KR20050121045A - Barium strontium ferrite particle and the manufacturing method thereof - Google Patents

Abstract

The present invention relates to a barium-strontium-based (MO.6Fe ₂ O ₃ : M = Ba, Sr) ferrite particles and a method for producing the same, comprising at least one of barium and strontium. A molten salt is prepared by melting a chloride including any one or more of barium chloride and strontium chloride or a carbonate including at least one of barium carbonate and strontium carbonate in a mixture including any one or more, and then carbonizing the molten salt again. A carbonate containing at least any one of barium and strontium carbonate and δ-FeOOH were mixed at a predetermined composition ratio, and then thermally calcined to prepare barium-strontium-based ferrite particles.

As a result, barium having a particle size of 10 to 100 nm and a platelet ratio of 6 to 10 suitable as an additive or a coating material as a magnetic material and an electromagnetic wave absorber, a saturation magnetization value of 43 to 56 emu / g and a coercive force value of 3,000 to 4,050 Oe Strontium-based ferrite particles could be produced.

Description

Barium-strontium-based ferrite particles and method for manufacturing the same {BARIUM STRONTIUM FERRITE PARTICLE AND THE MANUFACTURING METHOD THEREOF}

The present invention relates to barium-strontium-based ferrite particles and a method for manufacturing the same. Particularly, barium and strontium ferrite particles have a performance of an electromagnetic wave absorber as a magnetic material, and have a well-dispersed fine particle and plate ratio suitable as an additive or a coating material, and whose particle size is adjustable. It relates to barium-strontium-based ferrite particles containing at least one or more of strontium and a method for producing the same.

Recently, with the development of information and communication devices such as mobile phones and computers, the risk of human health and device malfunction due to the flooding of electromagnetic waves is increasing. In particular, as the high frequency of the operating frequency is rapidly advanced, the use of the GHz band is greatly increased.

In general, in order to absorb such electromagnetic waves, a material having a high energy loss in the frequency band of incident electromagnetic waves is used as an absorber. That is, as the electromagnetic wave absorber for each frequency band, rubber ferrite is used in the wide band, oxide magnetic materials are frequently used in the high frequency band above the MHz band, among which, spinel ferrite is used in the MHz band and hexagonal ferrite in the GHz band. Is mainly used.

Particularly, among the hexagonal ferrites, barium-strontium-based ferrite is a hexagonal oxide magnetic material used for permanent magnets and vertical recording, and has a large internal magnetic field due to uniaxial anisotropy. It is a material that is expected to have high absorption efficiency. The barium-strontium ferrite is MO.6Fe ₂ O ₃ (M = Ba, Sr), which is barium ferrite or barium strontium ferrite or strontium ferrite in which part or all of barium is replaced with strontium. The required particle diameter and shape are changed, and the obtained particle size, particle size, hexagonal plate-like properties, and the like also vary depending on the production method.

Particularly, the finer and more uniform the particles are, the more preferably the powder of barium-strontium-based ferrite is mixed or coated to be used as a recording material or a radio wave absorber. The barium-strontium-based ferrite particles have a hexagonal plate shape so that they can be easily oriented. However, the barium-strontium-based ferrite particles have a platelet diameter of about 10 due to their large diameter and thinness.

Therefore, in order to use this as a mixed addition or coating material, in view of the loss of magnetism in small single crystal particles of 10 nm or less, generally fine particles having a plate diameter of at least 10 nm or more as uniform fine particles having a platelet ratio of 6 to 10. It should be prepared, the particle size should be easy to control, the particles should be well dispersed and no aggregation.

Barium-strontium ferrite powders developed to date include solid phase reaction method, coprecipitation method, glass crystallization method, hydrothermal synthesis method, sol-gel method, molten salt method, and many other manufacturing techniques have been developed. There are not many techniques for producing particulate powder to meet.

