JP2017183322A - Bond magnet arranged by use of iron nitride-based magnetic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bond magnet arranged by use of iron nitride-based magnetic powder including an FeNcompound phase as a main phase, holding a high residual magnetic flux density and having a high orientation degree.SOLUTION: A bond magnet is arranged by use of iron nitride-based magnetic powder including an FeNphase. The iron nitride-based magnetic powder comprises: iron nitride-based particles including main phases of FeN; and graphite particles. As to the iron nitride-based magnetic powder, the ratio given by (Average particle diameter of the graphite particles)/(Average particle diameter of the iron nitride-based particles) is 0.50 or less, and the ratio given by (Volume of the graphite particles)/(Volume of the iron nitride-based particles) is 0.1-0.4.SELECTED DRAWING: None

Description

The present invention provides a bonded magnet using an iron nitride-based magnetic powder having a Fe ₁₆ N ₂ compound phase as a main phase and having a high orientation while maintaining a high residual magnetic flux density.

  In recent years, Nd-Fe-B magnets have been widely used as motor magnets for electric vehicles and hybrid vehicles. However, rare earths typified by Nd are raw materials for high-value-added members that support the industrial field, and since demand is increasing in recent years, there are concerns that resource depletion and raw material prices are unstable. . Furthermore, there is a problem in securing a stable supply because the demand is growing significantly in developing countries and the dependence on specific producing countries is high due to its uneven distribution.

Due to the above problems, Fe ₁₆ N ₂ made of elements (iron, nitrogen) inexhaustible in nature has attracted attention as one of materials exhibiting a larger saturation magnetization than Fe.

In magnets, the degree of orientation, which is an index indicating the degree to which the crystal axes of the constituent particles coincide with the easy axis of magnetization, is one of the important characteristics of anisotropic magnets. it is, while indicating like squareness of goodness of demagnetization curve of the magnetic hysteresis _loop, in order to ensure a sufficient coercive force in _Fe 16 _{N 2,} the particle diameter of the _Fe 16 _{N 2} particles _{Fe 16} N Therefore, it is necessary to make the nano-size less than 100 nm, which is considered to be a single domain critical diameter of No. _2. Therefore, the particles are likely to be aggregated, and the frictional force acting between the aggregated particles makes the alignment by an external magnetic field difficult.

In Patent Document 1 and Patent Document 2, iron nitride magnetic powder containing Fe ₁₆ N ₂ phase is produced by reducing and nitriding iron oxyhydroxide, and the magnetic powder is used as a solvent / resin. The magnetic sheet is obtained by kneading and applying it as a slurry and applying an orientation treatment, followed by drying. However, none of them eliminates aggregation of Fe ₁₆ N ₂ nanoparticles, and a sufficient degree of orientation cannot be obtained. Thus, when the iron nitride magnetic powder obtained by the prior art is used, a sufficient degree of orientation cannot be obtained in an anisotropic magnet subjected to orientation treatment by applying a magnetic field at the time of magnet molding, and Fe ₁₆ N ₂ has Very high saturation magnetization cannot be used effectively.

JP 2008-103510 A JP2013-69926A

Therefore, the present invention has been made in view of the above, and provides a bonded magnet using an iron nitride-based magnetic powder having a high orientation while maintaining a high saturation magnetization with the Fe ₁₆ N ₂ compound phase as a main phase. For the purpose.

The present invention is a bonded magnet using an iron nitride-based magnetic powder containing an Fe ₁₆ N ₂ phase, and the iron nitride-based magnetic powder is composed of iron nitride-based particles having Fe ₁₆ N ₂ as a main phase and graphite particles. And the ratio represented by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is 0.50 or less, and at the same time, (volume of graphite particles) / (of iron nitride-based particles) A bonded magnet using iron nitride magnetic powder having a ratio expressed by volume) of 0.1 or more and 0.4 or less. The presence of graphite particles with particularly high lubricity as solids between the iron nitride-based particles alleviates the friction that occurs in the aggregates of the iron nitride-based magnetic powder during the orientation treatment, and the iron nitride-based particles in which the aggregates exist Even in a bonded magnet using magnetic powder, a high degree of orientation can be obtained, so that the squareness, which is one of the important characteristics of the magnet, is improved.

