[go: up one dir, main page]

EP0000749A1 - Procédé de préparation d'oxyde ferrique aciculaire ferrimagnétique et son application - Google Patents

Procédé de préparation d'oxyde ferrique aciculaire ferrimagnétique et son application Download PDF

Info

Publication number
EP0000749A1
EP0000749A1 EP7878100535A EP78100535A EP0000749A1 EP 0000749 A1 EP0000749 A1 EP 0000749A1 EP 7878100535 A EP7878100535 A EP 7878100535A EP 78100535 A EP78100535 A EP 78100535A EP 0000749 A1 EP0000749 A1 EP 0000749A1
Authority
EP
European Patent Office
Prior art keywords
iron
iii
acicular
oxides
oxide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP7878100535A
Other languages
German (de)
English (en)
Other versions
EP0000749B1 (fr
Inventor
Rudolf Dr. Brodt
Helmut Dr. Jakusch
Eberhard Dr. Koester
Werner Dr. Loeser
Manfred Dr. Ohlinger
Wilhelm Dr. Sarnecki
Werner Dr. Steck
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP0000749A1 publication Critical patent/EP0000749A1/fr
Application granted granted Critical
Publication of EP0000749B1 publication Critical patent/EP0000749B1/fr
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • G11B5/70652—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides gamma - Fe2 O3
    • G11B5/70663—Preparation processes specially adapted therefor, e.g. using stabilising agents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/02—Oxides; Hydroxides
    • C01G49/06—Ferric oxide [Fe2O3]
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • G11B5/70647—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides with a skin
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
    • G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
    • G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
    • G11B5/70652—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides gamma - Fe2 O3
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/54—Particles characterised by their aspect ratio, i.e. the ratio of sizes in the longest to the shortest dimension
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/42—Magnetic properties

