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
  • 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
  • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
  • C30B15/10—Crucibles or containers for supporting the melt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
  • C23C24/082—Coating starting from inorganic powder by application of heat or pressure and heat without intermediate formation of a liquid in the layer
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
  • C23C8/10—Oxidising
  • C23C8/16—Oxidising using oxygen-containing compounds, e.g. water, carbon dioxide
• • 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
  • 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
  • C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
  • C30B35/002—Crucibles or containers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]

Definitions

• the present invention aims to provide a new type of surface coating for materials, and more particularly crucibles, intended to be brought into contact with high temperature liquid materials, such as liquid silicon, in order to allow a solidification, for example in the form of ingots.
• Photovoltaic cells are mainly made from mono- or poly-crystalline silicon, in dies that involve the solidification of ingots from a liquid bath. The ingot is then cut into platelets which serve as a basis for the manufacture of the cells.
• the most common technique is based on the implementation of a silicon nitride coating on the inner faces of the crucibles to be in contact with the molten silicon.
• the mechanism proposed to explain the detachment is a rupture, in the deposition zone, due to the differential expansion stresses between the silicon ingot and the thus treated surface-treated silica crucible. Indeed, the mechanical cohesion of the deposition layer is low, the annealing being made at temperatures too low to initiate sintering of the powders.
• US Pat. No. 6,491,971 describes a universal technology making it possible to apply a wide variety of coatings such as silicon nitride, silicon carbide, zirconium oxide, magnesium or barium zirconate, on the inner surface of crucible.
• silicon carbide as a coating material may, at first glance, seem to be an advantageous alternative. Unfortunately, it is not totally devoid of inconvenience. Thus, great difficulties during the sawing step are associated with the presence of silicon carbide precipitates in the ingots. At the scale of the p-n junction of the photovoltaic cells, the precipitated silicon carbide, on the dislocations and other crystallographic defects, plays the role of a short-circuit and thus limits the performances of the devices (2).
• the main object of the invention is to provide a method for producing a non-stick coating which does not have the difficulties or limitations set forth above.
• the invention aims to provide a simple and inexpensive coating system for crucibles intended more particularly for implementation in the field of the manufacture of silicon ingot or other materials.
• An object of the invention is in particular to provide an economical method of producing a non-stick coating formed of a silicon carbide structure and silicon oxide, as defined below.
• the invention relates to a method useful for forming a release coating, particularly with respect to solid silicon, on the surface of the face (s) of a material comprising at least the steps of:
• step (2) depositing said medium on the surface of the face (s) of the material to be treated in an amount sufficient to provide, upon drying of the applied composition, a film formed at least of silicon carbide grains, (3) exposing the treated material according to step (2) to a heat treatment under an oxidizing atmosphere and under conditions sufficient to cause the formation of a silicon oxide layer on the surface of the silicon carbide grains.
• the coating formed according to the present invention comprises at least one porous layer formed of grains of silicon carbide which are coated at least in part with a nanometric layer of silica.
• the porosity can be from 30% to 60% by volume. It can be controlled by the initial composition of the fluid.
• the composition of step (1) further comprises at least one binder.
• the dry film obtained at the end of step (2) is formed of grains of silicon carbide and of said binder, and the heat treatment exposed in step (3) is suitable for ensuring debinding of this film. .
• step (2) may be renewed one or more times before implementation of step (3).
• the method according to the invention as defined above can be reproduced at the end of step (3).
• the layer formed of silicon carbide grains coated with a nanometric layer of silica is covered with a new thickness of the fluid composition as defined in step (1) and this deposited layer undergoes step (3). ) consecutive.
• the coating formed in the context of the present invention is advantageous for several reasons. It simultaneously exhibits good adhesion properties to the base material forming the crucible, satisfactory anti-adhesion properties with respect to the ingot formed by solidification of the liquid silicon poured into this crucible and good mechanical resistance to liquid silicon.
