JP5321469B2 - Powder and production method thereof - Google Patents

Abstract

The powder of the invention comprises metal powder, an apatite layer covering the metal powder and silica particles attached to the metal powder or apatite layer. The powder of the invention allows annealing to 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 therefore maintained, and a powder magnetic core with sufficiently high magnetic permeability can be obtained.

Description

  The present invention relates to a powder suitable as a raw material powder for a dust core having a low iron loss.

  There are many products using electromagnetism around us, such as transformers, motors, generators, speakers, induction heaters, and various actuators. In order to achieve high performance and miniaturization, it is essential to improve the performance of the magnetic core, which is a compacted body of soft magnetic material.

  Conventionally, the magnetic core is manufactured by alternately laminating a plurality of silicon steel thin films and insulating layers and punching them with a mold (magnetic steel sheet). However, this method has many inconveniences in terms of product size reduction and complex shape, and has a problem in reducing eddy current loss.

  In recent years, as a magnetic core excellent in moldability and capable of being manufactured at low cost, a powder magnetic core obtained by compression-molding a soft magnetic metal powder has attracted attention, and various research and development have been made.

  Such a dust core is required to increase the magnetic permeability in order to increase the magnetic flux density. In particular, a magnetic core for a motor is often used in an alternating magnetic field, but if the iron loss is large, the energy conversion efficiency is deteriorated, so that the iron loss is required to be small (low iron loss).

  The iron loss includes a hysteresis loss, an eddy current loss, and a residual loss. The main problems are hysteresis loss and eddy current loss.

  The increase in hysteresis loss in the dust core is caused by the fact that enormous processing strain is applied to the soft magnetic metal powder when the soft magnetic metal powder is compression-molded into a dust core. Therefore, to reduce the hysteresis loss, it is effective to release the strain applied to the soft magnetic metal powder by annealing the obtained molded body after compression molding, and the annealing temperature is 600 ° C. or higher. Is said to be preferred.

  On the other hand, in order to reduce eddy current loss, it is effective to coat soft magnetic metal powder with an insulating material. However, when the insulating material generally used conventionally is annealed to reduce the hysteresis loss, the insulating material has low heat resistance, so that decomposition occurs and the insulating property is remarkably lowered. Therefore, coexistence of reduction of eddy current loss and reduction of hysteresis loss is a very big problem.

  Therefore, in order to solve such a problem, an insulating material having excellent heat resistance has been developed. In particular, those using iron powder as a soft magnetic metal powder are inexpensive and can produce a dust core having a high magnetic flux density, so various research and development have been made. For example, Patent Document 1 proposes a method in which silica particles are used as an insulating coating having excellent heat resistance. The literature discloses a method of obtaining a metal powder coated with silica powder by mixing iron powder whose surface has been subjected to phosphoric acid treatment and a suspension containing silica particles, and drying the mixture.

  However, when an attempt is made to produce a powder magnetic core using the iron powder coated with the silica particles, the annealing temperature is a normal process around 600 ° C. in order to obtain a sufficient bonding force between the metal powders. It was necessary to make it higher (for example, 800 ° C. or higher). However, if the annealing temperature is set too high, the Curie temperature of iron is 769 ° C., so the magnetic properties of the dust core tend to deteriorate.

Further, in Patent Document 2, an oxide layer and an insulating layer are formed on the surface of the soft magnetic metal powder, and a bond strengthening treatment is performed in a reducing atmosphere under a high temperature condition. A method of forming an excellent single layer has been proposed.
JP-A-9-180924 JP 2007-194273 A

  It is said that when a soft magnetic metal powder produced by the method disclosed in Patent Document 2 is used, a dust core having excellent heat resistance can be provided. However, in the case of this method, because of the high energy cost related to annealing and the like for the process, and because it is not very suitable for mass production, it is a simpler method with a soft magnetic film having excellent heat resistance. Considered obtaining metal powder.

  In order to increase the magnetic flux density, it is effective to form an insulating layer as thin and as wide as possible on the soft magnetic metal powder, but a simple and low cost method has not been known so far.

  The present invention has been made in view of the above-described problems of the prior art. In the dust core, it is possible to achieve both hysteresis loss reduction and eddy current loss reduction, and low iron loss and high magnetic flux density. An object of the present invention is to provide a soft magnetic metal raw material powder that can be compatible.

  In order to solve the above-mentioned problems, the present invention provides a powder comprising metal powder, an apatite layer covering the metal powder, and silica particles attached to the metal powder or the apatite layer.

  According to the present invention, it is possible to form an insulating coating that can withstand an annealing temperature of 600 ° C. or higher on the surface of the metal powder by coating the metal powder with the apatite layer and attaching silica particles to the metal powder or the apatite layer. Become. The adoption of such a configuration and the effects thereof are based on the knowledge of the present inventors that it is effective to form a good heat-resistant insulating film that can withstand an annealing temperature of 600 ° C. or higher in order to reduce hysteresis loss. It is.

In the present invention, the apatite layer preferably contains a compound represented by the following general formula (Ia) or (Ib).
Ca ₁₀ (PO ₄ ) ₆ X ₂ (Ia)
Ca _{(10- (m × n) / 2)} M _n (PO ₄ ) ₆ X ₂ (I-b)
(In the formula, M represents an atom or a group of atoms giving a cation, m represents a valence of a cation given by M, n is more than 0 and 5 or less, and X is an atom giving a monovalent anion. Or an atomic group.)

  Moreover, it is preferable that the said silica particle is a silica particle surface-modified with the organic group.

Furthermore, it is preferable that the silica particle surface-modified with the organic group is a silica particle surface-modified using a compound represented by the following general formula (II) or (III).
R ¹ _n Si (OR ² ) _4-n (II)
R ¹ _n SiX _4-n (III)
(In the formula, n is an integer of 1 to 3, R ¹ and R ² represent a monovalent organic group, and X represents a halogen).

  The metal powder is preferably a soft magnetic material powder.

  The powder of the present invention is suitable as a powder for a dust core.

