Extrinsic Two-Dimensional Flux Pinning Centers in MgB<sub>2</sub> Superconductors Induced by Graphene-Coated Boron

Li, Wenxian; Kang, J.-H.; Liu, Yang; Liu, Ying; Qu, Jiangtao; Zheng, Rongkun; Xu, Jiasheng; Liu, Bin

doi:10.1021/acsami.8b19645

Cited by 19 publications

(18 citation statements)

References 72 publications

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“…Their studies revealed the homogeneous graphene coating in the microstructure and also similar irreversibility field values. [42] Based on the abovementioned discussion, we can conclude that the present results represent an optimized scenario with improved superconducting performance of bulk MgB 2 , while maintaining the uniform carbon doping and high T c when compared with other carbon doping techniques.…”

Section: Resultssupporting

confidence: 64%

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Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂

et al. 2020

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Carbon has been a standard doping agent in MgB 2 for long time. It, however, has also participated in a non-uniform distribution of the constituents throughout the bulk MgB 2. To address this issue, carbon encapsulated boron (CEB) was used instead of the manually added mixture of boron and carbon. The previous studies confirmed that only low concentrations of carbon in CEB were effective for synthesis of a high-performance bulk MgB 2. Here, a further step in optimization carbon content in CEB is reported. Carbon content in CEB varied as 1, 1.1, 1.35, 1.5, and 1.9 wt%. X-ray diffraction (XRD) results depict a slight shift in peaks corresponding to a-b plane, indicating carbon substitution into the lattice. High superconducting critical current density in self-field, such as 660, 550, and 435 kA cm À2 , was observed in the samples with 1.5 wt% CEB at 10, 15, and 20 K, respectively. In addition, J c of 75 kA cm À2 at 2 T and 20 K was observed in the 1.5 wt% CEB sample, which is thrice the value observed in the pure sample, with a minute tradeoff in T c (around 37.5 K). Scanning electron microscope (SEM) images reveal that small particles of size ranging from 50 to 200 nm contribute to J c improvement. Energy-dispersive X-ray (EDX) results show carbon uniformly distributed throughout the bulk.

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Section: Resultssupporting

confidence: 64%

“…Their studies revealed the homogeneous graphene coating in the microstructure and also similar irreversibility field values. [ 42 ]…”

Section: Resultsmentioning

confidence: 99%

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂

et al. 2020

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“…Li et al [103] have fabricated MgB 2 by the boron particles with a graphene coating via in situ method, hydrothermal process, successfully induced 2D flux pinning centers and achieved optimized graphene distribution. And the MgB 2 bulks fabricated by the in situ (iG−x) and diffusion (dG−x) methods were compared to study the connectivity and flux pinning effect.…”

Section: Two-dimensional Flux Pinning Centersmentioning

confidence: 99%

Research Progress of Electromagnetic Properties of MgB2 Induced by Carbon-Containing Materials Addition and Process Techniques

Liu

et al. 2020

Acta Metall. Sin. (Engl. Lett.)

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For the high transition temperature (T c ) and low cost taking both raw materials and fabrication process into account, MgB 2 has been a competitive candidate to replace the conventional NiTi superconductor for high-temperature application in fault current limiters, transformers, motors, magnetic resonance imaging, adiabatic demagnetization refrigerators, generators, etc. The carbon-containing materials addition induced high critical current density (J c ) is reviewed based on their influences on the upper critical field (H c2 ), flux pinning force, and connectivity. The doping effects were compared in the overview focusing on SiC, organic dopants, and graphene-related dopants. SiC doping is featured for the high-field critical current density, which is caused by the increased H c2 attributed to the substitution of carbon on boron site and the strong flux pinning force offered by the nanosized secondary phases in the MgB 2 matrix. Organic dopants have the advantage over SiC dopant for their relatively homogeneous distribution in the MgB 2 matrix based on wet mixing of the organics and the raw boron powders. Low doping level of two-dimensional materials can improve the superconducting properties in all measured fields because of the combined advantages of carbon substitution effect and grain connectivity. MgB 2 fabricated with carbon-encapsulated boron also introduces strong flux pinning centers in MgB 2 , which show weak destruction of the connectivity of the MgB 2 grains as reflected by the low-magnetic-supercurrent behavior. High-pressure treatment and diffusion method can fabricate highdensity MgB 2 superconductors with better connectivity and increase the J c compared with the in situ and ex situ methods. KeywordsCritical current density (J c ) • Flux pinning • Doping • 2D flux pinning centers * Chuanbing Cai

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“…As one of the largest commercial applications of a superconductor, liquid helium (LHe)-cooled niobium–titanium (Nb–Ti)-based superconducting magnets are routinely used in magnetic resonance imaging (MRI) to produce a strong, uniform, and ultrastable magnetic field for obtaining high-resolution images . In recent times, however, there has been a shortage of helium gas, so that its price is also continuously increasing. − Magnesium diboride (MgB 2 ) conductors are known to be a good choice for LHe-free MRI magnet applications to minimize reliance on LHe. ,− …”

Section: Introductionmentioning

confidence: 99%

Superconducting Joining Concept for Internal Magnesium Diffusion-Processed Magnesium Diboride Wires

Patel

Matsumoto

Kumakura

et al. 2021

ACS Appl. Mater. Interfaces

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A superconducting joint of unreacted monofilament internal magnesium diffusion-processed magnesium diboride (MgB 2 ) wires was fabricated by exploiting the phenomenon of magnesium diffusion into the boron layer inside the superconducting joint. Unprecedentedly, the joint was able to carry an almost identical transport current compared to the bare wire in a 2−7 T magnetic field at 20 K. The joint also exhibited very low joint resistance of 2.01 × 10 −13 Ω in self-field at 20 K. Among commercially available superconductors, this work is the first to successfully realize a superconducting joint that is capable of transferring current from one conductor to another without any notable degradation under strong magnetic fields. This work demonstrates great potential to apply MgB 2 in a range of practical applications, where superconducting joints are essential.

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Extrinsic Two-Dimensional Flux Pinning Centers in MgB₂ Superconductors Induced by Graphene-Coated Boron

Cited by 19 publications

References 72 publications

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂

Research Progress of Electromagnetic Properties of MgB2 Induced by Carbon-Containing Materials Addition and Process Techniques

Superconducting Joining Concept for Internal Magnesium Diffusion-Processed Magnesium Diboride Wires

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Extrinsic Two-Dimensional Flux Pinning Centers in MgB2 Superconductors Induced by Graphene-Coated Boron

Cited by 19 publications

References 72 publications

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB2

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB2

Research Progress of Electromagnetic Properties of MgB2 Induced by Carbon-Containing Materials Addition and Process Techniques

Superconducting Joining Concept for Internal Magnesium Diffusion-Processed Magnesium Diboride Wires

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Extrinsic Two-Dimensional Flux Pinning Centers in MgB₂ Superconductors Induced by Graphene-Coated Boron

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂

Optimization of Carbon Encapsulated Boron Doping for High‐Performance Bulk Sintered MgB₂