JP2006237548A - Mg-CONTAINING OXIDE FILM COATED IRON POWDER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide coated Fe powder for use to produce various electromagnetic circuit components requiring high specific resistance. <P>SOLUTION: There is provided an Mg-containing oxide coated iron (Fe) powder comprising an iron powder having its surface coated with an Mg-Fe-O ternary oxide deposition film containing at least (Mg, Fe)O, wherein the (Mg, Fe)O is a crystalline wustite having MgO solid dissolved therein, and wherein the Mg-Fe-O ternary oxide deposition film in a region of interface with iron powder has a sulfur enriched layer containing sulfur in a concentration higher than in the center region of the iron powder, further having a microcrystalline structure of 200 nm or less in crystal grain diameter, the outermost surface of which consists essentially of MgO. Furthermore, there is provided a composite soft magnetic material making use of the Mg-containing oxide coated iron (Fe) powder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an Mg-containing oxide film-coated iron powder in which an Mg—Fe—O ternary oxide deposition film containing at least (Mg, Fe) O is formed on the surface of the iron powder. The composite soft magnetic material made of film-coated iron powder is used as a material for various electromagnetic circuit components that require low iron loss, for example, various electromagnetic components such as motors, actuators, yokes, cores, and reactors.

  In general, soft magnetic materials used in various electromagnetic circuit components are required to have low iron loss. Therefore, electrical resistance is increased to reduce eddy current loss, and coercive force is reduced to reduce hysteresis loss. That is generally known. Furthermore, in recent years, since the miniaturization and high response of the electromagnetic circuit have been demanded, higher magnetic flux density is also regarded as important.

As an example of a raw material powder for producing such a soft magnetic material having a high specific resistance, a film known as Mg-containing ferrite ((MgFe) ₃ O ₄ ) and having a spinel crystal structure) is formed on the surface of iron powder. A coated Mg-containing oxide film-coated iron powder is known (see Patent Document 1).
Japanese Patent Laid-Open No. 11-1702

  However, conventional iron powder coated with Mg-containing oxide film coated with Mg-containing ferrite film is high-temperature strain-removed and fired on pressed green compact to coat Mg-containing ferrite film on the surface of iron powder by chemical method. In the composite soft magnetic material obtained by performing the above, the ferrite film becomes unstable and changes to lower the insulation, and the adhesion of the Mg-containing ferrite film to the surface of the iron powder is not sufficient. The composite soft magnetic material produced by press-molding and firing Mg-containing oxide film-coated iron powder coated with a film cannot exhibit sufficient insulation effect due to peeling or tearing of the Mg-containing ferrite film during press molding Therefore, there is a drawback that a sufficiently high specific resistance cannot be obtained.

Therefore, the present inventors are an iron powder in which the high resistance oxide film on the surface of the iron powder is not broken during the press molding, and the oxide film is firmly adhered to the surface during the press molding. Mg-containing oxide film with low resistance and low eddy current loss without reducing surface insulation even when baked, and reduced coercive force and reduced hysteresis loss when baked with strain relief annealing Research was carried out to produce coated iron powder. As a result, the iron powder was heated in an oxidizing atmosphere in advance to produce an iron powder in which an iron oxide film was formed on the surface of the iron powder (hereinafter referred to as oxidized iron powder), and Mg powder was added to the oxidized iron powder. After heating the mixed powder obtained by adding and mixing in an inert gas atmosphere or a vacuum atmosphere, and further performing an oxidation treatment after heating in an oxidizing atmosphere,
(B) Various Mg-Fe-O ternary systems such as (Mg, Fe) O, (Mg, Fe) ₃ O _{4 and the} like represented by the generally known MgO-FeO-Fe ₂ O ₃ systems Among the oxides, an Mg—Fe—O ternary oxide deposition film containing at least (Mg, Fe) O is formed on the surface of the iron powder, and this Mg—Fe— containing at least (Mg, Fe) O is formed. The Mg-containing oxide film-coated iron powder in which the O ternary oxide deposited film is coated on the surface of the iron powder is compared with the Mg-containing oxide film-coated iron powder in which the Mg-containing ferrite film is formed on the surface of the conventional iron powder. Since the adhesion of the oxide film to the iron powder is remarkably excellent, the oxide film, which is an insulating film, is hardly broken during press molding, and the iron powder is less likely to come into contact with each other. Maintains high resistance without degrading oxide insulation Therefore, the eddy current loss is reduced, and when the strain relief firing is performed, the coercive force can be further reduced, so that the hysteresis loss can be suppressed low. Therefore, a composite soft magnetic material having a low iron loss can be obtained. To obtain,
(B) (Mg, Fe) O contained in the Mg—Fe—O ternary oxide deposited film of the Mg-containing oxide film-coated iron powder is crystalline MgO solid solution wustite (MgO becomes wustite (FeO)). It is more preferable that the substance is a solid solution),
(C) In the interface region between the iron powder and the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O, sulfur contained as an inevitable impurity in the center of the iron powder A sulfur-enriched layer containing a high concentration of sulfur is formed,
(D) the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O has a fine crystal structure with a crystal grain size of 200 nm or less;
(E) The Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O formed on the surface of the iron powder is preferably as the amount of MgO contained in the outermost surface is larger, It has been found that it is most preferable that the outermost surface is substantially composed of MgO.

