JP6375738B2 - Iron nitride magnetic powder and magnet using the same - Google Patents
Iron nitride magnetic powder and magnet using the same Download PDFInfo
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Description
本発明は、窒化鉄系材料磁性粉に関する。また、該磁性粉を用いた磁石を提供する。 The present invention relates to an iron nitride-based material magnetic powder. Moreover, the magnet using this magnetic powder is provided.
磁石において、磁気的な配向性の指標として残留磁化の飽和磁化に対する比(以下、配向度と呼ぶ)が用いられ、配向度は異方性磁石における重要な特性のひとつである。配向度が高い状態とは、磁石内部で粒子の磁化容易軸の方向が揃っている状態であり、磁化のしやすさや残留磁化の大きさ、磁気ヒステリシスループにおける減磁曲線の角型性の良さなどを向上させる。 In a magnet, a ratio of residual magnetization to saturation magnetization (hereinafter referred to as orientation degree) is used as an index of magnetic orientation, and the degree of orientation is one of important characteristics in anisotropic magnets. A state with a high degree of orientation is a state in which the directions of the easy magnetization axes of particles are aligned inside the magnet, and the ease of magnetization, the magnitude of residual magnetization, and the good squareness of the demagnetization curve in the magnetic hysteresis loop. Etc. to improve.
一方、Fe−N系の化合物、特にFe16N2は、α−Feよりも巨大な飽和磁化を示す材料のひとつとして注目されている。Fe16N2を用いて高い保磁力を実現するには粒径を単磁区臨界径以下とする必要がある。Fe16N2の単磁区臨界径はおよそ100nm未満であると考えられており、保磁力向上のためにFe16N2をナノ粒子化する技術が検討されてきた。一方で、磁性粒子から異方性磁石を得るためには、外部磁界により配向処理を施すことで単磁区臨界径以下の粒子を回転させる必要があるが、ナノ粒子の配向処理では粒子同士の摩擦が大きく回転が妨げられ、配向させて異方性磁石を得ることは困難であった。 On the other hand, Fe-N compounds, particularly Fe 16 N 2, are attracting attention as one of materials exhibiting a larger saturation magnetization than α-Fe. In order to realize a high coercive force using Fe 16 N 2 , it is necessary to make the grain size equal to or smaller than the single domain critical diameter. The single domain critical diameter of Fe 16 N 2 is considered to be less than about 100 nm, and a technique for forming Fe 16 N 2 into nanoparticles has been studied in order to improve the coercive force. On the other hand, in order to obtain an anisotropic magnet from magnetic particles, it is necessary to rotate particles with a single-domain critical diameter or less by applying an orientation treatment with an external magnetic field. Therefore, it was difficult to obtain an anisotropic magnet by orienting it.
特許文献1及び特許文献2では、オキシ水酸化鉄に対して還元処理及び窒化処理を施すことでFe16N2相を含む窒化鉄系磁性粉を作製しており、該磁性粉を溶剤・樹脂等と混練してスラリーとして塗布し、N−N対向磁石を用いて配向処理を施した後乾燥させることで磁気シートを得ている。しかしながら、いずれもFe16N2ナノ粒子をスラリー中に分散させ、溶剤・樹脂等の存在下で配向処理を施すことで摩擦を低減しているため、シートの成形においては問題が起こらないが、粒子同士が密に詰まって摩擦が起こるバルク磁石を得るための配向技術としては適用できない。このことから、特許文献1及び特許文献2に記載の技術では異方性バルク磁石で十分な配向度は得られない。 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, applying an orientation treatment using an NN counter magnet, and drying. However, in both cases, Fe 16 N 2 nanoparticles are dispersed in the slurry, and the orientation treatment is performed in the presence of a solvent / resin to reduce the friction. It cannot be applied as an orientation technique for obtaining a bulk magnet in which particles are closely packed and friction occurs. For this reason, the techniques described in Patent Document 1 and Patent Document 2 cannot obtain a sufficient degree of orientation with an anisotropic bulk magnet.
