EP0118253B1 - Fine particles of ferromagnetic metal and process for producing the same - Google Patents

Fine particles of ferromagnetic metal and process for producing the same Download PDF

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Publication number
EP0118253B1
EP0118253B1 EP84301141A EP84301141A EP0118253B1 EP 0118253 B1 EP0118253 B1 EP 0118253B1 EP 84301141 A EP84301141 A EP 84301141A EP 84301141 A EP84301141 A EP 84301141A EP 0118253 B1 EP0118253 B1 EP 0118253B1
Authority
EP
European Patent Office
Prior art keywords
metal
oxyhydroxide
iron
added
amount
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.)
Expired
Application number
EP84301141A
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German (de)
English (en)
French (fr)
Other versions
EP0118253A1 (en
Inventor
Masashi Ushiyama
Takayoshi Yoshizaki
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.)
JNC Corp
Original Assignee
Chisso Corp
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 Chisso Corp filed Critical Chisso Corp
Publication of EP0118253A1 publication Critical patent/EP0118253A1/en
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Publication of EP0118253B1 publication Critical patent/EP0118253B1/en
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Classifications

    • 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
    • H01F1/04—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 metals or alloys
    • H01F1/06—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 metals or alloys in the form of particles, e.g. powder
    • H01F1/065—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 metals or alloys in the form of particles, e.g. powder obtained by a reduction
    • 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
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/18—Non-metallic particles coated with metal
    • 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
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B22F9/26—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions using gaseous reductors

