Classifications

• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
  • C30B11/002—Crucibles or containers for supporting the melt
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/02—Silicon
  • C01B33/021—Preparation
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
  • C04B41/5025—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials with ceramic materials
  • C04B41/5035—Silica
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/52—Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
  • C04B41/81—Coating or impregnation
  • C04B41/85—Coating or impregnation with inorganic materials
  • C04B41/87—Ceramics
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
  • C04B41/81—Coating or impregnation
  • C04B41/89—Coating or impregnation for obtaining at least two superposed coatings having different compositions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/06—Silicon
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/0087—Uses not provided for elsewhere in C04B2111/00 for metallurgical applications
  • C04B2111/00879—Non-ferrous metallurgy

Definitions

• the present invention relates more particularly to a crucible useful for the solidification of a silicon ingot from silicon in the molten state.
• It also relates to a process for preparing such a crucible and the use of such a crucible for the solidification of silicon.
• the crucibles considered for the growth of the ingot are generally silica crucibles, coated with a layer of oxidized silicon nitride to prevent adhesion of the ingot to the crucible after solidification.
• the anti-adherence behavior is based essentially on the presence of silicon nitride, S13N4, in the form of oxidized powders, on the surface of the inner walls of the crucibles to which the silicon adheres during its cooling.
• silicon nitride S13N4
• the silicon ingot is detached from these walls by cohesive rupture within the silicon nitride layer, thus relaxing the mechanical stresses resulting from the difference in coefficients of thermal expansion.
• this technique does not prevent contamination of silicon by the impurities present in the silicon nitride powder.
• this coating can not be used on all types of crucibles including ceramic crucibles such as carbide or silicon nitride. Indeed, these ceramics being chemically reducing, they will have the effect of deoxidizing the coating, which may lead to delamination of the latter.
• a natural solution would be to achieve a silica barrier layer, to prevent the gases produced during the heat treatment from escaping and thus to prevent the delamination of the coating.
• Unfortunately the phenomenon of differential expansion makes a pure silica layer not resistant to thermal cycling.
• the present invention aims precisely to provide new substrates, including new crucibles useful for the solidification of a silicon ingot from silicon in the molten state satisfying these needs.
• the present invention relates to a substrate coated at least partially at the surface with a coating containing at least one so-called "barrier” layer comprising silica and one or more material (s) X chosen from SiC, Si, S13N4. layer in which the mass quantity of X varies from 25% to 50% relative to the total mass of the barrier layer, said barrier layer being formed of grains of one or more materials X at least partially covered by a silica envelope the barrier layer being disposed in direct contact with the substrate.
• the inventors have, in fact, discovered that the problems developed above can be solved by at least partially covering the surface of a substrate dedicated to containing or supporting molten silicon, a low permeability coating formed of silica and one or more material (X) X selected from SiC, Si, S13N4, in specified proportions.
• the coating formed in the context of the present invention in which the barrier layer is in direct contact with the substrate, that is to say that there is no intermediate layer between the substrate and the barrier layer, is advantageous in many ways. he simultaneously exhibits good substrate adhesion properties, satisfactory gas barrier properties.
• said coating is constituted by said barrier layer.
• the barrier layer constitutes the outer layer of the substrate, in direct contact with the atmosphere or the container of the substrate, that is to say that the barrier layer is not covered with an additional layer .
• said coating is formed only in part by the barrier layer to which can be superimposed an additional layer, preferably said auxiliary layer is a release layer.
• Said adherent layer is then advantageously obtained by oxidizing the outer surface of the barrier layer.
• the coating formed according to the present invention comprises at least one barrier layer formed of grains of one or more materials X at least partially covered by a silica envelope.
• the cohesion of the grains is generally obtained by sintering the silica.
• the coating formed according to the present invention comprises at least one barrier layer in the form of a silica matrix in which are incorporated grains of one or more material (X) X.