本発明は、上記を鑑みたものであり、配向に適した窒化鉄系磁性粉及び該磁性粉を用いて作製した高い配向度を有する窒化鉄系磁石の提供を目的とする。 The present invention has been made in view of the above, and an object thereof is to provide an iron nitride magnetic powder suitable for orientation and an iron nitride magnet having a high degree of orientation produced using the magnetic powder.
本発明は、Fe16N2相を含み、粒径の個数分布において、粒径10nm以上50nm以下の範囲の粒子の個数が全体のx%、粒径100nm以上200nm以下の範囲の粒子が全体のy%とするとき、前記xが30≦x≦70であり、前記yが30≦y≦70であり、前記x及びyが60≦x+y≦100であることを特徴とする窒化鉄系磁性粉である(本発明1)。 The present invention includes a Fe 16 N 2 phase, and in the particle size distribution, the number of particles having a particle size in the range of 10 nm to 50 nm is x% of the whole, and the particles having a particle size in the range of 100 nm to 200 nm are wherein y is 30 ≦ x ≦ 70, y is 30 ≦ y ≦ 70, and x and y are 60 ≦ x + y ≦ 100. (Invention 1).
また、本発明は、本発明1に記載の窒化鉄系磁性粉を用いた磁石である(本発明2)。 Moreover, this invention is a magnet using the iron nitride magnetic powder of this invention 1 (this invention 2).
本発明によれば、配向に適した窒化鉄系磁性粉及び該磁性粉を用いて作製した高い配向度を有する窒化鉄系磁石を得ることができる。 According to the present invention, an iron nitride-based magnetic powder suitable for orientation and an iron nitride-based magnet having a high degree of orientation produced using the magnetic powder can be obtained.
以下、本発明の好適な実施形態について説明する。なお、本発明は以下に記載の実施形態及び実施例の内容により限定されるものではない。また、以下に記載の実施形態及び実施例にて示された構成要素は適宜組み合わせても良いし、適宜選択してもよい。 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.
本実施形態に係る磁性粉は、Fe16N2相を含み、粒径の個数分布において、粒径10nm以上50nm以下の範囲の粒子の個数が全体のx%、粒径100nm以上200nm以下の範囲の粒子が全体のy%とするとき、前記xが30≦x≦70であり、前記yが30≦y≦70であり、前記x及びyが60≦x+y≦100である。粒径が10nm以上50nm以下の範囲の粒子が、相対的に大きい100nm以上200nm以下の範囲の粒子の隙間に入り込むことで、粒子の体積より大きい隙間では隣接粒子との接触確率が小さくなり、粒子が回転しやすくなって配向度が向上する。窒化鉄の粒子同士は焼結しておらず、磁気的に完全に孤立していることが好ましい。粒径が10nm未満では粒子表面の酸化膜の割合が大きくなったり、超常磁性が発現したりするため、配向度が低下する傾向がある。粒径が100nm以上の粒子割合が70%を超える場合、粒子サイズが大きいため、単磁区臨界径以下の粒子割合が小さく、配向度が低下する可能性がある。また、粒径が10nm以上50nm以下の粒子の割合が70%を超える場合、粒子同士の摩擦が大きく、粒子の回転が妨げられるために十分な配向度が得られない。隙間を形成する大きい粒子が50nmを超えており100nm未満の場合では、粒径が10nm以上50nm以下の範囲の粒子の入り込む隙間が小さく、十分な配向度が得られない。隙間を形成する大きい粒子が200nmを超える場合、粒径が10nm以上50nm以下の範囲の粒子の入り込む隙間が大きく、隙間の中で小さい粒子同士が接するために十分な配向度が得られない。 The magnetic powder according to the present embodiment includes an Fe 16 N 2 phase, and in the particle size distribution, the number of particles having a particle size in the range of 10 nm to 50 nm is x% of the whole, and the particle size is in the range of 100 nm to 200 nm. When y is the total y%, x is 30 ≦ x ≦ 70, y is 30 ≦ y ≦ 70, and x and y are 60 ≦ x + y ≦ 100. Particles with a particle size in the range of 10 nm or more and 50 nm or less enter a gap between relatively large particles in the range of 100 nm or more and 200 nm or less, so that the contact probability with adjacent particles is reduced in a gap larger than the volume of the particle. Becomes easier to rotate and the degree of orientation is improved. It is preferred that the iron nitride particles are not sintered and are completely magnetically isolated. If the particle size is less than 10 nm, the ratio of the oxide film on the particle surface increases or superparamagnetism is exhibited, so that the degree of orientation tends to decrease. When the proportion of particles having a particle size of 100 nm or more exceeds 70%, the particle size is large, so the proportion of particles having a single domain critical diameter or less is small, and the degree of orientation may be reduced. Further, when the ratio of particles having a particle size of 10 nm or more and 50 nm or less exceeds 70%, the friction between the particles is large and the rotation of the particles is hindered, so that a sufficient degree of orientation cannot be obtained. When the large particles forming the gap are larger than 50 nm and smaller than 100 nm, the gap for entering particles having a particle size in the range of 10 nm to 50 nm is small, and a sufficient degree of orientation cannot be obtained. When the large particles forming the gap exceed 200 nm, the gap for entering the particles having a particle size in the range of 10 nm to 50 nm is large, and the small particles contact with each other in the gap, so that a sufficient degree of orientation cannot be obtained.
