JP2008066168A - Mgb2 superconducting wire rod and its manufacturing method - Google Patents
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本発明は、ＭｇＢ２超伝導線材とその製造法に関する。 The present invention relates to a MgB 2 superconducting wire and a method for producing the same.
電気抵抗ゼロの超伝導現象は損失無しに大きな電流を流したり、非常に強い磁界を発生させることが可能なため、エネルギーや環境問題に関連して種々の応用開発が進められている。超伝導現象を応用するためには、臨界温度や臨界磁界等の超伝導特性の優れた超伝導材料を線材化するための技術開発が必要である。特性の優れた超伝導材料のうち、塑性変形能を有し直接線材に加工することが可能なニオブーチタン（Ｎｂ−Ｔｉ）合金線材（臨界温度９Ｋ、臨界磁界１２Ｔ）が最も早くから実用化され、現在でも多くの超伝導機器に使われている。一方、Ｎｂ−Ｔｉよりも臨界温度、臨界磁界が高い超伝導材料は殆どが金属間化合物あるいは酸化物系に属し、硬く脆くて直接線材に加工することは不可能である。したがって、これらの材料を線材化するためには特殊な技術開発が必要となってくる。その中でニオブ３錫（Ｎｂ３Ｓｎ）金属間化合物超伝導体（臨界温度１８Ｋ、臨界磁界２５Ｔ）が拡散反応を使った方法によって最初に実用化され、さらに酸化物系高温超伝導材料の中のビスマス系（臨界温度８０−１１０Ｋ、臨界磁界１００Ｔ以上）が粉末法によって線材化されて現在各種の応用開発が進められている。 Since the superconducting phenomenon with zero electrical resistance can flow a large current without loss or generate a very strong magnetic field, various application developments are being promoted in relation to energy and environmental problems. In order to apply the superconducting phenomenon, it is necessary to develop a technology for forming a superconducting material with excellent superconducting properties such as critical temperature and critical magnetic field. Among superconducting materials with excellent properties, niobium-titanium (Nb-Ti) alloy wire (critical temperature 9K, critical magnetic field 12T) that has plastic deformability and can be directly processed into wire has been put into practical use from the earliest days. But it is used in many superconducting devices. On the other hand, most of the superconducting materials having a higher critical temperature and critical magnetic field than Nb—Ti belong to intermetallic compounds or oxides, are hard and brittle, and cannot be directly processed into a wire. Therefore, special technology development is required to make these materials into wires. Among them, niobium 3 tin (Nb 3 Sn) intermetallic compound superconductors (critical temperature 18K, critical magnetic field 25T) were first put into practical use by a method using a diffusion reaction. The bismuth system (critical temperature 80-110K, critical magnetic field 100T or more) has been made into a wire material by the powder method, and various application developments are currently underway.
