JP2002087820A - Deformed magnetic fine particle and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide deformed magnetic fine particles which are produced as starting particles from composite fine particles formed by bonding >=2 different kinds of particles. SOLUTION: The composite fine particles composed of a prismatic hematite particles and a plurality of planar goethite particles which are hetero-bonded to the prismatic hematite particles, are used as starting particles. The planar goethite particles radially grow in a C crystalline axis direction of the planar goethite particle in a radial form in mutually opposite directions with C crystalline axis of the prismatic hematite particles as a symmetry axis center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to bonded composite fine particles in which prismatic hematite particles are located at the center and a plurality of plate-like goethite particles grown radially around the center are hetero-joined. When observed from the C-axis direction of the columnar hematite particles, the composite fine particles having a star shape or the spindle-shaped hematite particles are located at the center, and one or more plate-like goethite particles grown around the periphery are hetero-joined. Magnetic fine particles using the bonded composite fine particles as starting particles and a method for producing the same.

[0002]

2. Description of the Related Art Conventional fine particles having a size of less than μm have a crystal habit peculiar to a substance, and therefore generally have a relatively simple and simple particle form. For example, it is known that hematite particles take a cubic or plate-like form, goethite particles take a needle-like or plate-like form, and magnetite particles take a cubic form. In addition, recent studies have also reported monodisperse hematite particles of the ellipsoid and peanut types (Materia, Vol. 35,
No. 9, 1996).

[0003]

However, all of these particles have a simple particle morphology and an irregular bonding morphology, but, on the contrary, have a complicated regular particle morphology. Are not reported. For this reason, the industrial applications of these particles are limited, and they cannot be used as fine component parts necessary for the development of micromachines and nanomachines in recent years, and new functions and physical properties cannot be expected. The situation.

The present invention has been proposed in view of such a conventional situation, and has been proposed in which two or more heterogeneous particles are bonded to each other. It is an object of the present invention to provide deformed magnetic fine particles having new functions and physical properties, and having a complicated and regular form, and a simple production method thereof.

[0005]

The modified magnetic fine particles of the present invention are, as starting particles, composite fine particles composed of prismatic hematite particles and a plurality of plate-like goethite particles hetero-joined to the prismatic hematite particles. The plate-like goethite particles are grown in the direction of the C-axis crystal axis of the plate-like goethite particles radially in opposite directions to each other with the C-axis crystal axis of the prismatic hematite particles as the center of symmetry. It is characterized by being.

Since the deformed magnetic fine particles according to the present invention as described above have a complicated form and a regular bonding form, they have new functions and physical properties based on the shape.

[0007] Further, the deformed magnetic fine particles of the present invention are composed of composite fine particles comprising spindle-shaped hematite particles and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles. Wherein the plate-like goethite particles are bonded to a crystal plane parallel to the C-crystal axis of the spindle-shaped hematite particles and grown in the C-crystal axis direction of the plate-like goethite particles. .

[0008] Since the deformed magnetic fine particles according to the present invention as described above have a complicated form and a regular joining form, they have new functionality and physical properties based on the shape.

Further, the method for producing irregular magnetic fine particles of the present invention comprises a prismatic hematite particle and a plurality of plate-like goethite particles hetero-joined to the prism-like hematite particle. The composite fine particles that are grown in the C-axis crystal axis direction of the plate-like goethite particles radially in opposite directions to each other with the C-axis crystal axis of the prismatic hematite particles as the center of symmetry as the starting particles, The composite fine particles are heated at 400 ° C. to 60 ° C. in air or inert gas.
After dehydration by heating at 0 ° C, 320 ° C to 42 ° C in a reducing gas.
It is characterized in that Fe ₃ O ₄ magnetic fine particles are reduced at 0 ° C.

[0010] In the above-described method for producing irregular magnetic fine particles according to the present invention, irregular magnetic fine particles having a complicated form and a regular bonding form can be obtained by a simple method. It will have new functionality and physical properties based on a simple shape.

Further, the method for producing irregular magnetic fine particles of the present invention comprises the step of forming spindle-shaped hematite particles and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles. The particles are bonded to a crystal plane parallel to the C crystal axis of the spindle-shaped hematite particles, and the composite fine particles, which are grown in the C crystal axis direction of the plate-like goethite particles, are used as starting particles, and the composite fine particles are After dehydration by heating at 400 ° C. to 600 ° C. in air or an inert gas, it is reduced at 320 ° C. to 420 ° C. in a reducing gas to form a Fe ₃ O ₄ crystal structure.

