EP0802886A1 - Preparation de poudres d'oxyde metallique par broyage a billes active - Google Patents

Preparation de poudres d'oxyde metallique par broyage a billes active

Info

Publication number
EP0802886A1
EP0802886A1 EP95933977A EP95933977A EP0802886A1 EP 0802886 A1 EP0802886 A1 EP 0802886A1 EP 95933977 A EP95933977 A EP 95933977A EP 95933977 A EP95933977 A EP 95933977A EP 0802886 A1 EP0802886 A1 EP 0802886A1
Authority
EP
European Patent Office
Prior art keywords
milling
milled
air
hematite
magnetic
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.)
Withdrawn
Application number
EP95933977A
Other languages
German (de)
English (en)
Inventor
Wieslaw Alexander Kaczmarek
Barry William Ninham
James Stanislaus Williams
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.)
Australian National University
Original Assignee
Australian National University
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
Priority claimed from AUPM8577A external-priority patent/AUPM857794A0/en
Priority claimed from AUPM8576A external-priority patent/AUPM857694A0/en
Application filed by Australian National University filed Critical Australian National University
Publication of EP0802886A1 publication Critical patent/EP0802886A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/0018—Mixed oxides or hydroxides
    • C01G49/0036—Mixed oxides or hydroxides containing one alkaline earth metal, magnesium or lead
    • 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
    • C01G49/08—Ferroso-ferric oxide [Fe3O4]
    • 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
    • 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
    • G11B5/70678—Ferrites
    • 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
    • G11B5/70678—Ferrites
    • G11B5/70684—Ferro-ferrioxydes
    • G11B5/70689—Magnetite
    • 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
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • 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
    • H01F1/0036—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties showing low dimensional magnetism, i.e. spin rearrangements due to a restriction of dimensions, e.g. showing giant magnetoresistivity
    • H01F1/0045—Zero dimensional, e.g. nanoparticles, soft nanoparticles for medical/biological use
    • H01F1/0063—Zero dimensional, e.g. nanoparticles, soft nanoparticles for medical/biological use in a non-magnetic matrix, e.g. granular solids
    • 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
    • H01F1/032—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 hard-magnetic materials
    • H01F1/10—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 hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
    • H01F1/11—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 hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/88—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by thermal analysis data, e.g. TGA, DTA, DSC
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • 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 present invention relates to new preparation technique concerns production of magnetic powder.
  • the present invention provides methods of improving the magnetic coercivity of a product.
  • the present invention relates to a method of improving the magnet coercivity in a magnetic oxide, and more particularly, in a hexagonal system ferrite powder.
  • the present invention relates to methods of reduction of hematite (Fe 2 O 3 ) and producing magnetite (Fe 3 O 4 ) powder.
  • the reduction method of the invention is based on combination of mechanical and a chemical activation processes, both performed in the same time and near room temperature.
  • the aim of the first part of the present study is to further exploit improved understanding of the milling process, its influence on changes in solid surface morphology and distinguish between solid state reactions either at the surface or in the bulk. Additionally, along with structural changes, we investigate the influence of heat treatment on the particle morphology, structure and magnetic properties in relation to preparation routes i.e. air and vacuum milling.
  • the example given hereinafter pertains to barium ferrite and improved magnetic coercivity therefor which can be realised under controlled activated milling.
  • Milling is a highly active mechanical process which consists of grinding through impact, compression and attrition.
  • the strain, shear, thermal and kinetic energy transforms all the solids involved from one phase or compound into another through polymorphic or solid state reactions.
  • the process can be performed in different gas pressure, temperature and in dry or wet (different dispersing agents) conditions.
  • polymorphic transformations the transition can take place from metastable to stable phases and vice versa, with possible binary coexistence in steady state equilibrium, depending on the mechanical treatment regime and conditions.
  • the second method of the present study concerns phase transitions in simple iron oxides, in particular the hematite - magnetite transformation.
  • Preparation and properties or iron oxides have been the subject of numerous studies because of their importance in magnetic materials technology.
