JP6519419B2 - Iron nitride based magnetic powder and bonded magnet using the same - Google Patents

Description

The present invention relates to an iron nitride-based magnetic powder having a Fe ₁₆ N ₂ compound phase as a main phase, maintaining high saturation magnetization, and having high coercivity. Furthermore, a bonded magnet using the iron nitride magnetic powder is provided.

  In recent years, Nd-Fe-B based magnets are widely used as magnets for motors of electric vehicles, hybrid vehicles and the like. However, rare earths typified by Nd are raw materials for high-value-added components that support industrial fields, and demand is expanding in recent years, so there is concern that resource exhaustion and raw material prices may be unstable. . Furthermore, the growing demand in developing countries and the high degree of reliance on specific producing countries due to their uneven distribution have led to problems with securing stable supply.

  In order to avoid the above problems, it is required to develop high-performance magnets from elements (iron, nitrogen) which are inexhaustible in nature without using rare earth.

Fe-N compounds, in particular Fe ₁₆ N _2, are attracting attention as one of the materials exhibiting a saturation magnetization larger than that of Fe.

  In Patent Document 1, an iron nitride-based magnetic powder is synthesized by a method of synthesizing iron oxide by a coprecipitation method, and reducing and nitriding it. However, due to the low coercivity of the obtained iron nitride powder, its use as a magnetic material for motor applications where high coercivity and high saturation magnetization are required is difficult. Also, the motor often becomes hot during use, and the iron nitride powder does not have sufficient moisture resistance at high temperatures.

JP, 2009-84115, A

The present invention has been made in view of the above, and it is an object of the present invention to provide an iron nitride-based magnetic powder having a high coercive force and excellent moisture resistance, and a bonded magnet using the magnetic powder.

That is, according to the present invention, the first coating layer is formed on the surface of Fe ₁₆ N ₂ particles having the Fe ₁₆ N ₂ phase as the main phase, and the _second coating layer is formed on the surface of the first coating layer. An iron nitride-based magnetic powder comprising iron-based magnetic particles, wherein the first coating layer is a metal or alloy comprising any one or more of Cr, Mn, V, Mo and W, and the second coating An iron nitride-based magnetic powder and the iron nitride-based magnetic powder characterized in that the layer is an alloy of a metal consisting of at least one of Ni and Co and a metal contained in the first covering layer. It relates to the bonded magnet used.

Furthermore, it relates to an iron nitride based magnetic powder and a bonded magnet using the iron nitride based magnetic powder, wherein the metal contained in the first coating layer contained in the alloy of the second coating layer is 1 to 10 at%. It is.

Furthermore, the present invention relates to a bonded magnet using the iron nitride magnetic powder and the iron nitride magnetic powder, wherein the thickness of the first covering layer is 5 nm or more.

Furthermore, the present invention relates to a bonded magnet using the iron nitride magnetic powder and the iron nitride magnetic powder, wherein the thickness of the second covering layer is 5 nm or more.

Since the first covering layer of Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder is made of nonmagnetic Cr, Mn, V, Mo, or W at least one metal, Fe ₁₆ N ₂ The effect of magnetically separating the particles from each other is exhibited, and the iron nitride-based magnetic powder can obtain good coercivity.

Since the second covering layer of Fe ₁₆ N ₂ particles constituting the iron nitride magnetic powder contains one or more metals of Ni and Co which are base metals, the moisture resistance of the iron nitride magnetic powder is good. You can get

Furthermore, since the second covering layer is an alloy of the metal contained in the first covering layer and the metal of the second covering layer, the adhesion between the second covering layer and the first covering layer It is believed that the iron nitride-based magnetic powder can obtain good moisture resistance because it has the effect of preventing peeling of the second coating layer at high temperatures.

By setting the metal contained in the first coating layer contained in the alloy of the second coating layer to 1 to 10 at%, the iron nitride-based magnetic powder can obtain even better moisture resistance.

When the thickness of the first covering layer is 5 nm or more, the iron nitride-based magnetic powder can obtain a further favorable coercive force. Preferably, the thickness of the first covering layer is 5 to 15 nm.

When the thickness of the second covering layer is 5 nm or more, the iron nitride-based magnetic powder can obtain even better moisture resistance. Preferably, the thickness of the first covering layer is 5 to 15 nm.

According to the present invention, it is possible to provide an iron nitride-based magnetic powder having a high coercive force and excellent corrosion resistance as compared to conventional iron nitride-based magnetic powders.

Hereinafter, preferred embodiments of the present invention will be described. The present invention is not limited by the contents of the embodiments and examples described below. In addition, the components shown in the embodiments and examples described below may be combined as appropriate or selected as appropriate.

An iron nitride-based magnetic powder according to an embodiment of the present invention has a first covering layer on the surface of Fe ₁₆ N ₂ particles having an Fe ₁₆ N ₂ phase as a main phase, and the first covering layer An iron nitride-based magnetic powder comprising iron nitride-based magnetic particles having a second covering layer on the surface, wherein the first covering layer is any one or more of Cr, Mn, V, Mo and W. Or an alloy, and the second covering layer is an alloy of a metal consisting of any one or more of Ni and Co and a metal contained in the first covering layer.

