JP4734521B2 - Metallic magnetic powder and method for producing the same - Google Patents
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Description
本発明は、飽和磁化が高く軟質磁気特性に優れた金属磁性粉末、およびその製造法に関する。 The present invention relates to a metal magnetic powder having high saturation magnetization and excellent soft magnetic properties, and a method for producing the same.
従来、ポリオールによる還元反応を利用した方法（以下「ポリオール法」という）によってＦｅ−Ｐｔ系、Ｃｏ−Ｐｔ系、Ｆｅ−Ｃｏ−Ｐｔ系等の合金微粉末を合成する手法が知られている（特許文献１、２）。これらの方法によると、粒径が例えば２０ｎｍ以下のナノ粒子が得られ、その保磁力も高いことから、超高密度磁気記録媒体に好適な磁性粉が得られる。 Conventionally, there has been known a method of synthesizing Fe-Pt-based, Co-Pt-based, Fe-Co-Pt-based and other alloy fine powders by a method using a reduction reaction with polyol (hereinafter referred to as "polyol method") ( Patent Documents 1 and 2). According to these methods, nanoparticles having a particle size of, for example, 20 nm or less are obtained, and the coercive force thereof is high, so that magnetic powder suitable for an ultra-high density magnetic recording medium can be obtained.
一方、Ｆｅと遷移金属（Ｃｏ等）との合金は、本来、低保磁力、高透磁率を呈する軟磁性合金として優れた特性を有することが知られている。これは、磁気記録媒体等の高保磁力が要求される硬磁性用途とは異なり、磁気ヘッド、電磁石の鉄心、トランスコア、電磁気シールド材といった軟磁性用途に適するものである。 On the other hand, it is known that an alloy of Fe and a transition metal (Co or the like) originally has excellent characteristics as a soft magnetic alloy exhibiting a low coercive force and a high magnetic permeability. This is suitable for soft magnetic applications such as a magnetic head, an iron core of an electromagnet, a transformer core, and an electromagnetic shield material, unlike a hard magnetic application that requires a high coercive force such as a magnetic recording medium.
しかしながら、上記Ｆｅと遷移金属との合金は、微粉末の状態で優れた軟磁気特性を呈するものを実現することは容易ではなく、粒径が５００ｎｍ以下の微粉末としては実用化されるには至っていない。その大きな要因の１つに、微粉末において高い飽和磁化を実現することが困難であったことが挙げられる。
本発明は、Ｆｅを主体とする磁性合金の微粉末において、飽和磁化が高く、優れた軟質磁気特性を呈するものを提供しようというものである。
However, it is not easy to realize an alloy of Fe and transition metal that exhibits excellent soft magnetic properties in a fine powder state, and it is not practical to use as a fine powder having a particle size of 500 nm or less. Not reached. One of the major factors is that it was difficult to achieve high saturation magnetization in the fine powder.
The present invention intends to provide a fine powder of a magnetic alloy mainly composed of Fe that has high saturation magnetization and exhibits excellent soft magnetic properties.
発明者らは種々検討の結果、ポリオール法でＦｅ合金微粉を合成する際に、溶媒および還元剤となるポリオールを１００℃以上の温度域で予め十分に脱酸素処理したのちに金属塩を投入し、還元することにより、飽和磁化の高い合金粉末が合成できることを見出した。 As a result of various studies, the inventors of the present invention, when synthesizing fine powders of Fe alloy by the polyol method, put a metal salt after sufficiently deoxidizing the solvent and polyol as a reducing agent in a temperature range of 100 ° C. or higher. It has been found that an alloy powder with high saturation magnetization can be synthesized by reduction.
すなわち本発明では、ＦｅX Ｃｏ 1-X（ただし、Ｘ：０.３５〜０.８５）の組成を有する平均粒子径ＤM：１４１.８〜２７１.３ｎｍの金属磁性粉であって、不活性ガスを吹き込みながら１００℃以上まで昇温し、脱酸素・脱水処理を施したポリオール溶媒に、できあがる金属磁性粉のＦｅとＣｏの原子比が１：（１−Ｘ）、ただしＸ：０.３５〜０.８５、となるようにこれらの元素を含む金属塩を投入し、その金属塩を溶媒のポリオールで１００℃以上の温度に保持することにより還元する手法で析出させた、保磁力Ｈｃが４００ Ｏｅ以下、飽和磁化σｓが１２０ｅｍｕ／ｇ以上、角形比σｒ／σｓが０.２０以下であり、さらに好ましくは耐候性Δσｓが４０％以下である金属磁性粉が提供される。
また、本発明では粉体粒子の形状が球状ないし多角形状であり、整粒性の高い金属磁性粉が提供される。すなわち、粉体を構成する粒子の平均アスペクト比が２.０以下であるもの、あるいはさらに、粉体を構成する粒子の８０個数％以上が、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲の粒径を有するものが提供される。
That is, in the present invention, it is a metal magnetic powder having an average particle diameter D M : 141.8 to 271.3 nm having a composition of Fe X Co 1-X ( where X: 0.35 to 0.85), While the inert gas is being blown in, the temperature is raised to 100 ° C. or higher, and the atomic ratio of Fe to Co in the resulting metal magnetic powder is 1: (1-X) in the polyol solvent subjected to deoxygenation / dehydration treatment, where X: 0 A coercive force deposited by a technique of reducing a metal salt containing these elements so as to be .35 to 0.85, and maintaining the metal salt at a temperature of 100 ° C. or higher with a solvent polyol. Provided is a metal magnetic powder having Hc of 400 Oe or less, saturation magnetization σs of 120 emu / g or more, squareness ratio σr / σs of 0.20 or less, more preferably weather resistance Δσs of 40% or less.
