WO2019137942A1 - Dispositif et procédé de fabrication de carbure de silicium - Google Patents

Dispositif et procédé de fabrication de carbure de silicium Download PDF

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Publication number
WO2019137942A1
WO2019137942A1 PCT/EP2019/050408 EP2019050408W WO2019137942A1 WO 2019137942 A1 WO2019137942 A1 WO 2019137942A1 EP 2019050408 W EP2019050408 W EP 2019050408W WO 2019137942 A1 WO2019137942 A1 WO 2019137942A1
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WO
WIPO (PCT)
Prior art keywords
substrate
silicon carbide
receptacle
temperature
fibers
Prior art date
Application number
PCT/EP2019/050408
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German (de)
English (en)
Inventor
Bettina Friedel
Original Assignee
Universität Paderborn
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Publication date
Application filed by Universität Paderborn filed Critical Universität Paderborn
Priority to EP19700652.1A priority Critical patent/EP3737645A1/fr
Publication of WO2019137942A1 publication Critical patent/WO2019137942A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • 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
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/007—Growth of whiskers or needles
    • 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
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides
    • 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
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/16—Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer

Definitions

  • the present invention relates to an apparatus and a method for producing crystalline silicon carbide in the form of nanoscale fibers.
  • Silicon carbide is preferred for a variety of applications. For example, it is known to use silicon carbide as an electrode material for batteries such as Fithium ion batteries.
  • the production of crystalline silicon carbide, in particular on a nanocrystalline or microcrystalline scale, is a complex process which requires precise control in order to produce defined silicon carbide, for example in the form of nanocrystalline fibers.
  • Document JP2013049599 describes an apparatus for producing carbon nanopowders having a reactor for forming the nanopipes. The generated nanopulses can pass through an opening means into a collecting container.
  • Documents WO 02/30816 and JP2005171443 A each describe reactors for producing carbon fibers in which the fibers form on a substrate within a reactor and are scraped from the substrate within the reactor to be collected in the reactor.
  • the document DE 691 19 838 T2 describes an apparatus for producing thin carbon fibers.
  • This device is based on production of the fibers by vapor phase pyrolysis.
  • a conveying means is provided on which components necessary for fiber production are conveyed through an oven in order to form the fibers.
  • the document JP 09143717 A describes an apparatus for a vacuum vapor deposition.
  • substrates are to be coated directly, which should be automatically attached to a rotating disk or detached from it.
  • the document US 2009/0053115 A1 discloses an apparatus for producing oriented carbon nanotubes. Using this reactor, substrates are transported through a reactor on which the nanotubes grow. From O. Klein et al., Induction eating during SiC growth by PVT: Aspects of Axisymmic Sinusoidal Modeling, it is known that inductive heating can be used to produce SiC single crystal based on SiC powder. However, this publication particularly aims at simulations of heat distribution by adjusting the voltage distribution in the coil. However, there is no focus on the production of Siliziumcarbidfasem in this document.
  • the present invention relates to an apparatus for producing silicon carbide as fibers, the fibers having a diameter d F comprising:
  • an induction coil for generating an alternating magnetic field
  • the coil is arranged such that at least the educt is heatable by a current induced by the alternating magnetic field current to a defined temperature in the range of> 1650 ° C, to about ⁇ 2000 ° C.
  • a current induced by the alternating magnetic field current to a defined temperature in the range of> 1650 ° C, to about ⁇ 2000 ° C.
  • a substrate for depositing fiber material produced from the educt wherein the substrate is positioned in fluid contact with the educt, and wherein the substrate is heatable to a temperature lower than the temperature of the educt by a temperature range of> 50 ° C ⁇ 100 ° C, and wherein the substrate has a seed having seed regions, the seed regions being spaced from each other by a distance d i that is larger than the diameter d F of the fibers to be formed.
  • the device described above is used to produce crystalline fibers of silicon carbide, in particular of silicon carbide as a single crystal as a cubic 3C silicon carbide.
  • a device is needed in which crystals of the silicon carbide in the form of fibers can be produced in a particularly reproducible manner by setting highly defined conditions.
