EP2226142A1 - Poudre et son procédé de production - Google Patents

Poudre et son procédé de production Download PDF

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Publication number
EP2226142A1
EP2226142A1 EP08860500A EP08860500A EP2226142A1 EP 2226142 A1 EP2226142 A1 EP 2226142A1 EP 08860500 A EP08860500 A EP 08860500A EP 08860500 A EP08860500 A EP 08860500A EP 2226142 A1 EP2226142 A1 EP 2226142A1
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European Patent Office
Prior art keywords
powder
apatite
metal powder
minutes
iron powder
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EP08860500A
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German (de)
English (en)
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EP2226142A4 (fr
Inventor
Satoko Kanai
Tetsushi Maruyama
Kei Kasuya
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Showa Denko Materials Co ltd
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Hitachi Chemical Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
    • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/16—Metallic particles coated with a non-metal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/08—Metallic powder characterised by particles having an amorphous microstructure

Definitions

  • the present invention relates to a powder suitable as a starting powder for production of a low iron loss powder magnetic core.
  • the magnetic core is produced by alternately layering a plurality of silicon steel thin-films and insulating layers, and punching the stack with a die (magnetic steel sheet).
  • a die magnetic steel sheet
  • Magnetic cores for motors are usually used in an alternating field, and since high iron loss impairs the energy conversion efficiency they are required to have low iron loss.
  • Iron loss includes hysteresis loss, eddy current loss and residual loss, with hysteresis loss and eddy current loss mainly constituting the problems.
  • Increased hysteresis loss in a powder magnetic core is due to application of a large degree of working strain to the soft magnetic metal powder when the soft magnetic metal powder is compression molded into a powder magnetic core.
  • it is effective to anneal the obtained compact after compression molding to relieve the strain on the soft magnetic metal powder, for which an annealing temperature of 600°C or higher is considered preferable.
  • Patent document 1 proposes a method of employing silica particles as an insulating film with excellent heat resistance.
  • the document discloses a method in which iron powder with a phosphated surface is mixed with a silica particle-containing suspension, and the mixture is dried to obtain metal powder coated with silica powder.
  • Patent document 2 proposes a method in which an oxide layer and an insulating layer are formed on the surface of soft magnetic metal powder and subjected to bond-strengthening treatment in a reducing atmosphere under high-temperature conditions, to form a monolayer with an excellent insulating property on the surface of the soft magnetic metal powder.
  • Patent document 1 Japanese Unexamined Patent Publication HEI No. 9-180924
  • Patent document 2 Japanese Unexamined Patent Publication No. 2007-194273
  • Soft magnetic metal powder produced by the method disclosed in Patent document 2 can be used to provide a powder magnetic core with excellent heat resistance.
  • the method is not suitable for mass production, more simple methods for obtaining coated soft magnetic metal powder with excellent heat resistance have been considered.
  • the present invention has been accomplished in light of the problems of the prior art as described above, and its object is to provide a soft magnetic metal starting powder that can both reduce hysteresis loss and reduce eddy current loss in powder magnetic cores, while also having low iron loss and high flux density.
  • the invention provides a powder comprising metal powder, an apatite layer covering the metal powder and silica particles attached to the metal powder or apatite layer.
  • metal powder is covered with an apatite layer and silica particles are attached to the metal powder or apatite layer, to allow forming an insulating film on the metal powder surface that can withstand annealing temperatures of 600°C or higher.
  • silica particles are attached to the metal powder or apatite layer, to allow forming an insulating film on the metal powder surface that can withstand annealing temperatures of 600°C or higher.
  • the apatite layer preferably contains a compound represented by the following formula (I-a) or (I-b).
  • M represents a cation-donating atom or group of atoms
  • m represents the valency of the cation donated by M
  • n is greater than 0 and not greater than 5
  • X represents an atom or group of atoms that donates a monovalent anion.
  • the silica particles are preferably silica particles that have been surface-modified with an organic group.
  • the silica particles that have been surface-modified with an organic group are preferably silica particles that have been surface-modified using a compound represented by the following formula (II) or (III).
  • R 1 n SiX 4-n (III) (In the formulas, n is an integer of 1-3, R 1 and R 2 represent monovalent organic groups, and X represents a halogen.)
  • the metal powder is preferably a soft magnetic material powder.
  • the powder of the invention is suitable as a powder for a powder magnetic core.
  • the invention provides a method for producing powder which comprises a first step of covering metal powder with apatite, a second step of attaching silica powder to the metal powder surface or apatite surface obtained in the first step, and a third step of pre-curing the powder obtained in the second step at not greater than 350°C to obtain powder comprising the metal powder, the apatite layer covering the metal powder, and silica particles attached to the metal powder or apatite layer.
  • the metal powder provided in the first step is preferably phosphated metal powder.
  • the powder of the invention is covered with an insulating layer comprising an apatite layer and silica particles attached thereto, and the insulating layer has excellent insulating properties and heat resistance. Annealing can therefore be carried out at high temperature without destruction of the insulating layer during production of powder magnetic cores. The insulating property of the insulating layer is thus maintained, and a powder magnetic core with sufficiently high magnetic permeability can be obtained.
  • Fig. 1 is a photograph showing a scanning electron microscope (SEM) image of a cross-section of the hydroxyapatite-covered iron powder obtained in Example 1 (magnification: 2500x).
