EP0878259B1 - Method for producing silicon-containing iron powder - Google Patents

Method for producing silicon-containing iron powder Download PDF

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Publication number
EP0878259B1
EP0878259B1 EP98107122A EP98107122A EP0878259B1 EP 0878259 B1 EP0878259 B1 EP 0878259B1 EP 98107122 A EP98107122 A EP 98107122A EP 98107122 A EP98107122 A EP 98107122A EP 0878259 B1 EP0878259 B1 EP 0878259B1
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Prior art keywords
silicon
iron powder
iron
containing iron
powder
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German (de)
French (fr)
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EP0878259A1 (en
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Joachim Dr. Simon
Reinhold Schlegel
Bernd Dr. Leutner
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BASF SE
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BASF SE
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/30—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis
    • B22F9/305—Making metallic powder or suspensions thereof using chemical processes with decomposition of metal compounds, e.g. by pyrolysis of metal carbonyls

Definitions

  • the invention relates to a method for producing silicon-containing iron powder.
  • Such cores contain carbonyl iron powder as fine-grained ferromagnetic material, the individual particles are separated from each other by a thin layer of an insulating agent. The more complete the Isolation of these particles, which are as small as possible, is less the same among others Ratios of losses due to eddy currents in the mass core. Because with carbonyl iron powder The electrical insulation is individual particles with an ideal spherical shape easier and safer than particles with irregular corners and Edge. In particular, when insulating under high pressure, the insulating layer not easily injured and there are no metallic contacts between the grains. Carbonyl iron powder is also used in the manufacture electromagnetic shielding used.
  • the magnetic properties of the Carbonyl iron powder can also be affected. So for the above described applications in electrical engineering a certain silicon content the iron powder may be desirable since using iron-silicon alloys a silicon content of 1 to 4% with a similarly high permeability have lower hysteresis losses and coercive forces than pure iron. In addition, iron-silicon alloys are more resistant to environmental influences as pure iron.
  • Fine-particle metal powders can also be used as catalysts. So is from the literature the catalytic effect of silicon-iron alloys known in the hydrogenation of CO in the Fischer-Tropsch process.
  • No. 4,468,474 describes a process for the production of catalytically active iron-silicon alloys by laser pyrolysis of a gaseous mixture of silanes or halosilanes with iron-organic compounds (iron pentacarbonyl, iron acetylacetonate and ferrocene) and hydrocarbons.
  • iron-organic compounds iron pentacarbonyl, iron acetylacetonate and ferrocene
  • hydrocarbons There are powders of iron-silicon-carbon alloys with 5 to 15 atom% of iron, 65 to 88 atom% of silicon and 2 to 30 atom% of carbon or iron-silicon alloys with 10 to 30 atom% of iron and 70 to 90 atomic% silicon.
  • the powders selectively catalyze the hydrogenation of CO to C 2 -C 6 alkanes.
  • the powders When using tetraethoxysilane and ethyldichlorosilane the powders have a low silicon content of 0.35 or 0.09% by weight when using triethylsilane and methylethyldichlorosilane the silicon content of the powders obtained is given as 0.
  • SU-A 344 014 describes a process for the production of finely divided powders made of iron-silicon alloy, in which a solution of (SiCl 3 ) 2 Fe (CO) 4 in benzene as a mist in a reaction chamber heated to 350 ° C. is introduced.
  • the solution also contains iron pentacarbonyl. Powders made of 50% by weight of iron and 50% by weight of silicon are produced; if iron pentacarbonyl is also used, powders of 94% by weight of iron and 6% by weight of silicon are produced.
  • the disadvantage of this process is the use of halogen-containing feedstocks because of the associated corrosion and disposal problems. In particular, the use of halogenated feedstocks can lead to the formation of salts. In addition, large amounts of solvent have to be used.
  • the invention has for its object a method for manufacturing silicon-containing iron powder with widely varying silicon content and a small proportion of minor components that make up the beneficial Properties of the carbonyl iron powder, particularly with regard to their further processing have to provide for a variety of applications.
  • the invention has for its object an uncomplicated and cost-effective process for producing silicon-containing Iron powder based on the processes for producing carbonyl iron powder provide.
  • the invention is based on the known production method silicon-containing iron powder by thermal decomposition of a gas mixture, containing iron pentacarbonyl and a volatile silicon compound, in which the gas mixture flows through and through a heated reaction chamber Heat conduction is heated.
  • the invention is defined in claim 1.
  • variable silicon content of the silicon-containing iron powder according to the invention which can be set by selecting the composition of the gas mixture leaves.
  • the ratio of iron pentacarbonyl to that volatile silicon compound arbitrarily selectable in the gas mixture whereby usually - based on weight - excess iron pentacarbonyl is used.
  • up to 50% by weight is preferred, especially preferably 0.4 to 25% by weight of the volatile silicon compound on the sum of iron pentacarbonyl and the volatile silicon compound, used.
  • Iron pentacarbonyl and the volatile silicon compound can be found in the Gas mixture used alone or in a mixture with other gases.
  • the gas mixture can also contain CO, H 2 and ammonia as further gases, which can be present alone or next to one another.
  • the gas mixture also contains carbon monoxide.
  • the carbon monoxide content is preferably up to 99% by volume, particularly preferably between 60 and 98% by volume. If ammonia is also used, products with an increased nitrogen content can be obtained. Up to 10% by volume of ammonia are preferably used, particularly preferably between 1 and 5% by volume. The use of ammonia is also advantageous in that ammonia presumably accelerates the decomposition of iron pentacarbonyl into iron and carbon monoxide.
  • hydrogen is also present in the gas mixture.
  • the hydrogen content of the gas mixture is preferably up to 60% by volume, particularly preferably between 1 and 40% by volume.
  • the silicon-containing iron powders produced according to the invention have one Silicon content from 0.5 to 25 wt .-%.
  • The is preferably Silicon content 0.5 to 10%, in particular 1 to 4% by weight.
  • the silicon content can be determined using known methods Elemental analysis, for example by X-ray micro-area analysis SEM images can be determined.
  • the silicon-containing iron powder can contain secondary components, especially oxygen, Contain carbon, hydrogen and nitrogen.
  • the oxygen content can be up to 30% by weight, preferably it is below 10% by weight, particularly preferably between 0.1 and 5% by weight.
  • the carbon content can be up to 10% by weight, preferably it is below 8% by weight, particularly preferably between 0.1 and 7% by weight.
  • the nitrogen content can up to 2% by weight. If ammonia is also used, it lies preferably between 0.5 and 2% by weight, without using ammonia preferably below 0.5% by weight.