The iron nitride-based magnetic powder according to the present invention comprises Fe ₁₆ N ₂ particles as the main phase. In addition to the main phase _may have a _{Fe 2 O 3, Fe 3 O} 4 and iron oxide phase such as FeO.

In the Fe ₁₆ N ₂ particles according to the present embodiment, the main phase is the Fe ₁₆ N ₂ compound phase, and the Fe ₁₆ N ₂ particles may include the Fe ₄ N compound phase. It may also have a phase of oxide on the surface of the Fe ₁₆ N ₂ particles.

The Fe ₁₆ N ₂ particles may contain a transition metal such as Mn, Ni, Co, Ti, Zn or the like.

The particle diameter of the Fe ₁₆ N ₂ particles is preferably 30 to 150 nm. If the particle size of the Fe ₁₆ N ₂ particles is within this range, the coercivity tends to increase.

The iron nitride-based magnetic particles according to the present invention have a first covering layer on the surface of Fe ₁₆ N ₂ particles that are the main phase, and have a second covering layer on the surface of the first covering layer. ing. A Si compound may be contained in part of the interface between the Fe ₁₆ N ₂ particles and the first covering layer.

The first covering layer is a metal or an alloy of any one or more of Cr, Mn, V, Mo and W, and may be in either crystalline or amorphous state.

The second covering layer is an alloy of at least one metal of Ni, Co and a metal contained in the first covering layer, and may be in a crystalline or amorphous state. By alloying the metal contained in the first covering layer with the metal of the second covering layer, the adhesion between the second covering layer and the first covering layer is enhanced, and the second covering at a high temperature is obtained. Since the effect of preventing layer peeling can be obtained, the iron nitride-based magnetic powder can obtain good moisture resistance.

In addition, preferably, the metal contained in the first coating layer contained in the alloy of the second coating layer is 1 to 10 at%, whereby the iron nitride magnetic powder can obtain even better moisture resistance. . At this time, when a plurality of metals are included in the first covering layer, a plurality of metals may be included in the first covering layer included in the alloy of the second covering layer. In that case, the total amount of the plurality of metals contained in the first covering layer contained in the alloy of the second covering layer is 1 to 10 at%.

The thickness of the first covering layer is preferably 5 nm or more, more preferably 5 to 15 nm. If the thickness of the first covering layer is less than 5 nm, a sufficient coercive force can not be obtained because the effect of magnetically separating Fe ₁₆ N ₂ particles is not exhibited sufficiently. In the case where the thickness of the first covering layer exceeds 15 nm, the proportion of the Fe ₁₆ N ₂ phase contained in the iron nitride magnetic powder decreases, and a sufficient saturation magnetization of the iron nitride magnetic powder can not be obtained. There is. Further preferably, the thickness of the second covering layer is 5 nm or more. When the thickness of the second covering layer is less than 5 nm, the iron nitride-based magnetic powder can not obtain good moisture resistance. In the case where the thickness of the second covering layer exceeds 15 nm, the proportion of the Fe ₁₆ N ₂ phase contained in the iron nitride magnetic powder decreases, and a sufficient saturation magnetization can not be obtained by the iron nitride based magnetic powder. There is.

The suitable manufacturing method of the iron nitride type magnetic powder which concerns on this embodiment is described. The iron nitride-based magnetic powder according to the present embodiment comprises first and second coated layers of Fe ₁₆ N ₂ particles obtained by synthesizing iron oxide particles and subsequently subjecting the iron oxide particles to reduction treatment and nitriding treatment in order Obtained by performing processing to form

The iron oxide particles can be produced by mixing an iron salt aqueous solution and an alkaline aqueous solution, ripening and washing.

Examples of the above-mentioned iron salt include sulfate, chloride, nitrate and the like, and these may be used in combination as appropriate. Also, their hydrates can be used.

As the aqueous alkali solution, one or more of aqueous sodium hydroxide solution, aqueous ammonia, aqueous ammonia salt solution, and aqueous urea solution can be used, but it is not limited thereto.

In addition, after iron oxide production, in-liquid aging reaction such as hydrothermal treatment with an autoclave may be performed to improve crystallinity and control particle size and particle shape.

After the production of iron oxide, the aqueous solution is filtered, and if necessary, washing treatment such as water washing can be performed to recover iron oxide particles.

  The said iron oxide particle may coat | cover a part of particle | grain surface with Si compound, in order to suppress that particle | grains sinter by reduction processing. As the Si compound, colloidal silica, a silane coupling agent, a silanol compound or the like can be used.

When the Si compound is coated, the coating amount is desirably 0.1% by mass or more and 20% by mass or less in terms of Si based on iron oxide particles. If the amount is less than 0.1% by mass, the effect of suppressing sintering between particles can not be sufficiently obtained during heat treatment, so that the finally obtained iron nitride-based magnetic particles become large. If it exceeds 20% by mass, the effect of suppressing sintering between particles during heat treatment becomes excessive, and the finally obtained Fe ₁₆ N ₂ particles become small.