The present invention was devised to solve the above problems, and an object of the present invention is to prepare a molten salt containing barium or strontium using a molten salt method, and then heat-treat with δ-FeOOH to produce a magnetic material and electromagnetic wave. The present invention provides barium-strontium-based ferrite particles having a fine particle and platelet ratio of a suitable degree as a mixed addition or coating material to an absorber and capable of controlling particle size, and a method of manufacturing the same.

As a feature of the present invention for achieving the above object, the barium-strontium-based ferrite particles according to the present invention has a particle size of 10 to 100nm and a platelet ratio of 6 to 10, the saturation magnetization value of 43 to 56emu / g And barium-strontium-based ferrite particles including at least one of barium and strontium having a coercive force value of 3,000 to 4,050 Oe.

In addition, as another feature of the present invention, the method for producing barium-strontium-based ferrite particles according to the present invention comprises a first chloride containing at least one of sodium chloride and potassium chloride, and at least one of barium carbonate and strontium carbonate. Preparing a molten salt by mixing and calcining the carbonate containing the mixture; and heat treating the molten salt with a mixture of carbonate and δ-FeOOH again containing at least one of barium carbonate and strontium carbonate. It characterized in that it comprises a step of producing.

In addition, as another feature of the present invention, the method for producing barium-strontium-based ferrite particles according to the present invention comprises a first chloride containing at least one of sodium chloride and potassium chloride, and at least one of barium chloride and strontium chloride. Preparing a molten salt by mixing and calcining a second chloride containing; and heat treating the molten salt with a mixture of carbonate and δ-FeOOH again containing at least one of barium carbonate and strontium carbonate. Characterized in that it comprises a step of producing a particle powder.

In addition, as another feature of the present invention, the molten salt is Na _1-2x Ba _x Cl, (Na _1-y K _y ) _1-2x Ba _x Cl, (Na _1-y K _y ) _1-2x (Ba _x Sr _1-x ) Cl, characterized in that one.

In another aspect of the present invention, the molar ratio of the first chloride to the number of moles of the total reactants is set to 2.

In addition, as another feature of the present invention, the method for producing barium-strontium ferrite particles according to the present invention comprises the steps of preparing a molten salt by calcining sodium chloride or potassium chloride, at least any one of barium carbonate and strontium carbonate And heat-treating the mixture obtained by mixing carbonate and δ-FeOOH containing one or more to prepare ferrite particle powder.

In addition, as another feature of the present invention, the heat treatment is characterized in that baked for 1 to 16 hours at 650 to 1000 ℃.

Hereinafter, the present invention will be described in detail.

In the present invention, barium-strontium-based ferrite powder is manufactured by using a molten salt method, which will be described in detail for each process as follows.

[Preparation of δ-FeOOH Powder]

The δ-FeOOH powder uses known techniques that are commonly used.

As an example, by using the coprecipitation method, Fe (OH) ₂ solution is prepared by _first reacting FeCl ₂ · 4H ₂ O solution 0.1M and NH ₄ OH solution 5M in a 1: 1 weight ratio. In addition, H ₂ O ₂ is injected into the Fe (OH) ₂ solution to prepare a δ-FeOOH suspension, followed by washing with water and drying to prepare the δ-FeOOH powder.

[Production of molten salt]

The preparation of the molten salt can be carried out in two ways first.

As a first method, a chloride containing at least one of sodium chloride and potassium chloride, which is a composition formula of mNaCl + (1-m) KCl (where 0 <m ≦ 1), and xBaCl ₂ + (1-x) SrCl ₂ ( At this time, a chloride containing at least one of barium chloride and strontium chloride having a composition formula of 0 <x≤1) was mixed, filtered and dried, and heat-treated and melted at about 800 ° C for about 2 hours, and then on a copper plate Quench to produce molten salt.

As a second method, a chloride containing at least one of sodium chloride and potassium chloride, which is a composition formula of mNaCl + (1-m) KCl (where 0 <m ≦ 1), and xBaCO ₃ + (1-x) SrCO ₃ ( At this time, the mixture obtained by mixing, filtering and drying the carbonate containing at least one of barium carbonate and strontium carbonate having a composition formula of 0 <x≤1) was heat-treated and melted for about 2 hours at around 800 ° C, which was then copper plated. Quench in a phase to produce molten salt. Both of the above methods have the same result as molten salt, but it is more convenient to use barium carbonate and strontium carbonate.