  • a schematic diagram of the whole process is presented below (see Fig. 1), where arrows represent chemical solid state reactions: oxidation or reduction (typically achieved by the use of hydrogen at high f emperature).
  • phase magnetite, (Fe 3 O 4 ) maghemite ( ⁇ -Fe 2 O 3 ) and hematite ( ⁇ -Fe 2 O 3 ) that are "central" in this diagram. Phase transformations and reactions of Fe 2 O 3 during grinding were extensively studied during the last two decades.
  • Ball milling of ores, with and without additives, to facilitate the comminution process is not new.
  • the early potential of ball milling for the reduction and extraction of ores has generally not been fulfilled, and interest in such ore processing technology has waned.
  • the development of a new form of high energy ball mill at The Australian National University, and the success that has been achieved in mechanical alloying work with that ball mill (see, for example, the specifications of International Patent Application Nos. PCT/AU91/00248, PCT/AU92/00073 and PCT/AU94/00057, have stimulated new interest in the cold milling of ores. That new ball mill, which is described in the specification of International Patent Application No.
  • PCT/AU90/00471 (WIPO Publication No. WO91 /04810), enables controlled energy milling of a charge to be effected.
  • the present inventors have now discovered that under certain milling conditions, minerals containing silica, such as zircon, can be reduced while being converted into a nanostructural form, and that silica and other minerals can be removed from this product (for example, using hydrochloric acid).
  • the present invention provides methods for production of a magnetic powder using ball milling.
  • the present invention provides a method of production of a desirable magnetic powder from reduction of an oxide, comprising the steps of: providing a mixture of oxide and a reducing agent (dispersing liquid); controlled milling said mixture in a substantially low oxygen pressure environment to effect transformation of said oxide to a magnetic powder.
  • said oxide comprises hematite (Fe 2 O 3 ), and wherein said magnetic powder comprises magnetite (Fe 3 O 4 ).
  • substantially complete transformation of hermatite to magnetite is effected.
  • said reducing agent comprises water.
  • said environment is substantially oxygen-free.
  • said milling step is performed as low-energy milling.
  • the present invention provides a method of production of magnetic power , comprising the steps of: milling a complex magnetic oxide, using a high energy milling device; and. annealing said milled product at a temperature of above about 700K (i.e. combined mechanical and chemical activation).
  • said annealing step is performed at about 1200K. to 1600K for about 1-6 hours.
  • said annealing step is performed at about 1273K.
  • said milling step is performed in dry conditions in a vacuum, air or other gas atmosphere.
  • particle size and size distribution of said milled product can be influenced depending on pressure and gas atmosphere.
  • said particle size of said milled product is about 0.1 to 0.5 ⁇ m, when milled in air, or about 1 ⁇ m when milled in a vacuum.
  • said milling step is performed utilising an organic solvent.
  • said magnetic oxide is barium ferrite (BaFe, 2 O 19 ).
  • said milling for both methods is effected in a ball mill of the type described and claimed in the specification of International Patent Application No. PCT/AU90/00471.
  • Fig. i illustrates a schematic diagram of the various iron oxides phases:
  • Fig. 2 illustrates the temperature versus oxygen pressure (T-PO 2 ) phase diagram of the iron-oxide system
  • Fig. 3 shows a SEM microphotograph of a barium ferrite (BaFe 12 O i9 ) powder used in the experimental procedure herein described;
  • Fig. 4 illustrates XRD evolution patterns of barium ferrite powder milled in air for different periods of time
  • Fig. 5 illustrates XRD evolution patterns of barium ferrite powder milled in vacuum for different periods of time
  • Fig. 6 shows the results of SEM analysis of powder morphology versus milling time performed on air (a) and vacuum (b) milled samples;
  • Fig. 7 shows the results of SEM analysis of V 1000 powder particles
  • Fig. 8 shows a TGA scan for as milled powders a) A 1000 and b) VI 000;
  • Fig. 9 illustrates the fragmentation (a, b and d), consolidation (e) and decomposition mechanism (c) occurring during prolonged ball milling of barium ferrite in air (a-d) and vacuum (a-b-e);
  • Fig. 10 illustrates magnetic hysteresis curves of unmilled barium ferrite (BaFe 12 O, 9 ) and some milled powders from Table I annealed at 1273K;
  • Fig. 11 illustrates a schematic diagram of a suitable mill used during method of the present invention
  • Fig. 12 shows x-ray diffraction (XRD) patterns of hematite milled in wet conditions (water); and, Fig. 13 illustrates the intensity ratios between XRD reflexes from ( 104) and ( 1 10) planes of the hematite structure versus milling time.
  • XRD x-ray diffraction
