JP3957176B2 - Method for producing multi-component alloy nanoparticles - Google Patents
Method for producing multi-component alloy nanoparticles Download PDFInfo
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- JP3957176B2 JP3957176B2 JP2002211154A JP2002211154A JP3957176B2 JP 3957176 B2 JP3957176 B2 JP 3957176B2 JP 2002211154 A JP2002211154 A JP 2002211154A JP 2002211154 A JP2002211154 A JP 2002211154A JP 3957176 B2 JP3957176 B2 JP 3957176B2
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- nanoparticles
- reverse micelle
- manufactured
- temperature
- reduction
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- FSVCELGFZIQNCK-UHFFFAOYSA-N N,N-bis(2-hydroxyethyl)glycine Chemical compound OCCN(CCO)CC(O)=O FSVCELGFZIQNCK-UHFFFAOYSA-N 0.000 description 3
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- 229910000510 noble metal Inorganic materials 0.000 description 3
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- KFTYKTFMIZRDHU-UHFFFAOYSA-L [O-]C(C([O-])=O)=O.N.N.N.[Fe+2] Chemical compound [O-]C(C([O-])=O)=O.N.N.N.[Fe+2] KFTYKTFMIZRDHU-UHFFFAOYSA-L 0.000 description 2
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- SNRUBQQJIBEYMU-UHFFFAOYSA-N dodecane Chemical compound CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 2
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- -1 hydrogen acids Chemical class 0.000 description 2
- NBZBKCUXIYYUSX-UHFFFAOYSA-N iminodiacetic acid Chemical compound OC(=O)CNCC(O)=O NBZBKCUXIYYUSX-UHFFFAOYSA-N 0.000 description 2
- APHGZSBLRQFRCA-UHFFFAOYSA-M indium(1+);chloride Chemical compound [In]Cl APHGZSBLRQFRCA-UHFFFAOYSA-M 0.000 description 2
- LZKLAOYSENRNKR-LNTINUHCSA-N iron;(z)-4-oxoniumylidenepent-2-en-2-olate Chemical compound [Fe].C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O.C\C(O)=C\C(C)=O LZKLAOYSENRNKR-LNTINUHCSA-N 0.000 description 2
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- CUIKFTLNDFGSMH-UHFFFAOYSA-N 2-[carboxymethyl(2,2-dihydroxyethyl)amino]acetic acid Chemical compound OC(O)CN(CC(O)=O)CC(O)=O CUIKFTLNDFGSMH-UHFFFAOYSA-N 0.000 description 1
- IWTIBPIVCKUAHK-UHFFFAOYSA-N 3-[bis(2-carboxyethyl)amino]propanoic acid Chemical compound OC(=O)CCN(CCC(O)=O)CCC(O)=O IWTIBPIVCKUAHK-UHFFFAOYSA-N 0.000 description 1
- FTEDXVNDVHYDQW-UHFFFAOYSA-N BAPTA Chemical compound OC(=O)CN(CC(O)=O)C1=CC=CC=C1OCCOC1=CC=CC=C1N(CC(O)=O)CC(O)=O FTEDXVNDVHYDQW-UHFFFAOYSA-N 0.000 description 1
- DPUOLQHDNGRHBS-UHFFFAOYSA-N Brassidinsaeure Natural products CCCCCCCCC=CCCCCCCCCCCCC(O)=O DPUOLQHDNGRHBS-UHFFFAOYSA-N 0.000 description 1
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- YUJOTZMQAMVBET-UHFFFAOYSA-N Cl.Cl.NCCN.CCC(O)=O.CCC(O)=O Chemical compound Cl.Cl.NCCN.CCC(O)=O.CCC(O)=O YUJOTZMQAMVBET-UHFFFAOYSA-N 0.000 description 1
- 229910019222 CoCrPt Inorganic materials 0.000 description 1
- 229910018936 CoPd Inorganic materials 0.000 description 1
- 229910018979 CoPt Inorganic materials 0.000 description 1
- 229910021591 Copper(I) chloride Inorganic materials 0.000 description 1
- URXZXNYJPAJJOQ-UHFFFAOYSA-N Erucic acid Natural products CCCCCCC=CCCCCCCCCCCCC(O)=O URXZXNYJPAJJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910002555 FeNi Inorganic materials 0.000 description 1
- 229910015187 FePd Inorganic materials 0.000 description 1
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 1
- OYHQOLUKZRVURQ-HZJYTTRNSA-N Linoleic acid Chemical compound CCCCC\C=C/C\C=C/CCCCCCCC(O)=O OYHQOLUKZRVURQ-HZJYTTRNSA-N 0.000 description 1
- OIJIKBGHGYBNFQ-UHFFFAOYSA-J O.[K+].[K+].[K+].[K+].C(C)(=O)[O-].C(C)(=O)[O-].C(C)(=O)[O-].C(C)(=O)[O-].NC(C(C1=CC=CC=C1)O)(N)O Chemical compound O.[K+].[K+].[K+].[K+].C(C)(=O)[O-].C(C)(=O)[O-].C(C)(=O)[O-].C(C)(=O)[O-].NC(C(C1=CC=CC=C1)O)(N)O OIJIKBGHGYBNFQ-UHFFFAOYSA-J 0.000 description 1
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- 238000004458 analytical method Methods 0.000 description 1
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- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 1
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- 239000001257 hydrogen Substances 0.000 description 1
- RXPAJWPEYBDXOG-UHFFFAOYSA-N hydron;methyl 4-methoxypyridine-2-carboxylate;chloride Chemical compound Cl.COC(=O)C1=CC(OC)=CC=N1 RXPAJWPEYBDXOG-UHFFFAOYSA-N 0.000 description 1
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- LAPRIVJANDLWOK-UHFFFAOYSA-N laureth-5 Chemical compound CCCCCCCCCCCCOCCOCCOCCOCCOCCO LAPRIVJANDLWOK-UHFFFAOYSA-N 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- DJQJFMSHHYAZJD-UHFFFAOYSA-N lidofenin Chemical compound CC1=CC=CC(C)=C1NC(=O)CN(CC(O)=O)CC(O)=O DJQJFMSHHYAZJD-UHFFFAOYSA-N 0.000 description 1
- OYHQOLUKZRVURQ-IXWMQOLASA-N linoleic acid Natural products CCCCC\C=C/C\C=C\CCCCCCCC(O)=O OYHQOLUKZRVURQ-IXWMQOLASA-N 0.000 description 1
- 235000020778 linoleic acid Nutrition 0.000 description 1
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- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
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- 239000010970 precious metal Substances 0.000 description 1
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- 238000004062 sedimentation Methods 0.000 description 1
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- 238000004544 sputter deposition Methods 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
- G11B5/65—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
