JPS622502A - Manufacture of spinel type ferrite base sintered magnetic material - Google Patents

Abstract

PURPOSE:To produce a magnetic head with easy sintering property, low porosity, high concentration as well as anisotropy, were proof and high mechanical strength by a method wherein a ferrite sintered body is produced using plate- type geothite with specified particle diameter and plate ratio. CONSTITUTION:A plate-type geothite with particle diameter of 0.01-0.5mum preferably 0.04-0.3mum is recommended to be formed into preferably 3-6 each of hexagonal plates or similar shape. Such a plate-type geothite can be produced by means of producing ferric hydroxide with 30-80 times mole of oxyalkyl amine such as ethanol amine added thereto when the ferric hydroxide is produced by making the ferric slat and alkali hydroxide react to each other together with water to water-heat-treat the slurry of produced ferric hydroxide. The general procedures to produce a ferrite base sintered body with spinel type structure using plate-type geothite as a part of initial material are those of material mixing, prebaking, crushing, granulating, forming and sintering operations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a ferrite-based sintered magnetic material having a spinel structure using plate-shaped goethite.

Since the spinel type ferrite sintered body has a high specific resistance, it can be used as a high frequency magnetic material, and since it exhibits anisotropy in its crystal structure, it can be applied to applications such as magnetic heads.

[Conventional technology and problems]

The structure of spinel-type ferrite is cubic and exhibits monoisotropic physical properties.

In recent years, when such ferrite sintered bodies are used in applications such as magnetic heads, they are subject to wear due to magnetic tapes.
Improvements are requested. Furthermore, such ferrite magnetic heads generally have low initial magnetic permeability and low magnetic flux density, and also have low mechanical strength.

In order to improve these points, it is necessary to improve the degree of sintering of ferrite. As a technology to create ferrite sintered bodies with low porosity.

For example, the hot press method is used.

It is an effective method to reduce the porosity and at the same time to produce a sintered body in which specific planes of the microcrystals constituting the sintered body are aligned, to increase wear resistance and mechanical strength.

Such methods are disclosed in, for example, Japanese Unexamined Patent Publication No. 48-46897 and Japanese Unexamined Patent Publication No. 129891-1989.

The starting material is platy (mica-like, scale-like) iron oxide (α
-Fe203) is disclosed to be effective. However, it is still not sufficient in terms of porosity and mechanical strength.

In addition, Hirota et al.
983), Mn-Z with spinel crystal structure
N-ferrite has a large amount of wear on the (1'11) crystal plane, so when a magnetic head is made of a ferrite sintered body, the (111) plane of the microcrystal that makes up the sintered body is attached to the track surface of the magnetic head. It is important to create an anisotropic sintered body that has a small amount of When you create .

<110> is resistant to wear because it is perpendicular to the <11', 1> plane.
It is said that this will improve the abrasion resistance of the magnetic head. In addition, in order to obtain such an anisotropic ferrite sintered body, plate-shaped α-Fe203 and strip-shaped α-Fe
It has been reported that using OOH as a raw material is effective.

However, this plate-like (mica-like) α-Fe203.

Although the plate-like ratio is high, it is difficult to produce fine particles with a large single particle diameter of 0.5 μm or less. Therefore, the filling properties of the particles are low, and it is difficult to increase the density of the obtained sintered body. Also, the strip-shaped α-Fθ001 (ha).

Generally acicular, and when made into strips, the particle length is 1 to 6 μm.
m1 width is 0.2 to 0.5 μm, and in this case too, the bulk density is high and the filling property is poor, resulting in high density.

It is difficult to obtain a sintered body with low porosity. Furthermore, when these raw materials are used, it is difficult to obtain sintered ferrite with high properties unless the temperature is 1300°C or higher.

The present inventors have solved the above-mentioned problems.

An attempt was made to obtain a ferrite for magnetic heads with low wear and high mechanical strength. Namely.

We attempted to obtain a ferrite sintered body with low porosity, high density, and high anisotropy in the crystal planes.

[Failure to solve the problem]

To solve this problem, one particle size is 0.01 to 0.5.
μm, platy goethite with a platy ratio of 1 to 10 (α-Fe20
It has been found that when a ferrite sintered body is obtained using 3), it has easy sinterability, low porosity, high density, and is anisotropic.

This spinel type anisotropic ferrite sintered body becomes a magnetic head with wear resistance and high mechanical strength.

In this invention, the plate-shaped goethite has a particle diameter of 0.01 to
0.5 μm, preferably 0.04-0.3 μml disk ratio 1-10. Preferably, a 3 to 6 hexagonal disc or a shape similar to the hexagonal disc is preferably used.

