less than 0.8%, or such or the ZrCl content, possibly stabilized, is greater than 1% and less than 15%, and or the SiCh content is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and or the CaO+MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and where the boron nitride content is greater than 1% and less than 20%, and o alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 1.5%, preferably less than 0.8%, The invention also relates to a sintered product obtained or capable of having been obtained by a process according to the invention. The invention also relates to a device selected from - a turbine, particularly for propulsion or energy generation, - a sensor other than a displacement sensor, particularly for a gas or a liquid, - a probe, particularly for a gas or a liquid, - a membrane for filtering gases or liquids, - a piece of armor or armor component, - a shield or shielding element, - a wear-resistant part or coating, - an element of the infrastructure of a baking oven, in particular a beam or a rim, - a thick or thin film substrate for electronic components or insulators for electrical conductors - a tool, including a chisel, a knife, a sharpener, a drill bit, a drill bit, a screwdriver, a file, - a millstone, grains for deburring or treating a surface, - a forming tool, in particular a die, an injection mold, - a cooking support, particularly for a ceramic kiln, - a prosthesis, including a dental implant, an orthopedic component, said device comprising a product according to the invention or obtained by a process according to the invention or capable of having been obtained by a process according to the invention. Definitions Any non-metallic and non-organic material is called a "ceramic material". An object which is transformed into said element by the execution of a process according to the invention is called a "precursor" of an element. Sublimation is an operation, usually carried out under vacuum, which consists of evaporating ice without melting it. The term "melting" refers to an operation that involves melting ice. - By "temporary," we mean "removed from the product during debinding or sintering." The solid constituents of a powder or suspended in a slip are called "particles." In a soil, dissolved matter does not constitute particles. The structure of a gel, obtained by the gelation of a soil, contains virtually no particles. In the sintered product, by extension, the term "particles" also refers to particles that agglomerate during sintering and were suspended in the slip used to manufacture the sintered product. The dimensional characteristics of a wafer within the sintered product can be evaluated by measurements on the product itself. - The "length" L1 of a plate is its largest observable dimension on a photograph taken along a direction perpendicular to the plane on which the said plate rests, flat. The "width" W2 and "thickness" W1 of a plate are the lengths of the major and minor axes, respectively, of the smallest possible ellipse E (i.e., of minimum area) in which the median cross-section of said plate can be inscribed (i.e., in the cutting plane A in Figure 1). Figure 1 shows a diagram of a plate 10. In figure 1a, the plate 10 is shown in perspective. Figure 1b shows the section of the plate 10 along the median transverse plane A (plane perpendicular to the direction of length Ll, passing through mid-length of the plate). A particle has a "platelet" shape when it meets the following two conditions: 1) 4 <L1 / W1, et 2) W2 > 1.5W1, preferably W2 > 2 Wl, preferably W2 > 3 Wl, preferably W2 > 4 Wl, preferably W2 > 5 Wl, preferably W2 > 7 Wl, preferably W2 > 9 Wl Preferably, the cross-section of a plate is substantially polygonal and has at least 4 sides. Even more preferably, the large faces of a plate are substantially flat, and preferably parallel to each other. The dimensions of a platelet can be easily evaluated from photographs of observations made on a powder. It is also possible to estimate the dimensions of the plates from observations of surfaces obtained by fracturing the product, in planes containing the large faces of said plates and in planes perpendicular to said large faces. The "median" value of a property of the particles in a set of particles is the value of that property that divides the particles in that set into first and second populations of equal size, each containing only particles with a value of that property greater than or equal to, or less than, respectively, the median value. For example, the median length of a set of particles is the length that divides the particles into first and second populations of equal size, each containing only particles with a length greater than or equal to, or less than, respectively, the median length. The length L of a sintered product according to the invention (Figure 4) is its largest dimension in a plane C parallel to the general plane in which the wafers extend. When the product is cylindrical, as in Figure 4, plane C can be any plane parallel to the general plane in which the wafers extend. Otherwise, as in Figure 5, plane C is chosen, from among all the planes parallel to the general plane in which the wafers extend, as the plane in which the product has its largest dimension. - The width l of a sintered product according to the invention is the largest dimension measured in the plane C in which the length is measured, along a direction perpendicular to the direction of the length. “Stabilized zirconia” is zirconia with less than 5% by mass of zirconia in a monoclinic crystallographic form, the remainder being zirconia in a stable and / or metastable, and / or cubic, tetragonal crystallographic form. By definition, a "bimodal" distribution shows two non-contiguous categories with the highest values, called "main peaks" or "main modes". Unless otherwise specified, a mean is an arithmetic mean. Unless otherwise indicated, all percentages relating to the composition of a slip according to the invention are volume percentages relative to the volume of the slip. - The volume percentages of a set of particles correspond to percentages calculated by considering the sum of the volumes of each of the particles in question. The sum of these volumes is conventionally calculated by dividing the mass of the set of particles by the absolute density of the material of said particles. For example, if the second particulate fraction represents less than 20% "of the volume of all the ceramic particles," or equivalently "of the volume of the ceramic particles," or "as a volume percentage based on all the ceramic particles," or "as a volume percentage based on the ceramic particles," the volumes to be compared are the volume of the powder particles constituting the second particulate fraction and the volume of all the ceramic particles. - The "relative density of a product" is equal to the ratio of the apparent density of the product divided by the absolute density of the product, expressed as a percentage. - For the purposes of this invention, the "apparent density of a product" is defined as the ratio of the product's mass to its volume. It can be measured by imbibition, according to Archimedes' principle. - By "absolute density of a product", for the purposes of the present invention, is meant the ratio equal to the mass of dry matter of said product after grinding at a fineness such that virtually no closed pores remain, divided by the volume of said mass of dry material after grinding. It can be measured by helium pycnometry. - A stack of plates is a structure in which the plates are superimposed flat on top of each other, with a possible lateral offset, as shown, for example, in Figure 2c. - The different characteristics of a product according to the invention can be determined by the characterization methods used for the examples below. Brief description of the figures Other features and advantages of the invention will become apparent upon examination of the drawing, provided by way of illustration and not limitation, in which: Figure 1 (la-lb) schematically represents a plate; Figure 2 (2a-2c) illustrates a process according to the prior art; Figure 3 illustrates a method according to the invention; Figures 4 and 5 represent, in perspective, sintered products according to the invention; Figure 6 illustrates the microstructure of the product of Example 2, according to the invention. In the figures, identical references have been used to designate identical or analogous objects. Detailed description Method according to the invention A product according to the invention can be manufactured by means of a process comprising steps a) to j) above. In step a) of slip preparation, a suspension of ceramic particles is prepared. The suspended particles preferably represent more than 1%, preferably more than 2%, preferably more than 5%, preferably more than 8% and less than 45%, preferably less than 40%, preferably less than 35%, preferably less than 30%, preferably less than 25%, preferably less than 20% of the volume of the slip. Ceramic particles preferably represent more than 95%, or even more than 99%, or even approximately 100% of the volume of suspended particles. The ceramic particles can be replaced, partially or totally, by equivalent quantities of precursors that transform into ceramic particles before step j). Preferably, the first and second particulate fractions together represent more than 85%, preferably more than 90%, preferably more than 95% of all ceramic particles, by volume percentage. In one embodiment, the first and second particulate fractions together represent more than 98%, preferably more than 99%, preferably approximately 100% of all ceramic particles, by volume percentage. The particle