JP2016096289A - Film-forming type iron nitride based magnetic powder and magnet using the same - Google Patents
Film-forming type iron nitride based magnetic powder and magnet using the same Download PDFInfo
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本発明は、Ｆｅ１６Ｎ２化合物相を主相とし、高い飽和磁化を維持しつつ、かつ高い保磁力を有する被膜形成型窒化鉄系磁性粉末および該窒化鉄系磁性粉末を用いた磁石を提供する。 The present invention provides a film-forming iron nitride-based magnetic powder having a Fe 16 N 2 compound phase as a main phase, maintaining a high saturation magnetization and having a high coercive force, and a magnet using the iron nitride-based magnetic powder To do.
近年、電気自動車やハイブリッド自動車などのモーター用磁石として、Ｎｄ−Ｆｅ−Ｂ系の磁石が広く使われている。しかしながら、Ｎｄに代表されるレアアースは、産業分野を支える高付加価値な部材の原料であり、近年需要が拡大しているため、資源の枯渇や原料価格が不安定であることが懸念されている。さらには、途上国においても著しく需要が拡大していることや、その偏在性ゆえに特定の産出国への依存度が高いことから、安定供給確保に対する問題が生じている。 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.
上記問題を回避するため、レアアースを使用しない、自然界に無尽蔵に存在する元素（鉄、窒素）から高性能磁石を開発することが求められている。 In order to avoid the above problems, it is required to develop a high-performance magnet from elements (iron, nitrogen) that do not use rare earth and exist infinitely in nature.
Ｆｅ−Ｎ系の化合物、特にＦｅ１６Ｎ２は、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。しかしながら、Ｆｅ１６Ｎ２は準安定化合物であるため、この化合物を単離した粉末として化学的に合成することは困難である。 Fe-N-based compounds, particularly Fe 16 N 2, are attracting attention as one of materials exhibiting a larger saturation magnetization than Fe. However, since Fe 16 N 2 is a metastable compound, it is difficult to chemically synthesize this compound as an isolated powder.
このような問題に対し、特許文献１では、共沈法により酸化鉄を合成し、還元・窒化する手法を用いて、Ｆｅ１６Ｎ２を含む窒化鉄系磁性粉末を単離した粉末として化学的に合成することに成功している。しかしながら、得られた窒化鉄系磁性粉末の保磁力が低いために、高保磁力かつ高飽和磁化が要求されるモーター用途の磁性材料としての使用には不十分である。
In order to deal with such a problem, in
本発明は、上記を鑑みたものであり、高い飽和磁化（１２０ｅｍｕ／ｇ以上）を有し、かつ高い保磁力（２．５ｋＯｅ以上）を有する窒化鉄系磁性粉及び該磁性粉を用いた磁石の提供を目的とする。 The present invention has been made in view of the above, and has a high saturation magnetization (120 emu / g or more) and a high coercive force (2.5 kOe or more), and a magnet using the magnetic powder. The purpose is to provide.
本発明は、Ｆｅ１６Ｎ２相を含む窒化鉄系磁性粉末であり、前記窒化鉄系磁性粉末の窒化鉄相の粒子径が１５ｎｍ以上１００ｎｍ以下であって、前記窒化鉄系磁性粉末の表面にＯ及びＨを含む被膜が形成されており、前記被膜の厚みが１ｎｍ以上５ｎｍ以下であることを特徴とする被膜形成型窒化鉄系磁性粉末に関するものである。（本発明１） The present invention is an iron nitride-based magnetic powder containing an Fe 16 N 2 phase, wherein the iron nitride-based magnetic powder has a particle size of an iron nitride phase of 15 nm or more and 100 nm or less on the surface of the iron nitride-based magnetic powder. The present invention relates to a film-forming iron nitride-based magnetic powder, wherein a film containing O and H is formed, and the thickness of the film is 1 nm or more and 5 nm or less. (Invention 1)
本発明１によれば、Ｆｅ１６Ｎ２相を含む窒化鉄系磁性粉末の窒化鉄相の粒子径が１５ｎｍ以上１００ｎｍ以下であって、前記窒化鉄系磁性粉末の表面にＯ及びＨを含む被膜が形成されており、前記被膜の厚みが１ｎｍ以上５ｎｍ以下であれば、高い飽和磁化（１２０ｅｍｕ／ｇ以上）を維持しつつ、高い保磁力（２．５ｋＯｅ以上）を有する被膜形成型窒化鉄系磁性粉末が得られる。 According to the first aspect of the present invention, the iron nitride magnetic powder containing the Fe 16 N 2 phase has a particle diameter of the iron nitride phase of 15 nm to 100 nm, and the surface of the iron nitride magnetic powder contains O and H. If the thickness of the film is 1 nm or more and 5 nm or less, the film-forming iron nitride system having high coercive force (2.5 kOe or more) while maintaining high saturation magnetization (120 emu / g or more) Magnetic powder is obtained.
