JP6778652B2 - Iron nitride based magnet - Google Patents

Description

The present invention relates to an iron nitride based magnet.

In recent years, Nd-Fe-B type magnets have been widely used as magnets for motors of electric vehicles and hybrid vehicles. However, rare earths represented by Nd are raw materials for high-value-added materials that support the industrial field, and since demand has been expanding in recent years, there are concerns about resource depletion and destabilization of raw material prices. Furthermore, there is a problem in securing a stable supply due to the remarkable expansion of demand in developing countries and the high dependence on specific producing countries due to their uneven distribution.

In order to avoid the above problems, it is required to develop high-performance magnets from elements (iron, nitrogen) that exist inexhaustibly in nature without using rare earths.

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

However, Fe ₁₆ N ₂ is decomposed by being exposed to a temperature of 200 ° C. or higher for a certain period of time, and the huge saturation magnetization disappears. Therefore, it cannot go through a process such as normal sintering. Therefore, it is not possible to obtain a sintered magnet using Fe ₁₆ N ₂ . That is, it is not possible to manufacture a bulk magnet that has been densified by sintering. Due to such problems, it has been studied to use Fe ₁₆ N ₂ for a magnet that can be produced without going through a process such as ordinary sintering. For example, Patent Document 1 describes an invention of an iron nitride based magnet containing a Fe ₁₆ N _2- phase. However, there is now a demand for magnets with further improved magnetic properties and mechanical strength. Further, Patent Document 2 describes that low melting point glass is added in order to increase the mechanical strength. However, even with the magnet described in Patent Document 2, desired mechanical properties may not be obtained.

JP-A-2016-134583 JP 2015-103770

The present invention has been made in view of the above, and an object of the present invention is to provide an iron nitride based magnet having high magnetic properties and high mechanical strength.

The iron nitride based magnet according to the present invention is
An iron nitride magnet composed of iron nitride magnetic particles and low melting point glass.
The low melting point glass contains at least one element contained in the iron nitride based magnetic particles.

The iron nitride based magnet according to the present invention has higher magnetic characteristics and higher mechanical strength than the conventional iron nitride based magnet.

The iron nitride based magnet according to the present invention is
The ratio represented by (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) is 0.10 or more and 0.40 or less.
The iron nitride-based magnetic particles contain P of 1.0 at% or more and 4.0 at% or less.
The low melting point glass is made of phosphate-based glass.
Even if the phosphate-based glass is composed of P ₂ O _5- Ag ₂ O glass, P ₂ O _5- V ₂ O ₅ glass, or P ₂ O _5- Ag ₂ O-V ₂ O ₅ glass. Good.

The ratio represented by the above (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) may be 0.20 or more and 0.30 or less.

The iron nitride-based magnetic particles may contain P of 2.1 at% or more and 3.0 at% or less.

The average circle-equivalent diameter of the iron nitride-based magnetic particles may be 30 nm or more to 150 nm.

FIG. 1 is a schematic cross-sectional view of a cut-out iron nitride magnet according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described based on the embodiments shown in the drawings. The present invention is not limited to the embodiments described below. In addition, the components shown in the embodiments and examples described below may be appropriately combined or appropriately selected.

As shown in FIG. 1, the cross section of the iron nitride based magnet 1 described in the present invention is composed of iron nitride based magnetic particles 2 and low melting point glass 3, and the low melting point glass is sandwiched between the iron nitride based magnetic particles 2. 3 is filled.

The iron nitride-based magnetic particles 2 contain iron nitride and are ferromagnetic. While _{content of the Fe} 16 _{N 2} compound was as iron nitride is _typically not limited to _{content of the Fe} 16 _{N 2} compound thereof, such as Fe ₄ N compound may be a compound consisting of Fe and N. Further, the iron nitride based magnetic particles 2 may contain transition metals such as Mn, Ni, Co, Ti and Zn. Further, the component contained in the iron nitride based magnetic particles 2 is not limited to the above component, and other components may be contained as long as the effect of the present invention is not impaired.

The proportion of iron nitride in the iron nitride-based magnetic particles 2 is not particularly limited, but is preferably 95% by weight or more. Further, it can be confirmed by using XRD that the iron nitride based magnetic particles 2 contain iron nitride. Further, the content of the above components is not particularly limited. For example, assuming that the entire iron nitride-based magnetic particles 2 are 100% by weight, the transition metals such as Mn, Ni, Co, Ti, and Zn may be contained in an amount of 1% by weight or less, and the other components may be contained in an amount of 1% by weight or less. Good.

Further, the surface of the iron nitride based magnetic particles 2 may be covered with an oxide (not shown). The oxide is not particularly limited, and examples thereof include iron oxides such as Fe ₂ O ₃ , Fe ₃ O ₄ , and Fe O. Further, the oxide may contain a trace amount of Si compound or the like.