本実施形態に係る磁性粉は、配向度が60%以上であり、好ましくは70%以上である。Fe16N2相を含み、粒径の個数分布において、粒径10nm以上50nm以下の範囲の粒子の個数が全体のx%、粒径100nm以上200nm以下の範囲の粒子が全体のy%とするとき、前記xが40≦x≦60であり、前記yが40≦y≦60であり、前記x及びyが80≦x+y≦100であるとき、より高い配向度が得られる。配向度が前記範囲未満の場合、磁性粉として十分な磁気特性であるとは言い難い。 The magnetic powder according to this embodiment has an orientation degree of 60% or more, preferably 70% or more. In the number distribution of particle diameters including the Fe 16 N 2 phase, the number of particles in the range of 10 nm to 50 nm is x% of the whole, and the particle in the range of 100 nm to 200 nm is y% of the total When x is 40 ≦ x ≦ 60, y is 40 ≦ y ≦ 60, and x and y are 80 ≦ x + y ≦ 100, a higher degree of orientation is obtained. When the degree of orientation is less than the above range, it is difficult to say that the magnetic properties are sufficient as magnetic powder.
次に、本実施形態に係る磁性粉の好適な製造法について述べる。 Next, the suitable manufacturing method of the magnetic powder which concerns on this embodiment is described.
本実施形態に係る磁性粉は、酸化鉄を原料として用いて、還元処理を行い、続いて窒化処理を行ったのちに、分級及び混合処理を施すことで得ることができる。 The magnetic powder according to the present embodiment can be obtained by performing a reduction treatment using iron oxide as a raw material, followed by a nitriding treatment, followed by classification and a mixing treatment.
原料である酸化鉄は、特に限定されないが、マグネタイト、γ−Fe2O3、α−Fe2O3、α−FeOOH、β−FeOOH、γ−FeOOH、FeOなどが挙げられる。 The raw material iron oxide is not particularly limited, and examples thereof include magnetite, γ-Fe 2 O 3 , α-Fe 2 O 3 , α-FeOOH, β-FeOOH, γ-FeOOH, and FeO.
原料である酸化鉄の粒子形状には特に限定はないが、針状、粒状、紡錘状、直方体状などいずれでもよい。 The particle shape of the iron oxide as a raw material is not particularly limited, but may be any shape such as a needle shape, a granular shape, a spindle shape, and a rectangular parallelepiped shape.
本実施形態においては、必要により、還元処理によって粒子同士が焼結することを抑制するために原料である酸化鉄の表面をSi化合物で被覆してもよい。 In the present embodiment, the surface of iron oxide, which is a raw material, may be coated with a Si compound in order to suppress sintering of particles by reduction treatment as necessary.
酸化鉄粒子を分散して得られる水懸濁液のpHを調整した後、Si化合物を添加して混合攪拌することにより、又は、必要により、混合攪拌後にpH値を調整することにより、前記酸化鉄粒子の表面をSi化合物で被覆し、その後、水洗、乾燥、粉砕することで粉末が得られる。 After adjusting the pH of the aqueous suspension obtained by dispersing the iron oxide particles, the oxidation is performed by adding the Si compound and mixing and stirring, or, if necessary, adjusting the pH value after mixing and stirring. The surface of the iron particles is coated with a Si compound, and then washed with water, dried and pulverized to obtain a powder.
