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JP3837532B2 - Method for producing magnesium boride nanowire - Google Patents

Method for producing magnesium boride nanowire Download PDF

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Publication number
JP3837532B2
JP3837532B2 JP2003006301A JP2003006301A JP3837532B2 JP 3837532 B2 JP3837532 B2 JP 3837532B2 JP 2003006301 A JP2003006301 A JP 2003006301A JP 2003006301 A JP2003006301 A JP 2003006301A JP 3837532 B2 JP3837532 B2 JP 3837532B2
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Japan
Prior art keywords
magnesium boride
magnesium
nanowire
boride
nanoparticle precursor
Prior art date
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JP2003006301A
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Japanese (ja)
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JP2004217463A (en
Inventor
義雄 板東
ルンチィ・マ
孝雄 森
デミトリー・ゴルバーグ
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National Institute for Materials Science
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National Institute for Materials Science
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Description

【0001】
【発明の属する技術分野】
この出願の発明は、ホウ化マグネシウムナノワイヤーの製造方法に関するものである。さらに詳しくは、この出願の発明は、超電導材料として有用なホウ化マグネシウムナノワイヤーの新規な製造方法に関するものである。
【0002】
【従来の技術】
ホウ化マグネシウムは、転移温度39Kを示す超電動材料である。ホウ化マグネシウムは、多結晶、薄膜、ワイヤー、テープ、単結晶等の各種の形態を有する。そして、粒子径約40〜100ナノメートルのホウ化マグネシウムのナノメートルサイズの球状粒子が圧力下で高温処理を施すことにより得られている(たとえば、非特許文献1参照。)。また、最近、直径50〜400ナノメートルの多結晶ホウ化マグネシウムナノワイヤーが高温反応により得られている(たとえば、非特許文献2参照。)。
【0003】
得られたホウ化マグネシウムナノワイヤーの超電導を示す転移温度は、いずれも33Kである。
【0004】
【非特許文献1】
A.Gmbel外,アプライド・フィジックス・レターズ(Appl.Phys.Lett.),2002年,第80巻,p.2725
【非特許文献2】
Y.Wu外,アドバンスト・マテリアルズ(Adv.Mater.),2001年,第13巻,p.1487
【0005】
【発明が解決しようとする課題】
この出願の発明は、これまでに提案されている方法とは異なる方法によりホウ化マグネシウムナノワイヤーを製造することを課題としている。
【0006】
【課題を解決するための手段】
この出願の発明は、上記の課題を解決するものとして、マグネシウム粉末と非晶質ホウ素粉末の混合物をアルゴン雰囲気中で700〜830℃に加熱し、ホウ化マグネシウムナノ粒子前駆物質を作製した後、このホウ化マグネシウムナノ粒子前駆物質をアルゴン気流中で850〜950℃に加熱することを特徴とするホウ化マグネシウムナノワイヤーの製造方法を提供する。
【0007】
以下、実施例を示しつつ、この出願の発明のホウ化マグネシウムナノワイヤーの製造方法についてさらに詳しく説明する。
【0008】
【発明の実施の形態】
この出願の発明のホウ化マグネシウムナノワイヤーの製造方法では、上述のとおり、マグネシウム粉末と非晶質ホウ素粉末を混合し、たとえば窒化ホウ素製のるつぼ等に入れ、アルゴン雰囲気中で700〜830℃に加熱してホウ化マグネシウムナノ粒子前駆物質を作製する。ホウ化マグネシウムナノ粒子前駆物質を作製する際の加熱温度は760℃が最適であるが、実験制御、精度等を考慮して700〜830℃とする。
【0009】
次いで、上記ホウ化マグネシウムナノ粒子前駆物質をアルゴン気流中で、たとえば赤外照射加熱炉等を用いて850〜950℃に加熱すると、結晶性のホウ化マグネシウムナノワイヤーが得られる。このときの加熱温度は900℃が最適であり、加熱時の実験制御、精度等を考慮して加熱温度は850〜950℃とする。
【0010】
得られたホウ化マグネシウムナノワイヤーは、転移温度39Kを示す超電導体であり、転移温度の上昇が見られる。
【0011】
【実施例】
マグネシウム粉末(純度99.9%、325メッシュ)と非晶質ホウ素粉末(純度99.9%、粒子径約50nm)の混合物(モル比2.5:1)を十分に混ぜ合わせた後、混合物を窒化ホウ素製のるつぼに入れた。このるつぼを石英管の中に配置し、高周波誘導加熱炉を用いてアルゴンガス雰囲気中で750〜780℃に2時間加熱した後、室温まで冷却した。ホウ化マグネシウムナノ粒子前駆物質が得られた。
【0012】
次いで、得られたホウ化マグネシウムナノ粒子前駆物質を、赤外線照射加熱炉を用いてアルゴンガスを流しながら急速に温度を上げ、5分以内に900℃まで上昇させ、この温度に40分間維持した。
【0013】
ホウ化マグネシウムナノ粒子前駆物質の走査型電子顕微鏡像を図1(a)に示した。粒子径が約100〜500ナノメートルのナノ粒子であると確認される。また、図1(b)は、ホウ化マグネシウムナノ粒子前駆物質のX線回折パターンであり、MgB2と少量の未反応マグネシウムからなっていることが確認される。
【0014】
図2(a)は、900℃で処理した後の試料のX線回折パターンであり、図1(b)のX線回折パターンと比較すると、未反応のマグネシウムのピークが消失しており、MgB2の相構造とよく一致している。また、X線回折パターンからは、少量の酸素とマグネシウムが反応したと考えられる酸化マグネシウムがわずかに存在していることが確認される。
【0015】
図2(b)は、900℃で処理した後の試料の走査型電子顕微鏡像であるが、10〜20ナノメートルの均一な直径を有するナノワイヤーが生成していることが確認される。一方、X線エネルギー拡散スペクトルと電子エネルギー損失スペクトルの測定結果からは、ホウ素とマグネシウムが主成分で少量の酸素が含まれおり、Mg:B:Oの原子比は1.0:2.0:0.3〜0.5であることが確認される。電子線回折の測定結果からは、試料は、六方晶系のホウ化マグネシウム(a=3.08Å、C=3.52Å)であると確認される。
【0016】
図3は、以上のホウ化マグネシウムナノ粒子前駆物質及びホウ化マグネシウムナノワイヤーの超電導性に関する磁化率と温度の関係について測定したグラフである。
【0017】
ホウ化マグネシウムナノ粒子前駆物質の転移温度が36.5Kであるのに対し、ホウ化マグネシウムナノワイヤーの転移温度は39Kであり、ナノワイヤーにすることによる転移温度の上昇が確認される。また、得られたホウ化マグネシウムナノワイヤーは、これまでのものに比べ、転移温度が高くなっている。
【0018】
【発明の効果】
以上詳しく説明したとおり、超電導材料として有用なホウ化マグネシウムナノワイヤーが、まったく新しい方法により得られ、しかも転移温度の上昇が実現される。
【図面の簡単な説明】
【図1】 (a)(b)は、それぞれ、実施例で得られたホウ化マグネシウムナノ粒子前駆物質の走査型電子顕微鏡像、X線回折スペクトルである。
【図2】 (a)(b)は、それぞれ、実施例で得られたホウ化マグネシウムナノワイヤーのX線回折スペクトル、走査型電子顕微鏡像である。
【図3】実施例で得られたホウ化マグネシウムナノ粒子前駆物質及びホウ化マグネシウムナノワイヤーの磁化率を示したグラフである。
[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a method for producing magnesium boride nanowires. More specifically, the invention of this application relates to a novel method for producing magnesium boride nanowires useful as a superconducting material.
[0002]
[Prior art]
Magnesium boride is a super electric material exhibiting a transition temperature of 39K. Magnesium boride has various forms such as polycrystal, thin film, wire, tape, single crystal and the like. And the spherical particle of the nanometer size of magnesium boride with a particle diameter of about 40-100 nanometer is obtained by performing a high temperature process under pressure (for example, refer nonpatent literature 1). Recently, polycrystalline magnesium boride nanowires having a diameter of 50 to 400 nanometers have been obtained by a high temperature reaction (see, for example, Non-Patent Document 2).
[0003]
The transition temperatures showing superconductivity of the obtained magnesium boride nanowires are all 33K.
[0004]
[Non-Patent Document 1]
A. Gmbel et al., Applied Physics Letters, 2002, 80, p. 2725
[Non-Patent Document 2]
Y. Wu et al., Advanced Materials (Adv. Mater.), 2001, Vol. 13, p. 1487
[0005]
[Problems to be solved by the invention]
An object of the invention of this application is to produce magnesium boride nanowires by a method different from the methods proposed so far.
[0006]