In the cross section of the iron nitride based magnet 1 according to the present embodiment, the ratio represented by (cross-sectional area of low melting point glass / cross-sectional area of iron nitride based magnetic particles) (hereinafter, may be simply referred to as “cross-sectional area ratio”). ) Is preferably in the range of 0.10 or more and 0.40 or less. When the cross-sectional area ratio is 0.10 or more, the amount of low melting point glass 3 in the cross section of the iron nitride based magnet 1 becomes sufficient, and voids are generated between the plurality of iron nitride based magnetic particles 2. It is easy to suppress and sufficiently improve the mechanical strength (particularly bending strength). Further, when the cross-sectional area ratio is 0.40 or less, the iron nitride having ferromagnetism tends to be sufficiently large in the iron nitride based magnet 1. That is, since the portion having ferromagnetism is sufficiently secured, the saturation magnetization is likely to be sufficiently improved. More preferably, the cross-sectional area ratio is in the range of 0.20 or more and 0.30 or less.

The low melting point glass 3 contains at least one element contained in the iron nitride based magnetic particles 2. In other words, the iron nitride based magnet 1 according to the present embodiment contains at least one element contained in both the low melting point glass 3 and the iron nitride based magnetic particles 2.

There is no particular limitation on the types of elements contained in both the low melting point glass 3 and the iron nitride based magnetic particles 2. For example, one or more selected from Fe, Mn, Ni, Co, Ti, Zn, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca. is there.

The case of "contained in both the low melting point glass 3 and the iron nitride based magnetic particles 2" means that "the content of the low melting point glass 3 is 0.1 at% or more and the iron nitride is contained." The content in the system magnetic particles 2 is 0.1 at% or more. ”

The element contained in both the low melting point glass 3 and the iron nitride-based magnetic particles 2 is preferably P. In this case, the amount of P contained in the iron nitride-based magnetic particles is preferably 1.0 at% or more and 4.0 at% or less. By containing P in the iron nitride based magnetic particles, P penetrates between the lattices of Fe ₁₆ N ₂ , or P replaces a part of N constituting Fe ₁₆ N _2, thereby Fe ₁₆ N ₂ This is because the lattice of the iron nitride is distorted, the anisotropy of the iron nitride-based magnetic particles is increased, and a high coercive force can be obtained while maintaining a high saturation magnetization. The amount of P contained in the iron nitride-based magnetic particles is more preferably 2.1 at% or more and 3.0 at% or less. The low melting point glass 3 is preferably a phosphate-based glass. More preferably, the phosphate-based glass is composed of P ₂ O _5- Ag ₂ O glass, P ₂ O _5- V ₂ O ₅ glass or P ₂ O _5- Ag ₂ O-V ₂ O ₅ glass.

The type of low melting point glass 3 has an appropriate composition and particle size in consideration of a temperature at which the iron nitride magnet 1 can be sufficiently densified (condensation temperature) at the time of heat treatment described later. Low melting point glass is preferably selected. Further, additives may be appropriately added to the low melting point glass 3 as long as the effects of the present invention are not impaired. Examples of the additive include B ₂ O ₃ and Zn O, but this is not the case.

The reason why the iron nitride based magnet 1 according to the present embodiment has a high coercive force is that the low melting point glass 3 exists between the plurality of iron nitride based magnetic particles 2 and the low melting point glass 3 is non-magnetic. It is considered that this is because the iron nitride based magnetic particles 2 are magnetically separated. Further, the fact that the iron nitride-based magnetic particles 2 contain a predetermined amount of P changes the magnetocrystalline anisotrope of the iron nitride-based magnetic particles 2 is also a reason for improving the coercive force of the iron nitride-based magnet 1. it is conceivable that. Further, it is considered that the coercive force and the saturation magnetization can be compatible with each other by adjusting the cross-sectional area ratio.

Further, the reason why the iron nitride magnet 1 according to the present embodiment has high mechanical strength (particularly bending strength) is that both the iron nitride magnetic particles 2 and the low melting point glass 3 contain a common element, which is good. It is considered that this is because it shows wettability. Further, it is considered that the low melting point glass 3 acts as a binder for the iron nitride-based magnetic particles 2 to improve the mechanical strength.

Here, a method for identifying the iron nitride-based magnetic particles 2 and the low melting point glass 3 will be described, and a method for identifying the cross-sectional area ratio and the like will be described.

The iron nitride-based magnetic particles 2 and the low-melting point glass 3 can be identified by observing the cross section of the iron nitride-based magnet 1. For example, a transmission electron microscope is used to observe a cross section of a measurement region of 1.0 μm × 1.0 μm at a magnification of 200,000 times, and element distribution mapping is performed by EDS. In the element mapping image, a portion containing an iron nitride-derived element is observed. Is an iron nitride based magnetic particle 2. Specifically, the portion where Fe and N are detected by element mapping is designated as iron nitride based magnetic particles 2. On the other hand, the portion containing only the element derived from the low melting point glass and substantially not containing the element derived from iron nitride is referred to as the low melting point glass 3. When the low melting point glass is the above-mentioned phosphate glass, specifically, Fe and N are not detected by the element distribution mapping and are contained in both the iron nitride based magnetic particles 2 and the low melting point glass. The portion where the element is detected by the element distribution mapping and Ag and / or V is detected by the element distribution mapping is identified as the low melting point glass 3. When a low melting point glass containing N is used, Fe is not detected by the element distribution mapping, and the elements contained in both the iron nitride-based magnetic particles 2 and the low melting point glass are detected by the element distribution mapping. , The portion where the element contained only in the low melting point glass containing N is detected by the element distribution mapping is identified as the low melting point glass 3.