本発明の対象となっているに二硼化マグネシウム（ＭｇＢ２）超伝導体は２００１年に新たに発見され、金属間化合物の中ではずば抜けて高い臨界温度（３９Ｋ）をもつことから、物性面のみならず応用面からも非常に注目されている超伝導材料である。特に従来の金属系超伝導線材では困難であった冷凍機冷却による中温度（約２０−３０Ｋ）での応用が可能となるため、一刻も早い線材化が切望されている。しかし、ＭｇＢ２はＮｂ３Ｓｎと同様に金属間化合物の範疇に属し、硬く脆いため直接線材に加工することは不可能である。現在種々の線材化法が試みられているが、粉末を金属管に詰めて加工するＰＩＴ（Ｐｏｗｄｅｒ−ｉｎ−ｔｕｂｅ）法が最も多く研究されている。ＭｇＢ２のＰＩＴ法では、直接ＭｇＢ２粉末を詰めて加工するエクス・シチュー（ｅｘ−ｓｉｔｕ）法とＭｇとＢとの混合粉末を詰めて加工、熱処理するイン・シチュー（ｉｎ−ｓｉｔｕ）法とが開発されている。イン・シチュー法の方が他元素添加による高磁界特性の改善がより効果的に行える利点があることからより多く研究されているが、Ｍｇ、Ｂともに難加工性の元素であるため粉末の混合体として詰め込む以外に手段の無いのが現状である。この場合ＭｇＢ２の生成原理はＭｇ粒子とＢ粒子との焼結反応を基本とし、さらにＭｇとＢとが反応してＭｇＢ２に変化する時に収縮が起こるため内部に空孔の生成が起こり、高密度を達成することが本質的に不可能な欠点を有する。そのため、ＰＩＴ法では実用に足る十分な臨界電流密度特性が得られていないのが現状である。 The magnesium diboride (MgB 2 ) superconductor, which is the object of the present invention, was newly discovered in 2001, and has a high critical temperature (39K), which is extremely high among the intermetallic compounds. It is a superconducting material that is attracting a great deal of attention not only from the application standpoint. In particular, since it can be applied at a medium temperature (about 20-30 K) by cooling a refrigerator, which was difficult with conventional metal-based superconducting wires, it is desired to make wires as soon as possible. However, MgB 2 belongs to the category of intermetallic compounds like Nb 3 Sn and is hard and brittle, so it cannot be processed directly into a wire. At present, various wire rod forming methods have been tried, but the PIT (Powder-in-tube) method, in which powder is packed in a metal tube and processed, has been most studied. The MgB 2 PIT method includes an ex-situ method in which MgB 2 powder is directly packed and processed, and an in-situ method in which a mixed powder of Mg and B is processed and heat-treated. Has been developed. The in-situ method has been studied more because it has the advantage that it can improve the high magnetic field characteristics more effectively by adding other elements, but since both Mg and B are difficult-to-work elements, powder mixing There is currently no means other than stuffing as a body. In this case, the formation principle of MgB 2 is based on the sintering reaction between Mg particles and B particles, and further, shrinkage occurs when Mg and B react to change to MgB 2 , so that voids are generated inside, It has the disadvantage that it is essentially impossible to achieve high density. For this reason, the PIT method does not provide sufficient critical current density characteristics sufficient for practical use.
本発明は、このような実情に鑑み、良好な超伝導臨界電流を有しながら加工性をも向上したＭｇＢ２超伝導線材とその製造法を提供することを目的とした。 In view of such circumstances, an object of the present invention is to provide a MgB 2 superconducting wire having a good superconducting critical current and improved workability and a method for producing the same.
発明１のＭｇＢ２超伝導線材は、マグネシウム（Ｍｇ）−リチウム（Ｌｉ）―ボロン（Ｂ）合金層と二硼化マグネシウム（ＭｇＢ２）超伝導層とが積層されてなることを特徴とする。 MgB2 superconducting wire of the invention 1, magnesium (Mg) - Lithium (Li) - boron (B) alloy layer and the magnesium diboride (MgB 2) and the superconducting layer is equal to or formed by stacking.
発明２のＭｇＢ２超伝導線材は、発明２において、ボロン（Ｂ）に対し、１〜１０原子％のナノサイズ炭化珪素（ＳｉＣ）が添加されてなることを特徴とする。 The MgB2 superconducting wire of the invention 2 is characterized in that, in the invention 2, 1 to 10 atomic% of nanosize silicon carbide (SiC) is added to boron (B).