size distribution of the ceramic particles in the suspension is preferably bimodal, with the two main modes corresponding to the first and second particle fractions, respectively. First particulate fraction The first particulate fraction, or "platelet fraction", preferably represents more than 85%, preferably more than 88%, preferably more than 90%, preferably more than 92%, preferably more than 94% of all ceramic particles, in volume percentage. In a preferred embodiment, more than 50%, preferably more than 55%, preferably more than 60%, preferably more than 65%, preferably more than 70%, preferably more than 75%, preferably more than 80%, preferably more than 85%, preferably more than 90%, preferably more than 95%, preferably more than 99% by volume of the platelets of the first particulate fraction comprise more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, by mass of alumina. Preferably, in the platelets of the first particulate fraction, the complement to alumina consists of more than 90% by mass, preferably more than 95%, preferably more than 97%, preferably more than 99% by mass of oxides. In one embodiment, the first particulate fraction comprises, for a total of more than 90%, preferably more than 95%, preferably more than 99%, - more than 60% by volume, based on the volume of the first particulate fraction, of platelets comprising more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, by mass of alumina, and - less than 40% by volume of platelets containing more than 90%, preferably more than 95% by mass of boron nitride. Preferably, more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, by volume, of the platelets of the first particulate fraction, have a length of less than 70 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 25 pm, preferably less than 20 pm, or even less than 15 pm and preferably greater than 2 pm, preferably greater than 4 pm, preferably greater than 5 pm. Preferably, more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, by volume, of the platelets in the first particulate fraction have a width less than or equal to 20 pm, preferably less than 15 pm, preferably less than 10 pm, and preferably greater than 2 pm, preferably greater than 3 pm, preferably greater than 4 pm. Preferably, more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, by volume, of the platelets in the first particulate fraction have a thickness less than or equal to 3 pm, preferably less than or equal to 2.5 pm, preferably less than or equal to 2 pm, preferably less than or equal to 1.5 pm, or even less than or equal to 1 pm. Second particulate fraction Remarkably, the presence of fine particles from the second particulate fraction significantly improves the density of the sintered product. The second particulate fraction preferably represents more than 2%, preferably more than 3%, preferably more than 4% and less than 10%, preferably less than 9%, preferably less than 8%, preferably less than 7%, preferably less than 6% of the ceramic particles, as a volume percentage based on all the ceramic particles. In one embodiment, more than 90%, preferably more than 95%, preferably more than 98%, by number of particles in the second particulate fraction, have a length at least 15 times, preferably at least 20 times, preferably at least 25 times, preferably at least 30 times shorter than LI50. Preferably, the particles of the second particulate fraction consist of more than 93%, preferably more than 95%, preferably more than 97%, preferably more than 98%, preferably more than 99%, preferably more than 99.5%, preferably more than 99.9% oxides. In one embodiment, the second particulate fraction consists of more than 80%, preferably more than 90%, preferably approximately 100% by volume, of ceramic particles that are not glass particles, preferably alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, preferably alumina particles. In another embodiment, the second particulate fraction does not include glass and / or glass-ceramic particles. Stabilized zirconia is preferably zirconia stabilized with yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, scandium oxide and mixtures thereof. In a preferred embodiment, the second particulate fraction comprises glass and / or glass-ceramic particles, preferably glass particles, preferably mixed with ceramic particles that are not glass particles, preferably alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, preferably alumina particles. Glass particles and / or glass-ceramic particles may be replaced, partially or totally, by equivalent quantities of glass precursor particles and / or glass-ceramic particles, respectively. This substitution also applies to all optional characteristics relating to glass particles and glass-ceramic particles described below. Preferably, the set of glass and / or glass-ceramic particles has a median length Dsov at least 50 times less than LI50, preferably at least 100 times less than L150, preferably at least 150 times less than LI50, preferably at least 200 times less than LI50, preferably at least 300 times less than LI50. In a preferred embodiment, the quantity of glass particles and / or glass-ceramic particles is greater than 0.5%, preferably greater than 1% by volume percentage based on all ceramic particles. Even more preferably, the quantity of glass particles and / or glass-ceramic particles is less than 18%, or even less than 10%, or even less than 5%, as a volume percentage based on all suspended ceramic particles. Preferably, the ratio of the volumetric quantity of particles that are neither glass particles nor glass-ceramic particles to the total volumetric quantity of glass particles and glass-ceramic particles is greater than 0.5, preferably greater than 1 and / or less than 4, preferably less than 3, preferably less than 2.5. Preferably, the median length Dsoc of particles that are neither glass particles nor glass-ceramic particles is greater than 0.5 times, preferably greater than 0.7 times, preferably greater than 0.8 times the product - the volume percentage of the second particulate fraction based on all the ceramic particles in the slip and - of the average thickness of the particles of the first particulate fraction Wl*, and preferably less than 1.5 times, preferably 1.3, preferably 1.2 times said product. Preferably, the median length of the glass particles and / or glass-ceramic particles of the second particulate fraction Dsov is at least 2 times, preferably at least 4 times, preferably at least 5 times less than the median length of the particles that are not glass particles of the second particulate fraction. Preferably, the glass transition temperature of the glass particles is between the densification start temperature and the densification end temperature, the start and end temperatures being measured on a product obtained by the same process and from the same slurry but containing no glass particles. The start and end temperatures of densification are measured on a dilatometer and correspond to the temperature at which shrinkage begins and ends, respectively. Preferably, the glass particles are chosen from the group consisting of glasses containing silica, glasses containing boron oxide, and mixtures thereof. Glass containing silica Preferably, the glass particles are chosen from the group of glasses comprising, preferably, more than 90%, preferably more than 95% by mass of SiCh on the one hand, and of CaO and / or MgO and / or Na2O and / or TiCh and / or K2O and / or Al2O3 on the other hand, of preference for SiCh, and for CaO and / or MgO and / or Al2O3, preference for SiCh, and for CaO and / or MgO. In one embodiment, the second particulate fraction consists of more than 80%, preferably more than 90%, preferably substantially 100% by volume, of alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, and / or glass particles consisting of more than 90%, preferably more than 95% by mass of SiCh on the one hand, and of CaO and / or MgO and / or Na2O and / or TiO2 and / or K2O and / or Al2O3 on the other hand, preferably of SiO2, and of CaO and / or MgO and / or Al2O3, preferably of SiO2, and of CaO and / or MgO. Preferably, the silica content of said silica-containing glass particles is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, or greater than 80% by mass. Preferably, the glass contains SiO2 on the one hand, and CaO and / or Al2O3 on the other. Preferably, the glass contains SiO2, CaO, and Al2O3. In one embodiment, the SiO2 / CaO molar ratio is between 2 and 4, preferably between 2.5 and 3.5, or even approximately 3. Glass containing boron oxide Glasses containing boron oxide may be glasses comprising B2O3 on the one hand, and CaO and / or Na2O and / or TiO2 and / or K2O and / or Al2O3 on the other. Preferably, the B2O3 content of said boron oxide-based glasses is greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, greater than 80% by mass. Liquid phase The liquid phase preferably contains more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, or more than 95% water, as a volume percentage based on the liquid phase. The liquid phase may consist of water. The quantity of liquid phase is preferably greater than 50%, preferably greater than 60%, preferably greater than 70%, preferably greater than 80%, or even greater than 90%, as a percentage by volume of the slip. The slip preferably contains a dispersant to facilitate obtaining a homogeneous suspension. Preferably, the dispersant content is between 0.1% and 3%, preferably between 0.2% and 2%, preferably between 0.5% and 1.5%, by mass based on the mass of the ceramic particles in the slip. Dispersants commonly used for manufacturing sintered products by slip casting can be employed, for