This invention is made based on such knowledge,
(1) An Mg-containing oxide film-coated iron powder in which an Mg-Fe-O ternary oxide deposition film containing at least (Mg, Fe) O is coated on the surface of the iron powder;
(2) (Mg, Fe) O contained in the Mg—Fe—O ternary oxide deposited film of the Mg-containing oxide film-coated iron powder is crystalline MgO solid solution wustite according to (1) above Mg-containing oxide film-coated iron powder,
(3) The Mg-containing oxide film-coated iron powder is formed in an interface region between the iron powder and the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O at the center of the iron powder. The Mg-containing oxide film-coated iron powder according to the above (1) or (2), which has a sulfur-concentrated layer containing a higher concentration of sulfur than the contained sulfur
(4) The Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O has a fine crystal structure with a crystal grain size of 200 nm or less (1), (2) or (3 Mg-containing oxide film-coated iron powder according to
(5) The Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O has the outermost surface substantially composed of MgO (1), (2), ( It is characterized by the Mg-containing oxide film-coated iron powder according to 3) or (4).

The Mg-containing oxide film-coated iron powder according to (1) to (4) of the present invention is an oxidized iron powder in which an iron oxide film is formed on the surface of the iron powder by heating the iron powder in an oxidizing atmosphere in advance. The mixed powder obtained by adding and mixing Mg powder to this oxidized iron powder is heated in an inert gas atmosphere or vacuum atmosphere, and then heated in an oxidizing atmosphere, followed by oxidation treatment. Although it has already been described that it can be produced by application, more specifically, iron powder is heated on an oxidizing atmosphere in advance in an oxidizing atmosphere at a temperature of 50 to 500 ° C. to oxidize the iron powder on the surface of the iron powder. An oxidized iron powder having a film formed thereon was prepared, and mixed powder obtained by adding and mixing Mg powder to this oxidized iron powder was temperature: 150 to 1100 ° C., pressure: 1 × 10 ⁻¹² to 1 × 10. ^-1 MPa of inert After heating in a scan atmosphere or vacuum atmosphere, further oxidizing atmosphere, temperature: 50 to 350 produced by the oxidation process is subjected after heating at ° C..

The Mg—Fe—O ternary oxide deposited film containing the MgO solid solution wustite phase, the outermost surface of which is substantially composed of MgO according to (5) of the present invention, the iron powder in an oxidizing atmosphere in advance, Temperature: An oxidized iron powder having an iron oxide film formed on the surface of the iron powder is prepared by heating to 50 to 500 ° C., and adding more Mg powder to the oxidized iron powder and mixing. The obtained mixed powder was heated in an inert gas atmosphere or vacuum atmosphere at a temperature of 150 to 1100 ° C. and a pressure of 1 × 10 ⁻¹² to 1 × 10 ⁻¹ MPa, and then further in an oxidizing atmosphere for a longer time. It is obtained by subjecting it to an oxidation treatment after heating.