[Production of Barium-Strontium Ferrite Particle Powder]

In the molten salt prepared as described above, a carbonate comprising at least one of barium carbonate and strontium carbonate, which is a composition formula of xBaCO ₃ + (1-x) SrCO ₃ (where 0 <x ≦ 1), The prepared δ-FeOOH was mixed and ground again at a predetermined composition ratio, filtered and dried. Then, it is calcined by heat treatment for 1 to 16 hours in a temperature range of 650 to 1000 ℃, and then quenched on a copper plate. Then, the final barium-strontium-based ferrite powder is prepared by washing with water, filtration and drying.

In this case, the barium-strontium-based ferrite powder, barium-strontium ferrite powder, barium-strontium ferrite powder, etc. may be prepared by adjusting the amount (x) of Ba substituted with Sr in all the above processes. Will be.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in more detail. However, the examples described below are provided to help the overall understanding of the present invention, and the present invention is not limited only to the following examples.

Example 1

In Example 1, barium ferrite powder was prepared using Na _{1-2 ×} Ba _× Cl molten salt.

First, Na _1-2x Ba _x Cl molten salt was prepared by mixing NaCl and BaCO ₃ . At this time, the molar ratio of NaCl was fixed to 2 relative to the number of moles of the total reactants.

That is, a NaCl solution with m = 1 in composition mNaCl + (1-m) KCl was used as a solvent, and BaCO ₃ with x = 1 in xBaCO ₃ + (1-x) SrCO ₃ was used as a wet ball mill in an alcohol medium. Mix and filter and dry to 60 ° C. Then, the dried powder was calcined at 800 ° C. for 2 hours, and then quenched on a copper plate to prepare a Na _{1-2 ×} Ba _× Cl molten salt.

And Na _1-2x Ba _x Cl molten salt prepared as described above, BaCO ₃ in which x = 1 in xBaCO ₃ + (1-x) SrCO ₃ , and δ-FeOOH prepared separately by coprecipitation method, respectively. After compounding at a predetermined composition ratio, the mixture was ground and filtered for 12 hours with a wet ball mill of methyl alcohol medium and dried in a 60 ° C. drying furnace. At this time, the molar ratio of δ-FeOOH and BaCO ₃ was 12: 1.

The dried mixture was heated in an electric furnace at a rate of 5 ° C./min, calcined while varying the heat treatment firing time for 1 to 16 hours at a temperature range of 650 to 1000 ° C. at 50 ° C., and then quenched on a copper plate. The quenched reaction product was washed with hot water until no chlorine ions (Cl ⁻ ) were detected, and then filtered and dried to prepare a particle powder of the final barium ferrite.

Example 2

Although the second embodiment in the same manner as in Example 1 using Na _1-2x BaxCl molten salt producing a barium ferrite powder, in Example 1, in contrast it was used as BaCl _2, BaCO ₃ in place of molten salt produced, the remainder Same as Example 1.

First, a NaCl solution having m = 1 in the composition formula mNaCl + (1-m) KCl was used as a solvent, and BaCl ₂ was mixed and filtered with a wet ball mill of an alcohol medium and dried at 60 ° C. Then, the dried powder was calcined at 800 ° C. for 2 hours, and then quenched on a copper plate to prepare a Na _{1-2 ×} Ba _× Cl molten salt.

Then, BaCO ₃ having x = 1 in xBaCO ₃ + (1-x) SrCO ₃ and x-FeOOH prepared separately by coprecipitation in a Na _1-2x Ba _x Cl molten salt at a predetermined composition ratio. After blending, the mixture was ground and filtered for 12 hours with a wet ball mill of methyl alcohol medium and dried in a 60 ° C. drying furnace. At this time, the molar ratio of δ-FeOOH to (BaCO ₃ + BaCl ₂ ) was set to 12: 1. The dried mixture was heated in an electric furnace at a rate of 5 ° C./min, calcined while varying the heat treatment firing time for 1 to 16 hours at a temperature range of 650 to 1000 ° C. at a temperature of 50 ° C., and then quenched on a copper plate. The quenched reaction product was washed with hot water until no chlorine ions were detected, and then filtered and dried to prepare a particle powder of the final barium ferrite.