Si化合物としては、オルトケイ酸ナトリウム、メタケイ酸ナトリウム、コロイダルシリカ、シランカップリング剤等が使用できる。 As the Si compound, sodium orthosilicate, sodium metasilicate, colloidal silica, silane coupling agent and the like can be used.
Si化合物の被覆量は、酸化鉄に対しSi換算で0.1質量%以上20質量%以下が好ましい。0.1質量%未満の場合には熱処理時に粒子間の焼結を抑制する効果が十分とは言い難い。20質量%を超える場合には、非磁性成分が増加することとなり好ましくない。より好ましい表面被覆量は0.15質量%以上15質量%以下、更により好ましくは0.2質量%以上10質量%以下である。 The coating amount of the Si compound is preferably 0.1% by mass or more and 20% by mass or less in terms of Si with respect to iron oxide. When the amount is less than 0.1% by mass, it is difficult to say that the effect of suppressing the sintering between particles during heat treatment is sufficient. When it exceeds 20 mass%, a nonmagnetic component will increase and it is not preferable. A more preferable surface coating amount is 0.15% by mass or more and 15% by mass or less, and further more preferably 0.2% by mass or more and 10% by mass or less.
次に、酸化鉄又は粒子表面がSi化合物によって被覆された酸化鉄について還元処理を行う。 Next, reduction treatment is performed on iron oxide or iron oxide whose particle surface is coated with a Si compound.
還元処理の温度は200〜600℃が好ましい。還元処理の温度が200℃未満の場合には酸化鉄が十分に金属鉄に還元されない。還元処理の温度が600℃を超える場合には酸化鉄は十分に還元されるが、粒子間の焼結も進行することになり、好ましくない。より好ましい還元温度は250〜450℃である。 The temperature of the reduction treatment is preferably 200 to 600 ° C. When the temperature of the reduction treatment is less than 200 ° C., iron oxide is not sufficiently reduced to metallic iron. When the temperature of the reduction treatment exceeds 600 ° C., iron oxide is sufficiently reduced, but sintering between particles also proceeds, which is not preferable. A more preferable reduction temperature is 250 to 450 ° C.
還元処理の時間は特に限定されないが、1〜96時間が好ましい。96時間を超えると還元温度によっては焼結が進み、窒化処理が進みにくくなる。1時間未満では十分な還元ができない場合が多い。より好ましくは2〜72時間である。 The time for the reduction treatment is not particularly limited, but is preferably 1 to 96 hours. If it exceeds 96 hours, sintering proceeds depending on the reduction temperature, and nitriding becomes difficult to proceed. In many cases, sufficient reduction cannot be achieved in less than 1 hour. More preferably, it is 2 to 72 hours.
還元処理の雰囲気は、水素雰囲気が好ましい。 The atmosphere for the reduction treatment is preferably a hydrogen atmosphere.
還元処理を行った後、窒化処理を行う。 After the reduction treatment, nitriding treatment is performed.
窒化処理の温度は100〜200℃である。窒化処理の温度が100℃未満の場合には窒化処理が十分に進行しない。窒化処理の温度が200℃を超える場合には、窒化が進行しすぎるため、Fe16N2化合物相の割合が著しく低下する。より好ましい窒化温度は120〜180℃である。 The temperature of the nitriding treatment is 100 to 200 ° C. When the nitriding temperature is less than 100 ° C., the nitriding does not proceed sufficiently. When the temperature of the nitriding treatment exceeds 200 ° C., nitriding proceeds excessively, so that the proportion of the Fe 16 N 2 compound phase is significantly reduced. A more preferable nitriding temperature is 120 to 180 ° C.
窒化処理の時間は特に限定されないが、1〜48時間が好ましい。48時間を超えると窒化温度によってはFe16N2化合物相の割合が著しく低下する。1時間未満では十分な窒化ができない場合が多い。より好ましくは3〜24時間である。 The nitriding time is not particularly limited, but is preferably 1 to 48 hours. If it exceeds 48 hours, depending on the nitriding temperature, the proportion of the Fe 16 N 2 compound phase is significantly reduced. In many cases, sufficient nitriding cannot be performed in less than 1 hour. More preferably, it is 3 to 24 hours.