The Mg—Fe—O ternary oxide deposited film formed on the surface of the iron powder of the present invention contains at least (Mg, Fe) O. (Mg, Fe) O contained in the Mg—Fe—O ternary oxide deposited film is more preferably a crystalline MgO solid solution wustite phase. Most preferably, the outermost surface of the deposited film containing at least (Mg, Fe) O is made of MgO. In addition to (Mg, Fe): O = 1: 1, O may have a solid solution width.
The term “deposited film” usually indicates a film in which atoms constituting the film formed by vacuum evaporation or sputtering are deposited on, for example, a substrate, but at least (Mg, Fe) O formed on the surface of the iron powder of the present invention. The Mg—Fe—O ternary oxide deposited film containing iron is a film in which iron oxide (Fe—O) and Mg on the surface of oxidized iron powder are deposited on the iron powder surface with a reaction. The film thickness of the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O formed on the surface of the iron powder is equal to the high magnetic flux density of the compacted composite soft magnetic material. In order to obtain a high specific resistance, it is preferably in the range of 5 nm to 500 nm. If the film thickness is less than 5 nm, the specific resistance of the powder-molded composite soft magnetic material is not sufficient and the eddy current loss increases. On the other hand, if the film thickness is thicker than 500 nm, it is not preferable. This is because the magnetic flux density is lowered, which is not preferable. A more preferable film thickness is in the range of 5 nm to 200 nm.

The Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O constituting the Mg-containing oxide film-coated iron powder of the present invention is composed of the Mg—Fe containing at least (Mg, Fe) O. In the interface region between the -O ternary oxide deposited film and the iron powder, a sulfur-enriched layer containing a higher concentration of sulfur than the sulfur contained in the central portion of the iron powder is provided. Having this sulfur-concentrated layer can be confirmed from the fact that the sulfur concentration is measured by Auger electron spectroscopy, and this is shown in a graph, showing a sulfur concentration peak. By having such a sulfur-concentrated layer in the interface region, the adhesion of the Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O to the iron powder surface becomes even better. The deposited film can follow the deformation of the powder at the time of compacting to prevent the coating from being torn, the contact bonding between the iron powders can be prevented even during firing, and high resistance can be maintained, Therefore, eddy current loss is reduced. The sulfur in the sulfur-concentrated layer is considered to be supplied from sulfur contained in the surface portion of the iron powder because the iron powder contains sulfur as an unavoidable impurity.

The Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O formed on the surface of the iron powder of the present invention is preferably as the crystal grains are finer, and the crystal grain size is It is preferable to have a fine crystal structure of 200 nm or less. By having such a fine crystal structure, the microcrystalline Mg—Fe—O ternary oxide deposited film can follow the deformation of the powder during compacting and prevent the coating from being broken. In addition, contact bonding between iron powders can be prevented, and even when high-temperature strain relief firing is performed, the oxide is stable and insulation deterioration can be prevented, and eddy current loss is reduced with high resistance. If the crystal grain size is larger than 200 nm, the Mg—Fe—O ternary oxide deposited film becomes thicker than 500 nm, and the magnetic flux density of the compacted composite soft magnetic material is lowered.
Further, the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O constituting the Mg-containing oxide film-coated iron powder of the present invention has a higher content of MgO on its outermost surface. Preferably, it is most preferably composed of MgO. When the outermost surface is substantially MgO, the diffusion of Fe is prevented even during firing of the green compact that has been press-molded, and contact bonding between iron powders can be prevented. This is because loss is reduced.
The Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O constituting the Mg-containing oxide film-coated iron powder of the present invention is a Mg-Fe-O ternary oxide deposited film containing 10% or less of Mg with respect to Mg. A pseudo ternary oxide deposited film substituted with one or more of Al, Si, Ni, Mn, Zn, Cu, and Co may be used.

As the Mg-containing oxide film-coated iron powder of the present invention, it is preferable to use a powder having an average particle size in the range of 5 to 500 μm. The reason is that if the average particle size is less than 5 μm, the compressibility of the powder is lowered, and the volume ratio of the powder is lowered, so the value of the magnetic flux density is lowered. On the other hand, the average particle size is less than 500 μm. If it is too large, the eddy current inside the powder increases and the magnetic permeability at high frequency decreases.