また、本発明は、本発明１に記載の被膜形成型窒化鉄系磁性粉末であり、窒化鉄系磁性粉末の表面に形成された被膜中のＨ量が粒子全体の０．０２質量％以上１．５質量％以下であって、前記被膜の構成相にＦｅＯＯＨを含むことを特徴とする被膜形成型窒化鉄系磁性粉末に関するものである。（本発明２）
Further, the present invention is the film-forming iron nitride magnetic powder according to the
本発明２によれば、本発明２に記載の被膜形成型窒化鉄系磁性粉末の表面に形成された被膜中のＨ量が粒子全体の０．０２質量％以上１．５質量％以下であって、前記被膜の構成相にＦｅＯＯＨを含むことで、さらに高い飽和磁化及び高い保磁力を有する被膜形成型窒化鉄系磁性粉末が得られる。
According to the
さらに、本発明は、本発明１又は本発明２に記載の被膜形成型窒化鉄系磁性粉末を用いた磁石に関するものである。（本発明３） Furthermore, the present invention relates to a magnet using the film-forming iron nitride magnetic powder according to the first or second aspect of the present invention. (Invention 3)
本発明３によれば、高い飽和磁化（１２０ｅｍｕ／ｇ以上）を維持しつつ、高い保磁力（２．５ｋＯｅ以上）を有する被膜形成型窒化鉄系磁性粉末を用いた磁石を得ることができる。 According to the third aspect of the present invention, a magnet using a film-forming iron nitride magnetic powder having a high coercive force (2.5 kOe or more) while maintaining high saturation magnetization (120 emu / g or more) can be obtained.
本発明によれば、高い飽和磁化（１２０ｅｍｕ／ｇ以上）を有し、かつ高い保磁力（２．５ｋＯｅ以上）を有する被膜形成型窒化鉄系磁性粉末及び該磁性粉末を用いた磁石を得ることができる。 According to the present invention, a film-forming iron nitride magnetic powder having a high saturation magnetization (120 emu / g or more) and a high coercive force (2.5 kOe or more) and a magnet using the magnetic powder are obtained. Can do.
