EP3661894A1 - Produit fritte dense - Google Patents

Produit fritte dense

Info

Publication number
EP3661894A1
EP3661894A1 EP18701763.7A EP18701763A EP3661894A1 EP 3661894 A1 EP3661894 A1 EP 3661894A1 EP 18701763 A EP18701763 A EP 18701763A EP 3661894 A1 EP3661894 A1 EP 3661894A1
Authority
EP
European Patent Office
Prior art keywords
less
content
particles
volume
product
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP18701763.7A
Other languages
German (de)
English (en)
French (fr)
Inventor
Nassira Benameur
Christian His
Jérôme LELOUP
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Original Assignee
Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saint Gobain Centre de Recherche et dEtudes Europeen SAS filed Critical Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Publication of EP3661894A1 publication Critical patent/EP3661894A1/fr
Pending legal-status Critical Current

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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B1/00—Producing shaped prefabricated articles from the material
    • B28B1/007—Producing shaped prefabricated articles from the material by freezing the material
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B28B17/00—Details of, or accessories for, apparatus for shaping the material; Auxiliary measures taken in connection with such shaping
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Definitions

  • the invention relates to a method for producing a dense sintered product of large width.
  • the invention also relates to such a product.
  • WO2015189659 discloses a method of manufacturing a dense product, obtained by a method comprising a step of oriented freezing of a slip having ceramic platelets, then a compression step. More precisely, freezing results from the presence of two temperature gradients F and F '(see FIG. 2) oriented perpendicular to the surface of a slip layer B, poured onto a horizontal surface. This progression directs the platelets P parallel to each other and substantially perpendicular to the horizontal surface. The removal of the 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 obtained is dense and has good mechanical properties, including good toughness. Its smallest dimension, that is to say its thickness e ', is conventionally measured in the direction of compression.
  • the method implemented in WO2015189659 does not make it possible to obtain products having a width greater than 50 mm.
  • the freezing requires that the slip layer extending on the horizontal plane is thin, and in particular less than 50 mm.
  • the compression is therefore carried out in a direction parallel to the general plane of this layer.
  • the width of the resulting product, measured (as the length) in a plane parallel to the plane of the wafers, is therefore substantially equal to the thickness of the slip layer and is therefore limited.
  • the dimension ⁇ shown in Figure 2 illustrates this problem.
  • An 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 first particulate fraction consisting of platelets having a length greater than or equal to 1 ⁇ and, preferably less than 70 ⁇ , the first particulate fraction having a median length LI 50 and representing more than 80% of the ceramic particles, in percentage by volume on the base of all the ceramic particles, more than 50% by volume of said platelets each comprising more than 50% by weight of alumina;
  • a second particulate fraction of particles having a length of less than 1 ⁇ , the second particulate fraction having a median length D50 at least ten times lower than LI 50 (ie D50 ⁇ LI 50/10) and representing more of 1% of the ceramic particles, in percentage by volume based on all the ceramic particles, the particles of said second particulate fraction consisting of more than 90% by mass of oxides;
  • steps h) and i) can be carried out in a single step;
  • a process according to the invention makes it possible in particular to manufacture a particularly dense sintered product exhibiting a non-brittle behavior in the SENB method and of which all the dimensions , and in particular the width, can be large.
  • a powder of particles consisting of pieces of the intermediate product and thus mainly consisting of agglomerated wafers is obtained.
  • the inventors have discovered that sintering with application of a pressure greater than 0.5 MPa is sufficient, if it is preceded by freezing steps. defrosting, 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 keep all the platelets parallel to each other from the freezing step to the pressing step.
  • the plates are oriented, it is no longer necessary to impose a pressing direction.
  • the frozen slip be in the form of a thin layer.
  • the length, the width and the thickness of the sintered product may advantageously be arbitrary, and in particular greater than 50 mm or greater than 80 mm.
  • a method according to the invention may also include one or more of the following optional features, which may be combined in any combination:
  • the first and second particulate fractions are chosen so that the sintered product obtained at the end of step i) is in accordance with the invention
  • step h) the shaping of the intermediate product is carried out by pressing at a pressure greater than 3 MPa
  • the particles in suspension represent more than 1% and less than 45% of the volume of the slip
  • the ceramic particles represent more than 95% of the volume of the particles in suspension, in step a), more than 95% by volume of the platelets of the first particulate fraction comprise more than 98% by weight of alumina,
  • step a) more than 99% by volume of the platelets of the first particulate fraction comprise more than 99% by weight of alumina
  • step a) more than 80% by volume of the platelets of the first particulate fraction have a length of less than 70 ⁇ ,
  • 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 one and the same step, preferably using an SPS method,
  • step d) the removal of the ice crystals is obtained by lyophilization
  • the second particulate fraction represents more than 3% and less than 10% of the ceramic particles, as a percentage by volume based on all the ceramic particles,
  • 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 amount 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 percentage by volume based on all the ceramic particles of the slip,
  • the glass particles are chosen from the group consisting of glasses containing silica, glasses containing boron oxide, and mixtures thereof, preferably chosen from the group of glasses comprising, preferably, more than 90% mass
  • the silica content being greater than 10% by mass, preferably greater than 80% by weight, preferably the SiO 2 / CaO molar ratio is between 2 and 4, or o B2O3 on the one hand, and CaO and / or Na 2 0 and / or T1O2 and / or K 2 0 and / or Al 2 O 3, on the other hand, the boron content being greater than 10% by weight, preferably greater than 80% by weight,
  • the second particulate fraction consists, for more than 80% by volume, of alumina particles, and / or of zirconia particles, and / or of stabilized zirconia particles, and / or of alumina-zirconia particles and / or glass particles made up of more than 90% by weight of SiO 2 on the one hand, and of CaO and / or MgO and / or Na 2 O and / or TiO 2 and / or K 2 O and / or AI2O3 on the other hand,
  • the ratio of the volume quantity of particles which are neither glass particles nor glass-ceramic particles to the total quantity of particles of glass and glass-ceramic particles is greater than 0.5, preferably greater than 1 and less than 4, preferably less than 2.5,
  • 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 less than the median length of the particles which are not not glass particles.
  • the invention also relates to a sintered product
  • the thickness (W1) of a wafer being the length of the minor axis of the ellipse (E) of minimum area in which may be inscribed the median cross section of said wafer, said median cross section being a section in a plane section (A) perpendicular to the direction of the length (L1) of said wafer and intersecting said wafer at mid-length, said length being the largest dimension of said wafer observable on a plate taken in a direction perpendicular to the plane on which rests, flat, said plate, the width () 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 wafers extend.
