KR20160073363A - Ferrite magnet with salt and manufacturing method of the same - Google Patents

Abstract

The present invention relates to a salt-ferrite magnet, and a manufacturing method thereof. The salt-ferrite magnet comprises: 40-99.9 wt% of ferrite; and 0.1-60 wt% of salt. The melting point of the salt is lower than a synthesis temperature of the ferrite, and the salt is melted to form a matrix between particles of the ferrite. According to the present invention, since a synthesizing reaction is quickly made at a lower temperature than the temperature of a general ferrite magnet; the present invention is capable of being advantageous for process conditions, obtaining high crystalline nanoparticles, and preventing particle growth and cohesion between the particles caused by melted salt. Since synthesized salt-ferrite magnetic powder is able to be sintered at a lower temperature than a common temperature during a forming process and a sintering process to manufacture the salt-ferrite magnet; the present invention is capable of preventing degradation of magnetic characteristics caused by the growth of the particles, and obtains higher magnetic characteristics as arrangement in a direction of easy magnetization axis is possible.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a ferrite magnet containing salt,

More particularly, the present invention relates to a salt-containing ferrite magnetic material having a high saturation magnetization and a coercive force and having little aggregation between ferrite particles, and a method for producing the ferrite magnetic material.

Soft ferrite is a material that has a high magnetic susceptibility even when it is magnetized only a little, and it is sufficient to weaken or invert the residual magnetism and sufficient magnetic field to sufficiently magnetize the material. device).

Hard ferrite is a permanent magnet made of ferrite. It requires a strong reverse magnetic field even when removing or reversing residual magnetism. It does not need to apply voltage and can generate a certain magnetic field without generating heat itself. It is used for many purposes.

The application of ferrite is made by molding and sintering, and it can be used in a wide range of fields because of its various shapes and low cost.

Soft ferrite is used for deflection yokes (DY) and fly-back transformers (FBT), which are cathode ray tube components, to improve the function of electronic deflection and power supply. Nowadays, in addition to the home appliance industry such as a flat TV (TV) and a digital TV (TV), a core for communication related to IMT and an electro magnetic interference (EMI) ) Core (core) are the main players.

Hard ferrite is widely applied to the conversion of electromechanical energy such as a speaker, a permanent magnet motor, a movable coil type device, a magnet generator, a microphone and the like, and is also used as a storage medium.

In order to apply the ferrite magnetic material to various fields as described above, it is important to obtain fine terminal sphere powder having excellent dispersibility.

There has been an attempt to obtain a fine ferrite magnetic powder of a single crystal by adding a salt. However, a technique of synthesizing barium ferrite (Ba-ferrite) by adding a large amount of sodium chloride or potassium chloride based on the solid- 10-0554500.

The above-described method is a process for synthesizing a ferrite precursor powder by mixing the starting material with a salt in accordance with the stoichiometric ratio according to a target material and characteristics, and performing a heat treatment for crystallization and then removing the salt .

Such a method can produce small particles of 100 nm or less, but in the process of removing the salt, the coagulation of the particles tends to occur due to the characteristics of the ferrite magnetic particles.

Also, even if fine particles are produced through the above complicated process, grain growth during the sintering process for manufacturing a magnetic body can not be prevented. Problems of this manufacturing method result in a decrease in the magnetic properties with an increase in the process cost.

It is difficult to inhibit the growth of the ferrite magnetic particles because the molding and sintering process proceeds after the molten salt is washed and removed to form a magnetic body. However, since the ferrite magnetic powder is synthesized by adding sodium chloride or potassium chloride, , There arises a problem that it is difficult to align the magnetic nanoparticles necessary for maximizing the magnetism.

Korean Patent Publication No. 10-0554500

A problem to be solved by the present invention is to provide a salt-containing ferrite magnetic material having a high saturation magnetization and a coercive force and having less aggregation between ferrite particles.

Another problem to be solved by the present invention is to provide a ferrite magnetic body which is capable of easily synthesizing nanocrystalline particles with high crystallization rate at a lower temperature than that of a conventional ferrite magnetic body, And the synthesized salt-containing ferrite magnetic powder can be sintered at a temperature lower than a normal temperature in a forming and sintering process for producing a salt-containing ferrite magnetic material, thereby preventing deterioration of magnetic properties due to grain growth, And a method of manufacturing a salt-containing ferrite magnetic body that can be aligned in an easy axis direction to obtain higher magnetic properties.

The present invention relates to a ferrite composition comprising 40 to 99.9 wt% of ferrite and 0.1 to 60 wt% of a salt, wherein the salt has a melting point lower than the synthesis temperature of the ferrite and the salt is melted to form a matrix between the ferrite particles Containing ferrite magnetic material.

The salt-containing ferrite magnetic material has a structure in which a plurality of ferrites are uniformly dispersed in a salt, and the ferrite is composed of secondary particles, and the secondary particles include a plurality of primary particles smaller than the secondary particles, It can form a united form.

The secondary particles may be spherical particles having a particle size of 0.1 to 20 占 퐉 or non-spherical particles having a size of 0.1 to 1000 占 퐉, and the primary particles may be particles having a size of 5 to 1000 nm.

The salt-containing ferrite magnetic body has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of more than 50%.

The salt may be at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt, wherein the metal chloride salt is at least one salt selected from the group consisting of NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ , ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ , and the metal sulfate salt is Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ ≪ / RTI >

The hexagonal ferrite may be in the form of MT ₁₂ O ₁₉ and the M may be in the form of at least one element selected from Ba, Sr and La, And may be composed of one or more selected elements.

The ferrite may be spinel ferrite, the spinel ferrite has a form of M ₃ O ₄ , and M may be composed of one or more elements selected from Fe, Co, Mg, Mn, Zn and Ni.

The present invention also provides a method of manufacturing a ferrite material, comprising: preparing a source material of ferrite to be synthesized; preparing a salt having a melting point lower than a synthesis temperature of the ferrite to be synthesized; mixing the source material of the ferrite and the salt; Containing ferrite magnetic powder to produce a salt-containing ferrite magnetic powder while melting the salt, and forming and sintering the salt-containing ferrite magnetic powder into a desired form to obtain a salt-containing ferrite magnetic material, wherein the salt- To 99.9% by weight of a salt and 0.1 to 60% by weight of a salt, wherein the salt is melted to form a matrix between the ferrite particles.

The salt is preferably a salt having a melting point lower than the temperature at which the salt-containing ferrite magnetic powder is synthesized, and the sintering is performed under a temperature condition in which the salt is melted or a temperature and a pressure condition in which the salt is melted desirable.

The salt-containing ferrite magnetic material has a structure in which a plurality of ferrites are uniformly dispersed in a salt, and the ferrite is composed of secondary particles, and the secondary particles include a plurality of primary particles smaller than the secondary particles, It can form a united form.

The secondary particles may be spherical particles having a particle size of 0.1 to 20 占 퐉 or non-spherical particles having a size of 0.1 to 1000 占 퐉, and the primary particles may be particles having a size of 5 to 1000 nm.

The salt-containing ferrite magnetic body has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of more than 50%.

The salt may be at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt, wherein the metal chloride salt is at least one salt selected from the group consisting of NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ , ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ , and the metal sulfate salt is Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ ≪ / RTI >

The source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4, BaO 2, Sr (NO 3) 2, SrCO 3, SrCl 2, SrSO 4, Sr (OH) 2 La (NO 3 _{) 3, LaCl 3 La 2 (} SO 4) 3 and La (OH) ₃ from among the selected one or more materials and _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH) ₃ , Co (NO ₃ ) ₂ , CoCO ₃ , CoCl _2, and CoSO ₄ , and the ferrite may be a hexagonal ferrite, and the hexagonal ferrite may be in the form of MT ₁₂ O ₁₉ M may be composed of at least one element selected from Ba, Sr and La, and T may be composed of at least one element selected from Fe and Co.

The source material of the ferrite is _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH) 3, Co (NO 3) 2, CoCO 3, CoCl 2, CoSO 4, Mn (NO ₃ ) ₂ , MnCO ₃ , MnCl ₂ , MnSO ₄ , MnO ₂ , Mg (NO ₃ ) ₂ , MgCO ₃ , MgCl ₂ , MgSO ₄ , Ni (NO ₃ ) ₂ , NiCO ₃ , NiCl ₂ , NiSO ₄ , Zn (NO ₃ ) ₂ , ZnCl ₂ , ZnSO ₄ and ZnO, the ferrite may be spinel ferrite, the spinel ferrite has the form of M ₃ O ₄ , Fe, Co, Mg, Mn, Zn and Ni.

The source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4, BaO 2, Sr (NO 3) 2, SrCO 3, SrCl 2, SrSO 4, Sr (OH) 2 La (NO 3 _{) 3, LaCl 3 La 2 (} SO 4) 3 and La (OH) ₃ from among the selected one or more materials and _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH) ₃ , Co (NO ₃ ) ₂ , CoCO ₃ , CoCl _2, and CoSO ₄ , and the step of synthesizing the salt-containing ferrite magnetic powder comprises the steps of: Supplying power to the heating means and heating the reaction chamber to maintain a constant temperature above the melting point of the salt; feeding the carrier gas to a sprayer containing a mixture of the source material of the ferrite and the salt; Wherein the mixture contained in the sprayer is vibrated by the ultrasonic vibrator and is generated as droplets in the sprayer, And introducing the carrier gas into the reaction chamber and synthesizing the droplet introduced into the reaction chamber into a salt-containing ferrite magnetic powder through thermal decomposition and oxidation reaction.