以下、図面を参照しながら、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 with reference to the drawings. 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、図１に示すように窒化鉄相１及びＯ及びＨを含む被膜２を備える。窒化鉄相１はＦｅ１６Ｎ２相を含む窒化鉄系磁性粉末であり、前記窒化鉄系磁性粉末の窒化鉄相の粒子径が１５ｎｍ以上１００ｎｍ以下であって、前記窒化鉄系磁性粉末の表面にＯ及びＨを含む被膜２が形成されており、前記被膜の厚みが１ｎｍ以上５ｎｍ以下である。窒化鉄相の粒子径が１５ｎｍ未満では超常磁性が発現するため、飽和磁化および保磁力が低下する傾向がある。窒化鉄相の粒子径が１００ｎｍを超える場合には、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、保磁力が低下する。Ｏ及びＨを含む被膜の厚みが１ｎｍ未満では、保磁力向上の効果は十分とは言い難い。Ｏ及びＨを含む被膜の厚みが５ｎｍを超えると、前記Ｏ及びＨを含む被膜の体積比率が大きいため、飽和磁化が大幅に低下する。窒化鉄相の粒子径が１５ｎｍ以上１００ｎｍ以下であって、前記窒化鉄系磁性粉末の表面にＯ及びＨを含む被膜が形成されており、前記被膜の厚みが１ｎｍ以上５ｎｍ以下であれば、高い飽和磁化を維持しつつ、高い保磁力が得られる。これは、ＦｅＯＯＨやＦｅ（ＯＨ）２などのＯ及びＨを含む化合物及びその混相となることで、粒子間焼結を起こしている粒子同士を磁気的に分断できるためである。
The magnetic powder according to the present embodiment includes an
また、本実施形態に係る磁性粉末は、窒化鉄系磁性粉末の表面に形成された被膜中のＨ量が粒子全体の０．０２質量％以上１．５質量％以下であって、前記被膜の構成相にＦｅＯＯＨを含むことが好ましい。Ｈ量が粒子全体の０．０２質量％以上１．５質量％以下であれば、ＦｅＯＯＨやＦｅ（ＯＨ）２などのＯ及びＨを含む化合物及びその混相がより生成しやすく、特にＦｅＯＯＨが生成しやすくなり、粒子間焼結を起こしている粒子同士の磁気的な分断効果が大きくなる。 In the magnetic powder according to the present embodiment, the amount of H in the film formed on the surface of the iron nitride magnetic powder is 0.02% by mass or more and 1.5% by mass or less of the entire particle, The constituent phase preferably contains FeOOH. If the amount of H is 0.02% by mass or more and 1.5% by mass or less of the whole particle, a compound containing O and H such as FeOOH and Fe (OH) 2 and a mixed phase thereof are more easily generated, and particularly FeOOH is generated. This increases the magnetic separation effect between the particles causing interparticle sintering.
本実施形態に係る磁性粉末は、１２０ｅｍｕ／ｇ以上の飽和磁化を有し、かつ２．５ｋＯｅ以上の保磁力を有する。好ましくは飽和磁化が１４０ｅｍｕ／ｇ以上で、かつ保磁力が２．８ｋＯｅ以上である。窒化鉄相の粒子径を２０ｎｍ以上８０ｎｍ以下としたとき、より高い飽和磁化および保磁力が得られる。また、前記Ｏ及びＨを含む被膜の厚みを２ｎｍ以上４ｎｍ以下としたとき、より高い飽和磁化及びより高い保磁力が得られる。 The magnetic powder according to this embodiment has a saturation magnetization of 120 emu / g or more and a coercive force of 2.5 kOe or more. Preferably, the saturation magnetization is 140 emu / g or more and the coercive force is 2.8 kOe or more. When the particle size of the iron nitride phase is 20 nm or more and 80 nm or less, higher saturation magnetization and coercive force can be obtained. Further, when the thickness of the coating containing O and H is 2 nm or more and 4 nm or less, higher saturation magnetization and higher coercive force can be obtained.
窒化鉄系磁性粉末の表面に形成するＯ及びＨを含む被膜の構成相は、特に限定されないが、Ｏ及びＨを含んでいればＦｅ３Ｏ４、γ−Ｆｅ２Ｏ３、α−Ｆｅ２Ｏ３、α−ＦｅＯＯＨ、β−ＦｅＯＯＨ、γ−ＦｅＯＯＨ、ＦｅＯなどいずれの化合物の混相でもよい。 The constituent phase of the coating containing O and H formed on the surface of the iron nitride magnetic powder is not particularly limited, but Fe 3 O 4 , γ-Fe 2 O 3 , α-Fe 2 as long as O and H are included. A mixed phase of any compound such as O 3 , α-FeOOH, β-FeOOH, γ-FeOOH, and FeO may be used.
次に、本実施形態に係る磁性粉末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末は、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、Ｏ及びＨを含む被膜を形成させる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 a treatment for forming a film containing O and H. .