The iron oxide particles preferably have an average particle size of 10 nm or more and 150 nm or less. By setting the average particle size to this range, the average particle size of Fe ₁₆ N ₂ particles finally obtained can be set to 30 to 150 nm.

The iron oxide particles are not limited to magnetite, γ-Fe ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, β-FeOOH, γ-FeOOH, FeO, and the like.

The particle shape of the iron oxide particles may be spherical, needle-like, granular, spindle-like, rectangular or the like.

Next, reduction processing of the obtained iron oxide particles is performed to obtain iron particles. The temperature of the reduction treatment is 200 to 400 ° C. When the temperature of the reduction treatment is less than 200 ° C., the iron oxide particles are not sufficiently reduced. When the temperature of the reduction treatment exceeds 400 ° C., the iron oxide particles are sufficiently reduced, but this is not preferable because sintering between particles proceeds. More preferably, it is 230 to 350 ° C.

Although the time of a reduction process is not specifically limited, 1 to 96 hours are preferable. If it exceeds 96 hours, depending on the reduction temperature, sintering will proceed and it will be difficult to advance the subsequent stage nitriding treatment. The reduction does not proceed sufficiently in less than one hour. More preferably, it is 2 to 72 hours.

The atmosphere of the reduction treatment is a hydrogen atmosphere.

Next, the iron particles obtained are subjected to a nitriding treatment to obtain Fe ₁₆ N ₂ particles. The temperature of the nitriding treatment is 100 to 200 ° C. When the temperature of the nitriding treatment is less than 100 ° C., the nitriding does not proceed sufficiently. When the temperature of the nitriding treatment exceeds 200 ° C., the nitriding progresses excessively, and the magnetic properties are degraded. More preferably, it is 120-180 ° C.

Although the time of the nitriding treatment is not particularly limited, 1 to 48 hours are preferable. If it exceeds 48 hours, depending on the nitriding temperature, the magnetic properties deteriorate. In less than one hour, sufficient reduction can often not be achieved. More preferably, it is 3 to 24 hours.

The atmosphere for the nitriding treatment is preferably an NH ₃ atmosphere, and in addition to NH ₃ , N ₂ , H _{2 and the} like may be mixed.

At this time, the Fe ₁₆ N ₂ particles may have an iron oxide phase on the particle surface.

The obtained Fe ₁₆ N ₂ particles are mixed with a fully dehydrated organic solvent, and a dispersant is further added to prepare a slurry containing Fe ₁₆ N ₂ particles.

A single liquid or mixed liquid using any one or more of alkanes such as hexane, cyclohexane and octane, and ketones such as cyclohexanone can be used as the organic solvent, but the present invention is not limited thereto.

  As the dispersant, any one or more of oleic acid, oleylamine, trioctylamine and the like can be used, but it is not limited thereto.

The addition amount of the dispersant is 0.1% by mass or more and 5% by mass or less with respect to the Fe ₁₆ N ₂ particles. By setting the amount of the dispersant in this range, it is possible to control the aggregation of the Fe ₁₆ N ₂ particles during the process of forming the coating layer in the latter stage.

Any of nonmagnetic metal carbonyls such as Cr hexacarbonyl, diMndecacarbonyl, V hexacarbonyl, Mo hexacarbonyl, W hexacarbonyl, etc. is added to the slurry containing the Fe ₁₆ N ₂ particles, and the treatment temperature is 120 to 150 ° C. Stir for 1 to 48 hours to prepare a slurry containing iron nitride-based magnetic particles having a first covering layer. If the treatment temperature at this time is less than 120 ° C., decomposition of metal carbonyl does not proceed, and the first covering layer can not be sufficiently formed on the surface of the Fe ₁₆ N ₂ particles. If the treatment temperature at this time exceeds 150 ° C., the metal formed by the decomposition of the metal carbonyl is formed as particles, so that the first covering layer can not be formed on the surface of the iron nitride-based magnetic particles. More preferably, the temperature is 130 ° C to 140 ° C. When the stirring time is less than 1 hour, the metal carbonyl is not completely decomposed, so that the first covering layer can not be sufficiently formed on the surface of the Fe ₁₆ N ₂ particles. When the stirring time exceeds 48 hours, depending on the treatment temperature, the magnetic properties of the finally obtained iron nitride-based magnetic powder deteriorate. More preferably, it is 3 to 24 hours.

The slurry containing iron nitride-based magnetic particles having the first covering layer is added with any of base metal carbonyls such as Co octacarbonyl and Ni tetracarbonyl, and nonmagnetic metal carbonyl used for forming the first covering layer The mixture is stirred at a treatment temperature of 100 to 130 ° C. for 1 to 48 hours to prepare a slurry containing iron nitride-based magnetic particles having a second covering layer. When the treatment temperature at this time is less than 100 ° C., decomposition of metal carbonyl does not proceed, and a sufficient second covering layer can not be formed on the surface of the first covering layer. If the treatment temperature at this time exceeds 130 ° C., the metal formed by the decomposition of the metal carbonyl is formed as particles, so that the second covering layer can not be formed on the surface of the first covering layer. More preferably, it is 110-120 degreeC. When the stirring time is less than 1 hour, the metal carbonyl is not completely decomposed, so that the second covering layer can not be sufficiently formed on the surface of the first covering layer. More preferably, it is 3 to 24 hours.