The method for producing a salt-containing ferrite magnetic material of the present invention is advantageous in terms of the process conditions because synthesis reaction occurs rapidly at a lower temperature than a general ferrite magnetic material, and nano-sized particles of high crystallinity can be easily obtained. And the synthesized salt-containing ferrite magnetic powder can be sintered at a temperature lower than a normal temperature in a forming and sintering process of producing a salt-containing ferrite magnetic material, thereby preventing deterioration of magnetic properties due to grain growth , Alignment in the direction of easy axis of magnetization is possible, and higher magnetic characteristics can be obtained.

According to the present invention, the synthesis of the ferrite magnetic powder proceeds in the molten salt so that the base of the liquid phase sintering is applied and the diffusion rate of the particles is higher than that of the synthesis in the general solid phase, It is possible not only to obtain a highly crystalline powder but also to prevent agglomeration of magnetic particles in the molten salt.

In addition, due to the securing of fluidity by the residual salt, alignment of the magnetic body particles during sintering is induced to exhibit higher magnetic properties.

In addition, the conventional sintering process has a disadvantage that it proceeds at a temperature higher than the temperature at which the grain growth of ferrite occurs and affects magnetic properties. However, in the present invention, the temperature at which grain growth of ferrite does not occur (for example, It is possible to sinter the ferrite magnetic material without affecting the magnetic properties of the ferrite magnetic material.

The salt-containing ferrite magnetic material of the present invention can be used in all electronic devices and parts using soft or hard ferrite magnetic material.

1 is a schematic view of a salt-containing ferrite magnetic powder.
Fig. 2 shows a schematic diagram of a process for producing a salt-containing ferrite magnetic body.
FIG. 3 is a graph showing an X-ray diffraction (XRD) pattern of a sodium chloride-containing barium ferrite magnetic powder synthesized according to Examples 1 to 3. FIG.
FIGS. 4 and 5 are scanning electron microscope (SEM) photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 1. FIG.
6 and 7 are scanning electron microscope (SEM) photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 2. Fig.
8 and 9 are scanning electron microscope (SEM) photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 3. Fig.
10 is a graph showing an X-ray diffraction (XRD) pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Examples 4 to 6. FIG.
11 and 12 are SEM micrographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 4. FIG.
13 and 14 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 5. Fig.
Figs. 15 and 16 are SEM photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 6. Fig.
FIG. 17 is a graph showing an X-ray diffraction (XRD) pattern of barium ferrite magnetic powder synthesized according to Comparative Examples 1 to 3. FIG.
18 and 19 are scanning electron microscope (SEM) photographs of barium ferrite magnetic powder synthesized according to Comparative Example 1. Fig.
FIGS. 20 and 21 are SEM photographs of barium ferrite magnetic powder synthesized according to Comparative Example 2. FIG.
FIGS. 22 and 23 are SEM photographs of barium ferrite magnetic powder synthesized according to Comparative Example 3. FIG.
24 is a graph showing an X-ray diffraction (XRD) pattern of a sodium chloride-containing barium ferrite magnetic powder synthesized according to Examples 7 to 9. FIG.
25 and 26 are SEM micrographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 7. Fig.
27 and 28 are SEM micrographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 8. Fig.
29 and 30 are SEM micrographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 9. Fig.
31 is a graph showing an X-ray diffraction (XRD) pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Examples 10 to 12. FIG.
32 and 33 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 10. Fig.
34 and 35 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 11. Fig.
36 and 37 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 12. Fig.
FIG. 38 is a graph showing an X-ray diffraction (XRD) pattern of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 13 and Example 14. FIG.
39 and 40 are scanning electron microscope (SEM) photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 13. Fig.
Figs. 41 and 42 are SEM photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 14. Fig.
FIG. 43 is a graph showing a magnetic characteristic evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 15. FIG.
44 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 15. Fig.
45 and 46 are scanning electron micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 15. Fig.
FIG. 47 is a graph showing a magnetic property evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 16. FIG.
48 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 16. Fig.
Figs. 49 and 50 are SEM micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 16. Fig.
51 is a graph showing magnetic property evaluation using a VSM (vibrating sample magnetometer) for the salt-containing barium ferrite magnetic material prepared according to Example 17. Fig.
52 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 17. Fig.
Figs. 53 and 54 are scanning electron micrographs showing fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 17. Fig.
FIG. 55 is a graph showing magnetic property evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 18. FIG.
56 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 18. Fig.
Figs. 57 and 58 are SEM micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 18. Fig.
FIG. 59 is a graph showing a magnetic property evaluation using a VSM (vibrating sample magnetometer) for a salt-containing barium ferrite magnetic substance prepared according to Example 19. FIG.
60 is an X-ray diffraction graph of the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 19. Fig.
Figs. 61 and 62 are scanning electron micrographs showing fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 19. Fig.
63 is a graph showing magnetic property evaluation using VSM (vibrating sample magnetometer) for the salt-containing barium ferrite magnetic material prepared according to Example 20. Fig.
64 is an X-ray diffraction graph for a sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 20. Fig.
65 and 66 are scanning electron micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 20. Fig.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not.

The salt containing ferrite magnetic material according to a preferred embodiment of the present invention comprises 40 to 99.9 wt% of ferrite and 0.1 to 60 wt% of salt, wherein the salt has a melting point lower than the synthesis temperature of the ferrite, And form a matrix between the ferrite particles. In the salt-containing ferrite magnetic material of the present invention, the ferrite is contained in an amount of 40 to 99.9 wt%, preferably 65 to 99.9 wt%, and the salt is contained in an amount of 0.1 to 60 wt%, preferably 0.1 to 35 wt% .

The salt-containing ferrite magnetic material has a structure in which a plurality of ferrites are uniformly dispersed in a salt, the ferrite is composed of secondary particles, and the secondary particles include a plurality of primary particles smaller than the secondary particles, It can form a united form.

The secondary particles may be spherical particles having a particle size of 0.1 to 20 μm, and the primary particles may be particles having a size of 5 to 1000 nm. The secondary particles may be composed of non-spherical particles having a size of 0.1 to 1000 mu m. The primary particles may be hexagonal plate-like or rod-shaped particles.

The salt-containing ferrite magnetic body has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of more than 50%. The Mr / Ms value is higher than 50%, for example higher than 50% and lower than 99.9%.

The salt may be at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt, wherein the metal chloride salt is at least one salt selected from the group consisting of NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ , ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ , and the metal sulfate salt is Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ ≪ / RTI >

The hexagonal ferrite may be in the form of MT ₁₂ O ₁₉ and the M may be in the form of at least one element selected from Ba, Sr and La, And may be composed of one or more selected elements.

The ferrite may be spinel ferrite, the spinel ferrite has a form of M ₃ O ₄ , and M may be composed of one or more elements selected from Fe, Co, Mg, Mn, Zn and Ni.

A method of producing a salt-containing ferrite magnetic material according to a preferred embodiment of the present invention includes the steps of preparing a source material of ferrite to be synthesized, preparing a salt having a melting point lower than a synthesis temperature of the ferrite to be synthesized, Mixing the source material with the salt; synthesizing a salt-containing ferrite magnetic powder while allowing the salt to melt; and molding and sintering the salt-containing ferrite magnetic powder to obtain a salt-containing ferrite magnetic material Wherein the salt containing ferrite magnetic material comprises from 40 to 99.9% by weight of ferrite and from 0.1 to 60% by weight of salt, and the salt is melted to form a matrix between the ferrite particles.

Hereinafter, the synthesis temperature of the ferrite refers to the temperature at which the ferrite magnetic powder is synthesized. The ferrite magnetic powder can be synthesized by various methods such as spray pyrolysis. For example, when the spray pyrolysis method is used, the synthesis temperature of the ferrite is a temperature at which the droplet passes through the reaction chamber to synthesize the ferrite magnetic powder, Quot; means the highest temperature among the inlet and outlet of < RTI ID = 0.0 >

The salt is preferably a salt having a melting point lower than the temperature at which the salt-containing ferrite magnetic powder is synthesized, and the sintering is performed under a temperature condition in which the salt is melted or a temperature and a pressure condition in which the salt is melted desirable. If pressurization is not performed during the sintering, it is preferable that sintering is performed at a temperature higher than the melting point of the salt (800 DEG C for NaCl and 776 DEG C for KCl), and when pressurization is performed during the sintering, The salt can be melted. The pressure during the sintering is preferably in the range of about 20 to 200 MPa.

The salt may be at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt, wherein the metal chloride salt is at least one salt selected from the group consisting of NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ , ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ , and the metal sulfate salt is Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ ≪ / RTI >

In the present invention, a salt capable of being present in a liquid state at the sintering conditions (sintering temperature and pressure) of the ferrite together with the source material of ferrite is added to induce the ferrite magnetic body to be synthesized in the liquid phase salt during sintering, The salt is used without washing.