  The present invention also includes a first step of coating the 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 the second step. The powder obtained in the process is pre-cured at 350 ° C. or lower to obtain a powder comprising the metal powder, an apatite layer covering the metal powder, and silica particles attached to the metal powder or the apatite layer. And a third step. A method for producing a powder is provided.

  As the metal powder used in the first step, it is preferable to use a metal powder that has been subjected to phosphoric acid treatment.

  The powder of the present invention is coated with an apatite layer and an insulating layer having silica particles attached thereto, and the insulating layer is excellent in insulation and heat resistance. Therefore, when producing a dust core, annealing can be performed at a high temperature without causing damage to the insulating layer. Therefore, it is possible to obtain a dust core having a sufficiently high permeability while maintaining the insulating properties of the insulating layer.

It is a photograph which shows the scanning electron microscope (SEM) image of the cross section of the hydroxyapatite covering iron powder obtained in Example 1 (magnification: 2500 times). It is a photograph which shows the SEM image of the cross section of the hydroxyapatite covering iron powder obtained in Example 1 (magnification: 50000 times). It is a photograph which shows the SEM image of the cross section of the nano silica adhesion hydroxyapatite coating iron powder obtained in Example 1 (magnification: 1000 times). It is a photograph which shows the SEM image of the cross section of the nano silica adhesion hydroxyapatite coating iron powder obtained in Example 1 (magnification: 100000 times).

  One aspect of the powder of the present invention is a powder comprising a metal powder, an apatite layer covering the metal powder, and silica particles attached to the metal powder or the apatite layer. Hereinafter, each component of the powder of the present invention will be described in order.

(Metal powder)
The metal powder used in the present invention can be used without particular limitation as long as the metal powder has ferromagnetism and exhibits a high saturation magnetic flux density. Specifically, for example, iron powder, silicon steel powder, Sendust Examples include soft magnetic materials such as powder, amorphous powder, permendur powder, soft ferrite powder, amorphous magnetic alloy powder, nanocrystal magnetic alloy powder, and permalloy powder. These may be used alone or in combination of two or more. Can be used. Among these, iron powder is preferable because it is strong in magnetism and inexpensive.

  Among iron powders, pure iron powder is particularly preferable because it is excellent in magnetic properties such as saturation magnetic flux density and magnetic permeability, and is excellent in compressibility. Specific examples of such pure iron powder include atomized iron powder, reduced iron powder, and electrolytic iron powder. Examples thereof include 300NH manufactured by Kobe Steel, Ltd.

  Moreover, as a metal powder, you may use what adjusted the content element in the range which does not have a bad influence on compressibility, the magnetic characteristic of a powder magnetic core, etc. Specifically, for example, phosphorus element can be added for the purpose of preventing oxidation of metal powder, or elements such as cobalt, nickel, manganese, chromium, molybdenum, copper, etc. can be added for the purpose of improving magnetic properties. .

  There is no restriction | limiting in particular as a particle size of metal powder, According to the use and required characteristic of a powder magnetic core, it can determine suitably. Generally, the particle size that can be observed with a scanning electron microscope (SEM) or the like can be selected from those having a size in the range of 1 μm to 300 μm. If the particle size is 1 μm or more, there is a tendency to be easily molded when the dust core is formed, and if it is 300 μm or less, an increase in eddy current of the dust core can be suppressed, and the apatite layer tends to be coated. There is. Moreover, as an average particle diameter (average secondary particle diameter calculated | required by the screening method), the thing of 50-250 micrometers is preferable.

  The shape of the metal powder is not particularly limited, and a spherical or lump shape, or a flat powder that has been flattened by a known production method or machining may be used.

(Apatite layer)
The apatite layer covering the powder surface of the present invention has a function as an insulating coating of the metal powder. From this point of view, it is preferable that the apatite layer has a coating structure that covers the surface of the metal powder in layers.

An apatite layer is a layer composed of a substance having an apatite structure. Preferable examples of the substance having an apatite structure of the apatite layer include compounds represented by the following general formula (Ia) or (Ib).
Ca ₁₀ (PO ₄ ) ₆ X ₂ (Ia)
Ca _{(10- (m × n) / 2)} M _n (PO ₄ ) ₆ X ₂ (I-b)
(In the formula, M represents an atom which gives a cation, m represents a valence of a cation given by M, n is more than 0 and 5 or less, and X is an atom or atomic group which gives a monovalent anion. Is shown.)

  In the general formula (Ib), the atom M that gives a cation is preferably a metal that can be substituted with calcium. Specific examples of such metals include metals having an ionic radius of 0.80 to 1.40%, 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, bismuth and the like. M in the general formula (Ib) may be one type or two or more types. In the general formula (Ib), the range of n is more than 0 and 5 or less, more preferably more than 0 and 2.5 or less, and more than 0 and 1.0 or less. Is more preferable. In the general formulas (Ia) and (Ib), X is preferably a hydroxyl group (OH) and a halogen (F, Cl, B, I, etc.), more preferably a hydroxyl group and fluorine. When X is a hydroxyl group, it is preferable from the viewpoint of excellent applicability to metal powder, and when X is fluorine, it is preferable from the viewpoint of excellent strength.

As the substance having the apatite structure of the apatite layer, the compound represented by the general formula (Ia) is more preferable in terms of excellent insulation, heat resistance and mechanical properties when formed into a dust core. It is particularly preferable to use apatite (Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ ) or fluoroapatite (Ca ₁₀ (PO ₄ ) ₆ F ₂ ).

  In the powder of the present invention, “coating metal powder with an apatite layer” means a state in which at least a part of the metal powder is covered with an apatite layer. Therefore, the “apatite-coated metal powder” to be described later is not limited to a metal powder completely covered with apatite, but may be a metal powder that is partially exposed. On the other hand, as the degree of coating of the metal powder with the apatite layer, a higher covering ratio is preferable in that silica described later tends to adhere and as a result, the bending strength is improved. Specifically, it is preferable that the surface of the metal powder is covered by 90% or more with the apatite layer, more preferably 95% or more, and even more preferably (over 100%). .