  • One mode of the powder of the invention is a powder comprising metal powder, an apatite layer covering the metal powder and silica particles attached to the metal powder or apatite layer.
  • the metal powder used for the invention is not particularly restricted so long as it is metal powder with ferromagnetism and exhibiting high saturated flux density, and as specific examples there may be mentioned soft magnetic materials such as iron powder, silicon-steel powder, sendust powder, amorphous powder, permendur powder, soft ferrite powder, amorphous magnetic alloy powder, nanocrystal magnetic alloy powder and permalloy powder, which may be used alone or in mixtures of two or more. Iron powder is preferred among these from the viewpoint of strong magnetism and low cost.
  • pure iron powder is especially preferred from the standpoint of excellent magnetic properties including saturated flux density and magnetic permeability, and excellent compressibility.
  • pure iron powders there may be mentioned atomized iron powder, reduced iron powder and electrolytic iron powder, such as 300NH by Kobe Steel, Ltd.
  • the metal powder used may be the metal powder with a modified element composition in a range that does not adversely affect the compressibility or the magnetic properties of the powder magnetic core.
  • elemental phosphorus may be added to prevent oxidation of the metal powder, or an element such as cobalt, nickel, manganese, chromium, molybdenum or copper may be added to improve the magnetic properties.
  • the particle size of the metal powder there are no particular restrictions on the particle size of the metal powder, and it may be appropriately selected according to the purpose and properties required for the powder magnetic core. Generally speaking, it may be selected so that the size of the particles as observed under a scanning electron microscope (SEM) is in the range of 1 ⁇ m-300 ⁇ m. A particle size of 1 ⁇ m or greater will tend to facilitate molding during production of the powder magnetic core, while a particle size of 300 ⁇ m or smaller will help prevent increased eddy current of the powder magnetic core and tend to facilitate coating of the apatite layer.
  • the mean particle size (the mean secondary particle size determined by screening) is preferably 50-250 ⁇ m.
  • the form of the metal powder is not particularly restricted and may be spherical or globular, or flat powder obtained by flattening treatment by a known process or machining method.
  • the apatite layer covering the surface of the powder of the invention functions as an insulating film for the metal powder.
  • the apatite layer preferably has a coating film structure covering the surface of the metal powder in a laminar fashion.
  • An apatite layer is a layer composed of a substance with an apatite structure.
  • substances with apatite structures for the apatite layer there may be mentioned compounds represented by the following formula (I-a) or (I-b).
  • M represents a cation-donating atom
  • m represents the valency of the cation donated by M
  • n is greater than 0 and not greater than 5
  • X represents an atom or group of atoms that donates a monovalent anion.
  • the cation-donating atom M is preferably a metal that can replace calcium.
  • metals there may be mentioned, specifically, metals with ion radii of 0.80-1.40 A, such as sodium, magnesium, potassium, calcium, scandium, titanium, chromium, manganese, iron, cobalt, nickel, zinc, strontium, yttrium, zirconium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, barium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, platinum, gold, mercury, thallium, lead or bismuth.
  • M in formula (I-b) may be of a single type or two or more types.
  • the range for n in formula (I-b) is greater than 0 and not greater than 5, more preferably greater than 0 and not greater than 2.5, and even more preferably greater than 0 and not greater than 1.0.
  • each X in formula (I-a) and (I-b) is preferably hydroxyl (OH) or a halogen (such as F, Cl, B or I) and is more preferably hydroxyl or fluorine.
  • X is preferably a hydroxyl group from the viewpoint of excellent coatability onto metal powder, and it is preferably fluorine from the viewpoint of excellent strength.
  • the substance with an apatite structure for the apatite layer is more preferably a compound represented by formula (I-a), and especially preferably hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) or fluoroapatite (Ca 10 (PO 4 ) 6 F 2 ), from the viewpoint of excellent insulating properties, heat resistance and dynamic properties when made into a powder magnetic core.
  • covering the metal powder with the apatite layer in regard to the powder of the invention means that at least a portion of the metal powder is covered by the apatite layer.
  • apatite-covered metal powder used below, therefore, includes not only metal powder completely covered with apatite but metal powder that is partially exposed.
  • the extent of coverage of the metal powder by the apatite layer is preferably to a higher coverage factor from the viewpoint of facilitating adhesion of silica, described hereunder, and resulting in improved transverse strength. Specifically, preferably at least 90% of the surface, more preferably at least 95% and even more preferably all (essentially 100%) of the metal powder is covered by the apatite layer.
  • the apatite layer in the powder of the invention has a thickness of preferably 10 nm-1000 nm and more preferably 20-500 nm.
  • a thickness of 10 nm or greater will tend to provide an insulating effect, while a thickness of not greater than 1000 nm will tend to provide a density-improving effect.
  • the method of forming the apatite layer on the metal powder may be a method in which an aqueous solution containing calcium ion or additionally the ion of the cation-donating atom or group of atoms M of formula (1-b) in a prescribed ratio is reacted with an aqueous solution containing phosphate ion, to deposit a substance that adopts an apatite structure on the metal powder surface.
  • an aqueous solution containing calcium ion or additionally the ion of the cation-donating atom or group of atoms M of formula (1-b) in a prescribed ratio is reacted with an aqueous solution containing phosphate ion, to deposit a substance that adopts an apatite structure on the metal powder surface.