example, ammonium polymethacrylates such as Darvan 7-NS, manufactured by Vanderbilt. The slip preferably contains a thickening agent. Preferably, the thickening agent content is between 0.1% and 3%, preferably between 0.1% and 1%, by mass based on the mass of the ceramic particles in the slip. Carbopol EDT 2691, marketed by Lubrizol, can be used as a thickening agent, for example. The slip may contain a binder, preferably a temporary one. Preferably, the binder content is between 0.5% and 5% by mass, based on the mass of the ceramic particles in the slip. Temporary binders commonly used in the manufacture of sintered products can be employed, for example, polyvinyl alcohol (PVA) and polyethylene glycols (PEG). The slip may also contain an antifoaming agent. Preferably, the antifoaming agent content is between 0.1 and 3%, and more preferably between 0.1% and 1% by mass based on the mass of the ceramic particles in the slip. Antifoaming agents commonly used for the manufacture of slip-cast sintered products can be employed, for example, CONTRASPUM CONC, marketed by Zschimmer & Schwarz. In one embodiment, the ceramic particles, water, optional dispersant, optional thickening agent, optional binder, optional antifoaming agent together represent more than 80%, more than 90%, more than 95%, more than 99%, or even substantially 100% of the slip volume. Preferably the different constituents of the slip are added under agitation. The mixing of the various components of the slip can be carried out using any technique known to those skilled in the art, for example, in a mixer, a turbulate mixer, or a jar mill with balls, preferably of the same type as the suspended ceramic powder. The intensity of the mixing and / or the mixing time are preferably adjusted so as not to break the slips. To this end, the slips are preferably introduced last into a premix containing the other components. If a jar grinder is used, the mixing time is preferably greater than 0.5 hours and less than 20 hours. Preferably, a jar grinder is used, with the wood chips being introduced in a premix that has been premixed for 12 hours, the mixing time from the introduction of the plates into the slip being greater than 30 minutes and preferably less than 4 hours. The mixing can be facilitated by passing the slip through ultrasound. In step b), preferred, air bubbles are eliminated, preferably by vacuum degassing or ultrasonic degassing. In step c), the slip is cooled in such a way as to solidify the water and form ice crystals. Any technique known to a person skilled in the art for freezing slip may be used, for example ice templating techniques, or freeze granulation techniques, or techniques involving plunging a quantity of slip into a freezing bath, preferably in liquid nitrogen. Preferably, especially when the slip is immersed in a freezing bath or in the case of oriented freezing, the freezing rate is greater than 1 pm / s, preferably greater than 5 pm / s, preferably greater than 10 pm / s, preferably greater than 12 pm / s, or even greater than 15 pm / s, or even greater than 20 pm / s, or even greater than 40 pm / s and less than 400 pm / s, preferably less than 300 pm / s, preferably less than 200 pm / s, preferably less than 100 pm / s. In one embodiment, the freezing step is oriented along a preferred direction constituting a solidification front. In this embodiment, preferably, the thermal gradient is greater than 10°C / cm, or even greater than 20°C / cm and less than 200°C / cm, or even less than 150°C / cm, or even less than 100°C / cm. The size of ice crystals depends primarily on the speed of movement of the solidification front and the thermal gradient associated with this solidification front. The higher the solidification speed, the smaller the size of the ice crystals. In a preferred embodiment, however, the slip is frozen without favoring any particular freezing direction. This considerably simplifies the process. Preferably, the slip is immersed in a cooling bath, preferably liquid nitrogen, and preferably, the slip is removed from it when it is substantially completely frozen. Preferably, all of the slip is solidified during step c). In step d), the solidified slip is placed under pressure and temperature conditions that lead to the removal of ice crystals, preferably by sublimation. Advantageously, sublimation occurs substantially without displacement of the particles arranged between the crystals. For example, ice crystals can be sublimated by heating them at very low pressure, typically below 0.5 mbar, preferably below 0.3 mbar. You can also melt the ice crystals and let the resulting liquid water flow out. Step d) is preferably continued until all ice crystals have been removed. This yields an intermediate product, in the form of a block or agglomerates. The intermediate product can be dried if it is moist, drying preferably being carried out at a temperature between 50°C and 110°C, for a period preferably greater than 2 hours, preferably greater than 10 hours. Preferably, step d) is a step of removing ice crystals by sublimation thereof and the process according to the invention then does not require such drying. In step e), if the intermediate product is not in powder form, it is ground and / or sieved to transform it into powder. The product is considered not to be in powder form if it cannot pass through a sieve with square meshes of 25 mm on each side, preferably 15 mm, preferably 10 mm, preferably 5 mm, preferably 4 mm, preferably 3 mm, preferably 2 mm on each side. Grinding can be carried out by dry method using any technique known to a person skilled in the art, preferably with the aid of a bowl containing moving parts (rings, pucks or balls), a hand press or a mortar and pestle. Sieving is preferably carried out using sieves with an opening of less than 1 mm, or even less than 500 µm, or even less than 400 µm. Advantageously, this step allows the largest agglomerates to be removed. In step f), which is optional, debinding removes organic matter. This is preferably carried out using heat treatment, preferably at a temperature between 300°C and 500°C, preferably in air. The holding time at the maximum temperature is preferably less than or equal to 2 hours. The optional heat pretreatment step (g) promotes the adhesion of particles from the second particulate fraction to the platelets of the first particulate fraction. The maximum temperature reached at step g) is preferably greater than 600°C, preferably greater than 700°C, preferably greater than 800°C and preferably less than 1200°C. The time spent at the maximum temperature is preferably less than 5 hours, preferably less than 2 hours. In a preferred embodiment, the time spent at the maximum temperature is substantially zero. When the first particulate fraction contains boron nitride platelets, this step is preferably carried out in a nitrogen atmosphere. In step h), the intermediate product in powder form is shaped by pressing, injection molding or extrusion to obtain a preform. All injection molding techniques are possible. Preferably, in the case of injection molding, the intermediate product in powder form is typically mixed with a wax or polymer to obtain a compound with a rheology suitable for injection molding. All extrusion techniques are possible. Preferably, in the case of shaping by extrusion, the intermediate product in powder form is typically mixed with water and extrusion-promoting agents, preferably organic, such as plasticizers and lubricants. The quantity of plasticizers and lubricants can be between 1% and 5%, preferably between 1.5% and 3% by mass, based on the sum of the mass of the intermediate product powder, water, and said plasticizers and lubricants. The quantity of water can be between 10% and 25%, preferably between 15% and 20% by mass based on the sum mass of the powder of the intermediate product, water and said plasticizers and lubricants. Extrusion can be carried out at atmospheric pressure or under vacuum. In the case of shaping by injection molding or extrusion, drying and / or debinding is preferably carried out after shaping, preferably by heat treatment, the temperature of which depends on the plasticizers, lubricants, polymers and waxes used during shaping. Preferably, the powder is shaped by pressing. This advantageously simplifies the process. Preferably, the pressing is configured so that the sintering of the preform in step i) results in a sintered product having a relative density greater than 90%, or even greater than 95%. All pressing techniques are possible. Preferably, the pressing method chosen is either uniaxial pressing or cold isostatic pressing. In the case of forming by pressing, the intermediate product in powder form is poured into a mold and then subjected to a pressure preferably greater than 3 MPa, preferably greater than 5 MPa, or even greater than 10 MPa, or even greater than 50 MPa, and preferably less than 200 MPa, or even less than 150 MPa, so as to form a raw part, or "preform". The agglomerates of the powder deform efficiently under the effect of this pressure. In step i), the preform is sintered in an oxidizing, neutral or reducing atmosphere. Preferably, when the product contains boron nitride, the atmosphere during sintering is neutral, preferably under vacuum. Preferably, sintering is carried out under vacuum, preferably in a vacuum of less than 10 mbar, preferably less than 5 mbar. The pressure applied during step i) is greater than 1 MPa, preferably greater than 2 MPa, preferably greater than 3 MPa, preferably greater than 4 MPa, preferably greater than 5 MPa, preferably greater than 6 MPa, preferably greater than 7 MPa, preferably greater than 8 MPa, preferably greater than 9 MPa, preferably