High Trapped Fields in C-doped MgB2 Bulk Superconductors Fabricated by Infiltration and Growth Process

Bhagurkar, A. G.; Yamamoto, Akiyasu; Wang, L.; Xia, Ming; Dennis, Anthony; Durrell, John; Aljohani, Talal A.; Babu, N. Hari; Cardwell, D. A.

doi:10.1038/s41598-018-31416-3

Cited by 35 publications

(18 citation statements)

References 58 publications

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“…Although MgB2 cannot compete with the exceptional high field properties of the cuprate HTS compounds, the maximum trapped field achieved in MgB2 bulks of 5.4 T at 12 K [3] is significantly higher than the maximum magnetic fields of about 1.5 T that can be achieved with ferromagnet assemblies [4]. Since the trapped field in bulk superconductors is directly related to critical current density (Jc), extensive research has been carried out to improve Jc(B) performance of MgB2 samples [3,5,6]. Collings et al have pointed out that we need to consider both 'intrinsic' and 'extrinsic' effects when attempting to improve the Jc values in MgB2 [7].…”

Section: Introductionmentioning

confidence: 99%

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors

gao

Santra

Grovenor

et al. 2022

Supercond. Sci. Technol.

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MgB2 is a promising material for intermediate temperature applications where conventional low temperature superconductors cannot be used, especially if the range of magnetic fields over which is has acceptable current carrying performance can be expanded. However, its applicability is limited by poor properties at elevated magnetic fields. Carbon-based dopants can be used to dramatically improve the high-field performance of MgB2, but at the cost of a reduction in the superconducting transition temperature (Tc) that limits the operation temperature to 20 K or below. Here we report an enhancement of superconducting performance of MgB2 with the addition of cubic and hexagonal boron nitride, without any significant reduction in Tc. Ex-situ bulk samples of MgB2 with two forms of boron nitride addition were manufactured by the field assisted sintering technique (FAST) after high energy ball milling of powder mixtures. We find that hexagonal BN (hBN) nanoparticles mixed homogenously with MgB2 powder react much more easily to produce Mg-N-B impurities than larger cubic BN (cBN) particles (~ 10 µm) under the same processing conditions. The addition of 1 wt% hBN or 5 wt% cBN combined with 6 h of milling has been demonstrated to improve the critical current density (Jc) of MgB2 over the entire magnetic field range. It is proposed that the nano-sized Mg-N-B impurities, that typically reside at MgB2 grain boundaries, increase pinning strength by introducing additional flux pinning centres. In addition, excess Mg may benefit the low-field performance by improving the connectivity. This work shows the significance of microstructural characterization on inhomogeneous superconducting materials to analyse their performance.

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Section: Introductionmentioning

confidence: 99%

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors

gao

Santra

Grovenor

et al. 2022

Supercond. Sci. Technol.

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“…6 on the surface of a single bulk sample (20 mm diameter and 8 mm height) and it is higher than 2.2 T measured at 7.5 K in Ref. 22 on the surface of a stack of five discs (32 mm diameter, 6 mm thickness).…”

Section: Resultsmentioning

confidence: 54%

Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5 T

Badica

Aldica

Grigoroscuta

et al. 2020

Sci Rep

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Bulk discs (20 mm diameter and 4.3 mm thickness) of MgB2 added with Ge2C6H10O7 were obtained by Spark Plasma Sintering. Six samples with composition MgB2(Ge2C6H10O7)0.0014 and one undoped sample were fabricated under similar conditions and were magnetically characterized in order to determine the scattering of properties and reproducibility. The main source of the scattering of the properties is the decomposition of the additive due to elimination of the organic part in gas form, which occurs stepwise with intensive vacuum drops at around ~ 560 and ~ 740 °C. A third drop, which is sometimes not well resolved being part of the second peak at 740 °C, occurs at ~ 820 °C. The critical temperature at the midpoint of the transition, Tc, shows only a relatively small variation between 37.4 and 38 K, and the irreversibility field at a low temperature of 5 K takes values between 8 and 10 T. The pinning force and pinning force related parameters do not correlate with the carbon substituting for boron in MgB2 and suggest a synergetic influence of the microstructural details and carbon. Overall, despite the superconducting properties scattering, the samples are of high quality. Stacked into a column of six samples, they can trap at the center and on the surface of the column a magnetic field of 6.78 and 5.19 T at 12 K, 5.20 and 3.98 T at 20 K and 2.39, and 1.96 T at 30 K. These promising values, combined with facile fabrication of the samples with relatively high quality and reproducibility, show the feasibility of their use in building complex and large compound arrangements for bulk magnets and other applications.

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“…Finding ways for reducing the AC-losses in a SC wire while maintaining its is not trivial, as these are fundamentally constrained by the material properties of the composite, and the robustness of its magnetic flux pinning. Thence, microscopical or macroscopical approaches can be taken, with the first commonly focused on the crystallographic or microstructural properties of the SC compound, despite neither their role on the pairing mechanism leading to the SC phenomenon 38 – 40 , nor their influence on the vortex pinning dynamics 41 – 44 are fully understood.…”

Section: Possible Alternatives For the Reduction Of Energy Losses In ...mentioning

confidence: 99%

Maximum reduction of energy losses in multicore MgB2 wires by metastructured soft-ferromagnetic coatings

Kapolka

2022

Sci Rep

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When compared with rare-earth coated conductors, magnesium diboride superconducting cables are known to show significant advantages by cost and easy production. However, the inherent difficulty for achieving a significant reduction of their magnetization losses in multifilamentary wires, without degrading the high critical current density that is so characteristic of the monowire, is considered as one of the major drawbacks for their practical use in high power density applications. Being this one of the major markets for superconducting cables, from fundamental principles and computational optimization techniques, in this paper we demonstrate how the embedding of the superconducting filaments into soft-ferromagnetic metastructures can render to their full magnetic decoupling, and therefore, to the maximum reduction of the energy losses that can be achieved without deteriorate the critical current density of the cable. The designed multifilamentary metastructure is made of NbTi coated MgB2 superconducting filaments in a Cu-matrix, serving as a reference for validating our model with actual experimental measurements in monowires and multifilamentary wires. The novelty in our computationally aided multifilamentary wires, is that each one of the filaments is embedded within a thin metastructure made of a soft-ferromagnetic layer and a resistive layer. We have found that for soft-ferromagnetic layers with magnetic permeabilities in the range of $$\mu _{r}=$$ μ r = 20–100, nearly a full magnetic decoupling between the superconducting filaments can be achieved, leading to efficiencies higher than $$92\%$$ 92 % , and an overall reduction of the AC-losses (including eddy currents at the Cu-matrix) higher than $$50\%$$ 50 % .

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High Trapped Fields in C-doped MgB2 Bulk Superconductors Fabricated by Infiltration and Growth Process

Cited by 35 publications

References 58 publications

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors

Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5 T

Maximum reduction of energy losses in multicore MgB2 wires by metastructured soft-ferromagnetic coatings

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High Trapped Fields in C-doped MgB2 Bulk Superconductors Fabricated by Infiltration and Growth Process

Cited by 35 publications

References 58 publications

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB2 superconductors

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB2 superconductors

Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5 T

Maximum reduction of energy losses in multicore MgB2 wires by metastructured soft-ferromagnetic coatings

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Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors

Effect of cubic and hexagonal boron nitride additions on the microstructure and properties of bulk MgB₂ superconductors