- G11B5/70605—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
- H01F41/30—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates for applying nanostructures, e.g. by molecular beam epitaxy [MBE]
Description
【０００１】
【発明の属する技術分野】
本発明は、強磁性を発揮し得る多元系合金ナノ粒子の製造方法に関する。
【０００２】
【従来の技術】
磁性層に含有される磁性体の粒子サイズを小さくすることは、磁気記録密度を高くする上で必要である。たとえば、ビデオテープ、コンピュータテープ、ディスクなどとして広く用いられている磁気記録媒体では、強磁性体の質量が同じ場合、粒子サイズを小さくしていった方がノイズは下がる。
ＣｕＡｕ型あるいはＣｕ3Ａｕ型硬磁性規則合金は、規則化時に発生する歪みのために、結晶磁気異方性が大きく、粒子サイズを小さくし、いわゆるナノ粒子といわれる状態としても硬磁性を示すことから、磁気記録密度向上に有望な素材である。
【０００３】
ＣｕＡｕ型あるいはＣｕ3Ａｕ型合金を形成しうるナノ粒子の合成法としては、沈殿法で分類すると、▲１▼１級アルコールを用いるアルコール還元法、▲２▼２級、３級、２価または３価のアルコールを用いるポリオール還元法、▲３▼熱分解法、▲４▼超音波分解法、▲５▼強力還元剤還元法、などがある。
また、反応系で分類すると、▲６▼高分子存在法、▲７▼高沸点溶媒法、▲８▼正常ミセル法、▲９▼逆ミセル法、などがある。
【０００４】
▲１▼のアルコール還元法の場合は、還元力が弱く、貴な金属と卑な金属とを同時に還元する場合、均一合金が生成しにくく、コア／シェル構造になることが多い。▲２▼のポリオール還元法、および▲３▼の熱分解法の場合は、高温反応が必要であるため製造適性が劣る。▲４▼の超音波分解法、および▲５▼の強力還元剤還元法は、比較的簡便な方法であるが、凝集や沈殿が発生しやすく、反応系を工夫しないと単分散で小さいナノ粒子を得ることが困難である。
【０００５】
また、▲１▼と▲６▼とを組み合わせた系として、ポリビニルピロリドン中のエタノール還元法があるが、この場合、合成後のポリマー量が非常に多く、必要量まで減少させることが困難である。
▲２▼、▲３▼および▲７▼を組み合わせた系として、特開２０００−５４０１２号、ＵＳ６，２５４，６６２号が知られている。この方法は、毒性の高い物質を用いるため危険性が高く、さらに、不活性ガス中で、かつ３００℃近い高温で反応させる必要があるため、装置構成が複雑で製造適性が劣る欠点を有している。
▲５▼と▲８▼を組み合わせた系、▲５▼と▲９▼を組み合わせた系は一般的な方法ではあるが、目的とする組成および粒子サイズを有する金属ナノ粒子を得る方法についての詳しい条件等は未だ見出されていない。
【０００６】
上記方法で合成されたナノ粒子の構造は、面心立方晶となる。面心立方晶は通常、軟磁性あるいは常磁性を示す。軟磁性あるいは常磁性では記録媒体用には適していない。磁気記録媒体に必要な９５．５ｋＡ／ｍ（１２００Ｏｅ）以上の保磁力を有する硬磁性規則合金を得るには、不規則相から規則相へ変態する変態温度以上でアニール処理を施す必要がある。
しかし、上記方法で製造されたナノ粒子を支持体上に塗布し、アニール処理を施して磁気記録媒体を作製する場合、ナノ粒子が互いに凝集しやすいため塗布適性が低下し、磁気特性が低下したり、得られるナノ粒子の粒径が不均一なため熱処理を施しても完全に規則相とすることが困難で、所望の硬磁性が得られなかったりすることがあった。
【０００７】
また、変態温度は通常５００℃以上と高く、一般に使用されている有機支持体では耐熱性に問題があるため、該有機支持体上にナノ粒子を塗布しアニール処理を施して磁性膜を形成することは困難であった。
【０００８】
【発明が解決しようとする課題】
以上から、本発明は、変態温度が低く、凝集しにくく、塗布適性に優れ、また、粒子のサイズおよび組成が制御可能で、強磁性を発現し得る多元系合金ナノ粒子を高収率で製造する方法を提供することを目的とする。
【０００９】
【課題を解決するための手段】
上記の課題を解決すべく鋭意検討の結果、本発明者は、下記本発明により上記課題を解決できることを見出した。すなわち、本発明は、
金属塩を含む１種以上の逆ミセル溶液（Ｉ）と還元剤を含む逆ミセル溶液（ＩＩ）とを混合して還元処理を施す還元工程と、前記還元処理後に熟成処理を施す熟成工程と、を経て多元系合金からなるナノ粒子を製造する方法であって、
前記多元系合金を構成する少なくとも２種の金属が短周期表におけるＶＩｂ族およびＶＩＩＩ族の中から選択され、
前記多元系合金を構成する少なくとも１種の金属がＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族の中から選択され、その選択された金属の含有量が前記多元系合金全体の１〜３０原子％、であり、
前記熟成工程における熟成温度が、前記還元工程における還元温度より５℃以上高いことを特徴とする多元系合金ナノ粒子の製造方法である。
強磁性で硬磁性を発現させるため、前記多元系合金を構成する少なくとも２種の金属が短周期表におけるＶＩｂ族およびＶＩＩＩ族の中から選択される場合、これらの金属によりＣｕＡｕ型もしくはＣｕ3Ａｕ型の合金が形成されていることが好ましい。
【００１０】
【発明の実施の形態】
＜多元系合金ナノ粒子の製造方法＞
本発明のナノ粒子の製造方法は、金属塩を含む１種以上の逆ミセル溶液（Ｉ）と還元剤を含む逆ミセル溶液（ＩＩ）とを混合して還元処理を施す還元工程と、前記還元処理後に熟成処理を施す熟成工程とを有する。かかる製造方法により、多元系合金ナノ粒子（以下、単に「ナノ粒子」ということがある）が製造される。
以下、各工程について説明する。
【００１１】
（還元工程）
まず、界面活性剤を含有する非水溶性有機溶媒と金属塩水溶液とを混合した逆ミセル溶液（Ｉ）を調製する。逆ミセル溶液（Ｉ）には多元系合金を形成するのに用いられる複数種の金属塩が混合して含有されていてもよく、また、それぞれ別々に含有させた逆ミセル溶液を調製して、それぞれを逆ミセル溶液（Ｉ）としてもよい。
例えば、ＶＩｂ族およびＶＩＩＩ族の中から選択される金属を含有する逆ミセル溶液（Ｉa）と、これとは別にＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族の中から選択される金属を含有する逆ミセル溶液（Ｉb）とを別々に調製しておき適宜これらを混合などしてもよい。
【００１２】
前記界面活性剤としては、油溶性界面活性剤が用いられる。具体的には、スルホン酸塩型（例えば、エーロゾルＯＴ（和光純薬製））、４級アンモニウム塩型（例えば、セチルトリメチルアンモニウムブロマイド）、エーテル型（例えば、ペンタエチレングリコールドデシルエーテル）などが挙げられる。
【００１３】
前記界面活性剤を溶解する非水溶性有機溶媒として好ましいものは、アルカンおよびエーテルである。アルカンは、炭素数７〜１２のアルカン類であることが好ましい。具体的には、ヘプタン、オクタン、ノナン、デカン、ウンデカン、ドデカンが好ましい。エーテルは、ジエチルエーテル、ジプロピルエーテル、ジブチルエーテルが好ましい。
非水溶性有機溶媒中の界面活性剤量は、２０〜２００ｇ／リットルであることが好ましい。
【００１４】
金属塩水溶液に含有される金属塩としては、硝酸塩、硫酸塩、塩酸塩、酢酸塩、塩素イオンを配位子とする金属錯体の水素酸、塩素イオンを配位子とする金属錯体のカリウム塩、塩素イオンを配位子とする金属錯体のナトリウム塩、シュウ酸イオンを配位子とする金属錯体のアンモニウム塩などから任意に選択して使用できる。
【００１５】
また、金属として、少なくとも２種は短周期表におけるＶＩｂ族およびＶＩＩＩ族の中から選択され、さらに少なくとも１種はＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族の中から選択される。
ＶＩｂ族およびＶＩＩＩ族の中から選択される金属により、硬磁性を発現し得るナノ粒子が製造される。また、Ｉｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族の中から選択される金属により、上記ナノ粒子の硬磁性を発現させるための相変態温度を低くすることができる。その結果、当該ナノ粒子を使用して磁気記録媒体等を作製しようとする場合に、支持体等の耐熱性を考慮する必要がなくなるため、有機物からなる支持体に当該ナノ粒子を含有する磁性層を効率よく形成することができる。
【００１６】
ＶＩｂ族およびＶＩＩＩ族から構成される２元系および３元系の合金組成の例としては、ＦｅＰｔ、ＦｅＰｄ、ＦｅＮｉ、ＣｏＰｔ、ＣｏＰｄ、ＣｏＡｕ、ＣｏＣｒＰｔ、ＣｏＣｒＰｄ、ＦｅＮｉＰｔ、ＦｅＣｏＰｔなどが挙げられる。
また、多元系合金にするために含有されるＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族から選ばれる他の元素としては、特に、Ｃｕ、Ａｇ、Ｂ、Ｉｎ、Ｓｎ、Ｐｂ、Ｐ、Ｓｂ、Ｂｉなどから選ばれることが好ましい。Ｉｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族から選ばれる元素の添加量（含有量）は、多元系合金全体の１〜３０原子％とし、５〜２０原子％とすることが好ましい。
添加量が１原子％未満では、変態温度を下げる効果が低減し添加する意義がなくなる。３０原子％を超えるとアニール処理後にナノ粒子の結晶構造が硬磁性を示す規則相を形成できなくなってしてしまう。
なお、多元系合金は、ＶＩｂ族およびＶＩＩＩ族から選ばれる２元素およびＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族から選ばれる１元素を含めて、合計で３〜５元素で構成されることが好ましい。
【００１７】
各々の金属塩水溶液中の濃度（金属塩濃度として）は、０．１〜２０００μモル／ｍｌであることが好ましく、１〜５００μモル／ｍｌであることがより好ましい。
【００１８】
得られる粒子のそれぞれが互いに均一な組成となるために、金属塩水溶液中にキレート剤を添加することが好ましい。キレート安定度定数（ｌｏｇＫ）としては、１０以下が好ましい。具体的には、ＤＨＥＧ（二ヒドロキシエチルグリシン）、ＩＤＡ（イミノ二酢酸）、ＮＴＰ（ニトリロ三プロピオン酸）、ＨＩＤＡ（二ヒドロキシエチルイミノ二酢酸）、ＥＤＤＰ（エチレンジアミン二プロピオン酸二塩酸塩）、ＢＡＰＴＡ（二アミノフェニルエチレングリコール四酢酸四カリウム塩水和物）、などを使用することが好ましい。
【００１９】
キレート剤の添加量は、金属塩１モル当たり、０．１〜１０モルが好ましく、０．３〜３モルがより好ましい。
【００２０】
次に、界面活性剤を含有する非水溶性有機溶媒と還元剤水溶液とを混合した逆ミセル溶液（ＩＩ）を調製する。２種以上の還元剤を用いる場合は、これらを一緒に混合して逆ミセル溶液（ＩＩ）としてもよいが、液安定性や作業性等を考慮して、それぞれ別々に非水溶性有機溶媒に混合して、別々の逆ミセル溶液（ＩＩa）、（ＩＩb）（ＩＩc）等として調製し、これらを適宜混合等して使用することが好ましい。
【００２１】
還元剤水溶液中の還元剤としては、アルコール類；ポリアルコール類；Ｈ2；ＨＣＨＯ、Ｓ2Ｏ6 2-、Ｈ2ＰＯ2 -、ＢＨ4 -、Ｎ2Ｈ5 +、Ｈ2ＰＯ3 -などを含む化合物；を単独で使用、または２種以上を併用することが好ましい。
水溶液中の還元剤量は、金属塩１モルに対して、３〜５０モルであることが好ましい。
【００２２】
逆ミセル溶液（Ｉ）および（ＩＩ）のそれぞれについて含有される水と界面活性剤との質量比は（水／界面活性剤）は、２０以下となるようにするのが好ましい。質量比が２０を超えると、沈殿が起きやすく、粒子も不揃いとなりやすいといった問題が生じることがある。質量比は、１５以下とすることがより好ましく、０．５〜１０とすることがさらに好ましい。
【００２３】