[Means for Solving the Problems]
The invention of this application is to solve the above-mentioned problem, after heating a mixture of magnesium powder and amorphous boron powder to 700 to 830 ° C. in an argon atmosphere to prepare a magnesium boride nanoparticle precursor, Provided is a method for producing a magnesium boride nanowire, wherein the magnesium boride nanoparticle precursor is heated to 850 to 950 ° C. in an argon stream.
[0007]
Hereinafter, the manufacturing method of the magnesium boride nanowire of invention of this application is demonstrated in more detail, showing an Example.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the manufacturing method of the magnesium boride nanowire of the invention of this application, as described above, the magnesium powder and the amorphous boron powder are mixed, put into a crucible made of boron nitride, for example, and heated to 700 to 830 ° C. in an argon atmosphere. Heat to produce magnesium boride nanoparticle precursor. The optimum heating temperature for preparing the magnesium boride nanoparticle precursor is 760 ° C., but it is set to 700 to 830 ° C. in consideration of experimental control and accuracy.
[0009]
Next, when the magnesium boride nanoparticle precursor is heated to 850 to 950 ° C. in an argon stream using, for example, an infrared irradiation heating furnace, a crystalline magnesium boride nanowire is obtained. The heating temperature at this time is optimally 900 ° C., and the heating temperature is set to 850 to 950 ° C. in consideration of experimental control and accuracy during heating.
[0010]
The obtained magnesium boride nanowire is a superconductor exhibiting a transition temperature of 39K, and an increase in the transition temperature is observed.
[0011]
【Example】
After thoroughly mixing a mixture of magnesium powder (purity 99.9%, 325 mesh) and amorphous boron powder (purity 99.9%, particle size approximately 50 nm) (molar ratio 2.5: 1), the mixture is made of a boron nitride crucible. Put in. The crucible was placed in a quartz tube, heated to 750 to 780 ° C. for 2 hours in an argon gas atmosphere using a high frequency induction heating furnace, and then cooled to room temperature. Magnesium boride nanoparticle precursor was obtained.
[0012]
Next, the obtained magnesium boride nanoparticle precursor was rapidly heated while flowing argon gas using an infrared irradiation heating furnace, raised to 900 ° C. within 5 minutes, and maintained at this temperature for 40 minutes.
[0013]
A scanning electron microscope image of the magnesium boride nanoparticle precursor is shown in FIG. 1 (a). It is confirmed that the particle diameter is about 100 to 500 nanometers. FIG. 1 (b) is an X-ray diffraction pattern of the magnesium boride nanoparticle precursor, which is confirmed to be composed of MgB 2 and a small amount of unreacted magnesium.
[0014]
Fig. 2 (a) is an X-ray diffraction pattern of the sample after being treated at 900 ° C. Compared with the X-ray diffraction pattern of Fig. 1 (b), the unreacted magnesium peak disappeared, and MgB It is in good agreement with the phase structure of 2 . In addition, the X-ray diffraction pattern confirms the presence of a small amount of magnesium oxide that is thought to have reacted with a small amount of oxygen and magnesium.
[0015]
FIG. 2 (b) is a scanning electron microscope image of the sample after processing at 900 ° C., and it is confirmed that nanowires having a uniform diameter of 10 to 20 nanometers are generated. On the other hand, from the measurement results of the X-ray energy diffusion spectrum and the electron energy loss spectrum, boron and magnesium are the main components and a small amount of oxygen is included, and the atomic ratio of Mg: B: O is 1.0: 2.0: 0.3 to 0.5. It is confirmed that there is. The measurement result of the electron diffraction confirms that the sample is hexagonal magnesium boride (a = 3.083.0, C = 3.52Å).
[0016]
FIG. 3 is a graph obtained by measuring the relationship between magnetic susceptibility and temperature related to the superconductivity of the above magnesium boride nanoparticle precursor and magnesium boride nanowire.
[0017]
The transition temperature of magnesium boride nanoparticle precursor is 36.5K, whereas the transition temperature of magnesium boride nanowire is 39K, and it is confirmed that the transition temperature is increased by using nanowire. Moreover, the obtained magnesium boride nanowire has a high transition temperature compared to the conventional ones.
[0018]
【The invention's effect】
As described above in detail, magnesium boride nanowires useful as a superconducting material can be obtained by a completely new method, and the transition temperature can be increased.
[Brief description of the drawings]
FIGS. 1A and 1B are a scanning electron microscope image and an X-ray diffraction spectrum of a magnesium boride nanoparticle precursor obtained in an example, respectively.
FIGS. 2A and 2B are an X-ray diffraction spectrum and a scanning electron microscope image, respectively, of magnesium boride nanowires obtained in Examples.
FIG. 3 is a graph showing the magnetic susceptibility of magnesium boride nanoparticle precursors and magnesium boride nanowires obtained in Examples.

Claims (1)

マグネシウム粉末と非晶質ホウ素粉末の混合物をアルゴン雰囲気中で700〜830℃に加熱し、ホウ化マグネシウムナノ粒子前駆物質を作製した後、このホウ化マグネシウムナノ粒子前駆物質をアルゴン気流中で850〜950℃に加熱することを特徴とするホウ化マグネシウムナノワイヤーの製造方法。After heating a mixture of magnesium powder and amorphous boron powder to 700 to 830 ° C. in an argon atmosphere to prepare a magnesium boride nanoparticle precursor, the magnesium boride nanoparticle precursor was added to an argon gas stream at 850 to A method for producing magnesium boride nanowires, which is heated to 950 ° C.
JP2003006301A 2003-01-14 2003-01-14 Method for producing magnesium boride nanowire Expired - Lifetime JP3837532B2 (en)

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Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7018954B2 (en) * 2001-03-09 2006-03-28 American Superconductor Corporation Processing of magnesium-boride superconductors
JP2007521664A (en) * 2003-12-11 2007-08-02 イエール ユニバーシティ Growth of boron nanostructures with controlled diameter
DE102008045858B4 (en) * 2008-09-05 2017-08-10 H.C. Starck Gmbh reduction process
CN114735714B (en) * 2021-12-03 2023-08-22 上海市第十人民医院 Mg 1-x R x B 2 Preparation method and application of material
CN115465870B (en) * 2022-08-31 2024-02-02 青岛科技大学 Preparation method of magnesium boride nano-sheet and application of magnesium boride nano-sheet in Li-S battery diaphragm

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