greater than 10 MPa, preferably greater than 11 MPa, preferably greater than 12 MPa, preferably greater than 13 MPa, preferably greater than 14 MPa, preferably greater than 15 MPa, preferably greater than 16 MPa, preferably greater than 17 MPa, preferably greater than 20 MPa, preferably greater than 25 MPa, preferably greater than 30 MPa, preferably greater than 35 MPa, preferably greater than 40 MPa, preferably greater than 45 MPa, and preferably less than 150 MPa, preferably less than 100 MPa. Preferably, more than 20%, preferably more than 50% of the pressure is applied over more than 50%, preferably more than 70%, preferably more than 90% of the cycle, counting only the temperature rise and any plateau at the maximum temperature. The holding time, temperature, and atmosphere of the sintering process are determined according to the nature and characteristics of the product to be manufactured. These parameters are well known to those skilled in the art. The maximum temperature reached during sintering is preferably between 1300°C and 1700°C, preferably between 1450°C and 1550°C. At the end of step i), a sintered product according to the invention is obtained. Steps h) and i) are preferably carried out in a single step, for example using a hot pressing or SPS (Spark Plasma Sintering) process. Preferably, steps h) and i) are carried out in a single step using an SPS process. Preferably, the SPS is performed: under vacuum, and / or at a maximum temperature between 1300°C and 1700°C, preferably between 1450°C and 1550°C, and / or at a pressure greater than 30 MPa, preferably greater than 40 MPa. At step j), the sintered product can be machined by any technique known to a person skilled in the art. In one embodiment, step j) can be performed on the preform before step i). In a preferred embodiment, the method according to the invention comprises the following characteristics: - At step a): The suspended particles represent more than 8% and less than 20% of the slip volume, and Ceramic particles represent more than 95% of the volume of suspended particles, and The first and second particulate fractions together represent more than 99% of all ceramic particles, by volume percentage, and The particle size distribution of the ceramic particles in the suspension is bimodal, the two main modes corresponding to the first and second particle fractions, respectively, and The first particulate fraction, or "platelet fraction", represents more than 94% of all ceramic particles, by volume percentage, and more than 99% by volume of the platelets in the first particulate fraction contain more than 99%, by mass, of alumina, and more than 95%, by volume, of the platelets in the first particulate fraction, have a length less than 20 pm and greater than 4 pm, a width less than 10 pm and greater than 3 pm, and a thickness less than or equal to 1.5 pm, and the second particulate fraction represents more than 3% and less than 6% of the ceramic particles, as a volume percentage based on all the ceramic particles, and over 95%, by number, of the particles in the second particulate fraction have a length at least 25 times shorter than LI50, and the second particulate fraction comprises glass particles mixed with alumina particles, the ratio of the volume of particles that are neither glass particles nor glass-ceramic particles to the total volume of glass and glass-ceramic particles is greater than 0.5 and less than 2.5, and the glass particles are chosen from the group of glasses composed of more than 90% by mass of SiCh on the one hand, and of CaO and / or MgO on the other, and - in step c), the freezing rate is greater than 10 pm / s and less than 100 pm / s, and - step d) is a step of removing ice crystals by sublimation of these crystals, and - steps h) and i) are carried out in a single step using an SPS process, carried out under vacuum, at a maximum temperature between 1300°C and 1700°C, and at a pressure greater than 30 MPa. A process according to the invention makes it possible to manufacture a product according to the invention exhibiting remarkable mechanical properties, and in particular toughness. Product according to the invention A sintered product according to the invention can be obtained or may have been obtained by a process according to the invention. In a preferred embodiment, more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% by number of the sintered product wafers comprise more than 50%, preferably 60%, preferably 70%, preferably 80%, preferably more than 85%, preferably more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99% alumina by mass. In one embodiment, the sintered product contains more than 1%, or even more than 5%, or more than 10%, or more than 15%, and less than 20% boron nitride by mass based on the mass of the product, the boron nitride being present in the form of wafers. Preferably, the other wafers present are wafers comprising more than 50%, preferably 60%, preferably 70%, preferably 80%, preferably more than 85%, preferably more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99% alumina by mass. Surprisingly, the addition of boron nitride in the form of wafers does not significantly alter the relative density of the sintered product after sintering and its non-brittle behavior in the SENB method. Preferably more than 90%, preferably more than 95%, preferably more than 98%, in number of platelets have a length less than 70 pm, preferably less than 60 pm, preferably less than 50 pm, preferably less than 40 pm, preferably less than 25 pm and preferably more than 2 pm, preferably more than 4 pm. Ceramic particles other than platelets may be at least partially invisible after sintering step i), making their quantification difficult. However, they contribute to obtaining a sintered product with a high relative density. The relative density of a sintered product according to the invention is preferably greater than 92%, preferably greater than 94%, preferably greater than 95%, preferably greater than at 96%, preferably above 97%, preferably above 97.5%, preferably above 98%, preferably above 98.5%. The wafers are stacked one on top of the other. They therefore extend along substantially parallel planes, as can be seen in Figure 6, which shows a photograph of the microstructure of the product of Example 2 according to the invention. More specifically, the mean standard deviation around the mean principal orientation is less than 20°, preferably less than 16°, the mean principal orientation and the mean standard deviation around the mean principal orientation being determined by the method described for the examples. A reduction in the mean standard deviation around the mean principal orientation significantly improves the Kic and KjC toughness of the sintered product. The average thickness of the sintered product wafers is preferably less than 2.5 pm, preferably less than 2.0 pm, preferably less than 1.5 pm, preferably less than 1.0 pm. Advantageously, the mechanical properties, particularly the modulus of fracture, are improved. In one embodiment, the width l of the sintered product is greater than 60 mm and less than or equal to 80 mm. In another embodiment, the width of the sintered product is greater than 80 mm, greater than 81 mm, greater than 85 mm, or even greater than 90 mm, or even greater than 100 mm, or even greater than 150 mm. A sintered product manufactured according to a process according to the invention exhibits remarkable toughness. Preferably, the crack initiation toughness Kic is greater than 4 MPa.m1 / 2, preferably greater than 4.5 MPa.m1 / 2, preferably greater than 5 MPa.m1 / 2, preferably greater than 5.5 MPa.m1 / 2, preferably greater than 6 MPa.m1 / 2. Preferably, the KjC toughness is greater than 7 MPa.m1 / 2, preferably greater than 8 MPa.m1 / 2, preferably greater than 9 MPa.m1 / 2. The Kic and KjC toughnesses can be determined using the methods described for the examples. Preferably, the sintered product comprises more than 80% by mass, preferably more than 95%, preferably more than 97%, preferably more than 99% by mass of oxides. In one embodiment, more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99%, preferably substantially 100% number of the plates comprise more than 50%, preferably 60%, preferably 70%, preferably 80%, preferably more than 85%, preferably more than 90%, preferably more than 95%, preferably more than 98%, preferably more than 99% alumina by mass. In a first principal embodiment, the chemical analysis of the sintered product is as follows, in mass percentages: - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the CaO + MgO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and / or preferably less than 4.5%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%, and - alumina and other elements making up the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. Preferably in this first main embodiment, the Al2O3 content is greater than 81%, preferably greater than 85%, preferably greater than 89%, preferably greater than 90%, preferably greater than 92%, preferably greater than 94%, preferably greater than 95%, preferably greater than 96.9%, and preferably less than 99.7%, preferably less than 99.5%. In a second principal embodiment, the chemical analysis of the product is as follows, in mass percentages: - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the CaO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and preferably less than 4.5%, preferably less than 3%, of preference less than 2%, preference less than 1.5%, preference less than 1%, preference less than 0.8%, preference less than 0.5%, and - the MgO content is less than 0.3%, preferably less than 0.25%, preferably less than 0.2%, preferably