  • the hydrogen content can be up to amount to 1% by weight, preferably it is below 0.5% by weight.
  • Another advantage of the method according to the invention is that which is special low content of silicon-containing iron powder in foreign metals.
  • the foreign element content can be determined using Atomic absorption spectral analysis can be determined.
  • the silicon-containing iron powder is obtained in finely divided form in the process according to the invention and that mechanical post-treatment, for example by grinding, can be dispensed with.
  • the silicon-containing iron powder is obtained in the form of essentially spherical particles with an average diameter between 0.005 and 10 ⁇ m, which can be agglomerated into threads or bulbous aggregates.
  • the average diameter of the substantially spherical particles is preferably between 0.01 ⁇ m and 5 ⁇ m.
  • the BET surface area of the particles is preferably up to 30 m 2 / g.
  • the bulk density of the powders according to the invention, which decreases with increasing silicon content, is preferably between 0.4 and 4 g / cm 3 .
  • the reaction is preferably carried out continuously in a heated one Reaction space through which the gas mixture flows.
  • the implementation can, for example, in a heatable decomposer such as that used for the production of carbonyl iron powder by thermal decomposition of iron pentacarbonyl is used and in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A14, page 599 become.
  • a decomposer comprises a tube made of a heat-resistant one Material such as quartz glass or V2A steel, preferably in a vertical position, that of a heating device, for example consisting of heating tapes, Heating wires or from a heating jacket through which a heating medium flows, is surrounded.
  • the heating device is preferred for setting one Zone of low temperature and a zone of higher temperature in at least 2 segments divided.
  • the gases are premixed and preferably introduced into the decomposition tube from above, the gas mixture entering the zone low temperature happens first.
  • the temperature is preferably in lower part of the tube by at least 20 ° C higher than in the upper part of the Tube.
  • the silicon-containing iron powder formed is known Methods using gravity, centrifugal force or separated from the gas stream by means of a filter device. This can happen, for example, in that the gas stream is a separation vessel happens and is redirected there. With larger particles the separation can also easily done by removing the particles from the Let the decomposer trickle out and catch it in a storage container. For the If solid particles can be carried away by the gas flow, a filter device is preferably additionally used.
  • the reaction in the decomposer is preferably carried out at temperatures between 200 and 600 ° C, particularly preferably between 250 and 350 ° C.
  • the reaction can be carried out at pressures of up to 40 bar.
  • the pressure is preferably between 1 and 2 bar absolute.
  • Another advantage of the method according to the invention is that by choice the reaction parameters such as pressure, temperature and flow rate and the gas composition, the average particle size of the powder can be varied.
  • the silicon-containing iron powder obtained by the process described can from Carbon, oxygen and nitrogen are largely liberated by being in the heat a hydrogen flow can be reduced.
  • the powders are preferably at temperatures reduced between 300 and 600 ° C, particularly preferably between 400 and 500 ° C.
  • the Reduced powders can have a carbon content of ⁇ 0.05% by weight, a nitrogen content of ⁇ 0.01% by weight and an oxygen content of ⁇ 0.2% by weight.
  • the silicon-containing iron powders produced according to the invention are particularly suitable for Applications in electronics or electrical engineering, both reduced and unreduced powders can be used. So that manufactured according to the invention silicon-containing iron powder used for the production of coil core or magnet become. The significantly lower hysteresis losses and are particularly advantageous Coercive forces of the iron-silicon alloy.
  • the silicon-containing iron powder can be like Carbonyl iron powder can be processed, for example by using a hardening agent Binders, e.g. a phenolic resin or an epoxy resin, kneaded, granulated and dry is pressed to the desired shaped bodies, rings, rods and screw core. This are then cured thermally.
  • Binders e.g. a phenolic resin or an epoxy resin, kneaded, granulated and dry is pressed to the desired shaped bodies, rings, rods and screw core. This are then cured thermally.
  • Such magnetic bonded cores can be produced by compression molding, but also by injection molding
  • the powder cores thus produced are that the powder is very fine.
  • Insulation can thus significantly reduce eddy current losses
  • Powder cores can be achieved which are made from coarser powder. This reduction the eddy current loss is reflected in an increase in quality.
  • a special one high quality is achieved when the insulation is so strong that it is between the individual primary powder particles do not come into contact. Isolation of the powder particles with a constant, insulating layer, for example by treating the silicon-containing iron powder with a dilute solution of Phosphoric acid take place in an organic solvent, the surface of the Particles form an iron phosphate layer.
  • the silicon-containing iron powders produced according to the invention can be used Process microwave absorbing or radar absorbing materials. To do this the powders are introduced into plastic or rubber-like materials as well as in coating systems.
  • the silicon-containing iron powder according to the invention is particularly suitable as an absorber for electromagnetic radiation in the frequency range from 1 to 100 gigahertz.
  • the silicon-containing iron powder due to their high silicon content and their large specific surface area as catalysts for the hydrogenation of Carbon monoxide can be used in the Fischer-Tropsch process.
  • the apparatus for the thermal decomposition of iron pentacarbonyl [Fe (CO) 5 ] and silane (SiH 4 ) consists of a decomposer tube made of V2A steel with a length of 1 m and an inner diameter of 20 cm.
  • the decomposer tube is heated so that the temperature in the lower third is about 20 ° C higher than the temperature T 1 in the upper part of the tube.
  • the liquid Fe (CO) 5 is evaporated in an electrically heated storage vessel and the steam together with SiH 4 (0-60 l / h), H 2 (0-500 l / h), NH 3 (0-150 l / h) and possibly CO (0-100 l / h) introduced into the decomposition tube from above.
  • the formation of the silicon-containing iron powder in the decomposition tube releases CO and H 2 .
  • the silicon-containing iron powder that is formed passes with the gas stream into a separator vessel in which it is separated from the gas stream by deflecting it. Solid clay particles remaining in the gas stream are retained by a filter candle.
  • the silicon content of the iron powder is determined by elemental analysis and corresponds to the amount of monosilane used within the accuracy of the analysis. About 2 ppm SiH 4 are still detected in the exhaust gas by IR spectrometry, so that it can be concluded that the silane has been converted practically completely.
  • the elemental composition of the particles was determined by means of AAS (atomic absorption spectroscopy), and their specific surface area (BET surface area) was measured by nitrogen adsorption in accordance with DIN 66 132.