  • the device described above thus serves as a reactor to form fibers from the starting material from a suitable educt by means of a temperature treatment.
  • the device serves as a reactor to form fibrous silicon carbide from a silicon-containing and carbon-containing educt under defined conditions.
  • the starting material should thus be heatable in a very defined manner to a suitable temperature, in particular in order to at least partially convert the educt into the gas phase.
  • the substances in the gas phase or forming can be deposited as crystalline and fibrous silicon carbide.
  • several educts, for example carbon and silicon dioxide, are finely mixed, at the molecular level, or carbon-rich glass, in the gas phase and react to form silicon carbide, wherein the formation of the silicon carbide can optionally take place on the substrate.
  • the device comprises at least the following components.
  • the device comprises a receptacle.
  • This serves to suspend and in particular to include an at least partially electrically conductive educt.
  • the starting material serves to serve as a starting material to pass through a Heat treatment silicon carbide form.
  • the starting material is preferably carbon-containing and silicon-containing, with basically any such starting material appearing suitable.
  • this may have a material lock or be closed about by a lid.
  • an induction coil for generating an alternating magnetic field is further provided as a heating device.
  • the coil is arranged such that at least the starting substance or the educt can be heated by the current thereby induced to a defined temperature. Accordingly, the receptacle can be arranged in a desired position within the induction coil.
  • the coil can be designed in this way or the receiving means can be positioned such that the starting substance is heatable to a temperature in the range of> 1650 ° C, approximately to ⁇ 2000 ° C, for example in a range of> 1750 ° C to ⁇ 2000 ° C, such as from> 1750 ° C to ⁇ 1850 ° C.
  • the starting material can be transformed into suitable species in the gas phase, which deposit from these species silicon carbide as nanocrystalline fibers, as described below.
  • the device further comprises a substrate for depositing fiber material produced from the educt.
  • the substrate has a deposition surface or a plurality of deposition surfaces, wherein the deposition surface or the deposition surfaces serve for the deposition of fibrous material, in particular silicon carbide.
  • the deposition surface or the deposition surfaces serve for the deposition of fibrous material, in particular silicon carbide.
  • the invention will be described with reference to a deposition surface, wherein it is explicitly pointed out that the corresponding embodiments can serve for one, a plurality or all of the deposition surfaces provided.
  • the substrate or at least the deposition surface is formed from graphite.
  • a suitable positioning of the substrate should be ensured within the coil, so that the substrate is heated in not too strong.
  • the substrate may be made of glassy carbon, monocrystalline silicon carbide, polycrystalline silicon carbide, or a high temperature stable metal such as tungsten, tantalum or molybdenum.
  • a high temperature stable metal such as tungsten, tantalum or molybdenum.
  • all substances which are stable at the temperatures used and the reducing atmosphere used, such as oxides, carbides or yttrium compounds, may be suitable, although the substances should not be limited thereto.
  • the temperature in the reactor and the temperature of the substrate or the deposition surface are different from each other.
  • a sufficiently high temperature is present within the receptacle in order to bring the corresponding substances or the educt or in the gas phase or to keep in the gas phase.
  • the interior of the receptacle serves as a reaction space having a volume in which the starting materials of Siliziumcarbidher ein go into the gas phase or remain in the gas phase.
  • the substrate may also be advantageous for the substrate to have a temperature which is reduced compared to the temperature in the reaction space or the educt.
  • the substrate or the deposition surface is temperature-controllable to a second temperature T 2 different from the first temperature Ti, wherein T 2 is preferably less than Ti .
  • T 2 is preferably less than Ti
  • the substrate or the deposition surface is heatable to a range which is cooler in a range of> 50 ° C to ⁇ 100 ° C, than the educt.
  • the substrate and thus at least a part of the substrate is arranged such that the gas phase in which the starting substance or the starting materials for silicon carbide formation are located can come into contact with the substrate or the deposition surface, ie in fluid Connection to the substrate is.
  • the substrate or the deposition surface has a seed structure with seed regions, wherein the seed regions are spaced apart by a distance di which is greater than the diameter d F of the fiber material to be produced.