  • the product according to the invention also has one or more of the following optional characteristics:
  • a tenacity Kj c greater than 6 MPa.m 172 , preferably greater than 8 MPa.m 172 ,
  • more than 70%, preferably more than 95%, by number of platelets of the sintered product comprise more than 70%, preferably more than 95% by weight of alumina,
  • boron nitride content greater than 1% and less than 20% by weight based on the mass of said product, the boron nitride being present in the form of platelets, more than 90% by number of platelets of said product a length less than 70 ⁇ and greater than 2 ⁇ ,
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and
  • 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
  • the content of other elements being less than 2%, preferably less than 1, 5%, preferably less than 0.8%,
  • the Al 2 O 3 content is greater than 95%, preferably greater than 96.9% and less than 99.7%, preferably less than 99.5%.
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and the CaO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and
  • the MgO content is less than 0.3%, preferably less than 0.1%, and the alumina and the other elements constituting the 100% complement, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 0.8%,
  • the Al 2 O 3 content is preferably greater than 95%, preferably greater than
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and
  • the MgO content is greater than 0.1% and less than 4.5%, preferably less than 1.5%, preferably less than 0.8%, and
  • the CaO content is less than 0.3%, preferably less than 0.1%, and the alumina and the other elements constituting the 100% complement, the content of other elements being less than 2%, preferably less than 1.5%, preferably less than 0.8%,
  • the Al 2 O 3 content is preferably greater than 95%, preferably greater than
  • the Zr0 2 content, optionally stabilized, is greater than 1% and less than 15%, and
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and
  • 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
  • the alumina and the other elements constituting the 100% complement the content of other elements being less than 10%, preferably less than 1.5%, preferably less than 0.8%,
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and 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
  • the boron nitride content is greater than 1% and less than 20%, and the alumina and the other elements constituting the 100% complement, the content of other elements being less than 10%, preferably less than 10%; 1.5%, preferably less than 0.8%,
  • the Zr0 2 content, optionally stabilized, is greater than 1% and less than 15%, and
  • the content of SiO 2 is greater than 0.2% and less than 13.5%, preferably less than 2%, preferably less than 1.5%, and
  • 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
  • the boron nitride content is greater than 1% and less than 20%, and the alumina and the other elements constituting the 100% complement, 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 likely to have been obtained by a process according to the invention
  • the invention also relates to a device selected from
  • a sensor other than a displacement sensor in particular for a gas or a liquid
  • a probe in particular for a gas or a liquid
  • an element of the infrastructure of a cooking oven in particular a beam or a bank
  • a tool in particular a chisel, a knife, a sharpener, a bit, a drill, a screwdriver, a file, - a grinding wheel,
  • a forming tool in particular a die, an injection mold,
  • a firing support in particular a ceramic firing furnace
  • a prosthesis in particular a dental implant, an orthopedic element
  • said device comprising a product according to the invention or obtained by a process according to the invention or capable of have been obtained by a process according to the invention.
  • ceramic material refers to any non-metallic and non-organic material.
  • a "precursor" of an element is called an object that is transformed into said element by the execution of a method according to the invention.
  • Sublimation is an operation, usually under vacuum, which consists of evaporating ice without melting it.
  • a merger is an operation that consists of melting ice.
  • Temporal means "removed from the product during debinding or sintering".
  • the solid elements constituting a powder or suspended in a slip are called "particles".
  • the dissolved material does not constitute particles.
  • the structure of a gel, obtained by gelation of a soil, has substantially no particles.
  • particles are the agglomerated particles during sintering which were suspended in the slurry used to make the sintered product. The dimensional characteristics relating to a wafer within the sintered product can be evaluated by measurements on said product.
  • the "length" L1 of a wafer is its largest dimension observable on a photograph taken in a direction perpendicular to the plane on which lies flat, said wafer.
  • the "width" W2 and the “thickness” W1 of a wafer are the lengths of the large and small axes, respectively, of the smallest possible ellipse E (that is to say of minimum area) in which can be inscribed the median cross section of said wafer (that is to say in the sectional plane A in Figure 1).
  • FIG. 1 shows the diagram of a wafer 10.
  • the wafer 10 is shown in perspective.
  • FIG. 1b represents the section of the wafer 10 according to FIG. median transverse plane A (plane perpendicular to the direction of the length L1, passing mid-length of the wafer).
  • a particle has a "wafer" shape when it meets both of the following conditions:
  • the cross section of a wafer is substantially polygonal and has at least 4 sides. More preferably, the large faces of a wafer are substantially planar, and preferably parallel to each other.
  • the dimensions of a wafer can be easily evaluated on snapshots of observations made on a powder.
  • the "median" value of a property of the particles of a set of particles is the value of this property which divides the particles of said set into first and second populations equal in number, these first and second populations comprising only particles having a value of said property greater than or equal to, or less than, the median value, respectively.
  • the median length of a set of particles is the length dividing the particles into first and second populations equal in number, these first and second populations comprising only particles having 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 is its largest dimension in a plane C parallel to the general plane in which the wafers extend.
  • the plane C may be any plane parallel to the general plane in which the plates extend. Otherwise, as in FIG. 5, the plane C is chosen from among all the planes parallel to the general plane in which the plates extend, as the plane in which the product has the largest dimension.
  • the width / of a sintered product according to the invention is the largest dimension measured in the plane C in which the length is measured, in a direction perpendicular to the direction of the length.
  • stabilized zirconia means a zirconia having a quantity of zirconia in a monoclinic crystallographic form of less than 5% by weight, the balance being constituted by zirconia in a quadratic crystallographic form, stable and / or metastable, and / or cubic.
  • a "bimodal" distribution shows two non-contiguous categories with the highest values, called “main peaks” or “main modes”.
  • an average is an arithmetic mean.
  • the percentages by volume of a set of particles correspond to percentages by considering the sum of the volumes of each of the particles considered.
  • the sum of these volumes is conventionally calculated by the ratio of the mass of said set of particles divided by the absolute density of the material of said particles. For example, if the second particulate fraction is less than 20% "of the volume of all the ceramic particles", or equivalent of "the volume of the ceramic particles” or “as a percentage by volume based on all the ceramic particles Or "in percentage by volume on the basis of the ceramic particles", the volumes to be compared are the volume of the particles of the powder 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.
  • buoyancy of a product is meant in the sense of the present invention, the ratio equal to the mass of the product divided by the volume occupied by said product. It can be measured by imbibition, according to the principle of buoyancy.
  • absolute density of a product is meant in the sense of the present invention, the ratio equal to the mass of dry matter of said product after milling to a fineness such that there remains substantially no closed porosity, divided by the volume of said mass of dry matter after grinding. It can be measured by helium pycnometry.
  • a wafer stack is a structure in which the wafers are superimposed flat on each other, with a possible lateral offset, as shown, for example, in Figure 2c.