In addition, the present invention provides a metal magnetic powder having powder particles having a spherical or polygonal shape and high particle size control. That is, particles having an average aspect ratio of 2.0 or less, or more than 80% by number of particles constituting the powder, having an average particle diameter D M × 0.5 or more, Those having a particle size in the range of diameter D M × 2 or less are provided.
ここで、平均粒子径ＤMおよび平均アスペクト比は、ＴＥＭ（透過型電子顕微鏡）またはＳＥＭ（走査型電子顕微鏡）により観察される粉末粒子の画像において、任意に選んだ１００個以上の粒子の粒径（長径および短径）を測定することによって求められる。各粒子の粒径は画像上に現れる長径および短径を測定して求める。例えば画像をプリントアウトした写真上でノギスまたはデジタイザーによって粒径を測定する方法が採用できる。平均粒子径ＤMは各測定粒子の長径を算術平均したものである。各粒子のアスペクト比は長径／短径の値（１が最小）で表され、平均アスペクト比は各測定粒子のアスペクト比を算術平均したものである。 Here, the average particle diameter DM and the average aspect ratio are particles of 100 or more particles arbitrarily selected in an image of powder particles observed by a TEM (transmission electron microscope) or SEM (scanning electron microscope). It is determined by measuring the diameter (major axis and minor axis). The particle size of each particle is determined by measuring the major axis and minor axis appearing on the image. For example, a method of measuring the particle diameter with a caliper or a digitizer on a photograph in which an image is printed out can be adopted. The average particle diameter D M is obtained by the arithmetic mean of the major axis of each particle measured. The aspect ratio of each particle is represented by a value of major axis / minor axis (1 is minimum), and the average aspect ratio is an arithmetic average of the aspect ratios of the respective measured particles.
本発明では特に、この金属磁性粉において、不純物としてフェライトを含まないものが提供される。
ここで「フェライトを含まない」とは、当該粉末のＸ線回折パターンにおいてフェライトの存在が確認されないことをいう。極めて微量のフェライトが含まれているとしても、その回折ピークがノイズに埋もれて判別できない場合は、「フェライトを含まない」に該当する。ここでいうフェライトとは、マグネタイト、Ｃｏフェライト、Ｎｉフェライト等、原料塩から生成されうるフェライトを含み、これらの混在する状態のものをも含む。
In the present invention, in particular, this metal magnetic powder is provided which does not contain ferrite as an impurity.
Here, “not containing ferrite” means that the presence of ferrite is not confirmed in the X-ray diffraction pattern of the powder. Even if a very small amount of ferrite is contained, if the diffraction peak is buried in noise and cannot be discriminated, it corresponds to “does not contain ferrite”. Here, the ferrite includes ferrite that can be generated from a raw material salt, such as magnetite, Co ferrite, and Ni ferrite, and also includes those in a state where these are mixed.
また本発明では、これらの金属磁性粉の製造法として、不活性ガスを吹き込みながら１００℃以上まで昇温し、脱酸素・脱水処理を施したポリオール溶媒に、できあがる金属磁性粉のＦｅとＣｏの原子比が１：（１−Ｘ）、ただしＸ：０.３５〜０.８５、となるようにこれらの元素を含む金属塩を投入し、その金属塩を溶媒のポリオールで１００℃以上の温度に保持することにより還元して合金粒子を析出させる製造法が提供される。
ここで、還元反応に伴って生成する水の少なくとも一部を溶媒中から除去しながら還元を進行させることが好ましい。例えば一旦蒸発した水ができるだけ溶媒中に戻らないように分離・除去する手法が採用できる。
不活性ガスは、希ガスおよび窒素ガスをいう。Ｆｅの原料には２価の鉄塩を用いることが、フェライトの生成を抑止する上で極めて有効である。
Also, in the present invention, as a method for producing these metal magnetic powders, the temperature of the metal magnetic powder is increased to 100 ° C. or higher while blowing an inert gas, and the resulting metal magnetic powder Fe and Co are added to the deoxidized / dehydrated polyol solvent. A metal salt containing these elements is added so that the atomic ratio is 1: (1-X), where X is from 0.35 to 0.85, and the metal salt is heated to 100 ° C. or higher with a polyol as a solvent. A production method is provided in which the alloy particles are reduced by being held in a reduced state.
Here, it is preferable to proceed the reduction while removing at least a part of the water produced by the reduction reaction from the solvent. For example, a method of separating and removing water so that water once evaporated is not returned to the solvent as much as possible can be adopted.
Inert gas refers to noble gas and nitrogen gas. Use of a divalent iron salt as a raw material for Fe is extremely effective in suppressing the formation of ferrite.
本発明によれば、飽和磁化の高い合金磁性粉末が提供された。この粉末は、アスペクト比が２.０以下と粒子の形状異方性が小さく、また、粉砕により作製した粒子のように角張っておらず、球状ないしは多角形状の滑らかな表面をもち、整粒性も高い。本発明の金属磁性粉は以下のような用途への適用が期待される。
i) ＭＨｚ〜ＧＨｚの広帯域で使用可能な電波吸収体。
ii) 分子やＤＮＡの分離技術。すなわち、磁気を利用して当該磁性粒子の周囲に特定の分子をくっつけ、この分子と反応性の高い分子やＤＮＡなどを分離する。
iii) 温熱治療。すなわち、体内の病理組織（癌細胞など）の周囲に当該磁性粒子をドーピングし、外部から振動磁界を付与して磁性粒子を発熱させ、その病理組織を死滅させてしまう。
According to the present invention, an alloy magnetic powder having a high saturation magnetization is provided. This powder has an aspect ratio of 2.0 or less and small particle shape anisotropy, and is not angular like particles produced by pulverization, has a smooth spherical or polygonal surface, and has a grain-sizing property. Is also expensive. The metal magnetic powder of the present invention is expected to be applied to the following uses.
i) An electromagnetic wave absorber that can be used in a wide band from MHz to GHz.
ii) Molecular and DNA separation technology. That is, a specific molecule is attached around the magnetic particle by using magnetism, and a molecule or DNA having high reactivity with this molecule is separated.
iii) Hyperthermia. That is, the magnetic particles are doped around a pathological tissue (such as cancer cells) in the body, and an oscillating magnetic field is applied from the outside to cause the magnetic particles to generate heat and kill the pathological tissue.
発明者らの詳細な検討によれば、合金粉末を合成するためのポリオール法において、金属塩をポリオールで還元する前に、予めポリオール中に含まれる溶存酸素と水分を十分除去しておくと、飽和磁化の高い金属磁性粉が得られることがわかった。その理由については未解明の部分も多いが、溶媒中の溶存酸素や水分が少ない状態で金属塩を還元したとき、析出後に分離・抽出された合金粉中への不純物フェライトの混入が顕著に防止されるという現象が見られた。この現象は、１００℃以上の温度域での脱酸素・脱水処理を予め施していないポリオールを溶媒に用いて還元する従来一般的な方法では起こらない。すなわち、従来一般的なポリオール法では不純物としてフェライトの混入が避けられなかったが、予め１００℃以上の温度域で脱酸・脱水素処理したのち還元反応を開始するとフェライトが検出されない合金粉が得られるのである。このことが飽和磁化の改善に大きく寄与しているものと推察される。 According to the inventors' detailed examination, in the polyol method for synthesizing the alloy powder, before reducing the metal salt with the polyol, the dissolved oxygen and moisture contained in the polyol are sufficiently removed in advance. It was found that metallic magnetic powder with high saturation magnetization can be obtained. There are many unexplained reasons for this, but when metal salts are reduced with a low amount of dissolved oxygen and moisture in the solvent, the inclusion of impurity ferrite in the alloy powder separated and extracted after precipitation is significantly prevented. The phenomenon that was done was seen. This phenomenon does not occur in a conventional general method in which a polyol that has not been previously subjected to deoxygenation / dehydration treatment in a temperature range of 100 ° C. or higher is used as a solvent. That is, in the conventional polyol method, the inclusion of ferrite as an impurity was unavoidable, but when deoxidation / dehydrogenation treatment was performed in a temperature range of 100 ° C. or higher in advance, an alloy powder in which ferrite was not detected was obtained. It is done. This is presumed to have contributed greatly to the improvement of saturation magnetization.
以下、本発明を特定するための事項について説明する。
〔組成〕
本発明の合金粉末は原子比でＦｅX Ｃｏ 1-Xの組成をもつ。
Hereinafter, matters for specifying the present invention will be described.
〔composition〕
The alloy powder of the present invention has a composition of Fe x Co 1-x by atomic ratio .
Ｆｅの原子比を表すＸは０.３５〜０.８５の範囲とする。Ｘがこの範囲を外れると保磁力Ｈｃを４００ Ｏｅ以下、飽和磁化を安定して１２０ｅｍｕ／ｇ以上に安定して向上させること、角形比σｒ／σｓが０.２以下の軟磁気特性を安定して得ること、あるいはさらに耐候性Δσｓを４０％以下に安定して改善することが難しくなる。 X representing the atomic ratio of Fe is in the range of 0.35 to 0.85. When X is out of this range, the coercive force Hc is 400 Oe or less, the saturation magnetization is stably improved to 120 emu / g or more, and the soft magnetic characteristics having a squareness ratio σr / σs of 0.2 or less are stabilized. Or further improving the weather resistance Δσs stably to 40% or less.
〔平均粒子径、アスペクト比〕
平均粒子径ＤMは５〜５００ｎｍの範囲をとることができるが、高密度磁気記録媒体の場合とは異なり、磁性粒子の粒径を特に小さくする必要はない。本発明ではＤ M が１４１.８〜２７１.３ｎｍのものを対象とする。また、平均アスペクト比は２.０以下であることが好ましい。さらに、粉体を構成する粒子のＤMのバラツキが小さいこと、すなわち整粒性が高いことが望ましく、具体的には、粉体を構成する粒子の８０個数％以上が、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲の粒径を有するものが好ましい対象となる。粉体を構成する粒子の９５個数％以上が、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲の粒径を有するものが一層好ましい対象となる。
平均粒子径ＤMは、核剤や界面活性剤といった添加物の種類および添加量を制御することによってコントロール可能である。平均アスペクト比や整粒性は、後述の製造法を実施することによって適正化される。
[Average particle size, aspect ratio]
The average particle diameter D M can range from 5 to 500 nm, unlike the case of a high-density magnetic recording medium is not particularly necessary to reduce the particle size of the magnetic particles. In the present invention directed to what D M is 141.8～271.3Nm. The average aspect ratio is preferably 2.0 or less. Further, variation in the D M of the particles constituting the powder is small, that it is desirable high sizing property, specifically, more than 80% by number of the particles constituting the powder, the average particle diameter D M Those having a particle size in a range of × 0.5 or more and an average particle size D M × 2 or less are preferable targets. More preferably, 95% by number or more of the particles constituting the powder have a particle size in the range of the average particle size D M × 0.5 or more and the average particle size D M × 2 or less.
The average particle diameter D M can be controlled by controlling the kind and amount of additives such as nucleating agent or a surfactant. The average aspect ratio and grain size are optimized by carrying out the manufacturing method described later.
〔磁気特性〕
粉末としての磁気特性はＶＳＭを用いて最大印加磁場強度１０ｋＯｅをかけ、従来一般的な方法で測定することができる。磁気特性の測定温度は特に断らない限り室温とする。
本発明の合金粉は、飽和磁化σｓが１２０ｅｍｕ／ｇ以上を呈するものである。飽和磁化σｓの上限は特に規定されないが、前記i)〜iii)の用途では概ね１２０〜２５０ｅｍｕ／ｇの範囲で良好な結果が得られ、１５０ｅｍｕ／ｇ以上とするのが一層好ましい。飽和磁化σｓは、組成を前述のようにするとともに、フェライトの混入防止を図ることによって１２０ｅｍｕ／ｇ以上にコントロールできる。
[Magnetic properties]
The magnetic properties as a powder can be measured by a conventional method using a VSM with a maximum applied magnetic field strength of 10 kOe. Unless otherwise specified, the magnetic property measurement temperature is room temperature.
The alloy powder of the present invention has a saturation magnetization σs of 120 emu / g or more. Although the upper limit of the saturation magnetization σs is not particularly defined, good results are generally obtained in the range of 120 to 250 emu / g in the applications i) to iii), and more preferably 150 emu / g or more. The saturation magnetization σs can be controlled to 120 emu / g or more by setting the composition as described above and preventing ferrite from being mixed.
保磁力については、あまり大きいと軟磁気特性を阻害するので、４００ Ｏｅ以下に抑えることが望ましい。特に良好な軟磁気特性が要求される用途では２００ Ｏｅ以下あるいはさらに１００ Ｏｅ以下にすることが一層好ましい。角形比（＝残留磁化／飽和磁化）は０.０５〜０.２程度とすることができる。金属塩濃度や還元温度、時間、添加物量などのプロセスパラメータによってコントロールすることができる。 As for the coercive force, if it is too large, the soft magnetic properties are hindered. In applications where particularly good soft magnetic properties are required, it is even more preferable to make it 200 Oe or less, or even 100 Oe or less. The squareness ratio (= residual magnetization / saturation magnetization) can be about 0.05 to 0.2. It can be controlled by process parameters such as metal salt concentration, reduction temperature, time, and additive amount.
耐候性を示す指標として、Δσｓを用いる。この指標は、粉体作製直後に測定した飽和磁化σｓ（０日目）と、温度６０℃、湿度９０％の雰囲気に７日間暴露した後に測定した飽和磁化σｓ（７日目）の値から次式により定められる。
Δσｓ（％）＝｛σｓ（０日目）−σｓ（７日目）｝／σｓ（０日目）×１００
Δσｓについては、その値が大きいと、使用中に時間の経過とともに酸化により飽和磁化σｓが小さくなってしまい、状況によっては金属粉が発火してしまうこともある。前記の用途を考慮したとき、Δσｓは４０％以下であることが望ましく、３０％以下がより好ましく、２０％以下が一層好ましい。このΔσｓは、金属粉を徐酸化することにより酸化被膜を形成することや、無機物・有機物をコーティングすることによって、コントロールすることができる。
Δσs is used as an indicator of weather resistance. This index is calculated from the values of the saturation magnetization σs (day 0) measured immediately after the production of the powder and the saturation magnetization σs (day 7) measured after exposure to an atmosphere at a temperature of 60 ° C. and a humidity of 90% for 7 days. It is determined by the formula.
Δσs (%) = {σs (day 0) −σs (day 7)} / σs (day 0) × 100
With respect to Δσs, if the value is large, the saturation magnetization σs becomes small due to oxidation over time during use, and the metal powder may ignite depending on the situation. In consideration of the above applications, Δσs is desirably 40% or less, more preferably 30% or less, and even more preferably 20% or less. This Δσs can be controlled by forming an oxide film by gradually oxidizing the metal powder, or by coating an inorganic or organic substance.
〔製造法〕
本発明においては、ポリオールを予め１００℃以上の温度域で脱酸素処理しておくことを除き、基本的にはポリオール中で金属塩を還元して合金を析出させ、これを分離抽出する従来のポリオール法の手順が採用できる。
[Production method]
In the present invention, except that the polyol is previously deoxygenated in a temperature range of 100 ° C. or higher, basically, a metal salt is reduced in the polyol to precipitate an alloy, and this is separated and extracted. The polyol method procedure can be employed.
ポリオールは複数の水酸基を有する有機物質であり、多価アルコールとも言われる。その代表的なものとしてエチレングリコールが挙げられる。また、ポリオールの誘導体を溶媒に使用することもできる。本発明では、その誘導体もポリオールとして取り扱う。 A polyol is an organic substance having a plurality of hydroxyl groups, and is also called a polyhydric alcohol. A typical example is ethylene glycol. A polyol derivative can also be used as a solvent. In the present invention, the derivative is also handled as a polyol.
まず、ポリオールを脱酸素・脱水処理する。この処理は、ポリオールに不活性ガスを吹き込みながら１００℃以上まで昇温を行い、さらに、１００℃以上の温度で、所定の時間（例えば２０ｍｉｎ以上）保持することにより、実施される。不活性ガスによるバブリング自体で攪拌効果が得られるが、機械的攪拌を兼用することが望ましい。ただし、特段の強攪拌は必要ない。不活性ガスの吹き込みおよび攪拌は、常温からの昇温過程で既に開始することができる。還元温度は使用する溶媒の沸点以下で実施する。沸点以上では、耐圧容器等特殊な反応設備を必要とし、不経済である。 First, the polyol is deoxygenated and dehydrated. This treatment is performed by raising the temperature to 100 ° C. or higher while blowing an inert gas into the polyol, and further holding the temperature at 100 ° C. or higher for a predetermined time (for example, 20 min or longer). Although bubbling with an inert gas itself can provide a stirring effect, it is desirable to combine mechanical stirring. However, special strong stirring is not necessary. Blowing and stirring of the inert gas can already be started in the process of raising the temperature from room temperature. The reduction temperature is carried out below the boiling point of the solvent used. Above the boiling point, special reaction equipment such as a pressure vessel is required, which is uneconomical.
次いで、１００℃以上の温度域で脱酸素処理したポリオール中に金属塩を投入する。Ｆｅを含む金属塩と、Ｃｏを含む金属塩を、できあがる金属磁性粉のＦｅとＭ成分の原子比が１：（１−Ｘ）、ただしＸ：０.３５〜０.８５、となるように投入する。反応条件にもよるが、例えば、標準電極電位の低い金属は還元されにくく液中に残りやすい傾向があるので、標準電極電位の低い金属の添加割合を目標組成に対し多めにすると良好な結果が得られやすい。Ｆｅを含む金属塩としては例えば塩化第一鉄が挙げられ、Ｃｏを含む金属塩としては例えば酢酸コバルトが挙げられる。Ｆｅの原料に関しては３価の金属塩より２価の金属塩を採用する方が還元速度の向上およびマグネタイト等の酸化物の生成抑制に効果的である。金属塩の濃度は、ＦｅとＣｏの総量が０.０２〜０.１ｍｏｌ／Ｌの範囲になるように調整することが好ましい。また、溶媒に可溶な塩基性物質（ＮａＯＨなど）を投入することで、液中での還元反応速度をコントロールすることができる。添加する塩基性物質は、ＯＨ濃度で０.５〜１０ｍｏｌ／Ｌとすることが好ましい。そうすることにより、軟磁気特性に優れた粒子を合成することができる。 Next, a metal salt is charged into the polyol deoxidized in a temperature range of 100 ° C. or higher. A metal salt containing Fe and a metal salt containing Co so that the atomic ratio of Fe to M component in the resulting metal magnetic powder is 1: (1-X), where X is 0.35 to 0.85. throw into. Depending on the reaction conditions, for example, metals with a low standard electrode potential tend to be less likely to be reduced and remain in the liquid. Easy to obtain. The metal salt containing Fe example include ferrous chloride, as a metal salt containing Co e.g. cobalt acetate can be mentioned up. Regarding the Fe raw material, the use of a divalent metal salt over a trivalent metal salt is more effective in improving the reduction rate and suppressing the production of oxides such as magnetite. The concentration of the metal salt is preferably adjusted so that the total amount of Fe and Co is in the range of 0.02 to 0.1 mol / L. In addition, by introducing a basic substance (such as NaOH) that is soluble in a solvent, the reduction reaction rate in the liquid can be controlled. The basic substance to be added is preferably 0.5 to 10 mol / L in terms of OH concentration. By doing so, it is possible to synthesize particles having excellent soft magnetic properties.
金属塩（必要に応じてさらに塩基性物質）投入時のポリオール温度は９０℃以上とすることが望ましい。通常は、不活性ガスの吹き込みおよび攪拌を継続しながら金属塩を投入すればよい。還元反応を促進するためには１２０℃以上に昇温することが望ましい。１５０℃以上に昇温することがより好ましい。実際には加熱を継続しながらポリオールの沸点まで昇温していき、その後、還流状態で還元反応を進めるとよい。エチレングリコールの場合、沸点は１９７.６℃である。ただし、沸点が３００℃を超える溶媒の場合は、概ね３００℃前後で還流を行うことが望ましい。還元反応が進行すると合金が析出してくる。投入した金属塩が全量反応し終えるまで還元を続けることが好ましい。金属塩の濃度が上記範囲であるとき、還流状態で概ね２ｈ程度保持すると全量を十分に反応させることができる。 It is desirable that the polyol temperature at the time of charging the metal salt (if necessary, further basic substance) is 90 ° C. or higher. Normally, the metal salt may be added while continuing the blowing and stirring of the inert gas. In order to promote the reduction reaction, it is desirable to raise the temperature to 120 ° C. or higher. It is more preferable to raise the temperature to 150 ° C. or higher. In practice, it is preferable to raise the temperature to the boiling point of the polyol while continuing the heating, and then proceed with the reduction reaction in a reflux state. In the case of ethylene glycol, the boiling point is 197.6 ° C. However, in the case of a solvent having a boiling point exceeding 300 ° C., it is desirable to perform the reflux at about 300 ° C. As the reduction reaction proceeds, an alloy is deposited. It is preferable to continue the reduction until all of the charged metal salt has reacted. When the concentration of the metal salt is within the above range, the total amount can be sufficiently reacted by maintaining about 2 h in the reflux state.
金属塩を添加する前に予め脱水処理を行っても、還元反応に伴って金属塩の結晶水に由来する水や、ポリオールの分解に起因する水が、溶媒中に生じてくる。金属塩の仕込み濃度が低いときには影響が小さいが、前述の脱酸素・脱水処理を行ってもフェライトが生成する場合には、還元中に生成する水も溶媒中より除去することが望ましい。しかし、還元中は還流状態であるため、水は溶媒からいったん蒸発しても再び溶媒中へ戻ってくることになる。このような場合は、反応容器と還流器（冷却器）の途中に、モレキュラーシーブでトラップを作る等の工夫をすることにより、効果的に水の除去が可能である。 Even if the dehydration treatment is performed in advance before adding the metal salt, water derived from the crystal water of the metal salt and water resulting from the decomposition of the polyol are generated in the solvent along with the reduction reaction. Although the influence is small when the charged concentration of the metal salt is low, it is desirable to remove water generated during the reduction from the solvent when ferrite is generated even after the above-described deoxygenation / dehydration treatment. However, since it is in a reflux state during the reduction, water once again evaporates from the solvent and returns to the solvent. In such a case, water can be effectively removed by making a trap with a molecular sieve in the middle of the reaction vessel and the reflux (cooler).
還元終了後、溶液を室温まで冷却する。強制冷却してもよいし、放冷してもよい。その後、析出粒子を洗浄すれば目的の金属磁性粉が得られる。洗浄は、例えば溶媒中の析出粒子を取り出してエタノール等の液中に移し、遠心分離→回収→液中に移す、という操作を繰り返す方法により行うことができる。 After the reduction is complete, the solution is cooled to room temperature. It may be forcedly cooled or allowed to cool. Thereafter, the target metal magnetic powder can be obtained by washing the deposited particles. Washing can be performed, for example, by a method in which the precipitated particles in the solvent are taken out and transferred to a liquid such as ethanol, and the operation of centrifugation → recovery → transfer to the liquid is repeated.
〔実施例１〕
ポリオール法でＦｅ−Ｃｏ合金粒子を合成した。ポリオールとしてエチレングリコール（沸点１９７.６℃）を使用した。Ｆｅ供給源として塩化第一鉄４水和物ＦｅＣｌ2・４Ｈ2Ｏ、Ｃｏ供給源として酢酸コバルト４水和物Ｃｏ(ＣＨ3ＣＯＯ)2・４Ｈ2Ｏを使用した。
まず、溶媒および還元剤として働くエチレングリコール１００ｍＬを還流器のついたガラス容器に入れ、窒素ガスをガラス管により底部付近から吹き込んだ。窒素ガスの吹き込み量は４００ｍＬ／ｍｉｎとした。併せてテフロン（登録商標）攪拌羽根により１６０ｒｐｍの回転速度で液を機械攪拌した。この状態で溶媒を加熱し、液温が１００℃になってから１２０℃になるまでの間、約３０ｍｉｎ、窒素ガスの吹き込みと機械攪拌を継続することにより脱酸素・脱水処理を行った。
[Example 1]
Fe-Co alloy particles were synthesized by the polyol method. Ethylene glycol (boiling point 197.6 ° C.) was used as the polyol. Ferrous chloride tetrahydrate FeCl 2 .4H 2 O was used as the Fe source, and cobalt acetate tetrahydrate Co (CH 3 COO) 2 .4H 2 O was used as the Co source.
First, 100 mL of ethylene glycol serving as a solvent and a reducing agent was put in a glass container equipped with a refluxer, and nitrogen gas was blown from the bottom near the glass tube. The amount of nitrogen gas blown was 400 mL / min. In addition, the liquid was mechanically stirred with a Teflon (registered trademark) stirring blade at a rotation speed of 160 rpm. In this state, the solvent was heated, and from the time when the liquid temperature reached 100 ° C. to 120 ° C., nitrogen gas was blown in and mechanical stirring was continued for about 30 minutes to perform deoxygenation / dehydration treatment.