Furthermore, it is a bonded magnet using an iron nitride magnetic powder in which the average particle diameter of the iron nitride particles is 30 nm or more and 150 nm or less.

According to the present invention, it is possible to of the Fe ₁₆ N ₂ compound phase as a main phase, while maintaining a high saturation magnetization, provides a bonded magnet using the iron nitride-based magnetic powder having a high orientation.

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 constituent elements shown in the embodiments and examples described below may be appropriately combined or may be appropriately selected.

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

The iron nitride-based particles have a main phase of Fe ₁₆ N ₂ and may contain an iron nitride phase such as Fe ₄ N or FeN. Moreover, you may have the phase which consists of an oxide on the surface of an iron nitride type particle | grain.

The iron nitride-based particles may contain a transition metal such as Mn, Ni, Co, Ti, Zn.

The average particle size of the iron nitride particles is preferably 20 to 180 nm. When the particle diameter of the iron nitride-based particles is less than 20 nm, superparamagnetism develops, and when it exceeds 180 nm, the proportion of particles that are not single magnetic domains increases, and in either case, sufficient coercive force cannot be obtained. Sometimes. More preferably, it is 30-150 nm.

  The graphite particles contained in the iron nitride-based magnetic powder have a main phase made of graphite. In addition to the main phase, a phase such as diamond, fullerene, carbon nanotube, or carbon nanohorn may be included.

In the iron nitride magnetic powder contained in the bonded magnet according to the present invention, the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride particles) is preferably 0.50 or less. . Even when the volume ratio of iron nitride-based particles and graphite particles contained in the bond magnet is the same, the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is 0.50. By being the following, a large number of graphite particles exist around the iron nitride-based particles, and sufficient friction relaxation can be obtained while ensuring high saturation magnetization. On the other hand, when the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is more than 0.50, the number of graphite particles in contact with the iron nitride-based particles is small and sufficient. Friction relaxation does not occur and sufficiently high orientation cannot be obtained. More preferably, the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is 0.36 or less.

In the iron nitride magnetic powder contained in the bonded magnet according to the present invention, the ratio represented by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is 0.50 or less, The ratio of the total volume of the iron nitride-based particles to the total volume of the graphite particles, (volume of graphite particles) / (volume of iron nitride-based particles) is 0.1 or more and 0.4 or less, so that the graphite particles are iron nitride. A sufficient number of particles are present around the system particles, and good frictional relaxation can be obtained. On the other hand, when the ratio represented by (volume of graphite particles) / (volume of iron nitride-based particles) is less than 0.1, the number of graphite particles in contact with the iron nitride-based particles is small, and sufficient friction relaxation does not occur. High orientation cannot be obtained. Further, when the ratio expressed by (volume of graphite particles) / (volume of iron nitride-based particles) is more than 0.4, Fe ₁₆ N ₂ phase contained in the iron nitride-based magnetic powder is small and sufficient saturation is achieved. Magnetization cannot be obtained. More preferably, the ratio expressed by (volume of graphite particles) / (volume of iron nitride-based particles) is 0.2 or more and 0.3 or less.

A suitable method for producing the iron nitride magnetic powder constituting the bonded magnet according to the present invention will be described. The iron nitride magnetic powder according to this embodiment is obtained by synthesizing an iron oxide powder in which graphite particles and iron oxide particles are mixed, and then subjecting the iron oxide particles to reduction treatment and nitriding treatment in this order.

The iron oxide powder is a mixture of iron oxide particles and graphite particles, and the average particle diameter of the iron oxide particles is preferably 10 nm or more and 150 nm or less. By setting the average particle size within this range, the average particle size of the finally obtained Fe ₁₆ N ₂ particles can be 20 to 180 nm.

Examples of the iron oxide particles include magnetite, γ-Fe ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, β-FeOOH, γ-FeOOH, and FeO, but are not limited thereto.