  • a pigment is a powder which, when incorporated in a preform, provides a particular color to the sintered product. In particular, the coloring may result from the sintering of said preform.
  • a pigment is a powder whose median particle size is less than 50 ⁇ .
  • Figure 1 (la-lb) schematically shows a wafer
  • Figure 2 (2a-2c) illustrates a method according to the prior art
  • FIG. 3 illustrates a method according to the invention
  • FIGS 4 and 5 show, in perspective, sintered products according to the invention
  • Figure 6 illustrates the microstructure of the product of Example 2 according to the invention.
  • a product according to the invention may be manufactured according to a process comprising steps a) to j) above.
  • step a) of preparing the slip a suspension of ceramic particles is prepared.
  • the particles in suspension 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.
  • the ceramic particles preferably represent more than 95% or even more than 99% or even substantially 100% of the volume of the particles in suspension.
  • the ceramic particles may be replaced, partially or totally, by equivalent amounts of precursors which become ceramic particles before step j).
  • the first and second particulate fractions together represent more than 85%, preferably more than 90%, preferably more than 95% of all the ceramic particles, as a percentage by volume. In one embodiment, the first and second particulate fractions together represent, more than 98%, preferably more than 99%, preferably substantially 100% of all the ceramic particles, as a percentage by volume.
  • the particle size distribution of the ceramic particles of the suspension is preferably bimodal, the two main modes corresponding to the first and second particulate fractions, respectively.
  • all the ceramic particles in suspension comprise a pigment.
  • the pigment is an oxide.
  • the pigment is an oxide comprising the aluminum element or a compound forming, during the sintering step i), an oxide comprising the aluminum element.
  • the amount of pigment is greater than 1%, preferably greater than 2%, preferably greater than 4% and less than 15%, preferably less than 13% of all the ceramic particles, in percentage by volume.
  • the pigment may be partially or fully included in the second particulate fraction.
  • First particulate fraction first particulate fraction
  • the first particulate fraction preferably represents more than 85%, preferably more than 88%, preferably more than 90%, more preferably more than 92%, more preferably more than 94%. ceramic particles as a percentage by volume.
  • more than 50%, preferably more than 55%, preferably more than 60%, preferably more than 65%, preferably more than 70%, preferably more than 75%, more preferably preferably more than 80%, preferably more than 85%, preferably more than 90%, preferably more than 95%, more 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%, more preferably preferably more than 99% by weight of alumina.
  • the complement to the alumina is more than 90% by weight, preferably more than 95%, preferably more than 97%, more preferably more than 90% by weight. 99% by weight of oxides.
  • the first particulate fraction comprises, for a total of greater than 90%, preferably more than 95%, preferably more than 99%,
  • 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 weight of alumina, and
  • platelets of the first particulate fraction have a length less than 70 ⁇ , preferably less than 60 ⁇ , preferably less than 50 ⁇ , preferably less than 40 ⁇ , preferably less than 25 ⁇ , preferably less than 20 ⁇ , or even less than 15 ⁇ and preferably greater than 2 ⁇ , preferably greater than 4 ⁇ , preferably greater than 5 ⁇ .
  • platelets of the first particulate fraction have a width less than or equal to 20 ⁇ , preferably less than 15 ⁇ , preferably less than 10 ⁇ , and preferably greater than 2 ⁇ , preferably greater than 3 ⁇ , preferably greater than 4 ⁇ .
  • platelets of the first particulate fraction have a thickness less than or equal to 3 ⁇ , of preferably less than or equal to 2.5 ⁇ , preferably less than or equal to 2 ⁇ , preferably less than or equal to 1.5 ⁇ , or even less than or equal to 1 ⁇ .
  • platelets of the first particulate fraction have a length less than 10 ⁇ , preferably less than 8 ⁇ , preferably less than 6 ⁇ , preferably less than 4 ⁇ , and preferably greater than 1 ⁇ ; and a width less than 10 ⁇ , preferably less than 8 ⁇ , preferably less than 6 ⁇ , preferably less than 4 ⁇ , and preferably greater than 1 ⁇ ; and a thickness less than or equal to 1.5 ⁇ , preferably less than or equal to 1 ⁇ , preferably less than or equal to 0.8 ⁇ , preferably less than or equal to 0.5 ⁇ , preferably less than or equal to 0; , 5 ⁇ , preferably less than or equal to 0.3 ⁇ , preferably less than or equal to 0.1 ⁇ .
  • the modulus of rupture is improved.
  • Second Particulate Part Remarkably, the presence of the fine particles of 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 percentage by volume based on all the ceramic particles.
  • more than 90%, preferably more than 95%, preferably more than 98% by number of the particles of the second particulate fraction have a length of at least 15 times, preferably at least 20 times. , preferably at least 25 times, preferably at least 30 times less than 50 Ll.
  • the particles of the second particulate fraction are 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%) of oxides.
  • the second particulate fraction is more than 80%, preferably greater than 90%, preferably substantially 100% by volume, of ceramic particles which are not glass particles, preferably particles of alumina, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, preferably alumina particles. In one embodiment, the second particulate fraction does not include glass and / or glass-ceramic particles.
  • the stabilized zirconia is preferably an yttria stabilized zirconia, cerium oxide, calcium oxide, magnesium oxide, scandium oxide and mixtures thereof.
  • the second particulate fraction comprises pigment particles.
  • the second particulate fraction comprises glass and / or glass-ceramic particles, preferably glass particles, preferably in admixture with ceramic particles which are not glass particles, preferably particles. of alumina, and / or zirconia particles, and / or stabilized zirconia particles, and / or alumina-zirconia particles, preferably alumina particles.
  • the glass particles and / or glass-ceramic particles may be replaced, partially or totally, by equivalent amounts of glass precursor particles and / or glass-ceramic particles, respectively. This substitution is also applicable for all the optional characteristics relating to the glass particles and to the vitroceramic particles described hereinafter.
  • all of the glass particles and / or glass-ceramic has a median length Dsov at least 50 times lower than LI 50, preferably at least 100 times lower than LI 50, preferably at least 150 times lower than LI 50 preferably at least 200 times lower than LI 50, preferably at least 300 times lower than LI 50.
  • the amount of glass particles and / or glass-ceramic particles is greater than 0.5%, preferably greater than 1% by volume percentage based on all the ceramic particles. More preferably, the amount of glass particles and / or glass-ceramic particles is less than 18%, or even less than 10%, or even less than 5%, as a percentage by volume based on all the ceramic particles in suspension.
  • the ratio of the volume amount 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, preferably higher than at 1 and / or less than 4, preferably less than 3, preferably less than 2.5.
  • the median length Dsoc of the particles which 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 average particle thickness of the first particulate fraction Wl * and preferably less than 1.5 times, preferably 1.3, preferably 1.2 times said product.