逆ミセル溶液（Ｉ）と（ＩＩ）の水と界面活性剤との質量比は同じでも、また、異なっていてもかまわないが、系を均一にするために同じであることが好ましい。
【００２４】
以上のようにして、調製した逆ミセル溶液（Ｉ）と（ＩＩ）とを混合する。混合方法としては、特に限定されるものではないが、還元の均一性を考慮して、逆ミセル溶液（ＩＩ）を撹拌しながら、逆ミセル溶液（Ｉ）を添加していって混合することが好ましい。混合終了後、還元反応を進行させることになるが、その際の温度は、−５〜３０℃の範囲で、一定の温度とする。
還元温度が−５℃未満では、水相が凝結して還元反応が不均一になるといった問題が生じ、３０℃を超えると、凝集または沈殿が起こりやすく系が不安定となる。好ましい還元温度は０〜２５℃であり、より好ましくは５〜２５℃である。ここで、前記「一定温度」とは、設定温度をＴ（℃）とした場合、当該ＴがＴ±３℃の範囲にあることをいう。なお、このようにした場合であっても、当該Ｔの上限および下限は、上記還元温度（−５〜３０℃）の範囲にあるものとする。
【００２５】
還元反応の時間は、逆ミセル溶液の量等により適宜設定する必要があるが、１〜３０分とすることが好ましく、５〜２０分とすることがより好ましい。
【００２６】
還元反応は、粒径分布の単分散性に大きな影響を与えるため、できるだけ高速攪拌（例えば約３０００ｒｐｍ以上）しながら行うことが好ましい。
好ましい攪拌装置は高剪断力を有する攪拌装置であり、詳しくは、攪拌羽根が基本的にタービン型あるいはパドル型の構造を有し、さらに、その羽根の端もしくは、羽根と接する位置に鋭い刃を付けた構造であり、羽根をモーターで回転させる攪拌装置である。具体的には、ディゾルバー（特殊機化工業製）、オムニミキサー（ヤマト科学製）、ホモジナイザー（ＳＭＴ製）などの装置が有用である。これらの装置を用いることにより、単分散なナノ粒子を安定な分散液として合成することができる。
【００２７】
前記逆ミセル溶液（Ｉ）および（ＩＩ）の少なくともいずれかに、アミノ基またはカルボキシ基を１〜３個有する少なくとも１種の分散剤を、作製しようとする金属ナノ粒子１モル当たり、０．００１〜１０モル添加することが好ましい。
【００２８】
かかる分散剤を添加することで、より単分散で、凝集の無いナノ粒子を得ることが可能となる。
添加量が、０．００１未満では、ナノ粒子の単分散性をより向上させることできない場合があり、１０モルを超えると凝集が起こる場合がある。
【００２９】
前記分散剤としては、金属ナノ粒子表面に吸着する基を有する有機化合物が好ましい。具体的には、アミノ基、カルボキシ基、スルホン酸基またはスルフィン酸基を１〜３個有するものであり、これらを単独または併用して用いることができる。
構造式としては、Ｒ−ＮＨ2、ＮＨ2−Ｒ−ＮＨ2、ＮＨ2−Ｒ（ＮＨ2）−ＮＨ2、Ｒ−ＣＯＯＨ、ＣＯＯＨ−Ｒ−ＣＯＯＨ、ＣＯＯＨ−Ｒ（ＣＯＯＨ）−ＣＯＯＨ、Ｒ−ＳＯ3Ｈ、ＳＯ3Ｈ−Ｒ−ＳＯ3Ｈ、ＳＯ3Ｈ−Ｒ（ＳＯ3Ｈ）−ＳＯ3Ｈ、Ｒ−ＳＯ2Ｈ、ＳＯ2Ｈ−Ｒ−ＳＯ2Ｈ、ＳＯ2Ｈ−Ｒ（ＳＯ2Ｈ）−ＳＯ2Ｈで表される化合物であり、式中のＲは直鎖、分岐または環状の飽和、不飽和の炭化水素である。
【００３０】
分散剤として特に好ましい化合物はオレイン酸である。オレイン酸はコロイドの安定化において周知の界面活性剤であり、鉄ナノ粒子を保護するのに用いられてきた。オレイン酸の比較的長い（たとえば、オレイン酸は１８炭素鎖を有し長さは〜２０オングストローム（〜２ｎｍ）である。オレイン酸は脂肪族ではなく二重結合が１つある）鎖は粒子間の強い磁気相互作用を打ち消す重要な立体障害を与える。
エルカ酸やリノール酸など類似の長鎖カルボン酸もオレイン酸同様に（たとえば、８〜２２の間の炭素原子を有する長鎖有機酸を単独でまたは組み合わせて用いることができる）用いられる。オレイン酸は（オリーブ油など）容易に入手できる安価な天然資源であるので好ましい。また、オレイン酸から誘導されるオレイルアミンもオレイン酸同様有用な分散剤である。
【００３１】
（熟成工程）
還元反応終了後、反応後の溶液を熟成温度まで昇温する。
前記熟成温度は、３０〜９０℃で一定の温度とすることが好ましく、その温度は、前記還元反応の温度より高くする。また、熟成時間は、５〜１８０分とすることが好ましい。熟成温度および時間が上記範囲より高温長時間側にずれると、凝集または沈殿が起きやすく、逆に低温短時間側にずれると、反応が完結しなくなり組成が変化する。より好ましい熟成温度および時間は４０〜８０℃および１０〜１５０分であり、さらに好ましい熟成温度および時間は４０〜７０℃および２０〜１２０分である。
【００３２】
ここで、前記「一定温度」とは、還元反応の温度の場合と同義（但し、この場合、「還元温度」は「熟成温度」となる）であるが、特に、上記熟成温度の範囲（３０〜９０℃）内で、前記還元反応の温度より５℃以上高いことが好ましく、１０℃以上高いことがより好ましい。５℃未満では、処方通りの組成が得られないことがある。
【００３３】
以上のような熟成工程では、還元工程で還元析出した卑な金属上に貴な金属が析出する。すなわち、卑な金属上でのみ貴な金属の還元が起こり、卑な金属と貴な金属とが別々に析出することが無いため、効率良くＣｕＡｕ型あるいはＣｕ3Ａｕ型硬磁性規則合金を形成し得るナノ粒子を、高収率で処方組成比どおりに作製することが可能で、所望の組成に制御することができる。また、熟成の際の温度で撹拌速度を適宜調整することで、得られるナノ粒子の粒径を所望なものとすることができる。
【００３４】
前記熟成を行った後は、水と１級アルコールとの混合溶液で前記熟成後の溶液を洗浄し、その後、１級アルコールで沈殿化処理を施して沈殿物を生成させ、該沈殿物を有機溶媒で分散させる洗浄・分散工程を設けることが好ましい。
かかる洗浄工程を設けることで、不純物が除去され、磁気記録媒体の磁性層を塗布により形成する際の塗布性をより向上させることができる。
上記洗浄および分散は、少なくともそれぞれ１回、好ましくは、それぞれ２回以上行う。
【００３５】
洗浄で用いる前記１級アルコールとしては、特に限定されるものではないが、メタノール、エタノール等が好ましい。体積混合比（水／１級アルコール）は、１０／１〜２／１の範囲にあることが好ましく、５／１〜３／１の範囲にあることがより好ましい。
水の比率が高いと、界面活性剤が除去されにくくなることがあり、逆に１級アルコールの比率が高いと、凝集を起こしてしまうことがある。
【００３６】
以上のようにして、溶液中に分散したナノ粒子が得られる。当該ナノ粒子は、単分散であるため、支持体に塗布しても、これらが凝集することなく均一に分散した状態を保つことができる。従って、アニール処理を施しても、それぞのナノ粒子が凝集することがないため、効率良く硬磁性化することが可能で、塗布適性に優れる。
【００３７】
本発明における、アニール前のナノ粒子の粒径は１〜２０ｎｍであることが好ましく、３〜１０ｎｍであることがより好ましい。磁気記録媒体として用いるにはナノ粒子を最密充填することが記録容量を高くする上で好ましい。そのためには、本発明の金属ナノ粒子の粒径分布における変動係数は１５％以下が好ましく、より好ましくは８％以下である。
粒径が小さすぎると、熱揺らぎのため超常磁性となり好ましくない。構成元素によって最小安定粒径が異なるが、必要な粒径を得るために、Ｈ2Ｏ／界面活性剤質量比を変化させて合成することが有効である。
【００３８】
本発明で製造されたナノ粒子の粒径評価には透過型電子顕微鏡（ＴＥＭ）を用いることができる。加熱により硬磁性化したナノ粒子の結晶系を決めるにはＴＥＭによる電子線回折でもよいが、精度高く行うにはＸ線回折を用いた方が良い。硬磁性化したナノ粒子の内部の組成分析には電子線を細く絞ることができるＦＥ−ＴＥＭにＥＤＡＸを付け評価することが好ましい。硬磁性化したナノ粒子の磁気的性質の評価はＶＳＭを用いて行うことができる。
【００３９】
後述するアニール処理を施した後のナノ粒子の保磁力は９５．５〜１１９３．８ＫＡ／ｍ（１２００〜１５０００Ｏｅ）であることが好ましい。
【００４０】
ナノ粒子を変態温度以上に加熱する方法は任意でよいが、ナノ粒子の融合を避けるために、支持体に塗布した後加熱する方が好ましい。
本発明の製造方法により得られるナノ粒子は変態温度が低いため、耐熱温度の低い有機支持体にも好適に使用できるが、この場合、変態温度に加熱する手段としてパルスレーザを用いれば、有機支持体の熱による変質や変形をより効率よく防ぐことができる。
【００４１】
硬磁性化したナノ粒子は、ビデオテープ、コンピュータテープ、フロッピー（Ｒ）ディスク、ハードディスクに好ましく用いることができる。また、ＭＲＡＭへの適用も好ましい。
【００４２】
＜磁気記録媒体＞
本発明の製造方法により製造されたナノ粒子を用いた磁気記録媒体は、少なくとも、支持体上に磁性層が形成されており、前記磁性層が、本発明の製造方法によって得られたナノ粒子を含有している。当該磁性層は、上記ナノ粒子を分散した塗布液を支持体上に塗布し、アニール処理を施して形成される。また、必要に応じて他の層を有してなる。
即ち、かかる磁気記録媒体は、支持体表面にナノ粒子を含有する磁性層を有し、必要に応じて磁性層と支持体の間に非磁性層が設けられたり、ディスクの場合では支持体の反対側の面にも同様に磁性層、必要に応じ磁性層と非磁性層を設けられたりする。テープの場合では、磁性層の反対側の支持体上にはバックコート層が設けられたりする。
【００４３】
【実施例】
本発明を以下に示す実施例をもとに、さらに詳細に説明するが、本発明はこれらに限定されるものではない。
【００４４】
〔実施例１〕
高純度Ｎ2ガス中で下記の操作を行った。
三シュウ酸三アンモニウム鉄（Ｆｅ（ＮＨ4）3（Ｃ2Ｏ4）3）（和光純薬製）０．３５ｇと塩化白金酸カリウム（Ｋ2ＰｔＣｌ4）（和光純薬製）０．３５ｇとをＨ2Ｏ（脱酸素処理済み）２４ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ１０．８ｇをデカン８０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（Ｉa）を調製した。
【００４５】
ＮａＢＨ4（和光純薬製）０．５７ｇをＨ2Ｏ（脱酸素処理済み）１２ｍｌに溶解した還元剤水溶液に、エーロゾルＯＴ（和光純薬製）５．４ｇとオレイルアミン（東京化成製）２ｍｌとをデカン（和光純薬製）４０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（ＩＩa）を調製した。
【００４６】
塩化銅（ＣｕＣｌ2・６Ｈ2Ｏ）（和光純薬製）０．０７ｇをＨ2Ｏ（脱酸素処理済み）２ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ２．７ｇをデカン２０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（Ｉb）を調製した。
【００４７】
アスコルビン酸（和光純薬製）０．８８ｇをＨ2Ｏ（脱酸素処理済み）１２ｍｌに溶解した還元剤水溶液に、エーロゾルＯＴ（和光純薬製）５．４ｇをデカン（和光純薬製）４０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（ＩＩb）を調製した。
【００４８】
逆ミセル溶液（Ｉa）を２２℃でオムニミキサー（ヤマト科学製）で高速攪拌しながら、逆ミセル溶液（ＩＩa）を瞬時に添加した。３分後、さらに、逆ミセル溶液（Ｉb）を約２．４ｍｌ／分の速度で約１０分かけて添加した。添加終了５分後に、マグネチックスターラー攪拌に変更して、４０℃に昇温した後、逆ミセル溶液（ＩＩb）を添加して、１２０分間熟成した。
室温に冷却後、オレイン酸（和光純薬製）２ｍｌを添加、混合して、大気中に取出した。逆ミセルを破壊するために、Ｈ2Ｏ２００ｍｌとメタノール２００ｍｌとの混合液を添加して水相と油相とに分離した。油相側に金属ナノ粒子が分散した状態が得られた。油相側をＨ2Ｏ６００ｍｌ＋メタノール２００ｍｌで５回洗浄した。その後、メタノールを１３００ｍｌ添加して金属ナノ粒子にフロキュレーションを起こさせて沈降させた。上澄み液を除去して、ヘプタン（和光純薬製）２０ｍｌを添加して再分散した。さらに、メタノール１００ｍｌ添加による沈降とヘプタン２０ｍｌ分散を２回繰り返して、最後にオクタン（和光純薬製）５ｍｌを添加して、ＦｅＣｕＰｔナノ粒子分散液を得た。