  • this embodiment can lead to fibers can be generated in a defined manner.
  • the Impf Geben are spaced apart by a distance di, which is greater than the diameter d F of the fiber material to be produced, it is possible in a particularly defined manner to deposit fibers, because it can be effectively prevented that the individual themselves Depositing fibers hinder each other in their growth or influence and thus affect the shape of the deposited fibers in not or only poorly controllable way.
  • induction coils for the heating of the educt can be of great advantage.
  • indirect heating such as by means of resistance heaters such as graphite or molybdenum silicides
  • heating by induction at an at least partially electrically conductive starting material allows the direct internal heating of the substance itself.
  • This allows a locally and dynamically highly controllable thermal treatment, which allows high-temperature reactions and phase transformations in a very defined manner and thus makes it particularly easy to control.
  • This in turn allows a particularly defined growth of nanocrystalline silicon carbide fibers.
  • heating the starting material by means of induction offers the advantage that very fast and precisely definable temperature ramps can be set. This can be of great advantage for local chemical reactions and phase transformations of the material and thus for fiber growth of the silicon carbide fibers. Furthermore, this allows a particularly defined incorporation of dopants from educt additives in the fiber.
  • induction by a high-frequency generator for driving the induction coil to produce a power that the starting material and optionally the receptacle to a sufficient for the phase transformation or the reaction to silicon carbide temperature in a range of> 1650 ° C, about > to heat up l50 ° C.
  • a high-frequency generator for driving the induction coil to produce a power that the starting material and optionally the receptacle to a sufficient for the phase transformation or the reaction to silicon carbide temperature in a range of> 1650 ° C, about > to heat up l50 ° C.
  • these are for example l2kW at a frequency of 15 25 kHz.
  • Induction heating also has the advantage of being fast and locally possible, unlike other methods. This allows the temperature to be raised and lowered within a few seconds.
  • such heating means are easy and adaptable to manufacture and further easily interchangeable, particularly depending on the connection of the cooling, such as a coolant connection, and an electrical connection. Due to the configuration of the coil, in particular with regard to the diameter and the length, different temperature gradients in the receptacle or the educt can be adjustable.
  • the device described above has the advantage that it enables the production of qualitatively extremely high-quality silicon carbide in the form of fibers, since very defined conditions can be set.
  • the set parameters are not only adjustable adjustable, but also easily adaptable to the desired field of application, so that further not only high quality but also very adaptable or variable silicon carbide crystals can be generated.
  • the parameters to be set for this include, for example, the selected temperature within the reactor or in the reaction space and the selected temperature of the Substrate, including the selected temperature gradient between the reaction space or reactant and substrate.
  • the properties of the produced silicon carbide crystals can be set in a simple and defined manner, such as the diameter of crystalline fibers produced, their length and crystalline quality.
  • the induction coil may be provided with the receptacle disposed therein in a heating chamber.
  • This can preferably be tempered, in particular coolable, for example by the provision of water cooling.
  • the heating chamber is configured in such a gastight manner that it can be operated with a certain overpressure.
  • a closable vacuum port may be provided to evacuate oxygen from the volume of the heating chamber, and a gas port may be provided to select selected gases, such as argon, especially at a slight overpressure of about 100-300mbar, about 100mbar, especially over prevailing ones Atmospheric pressure, to allow.
  • induction coil which can be connected to a high-frequency generator.
  • the heating chamber may otherwise have thermocouples or quartz windows for optical pyrometers for temperature measurement.
  • the vaccine structures may be in particular defined topological, morphological or chemical inhomogeneities, which are provided on the deposition surface, as seed regions, wherein only individual ones may be any combination or all of the aforementioned inhomogeneities.
  • These inhomogeneities of the deposition surface or at least one deposition surface of the substrate may further form the seed regions of the seed structure.
  • the seed areas may be the areas where fibers grow, such as spots, whereas the seed structures have one or more of the seed areas.
  • a topological inhomogeneity can be understood as meaning, in particular, a surface structuring of the substrate or of the deposition surface.