Such platy goethite is produced by reacting an oxyalkylamine such as ethanolamine with a ferric salt when reacting a ferric salt with an alkali hydroxide in the presence of water to produce ferric hydroxide. It can be produced by adding 30 to 80 times the mole of ferric hydroxide to generate ferric hydroxide, and hydrothermally treating the resulting slurry of ferric hydroxide. Details of the disc-shaped goethite and its manufacturing method are described in, for example, Japanese Patent Application No. 1983-7832. In addition, other raw materials for the starting materials used together with this disc-shaped goethite include:

For example, oxides such as Zn+Ni+Mn, hydroxides, carbonates, nitrates, and organic acid salts are representative.

Other ingredients used with platy goethite.

Specific examples include zinc oxide, zinc hydroxide, and zinc nitrate.

Examples include zinc compounds such as zinc acetate, manganese compounds such as manganese dioxide, manganese carbonate, manganese nitrate, and manganese acetate, and nickel compounds such as nickel oxide, nickel hydroxide, nickel carbonate, nickel nitrate, and nickel acetate.

It is desirable that the particle diameters of the other component raw materials that can become the spinel type ferrite sintered body are as fine as possible.

For example, it is preferable that the particle size is smaller than the particle size of the disc-shaped goethite used. Note that it is desirable to use raw materials for other components insoluble in water and alcohol with a particle size of 0.5 μm or less.

A method for producing a ferritic sintered body having a spinel structure using the plate-like goethite of the present invention as part of the starting raw material generally involves the steps of mixing raw materials, pre-calcining, pulverizing, granulating, molding, and firing. method is adopted. A fully satisfactory product can be obtained by operating each step in a conventional manner. However, it is not necessary to complete all of these steps, and it is possible to partially omit, for example, calcination.

First, raw materials are mixed so that the raw materials have a desired ferrite composition. Mix the crabs to obtain a uniform composition. A wet method using a whole mill, vibration mill, etc. is preferable. Alcohol is the solvent at that time.

Although it is preferable to use water or the like, it is not limited to alcohol and water.

Preliminary firing is performed at a temperature approximately 200 to 600°C lower than the temperature for firing nine pieces. However, when performing a molding operation that imparts anisotropy, the temporary firing operation may not be performed.

For pulverization, it is preferable to employ wet pulverization using a ball mill, vibration mill, or the like. However, the method is not limited to these methods.

Granulation is something that is done to make the molding work easier.
9 Generally, pvA (polyvinyl alcohol) or CM is used to improve the orientation of powder particles and reduce friction with the molding die.
It is preferable to add C (carboxylmethyl cellulose) glycerin, zinc stearate, or the like.

Molding methods include compression molding, extrusion molding, isostatic pressing,
Any molding method such as heat molding may be used.

When molding by applying external vibration without pre-firing,
The degree of alignment of the plate-like goethite 1 or the powder obtained therefrom is higher when it is molded after removing a solvent such as alcohol or water. In general, the mixture is uniformly dispersed in sufficient alcohol or water, placed in a mold, and the water, alcohol, etc. are squeezed out by adding water in an axial manner, and a molded article is produced. The higher the pressure at this time, the better, but 1 usually 200 to 2
oooKg/- degree is used.

Firing is heating the ferrite molded body to complete the formation of ferrite, and determines the required dimensions, mechanical strength, and electromagnetic properties.

A suitable firing temperature is 1100 to 1500°C.

The longer the firing time, the better; however, if it is too long, it is not economical, so generally about 1 to 50 hours is preferred.

Furthermore, if ferrite is produced by sintering such a molded body using a conventional method, an anisotropic ferrite-based sintered body in which the <N1> plane of the ferrite is aligned in a direction almost perpendicular to the 0 plane in the molded body is produced. A magnetic material is obtained. When sintering this compact, a hot press firing method in which a uniaxial pressing force is applied from the outside is employed, resulting in a denser sintered compact with fewer pores and a higher density.

〔Example〕

Example 1 A solution of ferric chloride (FeCl2 H6H20) 500 S' dissolved in 10 tons of distilled water and maintained at 28°C was mixed with sodium hydroxide 7507 and monoethanolamine S
Z (45 times the mole relative to ferric chloride) was dissolved in distilled water 201, and added dropwise to the solution kept at 20°C.
While maintaining the temperature at °C, the mixture was sufficiently stirred and reacted to obtain a ferric hydroxide slurry.