発明３は、発明１又は２のＭｇＢ２超伝導線材の製造法であって、マグネシウム（Ｍｇ）−リチウム（Ｌｉ）合金層と接触する形でボロン（Ｂ）層を積層してなる複合体を構成し、これを線状あるいはテープ状に加工した後、マグネシウム（Ｍｇ）とボロン（Ｂ）の拡散反応温度で熱処理することによって二硼化マグネシウム（ＭｇＢ２）超伝導層を生成させることを特徴とする。 Invention 3 is a method for producing the MgB 2 superconducting wire of Invention 1 or 2, wherein a composite formed by laminating a boron (B) layer in contact with a magnesium (Mg) -lithium (Li) alloy layer is provided. A magnesium diboride (MgB 2 ) superconducting layer is produced by forming a linear or tape-like structure and then heat-treating at a diffusion reaction temperature of magnesium (Mg) and boron (B). And
発明４のＭｇＢ２超伝導線材の製造法は、発明３において、Ｍｇ−Ｌｉ合金の管を他の金属あるいは合金管の中に挿入した２重管を形成し、その内部にＢ粉末を封入することによって、マグネシウム（Ｍｇ）ーリチウム（Ｌｉ）合金層と接触する形でボロン（Ｂ）層を積層したことを特徴とする。 The manufacturing method of the MgB2 superconducting wire of the invention 4 is the invention 3, wherein the Mg-Li alloy tube is inserted into another metal or alloy tube to form a double tube, and the B powder is enclosed therein. Thus, the boron (B) layer is laminated in contact with the magnesium (Mg) -lithium (Li) alloy layer.
発明５のＭｇＢ２超伝導線材の製造法は、発明３において、金属あるいは合金管の中にその内径より小さい外形を有するＭｇ−Ｌｉ合金棒を挿入し、その周囲に形成された隙間にＢ粉末を充填することによって、マグネシウム（Ｍｇ）ーリチウム（Ｌｉ）合金層と接触する形でボロン（Ｂ）層を積層したことを特徴とする。 The manufacturing method of the MgB2 superconducting wire of the invention 5 is the invention 3, wherein the Mg-Li alloy rod having an outer shape smaller than the inner diameter is inserted into the metal or alloy tube, and the B powder is put in the gap formed around the rod. By filling, a boron (B) layer is laminated in contact with a magnesium (Mg) -lithium (Li) alloy layer.
発明６は、発明１又は２のＭｇＢ２超伝導線材の製造法であって、予め線状あるいはテープ状に加工したマグネシウム（Ｍｇ）−リチウム（Ｌｉ）合金層に、ボロン（Ｂ）層を接触させて形成し、マグネシウム（Ｍｇ）とボロン（Ｂ）の拡散反応温度で熱処理することによって二硼化マグネシウム（ＭｇＢ２）超伝導層を生成させることを特徴とする。 Invention 6 is a method for producing the MgB 2 superconducting wire of Invention 1 or 2, wherein a boron (B) layer is brought into contact with a magnesium (Mg) -lithium (Li) alloy layer which has been processed into a linear shape or a tape shape in advance. And forming a magnesium diboride (MgB 2 ) superconducting layer by heat treatment at a diffusion reaction temperature of magnesium (Mg) and boron (B).
発明７のＭｇＢ２超伝導線材の製造法は、発明５において、Ｍｇ−Ｌｉ合金管の中に他の金属あるいは棒を挿入した複合体を形成し、これを線状あるいはテープ状に加工したものを基材とし、その上に塗布法によりＢ層を形成させることを特徴とする。 The manufacturing method of the MgB2 superconducting wire of Invention 7 is the same as that of Invention 5, in which a composite is formed by inserting another metal or rod into an Mg-Li alloy tube, and this is processed into a linear or tape shape. A B layer is formed on the substrate by a coating method.
前記発明１により、品質の高いＭｇＢ２超伝導層が生成される。すなわちＭｇＢ２が層状に成長することにより、従来の方法（例えばＰＩＴ法）では得られなかった密度の高いＭｇＢ２超伝導相が得られる。また層状成長にともなって余分のＬｉあるいは過剰のＭｇ、Ｂが存在した場合は、これらは中心部にはき寄せられてＭｇ−Ｌｉ−Ｂ合金層となるが、この相はＭｇＢ２層と平行に層状に存在するため、超伝導電流の流れを阻害することはない。 Wherein the invention 1, a high MgB 2 superconductor layer quality is generated. That is, when MgB 2 grows in a layered form, a high-density MgB 2 superconducting phase that cannot be obtained by conventional methods (for example, PIT method) can be obtained. Further, when there is excess Li or excess Mg, B due to the layer growth, these are attracted to the central portion to become an Mg—Li—B alloy layer, but this phase is parallel to the MgB 2 layer. Therefore, the flow of superconducting current is not hindered.