The particle shape of the iron oxide particles may be any of spherical shape, needle shape, granular shape, spindle shape, rectangular parallelepiped shape, and the like.

The graphite particles are obtained by annealing the carbon black particles. By restricting the particle size of the carbon black particles used at that time, graphite particles having an arbitrary particle size can be obtained.

The particle diameter of the graphite particles is preferably such that the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is 0.50 or less. When the ratio expressed by (average particle diameter of graphite particles) / (average particle diameter of iron nitride-based particles) is more than 0.50, there are few graphite particles in contact with the iron nitride-based particles, and sufficient friction relaxation occurs. Therefore, high orientation cannot be obtained.

The iron oxide powder, which is a mixture of iron oxide particles and graphite particles, can be produced by mixing an iron salt aqueous solution, an alkali aqueous solution and the graphite particles, then aging and washing. By mixing graphite particles with iron salt aqueous solution, iron oxide particles and graphite particles are uniformly distributed at the stage when iron oxide particles are generated, and the iron oxide system in which graphite particles are present inside the aggregate of iron oxide particles A powder can be obtained.

The mixing ratio of the iron salt aqueous solution and the graphite particles is such that, in the iron nitride magnetic powder finally obtained through the generation of iron oxide particles, reduction and nitridation of the iron oxide particles, the volume of the iron nitride particles and the graphite The volume ratio of particles, (volume of graphite particles) / (volume of iron nitride-based particles) is set to 0.1 or more and 0.4 or less. When the ratio expressed by (volume of graphite particles) / (volume of iron nitride-based particles) is less than 0.1, the number of graphite particles in contact with the iron nitride-based particles is small, sufficient friction relaxation does not occur, and is high The orientation cannot be obtained. Further, when the ratio expressed by (volume of graphite particles) / (volume of iron nitride-based particles) is more than 0.4, Fe ₁₆ N ₂ phase contained in the iron nitride-based magnetic powder is small and sufficient saturation is achieved. Magnetization cannot be obtained.

  Further, after mixing the aqueous iron salt solution, the alkaline aqueous solution, and the graphite particles, a dispersion treatment such as ultrasonic treatment may be performed in order to obtain a higher dispersion state.

Examples of the iron salt include sulfate, chloride, nitrate and the like, and these may be used in appropriate combination. Moreover, those hydrates can be used.

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

In addition, after the production of iron oxide-based particles, an in-liquid aging reaction such as hydrothermal treatment with an autoclave may be performed for improving crystallinity, controlling particle size, and particle shape.

After the production of the iron oxide-based particles, the aqueous solution is filtered, and the iron oxide-based particles can be recovered by performing a washing treatment such as water washing as necessary.

  The iron oxide particles may be coated with a part of the particle surface with a Si compound in order to suppress the particles from being sintered by the reduction treatment. 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 preferably 0.1% by mass or more and 20% by mass or less in terms of Si with respect to the iron oxide particles. If the amount is less than 0.1% by mass, the effect of suppressing the sintering between particles during heat treatment cannot be obtained sufficiently, and the finally obtained iron nitride-based particles become large. If it exceeds 20% by mass, the effect of suppressing the sintering between particles during heat treatment becomes excessive, and the finally obtained iron nitride-based particles become small.

Next, the obtained iron oxide particles are subjected to reduction treatment 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 the particles proceeds. More preferably, it is 230-350 degreeC.

The time for the reduction treatment is not particularly limited, but is preferably 1 to 96 hours. If it exceeds 96 hours, depending on the reduction temperature, the sintering proceeds and the subsequent nitriding process becomes difficult to proceed. If it is less than 1 hour, the reduction does not proceed sufficiently. More preferably, it is 2 to 72 hours.

The atmosphere for the reduction treatment is a hydrogen atmosphere.

Next, the obtained iron particles are nitrided to obtain iron nitride-based particles. The temperature of the nitriding treatment is 100 to 200 ° C. When the nitriding temperature is less than 100 ° C., nitriding does not proceed sufficiently. When the temperature of the nitriding process exceeds 200 ° C., nitriding proceeds excessively, so that the magnetic characteristics are deteriorated. More preferably, it is 120-180 degreeC.