In the method for producing irregular magnetic fine particles according to the present invention as described above, irregular magnetic fine particles having a complicated form and a regular bonding form can be obtained by a simple method. It will have new functionality and physical properties based on a simple shape.

[0013]

Embodiments of the present invention will be described below. <First Embodiment> The deformed magnetic fine particles according to the present embodiment are composed of prismatic hematite particles and a plurality of plate-like goethite particles hetero-joined to the prismatic hematite particles. The starting particles are composite fine particles in which the particles grow radially in opposite directions to each other with the C-axis crystal axis of the prismatic hematite particles as the center of symmetry and in the C-axis crystal axis direction of the plate-like goethite particles. It is.

The crystal structure of the deformed magnetic fine particles is Fe ₃
O ₄ or γ-Fe ₂ O ₃ . Further, the surface of the deformed magnetic fine particles may be coated with a Co compound such as crystalline or amorphous Co hydroxide or Co ferrite.

According to the deformed magnetic fine particles obtained by using the composite fine particles in which the prismatic hematite particles and the plurality of plate-like goethite particles according to the present embodiment are hetero-joined as a starting material, complicated morphology and regularity are obtained. Composite fine particles can be obtained. Specifically, for example, when viewed from the C-axis crystal axis direction of the hematite particles, the particles exhibit a complex star-shaped morphology and a regular structure, so that a possibility of exhibiting new functionality and physical properties can be expected.

A method for producing such composite fine particles as a starting material for the deformed magnetic fine particles according to the present invention will be described.

First, a suspension containing a gel-like amorphous substance of at least one of ferric hydroxide and FeOOH containing a small amount of water therein is prepared, and a phosphate ion is contained in the suspension. By adding and ripening an alkaline phosphate solution having the above, composite fine particles composed of prismatic hematite particles and plate-like goethite particles as described above are obtained. These ferric hydroxides or FeOOH are:
It is produced by mixing a ferric salt solution and a strong alkaline solution.

The ferric iron used here includes, for example, ferric chloride, ferric sulfate and ferric nitrate. These ferric salts are dissolved in a solvent such as water and used for the reaction as a ferric salt solution.

The strong alkali mixed with the ferric salt is not particularly limited. For example, a strong alkali such as sodium hydroxide, potassium hydroxide or lithium hydroxide is dissolved in a solvent such as water. Used.

The phosphate added to the above-mentioned suspension and used as a phosphate ion source is not particularly limited.
For example, an alkali phosphate such as sodium phosphate, potassium phosphate, ammonium phosphate, sodium hydrogen phosphate or potassium hydrogen phosphate is dissolved in a solvent such as water before use.

Here, the concentration of the ferric salt in the suspension is 0.1.
It is desirable to prepare it in the range of 010 mol / l or more and 0.100 mol / l or less. The alkali phosphate solution added to the suspension has a molar ratio of phosphate ions to ferric ions of 0.010 or more,
It is desirable to prepare and add the alkali phosphate solution so as to be in a range of 0.020 or less.

By aging the suspension prepared as described above, composite fine particles in which the prismatic hematite particles and the plurality of plate-like goethite particles are hetero-joined as described above are obtained. At this time, the pH of the suspension is
It is desirable to keep the range of 10.5 or more and 12.5 or less. Further, it is desirable that the aging temperature is kept in a range from normal temperature to 55 ° C. However, room temperature refers to room temperature in a normal laboratory or the like.

As described above, by adding phosphate ions to the suspension obtained from the ferric chloride salt and the strong alkaline solution, the prismatic hematite particles and the plurality of plate-like goethite particles are hetero-joined. Composite fine particles having complex morphology and regularity, which are composite fine particles, can be easily obtained by a simple production method.

The order of mixing the ferric salt solution, the strong alkali solution and the alkali phosphate solution is not limited to the above example, and may be any method. That is, the ferric salt solution may be dropped into the strong alkaline solution and mixed, or vice versa.

In the above-described example, the composite fine particles are formed by using Fe. However, it is also possible to form the composite fine particles containing a metal other than Fe, for example, Co or Ni.

Using the composite fine particles obtained as described above as starting particles, modified magnetic fine particles according to the present embodiment are manufactured.