  • a structuring of the surface of the substrate or of the deposition surface can take place in various sizes in the nano- or macro-range. In the simplest case, this may be about a surface roughness or surface porosity.
  • a topological inhomogeneity can be made possible in particular by laser ablation, or focused ion beam etching or chemical etching.
  • specifically defined structures or patterns on the deposition surface can be made possible, such as points, columns, pyramids, lines, screens, carpets or others.
  • the vaccination areas can be particularly defined, which in turn can allow defined fiber growth in particular.
  • morphological inhomogeneity can be understood as meaning, in particular, a structural defect of the substrate or of the material present on the deposition surface.
  • An example may be an offset of the deposition surface or material thereof with silicon carbide.
  • Further examples include, for example, multiphase systems locations of a particular phase, phase orientations or Foreign materials. In particular, foreign materials are very well suited to favor fiber growth.
  • An example here is the decoration of the surface with metal particles, which function as a growth front at the tip of the fiber, for example in accordance with the vapour-liquid-solid mechanism (VLS).
  • VLS vapour-liquid-solid mechanism
  • examples include, for example, dopants, such as aluminum or other metals or materials that catalytically act on the one-dimensional growth.
  • Condensation of silicon carbide on a particular crystal surface may be energetically favored here, such as salts, metals or ceramic particles.
  • Another possibility would be a decoration of the substrate or of the deposition surface with silicon carbide, for example with silicon carbide particles, for example on a graphite substrate. Due to the comparatively soft surface of the substrate, the comparatively hard silicon carbide particles can be pressed into the deposition surface and thus fixed. In an exemplary application, this can be realized, for example, by polishing a deposition surface made of graphite, for example, with a paste containing silicon carbide particles. However, it could be more advantageous for highly pure, for example monocrystalline, silicon carbide particles to be applied to the surface. Thus, silicon carbide particles could also promote fiber growth as seed areas. Also in this embodiment, the seed areas can be particularly defined, which in turn can allow specifically defined fiber growth
  • chemical inhomogeneities in the sense of the present invention, it may be understood in particular that there is a locally limited deposition of atomic monolayers, that is to say in particular a specific compound on the substrate surface or deposition surface.
  • atomic monolayers that is to say in particular a specific compound on the substrate surface or deposition surface.
  • Examples include, for example, graphene deposition on a silicon carbide substrate or localized localization of chemical surface termination on seed sites.
  • Examples include treatment of graphite with nitric acid, which renders the surface reactive and wettable. Such a treatment may be the adsorption of silicon carbide influence.
  • a difference in surface energy, surface chemistry or surface reactivity can be made possible by chemical inhomogeneities.
  • Examples of applying the inhomogeneities for example, by applying nitric acid or self-assembled monolayers include, for example, dipping, spraying, spin coating, etc. Then, control of exposure time and / or solution concentration is sufficient to account for how much surface area has reacted , Another possibility is possibly even with a photoresist (photoresist) cover to allow local exposure. It may further be preferred that the seed regions have a distance in a range from> 20 nm to ⁇ 100 nm, for example from> 50 nm to ⁇ 20 pm, for example from> 50 nm to ⁇ 100 nm, to each other. In particular, in this embodiment, fibers of an advantageous thickness can be produced, which can make a variety of applications possible.
  • the seed areas cover the deposition surface of the substrate in a range of greater than or equal to 5% to less than or equal to 74%, based on the total deposition surface area.
  • fiber growth can be particularly preferably made possible since the seed points favor fiber growth, but the number of seed regions is not too high, so that with the limited number of seed regions, the silicon carbide deposits selectively on the fibers.
  • the above-described values can be dependent on the parameters to be set or the parameters to be selected can be selected in the operation of the device as a function of the overlap of the deposition surface with seed regions.
  • the receptacle is designed as a crucible. In this embodiment, a simple and inexpensive construction can be combined with particularly defined conditions of fiber growth.
  • the receptacle is designed as a crucible but not limited thereto, it may be provided that the substrate or the Abscheidenober Structure is positioned in the receptacle or part of it.