  Next, the obtained slurry containing the iron nitride-based magnetic particles having the second covering layer is dried at 100 ° C. for 20 hours in a nitrogen atmosphere to form a nitride having a first covering layer and a second covering layer. Iron-based magnetic powder can be produced.

A bonded magnet can be obtained using the iron nitride based magnetic powder obtained by the present embodiment. Hereafter, the manufacturing method is described.

First, an example of a method of manufacturing a bonded magnet using the iron nitride based magnetic powder obtained by the present embodiment will be described. The resin binder containing the resin and the magnetic powder are kneaded, for example, by a pressure kneader such as a pressure kneader to prepare a compound magnet composition (composition). Resins include thermosetting resins such as epoxy resins and phenol resins, styrene-based, olefin-based, urethane-based, polyester-based and polyamide-based elastomers, ionomers, ethylene propylene copolymer (EPM), ethylene-ethyl acrylate copolymer There is a thermoplastic resin such as coalescence. Among them, a thermosetting resin is preferable, and an epoxy resin or a phenol resin is more preferable, as a resin used in compression molding. The resin used for injection molding is preferably a thermoplastic resin. Further, if necessary, a coupling agent and other additives may be added to the bonded magnet compound.

Further, the content ratio of the iron nitride-based magnetic powder to the resin in the bonded magnet preferably includes 0.5% by mass or more and 20% by mass or less of the resin with respect to 100% by mass of the magnetic powder. When the content of the resin is less than 0.5% by mass with respect to 100% by mass of the magnetic powder, the shape retention tends to be impaired, and when the content of the resin exceeds 20% by mass, sufficiently excellent magnetic properties are obtained. It tends to be difficult to obtain.

After preparing the above-described bonded magnet compound, the bonded magnet compound including the magnetic powder and the resin can be obtained by injection molding the bonded magnet compound. When a bonded magnet is produced by injection molding, the bonded magnet compound is heated to the melting temperature of the binder (thermoplastic resin) as necessary to bring it into a fluidized state, and then the bonded magnet compound has a predetermined shape. It injects in the mold and performs molding. Then, it cools and takes out the molded article (bond magnet) which has a predetermined shape from a metal mold | die. Thus, a bonded magnet is obtained. The method of manufacturing the bonded magnet is not limited to the above-described injection molding method. For example, the bonded magnet containing a magnetic powder and a resin may be obtained by compression molding a bonded magnet compound. When producing a bonded magnet by compression molding, after preparing the above-mentioned bonded magnet compound, the bonded magnet compound is filled in a mold having a predetermined shape, and pressure is applied to have a predetermined shape from the mold Take out the molded product (bond magnet). When molding the bonded magnet compound with a mold and taking it out, it is carried out using a compression molding machine such as a mechanical press or hydraulic press. Thereafter, it is placed in a furnace such as a heating furnace or a vacuum drying furnace and hardened by applying heat to obtain a bonded magnet.

The shape of the bonded magnet obtained by molding is not particularly limited, and may be changed to, for example, a flat plate shape, a columnar shape, or a ring shape in cross section depending on the shape of a mold to be used. Further, the obtained bonded magnet may be plated or coated on its surface to prevent deterioration of the oxide layer, the resin layer and the like.

When the bonded magnet compound is formed into a predetermined shape, the magnetic field is applied to orient the iron nitride-based magnetic powder in a predetermined direction. As a result, the iron nitride-based magnetic powder is oriented in a specific direction, whereby a more strongly anisotropic bonded magnet is obtained.

Next, the iron nitride-based magnetic powder described in the present invention will be described in more detail using Examples and Comparative Examples, but the present invention is not limited to the embodiments shown in the Examples.

Example 1 An iron salt aqueous solution was prepared by dissolving 167 g of iron sulfate heptahydrate (FeSO ₄ · 7 H ₂ O) and 85 g of iron chloride hexahydrate (FeCl ₃ · 6 H ₂ O) in ion exchanged water. . After holding 600 g of a 2.5 mol aqueous ammonia solution at 30 ° C. and adding the previously prepared iron salt aqueous solution, the temperature is controlled to be constant at 70 ° C. as an in-liquid aging reaction, and after stirring for 30 minutes, centrifuge The reaction mixture was washed three times with 2 L of ion-exchanged water to prepare an iron oxide slurry.

To the above-mentioned iron oxide slurry, 5.0 g of tetraethoxysilane, 21 g of ethanol and 78 g of diethylene glycol monobutyl ether were added to carry out Si deposition treatment. The iron oxide slurry was dried at 85 ° C. for 24 hours to prepare iron oxide particles containing Fe ₂ O ₃ .