Definitions

  • This invention relates to a process for producing fine particles of ferromagnetic metal. More particularly it relates to a process for producing fine particles of ferromagnetic metal obtained by adding a compound such as a salt of a metal which is different from iron and exclusive of alkali metal (which metal will hereinafter be referred to as a « different kind metal») to an aqueous suspension of iron ⁇ -oxyhydroxide, to adhere the different kind metal onto the iron a-oxyhydroxide, followed by reduction, and such a process for producing the fine particles.
  • a compound such as a salt of a metal which is different from iron and exclusive of alkali metal (which metal will hereinafter be referred to as a « different kind metal»)
  • Fine particles of ferromagnetic metal iron having a high coercive force and a high magnetic flux density have recently been noted for elevating the performance of cassette tapes for audio and for developing video tapes for compact VTR (video tape recorders).
  • VTR video tape recorders
  • the coercive force is enhanced, but the dispersibility, weather resistance, orientativity, etc. of magnetic powder become inferior.
  • the starting iron ⁇ -oxyhydroxide is made finer, the resulting particles are liable to collapse at the time of being reduced on heating.
  • a process of adding a different kind metal to iron a-oxyhydroxide has been developed.
  • EP-A-0015485 discloses a process for producing a metal powder suitable for magnetic recording by precipitating and oxidising an aqueous iron-(II) salt solution to produce finely oxidised acicular iron-(II) oxide-hydroxide, stabilising it by treatment with cadmium, lead, calcium, magnesium, zinc, aluminium, chromium, tungsten, a phosphorus oxide and/or a boron oxide, converting it into ferromagnetic iron oxide and reducing it to metallic iron.
  • GB-A-2072639 discloses a process for preparing iron compound particles for use in magnetic recording medium.
  • the resulting iron a-oxyhydroxide has greatly varied particulate forms, depending on the kind, quantity and addition manner of the metal compound added, and all the characteristics of fine particles of metal obtained by heating and reduction are also much different from those in the case where no different kind metal is added. Further, depending on the quantity of the additive, branched particles may be formed or the acicularity of particles of iron a-oxyhydroxide may be lost, although this varies depending on the kind of the compound of the different kind metal added.
  • the dope process is promising as a process for improving the characteristics of the fine particles of metal, but the adhesion process is rather preferable for improving the objective characteristics of the fine particles.
  • the adhesion process includes a process of suspending in water, powder or a wet cake of iron ⁇ -oxyhydroxide and then adding an aqueous solution of a salt or the like of a different kind metal, to effect the adhesion : and a process of adding an acid or an alkali to the above aqueous suspension to once sufficiently disperse the agglomerate of iron a-oxyhydroxide, followed by adding an aqueous solution of a salt or the like of a different kind metal, and adding an alkali or an acid for neutralization to adhere the compound of the different kind metal, and thereafter filtering the resulting material.
  • the coexistent anions can be removed to a certain extent by water-washing after the heat treatment, but several tens % of their amount prior to the water-washing remain in iron a-oxyhydroxide, hence it is impossible to entirely remove the effect of anions.
  • water-washing is carried out without the heat treatment, it is inevitable that a portion of the metal compound to be adhered flows away. Further, according to these processes, only limited metals such as Ni, Co, Ca, Mn, Mg, etc. can be adhered.
  • the present invention provides a process for producing fine particles of ferromagnetic metal comprising :
  • the present invention further provides a process for producing fine particles of ferromagnetic metal comprising :
  • the said aqueous solution of at least one compound is a salt, metal acid salt, or oxide, (including an acidic or alkaline aqueous solution) and after the oxidation reaction the product is subjected to filtration, water-washing, drying prior to the reduction step.
  • the above aqueous suspension of iron a-oxyhydroxide may include a slurry formed by preparation of iron ⁇ -oxyhydroxide, or a suspension obtained by suspending in water, a wet cake or dried powder of iron ⁇ -oxyhydroxide obtained from the above slurry.
  • This aqueous suspension may be acidic, alkaline or neutral.
  • the present invention has a merit that even the slurry formed by preparation or iron a-oxyhydroxide can be used as it is.
  • alkali metals are excluded, because they dissolve in an aqueous solvent in large quantities and hardly deposit on iron ⁇ -oxyhydroxide.
  • the above aqueous solution of a compound such as salt of a different kind metal added may be used in the form of a neutral, acidic or alkaline aqueous solution.
  • a neutral, acidic and alkaline aqueous solutions which is choiced among the neutral, acidic and alkaline aqueous solutions, can be decided taking into account the solubility of the salt or the like of a different kind metal in the aqueous solutions, as well as whether or not a uniform adhesion occurs to a desired extent when the solutions are added to the aqueous suspension of iron a-oxyhydroxide.
  • These regulations of the solutions can be achieved by dissolving an acidic or alkaline substance in the solutions.
  • the atom/molecule ratio i. e. a ratio of the number of atoms to that of molecules ; this applies to the ratio hereinafter mentioned
  • M different kind metal
  • FeOOH iron a-oxyhydroxide
  • the ratio is too large, the resulting iron ⁇ -oxyhydroxide having the metal adhered thereon is liable to agglomerate.
  • the atom/molecule ratio of « Fe(II)/ ⁇ -FeOOH relative to iron ⁇ -oxyhydroxide, based on the amount of the metal adhered is in the range of from 0.0025 to 0.3.
  • the amount ratio of the compound such as salt of the different kind metal and the ferrous salt to be added is preferably 0.5 or higher in terms of the atom ratio of « Fe(II)/different kind metal (M) (i. e. the ratio of the respective numbers of the atoms ; this applies to those hereinafter mentioned), based on the amount of the metals adhered.
  • This ratio is not limited to the above range, but if the ratio is too small, the adhesion strength of the compound of the different kind metal onto iron a-oxyhydroxide is insufficient.
  • the reaction mixture may, if necessary, be adjusted to an appropriate pH, whereby a part or most part of the different kind metal precipitates or gels around iron ⁇ -oxyhydroxide or singly in the form of a compound such as hydroxide, its hydrate, oxide, etc. together with ferrous ions.
  • the precipitate or the like at this stage is not yet adhered onto iron a-oxyhydroxide, or even if adhered, it has a low adhesion strength ; hence the particles are liable to collapse at the time of reduction step.
  • the oxidation process by air or an oxidizing agent is carried out.
  • the precipitated Fe(II) is oxidized through the oxidation reaction and deposited or epitaxialized onto the surface of iron a-oxyhydroxide in the form of iron a-oxyhydroxide, and at that time, involves the different kind metal therein to effect a strong adhesion of the different kind metal onto iron a-oxyhydroxide. And the particles thus obtained hardly collapse at the time of reduction step.
  • Iron a-oxyhydroxide prepared according to conventional processes is observed to contain very fine particles which are much smaller than average size particles and cause degradation of transfer characteristics and extension of Hc (coercive force) distribution i. e. SFD (switching field distribution).
  • very fine particles are combined with larger particles and disappear ; hence particles of iron a-oxyhydroxide having the metal compound adhered thereon after oxidation reaction has a uniform particle size.
  • the thus combined very fine particles do not separate from the larger particles even in the reduction reaction, to give fine particles of metal well retaining the particulate form of iron ⁇ -oxyhydroxide after adhesion.
  • the Ni-adhered iron a-oxyhydroxide (500 g) was reduced by hydrogen at a flow amount of 20 I/min., at a reduction temperature of 500 °C for 5 hours to obtain fine particles of ferromagnetic metal retaining a good particulate form of the Ni-adhered iron a-oxyhydroxide.
  • the magnetic characteristic values of the thus prepared magnetic powder were as follows : Hc : 1,588 Oe * , ⁇ s : 159 emu/g, and ⁇ r/ ⁇ S : 0.53.
  • Hc 1,463 Oe *
  • Br 2,984 gauss **
  • Br/Bm 0.846
  • SFD 0.432
  • Magnetic powder was prepared in the same manner as in Example 1 except that the kind and amount of the salt of the different kind metal added and the atomic ratio of the different kind metal to Fe(II) were varied. As in the case of Example 1, nearly 100 % of the added metal was retained on the iron ⁇ -oxyhydroxide, and anions and Na + were scarcely observed ; thus, fine particles of ferromagnetic metal well retaining the particulate form of the adhered iron a-oxyhydroxide were obtained.
  • Example 1 An aqueous solution of NiS0 4 (0.5 mol/I) (1,290 ml) was added at a flow rate of 20 ml/min. to a reaction slurry of iron a-oxyhydroxide prepared as in Example 1, followed by adding an aqueous solution of FeS0 4 (0.5 mol/l) (1,290 ml) at a flow rate of 20 ml/min., stirring for 30 minutes, and carrying out oxidation reaction for 6 hours, while passing air at a low amount of 0.2 I/min. to obtain a Ni-adhered iron a-oxyhydroxide as in the case of Example 1. Reduction was carried out as in Example 1 to obtain fine particles of ferromagnetic metal well retaining the particulate form of the Ni-adhered iron oxyhydroxide.
  • Example 11 was repeated except that the kind and amount of the salt of the different kind metal and the reduction temperature were varied. Metal-adhered iron a-oxyhydroxides similar to that of Example 11 were formed, and fine particles of ferromagnetic metal well retaining their particulate form.
  • Water (12 I) was added to the same wet cake of iron a-oxyhydroxide (1,250 g ; dry weight 500 g) as in Example 1, followed by stirring for one hour, adding acetic acid so as to give a pH of 3.5, stirring for 30 minutes, adding an aqueous solution of NiS0 4 (0.5 mol/l) (562 ml), stirring for 30 minutes, adding a 28 % aqueous ammonia so as to give a pH of 9.5, stirring for 30 minutes, raising the temperature up to 90°C, aging for one hour, filtering, drying and reducing under the same conditions as in Example 1.
  • the resulting Ni-adhered iron a-oxyhydroxide contained 0.32 % of S0 4 2- , and collapse of particles due to reduction was observed.
  • the characteristic properties of the magnetic powder were as follows : Hc : 1.465 Oe * , ⁇ s : 155 emu/g and ⁇ r/ ⁇ S: 0.51. Further, SFD of the oriented sheet was 0.612, i. e. notably inferior to those of Examples.
  • Ni was adhered as in Comparative example 1, followed by filtering, washing with water (60 I), drying and reducing under the same conditions as in Example 1.
  • Comparative example 1 was repeated except that the added salt of the different kind metal was changed to AI Z (SO 4 ) 3 .