• the porous layer formed of silicon carbide grains may have a thickness ranging from 5 ⁇ m to 1 mm, in particular from 10 to 200 ⁇ m.
• the silica layer formed on the surface of the silicon carbide grains, it may have a thickness ranging from 2 to 100 nm, and in particular from 10 to 30 nm.
• the method according to the invention involves a first step for applying a fluid medium based on silicon carbide grains on the surface (s) of the material to be treated.
• the coating derived therefrom has the characteristic of being formed of silicon carbide grains coated wholly or partly with silica.
• the silicon carbide grains intended to form this coating generally have a particular size and dispersibility adequate to make them compatible with spray application by conventional methods.
• the silicon carbide grains considered in the context of the present invention may have a size less than 5 microns. More particularly, their size varies from 20 nm to 5 ⁇ m and in particular from 200 nm to 1 ⁇ m.
• This liquid medium besides the silicon carbide grains, may contain an effective amount of at least one organic binder having the appropriate chemical and physical properties to facilitate the application of the liquid coating mixture using conventional equipment.
• the organic binder considered in the context of the present invention may be chosen from polyvinyl alcohol, polyethylene glycol or carboxymethylcellulose.
• the mass ratio of silicon carbide / binder (s) may be at least 3: 1 and more preferably 5: 1.
• the fluid medium dedicated to forming the coating according to the invention combines from 0 to 20% by weight relative to its total weight of at least one binder, to 20 to 60% by weight of silicon carbide, the associated liquid medium, usually water, ensuring the balance to 100%.
• the corresponding fluid medium is formed by incorporation of silicon carbide grains and generally a binder to the liquid medium, generally water, under agitating so as to form a liquid mixture conducive to an application on the face or faces to be treated of the material in question.
• This mixture intended to form the coating may, of course, contain other additives intended either to improve its qualities at the time of spraying and / or application, or to give the corresponding coating additional properties.
• they may be polycarbonate dispersing agents, for example carboxylic acid or stearic acid.
• the silicon carbide grains, the binder and the solvent considered in the context of the present invention have the advantage of leading to crucible coatings which are non-contaminating for the material to be produced.
• the method according to the invention involves a first step aimed at applying a fluid medium based at least on silicon carbide grains on the surface or faces of the material to be treated.
• fluid means a deformable state, capable of flowing and which is therefore compatible with an application by brush and / or spray gun for example.
• the generally liquid fluid medium is transferred out of the spray gun at a pressure of compressed air and with a nozzle adjusted to obtain the desired coating thickness.
• 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 ambient temperature or at a higher temperature.
• the face or faces of the material to be treated according to the invention can be heated so as to be conducive to rapid drying of the applied coating layer.
• at least the face or faces of the material to be treated, or even the whole of the material can be heated to a temperature ranging from 25 to 80 ° C., especially from 30 to 50 ° C., thus leading to Evaporation of the solvent.
• the liquid mixture dedicated to form the coating is applied on the surface of the face (s) to be treated with a thickness adapted to prevent cracking during drying, for example less than 50 microns.
• step (2) it is possible to proceed to a new application of a layer of the liquid mixture dedicated to form the coating on a first layer of grains of silicon carbide applied and dried, that is to say as formed in result of step (2).
• the method according to the invention also comprises a heating step in an oxidizing atmosphere, at a temperature and within a time sufficient to allow the formation of a silicon oxide layer on the surface of the silicon carbide grains, or even the decomposition thermal binder, when it is present.
• This heat treatment is therefore carried out in an oxidizing atmosphere. It is more specifically air.
• this thermal step is carried out at a temperature below 1095 ° C.
• the oxidation step may be carried out in an oxidizing atmosphere for 1 to 5 hours at a temperature ranging from 500 ° C. to 1050 ° C., and more particularly from 800 ° C. to 1050 ° C.
• this heat treatment is in fact carried out at a temperature adjusted so as not to modify the porosity of the coating formed. In other words, this temperature remains below the temperature required to obtain sintering of the coating. Moreover, at the end of this annealing, the coating has a sufficient hardness with respect to the mechanical stresses it will have to undergo, typically less than 50 Shore A. At the end of this heat treatment, the piece is allowed to cool to room temperature.