• the grains of one or more material (X) X are coated at least in part with a nanometric layer of silica.
• the thickness of the "barrier" layer is between 10 and 100 ⁇ , between 20 and 50 ⁇ .
• the silica envelope that is to say the silica layer formed on the surface of the grains of material (x) X, it may have a thickness ranging from 2 to 100 nm, and in particular from 10 to 30 nm.
• the substrate is a crucible, in particular useful for the solidification of silicon.
• the presence of the coating according to the invention makes it possible to obtain a crucible which is reusable subject only to depositing the auxiliary layer, that is to say without requiring one or more pre-treatment steps before reuse.
• the substrate according to the invention is coated at least partially, and preferably entirely, at the surface, with a coating formed by at least one so-called "barrier" layer.
• the barrier layer according to the invention makes it possible to maintain the integrity of the substrate.
• the barrier layer comprises, or even consists of, silica and one or more material (s) X selected from SiC, Si, S13N4, and is such that the mass quantity of X in the barrier layer varies from 25% to 50% relative to the total mass of the barrier layer.
• the mass quantity of silica in the barrier layer advantageously varies from 50% to 75% relative to the total mass of the barrier layer.
• the barrier layer comprises, or even consists of, a mixture of silica and silicon carbide (SiC).
• the barrier layer comprises, or even consists of, a mixture of silica and silicon (Si).
• the barrier layer comprises, or even consists of, a mixture of silica and silicon nitride (Si 3 N 4 ).
• the barrier layer comprises, or even consists of, a mixture of silica and two materials X selected from SiC, Si, S13N4.
• the barrier layer comprises, or even consists of, a mixture of silica and the following three materials X SiC, Si, Si 3 N 4 .
• the particles of inorganic materials X used in the process for preparing the coating according to the invention, as described more particularly later, are preferably in the form of powders, preferably having a size or a mean diameter ranging from 500 nm to 5 microns, preferably from 0.8 microns to 2 microns.
• powders examples include silicon nitride (S1 3 N 4) in the form of micron-sized grains and sold under the reference S E10 ® by the company UBE,
• the particles of inorganic materials X may be prepared prior to the formation of the coating according to the invention.
• the skilled person is able to implement the methods suitable for the preparation of particles suitable for the invention.
• the permeability of the barrier layer is less than 10 -15 m, preferably less than 10 -8 m 2 .
• the permeability of this layer reflects its ability to be passed through by a reference fluid under the effect of a pressure gradient.
• the permeability (intrinsic or specific) of a substrate and more generally of a medium can be obtained from the Darcy equation: where dP / dx is the pressure gradient in the flow direction and ⁇ is the dynamic viscosity of the fluid.
• the intrinsic or specific permeability K is independent of the nature of the fluid but depends on the geometry of the medium, and it is expressed in m 2 . In the case of a single-phase flow, the intrinsic or specific permeability K is simplified to "permeability".
• the permeability is measured by means of a permeameter as described in US Pat. No. 5,361,625 or in patent application EP 1 821 093 A2.
• These permeameters are devices for measuring gas permeation through a material (M), they comprise a permeation chamber comprising a first and a second chamber separated by a material (M).
• the material M corresponds to the material whose permeability is to be measured.
• a gas or mixture of gases is introduced into the first chamber and then collected in the second chamber where they are analyzed by a suitable detector.
• the process of permeation of a gas through a material is based on the differences of partial pressures of this gas, also called permeant, on both sides of the material M.
• the partial pressure of each of the gases having passed through the sample increases until stabilizing when the material M is saturated by permeating.
• the permeability of the material to the gas considered is deduced by considering the thickness of the sample.
• the barrier layer preferably has the property of being very slightly porous: it has an open porosity ranging from 0 to 5%, preferably ranging from 0 to 2%.
• This porosity can be measured by the SEM image analysis method.
• the coating may be termed a substantially closed porosity coating.