原料である酸化鉄は、特に限定されないが、Ｆｅ３Ｏ４、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 Fe 3 O 4 , 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, still 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、ＮＨ３雰囲気が望ましく、ＮＨ３の他、Ｎ２、Ｈ２などを混合させてもよい。 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 .
窒化処理を行った後、Ｏ及びＨを含む被膜を形成させる処理を行う。この処理によって、窒化鉄相の表面を酸素ガス及びＨ２Ｏと同時に反応させることで、ＦｅＯＯＨやＦｅ（ＯＨ）２などのＯ及びＨを含む化合物及びその混相を含む被膜を形成させる。 After performing the nitriding treatment, a treatment for forming a film containing O and H is performed. By this treatment, the surface of the iron nitride phase is reacted simultaneously with oxygen gas and H 2 O to form a film containing a compound containing O and H such as FeOOH and Fe (OH) 2 and a mixed phase thereof.
Ｏ及びＨを含む被膜を形成させる処理の温度は１０〜７０℃である。前記処理の温度が１０℃未満の場合には処理が十分に進行しない。前記処理の温度が７０℃を超える場合には、被膜の厚みが大きくなり、Ｆｅ１６Ｎ２化合物相の割合が著しく低下する。より好ましい温度は２０〜５０℃である。 The temperature of the treatment for forming a film containing O and H is 10 to 70 ° C. When the temperature of the treatment is less than 10 ° C., the treatment does not proceed sufficiently. When the temperature of the treatment exceeds 70 ° C., the thickness of the coating is increased, and the proportion of the Fe 16 N 2 compound phase is significantly reduced. A more preferable temperature is 20 to 50 ° C.
Ｏ及びＨを含む被膜を形成させる処理の時間は特に限定されないが、１〜２４時間が好ましい。１時間未満では十分な被膜の形成ができない場合が多い。２４時間を超えると、温度によっては被膜の厚みが大きくなり、Ｆｅ１６Ｎ２化合物相の割合が著しく低下する。 Although the time of the process which forms the film containing O and H is not specifically limited, 1 to 24 hours are preferable. If it is less than 1 hour, a sufficient film cannot be formed in many cases. If it exceeds 24 hours, the thickness of the coating increases depending on the temperature, and the proportion of the Fe 16 N 2 compound phase is significantly reduced.
Ｏ及びＨを含む被膜を形成させる処理の雰囲気は、Ｈ２Ｏ及び酸素ガスを含む窒素雰囲気が望ましい。被膜中のＨ量を変えるには、露点か酸素ガスの濃度を変更すればよい。露点はガスをウェッターに通すことで制御することが可能で、露点の範囲は−５０〜−１０℃が好ましい。露点が−５０℃未満では、被膜に十分な量のＨが取り込まれない。ウェッターを通さずに酸素ガスと窒素ガスを流すと、露点は−５０℃未満となる。露点が−１０℃を超えると、被膜に含まれるＨ量が過剰になる。酸素ガスの濃度は、窒素ガスに対して０．０５〜３％が好ましい。酸素ガスの濃度が０．０５％未満では十分な厚みの被膜の形成ができない場合が多い。酸素ガスの濃度が３％を超えると、温度によっては被膜の厚みが大きくなり、Ｆｅ１６Ｎ２化合物相の割合が著しく低下する。 The atmosphere for the treatment for forming the film containing O and H is preferably a nitrogen atmosphere containing H 2 O and oxygen gas. In order to change the amount of H in the coating, the dew point or the concentration of oxygen gas may be changed. The dew point can be controlled by passing the gas through a wetter, and the range of the dew point is preferably -50 to -10 ° C. When the dew point is less than −50 ° C., a sufficient amount of H is not taken into the film. When oxygen gas and nitrogen gas are allowed to flow without passing through a wetter, the dew point becomes less than -50 ° C. If the dew point exceeds -10 ° C, the amount of H contained in the coating becomes excessive. The concentration of oxygen gas is preferably 0.05 to 3% with respect to nitrogen gas. When the concentration of oxygen gas is less than 0.05%, it is often impossible to form a film having a sufficient thickness. If the concentration of oxygen gas exceeds 3%, the thickness of the coating increases depending on the temperature, and the proportion of the Fe 16 N 2 compound phase decreases significantly.