Regarding the cross-sectional area ratio, first, the cross-sectional area of the iron nitride magnet 1 is observed in 500 different measurement regions, and the cross-sectional area ratio in each measurement region is calculated. Then, the cross-sectional area ratio of the iron nitride based magnet can be calculated by averaging the cross-sectional area ratios in the 500 regions.

Further, the content of the common element contained in the iron nitride based magnetic particles 2 can be identified by element mapping using EDS.

It is preferable that the average circle-equivalent diameter of the iron nitride-based magnetic particles 2 is 30 nm or more and 150 nm or less. When the average circle-equivalent diameter of the iron nitride-based magnetic particles 2 is within the above range, the coercive force tends to increase. The average circle-equivalent diameter of the iron nitride-based magnetic particles 2 can be calculated from the total area of the iron nitride-based magnetic particles 2 in each measurement region and the total number of iron nitride-based magnetic particles in each measurement region.

Hereinafter, a suitable manufacturing method of the iron nitride based magnet 1 according to the present embodiment will be described. Hereinafter, a suitable manufacturing method when the iron nitride-based magnet 1 is an iron nitride-based bonded magnet will be described, but the manufacturing method of the iron nitride-based magnet 1 according to the present embodiment is not limited to the following method.

First, iron oxide particles as a raw material for the iron nitride-based magnetic particles 2 are prepared. The iron oxide particles are obtained after mixing an aqueous iron salt solution containing an iron (II) salt and / or an iron (III) salt (hereinafter, may be simply referred to as "iron salt") and an alkaline aqueous solution. It can be produced by advancing the aging reaction.

The type of the iron salt is not particularly limited, and for example, sulfate, chloride, nitrate and the like can be used, and these may be used in combination as appropriate. Also, those hydrates can be used.

The type of the alkaline aqueous solution is not particularly limited, and for example, one or more selected from the group consisting of sodium hydroxide aqueous solution, ammonia water, ammonia salt aqueous solution, and urea aqueous solution can be used, but other alkaline aqueous solutions can be used. May be used.

The conditions of the aging reaction are not particularly limited, and can be appropriately selected depending on the type of the iron salt and the type of the alkaline aqueous solution.

Further, from the viewpoint of improving the crystallinity of iron oxide obtained after the aging reaction, controlling the particle size, and facilitating the control of the particle shape, the aging reaction can be carried out by an in-liquid aging reaction such as hydrothermal treatment by an autoclave. preferable.

By filtering the aqueous solution after the aging reaction, the iron oxide particles obtained by the aging reaction can be recovered. Further, an iron oxide slurry containing iron oxide particles may be obtained by subjecting the aqueous solution after the aging reaction to a washing treatment such as washing with water using a centrifuge or the like.

A part of the surface of the iron oxide particles may be coated with a Si compound in order to prevent the iron oxide particles from sintering each other by the reduction treatment described later. As the Si compound, sodium silicate, colloidal silica, silane coupling agent, silanol compound and the like can be used, but the Si compound is not limited thereto.

When coated with a Si compound, the coating amount of the Si compound is preferably 0.1% by weight or more and 20% by weight or less in terms of Si with respect to the iron oxide particles. By setting the content to 0.1% by weight or more, it becomes easy to sufficiently obtain the effect of suppressing sintering between iron oxide particles during heat treatment, and the average circle-equivalent diameter of the iron nitride-based magnetic particles 2 finally obtained is averaged. It becomes easy to control to 150 nm or less. By setting the content to 20% by weight or less, it becomes easy to appropriately suppress sintering between iron oxide particles during heat treatment, and it becomes easy to control the average circle-equivalent diameter of the finally obtained iron nitride-based magnetic particles 2 to 30 nm or more. ..

Further, the step of coating with the Si compound may be performed on the iron oxide particles obtained by filtration, or may be performed on the iron oxide slurry described above. Further, after the step of coating the iron oxide slurry with the Si compound, the iron oxide particles can be recovered by filtering the iron oxide slurry.

The average particle size of the iron oxide particles is not particularly limited, but is preferably 10 nm or more and 150 nm or less. By setting the average particle diameter to 10 nm or more and 150 nn or less, it becomes easy to control the average circle-equivalent diameter of the finally obtained iron nitride-based magnetic particles 2 to 30 nm or more and 150 nm or less.

Examples of the type of iron oxide particles include magnetite, γ-Fe ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, β-FeOOH, γ-FeOOH, FeO, and the like, but other types of oxidation. Iron particles may be used.