前記発明２により、超伝導特性のうち特に臨界電流特性が著しく改善される。すなわち添加されたナノサイズのＳｉＣからＣが効果的にＭｇＢ２相の結晶格子の中に組み込まれて、磁束のピン止め効果がより有効に発揮されて臨界電流が上昇する。 By the said invention 2, especially a critical current characteristic is remarkably improved among superconducting characteristics. That is, C is effectively incorporated into the crystal lattice of the MgB 2 phase from the added nano-sized SiC, and the pinning effect of the magnetic flux is more effectively exhibited and the critical current is increased.
前記発明３により、Ｍｇを主成分とする層とＢ（あるいはそれにナノサイズのＳｉＣを含む）層とが直接接触するようになり、両者間の拡散が効果的に進捗し、発明１の線材の作製が可能となる。 According to the invention 3, the layer mainly composed of Mg and the B (or nano-sized SiC) layer come into direct contact, and the diffusion between the two effectively proceeds, and the wire of the invention 1 Fabrication is possible.
前記発明４により、発明３の複合体の作製が極めて容易になる。すなわち難加工性の純Ｍｇの替わりに加工性の著しく優れたＭｇ−Ｌｉ合金を用いることによって、Ｍｇを主成分とする層とＢ（あるいはそれにナノサイズのＳｉＣを含む）層とが密着性良く線材の長手方向に平行に接触するようになり、拡散が効果的に進捗する。 The invention 4 makes it extremely easy to produce the composite of the invention 3. In other words, by using a Mg-Li alloy that is remarkably excellent in workability instead of pure Mg, which is difficult to process, the layer mainly composed of Mg and the B (or nano-sized SiC) layer have good adhesion. It comes in contact with the longitudinal direction of the wire, and diffusion effectively proceeds.
前記発明５により、発明３の複合体の作製が極めて容易になる。すなわち難加工性の純Ｍｇの替わりに加工性の著しく優れたＭｇ−Ｌｉ合金を用いることによって、Ｍｇを主成分とする層とＢ（あるいはそれにナノサイズのＳｉＣを含む）層とが密着性良く線材の長手方向に平行に接触するようになり、拡散が効果的に進捗する。 The invention 5 makes it extremely easy to produce the composite of the invention 3. In other words, by using a Mg-Li alloy that is remarkably excellent in workability instead of pure Mg, which is difficult to process, the layer mainly composed of Mg and the B (or nano-sized SiC) layer have good adhesion. It comes in contact with the longitudinal direction of the wire, and diffusion effectively proceeds.
前記発明６により、Ｍｇを主成分とする層とＢ（あるいはそれにナノサイズのＳｉＣを含む）層とが直接接触するようになり、両者間の拡散が効果的に進捗し、発明１の線材の作製が可能となる。 According to the invention 6, the Mg-based layer and the B (or nano-sized SiC) layer come into direct contact with each other, and the diffusion between the two effectively proceeds. Fabrication is possible.
前記発明７により、発明６の複合体の作製が極めて容易になる。すなわち難加工性の純Ｍｇの替わりに加工性の著しく優れたＭｇ−Ｌｉ合金を用いることによって、Ｍｇを主成分とする表面層を有する基板テープが作製可能となり、さらにＢ（あるいはそれにナノサイズのＳｉＣを含む）層を塗布することによって容易に目的とする複合体が形成される。 The invention 7 makes it extremely easy to produce the composite of the invention 6. That is, by using a Mg—Li alloy having remarkably excellent workability instead of pure Mg, which is difficult to process, a substrate tape having a surface layer mainly composed of Mg can be produced. The desired composite is easily formed by applying a layer containing SiC.