• the specific surface of the barrier layer is between 5 cm 2 / g and 5 m 2 / g, in particular between 100 cm 2 / g and 1 m 2 / g.
• the coating further comprises, on the surface of the barrier layer, a release layer, generally a conventional anti-adhesive layer.
• This release layer can be advantageously obtained by oxidizing the outer surface of the barrier layer, especially by annealing in air at a temperature ranging from 600 ° C. to 900 ° C.
• Said anti-adhesive layer is particularly advantageous when the substrate is intended for the formation of silicon ingots from molten silicon.
• the release layer is porous.
• the invention aims at providing a process for preparing a substrate according to the invention coated at least partially at the surface with a coating forming a gas barrier, said method comprising at least the steps of:
• s selected material
• the substrate is a crucible coated at least partially on its inner surface.
• the fluid medium used in step a) comprises one or more material (s) X in an amount ranging from 15 to 35% by weight relative to the total weight of said fluid.
• the fluid medium used in step a) comprises silica.
• the amount of silica in the fluid medium may range from 0% to 15% by weight relative to the total weight of said fluid. It preferably has a size or average diameter of less than 2 microns.
• the permeability of the barrier layer is advantageously less than 10 -15 m 2 , it can be controlled by the morphology of the initial powders and the characteristics of the heat treatments used.
• the material (s) X present in the fluid medium are generally silicon derivatives in the form of powders.
• the material (x) X generally has a micron order size.
• the powders of silicon X derivatives are of size ranging from 500 nm to 5 microns, preferably from 0.8 microns to 2 microns.
• Such a compound generally serves to facilitate the application of the liquid coating mixture using conventional equipment.
• organic binder considered in the context of the present invention may be chosen from polyvinyl alcohol, polyethylene glycol or carboxymethylcellulose.
• the ratio of the mixture "silica and material X" / binder (s) may be at least 3: 1 and more particularly 5: 1.
• the fluid medium dedicated to form the coating according to the invention combines from 0 to 20% by weight of at least one binder relative to the total weight of the fluid medium, from 10 to 50% by weight of a mixture of silica and inorganic material (s) X by weight relative to the total weight of the liquid medium, the complement to 100% by weight being water.
• This mixture may of course contain other additives intended either to improve these qualities at the time of spraying and / or application, or to give the corresponding coating additional properties required.
• they may be dispersing agents.
• the liquid medium used in step a) is generally a slip consisting of one or more inorganic material (s) X, water and optionally silica and at least one binder.
• the slip is generally screened beforehand by passing through a mill in order to reduce the agglomerates of powders.
• the method according to the invention comprises a step b) of applying the fluid medium to the surface to be treated in an amount sufficient to form a deposit.
• the use of a fluid medium makes it possible to produce a deposit having a very good surface state.
• such a gun with a 0.4 mm nozzle can be used at a compressed air pressure of 2.5 bar.
• This application of the liquid coating mixture can also be carried out by other modes of application, such as, for example, the brush or by soaking the parts in a bath.
• the application of the fluid mixture for forming the coating can be carried out at room temperature or at a higher temperature.
• the surface to be treated may be heated so as to be conducive to rapid drying of the applied coating layer.
• At least the surface to be treated, or even the whole of the material can be heated to a temperature ranging from 25 to 80 ° C., in particular from 30 to
• the liquid mixture dedicated to form the coating is applied to the surface of the surface to be treated with a thickness adapted to prevent cracking during drying, for example between 20 and 100 ⁇ .
• step (b) If necessary, it is possible to proceed to one or more other (s) deposit (s) of fluid mixture on the first deposit formed at the end of step (b). In this case the (s) other deposits, posterior, will take place after application and drying of the first deposit.
• step b) is repeated several times before the implementation of step c).