  • the substrate or the Abscheideoober configuration may be designed as a crucible lid or part of this.
  • the deposition surface is directed into the interior of the receptacle, such as the crucible.
  • a defined generation of the fibers can be combined with a simple removal of the fibers from the substrate, since the crucible lid can usually be easily removed.
  • the receptacle, such as the crucible is gas-tight lockable.
  • a gas phase can be produced with a particularly defined composition, which in turn can particularly define the conditions for fiber growth and make it reproducible.
  • the receptacle can be operated with a slight overpressure.
  • the receptacle is electrically conductive.
  • the receptacle can also be heated by the induction coil, which may also allow a particularly defined control of fiber growth, since not only the starting substance itself is heated but this is also heated by the receptacle, such as the crucible. This allows a constant temperature without significant fluctuations.
  • the receptacle can be made Graphite, be configured as a graphite crucible.
  • the reactor can be designed on the one hand cost and can withstand high temperatures on the other hand well. Thus, in this embodiment, a particularly high longevity of the device can be made possible.
  • the position of at least one of the receptacle and the substrate relative to the induction coil is variable by means of a displacement device.
  • a particularly advantageous and adaptable temperature control can be made possible, which can make the formation of fibers particularly defined.
  • a suitable temperature gradient between the educt and the substrate or the deposition surface and thus the growth region can be made possible, which in turn can enable the setting of particularly defined conditions.
  • the positioning of the receiving container with the starting substance or the substrate may in particular be configured such that the starting substance may be arranged in the comparatively hotter zone and the substrate or its deposition surface may be positioned in a comparatively colder region, since the mass transport of the comparatively warmer zone takes place to the relatively colder zone and so the fiber growth can be made possible.
  • the silicon carbide from precipitating or precipitating in amorphous form or deposited in a high temperature form, such as Christobalite (SiO 2 )
  • the Temperature of the coldest range is not less than 1750 ° C.
  • a heat shield is provided between the receptacle and the induction coil.
  • Losses are counteracted by radiative thermal transfer, for example through the hot receptacle, such as a glowing graphite crucible.
  • the heat shield or thermal insulation can be designed as a hollow cylinder or pipe and be positioned between the induction coil and the receiving device.
  • the material from which the heat shield or the thermal insulation is configured can preferably be selected from zirconium oxide, in particular stabilized zirconium oxide, for example stabilized with yttrium or cerium.
  • zirconium oxide in particular stabilized zirconium oxide, for example stabilized with yttrium or cerium.
  • Such materials are high temperature stable, so that they do not decompose during use of the device, the heat shield or subjected to a phase transformation. Furthermore, these materials are not electrically conductive so that the heat shield does not self-heat. Furthermore, these materials have limited thermal expansion and are inert to process gases encountered in the production of silicon carbide, such as carbon monoxide (CO), silica (SiO), and optionally chlorine gas (Cl 2 ). This can prevent the heat shield from being damaged. Furthermore, unwanted impurities can be prevented from being incorporated into the crystalline silicon carbide fiber, which further leads to defined processes.
  • CO carbon monoxide
  • SiO silica
  • Cl 2 optionally chlorine gas
  • a cooling device is provided for cooling the induction coil.
  • the coil has a reduced wear or that the coil is particularly long-term stability. Further, this embodiment may further contribute to enabling particularly defined conditions of fiber growth.
  • a particularly effective cooling can be made possible in particular by water cooling and, furthermore, a simple implementation into the device described here can be possible.
  • the silicon carbide produced has a high purity, so that it has semiconductor properties. This is an advantage over commercial fibers (eg, SCS, Silicon Carbide fibers) which, due to their limited purity, have no semiconductor properties but may only conduct.
  • the majority charge carriers electrons or holes
  • the silicon carbide which can be produced here, the majority charge carriers (electrons or holes) can be influenced by doping with regard to the type and concentration and the energetic properties, such as the position of the defect state in the band gap.
  • the present invention further provides a process for producing crystalline silicon carbide fiber material using a device as described above.