2 g of the iron oxide particles were placed in a baking boat and allowed to stand in a heat treatment furnace. The furnace was filled with nitrogen gas, and while flowing hydrogen gas at a flow rate of 1 L / min, the temperature was raised to 250 ° C. at a temperature rising rate of 5 ° C./min and held for 48 hours for reduction treatment. Thereafter, the supply of hydrogen gas was stopped, and the temperature was lowered to 140 ° C. while flowing nitrogen gas at a flow rate of 2 L / min. Subsequently, nitriding treatment was performed at 140 ° C. for 24 hours while flowing ammonia gas at 0.2 L / min. Thereafter, the temperature was lowered to 50 ° C. while flowing nitrogen gas at a flow rate of 2 L / min, air replacement was performed for 24 hours, and Fe ₁₆ N ₂ particles were obtained.

10 g of the obtained Fe ₁₆ N ₂ particles were mixed with 500 g of fully dehydrated octane, and 0.3 g of oleylamine was further added as a dispersant to prepare a slurry containing iron nitride-based magnetic particles. 4.0 g of Cr hexacarbonyl was added to the obtained slurry containing iron nitride based magnetic particles and stirred at 140 ° C. for 24 hours to prepare a slurry containing iron nitride based magnetic particles having a first coating layer of Cr metal. did.

  3.0 g of Ni tetracarbonyl and 0.03 g of Cr hexacarbonyl were added to the obtained slurry containing iron nitride-based magnetic particles having the first covering layer, and stirred at 110 ° C. for 24 hours, Cr metal was added to Ni metal. A slurry containing iron nitride based magnetic particles having a second covering layer made of a solid solution alloy was prepared.

  Next, the obtained slurry containing the iron nitride-based magnetic particles having the second covering layer was dried at 100 ° C. for 20 hours in a nitrogen atmosphere to produce an iron nitride-based magnetic powder.

  (Examples 2, 3, 4, 5) The amount of Cr hexacarbonyl added to a slurry containing iron nitride-based magnetic particles having a first covering layer is 0.04, 0.20, 0.40, 0.44 g An iron nitride-based magnetic powder was produced in the same manner as in Example 1 except that

  (Examples 6, 7, 8, 9) The amount of Ni tetracarbonyl added to a slurry containing iron nitride-based magnetic particles having a first covering layer is 0.6, 1.8, 6.0, 9.0 g An iron nitride magnetic powder was produced in the same manner as in Example 3 except that the amount of Cr hexacarbonyl was changed to 0.04, 0.12, 0.20, and 0.60 g.

(Examples 101, 12, and 13) Example 3 was repeated except that the amount of Cr hexacarbonyl added to the slurry containing Fe ₁₆ N ₂ particles was 0.8, 2.4, 8.0, and 12.0 g. An iron nitride based magnetic powder was produced in the same manner.

(Example 14) 4.0 g of 2 Mn decacarbonyl is added to a slurry containing Fe ₁₆ N ₂ particles, and the slurry containing iron nitride-based magnetic particles having a first covering layer is changed to Cr hexacarbonyl to obtain 2 Mn deca An iron nitride based magnetic powder was produced in the same manner as in Example 3 except that 0.20 g of carbonyl was added.

(Example 15) 4.0 g of V hexacarbonyl is added to a slurry containing Fe ₁₆ N ₂ particles, and Cr hexacarbonyl is changed to a slurry containing iron nitride-based magnetic particles having a first covering layer to obtain V decacarbonyl An iron nitride-based magnetic powder was produced in the same manner as in Example 3 except that 0.20 g was added.

(Example 16) 2.2 g of Mo hexacarbonyl was added to a slurry containing Fe ₁₆ N ₂ particles, and Cr hexacarbonyl was changed to a slurry containing iron nitride-based magnetic particles having a first covering layer to obtain Mo hexacarbonyl. An iron nitride based magnetic powder was produced in the same manner as in Example 3 except that 0.11 g was added.

Example 17 1.7 g of W hexacarbonyl is added to a slurry containing Fe ₁₆ N ₂ particles, and the Cr hexacarbonyl is changed to a slurry containing iron nitride-based magnetic particles having a first covering layer. An iron nitride based magnetic powder was produced in the same manner as in Example 3 except that 0.09 g was added.

  (Example 18) An iron nitride-based magnetic powder was produced in the same manner as in Example 3 except that 3.0 g of 2-Co octacarbonyl was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. .

  Example 19 An iron nitride-based magnetic powder was produced in the same manner as in Example 14 except that 3.0 g of 2-Co octacarbonyl was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. .

  Example 20 An iron nitride-based magnetic powder was produced in the same manner as in Example 15, except that 3.0 g of 2-Co octacarbonyl was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. .

  (Example 21) An iron nitride-based magnetic powder was produced in the same manner as in Example 16 except that 3.0 g of 2-Co octacarbonyl was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. .

  (Example 22) An iron nitride-based magnetic powder was produced in the same manner as in Example 17 except that 3.0 g of 2-Co octacarbonyl was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. .

Comparative Example 1 In the same manner as in Example 1, Fe ₁₆ N ₂ powder was produced.