  In the powder of the present invention, the apatite layer preferably has a thickness of 10 nm to 1000 nm, and more preferably 20 to 500 nm. If the thickness is 10 nm or more, there is a tendency to obtain an insulating effect, and if it is 1000 nm or less, there is a tendency to obtain an effect of improving density.

  As a method for forming an apatite layer on the metal powder, an aqueous solution containing calcium ions or atoms that give cations in the general formula (1-b) or ions of the atomic group M in a predetermined ratio, and phosphoric acid A method of depositing a substance having an apatite structure on the surface of the metal powder by a reaction of an aqueous solution containing ions can be given. In order to obtain a layer having an apatite structure, it is necessary to control the liquidity of the reaction solution from neutral to basic region (pH = 6.0 or more). In the acidic region, a calcium phosphate layer other than a substance having an apatite structure may be deposited.

In the case where hydroxyapatite is deposited as the apatite layer, for example, a method using a calcium nitrate aqueous solution and an ammonium dihydrogen phosphate aqueous solution can be mentioned. The stoichiometric composition of the hydroxyapatite thus obtained is Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ , but most of it has an apatite structure and is non-stoichiometric as long as it can be maintained. For example, a part of 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 the raw material for the apatite layer added is preferably 0.1 to 1.0 part by mass and more preferably 0.4 to 0.8 part by mass with respect to 100 parts by mass of the metal powder. Preferably, it is 0.5-0.7 mass part. If it is 0.1 mass part or more, there exists a tendency for sufficient specific resistance to be obtained when it is set as a powder magnetic core. Further, the obtained powder insulating layer becomes uniform, and the effect of improving the insulation can be sufficiently obtained. If it is 1.0 mass part or less, when it is set as a powder magnetic core, there exists a tendency which can prevent that a molded object density falls. The mass of the apatite layer can be determined by elemental analysis of the obtained powder and quantifying the amount of calcium (and metal M).

(Silica particles)
As the silica particles used in the powder of the present invention, conventionally known particles can be widely used, and specific examples include fumed silica, colloidal silica, etc. Colloidal silica is preferred. The shape of the silica particles is not particularly limited.

  The silica particles having various sizes can be used, but silica particles having a particle size of submicron or less are suitable for film forming properties. Specifically, the average primary particle size of the silica particles is preferably 50 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less.

  Further, the silica particles are preferably dispersed without being aggregated in the organic solvent. Therefore, the surface of the silica particles may be modified with an organic group for the purpose of improving the dispersibility of the silica particles. Examples of such an organic group include a cyclohexyl group, a phenyl group, a benzyl group, a phenethyl group, a C1 to C6 (C1 to C6) alkyl group, and the like.

  As a method for modifying the surface of the silica particles with such an organic group, a method of reacting the silane compound having the organic group in the molecular structure with the surface of the silica particle can be used. By doing in this way, the bending strength when it is set as a powder magnetic core can be improved, and a specific resistance can also be improved depending on the case.

As such a silane compound, specifically, an alkoxysilane represented by the following general formula (II) or a halogenosilane compound represented by the following general formula (III) can be used.
R ¹ _n Si (OR ² ) _4-n (II)
R ¹ _n SiX _4-n (III)
(In the formula, n is an integer of 1 to 3, R ¹ and R ² represent a monovalent organic group, and X represents a halogen.)

In the general formulas (II) and (III), examples of R ¹ include an organic group to be modified into silica particles. Specifically, cyclohexyl group, phenyl group, benzyl group, phenethyl group, C1-C6 (carbon Examples thereof include alkyl groups having 1 to 6). As the R ^2, it includes a monovalent organic group, specifically, methyl group, ethyl group and the like. Examples of X include chloro, bromo, iodo and the like.

Specific examples of the alkoxysilane represented by the general formula (II) include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, iso-propyltrimethoxysilane, and n-butyltrimethoxy. Trimethoxysilanes such as silane, tert-butyltrimethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, benzyltrimethoxysilane, and phenethyltrimethoxysilane;
Methyltriethoxysilane, ethyltriethoxysilane, n-propyltriethoxysilane, iso-propyltriethoxysilane, n-butyltriethoxysilane, tert-butyltriethoxysilane, n-pentyltriethoxysilane, n-hexyltriethoxy Triethoxysilanes such as silane, cyclohexyltriethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane, phenethyltriethoxysilane;
Dimethyldimethoxysilane, ethylmethyldimethoxysilane, methyl n-propyldimethoxysilane, methyl iso-propyldimethoxysilane, n-butylmethyldimethoxysilane, methyl tert-butyldimethoxysilane, methyl n-pentyldimethoxysilane, n-hexylmethyldimethoxysilane , Dimethoxysilanes such as cyclohexylmethyldimethoxysilane, methylphenyldimethoxysilane, benzylmethyldimethoxysilane, phenethylmethyldimethoxysilane;
Dimethyldiethoxysilane, ethylmethyldiethoxysilane, methyl n-propyldiethoxysilane, methyl iso-propyldiethoxysilane, n-butylmethyldiethoxysilane, methyl tert-butyldiethoxysilane, methyl n-pentyldiethoxysilane , N-hexylmethyldiethoxysilane, cyclohexylmethyldiethoxysilane, methylphenyldiethoxysilane, benzylmethyldiethoxysilane, phenethylmethyldiethoxysilane, and other diethoxysilanes.

Specific examples of the halogenosilane compound represented by the general formula (III) include:
Methyltrichlorosilane, ethyltrichlorosilane, n-propyltrichlorosilane, iso-propyltrichlorosilane, n-butyltrichlorosilane, tert-butyltrichlorosilane, n-pentyltrichlorosilane, n-hexyltrichlorosilane, cyclohexyltrichlorosilane, phenyltri Trichlorosilanes such as chlorosilane, benzyltrichlorosilane, and phenethyltrichlorosilane;
Dimethyldichlorosilane, ethylmethyldichlorosilane, methyl-n-propyldichlorosilane, methyl-iso-propyldichlorosilane, n-butylmethyldichlorosilane, methyl-tert-butyldichlorosilane, methyl-n-pentyldichlorosilane, n- Examples include dichlorosilanes such as hexylmethyldichlorosilane, cyclohexylmethyldichlorosilane, methylphenyldichlorosilane, benzylmethyldichlorosilane, and phenethylmethyldichlorosilane.