The particle shape of the iron oxide particles is not particularly limited, and may be spherical, needle-shaped, granular, spindle-shaped, rectangular parallelepiped, or the like. Further, the iron oxide particles may be dried, if necessary, before the obtained iron oxide particles are subjected to the reduction treatment described later. There are no particular restrictions on the drying conditions.

The iron nitride-based magnetic powder according to the present embodiment can be obtained by subjecting the iron oxide particles to a reduction treatment and subjecting the obtained iron particles to a nitriding treatment. Further, the obtained iron nitride-based magnetic powder may be subjected to a gradual oxidation treatment at a low temperature and under a low oxygen partial pressure to form an oxide on the surface of the iron nitride-based magnetic powder.

Hereinafter, the reduction treatment and the nitriding treatment will be described.

The temperature of the reduction treatment is not particularly limited, but is preferably 200 ° C. or higher and 400 ° C. or lower. By setting the temperature of the reduction treatment to 200 ° C. or higher, the iron oxide particles can be sufficiently reduced. By setting the temperature of the reduction treatment to 400 ° C. or lower, the iron oxide particles can be sufficiently reduced, and sintering between the particles can be appropriately suppressed. The temperature of the reduction treatment is more preferably 230 ° C. or higher and 350 ° C. or lower.

The time of the reduction treatment is not particularly limited, but is preferably 1 hour or more and 96 hours or less. When the reduction treatment time is 96 hours or less, it becomes difficult for the sintering between particles to proceed appropriately even if the temperature of the reduction treatment is raised. As a result, the subsequent nitriding process can easily proceed. If the reduction treatment time is 1 hour or more, the reduction can easily proceed. The time of the reduction treatment is more preferably 2 hours or more and 72 hours or less.

A reducing atmosphere processing is, for example, an H ₂ atmosphere.

Next, the iron particles obtained by the reduction treatment are subjected to the nitriding treatment. When the common element is P, in the present embodiment, a mixed gas of ammonia gas and phosphine gas is used in the nitriding treatment. By controlling the ratio of the phosphine gas to the mixed gas, the content of P in the iron nitride based magnetic powder can be controlled.

The ratio of phosphine gas to the mixed gas of ammonia gas and phosphine gas is preferably 0.8 mol% or more and 29 mol% or less. By setting the ratio of the phosphine gas to 0.8 mol% or more, the content of P in the iron nitride-based magnetic powder can be easily set to 0.1 at% or more, and the iron nitride contained in the finally obtained iron nitride-based magnet 1 can be easily obtained. The effect of invasion and replacement of P into the system magnetic particles 2 becomes sufficiently easy to obtain. Then, the content of P in the iron nitride-based magnetic particles 2 contained in the finally obtained iron nitride-based magnet 1 can be easily set to 1.0 at% or more. By setting the ratio of phosphine gas to 29 mol% or less, the content of P in the iron nitride-based magnetic powder can be easily set to 4.5 at% or less, and Fe ₃ P in which a part of iron nitride Fe ₁₆ N ₂ is an impurity. It becomes difficult to cause a reaction that changes to. Then, the content of P in the iron nitride-based magnetic particles 2 contained in the finally obtained iron nitride-based magnet 1 can be easily set to 4.0 at% or less.

The temperature of the nitriding treatment is preferably 100 or more and 200 ° C. or less. When the temperature of the nitriding treatment is 100 ° C. or higher, nitriding easily proceeds sufficiently. When the temperature of the nitriding treatment is 200 ° C. or lower, nitriding is less likely to proceed excessively, and it becomes easier to suppress a decrease in magnetic characteristics. The temperature of the nitriding treatment is more preferably 120 ° C. or higher and 180 ° C. or lower.

The nitriding treatment time is not particularly limited, but is preferably 1 hour or more and 48 hours or less. When the nitriding treatment time is 48 hours or less, the magnetic characteristics are less likely to deteriorate even if the nitriding treatment temperature is raised. When the nitriding treatment time is 1 hour or more, nitriding easily proceeds sufficiently. The nitriding treatment time is more preferably 3 hours or more and 24 hours or less.

At this time, iron oxide may be present on the surface of the iron nitride-based magnetic powder.

The phosphate-based glass powder according to the present embodiment can be produced by a vapor deposition method, a sputtering method, a flame spray pyrolysis method, a high-frequency thermal plasma method, or the like, but may be produced by other methods. At this time, the average particle size of the phosphate-based glass powder is preferably 10 nm or more and 30 nm or less. By setting the average particle size of the phosphate-based glass powder in the above range, the phosphate-based glass can be uniformly filled between the particles of the iron nitride-based magnetic particles in the molded body described later.