The nitriding time is not particularly limited, but is preferably 1 to 48 hours. If it exceeds 48 hours, the magnetic properties will deteriorate depending on the nitriding temperature. In many cases, sufficient reduction cannot be achieved in less than 1 hour. More preferably, it is 3 to 24 hours.

The atmosphere of the nitriding treatment is desirably an NH ₃ atmosphere, and N ₂ , H ₂ or the like may be mixed in addition to NH ₃ .

At this time, the iron nitride-based particle may have an iron oxide phase on the particle surface.

In the paragraph 0025, a method of mixing graphite powder during iron oxide synthesis was described, but the graphite powder was not mixed during iron oxide synthesis, and was obtained by reducing and nitriding iron oxide particles. An iron nitride magnetic powder may be obtained by mixing graphite powder with powder composed of particles. However, in order to sufficiently disperse the graphite particles between the iron nitride particles that are easily aggregated and to make use of the high solid lubricity of the graphite particles, a method of mixing at the time of iron oxide synthesis is preferable.

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

  The obtained iron nitride magnetic powder is mixed with a sufficiently dehydrated organic solvent, and further a dispersant is added to prepare a slurry containing iron nitride particles.

The organic solvent may be a single liquid or mixed liquid using any one or more of alkanes such as hexane, cyclohexane and octane, and ketones such as cyclohexanone, but is not limited thereto.

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

An example of the manufacturing method of the bonded magnet concerning this invention is demonstrated. A compound (composition) for a bond magnet is prepared by kneading a resin binder containing a resin and a slurry containing the iron nitride particles or the iron nitride magnetic powder with a pressure kneader such as a pressure kneader. To do. Resins include thermosetting resins such as epoxy resins and phenol resins, styrene, olefin, urethane, polyester and polyamide elastomers, ionomers, ethylene propylene copolymer (EPM), ethylene-ethyl acrylate copolymer There are thermoplastic resins such as coalescence. Among them, the resin used for compression molding is preferably a thermosetting resin, and more preferably an epoxy resin or a phenol resin. The resin used for injection molding is preferably a thermoplastic resin. Moreover, you may add a coupling agent and another additive to the compound for bonded magnets as needed.

Moreover, it is preferable that the content ratio of the magnetic powder and resin in a bond magnet contains 0.5 mass% or more and 20 mass% or less of resin with respect to 100 mass% of magnetic powder. If the resin content is less than 0.5% by mass with respect to 100% by mass of the magnetic powder, the shape retention tends to be impaired. If 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 containing magnetic powder and resin can be obtained by injection molding the bonded magnet compound. When producing a bonded magnet by injection molding, the bonded magnet compound is heated to the melting temperature of the binder (thermoplastic resin) as necessary to obtain a fluid state, and then the bonded magnet compound has a predetermined shape. Injection into the mold and molding. At this time, a molded body obtained by molding by applying a magnetic field is oriented in a certain direction. Then, it cools and the molded article (bond magnet) which has a predetermined shape is taken out from a metal mold | die. In this way, a bonded magnet is obtained. The method of manufacturing the bonded magnet is not limited to the above-described method by injection molding. For example, a bonded magnet containing magnetic powder and 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 during application of a magnetic field from the mold. A molded product (bonded magnet) having a predetermined shape is taken out. When forming and taking out a bonded magnet compound with a mold, a compression molding machine such as a mechanical press or a hydraulic press is used. Then, a bonded magnet is obtained by making it harden | cure by putting in furnaces, such as a heating furnace and a vacuum drying furnace, and applying heat.

The shape of the bonded magnet obtained by molding is not particularly limited, and can be changed, for example, to have a plate shape, a column shape, or a cross-sectional shape that is a ring shape, depending on the shape of the mold to be used. Further, the obtained bonded magnet may be plated or painted on the surface in order to prevent deterioration of the oxide layer, the resin layer, and the like.

Next, the bonded magnet using the iron nitride 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 embodiment shown in the examples. .

