JP4775713B2 - Coated fine metal powder and magnetic beads - Google Patents

Coated fine metal powder and magnetic beads Download PDF

Info

Publication number
JP4775713B2
JP4775713B2 JP2006262410A JP2006262410A JP4775713B2 JP 4775713 B2 JP4775713 B2 JP 4775713B2 JP 2006262410 A JP2006262410 A JP 2006262410A JP 2006262410 A JP2006262410 A JP 2006262410A JP 4775713 B2 JP4775713 B2 JP 4775713B2
Authority
JP
Japan
Prior art keywords
metal
fine particles
particles
oxide
powder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP2006262410A
Other languages
Japanese (ja)
Other versions
JP2008081779A (en
Inventor
久人 所
重男 藤井
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Metals Ltd
Original Assignee
Hitachi Metals Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Metals Ltd filed Critical Hitachi Metals Ltd
Priority to JP2006262410A priority Critical patent/JP4775713B2/en
Publication of JP2008081779A publication Critical patent/JP2008081779A/en
Application granted granted Critical
Publication of JP4775713B2 publication Critical patent/JP4775713B2/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Description

本発明は、磁気テープ若しくは磁気記録ディスク等の磁気記録媒体、電波吸収体、インダクタ若しくはプリント基板等の電子デバイス（ヨーク等の軟磁性体）、光触媒、核酸抽出用磁気ビーズ若しくは医療用マイクロスフィア等に用いる被覆金属微粒子の粉末に関する。   The present invention relates to a magnetic recording medium such as a magnetic tape or a magnetic recording disk, a radio wave absorber, an electronic device such as an inductor or a printed circuit board (soft magnetic material such as a yoke), a photocatalyst, a magnetic bead for nucleic acid extraction, a medical microsphere, etc. The present invention relates to powder of coated metal fine particles used in the above.

電子機器の高性能化及び小型軽量化に伴い、電子デバイスの高性能化及び小型軽量化とともに、電子デバイスを構成する材料の高性能化及びナノサイズ化も要求されている。例えば磁気テープに塗布する磁性粒子は、磁気記録密度の向上を目的として、ナノサイズ化と磁化の向上が同時に要求されている。   As electronic devices become more sophisticated and smaller and lighter, there is a demand for higher performance and smaller size and weight of electronic devices, as well as higher performance and nano-size of materials constituting electronic devices. For example, magnetic particles applied to magnetic tape are required to be nanosized and magnetized at the same time for the purpose of improving magnetic recording density.

ナノ磁性粒子は主に共沈法や水熱合成法等の液相合成法により製造されている。液相合成法で得られるナノ磁性粒子はフェライトやマグネタイト等の酸化物粒子である。最近では有機金属化合物の熱分解を利用した方法も採用されており、例えばＦｅ（ＣＯ）６からＦｅのナノ磁性粒子が製造されている。 Nanomagnetic particles are mainly produced by a liquid phase synthesis method such as a coprecipitation method or a hydrothermal synthesis method. Nanomagnetic particles obtained by the liquid phase synthesis method are oxide particles such as ferrite and magnetite. Recently, a method using thermal decomposition of an organometallic compound has also been adopted. For example, Fe nanoparticle of Fe is produced from Fe (CO) 6 .

金属の磁性粒子はフェライト等の酸化物粒子に比べて磁化が大きいため、工業的利用への期待が大きい。例えば、金属Ｆｅの飽和磁化は２１８Ａｍ２／ｋｇと酸化鉄に比べて非常に大きいので、磁界応答性に優れ、信号強度が大きくとれるという利点がある。しかし金属Ｆｅ等の金属微粒子は容易に酸化し、例えば１００μｍ以下、特に１μｍ以下の微粒子状にすると、比表面積の増大により大気中で激しく燃えるので、乾燥状態で取り扱うのが難しい。そのため、フェライトやマグネタイト等の酸化物粒子が広く利用されてきた。 Since metal magnetic particles have larger magnetization than oxide particles such as ferrite, they are highly expected for industrial use. For example, the saturation magnetization of metallic Fe is 218 Am 2 / kg, which is very large compared to iron oxide, and therefore has the advantage of excellent magnetic field response and high signal intensity. However, metal fine particles such as metal Fe readily oxidize. For example, if they are made into fine particles of 100 μm or less, particularly 1 μm or less, they burn intensely in the atmosphere due to an increase in specific surface area, and are difficult to handle in a dry state. Therefore, oxide particles such as ferrite and magnetite have been widely used.

乾燥した金属微粒子を取り扱う場合、金属微粒子を直接大気（酸素）に触れさせないように粒子表面に被覆を付与することが不可欠である。しかし、特許文献１のように自身の金属酸化物で表面を被覆する方法は、少なからず金属を酸化劣化させる。   When handling dried metal fine particles, it is essential to provide a coating on the particle surface so that the metal fine particles are not directly exposed to the atmosphere (oxygen). However, the method of covering the surface with its own metal oxide as in Patent Document 1 oxidizes and degrades the metal.

特許文献２は、カーボンブラック、天然黒鉛等の炭素質物質粒子と、金属単体の粒子若しくは金属化合物粒子（金属化合物は、金属酸化物、金属炭化物又は金属塩から選ばれる。）とを混合して、不活性ガス雰囲気中で１６００〜２８００℃に熱処理し、４５℃／分以下の冷却速度で冷却することにより、グラファイト被覆金属微粒子を製造する方法を提案している。しかし、この方法では、１６００〜２８００℃と極めて高い温度で金属含有物質粒子を熱処理するので、金属微粒子の焼結が懸念される。その上、金属微粒子にグラファイトを被覆する方法は生産効率が低いという問題もある。   In Patent Document 2, carbonaceous material particles such as carbon black and natural graphite are mixed with particles of a single metal or metal compound particles (the metal compound is selected from a metal oxide, a metal carbide, or a metal salt). A method for producing graphite-coated metal fine particles by heat treatment at 1600 to 2800 ° C. in an inert gas atmosphere and cooling at a cooling rate of 45 ° C./min or less is proposed. However, in this method, since the metal-containing material particles are heat-treated at an extremely high temperature of 1600 to 2800 ° C., there is a concern about sintering of the metal fine particles. In addition, the method of coating the fine metal particles with graphite has a problem that the production efficiency is low.

特開２０００−３０９２０号公報（図２、第１０頁左欄）JP 2000-30920 A (FIG. 2, page 10, left column) 特開平９−１４３５０２号公報（図６、第３頁）JP 9-143502 A (FIG. 6, page 3)

その上、グラファイトはグラフェンシートが積層した構造を有するため、球状の金属微粒子を被覆した場合、必ず格子欠陥が導入される。これらの欠陥が存在する被覆では、磁気ビーズ等、高耐食性が要求される用途では不満足である。そのため、高耐食性の金属微粒子が望まれている。   In addition, since graphite has a structure in which graphene sheets are laminated, lattice defects are always introduced when spherical metal fine particles are coated. Coatings with these defects are unsatisfactory for applications that require high corrosion resistance, such as magnetic beads. Therefore, highly corrosion-resistant metal fine particles are desired.

従って、本発明の目的は、耐食性に優れた被覆金属微粒子の粉末およびそれを用いた磁気ビーズを提供することである。   Accordingly, an object of the present invention is to provide a powder of coated metal fine particles having excellent corrosion resistance and a magnetic bead using the powder.

本発明の被覆金属微粒子の粉末は、ＴｉＯ ２ を主体とするＴｉ酸化物中に金属粒子を内包した被覆金属微粒子の粉末であって、前記金属はその酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属であり、前記金属粒子の粒径に対する個数分布が複数のピークを有することを特徴とする。前記被覆金属微粒子の粉末は、前記Ｔｉ酸化物中に複数の金属粒子を内包した被覆金属微粒子を有することが望ましい。Ｔｉ酸化物中に複数の金属粒子を内包した被覆金属微粒子の他に、Ｔｉ酸化物中に１つの金属粒子を内包した被覆金属微粒子を有してもよい。 The powder of the coated metal fine particles of the present invention is a powder of coated metal fine particles in which metal particles are encapsulated in a Ti oxide mainly composed of TiO 2 , and the metal has a standard free energy of formation of its oxide ΔG M− It is a metal satisfying the relationship of O 2 > ΔG TiO 2 , and the number distribution with respect to the particle diameter of the metal particles has a plurality of peaks. The powder of coated, fine metal particles, it is desirable to have a coated metal fine particles containing a plurality of metal particles in the Ti oxide. In addition to the coated metal fine particles in which a plurality of metal particles are encapsulated in Ti oxide, the coated metal fine particles in which one metal particle is encapsulated in Ti oxide may be included.

本発明の磁気ビーズは、ＴｉＯ ２ を主体とするＴｉ酸化物中に金属粒子を内包した被覆金属微粒子の粉末（前記金属粒子はＦｅ、Ｃｏ、Ｎｉから選ばれる少なくとも１つの元素を主成分としており、前記金属粒子の粒径に対する個数分布が複数のピークを有する。）と、前記被覆金属微粒子を分散する媒体とを有する。媒体は被覆金属微粒子を分散できる液体であることが望ましい。なお、媒体と接触させる前に、前記Ｔｉ酸化物からなる被覆の表面に更にＳｉ酸化物（シリカ）の被覆を形成しておくことがより好ましい。 The magnetic bead of the present invention is a powder of coated metal fine particles in which metal particles are encapsulated in Ti oxide mainly composed of TiO 2 (the metal particles are mainly composed of at least one element selected from Fe, Co, and Ni). The number distribution of the metal particles with respect to the particle diameter has a plurality of peaks), and a medium in which the coated metal fine particles are dispersed. The medium is desirably a liquid capable of dispersing the coated metal fine particles. It is more preferable to further form a Si oxide (silica) coating on the surface of the Ti oxide coating before contacting with the medium.

本発明に係る被覆金属微粒子の製造方法は、Ｔｉを含む粉末（ただしＴｉ酸化物粉末を除く）と、酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属Ｍの酸化物粉末とを混合し、得られた混合粉末を非酸化性雰囲気中で６５０〜９００℃の温度で熱処理することにより、前記金属Ｍの酸化物をＴｉにより還元するとともに、得られた金属Ｍの微粒子の表面をＴｉＯ2を主体とするＴｉ酸化物で被覆することを特徴とする。 The method for producing coated metal fine particles according to the present invention includes a powder containing Ti (excluding a Ti oxide powder) and an oxidation of metal M satisfying the relationship of ΔG M−O > ΔG TiO 2 where the standard free energy of formation of the oxide The resulting mixed powder is heat-treated at a temperature of 650 to 900 ° C. in a non-oxidizing atmosphere, whereby the oxide of the metal M is reduced with Ti and the obtained metal M is mixed. The surface of the fine particles is covered with a Ti oxide mainly composed of TiO 2 .