本実施形態によって得られた窒化鉄系磁性粉末を用いて、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 by using the iron nitride magnetic 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系磁性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、窒化鉄系磁性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-based magnetic 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. Further, a lubricant or resin may be applied to the surface of the iron nitride magnetic powder.
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末と樹脂との含有比率は、磁性粉末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。磁性粉末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, shape retention tends to be impaired, and 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４０℃まで降温し、４０℃に保持しながらＯ及びＨを含む被膜形成させる処理を行った。具体的には、ウェッターを通して露点を−２０〜−３０℃に制御しながら流量２Ｌ／ｍｉｎの窒素ガスと流量２ｍＬ／ｍｉｎの酸素ガスを１時間流した。
<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 40 ° C. while flowing nitrogen gas at a flow rate of 2 L / min, and a film containing O and H was formed while maintaining the temperature at 40 ° C. Specifically, nitrogen gas having a flow rate of 2 L / min and oxygen gas having a flow rate of 2 mL / min were allowed to flow for 1 hour while controlling the dew point to −20 to −30 ° C. through a wetter.
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１５ｎｍ程度の粒子を分離した。遠心分離は５０００ｒｐｍ３０ｍｉｎ、５０００ｒｐｍ６０ｍｉｎ、８０００ｒｐｍ３０ｍｉｎ、１００００ｒｐｍ３０ｍｉｎ、１２０００ｒｐｍ３０ｍｉｎ、１６０００ｒｐｍ３０ｍｉｎ、１８０００ｒｐｍ３０ｍｉｎ、２００００ｒｐｍ６０ｍｉｎの順で行い、平均粒子径１０５ｎｍ、１００ｎｍ、８０ｎｍ、６０ｎｍ、４０ｎｍ、２０ｎｍ、１５ｎｍ、１０ｎｍの粒子をそれぞれ分離した。得られた粒子のうち、１５ｎｍの粒子のみを取り出した。 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 15 nm. Centrifugation was performed in the order of 5000 rpm 30 min, 5000 rpm 60 min, 8000 rpm 30 min, 10000 rpm 30 min, 12000 rpm 30 min, 16000 rpm 30 min, 18000 rpm 30 min, 20000 rpm 60 min, and particles having an average particle size of 105 nm, 100 nm, 80 nm, 60 nm, 40 nm, 20 nm, 15 nm, and 10 nm were separated. Of the obtained particles, only 15 nm particles were taken out.
＜被膜の構成相の同定＞
得られた磁性粉末の被膜の構成相は、粉末Ｘ線回折装置（ＸＲＤ、リガク製ＲＩＮＴ−２５００）及びメスバウアー分光分析装置により同定を行った。メスバウアー測定は、アルゴン雰囲気のグローブボックス中で磁性粉末をラミネートパックに入れて封止した状態で行った。メスバウアースペクトルのピーク解析は、スペクトルを理想線型の足し合わせと仮定してカーブフィッティングを行い、ピーク位置を定めて各成分のピーク面積を算出した。ピークは左右対称のローレンツ型とし、成分毎のピーク半値幅はすべて等しく、対称位置にあるピーク高さはそれぞれ等しいと仮定した。ＸＲＤパターン及びメスバウアースペクトルより、被膜の構成相はＦｅＯＯＨを含有することがわかった。
<Identification of constituent phase of coating>
The constituent phases of the obtained magnetic powder coating were identified by a powder X-ray diffractometer (XRD, RINT-2500 manufactured by Rigaku) and a Mossbauer spectrometer. Mossbauer measurement was performed in a state where a magnetic powder was put in a laminate pack and sealed in a glove box in an argon atmosphere. In the peak analysis of the Mossbauer spectrum, curve fitting was performed on the assumption that the spectrum was an ideal linear addition, the peak position was determined, and the peak area of each component was calculated. The peaks were assumed to be symmetrical Lorentz type, and the peak half-value widths for each component were all equal, and the peak heights at the symmetrical positions were assumed to be equal. From the XRD pattern and Mossbauer spectrum, it was found that the constituent phase of the film contains FeOOH.