less than 0.15%, preferably less than 0.1%, or even less than 0.05%, and - alumina and other elements making up the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. Preferably in this second main embodiment, the Al2O3 content is greater than 81%, preferably greater than 85%, preferably greater than 89%, preferably greater than 90%, preferably greater than 92%, preferably greater than 94%, preferably greater than 95%, preferably greater than 96.8%, and preferably less than 99.7%, preferably less than 99.5% In a third principal embodiment, the chemical analysis of the product is as follows, in mass percentages: - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the MgO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and preferably less than 4.5%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%, and - the CaO content is less than 0.3%, preferably less than 0.25%, preferably less than 0.2%, preferably less than 0.15%, preferably less than 0.1%, or even less than 0.05%, and - alumina and other elements making up the complement to 100%, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. Preferably in this third main embodiment, the Al2O3 content is greater than 81%, preferably greater than 85%, preferably greater than 89%, preferably greater than 90%, preferably greater than 92%, preferably greater than 94%, preferably greater than 95%, preferably greater than 96.8%, and preferably less than 99.7%, preferably less than 99.5%. In a fourth principal embodiment, the chemical analysis of the product is as follows, in mass percentages: - the ZrU2 content, possibly stabilized, is greater than 1% and less than 15%, and - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the CaO + MgO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and preferably less than 4.5%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%, and - the content of alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 8%, preferably less than 5%, preferably less than 4%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. Preferably in this fourth principal embodiment, the zirconia ZrÛ2, possibly stabilized, comes exclusively from the second particulate fraction. In a fifth principal embodiment, the chemical analysis of the product is as follows, in mass percentages: - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the CaO + MgO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and preferably less than 4.5%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%, and - the boron nitride content is greater than 1% and less than 20%, and - the content of alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 8%, preferably less than 5%, preferably less than 4%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. In a sixth principal embodiment, the chemical analysis of the product is as follows, in mass percentages: - the ZrCh content, possibly stabilized, is greater than 1% and less than 15%, and - the SiCh content is greater than 0.2%, preferably greater than 0.3%, preferably greater than 0.5%, and preferably less than 13.5%, preferably less than 10%, preferably less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, and - the CaO + MgO content is greater than 0.1%, preferably greater than 0.15%, or even greater than 0.2%, and preferably less than 4.5%, preferably less than 3%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%, and - the boron nitride content is greater than 1% and less than 20%, and - the content of alumina and other elements constituting the complement to 100%, the content of other elements being less than 10%, preferably less than 8%, preferably less than 5%, preferably less than 4%, preferably less than 2%, preferably less than 1.5%, preferably less than 1%, preferably less than 0.8%, preferably less than 0.5%. Preferably in this sixth principal embodiment, the zirconia ZrÛ2, possibly stabilized, comes exclusively from the second particulate fraction. Regardless of the preceding principal embodiment, "other elements" refers to constituents other than those mentioned elsewhere; any zirconia stabilizers are not included in "other elements" if the zirconia is stabilized. Preferably, the sintered product consists of more than 85% of its volume, preferably more than 90% of its volume, preferably more than 95% of its volume, of a stack of ceramic wafers. The platelet volume of the sintered product can be estimated using fracture surface images obtained with a Scanning Electron Microscope (SEM), as described in the examples section of the description. Examples The following non-limiting examples are given for the purpose of illustrating the invention. The following raw materials were used: TM-DAR Taimicron alumina powder marketed by Krahn Chemie GmbH, - RonaFlair White Sapphire alumina platelet powder marketed by Merck, Nexsil 20K colloidal silica solution marketed by NYACOL, - Calcium carbonate powder (CaCO3) with a purity of 99% or higher, marketed by Sigma-Aldrich, - Darvan 7NS powder marketed by the company VanderBilt, - Carbopol EDT 2691 powder marketed by the Lubrizol company, - tergitol NP-9 marketed by the company Sigma-Aldrich, - Hexagonal boron nitride platelet powder Very BN PUHP 3016 marketed by the company Saint-Gobain. The products in the examples were manufactured according to a process according to the invention. Example 1 The product of example 1, excluding the invention, is the product of example 11 of WO2015189659. Example 2 The product of Example 2, according to the invention, is manufactured according to the following process: In step a), the constituents listed in the following table were mixed to form a slip, according to the following procedure: Darvan 7NS is dispersed in water; the second particulate fraction is then added, the whole is then mixed for 12 hours in a mixing jar, with alumina beads, to ensure good deagglomeration; 5 Carbopol EDT 2691 and the first particulate fraction are then added, and the suspension is then mixed for 3 hours in a mixing jar with alumina beads to obtain the slip. In tables 1a and 2a, %V denotes a volume percentage based on the volume of the slip. Constituents of Example 2 %V First particulate fraction: RonalFlair White Sapphire Powder 13.27 Second particulate fraction: TM-DAR Taimicron Alumina Powder 0.41 Second particulate fraction: Nexsil 20K Colloidal Silica Solution 0.95 Second particulate fraction: Calcium Carbonate CaCO3 0.14 Carbopol EDT 2691 0.25 Darvan 7NS 0.55 Deionized Water 84.43 Table the Characteristics of example 2 Volume % of all ceramic particles based on slip volume 13.97 Volume % of the first particulate fraction, based on the volume of all ceramic particles 95 Median length Lho of the first particulate fraction (pm) 9 Average thickness W150 of the first particulate fraction (pm) 0.5 Volume % of the second particulate fraction, based on all ceramic particles 5 Volume % of glass particles in the second particulate fraction, based on the volume of all ceramic particles 2.1 Volume % of ceramic particles in the second particulate fraction other than glass particles, based on the volume of all ceramic particles 2.9 Median length D50 of glass particles in the second particulate fraction (pm) 0,02 Median length D50 of ceramic particles that are not glass or glass precursor particles of the second particulate fraction (pm) 0.1 , Table 1b No degassing step b) was carried out. In step c), the slip is poured into a wide stainless steel container, with the slip level in the container being approximately 15 mm. The container is then quickly immersed in a liquid nitrogen bath. The slip freezes completely in about 20 minutes. The frozen slip is then removed from the mold. In step d), the frozen slip is placed in a freeze dryer. A temperature sensor placed under the frozen slip block monitors the freeze-drying process. The pressure inside the freeze dryer is set to 0.2 mbar absolute. The freeze-drying time is approximately 5 days. At the end of step d), an intermediate product is obtained in the form of a dry block with low mechanical strength. In step e), the block is crushed using a hand press and the resulting powder is sieved to 1 mm. In steps f) and g) (combined into a single step), the powder is placed in a furnace to undergo a heat treatment consisting of a temperature increase at 50°C / h, a one-hour holding period at 400°C, a temperature increase at 100°C / h up to 900°C, and a decrease at 300°C / h. This heat treatment removes organic elements from the powder and strengthens the adhesion of the ceramic particles of the second particulate fraction to the wafers. In step h), a graphite die, 80 mm in diameter, is filled with powder. The powder is then pressed at room temperature at a pressure of 5 MPa to form a preform. In step i), the die is placed in an SPS H-HP D 320 furnace from FCT Système GmbH. The preform then undergoes sintering under load at 1500°C for 15 minutes at a pressure of 50 MPa. The rate of temperature rise to the holding temperature is 100°C / min. At the end of step i), a sintered product according to the invention, with a diameter of 80 mm, is obtained. Example 3 For example 3, steps a), c), d), e), f) and g) identical to those of example 2 were carried out. At step h), the powder is shaped by pressing, with a pressure of 200 MPa in order to obtain a preform. In step i), the preform is sintered without the application of pressure during sintering, according to the following cycle: a temperature rise of 5°C / min is carried out up to 1500°C, the temperature is then maintained for 2 hours at 1500°C, the temperature is then lowered at a rate of 5°C / min. At the end of step i), a sintered product with a diameter of 80 mm is obtained. Example 3, comparative, is intended to illustrate the importance