より詳細には、本発明の被覆金属微粒子の製造方法は、Ｔｉを含む粉末（ＴｉＣを主成分とし、前記ＴｉＣの一部をＴｉＮで置換する）と、酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属Ｍの酸化物粉末とを混合し、得られた混合粉末を非酸化性雰囲気中で６５０〜９００℃の温度で熱処理することにより、前記金属Ｍの酸化物をＴｉにより還元するとともに、得られた金属Ｍの微粒子の表面をＴｉＯ２を主体とするＴｉ酸化物で被覆することを特徴とする。 More specifically, the method of producing coated, fine metal particles of the present invention, (the main component TiC, a part of the TiC is replaced by TiN) powder containing Ti and the standard free energy of oxide formation is .DELTA.G M The metal M oxide powder is mixed with a metal M oxide powder satisfying the relationship -O > ΔG TiO2 , and the obtained mixed powder is heat-treated at a temperature of 650 to 900 ° C in a non-oxidizing atmosphere. Is reduced by Ti, and the surface of the obtained metal M fine particles is covered with a Ti oxide mainly composed of TiO 2 .

前記熱処理において、酸化物の標準生成自由エネルギーΔＧＭ−ＯがＴｉＯ2の標準生成自由エネルギーΔＧＴｉＯ２より大きい金属Ｍの酸化物粉末を用いることにより、金属Ｍの酸化物粉末がＴｉにより還元されると同時に、ＴｉＯ2を主体とするＴｉ酸化物の被覆が形成される。ＴｉＯ2を主体とするＴｉ酸化物被覆層は高結晶性であり、コアとなる金属微粒子（金属のコア粒子）を十分に保護することができる。ここで「ＴｉＯ2を主体とする」とは、Ｘ線回折測定で検出されるＴｉＯ2以外のＴｉ酸化物（例えば不定比組成のＴｉｎＯ２ｎ−１）も含むＴｉ酸化物に相当する回折ピークの中で、ＴｉＯ２に相当するピークの強度が最大であることを意味する。均一性の観点から、実質的にＴｉＯ2からなるのが好ましい。ここで「実質的にＴｉＯ2からなる」とは、Ｘ線回折パターンでＴｉＯ2以外のＴｉ酸化物のピークが明確に確認できない程度にＴｉＯ2の割合が多いことを言う。従って、Ｘ線回折パターンでノイズ程度にＴｉＯ2以外のＴｉ酸化物のピークがあっても、「実質的にＴｉＯ2からなる」の条件は満たす。 In the heat treatment, standard free energy .DELTA.G M-O oxides by using an oxide powder of standard free energy .DELTA.G TiO2 greater metal M TiO 2, oxide powder is reduced by Ti metal M At the same time, a Ti oxide coating mainly composed of TiO 2 is formed. The Ti oxide coating layer mainly composed of TiO 2 has high crystallinity and can sufficiently protect the metal fine particles (metal core particles) serving as the core. Here, “mainly composed of TiO 2 ” means diffraction corresponding to Ti oxide including Ti oxide other than TiO 2 detected by X-ray diffraction measurement (eg, Ti n O 2n-1 having non-stoichiometric composition). It means that the intensity of the peak corresponding to TiO 2 is the maximum among the peaks. From the viewpoint of uniformity, it is preferable that it is substantially made of TiO 2 . Here, “substantially composed of TiO 2 ” means that the proportion of TiO 2 is so large that a peak of Ti oxides other than TiO 2 cannot be clearly confirmed in the X-ray diffraction pattern. Therefore, even if there is a peak of Ti oxide other than TiO 2 in the X-ray diffraction pattern to the extent of noise, the condition of “substantially consisting of TiO 2 ” is satisfied.

前記金属（以下金属Ｍ）はＦｅ、Ｃｏ、Ｎｉから選ばれる少なくとも１つの元素を主成分とする磁性金属であるのが好ましく、特にＦｅであるのがより好ましい。ＴｉはＦｅより酸化物の標準生成エネルギーが小さいため、Ｆｅの酸化物を効率良く確実に還元することができる。従って、飽和磁化が高く耐食性に優れた磁性金属微粒子が得られる。   The metal (hereinafter referred to as metal M) is preferably a magnetic metal containing at least one element selected from Fe, Co, and Ni as a main component, and more preferably Fe. Since Ti has a lower standard generation energy of oxide than Fe, it is possible to efficiently and reliably reduce the oxide of Fe. Therefore, magnetic metal fine particles having high saturation magnetization and excellent corrosion resistance can be obtained.

金属Ｍの酸化物はＦｅ２Ｏ３であるのが好ましく、Ｔｉを含む粉末はＴｉＣであるのが好ましい。保磁力が低下し、分散性が向上した被覆金属微粒子を得るために、金属Ｍの酸化物粉末とＴｉを含む粉末の合計に対するＴｉを含む粉末の比率は３０〜５０ｍａｓｓ％とするのが好ましい。ｍａｓｓ％は質量百分率である。さらに前記金属Ｍの酸化物がＦｅ２Ｏ３であり、前記Ｔｉを含む粉末が少なくともＴｉＣであり、Ｆｅ２０３とＴｉＣの合計に対するＴｉＣの比率が３０〜５０ｍａｓｓ％であるのがより好ましい。 The metal M oxide is preferably Fe 2 O 3 , and the Ti-containing powder is preferably TiC. In order to obtain coated metal fine particles with reduced coercive force and improved dispersibility, the ratio of the powder containing Ti to the total of the metal M oxide powder and the powder containing Ti is preferably 30 to 50 mass%. mass% is a mass percentage. More preferably, the metal M oxide is Fe 2 O 3 , the Ti-containing powder is at least TiC, and the ratio of TiC to the total of Fe 2 O 3 and TiC is 30 to 50 mass%.

さらに不純物元素である炭素（Ｃ）と窒素（Ｎ）を低減して高い飽和磁化を得るためにはＴｉＣの一部をＴｉＮで置換することが好ましい。このとき、ＴｉＮの置換率が０．１〜０．５であることが好ましい。ＴｉＮの置換率は以下の［数１］の式により定義される。   Further, in order to reduce the impurity elements carbon (C) and nitrogen (N) and obtain high saturation magnetization, it is preferable to substitute a part of TiC with TiN. At this time, the substitution rate of TiN is preferably 0.1 to 0.5. The substitution rate of TiN is defined by the following equation [Equation 1].

耐食性に優れた磁性被覆金属微粒子を得るために、金属Ｍは磁性金属である必要があり、特に高飽和磁化のＦｅが好ましい。磁性金属を核とすることにより、磁気分離工程に用いるのが容易となり、被覆金属微粒子自体の精製、及び磁気ビーズ用途への使用が可能となる。   In order to obtain magnetic coated metal fine particles having excellent corrosion resistance, the metal M needs to be a magnetic metal, and particularly high saturation magnetization Fe is preferable. By using a magnetic metal as a nucleus, it can be easily used in a magnetic separation process, and the coated metal fine particles themselves can be purified and used for magnetic beads.

前記被覆金属微粒子は５０〜１８０Ａｍ２／ｋｇの飽和磁化を有するのが好ましい。これにより、被覆層と磁性層の量のバランスがとれた耐食性、磁気特性ともに優れた被覆金属微粒子とすることができる。前記被覆金属微粒子の飽和磁化はより好ましくは９５〜１８０Ａｍ２／ｋｇである。９５〜１８０Ａｍ２／ｋｇの範囲は、マグネタイト等の酸化物磁性体では得ることのできない範囲であり、優れた磁気分離性能を発揮する。 The coated metal fine particles preferably have a saturation magnetization of 50 to 180 Am 2 / kg. Thereby, it is possible to obtain coated metal fine particles excellent in both corrosion resistance and magnetic properties in which the amounts of the coating layer and the magnetic layer are balanced. The saturation magnetization of the coated metal fine particles is more preferably 95 to 180 Am 2 / kg. The range of 95 to 180 Am 2 / kg is a range that cannot be obtained with an oxide magnetic material such as magnetite, and exhibits excellent magnetic separation performance.

前記被覆金属微粒子は８ｋＡ／ｍ以下の保磁力を有するのが好ましい。これにより、残留磁化が極めて小さくなり、磁気凝集が極めて少ない分散性に優れた被覆金属微粒子とすることができる。より好ましい保磁力は４ｋＡ／ｍ以下である。   The coated metal fine particles preferably have a coercive force of 8 kA / m or less. Thereby, the remanent magnetization becomes extremely small, and the coated metal fine particles having excellent dispersibility with very little magnetic aggregation can be obtained. A more preferable coercive force is 4 kA / m or less.

本発明の被覆金属微粒子は、ＴｉＯ２を主体とするＴｉ酸化物で被覆された金属微粒子であって、前記金属はＦｅ、Ｃｏ、Ｎｉから選ばれる少なくとも１つの元素を主成分としている。前記被覆金属微粒子は不純物元素であるＣとＮの含有量が少ないことが好ましく、より好ましくはＣ含有量が０．２〜１．４ｍａｓｓ％、Ｎ含有量が０．０４〜０．２ｍａｓｓ％である。さらにより好ましくは、Ｃ含有量が０．３〜１．１ｍａｓｓ％、Ｎ含有量が０．０４〜０．１２ｍａｓｓ％である。これにより磁性成分の含有率が向上し、高い飽和磁化が得られる。さらに前記被覆金属微粒子は、Ｃ含有量０．２〜１．１ｍａｓｓ％およびＮ含有量０．０２〜０．１７ｍａｓｓ％とするのが良く、Ｃ含有量０．３〜１．１ｍａｓｓ％および窒素含有量０．０４〜０．１２ｍａｓｓ％とするのが特に高い磁気特性を得る上でより好ましい。ここで、０．０２ｍａｓｓ％は２００ｐｐｍに相当する。 The coated metal fine particles of the present invention are metal fine particles coated with a Ti oxide mainly composed of TiO 2 , and the metal contains at least one element selected from Fe, Co, and Ni as a main component. The coated metal fine particles preferably have a low content of impurity elements C and N, more preferably a C content of 0.2 to 1.4 mass% and an N content of 0.04 to 0.2 mass%. is there. Even more preferably, the C content is 0.3 to 1.1 mass%, and the N content is 0.04 to 0.12 mass%. Thereby, the content rate of a magnetic component improves and high saturation magnetization is obtained. Further, the coated metal fine particles may have a C content of 0.2 to 1.1 mass% and an N content of 0.02 to 0.17 mass%, a C content of 0.3 to 1.1 mass% and a nitrogen content. An amount of 0.04 to 0.12 mass% is more preferable for obtaining particularly high magnetic properties. Here, 0.02 mass% corresponds to 200 ppm.