  • Silicon carbide can be produced in the form of particular nanocrystalline or nanoscale fibers.
  • the method can particularly preferably have the following steps:
  • the process can be carried out completely or individual process steps a) to c) preferably under protective gas, in particular argon or nitrogen.
  • the process comprises the incorporation of an educt, for example as precursor mixture with a silicon source, a carbon source and optionally a dopant in the receptacle acting as a reactor.
  • precursor mixture in the context of the present invention is intended to mean that at least one silicon source and one carbon source is used in the precursor mixture or educt mixture, regardless of their design, ie whether the carbon source and the silicon source as different solids, as different substances in one Solid or solid particles, or in completely different forms of occurrence.
  • the silicon source and the carbon source serve to be able to form silicon carbide in a further process by a reaction of the carbon source with the silicon source. Therefore, the silicon source and the carbon source should be selected to be in the conditions described below, particularly in the following Temperatures, such as at atmospheric pressure (lbar) or a slight overpressure by the method described silicon carbide can form.
  • the choice of the silicon source or the carbon source is thus not fundamentally limited.
  • solid particles comprising carbon and silicon in each of the particles can be used immediately. These can be produced, for example, by a sol-gel process.
  • the dopant as may be added as gas in the receptacle, about also by a feed, wherein the mixture for process step a) can form directly in the reactor before the temperature treatment.
  • the dopant may be present as a gas.
  • gaseous nitrogen can serve as a dopant.
  • the dopant this can be selected based on the desired doping. It may also be the dopant constituent of the solid granules or the reactant in step a). Alternatively, it is also conceivable that the doping of the forming silicon carbide, such as forming fibers or as 3C silicon carbide nanocrystals during the thermal treatment is carried out via the gas phase in the reactor or receptacle.
  • doping materials phosphorus (P) or nitrogen (N) may be preferably used for n-type doping, which is most advantageous for an electrode, or boron (B) or aluminum (Al) may be used for p-type doping. By doping a particularly good electrical conductivity of the fiber material can be adjusted.
  • the process further comprises applying the starting material provided in process step a) in the receiving container having a gasification temperature serving as a reactor.
  • the starting materials should thus be heated so that they go into the gas phase.
  • the reactor or the receiving container and in particular the educt can be heated, for example, to a temperature which is in a range from> 1650 ° C., to approximately ⁇ 2000 ° C., for example in a range from> 1750 ° C. to ⁇ 2000 ° C., such as from> 1750 ° C to ⁇ 1850 ° C, such as at atmospheric pressure (lbar) or a slight overpressure.
  • nanoscale fibers of the silicon carbide can be formed in a particularly advantageous manner when adjusting the temperature in method step b) to a prescribed range.
  • a suitable reaction temperature may vary with the doping.
  • the most suitable temperature is adjustable by simply checking the set temperature in the aforementioned range.
  • the formation of a temperature gradient may be advantageous so that the precursor mixture or educt or educt mixture can at least partially pass into the gas phase at a position which has a comparatively higher temperature and can deposit silicon carbide fibers at the comparatively lower temperature the substrate.
  • the temperature of the substrate may be decreased by a temperature ranging from> 50 ° C to ⁇ 100 ° C as compared with the temperature basically set in the reactor in the aforementioned range of> 1,650 ° C to ⁇ 2,000 ° C C, in particular> 1750 ° C. It can also be made possible by adjusting the temperature that the silicon carbide produced is nanocrystalline and in detail a cubic 3C structure of the silicon carbide is made possible.
  • the silicon carbide (SiC) is in the form of a silicon carbide single crystal, preferably a monocrystalline cubic 3C-SiC, the monocrystalline silicon carbide fibers combine high thermal conductivity.
  • a nanostructured silicon carbide may, in particular, be understood to mean a silicon carbide which has a maximum spatial extent in the nanometer range, in particular of less than or equal to 100 nm, in at least one dimension, wherein the lower limit may be limited by the production method.
  • the lower limit of the diameter of the fibers can be determined by the temperature at the growth site, the set temperature gradient and the time to grow the fibers.