  • Fig. 4 The X-ray diffraction patterns of the materials obtained on milling BaFe,,0 19 powder in air for different periods of time are shown in Fig. 4. As can readily be seen several distinctive features occur on ball-milling in comparison with the XRD pattern for the pre-milled powder.
  • the XRD pattern of the sample milled for 1000 hours allows a semi quantitative analysis of the discernible peaks.
  • the (107)- 37.5°, (114)- 39.8°, (205)- 47.16°and (206)- 49.7° reflections of hexagonal Ba ferrite can be indexed along with the following dominant lines of the hematite ⁇ -Fe 2 0 3 structure (012) - 28.1°, (104) - 38.7°, (1 10) - 41.6°, (1 13) - 47.8°, (024) - 58.2° and (116) - 63.7°.
  • Fig. 5 shows the XRD pattern evolution for BaFe.- j O,, powder processed in vacuum.
  • the decrease of the peak intensities and continuous broadening of the Bragg peaks are evidence for the formation of a nanocrystalline phase and the effect is similar to that described above for air milled powder.
  • the most evident changes here in comparison with Fig. 4 are the absence of strong material decomposition for the 690 h and 1000 h milled powders.
  • a weak tendency for the onset of new peaks can be observed.
  • the d, 07 spacing of the Ba-ferrite structure increases for vacuum milled powder contrary to the trend observed for air milled powder.
  • We attribute this effect to mechanically induced structural deformations (responsible for long range disorder) of vacuum ball-milled material.
  • the structural decomposition of Ba-ferrite is due to high oxygen gas adsorption on the particle surfaces. This effect will be clarified from detailed analysis of thermo-gravimetric data described below.
  • micrograph (a) the cluster of small -1 ⁇ m particles around a larger one -10 ⁇ m is visible.
  • the effect is due to strong magnetic interactions where the largest particle has a higher magnetic remanence. This will be discussed in detail below.
  • the small particles and a large one are "alloyed" together. This behaviour is similar to mechanical alloying of metal particles where simultaneous plastic deformation and fracture of powder particles coexists.
  • the particle surface evolves. It was found to be irregular, but the whole particle remains spherical. The surface layer seems to be highly disordered with crystal grains below 50 nm and the amount of these particles increases with milling time.
  • thermo-gravimetric analysis (TGA) of AlOOO and VI 000 powders show directly the composition difference between each type of as milled sample.
  • the observed weight decrease for air milled powder in the temperature range of 330-1070 K has a significantly high value of 6.62 wt. %. It was identified that oxygen loss (desorption) is mainly responsible.
  • the final weight decrease in the temperature range of 920-1070 K can be attributed to barium ferrite structural restoration.
  • the number of oxygen molecules 0 2 per one crystallographic Ba-ferrite unit cell (2 x at room temperature can be obtained by calculation from the weight loss and was found to be -1.2.
  • Magnetic hysteresis parameters M s - volume saturation, M r - remanence and H c - coercivity. All parameters measured at room temperature. Maximum magnetic field applied I T. Second letter in sample description: A - annealed in air and V - annealed in vacuum.
  • the hematite ( ⁇ -Fe 2 O 3 ) analytical purity 99.9% powder with particle size distribution into range 20-70 ⁇ m was introduced into the vial with or without dispersing liquid (5 ml) and sealed.
  • the gas atmosphere inside the vial was controlled by a pressure valve. In this way air, argon, and low or high vacuum were used in the preparations.
  • Fig 12 shows the time olut ⁇ on of XRD patterns oi ' milled hematite in el conditions
  • the air was removed and consequently after each vial opening to take samples.
  • the hematite - magnetite transformation was complete
  • the product was found to be pure magnetite with perfect cubic crystallographic structure, described by space group Fd3m.
  • Particle size distribution was decreased from 70-20 ⁇ m for ⁇ -Fe,0 3 to the micron range of 2-0. I ⁇ m for the final product. No other phases or amorphization effects were observed during processing or thereafter. No significant contamination from mill was detected (the mass of the balls remain constant).
  • Some of the typical solvents used were: water, glycol (diethylene) and benzene compounds. The first two have dipolar molecules (polar type solvent) and the last one is a hydrocarbon.
  • Full transformation occurs after - 220 hours and the process is 3 times slower than that for a sample milled directly without oxygen (vacuum or argon). It is noted again that the particle size influences the time required for transformation and the reduction mechanism is of physical rather than chemical origin. The effect of rupture of oxide surface layers under mechanical action may be taken into consideration, as well as surface stress as a driving force for the reduction and removal of oxygen.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Nanotechnology (AREA)
  • Power Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Biomedical Technology (AREA)
  • Health & Medical Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Compounds Of Iron (AREA)
  • Hard Magnetic Materials (AREA)