  • a calcium phosphate layer may sometimes be deposited in addition to the substance with an apatite structure.
  • hydroxyapatite When hydroxyapatite is deposited as the apatite layer, a method using a calcium nitrate aqueous solution and ammonium dihydrogenphosphate aqueous solution may be employed.
  • the stoichiometric composition of the hydroxyapatite obtained in this manner is Ca 10 (PO 4 ) 6 (OH) 2 , but it may be a nonstoichiometric composition so long as the majority is an apatite structure and it can be maintained, and for example, a portion may be Ca 10-Z (HPO 4 ) Z (PO 4 ) 6-Z (OH) 2-Z (0 ⁇ Z ⁇ 1, 1.50 ⁇ Ca/P (atomic weight ratio) ⁇ 1.67).
  • the amount of apatite layer starting material added is preferably 0.1-1.0 part by mass, more preferably 0.4-0.8 part by mass and even more preferably 0.5-0.7 part by mass with respect to 100 parts by mass of the metal powder.
  • An amount of at least 0.1 part by mass will tend to result in adequate resistivity when the powder is formed into a powder magnetic core.
  • a uniform insulating layer can also be formed on the powder, and an effect of improved insulation can be satisfactorily obtained.
  • An amount of not greater than 1.0 part by mass will help prevent reduction in the compact density when the powder is formed into a powder magnetic core.
  • the mass of apatite layer can be determined by quantifying the amount of calcium (and metal M) by elemental analysis of the obtained powder.
  • the silica particles used for the powder of the invention may be any that are known in the prior art, among which fumed silica and colloidal silica may be mentioned specifically, but colloidal silica is preferred from the viewpoint of easy manageability. There are no restrictions on the shapes of the silica particles.
  • the particle size of the silica particles may be any of various sizes, but silica particles having a submicron particle size are preferred for film formability. Specifically, the mean primary particle size of the silica particles is preferably not greater than 50 nm, more preferably not greater than 30 nm and even more preferably not greater than 20 nm.
  • the silica particles are preferably dispersed without aggregation in an organic solvent.
  • the silica particle surfaces may be modified with an organic group.
  • organic groups there may be mentioned cyclohexyl, phenyl, benzyl, phenethyl and C1-C6 (1-6 carbon atoms) alkyl groups.
  • the method of modifying the silica particle surfaces with the organic group may be a method of reacting the silica particle surfaces with a silane compound having an organic group in the molecular structure. This can increase the transverse strength and often improve the resistivity, when the powder is formed into a powder magnetic core.
  • silane compounds include alkoxysilanes represented by the following formula (II) and halogenosilane compounds represented by the following formula (III).
  • R 1 n SiX 4-n (III) (In the formulas, n is an integer of 1-3, R 1 and R 2 represent monovalent organic groups, and X represents a halogen.)
  • R 1 in formulas (II) and (III) is the organic group that is to modify the silica particles, and specifically there may be mentioned cyclohexyl, phenyl, benzyl, phenethyl and C1-C6 (1-6 carbon atoms) alkyl groups.
  • R 2 may be a monovalent organic group, and specifically methyl, ethyl or the like.
  • X may be chloro, bromo, iodo or the like.
  • alkoxysilanes represented by formula (II) include trimethoxysilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, iso-propyltrimethoxysilane, n-butyltrimethoxysilane, tert-butyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, benzyltrimethoxysilane and phenethyltrimethoxysilane; triethoxysilanes such as methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane, iso-propyltriethoxysilane, n-
  • halogenosilane compounds represented by formula (III) include:
  • silane compounds may be used alone or in combinations of two or more.
  • the surface modification of the silica particles can generally be accomplished by adding the alkoxysilane compound or halogenosilane compound to a dispersion of the silica particles and stirring the mixture. In this case, it is preferably added in a range of 0.4-0.6 part by weight to 1 part by solid weight of the silica particles. Limited to not greater than 0.6 part by weight, there will be no residual unreacted silane compound added, and in an amount of at least 0.4 part by weight a sufficient effect of organic group modification of the silica particles can be achieved.
  • the silica particles may be dispersed in water or dispersed in an organic solvent.
  • an acid catalyst such as an inorganic acid, organic acid or acidic ion exchange resin.
  • an acid catalyst such as an inorganic acid, organic acid or acidic ion exchange resin.
  • hydrochloric acid, nitric acid, acetic acid, citric acid, formic acid, oxalic acid or the like common acids can react with apatite and impair its properties, and therefore hydrochloric acid and acetic acid are especially preferred for their high volatility to escape from the system.
  • the amount of acid catalyst added is preferably 0.05-0.1 part by weight to 1 part by solid weight of the silica particles.
  • the temperature for the modification reaction is preferably 0-50°C and more preferably 10-40°C, to prevent aggregation of the silica particles.
  • the silica particles are preferably dispersed in an organic solvent such as isopropyl alcohol, polyethyleneglycol monomethyl ether acetate, toluene or xylene.
  • the method for producing the powder of the invention comprises a first step of covering metal powder with apatite to form metal powder covered with an apatite layer (hereunder referred to as "apatite-covered metal powder"), a second step of attaching silica powder to the metal powder or apatite layer of the apatite-covered metal powder obtained in the first step, and a third step of pre-curing the powder obtained in the second step at not greater than 350°C to obtain powder comprising the metal powder, the apatite layer covering the metal powder, and silica particles attached to the metal powder or apatite layer.