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Hard Magnetic Materials (AREA)
  • Paints Or Removers (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
EP84301141A 1983-02-22 1984-02-22 Fine particles of ferromagnetic metal and process for producing the same Expired EP0118253B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP28149/83 1983-02-22
JP58028149A JPS59153810A (ja) 1983-02-22 1983-02-22 強磁性金属微粒子の製造法

Publications (2)

Publication Number Publication Date
EP0118253A1 EP0118253A1 (en) 1984-09-12
EP0118253B1 true EP0118253B1 (en) 1986-12-30

Family

ID=12240703

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EP84301141A Expired EP0118253B1 (en) 1983-02-22 1984-02-22 Fine particles of ferromagnetic metal and process for producing the same

Country Status (3)

Country Link
EP (1) EP0118253B1 (enrdf_load_stackoverflow)
JP (1) JPS59153810A (enrdf_load_stackoverflow)
DE (1) DE3461871D1 (enrdf_load_stackoverflow)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8601635A (nl) * 1986-06-27 1988-01-18 Vmei Lenin Nis Hittebestendig amorf ferromagnetisch poeder alsmede een werkwijze en inrichting voor de bereiding ervan.
US5965194A (en) * 1992-01-10 1999-10-12 Imation Corp. Magnetic recording media prepared from magnetic particles having an extremely thin, continuous, amorphous, aluminum hydrous oxide coating
CN101088672B (zh) * 2007-07-18 2010-05-12 重庆扬子粉末冶金有限责任公司 铜、锡、锌、铅合金包铁复合粉及其制造方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2909995C2 (de) * 1978-03-16 1984-06-28 Kanto Denka Kogyo Co., Ltd., Tokyo Verfahren zur Herstellung eines Magnetpulvers
DE2909480A1 (de) * 1979-03-10 1980-09-11 Bayer Ag Ferromagnetisches, im wesentlichen aus eisen bestehendes metallpigment und verfahren zu dessen herstellung
US4251592A (en) * 1979-04-03 1981-02-17 Toda Kogyo Corp. Stabilization treatment of acicular ferromagnetic iron or iron-alloy particles against the oxidation thereof
JPS56109827A (en) * 1980-02-05 1981-08-31 Mitsui Toatsu Chem Inc Manufacture of iron compound particle for magnetic recording medium
DE3026696A1 (de) * 1980-07-15 1982-02-18 Basf Ag, 6700 Ludwigshafen Ferromagnetische, im wesentlichen aus eisen bestehende metallteilchen mit einem oberflaechenueberzug, verfahren zu deren herstellung sowie ihre verwendung zur herstellung von magnetischen aufzeichnungstraegern

Also Published As

Publication number Publication date
EP0118253A1 (en) 1984-09-12
JPH0348243B2 (enrdf_load_stackoverflow) 1991-07-23
JPS59153810A (ja) 1984-09-01
DE3461871D1 (en) 1987-02-05

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