Next, a method for producing a composite soft magnetic material using the Mg-containing oxide film-coated iron powder of the present invention will be described.
The Mg-containing oxide film-coated iron powder of the present invention can be produced by compacting and firing by an ordinary method.
A composite soft magnetic material having a high specific resistance produced by using the Mg-containing oxide film-coated iron powder of the present invention comprises an iron particle phase and a grain boundary phase surrounding the iron particle phase, and the grain boundary phase includes crystals. It is preferable to include a Mg—Fe—O ternary oxide containing a high-quality MgO solid solution wustite phase.
In addition, 0.05 to 1% by mass of one or two of silicon oxide and aluminum oxide having an average particle size of 0.5 μm or less is contained, and the balance is composed of the Mg-containing oxide film-coated iron powder of the present invention. The mixed powder can be prepared by mixing and mixing as described above, and the mixed powder can be compacted and fired by a conventional method. According to this manufacturing method, the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O constituting the Mg-containing oxide film-coated iron powder of the present invention reacts with silicon oxide or aluminum oxide. A composite soft magnetic material having a high specific resistance in which a composite oxide is formed and a composite oxide having a high resistance intervenes in the grain boundary of iron powder is obtained, and is fired through silicon oxide or aluminum oxide. A composite soft magnetic material having excellent mechanical strength can be produced. In this case, the coercive force can be kept small from being fired mainly with silicon oxide or aluminum oxide, and thus a composite soft magnetic material with low hysteresis loss can be produced. It is preferably performed at a temperature of 400 to 1300 ° C. in a gas atmosphere or an oxidizing gas atmosphere.
In addition, a wet solution such as a silica sol-gel (silicate) solution or an alumina sol-gel solution is added to the Mg-containing oxide film-coated iron powder of the present invention, and the mixture is dried, and the dried mixture is compression-molded and then inert gas. A composite soft magnetic material can be produced by firing at a temperature of 400 to 1300 ° C. in an atmosphere or an oxidizing gas atmosphere. A composite soft magnetic material having a high specific resistance produced using these Mg-containing oxide film-coated iron powders of the present invention comprises an iron particle phase and a grain boundary phase surrounding the iron particle phase. Preferably contains a Mg—Fe—O ternary oxide containing a crystalline MgO solid solution wustite phase.

Furthermore, when the Mg-containing oxide film-coated iron powder of the present invention is mixed with an organic insulating material, an inorganic insulating material, or a mixed material of an organic insulating material and an inorganic insulating material, and molded and fired, a composite having further improved specific resistance and strength A soft magnetic material can be produced. In this case, as the organic insulating material, epoxy resin, fluorine resin, phenol resin, urethane resin, silicone resin, polyester resin, phenoxy resin, urea resin, isocyanate resin, acrylic resin, polyimide resin, or the like can be used. As the inorganic insulating material, phosphates such as iron phosphate, various glassy insulators, water glass mainly composed of sodium silicate, insulating oxides, and the like can be used.
In addition, one or more of boron oxide, vanadium oxide, bismuth oxide, antimony oxide, and molybdenum oxide are added to the Mg-containing oxide film-coated iron powder of the present invention as B ₂ O ₃ , V ₂ O ₅ , Bi _{2. O 3, Sb 2 O 3,} MoO 3 powder was molded were mixed by blending 0.05 mass% in terms of the resulting powder compact temperature composite by calcining at 500 to 1000 ° C. A soft magnetic material can be produced. The composite soft magnetic material produced in this way is composed of one or more of boron oxide, vanadium oxide, bismuth oxide, antimony oxide and molybdenum oxide, B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O _3. , Sb ₂ O ₃ , MgO _{3 in} terms of MoO ₃ , 0.05 to 1% by mass, with the balance being composed of the Mg-containing oxide film-coated iron powder of the present invention, Mg containing at least (Mg, Fe) O A film is formed in which the —Fe—O ternary oxide deposited film reacts with one or more of boron oxide, vanadium oxide, bismuth oxide, antimony oxide, and molybdenum oxide.
Further, this composite soft magnetic material is composed of a boron oxide sol solution or powder, a vanadium oxide sol solution or powder, a bismuth oxide sol solution or powder, an antimony oxide sol solution or powder, and a molybdenum oxide sol solution or powder. 1 to 2 or more of B ₂ O ₃ , V ₂ O ₅ , Bi ₂ O ₃ , Sb ₂ O ₃ , MoO _{3 in} terms of 0.05 to 1% by mass, and the balance being the Mg-containing oxide film of the present invention A mixed oxide formed by mixing, drying, and coating the Mg-containing oxide film-coated iron powder of the present invention with an oxide-dried gel or a mixed oxide composed of a powder so as to have a composition composed of a coated iron powder It can be obtained by preparing a coated iron powder, compacting and molding the mixed oxide-coated iron powder, followed by firing at a temperature of 500 to 1000 ° C. A composite soft magnetic material having a high specific resistance produced using these Mg-containing oxide film-coated iron powders of the present invention comprises an iron particle phase and a grain boundary phase surrounding the iron particle phase. Preferably contains a Mg—Fe—O ternary oxide containing a crystalline MgO solid solution wustite phase.