Definitions

  • the invention relates to a process for the production of acicular ferrimagnetic iron oxides by dewatering acicular iron (III) oxide hydroxides.
  • acicular iron (III) oxides subsequent reduction of these iron (III) oxides at temperatures between 300 and 650 ° C by means of organic compounds which decompose in this temperature range and oxidation of the resulting products with oxygen-containing gases at 200 to 500 ° C and their use for the production of magnetic recording media.
  • Acicular ferrimagnetic iron oxides such as magnetite and gamma-iron (III) oxide
  • GB-PS 675 260 already describes a process for the extraction of gamma-iron (III) oxide, in which acicular ⁇ -iron oxide hydroxide (goethite) dehydrates to ⁇ -iron (III) oxide, in a reducing atmosphere "Converted to magnetite at more than 300 ° C and oxidized to acicular gamma-iron (III) oxide in air at temperatures below 4500C.
  • this process has been in its individual stages varied several times, and also modified by changing the input materials.
  • suitable magnetic iron oxides were obtained in the manner disclosed in DE-PS 801 352, namely by treating non-magnetic iron oxides with the salts of short-chain carboxylic acids and then heating them.
  • the magnetite obtained afterwards can also be converted into gamma-iron (III) oxide by oxidation at 200 to 400 ° C.
  • 2,900,236 specifies all the corresponding organic substances with particular mention of wax, starch and oil as being useful in DE-AS 12 03 656 salts of soluble soaps precipitated on iron oxide, in DE-OS 20 64 804 Both higher hydrocarbons, higher alcohols and amines, higher fatty acids and their salts, as well as oils, fats and waxes, in DE-PS 91 017 also long-chain carboxylic acids or their salts, in DE-AS 17 71 327 aliphatic monocarboxylic acids with 8 to 24 Carbon- atoms, optionally in a mixture with morpholine and in JP-OS 80 499/1975 organic compounds, such as ethanol, containing inert gases as reducing agents for the production of magnetite from non-magnetic iron oxides.
  • the known process mentioned is partly heated in the absence of air, the reaction remaining at the magnetite stage or in the presence of air, as a result of which the magnetite is immediately oxidized to gamma-iron (III) oxide
  • the starting materials for the transformation of iron oxides by means of organic substances were predominantly the corresponding ⁇ -modifications, such as ⁇ -FeOOH or a-Fe 2 O 3 , but ⁇ -FeOOH (DE-AS 12 03 656) and ⁇ -FeOOH ( DE-OS 22 12 435) used successfully.
  • the invention was therefore based on the object of improving the known acicular ferrimagnetic iron oxides and of eliminating the disadvantages to date.
  • the object of the invention was to provide acicular gamma-iron (III) oxide which is distinguished by high values for the coercive field strength and the remanence, by good crystallinity and by mechanical and magnetic stability.
  • acicular ferromagnetic iron oxides are formed by dewatering acicular iron (III) oxide hydroxides to acicular iron (III) oxides, then reducing these iron (III) oxides at temperatures between 300 and 650 ° C by means of organic compounds which are decomposable in this temperature range Allow oxidation of the reduction product with oxygen-containing gases at 200 to 500 ° C with the properties required by the task if the needle-shaped iron (III) oxide hydroxide used consists of a mixture of goethite and lepidocrocite with a lepidocrocite content of at least 60% and at temperatures of 200 to 700 ° C is dewatered.
  • the acicular iron (III) oxide hydroxides of the mixture have a length to thickness ratio of at least 10 and are dewatered at 300 to 650 ° C.
  • the iron (III) oxide hydroxides composed of goethite and lepidocrocite consist of 60 to 98%, preferably 70 to 98%, of lepidocrocite.
  • the mixture used for the process according to the invention can be prepared under suitable reaction conditions from iron (III) salt solutions with alkalis with simultaneous oxidation. It has proven particularly expedient to use iron (III) oxide hydrate seeds from an aqueous iron (II) chloride solution using alkalis, such as alkali hydroxide or ammonia, at temperatures between 10 and 32 ° C.
  • the solids content of iron (III) oxide hydroxide in the aqueous suspension should be between 10 and 50 g / l, preferably 15 to 45 g / l. After filtering off and washing out the precipitate, the iron (III) oxide hydrate mixture obtained in this way is dried at 60 to 200 ° C.
  • Stable crystal needles of the goethite-lepicrocite mixture with at least 60% lepidocrocite, which have almost no dendritic branches, can be obtained by the procedure described by way of example.
  • acicular goethite-lepikrokite mixture suitable for use in the method according to the invention are an average particle size of 0.2 to 1.5 and preferably of 0.3 to 1.2 ⁇ m.
  • the length-to-thickness ratio is at least 10, with corresponding ratios of 12 to 40 having been found to be expedient.
  • the particle surface measured according to BET is between 18 and 70 m2 / g.
  • a goethite-lepidocrocite mixture characterized in this way is dewatered according to the invention at temperatures between 200 and 700 ° C., preferably between 300 and 650 ° C. and in particular between 450 and 600 ° C., before further processing into ferrimagnetic iron oxides known per se, surprisingly improve the values for coercive field strength and remanence of the end products obtainable therefrom.
  • the dewatering can be carried out both in air and in an inert gas atmosphere.
  • the product present after the dewatering step is converted into acicular ferric magnetic at temperatures between 300 and 650 ° C. in a manner known per se with largely ash- and tar-free decomposable organic substances Converted iron oxides.