In the case of the present invention, the synthesis of the ferrite magnetic powder proceeds in the molten salt so that the mechanism of the liquid phase sintering is applied, and the diffusion rate of the particles is higher than that in the general solid phase, It is possible not only to obtain a highly crystalline powder at a low temperature but also to prevent agglomeration of magnetic particles in the molten salt.

In addition, due to the securing of fluidity by the residual salt, alignment of the magnetic body particles during sintering is induced to exhibit higher magnetic properties.

In addition, the conventional sintering process has a disadvantage that it proceeds at a temperature higher than the temperature at which the grain growth of ferrite occurs and affects magnetic properties. However, in the present invention, the temperature at which grain growth of ferrite does not occur (for example, It is possible to sinter the ferrite magnetic material without affecting the magnetic properties of the ferrite magnetic material.

In the present invention, a salt-containing ferrite magnetic powder is synthesized by forming and sintering a salt-containing ferrite magnetic powder in a state that the salt is contained as it is without removing the salt by washing with water after the salt-containing ferrite magnetic powder is synthesized and the molten salt is directly used for the magnetic material .

Methods that can be used to obtain ferrite magnetic powders include solid phase reaction, coprecipitation, sol-gel method, free crystallization, hydrothermal synthesis, and aerosol method.

In the solid phase reaction method, the starting material is mixed and pulverized at a molar ratio of metal ions together with deionized water, followed by drying, followed by pulverization and sintering to obtain powder.

The coprecipitation method is a method of dissolving the starting material in deionized water at a composition ratio of metal ions, precipitating it as a precipitant after the precipitation, repeating the washing process, adjusting the pH, filtering and drying, and then sintering to obtain a powder.

The sol-gel method is a method of dissolving the starting material in a solvent, adding the additive into a sol state, obtaining a powder sample through drying, and then obtaining a powder by sintering.

In the free crystallization method, the starting material is mixed according to the composition ratio of the metal ion, and the mixture is melted at a high temperature and then charged into water to quench the amorphous material. The amorphous material is sintered to be pulverized, and the glassy and surplus elements are melted. .

In the hydrothermal synthesis method, a starting material is placed in a high-pressure reaction vessel and reacted at a temperature and a pressure to obtain a powder.

The aerosol method is a method of producing a powder by combustion or calcination while passing the starting material through a tubular shape in the form of a gas.

The preparation of the salt-containing ferrite magnetic body can be carried out using various conventional methods for synthesizing the ferrite magnetic powder, so that the method can be selected in accordance with the purpose and the characteristics of the material, and the synthesis can be carried out without limitation to the ferrite type.

For example, as the source material of the ferrite, Ba (NO ₃ ) ₂ , BaCO ₃ , BaCl ₂ , BaSO ₄ , BaO ₂ , Sr (NO ₃ ) ₂ , SrCO ₃ , SrCl ₂ , SrSO ₄ , Sr _{2 La (NO 3) 3,} LaCl 3 La 2 (SO 4) 3 and La (OH) at least one selected from the _third material and _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2 , Fe (OH) ₃ , Co (NO ₃ ) ₂ , CoCO ₃ , CoCl ₂ and CoSO ₄ , and the ferrite may be hexagonal ferrites, The ferrite may have the form of MT ₁₂ O ₁₉ , M may be composed of at least one element selected from Ba, Sr and La, and T may be composed of at least one element selected from Fe and Co.

Further, as the source material of the ferrite _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH) 3, Co (NO 3) 2, CoCO 3, CoCl 2, CoSO ₄ , Mn (NO ₃ ) ₂ , MnCO ₃ , MnCl ₂ , MnSO ₄ , MnO ₂ , Mg (NO ₃ ) ₂ , MgCO ₃ , MgCl ₂ , MgSO ₄ , Ni (NO ₃ ) ₂ , NiCO ₃ , NiCl ₂ , NiSO ₄ , Zn (NO ₃ ) ₂ , ZnCl ₂ , ZnSO ₄ and ZnO. The ferrite may be spinel ferrites, and the spinel ferrite may be selected from the group consisting of M ₃ O ₄ And M may be composed of at least one element selected from Fe, Co, Mg, Mn, Zn and Ni.

Hot pressing, Hot Isostatic Pressing (HIP), Gas Pressure Sintering (GPS), Spark Plasma Sintering (SMA), and Spark Plasma Sintering (SMA) are methods for sintering the salt-containing ferrite magnetic powder. SPS), and the method can be selected according to the purpose and the characteristics of the material, and sintering is possible without being limited to the type of ferrite.

Fig. 1 shows a schematic view of a salt-containing ferrite magnetic powder synthesized according to the present invention. In FIG. 1, reference numeral 10 denotes a primary ferrite magnetic particle, reference numeral 20 denotes a molten salt, and a salt-containing ferrite magnetic powder has a ferrite magnetic particle dispersed in a matrix composed of a molten salt, In the form of a composite powder.

The magnetic powder containing the salt is used in the form of a magnetic powder for producing a salt-containing ferrite magnetic body. In the powder sintering, the fluidity is increased due to the melting of the salt remaining under the pressurized heating condition above the melting point of the salt, so that the arrangement of the magnetic particles can be induced and the molding density can also be improved. Alignment of the magnetic particles increases the residual magnetism value (B _r ) and the coercive force (H _c ), thereby achieving an improvement in the overall magnetic property.

As the source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4, BaO 2, Sr (NO 3) 2, SrCO 3, SrCl 2, SrSO 4, Sr (OH) 2 La (NO _{3) 3, LaCl 3 La 2} (SO 4) 3 and La (OH) NO (one or more kinds selected from a _third material, and _{Fe 3) 3, FeCO 3,} FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH ) ₃ , Co (NO ₃ ) ₂ , CoCO ₃ , CoCl _2, and CoSO ₄ , and the step of synthesizing the salt-containing ferrite magnetic powder may include the step of coating the periphery of the reaction chamber of the spray pyrolysis apparatus Supplying power to the heating means and heating the reaction chamber to maintain a constant temperature above the melting point of the salt; feeding the carrier gas to a sprayer containing a mixture of the source material of the ferrite and the salt; Wherein the mixture contained in the sprayer is vibrated by the ultrasonic vibrator to generate droplets in the sprayer, And a step in which a droplet introduced into the reaction chamber is introduced into the reaction chamber by a gas carrier gas and is synthesized into a salt-containing ferrite magnetic powder through thermal decomposition and oxidation reaction.

Fig. 2 shows a schematic diagram of a process for producing a salt-containing ferrite magnetic body. 2, '30' is a salt-containing ferrite magnetic powder before molding, '40' is a sintered body after molding and sintering, and the rightmost drawing in FIG. 2 is an enlarged view of the microstructure of a sintered body, Are ferrite magnetic particles and molten salt, respectively. The sintered body shows that the ferrite magnetic particles are arranged on the molten salt matrix.

The salt-containing ferrite magnetic material has a structure in which a plurality of ferrite is uniformly dispersed in a salt, and the ferrite is composed of secondary particles, and the secondary particles are a plurality of primary particles smaller than the secondary particles, Can be achieved. The secondary particles may be spherical particles having a particle size of 0.1 to 20 μm, and the primary particles may be particles having a size of 5 to 1000 nm. The secondary particles may be composed of non-spherical particles having a size of 0.1 to 1000 mu m. The primary particles may be hexagonal plate-like or rod-shaped particles. The salt-containing ferrite magnetic material having such a structure has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of more than 50%. The Mr / Ms value is higher than 50%, for example higher than 50% and lower than 99.9%.

In the embodiments of the present invention described below, spray pyrolysis in which a liquid precursor is sprayed in an aerosol method to prepare a salt-containing ferrite magnetic material is used as an example. The method of manufacturing the ferrite magnetic body is not limited to this.

The spray pyrolysis method can synthesize particles at a time without complicated post-heat treatment process in a short time, but there is a problem that the primary particles formed in the sprayed droplets strongly aggregate in the form of secondary particles. However, by additionally adding a salt in addition to the source material of ferrite, it is possible to prevent aggregation between the primary particles as described above, and to obtain secondary particles in which highly crystalline particles are mixed with the molten salt.

As an example of the present invention, barium ferrite (BaFe ₁₂ O ₁₉ ), which is one of the ferrite magnetic materials, was prepared as an example, and sodium chloride (NaCl) or calcium chloride (KCl) was used as an additionally added salt.

The ferrite magnetic material is not limited to barium ferrite, and may be spinel ferrite or hexagonal ferrite, and may be selected according to the purpose.

The spinel ferrite has a basic form of M ₃ O ₄ , and the site of M may contain one element such as Fe, Co, Mg, Mn, Zn, Ni, etc., or two or more kinds of elements may be combined. Such spinel ferrites include cobalt ferrite, nickel ferrite, manganese ferrite, magnesium ferrite, zinc ferrite, manganese ferrite, nickel zinc ferrite, (NiZn ferrite).

The hexagonal ferrite has a form of MT ₁₂ O ₁₉ , and one or more elements such as Ba, Sr, and La may be contained in the M site, and two or more elements may be combined. Or one or more of the elements may be combined. Examples of such hexagonal ferrite include barium ferrite, strontium ferrite (Sr ferrite), lanthanum ferrite (La ferrite), barium strontium ferrite (BaSr ferrite), barium lanthanum ferrite (BaLa ferrite), strontium lanthanum ferrite .