As the phosphate-based glass, P ₂ O _5- Ag ₂ O, P ₂ O _5- V ₂ O ₅ , and P ₂ O _5- Ag ₂ O-V ₂ O ₅ can be used. There is no particular limitation on the ratio of each component in each phosphate-based glass. The softening point (melting point) of each phosphate-based glass can be controlled by changing the composition ratio and particle size of each component, and is at 150 ° C. or lower, which is the temperature at which the iron nitride-based magnet is densified. Control to soften. More specifically, there is a tendency that the softening point is increased by increasing the content of P ₂ O ₅ contained in the phosphate type glass. The softening point can also be controlled by changing the content ratio of Ag ₂ O and / or V ₂ O ₅ . Further, the softening point tends to be lowered by reducing the particle size of the phosphate-based glass.

When the common element is other than P, the iron nitride-based magnetic powder and the glass powder contain the common element by a known method.

Next, the iron nitride-based magnetic powder and the phosphate-based glass powder are mixed to obtain a mixed powder. The mixing method is not particularly limited, and may be wet mixing or dry mixing. The mixed powder is put into a mold having an arbitrary shape and size, and a load of 3 kgf / cm ² or more and 20 kgf / cm ² or less is applied to prepare a molded product. By setting the load in this range, the molded body has sufficient shape retention and cracks generated in the molded body can be suppressed. More preferably, it is 10 kgf / cm ² or more and 20 kgf / cm ² or less.

When molding the molded product into a predetermined shape, the molded product may be molded while applying a magnetic field. By molding while applying a magnetic field, the iron nitride-based magnet 1 finally obtained is oriented in a specific direction, so that the iron nitride-based magnet 1 having more excellent magnetic characteristics can be obtained.

The obtained molded product is densified by heat treatment at a temperature of 150 ° C. or lower to obtain an iron nitride based magnet 1. When the heat treatment is performed at a temperature exceeding 150 ° C., the iron nitride (Fe ₁₆ N ₂ compound) contained in the iron nitride-based magnetic particles 2 may be decomposed and the magnetic properties may be significantly deteriorated. The heat treatment temperature is more preferably 130 ° C. or lower. It is also possible to make it denser by applying an energization treatment by SPS.

There is no particular limitation on the atmosphere in the heat treatment for _example, N 2, He, is preferably an inert atmosphere or a vacuum such as Ar.

As the heat treatment, in addition to the general normal pressure heat treatment, for example, a pressure heat treatment such as hot press, HIP, SPS, etc. can be selected, but the heat treatment is not limited to these methods, and other methods are adopted. You can also do it.

The obtained iron nitride based magnet 1 may be plated or painted in order to prevent deterioration of the surface.

Next, the iron nitride based magnet according to the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the embodiments shown in the Examples.

(Example 1) was dissolved in iron sulfate heptahydrate _{(FeSO 4 · 7H 2 O)} 167g and iron chloride hexahydrate _{(FeCl 3 · 6H 2 O)} 85g and ion exchange water 248 mL, the iron salt solution Made. 600 g of a 2.5 mol / L ammonia aqueous solution prepared separately from the iron salt aqueous solution was maintained at 30 ° C., and 500 g of the previously prepared iron salt aqueous solution was added to 600 g of the ammonia aqueous solution. Then, the temperature of the aqueous ammonia solution was controlled so as to be constant at 70 ° C., and the mixture was stirred for 30 minutes to advance the aging reaction in the liquid to generate iron oxide. Then, an iron oxide slurry was prepared by washing with 2 L of ion-exchanged water three times using a centrifuge.

To 1000 g of the iron oxide slurry, 5.0 g of tetraethoxysilane, 21 g of ethanol, and 78 g of diethylene glycol monobutyl ether were added, and Si adhesion treatment was performed. The iron oxide slurry subjected to the Si adhesion treatment was filtered and then 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 firing boat and allowed to stand in a heat treatment furnace. After filling the furnace with nitrogen gas, the temperature is raised to 250 ° C. at a heating rate of 5 ° C./min while flowing hydrogen gas at a flow rate of 1 L / min, and the temperature is maintained at 250 ° C. for 48 hours for reduction treatment. It was. After holding at 250 ° C. for 48 hours, the temperature was lowered to 140 ° C. while the supply of hydrogen gas was stopped and nitrogen gas was flowed at a flow rate of 2 L / min.

Subsequently, the flow rate of ammonia gas was set to 165 mL / min and the flow rate of phosphine gas was set to 35 mL / min, and a mixed gas of ammonia gas and phosphine gas was flown and held at 140 ° C. for 24 hours for nitriding. After holding at 140 ° C. for 24 hours, the temperature was lowered to 50 ° C. while flowing nitrogen gas at a flow rate of 2 L / min. Finally, air substitution was carried out for 24 hours to prepare an iron nitride based magnetic powder.

Next, to obtain a _{40P 2 O} 5 -60Ag 2 _O glass powder having an average particle diameter of about 20nm by sputtering. _{Specifically,} by irradiating the sputtering target material of P 2 _{O 5} and Ag _{2 O,} to give a 40P ₂ O 5 -60Ag ₂ O glass powder. The sputtering conditions were air, a pressure of 20 Pa, a vapor deposition current of about 10 mA, and a reaction time of 15 min. Note that _{"40P 2 O} 5 -60Ag 2 _O", P ₂ O 5: refers to Ag ₂ O is 40:60 in molar ratio.