金属ＭがＦｅの場合、前記被覆金属微粒子の表面部をＸ線光電子分光（ＸＰＳ）分析によってＯ、Ｆｅ、Ｔｉの３元素について定量分析すると、Ｆｅ含有量が１４〜２０ａｔ％であり、全Ｆｅに対する金属Ｆｅ成分の比率が７〜１１％であることが好ましい。Ｆｅの含有率が１４ａｔ％以上で、尚且つ金属Ｆｅ成分の比率が７％以上であることにより、金属Ｆｅ成分の含有量が高く、高い飽和磁化が得られる。Ｆｅ含有量の上限は２０ａｔ％であり、金属Ｆｅ成分の比率がＦｅ全体の１１％を上限とすることが望ましい。ここでａｔ％は原子百分率であり、定量分析で検出したＯ、Ｆｅ及びＴｉの総和を１００ａｔ％とする。   When the metal M is Fe, the surface portion of the coated fine metal particles is quantitatively analyzed for three elements of O, Fe, and Ti by X-ray photoelectron spectroscopy (XPS) analysis, and the Fe content is 14 to 20 at%. It is preferable that the ratio of the metal Fe component to 7 to 11%. When the Fe content is 14 at% or more and the ratio of the metal Fe component is 7% or more, the content of the metal Fe component is high and high saturation magnetization is obtained. The upper limit of the Fe content is 20 at%, and the ratio of the metal Fe component is desirably 11% of the total Fe. Here, at% is an atomic percentage, and the total of O, Fe, and Ti detected by quantitative analysis is 100 at%.

金属ＭがＦｅの場合、濃度６Ｍのグアニジン塩酸塩水溶液中に前記被覆金属微粒子を２５℃で２４時間浸漬（前記水溶液１ｍＬあたり前記被覆金属微粒子２５ｍｇの割合）した後のＦｅイオン溶出量が５０ｍｇ／Ｌ以下であるのが好ましい。高カオトロピック塩濃度でも高い耐食性を示す被覆金属微粒子は、ＤＮＡ抽出等の用途に好適である。   When the metal M is Fe, the elution amount of Fe ions after immersing the coated metal fine particles in an aqueous guanidine hydrochloride solution having a concentration of 6M at 25 ° C. for 24 hours (a ratio of 25 mg of the coated metal fine particles per 1 mL of the aqueous solution) is 50 mg / L or less is preferable. The coated metal fine particles exhibiting high corrosion resistance even at a high chaotropic salt concentration are suitable for uses such as DNA extraction.

本発明により、耐食性に優れた被覆金属微粒子の粉末が得られる。本発明の被覆金属微粒子は、金属ＭがＦｅ、Ｃｏなどの場合は磁性粒子として機能し、高磁化を発現する。また磁性金属粒子は高耐食性のＴｉ酸化物層に被覆されているので、腐食性の溶液中で使用するために高い耐食性が要求される磁気ビーズ等に好適である。   According to the present invention, a powder of coated metal fine particles having excellent corrosion resistance can be obtained. The coated metal fine particles of the present invention function as magnetic particles when the metal M is Fe, Co or the like, and exhibit high magnetization. In addition, since the magnetic metal particles are coated with a highly corrosion-resistant Ti oxide layer, they are suitable for magnetic beads and the like that require high corrosion resistance for use in corrosive solutions.

［１］被覆金属微粒子の製造方法
酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属Ｍの酸化物粉末と、Ｔｉを含む粉末（ただしＴｉ酸化物粉末を除く）とを混合し、得られた混合粉末を非酸化性雰囲気中で熱処理することにより、金属Ｍの酸化物をＴｉにより還元するとともに、得られた金属Ｍの微粒子の表面をＴｉＯ２を主体とするＴｉ酸化物で被覆する。 [1] Method for Producing Coated Metal Fine Particles An oxide powder of metal M that satisfies the relationship of ΔG M−O > ΔG TiO 2 with a standard free energy of formation of oxide, and a powder containing Ti (excluding Ti oxide powder) Then, the obtained mixed powder is heat-treated in a non-oxidizing atmosphere to reduce the metal M oxide with Ti, and the surface of the obtained metal M fine particles is made of Ti 2 mainly composed of TiO 2. Cover with oxide.

（１）金属Ｍの酸化物粉末
金属Ｍの酸化物粉末の粒径は、被覆金属微粒子の目標粒径に合わせて選択し得るが、０．００１〜５μｍの範囲内であるのが好ましい。粒径が０．００１μｍ未満では、金属酸化物粉末の「かさ」が大きくなるだけでなく２次凝集が激しいため、以下の製造工程での取り扱いが困難である。また５μｍ超だと、金属酸化物粉末の比表面積が小さすぎ、還元反応が進行しにくい。金属酸化物粉末の実用的な粒径は０．００５〜１μｍである。金属Ｍは遷移金属、貴金属及び希土類金属から選ばれるが、磁性材用であればＦｅ、Ｃｏ、Ｎｉ又はこれら合金が好ましく、その酸化物としてはＦｅ２Ｏ３、Ｆｅ３Ｏ４、ＣｏＯ、Ｃｏ３Ｏ４、ＮｉＯ等が挙げられる。特にＦｅは飽和磁化が高いため好ましく、酸化物としてはＦｅ２Ｏ３が安価である点で好ましい。ＴｉはＦｅより酸化物の標準生成エネルギーが小さいため、Ｆｅ酸化物を効率良くかつ確実に還元することができる。 (1) Metal M Oxide Powder The particle size of the metal M oxide powder can be selected according to the target particle size of the coated metal fine particles, but is preferably in the range of 0.001 to 5 μm. When the particle size is less than 0.001 μm, not only the “bulk” of the metal oxide powder becomes large but also the secondary aggregation is severe, and therefore it is difficult to handle in the following production process. If it exceeds 5 μm, the specific surface area of the metal oxide powder is too small and the reduction reaction does not proceed easily. The practical particle size of the metal oxide powder is 0.005 to 1 μm. The metal M is selected from transition metals, noble metals and rare earth metals, but for magnetic materials, Fe, Co, Ni or alloys thereof are preferred, and the oxides thereof are Fe 2 O 3 , Fe 3 O 4 , CoO, Co 3 O 4 , NiO and the like can be mentioned. In particular, Fe is preferable because of its high saturation magnetization, and Fe 2 O 3 is preferable as an oxide because it is inexpensive. Since Ti has a lower standard generation energy of oxide than Fe, Fe oxide can be reduced efficiently and reliably.

酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属Ｍの酸化物であれば、Ｔｉを含む非酸化物粉末により還元することができる。ΔＧＭ−Ｏは金属Ｍの酸化物の標準生成エネルギーであり、ΔＧＴｉＯ２（−８８９ｋＪ／ｍｏｌ）はＴｉの酸化物の標準生成エネルギーである。例えばＦｅ２Ｏ３（ΔＧＦｅ２Ｏ３＝−７４０ｋＪ／ｍｏｌ）はΔＧＦｅ２Ｏ３＞ΔＧＴｉＯ２を満たすので、Ｔｉを含む非酸化物粉末により還元される。ＴｉＯ２の被覆が形成されるため被覆金属微粒子の比重が低下する。さらに、ＴｉＯ２は親水性であるので、ＴｉＯ２被覆金属微粒子は、例えば磁気ビーズ用のように溶液中（例えば、水中）に分散させる場合に好適である。 If the standard free energy of formation of the oxide is an oxide of metal M satisfying the relationship of ΔG M−O > ΔG TiO 2, it can be reduced with a non-oxide powder containing Ti. ΔG M-O is the standard generation energy of the metal M oxide, and ΔG TiO2 (−889 kJ / mol) is the standard generation energy of the Ti oxide. For example, since Fe 2 O 3 (ΔG Fe2O3 = -740kJ / mol) satisfies ΔG Fe2O3> ΔG TiO2, is reduced by the non-oxide powder containing Ti. Since the coating of TiO 2 is formed, the specific gravity of the coated metal fine particles is lowered. Furthermore, since TiO 2 is hydrophilic, the TiO 2 -coated metal fine particles are suitable when dispersed in a solution (for example, in water), for example, for magnetic beads.

（２）Ｔｉを含む粉末
Ｔｉを含む粉末は、Ｔｉ単体粉末の他、Ｔｉ−Ｘ（ただしＸは、標準酸化物生成自由エネルギーΔＧＸ−ＯがＴｉＯ２の生成標準自由エネルギーΔＧＴｉＯ２より大きい元素である。）により表されるＴｉ化合物又はそれらの混合物の粉末である。具体的には、ＸはＡｇ、Ａｕ、Ｂ、Ｂｉ、Ｃ、Ｃｕ、Ｃｓ、Ｃｄ、Ｇｅ、Ｇａ、Ｈｇ、Ｋ、Ｎ、Ｎａ、Ｐｄ、Ｐｔ、Ｒｂ、Ｒｈ、Ｓ、Ｓｎ、Ｔｌ、Ｔｅ及びＺｎからなる群から選ばれた少なくとも１種である。Ｔｉ酸化物は還元剤として機能しないので、Ｔｉを含む粉末から除く。ΔＧＸ−Ｏ＜ΔＧＴｉＯ２を満たす元素Ｘの場合、元素Ｘが還元剤として作用するので、Ｔｉ酸化物が生成しなくなる。Ｍ酸化物を還元するに足るＴｉが含まれていれば、Ｘの含有量は特に限定されない。Ｔｉ−Ｘとしては、反応後にＴｉＯ２以外の相が形成されにくいので、ＴｉＣが好ましい。更に熱処理後にＸの残留を抑制し、ＭとＴｉＯ２以外の不純物相を低減するためにはＴｉＣを主成分とし、前記ＴｉＣの一部をＴｉＮで置換することが好ましい。ＴｉＮの置換によってＣ含有量が低減すると共に、ＴｉＮ中のＮは熱処理過程で気化してしまうため、実質的にＴｉだけを試料中に残すことができる。 (2) Powder containing Ti The powder containing Ti is Ti-X (where X is an element whose standard oxide free energy ΔG X-O is larger than the standard free energy ΔG TiO2 of TiO 2 in addition to Ti simple powder) A powder of a Ti compound represented by the above or a mixture thereof. Specifically, X is Ag, Au, B, Bi, C, Cu, Cs, Cd, Ge, Ga, Hg, K, N, Na, Pd, Pt, Rb, Rh, S, Sn, Tl, Te. And at least one selected from the group consisting of Zn. Since Ti oxide does not function as a reducing agent, it is removed from the powder containing Ti. In the case of the element X satisfying ΔG X−O <ΔG TiO 2 , the element X acts as a reducing agent, so that no Ti oxide is generated. The content of X is not particularly limited as long as Ti is sufficient to reduce the M oxide. As Ti—X, TiC is preferable because a phase other than TiO 2 is hardly formed after the reaction. Further, in order to suppress residual X after the heat treatment and reduce impurity phases other than M and TiO 2 , it is preferable that TiC is a main component and a part of the TiC is replaced with TiN. Substitution of TiN reduces the C content and vaporizes N in TiN during the heat treatment process, so that substantially only Ti can be left in the sample.

