Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1991-04-04
1993-02-23
Buffalow, Edith
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
427127, 427216, 427217, B32B 516
Patent
active
051888980
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to ferromagnetic metal particles which are a magnetic powder used for magnetic recording media suitable for high density recording, and the surface layer of which characteristically comprises laminatedly covered films of a ferrite compound having a spinel structure composed of iron and at least one metal selected from cobalt, zinc, manganese, aluminum, chromium, nickel and copper, and a preparation process thereof.
BACKGROUND ART
Customarily, the magnetic powder used for magnetic recording media, represented by audio and video tapes, has been predominantly of .gamma.-iron oxide and of Co-.gamma.-iron oxide.
In recent years, high density magnetic recording media have been desired.
It has been known that ferromagnetic metal particles composed primarily of metallic iron or an alloy thereof obtained by the catalytic reduction of a powder mainly comprising iron oxyhydroxide or iron oxide with a reducing gas possess a high coercive force and high saturation magnetization. Thus, these particles have been investigated as high density magnetic recording media.
High density magnetic recording media for audio and video applications are demanded to produce higher outputs and less noises in broad frequency bands.
Factors demanded for the magnetic particles for this purpose are such that the size of the particles should be more minute, their shape be acicular or prismatic, they be more stable to oxidation, and they should maintain high saturation magnetization after environmental deterioration or corrosion tests.
Several processes have been proposed to date to obtain powdery ferromagnetic metal particles composed of iron or primarily of iron by heating and reducing iron or metallic compounds composed mainly of iron as a starting material in a reducing atmosphere.
(1) For example, Japanese Patent Laid-Open No. 134858/1977 discloses a process for producing ferromagnetic metallic iron comprising doping iron oxyhydroxide or oxide with specific elements to form a starting material, attaching the hydroxide of Si or Al to the starting material and subsequently heating and reducing the resulting material.
(2) Japanese Patent Laid-Open Nos. 122663/1979 and 2664/1979 (GB 2016526) describe processes for producing ferromagnetic metallic iron by heating and reducing iron oxyhydroxide or oxide with or without specific elements doped, which has been attached with the hydroxide of Zn, Cr, Cu, Co, Ni, Mn or Sb.
(3) Japanese Patent Laid-Open No. 173209/1984 teaches a process for producing ferromagnetic metal particles comprising neutralizing aqueous solutions containing a compound of Mg, Ti, Mn, Co, Ni, Cu or Zn and ferrous ions (Fe.sup.2+) individually to form the hydroxides, blowing thereto air to convert them spinel-type compounds, attaching these compounds onto iron oxyhydroxide particles, and reducing the resulting materials.
(4) The iron or a metal mainly comprising iron obtained by heating and reduction tends to be oxidized or burned in the air when left as it is, and hence its magnetic property is degraded time-dependently with the progress of oxidation. Then, Japanese Patent Laid-Open No. 55503/1981 discloses a process for producing metallic magnetic powder excellent in corrosion resistance by further forming oxide films on the surface of the aforesaid metal particles in the atmosphere of low oxygen concentrations.
As described above, the demand for ferromagnetic metal particles as a magnetic powder for high density recording is such that the particles be more minute without impairing high saturation magnetization.
Thus, many further difficulties are left, including imparting the stability to oxidation to the minute particles and controlling the morphology of the minute particles by preventing their sintering.
The following problems are involved in the prior art processes by way of example.
(1) In the process for producing ferromagnetic metal particles by the attachment of the hydroxide of Al or Si to iron oxyhydroxide, etc. followed by reduction, the more minute the particles, the more
REFERENCES:
patent: 4066565 (1978-01-01), Sasazawa et al.
patent: 4296149 (1981-10-01), Rudolf et al.
patent: 4770903 (1988-09-01), Schwab et al.
patent: 4876022 (1989-10-01), Yamazaki et al.
patent: 4911957 (1990-03-01), Oishi et al.
Hayashi Fujio
Kiba Shigeo
Suda Satoru
Tagawa Kimiteru
Takahashi Seiichi
Buffalow Edith
Forman Mark A.
Mitsui Toatsu Chemicals Incorporated
LandOfFree
Ferromagnetic metal particles and preparation process thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ferromagnetic metal particles and preparation process thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ferromagnetic metal particles and preparation process thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2203671