  • the dewatered goethite-lepidocrocite mixture is mechanically mixed with the solid or liquid organic substance or coated in a suitable solution or suspension of the substance and then heated to temperatures of 300 to 650 ° C. under inert gas.
  • the method can be carried out by means of gaseous organic substances which are added to the inert gas.
  • Organic compounds which can be used in the process according to the invention are all compounds which are stated to be suitable according to the prior art, provided they can be added at temperatures between 300 and 650 ° C. Expediently, higher fatty acids, their derivatives, glycerin, inert gas / alcohol vapor mixtures and also methane are used for this purpose.
  • the conversion of the dewatered goethite-lepidocrocite mixture to the acicular magnetite is complete after about 1 to 120 minutes.
  • the acicular magnetite obtained after this reduction reaction is usually oxidized to gamma-iron (III) oxide, expediently by passing air over it or adding oxygen at temperatures of 200 to 500 ° C.
  • the acicular ferrimagnetic iron oxides produced according to the invention show unexpectedly advantageous properties in the processing Use as magnetic pigments for the production of magnetogram carriers.
  • the gamma-iron (III) oxide is dispersed in polymeric binders.
  • binders such as homopolymers and copolymers of polyvinyl derivatives, polyurethanes, polyesters and the like.
  • the binders are used in solutions in suitable organic solvents, which may optionally contain further additives.
  • the magnetic layers are. applied to rigid or flexible supports such as plates, foils and cards.
  • the acicular ferrimagnetic iron oxides produced according to the invention differ significantly from the known gamma iron (III) oxides in that they have a more uniform needle shape, since agglomeration is prevented by sintering together. by their improved crystallinity and by the higher coercive field strength and remanence, which can surprisingly be achieved in the process according to the invention. These improvements in the magnetic material are also very noticeable in the magnetic tapes made therefrom.
  • the coercive force (H o ) is given in [kA / m]
  • the specific remanence (M r / ⁇ ) and the specific magnetization (M m / g) are given in [nT cm 3 / g].
  • the suspension is washed on a suction filter with water until the filtrate is chloride-free and then dried at 130 ° C. in a drying cabinet.
  • the resulting iron oxide hydroxide is a mixture of 94% lepidocrocite and 6% goethite, has a length-to-thickness ratio of 31 and a BET specific surface area of 34.7 m 2 / g.
  • This goethite-lepidocrocite mixture is heated to 490 ° C. for one hour for air dewatering.
  • the resulting product is now mixed with 2% by weight of stearic acid, divided into three equal samples 1A, 1B and 1C and converted to magnetite under nitrogen under the conditions specified in Table 1 and to gamma-iron (III) oxide in air oxidized.
  • the magnetic properties are also shown in Table 1.
  • iron (III) oxide hydroxide mixtures with a lepidocrocite content of 72% with a BET specific surface area of 33.2 m 2 / g are produced. These goethite-lepidocrocite mixtures are dehydrated in air at the temperatures given in Table 2 for one hour each, then at 300 ° C with a nitrogen-methanol vapor mixture reduced to magnetite and then oxidized in air at 400 ° C to gamma-iron (III) oxide.
  • the nitrogen-methanol mixture is formed when nitrogen is passed through in an amount of 50 l per hour through a container heated to 105 ° C., to which methanol is added.
  • Table 2 The resulting magnetic values of the tests are also shown in Table 2.
  • Table 5 shows samples which were dewatered in 30 minutes at the lower dewatering temperature of 400 ° C and then converted to ⁇ -Fe 2 O 3 .
  • the germ suspension was heated to 33 ° C. in 20 minutes.
  • the amount of air was then increased to 8 m 3 / h and the pH was adjusted to 5.5 by adding aqueous sodium hydroxide solution. and regulated to this value until the end of the reaction.
  • the mixture was simultaneously heated to 38 to 39 ° C. in 30 minutes and this temperature was maintained until the end of the growth reaction.
  • the oxidation was complete after 1 hour and 40 minutes. After filtration through a filter press, the product is washed with water until the filtrate is chloride-free and then dried at 110 ° C. in a drying cabinet.
  • the resulting ferric oxide hydrate sets in.
  • Mixture of 92% lepidocrocite and 8% goethite has a length-to-thickness ratio of 16 and a BET specific surface area of 23.3 m 2 / g.
  • Magnetic pigment dispersions and then magnetic tapes are produced from the two gamma-iron (III) oxide samples H and J.
  • K value 58
  • the film After drying, the film carries mecanic'Magnet Mrs of 5 / um thickness. By going The magnetic layer is compacted between heated rollers (80 ° C under a line pressure of approx. 3 kg / cm). The coated film is cut into strips 6.25 mm wide.
  • the electroacoustic measurement is carried out in accordance with DIN 45 512, Part II.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Dermatology (AREA)
  • General Health & Medical Sciences (AREA)
  • Hard Magnetic Materials (AREA)
  • Compounds Of Iron (AREA)
EP78100535A 1977-08-05 1978-07-28 Procédé de préparation d'oxyde ferrique aciculaire ferrimagnétique et son application Expired EP0000749B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2735316A DE2735316C3 (de) 1977-08-05 1977-08-05 Verfahren zur Herstellung von nadeiförmigen, ferrimagnetischen Eisenoxiden
DE2735316 1977-08-05