• the process according to the invention comprises between step b) of formation of a deposit and step c) of treatment under oxidizing atmosphere, at least one drying step at a temperature below 50 ° C and preferably from
• the method according to the invention further comprises a step c) of heating in an oxidizing atmosphere, at a temperature and within a time sufficient to allow the formation of the expected barrier layer.
• the heat treatment of step c) is carried out in an oxidizing atmosphere, more particularly in the presence of air.
• this step is carried out in an oxidizing atmosphere at a temperature ranging from 1100 ° C. to 1300 ° C., and more particularly from 1150 ° to 1200 ° C.
• this step is carried out for a period ranging from 1 hour to 5 hours, preferably from 2 hours to 3 hours.
• this heat treatment is in fact carried out at a temperature adjusted to allow sintering and in particular sintering of the silicon oxide to be obtained, which makes it possible to obtain the permeability in the right range.
• the piece is allowed to cool to room temperature.
• the expected barrier layer is obtained, which is generally a silica matrix in which the unoxidized part of the grains of X is incorporated.
• This layer may also be characterized by an oxygen mass fraction, evaluated according to the IGA technique, ranging from 25% to 40%.
• the process according to the invention may comprise, after the treatment under oxidizing atmosphere carried out in step c), a treatment step in the presence of a neutral gas at a temperature of between 1400 ° C. and 1500 ° C. .
• Such a step has the effect of further reducing the creep porosity of the silica.
• the present invention also relates to substrates having a coating obtained by the process as described above.
• the substrate treated according to the invention is advantageously a crucible or a mold.
• the coating according to the invention can be used on all types of substrates such as crucibles, molds or platelets, leaflets, of any kind and known to those skilled in the art to be compatible with the silicon fusion without risks of harmful interactions between the substrate and its contents, in particular between the crucible and the liquid silicon.
• the substrate is formed by a material chosen from SiC silicon carbide, S13N4 silicon nitride, and composites comprising graphite and silicon carbide or comprising graphite and silicon nitride and silicided graphite.
• the invention also relates to the use of a crucible according to the invention or prepared according to the method of the invention in particular for the solidification of silicon.
• a slip consisting of 23% of a mixture of S13N4 powder, 4% PVA polyvinyl alcohol and 73% water in percentages by weight, is passed through a planetary mill filled with silicon carbide or agate balls.
• silicon carbide or agate balls Since the purpose of the silicon carbide or agate balls is only to reduce the powder agglomerates, silicon nitride balls are also conceivable, the risk of nitrogen pollution being very limited.
• the fluid medium thus formed is then spray-dried (compressed air pressure of 2.5 bar, 0.4 mm nozzle placed at about thirty centimeters from the substrate) over the entire internal surface of a crucible to be coated.
• the deposit thus obtained is dried in hot air at a temperature below
• This layer is then subjected to a step of 3 hours at 1100 ° C. in air for debinding and oxidation of the powders.
• the mass fraction of oxygen in the coating is 29% measured by the IGA (Interstitial Gas Analysis) technique.
• IGA Interstitial Gas Analysis
• Figure 1 is presented the coating obtained at the end of Example 1.
• This coating is in the form of a matrix of SiO 2 in which are incorporated grains of non-oxidized Si 3 N 4 .

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Inorganic Chemistry (AREA)
• Metallurgy (AREA)
• Crystallography & Structural Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Silicon Compounds (AREA)
• Manufacturing & Machinery (AREA)
• Dispersion Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)

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• 2013
  • 2013-09-16 FR FR1358900A patent/FR3010715B1/fr not_active Expired - Fee Related
• 2014
  • 2014-09-12 US US15/022,461 patent/US10287703B2/en not_active Expired - Fee Related
  • 2014-09-12 CN CN201480050801.7A patent/CN105593193A/zh active Pending
  • 2014-09-12 WO PCT/IB2014/064472 patent/WO2015036974A1/fr active Application Filing
  • 2014-09-12 EP EP14780618.6A patent/EP3046895A1/de not_active Withdrawn

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