• the present invention also relates to materials having a coating formed by the method as described above.
• the material treated according to the invention is advantageously a crucible.
• This crucible is generally based on silicon, such as silica or silicon carbide but can also be based on graphite.
• a slip consisting of 23% silicon carbide 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 to reduce the losses. agglomerates of powder.
• the size of the grains of silicon carbide formed is between 500 nm and 1 ⁇ m.
• the fluid medium thus formed is then spray-dried (compressed air pressure 2.5 bar, 0.4 mm nozzle placed at about thirty centimeters from the substrate) on the internal faces of a crucible (of a chemical nature) to be coated. .
• the deposit thus obtained is dried with hot air at a temperature below 50 ° C.
• the thickness of the coating finally obtained is of the order of 200 microns, and the thickness of the oxide layer on the silicon carbide grains is of the order of 30 nm.
• the coating obtained according to the present invention is very porous.
• the procedure of elaboration of a layer (deposition of layers with intermediate drying then high temperature annealing for debinding and oxidation of the powders) can be repeated several times. times.
• a slurry consisting of 52% pre-sieved powder, 16% polyethylene glycol (PEG) and 32% water in percentages by weight, is passed through a planetary mill filled with silicon carbide or agate balls to reduce powder agglomerates. .
• the slip is also passed to the ultrasound.
• the slip is then either deposited by spray guns (compressed air pressure of 2.5 bars, 0.4 mm nozzle placed at about thirty centimeters from the substrate) or with the aid of a brush on the crucible to be coated.
• the deposit thus obtained is dried in ambient air or hot (temperature below 50 0 C).
• This layer is subjected to a step of 3 hours at 900 ° C. under air to dilute and oxidize the powders.
• the thickness of the oxide layer obtained on the silicon carbide grains is of the order of 30 nm.
• a slip consisting of 57% of previously screened powder and 43% of water in percentages by weight, is passed through a planetary mill filled with silicon carbide balls or agate to reduce powder agglomerates. The slip is also passed to the ultrasound.
• the slip is then either deposited by spray guns (compressed air pressure of 2.5 bars, 0.4 mm nozzle placed at about thirty centimeters from the substrate) or with the aid of a brush on the crucible to be coated.
• the deposit thus obtained is dried in ambient air or hot (temperature below 50 0 C).
• This pistol (or brush) and drying procedure is repeated until the desired layer thickness is obtained.
• This layer is subjected to a step of 3 hours at 900 ° C. under air to dilute and oxidize the powders.
• the thickness of the oxide layer obtained on the silicon carbide grains is of the order of 30 nm.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Plasma & Fusion (AREA)
• Physics & Mathematics (AREA)
• Ceramic Products (AREA)
• Carbon And Carbon Compounds (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Catalysts (AREA)

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• 2008
  • 2008-09-05 FR FR0855971A patent/FR2935618B1/fr not_active Expired - Fee Related
• 2009
  • 2009-09-03 JP JP2011525597A patent/JP5492208B2/ja not_active Expired - Fee Related
  • 2009-09-03 BR BRPI0918852A patent/BRPI0918852A2/pt not_active IP Right Cessation
  • 2009-09-03 CN CN200980134956.8A patent/CN102144053B/zh not_active Expired - Fee Related
  • 2009-09-03 WO PCT/FR2009/051666 patent/WO2010026342A1/fr active Application Filing
  • 2009-09-03 EP EP09741363A patent/EP2347037A1/fr not_active Withdrawn
  • 2009-09-03 KR KR1020117007630A patent/KR101451322B1/ko not_active IP Right Cessation
  • 2009-09-03 RU RU2011107880/05A patent/RU2479679C2/ru not_active IP Right Cessation
  • 2009-09-03 US US13/062,456 patent/US20110268958A1/en not_active Abandoned

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