本発明の特徴は、難加工性のＭｇにＬｉを添加すると加工性が著しく改善されることに着目し、Ｍｇ−Ｌｉ合金をＰＩＴ法における被覆材側の一部として組み込み、反応を粒子間の反応から界面拡散方式に変化させて緻密で不純物の混入が無い高品質のＭｇＢ２超伝導層を生成させることにある。図１の平衡状態図に示すように、Ｍｇは通常六方晶の結晶系に属しそのことが加工性を困難にしているが、約３０原子％以上のＬｉを合金化すると結晶系が体心立方格子に変化して中間焼鈍なしに大きな加工率で塑性変形させることが可能となる。 The feature of the present invention is that the workability is remarkably improved when Li is added to difficult-to-work Mg, and the Mg-Li alloy is incorporated as a part of the coating material side in the PIT method, and the reaction is performed between the particles. By changing from reaction to interfacial diffusion, a high-quality MgB 2 superconducting layer free from impurities is produced. As shown in the equilibrium diagram of FIG. 1, Mg usually belongs to a hexagonal crystal system, which makes workability difficult. However, when about 30 atomic% or more of Li is alloyed, the crystal system becomes a body-centered cubic. By changing to a lattice, it becomes possible to perform plastic deformation at a large processing rate without intermediate annealing.
図２（ａ）は本発明の原理図を示した。すなわち純鉄，（Ｆｅ）管の中に、さらにＭｇ−Ｌｉ合金の管を挿入して２重の複合管とし、その中にボロン粉末を充填した複合体を形成した。複合体は中間焼鈍を加えなくても大きな減面率で冷間加工することが可能で、目的とする線状あるいはテープ状に容易に成形できる。得られた線あるいはテープは、最内層がＢ、中間層がＭｇ−Ｌｉ合金、最外層がＦｅの複合体である。次にこの複合体に熱処理を施すとＭｇ−Ｌｉ合金層とＢ層との界面で反応を起こしＭｇＢ２超伝導体が生成される。
その際、Ｌｉは生成されたＭｇＢ２の中に入らず、中心部に移動しＭｇ−Ｌｉ−Ｂ合金層として存在するためＭｇＢ２の超伝導特性を害することはない。
FIG. 2 (a) shows the principle of the present invention. That is, a Mg-Li alloy pipe was further inserted into a pure iron (Fe) pipe to form a double composite pipe, and a composite filled with boron powder was formed therein. The composite can be cold worked with a large reduction in area without adding intermediate annealing, and can be easily formed into the desired linear or tape shape. The obtained wire or tape is a composite in which the innermost layer is B, the intermediate layer is an Mg—Li alloy, and the outermost layer is Fe. Next, when this composite is subjected to a heat treatment, a reaction occurs at the interface between the Mg—Li alloy layer and the B layer to produce a MgB 2 superconductor.
At that time, Li does not enter into the generated MgB 2 , moves to the center and exists as an Mg—Li—B alloy layer, and therefore does not impair the superconducting properties of MgB 2 .
その際ＭｇＢ２の成長は界面から内部に向けて層状に進行し、またＭｇの供給がＭｇ−Ｌｉ合金層から拡散によって絶えず行われるため、ＭｇＢ２生成に必要なＭｇの供給が過不足無く行われる。そのため生成されたＭｇＢ２層の密度が高く、臨界電流密度特性の優れたＭｇＢ２線材が得られる利点を有する。熱処理は６５０℃から７５０℃の間の温度で行うことが望ましい。なお、最外層の金属は純鉄に限定されないが、熱処理によってＭｇ、ＬｉさらにはＢと反応を起こし超伝導特性を劣化させるものは好ましくない。 At this time, the growth of MgB 2 proceeds in layers from the interface to the inside, and the supply of Mg is constantly performed by diffusion from the Mg—Li alloy layer, so that the supply of Mg necessary for MgB 2 generation is performed without excess or deficiency. Is called. Therefore, the MgB 2 layer produced has a high density and has an advantage of obtaining an MgB 2 wire excellent in critical current density characteristics. The heat treatment is desirably performed at a temperature between 650 ° C. and 750 ° C. Although the outermost layer metal is not limited to pure iron, it is not preferable to cause a reaction with Mg, Li or B by heat treatment to deteriorate the superconducting properties.
