JPS5961903A - Manufacture of acicular magnetic metal powder - Google Patents

Abstract

PURPOSE:To obtain acicular magnetic metal powder with high magnetic resistance and large saturated magnetism by a method wherein the surface of acicular iron oxide or hydrated iron oxide powder is coated by organic material film and the film is deoxidized after it is processed by carbonizing treatment. CONSTITUTION:The surface of a acicular particle as original material, for instance, alpha-FeeOOH (alphaFe2O3) or gamma-Fe2O3 is coated uniformly by organic material, for instance, poly-acryl nitryl and oxidized in an oxidizing atmosphere at 200- 400 deg.C. Then the particles are processed by carbonizing treatment at 250-600 deg.C for about 5min in an atmosphere of inert gas or inert gas containing little amount of oxygen so that a carbon film is formed on the surface of the particle by precipitation. Then CO2 is mixed into deoxidizing gas H2 and CO is generated by carbon C and the iron oxide is deoxidizing. CO2 generated by deoxidizing is repeatedly circulated and the reaction is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording nails for high output and high density recording, magnetic H
An example of a magnetic powder suitable for use as a wire material is as follows.

Back technology and its problems As the sandy material used in magnetic recording media for high output and high density recording, materials with a large saturation magnetization O5 and high coercive force are used, but they have been widely used in the past. γ−f”
e 203 , Fe 304 or intermediates thereof,
and ferromagnetic Tlium dioxide (Cr02) has saturation magnetization σ5
is about 70 to 90 emu/g, and the anti-+a force is also 250.
~600Ue is one ship.

In addition, for Co-containing iron oxide powder, CO addition: Possible; adjustment 1
ITJ' can increase the coercive force by
M! However, the saturation magnetization σS is 60~80erom/j
j i\) < y, and in either case, it is sufficient to reduce the value of high-output, high-density recording media by 1↑ (G', l゛, (y).

Therefore, the saturation concentration is large (as a 1% aphrodisiac with high resistance to force, the main components are Fc and Pc, and C”o, or N
Metal magnetic powder containing i has been developed.

Wet reduction methods, dry reduction methods, evaporation methods, etc. are known as methods for obtaining this kind of metal magnetic powder.

In the dry reduction method, acicular magnetic 1A iron hydroxide or ferric hydroxide is added with extra volume such as Co or Ni according to the need for safety, and then reconstituted in a reducing gas to remove the acicular skeleton. It is something to leave behind. In practice, in order to prevent sintering and the like during reduction, the starting material is colored with silicone oil, silane coupling f1, water glass, etc. and then rust-prevented.

However, with these materials, it is difficult to uniformly adhere them to the entire surface of the iron oxide, and the organic components of the adhered materials may be present in the glutinous body, causing the final The disadvantage is that the obtained acicular magnetic fine powder of metal cannot exhibit sufficient magnetic properties.

OBJECTS OF THE INVENTION The present invention provides a method for producing acicular magnetic metal powder based on a dry reduction method in order to improve magnetic properties.

Summary of the Invention The present invention involves forming an organic coating on the surface of sword-shaped iron oxide or hydrated iron oxide powder, carbonizing the coating, and then reducing it to obtain needle-shaped metal magnetic powder.

In the embodiment, in the present invention, an organic substance such as polyacrylonitrile is uniformly adhered to the surface of acicular particles such as α-FeOOH (αFe2O3) or similarly acicular γ-Fe2O3 as a starting material, and then the mixture is heated in an oxidizing atmosphere. 200
oxidized at ~400C, then oxidized at ~250C in an inert gas or an inert gas containing a small amount of oxygen.
Carbonization treatment is carried out by heat treatment at 00C for about 5 minutes to precipitate a carbon film on the surface of the acicular particles. This is then reduced to obtain the desired sword-shaped metal magnetic powder. In this case, when CO2 is mixed into the reducing gas Ih, carbon C on the particle surface generates CO according to the following reaction formula, CO2+C→2CO...(1), which converts iron oxide into 3CO+
Fe2O3-) 2Fe + 3CO2-121 + 11 The reactions of formula (2) and formula (2) can be repeatedly cycled.

Example 1 Acicular r-1 with a long axis of 0.3 to 0.4 μm and an axial ratio of 8 to 1o
``After mixing C203 with a solution of polyacrylonitrile dissolved in the organic solvent methyl ethyl ketone (MEK), MEK is evaporated to form polyacrylonitrile into acicular γ-1!'' uniformly on the surface of C203 particles. Attach it to.

This is then heat treated in the presence of a suitable 02 and then calcined at 300 C or higher in an inert gas (N2). In this way, charcoal,7. Acicular iron oxide particles whose surface is uniformly layered with atoms are placed in a heating furnace in a well loosened state and heated to 300 to 500 ml while flowing CO2 and/or I2 gas.
Reduction is performed at 00 G for a predetermined time to obtain acicular iron particles. When this was taken out into the air, it burned, and in step 5, it was immersed in a methanol solution, and the methanol solution was gradually evaporated to form an oxide film on the surface of this needle-shaped iron rod.

Is the acicular ferromagnetic powder published in this way? When observed with a microscope, the length was 2 to 3 μm, the sword ratio was 7 to 80, and the coercive force 1rc was 12500c, and the magnetization σ5 was 175em.
It was u/g.

As mentioned above, the carbonization treatment is carried out in an inert gas or in a small amount.
It is preferable to carry out heat treatment at 250 ic to 6000 ic or more in an inert gas containing 02
If it is less than 50C, the carbonization process will take too long;
If the temperature exceeds 0C, there is a possibility of sintering between needle-shaped particles.

Effects of the Invention The wire-shaped metal powder obtained by the manufacturing method of the present invention has a high coercive force 1-1c and a large saturation magnetization σ5, which is due to the sintering prevention effect formed on the surface of the metal magnetic powder. Carbon atoms are generated in the film, and this carbon evaporates into carbon monoxide and carbon dioxide, scattering and disappearing, and finally, almost all of this non-magnetic film of carbon remains on the surface of the metal magnetic fine particles. This seems to be due to the fact that it does not work.

Claims (1)

[Claims] Needle-like f) Formation of an organic layer on two sides of acicular iron or hydrated iron chloride powder, and reduction after carbonization of the film ↑ ? A method for producing acicular magnetic metal powder.