窒化処理の雰囲気は、アンモニア雰囲気が望ましく、アンモニアの他、窒素、水素などを混合させてもよい。 The atmosphere of the nitriding treatment is preferably an ammonia atmosphere, and in addition to ammonia, nitrogen, hydrogen, or the like may be mixed.
本実施形態によって得られた窒化鉄粉末を用いて、バルク磁石や異方性ボンド磁石といった磁石を得ることができる。以下、その製造方法を述べる。 A magnet such as a bulk magnet or an anisotropic bonded magnet can be obtained using the iron nitride powder obtained by the present embodiment. Hereinafter, the manufacturing method will be described.
まず、バルク磁石の製造方法について一例を説明する。本実施形態によって得られた窒化鉄粉末は圧縮成形をすることにより、圧粉磁石とすることが可能である。ここで、圧縮成形の条件は、特に限定されず、作製するバルク磁石の要求特性値になるよう調整すればよい。例えば、圧縮成形圧力を1〜10ton/cm2とすることができる。また、成形時に磁場配向をおこなってもよい。さらに、窒化鉄粉末表面に潤滑剤や樹脂を付与してもよい。 First, an example of a method for manufacturing a bulk magnet will be described. The iron nitride powder obtained by the present embodiment can be formed into a dust magnet by compression molding. Here, the compression molding conditions are not particularly limited, and may be adjusted so as to be the required characteristic values of the bulk magnet to be manufactured. For example, the compression molding pressure can be 1 to 10 ton / cm 2 . Further, magnetic field orientation may be performed during molding. Furthermore, you may provide a lubricant and resin to the iron nitride powder surface.
また、作製したバルク磁石に樹脂を含む樹脂バインダーを含浸させ、ボンド磁石としてもよい。樹脂は、エポキシ樹脂、フェノール樹脂等の熱硬化性樹脂や、スチレン系、オレフィン系、ウレタン系、ポリエステル系、ポリアミド系のエラストマー、アイオノマー、エチレンプロピレン共重合体(EPM)、エチレン−エチルアクリレート共重合体等の熱可塑性樹脂がある。必要に応じて、カップリング剤やその他の添加材を加えてもよい。 Alternatively, the produced bulk magnet may be impregnated with a resin binder containing a resin to form a bonded magnet. 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. A coupling agent and other additives may be added as necessary.
ボンド磁石における磁性粉と樹脂との含有比率は、磁性粉100質量%に対して、樹脂を例えば0.5質量%以上20質量%以下含むことが好ましい。磁性粉100質量%に対して、樹脂の含有量が0.5質量%未満であると、保形性が損なわれる傾向があり、樹脂が20質量%と超えると、十分に優れた磁気特性が得られ難くなる傾向がある。 The content ratio of the magnetic powder and the resin in the bonded magnet preferably includes, for example, 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. 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.
得られる磁石の形状は特に限定されるものではなく、用いる金型の形状に応じて、例えば平板状、柱状、断面形状がリング状等、変更することができる。また、得られた磁石は、その表面上に酸化層や樹脂層等の劣化を防止するためにめっきや塗装を施すようにしてもよい。 The shape of the magnet to be obtained is not particularly limited, and can be changed, for example, in a plate shape, a column shape, or a cross-sectional shape in a ring shape, depending on the shape of the mold to be used. Further, the obtained magnet may be plated or painted on the surface in order to prevent deterioration of the oxide layer, the resin layer, and the like.