Example 3

In Example 3, barium ferrite powder was prepared using a (Na _1-y K _y ) _1-2x Ba _x Cl molten salt.

That is, in the composition formula mNaCl + (1-m) KCl, a mixture of NaCl and KCl was used as a solvent in a range of 0 <m <1, and x = 1 in xBaCO ₃ + (1-x) SrCO ₃ . BaCO ₃ was mixed, filtered, dried and calcined in the same manner as in Example 1 to prepare a (Na _1-y K _y ) _1-2x Ba _x Cl molten salt. Then, the molten salt was mixed with barium carbonate and δ-FeOOH in which x = 1 in xBaCO ₃ + (1-x) SrCO ₃ at a predetermined molar ratio and calcined in the same manner as in Example 1 to obtain the final barium ferrite. Powder was prepared.

Example 4

In Example 4, barium strontium ferrite powder was prepared using NaCl solution as a solvent.

That is, a molten salt was prepared in the same manner as in Example 1 from a mixture of barium carbonate and strontium carbonate having a range of 0 <x <1 in xBaCO ₃ + (1-x) SrCO ₃ and a solution of NaCl as a solvent. It was. And, in the molten salt, again as that of Example 1, similarly xBaCO ₃ + (1-x) in the SrCO ₃ 0 <x <1, respectively a mixture of carbonated water and, δ-FeOOH of barium carbonate and strontium carbonate in the range of Mixed and calcined to produce a predetermined barium strontium ferrite particle powder.

Example 5

In Example 5, barium strontium ferrite powder was prepared using a mixture of NaCl and KCl as a solvent.

That is, a mixture of NaCl and KCl is used as a solvent in the composition formula mNaCl + (1-m) KCl in the range of 0 <m <1, and in the range of 0 <x <1 in xBaCO ₃ + (1-x) SrCO ₃ . To prepare a molten salt in the same manner as in Example 1 using a mixture of barium carbonate and strontium carbonate, and heat treatment and baking the δ-FeOOH and the molten salt in the same manner as in Example 1 to synthesize a predetermined barium strontium ferrite powder It was.

Example 6

In Example 6, barium ferrite powder was prepared using NaCl solution as a solvent.

That is, only NaCl was heat-treated to melt molten salt as in Example 1, and then BaCO ₃ and δ-FeOOH were mixed with the molten salt and calcined by heat treatment in the same manner as in Example 1 to prepare barium ferrite particle powder.

Figure 1 shows an electron micrograph of barium ferrite prepared using (Na _1-y K _y ) _1-2x Ba _x Cl molten salt.

In the present invention, after firing the barium ferrite powder by the sequence reaction at a temperature increase rate of 5 ° C./min, the nuclear growth is induced by uniform nucleation, and thus the particle size of the particles can be obtained with a relatively even distribution in the range of 10 to 100 nm. there was. In addition, the produced barium strontium ferrite was confirmed that the plate-shaped diameter is about 200nm, the dispersion is good hexagonal plate shape of about 30nm, the platelet ratio was within the range of 6-10.

Table 1 shows the maximum magnetic properties of the barium strontium-based ferrite powder prepared according to each example.