  The above silane compounds can be used alone or in combination of two or more.

  The surface modification of the silica particles can usually be performed by adding the alkoxysilane compound or the halogenosilane compound to a dispersion of silica particles and stirring. In that case, it is preferable to add in the range of 0.4-0.6 weight part with respect to 1 weight part of silica particle solid content. If it is 0.6 parts by weight or less, the added silane compound does not remain unreacted, and if it is 0.4 parts by weight or more, the effect of modifying the organic group on the silica particles can be sufficiently obtained. The silica particles may be dispersed in water or dispersed in an organic solvent.

  In addition, it is preferable to use an acid catalyst such as an inorganic acid, an organic acid, or an acidic ion exchange resin in order to rapidly proceed the modification reaction of the organic group on the silica particle surface under mild conditions. In this case, it is particularly preferable to use hydrochloric acid, nitric acid, acetic acid, citric acid, formic acid, oxalic acid and the like. In general, an acid can react with the apatite and deteriorate characteristics, so that hydrochloric acid and acetic acid are more preferable in that they are highly volatile and hardly remain in the system. The addition amount of the acid catalyst is preferably 0.05 to 0.1 parts by weight with respect to 1 part by weight of the silica particle solid content.

  The temperature of the modification reaction is preferably 0 to 50 ° C., more preferably 10 to 40 ° C., in order to prevent the silica particles from aggregating. The silica particles are preferably dispersed in an organic solvent such as isopropyl alcohol, polyethylene glycol monomethyl ether acetate, toluene, and xylene.

(Production method)
The powder production method of the present invention is obtained in a first step of forming a metal powder coated with an apatite by coating a metal powder with an apatite layer (hereinafter referred to as apatite-coated metal powder) and the first step. A second step of attaching silica powder to the metal powder in the apatite-coated metal powder or the apatite layer, and pre-curing the powder obtained in the second step at 350 ° C. or less, the metal powder, And a third step of obtaining a powder comprising an apatite layer covering the metal powder and silica particles adhering to the metal powder or the apatite layer.

(Phosphoric acid treatment of metal powder)
Moreover, it is preferable to use the metal powder by which the phosphoric acid process was used as a metal powder with which it uses for a 1st process at the point which can prevent the oxidation of a metal powder. In the manufacturing method of the powder of this invention, the said phosphoric acid process may be provided before a 1st process, and what is marketed as a metal powder by which the phosphoric acid process was carried out may be used. The phosphoric acid treatment can be performed by a conventionally known method.

(Formation of apatite layer)
As described above, as a method of forming an apatite layer on the metal powder, an aqueous solution containing calcium ions (and atoms or ions of atomic group M that give cations other than calcium as needed), and phosphoric acid, The method of depositing apatite on the metal powder surface by reaction of the aqueous solution containing ion can be mentioned. Specifically, a method in which an aqueous solution serving as a calcium source and metal powder are placed in a flask and the aqueous solution serving as a phosphoric acid source is added dropwise while stirring. Alternatively, a method in which water and metal powder are placed in a flask and the aqueous solution serving as the calcium source and the aqueous solution serving as the phosphoric acid source are dropped simultaneously or sequentially while stirring can be used. In the case of sequential dropping, either order may be dropped first.

  The calcium source is not particularly limited as long as it is a water-soluble calcium compound. Specifically, for example, calcium salts of inorganic bases such as calcium hydroxide, calcium salts of inorganic acids such as calcium nitrate, calcium acetate, etc. And calcium salts of organic acids and calcium salts of organic bases. Examples of the phosphoric acid source include phosphoric acid and phosphates such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

  In order to obtain a layer having an apatite structure, the reaction solution is preferably a neutral region to a basic region, and the pH is preferably 7 or more, more preferably 8 or more, further preferably 9 or more, 10 The above is particularly preferable. Since the calcium phosphate layer other than apatite may precipitate in the acidic region, the pH of the aqueous solution serving as the calcium source and the aqueous solution serving as the phosphoric acid source may be previously set to 7 or more with a base such as ammonia water. preferable.

  The reaction temperature may be room temperature, but is preferably 50 ° C. or higher, preferably 70 ° C. or higher, and particularly preferably 90 ° C. or higher for promoting the reaction. When the solvent is water, the upper limit temperature is the reflux temperature of the reaction solution, which is around 100 ° C.

The reaction time varies depending on the concentrations of the aqueous solution serving as the calcium source and the aqueous solution serving as the phosphoric acid source. The higher the concentration, the shorter the reaction time. The lower the concentration, the longer the reaction time. In the production method of the present invention, the concentration of the aqueous solution serving as the calcium source and the concentration of the aqueous solution serving as the phosphoric acid source are respectively 0.003 to 0.5.
The range of M is preferable, and the reaction time in this case is preferably 1 to 10 hours.

(Silica powder adhesion)
Next, the silica particles are adhered to the apatite-coated metal powder obtained as described above. Examples of this method include a method in which the dispersion of silica particles is added to the apatite-coated metal powder, followed by shaking and stirring. When a commercially available organosilica sol is used, it may be diluted to an appropriate concentration. As described above, when the surface of silica particles in a commercially available organosilica sol is surface-modified with an organic group such as a silane compound, the reaction solution used for the surface modification may be used as it is. In addition, even if the silica particle used here is adhering to an apatite layer, it may be adhering to the exposed metal powder surface of a defective part with insufficient coating of an apatite layer.

  The solvent for dispersing the silica particles is not particularly limited, and specific examples include alcohol solvents typified by isopropyl alcohol, ketone solvents typified by methyl ethyl ketone, and aromatic solvents typified by toluene. . In particular, an aromatic solvent in which the silica particles in the organosilica sol easily maintain a colloidal solution state is preferable.