  • crystalline silicon carbide may deposit on the substrate by adjusting a crystallization temperature. It can be made possible by a targeted adjustment of the temperature, in a range of> l650 ° C to ⁇ 2000 ° C, in particular in the receptacle and a relatively reduced by about> 50 ° C to ⁇ 100 ° C temperature of the substrate that crystalline fibers of the silicon carbide precipitate.
  • fibers With reference to fibers, these may in particular be structures in which the ratio of length to diameter is at least greater than or equal to 3: 1, for example greater than or equal to 10: 1, in particular greater than or equal to 100: 1, for example greater than or equal to 1000: 1.
  • fibers with a diameter in the range of> 10 nm to ⁇ 3 ⁇ m and a length of a few millimeters, for example in a range of> 1 mm to ⁇ 20 mm can be produced in a targeted manner. Fibers differ from nanowhiskem (nano- Rods) in particular by the bending radius, since rods are only slightly bendable, but fibers very flexible.
  • the aforementioned method may be suitable, for example, to produce silicon carbide fibers as electrode material for a battery, such as in particular a lithium-ion battery. Because of the good thermal properties of the fibers, the thermal management of the battery can be improved. Furthermore, the chemical and thermal durability of the fibers may be advantageous for fishing time stability, and the flexibility of the silicon carbide, especially as fibers, may be advantageous for high cycle stability. However, polycrystalline forms of the silicon carbide are also conceivable within the scope of the present invention. It is also advantageous that silicon carbide can have a high capacitance as an electrode material, so that an electrode material produced as described can further enable a good power capability of a battery.
  • silicon carbide thus produced include, for example, areas of photonics, such as solar cells, for example, which can act accordingly differently doped Siliziumcarbidfasem, FEDs in which, for example, organic wet surfaces may be provided in damp textiles based on silicon carbide, or the structural reinforcement, such as other fibers.
  • the process is very effective because very large amounts of silicon carbide can be produced in a comparatively short time under given conditions.
  • FIG. 1 is a schematic sectional view through a device according to the invention
  • FIG. 2 is a schematic plan view of a deposition surface of a substrate.
  • FIG. 1 shows an apparatus 10 for producing silicon carbide as fibers.
  • the device comprises a receptacle 12 for receiving an at least partially electrically conductive starting material, which can be arranged at the bottom of the receptacle 12.
  • the receptacle 12 is designed as a particular made of graphite and thus electrically conductive ausgestalteter crucible comprising a crucible pan 16 and a crucible lid 18. By arranging the crucible lid 18 on the crucible pan 16 of the crucible or the receptacle 12 is closed gas-tight.
  • the crucible lid 18 serves as a substrate 20 for depositing fibers.
  • the substrate 20 it can be easily possible for the substrate 20 to be positioned in fluid contact with the educt. Furthermore, the substrate 20 is described with reference to FIG.
  • the substrate 20 has a seed structure 22 with seed regions 24, wherein the seed regions 24 are spaced apart by a distance d 1 is greater than the diameter of the fiber material to be produced.
  • the distance di may be in a range from> 20 nm to ⁇ 1 OOmhi, for example from> 50 nm to ⁇ 20mhi, for example from> 50 nm to ⁇ 100 nm.
  • the seed regions 24 may be formed at least in part by topological inhomogeneities, at least in part by morphological inhomogeneities and / or at least in part by chemical inhomogeneities. There may be one or a selectable combination of the aforementioned inhomogeneities. In principle, it may be advantageous if the substrate 20 has been germinated with aluminum or silicon carbide.
  • the device 10 is shown to include an induction coil 26 for generating electromagnetic radiation.
  • the induction coil 26 is arranged such that at least the educt is heated by the electromagnetic radiation to a defined temperature, which is in a range of> 1650 ° C to about ⁇ 2000 ° C.
  • the substrate 20 can be heated to a temperature which is lower than the temperature of the educt by a temperature range of> 50 ° C to ⁇ 100 ° C. This can be achieved by a suitable positioning of educt and substrate 20, for example, of the crucible or the receptacle 12 within the induction coil 26.