＜粒子の組成と粒子径、被膜の厚みの評価＞
得られた磁性粉末を透過型電子顕微鏡（ＴＥＭ、日本電子製ＪＥＭ−２０００ＦＸ）により観察し、ＥＤＳを用いて粒子組成を分析した。ＴＥＭ観察像の中から無作為に選別した１００個の粒子のコントラストの異なる外殻部を被膜として組成分析を行い、Ｏ及びＨが含まれることを確認した。得られた磁性粉末のＨ量は、発生ガス分析（ＣＨＮ元素分析）により行った。サンプルを正確に秤量してスズカプセルに入れ、燃焼管内で酸素とともに燃焼させて発生したガスを熱伝導度検出器によって検出することで元素含有量を求めた。前処理として試料乾燥を行うことで吸着水分を除去し、Ｈは全量被膜由来であると仮定して算出した。求めた被膜のＨ量は０．２４質量％であった。次に、画像処理により、ＴＥＭ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子径として算出した。続いて、前記１０００個の粒子のコントラストの異なる内殻部を窒化鉄相として円面積相当径を算出した。粒子の円面積相当径の平均から窒化鉄相の円面積相当径の平均を減算した値を被膜の厚みとして算出した。前記の方法により算出した窒化鉄相の円面積相当径の平均は１５ｎｍ、被膜の厚みは１ｎｍであった。
<Evaluation of particle composition, particle diameter, and coating thickness>
The obtained magnetic powder was observed with a transmission electron microscope (TEM, JEM-2000FX, manufactured by JEOL), and the particle composition was analyzed using EDS. Composition analysis was performed using the outer shell portion having a different contrast of 100 particles randomly selected from the TEM observation images, and it was confirmed that O and H were contained. The amount of H in the obtained magnetic powder was analyzed by evolved gas analysis (CHN elemental analysis). The sample was accurately weighed and placed in a tin capsule, and the element content was determined by detecting the gas generated by burning with oxygen in the combustion tube with a thermal conductivity detector. The sample was dried as a pretreatment to remove adsorbed moisture, and H was calculated assuming that the entire amount was derived from the film. The obtained H amount of the coating was 0.24% by mass. Next, the diameter equivalent to the circular area of 1000 particles randomly selected from the TEM observation image by image processing was calculated as the particle diameter. Subsequently, the equivalent diameter of the circular area was calculated with the inner shell portion having a different contrast of the 1000 particles as an iron nitride phase. The value obtained by subtracting the average of the equivalent circular area diameter of the iron nitride phase from the average of the equivalent circular area diameter of the particles was calculated as the thickness of the coating. The average equivalent circular area diameter of the iron nitride phase calculated by the above method was 15 nm, and the thickness of the coating was 1 nm.
＜磁気特性の評価＞
得られた窒化鉄系磁性粉末の飽和磁化と保磁力を振動試料型磁力計（ＶＳＭ、東英工業製ＶＳＭ−５−２０）を用いて２９６Ｋにて、−２０〜２０ｋＯｅの磁場中で測定した。飽和磁化は１４０ｅｍｕ／ｇ、保磁力は２．６１ｋＯｅであった。
<Evaluation of magnetic properties>
The saturation magnetization and coercivity of the obtained iron nitride magnetic powder were measured in a magnetic field of -20 to 20 kOe at 296 K using a vibrating sample magnetometer (VSM, VSM-5-20 manufactured by Toei Kogyo). . The saturation magnetization was 140 emu / g, and the coercive force was 2.61 kOe.