To prepare a slurry by mixing the iron nitride-based magnetic powder 59g and the _{40P 2 O} 5 -60Ag 2 _O glass powder 4.8g and thoroughly dehydrated toluene 1000 g. After the slurry was dispersed by a homomixer, followed by drying for 24 hours at 25 ° C., to obtain a mixed powder composed of iron nitride-based magnetic particles and _{40P 2 O} 5 -60Ag 2 _O glass particles.

The obtained mixed powder was filled in a mold of 12 × 12 mm, and a pressure of 10 kgf / cm ² was applied at room temperature to obtain a molded body for magnetic property evaluation. Further, it was filled in a mold of 90 × 12 mm and a pressure of 10 kgf / cm ² was applied at room temperature to obtain a molded product for measuring bending strength.

Each of the obtained compacts was allowed to stand in a heat treatment furnace, and the furnace was filled with argon gas. Then, while flowing argon gas at a flow rate of 2 L / min, the molded body was densified by heat treatment at 130 ° C. for 2 hours to obtain an iron nitride based magnet.

(Example 2) The amount of tetraethoxysilane added to the iron oxide slurry is 4.0 g, the flow rate of ammonia gas during the nitriding treatment is 166 mL / min, the flow rate of phosphine gas is 34 mL / min, and the amount of the mixed powder blended. the iron nitride-based magnetic powder _{63 g,} except that the _{40P 2} O 5 -60Ag 2 O glass powder 4.8 g, to prepare an iron nitride-based magnetic in the same manner as in example 1.

(Example 3) The amount of tetraethoxysilane added to the iron oxide slurry is 2.5 g, the flow rate of ammonia gas during the nitriding treatment is 185 mL / min, the flow rate of phosphine gas is 16 mL / min, and the amount of the mixed powder blended. the iron nitride-based magnetic powder _{56 g,} except that the _{40P 2} O 5 -60Ag 2 O glass powder 4.8 g, to prepare an iron nitride-based magnetic in the same manner as in example 1.

(Example 4) Except that the amount of tetraethoxysilane added to the iron oxide slurry was 2.5 g, the flow rate of ammonia gas during the nitriding treatment was 170 mL / min, and the flow rate of phosphine gas was 30 mL / min. An iron nitride based magnet was produced in the same manner as in Example 1.

(Example 5) Except that the amount of tetraethoxysilane added to the iron oxide slurry was 2.5 g, the flow rate of ammonia gas during the nitriding treatment was 164 mL / min, and the flow rate of phosphine gas was 36 mL / min. An iron nitride based magnet was produced in the same manner as in Example 1.

(Example 6) The amount of tetraethoxysilane added to the iron oxide slurry is 2.5 g, the flow rate of ammonia gas during the nitriding treatment is 160 mL / min, the flow rate of phosphine gas is 40 mL / min, and the amount of the mixed powder blended. the iron nitride-based magnetic powder _{59 g,} except that the _{40P 2} O 5 -60Ag 2 O glass powder 4.8 g, to prepare an iron nitride-based magnetic in the same manner as in example 1.

(Example 7) Except that the amount of tetraethoxysilane added to the iron oxide slurry was 2.5 g, the flow rate of ammonia gas during the nitriding treatment was 150 mL / min, and the flow rate of phosphine gas was 50 mL / min. An iron nitride based magnet was produced in the same manner as in Example 1.

(Example 8) the amount of tetraethoxysilane is added to the iron oxide slurry and 2.5g, the amount of iron nitride-based magnetic powder 234g of the mixed _powder, was 40P ₂ O 5 -60Ag ₂ O glass powder 4.8g An iron nitride based magnet was produced in the same manner as in Example 1 except for the points.

(Example 9) The amount of tetraethoxysilane added to the iron oxide slurry is 2.5 g, the flow rate of ammonia gas during the nitriding treatment is 164 mL / min, the flow rate of phosphine gas is 36 mL / min, and the amount of the mixed powder blended. the iron nitride-based magnetic powder _{77 g,} except that the _{40P 2} O 5 -60Ag 2 O glass powder 4.8 g, to prepare an iron nitride-based magnetic in the same manner as in example 1.

(Example 10) The amount of tetraethoxysilane added to the iron oxide slurry is 2.5 g, the flow rate of ammonia gas during the nitriding treatment is 166 mL / min, the flow rate of phosphine gas is 34 mL / min, and the amount of the mixed powder blended. the iron nitride-based magnetic powder _{47 g,} except that the _{40P 2} O 5 -60Ag 2 O glass powder 4.8 g, to prepare an iron nitride-based magnetic in the same manner as in example 1.

(Example 11) the amount of tetraethoxysilane is added to the iron oxide slurry and 2.5g, the amount of iron nitride-based magnetic powder _29g of the mixed powder, was _{40P 2} O 5 -60Ag 2 O glass powder 4.8g An iron nitride based magnet was produced in the same manner as in Example 1 except for the points.