  • the metal powder provided in the first step is preferably phosphated metal powder, from the viewpoint of preventing oxidation of the metal powder.
  • the phosphating treatment may be carried out before the first step, or a commercially available metal powder that has been subjected to phosphating treatment may be used.
  • the phosphating treatment may be carried out by a method known in the prior art.
  • the method of forming the apatite layer on the metal powder may be a method in which an aqueous solution containing calcium ion (if necessary with the ion of a cation-donating atom or group of atoms M other than calcium) is reacted with an aqueous solution containing phosphate ion, as explained above, to deposit apatite on the metal powder surface.
  • the aqueous solution used as the calcium source may be placed in a flask together with the metal powder and stirred therewith while adding the aqueous solution as the phosphate source in a dropwise manner.
  • water and the metal powder may be placed in a flask and stirred while adding the aqueous solution as the calcium source and the aqueous solution as the phosphate source in a dropwise manner, either simultaneously or successively. In the case of successive dropwise addition, they may be added in either order.
  • the calcium source is not particularly restricted so long as it is a water-soluble calcium compound, and as specific examples there may be mentioned calcium salts of inorganic bases such as calcium hydroxide, calcium salts of inorganic acids such as calcium nitrate, calcium salts of organic acids such as calcium acetate, and calcium salts of organic bases.
  • calcium salts of inorganic bases such as calcium hydroxide
  • calcium salts of inorganic acids such as calcium nitrate
  • calcium salts of organic acids such as calcium acetate
  • calcium salts of organic bases such as calcium acetate
  • phosphate sources there may be mentioned phosphoric acid, and phosphoric acid salts such as ammonium dihydrogenphosphate and diammonium hydrogenphosphate.
  • the reaction mixture is preferably in the neutral range to basic range, with a pH of preferably 7 or higher, more preferably 8 or higher, even more preferably 9 or higher and especially preferably 10 or higher. Because a layer of calcium phosphate other than apatite may be deposited in the acidic range, the aqueous solution as the calcium source and the aqueous solution as the phosphate source is preferably preadjusted to a pH of 7 or higher with a base such as ammonia water.
  • the reaction temperature may be room temperature, but it is preferably 50°C or higher, more preferably 70°C or higher and even more preferably 90°C or higher to promote the reaction. If the solvent is water, the upper limit for the temperature will be the reflux temperature of the reaction mixture, i.e. near 100°C.
  • the reaction time will depend on the concentrations of the aqueous solution as the calcium source and the aqueous solution as the phosphate source, with a shorter reaction time being sufficient for higher concentrations and a longer reaction time preferred for lower concentrations.
  • concentrations of the aqueous solution as the calcium source and the aqueous solution as the phosphate source in the production method of the invention are preferably each in the range of 0.003-0.5M, in which case the reaction time is preferably 1-10 hours.
  • Silica particles are attached to the apatite-covered metal powder obtained in the manner described above.
  • the method may involve adding a dispersion of the silica particles to the apatite-covered metal powder and shaking and stirring the mixture. If a commercially available organosilica sol is used, it may be diluted to an appropriate concentration. When the surfaces of the silica particles are surface-modified with an organic group such as a silane compound in a commercially available organosilica sol as described above, the reaction mixture used for the surface modification may be used directly.
  • the silica particles used in this case may be attached to an apatite layer or they may be attached to the exposed metal powder surface at defect sections where the apatite layer covering is lacking.
  • the solvent used to disperse the silica particles is not particularly restricted, and as specific examples there may be mentioned alcohol-based solvents such as isopropyl alcohol, ketone-based solvents such as methyl ethyl ketone, and aromatic-based solvents such as toluene. Particularly preferred are aromatic solvents that allow the colloidal solution state of the silica particles in the organosilica sol to be maintained more easily.
  • the apatite-covered metal powder having silica particles attached to the surface is then pre-cured at not greater than 350°C. This can cure the apatite layer to form a strong heat-resistant coating. Without pre-curing, the silica particles on the surface will become embedded in the apatite layer when the starting powder is compression molded to produce a powder magnetic core, tending to result in an insufficient insulating property.
  • the temperature for pre-curing is preferably 100-300°C.
  • the amount of silica particles used for the invention is preferably 0.05-1.0 part by mass with respect to 100 parts by mass of the metal powder used.
  • An amount of at least 0.05 part by mass will allow uniform coverage of the metal powder by the silica particles, tending to produce an effect of improving the insulating property.
  • An amount of not greater than 1.0 part by mass will help prevent reduction in the compact density when the powder is formed into a powder magnetic core, as well as prevent reduction in the transverse strength of the obtained powder magnetic core.
  • the powder for a powder magnetic core according to the invention may be formed into a powder magnetic core by compression molding a mixed powder with admixture of a lubricant if necessary.
  • the lubricant may also be used by coating and drying a dispersion thereof onto the die wall face.
  • metal soaps such as zinc stearate, calcium stearate and lithium stearate, long-chain hydrocarbons such as waxes, and silicone oils.
  • the molding pressure is preferably 500-1500 MPa.
  • the obtained powder magnetic core may be annealed to lower the hysteresis loss.