Publications (2)

Publication Number Publication Date
EP0000749A1 true EP0000749A1 (fr) 1979-02-21
EP0000749B1 EP0000749B1 (fr) 1980-07-23

Family

ID=6015703

Family Applications (1)

Application Number Title Priority Date Filing Date
EP78100535A Expired EP0000749B1 (fr) 1977-08-05 1978-07-28 Procédé de préparation d'oxyde ferrique aciculaire ferrimagnétique et son application

Country Status (4)

Country Link
US (1) US4213959A (fr)
EP (1) EP0000749B1 (fr)
JP (1) JPS5428299A (fr)
DE (2) DE2735316C3 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2416868A1 (fr) * 1978-02-09 1979-09-07 Basf Ag Procede de preparation d'oxydes de fer ferrimagnetiques aciculaires
FR2416869A1 (fr) * 1978-02-10 1979-09-07 Basf Ag Procede de preparation d'oxydes de fer ferrimagnetiques aciculaires
FR2424910A1 (fr) * 1978-05-03 1979-11-30 Nippon Shinyaku Co Ltd Derives de moranoline n-substitues et leur utilisation, notamment pour le traitement de l'hyperglycemie
EP0040722A1 (fr) * 1980-05-23 1981-12-02 BASF Aktiengesellschaft Procédé pour la production de lépidocrocite synthétique

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3143870A1 (de) * 1981-11-05 1983-05-11 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung von nadelfoermigen, ferrimagnetischen eisenoxiden
JPS58199725A (ja) * 1982-05-12 1983-11-21 Fuji Photo Film Co Ltd 強磁性酸化鉄の製造方法
DE3224325A1 (de) * 1982-06-30 1984-01-05 Basf Ag, 6700 Ludwigshafen Verfahren zur herstellung von nadelfoermigen, ferrimagnetischen eisenoxiden
JPS61106408A (ja) * 1984-10-25 1986-05-24 Daikin Ind Ltd 炭化鉄を含有する針状粒子の製造法
US5219554A (en) * 1986-07-03 1993-06-15 Advanced Magnetics, Inc. Hydrated biodegradable superparamagnetic metal oxides
US5069216A (en) * 1986-07-03 1991-12-03 Advanced Magnetics Inc. Silanized biodegradable super paramagnetic metal oxides as contrast agents for imaging the gastrointestinal tract
EP0604849B1 (fr) * 1992-12-29 1996-10-16 Ishihara Sangyo Kaisha, Ltd. Oxyde de fer magnétique contenant du cobalt et procédé pour sa production
US5814164A (en) * 1994-11-09 1998-09-29 American Scientific Materials Technologies L.P. Thin-walled, monolithic iron oxide structures made from steels, and methods for manufacturing such structures
US6461562B1 (en) 1999-02-17 2002-10-08 American Scientific Materials Technologies, Lp Methods of making sintered metal oxide articles
JP7132901B2 (ja) 2019-10-01 2022-09-07 株式会社Soken 電力変換装置
CN115676898B (zh) * 2022-10-31 2024-05-07 昆明理工大学 一种一步碳热还原制备Fe3O4的方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3082067A (en) * 1959-04-28 1963-03-19 Bayer Ag Process for the production of isometric ferromagnetic gamma-ferric oxide
FR2130407A1 (fr) * 1971-03-17 1972-11-03 Pfizer

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1138750B (de) * 1950-05-26 1962-10-31 Basf Ag Verfahren zur Herstellung magnetisierbarer Eisenoxyde
US2900236A (en) * 1955-08-03 1959-08-18 Audio Devices Inc Production of ferromagnetic iron oxide
US3117933A (en) * 1959-06-12 1964-01-14 Bayer Ag Process for the production of needleshaped, cobalt-containing gamma-ferric oxide crystalline particles
JPS5016859B2 (fr) * 1971-09-30 1975-06-17
JPS5327719B2 (fr) * 1972-05-23 1978-08-10
JPS5241758B2 (fr) * 1972-09-01 1977-10-20
JPS5719056B2 (fr) * 1974-04-08 1982-04-20
JPS5437680B2 (fr) * 1975-03-22 1979-11-16

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3082067A (en) * 1959-04-28 1963-03-19 Bayer Ag Process for the production of isometric ferromagnetic gamma-ferric oxide
FR2130407A1 (fr) * 1971-03-17 1972-11-03 Pfizer