The ferrite may be a raw material suitable for each metal element depending on the type of ferrite. Source materials of the barium as a source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4 or BaO may be _2, the source material of strontium _{Sr (NO 3) 2, SrCO} 3, SrCl 2, SrSO ₄ or Sr (OH) may be _2, the source material of lanthanum is _{La (NO 3) 3, LaCl} 3 La 2 (SO 4) 3 or La (OH) may be _3, the source material of iron Fe ( (NO ₃ ) ₃ , FeCO ₃ , FeCl _{3 ,} Fe ₂ O ₃ , FeCl ₂ or Fe (OH) ₃ and the source material of cobalt may be Co (NO ₃ ) ₂ , CoCO ₃ , CoCl ₂ or CoSO ₄ And the source material of manganese may be Mn (NO ₃ ) ₂ , MnCO ₃ , MnCl ₂ , MnSO ₄ or MnO ₂ and the source material of magnesium may be Mg (NO ₃ ) ₂ , MgCO ₃ , MgCl ₂ or MgSO ₄ And the source material of nickel may be Ni (NO ₃ ) ₂ , NiCO ₃ , NiCl ₂ or NiSO ₄ and the source material of zinc may be Zn (NO ₃ ) ₂ , ZnCl ₂ , ZnSO ₄ or ZnO.

The salts are chloride salts (NaCl, KCl, LiCl, CaCl _2, MgCl _2, etc.), nitric acid salt _{(NaNO 3, KNO 3, LiNO} 3, Ca (NO 3) 2, Mg (NO 3) 2 , etc.) or a sulfuric acid metal salt (Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ , MgSO ₄ Etc.), may be in the form of a single or mixed salt, and may optionally be selected from the salts which may exist in the molten state at the sintering temperature.

In the embodiments of the present invention, spark plasma sintering (hereinafter referred to as SPS) was used for forming and sintering the synthesized salt-containing ferrite magnetic powder. SPS is an energizing and pressurizing method using a DC pulse in a vacuum high-temperature compression method and can be instantaneously heated and cooled by using a spark plasma, thereby minimizing the influence on the formed crystal phase . In the examples, the target sintering temperature of 700 ° C and 800 ° C and the pressure of 100 MPa were molded for 2 minutes, and the heating rate was 100 ° C / min.

Hereinafter, embodiments according to the present invention will be specifically shown, and the present invention is not limited to the following embodiments.

≪ Example 1 >

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

The starting material was prepared by adding sodium chloride (NaCl) to the source material of the wind ferrite. The sodium chloride was weighed and added so as to have a weight ratio of 19% (19% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) to the salt-containing ferrite magnetic powder.

The starting material was sprayed to form a droplet, and a salt-containing barium ferrite magnetic powder was synthesized with the carrier gas (O ₂ ) passing through a reaction chamber heated at an inlet temperature of 400 ° C. and an outlet temperature of about 850 ° C.

Hereinafter, by using the spray pyrolysis method, The method of forming the barium ferrite magnetic powder will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated to be maintained at a temperature of 400 ° C at the inlet and 850 ° C at the outlet.

A carrier gas was supplied to the atomizer containing the starting material. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The starting material contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer, and the droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form a sodium chloride-containing barium ferrite magnetic powder . The sodium chloride - containing barium ferrite magnetic powder formed by pyrolysis and oxidation reaction was collected in a collector consisting of a paper filter.

≪ Example 2 >

As in Example 1, starting material was prepared using barium ferrite source material and sodium chloride, except that sodium chloride was added at a weight ratio of 31% (31 wt% based on 100 wt% of salt-containing ferrite magnetic powder, ). ≪ / RTI >

The starting material was sprayed to form a droplet, and the solution was passed through a reaction chamber heated at a temperature of 400 ° C. at the inlet and 850 ° C. at the outlet together with the carrier gas (O ₂ ), thereby obtaining a salt-containing barium ferrite Magnetic powder was synthesized.

≪ Example 3 >

The starting material was prepared by using a barium ferrite source material and sodium chloride in the same manner as in Example 1, except that sodium chloride was added in an amount of 53% by weight (relative to 100% by weight of the salt-containing ferrite magnetic powder, 53% ). ≪ / RTI >

The starting material was sprayed to form a droplet, and the solution was passed through a reaction chamber heated at a temperature of 400 ° C. at the inlet and 850 ° C. at the outlet together with the carrier gas (O ₂ ), thereby obtaining a salt-containing barium ferrite Magnetic powder was synthesized.

FIG. 3 is a graph showing an X-ray diffraction (XRD) pattern of a sodium chloride-containing barium ferrite magnetic powder synthesized according to Examples 1 to 3. FIG. 3 (a) shows an X-ray diffraction pattern of a sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 1, and (b) shows a sodium chloride-containing barium ferrite synthesized according to Example 2 Ray diffraction pattern of ferrite magnetic powder, and (c) shows an X-ray diffraction pattern of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 3 .

Referring to FIG. 3, sodium chloride (NaCl) and barium ferrite (BaFe ₁₂ O ₁₉ ) crystal phases were observed in all of Examples 1 to 3. In the case of Examples 2 and 3, hematite, -Fe ₂ O ₃ ) crystal phase. It was found that the peak of sodium chloride was increased in proportion to the amount of sodium chloride added. In addition, hematite (α-Fe ₂ O ₃ ) phase appeared when excess sodium chloride was added (in the case of Example 2 and Example ₃ ), which corresponds to the intermediate phase in the production of barium ferrite, It means that I could not get up. In the case where sodium chloride is excessively contained, the diffusion path between the barium ferrite precursor particles in the molten sodium chloride base becomes long and the reaction time is long, which is considered to result in the above results.

FIGS. 4 and 5 are scanning electron microscope (SEM) photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 1, and FIGS. 6 and 7 are photographs of sodium chloride-containing barium ferrite synthesized according to Example 2 8 and 9 are SEM micrographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 3. Fig. 8 is a scanning electron microscope (SEM) photograph of the magnetic powder.

4 to 9, it can be confirmed that a barium ferrite magnetic powder containing sodium chloride was well formed. The formed sodium barium ferrite particles showed a primary particle size of 100 nm or less, and the secondary particles The particle size was 5 탆 or less. As shown in FIG. 5, FIG. 7 and FIG. 9, in the enlarged photograph, the primary particle size tended to decrease as the sodium chloride content increased.

<Example 4>

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

A starting material was prepared by adding potassium chloride (KCl) to the source material of the barium ferrite. The potassium chloride was weighed and added so as to have a weight ratio of 19% (19% by weight based on 100% by weight of potassium chloride ferrite magnetic powder) to the potassium chloride ferrite magnetic powder.

The starting material was sprayed to form a droplet, and the powder was passed through a reaction chamber heated to 400 ° C at the inlet and 850 ° C at the outlet together with the carrier gas (O ₂ ) to synthesize a potassium barium chloride ferrite magnetic powder.

Hereinafter, by spray pyrolysis, potassium chloride The method of forming the barium ferrite magnetic powder will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated to be maintained at a temperature of 400 ° C at the inlet and 850 ° C at the outlet.

A carrier gas was supplied to the atomizer containing the starting material. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The starting material contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer. The droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form a potassium chloride-containing barium ferrite magnetic powder . Potassium chloride - containing barium ferrite magnetic powders formed by pyrolysis and oxidation reaction were collected in a collector consisting of a paper filter.

&Lt; Example 5 >

The starting material was prepared by using a barium ferrite source material and potassium chloride as in Example 4, except that 31% by weight of potassium chloride (31% by weight based on 100% by weight of potassium chloride ferrite magnetic powder) was added to the potassium chloride ferrite magnetic powder &Lt; / RTI &gt;

So as to pass through the reaction chamber and heated to the Example 4 in the same way as the spray (spray) the starting material and the formed liquid droplets and a carrier gas (O ₂₎ and the inlet temperature is 400 ℃, exit 850 ℃ degree with potassium chloride, barium ferrite magnetic Powder was synthesized.

&Lt; Example 6 >

The starting material was prepared by using the barium ferrite source material and potassium chloride as in Example 4 except that the potassium chloride was 53% by weight of the potassium chloride ferrite magnetic powder (53% by weight based on 100% by weight of the potassium chloride magnetic powder) &Lt; / RTI &gt;

So as to pass through the reaction chamber and heated to the Example 4 in the same way as the spray (spray) the starting material and the formed liquid droplets and a carrier gas (O ₂₎ and the inlet temperature is 400 ℃, exit 850 ℃ degree with potassium chloride, barium ferrite magnetic Powder was synthesized.

10 is a graph showing an X-ray diffraction (XRD) pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Examples 4 to 6. FIG. 10 (a) shows an X-ray diffraction pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 4, and FIG. 10 (b) Ray diffraction pattern of ferrite magnetic powder and (c) shows an X-ray diffraction pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 6 .

Referring to FIG. 10, potassium chloride (KCl) and barium ferrite (BaFe ₁₂ O ₁₉ ) crystal phases were observed in all of Examples 4 to 6. In Example 5, hematite (α-Fe ₂ O ₃ ) Crystalline phase appeared. As the amount of salt added increased, the peak of potassium chloride increased. However, the barium ferrite phase was not observed in Example 4 in which the addition amount of the salt was small.