その後、液温が約１２０℃の状態で上記Ｆｅ塩とＣｏ塩を溶媒中に投入した。Ｆｅ塩とＣｏ塩の量比はＦｅとＣｏの原子比が８０：２０となるように調整し、ＦｅとＣｏの総濃度［Ｍ］が０.０６５ｍｏｌ／Ｌとなる量を投入した。さらに、［Ｍ］に対するＯＨの総濃度［ＯＨ］の比［ＯＨ］／［Ｍ］が４０となるようにＮａＯＨを投入した。この間、容器は還流器のついたガラス容器であるが、脱水のために、還流器（冷却器）には冷却水を流さない。
上記工程終了後、還流器に冷却しを流し、窒素ガスの吹き込みおよび機械攪拌を継続しながら加熱して、１８０℃の状態で還流しながら２ｈ保持し、還元反応させた。析出した粒子は、溶液を室温まで放冷してからエタノール中に移し、遠心分離→回収→エタノール中に移す、という操作を数回繰り返すことにより洗浄し、エタノール中に保管した。
Thereafter, the Fe salt and Co salt were put into a solvent at a liquid temperature of about 120 ° C. The amount ratio of Fe salt to Co salt was adjusted so that the atomic ratio of Fe to Co would be 80:20, and an amount such that the total concentration [M] of Fe and Co would be 0.065 mol / L was added. Further, NaOH was added so that the ratio [OH] / [M] of the total concentration [OH] of OH to [M] was 40. During this time, the container is a glass container with a reflux, but cooling water is not allowed to flow through the reflux (cooler) for dehydration.
After completion of the above steps, cooling was applied to the refluxing device, and heating was continued while blowing nitrogen gas and mechanical stirring, and the reaction was held at refluxing temperature at 180 ° C. for 2 hours for reduction reaction. The precipitated particles were washed by repeating the operation of allowing the solution to cool to room temperature and then transferring it into ethanol and centrifuging → recovery → transfer to ethanol several times, and stored in ethanol.
得られた粉末についてＣｕ−ｋα線によるＸ線回折を行った。そのＸ線回折パターンを図１に示す。ＦｅＣｏ合金（ｆｃｃ構造）の各回折ピークが認められた。また、Ｘ線回折パターンにはフェライトの回折ピークは認められなかった。
この粉末粒子をＳＥＭにより観察し、平均粒子径ＤMを求めた。図２にＳＥＭ像の１例を示す。個々の粒子は球状性の高いものであることがわかる。このようなＳＥＭ像において、任意に選んだ１００個以上の粒子の直径（長径）を測定し、その平均値を算出することで平均粒子径ＤMを求めた。その結果、平均粒子径ＤMは約１８０.７ｎｍ、平均アスペクト比は１.１５であり、測定した全ての粒子の粒径は、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲であった。
この粉末についてＶＳＭにより磁気測定を行った。そのヒステリシス曲線を図３に例示する。保磁力Ｈｃ＝１６３.１ Ｏｅ、飽和磁化σｓ＝２１０.３ｅｍｕ／ｇ、角形比０.０７８４であった。この粉末は飽和磁化が大きく、優れた軟磁気特性を呈するものである。また、耐候性Δσｓ＝３６％であった。
The obtained powder was subjected to X-ray diffraction by Cu-kα rays. The X-ray diffraction pattern is shown in FIG. Each diffraction peak of the FeCo alloy (fcc structure) was observed. Further, no diffraction peak of ferrite was observed in the X-ray diffraction pattern.
The powder particles were observed by SEM, and the average particle diameter DM was determined. FIG. 2 shows an example of an SEM image. It can be seen that the individual particles are highly spherical. In such a SEM image of 100 or more particles arbitrarily selected diameter (major axis) was measured to determine the average particle diameter D M by calculating the average value. As a result, the average particle diameter D M is about 188.7 nm and the average aspect ratio is 1.15. The particle diameters of all the measured particles are the average particle diameter D M × 0.5 or more, and the average particle diameter D M It was the range of x2 or less.
This powder was magnetically measured by VSM. The hysteresis curve is illustrated in FIG. The coercive force Hc was 163.1 Oe, the saturation magnetization σs was 210.3 emu / g, and the squareness ratio was 0.0784. This powder has a large saturation magnetization and exhibits excellent soft magnetic properties. Further, the weather resistance Δσs = 36%.
〔実施例２〕
実施例１において、金属塩投入量をＦｅとＣｏの総濃度［Ｍ］が０.０２５ｍｏｌ／Ｌとなるように変えたことを除き、実施例１と同様の方法で実験を行った。
Ｘ線回折パターンには、実施例１と同様にＦｅＣｏ合金（ｆｃｃ構造）の各回折ピークが認められ、フェライトの回折ピークは認められなかった。ＳＥＭ像から求めた平均粒子径ＤMは１４１.８ｎｍ、平均アスペクト比は１.１４であり、測定した全ての粒子の粒径は、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲であった。ＶＳＭによる磁気測定の結果、保磁力Ｈｃ＝３８９.６ Ｏｅ、飽和磁化σｓ＝１６６.８ｅｍｕ／ｇ、角形比０.１４１３であった。また、耐候性Δσｓ＝３８％であった。
[Example 2]
In Example 1, the experiment was performed in the same manner as in Example 1 except that the metal salt input amount was changed so that the total concentration [M] of Fe and Co was 0.025 mol / L.