実施例２〜１６及び比較例１〜８についても、ウェッターを通した窒素ガスと酸素ガスの流す時間を変更して、表１に示す通りの窒化鉄相の粒子径及び被膜の厚みとし、露点を−５０〜−１０℃の範囲で調整することにより表１に示す通りの被膜のＨ量を得たこと以外は実施例１と同様にして試料を作製した。ウェッターを通した窒素ガスと酸素ガスを流す時間は、被膜の厚みを０ｎｍ、１ｎｍ、２ｎｍ、３ｎｍ、４ｎｍ、５ｎｍ、５．５ｎｍとするとき、それぞれ０時間、１時間、２時間、６時間、１２時間、２４時間、３０時間とした。 Also in Examples 2-16 and Comparative Examples 1-8, the flow time of the nitrogen gas and oxygen gas through the wetter was changed, and the particle diameter of the iron nitride phase and the thickness of the coating film as shown in Table 1, the dew point Was adjusted in the range of −50 to −10 ° C., and a sample was prepared in the same manner as in Example 1 except that the H content of the coating film as shown in Table 1 was obtained. The flow time of nitrogen gas and oxygen gas through the wetter is 0 hour, 1 hour, 2 hours, 6 hours, respectively, when the thickness of the film is 0 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, and 5.5 nm. They were 12 hours, 24 hours, and 30 hours.
比較例９〜１０については、ウェッターを通した窒素ガスと酸素ガスを流す工程をウェッターを通さずに行い、ガスを流す時間と酸素ガスの流量を変更して、表１に示す通りの窒化鉄相の粒子径及び被膜の厚みとしたこと以外は実施例１と同様にして試料を作製した。ウェッターを通さず露点を−５０℃未満とすることで、被膜にＨが取り込まれないようにした。窒素ガスと酸素ガスを流す時間は、６時間とした。酸素ガス流量は２ｍＬ／ｍｉｎとした。 For Comparative Examples 9 to 10, the step of flowing nitrogen gas and oxygen gas through a wetter was performed without passing through the wetter, and the time for flowing the gas and the flow rate of oxygen gas were changed, and iron nitride as shown in Table 1 A sample was prepared in the same manner as in Example 1 except that the phase particle diameter and the coating thickness were used. By making the dew point less than −50 ° C. without passing through a wetter, H was prevented from being taken into the film. The time for flowing nitrogen gas and oxygen gas was 6 hours. The oxygen gas flow rate was 2 mL / min.
＜評価結果＞
実施例１〜２８及び比較例１〜１０で得られた試料について、窒化鉄相の粒子径と被膜の厚み、被膜のＨ量、飽和磁化と保磁力を表１に示す。実施例１〜２８及び比較例１〜１０のいずれも被膜にＯを含有し、実施例１〜２８及び比較例２、比較例３、比較例５〜６、比較例８はいずれも被膜にＨを含有していた。比較例９〜１０については、被膜中にＨは検出されなかった。また、実施例１、実施例３〜５、実施例７〜１１、実施例１３〜１５、実施例１７〜２２、実施例２４〜２６、実施例２８、比較例２〜３、比較例５〜６、比較例８はいずれもＸＲＤ及びメスバウアー分光分析よりＦｅＯＯＨを含有していることがわかった。比較例９〜１０については、いずれもＸＲＤ及びメスバウアー分光分析より被膜の構成相はＦｅ３Ｏ４であることがわかった。
<Evaluation results>
Table 1 shows the particle diameter of the iron nitride phase, the thickness of the coating, the H content of the coating, the saturation magnetization, and the coercivity of the samples obtained in Examples 1 to 28 and Comparative Examples 1 to 10. Each of Examples 1 to 28 and Comparative Examples 1 to 10 contains O in the coating, and Examples 1 to 28 and Comparative Examples 2, Comparative Example 3, Comparative Examples 5 to 6, and Comparative Example 8 are all H in the coating. Contained. About Comparative Examples 9-10, H was not detected in the film. Moreover, Example 1, Examples 3-5, Examples 7-11, Examples 13-15, Examples 17-22, Examples 24-26, Example 28, Comparative Examples 2-3, Comparative Examples 5-5 6 and Comparative Example 8 were both found to contain FeOOH from XRD and Mossbauer spectroscopy. Comparative Example 9-10 Both XRD and Mössbauer spectroscopy than the coating constituent phases was found to be is Fe 3 O 4.