還元反応を効率的に行うためには、Ｔｉを含む非酸化物粉末の粒径は０．０１〜２０μｍであるのが好ましい。０．０１μｍ未満の粒径であると、大気中でＴｉを含む非酸化物粉末が酸化し易いので、ハンドリングが難しい。また２０μｍ超であると比表面積が小さく、還元反応が進行しにくい。特に０．１μｍ〜５μｍの粒径であれば、大気中での酸化を抑制しつつ、還元反応の十分な進行を図ることができる。   In order to perform the reduction reaction efficiently, the particle size of the non-oxide powder containing Ti is preferably 0.01 to 20 μm. When the particle diameter is less than 0.01 μm, the non-oxide powder containing Ti is easily oxidized in the atmosphere, so that handling is difficult. If it exceeds 20 μm, the specific surface area is small and the reduction reaction does not proceed easily. In particular, when the particle diameter is 0.1 μm to 5 μm, the reduction reaction can proceed sufficiently while suppressing oxidation in the air.

（３）還元反応
Ｍ酸化物の粉末に対するＴｉ含有粉末の比率は、少なくとも還元反応の化学量論比であることが好ましい。Ｔｉが不足すると、熱処理中にＭ酸化物粉末が焼結し、バルク化してしまう。例えばＦｅ２Ｏ３とＴｉＣとの組合せの場合、Ｆｅ２Ｏ３＋ＴｉＣに対してＴｉＣは２５ｍａｓｓ％以上であることが好ましい。ＴｉＣが２５ｍａｓｓ％未満であると、ＴｉＣによるＦｅ２Ｏ３の還元が不十分である。一方、ＴｉＣの比率が高くなりすぎると、Ｆｅの比率が低下し、得られるＴｉＯ２被覆Ｆｅ微粒子の飽和磁化が低下し、保磁力が増大する。従って、ＴｉＣの上限は５０ｍａｓｓ％が好ましい。Ｆｅ２Ｏ３＋ＴｉＣに対するＴｉＣの比率はより好ましくは３０〜５０ｍａｓｓ％であり、最も好ましくは３０〜４０ｍａｓｓ％であり、特に好ましくは３０〜３５ｍａｓｓ％である。保磁力は、ＴｉＣが３５ｍａｓｓ％になると８ｋＡ／ｍに達し、４０ｍａｓｓ％になると１０ｋＡ／ｍに達し、５０ｍａｓｓ％になると１５ｋＡ／ｍに達する。 (3) Reduction reaction The ratio of the Ti-containing powder to the M oxide powder is preferably at least the stoichiometric ratio of the reduction reaction. When Ti is insufficient, the M oxide powder is sintered and bulked during the heat treatment. For example, in the case of a combination of Fe 2 O 3 and TiC, it is preferred for Fe 2 O 3 + TiC TiC is at least 25 mass%. When TiC is less than 25 mass%, the reduction of Fe 2 O 3 by TiC is insufficient. On the other hand, if the TiC ratio becomes too high, the Fe ratio decreases, the saturation magnetization of the resulting TiO 2 -coated Fe fine particles decreases, and the coercive force increases. Therefore, the upper limit of TiC is preferably 50 mass%. The ratio of TiC to Fe 2 O 3 + TiC is more preferably 30 to 50 mass%, most preferably 30 to 40 mass%, and particularly preferably 30 to 35 mass%. The coercive force reaches 8 kA / m when TiC reaches 35 mass%, reaches 10 kA / m when 40 mass%, and reaches 15 kA / m when 50 mass%.

また、ＴｉＣの一部をＴｉＮで置換する場合、その置換率は０．１〜０．５が好ましい。ここでＴｉＮの置換率は［数１］の式により定義される。ＴｉＮの置換率が０．１未満の場合は不純物元素（Ｃ、Ｎ）の低減が不十分であり、ＴｉＮを添加した効果が得られない。またＴｉＮ置換率が０．５を越えるとＣが不足することにより、酸化物から金属Ｍへの還元が不十分となり、完全な被覆金属微粒子が得られない。Ｍ酸化物粉末とＴｉ含有非酸化物粉末との混合には、乳鉢、スターラ、Ｖ字型ミキサ、ボールミル、振動ミル等の攪拌機を用いる。   Moreover, when substituting a part of TiC with TiN, the substitution rate is preferably 0.1 to 0.5. Here, the substitution rate of TiN is defined by the equation [Equation 1]. When the substitution rate of TiN is less than 0.1, the reduction of impurity elements (C, N) is insufficient, and the effect of adding TiN cannot be obtained. On the other hand, if the TiN substitution rate exceeds 0.5, C is insufficient, so that the reduction from the oxide to the metal M becomes insufficient, and complete coated metal fine particles cannot be obtained. For mixing the M oxide powder and the Ti-containing non-oxide powder, a stirrer such as a mortar, stirrer, V-shaped mixer, ball mill, vibration mill or the like is used.

Ｍ酸化物粉末とＴｉ含有粉末（Ｔｉ酸化物粉末を除く）の混合粉末を非酸化性雰囲気中で熱処理すると、Ｍ酸化物粉末とＴｉ含有粉末との還元反応が起こり、ＴｉＯ２を主体とするＴｉ酸化物で被覆された金属Ｍの粒子が生成する。熱処理雰囲気は非酸化性であるのが好ましい。非酸化性雰囲気としては、例えばＡｒ，Ｈｅ等の不活性ガスや、Ｎ２、ＣＯ２、ＮＨ３等が挙げられるが、これらに限定されない。熱処理温度は６５０〜９００℃が好ましい。６５０℃未満であると還元反応が十分に進行せず、また９００℃超であると不定比組成のＴｉｎＯ２ｎ−１が主として生成することがある。ＴｉｎＯ２ｎ−１は、９００℃超で金属ＭがＴｉＯ２から酸素を取り込むか、ＴｉＯ２が非酸化性雰囲気中に酸素を放出することにより生成する。その結果、金属Ｍの還元が不十分であるか、被覆層が不完全となる。熱処理温度が６５０〜９００℃の場合に、欠陥が少なく、均一性の高いほぼＴｉＯ２からなる被覆（被覆層）が形成される。ＴｉＯ２からなる被覆は、光触媒用の被覆金属微粒子を作製するのに好適である。 When a mixed powder of M oxide powder and Ti-containing powder (excluding Ti oxide powder) is heat-treated in a non-oxidizing atmosphere, a reduction reaction occurs between the M oxide powder and the Ti-containing powder, and TiO 2 is the main component. Metal M particles coated with Ti oxide are produced. The heat treatment atmosphere is preferably non-oxidizing. Examples of the non-oxidizing atmosphere include, but are not limited to, inert gases such as Ar and He, N 2 , CO 2 , and NH 3 . The heat treatment temperature is preferably 650 to 900 ° C. If it is lower than 650 ° C., the reduction reaction does not proceed sufficiently, and if it exceeds 900 ° C., Ti n O 2n-1 having a non - stoichiometric composition may be mainly produced. Ti n O 2n-1 is generated when the metal M takes in oxygen from TiO 2 at over 900 ° C. or TiO 2 releases oxygen into the non-oxidizing atmosphere. As a result, the reduction of the metal M is insufficient or the coating layer is incomplete. When the heat treatment temperature is 650 to 900 ° C., a coating (coating layer) made of almost TiO 2 with few defects and high uniformity is formed. A coating made of TiO 2 is suitable for producing coated metal fine particles for a photocatalyst.

（４）磁気分離
得られる磁性被覆金属微粒子は非磁性成分（ＴｉＯ２を主体とするＴｉ酸化物）を過剰に含んでいる場合があるため、必要に応じて永久磁石を用いて磁気分離操作を複数回行い、磁性粒子だけを回収するのが好ましい。 (4) Magnetic separation Since the obtained magnetic coated metal fine particles may contain an excessive amount of nonmagnetic components (Ti oxide mainly composed of TiO 2 ), the magnetic separation operation may be performed using a permanent magnet as necessary. It is preferable to perform multiple times to recover only the magnetic particles.

［２］被覆金属微粒子の構造及び特性
（１）被覆金属微粒子の粒径
上記方法により得られる被覆金属微粒子の粒径は、Ｍ酸化物粉末の粒径に依存する。高い耐食性及び分散性を得るためには、被覆金属微粒子の平均粒径ｄ５０（メジアン径）は０．１〜１０μｍが好ましく、０．１〜６μｍがより好ましい。平均粒径が０．１μｍ未満であると、被覆金属微粒子は十分な厚さの被覆を確保できずに耐食性が低くなるだけでなく、1粒子当たりの磁化が極めて小さくなり磁気応答性が低くなってしまう。また平均粒径が１０μｍを超えると、液体中での被覆金属微粒子の分散性が低下する。平均粒径ｄ５０はレーザー回折による湿式粒径測定器で測定した。 [2] Structure and properties of coated metal fine particles (1) Particle size of coated metal fine particles The particle size of the coated metal fine particles obtained by the above method depends on the particle size of the M oxide powder. In order to obtain high corrosion resistance and dispersibility, the average particle diameter d50 (median diameter) of the coated metal fine particles is preferably 0.1 to 10 μm, and more preferably 0.1 to 6 μm. If the average particle size is less than 0.1 μm, the coated metal fine particles cannot ensure a sufficient thickness of coating and have low corrosion resistance, and also the magnetization per particle is extremely small and magnetic response is low. End up. On the other hand, when the average particle diameter exceeds 10 μm, the dispersibility of the coated metal fine particles in the liquid is lowered. The average particle size d50 was measured with a wet particle size measuring device by laser diffraction.

なお、粒径に対する個数分布については、被覆金属微粒子をＳＥＭ（走査型電子顕微鏡）で撮影した写真から粒径と個数を測定した。ＳＥＭ写真では、金属粒子がＴｉ酸化物のみの部分よりも強く白色を呈するので、内包される金属粒子（例えばＦｅ粒子）の外形を確認できる。ＳＥＭ写真上で被覆金属微粒子の外形を観察し、その長手方向の長さ寸法を被覆金属微粒子の粒径とする。同様に金属粒子の外形を観察し、その長手方向の長さ寸法を金属粒子の粒径とする。好ましくは２０個以上の金属粒子を測定する。金属粒子は上述の還元反応によって生成されるが、生成過程において近接する金属粒子同士が結合し、より粒径の大きい１つの金属粒子を成すことがある。単一状態で成長した金属粒子の群のピークと、生成途中で結合して粒径がひとまわり大きくなった金属粒子の群のピークとが重畳すると、少なくとも２つのピークを有する個数分布になると考えられる。具体的にはピークの数が２となる。原料粉末の粒径が不揃いでｄ５０が３μｍ超のとき、ピーク数が３になることもある。   In addition, about the number distribution with respect to a particle size, the particle size and the number were measured from the photograph which image | photographed the coated metal fine particle with SEM (scanning electron microscope). In the SEM photograph, since the metal particles are whiter than the portion of only Ti oxide, the outer shape of the encapsulated metal particles (for example, Fe particles) can be confirmed. The outer shape of the coated metal fine particles is observed on the SEM photograph, and the length dimension in the longitudinal direction is defined as the particle size of the coated metal fine particles. Similarly, the outer shape of the metal particles is observed, and the length in the longitudinal direction is defined as the particle size of the metal particles. Preferably, 20 or more metal particles are measured. Although metal particles are produced by the above-described reduction reaction, adjacent metal particles may be combined in the production process to form one metal particle having a larger particle size. When the peak of a group of metal particles grown in a single state overlaps with the peak of a group of metal particles that have been combined and formed a particle size that has become larger in size, the number distribution having at least two peaks is considered. It is done. Specifically, the number of peaks is 2. When the particle sizes of the raw material powders are not uniform and d50 is more than 3 μm, the number of peaks may be 3.