(Pre-curing)
The apatite-coated metal powder having the silica particles attached to the surface in this way is pre-cured at 350 ° C. or lower. By doing in this way, an apatite layer can harden | cure and it can form a firm heat resistant film. Without pre-curing, when these powders are compression molded to produce a powder magnetic core, the silica particles on the surface are embedded in the apatite layer, and there is a tendency that sufficient insulation is not obtained. The pre-curing temperature is preferably 100 to 300 ° C.

  In addition, it is preferable that the addition amount of the silica particle in this invention shall be 0.05-1.0 mass part with respect to 100 mass parts of metal powder to be used. If the addition amount is 0.05 parts by weight or more, the silica particles can be uniformly coated on the metal powder, and the effect of improving the insulation tends to be obtained. On the other hand, if the amount is 1.0 part by mass or less, there is a tendency that when the powder magnetic core is formed, a reduction in the density of the molded body can be prevented and a reduction in the bending strength of the obtained powder magnetic core can be prevented.

(Manufacture of dust core)
The powder for a powder magnetic core of the present invention can be formed into a powder magnetic core by compression molding a mixed powder mixed with a lubricant as necessary. The lubricant can be used after the dispersion is applied to the mold wall surface and dried. As the lubricant, metal soap such as zinc stearate, calcium stearate and lithium stearate, long chain hydrocarbons such as wax, silicone oil and the like can be used. The molding pressure is preferably 500-1500 MPa. Furthermore, the obtained powder magnetic core can be annealed to reduce hysteresis loss. In this case, the annealing temperature is preferably selected in the range of 500 to 800 ° C. This annealing is preferably performed under an inert gas such as nitrogen or argon.

The dust core produced by the above method exhibits high molded body density and insulation. Although the mechanism showing such characteristics has not been clearly clarified, the present inventors presume the following mechanism. That is, when the apatite layer is coated on the metal powder, the silica particles are more likely to adhere to the metal powder due to the high adsorption force unique to apatite. Further, the silica particles are effectively filled in the crack portion of the apatite layer generated when the silica particles attached in this way are molded, so that a high molded body density (for example, 7.0 g / cm ³ or more), and It is estimated that high heat resistance and insulation can be maintained. As described above, it is preferable that the silica particles have a particle size of submicron or less because the small silica particles are easy to move, and thus the silica particles are more effectively filled into the cracks of the apatite layer. It is done.

The density of the compact of the powder magnetic core prepared from the powder of the present invention is preferably 7.0 g / cm ³ or more, and more preferably 7.4 g / cm ³ or more. If the density is 7.4 g / cm ³ or more, the magnetic flux density of the dust core tends to be improved.

  The electric resistance value on the surface of the dust core is preferably 30 μΩm or more, more preferably 50 μΩm or more, and further preferably 90 μΩm or more. If the electric resistance is 30 μΩm or more, there is a tendency that the effect of reducing the eddy current loss of the dust core can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

[Example 1]
A 300 mL four-necked flask was charged with 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% aqueous ammonia and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel). Further, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the contents of the four-necked flask at room temperature (25 ° C.), the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was added dropwise thereto over 10 minutes.

  Next, the four-necked flask was reacted in a 90 ° C. oil bath with stirring for 2 hours. The obtained slurry was filtered with suction, and the residue was dried in an oven at 110 ° C. to obtain a gray powder (yield 96% by mass). When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by X-ray photoelectron spectroscopy (XPS), the atomic abundance ratio was Fe: 4.58%, Ca: 15.7%, Ca / P ratio (molar ratio). Was 1.64, and it was confirmed that the iron powder was coated with hydroxyapatite.

  Further, 20 g of the obtained apatite-coated iron powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were mixed and shaken in a polypropylene bottle having a maximum internal volume of 50 mL for 10 minutes. Was taken out into a stainless steel petri dish and precured at 200 ° C. for 30 minutes. The powder obtained by pre-curing was passed through a 250 μm sieve to remove the giant associated particles to obtain nanosilica-attached apatite-coated iron powder.

  The SEM images of the cross section of the apatite-coated iron powder obtained as described above are shown in FIGS. 1 and 2, and the SEM images of the cross section of the nanosilica-attached apatite-coated iron powder are shown in FIGS. It was confirmed that a hydroxyapatite layer and a nanosilica layer were formed on the surface of these particles.

The obtained nanosilica-attached apatite-coated iron powder (5.92 g) was filled in a mold having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa. At this time, the thickness of the obtained tablet is about 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 μΩm. The density was 7.48 g / cm ³ . This tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after polishing the surface again, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 91 μΩm. The density was 7.47 g / cm ³ .

[Comparative Example 1]
In the same manner as in Example 1, hydroxyapatite-coated iron powder was prepared halfway as follows. That is, a calcium nitrate aqueous solution 75 mL (1.79 mmol, 0.024 M) adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300 NH manufactured by Kobe Steel) were placed in a 300 mL four-necked flask. . Further, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the contents of the four-necked flask at room temperature (25 ° C.), the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was added dropwise thereto over 10 minutes.

Next, the four-necked flask was reacted in a 90 ° C. oil bath with stirring for 2 hours. Then, the obtained slurry was subjected to suction filtration, and the residue was dried in an oven at 110 ° C. to obtain a gray powder. (Yield 96 mass%). The obtained powder was passed through a 250 μm sieve to obtain an apatite-coated metal powder. 5.95 g of apatite-coated metal powder was filled in a metal mold having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa. At this time, the thickness of the obtained tablet was about 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 μΩm. The density was 7.54 g / cm ³ . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 0.54 μΩm. The density was 7.53 g / cm ³ .

[Comparative Example 2]
Without providing the apatite layer, nanosilica was adhered to the iron powder by the method of attaching nanosilica in Example 1. That is, 20 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel, Ltd.) and 2 g of nanosilica toluene solution (solid content concentration: 3.0% by mass) are mixed and shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL. Then, it was precured at 200 ° C. for 30 minutes. The powder obtained by pre-curing was passed through a 250 μm sieve to remove the huge associating particles, thereby obtaining nano silica-attached metal powder. 5.99 g of the obtained powder was molded into a cylindrical tablet having a diameter of 1.4 cm and a thickness of 5.145 mm at 1000 MPa. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistance meter, and it was 79 μΩm. The density was 7.57 g / cm ³ . The polished tablet was annealed and fired at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 20 μΩm. The density was 7.57 g / cm ³ .