11 and 12 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 4, and Figs. 13 and 14 are photographs of the potassium chloride-containing barium ferrite synthesized according to Example 5 15 and 16 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 6. Fig. 15 is a scanning electron microscope (SEM) image of the magnetic powder.

11 to 16, it was confirmed that the barium ferrite magnetic powder containing potassium chloride was well formed, and the potassium chloride-containing barium ferrite particles formed showed a primary particle size of 100 nm or less, and the secondary particles The particle size was 5 탆 or less. In the high magnification photograph of FIG. 12, the particles were very small, which is considered to be the state before the barium ferrite phase is formed as amorphous particles when the X-ray diffraction results are collectively viewed. As a result, it can be seen that barium ferrite phase was not formed when potassium chloride was added at a synthesis temperature of 850 ° C of 19% or less of the potassium barium ferrite magnetic powder containing potassium chloride.

In order to more easily grasp the characteristics of the first to sixth embodiments, comparative examples which can be compared with the embodiments of the present invention will be presented. It should be noted that Comparative Examples 1 to 3, which will be described later, are merely provided for comparison with the characteristics of the embodiments, and are not the prior art of the present invention.

&Lt; Comparative Example 1 &

In the following comparative examples, a barium ferrite magnetic powder was synthesized without adding a salt.

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

The barium ferrite magnetic powder was synthesized by spraying a source material of barium ferrite to form a droplet and passing it through a reaction chamber heated at 400 ° C. at the inlet and 850 ° C. at the outlet together with the carrier gas (O ₂ ) .

Hereinafter, a method of forming a barium ferrite magnetic powder by spray pyrolysis will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated to be maintained at a temperature of 400 ° C at the inlet and 850 ° C at the outlet.

A carrier gas was supplied to the atomizer containing the source material of barium ferrite. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The source material of the barium ferrite contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer. The droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form barium ferrite magnetic powder Synthesized. The barium ferrite magnetic powder formed by thermal decomposition and oxidation reaction was collected in a collector made of paper filter.

&Lt; Comparative Example 2 &

As in Comparative Example 1, a source material of barium ferrite was used.

So as to pass through the reaction chamber by spraying (spray) a source material of the same barium ferrite and the Comparative Example 1, the formed liquid droplets and a carrier gas (O ₂₎ and 400 ℃ inlet with the outlet and heated to a temperature of about 900 ℃ barium Ferrite magnetic powder was synthesized.

&Lt; Comparative Example 3 &

As in Comparative Example 1, a source material of barium ferrite was used.

A source material of barium ferrite was sprayed to form a droplet and the mixture was passed through a reaction chamber heated at a temperature of 400 ° C. at the inlet and 950 ° C. at the outlet together with the carrier gas (O ₂ ) Ferrite magnetic powder was synthesized.

FIG. 17 is a graph showing X-ray diffraction (XRD) patterns of barium ferrite magnetic powders synthesized according to Comparative Examples 1 to 3. FIG. 17 (a) shows an X-ray diffraction pattern of barium ferrite magnetic powder synthesized according to Comparative Example 1, and FIG. 17 (b) shows a barium ferrite magnetic powder synthesized according to Comparative Example 2 (C) shows an X-ray diffraction pattern of the barium ferrite magnetic powder synthesized according to Comparative Example 3. FIG.

Referring to FIG. 17, barium ferrite (BaFe ₁₂ O ₁₉ ) phase was observed in all of Comparative Examples 1 to 3, and a hematite (α-Fe ₂ O ₃ ) crystal phase was observed in all of Examples 1 to ₃ .

FIGS. 18 and 19 are scanning electron microscope (SEM) photographs of barium ferrite magnetic powder synthesized according to Comparative Example 1. FIGS. 20 and 21 are photographs of the barium ferrite magnetic powder synthesized according to Comparative Example 1 FIG. 22 and FIG. 23 are SEM photographs of barium ferrite magnetic powder synthesized according to Comparative Example 3. FIG.

Referring to FIGS. 18 to 23, it was confirmed that as the temperature in the reaction chamber increases, the particles become larger. At 850 ° C., it is difficult to confirm that the particles are too small, and it was confirmed that the barium ferrite phase was formed as a result of X-ray diffraction.

As in the comparative examples, when the salt was not added, the intermediate phase hematite was found even at a high temperature of 950 ° C. However, when the salt was added (Examples 3 and 6) A barium ferrite phase having good properties was obtained. This shows that it is possible to synthesize highly crystalline ferrite magnetic bodies even in a reaction time of a second (sec) unit such as the spray pyrolysis method used in the comparative examples.

In addition, a single crystal of barium ferrite exists in a plate-like shape and a rod-like shape. In a sample not containing a salt, the crystals adhere to each other instead of growing in the form of a single crystal while the particles grow. However, in the case of adding a salt, it is possible to improve the magnetic properties when the crystals are arranged in a single crystal form without being adhered to each other.

&Lt; Example 7 >

After the preparation of the salt-containing barium ferrite, the experiment was carried out at lower temperature than in the case of Examples 1 to 3 in consideration of the molding conditions, and the salt addition amount was also used in a smaller amount.

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

The starting material was prepared by adding sodium chloride (NaCl) to the source material of the wind ferrite. The sodium chloride was weighed and added so as to have a weight ratio of 5% (5% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) to the salt-containing ferrite magnetic powder.

The starting material was sprayed to form a droplet, and a salt containing barium ferrite magnetic powder was synthesized with the carrier gas (O ₂ ) passing through a reaction chamber heated to 400 ° C. at the inlet and 800 ° C. at the outlet.

Hereinafter, by using the spray pyrolysis method, The method of forming the barium ferrite magnetic powder will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated to be maintained at a temperature of 400 ° C at the inlet and 850 ° C at the outlet.

A carrier gas was supplied to the atomizer containing the starting material. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The starting material contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer, and the droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form a sodium chloride-containing barium ferrite magnetic powder . The sodium chloride - containing barium ferrite magnetic powder formed by pyrolysis and oxidation reaction was collected in a collector consisting of a paper filter.

&Lt; Example 8 >

The starting material was prepared by using a barium ferrite source material and sodium chloride in the same manner as in Example 7, except that sodium chloride was used in an amount of 19% (19% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) ). &Lt; / RTI &gt;

The starting material was sprayed in the same manner as in Example 7 to form a droplet, and the solution was passed through a reaction chamber heated to 400 ° C. at the inlet and 800 ° C. at the outlet with the carrier gas (O ₂ ) Magnetic powder was synthesized.

&Lt; Example 9 >

As in Example 7, a starting material was prepared using a barium ferrite source material and sodium chloride, except that sodium chloride was added in an amount of 31% (31% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) ). &Lt; / RTI &gt;

The starting material was sprayed in the same manner as in Example 7 to form a droplet, and the solution was passed through a reaction chamber heated to 400 ° C. at the inlet and 800 ° C. at the outlet with the carrier gas (O ₂ ) Magnetic powder was synthesized.

24 is a graph showing an X-ray diffraction (XRD) pattern of a sodium chloride-containing barium ferrite magnetic powder synthesized according to Examples 7 to 9. FIG. 24 (a) shows the X-ray diffraction pattern of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 7, (b) shows the sodium chloride-containing barium ferrite synthesized according to Example 8 Ray diffraction pattern of ferrite magnetic powder, and (c) shows an X-ray diffraction pattern of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 9 .

Referring to FIG. 24, a barium ferrite crystal phase was observed in all of Examples 7 to 9, and a hematite (α-Fe ₂ O ₃ ) crystal phase was observed in Example 9. However, In the case of Example 7 and Example 8 in which the salt was added at a weight ratio of 19% or less of the powder, no hematite crystal phase was observed.

25 and 26 are scanning electron microscope (SEM) photographs of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 7, and Figs. 27 and 28 are graphs of the sodium chloride-containing barium ferrite synthesized according to Example 8 FIG. 29 and FIG. 30 are SEM photographs of sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 9. FIG. 29 is a scanning electron microscope (SEM)

25 to 30, it was confirmed that the barium ferrite magnetic powder containing sodium chloride was well formed, and the sodium chloride-containing barium ferrite particles formed showed a primary particle size of 100 nm or less, and the secondary particles The particle size was 5 탆 or less. When the salt was added at a weight ratio of 19% (in the case of Example 8) and 31% by weight (in the case of Example 9), the particle size was almost similar to that of the salt containing barium ferrite magnetic powder of 19% . However, when the salt was added at a weight ratio of 5% (in the case of Example 7), the particle size was smaller because no particle growth occurred in the case where more salt was added (in the case of Examples 8 and 9).

&Lt; Example 10 >

After the preparation of the salt-containing barium ferrite, experiments were carried out at lower temperatures than those of Examples 4 to 6 in consideration of the molding conditions, and the salt addition amount was also used in a smaller amount.

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

The starting material was prepared by adding potassium chloride (KCl) to the source material of the wind-ferrite. The potassium chloride was weighed and added so as to have a weight ratio of 5% (5% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) to the salt-containing ferrite magnetic powder.