Abstract

On soumet l'hématite à une transformation totale de phase pour produire de la magnétite, à la température ambiante, par activation magnétomécanique à l'état humide de l'hématite. L'activation mécanique à faible énergie de la surface oxydée est suffisante pour réaliser la transformation. Des liaisons oxygène sur une surface oxydée d'α-Fe2O3 sont apparemment rompues au cours du procédé d'activation mécanique et de l'oxygène est libéré (extrait) dans le liquide polaire de dispersion. La pression de l'oxygène au cours du procédé ainsi que la nature du liquide de dispersion ont une influence critique sur la rapidité et le succès de la transformation de phase. Ainsi, toutes les préparations réalisées en présence d'air, dans des conditions sèches ou avec des hydrocarbures saturés ou non polaires (benzène, anthracène) indiquent que le processus de réduction de l'hématite est inexistant ou très lent. Une pression d'air normale et/ou l'utilisation d'hydrocarbures ont pour effet de supprimer la transformation. Les effets d'un broyage prolongé en présence d'air et sous vide sur la morphologie des particules et la structure cristalline ionique de BaFe12O19 ont été analysés. Des expériences impliquant la diffraction des rayons X, la microscopie électronique à balayage et l'analyse thermique démontrent que, pour les matériaux broyés sous vide, la structure ordonnée se transforme progressivement en une phase nanocristalline désordonnée et stable. Pour des échantillons broyés à l'air, une décomposition chimique a été détectée en plus de la transformation structurale. L'application d'un traitement thermique reconstitue une structure cristalline de ferrite de baryum parfaite, les particules demeurant dans la plage submicronique. Lorsqu'il se produit des variations structurales au cours du recuit, les propriétés magnétiques sont modifiées. On a obtenu des comportements d'hystérésis radicalement différents pour des poudres recuites à 1273 K. La valeur de l'intensité d'aimantation, 4πMs = 335,4 - 347,2 kA/m, est proche de la valeur se rapportant aux poudres de ferrite prébroyées (inférieure de 10 %), mais la valeur de la force coercitive mesurée Hc = 393,9 - 445,6 kA/m, a été améliorée de façon notable par un facteur de 6 en raison de la structure fine des grains cristallins.
EP95933977A 1994-10-04 1995-10-04 Preparation de poudres d'oxyde metallique par broyage a billes active Withdrawn EP0802886A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
AUPM8576/94 1994-10-04
AUPM8577A AUPM857794A0 (en) 1994-10-04 1994-10-04 Method of production magnetite powder from hematite
AUPM8577/94 1994-10-04
AUPM8576A AUPM857694A0 (en) 1994-10-04 1994-10-04 Preparation of hexagonal system ferrite powder with high magnetic coercivity
PCT/AU1995/000653 WO1996010539A1 (fr) 1994-10-04 1995-10-04 Preparation de poudres d'oxyde metallique par broyage a billes active

Publications (1)

Publication Number Publication Date
EP0802886A1 true EP0802886A1 (fr) 1997-10-29

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EP95933977A Withdrawn EP0802886A1 (fr) 1994-10-04 1995-10-04 Preparation de poudres d'oxyde metallique par broyage a billes active

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EP (1) EP0802886A1 (fr)
JP (1) JPH10506365A (fr)
WO (1) WO1996010539A1 (fr)

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Publication number Priority date Publication date Assignee Title
CA2230443C (fr) 1995-08-28 2009-04-07 The University Of Western Australia Procede de production de particules ultrafines
US5958282A (en) * 1997-02-21 1999-09-28 Ferrofluidic Corporation Low cost method for manufacturing ferrofluid
US20040253175A1 (en) * 2002-08-21 2004-12-16 Stiffler Donald R. Electrostatically enhanced tribochemical methods and apparatus
DE102004004122A1 (de) * 2004-01-28 2005-08-18 Studiengesellschaft Kohle Mbh Verfahren zur Phasenumwandlung in molekularen Festkörpern
CN116726951B (zh) * 2023-06-15 2024-06-21 安徽建筑大学 一种改性硫铁尾矿基过硫酸盐催化剂的制备方法和用途

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Publication number Priority date Publication date Assignee Title
GB1050495A (fr) * 1963-11-18
JPS5770205A (en) * 1980-10-20 1982-04-30 Toshiba Corp Method for finely crushing rare earth element-cobalt type permanent magnet alloy
JPS62281308A (ja) * 1986-05-29 1987-12-07 Daido Steel Co Ltd Ｎｄ−Ｆｅ−Ｂ系プラスチツク磁石の製造方法
US4778542A (en) * 1986-07-15 1988-10-18 General Motors Corporation High energy ball milling method for making rare earth-transition metal-boron permanent magnets
SU1611870A1 (ru) * 1988-02-08 1990-12-07 Институт катализа СО АН СССР Способ получени магнетита
JPH03167803A (ja) * 1989-11-28 1991-07-19 Shin Etsu Chem Co Ltd 希土類永久磁石の製造方法

Non-Patent Citations (1)

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Title
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WO1996010539A1 (fr) 1996-04-11
JPH10506365A (ja) 1998-06-23

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