  • 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 which are not glass particles of the second particulate fraction.
  • the glass transition temperature of the glass of said glass particles is between the densification start temperature and the densification end temperature, the densification start and end temperatures being measured on a product obtained by the same process. and from the same slip but which has no glass particle.
  • the densification start and end densification temperature are measured on a dilatometer and correspond to the temperature at which the shrinkage starts and the temperature at which the shrinkage ends, respectively.
  • the glass particles are selected from the group consisting of silica-containing glasses, glasses containing boron oxide, and mixtures thereof.
  • the glass particles are chosen from the group of glasses comprising, preferably, more than 90%>, preferably more than 95% by weight of SiO 2 on the one hand, and of CaO and / or MgO and / or Na 2 0 and / or TiO 2 and / or K 2 0 and / or Al 2 O 3 on the other hand, preferably SiO 2, and CaO and / or MgO and / or Al 2 O 3, preferably SiO 2, and CaO and / or MgO.
  • the second particulate fraction consists, for more than 80%, preferably more than 90%, preferably substantially 100% by volume, of alumina particles, and / or zirconia particles, and and / or stabilized zirconia particles, and / or alumina-zirconia particles, and / or glass particles constituted for more than 90%, preferably for more than 95% by weight of SiO 2, on the one hand, and CaO and / or MgO and / or Na2O and / or TiO2 and / or K2O and / or Al2O3, on the other hand, preferably SiO2, and CaO and / or MgO and / or Al2O3, preferably SiO2, and CaO and / or MgO.
  • the silica content of said glass particles containing silica 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.
  • the glass contains S102 on the one hand, and CaO and / or Al2O3 on the other hand.
  • the glass contains S102 and CaO and Al2O3.
  • the SiO 2 / CaO molar ratio is between 2 and 4, preferably between 2.5 and 3.5, or even substantially equal to 3.
  • the glasses containing boron oxide may be glasses comprising B2O3 on the one hand, and CaO and / or Na2O and / or T1O2 and / or K2O and / or Al2O3, on the other hand.
  • the B2O3 content of said boron oxide 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.
  • the liquid phase preferably contains more than 50%, preferably more than 60%, more preferably more than 70%, more preferably more than 80%, more preferably more than 90% water, more preferably more preferably 95% o of water, as a percentage by volume based on the liquid phase.
  • the liquid phase may consist of water.
  • the amount 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%, by volume percentage of the slip.
  • the slip preferably contains a dispersant facilitating the production of a homogeneous suspension.
  • the dispersant content is between 0.1% and 3%, preferably between 0.2% and 2%, preferably between 0.5% and 1.5% by weight based on the weight of the ceramic particles of the slip.
  • the dispersants conventionally used for the manufacture of sintered products by slip casting can be used, for example ammonium polymethacrylates such as Darvan 7-NS, manufactured by Vanderbilt.
  • the slip preferably contains a thickening agent.
  • 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 of the slip.
  • Carbopol EDT 2691, marketed by the company Lubrizol can for example be used as a thickening agent.
  • the slip may contain a binder, preferably temporary.
  • the binder content is between 0.5% and 5% by weight based on the mass of the ceramic particles of the slip.
  • Temporary binders conventionally used for the manufacture of sintered products may be used, for example polyvinyl alcohol (PVA), polyethylene glycol (PEG).
  • the slip may also contain an anti-foaming agent.
  • the anti-foaming agent content is between 0.1 and 3%, preferably between 0.1% and 1% by weight based on the mass of the ceramic particles of the slip.
  • the anti-foaming agents conventionally used for the manufacture of sintered products by slip casting can be implemented, for example the CONTRASPUM CONC marketed by the company Zschimmer and Schwarz.
  • the ceramic particles, the water, the optional dispersant, the optional thickening agent, the optional binder, the optional anti-foaming agent together represent more than 80%, more than 90%, more than 95%, more than 99%, even substantially 100% of the volume of the slip.
  • the various constituents of the slip are added with stirring.
  • the mixture of the various constituents of the slip can be carried out according to any technique known to those skilled in the art, for example in a mixer, in a turbulence, in a jar mill with beads, preferably of the same nature as the ceramic powder in suspension .
  • the mixing intensity and / or the mixing time are preferably adapted so as not to break the wafers.
  • the platelets are preferably introduced last in a premix containing the other constituents.
  • the mixing time is preferably greater than 0.5 hours and less than 20 hours.
  • a jar mill is used, the wafers being introduced in a premix premixed for 12 hours, the mixing time from the introduction of platelets in the slip being greater than 30 minutes and preferably less than 4 hours.
  • step b) air bubbles are removed, preferably by degassing under vacuum or ultrasound.
  • step c) the slip is cooled so as to solidify the water and form ice crystals.
  • Any technique known to those skilled in the art for freezing a slip may be used, for example ice texturing techniques or “ice templating”, or techniques of freezing of slip drops, or “freeze granulation”, or techniques of immersing a quantity of slip in a cooling bath, preferably in liquid nitrogen.
  • the freezing rate is greater than 1 ⁇ / s, preferably greater than 5 ⁇ / s, preferably greater than 10 ⁇ / s , preferably greater than 12 ⁇ / s, or even greater than 15 ⁇ / s, or even greater than 20 ⁇ / s, or even greater than 40 ⁇ / s and less than 400 ⁇ / s, preferably less than 300 ⁇ / s, preferably less than 200 ⁇ / s, preferably less than 100 ⁇ / s.
  • the freezing step is oriented in a preferred direction constituting a solidification front.
  • 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 the ice crystals depends mainly on the speed of displacement of the solidification front and the thermal gradient associated with this solidification front. The higher the rate of solidification, the smaller the size of the ice crystals.
  • the slip is frozen without favoring a direction of freezing.
  • the process is considerably simplified.
  • the slip is immersed in a cooling bath, preferably liquid nitrogen, and preferably, the slip is removed when it is substantially completely frozen.
  • a cooling bath preferably liquid nitrogen
  • the slip is removed when it is substantially completely frozen.
  • all of the slip is solidified in step c).
  • the solidified slip is placed under pressure and temperature conditions leading to removal of the ice crystals, preferably by sublimation.
  • the sublimation is substantially without displacement of the particles arranged between the crystals.
  • the ice crystals can be sublimated by heating them at very low pressure, typically at a pressure of less than 0.5 mbar, preferably less than 0.3 mbar.
  • Step d) is preferably continued until the removal of all ice crystals.
  • An intermediate product is thus obtained in the form of a block or agglomerates.
  • the intermediate product can be dried if it is wet, the drying being preferably carried out at a temperature between 50 ° C and 110 ° C, for a period of preferably greater than 2 hours, preferably greater than 10 hours.