Abstract

Production of Si-containing Fe powder comprises thermally decomposing a gas mixture containing Fe-pentacarbonyl and a volatile Si-compound. The volatile Si-compound is a silane or organosilane, except triethylsilane and tetraethoxysilane. Also claimed is an apparatus for carrying out the process comprising: (a) a heated decomposition pipe; (b) a device for adjusting two different temperature zones; (c) a device for vaporising liquid Fe-pentacarbonyl; (d) a device for dosing and mixing gases; and (e) a separator for Si-containing Fe powder.

Description

Die Erfindung betrifft ein Verfahren zur Herstellung siliziumhaltiger Eisenpulver.The invention relates to a method for producing silicon-containing iron powder.

Mit der thermischen Zersetzung von Eisenpentacarbonyl in der Gasphase steht seit langem ein großtechnisch durchführbares, unaufwendiges und kostengünstiges Verfahren zur Erzeugung hochreiner, feiner Eisenpulver zur Verfügung. Auf diese Weise hergestelltes sogenanntes Carbonyleisenpulver kommt in einer Vielzahl von industriellen Anwendungen zum Einsatz. Eine große Bedeutung hat Carbonyleisenpulver beispielsweise auf dem Gebiet der Pulvermetallurgie erlangt, die auf der Reinheit, der niedrigen Entstehungstemperatur, der geringen Größe, der Kugelform und der damit verbundenen besonders guten Sinterfähigkeit der Pulverteilchen beruht. Wegen seiner günstigen magnetischen Eigenschaften wird Carbonyleisenpulver auch in großem Umfang für die Herstellung elektronischer Bauelemente verwendet. Gemischt mit einem indifferenten Bindemittel werden die Pulver durch Formpressen oder im Spritzguß zu plastikgebundenen Massekernen verarbeitet. Derartige Kerne enthalten Carbonyleisenpulver als feinkörniges Ferromagnetikum, dessen Einzelteilchen durch eine dünne Schicht eines Isoliermittels voneinander getrennt sind. Je vollständiger die Isolierung dieser möglichst kleinen Teilchen ist, umso geringer sind unter sonst gleichen Verhältnissen die Verluste durch Wirbelströme im Massekern. Da bei Carbonyleisenpulver die Einzelteilchen ideale Kugelgestalt besitzen, ist die elektrische Isolierung einfacher und sicherer als bei Teilchen mit unregelmäßigen Ecken und Kanten. Insbesondere wird beim Verpressen unter hohem Druck die Isolierschicht nicht so leicht verletzt, und es entstehen keine metallischen Kontakte zwischen den Körnern. Ferner wird Carbonyleisenpulver für die Herstellung elektromagnetischer Abschirmungen verwendet.With the thermal decomposition of iron pentacarbonyl in the gas phase has stood for a long time an industrially feasible, inexpensive and inexpensive process for Production of high-purity, fine iron powder available. Made in this way so-called carbonyl iron powder comes in a variety of industrial applications for use. Carbonyl iron powder is of great importance in the field, for example of powder metallurgy, which is based on purity, low generation temperature, small size, the spherical shape and the associated particularly good sinterability the powder particles are based. Because of its favorable magnetic properties, carbonyl iron powder also on a large scale for the production of electronic components used. The powders are mixed with an indifferent binder by compression molding or processed into plastic-bonded mass cores by injection molding. Such cores contain carbonyl iron powder as fine-grained ferromagnetic material, the individual particles are separated from each other by a thin layer of an insulating agent. The more complete the Isolation of these particles, which are as small as possible, is less the same among others Ratios of losses due to eddy currents in the mass core. Because with carbonyl iron powder The electrical insulation is individual particles with an ideal spherical shape easier and safer than particles with irregular corners and Edge. In particular, when insulating under high pressure, the insulating layer not easily injured and there are no metallic contacts between the grains. Carbonyl iron powder is also used in the manufacture electromagnetic shielding used.

Durch den Zusatz von Silizium können die magnetischen Eigenschaften der Carbonyleisenpulver zusätzlich beeinflußt werden. So kann für die oben geschilderten Anwendungen in der Elektrotechnik ein bestimmter Siliziumgehalt der Eisenpulver wünschenswert sein, da Eisen-Silizium-Legierungen mit einem Siliziumgehalt von 1 bis 4 % bei ähnlich hoher Permeabilität deutlich geringere Hystereseverluste und Koerzitivkräfte als reines Eisen aufweisen. Darüber hinaus sind Eisen-Silizium-Legierungen gegen Umwelteinflüsse beständiger als reines Eisen.By adding silicon, the magnetic properties of the Carbonyl iron powder can also be affected. So for the above described applications in electrical engineering a certain silicon content the iron powder may be desirable since using iron-silicon alloys a silicon content of 1 to 4% with a similarly high permeability have lower hysteresis losses and coercive forces than pure iron. In addition, iron-silicon alloys are more resistant to environmental influences as pure iron.

Feinteilige Metallpulver kommen ferner als Katalysatoren in Frage. So ist aus der Literatur die katalytische Wirkung von Silizium-Eisen-Legierungen bei der Hydrierung von CO im Fischer-Tropsch-Verfahren bekannt.Fine-particle metal powders can also be used as catalysts. So is from the literature the catalytic effect of silicon-iron alloys known in the hydrogenation of CO in the Fischer-Tropsch process.

In D.J. Frurip et al., Journal of Non-Crystalline Solids 68 (1984), Seite 1 ist die Herstellung amorpher, 5 bis 30 nm großer Ferrosiliziumpartikel durch Laserpyrolyse einer gasförmigen Mischung von Fe(CO)5, SiH4 und SF6 beschrieben. Bei diesem Verfahren führt die Absorption von IR-Laserlicht durch SiH4 und SiF6 zu einer lokalen Erhitzung der Gasmischung auf 350 bis 600°C und dadurch zur thermischer Zersetzung der Komponenten.DJ Frurip et al., Journal of Non-Crystalline Solids 68 (1984), page 1, describes the production of amorphous, 5 to 30 nm large ferrosilicon particles by laser pyrolysis of a gaseous mixture of Fe (CO) 5 , SiH 4 and SF 6 . In this process, the absorption of IR laser light by SiH 4 and SiF 6 leads to a local heating of the gas mixture to 350 to 600 ° C and thereby to the thermal decomposition of the components.