（２）被覆構造
Ｍ金属粒子とＴｉ酸化物被覆層とは1対1のコア−シェル構造になっている必要はなく、ＴｉＯ２を主体とするＴｉ酸化物層中に２個以上のＭ金属粒子が分散した構造であっても良い。Ｔｉ酸化物の中に２個以上のＭ金属粒子が含まれていると、金属Ｍは高含有率で、かつ確実に被覆されるので好ましい。本発明では、Ｍ酸化物の還元によるＭ金属微粒子の形成と、Ｔｉ酸化物被覆の形成とが同時に行われるので、Ｍ金属微粒子とＴｉ酸化物被覆との間にＭ金属酸化物層が認められない。また６５０℃以上の熱処理により得られるＴｉ酸化物被覆の結晶性は高く、ゾル−ゲル法等により得られる非晶質又は低結晶性のＴｉ酸化物被覆より高い耐食性を示す。またＴｉＯ２を主体とした被覆を有する本発明の被覆金属微粒子は、被覆に欠陥が少ないので、不定比組成のＴｉｎＯ２ｎ−１の被覆を有するものより高い耐食性を示す。 (2) Coating structure The M metal particles and the Ti oxide coating layer do not have to have a one-to-one core-shell structure, and two or more M metals are contained in the Ti oxide layer mainly composed of TiO 2. A structure in which particles are dispersed may be used. It is preferable that two or more M metal particles are contained in the Ti oxide because the metal M has a high content and is reliably coated. In the present invention, formation of M metal fine particles by reduction of M oxide and formation of Ti oxide coating are performed at the same time, so that an M metal oxide layer is observed between the M metal fine particles and the Ti oxide coating. Absent. The Ti oxide coating obtained by heat treatment at 650 ° C. or higher has high crystallinity and higher corrosion resistance than the amorphous or low crystalline Ti oxide coating obtained by a sol-gel method or the like. Further, the coated metal fine particles of the present invention having a coating mainly composed of TiO 2 have a higher corrosion resistance than those having a coating of Ti n O 2n-1 having a non - stoichiometric composition because the coating has few defects.

（３）被覆厚さ
ＴｉＯ２を主体とするＴｉ酸化物被覆の厚さは１〜１００００ｎｍが好ましい。厚さが１ｎｍ未満であると、被覆金属微粒子は十分な耐食性を有さない。また厚さが１００００ｎｍ超であると、被覆金属微粒子が大きくすぎ、液中での分散性が低いだけでなく、磁性金属微粒子の場合は飽和磁化が低い。より好ましいＴｉ酸化物被覆の厚さは５〜５０００ｎｍである。被覆の厚さは被覆金属微粒子の透過電子顕微鏡（ＴＥＭ）写真により求める。Ｔｉ酸化物被覆の厚さが不均一な場合、最大厚さと最小厚さの平均をＴｉ酸化物被覆の厚さとする。なお、金属微粒子は、ＴｉＯ２を主体とするＴｉ酸化物で完全に被覆されている必要はなく、部分的に金属粒子が表面に露出しても構わないが、完全に被覆されているのが好ましい。 (3) Coating thickness The thickness of the Ti oxide coating mainly composed of TiO 2 is preferably 1 to 10,000 nm. When the thickness is less than 1 nm, the coated metal fine particles do not have sufficient corrosion resistance. If the thickness exceeds 10,000 nm, the coated metal fine particles are too large and the dispersibility in the liquid is low, and in the case of magnetic metal fine particles, the saturation magnetization is low. A more preferred thickness of the Ti oxide coating is 5 to 5000 nm. The thickness of the coating is determined from a transmission electron microscope (TEM) photograph of the coated metal fine particles. If the thickness of the Ti oxide coating is not uniform, the average of the maximum thickness and the minimum thickness is taken as the thickness of the Ti oxide coating. The metal fine particles need not be completely covered with a Ti oxide mainly composed of TiO 2 , and the metal particles may be partially exposed on the surface, but are completely covered. preferable.

（４）Ｔｉ酸化物の結晶性
被覆金属微粒子のＸ線回折パターンにおけるＴｉＯ２の最大ピークの半値幅が０．３°以下で、金属Ｍの最大ピークに対するＴｉＯ２の最大ピークの強度比が０．０３以上である場合に、Ｔｉ酸化物の結晶性が良い（従って、被覆金属微粒子の耐食性も良い）と判断した。非晶質又は低結晶性の場合、ピークは観察されないかブロードであるため、最大ピーク強度比は小さく、半値幅は広い。最大ピーク強度比はより好ましくは０．０５以上である。最大ピーク強度比が高くなると被覆の割合が多くなり、飽和磁化が低下する。そのため、最大ピーク強度比は３以下が好ましい。 (4) Crystallinity of Ti oxide The half-width of the maximum peak of TiO 2 in the X-ray diffraction pattern of the coated metal fine particles is 0.3 ° or less, and the intensity ratio of the maximum peak of TiO 2 to the maximum peak of metal M is 0. When it was 0.03 or more, it was judged that the crystallinity of the Ti oxide was good (therefore, the corrosion resistance of the coated metal fine particles was also good). In the case of amorphous or low crystallinity, since the peak is not observed or is broad, the maximum peak intensity ratio is small and the half width is wide. The maximum peak intensity ratio is more preferably 0.05 or more. As the maximum peak intensity ratio increases, the coating ratio increases and the saturation magnetization decreases. Therefore, the maximum peak intensity ratio is preferably 3 or less.

（５）磁性粒子としての機能
金属Ｍが磁性金属Ｆｅの場合、前記製法により得られた被覆金属微粒子は５０〜１８０Ａｍ２／ｋｇの範囲の飽和磁化を有し、磁性粒子として機能する。これは、被覆金属微粒子が磁性金属ＦｅとＴｉＯ２から形成されている場合、Ｆｅ＋Ｔｉに対するＴｉの比率が１１〜６７ｍａｓｓ％であることに相当する。Ｔｉの比率は、Ｘ線回折パターンから被覆金属微粒子がＦｅとＴｉＯ２からなることを確認した後で、被覆金属微粒子の飽和磁化の測定値から算出できる。磁性粒子の飽和磁化が５０Ａｍ２／ｋｇ未満と小さいと、磁界に対する応答が鈍い。また１８０Ａｍ２／ｋｇ超であるとＴｉＯ２を主体とするＴｉ酸化物の含有率が小さく（Ｆｅ＋Ｔｉに対するＴｉの質量比率が１１％未満）、金属Ｆｅ粒子を十分にＴｉ酸化物で被覆できないために耐食性が低く、磁気特性が劣化しやすい。従って、高い飽和磁化及び十分な耐食性を同時に得るために、被覆金属微粒子の飽和磁化は１８０Ａｍ２／ｋｇ以下とするのが好ましい。磁気ビーズ等に用いる場合の回収効率や磁気分離性能に優れるためには、被覆金属微粒子の飽和磁化は９５〜１８０Ａｍ２／ｋｇであるのがより好ましい。この範囲の飽和磁化は、９２Ａｍ２／ｋｇ程度の飽和磁化しか有さないマグネタイト（Ｆｅ３Ｏ４）では得られない。分散性の観点から、被覆金属微粒子の保磁力は１５ｋＡ／ｍ以下が好ましく、８ｋＡ／ｍ（１００Ｏｅ）以下がより好ましく、４ｋＡ／ｍ以下が最も好ましい。保磁力が大きい場合でもＴｉＯ２被覆を厚くすれば高分散性が得られるが、そうすると被覆金属微粒子の飽和磁化が低下してしまう。保磁力が８ｋＡ／ｍを超えると、磁性粒子は無磁界でも磁気的に凝集するので、液中での分散性が低下する。 (5) Function as magnetic particles When the metal M is magnetic metal Fe, the coated metal fine particles obtained by the above production method have a saturation magnetization in the range of 50 to 180 Am 2 / kg and function as magnetic particles. This corresponds to the ratio of Ti to Fe + Ti being 11 to 67 mass% when the coated metal fine particles are formed of magnetic metal Fe and TiO 2 . The ratio of Ti can be calculated from the measured value of saturation magnetization of the coated metal fine particles after confirming that the coated metal fine particles are composed of Fe and TiO 2 from the X-ray diffraction pattern. When the saturation magnetization of the magnetic particles is as small as less than 50 Am 2 / kg, the response to the magnetic field is dull. Further, if it exceeds 180 Am 2 / kg, the content of Ti oxide mainly composed of TiO 2 is small (the mass ratio of Ti to Fe + Ti is less than 11%), and metal Fe particles cannot be sufficiently covered with Ti oxide. Corrosion resistance is low and magnetic properties are likely to deteriorate. Therefore, in order to obtain high saturation magnetization and sufficient corrosion resistance at the same time, the saturation magnetization of the coated metal fine particles is preferably 180 Am 2 / kg or less. In order to be excellent in recovery efficiency and magnetic separation performance when used for magnetic beads or the like, the saturation magnetization of the coated metal fine particles is more preferably 95 to 180 Am 2 / kg. Saturation magnetization in this range cannot be obtained with magnetite (Fe 3 O 4 ) having only saturation magnetization of about 92 Am 2 / kg. From the viewpoint of dispersibility, the coercive force of the coated metal fine particles is preferably 15 kA / m or less, more preferably 8 kA / m (100 Oe) or less, and most preferably 4 kA / m or less. Even if the coercive force is large, if the TiO 2 coating is thickened, high dispersibility can be obtained. However, if this is done, the saturation magnetization of the coated metal fine particles is lowered. When the coercive force exceeds 8 kA / m, the magnetic particles aggregate magnetically even in the absence of a magnetic field, so that the dispersibility in the liquid is lowered.