以下、本発明について、実施例・比較例を用いてさらに詳細に説明する。 Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
実施例1
<出発原料の調整>
硫酸第一鉄、塩化第二鉄、水酸化ナトリウムを用いて酸化鉄を作製した。その後、試料1gに対して50mL相当の純水を加えて攪拌しながら、オルトケイ酸ナトリウム水溶液をSiが1.0質量%となるように加えた。得られた分散液を数時間静置して上澄み液を除去した。続けて、得られた試料1gに対して200mL相当の純水を加えて上澄み液を除去する作業を7回繰り返した。85℃の真空乾燥機で乾燥し、乳鉢及び乳棒を用いて解砕を行った。得られた試料のSi含有量は1.0質量%であった。
Example 1
<Adjustment of starting materials>
Iron oxide was prepared using ferrous sulfate, ferric chloride, and sodium hydroxide. Thereafter, while adding 50 mL of pure water to 1 g of the sample and stirring, an aqueous sodium orthosilicate solution was added so that Si might be 1.0 mass%. The obtained dispersion was allowed to stand for several hours to remove the supernatant. Subsequently, the operation of adding 200 mL of pure water to the obtained sample 1 g and removing the supernatant was repeated 7 times. It dried with the 85 degreeC vacuum dryer and crushed using the mortar and the pestle. The Si content of the obtained sample was 1.0% by mass.
<出発原料の還元処理及び窒化処理>
上記で得られた粉末5gを灰分測定用灰皿(50mm×30mm×深さ10mm)に入れ、熱処理炉に静置した。炉内に窒素ガスを充填した後、水素ガスを1L/minの流量で流しながら、5℃/minの昇温速度で300℃まで昇温し、24時間保持して還元処理を行った。その後、水素ガスの供給を止めて窒素ガスを2L/minの流量で流しながら150℃まで降温した。続いて、アンモニアガスを0.1L/minにて流しながら、150℃で9時間窒化処理を行った。その後、窒素ガスを2L/minの流量で流しながら50℃まで降温し、空気置換を12時間かけて行うことにより試料を得た。
<Reduction treatment and nitriding treatment of starting material>
5 g of the powder obtained above was placed in an ashtray for ash measurement (50 mm × 30 mm × depth 10 mm) and left in a heat treatment furnace. After filling the furnace with nitrogen gas, the temperature was raised to 300 ° C. at a rate of 5 ° C./min while flowing hydrogen gas at a flow rate of 1 L / min, and the reduction treatment was carried out for 24 hours. Thereafter, the supply of hydrogen gas was stopped, and the temperature was lowered to 150 ° C. while flowing nitrogen gas at a flow rate of 2 L / min. Subsequently, nitriding was performed at 150 ° C. for 9 hours while flowing ammonia gas at 0.1 L / min. Thereafter, the temperature was lowered to 50 ° C. while flowing nitrogen gas at a flow rate of 2 L / min, and air replacement was performed over 12 hours to obtain a sample.
熱処理炉から試料を取り出した後、遠心分離機(日立工機製CR22GIII)を用いて分級操作を行って10nm程度の粒子と100nm程度の粒子をそれぞれ分離した。分級は遠心分離の回転速度と時間を変更することによって行い、粒径が10nm未満の粒子、10nm以上50nm以下の粒子、50nmを超えて100nm未満の粒子、100nm以上200nm以下の粒子、200nmを超える粒子を、それぞれ20000rpm60min、16000rpm30min、12000rpm30min、5000rpm30min、2000rpm10minの条件で順に分離した。得られた粒子を、表1に示す個数の割合になるように秤量し、乳棒及び乳鉢を用いて混合した。 After removing the sample from the heat treatment furnace, a classification operation was performed using a centrifuge (CR22GIII manufactured by Hitachi Koki Co., Ltd.) to separate particles of about 10 nm and particles of about 100 nm. Classification is performed by changing the rotation speed and time of centrifugation, particles having a particle size of less than 10 nm, particles of 10 to 50 nm, particles of more than 50 nm and less than 100 nm, particles of 100 to 200 nm, exceeding 200 nm The particles were sequentially separated under the conditions of 20000 rpm 60 min, 16000 rpm 30 min, 12000 rpm 30 min, 5000 rpm 30 min, and 2000 rpm 10 min, respectively. The obtained particles were weighed so as to have the number ratio shown in Table 1, and mixed using a pestle and mortar.
