Tailored Materials for High‐Performance MgB<sub>2</sub> Wire

Kim, Jung Ho; Oh, Sangjun; Kumakura, Hiroaki; Matsumoto, Akiyoshi; Heo, Yoon-Uk; Song, Kyeongse; Kang, Yong‐Mook; Maeda, Masafumi; Rindfleisch, M.; Tomsic, M.; Choi, Seyong; Dou, Shi Xue

doi:10.1002/adma.201101243

Cited by 81 publications

(69 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Even at higher temperature (20 K), the critical current density in the malic acid-doped MgB 2 wire also exceeds 104 A cm −2 at 5 T. These critical current density values are the highest record published so far for an in situ processed wire. The measured critical temperature for the doped wire was estimated to be 34 K. It should be noted that the critical currents of the doped sample can be described by the percolation model (Kim et al 2011;Maeda et al 2013). All the fitting lines in Figure 1a were calculated from the percolation theory and are in good agreement with the measured data.…”

supporting

confidence: 70%

“…Here, only four fitting parameters -the upper critical field (B c2 ), the anisotropy parameter (γ), the pinning force maximum (F m ), and the percolation threshold (P c ) -are needed to describe the field dependence of the critical current for each temperature. We previously reported that for polycrystalline wire samples, the percolation threshold, P c , is usually 0.26 (Shahabuddin et al 2014a;Kim et al 2011).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Carbon doping induced imperfections on MgB2 superconducting wire

Kim

Choi

2015

J Anal Sci Technol

Self Cite

View full text Add to dashboard Cite

Carbon is known to be the most effective dopant for magnesium diboride, MgB 2 , especially for enhancing high-field electrical properties. Carbon increases the impurity scattering rate, and this, combined with the two-band nature of MgB 2 , raises the upper critical field and thereby the high-field critical current. In addition, microscopic analysis has shown that carbon doping induces crystalline imperfections as the origin of impurity scattering. Herein, further detailed transmission electron microscopy analysis has been applied to find more clues for understanding the role of carbon.

show abstract

supporting

confidence: 70%

mentioning

confidence: 99%

Carbon doping induced imperfections on MgB2 superconducting wire

Kim

Choi

2015

J Anal Sci Technol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Here we briefly discuss the origin of excellent low-field J c observed in the sintered ex-situ bulks. In addition to connectivity, flux pinning strength [9] and upper critical field [37] were reported to be essential factors that determine low-field J c of in-situ MgB 2 polycrystalline samples. Since microstructural analysis showed little sign of grain growth or refinement, we may assume that the predominant flux pinning, i.e.…”

Section: Microstructurementioning

confidence: 99%

Strongly connectedex situMgB₂polycrystalline bulks fabricated by solid-state self-sintering

Tanaka

Yamamoto

Shimoyama

et al. 2012

Supercond. Sci. Technol.

View full text Add to dashboard Cite

The transport current carrying capacity of ex-situ processed MgB 2 is expected to be greatly enhanced if a strong intergrain connectivity can be realized. Although percolation theory predicts that ex-situ MgB 2 samples should have a high connectivity of over 30% due to their high bulk density (P ≈ 75%), the reported connectivity of ex-situ MgB 2 bulks and wires are generally less than 10%. This is presumably because ex-situ MgB 2 has a much weaker intergrain connectivity than in-situ MgB 2 . It is well known that heat treatment after cold working of ex-situ MgB 2 improves the connectivity and the critical current density. However, it is currently unclear whether such heat treatment induces self-sintering that results in the formation of necks, the elimination of pores, and in increase in contact area. In the present study, we investigated the microstructure, normal-state electrical connectivity, and critical current density of ex-situ MgB 2 polycrystalline bulks prepared by systematically varying the sintering conditions under low pressure. Samples heated at a high temperature of ~900°C for a long period showed an increased packing factor, a larger intergrain contact area, and a significantly enhanced electrical connectivity, all of which indicate solid-state self-sintering of MgB 2 . Sintered ex-situ MgB 2 bulks from a laboratory-made ball-milled powder exhibited a greatly enhanced connectivity of 28%, which is the highest connectivity of pressureless ex-situ MgB 2 bulks, wires, and tapes. Surprisingly, grain growth did not occur during long-duration (~100 h) sintering in the sintered ex-situ MgB 2 bulks. This is in marked contrast to in-situ processed MgB 2 samples for which significant grain growth occurred during heat treatment at ~900°C, producing grains that are several tens of times larger than the initial boron grains.Consequently, the critical current density as a function of the external magnetic field at 20 K progressively improved with sintering due to the relatively small grain size and good intergrain connectivity. We thus conclude that solid-state self-sintering is an effective approach for producing strongly connected, dense ex-situ MgB 2 polycrystals without grain growth.