of applying a pressure greater than 0.5 MPa during step i) of sintering. Example 4 The product in example 4 is manufactured using the following process: In step a), the constituents listed in the following table 2a were mixed to form a slip, according to the following procedure: - The boron nitride plates are added to a mixture of water and tergitol, which allows them to be suspended, then the whole thing is stirred for 12 hours in a beaker, with a magnetic stirrer; - The Darvan 7NS is dispersed in the water; - the second particulate fraction is then added, the whole is then mixed for 12 hours in a jar turner, with alumina beads, to ensure good deagglomeration; - the alumina plates are then added and the slip is mixed for 3 hours in a pot turner; - Finally, the Carbopol and the BN tablets in suspension are added and the whole is mixed for 3 hours in a rotating jar. Constituents of Example 4 %V First particulate fraction: RonalFlair White Sapphire Powder 9.95 First particulate fraction: BN Very BN 3016 Powder 4.72 Second particulate fraction: TM-DAR Taimicron Alumina Powder 0.39 Second particulate fraction: Nexsil 20K Colloidal Silica Solution 0.89 Second particulate fraction: Calcium Carbonate CaCO3 0.13 Carbopol EDT 2691 0.24 Darvan 7NS 0.51 Tergitol 0.05 Deionized Water 83.12 Characteristics of example 4 Volume percentage of all ceramic particles, based on slip volume: 15.33; Volume percentage of the first particulate fraction, based on the volume of all ceramic particles: 95.7; Median length LI50 of the first particulate fraction (pm) - White Sapphire: 9; Average thickness W150 of the first particulate fraction (pm) - White Sapphire: 0.5; Median length LI50 of the first particulate fraction (pm) - BN: 16; Average thickness W150 of the first particulate fraction (pm) - BN: 1; Volume percentage of the second particulate fraction, based on the volume of all ceramic particles: 4.3; Volume percentage of glass particles in the second particulate fraction, based on the volume of all ceramic particles: 1.8; Volume percentage of ceramic particles in the second particulate fraction other than glass particles, based on the volume of all ceramic particles 2,5 Median length D50 of glass particles in the second particulate fraction (pm) 0.02 Median length D50 of ceramic particles that are not glass or glass precursor particles in the second particulate fraction (pm) 0.1 , Table 2b Steps c), d) and e) are identical to those in example 2. In steps f) and g) (combined into a single step), the intermediate product in powder form is placed in a furnace for heat treatment. This treatment is carried out in an air atmosphere up to 600°C, with a rate of increase of 50°C / h. At 600°C, the atmosphere is converted to nitrogen to prevent oxidation of the boron nitride. The temperature is then raised to 900°C at a rate of increase of 100°C / h. The temperature is then cooled at a rate of 300°C / h. 10 Steps h), i) and j) are identical to those in example 2. Example 4 is intended to illustrate the possibility of limited alumina content in the wafers. Characterization The following characterization methods were used: 15 The dimensions of the particles, (and the data derived from them, such as median dimensions), are determined by the following method. Particle powder is suspended in ethanol to ensure thorough dispersion. This suspension is then spread onto a conductive support, such as carbon tape used in electron microscopy. At least five images are acquired using a Scanning Electron Microscope (SEM), each image having a minimum resolution of 1280 x 960 pixels, excluding the scale bar. The magnification is set so that the image width allows visualization of between 2 and 20 individual, non-agglomerated particles. If this is not the case, the process must be repeated with a suspension having a lower particle-to-ethanol ratio. The image should show particles whose thickness appears approximately parallel to the viewing plane. The particle thickness, W1, is then measured by analyzing the images using the Fiji software. This involves drawing lines to delimit the particles and then using the "Analyze > Measure" tool in the software. The "length" column in the results table provides the average particle thickness. The correspondence between pixels and units of length can be established beforehand using the "Set Scale" tool and by measuring the number of pixels in the scale bar. The average particle thickness of the powder, W1*, is the average of the measured W1 thicknesses. The length L1 and width W2 of each particle is also measured. The orientation of the plates is determined by the following method: A strip of the product to be analyzed is cut perpendicular to the direction of the pressure applied during sintering. This bar is then notched in its center to a tenth of its thickness, bent and fractured using a hammer. A flat fracture surface, parallel to the direction of pressing, is thus created. At least 15 images of the fracture surface are taken using a Scanning Electron Microscope (SEM). Each image has a minimum resolution of 1280x950 pixels, excluding the scale bar. The orientation direction of the plates is estimated by the orientation of the pixels of each image, linked to the local gradient of the grey level, and measured using the OrientationJ tool of the ImageJ software, the function used being OrientationJ - OrientationJ Distribution. The average orientation direction is the average of the orientation directions calculated across all the shots. The average standard deviation around the average orientation direction is equal to the average of the standard deviations of the orientation directions calculated on each of the shots. The absolute density is measured by helium pycnometry. The apparent density is measured by imbibition, according to the principle of Archimedes' buoyancy. KjC toughness and Kic crack initiation toughness measurements are performed at room temperature, as described in "Strong, tough and stiff bioinspired ceramics from brittle constituents — supplementary information", Bouville et al., Nature Materials, Vol. 13, pages 508-514 (2014), with the following differences: - the test specimens used have dimensions equal to 3x6x36 mm3. - the cut made has a depth of 2.7 mm, • The test performed is a 4-point flexion test. The KjC toughness value corresponds to the toughness for a crack extension projected along the notch axis equal to 0.3 mm. The volume of sintered product wafers is estimated using the following method: Five strips of the product to be analyzed are cut randomly. Each bar is then notched in its center to a depth of one-tenth of its thickness, flexed, and fractured using a hammer. This creates a flat fracture surface. At least two images of the fracture surface are taken using a Scanning Electron Microscope (SEM). Each image has a minimum resolution of 1280x950 pixels, excluding the scale bar. The area covered by the plates is determined on each image. The average of the covered areas determined on each shot is an estimate of the volume of wafers of the sintered product. For elements other than nitrogen, the chemical analysis of sintered products is measured by "Inductively Coupled Plasma" or ICP for elements whose quantity does not exceed 0.5%; For the content of other elements, a bead of the product to be analyzed is made by melting the product, then the chemical analysis is carried out by X-ray fluorescence. The nitrogen content of the sintered product is classically determined by thermal conductivity, for example on a LECO TC 436DR series device. 5 Results The results obtained are summarized in the following table 3: Example 1* 2 3* 4 Chemical Analysis (% by mass) Al2O3 98.5 98.4 98.4 79.2 SiO2 0.86 0.75 0.75 0.75 CaO 0.14 0.25 0.25 0.25 BN - - - 19.1 Other elements 0.5 0.60 0.60 0.70 of which MgO <0.1 <0.1 <0.1 <0.1 Sintered product Part width (mm) 20 80 80 80 Relative density (%) 98.8 97.9 55.7 94.7 Wafer stacking Yes Yes Yes Yes More than 80% of the sintered product volume is composed of wafers Yes Yes Yes Yes Mean standard deviation around the mean orientation direction (°) 15 16.8 nd 18 Average plate thickness (pm) <3 <3 <3 <3 Crack initiation toughness Kic (MPa.m1 / 2) 6.2 6.3 nd 3.8 KjC (MPa.m1 / 2) 7.9 9.6 nd 8.1 nd: not determined * : comparative example Table 3 The process in Example 1 yields a product with high density, Kic toughness, and KjC toughness, equal to 98.8%, 6.2 MPa.m1 / 2, and 7.9 MPa.m1 / 2, respectively. However, the width of this product is necessarily less than 50 mm. The process in Example 2 yields a product with high density, Kic tenacity, and KjC tenacity, equal to 97.9%, 6.3 MPa.m1 / 2, and 9.6 MPa.m1 / 2, respectively. Advantageously, the width of this product is 80 mm. The process in Example 3 yields a product with a width of 80 mm. However, the absence of pressure exceeding 0.5 MPa during sintering step i) results in a density significantly lower than that of Example 1, at 55.7%. The process in Example 4 allows us to obtain a product with a width of 80 mm and a density of 94.7%, and not exhibiting brittle behavior, the value of KjC being greater than the value of Kic, these values ​​being 8.1 MPa.m1 / 2 and 3.8 MPa.m1 / 2 respectively. 5 As is now clear, the invention provides a process for manufacturing a remarkably dense sintered product that is not brittle and can have any dimensions. This process, which combines the preparation of a specific powder using a freezing / removal of ice crystals and pressure sintering, is advantageously simple to implement. 10 Of course, the present invention is not limited to the embodiments described and represented, provided by way of example. In particular, the invention is not limited by the shape of the products.