  Comparative Example 2 An iron nitride based magnetic powder was prepared in the same manner as in Example 1 except that the base metal carbonyl and the nonmagnetic metal carbonyl were not added to the slurry containing the iron nitride based magnetic particles having the first covering layer. did.

Comparative Example 3 An iron nitride-based magnetic powder was produced in the same manner as in Example 1 except that nonmagnetic metal carbonyl was not added to the slurry containing Fe ₁₆ N ₂ particles and only Ni tetracarbonyl was added.

  Comparative Example 4 An iron nitride based magnetic powder was produced in the same manner as in Example 1 except that the nonmagnetic metal carbonyl was not added to the slurry containing the iron nitride based magnetic particles having the first covering layer.

  Comparative Example 5 An iron nitride-based iron was obtained by the same method as Example 3, except that Cr hexacarbonyl was changed to a slurry containing iron nitride-based magnetic particles having a first covering layer and 0.11 g of Mo hexacarbonyl was added. Magnetic powder was produced.

  Comparative Example 6 The same procedure as Comparative Example 4 was repeated except that 3.0 g of dicooctacarbonyl was added to the slurry containing iron nitride-based magnetic particles having the first covering layer instead of Cr hexacarbonyl. Magnetic powder was produced.

Comparative Example 7 3.0 g of Ni tetracarbonyl and 0.03 g of Cr hexacarbonyl were added to a slurry containing Fe ₁₆ N ₂ particles, and Cr hexa hexahydrate was added to a slurry containing iron nitride-based magnetic particles having a first covering layer. An iron nitride based magnetic powder was produced in the same manner as in Example 1 except that 4.0 g of Cr hexacarbonyl was added instead of the carbonyl.

Comparative Example 8 3.0 g of Ni tetracarbonyl was added to a slurry containing Fe ₁₆ N ₂ particles, and Cr hexacarbonyl was changed to a slurry containing iron nitride-based magnetic particles having a first covering layer instead of Cr hexacarbonyl. An iron nitride based magnetic powder was produced in the same manner as in Example 1 except that 4.0 g was added.

«Constituent phase of iron nitride based magnetic powder»
The constituent phase of the obtained iron nitride-based magnetic powder was identified using a powder X-ray diffractometer (XRD, manufactured by Rigaku RINT-2500).

«Particle diameter of iron nitride magnetic powder, composition and thickness of first and second covering layers»
The Fe ₁₆ N ₂ particle diameter of the obtained iron nitride-based magnetic powder and the thickness of the first and second covering layers are observed with a transmission electron microscope (TEM, JEM-200 FX, manufactured by JEOL Ltd.), using EDS. Particle composition was analyzed. The sample for observation used was prepared by kneading the obtained iron nitride-based magnetic powder in an epoxy resin, curing the resin, and then thinning it. After performing elemental mapping by EDS of 100 particle cross sections selected from the inside of the TEM observation image, point analysis of the composition of the first and second coating layers was performed. At this time, Fe is detected from the Fe ₁₆ N ₂ particles of the example, and any element of Cr, Mn, V, Mo, W is detected from the first covering layer, and Ni from the second covering layer. And Co elements were detected. Next, by image processing, EDS measures the Fe ₁₆ N ₂ particle diameter, the thickness of each of the first and second covering layers from EDS based on the elemental mapping result of 1000 particle cross sections, and calculates the average value thereof. It was the thickness of the first and second covering layers. The calculation results are shown in Table 1.

«Coercive force of iron nitride magnetic powder (HcJ)»
The coercive force (HcJ) of the obtained iron nitride-based magnetic powder was determined from the measurement results of the demagnetization curve using a vibrating sample magnetometer (VSM, VSM-5-20 manufactured by Toei Kogyo Co., Ltd.). The iron nitride-based magnetic powder having a coercivity (HcJ) of 2.6 kOe or more is acceptable, and the measurement results are shown in Table 1.

«Humidity resistance of iron nitride magnetic powder»
The moisture resistance of the obtained iron nitride-based magnetic powder was measured by using the weight increase start temperature of the iron nitride-based magnetic powder in an atmosphere of humidity of 90% or more as the corrosion start temperature, and the higher the corrosion start temperature, the better the evaluation. The said corrosion start temperature calculated | required the temperature used as DTG> 0 as a corrosion start temperature by TG-DTA (Thermo Plus TG8120 made from RIGAKU). An iron nitride-based magnetic powder having a corrosion start temperature of 90 ° C. or more was accepted. When DTG> 0 in the vicinity of room temperature at the initial stage of measurement, the corrosion start temperature was not determined as measurement noise. The evaluation results are shown in Table 1.

In all the examples and comparative examples, it was confirmed that the Fe ₁₆ N ₂ phase is the main phase.

  As in the first, second, third, fourth and fifth examples, the first covering layer consisting of Cr metal on the surface of the iron nitride magnetic powder and the Ni and Cr metals on the surface of the first covering layer When the second covering layer made of an alloy was provided, it was confirmed that the coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 90 ° C. or more. In particular, when the metal contained in the first coating layer contained in the alloy of the second coating layer is 1 to 10 at%, good characteristics having a corrosion initiation temperature of 120 ° C. or higher were obtained.