【００４９】
〔実施例２〕
実施例１に対し、逆ミセル液（Ｉb）中の金属塩をＩｎＣｌ3（和光純薬製）０．０７ｇに変更した以外は実施例１と同様にして、ＦｅＩｎＰｔナノ粒子分散液を得た。
【００５０】
〔実施例３〕
実施例１に対し、逆ミセル液（Ｉb）中の金属塩をＰｂＣｌ2（和光純薬製）０．０８ｇに変更した以外は実施例１と同様にして、ＦｅＰｂＰｔナノ粒子分散液を得た。
【００５１】
〔実施例４〕
実施例１の逆ミセル溶液（Ｉa）および（Ｉb）の金属塩を以下のものにした以外は、実施例１と同様にして、ＣｏＢｉＰｔナノ粒子分散液を得た。
逆ミセル溶液（Ｉa）の金属塩：塩化コバルト（ＣｏＣｌ2・６Ｈ2Ｏ）０．２０ｇおよび塩化白金酸カリウム（Ｋ2ＰｔＣｌ4）（和光純薬製）０．３５ｇ逆ミセル溶液（Ｉb）の金属塩：硝酸ビスマス（Ｂｉ（ＮＯ3）3・５Ｈ2Ｏ）０．４１ｇ
【００５２】
〔実施例５〕
高純度Ｎ2ガス中で下記の操作を行った。
三シュウ酸三アンモニウム鉄（Ｆｅ（ＮＨ4）3（Ｃ2Ｏ4）3）（和光純薬製）０．１８ｇと塩化白金酸カリウム（Ｋ2ＰｔＣｌ4）（和光純薬製）０．３５ｇとをＨ2Ｏ（脱酸素処理済み）２４ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ１０．８ｇをデカン８０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（Ｉa）を調製した。
【００５３】
塩化コバルト（ＣｏＣｌ2・６Ｈ2Ｏ）（和光純薬製）０．１０ｇをＨ2Ｏ（脱酸素処理済）２ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ２．７ｇをデカン２０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（Ｉb）を調製した。
【００５４】
ＮａＢＨ4（和光純薬製）０．５７ｇをＨ2Ｏ（脱酸素）１２ｍｌに溶解した還元剤水溶液に、エーロゾルＯＴ（和光純薬製）５．４ｇとオレイルアミン（東京化成製）２ｍｌとをデカン（和光純薬製）４０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（ＩＩa）を調製した。
【００５５】
酢酸銅（Ｃｕ（ＣＨ3ＣＯＯ）2・Ｈ2Ｏ）（和光純薬製）０．０６ｇをＨ2Ｏ（脱酸素処理済）２ｍｌに溶解した金属塩水溶液に、エーロゾルＯＴ２．７ｇをデカン２０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（Ｉc）を調製した。
【００５６】
アスコルビン酸（和光純薬製）０．８８ｇをＨ2Ｏ（脱酸素処理済）１２ｍｌに溶解した還元剤水溶液に、エーロゾルＯＴ（和光純薬製）５．４ｇをデカン（和光純薬製）４０ｍｌに溶解したアルカン溶液を添加、混合して逆ミセル溶液（ＩＩb）を調製した。
【００５７】
逆ミセル溶液（Ｉ）を２２℃でオムニミキサー（ヤマト科学製）で高速攪拌しながら、逆ミセル溶液（Ｉb）を瞬時に添加した。２分後さらに、逆ミセル溶液（ＩＩa）を瞬時に添加した。３分後さらに、逆ミセル溶液（Ｉc）を約２．４ｍｌ／分の速度で約１０分かけて添加した。添加終了５分後に、マグネチックスターラー攪拌に変更して、４０℃に昇温した後、逆ミセル溶液（ＩＩb）を添加して、１２０分間熟成した。
【００５８】
洗浄、精製を実施例１と同様に行い、ＦｅＣｏＣｕＰｔナノ粒子分散液を得た。
【００５９】
〔実施例６〕
逆ミセル溶液（Ｉa）および（Ｉb）のそれぞれにキレート剤（ＤＨＥＧ）を
０．３３ｇ添加し、さらに、逆ミセル溶液（Ｉb）の金属塩をＩｎＣｌ3（和光純薬製）０．０７ｇにする以外は実施例５と同様にして、ＦｅＣｏＩｎＰｔナノ粒子分散液を得た。
【００６０】
〔比較例１〕
実施例１の逆ミセル溶液（Ｉb）および（ＩＩb）用いず、逆ミセル溶液（Ｉ
）を室温（２５℃）でマグネチックスターラー攪拌しながら、逆ミセル溶液（ＩＩa）を瞬時に添加して還元反応を起こさせ、そのままの温度で１２０分熟成した以外は、実施例１と同様にして、ＦｅＰｔナノ粒子分散液を得た。
【００６１】
〔比較例２〕
実施例１の逆ミセル溶液（Ｉb）を用いず、逆ミセル溶液（Ｉa）を２２℃で
オムニミキサー（ヤマト科学製）で高速攪拌しながら、逆ミセル溶液（ＩＩa）を瞬時に添加した。１０分後に、マグネチックスターラー攪拌に変更して、４０℃に昇温した後、逆ミセル溶液（ＩＩb）を添加して、１２０分間熟成した以外は実施例１と同様にして、ＦｅＰｔナノ粒子分散液を得た。
【００６２】
〔比較例３〕
高純度Ｎ2ガス中で下記の操作を行った。
白金アセチルアセトナート（Ｐｔ（ａｃａｃ）2）（和光純薬製）０．３９ｇ、１，１２−ドデカンジオール（和光純薬製）０．６ｍｌおよびジオクチルエーテル２０ｍｌを混合し、１００℃まで加熱した。その後、オレイン酸０．２８ｍｌ、オレイルアミン０．２６ｍｌおよび鉄アセチルアセトナート（Ｆｅ（ａｃａｃ）3）０．２５ｇを添加して、２９７℃まで昇温してから３０分間還流した。
【００６３】
冷却後、メタノール２００ｍｌを添加し、金属ナノ粒子にフロキュレーションを起こさせて沈降させた。上澄み液を除去した後、ヘプタンを２０ｍｌ添加して再分散させた。再度メタノール１００ｍｌ添加し沈降させた。ヘプタン分散、メタノール沈降をもう一度行った後、オクタン５ｍｌで分散し、ＦｅＰｔナノ粒子分散液を得た。
【００６４】
実施例１〜６および比較例１〜３で得られたナノ粒子を分析して、表１の結果が得られた。
表１中、組成および収率は、分散液を蒸発乾固後、濃硫酸で有機物を分解した後、王水に溶解して、ＩＣＰ分光分析（誘導結合高周波プラズマ分光分析）で測定した。
数平均粒径と分布は、ＴＥＭ撮影した粒子を計測して統計処理して算出した。保磁力測定は東英工業製の高感度磁化ベクトル測定機と同社製ＤＡＴＡ処理装置を使用し、印加磁場７９０ＫＡ／ｍ（１０ｋＯｅ）で測定した。測定したナノ粒子は、ナノ粒子分散液を蒸発乾固後、赤外線加熱炉（アルバック理工製）で、Ｈ2を５％含有したＡｒ混合ガス中でアニール処理（５５０℃または３５０℃）したものを使用した。
【００６５】
【表１】
表１から明らかなように、実施例１〜６のナノ粒子は、比較例１および３より、高い収率で処方値に近い組成が得られた。また、粒径分布の変動係数が小さく単分散であり、アニール処理後の保磁力が高かった。さらに、実施例１〜６のナノ粒子は、比較例１〜３に対して、低温（３５０℃）アニール処理においても、高い保磁力を示した。
【００６７】
実施例１〜６および比較例１〜３で調製したナノ粒子分散液を、焼成Ｓｉ基板（厚さ３００ｎｍのＳｉＯ2層がＳｉ表面に形成されたもの）上に、スピンコート法により塗布した。塗布量はそれぞれ０．１ｇ／ｍ2とした。
【００６８】
塗布後、それぞれの塗布試料を赤外線加熱炉（アルバック理工製）により、Ａｒ＋Ｈ2（５％）混合ガスで３５０℃、３０分間アニール処理を行って基板上に磁性層を形成した。
アニール処理後、スパッタ装置（芝浦メカトロニクス製）により磁性層表面に１０ｎｍのカーボンをで付け、さらにその上に、潤滑剤（ＦＯＭＢＬＩＮ：ＡＵＳＩＭＯＮＴ社製）をスピンコート法で約５ｎｍの厚みに塗布して磁気記録媒体とした。
【００６９】
磁気特性を評価した結果、比較例１〜３は硬磁性とならなかったのに対し、実施例１〜６は３１８．３ＫＡ／ｍ（４０００Ｏｅ）以上の保磁力を有する硬磁性を示した。
また、実施例１〜６のナノ粒子は、アニール処理によっても融合することなく、アニール処理前の粒径を維持していた。
【００７０】
【発明の効果】
以上、本発明のナノ粒子の製造方法によれば、変態温度が低く、凝集しにくく、塗布適性に優れ、また、粒子のサイズおよび組成が制御可能で、強磁性を発現し得るナノ粒子を高収率で製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing multi-component alloy nanoparticles capable of exhibiting ferromagnetism.
[0002]
[Prior art]
It is necessary to reduce the particle size of the magnetic substance contained in the magnetic layer in order to increase the magnetic recording density. For example, in a magnetic recording medium widely used as a video tape, a computer tape, a disk, etc., if the mass of the ferromagnetic material is the same, the noise decreases as the particle size is reduced.
CuAu-type or Cu 3 Au-type hard magnetic ordered alloy has large crystal magnetic anisotropy due to strain generated during ordering, small grain size, and exhibits hard magnetism even in the so-called nano-particle state. Therefore, it is a promising material for improving the magnetic recording density.
[0003]
As a method of synthesizing nanoparticles capable of forming a CuAu type or Cu 3 Au type alloy, when classified by precipitation method, (1) alcohol reduction method using primary alcohol, (2) secondary, tertiary, divalent or There are a polyol reduction method using a trivalent alcohol, (3) thermal decomposition method, (4) ultrasonic decomposition method, and (5) strong reducing agent reduction method.
Further, when classified by reaction system, there are (6) polymer existence method, (7) high boiling point solvent method, (8) normal micelle method, and (9) reverse micelle method.
[0004]
In the case of the alcohol reduction method (1), the reducing power is weak, and when a precious metal and a base metal are reduced at the same time, a uniform alloy is hardly formed, and a core / shell structure is often obtained. In the case of the polyol reduction method (2) and the thermal decomposition method (3), a high temperature reaction is required, so that the production suitability is poor. The ultrasonic decomposition method (4) and the strong reducing agent reduction method (5) are relatively simple methods. However, aggregation and precipitation are likely to occur, and if the reaction system is not devised, monodispersed and small nanoparticles Is difficult to get.
[0005]
In addition, as a system combining (1) and (6), there is an ethanol reduction method in polyvinylpyrrolidone, but in this case, the amount of polymer after synthesis is very large and it is difficult to reduce it to the required amount. .
JP-A-2000-54012 and US Pat. No. 6,254,662 are known as systems combining (2), (3) and (7). This method is highly dangerous because it uses a highly toxic substance, and further has a drawback that the apparatus configuration is complicated and the suitability for production is inferior because it is necessary to react in an inert gas at a high temperature close to 300 ° C. ing.
A system combining (5) and (8) and a system combining (5) and (9) are general methods, but details on a method for obtaining metal nanoparticles having a desired composition and particle size are available. Conditions have not been found yet.
[0006]
The structure of the nanoparticles synthesized by the above method is a face-centered cubic crystal. Face-centered cubic crystals are usually soft or paramagnetic. Soft magnetism or paramagnetism is not suitable for recording media. In order to obtain a hard magnetic ordered alloy having a coercive force of 95.5 kA / m (1200 Oe) or more necessary for a magnetic recording medium, it is necessary to perform an annealing treatment at a temperature higher than the transformation temperature at which the transformation from the disordered phase to the ordered phase occurs.
However, when the nanoparticles produced by the above method are coated on a support and subjected to annealing treatment to produce a magnetic recording medium, the nanoparticles tend to aggregate with each other, so the coating suitability is lowered and the magnetic properties are lowered. In addition, since the obtained nanoparticles have non-uniform particle sizes, it is difficult to obtain a completely ordered phase even when heat treatment is performed, and the desired hard magnetism may not be obtained.
[0007]
Further, the transformation temperature is usually as high as 500 ° C. or higher, and a generally used organic support has a problem of heat resistance. Therefore, nanoparticles are applied on the organic support and annealed to form a magnetic film. It was difficult.
[0008]
[Problems to be solved by the invention]
From the above, the present invention produces multi-component alloy nanoparticles with a low transformation temperature, hardly agglomerated, excellent coating suitability, controllable particle size and composition, and capable of expressing ferromagnetism in high yield. It aims to provide a way to do.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by the present invention described below. That is, the present invention
A reduction step in which one or more reverse micelle solutions (I) containing a metal salt and a reverse micelle solution (II) containing a reducing agent are mixed and subjected to a reduction treatment; and an aging step in which an aging treatment is performed after the reduction treatment; A method for producing nanoparticles made of a multi-component alloy via
At least two metals constituting the multi-component alloy are selected from Group VIb and Group VIII in the short periodic table;
At least one metal constituting the multi-component alloy is selected from the group Ib, IIIa, IVa and Va, and the content of the selected metal is 1 to 30 atomic% of the whole multi-component alloy. , der is,
The aging temperature in the aging step is 5 ° C. or more higher than the reduction temperature in the reduction step .
When at least two kinds of metals constituting the multi-component alloy are selected from the group VIb and group VIII in the short periodic table in order to exhibit ferromagnetism and hard magnetism, CuAu type or Cu 3 Au is selected depending on these metals. A mold alloy is preferably formed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
<Method for producing multi-component alloy nanoparticles>
The method for producing nanoparticles of the present invention comprises a reduction step of performing a reduction treatment by mixing at least one reverse micelle solution (I) containing a metal salt and a reverse micelle solution (II) containing a reducing agent, and the reduction And an aging step of performing an aging treatment after the treatment. By such a production method, multi-component alloy nanoparticles (hereinafter sometimes simply referred to as “nanoparticles”) are produced.
Hereinafter, each step will be described.
[0011]
(Reduction process)
First, a reverse micelle solution (I) in which a water-insoluble organic solvent containing a surfactant and a metal salt aqueous solution are mixed is prepared. The reverse micelle solution (I) may contain a mixture of a plurality of types of metal salts used to form a multi-component alloy, or prepare reverse micelle solutions that are separately contained, Each may be a reverse micelle solution (I).
For example, a reverse micelle solution (I a ) containing a metal selected from Group VIb and Group VIII and a metal selected from Group Ib, Group IIIa, Group IVa and Va separately The reverse micelle solution (I b ) to be prepared may be prepared separately and mixed as appropriate.