Claims

CLAIMS 1. Sintered product _ having a relative density greater than 90%, - consisting for more than 80% of its volume of a stack of flat ceramic plates (10), all of said plates having an average thickness of less than 3 μm, - having a width (Z) greater than 50 mm, and - comprising more than 20% alumina, as a percentage based on the mass of the product, the width (Z) of the product being the largest dimension measured in the plane (C) in which the length of the product is measured, in a direction perpendicular to the direction of said length, the length (L) of said product being its largest dimension in a plane parallel (C) to the general plane in which the plates extend.

2. Product according to the immediately preceding claim, having - a crack initiation toughness Kic greater than 3.5 MPa.m1 / 2, and / or - a KjC toughness greater than 6 MPa.m1 / 2, and / or -, a relative density greater than 95%, and / or - an average platelet thickness of less than 2.0 pm, and / or - a width greater than 60 mm, and / or in which *- more than 70% by number of the plates contain more than 70% by mass of alumina.

3. Product according to the immediately preceding claim, having » a crack initiation toughness Kic greater than 5 MPa.m1 / 2 and / or - a Kjc toughness greater than 8 MPa.m1 / 2, and / or - a relative density greater than 98%, and / or - an average platelet thickness of less than 1.5 pm, and / or - a width greater than 85 mm, and / or in which - more than 95% by number of the platelets contain more than 95% by mass of alumina.

4. A product according to claim 1, containing more than 1% and less than 20% boron nitride, by mass based on the mass of said product, the boron nitride being present in the form of platelets.

5. Product according to any one of the preceding claims, in which more than 90% by number of the platelets have a length less than 70 pm and greater than 2 pm.

6. Product according to any one of claims 1 to 3, and 5 preceding, having a chemical analysis such that, in mass percentages: - the SiCh content is greater than 0.2% and less than 13.5%, and - the CaO + MgO content is greater than 0.1% and less than 4.5%, and the total content of AI2O3 and “other elements” constituting the complement to 100%, the content of other elements being less than 2%, or such that - the SiO2 content is greater than 0.2% and less than 13.5%, and the CaO content is greater than 0.1% and less than 4.5%, and the MgO content is less than 0.3%, and - the total content of AI2O3 and “other elements” constituting the complement to 100%, the content of other elements being less than 2%, or such that - the SiO2 content is greater than 0.2%, and less than 13.5%, and the MgO content is greater than 0.1% and less than 4.5%, and the CaO content is less than 0.3%, and - the total content of AI2O3 and “other elements” constituting the complement at 100%, the content of other elements being less than 2%, or such that the ZrOj content, possibly stabilized, is greater than 1% and less than 15%, and the SiO2 content is greater than 0.2% and less than 13.5%, and the CaO + MgO content is greater than 0.1% and less than 4.5%, and the total content of AI2O3 and “other elements” constituting the complement to 100%, the content of other elements being less than 10%, or such that - the SiO? content is greater than 0.2% and less than 13.5%, and the CaO + MgO content is greater than 0.1% and less than 4.5%, and the boron nitride content is greater than 1% and less than 20%, and - the total content of AI2O3 and “other elements” constituting the complement at 100%, the content of other elements being less than 10%, or such that - the ZrO2 content, possibly stabilized, is greater than 1% and less than 15%, and - the S1O2 content is greater than 0.2% and less than 13.5%, and the CaO + MgO content is greater than 0.1% and less than 4.5%, and 1_ a—— ___—- J _ v - — - ~ _x____ _____ 1 1 n / -x : 1 / _x - m icucux eu uiuuic ucuuic csl supcucuiv ax 70 ci uuciicuic az,v7o? here the total content of AI2O3 and “other elements” constituting the complement at 100%, the content of other elements being less than 10%.

7. Product according to the preceding claim, having a chemical analysis such that, in mass percentages: the AI2O3 content is greater than 95% and less than 99.7%, and - the SiCh content is greater than 0.2% and less than 2%, and - the CaO + MgO content is greater than 0.1% and less than 1.5%, and - the content of other elements is less than 1.5%, or such that — the AI2O3 content is greater than 95% and less than 99.7%, and the SiO2 content is greater than 0.2% and less than 2%, and - the CaO content is greater than 0.1% and less than 1.5%, and - the MgO content is less than 0.3%, and the content of other elements is less than 1.5%, or such that - the AI2O3 content is greater than 95% and less than 99.7%, and the SiO2 content is greater than 0.2%, and less than 2%, and - the MgO content is greater than 0.1% and less than 1.5%, and - the CaO content is less than 0.3%, and the content of other elements is less than 1.5%, or such that the Z1O2 content, possibly stabilized, is greater than 1% and less than 15%, and * the SiOz content is greater than 0.2% and less than 2%, and the CaO + MgO content is greater than 0.1% and less than 1.5%, and the content of other elements is less than 1.5%, and the 100% complement is alumina, or such that - the SiOz content is greater than 0.2% and less than 2%, and - the CaO + MgO content is greater than 0.1% and less than 1.5%, and - the boron nitride content is greater than 1% and less than 20%, and - the content of other elements is less than 1.5%, and - the complement is alumina, or such that - the ZrOz content, possibly stabilized, is greater than 1% and less than 15%, and the SiOz content is greater than 0.2% and less than 2%, and - the CaO+MgO content is greater than 0.1% and less than 1.5%, and - the boron nitride content is greater than 1% and less than 20%, and - the content of other elements is less than 1.5%, and - the complement is alumina.

8. Product according to the preceding claim, having a chemical analysis such that, in mass percentages: - the AI2O3 content is greater than 96.9% and less than 99.5%, and the SiO2 content is greater than 0.2% and less than 1.5%, and the CaO + MgO content is greater than 0.1% and less than 0.8%, and the content of other elements is less than 0.8%, or such that the AI2O3 content is greater than 96.8% and less than 99.5%, and - the SiOz content is greater than 0.2% and less than 1.5%, and the CaO content is greater than 0.1% and less than 0.8%, and the MgO content is less than 0.1%, and - the content of other elements is less than 0.8%, or such that - the AI2O3 content is greater than 96.8% and less than 99.5%, and the SiOz content is greater than 0.2%, and less than 1.5%, and the MgO content is greater than 0.1% and less than 0.8%, and - the CaO content is less than 0.1%, and - the content of other elements is less than 0.8%, or such that the ZrOz content, possibly stabilized, is greater than 1% and less than 15%, and the SiOz content is greater than 0.2% and less than 1.5%, and the CaO + MgO content is greater than 0.1% and less than 0.8%, and - the content of other elements is less than 0.8%, and - the 100% complement is alumina, or such that - the SiOz content is greater than 0.2% and less than 1.5%, and - the CaO + MgO content is greater than 0.1% and less than 0.8%, and - the boron nitride content is greater than 1% and less than 20%, and the content of other elements is less than 0.8%, and - the complement is alumina, or such that - the ZrOz content, possibly stabilized, is greater than 1% and less than 15%, and - the SiOz content is greater than 0.2% and less than 1.5%, and - the CaO + MgO content is greater than 0.1% and less than 0.8%, and - the boron nitride content is greater than 1% and less than 20%, and ~ the content of other elements is less than 0.8%, and - the complement is alumina.

9. Method for manufacturing a sintered product, said method comprising the following steps: a) preparation of a bafbotine comprising a set of ceramic particles suspended in a liquid phase, the set of ceramic particles representing more than 90% of the volume of the particles in suspension and comprising: - a first particulate fraction consisting of platelets having a length greater than or equal to 1 pm, the first particulate fraction having a median length LI50 and representing more than 80% of the ceramic particles, in volume percentage based on all ceramic particles, more than 50% by volume of said platelets each comprising more than 50% by mass of alumina; and - a second particulate fraction of particles having a length of less than 1 pm, the second particulate fraction having a median length D50 at least ten times less than LI50 and representing more than 1% of the ceramic particles, in volume percentage based on all the ceramic particles, the particles of said second particulate fraction being made up of more than 90% by mass of oxides; b) optionally, elimination of air bubbles contained in the bafbotine, (c) freezing the slip so as to form a frozen slip incorporating ice crystals; d) removal of ice crystals, so as to obtain an intermediate product, and possibly drying of said intermediate product; (e) if the intermediate product is not in the form of a powder whose particles pass through the square mesh of a 25 mm side sieve, grinding and / or sieving said intermediate product so that the intermediate product is in the form of such a powder; f) optionally, debinding of said intermediate product; g) optionally, heat pretreatment; (h) shaping the intermediate product by pressing, injection molding or extrusion so as to obtain a preform; i) sintering the preform with application of a pressure greater than 0.5 MPa so as to obtain a sintered product, steps h) and i) being able to be carried out in a single step; j) optionally, machining of said sintered product.