First, the obtained composite fine particles are heated and dehydrated at 400 ° C. to 600 ° C. in air or an inert gas. Thereafter, the composite fine particles are cooled to 320 ° C. to 420 ° C. in a reducing gas.
° C, the crystal structure of the composite fine particles becomes Fe
_By changing to ₃ O ₄ , the deformed magnetic fine particles according to the present invention are produced.

Furthermore, the above-mentioned irregular magnetic fine particles having a crystal structure of Fe ₃ O ₄ are treated at 200 ° C. to 4 ° C. in air or an oxidizing gas.
By oxidizing at 00 ° C., the crystal structure becomes γ-Fe ₂ O ₃
The above-mentioned modified magnetic fine particles can be obtained.

Furthermore, after dispersing the Fe ₃ O ₄ deformed magnetic fine particles or the γ-Fe ₂ O ₃ deformed magnetic fine particles in an alkali solution, the Co ²⁺ ion or Co ²⁺ ion and Fe ³⁺ ion are dispersed in the alkali solution. Solution and add the above alkaline solution to 5
By heating at 0 ° C to 100 ° C, the above Fe ₃ O ₄
Deformed magnetic fine particles in which the surface of the deformed magnetic fine particles or γ-Fe ₂ O ₃ deformed magnetic fine particles are coated with a Co compound can also be obtained.

According to the deformed magnetic fine particles obtained by starting from the composite fine particles obtained by heterojunction of the prismatic hematite particles and the plurality of plate-like goethite particles according to the present embodiment obtained as described above, Thus, composite fine particles having a complicated form and regularity can be obtained. Specifically, for example, when viewed from the C-axis crystal axis direction of the hematite particles, it shows a complex shape having a star shape and a structure having regularity.
The possibility of developing new functionality and physical properties can be expected.

In the above-described example, the deformed magnetic fine particles are formed by using Fe. However, metals other than Fe, for example, C
It is also possible to form irregularly shaped magnetic fine particles containing o or Ni.

<Second Embodiment> The deformed magnetic fine particles according to the present embodiment are composed of spindle-shaped hematite particles and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles. The composite fine particles formed by the plate-like goethite particles being bonded to the crystal plane parallel to the C-axis crystal axis of the spindle-shaped hematite particles and growing in the C-axis crystal axis direction of the plate-like goethite particles are the starting particles. It is.

The crystal structure of the irregular magnetic fine particles is Fe ₃
O ₄ or γ-Fe ₂ O ₃ . Further, the surface of the deformed magnetic fine particles may be coated with a Co compound such as crystalline or amorphous Co hydroxide or Co ferrite.

According to the modified magnetic fine particles obtained by using the composite fine particles in which the spindle-shaped hematite particles and the plurality of plate-like goethite particles according to the embodiment are hetero-joined as starting materials, they have a complicated form and regularity. Composite fine particles can be obtained. Specifically, for example, plate-like goethite particles,
It combines with the crystal plane parallel to the C crystal axis of the spindle-shaped hematite particles, and shows a complex morphology and regular structure grown in the C crystal axis direction of the plate-like goethite particles. Is expected to be expressed.

A method for producing such composite fine particles as starting materials for the deformed magnetic fine particles according to the present invention will be described.

First, a suspension containing a gel-like amorphous substance of at least one of ferric hydroxide and FeOOH containing a small amount of water therein is prepared, and phosphate ions are contained in the suspension. By adding and ripening an alkali phosphate solution having the above, composite fine particles composed of spindle-shaped hematite particles and plate-like goethite particles as described above are obtained. These ferric hydroxides or FeOOH are:
It is produced by mixing a ferric salt solution and a strong alkaline solution.

As the ferric used in the present invention, for example, ferric chloride, ferric sulfate or ferric nitrate is exemplified. These ferric salts are dissolved in a solvent such as water and used for the reaction as a ferric salt solution.

The strong alkali mixed with the ferric salt is not particularly limited. For example, a strong alkali such as sodium hydroxide, potassium hydroxide or lithium hydroxide is dissolved in a solvent such as water. Used.

The phosphate added to the above suspension and used as a phosphate ion source is not particularly limited.
For example, an alkali phosphate such as sodium phosphate, potassium phosphate, ammonium phosphate, sodium hydrogen phosphate or potassium hydrogen phosphate is dissolved in a solvent such as water before use.

Here, the concentration of the ferric salt in the suspension is 0.1.
It is desirable to prepare it in the range of 010 mol / l or more and 0.100 mol / l or less. The alkali phosphate solution added to the suspension has a molar ratio of phosphate ions to ferric ions of 0.010 or more,
It is desirable to prepare and add the alkali phosphate solution so as to be in a range of 0.020 or less.