Example 1
First, 10 g of carbon black having an average particle diameter of 3 nm was placed in a firing boat and left in a heat treatment furnace. After filling the furnace with nitrogen gas, with the nitrogen gas flowing at a flow rate of 1 L / min, the temperature was raised to 750 ° C. at a temperature rising rate of 5 ° C./min, maintained for 48 hours, and then at a rate of 1 ° C./min. Was taken out when the temperature was lowered to room temperature to obtain graphite powder.

Next, 83 g of iron sulfate heptahydrate (FeSO ₄ · 7H ₂ O) and 162 g of iron chloride hexahydrate (FeCl ₃ · 6H ₂ O) are dissolved in ion-exchanged water, and 4.7 g of the graphite particles are added. Then, an iron salt aqueous solution was prepared. After maintaining 600 g of 2.5 mol ammonia aqueous solution at 30 ° C. and adding the previously prepared iron salt aqueous solution, the temperature was controlled to be constant at 70 ° C. as a ripening reaction in the liquid, stirred for 30 minutes, and then centrifuged. Was washed 3 times with 2 L of ion-exchanged water to prepare an iron oxide slurry containing graphite particles.

To the iron oxide slurry, 5.0 g of tetraethoxysilane, 21 g of ethanol, and 78 g of diethylene glycol monobutyl ether were added to perform Si deposition treatment. This iron oxide slurry was dried at 85 ° C. for 24 hours to produce iron oxide-based particles containing Fe ₂ O ₃ particles and graphite particles.

2 g of the iron oxide particles were placed in a firing boat and left in a heat treatment furnace. After filling the furnace with nitrogen gas, the temperature was raised to 250 ° C. at a temperature rising rate of 5 ° C./min while flowing hydrogen gas at a flow rate of 1 L / min, and the reduction treatment was performed for 48 hours. 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 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, and air substitution was performed for 24 hours to obtain an iron nitride-based magnetic powder.

  1 g of the obtained iron nitride magnetic powder was mixed with 60 g of sufficiently dehydrated octane, and 3 g of oleylamine was further added as a dispersant to prepare a slurry containing iron nitride magnetic powder.

  The obtained slurry containing the iron nitride magnetic powder and the resin binder containing the epoxy resin are kneaded at a ratio of 10 wt% of the resin content with respect to 100 wt% of the iron nitride magnetic powder, and the compound for the bond magnet is obtained. Prepared.

Next, the obtained bonded magnet compound was put into a 7 mm square rectangular metal mold and subjected to compression molding by applying a load of 3 kgf / cm ² while volatilizing the solvent in a heated and reduced pressure atmosphere. At this time, a magnetic field of 10 kOe was applied in a direction perpendicular to the load direction as a magnetic orientation treatment. Thereafter, heating at 130 ° C. in a heating furnace was performed for 1 hour to cure the epoxy resin, thereby producing a bonded magnet using iron nitride magnetic powder.

(Examples 2, 5, 12, 13, 14, 15)
It was produced in the same manner as in Example 1 except that the amount of tetraethoxysilane added to the iron oxide slurry was changed to 4.0 g, 2.5 g, 1.8 g, 0.8 g, 0.6 g, and 0.2 g.

(Examples 3, 9, and 10)
It was produced in the same manner as in Example 1 except that the graphite particles added to the iron salt aqueous solution were changed to 3.2 g, 6.0 g, and 7.3 g.

(Examples 6, 7, and 8)
The carbon black particles were produced in the same manner as in Example 1 except that the average particle size of the carbon black particles was 10 nm, 20 nm, and 30 nm.

Example 4
Except for the amount of tetraethoxysilane added to the iron oxide slurry being 2.5 g, the average particle size of the carbon black particles being 30 nm, and the graphite particles being added to the iron salt aqueous solution being 3.2 g, the same as in Example 1. Produced.

(Example 11)
It was produced in the same manner as in Example 4 except that the amount of graphite particles added to the iron salt aqueous solution was 7.3 g.

(Example 16)
It was produced in the same manner as in Example 1 except that the amount of tetraethoxysilane added to the iron oxide slurry was 0.2 g and the average particle size of the carbon black particles was 35 nm.