The composite soft magnetic material produced using the Mg-containing oxide film-coated iron powder of the present invention has high density, high strength, high specific resistance and high magnetic flux density. This composite soft magnetic material has high magnetic flux density and low frequency. Since it has the feature of iron loss, it can be used as a material for various electromagnetic circuit components that take advantage of this feature. Examples of the electromagnetic circuit component include a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor, a transformer, a choke coil core, and a magnetic sensor core. In addition, an electric device incorporating an electromagnetic circuit component made of a composite soft magnetic material having high resistance using the Mg-containing oxide film-coated iron powder of the present invention includes an electric motor, a generator, a solenoid, an injector, an electromagnetically driven valve, an inverter There are converters, transformers, relays, magnetic sensor systems, etc., which can improve the efficiency, performance, size and weight of electrical equipment.

  When a composite soft magnetic material is manufactured using the Mg-containing oxide film-coated iron powder of this invention, it has a low specific eddy current loss because of its high specific resistance, and a low hysteresis loss because of its low coercive force. A soft magnetic material can be produced stably at a low cost, and has an excellent effect in the electrical and electronic industries.

Example 1
A pure iron powder having an average particle size of 70 μm and containing an extremely small amount of sulfur as an inevitable impurity was prepared as a raw material powder, and an Mg powder having an average particle size of 50 μm was prepared. The pure iron powder was oxidized in the atmosphere at a temperature of 220 ° C. for 2 hours to prepare an oxidized iron powder having an iron oxide film on the surface. To this oxidized iron powder, the previously prepared Mg powder was added at a ratio of oxidized iron powder: Mg powder = 99.8 mass%: 0.2 mass% to prepare a mixed powder. The mixed powder was kept at a temperature of 650 ° C. and a pressure of 2.7 × 10 ⁻⁴ MPa for 1 hour, and further held in the atmosphere at a temperature of 200 ° C. for 1 hour to cover the surface of the iron powder with a deposited film. The present invention Mg-containing oxide film-coated iron powder 1 was produced. The structure of the deposited film formed on the Mg-containing oxide film-coated iron powder 1 of the present invention was observed with an electron microscope, the thickness of the deposited film and the maximum crystal grain size were determined, and the results are shown in Table 1. Further, it was found from the electron diffraction pattern obtained from the deposited film of the Mg-containing oxide film-coated iron powder 1 of the present invention that the crystalline MgO solid solution wustite phase was contained.

  The deposited film formed on the surface of the Mg-containing oxide film-coated iron powder 1 of the present invention was analyzed by an X-ray photoelectron spectrometer, and the binding energy was analyzed. As a result, Mg containing at least (Mg, Fe) O was contained. It was found to be a —Fe—O ternary oxide deposited film. Furthermore, the graph of FIG. 1 shows the results of examining the interface region between the iron powder and the Mg—Fe—O ternary oxide deposited film by a method using an Auger electron spectrometer. In the graph of FIG. 1, the vertical axis represents the peak intensity of Auger electrons, while the horizontal axis represents the etching time of the coating deposited film, and the longer the etching time, the deeper the position of the coating deposited film. In the graph of sulfur concentration detected by Auger electron spectroscopy in FIG. 1, a sulfur concentration peak is shown. In this graph, in the interface region between the deposited film and the iron powder with an etching time of about 10 to 15 minutes, It contains sulfur at a higher concentration than the sulfur contained in the center of iron powder because sulfur is detected with a peak by Auger electron spectroscopy rather than the impurity sulfur (background) contained in the center of iron powder. It was found to have a sulfur enriched layer.