[0012]
An oil-soluble surfactant is used as the surfactant. Specifically, sulfonate type (for example, aerosol OT (manufactured by Wako Pure Chemical Industries), quaternary ammonium salt type (for example, cetyltrimethylammonium bromide), ether type (for example, pentaethylene glycol dodecyl ether) and the like can be mentioned. It is done.
[0013]
Preferable water-insoluble organic solvents for dissolving the surfactant are alkanes and ethers. The alkane is preferably an alkane having 7 to 12 carbon atoms. Specifically, heptane, octane, nonane, decane, undecane, and dodecane are preferable. The ether is preferably diethyl ether, dipropyl ether or dibutyl ether.
The amount of the surfactant in the water-insoluble organic solvent is preferably 20 to 200 g / liter.
[0014]
Metal salts contained in metal salt aqueous solutions include nitrates, sulfates, hydrochlorides, acetates, hydrogen acids of metal complexes with chloride ions as ligands, potassium salts of metal complexes with chloride ions as ligands In addition, a sodium salt of a metal complex having a chloride ion as a ligand, an ammonium salt of a metal complex having an oxalate ion as a ligand, and the like can be used.
[0015]
Further, as the metal, at least two kinds are selected from group VIb and group VIII in the short periodic table, and at least one kind is selected from group Ib, group IIIa, group IVa and Va.
A metal selected from the group VIb and group VIII produces nanoparticles capable of expressing hard magnetism. In addition, a metal selected from the group Ib, group IIIa, group IVa and group Va can lower the phase transformation temperature for developing the hard magnetism of the nanoparticles. As a result, when a magnetic recording medium or the like is to be manufactured using the nanoparticles, it is not necessary to consider the heat resistance of the support and the like, and therefore the magnetic layer containing the nanoparticles on a support made of an organic substance Can be formed efficiently.
[0016]
Examples of binary and ternary alloy compositions composed of VIb group and VIII group include FePt, FePd, FeNi, CoPt, CoPd, CoAu, CoCrPt, CoCrPd, FeNiPt, and FeCoPt.
In addition, as other elements selected from the Ib group, IIIa group, IVa group and Va group contained in order to form a multi-component alloy, in particular, Cu, Ag, B, In, Sn, Pb, P, Sb, It is preferably selected from Bi and the like. The addition amount (content) of an element selected from the group Ib, group IIIa, group IVa and Va is 1 to 30 atomic%, preferably 5 to 20 atomic% of the entire multi-component alloy.
When the addition amount is less than 1 atomic%, the effect of lowering the transformation temperature is reduced, and the significance of addition is lost. If it exceeds 30 atomic%, the crystal structure of the nanoparticles cannot form an ordered phase exhibiting hard magnetism after annealing.
The multi-element alloy may be composed of 3 to 5 elements in total including 2 elements selected from Group VIb and VIII and 1 element selected from Groups Ib, IIIa, IVa and Va. preferable.
[0017]
The concentration in each metal salt aqueous solution (as the metal salt concentration) is preferably 0.1 to 2000 μmol / ml, and more preferably 1 to 500 μmol / ml.
[0018]
It is preferable to add a chelating agent to the aqueous metal salt solution so that the obtained particles have a uniform composition. The chelate stability constant (log K) is preferably 10 or less. Specifically, DHEG (dihydroxyethylglycine), IDA (iminodiacetic acid), NTP (nitrilotripropionic acid), HIDA (dihydroxyethyliminodiacetic acid), EDDP (ethylenediamine dipropionic acid dihydrochloride), BAPTA (Diaminophenylethylene glycol tetraacetic acid tetrapotassium salt hydrate) is preferably used.
[0019]
0.1-10 mol is preferable with respect to 1 mol of metal salts, and, as for the addition amount of a chelating agent, 0.3-3 mol is more preferable.
[0020]
Next, a reverse micelle solution (II) in which a water-insoluble organic solvent containing a surfactant and a reducing agent aqueous solution are mixed is prepared. When two or more reducing agents are used, they may be mixed together to form a reverse micelle solution (II). However, in view of liquid stability and workability, each is separately added to a water-insoluble organic solvent. It is preferable to mix them and prepare them as separate reverse micelle solutions (II a ), (II b ) (II c ), etc., and to use them by appropriately mixing them.
[0021]
The reducing agent in the reducing agent solution, alcohols, poly alcohols; H 2; HCHO, S 2 O 6 2-, H 2 PO 2 -, BH 4 -, N 2 H 5 +, H 2 PO 3 - Are preferably used alone or in combination of two or more.
The amount of the reducing agent in the aqueous solution is preferably 3 to 50 mol with respect to 1 mol of the metal salt.
[0022]
The mass ratio of water to surfactant contained in each of the reverse micelle solutions (I) and (II) (water / surfactant) is preferably 20 or less. If the mass ratio exceeds 20, precipitation may easily occur and particles may become uneven. The mass ratio is more preferably 15 or less, and further preferably 0.5 to 10.
[0023]
The mass ratio of the water and the surfactant in the reverse micelle solutions (I) and (II) may be the same or different, but is preferably the same in order to make the system uniform.
[0024]
The reverse micelle solutions (I) and (II) prepared as described above are mixed. The mixing method is not particularly limited, but in consideration of the reduction uniformity, the reverse micelle solution (I) may be added and mixed while stirring the reverse micelle solution (II). preferable. After completion of mixing, the reduction reaction is allowed to proceed, and the temperature at that time is set to a constant temperature in the range of −5 to 30 ° C.
If the reduction temperature is less than −5 ° C., there arises a problem that the aqueous phase is condensed and the reduction reaction becomes non-uniform, and if it exceeds 30 ° C., aggregation or precipitation is likely to occur and the system becomes unstable. A preferable reduction temperature is 0 to 25 ° C, more preferably 5 to 25 ° C. Here, the “constant temperature” means that when the set temperature is T (° C.), the T is in the range of T ± 3 ° C. Even in such a case, the upper limit and the lower limit of the T are in the range of the reduction temperature (−5 to 30 ° C.).
[0025]
The time for the reduction reaction needs to be appropriately set depending on the amount of the reverse micelle solution and the like, but is preferably 1 to 30 minutes, and more preferably 5 to 20 minutes.
[0026]
Since the reduction reaction has a great influence on the monodispersity of the particle size distribution, it is preferable to carry out the reduction reaction while stirring as fast as possible (for example, about 3000 rpm or more).
A preferred stirring device is a stirring device having a high shearing force. Specifically, the stirring blade basically has a turbine-type or paddle-type structure, and a sharp blade is provided at the end of the blade or at a position in contact with the blade. It is an attached structure and is a stirring device that rotates a blade by a motor. Specifically, devices such as a dissolver (manufactured by Special Machine Industries), an omni mixer (manufactured by Yamato Kagaku), and a homogenizer (manufactured by SMT) are useful. By using these apparatuses, monodisperse nanoparticles can be synthesized as a stable dispersion.
[0027]
At least one dispersant having 1 to 3 amino groups or carboxy groups is added to at least one of the reverse micelle solutions (I) and (II) in an amount of 0.001 per mole of metal nanoparticles to be produced. It is preferable to add 10 mol.
[0028]
By adding such a dispersant, it is possible to obtain nanoparticles that are more monodispersed and have no aggregation.
If the addition amount is less than 0.001, the monodispersity of the nanoparticles may not be further improved, and if it exceeds 10 mol, aggregation may occur.
[0029]
As the dispersant, an organic compound having a group that adsorbs to the surface of the metal nanoparticles is preferable. Specifically, it has 1 to 3 amino groups, carboxy groups, sulfonic acid groups or sulfinic acid groups, and these can be used alone or in combination.
As structural formulas, R—NH 2 , NH 2 —R—NH 2 , NH 2 —R (NH 2 ) —NH 2 , R—COOH, COOH—R—COOH, COOH—R (COOH) —COOH, R —SO 3 H, SO 3 H—R—SO 3 H, SO 3 H—R (SO 3 H) —SO 3 H, R—SO 2 H, SO 2 H—R—SO 2 H, SO 2 H— R (SO 2 H) —SO 2 H, wherein R is a linear, branched or cyclic saturated or unsaturated hydrocarbon.
[0030]
A particularly preferred compound as a dispersant is oleic acid. Oleic acid is a well-known surfactant in colloidal stabilization and has been used to protect iron nanoparticles. The relatively long chains of oleic acid (eg, oleic acid has 18 carbon chains and is ˜20 angstroms (˜2 nm). Oleic acid is not aliphatic but has one double bond). This gives an important steric hindrance to counteract strong magnetic interactions.
Similar long chain carboxylic acids such as erucic acid and linoleic acid are used as well as oleic acid (for example, long chain organic acids having between 8 and 22 carbon atoms can be used alone or in combination). Oleic acid is preferred because it is an inexpensive natural resource (such as olive oil) that is readily available. In addition, oleylamine derived from oleic acid is a useful dispersant like oleic acid.
[0031]
(Aging process)
After completion of the reduction reaction, the temperature of the solution after the reaction is raised to the aging temperature.
The aging temperature is preferably a constant temperature of 30 to 90 ° C., and the temperature is higher than the temperature of the reduction reaction. The aging time is preferably 5 to 180 minutes. If the aging temperature and time shift from the above range to the high temperature and long time side, aggregation or precipitation tends to occur. Conversely, if the aging temperature and time shift to the low temperature short time side, the reaction is not completed and the composition changes. More preferable aging temperature and time are 40 to 80 ° C. and 10 to 150 minutes, and further preferable aging temperature and time are 40 to 70 ° C. and 20 to 120 minutes.
[0032]
Here, the “constant temperature” is synonymous with the temperature of the reduction reaction (where “reduction temperature” is the “aging temperature”), but in particular, the range of the above aging temperature (30 It is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, than the temperature of the reduction reaction. If it is less than 5 ° C., the composition as prescribed may not be obtained.
[0033]
In the aging process as described above, noble metal is deposited on the base metal that has been reduced and deposited in the reduction process. That is, the reduction of the noble metal occurs only on the base metal, and the base metal and the noble metal do not separate separately, so that the CuAu type or Cu 3 Au type hard magnetic ordered alloy is efficiently formed. The obtained nanoparticles can be produced in a high yield according to the formulation composition ratio, and can be controlled to a desired composition. Moreover, the particle diameter of the nanoparticle obtained can be made into a desired thing by adjusting a stirring speed suitably with the temperature in the case of ageing | curing | ripening.
[0034]
After the aging, the solution after aging is washed with a mixed solution of water and a primary alcohol, and then subjected to a precipitation treatment with a primary alcohol to generate a precipitate. It is preferable to provide a washing / dispersing step for dispersing with a solvent.
By providing such a cleaning step, impurities can be removed, and the coating property when the magnetic layer of the magnetic recording medium is formed by coating can be further improved.
The washing and dispersion are each performed at least once, preferably twice or more.
[0035]
The primary alcohol used for washing is not particularly limited, but methanol, ethanol and the like are preferable. The volume mixing ratio (water / primary alcohol) is preferably in the range of 10/1 to 2/1, and more preferably in the range of 5/1 to 3/1.
When the ratio of water is high, the surfactant may be difficult to remove, and conversely, when the ratio of primary alcohol is high, aggregation may occur.
[0036]
As described above, nanoparticles dispersed in the solution are obtained. Since the nanoparticles are monodispersed, even when applied to a support, they can be kept uniformly dispersed without agglomeration. Therefore, even if annealing treatment is performed, the respective nanoparticles do not aggregate, so that the magnetic particles can be efficiently made hard and the application property is excellent.
[0037]
In the present invention, the particle size of the nanoparticles before annealing is preferably 1 to 20 nm, and more preferably 3 to 10 nm. For use as a magnetic recording medium, it is preferable to close-pack the nanoparticles to increase the recording capacity. For that purpose, the coefficient of variation in the particle size distribution of the metal nanoparticles of the present invention is preferably 15% or less, more preferably 8% or less.
If the particle size is too small, it becomes superparamagnetic due to thermal fluctuation, which is not preferable. Although the minimum stable particle size varies depending on the constituent elements, it is effective to synthesize by changing the H 2 O / surfactant mass ratio in order to obtain the required particle size.
[0038]
A transmission electron microscope (TEM) can be used for particle size evaluation of the nanoparticles produced in the present invention. Electron beam diffraction by TEM may be used to determine the crystal system of the nanoparticles that have become hard magnetic by heating, but X-ray diffraction is better used for high accuracy. For composition analysis inside the hard magnetized nanoparticles, it is preferable to evaluate by attaching EDAX to FE-TEM that can narrow the electron beam. Evaluation of the magnetic properties of the hard magnetized nanoparticles can be performed using VSM.
[0039]
It is preferable that the coercive force of the nanoparticles after annealing described below is 95.5 to 1193.8 KA / m (1200 to 15000 Oe).
[0040]
The method for heating the nanoparticles to the transformation temperature or higher may be arbitrary, but in order to avoid the fusion of the nanoparticles, it is preferable to heat the nanoparticles after coating on the support.
Since the nanoparticles obtained by the production method of the present invention have a low transformation temperature, they can be suitably used for an organic support having a low heat resistance temperature. In this case, if a pulse laser is used as a means for heating to the transformation temperature, the organic support is used. Deterioration and deformation due to body heat can be prevented more efficiently.
[0041]
The hard magnetic nanoparticles can be preferably used for video tapes, computer tapes, floppy (R) disks, and hard disks. Moreover, application to MRAM is also preferable.
[0042]
<Magnetic recording medium>
A magnetic recording medium using nanoparticles produced by the production method of the present invention has at least a magnetic layer formed on a support, and the magnetic layer contains nanoparticles obtained by the production method of the present invention. Contains. The magnetic layer is formed by applying a coating solution in which the nanoparticles are dispersed on a support and performing an annealing treatment. Moreover, it has another layer as needed.
That is, such a magnetic recording medium has a magnetic layer containing nanoparticles on the surface of the support, and a nonmagnetic layer is provided between the magnetic layer and the support as necessary. Similarly, a magnetic layer and, if necessary, a magnetic layer and a nonmagnetic layer may be provided on the opposite surface. In the case of a tape, a back coat layer is provided on the support opposite to the magnetic layer.
[0043]
【Example】
The present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.
[0044]
[Example 1]
The following operation was performed in high purity N 2 gas.
Triammonium iron oxalate (Fe (NH 4 ) 3 (C 2 O 4 ) 3 ) (manufactured by Wako Pure Chemical Industries) 0.35 g and potassium chloroplatinate (K 2 PtCl 4 ) (manufactured by Wako Pure Chemical Industries) 0.35 g An alkane solution having 10.8 g of aerosol OT dissolved in 80 ml of decane was added to and mixed with an aqueous solution of metal salt dissolved in 24 ml of H 2 O (deoxygenated) to prepare a reverse micelle solution (I a ).
[0045]
To a reducing agent aqueous solution obtained by dissolving 0.57 g of NaBH 4 (manufactured by Wako Pure Chemical Industries) in 12 ml of H 2 O (deoxygenated), 5.4 g of aerosol OT (manufactured by Wako Pure Chemical Industries) and 2 ml of oleylamine (manufactured by Tokyo Chemical Industry) Was added to and mixed with 40 ml of decane (manufactured by Wako Pure Chemical Industries) and mixed to prepare a reverse micelle solution (II a ).
[0046]
Alkane solution in which 0.07 g of copper chloride (CuCl 2 · 6H 2 O) (manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in 2 ml of H 2 O (deoxygenated) in an aqueous metal salt solution and 2.7 g of aerosol OT is dissolved in 20 ml of decane. Were added and mixed to prepare a reverse micelle solution (I b ).
[0047]
Ascorbic acid (manufactured by Wako Pure Chemical Industries, Ltd.) 0.88 g of H 2 O (deoxygenated) dissolved in 12 ml of a reducing agent aqueous solution, aerosol OT (manufactured by Wako Pure Chemical Industries, Ltd.) 5.4 g, decane (manufactured by Wako Pure Chemical Industries, Ltd.) 40 ml A reverse micelle solution (II b ) was prepared by adding and mixing the alkane solution dissolved in 1.
[0048]
While the reverse micelle solution (I a ) was rapidly stirred at 22 ° C. with an omni mixer (manufactured by Yamato Kagaku), the reverse micelle solution (II a ) was added instantaneously. After 3 minutes, further reverse micelle solution (I b ) was added at a rate of about 2.4 ml / min over about 10 minutes. Five minutes after the end of the addition, the stirring was changed to magnetic stirrer and the temperature was raised to 40 ° C., then the reverse micelle solution (II b ) was added and aged for 120 minutes.
After cooling to room temperature, 2 ml of oleic acid (manufactured by Wako Pure Chemical Industries) was added, mixed, and taken out into the atmosphere. In order to destroy the reverse micelle, a mixed solution of 200 ml of H 2 O and 200 ml of methanol was added to separate into an aqueous phase and an oil phase. A state in which the metal nanoparticles were dispersed on the oil phase side was obtained. The oil phase side was washed 5 times with 600 ml of H 2 O + 200 ml of methanol. Thereafter, 1300 ml of methanol was added to cause flocculation of the metal nanoparticles and sedimentation. The supernatant was removed, and 20 ml of heptane (manufactured by Wako Pure Chemical Industries, Ltd.) was added and redispersed. Furthermore, precipitation by adding 100 ml of methanol and dispersion with 20 ml of heptane were repeated twice, and finally 5 ml of octane (manufactured by Wako Pure Chemical Industries, Ltd.) was added to obtain a FeCuPt nanoparticle dispersion.
[0049]
[Example 2]
A FeInPt nanoparticle dispersion was obtained in the same manner as in Example 1 except that the metal salt in the reverse micelle solution (I b ) was changed to 0.07 g of InCl 3 (manufactured by Wako Pure Chemical Industries). .
[0050]
Example 3
An FePbPt nanoparticle dispersion was obtained in the same manner as in Example 1 except that the metal salt in the reverse micelle solution (I b ) was changed to 0.08 g of PbCl 2 (manufactured by Wako Pure Chemical Industries). .
[0051]
Example 4
A CoBiPt nanoparticle dispersion was obtained in the same manner as in Example 1 except that the metal salts of the reverse micelle solutions (I a ) and (I b ) of Example 1 were changed to the following.
Metal salt of reverse micelle solution (I a ): 0.20 g of cobalt chloride (CoCl 2 · 6H 2 O) and potassium chloroplatinate (K 2 PtCl 4 ) (manufactured by Wako Pure Chemical Industries) 0.35 g Reverse micelle solution (I b ) Metal salt: 0.41 g of bismuth nitrate (Bi (NO 3 ) 3 .5H 2 O)
[0052]
Example 5
The following operation was performed in high purity N 2 gas.