  As in Examples 3, 6, 7, 8 and 9, the first covering layer consisting of Cr metal on the surface of the iron nitride magnetic powder and Ni metal and Cr metal on the surface of the first covering layer When the second covering layer made of an alloy was provided, it was confirmed that the coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 90 ° C. or more. In particular, when the thickness of the second covering layer is 5 nm or more, good characteristics having a corrosion start temperature of 130 ° C. or more were obtained.

  As in Examples 3, 10, 11, 12 and 13, the first covering layer consisting of Cr metal on the surface of the iron nitride based magnetic powder, and Ni metal and Cr metal on the surface of the first covering layer When the second covering layer made of an alloy was provided, it was confirmed that the coercive force (HcJ) was 2.6 kOe or more, and the corrosion start temperature was 130 ° C. or more. In particular, when the thickness of the first covering layer was 5 nm or more, good characteristics with a coercive force (HcJ) of 3.0 kOe or more were obtained.

  As in Example 14, a first covering layer consisting of Mn metal is formed on the surface of iron nitride based magnetic powder, and a second covering layer consisting of an alloy of Ni metal and Mn metal is formed on the surface of the first covering layer. When it has, it has confirmed that coercive force (HcJ) was 3.0 kOe or more, and the corrosion start temperature was 130 degreeC or more.

  A first covering layer consisting of V metal is formed on the surface of iron nitride based magnetic powder as in Example 15, and a second covering layer consisting of an alloy of Ni metal and V metal is formed on the surface of the first covering layer. When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 135 degreeC or more.

  A first covering layer consisting of Mo metal on the surface of an iron nitride based magnetic powder as in Example 16, and a second covering layer consisting of an alloy of Ni metal and Mo metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 135 degreeC or more.

  The first covering layer consisting of W metal on the surface of the iron nitride based magnetic powder as in Example 17, and the second covering layer consisting of an alloy of Ni metal and W metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 135 degreeC or more.

  The first covering layer consisting of Cr metal on the surface of the iron nitride magnetic powder as in Example 18, and the second covering layer consisting of an alloy of Co metal and Cr metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 100 degreeC or more.

  A first covering layer consisting of Mn metal is provided on the surface of an iron nitride based magnetic powder as in Example 19, and a second covering layer consisting of an alloy of Co metal and Mn metal is provided on the surface of the first covering layer. When it had, it has confirmed that coercive force (HcJ) was 3.0 kOe or more, and the corrosion start temperature was 95 degreeC or more.

  A first covering layer consisting of V metal is formed on the surface of an iron nitride based magnetic powder as in Example 20, and a second covering layer consisting of an alloy of Co metal and V metal is formed on the surface of the first covering layer. When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 100 degreeC or more.

  A first covering layer consisting of Mo metal on the surface of an iron nitride based magnetic powder as in Example 21, and a second covering layer consisting of an alloy of Co metal and Mo metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 100 degreeC or more.

  A first covering layer consisting of W metal on the surface of an iron nitride based magnetic powder as in Example 22, and a second covering layer consisting of an alloy of Co metal and W metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 105 degreeC or more.

When the first covering layer and the second covering layer of Fe ₁₆ N ₂ particles are not provided as in Comparative Example 1, the coercive force (HcJ) is 2.4 kOe, and the iron nitride based magnetic powder is exposed to the normal temperature atmosphere. Since combustion occurred at the same time, it was not possible to measure the corrosion start temperature. This is because the nonmagnetic metal contained in the first covering layer does not exhibit the effect of magnetically separating the Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder, so the coercivity is low. It is thought that it is because it became. Furthermore, since the surface of the iron nitride-based magnetic powder is not protected by the base metal layer, it is considered that combustion occurred by exposure to normal temperature air.

  As in Comparative Example 2, when the first coated layer made of Cr metal is provided on the surface of the iron nitride-based magnetic powder and the second coated layer is not provided, the magnetic force (HcJ) is 3.0 kOe. However, since the iron nitride-based magnetic powder was burned when exposed to ambient temperature air, the corrosion initiation temperature could not be measured. The surface of the iron nitride-based magnetic powder is not protected by the base metal layer, and this is considered to be burning by exposure to normal temperature air.

As in Comparative Example 3, in the case where the surface of the iron nitride-based magnetic powder does not have the first covering layer but has the second covering layer consisting only of Ni metal, the coercivity (HcJ) is 2.2 kOe It was confirmed that the corrosion start temperature was 85 ° C. This is because, since the nonmagnetic metal contained in the first covering layer is not present, the effect of magnetically separating Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder is not exhibited. It is believed that the magnetic force is lowered. Furthermore, the adhesion between the second covering layer and the Fe ₁₆ N ₂ particles is improved by the absence of the first covering layer and the absence of the metal constituting the first covering layer in the second covering layer. Since it became inadequate and the 2nd coating layer exfoliated during moisture resistance evaluation, it is thought that iron nitride system magnetic powder was not able to acquire sufficient moisture resistance.