By aging the suspension prepared as described above, the spindle-shaped hematite particles as described above and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles are combined. Are obtained. At this time, the pH of the suspension was 10.0 or more,
It is desirable to keep it in the range of 12.0 or less. Also,
The aging temperature is desirably maintained in the range of 75 ° C. or higher and the boiling point of the suspension at atmospheric pressure or lower.

As described above, by adding phosphate ions to the suspension obtained from the ferric chloride salt and the strong alkaline solution, one or more of the spindle-shaped hematite particles and one or more heterojunctions hetero-joined to the spindle-shaped hematite particles can be obtained. And composite fine particles having a complex morphology and regularity can be easily obtained by a simple production method.

The order of mixing the ferric salt solution, the strong alkali solution and the alkali phosphate solution is not limited to the above-mentioned example, but may be any method. That is, the ferric salt solution may be dropped into the strong alkaline solution and mixed, or vice versa.

In the above-described example, the composite fine particles are formed using Fe. However, it is also possible to form the composite fine particles containing a metal other than Fe, for example, Co or Ni.

Then, using the composite fine particles obtained as described above as starting particles, modified magnetic fine particles according to the present embodiment are manufactured.

First, the obtained composite fine particles are dehydrated by heating at 400 ° C. to 600 ° C. in air or an inert gas. Thereafter, the composite fine particles are cooled to 320 ° C. to 420 ° C. in a reducing gas.
° C, the crystal structure of the composite fine particles becomes Fe
_By changing to ₃ O ₄ , the deformed magnetic fine particles according to the present invention are produced.

Further, the above-mentioned irregular magnetic fine particles having a crystal structure of Fe ₃ O ₄ are treated in air or an oxidizing gas at 200 ° C. to 4 ° C.
By oxidizing at 00 ° C., the crystal structure becomes γ-Fe ₂ O ₃
The above-mentioned modified magnetic fine particles can be obtained.

Further, after dispersing the Fe ₃ O ₄ deformed magnetic fine particles or the γ-Fe ₂ O ₃ deformed magnetic fine particles in an alkaline solution, Co ²⁺ ions or Co ²⁺ ions and Fe ³⁺ ions are dispersed in the alkali solution. Solution and add the above alkaline solution to 5
By heating at 0 ° C to 100 ° C, the above Fe ₃ O ₄
Deformed magnetic fine particles in which the surface of the deformed magnetic fine particles or γ-Fe ₂ O ₃ deformed magnetic fine particles are coated with a Co compound can also be obtained.

The composite fine particles comprising the spindle-shaped hematite particles according to the present embodiment and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles obtained as described above are used as starting materials. According to the obtained modified magnetic fine particles, composite fine particles having a complicated form and regularity can be obtained. Specifically, for example, the plate-like goethite particles are bonded to the crystal plane parallel to the C-crystal axis of the spindle-shaped hematite particles, and the complex morphology and regularity grown in the C-crystal axis direction of the plate-like goethite particles are increased. Since it has a structure having, the possibility of expressing new functionality and physical properties can be expected.

In the above-described example, the deformed magnetic fine particles are formed using Fe. However, metals other than Fe, for example, C
It is also possible to form irregularly shaped magnetic fine particles containing o or Ni.

[0051]

EXAMPLES Next, examples performed to confirm the effects of the present invention will be described. In the following description, specific numerical values and the like are given, but the present invention is not limited to these examples.

First, in Examples 1 to 3, trisodium phosphate was added to a suspension containing a gel amorphous substance of at least one of ferric hydroxide and FeOOH containing a trace amount of water. The solution was added to prepare composite fine particles in which prismatic hematite particles and a plurality of plate-like goethite particles were hetero-joined, and deformed magnetic fine particles were prepared using the composite fine particles as starting particles.

Example 1 Ferric chloride hexahydrate (FeC
l ₃ · 6H the ₂ O) was dissolved in distilled water, 0.075 mol /
One liter of a 500 ml ferric chloride solution was prepared.

While stirring this ferric chloride solution, 0.46 sodium hydroxide (NaOH) was dissolved in distilled water.
250 ml of a 9 mol / l sodium hydroxide solution is dropped and mixed, and ferric hydroxide or Fe containing a small amount of water therein is added.
A suspension containing a gel-like amorphous material of at least one of OOH was prepared.