（６）不純物の濃度
被覆金属微粒子に含有されるＣ量は０．２〜１．４ｍａｓｓ％以下が好ましい。含有されているＣは主に原料として用いたＴｉＣ粉の余剰分の残留が原因である。すなわち本発明の製法において、金属Ｍの酸化物を主としてＴｉが還元剤となって金属Ｍへと還元するのであるが、ＴｉＣ中のＣも還元剤の役割を果たし、金属Ｍの酸化物を補助的に還元している。Ｃ量が０．２ｍａｓｓ％未満であることは、Ｍ酸化物の還元が不十分であることを意味しており好ましくない。Ｃ量が１．４ｍａｓｓ％超であると金属成分の含有率が低下し、その金属がＦｅ，Ｃｏ，Ｎｉから選ばれる少なくとも一つの元素を主成分としている場合は、飽和磁化の低下を招く。またＣの残留によって被覆金属微粒子が疎水性となり、水溶液中での分散性が低下するので磁気ビーズ等の用途に用いる場合には特に好ましくない。また被覆金属微粒子に含まれるＮ量は０．０４〜０．２ｍａｓｓ％が好ましい。含有されているＮは主に熱処理中にＴｉが窒化したことによる。Ｎ量が０．０４ｍａｓｓ％未満であるとＴｉ不足による金属微粒子の被覆が不十分となり好ましくない。Ｎ量が０．２ｍａｓｓ％超であると非磁性成分の窒化チタンの含有率が増え、飽和磁化が低下するので好ましくない。上記Ｃ量、Ｎ量の好適範囲は金属ＭとＴｉＯ２以外の相の含有率が極めて少ないことを表す。ここで上記被覆金属微粒子中のＣ含有量は高周波加熱赤外吸収法によって測定され、Ｎ含有量は不活性ガス中加熱熱伝導法によって測定される。 (6) Impurity concentration The amount of C contained in the coated metal fine particles is preferably 0.2 to 1.4 mass% or less. The contained C is mainly due to the remaining residual TiC powder used as a raw material. That is, in the production method of the present invention, the metal M oxide is mainly reduced by the Ti as a reducing agent to the metal M, but C in TiC also serves as a reducing agent, assisting the metal M oxide. Has been reduced. If the amount of C is less than 0.2 mass%, it means that the reduction of the M oxide is insufficient, which is not preferable. When the amount of C exceeds 1.4 mass%, the content of the metal component decreases, and when the metal contains at least one element selected from Fe, Co, and Ni as a main component, the saturation magnetization decreases. Moreover, since the coated metal fine particles become hydrophobic due to residual C and dispersibility in an aqueous solution is lowered, it is not particularly preferable when used for applications such as magnetic beads. The amount of N contained in the coated metal fine particles is preferably 0.04 to 0.2 mass%. The contained N is mainly due to the fact that Ti was nitrided during the heat treatment. If the amount of N is less than 0.04 mass%, the coating of metal fine particles due to insufficient Ti becomes insufficient, which is not preferable. If the amount of N is more than 0.2 mass%, the content of the nonmagnetic component titanium nitride increases and the saturation magnetization decreases, which is not preferable. The preferable ranges of the C content and the N content indicate that the content of phases other than the metal M and TiO 2 is extremely small. Here, the C content in the coated metal fine particles is measured by a high-frequency heating infrared absorption method, and the N content is measured by a heating heat conduction method in an inert gas.

（７）耐食性
モル濃度が６Ｍのグアニジン塩酸塩水溶液１ｍＬ当たり被覆金属微粒子（金属ＭがＦｅである）２５ｍｇの割合として２５℃で２４時間浸漬したときのＦｅイオン溶出量は５０ｍｇ／Ｌ以下であるのが好ましい。この被覆金属微粒子は高カオトロピック塩濃度においても高い耐食性を示すため、カオトロピック塩水溶液中での処理を必要とするＤＮＡ抽出等の用途に好適である。Ｆｅイオン溶出量が５０ｍｇ／Ｌ以下の耐食性レベルは、アルカリ処理を施さない場合でも発現することがあるが、確実に上記耐食性レベルを得るためにはアルカリ処理を行うのが好ましい。なお、本願明細書の耐食性やＸ線回折に係る記述から判るとおり、本発明の被覆金属粒子は被覆金属粒子の粉末に相当する用語として用いている。 (7) Corrosion resistance As a ratio of 25 mg of coated metal fine particles (metal M is Fe) per 1 mL of guanidine hydrochloride aqueous solution having a molar concentration of 6 M, Fe ion elution amount when immersed at 25 ° C. for 24 hours is 50 mg / L or less Is preferred. Since the coated metal fine particles exhibit high corrosion resistance even at high chaotropic salt concentrations, they are suitable for uses such as DNA extraction that require treatment in an aqueous chaotropic salt solution. Although the corrosion resistance level with an Fe ion elution amount of 50 mg / L or less may appear even when the alkali treatment is not performed, it is preferable to perform the alkali treatment in order to reliably obtain the above corrosion resistance level. As can be seen from the description relating to corrosion resistance and X-ray diffraction in the present specification, the coated metal particles of the present invention are used as terms corresponding to the powder of the coated metal particles.

以下、本発明についてさらに具体的な実施例を用いて説明する。ただし、これら実施例により本発明が必ずしも限定されるものではない。   Hereinafter, the present invention will be described using more specific examples. However, the present invention is not necessarily limited by these examples.

（実施例１）
平均粒径０．０３μｍのα−Ｆｅ２Ｏ３粉末と、平均粒径１μｍのＴｉＣ粉末とを、７：３の質量比（ＴｉＣ：３０ｍａｓｓ％）でボールミルにより１０時間混合し、得られた混合粉末をアルミナボート内で、窒素ガス中で７００℃で２時間熱処理し、室温まで冷却した。得られた試料粉末のＸ線回折パターンを図１に示す。図１の横軸は回折の２θ（°）を示し、縦軸は回折強度（相対値）を示す。ＭＤＩ社製解析ソフト「Ｊａｄｅ，Ｖｅｒ．５」による解析の結果、回折ピークはα−Ｆｅ及びＴｉＯ２（ルチル構造）と同定された。 Example 1
Α-Fe 2 O 3 powder with an average particle size of 0.03 μm and TiC powder with an average particle size of 1 μm were mixed at a mass ratio of 7: 3 (TiC: 30 mass%) for 10 hours by a ball mill, and the resulting mixture was obtained The powder was heat-treated in nitrogen gas at 700 ° C. for 2 hours in an alumina boat and cooled to room temperature. The X-ray diffraction pattern of the obtained sample powder is shown in FIG. The horizontal axis in FIG. 1 indicates 2θ (°) of diffraction, and the vertical axis indicates diffraction intensity (relative value). As a result of analysis using analysis software “Jade, Ver. 5” manufactured by MDI, diffraction peaks were identified as α-Fe and TiO 2 (rutile structure).

α−Ｆｅの（２００）ピークの半値幅からシェラーの式を用いて算出されたＦｅの平均結晶子サイズは９０ｎｍであった。２θ＝２７．５°のとき得られたＴｉＯ２の最大回折ピークの半値幅は０．１４であり、ＴｉＯ２の最大回折ピーク強度のα−Ｆｅの最大回折ピーク［（１１０）ピーク］強度に対する比は０．１８であった。これから、ＴｉＯ２が高い結晶性を有することが分かる。レーザー回折粒度分布測定機（ＨＯＲＩＢＡ製：ＬＡ−９２０）で測定したこの試料粉末の平均粒径ｄ５０は３．１μｍであった。 The average crystallite size of Fe calculated by using the Scherrer equation from the half-value width of the (200) peak of α-Fe was 90 nm. The half-width of the maximum diffraction peak of TiO 2 obtained when 2θ = 27.5 ° is 0.14, and the maximum diffraction peak intensity of TiO 2 is relative to the maximum diffraction peak [(110) peak] intensity of α-Fe. The ratio was 0.18. From this, it can be seen that TiO 2 has high crystallinity. The average particle diameter d50 of this sample powder measured by a laser diffraction particle size distribution analyzer (manufactured by HORIBA: LA-920) was 3.1 μm.

試料粉末のＳＥＭ写真（図２）では、粒径数μｍの被覆金属微粒子が観察される。ほとんどの被覆金属微粒子には、ＴｉＯ２層１に被覆された複数のＦｅ粒子２（白色微粒子）が認められた。例えば、矢印で示したＴｉＯ２層に包含されているＦｅ粒子２の粒径は約０．５μｍであった。酸化物の標準生成エネルギーは、ΔＧＦｅ２Ｏ３＝−７４０ｋＪ／ｍｏｌに対して、ΔＧＴｉＯ２＝−８８９ｋＪ／ｍｏｌであるため、ＴｉＯ２の標準生成エネルギーの方が小さい。従って、α−Ｆｅ２Ｏ３がＴｉにより還元され、ＴｉＯ２が生成したと言える。図３は。図２の写真に符号等を記入した概略図である。両端が矢印の線はＦｅ粒子２の長手方向寸法を表し、両端が三角形状の矢印の線は被覆金属微粒子１の長手方向寸法を表す。不定形で長手方向を判別し難い場合には、長いと思われる複数の方向に矢印を引き、それらの内で最も長径となるものを長手方向寸法とした。 In the SEM photograph of the sample powder (FIG. 2), coated metal fine particles having a particle size of several μm are observed. In most coated metal fine particles, a plurality of Fe particles 2 (white fine particles) coated with the TiO 2 layer 1 were observed. For example, the particle size of the Fe particles 2 included in the TiO 2 layer indicated by the arrow was about 0.5 μm. The standard generation energy of oxide is ΔG TiO2 = −889 kJ / mol with respect to ΔG Fe2O3 = −740 kJ / mol, so the standard generation energy of TiO 2 is smaller. Therefore, it can be said that α-Fe 2 O 3 was reduced by Ti to produce TiO 2 . FIG. It is the schematic which entered the code | symbol etc. in the photograph of FIG. Both ends of the arrow line represent the longitudinal dimension of the Fe particle 2, and both ends of the triangular arrow line represent the longitudinal dimension of the coated metal fine particle 1. When it was difficult to distinguish the longitudinal direction due to the irregular shape, arrows were drawn in a plurality of directions considered to be long, and the dimension having the longest diameter among them was taken as the longitudinal dimension.

試料粉末について、図２の写真から粒径に対する個数分布（図４）を測定したところ、Ｆｅ粒子の粒径の個数分布（●印）は２つのピークを有し、被覆微粒子の粒径の個数分布（◇印）は３つのピークを有することがわかった。印をつなぐカーブは個数分布の傾向をわかりやすくする為に補助的に記載した。なお、粒径を測定する際には、０．０５μｍ未満の端数は四捨五入し、０．１μｍピッチで個数を振り分けた。   For the sample powder, the number distribution with respect to the particle diameter (FIG. 4) was measured from the photograph in FIG. 2, and the number distribution of the particle diameter of Fe particles (marked with ●) has two peaks. The distribution (marked with ◇) was found to have three peaks. The curves connecting the marks are supplementary to make the number distribution trend easier to understand. When measuring the particle size, fractions less than 0.05 μm were rounded off and the numbers were distributed at a pitch of 0.1 μm.