  • the position of at least the receptacle 12 relative to the induction coil 26 by means of a traversing device 28 is variable.
  • a pull rod 30 is provided, which is hinged to the receptacle 12 and a crucible holder 32 and thus this in particular in the axial direction in the induction coil 26 is movable.
  • the induction coil 26 and the receptacle 12 are arranged in a housing 34.
  • the housing 34 can thus form a heating chamber.
  • the housing 34 has a first viewing window 36 for a temperature measurement, such as Using a thermal camera and further has another viewing window 38.
  • two gas ports 38 are provided, through which protective gas, such as argon can be introduced and also a gas port 40 for connecting a vacuum pump.
  • the receptacle 12 can be removed from the housing 34 or accessible in the housing 34 in order to equip it with educt and / or to remove the fibers.
  • a method may be suitably controlled, particularly with respect to temperature control to produce silicon carbide fibers.
  • a graphite crucible can serve as a receptacle 12 in an induction coil 26 with lOOmm length and 60mm diameter at a certain time a temperature of 1850 ° C in the center but only l750 ° C in the end, or in the axial or radial outer region, since the magnetic field in Regions outside the induction coil 26 becomes weaker.
  • a method for producing fiber material made of silicon carbide can thus be carried out.
  • Such a method can have the following method steps in the broadest application:
  • silicon carbide in particular a composite or a compound which contains suitable proportions of carbon and silicon, for example in a ratio of 4: 1, may be suitable.
  • silicon carbide may be, for example, organometallic precursors, silicates, elemental silicon, and / or carbohydrates or polymers.
  • the reducing effect of the carbon begins, on the one hand directly via elemental carbon, indirectly via carbon monoxide (CO) in the resulting gas as a carbothermal reduction .
  • the carbon can reduce the C / Si precursor or the educt, especially Si0 2 , in contact or via the gas phase to SiO gas and subsequently to silicon carbide on the substrate 20.
  • the educt or the carbonaceous and silicon-containing precursor is thereby inserted, for example, in the graphite crucible and positioned in the middle of the induction coil 26, which can be suitably connected to a high-frequency generator.
  • the alternating magnetic field generated in the induction coil 26 induces a current in the at least partially electrically conductive starting material and optionally in a conductive wall of the receiving container 12.
  • the educt is heated by the electrical resistance in a very defined manner.
  • the receptacle 12 is also electrically conductive, it can thus also be heated.
  • it is electrically insulating, which is basically possible, such as made of aluminum oxide (Al 2 O 3 ) only the starting material can be heated, both variants can have application-related advantages.

Abstract

La présente invention concerne un dispositif pour fabriquer du carbure de silicium sous forme de fibres, les fibres présentant un diamètre dF, qui comprend : - un réceptacle (12) pour recevoir un produit de départ au moins partiellement électroconducteur ; une bobine d'induction (26) pour produire un champ magnétique alternatif, la bobine d'induction (26) étant agencée de manière à ce qu'au moins le produit de départ puisse être chauffé par un courant induit par le champ magnétique alternatif à une température définie qui se situe dans une plage ≥ 1650 °C ; et - un substrat (20) pour séparer le matériau fibreux produit à partir du produit de départ du carbure de silicium, le substrat (20) étant positionné en contact fluidique par rapport au produit de départ et le substrat (20) pouvant être chauffé à une température inférieure à la température du produit de départ se situant dans une plage de températures de ≥ 50 °C à ≤ 100 °C, et le substrat (20) présentant une structure d'implantation (22) avec des zones d'implantation (24), les zones d'implantation (24) étant écartées les unes des autres d'une distance d1 supérieure au diamètre dF des fibres à produire.
PCT/EP2019/050408 2018-01-12 2019-01-09 Dispositif et procédé de fabrication de carbure de silicium WO2019137942A1 (fr)

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DE102018100679.9A DE102018100679A1 (de) 2018-01-12 2018-01-12 Vorrichtung und Verfahren zum Herstellen von Siliziumcarbid
DE102018100679.9 2018-01-12

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