Subsequently, trisodium phosphate (N
a ₃ PO ₄ ) was dissolved in distilled water, 18.8 ml of a 0.02 mol / l trisodium phosphate solution was added, and 190 ml of distilled water was further added to adjust the ferric salt concentration, followed by stirring and mixing. did.

The concentration of the ferric salt in this suspension was 0.039.
mol / l, and the pH was 12.0. The molar ratio of phosphate ion / ferric ion was 0.01.

Thereafter, the suspension was transferred to an aging incubator and aged at an aging temperature of 55 ° C. for 168 hours to obtain heterozygous composite fine particles.

The composite fine particles were used as starting particles, and after being heated and dehydrated at 450 ° C. in the air, 50 mol% H ₂ -50
reduced at 380 ° C. in a mol% Ar mixed gas to obtain Fe ₃ O ₄
Irregular magnetic fine particles were obtained.

When the magnetic properties of the Fe ₃ O ₄ irregular magnetic fine particles were measured by a vibrating sample magnetometer, the saturation magnetization (σs) was obtained.
Is 70.9 emu / g, coercive force (Hc) is 260 Oe,
The squareness ratio (σr / σs) was 0.393. The sample was in a powder state and the external magnetic field was 5 kOe.

FIGS. 1 and 2 show a TEM photograph and an electron diffraction image of the composite fine particles obtained in this example as described above. FIGS. 3 and 4 show a TEM photograph and an electron beam diffraction image of the composite fine particles after the heat dehydration. FIGS. 5 and 6 show a TEM photograph and an electron diffraction image of the obtained Fe ₃ O ₄ deformed magnetic fine particles, respectively.

Example 2 Fe ₃ O ₄ obtained in Example 1
The deformed magnetic fine particles were oxidized in a 1 mol% O ₂ -99 mol% N ₂ mixed gas at 300 ° C. to obtain γ-Fe ₂ O ₃ deformed magnetic fine particles.

When the magnetic characteristics of the γ-Fe ₂ O ₃ irregular magnetic particles were measured with a vibrating sample magnetometer, the saturation magnetization (σ
s) is 65.5 emu / g and the coercive force (Hc) is 235O
e, the squareness ratio (σr / σs) was 0.390. The sample was in a powder state and the external magnetic field was 5 kOe.

Example 3 Fe ₃ O ₄ obtained in Example 1
After stirring and dispersing the magnetic fine particles in a 1N NaOH solution,
CoCl ₂ solution was added and the entrainment was continued. A CoCl ₂ solution was added so that the Co ratio to Fe in the Fe ₃ O ₄ magnetic fine particles was 5 atomic%. This alkaline suspension is mixed with 90
After heating at ° C. and holding for a predetermined time, it was washed with high-purity ion-exchanged water to lower the pH to a neutral region. Thereafter, the cake obtained by filtering this suspension was dried at 80 ° C. and pulverized to obtain deformed Fe ₃ O ₄ magnetic fine particles coated with a Co compound.

When the magnetic characteristics of the Co—Fe ₃ O ₄ irregular magnetic fine particles were measured by a vibrating sample magnetometer, the saturation magnetization (σs) was 66.0 emu / g and the coercive force (Hc) was 58.
0 Oe and the squareness ratio (σr / σs) were 0.450. The sample was in a powder state and the external magnetic field was 5 kOe.

Next, in Examples 4 to 6, in the suspension containing at least one of gelled amorphous material of ferric hydroxide and FeOOH containing a trace amount of water, the phosphoric acid was added to the suspension. A sodium solution is added to produce composite fine particles composed of spindle-shaped hematite particles and one or more plate-like goethite particles hetero-joined to the spindle-shaped hematite particles, and the composite particles are used as starting particles to form irregular particles. Magnetic fine particles were produced.

Example 4 Ferric chloride hexahydrate (FeC
l ₃ · 6H the ₂ O) was dissolved in distilled water, 0.075 mol /
One liter of a 500 ml ferric chloride solution was prepared.

While stirring the ferric chloride solution wave, 0.46% sodium hydroxide (NaOH) was dissolved in distilled water.
220 mol of 9 mol / l sodium hydroxide solution is dropped and mixed, and ferric hydroxide or Fe containing a small amount of water therein is added.
A suspension containing a gel-like amorphous material of at least one of OOH was prepared.