  • step d) is a step of removing the ice crystals by sublimation thereof and the method according to the invention does not then require such drying.
  • step e) if the intermediate product is not in the form of a powder, it is ground and / or sieved so as to turn it into powder.
  • the product is considered not to be in the form of a powder if it can not pass through a sieve of square mesh of 25 mm side, preferably 15 mm, preferably 10 mm, preferably 5 mm preferably 4 mm, preferably 3 mm, preferably 2 mm side.
  • Grinding can be carried out in the dry process by any technique known to those skilled in the art, preferably with the aid of a bowl containing mobile (rings, pucks or balls) set in motion, a hand press or a mortar and pestle.
  • the sieving is preferably carried out using sieves of less than 1 mm opening, or even less than 500 ⁇ , or even less than 400 ⁇ .
  • this step makes it possible to eliminate the larger agglomerates.
  • step f) optional debinding eliminates organic matter. It is preferably carried out using a 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.
  • Stage g) of optional thermal pretreatment makes it possible to promote the attachment of the particles of the second particulate fraction to the platelets of the first particulate fraction.
  • the maximum temperature reached in 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 holding time at the maximum temperature is preferably less than 5 hours, preferably less than 2 hours. In a preferred embodiment, the hold time at the maximum temperature is substantially zero.
  • this step is preferably carried out in a nitrogen atmosphere.
  • step h the intermediate product in powder form is shaped by pressing, by injection molding or by extrusion so as to obtain a preform.
  • the intermediate product in the form of a powder is conventionally mixed with a wax or a polymer so as to obtain a compound having a rheology suitable for molding by molding. injection. All extrusion techniques are possible.
  • the intermediate product in the form of a powder is conventionally mixed with water and with products, preferably organic, which promote extrusion, in particular plasticizers and lubricants.
  • the amount of plasticizers and lubricants can be between 1% and 5%, preferably between 1.5% and 3% by weight based on the summed mass of the powder of the intermediate product, water and said plasticizers and lubricants.
  • the amount of water may be from 10% to 25%, preferably from 15% to 20% by weight based on the summed mass of the intermediate product powder, water and said plasticizers and lubricants.
  • the extrusion can be carried out at atmospheric pressure or under vacuum.
  • drying and / or debinding is preferably carried out after forming, preferably by heat treatment whose temperature is a function of plasticizers, lubricants, polymers and waxes used during the shaping.
  • the shaping of the powder is carried out by pressing. The process is advantageously simplified.
  • the pressing is configured so that the sintering of the pre form 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.
  • the pressing is chosen from uniaxial pressing and cold isostatic pressing.
  • the intermediate product in powder form is poured into a mold, then subjected to a pressure preferably greater than 3 MPa, preferably greater than 5 MPa, or even greater than 10 MPa, even greater than 50 MPa and preferably less than 200 MPa, or even less than 150 MPa, so as to constitute a green part, or "preform".
  • a pressure preferably greater than 3 MPa, preferably greater than 5 MPa, or even greater than 10 MPa, even greater than 50 MPa and preferably less than 200 MPa, or even less than 150 MPa
  • step i) the preform is sintered in an oxidizing, neutral or reducing atmosphere.
  • the atmosphere during sintering is neutral, preferably under vacuum.
  • the 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, preference 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.
  • 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 rise in temperature and the eventual bearing at the maximum temperature.
  • the residence time, the temperature and the sintering atmosphere 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 the sintering is preferably between 1300 ° C and 1700 ° C, preferably between 1450 ° C and 1550 ° C.
  • step i a sintered product according to the invention is obtained.
  • Steps h) and i) are preferably carried out in one and the same step, for example using a hot pressing method or SPS ("Spark Plasma Sintering").
  • steps h) and i) are performed in a single step using an SPS method.
  • the SPS is made:
  • step j the sintered product can be machined by any technique known to those skilled in the art.
  • step j) can be performed on the preform before step i).
  • the method according to the invention comprises the following characteristics:
  • the particles in suspension represent more than 8% and less than 20%> of the volume of the slip
  • the ceramic particles represent more than 95% of the volume of the particles in suspension, and the first and second particulate fractions together represent more than 99% of all the ceramic particles, in percentage by volume, and the particle size distribution of the ceramic particles of the suspension is bimodal, the two main modes corresponding to the first and second particulate fractions, respectively , and
  • the first particulate fraction represents more than 94% of all the ceramic particles, in percentage by volume, and
  • platelets of the first particulate fraction have a length less than 20 ⁇ , and greater than 4 ⁇ , a width less than 10 ⁇ and greater than 3 ⁇ , and a thickness less than or equal to at 1.5 ⁇ , and
  • the second particulate fraction represents plus 3% and less than 6%> of the ceramic particles, as a percentage by volume based on all the ceramic particles, and
  • the second particulate fraction comprises glass particles in admixture with alumina particles, the ratio of the volume amount of particles which are neither glass particles nor glass-ceramic particles to the total volume quantity of glass particles and of glass ceramic particles, is greater than 0.5 and less than 2.5, and
  • the glass particles are chosen from the group of glasses made up of more than 90% by weight of SiO 2 on the one hand, and of CaO and / or MgO on the other hand, and in step c), the speed of freezing is greater than 10 ⁇ / s and less than 100 ⁇ / s, and
  • step d) is a step of removing ice crystals by sublimation thereof.
  • steps h) and i) are carried out in a single step using a SPS process, carried out under vacuum, at a maximum temperature of between 1300 ° C and 1700 ° C, and at a pressure greater than 30 MPa.
  • a method according to the invention makes it possible to manufacture a product according to the invention having mechanical properties, and in particular tenacities, which are remarkable.
  • a sintered product according to the invention may be obtained or may have been obtained by a process according to the invention.
  • more than 50%, preferably more than 60%, more preferably more than 70%, more preferably more than 80%, more preferably more than 90%, more preferably more than 95%. preferably more than 98%, preferably more than 99%, preferably substantially 100% by number of the platelets of the sintered product comprise more than 50%, preferably 60%, preferably 70%, preferably %>, preferably more than 85%, preferably more than 90%>, preferably more than 95%, preferably more than 98%, more preferably more than 99% alumina by mass.
  • the sintered product contains more than 1% or even more than 5% or even more than 10%), or even more than 15% and less than 20% of boron nitride, in mass on the basis of mass. of the product, the boron nitride being present in the form of platelets.
  • the other platelets present are platelets 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.
  • the addition of boron nitride in the form of platelets does not modify or slightly the relative density of the sintered product after sintering and the non-brittle behavior in the SENB method.