In X. Gao et al., Journal of Inorganic Materials, 7 (1992), Seite 429 bis 434 ist ein ähnliches, kontinuierlich betriebenes Verfahren zur Herstellung von ultrafeinen Eisen-Silizium-Partikeln mit einem CW-CO2-Laser, das ohne Zugabe von SF6 als lichtempfindlichem Mittel auskommt, beschrieben. Es werden u.a. Partikel der Zusammensetzung Fe3Si, Fe2Si, Fe5Si3, FeSi und FeSi2 gebildet.In X. Gao et al., Journal of Inorganic Materials, 7 (1992), pages 429 to 434, a similar, continuously operated process for the production of ultrafine iron-silicon particles with a CW-CO 2 laser, which is without addition SF 6 as a photosensitive agent. Particles of the composition Fe 3 Si, Fe 2 Si, Fe 5 Si 3 , FeSi and FeSi 2 are formed.

In US 4,468,474 ist ein Verfahren zur Herstellung katalytisch wirksamer Eisen-Silizium-Legierungen durch Laserpyrolyse einer gasförmigen Mischung von Silanen oder Halogensilanen mit eisenorganischen Verbindungen (Eisenpentacarbonyl, Eisenacetylacetonat und Ferrocen) und Kohlenwasserstoffen beschrieben. Es werden Pulver aus Eisen-Silizium-Kohlenstoff-Legierungen mit 5 bis 15 Atom-% Eisen, 65 bis 88 Atom-% Silizium und 2 bis 30 Atom-% Kohlenstoff bzw. Eisen-Silizium-Legierungen mit 10 bis 30 Atom-% Eisen und 70 bis 90 Atom-% Silizium erhalten. Die Pulver katalysieren selektiv die Hydrierung von CO zu C2-C6-Alkanen.No. 4,468,474 describes a process for the production of catalytically active iron-silicon alloys by laser pyrolysis of a gaseous mixture of silanes or halosilanes with iron-organic compounds (iron pentacarbonyl, iron acetylacetonate and ferrocene) and hydrocarbons. There are powders of iron-silicon-carbon alloys with 5 to 15 atom% of iron, 65 to 88 atom% of silicon and 2 to 30 atom% of carbon or iron-silicon alloys with 10 to 30 atom% of iron and 70 to 90 atomic% silicon. The powders selectively catalyze the hydrogenation of CO to C 2 -C 6 alkanes.

Nachteilig an den o.g. Verfahren ist die Verwendung von Infrarot-Lasern hoher Leistung zur Aufheizung der Gasmischung, die das Verfahren aufwendig und teuer macht und damit für den großtechnischen Einsatz als ungeeignet erscheinen läßt.A disadvantage of the above The procedure is the use of infrared lasers high performance for heating the gas mixture, which makes the process expensive and makes it expensive and therefore unsuitable for large-scale use lets appear.

In V. G. Syrkin et al., Soviet Powder Metallurgy and Metal Ceramics 1970, Seite 447 bis 449 ist die Verwendung bestimmter Additive zur Steuerung der Teilchengröße bei der Herstellung von Eisenpulver durch thermische Zersetzung von Eisenpentacarbonyl beschrieben. Als Additive werden u. a. Organosilizium-Verbindungen wie Tetraethoxysilan, Triethylsilan, Ethyldichlorsilan und Methylethyldichlorsilan eingesetzt. In Gegenwart der genannten Additive werden Eisenpulver mit einer mittleren Teilchengröße um 2,5 µm bzw. Eisenwolle gebildet. Bei Verwendung von Tetraethoxysilan und Ethyldichlorsilan weisen die Pulver einen geringen Siliziumgehalt von 0,35 bzw. 0,09 Gew.-% auf, bei Verwendung von Triethylsilan und Methylethyldichlorsilan wird der Siliziumgehalt der erhaltenen Pulver mit 0 angegeben. In V. G. Syrkin et al., Soviet Powder Metallurgy and Metal Ceramics 1970, pages 447 to 449 is the use of certain additives for control the particle size in the production of iron powder by thermal Decomposition of iron pentacarbonyl described. As additives u. a. Organosilicon compounds such as tetraethoxysilane, triethylsilane, ethyldichlorosilane and methylethyldichlorosilane used. In the presence of the above Additives are iron powder with an average particle size of around 2.5 µm or iron wool formed. When using tetraethoxysilane and ethyldichlorosilane the powders have a low silicon content of 0.35 or 0.09% by weight when using triethylsilane and methylethyldichlorosilane the silicon content of the powders obtained is given as 0.

Über die verwendeten Mengen an Organosilizium-Verbindung werden keine Angaben gemacht.Nothing is said about the amounts of organosilicon compound used Information provided.

In der SU-A 344 014 ist ein Verfahren zur Herstellung von feinteiligen Pulvern aus Eisen-Silizium-Legierung beschrieben, bei dem eine Lösung von (SiCl3)2Fe(CO)4 in Benzol als Nebel in einen auf 350°C aufgeheizten Reaktionsraum eingebracht wird. Wahlweise enthält die Lösung zusätzlich Eisenpentacarbonyl. Es entstehen Pulver aus 50 Gew.-% Eisen und 50 Gew.-% Silizium, bei Mitverwendung von Eisenpentacarbonyl entstehen Pulver aus 94 Gew.-% Eisen und 6 Gew.-% Silizium. Nachteilig an diesem Verfahren ist die Verwendung halogenhaltiger Einsatzstoffe wegen der damit verbundenen Korrosions- und Entsorgungsprobleme. Insbesondere kann die Verwendung halogenhaltiger Einsatzstoffe zur Bildung von Salzen führen. Hinzu kommt, daß unter Verwendung großer Mengen an Lösungsmittel gearbeitet werden muß.SU-A 344 014 describes a process for the production of finely divided powders made of iron-silicon alloy, in which a solution of (SiCl 3 ) 2 Fe (CO) 4 in benzene as a mist in a reaction chamber heated to 350 ° C. is introduced. Optionally, the solution also contains iron pentacarbonyl. Powders made of 50% by weight of iron and 50% by weight of silicon are produced; if iron pentacarbonyl is also used, powders of 94% by weight of iron and 6% by weight of silicon are produced. The disadvantage of this process is the use of halogen-containing feedstocks because of the associated corrosion and disposal problems. In particular, the use of halogenated feedstocks can lead to the formation of salts. In addition, large amounts of solvent have to be used.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Herstellung siliziumhaltiger Eisenpulver mit in weiten Grenzen variierbarem Siliziumgehalt und einem geringen Anteil an Nebenbestandteilen, die die vorteilhaften Eigenschaften der Carbonyleisenpulver insbesondere hinsichtlich ihrer Weiterverarbeitung aufweisen, für eine Vielzahl von Anwendungen bereitzustellen. Insbesondere liegt der Erfindung die Aufgabe zugrunde, ein unaufwendiges und kostengünstig durchführbares Verfahren zur Herstellung siliziumhaltiger Eisenpulver auf der Basis der Verfahren zur Herstellung von Carbonyleisenpulver bereitzustellen.The invention has for its object a method for manufacturing silicon-containing iron powder with widely varying silicon content and a small proportion of minor components that make up the beneficial Properties of the carbonyl iron powder, particularly with regard to their further processing have to provide for a variety of applications. In particular, the invention has for its object an uncomplicated and cost-effective process for producing silicon-containing Iron powder based on the processes for producing carbonyl iron powder provide.