(Example 17)
After preparing an iron nitride magnetic powder not containing graphite particles without adding graphite powder to an iron salt aqueous solution, when preparing a slurry containing the iron nitride magnetic powder described in 0054, except adding and mixing the graphite powder Was prepared in the same manner as in Example 4.

(Examples 18 and 19)
The carbon black particles were produced in the same manner as in Example 17 except that the average particle size of the carbon black particles was 3 nm and the graphite particles added to the iron salt aqueous solution were 4.7 g and 7.3 g.

(Example 20)
It was produced in the same manner as in Example 17 except that the amount of graphite particles added to the iron salt aqueous solution was changed to 7.3 g.

(Comparative Example 1)
It was produced in the same manner as in Example 1 except that the amount of tetraethoxysilane added to the iron oxide slurry was 4.0 g and the average particle size of the carbon black particles was 8 nm.

(Comparative Example 2)
It was produced in the same manner as in Example 1 except that the average particle size of the carbon black particles was 35 nm.

(Comparative Example 3)
It was prepared in the same manner as in Example 1 except that an iron oxide slurry containing no graphite particles was prepared without adding graphite powder to the iron salt aqueous solution.

(Comparative Examples 4 and 5)
It was produced in the same manner as in Example 1 except that the graphite particles added to the iron salt aqueous solution were 2.5 g and 8.0 g.

  The constituent phase, saturation magnetization (Js), residual magnetization (Jr), and coercive force (Hcj) of the bonded magnet thus obtained were measured by the following methods. The results are shown in Table 1.

≪Constituent phase in bonded magnet using iron nitride magnetic powder, volume ratio of Fe ₁₆ N ₂ phase and graphite phase in the constituent phase≫
The obtained bonded magnet was put in an agate mortar and sufficiently pulverized, and then an X-ray diffraction profile was obtained with a powder X-ray diffractometer (XRD, RINT-2500 manufactured by Rigaku), and the constituent phases were identified. By performing the Rietveld analysis, the weight ratio of the Fe ₁₆ N ₂ phase and the graphite phase was determined, and the volume ratio was converted from the respective densities.

≪Average particle size of iron nitride particles and graphite particles in bonded magnets using iron nitride magnetic powder≫
The obtained bonded magnet is cut out so that a cross section appears. The cross section of the bonded magnet is observed with a transmission electron microscope (TEM, JEM-2100FCS manufactured by JEOL), and the elements contained in the particles are analyzed using EDS. did. EDS element mapping was performed for C and the transition metal element containing Fe detected in the above powder X-ray diffraction. When the total detected value constituent ratio for the transition metal element is 80 wt% or more in the constituent ratio of the measured detected value for the transition metal and C in each of the observed particles, the particles are classified as iron nitride-based particles, C When the detected value component ratio exceeded 20 wt%, the particles were defined as graphite particles. Next, 200 iron nitride-based particles and 200 graphite particles as defined above are selected from the TEM observation images, respectively, and the diameter of a circle having a cross-sectional area of each particle is analyzed by image analysis of the obtained observation images (equivalent to a circle). The average particle diameter was calculated as the average particle diameter.

≪Saturation magnetization (Js), residual magnetization (Jr), coercive force (Hcj), and orientation degree Jr / Js of a bond magnet using iron nitride magnetic powder >>
BH tracer (TRE-5BH manufactured by Toei Kogyo Co., Ltd.) was used for the saturation magnetization Js, residual magnetization Jr, and coercive force Hcj of the obtained bonded magnet. The magnetization of the bond magnet was measured by applying an external magnetic field of 20 kOe to -20 kOe parallel to the magnetic field orientation direction, and each value was obtained from the obtained demagnetization curve. However, the orientation degree was calculated from the ratio Jr / Js of the saturation magnetization Js and the residual magnetization Jr, and a bonded magnet having a saturation magnetization Js of 2.0 kG or more and an orientation degree (Jr / Js) of 0.75 or more was allowed.

In all Examples and Comparative Examples, it was confirmed that the Fe ₁₆ N ₂ phase was the main phase.