なお最初に構成物を形成する際、図２（ｂ）に示したように、Ｍｇ−Ｌｉ合金を棒状として最内部に挿入し、純鉄管との隙間にＢ粉末を充填する構造でも最終的に同じ線材が作製可能である。 In addition, when forming a structure for the first time, as shown in FIG.2 (b), Mg-Li alloy is inserted in the innermost part as a rod shape, and finally it is the structure filled with B powder in a gap with a pure iron pipe. The same wire can be produced.
本発明の原理をＰＩＴ法以外の方法に適用することも可能である。図３はＭｇ−Ｌｉ合金を塗布法の基材の一部として構成させた場合の製造工程である。すなわち、Ｍｇ−Ｌｉ合金の管にＦｅ棒を挿入した複合体をテープ状あるいは線状に加工する。加工は中間焼鈍無しで大きな減面率で行うことが可能である。得られたＦｅ／Ｍｇ−Ｌｉ複合線材の上にディップコート（塗布）法などによってＢ層を形成し、熱処理を加えると同様の原理でＭｇＢ２超伝導層を生成させることが可能である。 It is possible to apply the principle of the present invention to a method other than the PIT method. FIG. 3 shows a manufacturing process in the case where the Mg—Li alloy is configured as a part of the base material of the coating method. That is, a composite in which an Fe bar is inserted into a Mg-Li alloy tube is processed into a tape shape or a linear shape. Processing can be performed with a large reduction in area without intermediate annealing. When a B layer is formed on the obtained Fe / Mg—Li composite wire by a dip coating (coating) method and heat treatment is applied, a MgB 2 superconducting layer can be generated on the same principle.
なお、ＰＩＴ法ではＭｇとＢとの混合粉体にナノサイズの炭化珪素（ＳｉＣ）を添加すると臨界磁界が高くなり、高磁界での臨界電流密度が改善されることが知られている。本発明の方法では、Ｂ粉末に１−１０原子％のＳｉＣを添加することによって同様の高磁界特性の改善が得られる。 In the PIT method, it is known that when nano-sized silicon carbide (SiC) is added to a mixed powder of Mg and B, the critical magnetic field increases and the critical current density in a high magnetic field is improved. In the method of the present invention, the same high magnetic field characteristics can be improved by adding 1-10 atomic% of SiC to the B powder.
外径４ｍｍ、内径３ｍｍのマグネシウムーリチウム（Ｍｇ−Ｌｉ）合金（Ｌｉ含有量：約３５原子％）の管を外径６ｍｍ、内径４ｍｍの純鉄（Ｆｅ）管の中に挿入し、さらにその中にボロン（Ｂ）粉末あるいはボロン粉末に５原子％ないしは１０原子％のＳｉＣ微粉末（粒サイズ約２０ｎｍ）を添加した混合粉末を封入した複合体を形成した（図２（ａ））。この複合体は中間焼鈍無しに加工が可能で、溝ロール、圧延によって最終的に厚み約０．６ｍｍ、幅約４ｍｍの複合テープ状に成形した。
この複合体テープをアルゴンガス雰囲気中で、５５０−８００℃で１時間の熱処理を行った。これらの試料について、液体ヘリウム中で２００Ａまでの通電試験を行い、超伝導の臨界電流測定を行った。表１は測定の結果を一覧として示した。５％ＳｉＣ添加で最も良好な臨界電流値（Ｉｃ）が得られ、また熱処理温度としては６５０−７００℃の範囲で最も高いＩｃが得られた。
Insert a magnesium-lithium (Mg-Li) alloy tube (Li content: about 35 atomic%) with an outer diameter of 4 mm and an inner diameter of 3 mm into a pure iron (Fe) tube with an outer diameter of 6 mm and an inner diameter of 4 mm, and A composite in which boron (B) powder or a mixed powder obtained by adding 5 atomic% to 10 atomic% of SiC fine powder (grain size: about 20 nm) was enclosed was formed (FIG. 2A). This composite can be processed without intermediate annealing, and finally formed into a composite tape having a thickness of about 0.6 mm and a width of about 4 mm by groove rolling and rolling.