Example 2
The oxidized iron powder having an iron oxide film on the surface was produced by oxidizing the pure iron powder prepared in Example 1 in the atmosphere at a temperature of 210 ° C. for 3 hours. To this oxidized iron powder, the previously prepared Mg powder was added and mixed at a ratio of oxidized iron powder: Mg powder = 99.5 mass%: 0.5 mass% so as to be larger than in Example 1. The powder was prepared, and the obtained mixed powder was maintained at a temperature of 670 ° C., a pressure of 1 × 10 ⁻⁵ MPa for 1 hour, and further held in the atmosphere at a temperature of 200 ° C. for 1 hour, thereby the surface of the iron powder. The Mg-containing oxide film-coated iron powder 2 of the present invention coated with a deposited film was prepared. The structure of the deposited film of the Mg-containing oxide film-coated iron powder 2 of the present invention was observed with an electron microscope, the thickness of the deposited film and the maximum crystal grain size were determined, and the results are shown in Table 1. Further, it was found from the electron diffraction pattern obtained from the deposited film that it contained a crystalline MgO solid solution wustite phase.
Furthermore, when the deposited film formed on the surface of the Mg-containing oxide film-coated iron powder 2 of the present invention was analyzed by an X-ray photoelectron spectrometer and the binding energy was analyzed, this deposited film was at least (Mg, Fe) O. It was found that the Mg—Fe—O ternary oxide deposited film containing Mg and the outermost surface of the Mg—Fe—O ternary oxide deposited film are composed of MgO. Further, when the concentration distribution of Mg, O and Fe was examined by a method using an Auger electron spectrometer in the same manner as in Example 1, it was found in the interface region between the iron powder and the Mg—Fe—O ternary oxide deposited film. It was found to have a sulfur enriched layer containing a higher concentration of sulfur than the sulfur contained in the center of the iron powder.

Example 3
The pure iron powder prepared in Example 1 was oxidized in the atmosphere at a temperature of 220 ° C. and maintained for 1.5 hours to prepare an oxidized iron powder having an iron oxide film on the surface. To this oxidized iron powder, the previously prepared Mg powder was added and mixed at a ratio of oxidized iron powder: Mg powder = 99.7 mass%: 0.3 mass% so as to be larger than in Example 1. A powder was prepared, and the obtained mixed powder was maintained at a temperature of 640 ° C. and a pressure of 1 × 10 ⁻⁴ MPa for 1 hour, and then further maintained in the atmosphere at a temperature of 200 ° C. for 1.5 hours. The Mg-containing oxide film-coated iron powder 3 of the present invention having a deposited film coated on its surface was prepared. The structure of the deposited film was observed with an electron microscope, and the thickness and maximum crystal grain size are shown in Table 1.
The deposited film formed on the surface of the Mg-containing oxide film-coated iron powder 3 of the present invention was analyzed by an X-ray photoelectron spectrometer, and the binding energy was analyzed. As a result, Mg—Fe— containing at least (Mg, Fe) O was obtained. It was found that it was an O ternary oxide deposited film, and that the outermost surface of this Mg—Fe—O ternary oxide deposited film was composed of MgO. Furthermore, when the Mg, O, and Fe concentration distribution of this Mg—Fe—O ternary oxide deposited film was examined by the same method as in Example 1 using an Auger electron spectrometer, the iron particles and Mg—Fe— It was found that a sulfur-concentrated layer containing sulfur having a higher concentration than sulfur contained in the central portion of the iron powder was present in the interface region with the O ternary oxide deposited film.

  The Mg-containing oxide film-coated iron powders 1 to 3 of the present invention obtained in Examples 1 to 3 are placed in a mold and pressed to form a plate-like pressure having dimensions of 55 mm in length, 10 mm in width, and 5 mm in thickness. Powder and outer diameter: 35 mm, inner diameter: 25 mm, height: a ring-shaped green compact having a size of 5 mm was molded, and the obtained green compact was maintained in a nitrogen atmosphere at a temperature of 500 ° C. for 30 minutes. The composite soft magnetic material made of a plate-like and ring-like fired body was prepared, the specific resistance of the composite soft magnetic material made of this plate-like fired body was measured, and the result is shown in Table 1. A composite soft magnetic material made of a sintered product is wound, and magnetic flux density, coercive force, and iron loss at a magnetic flux density of 1.5 T and a frequency of 50 Hz, and an iron loss at a magnetic flux density of 1.0 T and a frequency of 400 Hz, etc. The magnetic properties were measured and the results are shown in Table 1.Moreover, when the composite soft magnetic material using the Mg-containing oxide film-coated iron powder 2 of the present invention obtained in Example 2 was observed with a transmission electron microscope, an iron particle phase and a grain boundary phase surrounding the iron particle phase were observed. From the electron diffraction pattern obtained from the grain boundary phase, it was found that the grain boundary phase contains a Mg—Fe—O ternary oxide containing a crystalline MgO solid solution wustite phase.