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ACTA CRYSTALLOGRAPHICA, Teil 13, November 1960, Seiten 932-935, Morphology of synthetic submicroscopic crystals of alpha and gamma FeOOH and of gamma Fe2O3 prepared from FeOOH, G.W. van Oosterhout *
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, Teil 18, Nr. 1, Januar '63, Seiten 106-116, An electron diffraction study and a theory of the transformation from gamma Fe2O3 to alpha Fe2O3, Sakeji Kachi *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2416868A1 (fr) * 1978-02-09 1979-09-07 Basf Ag Procede de preparation d'oxydes de fer ferrimagnetiques aciculaires
FR2416869A1 (fr) * 1978-02-10 1979-09-07 Basf Ag Procede de preparation d'oxydes de fer ferrimagnetiques aciculaires
FR2424910A1 (fr) * 1978-05-03 1979-11-30 Nippon Shinyaku Co Ltd Derives de moranoline n-substitues et leur utilisation, notamment pour le traitement de l'hyperglycemie
EP0040722A1 (fr) * 1980-05-23 1981-12-02 BASF Aktiengesellschaft Procédé pour la production de lépidocrocite synthétique

Also Published As

Publication number Publication date
JPS6140602B2 (fr) 1986-09-10
EP0000749B1 (fr) 1980-07-23
DE2735316A1 (de) 1979-02-08
JPS5428299A (en) 1979-03-02
DE2735316C3 (de) 1981-01-29
DE2735316B2 (de) 1980-04-30
US4213959A (en) 1980-07-22
DE2860071D1 (en) 1980-11-13

Similar Documents

Publication Publication Date Title
EP0000749B1 (fr) Procédé de préparation d'oxyde ferrique aciculaire ferrimagnétique et son application
DE2714588C2 (de) Verfahren zur Herstellung nadelförmiger ferromagnetischer Eisenteilchen
EP0014902B1 (fr) Procédé de préparation d'oxyde de fer magnétique aciculaire renfermant du cobalt
DE2705967C2 (de) Verfahren zur Herstellung von nadelförmigem kobalthaltigem magnetischem Eisenoxid
EP0014903B1 (fr) Procédé de préparation d'oxyde de fer magnétique aciculaire renfermant du cobalt
EP0018009A1 (fr) Oxyde de fer magnétique aciculaire modifié, procédé pour sa préparation et son utilisation pour la fabrication de supports d'enregistrements magnétiques
DE2805405C2 (fr)
DE2805621A1 (de) Verfahren zur herstellung von nadelfoermigen, ferrimagnetischen eisenoxiden
DE2212435C3 (de) Synthetisches magnetisches γ- Eisen-(III)-oxid, Verfahren zu dessen Herstellung sowie dessen Verwendung
EP0097900B1 (fr) Procédé de préparation d'oxydes de fer ferromagnétiques aciculaires
EP0198110A2 (fr) Procédé pour la fabrication de dioxyde de chrome ferromagnétique
EP0160877B1 (fr) Procédé pour la fabrication d'une poudre isotrope de ferrite finement divisé contenant du cobalt
DE2045561C3 (de) Verfahren zur Herstellung feiner Goethitkristalle
DE2419800A1 (de) Kobalt-modifizierte eisenoxide
DE2550308A1 (de) Verfahren zur herstellung von nadelfoermigem alpha-eisen(iii)-oxidhydrat
DE3325613A1 (de) Verfahren zur herstellung von kobalt und zweiwertiges eisen enthaltendem, ferromagnetischem eisenoxid
DE2144553C2 (de) Kristallines γ-Eisen (III)oxid, Verfahren zu dessen Herstellung sowie Verwendung desselben
EP0158240A2 (fr) Procédé de préparation d'oxydes de fer isotropes magnétiques contenant du cobalt
DE3004056A1 (de) Verfahren zur herstellung eines feooh-pigments
EP0014889A1 (fr) Procédé de préparation de particules de fer aciculaire ferromagnétique
EP0110115A1 (fr) Particules de dioxyde de chrome ferromagnétiques aciculaires
EP0047368B1 (fr) Oxyde de fer aciculaire magnétique et procédé pour sa fabrication
DE2735315A1 (de) Verfahren zur herstellung von nadelfoermigem gamma-eisen(iii)oxid
EP0256459A2 (fr) Procédé pour la fabrication d'un oxyde de fer aciculaire ferrimagnétique
EP0201822A2 (fr) Procédé pour la fabrication d'oxydes de fer aciculaire contenant du cobalt

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): DE FR GB

17P Request for examination filed
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): DE FR GB

REF Corresponds to:

Ref document number: 2860071

Country of ref document: DE

Date of ref document: 19801113

KL Correction list

Free format text: 81/01

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19940624

Year of fee payment: 17

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19940715

Year of fee payment: 17

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19940725

Year of fee payment: 17

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19950728

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19950728

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19960402

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19960430

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT