JP2004018932A - Particle for permanent magnet and its manufacturing method, and permanent magnet and magnetic particulate - Google Patents
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Abstract
【課題】これまで提案されている永久磁石より磁気特性がすぐれ、かつ安定した永久磁石用粒子とその製造方法及び永久磁石を提供する。
【解決手段】硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子であることを特徴とする永久磁石用粒子。
【選択図】 図１Kind Code: A1 The present invention provides a permanent magnet particle which has better magnetic properties than previously proposed permanent magnets and is stable, a method for producing the same, and a permanent magnet.
SOLUTION: A hard magnetic phase and a soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase which do not form a solid solution with each other. Particles for a permanent magnet, characterized in that they are inclusion-type fine particles having an inclusion part that includes the periphery of the part.
[Selection diagram] Fig. 1
Description
【０００１】
【発明の属する技術分野】
本発明は、従来の磁石と比較して磁気特性が高くかつ安定した永久磁石用粒子とその製造方法及び該磁石用粒子を用いた永久磁石並びに磁性体微粒子に関するものである。
【０００２】
【従来の技術】
従来提案されている磁気特性にすぐれた永久磁石として、Ｎｄ−Ｆｅ−Ｂ系の焼結磁石が知られている。ところが、この焼結磁石のエネルギー積は４７０ｋＪ／ｍ３、ボンド磁石のエネルギー積は２３９ｋＪ／ｍ３未満が限界である。磁石応用製品の小型高性能化のためには、更なる向上が望まれる。
【０００３】
これに対し交換スプリング磁石が提案され、研究開発が活発に行われるようになってきている。この交換スプリング磁石は硬質磁性材料からなる硬磁性相と軟質磁性材料からなる軟磁性相が交互に配置された構造であり、その製造方法が種々検討されている。交換スプリング磁石を製造する主な方法としては、（１）急冷法（特開平８−１２４７３０等）、（２）薄膜作製法（特開平１１−２１４２１９、特開平９−２３７７１４等）、（３）針状鉄粉の表層に希土類金属元素やＢ元素を拡散する方法（特開平７−１０６１１０、特開平８−２０３７１５、特開平８−３３５５０７等）が提案されている。
【０００４】
上記（１）の急冷法による永久磁石用粒子の製造方法の一例を図４に示す。この方法は、原料となるＦｅ、Ｃｏ、Ｓｍをアルゴン雰囲気中で高周波誘導溶解させた後、急冷し、軟磁性相と硬磁性相から構成される磁性薄帯を作製し、この磁性薄帯を機械的粉砕処理して粒径３〜５μｍ程度のＦｅ−Ｃｏ−Ｓｍ系磁性粒子とし、さらにこれに窒化処理を施して、Ｆｅ−Ｃｏ−Ｓｍ−Ｎ系磁性粒子（永久磁石用粒子）を作り、この永久磁石用粒子を用いて、永久磁石とするものである。しかし、この方法の場合、軟磁性相と硬磁性相とからなる組織を制御することが難しいため、狙った磁気特性が得られていないという問題点がある。従って最大エネルギー積が４７０ｋＪ／ｍ３未満であり、ボンド磁石として作製すると最大エネルギー積が２３９ｋＪ／ｍ３未満であり、その所期の目的は達成されていない。
【０００５】
上記（２）の薄膜作成法は、蒸着法によって層状に軟磁性相と硬磁性相を並べることにより磁石を作製する方法であるが、この方法の場合、形状に制約があり、粉末状やバルク形状の磁石を作製できず、そのためボンド磁石や焼結磁石など立方体形状の磁石の作製が難しいという問題点がある。
【０００６】
上記（３）の針状鉄粉の表層に希土類金属元素やＢ元素を拡散する方法の場合は、特性的には従来の磁石をしのぎすぐれているが、今だに実用化されていない。その原因は特性が安定した磁石が得られていないためである。つまり軟質磁性相に希土類金属元素やＢ元素を被覆後、拡散により表面に硬磁性相をつくる方法では硬磁性相の厚さが一定にならない。均一に拡散しないので硬磁性相ができないこともある。
【０００７】
このように従来品あるいは従来法では、磁石応用製品の小型高性能化の要望に対応することができず、より磁気特性にすぐれかつ安定した永久磁石の実現が望まれていた。
【０００８】
【発明が解決しようとする課題】
本発明は、このような従来技術の実情に鑑みてなされたもので、これまで提案されている永久磁石より磁気特性がすぐれ、かつ安定した永久磁石用粒子とその製造方法及び永久磁石を提供することをその課題とする。
また、本発明は、新規な磁性体微粒子を提供することを別の課題とする。
【０００９】
【課題を解決するための手段】
本発明によれば、上記課題は下記の技術的手段により解決される。
（１）硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子であることを特徴とする永久磁石用粒子。
（２）該硬磁性相がＲ−Ｆｅ−Ｂ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、該軟磁性相がＦｅ、Ｆｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金であることを特徴とする前記（１）の永久磁石用粒子。
（３）該硬磁性相がＲ−Ｆｅ−Ｎ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、該軟磁性相がＦｅ−Ｍ−Ｎ（Ｍは遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金であることを特徴とする前記（１）の永久磁石用粒子。
（４）該コア部が硬磁性相からなり、該包接部が軟磁性相からなることを特徴とする前記（１）〜（３）のいずれかの永久磁石用粒子。
（５）該コア部が軟磁性相からなり、該包囲部が硬磁性相からなることを特徴とする前記（１）〜（３）のいずれかの永久磁石用粒子。
（６）全体形状が球状形状もしくはエッグ形状である前記（１）〜（５）のいずれかの永久磁石用粒子。
（７）該コア部の長手方向と垂直な面の直径が１０〜１００ｎｍであり、長手方向の長さが１０〜２０００ｎｍであり、かつ、該包接部の厚みが１０〜１００ｎｍであることを特徴とする前記（１）〜（６）のいずれかの永久磁石用粒子。
（８）硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子であって、該硬磁性相がＲ−Ｆｅ−Ｂ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、該軟磁性相がＦｅ、Ｆｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金である永久磁石用粒子を製造する方法において、
界面活性剤と有機溶媒の溶液中に、遷移金属塩化物の水溶液と希土類金属塩化物と塩化ホウ素の水溶液を滴下し、油中水滴型マイクロエマルションを形成する工程と、
微粒子形成剤を滴下することにより微粒子を形成させる工程と、
上記工程で形成した微粒子に対し、水素還元処理及びＣａ還元処理を順次施す工程とからなることを特徴とする永久磁石用粒子の製造方法。
（９）Ｃａ還元処理の後、窒化処理を施すことを特徴とする前記（８）に記載の永久磁石用粒子の製造方法。
（１０）硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子であって、該硬磁性相がＲ−Ｆｅ−Ｎ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、該軟磁性相がＦｅ−Ｍ−Ｎ（Ｍは遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金である永久磁石用粒子を製造する方法において、
界面活性剤と有機溶媒の溶液中に、遷移金属塩化物の水溶液と希土類金属塩化物の水溶液を滴下し、油中水滴型マイクロエマルションを形成する工程と、
微粒子形成剤を滴下することにより微粒子を形成させる工程と、
上記工程で形成した微粒子に対し、水素還元処理、Ｃａ還元処理及び窒化処理を順次施す工程とからなることを特徴とする永久磁石用粒子の製造方法。
（１１）前記（１）〜（７）のいずれかの永久磁石用粒子とバインダー樹脂からなることを特徴とする永久磁石。
（１２）該バインダー樹脂が、エポキシ樹脂、ナイロン樹脂又はアクリル樹脂であることを特徴とする前記（１１）の永久磁石。
（１３）焼結体であることを特徴とする前記（１１）又は（１２）の永久磁石。
（１４）硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の磁性体微粒子。
【００１０】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明による磁性体微粒子は、硬磁性相と軟磁性相とがナノスケールでコンポジット化した組織からなり、その硬磁性相と軟磁性相とは互いに固溶せず、かつ、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子であることを特徴とする。
本発明による磁性体微粒子は、その優れた磁気特性及び安定性が利用できる各種の用途として使用できるが、特に永久磁石を製造するために好ましく使用される。以下、本発明による磁性体微粒子を永久磁石用粒子に適当した場合を例に説明する。
【００１１】
本発明の永久磁石用粒子は、硬磁性相と軟磁性相とがコンポジット化した組織を有し、相互に固溶しない硬磁性相と軟磁性相からなり、一方の相をコア部とし、他方の相を該コア部の周囲を包接する包接部とした包接型構造の微粒子である。
【００１２】
本発明の永久磁石用粒子は、コア部が硬磁性相からなり、包接部が軟磁性相からなっていてもよく、反対に、コア部が軟磁性相からなり、包接部が硬磁性相からなっていてもよい。
【００１３】
本発明の永久磁石用粒子は、全体形状が球状形状又はエッグ形状（断面が楕円形）である。その形状は、後述する永久磁石用粒子の製造方法における成形工程で圧縮力を加えることにより、成形される。図１には、本発明の永久磁石用粒子に圧縮力を加えて、直方体あるいは立方体に近い形状になった状態を示す。
該永久磁石用粒子において、そのコア部の長手方向と垂直な面の直径は、好ましくは１０〜１００ｎｍ、より好ましくは２０〜８０ｎｍであり、長手方向の長さは、好ましくは１０〜１９００ｎｍ、より好ましくは２０〜１５００ｎｍである。コア部の長手方向と垂直な面の直径が１０ｎｍ未満であると、包接型微粒子の作製が困難となり、１００ｎｍより大きくなると、交換スプリング効果が得られなくなり、磁石にならない。また、コア部の長手方向の長さが１０ｎｍ未満であると、包接型微粒子の作製が困難となり、１９００ｎｍより大きくなると、保磁力が低下する。また、その包接部の厚みは、好ましくは１０〜１００ｎｍ、より好ましくは２０〜８０ｎｍである。包接部の厚みが１０ｍｍ未満であると、包接型微粒子の作製が困難となり、１００ｎｍより大きくなると、交換スプリング効果が得られなくなり、磁石にならない。
【００１４】
永久磁石用粒子自体としては、その長手方向と垂直な面の直径は、好ましくは２０〜２００ｎｍ、より好ましくは４０〜１５０ｎｍであり、長手方向の長さは、好ましくは２０〜２０００ｎｍ、より好ましくは４０〜１５００ｎｍである。永久磁石用粒子の長手方向と垂直な面の直径が２０ｎｍ未満であると、包接型微粒子の作製が困難となり、２００ｎｍより大きくなると、交換スプリング効果が得られなくなり、磁石にならない。また、永久磁石用粒子の長手方向の長さが２０ｎｍ未満であると、包接型微粒子の作製が困難となり、２０００ｎｍより大きくなると、保磁力が低下する。
【００１５】
本発明の永久磁石用粒子において、硬磁性相及び軟磁性相の組成は特に限定されないが、これらの好ましい組み合わせとしては下記（Ａ）、（Ｂ）として示すようなものが例示される。
【００１６】
（Ａ）硬磁性相：Ｒ−Ｆｅ−Ｎ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金
軟磁性相：Ｆｅ−Ｍ−Ｎ（ＭはＦｅ以外の遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金
希土類金属元素（Ｒ）としては、Ｓｍ、Ｎｄ、Ｙ、Ｐｒ、Ｔｂ、Ｄｙ、Ｌａ、Ｃｅ、Ｇｄ、Ｅｒ、Ｈｏ、Ｅｕ、Ｐｍ、Ｔｍ、Ｙｂのうちの少なくとも１種以上が使用されるが、これらのうち特に、Ｓｍ、Ｎｄ、Ｐｒ、Ｄｙ、あるいはこれらの組み合わせが好ましい。
遷移金属（Ｍ）としては、Ｃｏ、Ｎｉ、Ｍｎ、Ｃｕ、Ｈｆ、Ｚｒ、Ｔｉのうちの少なくとも１種以上が使用されるが、これらのうち特に、Ｃｏ、Ｎｉ、Ｍｎ、あるいはこれらの組み合わせが好ましい。
【００１７】
硬磁性相において、ＲとＦｅとＮの好ましい含有量は、Ｒが５〜３０ａｔ％、Ｆｅが６５〜９０ａｔ％、Ｎが１〜５ａｔ％である。Ｒの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。Ｆｅの含有量が上記範囲より多いと、保磁力が低下し、上記範囲より少ないと、飽和磁束密度が低下する。Ｎの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。
【００１８】
軟磁性相において、その組成は、（１）Ｆｅ−Ｍ−Ｎ又は（２）Ｆｅ−Ｎであるが、（１）の場合、ＦｅとＭとＮの含有量は、Ｆｅが７５〜９５ａｔ％、Ｍが２０ａｔ％以下、Ｎが１〜５ａｔ％であることが好ましい。Ｆｅの含有量が上記範囲より多いと、保磁力が低下し、上記範囲より少ないと、飽和磁束密度が低下する。Ｍが２０ａｔ％より多いと、保磁力が低下する。また、Ｎの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。
また（２）の場合、ＦｅとＮの含有量は、Ｆｅが９５〜９９ａｔ％、Ｎが１〜５ａｔ％であることが好ましい。Ｆｅの含有量が上記範囲より多いと、保磁力が低下し、上記範囲より少ないと、飽和磁束密度が低下する。また、Ｎの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。
【００１９】
上記のような構成及び組成の永久磁石用粒子は、４８０〜５５０ｋＪ／ｍ３と従来のものに比べて大きな最大エネルギー積を有する。
【００２０】
（Ｂ）硬磁性相：Ｒ−Ｆｅ−Ｂ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金
軟磁性相：Ｆｅ、Ｆｅ−Ｍ（ＭはＦｅ以外の遷移金属のうちの少なくとも１種以上）又はＦｅ−Ｎ組成を有する合金
希土類金属元素（Ｒ）としては、Ｓｍ、Ｎｄ、Ｙ、Ｐｒ、Ｔｂ、Ｄｙ、Ｌａ、Ｃｅ、Ｇｄ、Ｅｒ、Ｈｏ、Ｅｕ、Ｐｍ、Ｔｍ、Ｙｂのうちの少なくとも１種以上が使用されるが、これらのうち特に、Ｓｍ、Ｎｄ、Ｐｒ、Ｄｙ、あるいはこれらの組み合わせが好ましい。
遷移金属（Ｍ）としては、Ｃｏ、Ｎｉ、Ｍｎ、Ｃｕ、Ｈｆ、Ｚｒ、Ｔｉのうちの少なくとも１種以上が使用されるが、これらのうち特に、Ｃｏ、Ｎｉ、Ｍｎ、あるいはこれらの組み合わせが好ましい。
【００２１】
硬磁性相において、ＲとＦｅとＢの好ましい含有量は、Ｒが５〜３０ａｔ％、Ｆｅが６５〜９０ａｔ％、Ｂが１〜５ａｔ％である。Ｒの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。Ｆｅの含有量が上記範囲より多いと、保磁力が低下し、上記範囲より少ないと、飽和磁束密度が低下する。Ｂの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。
【００２２】
軟磁性相において、その組成は、（１）Ｆｅ、（２）Ｆｅ−Ｍ又は（３）Ｆｅ−Ｎであるが、（２）の場合、Ｍが２０ａｔ％以下であることが好ましい。Ｍが２０ａｔ％より多いと、飽和磁束密度が低下する。
また（３）の場合、ＦｅとＮの含有量は、Ｆｅが９５〜９９ａｔ％、Ｎが１〜５ａｔ％であることが好ましい。Ｆｅの含有量が上記範囲より多いと、保磁力が低下し、上記範囲より少ないと、飽和磁束密度が低下する。Ｎの含有量が上記範囲より多いと、飽和磁束密度が低下し、上記範囲より少ないと、保磁力が低下する。
【００２３】
上記のような構成及び組成の永久磁石用粒子も、４８０〜５５０ｋＪ／ｍ３と従来のものに比べて大きな最大エネルギー積を有する。
【００２４】
次に、本発明による永久磁石用粒子の製造方法について説明する。
本方法では、まず、油中水滴型（ｗ／ｏ）マイクロエマルションを利用する。このため、有機溶媒と界面活性剤の溶液を用意する。有機溶媒としては、シクロヘキサン（Ｃ６Ｈ１２）、メタノール（ＣＨ３ＯＨ）等を用いることができる。また、界面活性剤としては、ポリエチレングリコールモノ−４−ノニルフェニルエーテル（Ｃ９Ｈ１９−Ｃ６Ｈ４−（ＯＣ２Ｈ４）ｎＯＨ、ｎ＝５）、（Ｃ９Ｈ１９−Ｃ６Ｈ４−（ＯＣ２Ｈ４）ｎＯＨ、ｎ＝１０）等を用いることができる。有機溶媒に対する界面活性剤の混合割合（重量比）は５：１〜２０：１程度が好ましい。
次に、金属原料塩水溶液として、遷移金属塩化物の水溶液と希土類金属塩化物の水溶液を用意する。ここで遷移金属塩化物と希土類金属塩化物の割合は、最終目的である永久磁石用粒子の化学量論比に応じたものとする。なお、上記（Ｂ）のような系の永久磁石用粒子を製造する場合には、金属原料塩水溶液に塩化ホウ素の水溶液を加える。
そして、有機溶媒／界面活性剤の溶液中に、金属原料塩水溶液を滴下し、油中水滴型マイクロエマルションを形成させる。
次に、このマイクロエマルション溶液中に微粒子形成剤を滴下して、撹拌することにより油中水滴型マイクロエマルションの内核水相内で、希土類金属と繊維金属の水酸化物超微粒子を形成させる。ここで微粒子形成剤としては、アンモニア、尿素等のアルカリ源を使用することができる。
その後、微粒子を回収し、有機溶媒と界面活性剤を除去する。微粒子の回収法としては、例えば遠心分離を用いることができる。また、有機溶媒と界面活性剤の除去には、例えばプロパノール洗浄した後、乾燥及び空気焼成を行う方法を用いることができる。また、乾燥は１００〜２００℃で５〜１０時間程度行い、空気焼成は４００〜６００℃で１〜３時間程度行うことにより、粒子に付着した界面活性剤を除去する。これら処理により作製した、内部がＲ−Ｂ（Ｒは希土類金属のうちの少なくとも１種）組成を有する合金と、外部がＦｅ、Ｆｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）を有する合金を、８００〜１０００℃で１０時間程度Ａｒ雰囲気中で熱処理して相互拡散を行うことで、硬磁性相がＲ−Ｆｅ−Ｂ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、軟磁性相がＦｅ、Ｆｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）又は、その後窒化処理を行うことによりＦｅ−Ｎ組成を有する合金であることを特徴とする永久磁石用粒子を作製する。
一方、内部がＲ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金と、外部がＦｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）又はＦｅ組成を有する合金を、８００〜１０００℃で１０時間程度Ａｒ雰囲気中で熱処理して相互拡散を行うことで、内部がＲ−Ｆｅ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金と、外部がＦｅ、Ｆｅ−Ｍ（Ｍは遷移金属のうちの少なくとも１種以上）を作製し、その後窒化処理を行うことにより、硬磁性相がＲ−Ｆｅ−Ｎ（Ｒは希土類金属元素のうちの少なくとも１種以上）組成を有する合金であり、軟磁性相がＦｅ−Ｎ、Ｆｅ−Ｍ−Ｎ（Ｍは遷移金属のうちの少なくとも１種以上）組成を有する合金であることを特徴とする永久磁石用粒子を作製する。
次に、上記で形成した微粒子に対し、水素還元処理及びＣａ還元拡散処理を順次施す。水素還元処理は酸化鉄の還元を目的として、窒素雰囲気の条件で４００〜６００℃で１〜３時間程度行う。また、Ｃａ還元処理は、希土類金属酸化物の還元を目的としてアルゴン等の不活性ガス中において８４０〜１１００℃で１〜３時間程度行う。
Ｎを含む系の永久磁石用粒子を形成する場合には、Ｃａ還元拡散処理の後、窒化処理を行う。この窒化処理は、１〜８ＭＰａの窒素雰囲気の条件で３５０〜６００℃で１０〜８０時間程度行う。
以上の工程により、目的とする永久磁石用粒子が得られる。そして、上記で作製した永久磁石用粒子を用いて永久磁石を作製するには、焼結磁石作製の場合、永久磁石用粒子を造粒して成形した後、Ａｒ雰囲気の条件で８００〜１１００℃で１〜３時間焼結することで、最終製品である焼結磁石が得られる。また、ボンド磁石作製の場合には、上記で作製した永久磁石粒子にバインダー樹脂を加え、成形を行うことで、最終製品であるボンド磁石が得られる。この場合、バインダー樹脂としては、エポキシ樹脂、ナイロン樹脂あるいはアクリル樹脂を好ましく用いることができる。また、成形法としては、圧縮成形、射出成形、押出成形等の方法を用いることができる。
【００２５】
以上、本発明の磁性体微粒子を永久磁石用粒子を例に述べてきたが、本発明による磁性体微粒子は、磁気シールド材の他、磁性流体にも利用でき、マイクロマシンなどの用途に利用できる。
【００２６】
【実施例】
以下、本発明を実施例により更に詳細に説明する。
【００２７】
実施例１
包接型微粒子作製法として、油中水滴型（ｗ／ｏ）マイクロエマルションを利用した方法を用い、永久磁石用粒子を以下のようにして作製した。
まず、溶媒としてシクロヘキサン（Ｃ６Ｈ１２）を用いるとともに、界面活性剤としてポリエチレングリコールモノ−４−ノニルフェニルエーテル（Ｃ９Ｈ１９−Ｃ６Ｈ４−（ＯＣ２Ｈ４）ｎＯＨ、ｎ＝５）を用いて、溶媒／界面活性剤の溶液（０．５ｍｏｌ／ｌ、５００ｍｌ）を用意した。また、金属原料塩水溶液には、塩化鉄（ＦｅＣｌ２）、塩化コバルト（ＣｏＣｌ２）、塩化サマリウム（ＳｍＣｌ３）の水溶液を混合したものを用いた（（Ｃｏ＋Ｆｅ）／Ｓｍモル比＝（１７／２））。
次に、０．６ｍｍｏｌ／ｌ塩化鉄水溶液を９ｍｌ、０．６ｍｍｏｌ／塩化コバルト水溶液を１ｍｌ、０．１２ｍｍｏｌ／ｌ塩化サマリウム溶液を５．８ｍｌを界面活性剤／有機溶媒の溶液中に滴下して、油中水滴型（ｗ／ｏ）マイクロエマルションを形成させた。このマイクロエマルション溶液に微粒子形成剤であるアンモニア水を１．５ｍｌ滴下し、１時間攪拌して油中水滴型マイクロエマルションの内核水相内で、希土類金属と遷移金属の水酸化物超微粒子を形成させた。
その後、遠心分離によって微粒子を回収し、プロパノールで洗浄した後、乾燥（８０℃、１０時間）と空気焼成（５００℃、２時間）によって、有機溶媒と界面活性剤を除去した。そして、焼成処理（空気中、Ｔｃ＝８００℃、２時間）、水素還元処理（５００℃、２時間）、Ｃａ還元拡散処理（アルゴン中８５０℃、１０時間）、窒化処理（６００℃、１時間）を順次施して、幅３０ｎｍ、長さ２００ｎｍの硬磁性相（Ｓｍ２（Ｃｏ１Ｆｅ９）Ｎ３［化学量論比］：Ｓｍ１３．３（Ｃｏ６．７Ｆｅ６０．０）Ｎ２０［原子比］）に、厚さが１５ｎｍの軟磁性相（Ｆｅ９Ｃｏ１［化学量論比］：Ｆｅ９０Ｃｏ１０［原子比］）が包接した永久磁石用粒子を作製した。
次に、上記で得られた永久磁石用粒子を磁石成形機で成形し、焼結（８５０℃、１０時間）することで焼結磁石を作製した。
以上の手順を図２に概略的に示した。
【００２８】
上記で作製した永久磁石用粒子の形状を走査型電子顕微鏡で観察した。その観察結果である粒度分布を図３に示す。なお、蒸着法により作製した永久磁石用粒子（従来例）の粒度分布を比較のため図３に示す。
また、上記で作製した焼結磁石の磁力特性（残留磁気（Ｂｒ）、保磁力（Ｈｃｊ）、最大エネルギー積（ＢＨｍａｘ））を振動試料型磁力計で測定した。その結果を表１に示す。
【表１】
実施例２
実施例１において、塩化鉄（ＦｅＣｌ２）、塩化コバルト（ＣｏＣｌ２）、塩化サマリウム（ＳｍＣｌ３）の金属原料塩水溶液の（Ｃｏ＋Ｆｅ）／Ｓｍモル比を＝５．０〜１２．０まで可変させたこと以外は同様にして、永久磁石用粒子及び焼結磁石を作製した。これらの磁気特性を表２に示す。
【表２】
実施例３
実施例１において、Ｃａ還元拡散処理の温度を６００〜１１００℃まで可変させたこと以外は同様にして、永久磁石用粒子及び焼結磁石を作製した。これらの磁気特性を表３に示す。
【表３】
実施例４
実施例１において、窒化処理の温度を４００〜７５０℃まで可変させたこと以外は同様にして、永久磁石用粒子及び焼結磁石を作製した。これらの磁気特性を表４に示す。
【表４】
実施例５
包接型微粒子作製法として、油中水滴型（ｗ／ｏ）マイクロエマルションを利用した方法を用い、永久磁石用粒子を以下のようにして作製した。
まず、溶媒としてシクロヘキサン（Ｃ６Ｈ１２）を用いるとともに、界面活性剤としてポリエチレングリコールモノ−４−ノニルフェニルエーテル（Ｃ９Ｈ１９−Ｃ６Ｈ４−（ＯＣ２Ｈ４）ｎＯＨ、ｎ＝５）を用いて、溶媒／界面活性剤の溶液（０．５ｍｏｌ／ｌ、５００ｍｌ）を用意した。また、金属原料塩水溶液には、塩化鉄（ＦｅＣｌ２）、塩化コバルト（ＣｏＣｌ２）、塩化ネオジウム（ＮｄＣｌ３）、塩化ホウ素（Ｂ２Ｃｌ２）の水溶液を混合したものを用いた（（Ｃｏ＋Ｆｅ）／Ｎｄモル比＝８）。
次に、０．６ｍｍｏｌ／ｌ塩化鉄水溶液を１０ｍｌ、０．１２ｍｍｏｌ／塩化コバルト水溶液を１．２ｍｌ、０．１２ｍｍｏｌ／ｌ塩化ネオジウム溶液を９．７ｍｌ、０．６ｍｍｏｌ／ｌ塩化ホウ素水溶液を１ｍｌを界面活性剤／有機溶媒の溶液中に滴下して、油中水滴型（ｗ／ｏ）マイクロエマルションを形成させた。このマイクロエマルション溶液に微粒子形成剤であるアンモニア水を１．５ｍｌ滴下し、１時間攪拌して油中水滴型マイクロエマルションの内核水相内で、希土類金属と遷移金属の水酸化物超微粒子を形成させた。
その後、遠心分離によって微粒子を回収し、プロパノールで洗浄した後、乾燥（８０℃、１０時間）と空気焼成（５００℃、２時間）によって、有機溶媒と界面活性剤を除去した。そして、焼成処理（空気中、Ｔｃ＝８００℃、２時間）、水素還元処理（５００℃、２時間）、Ｃａ還元拡散処理（アルゴン中８５０℃、１０時間）を順次施して、幅３０ｎｍ、長さ２００ｎｍの硬磁性相（Ｎｄ２Ｆｅ１４Ｂ１［化学量論比］：Ｎｄ１１．８Ｆｅ８２．３Ｂ５．９［原子比］）に、厚さが１５ｎｍの軟磁性相（Ｆｅ９Ｃｏ１［化学量論比］：Ｆｅ９０Ｃｏ１０［原子比］）が包接した永久磁石用粒子を作製した。
次に、上記で得られた永久磁石用粒子を磁石成形機で成形し、焼結（８５０℃、２時間）することで焼結磁石を作製した。
【００３３】
上記で作製した焼結磁石の磁力特性（残留磁気（Ｂｒ）、保磁力（Ｈｃｊ）、最大エネルギー積（ＢＨｍａｘ））を振動試料型磁力計で測定した。その結果を表５に示す。
【表５】
実施例６
実施例１で得た永久磁石粒子にエポキシ樹脂（日本ペルノックス社製）を重量割合９８：２で混合した後、リング形状に成形し、ボンド磁石を作製した。このボンド磁石について上記と同様にして磁気特性を測定した。その結果を表６に示す。
【表６】
実施例７
実施例５で得た永久磁石粒子にエポキシ樹脂（日本ペルノックス社製）を重量割合９８：２で混合した後、リング形状に成形し、ボンド磁石を作製した。このボンド磁石について上記と同様にして磁気特性を測定した。その結果を表６に示す。
また、実施例７の方法でボンド磁石を２０個作製したときの特性分布と、従来例ではＮｄ粉末、Ｂ粉末、針状鉄粉よりなる混合物を水素を含有する還元ガス雰囲気中で還元し、さらにアルゴンガス中で熱処理（８５０℃で２時間）した粉体からボンド磁石を２０個作製したときの特性分布を、表７において比較して示す。表７から明らかなように、本発明例（実施例７）のものは、従来例と比較し、特性にばらつきがないことが確認された。
【表７】
【発明の効果】
本発明の永久磁石用粒子によれば、従来の永久磁石に比べて大きな最大エネルギー積（焼結磁石の場合は４７０ｋＪ／ｍ３より大、ボンド磁石の場合は２３９ｋＪ／ｍ３より大）を有する永久磁石が提供できる。また、本発明の永久磁石用粒子は、相互に固溶しない硬磁性相と軟磁性相を一方が他方の表面を被覆する包接型構造となっているので、硬磁性相と軟磁性相が均一でかつ磁気特性の安定な磁石が提供できる。
また、本発明の永久磁石用粒子の製造方法によれば、従来の永久磁石に比べて大きな最大エネルギー積を有し、相互に固溶しない硬磁性相と軟磁性相を一方が他方の表面を被覆した包接型構造の永久磁石用粒子が作製でき、この永久磁石用粒子を用いて作製した永久磁石は、従来の永久磁石に比べて大きな最大エネルギー積（焼結磁石の場合は４７０ｋＪ／ｍ３より大、ボンド磁石の場合は２３９ｋＪ／ｍ３より大）を有し、硬磁性相と軟磁性相が均一でかつ磁気特性の安定な磁石が提供できる。また、所望の磁気特性の磁石が安定して得られるので、生産性が高くなり、さらに磁石の形状に制約が少なく、応用の範囲が広がる利点もある。
また、本発明の永久磁石は、従来の永久磁石に比べて大きな最大エネルギー積（焼結磁石の場合は４７０ｋＪ／ｍ３より大、ボンド磁石の場合は２３９ｋＪ／ｍ３より大）を有し、硬磁性相と軟磁性相が均一でかつ磁気特性の安定である。さらに、本発明による磁性体微粒子は、磁気シールドの他、磁気流体にも利用でき、マイクロマシンなどの用途に適用することができる。
【図面の簡単な説明】
【図１】本発明による永久磁石用粒子の構造の模式的に示す断面図である。
【図２】本発明による永久磁石を製造する工程を示す図である。
【図３】実施例１で作製した永久磁石用粒子の粒度分布を示す図である。
【図４】従来の永久磁石用粒子の製造方法を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to permanent magnet particles having higher and more stable magnetic properties than conventional magnets, a method for producing the same, a permanent magnet using the magnet particles, and magnetic fine particles.
[0002]
[Prior art]
As a conventionally proposed permanent magnet having excellent magnetic properties, an Nd-Fe-B based sintered magnet is known. However, the energy product of this sintered magnet is 470 kJ / m 3 The energy product of the bonded magnet is 239 kJ / m 3 Less than is the limit. Further improvement is desired for miniaturization and high performance of magnet application products.
[0003]
In response, exchange spring magnets have been proposed, and research and development have been actively conducted. The exchange spring magnet has a structure in which a hard magnetic phase made of a hard magnetic material and a soft magnetic phase made of a soft magnetic material are alternately arranged, and various methods for manufacturing the same have been studied. The main methods of manufacturing the exchange spring magnet include (1) a quenching method (Japanese Patent Application Laid-Open No. 8-124730, etc.), (2) a thin film manufacturing method (Japanese Patent Application Laid-Open No. 11-214219, Japanese Patent Application Laid-Open No. 9-237714, etc.), and (3). A method of diffusing a rare earth metal element or a B element into the surface layer of acicular iron powder (JP-A-7-106110, JP-A-8-203715, JP-A-8-335507, etc.) has been proposed.
[0004]
FIG. 4 shows an example of a method for producing particles for permanent magnets by the rapid cooling method (1). In this method, Fe, Co, and Sm as raw materials are melted by high frequency induction in an argon atmosphere, then quenched to produce a magnetic ribbon composed of a soft magnetic phase and a hard magnetic phase. Fe-Co-Sm-based magnetic particles having a particle size of about 3 to 5 µm are mechanically pulverized, and further subjected to nitriding treatment to produce Fe-Co-Sm-N-based magnetic particles (particles for permanent magnets). The permanent magnet particles are used to form a permanent magnet. However, in the case of this method, it is difficult to control the structure composed of the soft magnetic phase and the hard magnetic phase, and therefore, there is a problem that the intended magnetic properties cannot be obtained. Therefore, the maximum energy product is 470 kJ / m 3 And when manufactured as a bonded magnet, the maximum energy product is 239 kJ / m 3 And its intended purpose has not been achieved.
[0005]
The thin film forming method of the above (2) is a method of manufacturing a magnet by arranging a soft magnetic phase and a hard magnetic phase in a layered manner by a vapor deposition method. However, there is a problem that it is difficult to manufacture a cubic magnet such as a bonded magnet or a sintered magnet.
[0006]
The method of (3) for diffusing a rare earth metal element or B element into the surface layer of acicular iron powder is superior to a conventional magnet in terms of characteristics, but has not yet been put to practical use. The reason is that a magnet having stable characteristics has not been obtained. That is, the thickness of the hard magnetic phase is not constant in the method of forming the hard magnetic phase on the surface by diffusion after coating the soft magnetic phase with the rare earth metal element or the B element. The hard magnetic phase may not be formed due to non-uniform diffusion.
[0007]
As described above, the conventional product or the conventional method cannot respond to the demand for a small and high-performance magnet-applied product, and it has been desired to realize a permanent magnet with more excellent magnetic properties and stability.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of such a situation of the related art, and provides a permanent magnet particle which has superior magnetic properties and is more stable than conventionally proposed permanent magnets, a method for producing the same, and a permanent magnet. That is the subject.
Another object of the present invention is to provide novel magnetic fine particles.
[0009]
[Means for Solving the Problems]
According to the present invention, the above-mentioned problem is solved by the following technical means.
(1) A hard magnetic phase and a soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. One phase is a core part, and the other phase is the core part. Particles for a permanent magnet, characterized in that they are fine particles of an inclusion structure in which an inclusion portion is included around the periphery of the permanent magnet.
(2) The hard magnetic phase is an alloy having a composition of R-Fe-B (R is at least one of rare earth metal elements), and the soft magnetic phase is Fe, Fe-M (M is a transition metal At least one of the above) or an alloy having an Fe—N composition.
(3) The hard magnetic phase is an alloy having a composition of R-Fe-N (R is at least one of rare earth metal elements), and the soft magnetic phase is Fe-M-N (M is a transition metal At least one of the above) or an alloy having an Fe—N composition.
(4) The particles for permanent magnets according to any one of (1) to (3), wherein the core portion is made of a hard magnetic phase, and the inclusion portion is made of a soft magnetic phase.
(5) The particles for permanent magnet according to any one of (1) to (3), wherein the core portion is made of a soft magnetic phase, and the surrounding portion is made of a hard magnetic phase.
(6) The particles for permanent magnet according to any one of (1) to (5), wherein the whole shape is a spherical shape or an egg shape.
(7) The diameter of a surface perpendicular to the longitudinal direction of the core portion is 10 to 100 nm, the length in the longitudinal direction is 10 to 2000 nm, and the thickness of the inclusion portion is 10 to 100 nm. The permanent magnet particles according to any one of the above (1) to (6).
(8) The hard magnetic phase and the soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. One of the phases is a core part, and the other phase is the core part. Are fine particles having an inclusion structure in which an inclusion portion is included around the periphery of the alloy, wherein the hard magnetic phase is an alloy having a composition of R-Fe-B (R is at least one of rare earth metal elements). A method for producing particles for permanent magnets, wherein the soft magnetic phase is Fe, Fe-M (M is at least one of transition metals) or an alloy having an Fe-N composition;
A step of dropping an aqueous solution of a transition metal chloride, an aqueous solution of a rare earth metal chloride and boron chloride into a solution of a surfactant and an organic solvent, and forming a water-in-oil microemulsion;
A step of forming fine particles by dropping a fine particle forming agent,
A method of sequentially performing a hydrogen reduction treatment and a Ca reduction treatment on the fine particles formed in the above step, characterized by comprising:
(9) The method for producing particles for permanent magnets according to (8), wherein a nitriding treatment is performed after the Ca reduction treatment.
(10) A hard magnetic phase and a soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. One phase is a core part and the other phase is the core part. And a hard magnetic phase having an R-Fe-N (R is at least one of rare earth metal elements) composition. A method for producing permanent magnet particles, wherein the soft magnetic phase is Fe-MN (M is at least one of transition metals) or an alloy having an Fe-N composition;
A step of dropping an aqueous solution of a transition metal chloride and an aqueous solution of a rare earth metal chloride in a solution of a surfactant and an organic solvent to form a water-in-oil microemulsion,
A step of forming fine particles by dropping a fine particle forming agent,
A process of sequentially performing a hydrogen reduction treatment, a Ca reduction treatment, and a nitridation treatment on the fine particles formed in the above step, wherein the method comprises the steps of:
(11) A permanent magnet comprising the permanent magnet particles of any one of (1) to (7) and a binder resin.
(12) The permanent magnet according to (11), wherein the binder resin is an epoxy resin, a nylon resin or an acrylic resin.
(13) The permanent magnet according to (11) or (12), which is a sintered body.
(14) A hard magnetic phase and a soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. One phase is a core part and the other phase is the core part. Magnetic particles having an inclusion structure in which the surrounding portion is included.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The magnetic fine particles according to the present invention have a structure in which a hard magnetic phase and a soft magnetic phase are composited on a nanoscale. The hard magnetic phase and the soft magnetic phase do not form a solid solution with each other, and one of the cores forms a core. And fine particles having an inclusion type structure in which the other phase is an inclusion portion that covers the periphery of the core.
The magnetic fine particles according to the present invention can be used for various applications in which their excellent magnetic properties and stability can be utilized, but are particularly preferably used for producing permanent magnets. Hereinafter, a case where the magnetic fine particles according to the present invention are suitable for permanent magnet particles will be described as an example.
[0011]
The particles for a permanent magnet of the present invention have a structure in which a hard magnetic phase and a soft magnetic phase are composited, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. Are microparticles having an inclusion type structure in which the phase of (1) is an inclusion portion that includes the periphery of the core portion.
[0012]
In the particles for a permanent magnet of the present invention, the core portion may be composed of a hard magnetic phase, and the inclusion portion may be composed of a soft magnetic phase. Conversely, the core portion may be composed of a soft magnetic phase, and the inclusion portion may be composed of a hard magnetic phase. It may consist of phases.
[0013]
The permanent magnet particles of the present invention have a spherical shape or an egg shape (an elliptical cross section). The shape is formed by applying a compressive force in a forming step in a method for producing particles for permanent magnets described below. FIG. 1 shows a state in which the permanent magnet particles of the present invention have a shape close to a rectangular parallelepiped or a cube by applying a compressive force.
In the permanent magnet particles, the diameter of a surface perpendicular to the longitudinal direction of the core portion is preferably 10 to 100 nm, more preferably 20 to 80 nm, and the length in the longitudinal direction is preferably 10 to 1900 nm. Preferably it is 20 to 1500 nm. If the diameter of the surface perpendicular to the longitudinal direction of the core portion is less than 10 nm, it becomes difficult to produce inclusion particles, and if it exceeds 100 nm, the exchange spring effect cannot be obtained and the magnet will not be formed. Further, if the length of the core portion in the longitudinal direction is less than 10 nm, it is difficult to produce the inclusion particles, and if it exceeds 1900 nm, the coercive force decreases. Further, the thickness of the clathrate is preferably 10 to 100 nm, more preferably 20 to 80 nm. If the thickness of the clathrate is less than 10 mm, it becomes difficult to produce the clathrate-type fine particles.
[0014]
As the permanent magnet particles themselves, the diameter of the surface perpendicular to the longitudinal direction is preferably 20 to 200 nm, more preferably 40 to 150 nm, and the length in the longitudinal direction is preferably 20 to 2000 nm, more preferably 40 to 1500 nm. If the diameter of the surface perpendicular to the longitudinal direction of the particles for permanent magnets is less than 20 nm, it becomes difficult to produce the inclusion particles, and if it exceeds 200 nm, the exchange spring effect cannot be obtained and the magnet does not become a magnet. If the length in the longitudinal direction of the particles for permanent magnets is less than 20 nm, it becomes difficult to produce inclusion-type fine particles, and if it exceeds 2000 nm, the coercive force decreases.
[0015]
In the permanent magnet particles of the present invention, the compositions of the hard magnetic phase and the soft magnetic phase are not particularly limited, but preferred combinations thereof are as shown in the following (A) and (B).
[0016]
(A) Hard magnetic phase: alloy having a composition of R-Fe-N (R is at least one of rare earth metal elements)
Soft magnetic phase: Fe-M-N (M is at least one of transition metals other than Fe) or alloy having Fe-N composition
As the rare earth metal element (R), at least one of Sm, Nd, Y, Pr, Tb, Dy, La, Ce, Gd, Er, Ho, Eu, Pm, Tm, and Yb is used. Of these, Sm, Nd, Pr, Dy, or a combination thereof is particularly preferable.
As the transition metal (M), at least one of Co, Ni, Mn, Cu, Hf, Zr, and Ti is used. Among them, particularly, Co, Ni, Mn, or a combination thereof is used. preferable.
[0017]
In the hard magnetic phase, the preferable contents of R, Fe, and N are 5 to 30 at% for R, 65 to 90 at% for Fe, and 1 to 5 at% for N. When the content of R is more than the above range, the saturation magnetic flux density decreases, and when it is less than the above range, the coercive force decreases. If the Fe content is higher than the above range, the coercive force decreases, and if it is lower than the above range, the saturation magnetic flux density decreases. If the N content is more than the above range, the saturation magnetic flux density will decrease, and if it is less than the above range, the coercive force will decrease.
[0018]
In the soft magnetic phase, the composition is (1) Fe-M-N or (2) Fe-N. In the case of (1), the content of Fe, M, and N is such that Fe is 75 to 95 at%. , M is preferably 20 at% or less, and N is preferably 1 to 5 at%. If the Fe content is higher than the above range, the coercive force decreases, and if it is lower than the above range, the saturation magnetic flux density decreases. When M is more than 20 at%, the coercive force decreases. On the other hand, when the content of N is larger than the above range, the saturation magnetic flux density decreases, and when it is smaller than the above range, the coercive force decreases.
In the case of (2), the content of Fe and N is preferably 95 to 99 at% for Fe and 1 to 5 at% for N. If the Fe content is higher than the above range, the coercive force decreases, and if it is lower than the above range, the saturation magnetic flux density decreases. On the other hand, when the content of N is larger than the above range, the saturation magnetic flux density decreases, and when it is smaller than the above range, the coercive force decreases.
[0019]
The particles for permanent magnet having the above configuration and composition are 480 to 550 kJ / m. 3 Has a larger maximum energy product than the conventional one.
[0020]
(B) Hard magnetic phase: an alloy having a composition of R-Fe-B (R is at least one of rare earth metal elements)
Soft magnetic phase: Fe, Fe-M (M is at least one of transition metals other than Fe) or alloy having Fe-N composition
As the rare earth metal element (R), at least one of Sm, Nd, Y, Pr, Tb, Dy, La, Ce, Gd, Er, Ho, Eu, Pm, Tm, and Yb is used. Of these, Sm, Nd, Pr, Dy, or a combination thereof is particularly preferable.
As the transition metal (M), at least one of Co, Ni, Mn, Cu, Hf, Zr, and Ti is used. Among them, particularly, Co, Ni, Mn, or a combination thereof is used. preferable.
[0021]
In the hard magnetic phase, the preferable contents of R, Fe and B are 5 to 30 at% for R, 65 to 90 at% for Fe, and 1 to 5 at% for B. When the content of R is more than the above range, the saturation magnetic flux density decreases, and when it is less than the above range, the coercive force decreases. If the Fe content is higher than the above range, the coercive force decreases, and if it is lower than the above range, the saturation magnetic flux density decreases. When the content of B is more than the above range, the saturation magnetic flux density decreases, and when it is less than the above range, the coercive force decreases.
[0022]
In the soft magnetic phase, the composition is (1) Fe, (2) Fe-M or (3) Fe-N. In the case of (2), M is preferably 20 at% or less. When M is more than 20 at%, the saturation magnetic flux density decreases.
In the case of (3), the content of Fe and N is preferably 95 to 99 at% for Fe and 1 to 5 at% for N. If the Fe content is higher than the above range, the coercive force decreases, and if it is lower than the above range, the saturation magnetic flux density decreases. If the N content is more than the above range, the saturation magnetic flux density will decrease, and if it is less than the above range, the coercive force will decrease.
[0023]
The particles for permanent magnet having the above configuration and composition are also 480 to 550 kJ / m. 3 Has a larger maximum energy product than the conventional one.
[0024]
Next, the method for producing permanent magnet particles according to the present invention will be described.
The method first utilizes a water-in-oil (w / o) microemulsion. For this purpose, a solution of an organic solvent and a surfactant is prepared. As an organic solvent, cyclohexane (C 6 H 12 ), Methanol (CH 3 OH) can be used. As the surfactant, polyethylene glycol mono-4-nonylphenyl ether (C 9 H 19 -C 6 H 4 − (OC 2 H 4 ) n OH, n = 5), (C 9 H 19 -C 6 H 4 − (OC 2 H 4 ) n OH, n = 10) and the like can be used. The mixing ratio (weight ratio) of the surfactant to the organic solvent is preferably about 5: 1 to 20: 1.
Next, an aqueous solution of a transition metal chloride and an aqueous solution of a rare earth metal chloride are prepared as the aqueous metal source salt solution. Here, the ratio between the transition metal chloride and the rare earth metal chloride depends on the stoichiometric ratio of the permanent magnet particles which is the final purpose. In the case of producing particles for a permanent magnet of the type (B), an aqueous solution of boron chloride is added to the aqueous solution of the salt of the metal raw material.
Then, the aqueous solution of the salt of the metal raw material is dropped into the solution of the organic solvent / surfactant to form a water-in-oil type microemulsion.
Next, a microparticle forming agent is dropped into the microemulsion solution and stirred to form ultra-fine hydroxide of rare earth metal and fiber metal in the core aqueous phase of the water-in-oil microemulsion. Here, an alkali source such as ammonia and urea can be used as the fine particle forming agent.
Thereafter, the fine particles are collected, and the organic solvent and the surfactant are removed. As a method for collecting fine particles, for example, centrifugation can be used. For removing the organic solvent and the surfactant, for example, a method of washing with propanol, followed by drying and baking with air can be used. Drying is performed at 100 to 200 ° C. for about 5 to 10 hours, and air calcination is performed at 400 to 600 ° C. for about 1 to 3 hours to remove the surfactant attached to the particles. An alloy having an RB (R is at least one kind of rare earth metal) composition inside and Fe and Fe-M (M is at least one kind of transition metal) outside are prepared by these processes. The hard magnetic phase is made of R—Fe—B (R is at least one of rare earth metal elements) by heat-treating the alloy having a temperature of 800 to 1000 ° C. for about 10 hours in an Ar atmosphere to perform interdiffusion. Wherein the soft magnetic phase is Fe, Fe-M (M is at least one of transition metals) or an alloy having an Fe-N composition by performing a nitriding treatment thereafter. To produce permanent magnet particles.
On the other hand, an alloy having an internal R (R is at least one of the rare earth metal elements) composition and an external alloy having an Fe-M (M is at least one of the transition metals) or Fe composition are used. By performing heat diffusion in an Ar atmosphere at 800 to 1000 ° C. for about 10 hours to perform interdiffusion, an alloy having an internal R—Fe (R is at least one of rare earth metal elements) composition, By producing Fe and Fe-M (M is at least one of transition metals) and then performing a nitriding treatment, the hard magnetic phase becomes R-Fe-N (R is at least one of the rare earth metal elements). And a soft magnetic phase having an Fe-N, Fe-M-N (M is at least one of transition metals) composition. Make particles.
Next, the fine particles formed as described above are sequentially subjected to a hydrogen reduction treatment and a Ca reduction diffusion treatment. The hydrogen reduction treatment is performed at 400 to 600 ° C. for about 1 to 3 hours under a nitrogen atmosphere for the purpose of reducing iron oxide. The Ca reduction treatment is performed at 840 to 1100 ° C. for about 1 to 3 hours in an inert gas such as argon for the purpose of reducing rare earth metal oxides.
In the case of forming N-containing permanent magnet particles, nitriding treatment is performed after Ca reduction diffusion treatment. This nitriding treatment is performed at 350 to 600 ° C. for about 10 to 80 hours under a nitrogen atmosphere of 1 to 8 MPa.
Through the above steps, the desired permanent magnet particles are obtained. Then, in order to produce a permanent magnet using the particles for permanent magnet produced above, in the case of producing a sintered magnet, after granulating and molding the particles for permanent magnet, under an Ar atmosphere condition at 800 to 1100 ° C. And sintered for 1 to 3 hours to obtain a sintered magnet as a final product. In the case of producing a bonded magnet, a binder resin as a final product is obtained by adding a binder resin to the permanent magnet particles produced above and performing molding. In this case, an epoxy resin, a nylon resin or an acrylic resin can be preferably used as the binder resin. As a molding method, a method such as compression molding, injection molding, or extrusion molding can be used.
[0025]
As described above, the magnetic fine particles of the present invention have been described using permanent magnet particles as an example. However, the magnetic fine particles of the present invention can be used not only for magnetic shielding materials but also for magnetic fluids, and can be used for applications such as micromachines.
[0026]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
[0027]
Example 1
As a method for producing inclusion particles, a method using a water-in-oil (w / o) microemulsion was used to produce particles for permanent magnets as follows.
First, cyclohexane (C 6 H 12 ) And using polyethylene glycol mono-4-nonylphenyl ether (C 9 H 19 -C 6 H 4 − (OC 2 H 4 ) n OH, n = 5) to prepare a solvent / surfactant solution (0.5 mol / l, 500 ml). In addition, an aqueous solution of a salt of a metal raw material contains iron chloride (FeCl 2). 2 ), Cobalt chloride (CoCl 2 ), Samarium chloride (SmCl 3 ) Was used (molar ratio of (Co + Fe) / Sm = (17/2)).
Next, 9 ml of a 0.6 mmol / l aqueous solution of iron chloride, 1 ml of a 0.6 mmol / l aqueous solution of cobalt chloride, and 5.8 ml of a 0.12 mmol / l samarium chloride solution were added dropwise to a surfactant / organic solvent solution. A water-in-oil (w / o) microemulsion was formed. To this microemulsion solution, 1.5 ml of aqueous ammonia, which is a fine particle forming agent, is added dropwise and stirred for 1 hour to form ultrafine particles of rare earth metal and transition metal hydroxide in the core aqueous phase of the water-in-oil type microemulsion. I let it.
Thereafter, the fine particles were collected by centrifugation, washed with propanol, and dried (80 ° C., 10 hours) and calcined with air (500 ° C., 2 hours) to remove the organic solvent and the surfactant. Then, firing treatment (in air, Tc = 800 ° C., 2 hours), hydrogen reduction treatment (500 ° C., 2 hours), Ca reduction diffusion treatment (850 ° C. in argon, 10 hours), nitriding treatment (600 ° C., 1 hour) ) In order to obtain a hard magnetic phase (Sm2 (Co1Fe9) N3 [stoichiometric ratio]: Sm having a width of 30 nm and a length of 200 nm) 13.3 (Co 6.7 Fe 60.0 ) N 20 [Atomic ratio]) has a soft magnetic phase (Fe9Co1 [stoichiometric ratio]: Fe) having a thickness of 15 nm. 90 Co 10 [Atomic ratio]) was prepared.
Next, the permanent magnet particles obtained above were molded by a magnet molding machine and sintered (850 ° C., 10 hours) to produce a sintered magnet.
The above procedure is schematically shown in FIG.
[0028]
The shape of the particles for permanent magnet produced above was observed with a scanning electron microscope. FIG. 3 shows the particle size distribution as the observation result. FIG. 3 shows the particle size distribution of the permanent magnet particles (conventional example) produced by the vapor deposition method for comparison.
The magnetic properties (remanence (Br), coercive force (Hcj), and maximum energy product (BHmax)) of the sintered magnet prepared above were measured using a vibrating sample magnetometer. Table 1 shows the results.
[Table 1]
Example 2
In Example 1, iron chloride (FeCl 2 ), Cobalt chloride (CoCl 2 ), Samarium chloride (SmCl 3 The particles for permanent magnets and the sintered magnets were prepared in the same manner except that the (Co + Fe) / Sm molar ratio of the aqueous metal source salt solution was changed from 5.0 to 12.0. Table 2 shows these magnetic properties.
[Table 2]
Example 3
In Example 1, particles for permanent magnets and sintered magnets were produced in the same manner except that the temperature of the Ca reduction diffusion treatment was varied from 600 to 1100 ° C. Table 3 shows these magnetic properties.
[Table 3]
Example 4
In Example 1, permanent magnet particles and sintered magnets were produced in the same manner except that the temperature of the nitriding treatment was varied from 400 to 750 ° C. Table 4 shows these magnetic properties.
[Table 4]
Example 5
Particles for permanent magnets were prepared as follows by using a method using a water-in-oil (w / o) microemulsion as a method for preparing inclusion fine particles.
First, cyclohexane (C 6 H 12 ) And using polyethylene glycol mono-4-nonylphenyl ether (C 9 H 19 -C 6 H 4 − (OC 2 H 4 ) n OH, n = 5) to prepare a solvent / surfactant solution (0.5 mol / l, 500 ml). In addition, an aqueous solution of a salt of a metal raw material contains iron chloride (FeCl 2). 2 ), Cobalt chloride (CoCl 2 ), Neodymium chloride (NdCl 3 ), Boron chloride (B 2 Cl 2 ) Was used (molar ratio of (Co + Fe) / Nd = 8).
Next, 10 ml of a 0.6 mmol / l iron chloride aqueous solution, 1.2 ml of a 0.12 mmol / l cobalt chloride aqueous solution, 9.7 ml of a 0.12 mmol / l neodymium chloride solution, and 1 ml of a 0.6 mmol / l boron chloride aqueous solution were added. Drops were added into the surfactant / organic solvent solution to form a water-in-oil (w / o) microemulsion. 1.5 ml of aqueous ammonia, which is a fine particle forming agent, is dropped into this microemulsion solution and stirred for 1 hour to form ultrafine particles of rare earth metal and transition metal hydroxide in the core aqueous phase of the water-in-oil microemulsion. I let it.
Thereafter, the fine particles were collected by centrifugation, washed with propanol, and dried (80 ° C., 10 hours) and calcined with air (500 ° C., 2 hours) to remove the organic solvent and the surfactant. Then, a firing process (in air, Tc = 800 ° C., 2 hours), a hydrogen reduction process (500 ° C., 2 hours), and a Ca reduction diffusion process (850 ° C. in argon, 10 hours) are sequentially performed to obtain a width of 30 nm and a length of 30 nm. 200 nm hard magnetic phase (Nd2Fe14B1 [stoichiometric ratio]: Nd 11.8 Fe 82.3 B 5.9 [Atomic ratio]), a soft magnetic phase (Fe9Co1 [stoichiometric ratio]: Fe) having a thickness of 15 nm 90 Co 10 [Atomic ratio]) was prepared.
Next, the particles for permanent magnet obtained above were molded by a magnet molding machine and sintered (850 ° C., 2 hours) to produce a sintered magnet.
[0033]
The magnetic properties (residual magnetism (Br), coercive force (Hcj), and maximum energy product (BHmax)) of the sintered magnet produced above were measured with a vibrating sample magnetometer. Table 5 shows the results.
[Table 5]
Example 6
The permanent magnet particles obtained in Example 1 were mixed with an epoxy resin (manufactured by Nippon Pernox Co., Ltd.) at a weight ratio of 98: 2, and then molded into a ring shape to produce a bonded magnet. The magnetic properties of this bonded magnet were measured in the same manner as described above. Table 6 shows the results.
[Table 6]
Example 7
An epoxy resin (manufactured by Nippon Pernox Co., Ltd.) was mixed with the permanent magnet particles obtained in Example 5 at a weight ratio of 98: 2, and then molded into a ring shape to produce a bonded magnet. The magnetic properties of this bonded magnet were measured in the same manner as described above. Table 6 shows the results.
Further, the characteristic distribution when 20 bonded magnets were produced by the method of Example 7 and the mixture of Nd powder, B powder, and needle-shaped iron powder in the conventional example were reduced in a reducing gas atmosphere containing hydrogen, Further, Table 7 shows a comparison of characteristic distributions when 20 bonded magnets were produced from powders heat-treated in an argon gas (850 ° C. for 2 hours). As is clear from Table 7, it was confirmed that the example of the present invention (Example 7) had no variation in characteristics as compared with the conventional example.
[Table 7]
【The invention's effect】
According to the particles for a permanent magnet of the present invention, the maximum energy product (470 kJ / m in the case of a sintered magnet) is larger than that of a conventional permanent magnet. 3 Larger, 239 kJ / m for bonded magnets 3 Larger) can be provided. Further, since the permanent magnet particles of the present invention have an inclusion structure in which one of the hard magnetic phase and the soft magnetic phase that does not form a solid solution with each other covers the other surface, the hard magnetic phase and the soft magnetic phase A magnet with uniform and stable magnetic properties can be provided.
In addition, according to the method for producing particles for permanent magnets of the present invention, one has a hard magnetic phase and a soft magnetic phase which have a larger maximum energy product than conventional permanent magnets and do not form a solid solution with each other. The coated permanent magnet particles of the inclusion type can be produced, and the permanent magnet produced using the permanent magnet particles has a larger maximum energy product (470 kJ / m in the case of a sintered magnet) than a conventional permanent magnet. 3 Larger, 239 kJ / m for bonded magnets 3 And a hard magnetic phase and a soft magnetic phase are uniform, and a magnet having stable magnetic properties can be provided. In addition, since a magnet having desired magnetic properties can be obtained stably, productivity is increased, and there are advantages that the shape of the magnet is less restricted and the range of application is expanded.
Further, the permanent magnet of the present invention has a larger maximum energy product (470 kJ / m in the case of a sintered magnet) than a conventional permanent magnet. 3 Larger, 239 kJ / m for bonded magnets 3 Larger), the hard magnetic phase and the soft magnetic phase are uniform and the magnetic properties are stable. Further, the magnetic fine particles according to the present invention can be used not only for magnetic shields but also for magnetic fluids, and can be applied to uses such as micromachines.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing the structure of particles for a permanent magnet according to the present invention.
FIG. 2 is a view showing a process of manufacturing a permanent magnet according to the present invention.
FIG. 3 is a view showing a particle size distribution of particles for a permanent magnet produced in Example 1.
FIG. 4 is a view showing a conventional method for producing particles for permanent magnets.
Claims (14)
界面活性剤と有機溶媒の溶液中に、遷移金属塩化物の水溶液と希土類金属塩化物と塩化ホウ素の水溶液を滴下し、油中水滴型マイクロエマルションを形成する工程と、
微粒子形成剤を滴下することにより微粒子を形成させる工程と、
上記工程で形成した微粒子に対し、水素還元処理及びＣａ還元処理を順次施す工程とからなることを特徴とする永久磁石用粒子の製造方法。The hard magnetic phase and the soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. Fine particles having an inclusion structure as an inclusion portion to be included, wherein the hard magnetic phase is an alloy having a composition of R-Fe-B (R is at least one of rare earth metal elements); A method for producing particles for permanent magnets, wherein the magnetic phase is Fe, Fe-M (M is at least one of transition metals) or an alloy having an Fe-N composition,
A step of dropping an aqueous solution of a transition metal chloride, an aqueous solution of a rare earth metal chloride and boron chloride into a solution of a surfactant and an organic solvent, and forming a water-in-oil microemulsion;
A step of forming fine particles by dropping a fine particle forming agent,
A method of sequentially performing a hydrogen reduction treatment and a Ca reduction treatment on the fine particles formed in the above step, characterized by comprising:
界面活性剤と有機溶媒の溶液中に、遷移金属塩化物の水溶液と希土類金属塩化物の水溶液を滴下し、油中水滴型マイクロエマルションを形成する工程と、
微粒子形成剤を滴下することにより微粒子を形成させる工程と、
上記工程で形成した微粒子に対し、水素還元処理、Ｃａ還元処理及び窒化処理を順次施す工程とからなることを特徴とする永久磁石用粒子の製造方法。The hard magnetic phase and the soft magnetic phase have a composite structure, and are composed of a hard magnetic phase and a soft magnetic phase that do not form a solid solution with each other. Fine particles having an inclusion structure as an inclusion portion to be included, wherein the hard magnetic phase is an alloy having a composition of R-Fe-N (R is at least one of rare earth metal elements); A method for producing particles for permanent magnets, wherein the magnetic phase is Fe-MN (M is at least one of transition metals) or an alloy having an Fe-N composition,
A step of dropping an aqueous solution of a transition metal chloride and an aqueous solution of a rare earth metal chloride in a solution of a surfactant and an organic solvent to form a water-in-oil microemulsion,
A step of forming fine particles by dropping a fine particle forming agent,
A process of sequentially performing a hydrogen reduction treatment, a Ca reduction treatment, and a nitridation treatment on the fine particles formed in the above step, wherein the method comprises the steps of:
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| JP2004363474A (en) * | 2003-06-06 | 2004-12-24 | Yaskawa Electric Corp | Method for producing particles for permanent magnet |
| JP2006179617A (en) * | 2004-12-21 | 2006-07-06 | Yaskawa Electric Corp | Permanent magnet and method for manufacturing the same |
| WO2008065539A2 (en) | 2006-11-29 | 2008-06-05 | Toyota Jidosha Kabushiki Kaisha | Production method for nanocomposite magnet |
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| JP2004363474A (en) * | 2003-06-06 | 2004-12-24 | Yaskawa Electric Corp | Method for producing particles for permanent magnet |
| JP2006179617A (en) * | 2004-12-21 | 2006-07-06 | Yaskawa Electric Corp | Permanent magnet and method for manufacturing the same |
| WO2008053371A3 (en) * | 2006-11-01 | 2008-07-17 | Toyota Motor Co Ltd | Production method for nanocomposite magnet |
| US7976643B2 (en) | 2006-11-29 | 2011-07-12 | Toyota Jidosha Kabushiki Kaisha | Production method for nanocomposite magnet |
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