Subsequently, the suspension was added to trisodium phosphate (N
a ₃ PO ₄ ) was dissolved in distilled water, and 18.8 ml of a 0.02 mol / l trisodium phosphate solution was added. To adjust the ferric salt concentration, 230 ml of distilled water was added, followed by stirring and mixing. did.

The concentration of ferric salt in this suspension was 0.039
mol and the pH was 11.0. The molar ratio of phosphate ion / ferric ion was 0.01.

Thereafter, the suspension was transferred to an aging incubator and aged at an aging temperature of 80 ° C. for 140 hours to obtain heterozygous composite fine particles.

Using these composite fine particles as starting particles, after dehydration by heating at 450 ° C. in the air, 50 mol% H ₂ -50
reduced at 380 ° C. in a mol% Ar mixed gas to obtain Fe ₃ O ₄
Irregular magnetic fine particles were obtained.

When the magnetic properties of the Fe ₃ O ₄ irregular magnetic fine particles were measured by a vibrating sample magnetometer, the saturation magnetization (σs) was obtained.
Is 75.7 emu / g, coercive force (Hc) is 268 Oe,
The squareness ratio (σr / σs) was 0.395. The sample was in a powder state and the external magnetic field was 5 kOe.

FIGS. 7 and 8 show a TEM photograph and an electron diffraction image of the composite fine particles obtained in this example as described above. 9 and 10 show a TEM photograph and an electron diffraction image of the composite fine particles after the dehydration by heating. FIG. 1 shows a TEM photograph and an electron diffraction image of the obtained Fe ₃ O ₄ deformed magnetic fine particles.
1 and FIG.

Example 5 Fe ₃ O ₄ obtained in Example ₄
The deformed magnetic fine particles were oxidized at 300 ° C. in a 1 mol% O ₂ -99 mol% N ₂ mixed gas to obtain γ-Fe ₂ O ₃ deformed magnetic fine particles.

When the magnetic characteristics of the γ-Fe ₂ O ₃ irregular magnetic fine particles were measured by a vibrating sample magnetometer, the saturation magnetization (σ
s) is 70.5 emu / g and coercive force (Hc) is 255O
e, the squareness ratio (σr / σs) was 0.398. The sample was in a powder state and the external magnetic field was 5 kOe.

Example 6 Fe ₃ O ₄ obtained in Example ₄
After dispersing the deformed magnetic fine particles in a 1N NaOH solution with stirring, a CoCl ₂ solution was added, and the dispersion with the mixture was continued. Fe ₃ O
_{4 A} CoCl ₂ solution was added so that the Co ratio to Fe in the magnetic fine particles was 5 atomic%. This alkali suspension was heated at 90 ° C. and maintained for a predetermined time, and then washed with high-purity ion-exchanged water to lower the pH to a neutral region. Thereafter, the cake obtained by filtering this suspension was dried at 80 ° C. and pulverized to obtain Fe ₃ O ₄ irregular magnetic fine particles coated with a Co compound.

When the magnetic properties of the deformed Co—Fe ₃ O ₄ particles were measured by a vibrating sample magnetometer, the saturation magnetization (σs) was obtained.
Is 74.5 emu / g, coercive force (Hc) is 650 Oe,
The squareness ratio (σr / σs) was 0.455. The sample was in a powder state and the external magnetic field was 5 kOe.

Comparative Example 1 Ferric chloride hexahydrate (FeC
l ₃ · 6H the ₂ O) was dissolved in distilled water, 0.075 mol /
One liter of a 500 ml ferric chloride solution was prepared.

While the ferric chloride solution was used as a binder, 0.46 g of sodium hydroxide (NaOH) was dissolved in distilled water.
250 ml of a 9 mol / l sodium hydroxide solution is dropped and mixed, and ferric hydroxide or Fe containing a small amount of water therein is added.
A suspension containing a gel-like amorphous material of at least one of OOH was prepared.

Subsequently, trisodium phosphate (N
a ₃ PO ₄₎ was added trisodium phosphate solution 28.1ml which was dissolved in distilled water and 0.008 mol / l and was further added distilled water 180ml to prepare the ferric salt concentration攬絆Mixed.

The ferric salt concentration in this suspension was 0.039
mol / l, and the pH was 12.0. The molar ratio of phosphate ion / ferric ion was 0.006.

Thereafter, the suspension was transferred to an aging incubator and aged at an aging temperature of 55 ° C. for 183 hours to obtain product particles. The generated particles were almost plate-like goethite, and the generation of heterojunction composite fine particles was extremely small.