  • the annealing temperature in this case is preferably selected within the range of 500-800°C.
  • the annealing is preferably carried out in an inert gas such as nitrogen or argon.
  • the powder magnetic core produced by this method exhibits high compact density and insulating properties.
  • the mechanism by which these properties are exhibited has not been fully elucidated, but the present inventors conjecture that it is the following.
  • the high adsorptive power of the apatite facilitates attachment of the silica particles to the metal powder. It is believed that the attached silica particles effectively fill the fissures in the apatite layer created during molding, thereby allowing a high compact density (for example, 7.0 g/cm 3 or greater) and high heat resistance and insulation to be maintained.
  • the reason that a particle size below the submicron level is preferred for the silica particles may be that smaller silica particles move more easily and the silica particles therefore more effectively fill in the fissures of the apatite layer.
  • the compact density of the powder magnetic core formed from the powder of the invention is preferably 7.0 g/cm 3 or greater and more preferably 7.4 g/cm 3 or greater. A density of at least 7.4 g/cm 3 will tend to improve the flux density of the powder magnetic core.
  • the electrical resistance value of the surface of the powder magnetic core is preferably at least 30 ⁇ m, more preferably at least 50 ⁇ m and even more preferably at least 90 ⁇ m. An electrical resistance of at least 30 ⁇ m will tend to produce an effect of reducing the eddy current loss of the powder magnetic core.
  • the 4-necked flask was reacted for 2 hours while stirring in an oil bath at 90°C.
  • the obtained slurry was suction filtered and the filtered product was dried in an oven at 110°C to obtain a gray powder (yield: 96 mass%).
  • XPS X-ray photoelectron spectroscopy
  • Figs. 1 and 2 show SEM photographs of the cross-sections of apatite-covered iron powder obtained in this manner
  • Figs. 3 and 4 show SEM photographs of the cross-sections of nanosilica-attached apatite-covered iron powder. It was confirmed that a hydroxyapatite layer and nanosilica layer had been formed on the particle surfaces.
  • the obtained nanosilica-attached apatite-covered iron powder After packing 5.92 g of the obtained nanosilica-attached apatite-covered iron powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa. The thickness of the obtained tablet was approximately 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 296 ⁇ m. The density was 7.48 g/cm 3 . The tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 91 ⁇ m. The density was 7.47 g/cm 3 .
  • Hydroxyapatite-covered iron powder was prepared as follows, partly in the same manner as Example 1. Specifically, in a 300 mL 4-necked flask there were placed 75 mL (1.79 mmol, 0.024 M) of a calcium nitrate aqueous solution prepared to pH 11 or higher with 25% ammonia water, and 30 g of iron powder (pure iron powder 300NH, by Kobe Steel, Ltd.). Also, 75 mL (1.07 mmol, 0.014 M) of an ammonium dihydrogenphosphate aqueous solution prepared to pH 11 or higher with 25% ammonia water was placed in a dropping funnel with a bypass line and the funnel was attached to the 4-necked flask. The contents of the 4-necked flask were stirred at room temperature (25°C) while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes.
  • the 4-necked flask was reacted for 2 hours while stirring in an oil bath at 90°C.
  • the obtained slurry was then suction filtered and the filtered product dried in an oven at 110°C to obtain a gray powder. (Yield: 96 mass%).
  • the obtained powder was passed through a 250 ⁇ m sieve to obtain apatite-covered metal powder. After packing 5.95 g of the obtained apatite-covered metal powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa. The thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 144 ⁇ m.
  • the density was 7.54 g/cm 3 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 0.54 ⁇ m.
  • the density was 7.53 g/cm 3 .
  • Nanosilica was attached to iron powder by the method of attaching nanosilica used in Example 1, but without providing an apatite layer. Specifically, 20 g of iron powder (pure iron powder 300NH by Kobe Steel, Ltd.) and 2 g of a nanosilica-toluene solution (solid concentration: 3.0 mass%) were mixed and shaken for 10 minutes in a polypropylene bottle with a maximum internal volume of 50 mL, and pre-cured at 200°C for 30 minutes. The pre-cured powder was passed through a 250 ⁇ m sieve to remove the giant aggregate particles, to obtain nanosilica-attached metal powder.
  • a 5.99 g portion of the obtained powder was molded at 1000 MPa into a cylindrical tablet with a diameter of 1.4 cm and a thickness of 5.145 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 79 ⁇ m.
  • the density was 7.57 g/cm 3 .
  • the polished tablet was annealed and fired under a nitrogen atmosphere, at 600°C for one hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 20 ⁇ m.
  • the density was 7.57 g/cm 3 .
  • hydroxyapatite covering and silica particle attachment are both essential for obtaining high resistivity.
  • the compact density in Example 1 did not lower than the compact densities in Comparative Example 1 and Comparative Example 2, even though the powder in Example 1 was subjected to hydroxyapatite covering and silica particle attachment. This is attributed to destruction during compression molding, and embedding of the silica particles in the pores at the fissures of the produced apatite layer.
  • silica particles were attached to pure iron powder having a different surface form, and apatite-covered iron powder, and the degree of silica particles remaining on the surface was compared by quantitative analysis.
  • 3.0 g of each powder was added to 5.0 g of organosilica sol solution (medium: toluene) containing silica particles with a mean particle size of 20 nm measured by dynamic light scattering using an HPPS by Malvern Co. (solid concentration: 3.0 mass%), that had been placed in a glass screw tube with a maximum volume of 10 mL.