  Table 1 shows the measurement results of the density and specific resistance of the powder magnetic core thus obtained.

  Referring to Table 1, both hydroxyapatite coating and silica particle deposition are essential to obtain a high resistivity. Further, the density of the molded body of Example 1 is almost lower than the density of the molded body of Comparative Example 1 and Comparative Example 2 even though hydroxyapatite coating and silica particle adhesion are performed in Example 1. Not. This can be presumed to be because silica particles were embedded in the pores of the cracks of the apatite layer that were broken during compression molding.

Next, in order to estimate the strength of the adsorption force between the apatite layer and the silica particles, silica particles are adhered to pure iron powder and apatite-coated iron powder having different surface states, respectively, and how much silica particles remain on the surface. Were compared through quantitative analysis. As a method, in 5.0 g of an organosilica sol solution (medium: toluene) (solid content concentration: 3.0% by mass) containing silica particles having an average particle diameter of 20 nm measured by a dynamic light scattering method using HPPS manufactured by Mlvern Was placed in a glass screw tube with a maximum capacity of 10 mL, and 3.0 g of various powders were added therein. The screw tube was agitated for 3 hours with a mix rotor whose rotational speed was set to 105 rpm. The liquid after stirring was designated as No. for quantitative analysis. Suction filtration was performed using 5B (JIS P3801) filter paper, and the residue was washed with toluene and vacuum dried to obtain each powder.
The obtained powder was subjected to elemental analysis using the ICP-OES method, and the silica particles adhering to the powder were quantified as the amount of silicon atoms. The results are shown in Table 2.

  From the results in Table 2, the amount of silicon atoms determined from the iron powder coated with apatite is about twice as large as that of pure iron powder. Since silicon atoms are only derived from silica particles, the amount of silica particles adhering was large, and it was found that the apatite layer had a stronger adsorption force for silica particles than the pure iron powder surface layer.

[Example 2]
After adding iron powder to the calcium nitrate aqueous solution in Example 1, a step of stirring in an oil bath at 30 ° C. for 15 minutes was added.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was added dropwise thereto over 10 minutes.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was subjected to suction filtration, and the residue was dried in an oven at 110 ° C. to obtain a gray powder. When the atomic abundance ratio near the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 3.31%, Ca 17.1%, Ca / P ratio (molar ratio) was 1.63, and the powder was hydroxy. It was confirmed that it was covered with apatite.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were mixed and shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL. It was dried under pressure for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The powder obtained after precuring was passed through a 250 μm sieve.
Of the iron powder applied to the sieve, 6 g was filled in a mold having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 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 236 μΩm. The compact density was 7.50 g / cm ² . The polished tablet was baked at 600 ° C. for 1 hour in a nitrogen atmosphere, and after polishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 75 μΩm. The compact density was 7.50 g / cm ² .

[Example 3]
In Example 2, after adding ammonium dihydrogen phosphate aqueous solution to the contents of the four-necked flask, a step of stirring in an oil bath at 30 ° C. for 1.5 hours was added.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was subjected to suction filtration, and the residue was dried in an oven at 110 ° C. to obtain a gray powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 5.56%, Ca 14.85%, Ca / P ratio (molar ratio) was 1.63, and the powder was hydroxy. It was confirmed that it was covered with apatite.

Furthermore, 20 g of the obtained apatite-coated powder and 2 g of organosilica sol toluene solution (solid content concentration: 3.0% by mass) were mixed and shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL. It took out to the stainless steel petri dish, it dried for 5 minutes at the pressure of 1 Mpa or less, and the taken-out powder was precured for 25 minutes at 200 degreeC. The iron powder obtained by pre-curing was passed through a 250 μm sieve.
6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 111 μΩm. The compact density was 7.51 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 55 μΩm. The compact density was 7.51 g / cm ² .

[Example 4]
In Example 3, the 90 ° C. reaction time was changed from 2 hours to 10 minutes.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 10 minutes while stirring. Then, the obtained slurry was filtered by suction and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 6.79%, Ca 12.77%, and the Ca / P ratio (molar ratio) was 1.44.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 214 μΩm. The compact density was 7.50 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 53 μΩm. The compact density was 7.49 g / cm ² .

[Example 5]
In Example 3, the reaction time at 90 ° C. was changed from 2 hours to 5 hours.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 5 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio near the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 6.07%, Ca 13.98%, Ca / P ratio 1.67, and the powder was coated with hydroxyapatite. I was able to confirm that.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 218 μΩm. Further, the density of the molded body was 7.47 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 93 μΩm. Further, the density of the molded body was 7.47 g / cm ² .

[Example 6]
In Example 3, the reaction temperature of 90 ° C. was changed to 30 ° C.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. 3 Stir for 5 hours.

  Then, the obtained slurry was filtered by suction and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 7.84%, Ca 11.67%, Ca / P ratio (molar ratio) was 1.65, and the iron powder was It was confirmed that it was coated with hydroxyapatite.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 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 μΩm. Moreover, the molding density was 7.53 g / cm ² .
The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 31 μΩm. The density was 7.53 g / cm ² .

[Example 7]
In Example 3, the 90 ° C. reaction temperature was changed to 50 ° C.
That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 50 ° C. over 5 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 7.08%, Ca 13.24%, Ca / P ratio (molar ratio) was 1.77, and the iron powder was It was confirmed that it was coated with hydroxyapatite.

  Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum content of 50 mL, and then the contents were made of a stainless steel dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve.

6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 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 μΩm. The compact density was 7.46 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 53 μΩm. Further, the density of the molded body was 7.47 g / cm ² .

[Example 8]
In Example 3, the 90 ° C. reaction temperature was changed to 30 ° C., and firing at 110 ° C. was not performed.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. 3 Stir for 5 hours.