実施例と比較例を比べると、実施例では高い飽和磁化（１２０ｅｍｕ／ｇ以上）を維持しつつ、かつ高い保磁力（２．５ｋＯｅ以上）が得られている。窒化鉄相の粒子径が１５ｎｍ以上１００ｎｍ以下の範囲では、単磁区臨界径以下の粒子割合が大きく、高い保磁力が得られる。また、Ｏ及びＨを含む被膜の厚みが１ｎｍ以上５ｎｍ以下であれば、飽和磁化の低減を最低限に抑えつつ、粒子間焼結を起こしている粒子同士をＯ及びＨを含む被膜により磁気的に分断することで高い保磁力が得られる。 When the example and the comparative example are compared, in the example, a high coercive force (2.5 kOe or more) is obtained while maintaining a high saturation magnetization (120 emu / g or more). When the particle diameter of the iron nitride phase is 15 nm or more and 100 nm or less, the ratio of particles having a single domain critical diameter or less is large, and a high coercive force is obtained. Further, if the thickness of the coating containing O and H is 1 nm or more and 5 nm or less, the particles causing interparticle sintering are magnetically separated by the coating containing O and H while minimizing the reduction of saturation magnetization. A high coercive force can be obtained by dividing into two.
比較例１〜８のように、窒化鉄相の粒子径またはＯ及びＨを含む被膜の厚みが請求の範囲外であると、高い飽和磁化を維持しつつ高い保磁力を実現できない。比較例１〜３は、窒化鉄相の粒子径が１５ｎｍ未満では超常磁性が発現するため、飽和磁化および保磁力が低下した。比較例４〜６は、窒化鉄相の粒子径が１００ｎｍを超えており、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、保磁力が低下した。比較例７のように、Ｏ及びＨを含む被膜の厚みが１ｎｍ未満では、保磁力は向上しなかった。比較例８のように、Ｏ及びＨを含む被膜の厚みが５ｎｍを超えると、前記Ｏ及びＨを含む被膜の体積比率が大きいため、飽和磁化が大幅に低下した。 As in Comparative Examples 1 to 8, when the particle diameter of the iron nitride phase or the thickness of the coating containing O and H is outside the scope of claims, high coercivity cannot be achieved while maintaining high saturation magnetization. In Comparative Examples 1 to 3, superparamagnetism is manifested when the particle size of the iron nitride phase is less than 15 nm, so that the saturation magnetization and the coercive force are reduced. In Comparative Examples 4 to 6, the particle size of the iron nitride phase exceeded 100 nm and the particle size was large, so the ratio of particles having a single domain critical diameter or less was small, and the coercivity was reduced. As in Comparative Example 7, the coercive force was not improved when the thickness of the film containing O and H was less than 1 nm. As in Comparative Example 8, when the thickness of the coating containing O and H exceeded 5 nm, the saturation magnetization was significantly reduced because the volume ratio of the coating containing O and H was large.
比較例９〜１０のように、窒化鉄相の粒子径と被膜の厚みが請求の範囲内でも、被膜にＯ及びＨの両方が含まれない場合は高い飽和磁化を維持しつつ高い保磁力を実現できない。これは、ＦｅＯＯＨやＦｅ（ＯＨ）２などのＯ及びＨを含む化合物及びその混相が存在しない場合は、粒子間焼結を起こしている粒子同士を磁気的に分断する効果が小さいためである。 As in Comparative Examples 9 to 10, even when the particle diameter of the iron nitride phase and the thickness of the coating are within the scope of claims, when the coating does not contain both O and H, a high coercive force is maintained while maintaining high saturation magnetization. Cannot be realized. This is because in the absence of a compound containing O and H such as FeOOH and Fe (OH) 2 and a mixed phase thereof, the effect of magnetically separating the particles causing interparticle sintering is small.
１・・・窒化鉄相、２・・・Ｏ及びＨを含む被膜。 1 ... Iron nitride phase, 2 ... O and H-containing coating.
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