The starting material was sprayed to form a droplet, and a salt containing barium ferrite magnetic powder was synthesized with the carrier gas (O ₂ ) passing through a reaction chamber heated to 400 ° C. at the inlet and 800 ° C. at the outlet.

Hereinafter, a method of forming a salt-containing barium ferrite magnetic powder by spray pyrolysis will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated and maintained at a temperature of about 400 캜 at the inlet and 800 캜 at the outlet.

A carrier gas was supplied to the atomizer containing the starting material. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The starting material contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer. The droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form a potassium chloride-containing barium ferrite magnetic powder . Potassium chloride - containing barium ferrite magnetic powders formed by pyrolysis and oxidation reaction were collected in a collector consisting of a paper filter.

&Lt; Example 11 >

As in Example 10, a starting material was prepared by using a barium ferrite source material and potassium chloride. The potassium chloride was used in an amount of 19% by weight based on 100% by weight of the salt-containing ferrite magnetic powder, ). &Lt; / RTI &gt;

The starting material was sprayed in the same manner as in Example 10 to form a droplet, and the solution was passed through a reaction chamber heated at a temperature of about 400 ° C at the inlet and 800 ° C at the outlet together with the carrier gas (O ₂ ) Magnetic powder was synthesized.

&Lt; Example 12 >

The starting material was prepared by using the barium ferrite source material and potassium chloride as in Example 10, except that the potassium chloride was used in an amount of 31% (31% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) ). &Lt; / RTI &gt;

The starting material was sprayed in the same manner as in Example 10 to form a droplet, and the solution was passed through a reaction chamber heated at a temperature of about 400 ° C at the inlet and 800 ° C at the outlet together with the carrier gas (O ₂ ) Magnetic powder was synthesized.

31 is a graph showing an X-ray diffraction (XRD) pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Examples 10 to 12. FIG. 31 (a) shows an X-ray diffraction pattern of a potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 10, and (b) shows a barium ferrite containing potassium chloride- Ray diffraction pattern of ferrite magnetic powder and (c) shows an X-ray diffraction pattern of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 12 .

31, a barium ferrite crystal phase was shown in Example 12, and in Example 10 and Example (Example 12) except for the case where a salt was added at a weight ratio of 31% to the salt containing barium ferrite magnetic powder (in the case of Example 12) 11, barium ferrite crystal phase was not observed. In all of Examples 10 to 12, a potassium chloride phase was observed.

FIGS. 32 and 33 are scanning electron microscope (SEM) photographs of the potassium chloride-containing barium ferrite magnetic powder synthesized according to Example 10, and FIGS. 34 and 35 are graphs of the potassium chloride-containing barium ferrite synthesized according to Example 11 FIG. 36 and FIG. 37 are SEM photographs of magnetic powders of barium ferrite containing potassium chloride synthesized according to Example 12. FIG. 36 is a scanning electron microscope (SEM)

32 to 37, the morphology of barium ferrite particles was not clearly observed except for the case where a salt was added at a weight ratio of 31% to the salt containing barium ferrite magnetic powder (in the case of Example 12). In the case of Example 10 and Example 10, it is considered that barium ferrite crystal phase is not formed and amorphous state is taken into consideration in consideration of the fact that barium ferrite phase does not appear in X-ray diffraction.

&Lt; Example 13 >

After the preparation of the salt-containing barium ferrite, the experiment was carried out at lower inlet temperatures than in the case of Examples 7 to 9 in consideration of the molding conditions, and the salt addition amount was also used in a smaller amount.

Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were used as the source materials of barium ferrite. The source material of the barium ferrite was a mixture of Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O in a molar ratio of 1:12. Specifically, Ba (NO ₃ ) ₂ and Fe (NO ₃ ) ₃ .9H ₂ O were added to deionized water and stirred for about 1 hour to obtain Ba (NO ₃ ) ₂ with a molarity of 0.05M and Fe (NO ₃ ) ₃ .9H ₂ O has a molar concentration of 0.6 M, a source material of barium ferrite was prepared.

The starting material was prepared by adding sodium chloride (NaCl) to the source material of the wind ferrite. Sodium chloride was weighed and added so as to have a weight ratio of 5% (5% by weight based on 100% by weight of the salt-containing ferrite magnetic powder) to the salt-containing ferrite magnetic powder.

The starting material was sprayed in the same manner as in Example 1 to form a droplet, and the solution was passed through a reaction chamber heated at a temperature of 250 ° C at the inlet and 850 ° C at the outlet together with the carrier gas (O ₂ ) Magnetic powder was synthesized.

Hereinafter, by using the spray pyrolysis method, The method of forming the barium ferrite magnetic powder will be described in more detail.

Power was supplied to the heating means surrounding the reaction chamber of the spray pyrolysis apparatus, and the reaction chamber was heated to be maintained at a temperature of 250 DEG C at the inlet and 850 DEG C at the outlet.

A carrier gas was supplied to the atomizer containing the starting material. Oxygen (O ₂ ) gas was used as the carrier gas. The supply flow rate of the carrier gas was set to about 1.5 L / min.

The starting material contained in the atomizer is vibrated by the ultrasonic vibrator to generate a droplet in the atomizer, and the droplet is introduced into the reaction chamber by the carrier gas and pyrolyzed and oxidized to form a sodium chloride-containing barium ferrite magnetic powder . The sodium chloride - containing barium ferrite magnetic powder formed by pyrolysis and oxidation reaction was collected in a collector consisting of a paper filter.

&Lt; Example 14 >

As in Example 13, a starting material was prepared by using a barium ferrite source material and potassium chloride as a starting material, except that the potassium chloride was 3% by weight of the potassium chloride ferrite magnetic powder (3% by weight based on 100% by weight of the potassium ferrite magnetic powder) &Lt; / RTI &gt;

The starting material was sprayed in the same manner as in Example 13 to form a droplet. The droplet was passed through the reaction chamber heated at a temperature of about 250 ° C at the inlet and about 850 ° C at the outlet, together with the carrier gas (O ₂ ) Powder was synthesized.

FIG. 38 is a graph showing an X-ray diffraction (XRD) pattern of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 13 and Example 14. FIG. 28 (a) shows the X-ray diffraction pattern of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 13, (b) shows the sodium chloride-containing barium sulfate The X-ray diffraction pattern of the ferrite magnetic powder is shown.

Referring to Fig. 38, neither barium ferrite crystal phase nor barium ferrite phase was observed in both Example 13 and Example 14.

39 and 40 are scanning electron microscope (SEM) photographs of the sodium chloride-containing barium ferrite magnetic powder synthesized according to Example 13, and Figs. 41 and 42 are graphs showing the results of a scanning electron microscope 2 is a scanning electron microscope (SEM) photograph of a magnetic powder.

Referring to Figs. 39 to 42, the morphology of barium ferrite particles was not clearly observed in both Example 13 and Example 14. Considering that the barium ferrite phase does not appear in the X-ray diffraction, it seems that the barium ferrite crystal phase is not formed and becomes amorphous.

&Lt; Example 15 >

Example 7 (prepared by forming and sintering (spark plasma sintering) a salt-containing barium ferrite magnetic powder synthesized according to the method (when sodium chloride was added at a weight ratio of 5% to the salt-containing barium ferrite magnetic powder and synthesized at a temperature of 800 ° C) The magnetic properties were evaluated with a sintered body (salt-containing barium ferrite magnetic body).

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 7 was filled in a mold made of a carbon material, and then heated at a temperature raising rate of 100 ° C per minute to 700 ° C in an Aron atmosphere. The mold having been heated to 700 캜 was maintained at a pressure of 100 MPa for 2 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

FIG. 43 is a graph showing a magnetic characteristic evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 15. FIG.

Referring to FIG. 43, the in plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 59.436 emu / g, a residual magnetization (Mr) of 32,397 emu / (Hc) 4954 Oe, and Mr / Ms was 54.51%.

Out of plane is the result of measurement of the magnetic properties in the vertical direction of the disk and each value is 53.986 emu / g of saturation magnetization (Ms), 30.634 emu / g of residual magnetization (Mr), 5001 of coercive force (Hc) Oe, and Mr / Ms was 56.74%.

When Mr / Ms is 50%, it means that the magnetic particles are not completely aligned, and when they are 100%, they are perfectly aligned. The value measured perpendicular to the disk is 56.74%, which is slightly higher than that measured horizontally.

44 is an X-ray diffraction graph of a sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 15. Fig.

Referring to FIG. 44, the barium ferrite phase well formed, but the γ-Fe ₂ O ₃ powder which was not observed in the X-ray diffraction graph of the salt-containing barium ferrite magnetic powder synthesized according to Example 7 Phase. This is because the barium ferrite reverse reaction occurs due to the carbon component from the carbon mold (molding die) used in the spark plasma sintering (SPS), and barium ferrite on the surface of the molded body is decomposed into? -Fe ₂ O ₃ .

45 and 46 are scanning electron micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 15. Fig.

Referring to FIGS. 45 and 46, the shape of the magnetic particle as a whole retains a spherical shape of the secondary particle, and a part that has partially melted is observed in the fractured surface image. In the portion where the secondary particles were destroyed, the primary particles showed a size of about 100 nm.