  • the screw tube was stirred for 3 hours with a mix rotor set to a rotational speed of 105 rpm.
  • the stirred solution was suction filtered using No.5B (JIS P3801) filter paper for quantitative analysis, and the filtered product was rinsed with toluene and vacuum dried to obtain each powder.
  • the obtained powder was subjected to elemental analysis by ICP-OES, and the silica particles attached to the powder were quantified based on the quantity of silicon atoms. The results are shown in Table 2.
  • the quantity of silicon atoms quantified from the apatite-covered iron powder was approximately twice that of the pure iron powder. Since the silicon atoms derive only from the silica particles, this indicated an increased degree of silica particle attachment, and stronger adsorptive power of the silica particles with the apatite layer than with the pure iron powder surface layer.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and the filtered product was dried in an oven at 110°C to obtain a gray powder.
  • the atomic abundance ratio was Fe: 3.31%, Ca: 17.1% and the Ca/P ratio (molar ratio) was 1.63, and the powder was confirmed to be covered with hydroxyapatite.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 236 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the polished tablet was fired under a nitrogen atmosphere, at 600°C for 1 hour, and after polishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 75 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and the filtered product was dried in an oven at 110°C to obtain a gray powder.
  • the atomic abundance ratio was Fe: 5.56%, Ca: 14.85% and the Ca/P ratio (molar ratio) was 1.63, and the powder was confirmed to be covered with hydroxyapatite.
  • the obtained nanosilica-attached apatite-covered iron powder After packing 6 g of the obtained nanosilica-attached apatite-covered iron powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa/cm 2 . The thickness of the obtained tablet was approximately 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 111 ⁇ m. The compact density was 7.51 g/cm 2 . The polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 55 ⁇ m. The compact density was 7.51 g/cm 2 .
  • the 90°C reaction time in Example 3 was changed from 2 hours to 10 minutes.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 10 minutes while stirring.
  • the obtained slurry was then suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 6.79%, Ca: 12.77% and the Ca/P ratio (molar ratio) was 1.44.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 214 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 53 ⁇ m.
  • the compact density was 7.49 g/cm 2 .
  • the reaction time at 90°C in Example 3 was changed from 2 hours to 5 hours.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 5 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 6.07%, Ca: 13.98% and the Ca/P ratio was 1.67, and the powder was confirmed to be covered with hydroxyapatite.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 218 ⁇ m.
  • the compact density was 7.47 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 93 ⁇ m.
  • the compact density was 7.47 g/cm 2 .
  • the reaction temperature of 90°C in Example 3 was changed to 30°C.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 3.5 hours while keeping the temperature of the oil bath at 30°C.
  • the obtained slurry was then suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 7.84%, Ca: 11.67% and the Ca/P ratio (molar ratio) was 1.65, and the iron powder was confirmed to be covered with hydroxyapatite.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 119 ⁇ m.
  • the compact density was 7.53 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 31 ⁇ m.
  • the density was 7.53 g/cm 2 .
  • the reaction temperature of 90°C in Example 3 was changed to 50°C. Specifically, in a 300 mL 4-necked flask there were placed 75 mL (1.79 mmol, 0.024 M) of a calcium nitrate aqueous solution prepared to pH 11 or higher with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH, by Kobe Steel, Ltd.), and the mixture was stirred for 15 minutes in an oil bath at 30°C. Next, 75. mL (1.07 mmol, 0.014 M) of an ammonium dihydrogenphosphate aqueous solution prepared to pH 11 or higher with 25% ammonia water was placed in a dropping funnel with a bypass line and the funnel was attached to the 4-necked flask.
  • 75 mL (1.07 mmol, 0.014 M) of an ammonium dihydrogenphosphate aqueous solution prepared to pH 11 or higher with 25% ammonia water was placed in a dropping funnel with a bypass line and the funnel was attached
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 50°C over a period of 5 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 7.08%, Ca: 13.24% and the Ca/P ratio (molar ratio) was 1.77, and the iron powder was confirmed to be covered with hydroxyapatite.
  • the obtained nanosilica-attached apatite-covered iron powder After packing 6 g of the obtained nanosilica-attached apatite-covered iron powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa/cm 2 . The thickness of the obtained tablet was approximately 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 176 ⁇ m. The compact density was 7.46 g/cm 2 . The polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 53 ⁇ m. The compact density was 7.47 g/cm 2 .
  • the reaction temperature of 90°C in Example 3 was changed to 30°C, and firing at 110°C was not carried out.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 3.5 hours while keeping the temperature of the oil bath at 30°C.
  • the obtained slurry was then suction filtered, removed into a stainless steel dish and dried for 5 minutes at a pressure of not greater than 1 MPa to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 5.53%, Ca: 13.63% and the Ca/P ratio (molar ratio) was 1.52.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 168 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after polishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 56 ⁇ m.
  • the compact density was 7.49 g/cm 2 .
  • the reaction temperature of 90°C in Example 3 was changed to 50°C, and firing at 110°C was not carried out.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 50°C over a period of 5 minutes, and the contents of the 4-necked flask were reacted at 90°C for 2 hours while stirring.