<粒径及び粒度分布の評価>
原料である酸化鉄及び得られた磁性粉を透過型電子顕微鏡(TEM、日本電子製JEM−2000FX)により観察した。次に、画像処理により、観察像の中から無作為に選別した1000個の粒子の円面積相当径を粒径として算出し、粒径の個数分布を求めた。続いて、前記個数分布を10nm未満の粒子、10nm以上50nm以下の粒子、50nmを超えて100nm未満の粒子、100nm以上200nm以下の粒子、200nmを超える粒子の5種類に分類して、それぞれの範囲に存在する粒子数が全体の個数に対して占める割合を算出した。
<Evaluation of particle size and particle size distribution>
The raw material iron oxide and the obtained magnetic powder were observed with a transmission electron microscope (TEM, JEM-2000FX, manufactured by JEOL). Next, the diameter equivalent to the circular area of 1000 particles randomly selected from the observed image was calculated as the particle size by image processing, and the number distribution of the particle size was obtained. Subsequently, the number distribution is classified into five types: particles of less than 10 nm, particles of 10 nm or more and 50 nm or less, particles of more than 50 nm and less than 100 nm, particles of 100 nm or more and 200 nm or less, and particles of more than 200 nm. The ratio of the number of particles present to the total number was calculated.
<配向度の評価>
得られた窒化鉄粉末を圧縮成形して圧粉磁石とした。圧縮成形圧力を6ton/cm2とし、配向処理として10000Oeの磁界中で成形を行った。得られた圧粉磁石の磁気特性は、振動試料型磁力計(VSM、東英工業製VSM−5−20)を用いて296Kにて測定した。測定結果より得られた飽和磁化に対する残留磁化の比を配向度の指標とした。
<Evaluation of orientation>
The obtained iron nitride powder was compression molded to obtain a dust magnet. The compression molding pressure was 6 ton / cm 2 and the molding was performed in a magnetic field of 10000 Oe as the orientation treatment. The magnetic properties of the obtained dust magnet were measured at 296K using a vibrating sample magnetometer (VSM, VSM-5-20 manufactured by Toei Industry Co., Ltd.). The ratio of the residual magnetization to the saturation magnetization obtained from the measurement results was used as an index of the degree of orientation.
実施例2〜12及び比較例1〜6についても、分級操作の際に取り出して混合する粒子を表1に示す割合となるよう混合した以外は実施例1と同様にして試料を得た。 For Examples 2 to 12 and Comparative Examples 1 to 6, samples were obtained in the same manner as in Example 1 except that the particles to be taken out and mixed in the classification operation were mixed so as to have the ratio shown in Table 1.
<評価結果>
実施例1〜12及び比較例1〜6で得られた試料の配向度と、粒径の個数分布より求めた各粒径範囲の粒子が全体の個数に対して占める割合を表1に示す。
<Evaluation results>
Table 1 shows the degree of orientation of the samples obtained in Examples 1 to 12 and Comparative Examples 1 to 6 and the ratio of the particles in each particle size range obtained from the particle size distribution to the total number.
実施例と比較例を比べると、実施例の方が高い配向度が得られている。これは、粒径の小さい窒化鉄粒子だけでは粒子が密に詰まり摩擦が大きく回転しづらいが、相対的に大きい粒子の隙間に入り込むことで隣接粒子との接触確率が小さくなり、回転しやすくなることにより配向度が向上すると考えられる。比較例1から比較例6のように、粒径の個数分布が請求項の範囲外となる場合は、十分な効果は得られず配向度が低下する。 When the example and the comparative example are compared, the degree of orientation is higher in the example. This is because the iron nitride particles with a small particle size alone are densely packed and the friction is large and difficult to rotate, but entering the gaps between relatively large particles reduces the probability of contact with adjacent particles and facilitates rotation. This is considered to improve the degree of orientation. When the number distribution of particle diameters is outside the scope of the claims as in Comparative Examples 1 to 6, sufficient effects cannot be obtained, and the degree of orientation decreases.
Claims (1)
In the number distribution of particle diameters including the Fe 16 N 2 phase, the number of particles in the range of 10 nm to 50 nm is x% of the whole, and the particle in the range of 100 nm to 200 nm is y% of the total Wherein x is 30 ≦ x ≦ 70, y is 30 ≦ y ≦ 70, and x and y are 60 ≦ x + y ≦ 100, and the magnet using iron nitride magnetic powder .
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