  Next, the obtained slurry was suction filtered, taken out into a stainless steel petri dish, and dried at a pressure of 1 MPa or less for 5 minutes to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 5.53%, Ca 13.63%, and the Ca / P ratio (molar ratio) was 1.52.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve.
6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 168 μΩm. The compact density was 7.50 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after polishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 56 μΩm. The compact density was 7.49 g / cm ² .

[Example 9]
In Example 3, the 90 ° C. reaction temperature was changed to 50 ° C., and firing at 110 ° C. was not performed.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 50 ° C. over 5 minutes, and the contents of the four-necked flask were reacted at 90 ° C. for 2 hours while stirring. The obtained slurry was suction filtered, taken out into a stainless steel petri dish, and dried at a pressure of 1 MPa or less for 5 minutes to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 4.89%, Ca 15.54%, Ca / P ratio (molar ratio) was 1.77, and the powder was hydroxy. It was confirmed that it was covered with apatite.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 137 μΩm. The compact density was 7.50 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 44 μΩm. The compact density was 7.50 g / cm ² .

[Example 10]
In Example 3, baking at 110 ° C. was not performed.

  That is, in a 300 mL four-necked flask, 75 mL (1.79 mmol, 0.024 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.07 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry liquid was subjected to suction filtration and vacuum dried at 0 MPa to obtain gray iron powder. When the obtained iron powder was analyzed by XPS, the atomic abundance ratio was Fe 3.85%, Ca 16.63%, and the Ca / P ratio (molar ratio) was 1.56.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 137 μΩm. The compact density was 7.50 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 30 μΩm. The compact density was 7.50 g / cm ² .

[Example 11]
In Example 3, the charge amount of calcium nitrate was changed from 1.79 mmol to 0.60 mmol, and the charge amount of ammonium dihydrogen phosphate was changed from 1.07 mmol to 0.36 mmol.

  That is, in a 300 mL four-necked flask, 75 mL (0.60 mmol, 0.008 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (0.36 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. 1 Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 7.29%, Ca 13.14%, and the Ca / P ratio (molar ratio) was 1.52.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 122 μΩm. Moreover, the molding density was 7.56 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 30 μΩm. Moreover, the molding density was 7.56 g / cm ² .

[Example 12]
In Example 3, the calcium nitrate charge was changed from 1.78 mmol to 2.98 mmol, and the ammonium dihydrogen phosphate charge was changed from 1.07 mmol to 1.78 mmol.

  That is, in a 300 mL four-necked flask, 75 mL (2.98 mmol, 0.040 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (1.78 mmol, 0.024 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or more with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 2.76%, Ca 17.59%, and the Ca / P ratio (molar ratio) was 1.67.

Further, 20 g of the obtained apatite-coated powder and 2 g of an organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of a stainless steel petri dish. And dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to find 213 μΩm. Moreover, the molding density was 7.44 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 88 μΩm. Moreover, the molding density was 7.44 g / cm ² .

[Example 13]
In the same manner as in Example 11, a hydroxyapatite-coated iron powder having a single hydroxyapatite layer was prepared, and the same treatment was repeated to prepare a hydroxyapatite-coated iron powder having a two-layer hydroxyapatite layer.

  That is, in a 300 mL four-necked flask, 75 mL (0.60 mmol, 0.008 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (0.36 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped into the contents over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. The mixture was stirred for 1.5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes, and the contents of the four-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%).

  Subsequently, 28.8 g of the obtained apatite single-layer coating powder and 72 mL (0.57 mmol, 0.008 M) of an aqueous calcium nitrate solution adjusted to pH 11 or more with 25% aqueous ammonia were placed in a 300 mL four-necked flask, and 30 ° C. In an oil bath for 15 minutes. Thereafter, 72 mL (0.34 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or more with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped into the contents over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. The mixture was stirred for 1.5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 7.05%, Ca 13.84%, and the Ca / P ratio (molar ratio) was 1.59.

Furthermore, after shaking 20 g of the obtained apatite two-layer coating powder and 2 g of organosilica sol toluene solution (solid content concentration of 3.0% by mass) in a polypropylene bottle having a maximum internal volume of 50 mL, the contents were made of stainless steel. The powder was taken out into a petri dish and dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 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 μΩm. Moreover, the molding density was 7.53 g / cm ² . The polished tablet was baked at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 59 μΩm. Moreover, the molding density was 7.53 g / cm ² .

[Example 14]
Similar to Example 13, a hydroxyapatite-coated iron powder having two hydroxyapatite layers was prepared, and the same treatment was repeated to prepare a hydroxyapatite-coated iron powder having a three-layer hydroxyapatite layer.

  That is, in a 300 mL four-necked flask, 75 mL (0.60 mmol, 0.008 M) of calcium nitrate aqueous solution adjusted to pH 11 or more with 25% ammonia water and 30 g of iron powder (pure iron powder 300NH manufactured by Kobe Steel) were added. The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 75 mL (0.36 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder.

  Subsequently, 29.5 g of the obtained apatite single-layer coated iron powder and 74 mL (0.59 mmol, 0.008 M) of an aqueous calcium nitrate solution adjusted to pH 11 or higher with 25% aqueous ammonia were placed in a 300 mL four-necked flask, and 30 The mixture was stirred for 15 minutes in an oil bath at 0 ° C. Thereafter, 74 mL (0.35 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes, and the contents of the four-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.

  29.5 g of the obtained apatite two-layer coated iron powder and 74 mL (0.59 mmol, 0.008 M) of an aqueous calcium nitrate solution adjusted to pH 11 or more with 25% aqueous ammonia are placed in a 300 mL four-necked flask and oil at 30 ° C. Stir in the bath for 15 minutes. Thereafter, 74 mL (0.35 mmol, 0.005 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or higher with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the aqueous solution of ammonium dihydrogen phosphate in the dropping funnel was dropped over 10 minutes, and then the temperature of the oil bath was maintained at 30 ° C. Stir for 5 hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the atomic abundance ratio in the vicinity of the surface of the obtained powder was analyzed by XPS, the atomic abundance ratio was Fe 10.33%, Ca 10.95%, and the Ca / P ratio (molar ratio) was 1.69.