Die Erfindung geht aus von dem bekannten Verfahren zur Herstellung siliziumhaltiger Eisenpulver durch thermische Zersetzung einer Gasmischung, enthaltend Eisenpentacarbonyl und eine flüchtige Siliziumverbindung, bei dem die Gasmischung einen beheizten Reaktionsraum durchströmt und durch Wärmeleitung aufgeheizt wird. Die Erfindung ist im Anspruch 1 definiert.The invention is based on the known production method silicon-containing iron powder by thermal decomposition of a gas mixture, containing iron pentacarbonyl and a volatile silicon compound, in which the gas mixture flows through and through a heated reaction chamber Heat conduction is heated. The invention is defined in claim 1.

Vorteilhaft an dem erfindungsgemäßen Verfahren ist der in weiten Grenzen variierbare Siliziumgehalt der erfindungsgemäßen siliziumhaltigen Eisenpulver, der sich durch Wahl der Zusammensetzung des Gasgemisches gezielt einstellen läßt. Grundsätzlich ist das Verhältnis von Eisenpentacarbonyl zu der flüchtigen Siliziumverbindung in der Gasmischung beliebig wählbar, wobei in der Regel - bezogen auf das Gewicht - Eisenpentacarbonyl im Überschuß verwendet wird. Vorzugsweise werden jedoch bis zu 50 Gew.-%, besonders bevorzugt 0,4 bis 25 Gew.-% der flüchtigen Siliziumverbindung, bezogen auf die Summe von Eisenpentacarbonyl und der flüchtigen Siliziumverbindung, eingesetzt.The advantage of the process according to the invention is that within wide limits variable silicon content of the silicon-containing iron powder according to the invention, which can be set by selecting the composition of the gas mixture leaves. Basically, the ratio of iron pentacarbonyl to that volatile silicon compound arbitrarily selectable in the gas mixture, whereby usually - based on weight - excess iron pentacarbonyl is used. However, up to 50% by weight is preferred, especially preferably 0.4 to 25% by weight of the volatile silicon compound on the sum of iron pentacarbonyl and the volatile silicon compound, used.

Eisenpentacarbonyl und die flüchtige Siliziumverbindung können in der Gasmischung allein oder in Mischung mit weiteren Gasen eingesetzt werden. Iron pentacarbonyl and the volatile silicon compound can be found in the Gas mixture used alone or in a mixture with other gases.

So kann die Gasmischung als weitere Gase noch CO, H2 und Ammoniak, die alleine oder nebeneinander vorliegen können, enthalten. In einer bevorzugten Ausführungsform enthält die Gasmischung noch Kohlenmonoxid. Vorzugsweise beträgt der Kohlenmonoxidanteil bis zu 99 Vol.-%, besonders bevorzugt zwischen 60 und 98 Vol.-%. Bei Mitverwendung von Ammoniak kann man Produkte mit einem erhöhten Stickstoffanteil erhalten. Bevorzugt werden bis zu 10 Vol.-% Ammoniak verwendet, besonders bevorzugt zwischen 1 und 5 Vol-%. Die Mitverwendung von Ammoniak ist auch insofern vorteilhaft, als Ammoniak vermutlich die Zersetzung von Eisenpentacarbonyl in Eisen und Kohlenmonoxid beschleunigt. In einer weiteren Ausführungsform liegt darüberhinaus noch Wasserstoff in der Gasmischung vor. Vorzugsweise beträgt der Wasserstoffgehalt der Gasmischung bis zu 60 Vol.-%, besonders bevorzugt zwischen 1 und 40 Vol.-%.The gas mixture can also contain CO, H 2 and ammonia as further gases, which can be present alone or next to one another. In a preferred embodiment, the gas mixture also contains carbon monoxide. The carbon monoxide content is preferably up to 99% by volume, particularly preferably between 60 and 98% by volume. If ammonia is also used, products with an increased nitrogen content can be obtained. Up to 10% by volume of ammonia are preferably used, particularly preferably between 1 and 5% by volume. The use of ammonia is also advantageous in that ammonia presumably accelerates the decomposition of iron pentacarbonyl into iron and carbon monoxide. In a further embodiment, hydrogen is also present in the gas mixture. The hydrogen content of the gas mixture is preferably up to 60% by volume, particularly preferably between 1 and 40% by volume.

Die erfindungsgemäß hergestellten siliziumhaltigen Eisenpulver weisen einen Siliziumgehalt von 0.5 bis zu 25 Gew.-% auf. Vorzugsweise beträgt der Siliziumgehalt 0,5 bis 10%, insbesondere 1 bis 4 Gew.-%. Der Siliziumgehalt kann nach bekannten Methoden der Elementaranalyse, beispielsweise durch Röntgenmikrobereichsanalyse aus REM-Aufnahmen, bestimmt werden.The silicon-containing iron powders produced according to the invention have one Silicon content from 0.5 to 25 wt .-%. The is preferably Silicon content 0.5 to 10%, in particular 1 to 4% by weight. The silicon content can be determined using known methods Elemental analysis, for example by X-ray micro-area analysis SEM images can be determined.

