Enhancing the critical current properties of internal Mg diffusion-processed MgB<sub>2</sub>wires by Mg addition

Ye, Shujun; Song, Myeong-Yeop; Matsumoto, Akiyoshi; Togano, K.; Zhang, Y; Kumakura, Hiroaki; Takeguchi, Masaki; Teranishi, Ryo; Toko, Kiyoshi

doi:10.1088/0953-2048/25/12/125014

Cited by 31 publications

(30 citation statements)

References 28 publications

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“…So the Mg is overestimated because the atomic ratio adds up to 100% for each region. However, the atomic ratio of Mg to B is expected to be a good indicator to estimate that the dark spots are unreacted B or B-rich regions, which is consistent to our previous research [10,17]. Figures 5(c) and (d) show SEM images of two filaments of the Ta-37 wires.…”

Section: Resultssupporting

confidence: 87%

“…Recently, Li et al [15] used a C-coated nano-sized B powder to fabricate the IMD-processed MgB 2 thin (diameter: 0.55 mm) wires and obtained the high J c of 1.07 × 10 5 A cm −2 and high J e of 1.67 × 10 4 A cm −2 at 4.2 K and 10 T for different wires. Our group also obtained comparable results by using the same B powders but with dimethylbenzene addition [16]. All these results suggest that IMD-processed MgB 2 wires are expected to be applied in large-scaled applications.…”

Section: Introductionsupporting

confidence: 62%

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The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

Matsumoto

Togano

et al. 2013

Supercond. Sci. Technol.

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Internal Mg diffusion (IMD)-processed MgB 2 wires are known to have a high-density MgB 2 core, which obviously leads to high critical current density (J c ). In this work, we first fabricated 37-filament MgB 2 wires by IMD processing, and we found that J c for SiC-added 37-filament IMD-processed MgB 2 wires achieved a value of 7.6 × 10 4 A cm −2 at 4.2 K and 10 T, which is higher than those of multi-filament wires with a smaller number of filaments (1 filament, 7 filaments) fabricated under the same conditions. We also investigated the critical current properties of both undoped and SiC-added 37-filament IMD-processed MgB 2 wires under different magnetic fields and temperatures. The undoped 37-filament IMD-processed MgB 2 wires achieved J c value of 1.6 × 10 5 A cm −2 at 20 K and 3 T. The engineering critical current density (J e ) achieved 2.8 × 10 3 A cm −2 at 20 K and 3 T. The microstructures observed by scanning electron microscopy support the view that the decrease in unreacted B particles by the short diffusion distance is mainly responsible for the high J c obtained.

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Section: Resultssupporting

confidence: 87%

Section: Introductionsupporting

confidence: 62%

The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

Matsumoto

Togano

et al. 2013

Supercond. Sci. Technol.

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“…The TEM results thus indicate that the MgB 2 layer is made up of small MgB 2 grains, most with sizes less than 100 nm, together with small MgO and unreacted B particles. However, similar grain sizes were also found for IMD-processed MgB 2 wires using SiC and Mg co-additives and a different type of B powder (99%, 325 mesh), for which a lower J c value of 5 × 10 4 A cm −2 at 10 T and 4.2 K was obtained, as has been previously reported [25]. Thus, one reason for the higher J c obtained in the present study is thought to be the lower concentration of unreacted B particles in the MgB 2 layer.…”

Section: Transmission Electron Microscopy Analysissupporting

confidence: 86%

High-performance MgB₂superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

Ye¹,

Song²,

Matsumoto³

et al. 2013

Supercond. Sci. Technol.

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MgB 2 has a superconducting transition temperature (T c ) of 39 K, which is much higher than that for practical metallic superconductors. Thus, it is hoped that MgB 2 can not only replace metallic superconductors, but can be used under liquid-helium-free conditions, for example, at temperatures of 10-20 K that can easily be achieved using cryocooling systems. However, to date, the reported critical current density (J c ) for MgB 2 wires is not high enough for large-scale applications in liquid-helium-free conditions. In the present study, successful fabrication of high-performance MgB 2 superconducting wires was carried out using an internal Mg diffusion (IMD) process, involving a p-dimethylbenzene (C 8 H 10 ) pre-treatment of carbon-coated B powder with nanometer-sized particles. The resulting wires exhibited the highest ever J c of 1.2 × 10 5 A cm −2 at 4.2 K and 10 T, and an engineering critical current density (J e ) of about 1 × 10 4 A cm −2 . Not only in 4.2 K, but also in 10 K, the J c values for the wires fabricated in the present study are in fact higher than that for Nb-Ti wires at 4.2 K for the magnetic fields at which the measurements were carried out. At 20 K and 5 T, the J c and J e were about 7.6 × 10 5 A cm −2 and 5.3 × 10 3 A cm −2 , respectively, which are the highest values reported for MgB 2 wires to date. The results of a detailed microstructural analysis suggested that the main reason for the superior electrical performance was the high density of the MgB 2 layer rather than just the small grain size, and that the critical current could be further increased by suitable control of the microstructure. These high-performance IMD-processed MgB 2 wires are thus promising superconductors for applications such as magnetic resonance imaging and maglev trains that can operate under liquid-helium-free conditions.

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“…The density of all sintered samples is similar and about half of the theoretical value (2.62 g/cm 3 ), but higher than the other ones in previous studies using the similar preparation technique 32 . Generally, the chemical reaction between Mg and B forming MgB 2 results in about 30% volume reduction and porosity is known to be difficult to avoid during the sintering process 33 . This is the main reason why the in-situ sintering density of Mg 11 B 2 bulks is generally lower than their theoretical value.…”

Section: Resultsmentioning

confidence: 99%

Improved Superconducting properties in the Mg11B2 low activation superconductor prepared by low-temperature sintering

Cheng

Liu

et al. 2016

Sci Rep

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Mg11B2 has a great application prospect in the superconducting coils for fusion reactor as the “low activation superconductors”. The un-doped Mg11B2 and Cu-doped Mg11B2 bulks using 11B as a boron precursor were fabricated by low-temperature sintering in present work. It was found that the prepared Mg11B2 low activation superconductors exhibit better Jc performance than all of other Mg11B2 samples reported in previous studies. As for Cu doped Mg11B2, minor Cu addition can obviously improve the Mg11B2 grain crystallization and reduce the amount of MgO impurity. Hence, improved grain connectivity and higher Jc at low fields is obtained in Cu doped Mg11B2 samples. For un-doped samples, refined grains and more MgO impurity with proper size brought about more flux pinning centers, resulting in better Jc performance at high fields.

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Enhancing the critical current properties of internal Mg diffusion-processed MgB₂wires by Mg addition

Cited by 31 publications

References 28 publications

The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

High-performance MgB₂superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

Improved Superconducting properties in the Mg11B2 low activation superconductor prepared by low-temperature sintering

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Enhancing the critical current properties of internal Mg diffusion-processed MgB2wires by Mg addition

Cited by 31 publications

References 28 publications

The critical current properties of 37-filament internal Mg diffusion-processed MgB2wires

The critical current properties of 37-filament internal Mg diffusion-processed MgB2wires

High-performance MgB2superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

Improved Superconducting properties in the Mg11B2 low activation superconductor prepared by low-temperature sintering

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Enhancing the critical current properties of internal Mg diffusion-processed MgB₂wires by Mg addition

The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

The critical current properties of 37-filament internal Mg diffusion-processed MgB₂wires

High-performance MgB₂superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process