Triammonium iron oxalate (Fe (NH 4 ) 3 (C 2 O 4 ) 3 ) (manufactured by Wako Pure Chemical Industries) 0.18 g and potassium chloroplatinate (K 2 PtCl 4 ) (manufactured by Wako Pure Chemical Industries) 0.35 g An alkane solution having 10.8 g of aerosol OT dissolved in 80 ml of decane was added to and mixed with an aqueous solution of metal salt dissolved in 24 ml of H 2 O (deoxygenated) to prepare a reverse micelle solution (I a ).
[0053]
Alkane solution in which 0.10 g of cobalt chloride (CoCl 2 · 6H 2 O) (manufactured by Wako Pure Chemical Industries) is dissolved in 2 ml of H 2 O (deoxygenated) and 2.7 g of aerosol OT is dissolved in 20 ml of decane. Were added and mixed to prepare a reverse micelle solution (I b ).
[0054]
Decanted 5.4 g of aerosol OT (manufactured by Wako Pure Chemical Industries) and 2 ml of oleylamine (manufactured by Tokyo Chemical Industry) in an aqueous reducing agent solution in which 0.57 g of NaBH 4 (manufactured by Wako Pure Chemical Industries) was dissolved in 12 ml of H 2 O (deoxygenated). An alkane solution dissolved in 40 ml (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed to prepare a reverse micelle solution (II a ).
[0055]
To a metal salt aqueous solution in which 0.06 g of copper acetate (Cu (CH 3 COO) 2 .H 2 O) (manufactured by Wako Pure Chemical Industries) was dissolved in 2 ml of H 2 O (deoxygenated), 2.7 g of aerosol OT was added to 20 ml of decane. A reverse micelle solution (I c ) was prepared by adding and mixing the alkane solution dissolved in 1.
[0056]
Ascorbic acid (manufactured by Wako Pure Chemical Industries, Ltd.) 0.88 g of H 2 O (deoxygenated) dissolved in 12 ml of a reducing agent aqueous solution, aerosol OT (manufactured by Wako Pure Chemical Industries, Ltd.) 5.4 g, decane (manufactured by Wako Pure Chemical Industries, Ltd.) 40 ml A reverse micelle solution (II b ) was prepared by adding and mixing the alkane solution dissolved in 1.
[0057]
The reverse micelle solution (I b ) was instantaneously added while stirring the reverse micelle solution (I) at 22 ° C. with an omni mixer (manufactured by Yamato Kagaku). Two minutes later, further reverse micelle solution (II a ) was added instantaneously. Three minutes later, reverse micelle solution (I c ) was further added at a rate of about 2.4 ml / min over about 10 minutes. Five minutes after the end of the addition, the stirring was changed to magnetic stirrer and the temperature was raised to 40 ° C., then the reverse micelle solution (II b ) was added and aged for 120 minutes.
[0058]
Washing and purification were performed in the same manner as in Example 1 to obtain a FeCoCuPt nanoparticle dispersion.
[0059]
Example 6
0.33 g of chelating agent (DHEG) was added to each of the reverse micelle solutions (I a ) and (I b ), and the metal salt of the reverse micelle solution (I b ) was further added to InCl 3 (manufactured by Wako Pure Chemical Industries). A FeCoInPt nanoparticle dispersion was obtained in the same manner as in Example 5 except that the amount was 07 g.
[0060]
[Comparative Example 1]
Without using the reverse micelle solution (I b ) and (II b ) of Example 1, the reverse micelle solution (I
) Was stirred with a magnetic stirrer at room temperature (25 ° C.), the reverse micelle solution (II a ) was added instantaneously to cause a reduction reaction, and the mixture was aged at the same temperature for 120 minutes. Thus, a FePt nanoparticle dispersion was obtained.
[0061]
[Comparative Example 2]
Without using the reverse micelle solution (I b ) of Example 1, the reverse micelle solution (II a ) was instantaneously added while stirring the reverse micelle solution (I a ) at 22 ° C. with an omni mixer (manufactured by Yamato Kagaku). did. After 10 minutes, the magnetic stirrer was changed to stirring, the temperature was raised to 40 ° C., the reverse micelle solution (II b ) was added, and the mixture was aged for 120 minutes. A dispersion was obtained.
[0062]
[Comparative Example 3]
The following operation was performed in high purity N 2 gas.
Platinum acetylacetonate (Pt (acac) 2 ) (manufactured by Wako Pure Chemical Industries) 0.39 g, 1,12-dodecanediol (manufactured by Wako Pure Chemical Industries) 0.6 ml and dioctyl ether 20 ml were mixed and heated to 100 ° C. Thereafter, 0.28 ml of oleic acid, 0.26 ml of oleylamine and 0.25 g of iron acetylacetonate (Fe (acac) 3 ) were added, the temperature was raised to 297 ° C., and the mixture was refluxed for 30 minutes.
[0063]
After cooling, 200 ml of methanol was added, and the metal nanoparticles were caused to flocculate and settle. After removing the supernatant, 20 ml of heptane was added and redispersed. Again 100 ml of methanol was added and allowed to settle. After carrying out heptane dispersion and methanol precipitation once again, it was dispersed with 5 ml of octane to obtain a FePt nanoparticle dispersion.
[0064]
The results of Table 1 were obtained by analyzing the nanoparticles obtained in Examples 1 to 6 and Comparative Examples 1 to 3.
In Table 1, the composition and yield were measured by ICP spectroscopic analysis (inductively coupled high-frequency plasma spectroscopic analysis) after evaporating the dispersion to dryness, decomposing organic matter with concentrated sulfuric acid, and then dissolving in aqua regia.
The number average particle size and distribution were calculated by measuring particles taken by TEM and performing statistical processing. The coercive force was measured using a highly sensitive magnetization vector measuring machine manufactured by Toei Kogyo Co., Ltd. and a DATA processing apparatus manufactured by the same company, with an applied magnetic field of 790 KA / m (10 kOe). The measured nanoparticles were obtained by evaporating and drying the nanoparticle dispersion and then annealing (550 ° C. or 350 ° C.) in an Ar mixed gas containing 5% of H 2 in an infrared heating furnace (manufactured by ULVAC-RIKO). used.
[0065]
[Table 1]
As is clear from Table 1, the nanoparticles of Examples 1 to 6 had a higher yield and a composition close to the prescribed value than Comparative Examples 1 and 3. Further, the coefficient of variation of the particle size distribution was small and monodispersed, and the coercive force after annealing was high. Furthermore, the nanoparticles of Examples 1 to 6 exhibited a high coercive force even in the low temperature (350 ° C.) annealing treatment as compared with Comparative Examples 1 to 3.
[0067]
The nanoparticle dispersions prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were applied on a fired Si substrate (a 300 nm thick SiO 2 layer formed on the Si surface) by a spin coating method. The coating amount was 0.1 g / m 2 , respectively.
[0068]
After coating, each coated sample was annealed with an Ar + H 2 (5%) mixed gas at 350 ° C. for 30 minutes in an infrared heating furnace (manufactured by ULVAC-RIKO) to form a magnetic layer on the substrate.
After the annealing treatment, 10 nm of carbon is applied to the surface of the magnetic layer by a sputtering apparatus (manufactured by Shibaura Mechatronics), and a lubricant (FOMBLIN: made by AUSIMINT) is further applied to the thickness of about 5 nm by spin coating. A magnetic recording medium was obtained.
[0069]
As a result of evaluating the magnetic characteristics, Comparative Examples 1 to 3 did not become hard magnetism, whereas Examples 1 to 6 showed hard magnetism having a coercive force of 318.3 KA / m (4000 Oe) or more.
Moreover, the nanoparticle of Examples 1-6 was maintaining the particle size before annealing, without fuse | melting also by annealing.
[0070]
【The invention's effect】
As described above, according to the method for producing nanoparticles of the present invention, the transformation temperature is low, the aggregation is difficult, the coating suitability is excellent, the size and composition of the particles are controllable, and the nanoparticles capable of expressing ferromagnetism are increased. It can be produced in a yield.
Claims (2)
前記多元系合金を構成する少なくとも２種の金属が短周期表におけるＶＩｂ族およびＶＩＩＩ族の中から選択され、
前記多元系合金を構成する少なくとも１種の金属がＩｂ族、ＩＩＩａ族、ＩＶａ族およびＶａ族の中から選択され、その選択された金属の含有量が前記多元系合金全体の１〜３０原子％、であり、
前記熟成工程における熟成温度が、前記還元工程における還元温度より５℃以上高いことを特徴とする多元系合金ナノ粒子の製造方法。A reduction step in which one or more reverse micelle solutions (I) containing a metal salt and a reverse micelle solution (II) containing a reducing agent are mixed and subjected to a reduction treatment; and an aging step in which an aging treatment is performed after the reduction treatment; A method for producing nanoparticles made of a multi-component alloy via
At least two metals constituting the multi-component alloy are selected from Group VIb and Group VIII in the short periodic table;
At least one metal constituting the multi-component alloy is selected from Group Ib, IIIa, IVa and Va, and the content of the selected metal is 1 to 30 atomic% of the whole multi-component alloy. , And
A method for producing multi-component alloy nanoparticles, wherein the aging temperature in the aging step is 5 ° C. or more higher than the reduction temperature in the reduction step.
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| DE60302682T DE60302682T2 (en) | 2002-02-18 | 2003-02-18 | Process for the preparation of nanoparticles |
| EP03003149A EP1338361B1 (en) | 2002-02-18 | 2003-02-18 | Method of producing nanoparticle |
| US10/367,873 US7066978B2 (en) | 2002-02-18 | 2003-02-19 | Nanoparticle, method of producing nanoparticle and magnetic recording medium |
| US11/080,492 US20050158506A1 (en) | 2002-02-18 | 2005-03-16 | Nanoparticle, method of producing nanoparticle and magnetic recording medium |
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