In the X-ray diffraction pattern, each diffraction peak of the FeCo alloy (fcc structure) was observed as in Example 1, and no diffraction peak of ferrite was observed. The average particle diameter D M determined from SEM image 141.8Nm, average aspect ratio was 1.14, the particle size of all particles measured is an average particle diameter D M × 0.5 or more, an average particle diameter D The range was M × 2 or less. As a result of magnetic measurement by VSM, the coercive force Hc = 389.6 Oe, the saturation magnetization σs = 166.8 emu / g, and the squareness ratio 0.1413. Further, the weather resistance Δσs = 38%.
〔実施例３〕
実施例１において、金属塩投入量をＦｅとＣｏの総濃度［Ｍ］が０.０７０ｍｏｌ／Ｌとなるように変えたことを除き、実施例１と同様の方法で実験を行った。
Ｘ線回折パターンには、実施例１と同様にＦｅＣｏ合金（ｆｃｃ構造）の各回折ピークが認められ、フェライトの回折ピークは認められなかった。ＳＥＭ像から求めた平均粒子径ＤMは２７１.３ｎｍ、平均スペクト比は１.７９であり、測定した全ての粒子の粒径は、平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲であった。ＶＳＭによる磁気測定の結果、保磁力Ｈｃ＝１０１.９ Ｏｅ、飽和磁化σｓ＝２０３.８ｅｍｕ／ｇ、角形比０.０５９であった。また、耐候性Δσｓ＝３４％であった。
Example 3
In Example 1, the experiment was performed in the same manner as in Example 1 except that the metal salt input amount was changed so that the total concentration [M] of Fe and Co was 0.070 mol / L.
In the X-ray diffraction pattern, each diffraction peak of the FeCo alloy (fcc structure) was observed as in Example 1, and no diffraction peak of ferrite was observed. The average particle diameter D M obtained from the SEM image was 271.3 nm and the average spectrum ratio was 1.79. The particle diameters of all the measured particles were the average particle diameter D M × 0.5 or more, the average particle diameter D The range was M × 2 or less. As a result of the magnetic measurement by VSM, the coercive force Hc = 101.9 Oe, the saturation magnetization σs = 203.8 emu / g, and the squareness ratio 0.059. Further, the weather resistance Δσs = 34%.
〔比較例１〕
実施例１において、窒素ガス吹き込みおよび機械攪拌による脱酸素処理を室温の状態で行ったのち、室温の状態で金属塩を投入し、その後加熱して沸騰状態で還流しながら２ｈ保持して還元反応を進行させたこと、および金属塩投入量をＦｅとＣｏの総濃度［Ｍ］が０.１０ｍｏｌ／Ｌとなるようにしたことを除き、実施例１と同様の方法で実験を行った。
得られた粉末のＸ線回折パターンを図４に示す。ＦｅＣｏ合金（ｆｃｃ構造）の各回折ピークとともに、フェライトの回折ピークも認められた。マグネタイトとＣｏフェライトは回折ピークの位置がたいへん近いため、今回の測定では、どちらか同定することはできなかった。図５にＳＥＭ像を例示する。ＳＥＭ像から平均粒子径ＤMは１６４.４ｎｍ、平均アスペクト比は２.３２であり、測定した粒子のうち、粒径が平均粒子径ＤM×０.５以上、平均粒子径ＤM×２以下の範囲に入るものは５２個数％であり、粒度のバラツキが大きかった。ＶＳＭによる磁気測定のヒステリシス曲線を図６に例示する。保磁力Ｈｃ＝３６７.５ Ｏｅ、飽和磁化σｓ＝１１５.０ｅｍｕ／ｇ、角形比０.１６であった。この粉末は保磁力が大きいとともに飽和磁化が小さく、上記各実施例のものと比べ、軟質磁気特性に劣る。また、耐候性Δσｓ＝３２％であった。
[Comparative Example 1]
In Example 1, after performing deoxygenation treatment by blowing nitrogen gas and mechanical stirring at room temperature, a metal salt was charged at room temperature, and then heated and held for 2 hours while refluxing in a boiling state for reduction reaction. The experiment was conducted in the same manner as in Example 1 except that the amount of metal salt input was such that the total concentration [M] of Fe and Co was 0.10 mol / L.
The X-ray diffraction pattern of the obtained powder is shown in FIG. Along with each diffraction peak of the FeCo alloy (fcc structure), a diffraction peak of ferrite was also observed. Since magnetite and Co ferrite have very close diffraction peak positions, it was not possible to identify either one in this measurement. FIG. 5 illustrates an SEM image. From the SEM image, the average particle size D M is 164.4 nm, the average aspect ratio is 2.32, and among the measured particles, the particle size is average particle size D M × 0.5 or more, and average particle size D M × 2 The number within the following range was 52% by number, and the variation in particle size was large. FIG. 6 illustrates a hysteresis curve of magnetic measurement by VSM. The coercive force Hc was 367.5 Oe, the saturation magnetization σs was 115.0 emu / g, and the squareness ratio was 0.16. This powder has a large coercive force and a small saturation magnetization, and is inferior in soft magnetic properties as compared with the above examples. Further, the weather resistance Δσs = 32%.
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| JP2003226901A (en) * | 2002-02-05 | 2003-08-15 | Hitachi Maxell Ltd | Binary alloy fine particle and production method therefor |
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