Das siliziumhaltige Eisenpulver kann Nebenbestandteile, insbesondere Sauerstoff, Kohlenstoff, Wasserstoff und Stickstoff enthalten. Der Sauerstoffgehalt kann bis zu 30 Gew.-% betragen, vorzugsweise liegt er unterhalb 10 Gew.-%, besonders bevorzugt zwischen 0,1 und 5 Gew.-%. Der Kohlenstoffgehalt kann bis zu 10 Gew.-% betragen, bevorzugt liegt er unterhalb 8 Gew.-%, besonders bevorzugt zwischen 0,1 und 7 Gew.-%. Der Stickstoffgehalt kann bis zu 2 Gew.-% betragen. Bei Mitverwendung von Ammoniak liegt er vorzugsweise zwischen 0,5 und 2 Gew.-%, ohne Verwendung von Ammoniak vorzugsweise unterhalb von 0,5 Gew.-%. Der Wasserstoffgehalt kann bis zu 1 Gew.-% betragen, vorzugsweise liegt er unterhalb 0,5 Gew.-%.The silicon-containing iron powder can contain secondary components, especially oxygen, Contain carbon, hydrogen and nitrogen. The oxygen content can be up to 30% by weight, preferably it is below 10% by weight, particularly preferably between 0.1 and 5% by weight. The carbon content can be up to 10% by weight, preferably it is below 8% by weight, particularly preferably between 0.1 and 7% by weight. The nitrogen content can up to 2% by weight. If ammonia is also used, it lies preferably between 0.5 and 2% by weight, without using ammonia preferably below 0.5% by weight. The hydrogen content can be up to amount to 1% by weight, preferably it is below 0.5% by weight.

Ein weiterer Vorteil des erfindungsgemäßen Verfahrens ist der besonders geringe Gehalt der siliziumhaltigen Eisenpulver an Fremdmetallen. Bevorzugt weisen die erfindungsgemäß erhaltenen siliziumhaltigen Eisenpulver folgenden Gehalt an Fremdelementen auf: Nickel < 100 ppm, Chrom < 150 ppm, Molybdän < 20 ppm, Arsen < 2 ppm, Blei < 10 ppm, Cadmium < 1 ppm, Kupfer < 5 ppm, Mangan < 10 ppm, Quecksilber < 1 ppm, Zink < 10 ppm, Schwefel < 10 ppm. Der Fremdelementgehalt kann mittels Atomabsorptions-Spektralanalyse bestimmt werden.Another advantage of the method according to the invention is that which is special low content of silicon-containing iron powder in foreign metals. Prefers the silicon-containing iron powders obtained according to the invention have the following Content of foreign elements on: nickel <100 ppm, chromium <150 ppm, Molybdenum <20 ppm, arsenic <2 ppm, lead <10 ppm, cadmium <1 ppm, copper <5 ppm, manganese <10 ppm, mercury <1 ppm, zinc <10 ppm, sulfur <10 ppm. The foreign element content can be determined using Atomic absorption spectral analysis can be determined.

Weiterhin ist vorteilhaft, daß das siliziumhaltige Eisenpulver in dem erfindungsgemäßen Verfahren in feinteiliger Form anfällt und insoweit eine mechanische Nachbehandlung, beispielsweise durch Mahlen, entfallen kann. Das siliziumhaltige Eisenpulver fällt bei der Umsetzung in Form von im wesentlichen kugelförmigen Teilchen mit einem mittleren Durchmesser zwischen 0,005 und 10 µm, die zu Fäden oder knolligen Aggregaten agglomeriert sein können, an. Vorzugsweise beträgt der mittlere Durchmesser der im wesentlichen kugelförmigen Teilchen zwischen 0,01 µm und 5 µm. Die BET-Oberfläche der Teilchen beträgt vorzugsweise bis zu 30 m2/g. Die Schüttdichte der erfindungsgemäßen Pulver, die sich mit steigendem Siliziumgehalt verringert, beträgt vorzugsweise zwischen 0,4 und 4 g/cm3.It is also advantageous that the silicon-containing iron powder is obtained in finely divided form in the process according to the invention and that mechanical post-treatment, for example by grinding, can be dispensed with. The silicon-containing iron powder is obtained in the form of essentially spherical particles with an average diameter between 0.005 and 10 μm, which can be agglomerated into threads or bulbous aggregates. The average diameter of the substantially spherical particles is preferably between 0.01 μm and 5 μm. The BET surface area of the particles is preferably up to 30 m 2 / g. The bulk density of the powders according to the invention, which decreases with increasing silicon content, is preferably between 0.4 and 4 g / cm 3 .

Die Umsetzung erfolgt vorzugsweise kontinuierlich in einem beheizten Reaktionsraum, der von der Gasmischung durchströmt wird. Die Umsetzung kann beispielsweise in einem beheizbaren Zersetzer, wie er für die Herstellung von Carbonyleisenpulver durch thermische Zersetzung von Eisenpentacarbonyl verwendet wird und in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A14, page 599, beschrieben ist, durchgeführt werden. Ein solcher Zersetzer umfaßt ein Rohr aus einem hitzebeständigen Material wie Quarzglas oder V2A-Stahl in vorzugsweise vertikaler Position, das von einer Heizeinrichtung, beispielsweise bestehend aus Heizbändern, Heizdrähten oder aus einem von einem Heizmedium durchströmten Heizmantel, umgeben ist. Bevorzugt ist die Heizeinrichtung zur Einstellung einer Zone niedriger Temperatur und einer Zone höherer Temperatur in mindestens 2 Segmente unterteilt. Die Gase werden vorgemischt und vorzugsweise von oben in das Zersetzerrohr eingeleitet, wobei die Gasmischung die Zone niedriger Temperatur zuerst passiert. Vorzugsweise ist die Temperatur im unteren Teil des Rohres um mindestens 20°C höher als im oberen Teil des Rohres. Das gebildete siliziumhaltige Eisenpulver wird nach bekannten Methoden unter Ausnutzung der Schwerkraft, der Zentrifugalkraft oder mittels einer Filtereinrichtung aus dem Gasstrom abgeschieden. Dies kann beispielsweise dadurch geschehen, daß der Gasstrom ein Abscheidegefäß passiert und dort umgelenkt wird. Bei größeren Teilchen kann die Abtrennung auch ohne weiteres dadurch erfolgen, daß man die Partikel aus dem Zersetzer herausrieseln läßt und in einem Vorlagegefäß auffängt. Für den Fall, daß Feststoffteilchen von der Gasströmung mitgerissen werden können, wird vorzugsweise zusätzlich eine Filtereinrichtung verwendet.The reaction is preferably carried out continuously in a heated one Reaction space through which the gas mixture flows. The implementation can, for example, in a heatable decomposer such as that used for the production of carbonyl iron powder by thermal decomposition of iron pentacarbonyl is used and in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A14, page 599 become. Such a decomposer comprises a tube made of a heat-resistant one Material such as quartz glass or V2A steel, preferably in a vertical position, that of a heating device, for example consisting of heating tapes, Heating wires or from a heating jacket through which a heating medium flows, is surrounded. The heating device is preferred for setting one Zone of low temperature and a zone of higher temperature in at least 2 segments divided. The gases are premixed and preferably introduced into the decomposition tube from above, the gas mixture entering the zone low temperature happens first. The temperature is preferably in lower part of the tube by at least 20 ° C higher than in the upper part of the Tube. The silicon-containing iron powder formed is known Methods using gravity, centrifugal force or separated from the gas stream by means of a filter device. This can happen, for example, in that the gas stream is a separation vessel happens and is redirected there. With larger particles the separation can also easily done by removing the particles from the Let the decomposer trickle out and catch it in a storage container. For the If solid particles can be carried away by the gas flow, a filter device is preferably additionally used.