&Lt; Example 16 >

Example 7 (prepared by forming and sintering (spark plasma sintering) a salt-containing barium ferrite magnetic powder synthesized according to the method (when sodium chloride was added at a weight ratio of 5% to the salt-containing barium ferrite magnetic powder and synthesized at a temperature of 800 ° C) The magnetic properties were evaluated with a sintered body (salt-containing barium ferrite magnetic body).

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 7 was filled in a mold made of a carbon material, and then heated at a temperature raising rate of 100 ° C per minute at 800 ° C in an argon (Ar) atmosphere. The mold having been heated to 800 DEG C was maintained at a pressure of 100 MPa for 2 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

FIG. 47 is a graph showing a magnetic property evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 16. FIG.

Referring to FIG. 47, the in plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 62.765 emu / g, a residual magnetization (Mr) of 32.233 emu / (Hc) 4437 Oe, and Mr / Ms was 51.36%.

Out of plane is the result of measurement of the magnetic property in the vertical direction of the disk and each value is 53.609 emu / g of saturation magnetization (Ms), 33.902 emu / g of residual magnetization (Mr), 4495 of coercive force (Hc) Oe, and Mr / Ms was 63.24%.

The value measured in the perpendicular direction to the disk was 63.24%, which was higher than that measured horizontally. This means that the easy magnetization axis of barium ferrite is aligned in the direction perpendicular to the disk during molding.

48 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 16. Fig.

Referring to FIG. 48, the barium ferrite phase well formed, but the γ-Fe ₂ O ₃ powder which was not observed in the X-ray diffraction graph of the salt-containing barium ferrite magnetic powder synthesized according to Example 7 Phase.

Figs. 49 and 50 are SEM micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 16. Fig.

Referring to FIGS. 49 and 50, it was observed that the shape of the original spherical secondary particles was hard to find overall, and the added sodium chloride was well melted. It is believed that the relatively well - melted salt contributed to the alignment of the barium ferrite particles and that the higher degree of alignment can be obtained when the conditions for producing the ferrite powder containing the molten salt and the conditions for sintering are optimized.

&Lt; Example 17 >

Example 10 (made by adding potassium chloride at a weight ratio of 5% with respect to the salt-containing barium ferrite magnetic powder and synthesizing it at a temperature of 800 ° C), was made by molding and sintering (spark plasma sintering) a salt-containing barium ferrite magnetic powder synthesized The magnetic properties were evaluated with a sintered body (salt-containing barium ferrite magnetic body).

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 10 was charged in a mold made of a carbon material, and then heated at a temperature raising rate of 100 ° C per minute at 700 ° C in an Aron atmosphere. The mold having been heated to 700 캜 was maintained at a pressure of 100 MPa for 2 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

51 is a graph showing magnetic property evaluation using a VSM (vibrating sample magnetometer) for the salt-containing barium ferrite magnetic material prepared according to Example 17. Fig.

Referring to FIG. 51, the in plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 57.930 emu / g, a residual magnetization (Mr) of 31.407 emu / (Hc) 4662 Oe, and Mr / Ms was 54.22%.

Out of plane is the result of measurement of the magnetic property in the vertical direction of the disk, and each value is 53.573 emu / g of saturation magnetization (Ms), 33.902 emu / g of remanence magnetization (Mr) Oe, and Mr / Ms was 56.75%.

When Mr / Ms was measured perpendicular to the disk, Mr / Ms was 56.75%, which was slightly higher than that measured horizontally.

52 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 17. Fig.

Referring to FIG. 52, it was confirmed that in Example 10, no crystalline peak for barium ferrite was observed, but a barium ferrite phase was well formed after molding and sintering. It can be considered that the barium ferrite phase was formed due to heat and pressure in the molding and sintering process. In addition, γ-Fe ₂ O ₃ The top was observed in the same manner as in Example 15 and Example 16. [

Figs. 53 and 54 are scanning electron micrographs showing fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 17. Fig.

Referring to Figs. 53 and 54, the shape of the magnetic particle as a whole retains the spherical secondary particle shape, and the melted portion is hard to observe. In the portion where the secondary particles were broken, the primary particles which were not observed in Example 10 were observed at a size of about 100 nm.

&Lt; Example 18 >

Example 10 (sintered body made by molding and sintering (spark plasma sintering) a salt-containing barium ferrite magnetic powder synthesized according to the method of synthesizing at 800 ° C by adding potassium chloride at a weight ratio of 5% to the salt containing barium ferrite magnetic powder Salt-containing barium ferrite magnetic body). The other molding conditions were the same as in Example 17, and the sintering temperature was as high as 800 占 폚.

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 10 was filled in a mold made of a carbon material, and then heated to a temperature of 800 ° C in an argon (Ar) atmosphere at a heating rate of 100 ° C per minute. The mold having been heated to 800 DEG C was maintained at a pressure of 100 MPa for 2 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

FIG. 55 is a graph showing magnetic property evaluation using a vibrating sample magnetometer (VSM) for a salt-containing barium ferrite magnetic material prepared according to Example 18. FIG.

Referring to FIG. 55, the In plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 62.131 emu / g, a residual magnetization (Mr) of 32.747 emu / (Hc) 4803 Oe, and Mr / Ms was 52.71%.

The Out of Plane is the result of measuring the magnetic properties in the vertical direction of the disk. The values are 53.372 emu / g of saturation magnetization (Ms), 32.811 emu / g of residual magnetization (Mr), 4859 of coercive force (Hc) Oe, and Mr / Ms was 61.48%.

The Mr / Ms value was 61.48% higher than that measured horizontally when the value of Mr / Ms was measured perpendicular to the disk. This indicates that the alignment of the barium ferrite particles in the direction of the axis of easy magnetization was perpendicular to the disk It means to be grieved.

56 is an X-ray diffraction graph for the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 18. Fig.

Referring to FIG. 56, in Example 10, no crystalline peak for barium ferrite was observed, but barium ferrite phase was well formed after molding and sintering. It can be considered that the barium ferrite phase was formed due to heat and pressure in the molding and sintering process. Further, by the carbon back-reaction, Fe ₃ O ₄ The top was observed in the same manner as in Examples 15 to 17. [

Figs. 57 and 58 are SEM micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 18. Fig.

Referring to FIGS. 57 and 58, it is considered that the potassium chloride is not completely melted as an intermediate step in which the added potassium chloride is melted and the interface of the particles disappears. It is possible to observe how much melting has occurred in the inside of the fracture section.

&Lt; Example 19 >

Containing barium ferrite magnetic powder synthesized according to Example 13 (when sodium chloride was added at a weight ratio of 5% to the salt-containing barium ferrite magnetic powder and synthesized at an inlet temperature of 250 ° C and an outlet temperature of 850 ° C) was molded and sintered Plasma sintering) to evaluate the magnetic properties of the sintered body (salt-containing barium ferrite magnetic body).

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 13 was filled in a mold made of a carbon material, and then heated at a temperature raising rate of 100 ° C per minute at 800 ° C in an argon (Ar) atmosphere. The molding frame heated to 800 DEG C was maintained at a pressure of 100 MPa for 5 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

FIG. 59 is a graph showing a magnetic property evaluation using a VSM (vibrating sample magnetometer) for a salt-containing barium ferrite magnetic substance prepared according to Example 19. FIG.

Referring to FIG. 59, the In plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 55.384 emu / g, a residual magnetization (Mr) of 28.458 emu / (Hc) 4526 Oe, and Mr / Ms was 51.77%.

The Out of Plane is the result of measuring the magnetic properties in the vertical direction of the disk. The values are 56.751 emu / g of saturation magnetization (Ms), 40.068 emu / g of residual magnetization (Mr), 4558 of coercivity (Hc) Oe, and Mr / Ms was 70.21%.

The value measured perpendicular to the disk was 70.21%, which was higher than that measured horizontally. This means that the easy magnetization axis of barium ferrite is aligned in the direction perpendicular to the disk during molding.

60 is an X-ray diffraction graph of the sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 19. Fig.

Referring to FIG. 60, in Example 13, no crystalline peak for barium ferrite was observed, but it was confirmed that a barium ferrite phase was well formed after molding and sintering. It can be considered that the barium ferrite phase was formed due to heat and pressure in the molding and sintering process.

Figs. 61 and 62 are scanning electron micrographs showing fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 19. Fig.

Referring to Figs. 61 and 62, it is observed that the shape of the original spherical secondary particles as a whole is difficult to find and that the added sodium chloride is well melted. It is believed that the relatively well - melted salt contributed to the alignment of the barium ferrite particles and that the higher degree of alignment can be obtained when the conditions for producing the ferrite powder containing the molten salt and the conditions for sintering are optimized.

&Lt; Example 20 >

Containing barium ferrite magnetic powder synthesized according to Example 14 (when sodium chloride was added at a weight ratio of 3% to the salt-containing barium ferrite magnetic powder and synthesized at an inlet temperature of 250 ° C and an outlet temperature of 850 ° C) was molded and sintered Plasma sintering) to evaluate the magnetic properties of the sintered body (salt-containing barium ferrite magnetic body).

The molding and sintering conditions are as follows. The salt-containing barium ferrite magnetic powder synthesized according to Example 14 was charged in a mold made of a carbon material, and then heated at a temperature raising rate of 100 ° C per minute at 800 ° C in an argon (Ar) atmosphere. The molding frame heated to 800 DEG C was maintained at a pressure of 100 MPa for 5 minutes and then cooled to obtain a sintered body (salt-containing barium ferrite magnetic body). The produced sintered body was a disk type, and the disk height was made to be at least 1/2 of the diameter.