（実施例２）
実施例１で得た試料粉末５ｇとイソプロピルアルコール（ＩＰＡ）５０ｍＬとを１００ｍＬのビーカに投入し、１０分間超音波を照射した。次いで永久磁石をビーカの外面に１分間接触させ、磁性粒子だけをビーカ内壁に吸着させ、黒灰色の上澄み液を除去した。この磁気分離操作を５０回繰り返し、得られた精製磁性粒子を室温で乾燥させた。この磁性粒子の磁気特性を、最大印加磁界を１．６ＭＡ／ｍとしてＶＳＭ（振動型磁力計）により測定した。また、磁性粒子におけるＴｉの比率は、Ｘ線回折パターンから被覆金属微粒子がＦｅとＴｉＯ２からなることを確認した後で、被覆金属微粒子の飽和磁化の測定値から算出した。結果を表1に示す。 (Example 2)
5 g of the sample powder obtained in Example 1 and 50 mL of isopropyl alcohol (IPA) were put into a 100 mL beaker and irradiated with ultrasonic waves for 10 minutes. Next, the permanent magnet was brought into contact with the outer surface of the beaker for 1 minute, and only the magnetic particles were adsorbed on the inner wall of the beaker, and the black gray supernatant was removed. This magnetic separation operation was repeated 50 times, and the resulting purified magnetic particles were dried at room temperature. The magnetic properties of the magnetic particles were measured with a VSM (vibrating magnetometer) with a maximum applied magnetic field of 1.6 MA / m. The ratio of Ti in the magnetic particles was calculated from the measured value of saturation magnetization of the coated metal fine particles after confirming that the coated metal fine particles consisted of Fe and TiO 2 from the X-ray diffraction pattern. The results are shown in Table 1.

（実施例３〜６）
α−Ｆｅ２Ｏ３粉末とＴｉＣ粉末の質量比を６．５：３．５とした以外実施例１と同様にして試料粉末を作製した。この試料粉末を実施例２と同様に精製することにより得た磁性粒子の組成及び磁気特性を実施例２と同様に測定した。結果を表１に示す。さらに、前記質量比を６：４、５：５、４：６と変えて同様に試料粉末を作製した。 (Examples 3 to 6)
A sample powder was prepared in the same manner as in Example 1 except that the mass ratio of the α-Fe 2 O 3 powder and the TiC powder was 6.5: 3.5. The composition and magnetic properties of the magnetic particles obtained by purifying the sample powder in the same manner as in Example 2 were measured in the same manner as in Example 2. The results are shown in Table 1. Furthermore, sample powders were similarly produced by changing the mass ratio to 6: 4, 5: 5, and 4: 6.

この磁性粒子は高い耐食性を有するが、飽和磁化Ｍｓは４８Ａｍ２／ｋｇとなり５０Ａｍ２／ｋｇより低く、保磁力ｉＨｃは１８ｋＡ／ｍとなり１５ｋＡ／ｍ超であった。以上より、金属Ｆｅ粒子の特性を生かして高い飽和磁化の値を維持するためにはＴｉＣ配合比は３０〜５０ｍａｓｓ％であることが好ましいことが分かる。 Although the magnetic particles had high corrosion resistance, the saturation magnetization Ms was 48 Am 2 / kg, which was lower than 50 Am 2 / kg, and the coercive force iHc was 18 kA / m, which was more than 15 kA / m. From the above, it can be seen that the TiC compounding ratio is preferably 30 to 50 mass% in order to maintain the high saturation magnetization value by utilizing the characteristics of the metal Fe particles.

（実施例７）
熱処理温度を８００℃とした以外は実施例１と同様に試料粉末を作製した。さらに実施例２と同様にして精製することにより磁性被覆金属微粒子を得た。この試料粉末について磁気特性を実施例１と同様にして測定した。試料粉末中のＣ量は高周波加熱赤外吸収法（ＨＯＲＩＢＡ製：ＥＭＩＡ−５２０）によって測定し、Ｎ量は不活性ガス中加熱熱伝導法（ＨＯＲＩＢＡ製：ＥＭＧＡ−１３００）によって測定した。結果を表２に示す。 (Example 7)
A sample powder was prepared in the same manner as in Example 1 except that the heat treatment temperature was 800 ° C. Further, magnetic coated metal fine particles were obtained by purification in the same manner as in Example 2. The magnetic properties of this sample powder were measured in the same manner as in Example 1. The amount of C in the sample powder was measured by a high-frequency heating infrared absorption method (manufactured by HORIBA: EMIA-520), and the amount of N was measured by a heating heat conduction method in an inert gas (manufactured by HORIBA: EMGA-1300). The results are shown in Table 2.

（実施例８〜１２）
原料配合において表３に示す配合比で平均粒径２．８μｍのＴｉＮ粉末を添加した以外は実施例７と同様にして磁性被覆金属微粒子を得た。この試料粉末の磁気特性、及びＣ、Ｎの含有量を実施例７と同様にして評価した。結果を表３に示す。 (Examples 8 to 12)
Magnetic coated metal fine particles were obtained in the same manner as in Example 7 except that TiN powder having an average particle diameter of 2.8 μm was added at the mixing ratio shown in Table 3 in the raw material mixing. The magnetic properties of this sample powder and the contents of C and N were evaluated in the same manner as in Example 7. The results are shown in Table 3.

ＴｉＮの添加量が増加するに従い、Ｃ及びＮの含有量が低下し、飽和磁化Ｍｓは向上している。特にＴｉＮ置換率が０．２〜０．４（実施例９〜１１）の場合はＣ量が１．３ｍａｓｓ％以下、Ｎ量が０．２ｍａｓｓ％以下であり、不純物元素の含有量は極めて少ない。なおかつＭｓは１５８Ａｍ２／ｋｇまで向上している。しかしＴｉＮ置換率が０．５となると（実施例１２）、Ｃ、Ｎ量は少ないもののＭｓは実施例７よりも低下している。これはＣ不足により還元反応の進行が不十分であることが原因である。 As the amount of TiN added increases, the content of C and N decreases and the saturation magnetization Ms improves. In particular, when the TiN substitution rate is 0.2 to 0.4 (Examples 9 to 11), the C content is 1.3 mass% or less, the N content is 0.2 mass% or less, and the content of impurity elements is extremely small. . Furthermore, Ms is improved to 158 Am 2 / kg. However, when the TiN substitution rate becomes 0.5 (Example 12), although the amount of C and N is small, Ms is lower than that of Example 7. This is because the progress of the reduction reaction is insufficient due to the lack of C.

また実施例７、実施例９〜１１の試料粉末についてアルバック・ファイ製：ＰＨＩ−Ｑｕａｎｔｅｒａ ＳＸＭにてＸ線光電子分光（ＸＰＳ）分析を実施した。Ｏの１ｓ、Ｆｅの２ｐ３、Ｔｉの２ｐ軌道電子についてそれぞれナロースペクトルを測定し、定量分析を行った。結果を表３に示す。   Further, X-ray photoelectron spectroscopy (XPS) analysis was carried out on the sample powders of Example 7 and Examples 9 to 11 by ULVAC-PHI: PHI-Quantera SXM. Narrow spectra were measured for 1s of O, 2p3 of Fe, and 2p orbital electrons of Ti, respectively, and quantitative analysis was performed. The results are shown in Table 3.

ＴｉＮ置換率が増加すると共にＦｅ含有量が増加し、Ｔｉ含有量が減少する傾向が見られる。これはＴｉＮの添加によってＦｅ含有率が増加することに対応している。また検出したＦｅには金属Ｆｅと酸化Ｆｅ成分が含まれており、ＴｉＮ置換率の増加に伴い金属Ｆｅ成分が増加している。特にＴｉＮ置換率が０．２〜０．４の場合の金属Ｆｅ成分の比率（金属Ｆｅ／全Ｆｅ）はいずれも６％以上である。これはＴｉＮ添加によってＴｉＯ２の被覆がより完全となり、表面付近でも金属Ｆｅが酸化されずに維持されているためである。 As the TiN substitution rate increases, the Fe content increases and the Ti content tends to decrease. This corresponds to an increase in the Fe content due to the addition of TiN. Further, the detected Fe contains metallic Fe and oxidized Fe components, and the metallic Fe components increase with an increase in the TiN substitution rate. In particular, when the TiN substitution rate is 0.2 to 0.4, the ratio of the metal Fe component (metal Fe / total Fe) is 6% or more. This is because the addition of TiN makes the coating of TiO 2 more complete, and the metal Fe is maintained without being oxidized even near the surface.

（実施例１３）
実施例７の試料粉末１ｇを濃度１ＭのＮａＯＨ水溶液５０ｍＬ中に投入し、６０℃で２４時間浸漬処理を行った（アルカリ処理）。このアルカリ処理後、水洗して試料粉末を乾燥させた。得られた試料粉末２５ｍｇを濃度６Ｍのグアニジン塩酸塩水溶液１ｍＬ中に２５℃で２４時間浸漬させた（浸漬試験）後のＦｅイオン溶出量をＩＣＰ分析装置（エスアイアイナノテクノロジー社製：ＳＰＳ３１００Ｈ）により測定した。結果を表４に示す。 (Example 13)
1 g of the sample powder of Example 7 was put into 50 mL of a 1 M NaOH aqueous solution and subjected to immersion treatment at 60 ° C. for 24 hours (alkali treatment). After the alkali treatment, the sample powder was dried by washing with water. The amount of Fe ion elution after 25 mg of the obtained sample powder was immersed in 1 mL of 6 M guanidine hydrochloride aqueous solution at 25 ° C. for 24 hours (immersion test) was measured using an ICP analyzer (manufactured by SII Nano Technology, Inc .: SPS3100H). It was measured. The results are shown in Table 4.

（実施例１４〜１６）
実施例９、１０、１１の試料粉末について実施例１３と同様のアルカリ処理を施し、Ｆｅイオン溶出量を評価した。結果を表４に示す。 (Examples 14 to 16)
The sample powders of Examples 9, 10, and 11 were subjected to the same alkali treatment as in Example 13, and the Fe ion elution amount was evaluated. The results are shown in Table 4.

アルカリ処理によってＦｅイオン溶出量が５０ｍｇ／Ｌ以下に低下していることが分かる。またＴｉＮ置換率が増えるほどＦｅイオン溶出量は小さくなる。特にＴｉＮ置換率０．４ではアルカリ処理を施す前でもＦｅイオン溶出量が１０ｍｇ／Ｌ未満と極めて小さく、耐食性に優れることが分かる。   It can be seen that the Fe ion elution amount is reduced to 50 mg / L or less by the alkali treatment. Moreover, the Fe ion elution amount decreases as the TiN substitution rate increases. In particular, when the TiN substitution rate is 0.4, the Fe ion elution amount is as small as less than 10 mg / L even before the alkali treatment, and it is found that the corrosion resistance is excellent.

実施例８〜１６と同条件で作製した被覆金属微粒子の試料粉末について、実施例１と同様にしてＸ線回折を行ったところ、いずれの試料粉末もＸ線回折パターンにおいてＴｉＯ2の最大ピークの半値幅が０．３°以下であり、かつ金属Ｍの最大ピークに対するＴｉＯ2の最大ピークの強度比が０．０３以上となった。 When X-ray diffraction was performed in the same manner as in Example 1 for the coated metal fine particle sample powders produced under the same conditions as in Examples 8 to 16, all of the sample powders had the maximum peak of TiO 2 in the X-ray diffraction pattern. The full width at half maximum was 0.3 ° or less, and the intensity ratio of the maximum peak of TiO 2 to the maximum peak of metal M was 0.03 or more.