Further, after shaking 20 g of the obtained apatite three-layer coated iron powder and 2 g of an organosilica sol toluene solution (solid content concentration of 3.0% by mass) in a polypropylene bottle having a maximum internal volume of 50 mL, the contents were It took out to the stainless steel petri dish, it dried for 5 minutes at the pressure of 1 Mpa or less, and the taken-out powder was precured for 25 minutes at 200 degreeC. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite three-layer coated iron powder was filled in a mold having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 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 95 μΩm. The compact density was 7.494 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 31 μΩm. The compact density was 7.50 g / cm ² .

[Example 15]
The amount of iron powder charged in Example 3 was changed to 33 times, and accordingly the reaction vessel volume, the amount of solvent, etc. were also changed to 33 times, and after dropping the ammonium dihydrogen phosphate aqueous solution into the contents of the four-necked flask, The stirring time in the oil bath was changed from 1.5 hours to 2 hours.

  That is, a calcium nitrate aqueous solution 250 mL (5.95 mmol, 0.024 M) adjusted to pH 11 or more with 25% ammonia water and 100 g of iron powder (pure iron powder 300 NH manufactured by Kobe Steel) were placed in a 1000 mL four-necked flask, The mixture was stirred for 15 minutes in an oil bath at 30 ° C. Thereafter, 250 mL (3.57 mmol, 0.014 M) of an aqueous solution of ammonium dihydrogen phosphate adjusted to pH 11 or more with 25% aqueous ammonia was placed in a dropping funnel with a side tube, and this was fixed to a four-necked flask. While stirring the four-necked flask in an oil bath at 30 ° C., the ammonium dihydrogen phosphate aqueous solution in the dropping funnel was dropped over 30 minutes, and then the temperature of the oil bath was maintained at 30 ° C. 2 Stir for hours.

  Next, the temperature of the oil bath was raised from 30 ° C. to 90 ° C. over 10 minutes and reacted at 90 ° C. for 2 hours with stirring. The obtained slurry was suction filtered and dried in an oven at 110 ° C. to obtain a gray iron powder. When the obtained iron powder was analyzed by XPS, it was confirmed that the atomic abundance ratio was Fe 3.85%, Ca 15.30%, Ca / P ratio was 1.76, and the iron powder was coated with hydroxyapatite. did it.

Further, 60 g of the obtained apatite-coated iron powder and 6 g of organosilica sol toluene solution (solid content concentration: 3.0% by mass) were shaken for 10 minutes in a polypropylene bottle having a maximum internal volume of 50 mL, and then the contents were made of stainless steel. The powder was taken out into a petri dish and dried at a pressure of 1 MPa or less for 5 minutes, and the taken-out powder was precured at 200 ° C. for 25 minutes. The iron powder obtained by pre-curing was passed through a 250 μm sieve. 6 g of the obtained nanosilica-attached apatite-coated iron powder was filled in a die having an inner diameter of 14 mm and molded into a cylindrical tablet at a molding pressure of 1000 MPa / cm ² . At this time, the thickness of the obtained tablet is about 5 mm. The surface of the molded tablet was polished, and the volume resistivity (resistivity) was measured with a four-terminal resistivity meter. As a result, it was 193 μΩm. The compact density was 7.51 g / cm ² . The polished tablet was annealed at 600 ° C. for 1 hour in a nitrogen atmosphere, and after repolishing the surface, the volume resistivity (resistivity) was measured with a four-terminal resistivity meter to be 41 μΩm. The compact density was 7.51 g / cm ² .

  The evaluation results regarding the hydroxyapatite-coated iron powder and nanosilica-attached hydroxyapatite-coated iron powder obtained in Examples 1 to 15 are summarized in Tables 3 to 5.

  Referring to Table 4, it was revealed that even if the synthesis method is different, the hydroxyapatite layer can be formed on the metal powder with the same coverage. Also, referring to Tables 3 and 5, it is clear that the powder magnetic core of the nanosilica-attached hydroxyapatite-coated iron powder including the step of pre-curing at 100 to 300 ° C. in the production process shows high specific resistance and compact density. is there.

Claims (6)

And metal powder, and the apatite layer covering the metal powder, Ri Na and a silica particles attached to the metal powder or apatite layer,
The silica particles are silica particles whose surface is modified with an organic group,
The powder whose silica particle surface-modified with the organic group is a silica particle surface-modified using a compound represented by the following general formula (II) or (III) .
R ¹ _n Si (OR ² ) _4-n (II)
R ¹ _n SiX _4-n (III)
(In the formula, n is an integer of 1 to 3, R ¹ and R ² represent a monovalent organic group, and X represents a halogen) The powder according to claim 1, wherein the apatite layer contains a compound represented by the following general formula (Ia) or (Ib).
Ca ₁₀ (PO ₄ ) ₆ X ₂ (Ia)
Ca _{(10- (m × n) / 2)} M _n (PO ₄ ) ₆ X ₂ (I-b)
(In the formula, M represents an atom which gives a cation, m represents a valence of a cation given by M, n is more than 0 and 5 or less, and X is an atom or atomic group which gives a monovalent anion. Is shown.) The powder according to claim 1 or 2 , wherein the metal powder is a powder of a soft magnetic material. The powder according to any one of claims 1 to 3 , which is a powder for a dust core. A first step of coating the metal powder with apatite to obtain the apatite-coated metal powder;
A second step of attaching silica powder to the metal powder surface or apatite layer surface of the apatite-coated metal powder obtained in the first step;
The powder obtained in the second step is precured at 350 ° C. or less, and has the metal powder, an apatite layer covering the metal powder, and silica particles attached to the metal powder or the apatite layer. A third step of obtaining a powder comprising:
A method for producing a powder. The manufacturing method of the powder of Claim 5 using the metal powder by which the phosphoric acid process was used as the said metal powder provided to a said 1st process.