63 is a graph showing magnetic property evaluation using VSM (vibrating sample magnetometer) for the salt-containing barium ferrite magnetic material prepared according to Example 20. Fig.

Referring to FIG. 63, the in plane is a result of measuring the magnetic characteristics in the horizontal direction of the disk, and each value has a saturation magnetization (Ms) of 55.928 emu / g, a residual magnetization (Mr) of 29.289 emu / (Hc) 4319 Oe, and Mr / Ms was 52.37%.

Out of plane is the result of measurement of the magnetic property in the vertical direction of the disk and each value is 58.443 emu / g of saturation magnetization (Ms), 40.319 emu / g of remnant magnetization (Mr) Oe, and Mr / Ms was 68.99%.

For the values measured perpendicular to the disk, the Mr / Ms values were 68.99% higher than those measured horizontally. This means that the easy magnetization axis of barium ferrite is aligned in the direction perpendicular to the disk during molding.

64 is an X-ray diffraction graph for a sintered body (salt-containing barium ferrite magnetic body) prepared according to Example 20. Fig.

Referring to FIG. 64, in Example 14, no crystalline peak for barium ferrite was observed, but it was confirmed that barium ferrite phase was well formed after molding and sintering. It can be considered that the barium ferrite phase was formed due to heat and pressure in the molding and sintering process.

65 and 66 are SEM micrographs showing the fractured sections of the sintered body (salt-containing barium ferrite magnetic body) produced according to Example 19. Fig.

Referring to FIGS. 65 and 66, the melted portion and the non-melted portion appear mixedly, which is presumably due to the low content of molten salt in comparison with Example 19 which is the same sintering condition. Nevertheless, the relatively high Mr / Ms value (68.99%) shows that the higher degree of alignment can be obtained when the ferrite powders containing molten salt are optimized and the sintering conditions are optimized.

A sample in which the phase of ferrite is not completely formed in the process of synthesizing the salt-containing ferrite magnetic powder also shows that the ferrite phase appears and can be applied in the sintering step as in Examples 17 to 20. [

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

10: Ferrite magnetic particles
20: molten salt
30: Ferrite magnetic powder containing salt
40: sintered body
50: Ferrite magnetic particles
60: molten salt

Claims (15)

From 65 to 99.9% by weight of ferrite and from 0.1 to 35% by weight of salt,
Wherein the salt has a melting point lower than the synthesis temperature of the ferrite,
Wherein the salt is melted during sintering to form a matrix between the ferrite particles.
The sintered ferrite sintered body according to claim 1, wherein the salt-containing ferrite sintered magnet body has a structure in which a plurality of ferrites are uniformly dispersed in a salt, and the magnetic powder is a secondary particle having a plurality of primary particles Containing ferrite sintered magnet body.
[Claim 3] The method according to claim 2, wherein the secondary particles are spherical particles having a particle size of 0.1 to 20 mu m or non-spherical particles having a size of 0.1 to 1000 mu m, and the primary particles are particles having a size of 5 to 1000 nm Containing ferrite sintered magnet body.
2. The salt-containing ferrite sintered magnet according to claim 1, wherein the salt-containing ferrite sintered magnet has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of higher than 50%.
The method according to claim 1, wherein the salt is at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt,
The metal chloride salt is at least one salt selected from NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ ,
Wherein the nitrate metal salt is at least one salt selected from NaNO ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ ,
The metal sulfate may be Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ Wherein the sintered ferrite sintered body is at least one selected from the group consisting of iron and iron.
The method according to claim 1, wherein the ferrite is hexagonal ferrite,
The hexagonal ferrite has the form of MF ₁₂ O ₁₉ ,
Wherein the M is at least one element selected from the group consisting of Ba, Sr, Co and La.
The method of claim 1, wherein the ferrite is spinel ferrite,
The spinel ferrite has the form of MF ₂ O ₄ or M ₂ FO ₄ ,
Wherein the M is at least one element selected from the group consisting of Co, Mg, Mn, Zn and Ni.
Preparing a source material of ferrite to be synthesized;
Preparing a salt having a melting point lower than the synthesis temperature of the ferrite to be synthesized;
Mixing the source material of the ferrite with the salt;
Synthesizing a salt-containing ferrite magnetic powder while allowing the salt to melt; And
Containing ferrite magnetic powder is formed into a desired shape and sintered to obtain a salt-containing ferrite sintered magnet body,
Wherein the salt containing ferrite sintered magnet body comprises from 65 to 99.9% by weight of ferrite and from 0.1 to 35% by weight of salt,
Wherein the sintering is performed under a temperature condition in which the salt is melted or a temperature and a pressure condition in which the salt is melted,
Wherein the salt is melted during the sintering to form a matrix between the ferrite particles. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
9. The method according to claim 8, wherein the salt-containing ferrite sintered magnet is a structure in which a plurality of ferrites are uniformly dispersed in a salt,
The ferrite is made of secondary particles, and the magnetic powder
Wherein the primary particles are secondary particles having a plurality of primary particles aggregated together with the salt.
The method according to claim 9, wherein the secondary particles are spherical particles having a particle size of 0.1 to 20 占 퐉 or non-spherical particles having a size of 0.1 to 1000 占 퐉, and the primary particles are particles having a size of 5 to 1000 nm Containing ferrite sintered magnet body.
9. The method for producing a salt-containing ferrite sintered magnet according to claim 8, wherein the salt-containing ferrite sintered magnet has a ratio (Mr / Ms) of residual magnetization (Mr / Ms) to a saturation magnetization (Ms) of higher than 50%.
9. The method according to claim 8, wherein the salt is at least one salt selected from a metal chloride salt, a metal nitrate salt and a metal sulfate salt,
The metal chloride salt is at least one salt selected from NaCl, KCl, LiCl, CaCl ₂ and MgCl ₂ ,
Wherein the nitrate metal salt is at least one salt selected from NaNO ₃ , KNO ₃ , LiNO ₃ , Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ ,
The metal sulfate may be Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , CaSO ₄ and MgSO ₄ Containing ferrite sintered magnet body.
The method of claim 8, wherein the source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4, BaO 2, Sr (NO 3) 2, SrCO 3, SrCl 2, SrSO 4, Sr (OH ) ₂ La (NO ₃ ) ₃ , LaCl ₃ La ₂ (SO ₄ ) ₃ , La (OH) _3, Co (NO ₃ ) ₂ , CoCO ₃ , CoCl ₂ and CoSO ₄ and Fe ₃ ) ₃ , FeCO ₃ , FeCl _3, Fe ₂ O ₃ , FeCl ₂ , and Fe (OH) ₃ ,
Wherein the ferrite is a hexagonal ferrite,
The hexagonal ferrite has the form of MF ₁₂ O ₁₉ ,
Wherein the M is at least one element selected from Ba, Sr, Co and La.
The method of claim 8, wherein the source material of the ferrite is _{Fe (NO 3) 3, FeCO} 3, FeCl 3, Fe 2 O 3, FeCl 2, Fe (OH) 3, Co (NO 3) 2, CoCO 3, CoCl _{2, CoSO 4, Mn (NO} 3) 2, MnCO 3, MnCl 2, MnSO 4, MnO 2, Mg (NO 3) 2, MgCO 3, MgCl 2, MgSO 4, Ni (NO 3) 2, NiCO 3, NiCl ₂ , NiSO ₄ , Zn (NO ₃ ) ₂ , ZnCl ₂ , ZnSO ₄ and ZnO,
Wherein the ferrite is spinel ferrite,
The spinel ferrite has the form of MF ₂ O ₄ or M ₂ FO ₄ ,
Wherein the M is at least one element selected from the group consisting of Co, Mg, Mn, Zn, and Ni.
The method of claim 8, wherein the source material of the ferrite is _{Ba (NO 3) 2, BaCO} 3, BaCl 2, BaSO 4, BaO 2, Sr (NO 3) 2, SrCO 3, SrCl 2, SrSO 4, Sr (OH ) ₂ La (NO ₃ ) ₃ , LaCl ₃ La ₂ (SO ₄ ) _3, La (OH) _3, Co (NO ₃ ) ₂ , CoCO ₃ , CoCl ₂ and CoSO ₄ and Fe ₃ ) ₃ , FeCO ₃ , FeCl _3, Fe ₂ O ₃ , FeCl ₂ and Fe (OH) ₃ ,
The step of synthesizing the salt-containing ferrite magnetic powder includes:
Supplying power to a heating means surrounding a reaction chamber of a spray pyrolyzer and heating the reaction chamber to maintain a constant temperature higher than the melting point of the salt;
Supplying a carrier gas to an atomizer containing a mixture of the source material of the ferrite and the salt;
The mixture contained in the atomizer being vibrated by the ultrasonic vibrator and being generated as droplets in the atomizer; And
Wherein the droplet is introduced into the reaction chamber by the carrier gas, and the droplet introduced into the reaction chamber is pyrolyzed and oxidized to synthesize a salt-containing ferrite sintered magnetic body &Lt; / RTI &gt;

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