  • more than 90%, preferably more than 95%, preferably more than 98%, in number of platelets have a length less than 70 ⁇ , preferably less than 60 ⁇ , preferably less than 50 ⁇ , of preferably less than 40 ⁇ , preferably less than 25 ⁇ and preferably greater than 2 ⁇ , preferably greater than 4 ⁇ .
  • Ceramic particles other than platelets may at least partially not be visible after sintering step i), making their quantification difficult. However, they contribute to obtaining a sintered product having 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 greater than 97%, preferably greater than 97.5%, preferably greater than 98%, preferably greater than 98.5%.
  • the pads are stacked on top of each other. They therefore extend in substantially parallel planes, as can be seen in FIG. 6, showing a snapshot of the microstructure of the product of example 2 according to the invention.
  • the average standard deviation around the average principal orientation is less than 20 °, preferably less than 16 °, the average main orientation and the average standard deviation around the average main orientation being determined by the method described for the examples.
  • a reduction in average standard deviation around the average main orientation considerably improves the toughness K lc and K c of the sintered product.
  • the average platelet thickness of the sintered product is preferably less than 2.5 ⁇ , preferably less than 2.0 ⁇ , preferably less than 1.5 ⁇ , preferably less than 1.0 ⁇ .
  • the mechanical properties, in particular the modulus of rupture are improved.
  • the width / sintered product is greater than 60 mm and less than or equal to 80 mm.
  • the width of the sintered product is greater than 80 mm, greater than 81 mm, greater than 85 mm, even greater than 90 mm, even greater than 100 mm, and even greater than 150 mm.
  • a sintered product manufactured according to a process according to the invention has a remarkable toughness.
  • the fracture initiation toughness K lc is greater than 4 MPa.m 172 , preferably greater than 4.5 MPa.m 172 , preferably greater than 5 MPa.m 172 , preferably greater than 5, 5 MPa.m 172 , preferably greater than 6 MPa.m 172 .
  • the toughness Kj c is greater than 7 MPa.m 172 , preferably greater than 8 MPa.m 172 , preferably greater than 9 MPa.m 172 .
  • the toughness K c and K v can be determined using the methods described for examples.
  • the sintered product comprises more than 80% by weight, preferably more than 95%, preferably more than 97%, preferably more than 99% by weight of oxides.
  • more than 50%, preferably more than 60%, preferably more than 70%, preferably more than 80%, more preferably more than 90%, more preferably more than 95%, more preferably 98%, preferably more than 99%, preferably substantially 100% the number of platelets comprises 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.
  • the chemical analysis of the sintered product is as follows, in percentages by weight:
  • the SiO 2 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
  • the alumina and the other elements constituting the 100% complement 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%.
  • the Al 2 O 3 content is greater than 8%, 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%.
  • the chemical analysis of the product is as follows, in percentages by weight:
  • the content of SiO 2 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 at 8%, preferably below 6%, preferably below 5%), preferably below 4%, preferably below 3%, preferably below 2%, preferably below 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 preferably less than 2%, preferably less than 1.5%, preferably less than P%, preferably less than 0.8%, preferably 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
  • the alumina and the other elements constituting the 100% complement 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%.
  • the content of Al 2 O 3 is greater than 8P / 0, preferably greater than 85%, preferably greater than 89%, preferably greater than 90%, preferably greater than 92%, of preferably greater than 94%, preferably greater than 95%, preferably greater than 96.8%, and preferably less than 99.7%), preferably less than 99.5%
  • the chemical analysis of the product is as follows, in percentages by weight:
  • the content of SiO 2 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 P / 0, 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 lower; at 0.05%, and
  • the alumina and the other elements constituting the 100% complement 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%.
  • the content of Al 2 O 3 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%.
  • the chemical analysis of the product is as follows, in percentages by weight:
  • the Zr0 2 content, optionally stabilized, is greater than 1% and less than 15%, and the content of S102 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 at 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%, of 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%.
  • the zirconia Zr0 2 comes exclusively from the second particulate fraction.
  • the chemical analysis of the product is as follows, in percentages by weight:
  • the content of SiO 2 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 at 8%, preferably less than 6%, preferably less than
  • 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 P / 0, preferably less than 0.8%, preferably less than 0.5%, and
  • the boron nitride content is greater than 1% and less than 20%
  • 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%.
  • the chemical analysis of the product is as follows, in percentages by weight:
  • the content of Zr0 2 , optionally stabilized, is greater than 1% and less than 15%, and the content of SiO 2 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 at 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%, of preferably less than 2%, preferably less than 1.5%, preferably less than P / 0, preferably less than 0.8%, preferably less than 0.5%, and
  • the boron nitride content is greater than 1% and less than 20%
  • the zirconia Zr0 2 comes exclusively from the second particulate fraction.
  • the "other elements" designate the constituents other than those mentioned elsewhere, the possible stabilizers of the zirconia not being part of the "other elements” if the zirconia is stabilized.
  • the sintered product contains a pigment, preferably in an amount greater than 1%, preferably greater than 3%, preferably greater than 5% and less than 15%, preferably less than 13%, preferably less than 11%, by mass percentage.
  • the sintered product is constituted for more than 85% of its volume, preferably for more than 90% of its volume, preferably for more than 95% of its volume of a stack of ceramic plates.
  • the platelet volume of the sintered product can be estimated using fracture surface plates made using a Scanning Electron Microscope (SEM), as described in the Examples section of the description.
  • zirconia powder TZ-3Y sold by the company Tosoh,
  • Example 1 Comparatively, pigment powder 220943 Co-Al-Zn-Si, marketed by the company Ferro.
  • the products of the examples were manufactured according to a process according to the invention.
  • Example 1
  • Example 2 The product of Example 1, excluding the invention, is the product of Example 11 of WO2015189659.
  • Example 2 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:
  • step a the constituents appearing in the following table were mixed, so as 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 the jar, with alumina balls, to ensure good deagglomeration; Carbopol EDT 2691 and the first particulate fraction are then added, and the suspension is then mixed for 3 hours in a jar with alumina balls to obtain the slip.
  • % V denotes a volume percentage based on the volume of the slip.
  • step c) the slip is poured into a wide stainless steel container, the slip height in the container being equal to about 15 mm.
  • the container is then immersed rapidly in a bath of liquid nitrogen. Total freezing of the slurry is carried out in about 20 minutes. The frozen slip is then removed from the mold.
  • step d) the frozen slip is placed in a lyophilizer.
  • a temperature sensor placed under the frozen slip block allows to follow the evolution of freeze drying.
  • the pressure setting inside the freeze dryer is set to 0.2 mbar absolute.
  • the duration of lyophilization is about 5 days.
  • an intermediate product is obtained in the form of a dry block, having a low mechanical strength.
  • step e) the block is crushed using a hand press and the powder obtained is sieved to 1 mm.