When the first covering layer consisting of Cr metal is provided on the surface of Fe ₁₆ N ₂ particles as in Comparative Example 4 and the second covering layer consisting only of Ni metal is provided, the coercivity (HcJ) Of 3.0 kOe and the corrosion initiation temperature of 85.degree. C. were confirmed. This is because the adhesion between the second covering layer and the first covering layer is insufficient because the second covering layer does not contain the metal contained in the first covering layer, and the moisture resistance is evaluated. It is considered that the iron nitride-based magnetic powder could not obtain sufficient moisture resistance because the second coating layer peeled off.

  As in Comparative Example 5, on the surface of iron nitride-based magnetic powder, a first covering layer consisting of Cr metal and a second covering layer consisting of an alloy of Ni metal and Mo metal on the surface of the first covering layer When it had, it has confirmed that coercive force (HcJ) was 2.9 kOe or more, and the corrosion start temperature was 85 degreeC or more. This is because the adhesion between the second covering layer and the first covering layer is insufficient because the second covering layer does not contain the metal contained in the first covering layer, and the moisture resistance is evaluated. It is considered that the iron nitride-based magnetic powder could not obtain sufficient moisture resistance because the second coating layer peeled off.

  As a result of observing the sample after measuring the corrosion start temperature of Comparative Examples 3 and 4 in the same microstructure as (0087), it was found that the second coating layer was peeled from the iron nitride-based magnetic particles. This is considered to be due to the fact that the second cover layer does not contain the same metal as the first cover layer.

  As in Comparative Example 6, when the surface of iron nitride-based magnetic powder has a first covering layer made of Cr metal and has a second covering layer made only of Co metal, the coercivity (HcJ) Is 2.9 kOe, and it has been confirmed that the corrosion initiation temperature is 70.degree. This is because the adhesion between the second covering layer and the first covering layer is insufficient because the second covering layer does not contain the metal contained in the first covering layer, and the moisture resistance is evaluated. It is considered that the iron nitride-based magnetic powder could not obtain sufficient moisture resistance because the second coating layer peeled off.

As in Comparative Example 7, the iron nitride-based magnetic powder has a first covering layer made of an alloy of Ni metal and Cr metal on the surface, and a second covering made of Cr metal on the surface of the first covering layer. In the case of having a layer, it was confirmed that the coercive force (HcJ) was 2.5 kOe or more and the corrosion start temperature was 90 ° C. or more. This is because the second coating layer is oxidized and exfoliated when the iron nitride-based magnetic powder is exposed to the normal temperature atmosphere, so that the effect of magnetically separating Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder is exhibited. It is considered that the coercivity was lowered because it did not occur. Furthermore, the adhesion between the first coating layer and the Fe ₁₆ N ₂ particles is insufficient, and the second coating layer is peeled off during the evaluation of the moisture resistance, so that the iron nitride-based magnetic powder can obtain sufficient moisture resistance. It is thought that it was not.

As in Comparative Example 8, it has a first covering layer made of Ni metal on the surface of iron nitride based magnetic powder, and has a second covering layer made of Cr metal on the surface of the first covering layer. It was confirmed that the coercivity (HcJ) was 2.3 kOe or more and the corrosion start temperature was 80 ° C. or more. This is because the second coating layer is oxidized and exfoliated when the iron nitride-based magnetic powder is exposed to the normal temperature atmosphere, so that the effect of magnetically separating Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder is exhibited. It is considered that the coercivity was lowered because it did not occur. Furthermore, the adhesion between the coating layer and the Fe ₁₆ N ₂ particles constituting the iron nitride-based magnetic powder is insufficient, and the second coating layer is peeled off during the evaluation of the moisture resistance, so that the iron nitride-based magnetic powder is sufficient. It can be considered that it was not possible to obtain good moisture resistance.

As described above, the iron nitride-based magnetic powder according to the present invention is useful as a magnet that does not use rare earth because it has sufficient coercivity and moisture resistance.

Claims (5)

Iron nitride-based magnetic particles having a first covering layer on the surface of Fe ₁₆ N ₂ particles having an Fe ₁₆ N ₂ phase as the main phase and having a second covering layer on the surface of the first covering layer An iron nitride-based magnetic powder, wherein the first coating layer is a metal or alloy composed of any one or more of Cr, Mn, V, Mo and W, and the second coating layer is Ni, Co An iron nitride-based magnetic powder comprising an alloy of a metal of any one or more of the foregoing and a metal contained in the first coating layer. The iron nitride-based magnetic powder according to claim 1, wherein the metal contained in the first cover layer contained in the alloy of the second cover layer is 1 to 10 at%. The iron nitride-based magnetic powder according to claim 1 or 2, wherein the thickness of the first covering layer is 5 nm or more. The iron nitride-based magnetic powder according to any one of claims 1 to 3, wherein the thickness of the second covering layer is 5 nm or more. A bonded magnet using the iron nitride based magnetic powder according to claim 1.