Using the formed particles as starting particles, the particles were heated and dehydrated at 450 ° C. in the air, and then 50 mol% H ₂ -50 m
The resultant mixture was reduced at 380 ° C. in an ol% Ar mixed gas to obtain Fe ₃ O ₄ tabular magnetic fine particles.

When the magnetic characteristics of the Fe ₃ O ₄ plate-like magnetic fine particles were measured with a vibrating sample magnetometer, the saturation magnetization (σs) was obtained.
Is 68.9 emu / g, coercive force (Hc) is 270 Oe,
The squareness ratio (σr / σs) was 0.395. The sample was in a powder state and the external magnetic field was 5 kOe.

Comparative Example 2 Ferric chloride hexahydrate (FeC
l ₃ · 6H the ₂ O) was dissolved in distilled water, 0.075 mol /
One liter of a 500 ml ferric chloride solution was prepared.

While stirring the ferric chloride solution, 0.46 sodium hydroxide (NaOH) was dissolved in distilled water.
290 ml of a 9 mol / l sodium hydroxide solution is dropped and mixed, and ferric hydroxide or Fe containing a small amount of water therein is added.
A suspension containing a gel-like amorphous material of at least one of OOH was prepared.

Subsequently, trisodium phosphate (N
a ₃ PO ₄₎ was added trisodium phosphate solution 18.8ml which was dissolved in distilled water and 0.02 mol / l and was further added distilled water 160ml to prepare the ferric salt concentration攬伴Mixed.

The concentration of ferric salt in this suspension was 0.039
mol / l and the pH was 12.5. The molar ratio of phosphate ion / ferric ion was 0.01.

Thereafter, the suspension was transferred to an aging incubator and aged at an aging temperature of 80 ° C. for 140 hours to obtain product particles. In this case, composite fine particles in which hematite particles and goethite particles are heterojunction are not generated, but only goethite particles having different minor axis lengths are generated.

Using the formed particles as starting particles, the particles were heated and dehydrated at 450 ° C. in the air, and then 50 mol% H ₂ -50 m
The resultant mixture was reduced at 380 ° C. in an ol% Ar mixed gas to obtain needle-like magnetic particles of Fe ₃ O ₄ .

When the magnetic characteristics of the Fe ₃ O ₄ needle-shaped magnetic fine particles were measured with a vibrating sample magnetometer, the saturation magnetization (σs) was obtained.
Is 70.3 emu / g, coercive force (Hc) is 285 Oe,
The squareness ratio (σr / σs) was 0.402. The sample was in a powder state and the external magnetic field was 5 kOe.

[0092]

According to the present invention, irregularly shaped magnetic fine particles starting from so-called hetero-joined composite fine particles in which two or more kinds of different types of particles are bonded are provided, and new functions and physical properties are provided. It is also possible to provide a deformed magnetic fine particle having a complicated and regular form, and a simple production method thereof.

[Brief description of the drawings]

FIG. 1 shows TE for composite fine particles obtained in Example 1.
It is an M photograph.

FIG. 2 is an electron diffraction image of the composite fine particles obtained in Example 1.

FIG. 3 is a TEM photograph of composite fine particles after dehydration by heating in Example 1.

FIG. 4 is an electron diffraction image of the composite fine particles after dehydration by heating in Example 1.

FIG. 5 is a TEM photograph of the Fe ₃ O ₄ irregular magnetic fine particles obtained in Example 1.

FIG. 6 is an electron diffraction image of Fe ₃ O ₄ irregular magnetic fine particles obtained in Example 1.

FIG. 7 shows TE for the composite fine particles obtained in Example 4.
It is an M photograph.

FIG. 8 is an electron diffraction image of the composite fine particles obtained in Example 4.

FIG. 9 is a TEM photograph of composite fine particles after dehydration by heating in Example 4.

FIG. 10 is an electron diffraction image of composite fine particles after dehydration by heating in Example 4.

FIG. 11 is a TEM photograph of Fe ₃ O ₄ irregular magnetic fine particles obtained in Example 4.