10. Method according to the immediately preceding claim, in which the first and second particulate fractions are chosen so that the sintered product obtained at the end of step i) conforms to any one of claims 1 to 8.

11. Method according to any one of the two immediately preceding claims, in which in step h), the shaping of the intermediate product is carried out by pressing at a pressure greater than 3 MPa.

12. A method according to any one of the three immediately preceding claims, wherein in step a), the suspended particles represent more than 1% and less than 45% of the volume of the slip.

13. A method according to any one of the four immediately preceding claims, wherein in step a), the ceramic particles represent more than 95% of the volume of the suspended particles.

14. A method according to any one of the five immediately preceding claims, wherein in step a), the first and second particulate fractions together represent more than 95% of the total ceramic particles, in volume percentage.

15. A method according to any one of the six immediately preceding claims, wherein in step a), more than 95% by volume of the platelets of the first particulate fraction comprise more than 98% by mass of alumina.

16. Method according to the immediately preceding claim, in which in step a), more than 99% by volume of the platelets of the first particulate fraction comprise more than 99% by mass of alumina.

17. A method according to any one of the eight immediately preceding claims, wherein in step a), more than 80% by volume of the platelets of the first particulate fraction have a length of less than 70 pm.

18. A method according to any one of the nine immediately preceding claims, wherein the pressure applied during step i) is greater than 20 MPa and less than 150 MPa.

19. Method according to the immediately preceding claim, in which the pressure applied during step i) is greater than 40 MPa and less than 100 MPa.

20. Method according to any one of the eleven immediately preceding claims, in which steps h) and i) are carried out within a single step.

21. A method according to the immediately preceding claim, wherein steps h) and i) are carried out in a single step using an SPS method.

22. Method according to any one of the thirteen immediately preceding claims, in which in step d), the elimination of ice crystals is obtained by freeze-drying.

23. A method according to any one of the fourteen immediately preceding claims, wherein the second particulate fraction represents more than 3% and less than 10% of the ceramic particles, as a volume percentage based on all of the ceramic particles.

24. A method according to any one of the fifteen immediately preceding claims, wherein more than 90% by number of the particles of the second particulate fraction have a length at least 15 times less than Llso.

25. A method according to the immediately preceding claim, in which more than 90% by number of the particles of the second particulate fraction have a length at least 25 times less than Llso- 26. A method according to any one of the seventeen immediately preceding claims, wherein the second particulate fraction consists, for more than 80% by volume, of alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles.

27. A method according to any one of the eighteen immediately preceding claims, wherein the second particulate fraction comprises glass particles and / or glass-ceramic particles, the total amount of glass particles and glass-ceramic particles being greater than 0.5% and less than 18%, as a volume percentage based on all the ceramic particles in the slip.

28. A method according to the immediately preceding claim, wherein the total amount of glass particles and glass-ceramic particles is greater than 1% and less than 5%, as a volume percentage based on all the ceramic particles in the slip.

29. A method according to any one of the twenty immediately preceding claims, wherein the glass particles are selected from the group consisting of silica-containing glasses, boron oxide-containing glasses, and mixtures thereof.

30. Method according to the immediately preceding claim, in which the glass particles are chosen from the group of glasses comprising, preferably consisting of more than 90% by mass - SiO2 on the one hand, and CaO and / or MgO and / or NazO and / or TiCh and / or K2O and / or AI2O3 on the other hand, the silica content being greater than 10% by mass, or - B2O3 on the one hand, and CaO and / or Na2O and / or TiO2 and / or KaO and / or AI2O3, on the other hand, the boron content being greater than 10% by mass.

31. Method according to the immediately preceding claim, in which - the silica content is greater than 80% by mass or the boron content is greater than 80% by mass, and / or - the molar ratio SiOVCaO is between 2 and 4.

32. Method according to any one of the two immediately preceding claims, in which the second particulate fraction consists, for more than 80% by volume, of alumina particles, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, and / or glass particles consisting for more than 90% by mass of SiO2 on the one hand, and of CaO and / or MgO and / or Na2O and / or T1O2 and / or K2O and / or AI2O3 on the other hand.

33. A method according to any one of the six immediately preceding claims, wherein the ratio of the volume quantity of particles which are neither glass particles nor glass-ceramic particles to the total quantity of glass particles and glass-ceramic particles is greater than 0.5 and less than 4.

34. A method according to the immediately preceding claim, wherein said ratio is greater than 1 and less than 2.

5.

35. A method according to any one of the eight immediately preceding claims, wherein, in the second particulate fraction, the median length of the glass particles and / or glass-ceramic particles of the second particulate fraction Dsov is at least 2 times less than the median length of the particles which are not glass particles.

36. A method according to the immediately preceding claim, wherein, in the second particulate fraction, the median length of the glass particles and / or glass-ceramic particles of the second particulate fraction Dsov is at least 5 times less than the median length of the particles which are not glass particles.

37. A method according to any one of the ten immediately preceding claims, wherein the median length Dsoc of the particles which are neither glass particles nor glass-ceramic particles is greater than 0.5 times and less than 1.5 times the product - the volume percentage of the second particle fraction based on all the ceramic particles in the slip and - the average thickness of the particles of the first particulate fraction Wl* 38. The method of claim 9, wherein: - in step a): - suspended particles represent more than 8% and less than 20% of the volume of the slip, and - ceramic particles represent more than 95% of the volume of suspended particles, and - the first and second particulate fractions together represent more than 99% of all ceramic particles, in volume percentage, and - the particle size distribution of the ceramic particles in the suspension is bimodal, the two main modes corresponding to the first and second particle fractions, respectively, and - the first particulate fraction, or “platelet fraction”, represents more than 94% of all ceramic particles, in volume percentage, and - more than 99% by volume of the platelets of the first particulate fraction comprise more than 99%, by mass of alumina, and -- more than 95%, by volume, of the platelets of the first particulate fraction have a length less than 20 pm and greater than 4 pm, a width less than 10 pm and greater than 3 pm, and a thickness less than or equal to 1.5 pm, and - the second particulate fraction represents more than 3% and less than 6% of the ceramic particles, as a volume percentage based on all the ceramic particles, and - more than 95%, by number of the particles of the second particulate fraction, have a length at least 25 times less than LI50, and - the second particulate fraction comprises glass particles mixed with alumina particles, the ratio of the volume quantity of particles which are neither glass particles nor glass-ceramic particles to the total volume quantity of glass particles and glass-ceramic particles is greater than 0.5 and less than 2.5, and - the glass particles are chosen from the group of glasses consisting of more than 90% by mass of SiCh on the one hand, and CaO and / or MgO on the other hand, and ■ - in step c), the freezing rate is greater than 10 pm / s and less than 100 pm / s, and - step d) is a step of eliminating ice crystals by sublimation thereof, and » steps h) and i) are carried out in a single step using an SPS process, carried out under vacuum, at a maximum temperature between 1300°C and 1700°C, and at a pressure greater than 30 MPa.

39. Device chosen from: - a turbine, - a sensor other than a displacement sensor, - a probe, - a membrane for filtering gases or liquids, - an armor or element of armor, “a shield or shielding element, - an anti-wear part or coating, - an element of the infrastructure of a cooking oven, - a thick or thin layer substrate for electronic components and insulators for electrical conductors, - a tool, - a grindstone, - grains for deburring or treating a surface, - a forming tool, in particular a die, an injection mold, - a ceramic firing support, - a prosthesis, in particular a dental implant, an orthopedic element, said device comprising a product according to any one of claims 1 to 8, or a product manufactured according to any one of claims 9 to 38.

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