  • the obtained slurry was then suction filtered, removed into a stainless steel dish and dried for 5 minutes at a pressure of not greater than 1 MPa to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 4.89%, Ca: 15.54% and the Ca/P ratio (molar ratio) was 1.77, and the powder was confirmed to be covered with hydroxyapatite.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 137 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 44 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • Example 3 The firing at 110°C in Example 3 was not carried out.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and vacuum dried at 0 MPa to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 3.85%, Ca: 16.63% and the Ca/P ratio (molar ratio) was 1.56.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-tenninal resistivity meter to be 137 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 30 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • Example 3 the calcium nitrate charging amount was changed from 1.79 mmol to 0.60 mmol and the ammonium dihydrogenphosphate charging amount was changed from 1.07 mmol to 0.36 mmol.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 7.29%, Ca: 13.14% and the Ca/P ratio (molar ratio) was 1.52.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 122 ⁇ m.
  • the compact density was 7.56 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 30 ⁇ m.
  • the compact density was 7.56 g/cm 2 .
  • Example 3 the calcium nitrate charging amount was changed from 1.78 mmol to 2.98 mmol and the ammonium dihydrogenphosphate charging amount was changed from 1.07 mmol to 1.78 mmol.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 2.76%, Ca: 17.59% and the Ca/P ratio (molar ratio) was 1.67.
  • the thickness of the obtained tablet was approximately 5 mm.
  • the surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 213 ⁇ m.
  • the compact density was 7.44 g/cm 2 .
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 88 ⁇ m.
  • the compact density was 7.44 g/cm 2 .
  • Hydroxyapatite-covered iron powder with a hydroxyapatite layer composed of a single layer was prepared in the same manner as Example 11, and the same treatment was also repeated to prepare hydroxyapatite-covered iron powder with a hydroxyapatite layer composed of a two-layer structure.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise thereto over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 1.0 minutes, and the contents of the 4-necked flask were reacted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder (yield: 96 mass%).
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise thereto over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 7.05%, Ca: 13.84% and the Ca/P ratio (molar ratio) was 1.59.
  • the obtained nanosilica-attached apatite-covered iron powder After packing 6 g of the obtained nanosilica-attached apatite-covered iron powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa/cm 2 . The thickness of the obtained tablet was approximately 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 131 ⁇ m. The compact density was 7.53 g/cm 2 . The polished tablet was fired under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 59 ⁇ m. The compact density was 7.53 g/cm 2 .
  • Hydroxyapatite-covered iron powder with a hydroxyapatite layer composed of two layers was prepared in the same manner as Example 13, and the same treatment was also repeated to prepare hydroxyapatite-covered iron powder with a hydroxyapatite layer composed of a three-layer structure.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and the contents of the 4-necked flask were reacted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • a 29.5 g portion of the obtained apatite two-layer-covered iron powder and 74 mL (0.59 mmol, 0.008 M) of a calcium nitrate aqueous solution prepared to pH 11 or higher with 25% ammonia water were placed in a 300 mL 4-necked flask, and the mixture was stirred for 15 minutes in an oil bath at 30°C.
  • 74 mL (0.35 mmol, 0.005 M) of an ammonium dihydrogenphosphate aqueous solution prepared to pH 11 or higher with 25% ammonia water was placed in a dropping funnel with a bypass line and the funnel was attached to the 4-necked flask.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 10 minutes, after which the mixture was stirred for 1.5 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 10.33%, Ca: 10.95% and the Ca/P ratio (molar ratio) was 1.69.
  • the polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 31 ⁇ m.
  • the compact density was 7.50 g/cm 2 .
  • Example 3 The amount of iron powder charged in Example 3 was changed to a 33-fold amount, the reactor volume and amount of solvent were correspondingly changed 33-fold, and the time for stirring in the 30°C oil bath after dropwise addition of the ammonium dihydrogenphosphate aqueous solution to the 4-necked flask contents was changed from 1.5 hours to 2 hours.
  • the contents of the 4-necked flask were stirred in the oil bath at 30°C, while adding the ammonium dihydrogenphosphate aqueous solution in the dropping funnel dropwise over a period of 30 minutes, after which the mixture was stirred for 2 hours while keeping the temperature of the oil bath at 30°C.
  • the oil bath temperature was then raised from 30°C to 90°C over a period of 10 minutes, and reaction was conducted at 90°C for 2 hours while stirring.
  • the obtained slurry was suction filtered and dried in an oven at 110°C to obtain a gray iron powder.
  • the atomic abundance ratio was Fe: 3.85%, Ca: 15.30% and the Ca/P ratio was 1.76, and the iron powder was confirmed to be covered with hydroxyapatite.
  • the obtained nanosilica-attached apatite-covered iron powder After packing 6 g of the obtained nanosilica-attached apatite-covered iron powder into a die with an inner diameter of 14 mm, it was molded into a cylindrical tablet with a molding pressure of 1000 MPa/cm 2 . The thickness of the obtained tablet was approximately 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 193 ⁇ m. The compact density was 7.51 g/cm 2 . The polished tablet was annealed under a nitrogen atmosphere, at 600°C for 1 hour, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 41 ⁇ m. The compact density was 7.51 g/cm 2 .