TABLE 1

Molten salt Na _1-2x Ba _x Cl (Example 1) (Na _1-y K _y ) _1-2x Ba _x Cl (Example 3) (Na _1-y K _y ) _1-2x (Ba _x Sr _1-x ) Cl (Example 5) NaCl (Example 6) Firing temperature (℃) 800 750 730 950 Saturation magnetization M _s (emu / g) 44 45 43 56 Coercivity MH _c (Oe) 4,050 3,500 3,000 3,000

In this case, the calcination temperature indicates the calcination temperature when the maximum magnetic characteristic value is shown in various calcination temperature ranges, and is made of (Na _1-y K _y ) _1-2x (Ba _x Sr _1-x ) Cl molten salt. In the case of powder (Example 5), the firing temperature was the lowest. In addition, the magnetic properties of the barium-strontium-based ferrite according to the type of molten salt used in each example are generally similar, but in the case of the saturation magnetization value Ms, the powder made of NaCl molten salt (Example 6) had the highest value. It showed, the coercive force values for MHc is a powder prepared in the Na _1-2x Ba _x Cl molten salt (example 1) showed the highest value.

As described above, in the present invention, a well-dispersed barium-strontium-based ferrite fine particle powder having excellent magnetic properties as a material of the magnetic body and the electromagnetic wave absorber and having a fine particle size of 10 to 100 nm and a platelet ratio of 6 to 10 was obtained. .

As described above, according to the present invention using the molten salt method NaCl, KCl, Na _1-2x Ba _x Cl, (Na _1-y K _y ) _1-2x Ba _x Cl, (Na _1-y K _y ) Barium-strontium-based ferrite particles can be produced by mixing and calcining a molten salt such as _1-2x (Ba _x Sr _1-x ) Cl, a carbonate such as barium carbonate and strontium carbonate, and δ-FeOOH.

The powder produced by the present invention has an even distribution of fine particles and a plate ratio suitable as a mixed addition or coating material, is well dispersed, and the size of the particles can be controlled by controlling the firing time.

In addition, a preferred embodiment of the present invention is disclosed for the purpose of illustration, those skilled in the art will be able to various modifications, changes, additions, etc. within the spirit and scope of the present invention, these modifications, changes, etc. should be seen as belonging to the claims. do.

Figure 1 is an electron micrograph of barium ferrite prepared using (Na _1-y K _y ) _1-2x Ba _x Cl molten salt.

Claims (7)

At least one of barium and strontium having a particle size of 10 to 100 nm and a platelet ratio of 6 to 10, and having a saturation magnetization value of 43 to 56 emu / g and a coercive force value of 3,000 to 4,050 Oe. Barium-strontium-based ferrite particles. Preparing a molten salt by mixing and firing a first chloride comprising at least one of sodium chloride and potassium chloride, and a carbonate comprising at least one of barium carbonate and strontium carbonate; At least any one of barium and strontium, wherein the molten salt comprises a step of heat-treating a mixture of at least one of barium carbonate and strontium carbonate and a mixture of δ-FeOOH again to produce ferrite particle powder. Barium-strontium-based ferrite particles comprising at least one method. Preparing a molten salt by mixing and calcining a first chloride comprising at least one of sodium chloride and potassium chloride with a second chloride comprising at least one of barium chloride and strontium chloride; At least any one of barium and strontium, wherein the molten salt comprises a step of heat-treating a mixture of at least one of barium carbonate and strontium carbonate and a mixture of δ-FeOOH again to produce ferrite particle powder. Barium-strontium-based ferrite particles comprising at least one method. The method of claim 2 or 3, wherein the molten salt is Na _1-2x Ba _x Cl, (Na _1-y K _y ) _1-2x Ba _x Cl, (Na _1-y K _y ) _1-2x (Ba _A method for producing barium-strontium-based ferrite particles comprising at least one of barium and strontium, characterized in that any one of _x Sr _1-x ) Cl. The method for producing barium-strontium-based ferrite particles according to claim 2 or 3, wherein the molar ratio of the first chloride to the number of moles of the total reactants is 2. . Calcining sodium chloride or potassium chloride to produce a molten salt; Heat-treating a mixture of δ-FeOOH and carbonate containing at least one of barium carbonate and strontium carbonate to the molten salt to produce a ferrite particle powder. Barium-strontium-based ferrite particles comprising at least any one or more. The barium comprising at least one of barium and strontium according to any one of claims 2, 3 and 6, wherein the heat treatment is fired at 650 to 1000 ° C for 1 to 16 hours. Method for producing strontium ferrite particles.