This composite tape was heat-treated at 550-800 ° C. for 1 hour in an argon gas atmosphere. These samples were subjected to an energization test up to 200 A in liquid helium, and the superconducting critical current was measured. Table 1 lists the measurement results. The best critical current value (Ic) was obtained with the addition of 5% SiC, and the highest Ic was obtained in the range of 650-700 ° C. as the heat treatment temperature.
実施例１のＭｇ−３５原子％Ｌｉ合金に替えて、純ＭｇあるいはＭｇにＬｉを１５および５０原子％含む合金を用いて同様の複合体を形成しテープ状に加工を試みた。
その結果、純ＭｇおよびＭｇ−１５原子％合金を用いた場合は、複合体内部でＭｇあるいはＭｇ−Ｌｉ合金層が一様に変形せず、均一な組織をもつ複合体は作製することは困難であった。これは図１の状態図に示すように結晶構造が変形困難な六方晶であるためである。一方、Ｍｇ−５０ａｔ％Ｌｉ合金の場合は複合体として均一な加工が可能であった。しかし、７００℃で１時間の熱処理を行った試料は約１０Ｋの超伝導性しか示さなかった。これは特性の良いＭｇＢ２相を生成するために十分なＭｇが供給されなかったためである。
A similar composite was formed using pure Mg or an alloy containing 15 and 50 atomic% of Li in Mg instead of the Mg-35 atomic% Li alloy of Example 1, and processing into a tape shape was attempted.
As a result, when pure Mg and Mg-15 atomic% alloy are used, it is difficult to produce a composite having a uniform structure because the Mg or Mg-Li alloy layer does not deform uniformly inside the composite. Met. This is because the crystal structure is a hexagonal crystal that is difficult to deform as shown in the phase diagram of FIG. On the other hand, in the case of an Mg-50 at% Li alloy, uniform processing was possible as a composite. However, the sample heat-treated at 700 ° C. for 1 hour showed only about 10K superconductivity. This is because sufficient Mg was not supplied to produce a MgB 2 phase having good characteristics.
外径２．５ｍｍのマグネシウムーリチウム（Ｍｇ−Ｌｉ）合金（Ｌｉ含有量：約３５原子％）の棒を外径６ｍｍ、内径４ｍｍの純鉄（Ｆｅ）管の中に挿入し、生じた隙間にボロン粉末に５原子％のＳｉＣ微粉末（粒サイズ約２０ｎｍ）を添加した混合粉末を充填した複合体を形成した（図２（ｂ））。
この複合体は中間焼鈍無しに加工が可能で、溝ロール、圧延によって最終的に厚み約０．６ｍｍ、幅約４ｍｍの複合テープ状に成形した。この複合体テープをアルゴンガス雰囲気中で、７００℃で１時間の熱処理を行った。得られた試料について、液体ヘリウム中で２００Ａまでの通電試験を行ったが２００Ａまで超伝導状態が保たれ、常伝導状態への遷移は起こらなかった。
A gap formed by inserting a rod of magnesium-lithium (Mg-Li) alloy (Li content: about 35 atomic%) with an outer diameter of 2.5 mm into a pure iron (Fe) tube with an outer diameter of 6 mm and an inner diameter of 4 mm. Then, a composite filled with a mixed powder prepared by adding 5 atomic% of SiC fine powder (grain size of about 20 nm) to boron powder was formed (FIG. 2B).