(Example 12) oxidation the amount of tetraethoxysilane is added to the iron slurry and 2.5g, using _{35P 2 O 5} -65V 2 _O 5 glass powder as glass powder, iron nitride-based magnetic powder the amount of the mixed powder 59 _g, except that the 35P ₂ O ₅ -65V ₂ O 5 glass powder 2.9g was prepared iron nitride-based magnetic in the same manner as in example 1.

(Example 13) the amount of tetraethoxysilane is added to the iron oxide slurry and 2.5g, using _{30P 2 O 5 -50Ag 2 O-} 20V 2 O 5 glass powder as glass powder, ammonia gas during nitriding in that the flow rate was 166 mL / min, the flow rate of the phosphine gas and 34 mL / min, the amount of iron nitride-based magnetic powder _59g of the mixed powder, was _{30P 2 O 5 -50Ag 2 O-} 20V 2 O 5 glass powder 4.1g An iron nitride based magnet was produced in the same manner as in Example 1 except for the above.

(Example 14) the amount of tetraethoxysilane is added to the iron oxide slurry and 1.8g, the amount of iron nitride-based magnetic powder _63g of the mixed powder, was _{40P 2} O 5 -60Ag 2 O glass powder 4.8g An iron nitride based magnet was produced in the same manner as in Example 1 except for the points.

(Example 15) Except that the amount of tetraethoxysilane added to the iron oxide slurry was 0.8 g, the flow rate of ammonia gas during the nitriding treatment was 166 mL / min, and the flow rate of phosphine gas was 34 mL / min. An iron nitride based magnet was produced in the same manner as in Example 1.

(Example 16) the amount of tetraethoxysilane is added to the iron oxide slurry and 0.6 g, the amount of iron nitride-based magnetic powder _56g of the mixed powder, was _{40P 2} O 5 -60Ag 2 O glass powder 4.8g An iron nitride based magnet was produced in the same manner as in Example 1 except for the points.

(Comparative Example 1) Iron nitride is the same as in Example 1 except that the amount of tetraethoxysilane added to the iron oxide slurry is 2.5 g and 60 g of iron nitride-based magnetic powder is used instead of the mixed powder. A system magnet was produced.

(Comparative Example 2) The amount of tetraethoxysilane added to the iron oxide slurry was 2.5 g, and the blending amount of the mixed powder was 59 g of iron nitride based magnetic powder and 4.2 g of 90Te ₂ O-10V ₂ O ₅ glass powder. An iron nitride based magnet was produced in the same manner as in Example 1 except for the above.

<Measurement of the amount of P contained in iron nitride powder>
The obtained iron nitride based magnet was weighed in 0.05 g in a Teflon (registered trademark) beaker and melted by heating at 120 ° C. or higher and 150 ° C. or lower. After cooling, 1 mL of hydrogen fluoride was added, the volume was adjusted to 50 mL, and the measurement was performed using an inductively coupled plasma emission spectrophotometer (ICP).

<Identification of iron nitride based magnetic particles and low melting point glass>
For the obtained iron nitride-based magnet, an X-ray diffraction profile was obtained by powder XRD (RINT-2500 manufactured by Rigaku), and iron nitride-based magnetic particles and low melting point glass were identified. The obtained iron nitride based magnet was machined so as to have a cross section. A transmission electron microscope (TEM, JEM-2100FCS manufactured by JEOL Ltd.) was used to observe a cross section of a measurement region of 1.0 μm × 1.0 μm at a magnification of 200,000 times, and an electron diffraction image was observed. Furthermore, element distribution mapping was performed by EDS. From the element mapping image, the portion containing Fe and N was identified as iron nitride-based magnetic particles, and the portion containing Fe and N, containing P, and containing Ag or V was identified as low melting point glass.

<Identification of P content in iron nitride based magnetic particles>
The P content in the iron nitride based magnetic particles was identified by element mapping by EDS.

<Identification of cross-sectional area ratio and calculation of equivalent circle diameter of iron nitride based magnetic particles>
By image analysis of the obtained element mapping image, the cross-sections of the iron nitride magnets were observed in 500 different measurement regions of 50 μm × 50 μm, and the cross-sectional area ratios in each region were calculated and averaged. By doing so, the cross-sectional area ratio of the iron nitride based magnet was calculated. Further, the equivalent circle diameter was calculated from the cross-sectional area of the obtained iron nitride-based magnetic particles and the number of iron nitride-based magnetic particles.

<Measurement of saturation magnetization Ms and coercive force Hc>
A BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) was used to measure the saturation magnetization Ms and coercive force Hc of the obtained iron nitride based magnet for magnetic measurement evaluation. The externally applied magnetic field was changed from 25 kOe to -25 kOe, and the saturation magnetization Ms and coercive force Hc were obtained from the obtained demagnetization curve. In this example, an iron nitride magnet having a saturation magnetization Ms of 6.0 kG or more and a coercive force Hc of 2.0 kOe or more has good magnetic characteristics. Further, the iron nitride magnet having a saturation magnetization Ms of 7.0 kG or more and a coercive force Hc of 2.5 kOe or more has further improved magnetic properties.