As in Example 1, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is ₂₁ nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.2. When the particle diameter ratio of the graphite particles to the iron nitride particles was 0.25, it was confirmed that the saturation magnetization (Js) was 2.0 kG or more and the degree of orientation (Jr / Js) was 0.75 or more. .

As in Example 2, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 33 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.2. When the particle size ratio of the graphite particles to the iron nitride particles is 0.13, the saturation magnetization (Js) is 2.5 kG or more, the degree of orientation (Jr / Js) is 0.85 or more, and the coercive force ( It was confirmed that Hcj) was particularly good characteristics with a value exceeding 2.0 kOe.

As in Examples 3 and 4, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 75 nm and 76 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. When the particle diameter ratio of the graphite particles to the iron nitride particles is 0.07 and 0.50, the saturation magnetization (Js) is 2.0 kG or more and the degree of orientation (Jr / Js) is 0.75. It was confirmed that this was the case.

As in Examples 5 and 6, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 74 nm and 75 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. 2 and when the particle diameter ratio of the graphite particles to the iron nitride particles is 0.07, 0.22, the saturation magnetization (Js) is 2.5 kG or more, and the degree of orientation (Jr / Js) is 0.85. It was confirmed that the characteristics were particularly good with the above-mentioned and coercive force (Hcj) exceeding 2.0 kOe.

As in Examples 7 and 8, the average particle diameter of the iron nitride particles constituting the bonded magnet using the iron nitride magnetic powder is 72 nm and 74 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. 2 and when the particle size ratio of the graphite particles to the iron nitride particles is 0.36 and 0.50, the saturation magnetization (Js) is 2.0 kG or more and the degree of orientation (Jr / Js) is 0.75. It was confirmed that this was the case.

As in Example 9, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 72 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.3. When the particle size ratio of the graphite particles to the iron nitride-based particles is 0.07, the saturation magnetization (Js) is 2.5 kG or more, the degree of orientation (Jr / Js) is 0.85 or more, and the coercive force ( It was confirmed that Hcj) was particularly good characteristics with a value exceeding 2.0 kOe.

As in Examples 10 and 11, the average particle diameter of the iron nitride particles constituting the bonded magnet using the iron nitride magnetic powder is 71 nm and 70 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. When the particle diameter ratio of the graphite particles to the iron nitride particles is 0.07 and 0.50, the saturation magnetization (Js) is 2.0 kG or more and the degree of orientation (Jr / Js) is 0.75. It was confirmed that this was the case.

As in Examples 12 and 13, the average particle diameter of the iron nitride particles constituting the bonded magnet using the iron nitride magnetic powder is 121 nm and 148 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. 2 and when the particle size ratio of the graphite particles to the iron nitride particles is 0.05 or 0.04, the saturation magnetization (Js) is 2.5 kG or more, and the degree of orientation (Jr / Js) is 0.85. It was confirmed that the characteristics were particularly good with the above-mentioned and coercive force (Hcj) exceeding 2.0 kOe.

As in Examples 14, 15, and 16, the average particle diameters of the iron nitride-based particles constituting the bond magnet using the iron nitride-based magnetic powder are 160 nm, 181 nm, and 178 nm, and the graphite phase and the Fe ₁₆ N ₂ phase When the volume ratio is 0.2, and the particle diameter ratio of the graphite particles to the iron nitride particles is 0.03, 0.05, 0.22, the saturation magnetization (Js) is 2.0 kG or more, the orientation degree ( Jr / Js) was confirmed to be 0.75 or more.

As in Example 17, in the step of obtaining the iron nitride magnetic powder, the graphite powder is mixed after obtaining the iron nitride particles, and the iron nitride system constituting the bond magnet using the iron nitride magnetic powder is used. When the average particle size of the particles is 73 nm, the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.1, and the particle size ratio of the graphite particles to the iron nitride-based particles is 0.50, saturation magnetization ( It was confirmed that Js) was 2.0 kG or more and the degree of orientation (Jr / Js) was 0.75 or more.