show abstract

“…MgB 2 attracted lots of attention because of its simple crystal structure, large coherence length, relatively high critical current density, and transparency of the grain boundaries. During the development for more than 10 years, MgB 2 has been fabricated [2][3][4][5][6][7][8][9][10]into bulks, single crystals, thin films, tapes and wires.…”

Section: Introductionmentioning

confidence: 99%

Superior critical current density obtained in Mg11B2 low activation superconductor by using reactive amorphous 11B and optimizing sintering temperature

Cheng

Liu

et al. 2015

Journal of Alloys and Compounds

View full text Add to dashboard Cite

. (2015). Superior critical current density obtained in Mg 11 B 2 low activation superconductor by using reactive amorphous 11 B and optimizing sintering temperature. Journal of Alloys and Compounds, Superior critical current density obtained in Mg11B2 low activation superconductor by using reactive amorphous 11B and optimizing sintering temperature AbstractThe un-doped Mg 11 B2 and Cu-doped Mg 11 B2 bulks using 11 B as a boron precursor were fabricated by solidstate reaction and sintered at different temperature in present work. By analyzing the sintering process, it was found that 11 B original powder is more reactive and can react with Mg severely even at low temperature before Mg melting, which leads to the formation of refined Mg 11 B2 grains. Consequently, the critical current density of Mg 11 B2 sample prepared in this work is higher than that of natural MgB2. Furthermore, it was found that proper Cu addition could obviously accelerate the reaction between Mg and 11 B and promote the formation of Mg 11 B2 due to the appearance of Mg-Cu liquid at low sintering temperature before Mg melting. On the other hand, Cu addition also introduced more MgCu 2 impurity, leading to a relatively lower critical current density on the whole. Interestingly, the critical current density of the Cu doped sample sintered at 800 °C is surprisingly enhanced at the low field, compared with that of the corresponding un-doped one. This is due to the peritectic reaction which generated small-sized MgCu 2 occurred that at 800 °C, providing MgCu 2 pinning centers well-distributed in the MgB2 matrix. On the other hand, Cu addition also introduced more MgCu 2 impurity, leading to a relatively lower critical current density on the whole. Interestingly, the critical current density of the Cu doped sample sintered at 800 o C is surprisingly enhanced at the low field, compared with that of the corresponding un-doped one. This is due to the peritectic reaction which generated small-sized MgCu 2 occurred that at 800 o C, providing MgCu 2 pinning centers well-distributed in the MgB 2 matrix.

show abstract

Tailored Materials for High‐Performance MgB₂ Wire

Cited by 81 publications

References 28 publications

Carbon doping induced imperfections on MgB2 superconducting wire

Carbon doping induced imperfections on MgB2 superconducting wire

Strongly connectedex situMgB₂polycrystalline bulks fabricated by solid-state self-sintering

Superior critical current density obtained in Mg11B2 low activation superconductor by using reactive amorphous 11B and optimizing sintering temperature

Contact Info

Product

Resources

About

Tailored Materials for High‐Performance MgB2 Wire

Cited by 81 publications

References 28 publications

Carbon doping induced imperfections on MgB2 superconducting wire

Carbon doping induced imperfections on MgB2 superconducting wire

Strongly connectedex situMgB2polycrystalline bulks fabricated by solid-state self-sintering

Superior critical current density obtained in Mg11B2 low activation superconductor by using reactive amorphous 11B and optimizing sintering temperature

Contact Info

Product

Resources

About

Tailored Materials for High‐Performance MgB₂ Wire

Strongly connectedex situMgB₂polycrystalline bulks fabricated by solid-state self-sintering