Die Umsetzung in dem Zersetzer erfolgt vorzugsweise bei Temperaturen zwischen 200 und 600°C, besonders bevorzugt zwischen 250 und 350°C. Die Umsetzung kann bei Drücken von bis zu 40 bar durchgeführt werden. Bevorzugt liegt der Druck zwischen 1 und 2 bar absolut.The reaction in the decomposer is preferably carried out at temperatures between 200 and 600 ° C, particularly preferably between 250 and 350 ° C. The reaction can be carried out at pressures of up to 40 bar. The pressure is preferably between 1 and 2 bar absolute.

Ein weiterer Vorteil des erfindungsgemäßen Verfahrens ist, daß durch Wahl der Reaktionsparameter wie Druck, Temperatur und Durchströmgeschwindigkeit sowie der Gaszusammensetzung die mittlere Teilchengröße der Pulver variiert werden kann. Another advantage of the method according to the invention is that by choice the reaction parameters such as pressure, temperature and flow rate and the gas composition, the average particle size of the powder can be varied.

Die nach dem beschriebenen Verfahren erhaltenen siliziumhaltigen Eisenpulver können von Kohlenstoff, Sauerstoff und Stickstoff weitgehend befreit werden, indem sie in der Hitze in einem Wasserstoffstrom reduziert werden. Vorzugsweise werden die Pulver bei Temperaturen zwischen 300 und 600°C, besonders bevorzugt zwischen 400 und 500°C reduziert. Die reduzierten Pulver können einen Kohlenstoffgehalt von < 0,05 Gew.-%, einen Stickstoffgehal von < 0,01 Gew.-% und einen Sauerstoffgehalt von <0,2 Gew.-% aufweisen.The silicon-containing iron powder obtained by the process described can from Carbon, oxygen and nitrogen are largely liberated by being in the heat a hydrogen flow can be reduced. The powders are preferably at temperatures reduced between 300 and 600 ° C, particularly preferably between 400 and 500 ° C. The Reduced powders can have a carbon content of <0.05% by weight, a nitrogen content of <0.01% by weight and an oxygen content of <0.2% by weight.

Die erfindungsgemäß hergestellten siliziumhaltigen Eisenpulver eignen sich besonders für Anwendungen in der Elektronik oder Elektrotechnik, wobei sowohl reduzierte als auch nichtreduzierte Pulver verwendet werden können. So kann das erfindungsgemäß hergestellte siliziumhaltige Eisenpulver für die Herstellung von Spulenkemen oder Magneten verwendet werden. Vorteilhaft sind insbesondere die deutlich geringeren Hystereseverluste und Koerzitivkräfte der Eisen-Silizium-Legierung. Das siliziumhaltige Eisenpulver kann wie Carbonyleisenpulver verarbeitet werden, indem es beispielsweise mit einem aushärtenden Bindemittel, z.B. einem Phenolharz oder einem Epoxidharz, verknetet, granuliert und trocken zu den gewünschten Formkörpern, Ringen, Stäben und Schraubkemen verpreßt wird. Diese werden anschließend thermisch ausgehärtet. Solche platikgebundenen Magnetkerne können durch Formpressen, aber auch im Spritzgußverfahren hergestellt werden. Ein großer Vorteil der so hergestellten Pulverkerne liegt darin, daß das Pulver sehr fein ist. Durch eine geeignete Isolierung kann somit eine wesentliche Verringerung der Wirbelstromverluste gegenüber Pulverkernen erreicht werden, die aus gröberem Pulver hergestellt sind. Diese Verringerung der Wirbelstromverluste macht sich in einer Steigerung der Güte bemerkbar. Eine besonders hohe Güte erreicht man, wenn die Isolierung so stark ist, daß es zwischen den einzelnen, primären Pulverteilchen zu keinem Kontakt kommt. Die Isolierung der Pulverteilchen mit einer gleichbleibenden, isolierenden Schicht kann beispielsweise durch Behandeln des siliziumhaltigen Eisenpulvers mit einer verdünnten Lösung von Phosphorsäure in einem organischen Lösungsmittel erfolgen, wobei an der Oberfläche der Teilchen eine Eisenphosphatschicht gebildet wird.The silicon-containing iron powders produced according to the invention are particularly suitable for Applications in electronics or electrical engineering, both reduced and unreduced powders can be used. So that manufactured according to the invention silicon-containing iron powder used for the production of coil core or magnet become. The significantly lower hysteresis losses and are particularly advantageous Coercive forces of the iron-silicon alloy. The silicon-containing iron powder can be like Carbonyl iron powder can be processed, for example by using a hardening agent Binders, e.g. a phenolic resin or an epoxy resin, kneaded, granulated and dry is pressed to the desired shaped bodies, rings, rods and screw core. This are then cured thermally. Such magnetic bonded cores can be produced by compression molding, but also by injection molding. A big advantage The powder cores thus produced are that the powder is very fine. By a suitable one Insulation can thus significantly reduce eddy current losses Powder cores can be achieved which are made from coarser powder. This reduction the eddy current loss is reflected in an increase in quality. A special one high quality is achieved when the insulation is so strong that it is between the individual primary powder particles do not come into contact. Isolation of the powder particles with a constant, insulating layer, for example by treating the silicon-containing iron powder with a dilute solution of Phosphoric acid take place in an organic solvent, the surface of the Particles form an iron phosphate layer.