<Measurement of bending strength>
The bending strength was measured by processing a sample for bending strength measurement into a size of 80 mm × 10 mm × 4 mm and using a bending strength tester (INSTRON5543 manufactured by Instron Japan Company Limited) according to JIS K7171 standard. Five test samples were prepared for each level, the bending strength was measured, and the average value was taken as the bending strength of each level. The case where the bending strength was 30 MPa or more was regarded as good. Further, the case where the bending strength was 45 MPa or more was made even better.

In all the embodiments, the iron nitride based magnet is composed of iron nitride based magnetic particles and phosphate glass which is a low melting point glass filled between the plurality of the iron nitride based magnetic particles. Was there. All the iron nitride-based magnetic particles contained P. The magnetic properties and bending strength were all good in all the examples.

As in Examples 4, 5, 6, 9, 10, 12, 13, and 14, the ratio represented by (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) is 0.20 or more and 0. When the P content in the iron nitride-based magnetic particles is 30 or less, the P content in the iron nitride-based magnetic particles is 2.0 at% or more and 3.0 at% or less, and the equivalent circle diameter of the iron nitride-based magnetic particles is 30 nm or more and 150 nm or less, the magnetic properties and bending The strength was even better.

On the other hand, in Comparative Example 1 in which the ratio represented by (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) was 0, the bending strength and the coercive force Hc were significantly reduced.

It is considered that the reason why the coercive force Hc was remarkably lowered in Comparative Example 1 was that the magnetic separation effect was not enhanced because the low melting point glass was not present between the iron nitride based magnetic particles. Further, the reason why the bending strength is remarkably lowered is that a large number of voids remain in the iron nitride-based magnet due to insufficient filling of the low melting point glass between the plurality of iron nitride-based magnetic particles, and the iron nitride-based magnetism It is considered that this is because the particles cannot be firmly connected to each other.

In Comparative Example 2 in which the low melting point glass was 90 Te ₂ O-10V ₂ O ₅ , the coercive force Hc and the bending strength were significantly reduced.

The reason why the bending strength was remarkably lowered in Comparative Example 2 is that the low melting point glass does not contain P, and the elements contained in the iron nitride based magnetic particles and the low melting point glass are all different elements, and the iron nitride based magnetic particles and the low melting point have a low melting point. It is considered that this is because the wettability with the glass has deteriorated. It is probable that due to the deterioration of the wettability between the iron nitride-based magnetic particles and the low-melting point glass, it was not possible to firmly bond the plurality of iron nitride-based magnetic particles to each other, and the bending strength was lowered.

The reason why the coercive force Hc was remarkably lowered in Comparative Example 2 is that the low melting point glass does not contain P, and the elements contained in the iron nitride based magnetic particles and the low melting point glass are all different elements, so that the magnetic anisotropy Is considered to be because was not sufficiently expressed. Further, since P is not present in the low melting point glass, the wettability between the iron nitride-based magnetic particles and the low melting point glass deteriorates, and as the wettability deteriorates, the low melting point glass between the plurality of iron nitride based magnetic particles Is not sufficiently filled, the magnetic separation effect is not enhanced, and it is considered that Hc is lowered.

As described above, the iron nitride based magnet according to the present invention is useful as a magnet that does not use rare earths because it has high magnetic properties (particularly saturation magnetization and coercive force) and high mechanical strength (particularly bending strength). Is.

1 Iron nitride based magnet 2 Iron nitride based magnetic particles 3 Low melting point glass

Claims (5)

An iron nitride magnet composed of iron nitride magnetic particles and low melting point glass.
An iron nitride magnet in which the low melting point glass contains at least one element contained in the iron nitride magnetic particles. The ratio represented by (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) is 0.10 or more and 0.40 or less.
The iron nitride-based magnetic particles contain P of 1.0 at% or more and 4.0 at% or less.
The low melting point glass is made of phosphate-based glass.
Claim 1 in which the phosphate-based glass comprises P ₂ O _5- Ag ₂ O glass, P ₂ O _5- V ₂ O ₅ glass, or P ₂ O _5- Ag ₂ O-V ₂ O ₅ glass. The iron nitride based magnet described in. The iron nitride magnet according to claim 2, wherein the ratio represented by the above (cross-sectional area of low melting point glass / cross-sectional area of iron nitride-based magnetic particles) is 0.20 or more and 0.30 or less. The iron nitride-based magnet according to claim 2 or 3, wherein the iron nitride-based magnetic particles contain P of 2.1 at% or more and 3.0 at% or less. The iron nitride-based magnet according to any one of claims 2 to 4, wherein the average circle-equivalent diameter of the iron nitride-based magnetic particles is 30 nm or more to 150 nm.

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