Dense sintered product

A process for manufacturing a sintered product, said process comprising the following steps:

• a) preparing a slip comprising an set of ceramic particles suspended in a liquid phase, the set of the ceramic particles representing more than 90% of the volume of the suspended particles and comprising:
• a first particulate fraction consisting of platelets having a length of greater than or equal to 1 μm, the first particulate fraction having a median length L150 and representing more than 80% of the ceramic particles, as percentage by volume on the basis of the set of the ceramic particles, more than 50% by volume of said platelets each comprising more than 50% by weight of alumina;
• and
• a second particulate fraction of particles having a length of less than 1 μm, the second particulate fraction having a median length D50 at least 10 times less than L150 and representing more than 1% of the ceramic particles, as percentage by volume on the basis of the set of the ceramic particles, the particles of said second particulate fraction being constituted, to more than 90% by weight, of oxides
• b) optionally, removing air bubbles contained in the slip,
• c) freezing the slip so as to form a frozen slip incorporating ice crystals;
• d) removing the ice crystals, so as to obtain an intermediate product, and optionally drying of said intermediate product;
• e) if the intermediate product is not in the form of a powder, the particles of which pass through the square meshes of a screen with sides of 25 mm, miffing and/or screening of said intermediate product so that the intermediate product is in the form of such a powder;
• f) optionally, debinding said intermediate product;
• g) optionally, thermal pretreatment;
• h) shaping of the intermediate product by pressing, by injection molding or by extrusion so as to obtain a preform;
• i) sintering the preform with application of a pressure of greater than 0.5 MPa so as to obtain a sintered product, it being possible for the steps h) and i) to be carried out in a single unique step;
• j) optionally, machining of said sintered product,
• wherein the first and second particulate fractions are selected so that the sintered product obtained at the end of step i) is a sintered product
• having a relative density of greater than 90%,
• comprising, to more than 80% of the volume thereof, a stack of ceramic platelets (10), a platelet having major faces that are substantially flat and parallel to one another, the ceramic platelets being stacked flat, so that said major faces of said platelets extend parallely to a general plane, the set of said platelets having a mean thickness of less than 3 μm,
• having a width (l) of greater than 50 mm, and
• comprising more than 20% of alumina, as a percentage on the basis of the weight of the product,
• the width (l) 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 the largest dimension thereof in a plane (C) parallel to the general plane in which the platelets extend.

A device selected from:

• a turbine,
• a sensor other than a displacement sensor,
• a probe,
• a membrane for the filtration of gases or liquids,
• an armor or armoring element,
• a shield or shielding element,
• a wear-resistant part or coating,
• an element of the infrastructure of a kiln,
• a thick or thin layered substrate for electronic components and insulators for electrical conductors,
• a tool,
• a grinding wheel,
• grains for debarring or treating a surface,
• a shaping tool, in particular a die, an injection mold,
• a support for firing ceramics,
• a prosthesis, in particular a dental implant, an orthopedic element, said device comprising a product
• having a relative density of greater than 90%,
• comprising, to more than 80% of the volume thereof, a stack of ceramic platelets (10), a platelet having major faces that are substantially flat and parallel to one another, the ceramic platelets being stacked flat, so that said major faces of said platelets extend parallely to a general plane, the set of said platelets having a mean thickness of less than 3 μm,
• having a width (l) of greater than 50 mm, and
• comprising more than 20% of alumina, as a percentage on the basis of the weight of the product,
• the width (l) 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 the largest dimension thereof in a plane (C) parallel to the general plane in which the platelets extend.