After this slurry was aged at 30°C for about 20 hours, the supernatant liquid was removed, and the pH of the slurry was adjusted to 11 by washing with an aqueous solution of sodium hydroxide with a concentration of 10%. The mixture was placed in an autoclave and subjected to hydrothermal treatment at +ao'C for 1 hour to obtain a plate-shaped goethite slurry.

The plate-shaped goethite slurry is washed with water and filtered.

After drying, a powdery plate-like goethite was obtained.

A transmission electron micrograph (magnified 50,000 times) of the obtained platy goethite powder is shown in FIG. Moreover, analysis by X-ray diffraction confirmed that this disc-shaped goethite had an α-Fe00H structure.

The platy goethite was observed using a transmission electron microscope (Tgn), and the particle diameter (disc diameter), disc ratio (particle diameter/thickness), etc. were measured. (Average of 30 grains) The results.

The particle size was 0.21 μm, and the platelet ratio was 6.5.

The plate-shaped goethite obtained by the above procedure (particle size 0.21
μm, disc ratio 3.5) i 37.4 r, Manga carbonate (Mnc03) 49.8? , and zinc hydroxide (Zn(OH)2) 32..27 with ethyl 7 A/
Co-/L/3001 was added and mixed in a ball mill for 10 hours.

This mixture was filled into a mold and 7 ethyl alcohol was removed. Thereafter, it was heat-formed under a uniaxial pressing force of 500 mm/shoulder and at a temperature of 800'C to produce a cylindrical molded body with a diameter of 20 mm and a height of 1011111 mm.

Next, this molded body is passed through a gas containing 2% oxygen,
It was baked at 1250°C for 15 hours.

The porosity of the obtained Mn-Zn ferrite sintered body was 2%.
(theoretical density 98%), and the average grain size is 55/j
It was about m. Further, when the degree of orientation was examined using X-rays, it was found that the <111> planes of the ferrite were approximately 55% aligned perpendicularly to the pressing direction during molding.

Example 2 A plate-shaped goethite was obtained in the same manner as in Example 1.

This disc-shaped goethite (particle size 0.21 μm, disc-shaped goethite,
5) 148r and nickel hydroxide [: Ni(OH)2]
2 B, 59, zinc hydroxide (Zn(OH)2) 5
Ethyl alcohol 3002 was added to L39 and mixed in a ball mill for 10 hours.

After removing the ethyl alcohol from this mixture.

Fill it into a mold for 500 Ky/cr? A cylindrical molded body was made using a uniaxial pressurizing horn of 800°C.

Next, this molded body was heated at 1250° in a gas containing 2% oxygen.
It was fired at C for 15 hours.

The porosity of the obtained Ni-Zn ferrite sintered body was 3% (
The theoretical density was 97 cm), and the average crystal grain size was about 32 μm.

In addition, when examining the degree of orientation with X-rays, it was found that <11
1> planes were arranged perpendicularly to the pressing direction during molding by about 55 inches.

Comparative example 1 α-Fe203 (particle size 10 μm, plate ratio 10) 13
39, nickel oxide (N10 particle size 0.5 μm).

Ethyl alcohol 30% to zinc oxide (particle size 0.6μm)
02 was added and mixed in a ball mill for 16 hours.

After removing the ethyl alcohol from this mixture.

The mixture was filled into a mold and molded at 800°C using a 5ooKp/- negative axis pressure/heating device to obtain a cylindrical molded body with a diameter of 201 o++ and a height of 10 m1.

Next, this molded body was heated to 1250"C in an oxygen-containing gas.
, baked for 15 hours.

The porosity of the obtained Ni-Zn ferrite sintered body was 7 inches (
The theoretical density is 96 cm), and the average grain size is .

It was about 22 μm. Further, when the degree of orientation was examined using X-rays, it was found that approximately 56% of the ferrite <111> planes were aligned perpendicularly to the pressing direction during molding.

〔Effect of the invention〕

According to the present invention, a ferrite-based sintered magnetic material with low porosity, high density, and high anisotropy can be obtained.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph that is converted into a drawing showing the particle morphology (magnification: 500 times) of the platy goethite used in Example 1.

Claims (2)

[Claims] (1) A method for producing a ferrite-based sintered magnetic material having a spinel-type structure, which is characterized by using plate-shaped goethite as part of the starting material. (2) A patent claim in which the disc-shaped goethite has a hexagonal disc shape or a shape similar to it, a particle diameter (disc diameter) of 0.01 to 0.5 μm, and a disc ratio (particle diameter/thickness) of 1 to 10. A method for producing a ferrite-based sintered magnetic material having a spinel structure according to item 1.