This composite can be processed without intermediate annealing, and finally formed into a composite tape having a thickness of about 0.6 mm and a width of about 4 mm by groove rolling and rolling. The composite tape was heat-treated at 700 ° C. for 1 hour in an argon gas atmosphere. The obtained sample was subjected to an energization test up to 200 A in liquid helium, but the superconducting state was maintained up to 200 A, and no transition to the normal state occurred.
外径４ｍｍ、内径３ｍｍのマグネシウムーリチウム（Ｍｇ−Ｌｉ）合金（Ｌｉ含有量：約３５原子％）の管に外径３ｍｍの純鉄棒を挿入した複合体を平ロールで厚さ５００μｍのテープ状に加工した。このテープを、ボロン粉末と５原子％のＳｉＣ微粉末（粒サイズ２０ｎｍ）をエタノール溶液に混ぜた縣濁液に浸漬して乾燥し、さらにアルゴン雰囲気中で７００℃、１時間の熱処理を行った。得られた試料について液体ヘリウム中で通電試験を行った結果、１８０Ａの臨界電流値Ｉｃが得られた。 Tape-like composite with a flat roll and a thickness of 500 μm in the form of a composite in which a pure iron rod with an outer diameter of 3 mm is inserted into a magnesium-lithium (Mg—Li) alloy tube (Li content: about 35 atomic%) with an outer diameter of 4 mm and an inner diameter of 3 mm It was processed into. This tape was dipped in a suspension obtained by mixing boron powder and 5 atomic% SiC fine powder (grain size 20 nm) in an ethanol solution and dried, and further subjected to heat treatment at 700 ° C. for 1 hour in an argon atmosphere. . As a result of conducting an energization test on the obtained sample in liquid helium, a critical current value Ic of 180 A was obtained.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2169735A1 (en) * | 2008-09-30 | 2010-03-31 | Brucker EAS GmbH | Superconductive compound, precursor product of a superconductive compound and method for producing same |
| JP2011014304A (en) * | 2009-06-30 | 2011-01-20 | Hitachi Ltd | Superconducting wire rod |
| JP2012074244A (en) * | 2010-09-29 | 2012-04-12 | Hitachi Ltd | Manufacturing method of superconducting wire rod, and wire rod |
| JP2012178226A (en) * | 2011-02-25 | 2012-09-13 | Hitachi Ltd | MgB2 SUPERCONDUCTING WIRE ROD |
| WO2015049776A1 (en) * | 2013-10-04 | 2015-04-09 | 株式会社日立製作所 | MgB2 SUPERCONDUCTING WIRE ROD, SUPERCONDUCTING CONNECTION STRUCTURE, SUPERCONDUCTING MAGNET USING MgB2 SUPERCONDUCTING WIRE ROD, AND SUPERCONDUCTING CABLE USING MgB2 SUPERCONDUCTING WIRE ROD |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2169735A1 (en) * | 2008-09-30 | 2010-03-31 | Brucker EAS GmbH | Superconductive compound, precursor product of a superconductive compound and method for producing same |
| US8318639B2 (en) | 2008-09-30 | 2012-11-27 | Bruker Eas Gmbh | Superconducting composite, preliminary product of superconducting composite and method for producing same |
| JP2011014304A (en) * | 2009-06-30 | 2011-01-20 | Hitachi Ltd | Superconducting wire rod |
| JP2012074244A (en) * | 2010-09-29 | 2012-04-12 | Hitachi Ltd | Manufacturing method of superconducting wire rod, and wire rod |
| JP2012178226A (en) * | 2011-02-25 | 2012-09-13 | Hitachi Ltd | MgB2 SUPERCONDUCTING WIRE ROD |
| WO2015049776A1 (en) * | 2013-10-04 | 2015-04-09 | 株式会社日立製作所 | MgB2 SUPERCONDUCTING WIRE ROD, SUPERCONDUCTING CONNECTION STRUCTURE, SUPERCONDUCTING MAGNET USING MgB2 SUPERCONDUCTING WIRE ROD, AND SUPERCONDUCTING CABLE USING MgB2 SUPERCONDUCTING WIRE ROD |
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