  • steps f) and g) (grouped in a single step), the powder is placed in a furnace to undergo a heat treatment consisting of a temperature rise at 50 ° C / h, a one hour step at 400 ° C , a rise at 100 ° C / h up to 900 ° C and a descent at 300 ° C / h.
  • This heat treatment makes it possible on the one hand to remove the organic elements from the powder, and on the other hand to to enhance the adhesion of the ceramic particles of the second particulate fraction on the platelets.
  • step h a graphite matrix with a diameter of 80 mm is filled with powder.
  • the powder is then pressed at room temperature at a pressure of 5 MPa to form a preform.
  • step i) the matrix is placed in an SPS H-HP D 320 oven of the company FCT System GmbH.
  • the preform is then sintered under load at 1500 ° C. for 15 minutes at a pressure equal to 50 MPa.
  • the rise rate at the bearing temperature is equal to 100 ° C / min.
  • step i a sintered product according to the invention, with a diameter of 80 mm, is obtained.
  • step h) the powder is shaped by pressing, with a pressure of 200 MPa so as to obtain a preform.
  • the preform is sintered without applying a pressure during sintering, according to the following cycle: a temperature rise equal to 5 ° C./min up to 1500 ° C. is carried out, the temperature is then maintained at 1500 ° C. for 2 hours, the temperature is reduced at a rate of 5 ° C./min.
  • Comparative Example 3 is intended to illustrate the importance of applying a pressure greater than 0.5 MPa during the sintering step i).
  • Example 4 The product of Example 4 is manufactured according to the following process:
  • step a the constituents in the following Table 2a were mixed, so as to form a slip, according to the following procedure:
  • the boron nitride platelets are added to a mixture of water and tergitol, which allows to suspend them, then the whole is stirred for 12 hours in a beaker, with a magnetic stirrer;
  • the alumina platelets are then added and the slip is mixed for 3 hours in a jar spinner;
  • Carbopol and BN platelets in suspension are added and the mixture is mixed for 3 hours in a jar.
  • steps f) and g) (grouped in a single step), the intermediate product in powder form is placed in an oven for heat treatment.
  • This treatment is done in an air atmosphere up to 600 ° C, with a rise to 50 ° C / h.
  • the atmosphere changes to nitrogen, in order to avoid the oxidation of boron nitride.
  • the temperature is then raised to 900 ° C with a rise rate of 100 ° C / h.
  • the descent is carried out at a speed equal to 300 ° C / h.
  • Steps h), i) and j) are identical to those of example 2.
  • Example 4 is intended to illustrate the possibility of limited alumina content in platelets.
  • Example 5 The product of Example 5 is manufactured according to the following process:
  • step a the constituents in the following Table 3a were mixed, so as 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 the jar, with alumina balls, to ensure good deagglomeration; Carbopol EDT 2691 and the first particulate fraction are then added, and the suspension is then mixed for 3 hours in a jar with alumina balls to obtain the slip.
  • step c) the slip is poured into a wide stainless steel container, the slip height in the container being equal to about 15 mm.
  • the container is then immersed rapidly in a bath of liquid nitrogen. Total freezing of the slurry is carried out in about 20 minutes. The frozen slip is then removed from the mold.
  • step d) the frozen slip is placed in a lyophilizer.
  • a temperature sensor placed under the frozen slip block allows to follow the evolution of freeze drying.
  • the pressure setting inside the freeze dryer is set to 0.2 mbar absolute.
  • the duration of lyophilization is about 5 days.
  • an intermediate product is obtained in the form of a dry block, having a low mechanical strength.
  • step e) the block is crushed using a hand press and the powder obtained is sieved to 1 mm.
  • steps f) and g) (grouped in a single step), the powder is placed in a furnace to undergo a heat treatment consisting of a temperature rise at 50 ° C / h, a one hour step at 400 ° C , a rise at 100 ° C / h up to 900 ° C and a descent at 300 ° C / h.
  • This heat treatment makes it possible on the one hand to remove the organic elements from the powder, and on the other hand to to enhance the adhesion of the ceramic particles of the second particulate fraction on the platelets.
  • step h a cylindrical graphite matrix, with a diameter of 80 mm, is filled with powder.
  • the powder is then pressed at room temperature at a pressure of 5 MPa to form a preform.
  • step i) the matrix is placed in an SPS H-HP D 320 oven of the company FCT System GmbH.
  • the preform is then sintered under load at 1500 ° C. for 15 minutes at a pressure equal to 50 MPa.
  • the rise rate at the bearing temperature is equal to 100 ° C / min.
  • a sintered product according to the invention with a diameter of 80 mm, is obtained.
  • Example 6 The product of Example 6 is manufactured according to the following process:
  • step a the constituents in the following Table 3a were mixed, so as to form a slip, according to the following procedure: Darvan 7NS is dispersed in water; the second particulate fraction and the pigment powder are then added, the whole is then mixed for 12 hours in the jar, with alumina balls, to ensure good deagglomeration; Carbopol EDT 2691 and the first particulate fraction are then added, and the suspension is then mixed for 3 hours in a jar with alumina balls to obtain the slip.
  • Part of the particles of the pigment powder 220943 have a length of less than 1 ⁇ .
  • step c) the slip is poured into a wide stainless steel container, the slip height in the container being equal to about 15 mm.
  • the container is then immersed rapidly in a bath of liquid nitrogen. Total freezing of the slurry is carried out in about 20 minutes. The frozen slip is then removed from the mold.
  • step d) the frozen slip is placed in a lyophilizer.
  • a temperature sensor placed under the frozen slip block allows to follow the evolution of freeze drying.
  • the pressure setting inside the freeze dryer is set to 0.2 mbar absolute.
  • the duration of lyophilization is about 5 days.
  • an intermediate product is obtained in the form of a dry block, having a low mechanical strength.
  • step e) the block is crushed using a hand press and the powder obtained is sieved to 1 mm.
  • steps f) and g) (grouped in a single step), the powder is placed in an oven to undergo a heat treatment consisting of a temperature rise at 50 ° C / h, a one-hour stop at 400 ° C, a rise to 100 ° C / h up to 900 ° C and a descent to 300 ° C / h.
  • This heat treatment makes it possible, on the one hand, to remove the organic elements from the powder and, on the other hand, to enhance the adhesion of the ceramic particles of the second particulate fraction to the wafers.
  • step h a graphite matrix with a diameter of 80 mm is filled with powder. The powder is then pressed at room temperature at a pressure of 5 MPa to form a preform.
  • step i) the matrix is placed in a SPS H-HP D 320 oven of the company FCT Système
  • step i a sintered product according to the invention, of blue color and of diameter equal to 80 mm, is obtained.
  • Example 6 is intended to illustrate the possibility of using a pigment powder to color the sintered product.