Conventional Example 1
A conventional oxide-coated iron powder 1 in which an Mg-containing ferrite layer is chemically formed on the surface of the pure iron powder prepared in Example 1 is prepared, and this conventional oxide-coated iron powder 1 is placed in a mold and press-molded. A plate-shaped green compact having dimensions of 55 mm in length, 10 mm in width, and 5 mm in thickness, and a ring-shaped green compact having dimensions of 35 mm in outer diameter, 25 mm in inner diameter, and 5 mm in height are obtained. The obtained green compact is fired in a nitrogen atmosphere at a temperature of 500 ° C. for 30 minutes to produce a composite soft magnetic material comprising a plate-like and ring-like fired body, and a composite soft magnetic material comprising a plate-like fired body. The specific resistance of the magnetic material was measured and the results are shown in Table 1. Further, the composite soft magnetic material made of the ring-shaped fired body was wound, and the magnetic flux density, coercive force, magnetic flux density 1.5T, frequency 50 Hz Iron loss and magnetic flux density 1.0T, frequency 4 The magnetic properties such as iron loss when 0Hz was measured. The results are shown in Table 1.

  From the results shown in Table 1, the composite soft magnetic material produced using the Mg-containing oxide film-coated iron powders 1 to 3 of the present invention is the conventional composite soft magnetic material produced using the oxide-coated iron powder 1 Compared to the composite soft magnetic material, the density is not much different, but the composite soft magnetic material produced using the Mg-containing oxide film-coated iron powders 1 to 3 of the present invention uses the conventional oxide-coated iron powder 1. Compared with the composite soft magnetic material produced in this way, the magnetic flux density is high, the coercive force is low, and the specific resistance is remarkably high, so that the iron loss is remarkably small, especially as the frequency increases, the iron loss decreases. Therefore, the Mg-containing oxide film-coated iron powders 1 to 3 of the present invention are soft magnetic raw material powders that can provide a composite soft magnetic material having more excellent characteristics than the conventional oxide-coated iron powder 1. I understand that.

It is a graph which shows the result of having measured the sulfur concentration distribution of the depth direction of the Mg-Fe-O ternary system oxide deposition film containing at least (Mg, Fe) O using the Auger electron spectrometer.

Claims (10)

An Mg-containing oxide film-coated iron powder, characterized in that an Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O is coated on the surface of the iron powder. 2. The (Mg, Fe) O contained in the Mg—Fe—O ternary oxide deposited film of the Mg-containing oxide film-coated iron powder is a crystalline MgO solid solution wustite phase. The Mg-containing oxide film-coated iron powder described. The Mg-containing oxide film-coated iron powder includes sulfur contained in the center of the iron powder in an interface region between the iron powder and the Mg—Fe—O ternary oxide deposited film containing at least (Mg, Fe) O. 3. The Mg-containing oxide film-coated iron powder according to claim 1, further comprising a sulfur-enriched layer containing a higher concentration of sulfur. The Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O has a fine crystal structure with a crystal grain size of 200 nm or less. Mg-containing oxide film-coated iron powder. The Mg-Fe-O ternary oxide deposited film containing at least (Mg, Fe) O has an outermost surface substantially composed of MgO. 4. The Mg-containing oxide film-coated iron powder according to 4. A composite soft magnetic material produced using the Mg-containing oxide film-coated iron powder according to any one of claims 1 to 5. It is composed of an iron particle phase and a grain boundary phase surrounding the iron particle phase, and the grain boundary phase contains a Mg—Fe—O ternary oxide containing a crystalline MgO solid solution wustite phase. The composite soft magnetic material according to claim 6. An electromagnetic circuit component comprising the composite soft magnetic material according to claim 6. 9. The electromagnetic circuit component according to claim 8, wherein the electromagnetic circuit component is a magnetic core, a motor core, a generator core, a solenoid core, an ignition core, a reactor, a transformer, a choke coil core, or a magnetic sensor core. 10. An electric device incorporating the electromagnetic circuit component.

Images