As in Example 18, in the step of obtaining the iron nitride magnetic powder, the graphite powder is mixed after obtaining the iron nitride particles, and the iron nitride system constituting the bond magnet using the iron nitride magnetic powder is used. When the average particle diameter of the particles is 73 nm, the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.2, and the particle diameter ratio of the graphite particles to the iron nitride-based particles is 0.07, saturation magnetization ( It was confirmed that Js) was 2.0 kG or more and the degree of orientation (Jr / Js) was 0.75 or more.

As in Examples 19 and 20, in the step of obtaining the iron nitride magnetic powder, the graphite powder is mixed after obtaining the iron nitride particles, and the nitriding that constitutes the bond magnet using the iron nitride magnetic powder is performed. The average particle diameter of the iron-based particles is 73 nm, the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0.4, and the particle diameter ratio of the graphite particles to the iron nitride-based particles is 0.07, 0.50. In this case, it was confirmed that the saturation magnetization (Js) was 2.0 kG or more and the degree of orientation (Jr / Js) was 0.75 or more.

As in Comparative Examples 1 and 2, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 23 nm and 71 nm, and the volume ratio of the graphite phase to the Fe ₁₆ N ₂ phase is 0. .2 and when the average particle diameter ratio of the graphite particles to the iron nitride particles was 0.63 and 0.57, the saturation magnetization (Js) was 3.0 kG and 2.9 kG. Jr / Js) were 0.65 and 0.72, and a sufficient degree of orientation could not be obtained. This is because the particle size of the graphite particles is larger than the particle size of the iron nitride particles, the number of graphite particles in contact with the iron nitride particles is reduced, and the frictional force acting between the iron nitride particles is sufficiently relaxed. It is thought that it was because there was not.

When the graphite particles were not included in the bonded magnet as in Comparative Example 3, the saturation magnetization (Js) was 3.6 kG, but the degree of orientation (Jr / Js) was 0.47, which was sufficient orientation The degree was not obtained. This is considered to be because the frictional force acting between the iron nitride particles was not relaxed inside the aggregate of iron nitride particles.

As in Comparative Example 4, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 73 nm, and the volume ratio of the graphite and the Fe ₁₆ N ₂ phase is 0.05, When the average particle diameter ratio of the graphite particles to the iron nitride particles is 0.07, the saturation magnetization (Js) is 3.4 kG, the degree of orientation (Jr / Js) is 0.60, and the degree of orientation is sufficient. It was not obtained. This is thought to be because the amount of graphite particles contained is small, and therefore the number of graphite particles in contact with the iron nitride-based particles decreases, and the frictional force acting between the iron nitride-based particles is not relaxed.

As in Comparative Example 5, the average particle diameter of the iron nitride-based particles constituting the bonded magnet using the iron nitride-based magnetic powder is 69 nm, and the volume ratio of the graphite and the Fe ₁₆ N ₂ phase is 0.45. When the average particle diameter ratio of the graphite particles to the iron nitride-based particles is 0.07, the saturation magnetization (Js) is 1.9 kG, the degree of orientation (Jr / Js) is 0.88, and sufficient saturation magnetization ( Js) was not obtained. This is presumably because Fe ₁₆ N ₂ phase contained in the iron nitride magnetic powder is reduced.

As described above, since the bond magnet using the iron nitride magnetic powder according to the present invention has sufficient saturation magnetization and orientation, Fe ₁₆ N ₂ which is a substance not containing a rare earth has a very high value. It is useful as a magnet that utilizes saturation magnetization.

Claims (2)

A bonded magnet using iron nitride magnetic powder, wherein the iron nitride magnetic powder is composed of iron nitride particles and graphite particles having Fe ₁₆ N ₂ as a main phase, and (average particle diameter of graphite particles) The ratio expressed by / (average particle diameter of iron nitride-based particles) is 0.50 or less, and at the same time, the ratio expressed by (volume of graphite particles) / (volume of iron nitride-based particles) is 0.1 or more. Bond magnet using iron nitride magnetic powder that is 0.4 or less. The bond magnet using the iron nitride magnetic powder according to claim 1, wherein the iron nitride particles have an average particle diameter of 30 nm or more and 150 nm or less.