Weiterhin lassen sich die erfindungsgemäß hergestellten siliziumhaltigen Eisenpulver zu mikrowellenabsorbierenden oder radarabsorbierenden Materialien verarbeiten. Dazu werden die Pulver in plastische oder gummiartige Werkstoffe wie auch in Lacksysteme eingebracht. Besonders eignet sich das erfindungsgemäße siliziumhaltige Eisenpulver als Absorber für elektromagnetische Strahlung im Frequenzbereich von 1 bis 100 Gigahertz.Furthermore, the silicon-containing iron powders produced according to the invention can be used Process microwave absorbing or radar absorbing materials. To do this the powders are introduced into plastic or rubber-like materials as well as in coating systems. The silicon-containing iron powder according to the invention is particularly suitable as an absorber for electromagnetic radiation in the frequency range from 1 to 100 gigahertz.

Ferner können die siliziumhaltigen Eisenpulver aufgrund ihres hohen Siliziumgehaltes und ihrer großen spezifischen Oberfläche als Katalysatoren für die Hydrierung von Kohlenmonoxid im Fischer-Tropsch-Verfahren verwendet werden.Furthermore, the silicon-containing iron powder due to their high silicon content and their large specific surface area as catalysts for the hydrogenation of Carbon monoxide can be used in the Fischer-Tropsch process.

Die Erfindung wird durch die nachfolgenden Beispiele näher erläutert:The invention is illustrated by the following examples:

BEISPIELE 1 BIS 13EXAMPLES 1 TO 13

Die Apparatur zur thermischen Zersetzung von Eisenpentacarbonyl [Fe(CO)5] und Silan (SiH4) besteht aus einem Zersetzerrohr aus V2A-Stahl von 1 m Länge und einem Innendurchmesser von 20 cm. Das Zersetzerrohr wird so beheizt, daß die Temperatur im unteren Drittel um etwa 20°C höher ist als die Temperatur T1 im oberen Teil des Rohres. Das flüssig vorgehaltene Fe(CO)5 wird in einem elektrisch beheizten Vorlagegefäß verdampft und der Dampf zusammen mit SiH4 (0-60 l/h), H2 (0-500 l/h), NH3 (0-150 l/h) und ggf. CO (0-100 l/h) von oben in das Zersetzerrohr eingeleitet. Im Zersetzerrohr läuft die Bildung des siliziumhaltigen Eisenpulvers unter Freisetzung von CO und H2 ab. Das gebildete siliziumhaltige Eisenpulver gelangt mit dem Gasstrom in ein Abscheidergefäß, in dem es durch Umlenken des Gasstromes aus diesem abgetrennt wird. Im Gasstrom verbleibende Feststonffteilchen werden von einer Filterkerze zurückgehalten. Der Siliziumgehalt der Eisenpulver wird durch Elementaranalyse bestimmt und entspricht im Rahmen der Analysegenauigkeit der eingesetzten Menge an Monosilan. Im Abgas werden IR-spektrometrisch noch ca. 2 ppm SiH4 nachgewiesen, so daß auf eine praktisch vollständige Umsetzung des Silans geschlossen werden kann. Die Elementzusammensetzung der Teilchen wurde mittels AAS (Atomabsorptionsspektroskopie) bestimmt, ihre spezifische Oberfläche (BET-Oberfläche) durch Stickstoffadsorption nach DIN 66 132 gemessen.The apparatus for the thermal decomposition of iron pentacarbonyl [Fe (CO) 5 ] and silane (SiH 4 ) consists of a decomposer tube made of V2A steel with a length of 1 m and an inner diameter of 20 cm. The decomposer tube is heated so that the temperature in the lower third is about 20 ° C higher than the temperature T 1 in the upper part of the tube. The liquid Fe (CO) 5 is evaporated in an electrically heated storage vessel and the steam together with SiH 4 (0-60 l / h), H 2 (0-500 l / h), NH 3 (0-150 l / h) and possibly CO (0-100 l / h) introduced into the decomposition tube from above. The formation of the silicon-containing iron powder in the decomposition tube releases CO and H 2 . The silicon-containing iron powder that is formed passes with the gas stream into a separator vessel in which it is separated from the gas stream by deflecting it. Solid clay particles remaining in the gas stream are retained by a filter candle. The silicon content of the iron powder is determined by elemental analysis and corresponds to the amount of monosilane used within the accuracy of the analysis. About 2 ppm SiH 4 are still detected in the exhaust gas by IR spectrometry, so that it can be concluded that the silane has been converted practically completely. The elemental composition of the particles was determined by means of AAS (atomic absorption spectroscopy), and their specific surface area (BET surface area) was measured by nitrogen adsorption in accordance with DIN 66 132.

Vergleichsbeispiel V1:Comparative Example V1:

Das Verfahren wurde wie oben beschrieben durchgeführt, doch wurde kein SiH4 verwendet.The procedure was carried out as described above, but no SiH 4 was used.

Die Reaktionsbedingungen und die Charakterisierung der Verfahrensprodukte sind der nachstehenden Tabelle zu entnehmen.

Figure 00120001
The reaction conditions and the characterization of the process products are shown in the table below.
Figure 00120001

Claims (5)

  1. A method for preparing silicon-containing iron powders having a silicon content of from 0.5 to 25 wt% by thermal, non-laser-pyrolytic decomposition of a gas mixture comprising iron pentacarbonyl and a volatile silicon compound, in which the gas mixture flows through a heated reaction chamber and heating of the gas mixture is effected by thermal conduction, wherein the volatile silicon compound used is SiH4.
  2. A method as claimed in claim 1, wherein the decomposition is carried out in the presence of ammonia and/or hydrogen.
  3. A method as claimed in claim 1 or 2, wherein the decomposition is carried out at from 200 to 600°C.
  4. A method as claimed in any one of claims 1 to 3, wherein the decomposition is carried out at pressures from 1 to 2 bar absolute.
  5. A method as claimed in any one of claims 1 to 4, wherein the silicon-containing iron powder obtained is reduced, after the decomposition, with gaseous hydrogen.
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CN1293970C (en) 2007-01-10
TW365556B (en) 1999-08-01
ES2190000T3 (en) 2003-07-16
JP4106413B2 (en) 2008-06-25
EP0878259A1 (en) 1998-11-18
CN1209367A (en) 1999-03-03
RU2207934C2 (en) 2003-07-10
ATE230322T1 (en) 2003-01-15
US5993569A (en) 1999-11-30

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