実施例２〜１６の被覆金属微粒子について、実施例１と同様にして粒径に対する個数分布を測定したところ、いずれも金属粒子のピークが２つとなる分布を得た。   For the coated metal fine particles of Examples 2 to 16, the number distribution with respect to the particle diameter was measured in the same manner as in Example 1. As a result, a distribution with two metal particle peaks was obtained.

（実施例１７）
実施例１１の被覆金属微粒子について、以下に説明する手法でシリカ被覆処理を施し、磁性シリカ粒子を作製した。第１に、上述の被覆金属微粒子の試料粉末５ｇをエタノール溶媒１００ｍＬ中に分散し、これにテトラエトキシシランを１ｍＬ添加した。次にこの溶媒を攪拌しながら純水２２ｇとアンモニア水４ｇの混合溶液を添加し、上記混合溶液を１時間攪拌した。攪拌後、磁性粒子を磁石でビーカ内壁に捕捉しながら上澄み液を除去した。第２に、上記磁性粒子に対して上述のシリカ被覆処理を同様に２回繰り返し、最後にイソプロピルアルコールで溶媒置換を行った後、磁性粒子をドラフト内で乾燥させて磁性シリカ粒子を得た。 (Example 17)
The coated metal fine particles of Example 11 were subjected to silica coating treatment by the method described below to produce magnetic silica particles. First, 5 g of the above sample powder of coated metal fine particles was dispersed in 100 mL of ethanol solvent, and 1 mL of tetraethoxysilane was added thereto. Next, a mixed solution of 22 g of pure water and 4 g of aqueous ammonia was added while stirring the solvent, and the mixed solution was stirred for 1 hour. After stirring, the supernatant was removed while trapping the magnetic particles on the inner wall of the beaker with a magnet. Secondly, the above silica coating treatment was repeated twice with respect to the magnetic particles. Finally, the solvent was replaced with isopropyl alcohol, and the magnetic particles were dried in a fume hood to obtain magnetic silica particles.

本発明の磁性シリカ粒子の磁気ビーズ性能を評価するため、Ｒｏｃｈ社製ＤＮＡ抽出キット「ＭａｇＮＡ Ｐｕｒｅ ＬＣ ＤＮＡ Ｉｓｏｌａｔｉｏｎ Ｋｉｔ Ｉ」を用いて馬血１００μＬからＤＮＡを精製した。磁性シリカ粒子１２ｍｇをイソプロピルアルコール（ＩＰＡ）１５０μＬ中に分散させた溶液を各々磁気ビーズ液として用いた以外は上記Ｋｉｔのプロトコルに準拠してＤＮＡを抽出し、ＤＮＡ抽出液を得た。ＤＮＡ抽出液中のＤＮＡ量はＵＶスペクトル測定機（日立ハイテクノロジーズ社製ダイオードアレー型バイオ光度計Ｕ−００８０Ｄ）を用いて測定した。その結果、馬血１００μＬから２．７μｇのＤＮＡを抽出した。   In order to evaluate the magnetic bead performance of the magnetic silica particles of the present invention, DNA was purified from 100 μL of horse blood using a DNA extraction kit “MagNA Pure LC DNA Isolation Kit I” manufactured by Roch. DNA was extracted according to the above Kit protocol except that a solution in which 12 mg of magnetic silica particles were dispersed in 150 μL of isopropyl alcohol (IPA) was used as a magnetic bead solution to obtain a DNA extract. The amount of DNA in the DNA extract was measured using a UV spectrum measuring device (diode array type biophotometer U-0080D manufactured by Hitachi High-Technologies Corporation). As a result, 2.7 μg of DNA was extracted from 100 μL of horse blood.

（参考例）
市販の磁気ビーズ（Ｒｏｃｈｅ製、ＭａｇＮＡＰｕｒｅ ＬＣ ＤＮＡ Ｉｓｏｌａｔｉｏｎ Ｋｉｔ Ｉに付属）を用いて実施例１０と同様にＤＮＡを抽出した結果、ＤＮＡ抽出量は２．７μｇであった。
以上より、本発明の被覆金属微粒子は磁気ビーズとして適用できることがわかった。 (Reference example)
As a result of extracting DNA using commercially available magnetic beads (Roche, attached to MagNAPure LC DNA Isolation Kit I), the amount of extracted DNA was 2.7 μg.
From the above, it was found that the coated metal fine particles of the present invention can be applied as magnetic beads.

実施例１の試料粉末のＸ線回折パターンである。2 is an X-ray diffraction pattern of the sample powder of Example 1. FIG. 図１に係る試料粉末を走査型電子顕微鏡で撮影した写真である。It is the photograph which image | photographed the sample powder concerning FIG. 1 with the scanning electron microscope. 図２の写真に符号等を記入した概略図である。It is the schematic which entered the code | symbol etc. in the photograph of FIG. 粒径に対する個数分布を示すグラフである。It is a graph which shows the number distribution with respect to a particle size.

符号の説明Explanation of symbols

１ ＴｉＯ２層、 ２ Ｆｅ粒子 1 TiO 2 layer, 2 Fe particles

Claims (4)

ＴｉＯ ２ を主体とするＴｉ酸化物中に金属粒子を内包した被覆金属微粒子の粉末であって、前記金属はその酸化物の標準生成自由エネルギーがΔＧＭ−Ｏ＞ΔＧＴｉＯ２の関係を満たす金属であり、前記金属粒子の粒径に対する個数分布が複数のピークを有することを特徴とする被覆金属微粒子の粉末。 A powder of coated metal fine particles in which metal particles are encapsulated in a Ti oxide mainly composed of TiO 2 , wherein the metal is a metal whose standard free energy of formation of the oxide satisfies the relationship of ΔG M−O > ΔG TiO 2. A powder of coated metal fine particles, wherein the number distribution with respect to the particle size of the metal particles has a plurality of peaks. 請求項１に記載の被覆金属微粒子の粉末であって、前記Ｔｉ酸化物中に複数の金属粒子を内包した被覆金属微粒子を有することを特徴とする被覆金属微粒子の粉末。 The powder of coated metal fine particles according to claim 1, comprising coated metal fine particles in which a plurality of metal particles are included in the Ti oxide. 請求項１又は２に記載の被覆金属微粒子の粉末であって、前記金属がＦｅ、Ｃｏ、Ｎｉから選ばれる少なくとも１つの元素を主成分としていることを特徴とする被覆金属微粒子の粉末。 3. The powder of coated metal fine particles according to claim 1, wherein the metal contains at least one element selected from Fe, Co, and Ni as a main component. 4. ＴｉＯ ２ を主体とするＴｉ酸化物中に金属粒子を内包した被覆金属微粒子の粉末（前記金属粒子はＦｅ、Ｃｏ、Ｎｉから選ばれる少なくとも１つの元素を主成分としており、前記金属粒子の粒径に対する個数分布が複数のピークを有する。）と、前記被覆金属微粒子を分散する媒体とを有する磁気ビーズ。 Powder of coated metal fine particles in which metal particles are encapsulated in Ti oxide mainly composed of TiO 2 (the metal particles are mainly composed of at least one element selected from Fe, Co and Ni, and the particle diameter of the metal particles And a medium in which the coated fine metal particles are dispersed.
JP2006262410A 2006-09-27 2006-09-27 Coated fine metal powder and magnetic beads Expired - Fee Related JP4775713B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2006262410A JP4775713B2 (en) 2006-09-27 2006-09-27 Coated fine metal powder and magnetic beads

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2006262410A JP4775713B2 (en) 2006-09-27 2006-09-27 Coated fine metal powder and magnetic beads

Publications (2)

Publication Number Publication Date
JP2008081779A JP2008081779A (en) 2008-04-10
JP4775713B2 true JP4775713B2 (en) 2011-09-21

Family

ID=39352936

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2006262410A Expired - Fee Related JP4775713B2 (en) 2006-09-27 2006-09-27 Coated fine metal powder and magnetic beads

Country Status (1)

Country Link
JP (1) JP4775713B2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP7059594B2 (en) * 2017-01-12 2022-04-26 Tdk株式会社 Soft magnetic materials, cores and inductors
US11015084B2 (en) 2017-09-20 2021-05-25 Ppg Industries Ohio, Inc. Coating compositions and elastic barrier coatings formed therefrom
US11059993B2 (en) 2018-09-07 2021-07-13 Ppg Industries Ohio, Inc. Coating composition exhibiting specific gloss properties for extreme washable coatings
CN109786100A (en) * 2019-03-29 2019-05-21 中国科学院宁波材料技术与工程研究所 A kind of preparation method of soft magnetic-powder core

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4288674B2 (en) * 2003-09-25 2009-07-01 日立金属株式会社 Method for producing magnetic metal fine particles and magnetic metal fine particles

Also Published As

Publication number Publication date
JP2008081779A (en) 2008-04-10

Similar Documents

Publication Publication Date Title
EP1568427B1 (en) Production method of fine composite metal particles
JP5105503B2 (en) ε Iron oxide production method
JP4766276B2 (en) Coated fine metal particles and method for producing the same
JP4853769B2 (en) Magnetic silica particles and method for producing the same
JP2005273011A (en) Iron based nanosize particle and production method therefor
JP5124826B2 (en) Ε iron oxide powder with good dispersibility
JP5359905B2 (en) Fine metal particles, method for producing the same, and magnetic beads
JP2006097123A (en) Metallic microparticle, manufacturing method therefor, and magnetic bead
JP4758858B2 (en) Metallic magnetic powder for magnetic recording medium and method for producing the same
JP6851315B2 (en) Metal oxide particles and their production method
JP4288674B2 (en) Method for producing magnetic metal fine particles and magnetic metal fine particles
JP4775713B2 (en) Coated fine metal powder and magnetic beads
JP6480715B2 (en) Precursor of iron-based oxide magnetic particle powder and method for producing iron-based oxide magnetic particle powder using the same
JP6461828B2 (en) Method for producing magnetic particles
JP2007046074A (en) Fine metal particle and manufacturing method therefor
WO2008035681A1 (en) Coated metal fine particles and process for production thereof
JP2007046074A5 (en)
JP2008081818A (en) Method for producing precursor powder of nickel-ferroalloy nanoparticle, precursor powder of nickel-ferroalloy nanoparticle, method for producing nickel-ferroalloy nanoparticle, and nickel-ferroalloy nanoparticle
JP4811658B2 (en) Coated metal fine particles and production method thereof,
JP2008069431A (en) Method for producing magnetic particle, and magnetic particle
Ennas et al. Mechanochemical route for the synthesis of cobalt ferrite–silica and iron–cobalt alloy–silica nanocomposites
JP2005281786A (en) Magnetic metal particle and production method therefor
JP4304668B2 (en) Metal fine particles and method for producing metal fine particles
JP2006179567A (en) Iron nitride magnetic powder displaying excellent storing stability
JP5024683B2 (en) Magnetic beads

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20090811

A521 Request for written amendment filed

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20100916

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20110210

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20110218

A521 Request for written amendment filed

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20110418

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20110603

A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20110616

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140708

Year of fee payment: 3

LAPS Cancellation because of no payment of annual fees