  • the dimensions of the particles are determined by the following method.
  • Particle powder is suspended in ethanol so as to disperse said particles well. This suspension is then spread on a conductive support, such as carbon scotch used in electronic imaging. At least 5 images are made using a Scanning Electron Microscope (SEM), each shot having a minimum of 1280x960 pixels, without the scale bar. The magnification is determined so that the width of the image allows to visualize between 2 and 20 individual particles, that is to say non-agglomerated. If this is not the case, it is necessary to start again with a suspension having a ratio of volume of particles to volume of ethanol lower. The plate must have particles whose thickness appears as substantially parallel to the viewing plane.
  • SEM Scanning Electron Microscope
  • the thickness of the particles, W1 is then measured by analyzing said photos using Fiji software, by drawing lines delimiting the particles and then using the "Analysis>Measure” tool of said software.
  • the "length” column of the result table provides the average thickness of the particles.
  • the correspondence between pixel and unit length can be done beforehand by using the tool “Set Scale” and by measuring the number of pixels of the scale bar.
  • the average thickness of the particles of the powder W1 * is the average of the thicknesses W1 measured.
  • the length L1 and the width W2 of each particle is also measured. Platelet orientation 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 cut in its center on a tenth of the thickness, bending and fractured with a hammer.
  • At least 15 snapshots of said fracture surface are made using a scanning electron microscopic (SEM).
  • SEM scanning electron microscopic
  • Each shot has a minimum of 1280x950 pixels, without the scale bar.
  • the orientation direction of the platelets is estimated by the orientation of the pixels of each image, linked to the local gradient of the gray level, and measured using the OrientationJ tool of the ImageJ software, the function used being OrientationJ - OrientationJ Distribution.
  • the average direction of orientation is the average of the orientation directions calculated on all the shots.
  • the average standard deviation around the mean orientation direction is equal to the average of the standard deviations of the orientation directions calculated on each of the images.
  • the absolute density is measured by helium pycnometry.
  • the apparent density is measured by imbibition, according to the principle of Archimedes' thrust.
  • the K C and tenacity tenacity measures Ki crack initiation c are performed at room temperature, as described in "Strong, tough and stiff bioinspired ceramics from brittle constituents - supplementary information," Bouville and AL, Nature Materials, Vol . 13, pages 508-514 (2014), with the following differences: the test pieces used have dimensions equal to 3 ⁇ 6 ⁇ 36 mm 3 ,
  • the cut made has a depth equal to 2.7 mm
  • test performed is a 4-point flexural test.
  • the toughness value K i c corresponds to the toughness for a crack extension projected in the notch axis equal to 0.3 mm.
  • the platelet volume of the sintered products is estimated using the following method:
  • Each bar is then cut in its center on a tenth of the thickness, flexed and fractured by a hammer. A plane fracture surface is thus created.
  • At least 2 snapshots of said fracture surface are made using a Scanning Electron Microscope (SEM). Each shot has a minimum of 1280x950 pixels, without the scale bar.
  • the area covered by the platelets is determined on each plate.
  • the average area covered determined on each plate is an estimate of the platelet volume of the sintered product.
  • the chemical analysis of the sintered products is measured by Inductively Coupled Plasma or ICP for the elements whose quantity does not exceed 0.5%; for the content of the other elements, a pearl of the product to be analyzed is manufactured by melting the product, then the chemical analysis is carried out by X-ray fluorescence.
  • the nitrogen content of the sintered product is conventionally determined by thermal conductivity, for example on a LECO TC 436DR series apparatus.
  • Example 1 makes it possible to obtain a product having a high density, toughness Kj c and toughness Kj c , equal to 98.8%>, 6.2 MPa.m 172 and 7.9 MPa. m 172 , respectively.
  • the width of this product is necessarily less than 50 mm.
  • Example 2 makes it possible to obtain a product having a high density, toughness Kj c and toughness Kj c , equal to 97.9%>, 6.3 MPa.m 172 and 9.6 MPa. m 172 , respectively.
  • the width of this product is 80 mm.
  • Example 3 makes it possible to obtain a product of width equal to 80 mm.
  • the method of Example 4 makes it possible to obtain a product of width equal to 80 mm and having a density equal to 94.7%, and not exhibiting a brittle behavior, the value of Kjc being greater than the value of K lc , these values being 8.1 MPa.m and 3.8 MPa.m respectively.
  • Example 5 makes it possible to obtain a product with a width equal to 80 mm and having a density of 98.3%, and not exhibiting a brittle behavior, the Kjc value being greater than the K value. 1c , these values being 9.7 MPa.m 172 and 6.1 MPa.m 172 respectively.
  • Example 6 makes it possible to obtain a product of blue color, with a width equal to 80 mm and having a density equal to 97.5%, and not exhibiting a brittle behavior, the value of Kj c being greater to the value of K lc , these values being 7.7 MPa.m 172 and 5.1 MPa.m 172 respectively.
  • the invention provides a method for producing a remarkably dense sintered product which is not brittle and may be of any size.
  • This process which combines the preparation of a specific powder by means of a freezing / removal of ice crystals operation, and a pressure sintering, is advantageously simple to implement.
  • the invention is not limited by the shape of the products.

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CN116536538B (zh) * 2023-07-05 2023-09-08 太原理工大学 一种超声辅助自浸渗氧化铝增强镁基复合材料的制备方法

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JPS6433055A (en) 1987-07-27 1989-02-02 Sumitomo Cement Co Sintered body of alumina having high strength and its production
CA2004280A1 (en) * 1989-11-30 1991-05-31 Sadashiv K. Nadkarni Process for producing silicon carbide platelets and the platelets so-produced
JPH1072249A (ja) * 1996-05-23 1998-03-17 Ngk Spark Plug Co Ltd アルミナ系セラミック焼結体及びアルミナ系セラミック部品
US7494704B2 (en) * 2002-08-15 2009-02-24 Eastman Kodak Company Material, article and method of preparing materials containing oriented anisotropic particles
RU2226516C1 (ru) * 2002-12-17 2004-04-10 "МАТИ"-Российский государственный технологический университет им. К.Э. Циолковского Способ получения композиционного материала al2o3-al
FR2989970A1 (fr) * 2012-04-27 2013-11-01 Saint Gobain Ct Recherches Produit en carbure de silicium dense
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CN107124880B (zh) * 2014-06-11 2018-12-04 法商圣高拜欧洲实验及研究中心 具有取向颗粒的陶瓷制品及其生产方法
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CN110475760A (zh) 2019-11-19
US11578005B2 (en) 2023-02-14
RU2754616C2 (ru) 2021-09-06
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JP2020506863A (ja) 2020-03-05
RU2019123926A3 (es) 2021-07-07

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