FIG. 12 is an electron diffraction image of Fe ₃ O ₄ irregular magnetic fine particles obtained in Example 4.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/11 H01F 1/11 M N

Claims (14)

[Claims] 1. A composite fine particle comprising prismatic hematite particles and a plurality of plate-like goethite particles hetero-joined to the prismatic hematite particles is used as a starting particle. The deformed magnetic fine particles characterized by being grown in the direction of the C-axis crystal axis of the plate-like goethite particles radially in opposite directions to each other with the C-axis crystal axis of the prismatic hematite particles as the center of symmetry. 2. The modified magnetic fine particles according to claim 1, wherein the crystal structure is Fe ₃ O ₄ or γ-Fe ₂ O ₃ . 3. The modified magnetic fine particles according to claim 1, wherein a Co compound is coated on the surface, and the Co compound is crystalline or amorphous Co hydroxide or Co ferrite. 4. A composite fine particle comprising spindle-shaped hematite particles and one or more plate-like goethite particles hetero-joined to the spindle-like hematite particles is used as a starting particle. And irregularly shaped magnetic fine particles bonded to a crystal plane parallel to the C crystal axis of the spindle-shaped hematite particles and grown in the C crystal axis direction of the plate-like goethite particles. 5. The modified magnetic fine particles according to claim 4, wherein the crystal structure is Fe ₃ O ₄ or γ-Fe ₂ O ₃ . 6. The modified magnetic fine particles according to claim 4, wherein a Co compound is coated on the surface, and said Co compound is crystalline or amorphous Co hydroxide or Co ferrite. 7. A prismatic hematite particle, and a plurality of plate-like goethite particles hetero-joined to the prismatic hematite particle, wherein the plate-like goethite particle is a C-axis crystal axis of the prismatic hematite particle. Radially in opposite directions to each other with respect to the axis of symmetry,
The composite fine particles grown in the axial crystal axis direction are used as starting particles, and the composite fine particles are heated at 400 ° C. to 6 ° C. in air or an inert gas.
After dehydration by heating at 00 ° C., 320 ° C. to 4 ° C. in a reducing gas.
A method for producing modified magnetic fine particles, characterized in that Fe ₃ O ₄ magnetic fine particles are reduced at 20 ° C. 8. The Fe ₃ O ₄ magnetic fine particles are further oxidized in air or an oxidizing gas at 200 ° C. to 400 ° C.
Fe ₂ O ₃ production process variants magnetic microparticles according to claim 7, characterized in that the magnetic particles. 9. The Fe ₃ O ₄ magnetic fine particles are further dispersed in an alkaline solution, and then Co ²⁺ ions or Co ²⁺ ions and Fe ³⁺ ions are added to the alkaline solution. The method for producing modified magnetic fine particles according to claim 7, wherein the coating is performed at a temperature of from 100C to 100C to coat the Co compound. 10. The γ-Fe ₂ O ₃ magnetic fine particles are further dispersed in an alkaline solution, and then dispersed with Co ²⁺ ions or Co ²⁺ ions.
²⁺ ions and Fe ³⁺ ions are added to the above alkaline solution,
The alkaline solution is heated at 50 to 100 ° C.
The method for producing irregular shaped magnetic fine particles according to claim 8, wherein the compound is coated with a compound. 11. A spindle-shaped hematite particle and one or more plate-like goethite particles hetero-joined to the spindle-like hematite particle, wherein the plate-like goethite particle is a C crystal of the spindle-like hematite particle. The composite fine particles, which are bonded to the crystal plane parallel to the axis and are grown in the C crystal axis direction of the plate-like goethite particles, are used as starting particles.
After dehydration by heating at 00 ° C., 320 ° C. to 4 ° C. in a reducing gas.
A method for producing deformed magnetic fine particles, which is reduced at 20 ° C. to obtain a Fe ₃ O ₄ crystal structure. 12. The Fe ₃ O ₄ magnetic fine particles are further oxidized in air or an oxidizing gas at 200 to 400 ° C.
Claim, characterized in that the -fe ₂ O ₃ magnetic particles 1
2. The method for producing irregularly shaped magnetic fine particles according to 1. 13. The Fe ₃ O ₄ magnetic fine particles are further dispersed in an alkaline solution, and then Co ²⁺ ions or Co ²⁺ ions and Fe ³⁺ ions are added to the alkaline solution. The method for producing modified magnetic fine particles according to claim 11, wherein the Co compound is coated by heating at a temperature of from 100C to 100C. 14. The γ-Fe ₂ O ₃ magnetic fine particles are further dispersed in an alkaline solution, and then dispersed with Co ²⁺ ions or Co ²⁺ ions.
²⁺ ions and Fe ³⁺ ions are added to the above alkaline solution,
The alkaline solution is heated at 50 to 100 ° C.
13. The method for producing modified magnetic fine particles according to claim 12, wherein the compound is coated with a compound.