  • Example 5 Examples Powder magnetic core properties Compact density (g/cm 3 ) Resistivity ( ⁇ m) Example 1 7.47 91 Example 2 7.50 75 Example 3 7.51 55 Example 4 7.49 53 Example 5 7.47 93 Example 6 7.53 31 Example 7 7.47 53 Example 8 7.48 56 Example 9 7.50 44 Example 10 7.50 30 Example 11 7.56 30 Example 12 7.44 88 Example 13 7.53 59 Example 14 7.50 31 Example 15 7.51 41
  • hydroxyapatite layers could be formed on the metal powders with the similar coverage factor regardless of the synthesis method. Also, judging from Tables 3 and 5, powder magnetic cores of the nanosilica-attached hydroxyapatite-covered iron powders obtained using a step of pre-curing at 100-300°C in the production process exhibited high resistivity and compact density.

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US20150022308A1 (en) * 2013-07-22 2015-01-22 Samsung Electro-Mechanics Co., Ltd. Magnetic material, method for manufacturing the same, and electronic component including the same
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KR20150002172A (ko) * 2013-06-28 2015-01-07 삼성전기주식회사 복합재 및 그 제조 방법, 그리고 상기 복합재를 이용하여 제조된 인덕터
CN105659337B (zh) * 2013-09-27 2018-04-10 日立化成株式会社 压粉磁芯、磁芯用压粉体的制造方法、压粉磁芯制造用的压模和模具装置、以及压粉磁芯制造用压模的润滑组合物
CN111842874A (zh) * 2019-04-24 2020-10-30 昆山磁通新材料科技有限公司 一种提高金属粉芯绝缘阻抗特性的方法及其金属粉芯
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Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2066851T3 (es) * 1988-05-24 1995-03-16 Anagen Uk Ltd Particulas atraibles magneticamente y metodo de preparacion.
DE69028360T2 (de) * 1989-06-09 1997-01-23 Matsushita Electric Ind Co Ltd Verbundmaterial sowie Verfahren zu seiner Herstellung
JP3062969B2 (ja) * 1991-10-14 2000-07-12 科学技術振興事業団 生体活性層のコーティング方法
JPH09180924A (ja) * 1995-12-27 1997-07-11 Kobe Steel Ltd 圧粉磁心及びその製造方法
AU1673797A (en) * 1996-02-20 1997-09-10 Mikuni Corporation Method for producing granulated material
JP3959564B2 (ja) * 1997-12-24 2007-08-15 村樫石灰工業株式会社 表層から芯部まで多孔質アパタイトに転換された固体物質の製造方法
JP4060101B2 (ja) * 2002-03-20 2008-03-12 株式会社豊田中央研究所 絶縁皮膜、磁心用粉末および圧粉磁心並びにそれらの製造方法
JP4328170B2 (ja) * 2003-10-03 2009-09-09 トライアル株式会社 被覆樹脂粒子の製造方法
JP2006348335A (ja) * 2005-06-14 2006-12-28 Jfe Steel Kk 粉末冶金用鉄基混合粉
JP2007027480A (ja) * 2005-07-19 2007-02-01 Sumitomo Metal Mining Co Ltd 樹脂結合型磁石組成物、その製造方法及びそれを用いた樹脂結合型磁石
JP2007194273A (ja) 2006-01-17 2007-08-02 Jfe Steel Kk 圧粉磁心用の軟磁性金属粉末および圧粉磁心

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2009075173A1 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130015939A1 (en) * 2010-03-26 2013-01-17 Hitachi Powdered Metals Co. Ltd. Powder magnetic core and method for producing the same
US9646756B2 (en) * 2010-03-26 2017-05-09 Hitachi Powdered Metals Co., Ltd. Powder magnetic core and method for producing the same
EP2555210A4 (fr) * 2010-03-26 2017-09-06 Hitachi Powdered Metals Co., Ltd. Noyau à poudre de fer et procédé de production associé
US20130057371A1 (en) * 2010-04-09 2013-03-07 Takehiro Shimoyama Coated metal powder, powder magnetic core and method for producing same
EP2682960A4 (fr) * 2011-03-04 2015-06-24 Sumitomo Electric Industries Comprimé cru, procédé de production de comprimé cru, réacteur, convertisseur, et dispositif de conversion de puissance
US9978490B2 (en) 2011-03-04 2018-05-22 Sumitomo Electric Industries, Ltd. Compact, method for producing compact
US20150022308A1 (en) * 2013-07-22 2015-01-22 Samsung Electro-Mechanics Co., Ltd. Magnetic material, method for manufacturing the same, and electronic component including the same
US11915847B2 (en) * 2017-03-09 2024-02-27 Tdk Corporation Dust core
WO2021096878A1 (fr) * 2019-11-11 2021-05-20 Carpenter Technology Corporation Matériaux composites magnétiques doux et procédés et poudres pour produire ceux-ci

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EP2226142A4 (fr) 2017-04-12
CA2708830C (fr) 2013-01-22
TWI433741B (zh) 2014-04-11
JP5321469B2 (ja) 2013-10-23
CN102717069B (zh) 2014-12-17
CN101896300A (zh) 2010-11-24
WO2009075173A1 (fr) 2009-06-18
CA2708830A1 (fr) 2009-06-18
TW200932404A (en) 2009-08-01
JPWO2009075173A1 (ja) 2011-04-28
CN102717069A (zh) 2012-10-10
CN101896300B (zh) 2012-08-22

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