Strong enhancement of high-field critical current properties and irreversibility field of MgB₂superconducting wires by coronene active carbon source addition via the new B powder carbon-coating method

Abstract

We report an effective carbon-containing additive, coronene (C 24 H 12 ), for MgB 2 superconducting wires. We used B powder coated with C 24 H 12 to fabricate MgB 2 wires using the powder-in-tube (PIT) and internal Mg diffusion (IMD) processes. The in-field critical current properties are strongly enhanced for both PIT-and IMD-processed MgB 2 wires. For PIT MgB 2 wires, a critical current density (J c ) value of 1.8 × 10 4 A cm −2 is obtained at 4.2 K and 10 T. For IMD MgB 2 wires, we obtained a J c of 1.07 × 10 5 A cm −2 and an engineering J c (J e ) of 1.12 × 10 4 A cm −2 at 4.2 K and 10 T. These J c and J e values are similar to the highest values reported for MgB 2 wires thus far. Furthermore, the irreversibility field, B irr , determined with a current density criterion of 100 A cm −2 , is strongly enhanced to 25 T at 4.2 K, which is also the highest value reported for MgB 2 superconducting wires thus far. Coronene is an active carbon source for MgB 2 superconducting wires because (1) coronene has a high carbon content (96 wt%) with a small amount of hydrogen (impurity), (2) the decomposition temperature for coronene is near the reaction temperature between Mg and B, and (3) uniform dispersion of coronene on the B surface can be obtained due to the melting point of coronene being lower than the decomposition temperature. Carbon substitution for B caused by the coronene active carbon source is mainly responsible for the high field critical current properties and the high B irr obtained in this work.

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

“…Apart from that, these irregularities in the matrix reduce coherence length, which leads to inter‐band scattering, causing increment in H c2 (upper critical field). [ 23,24 ] So far, carbon was doped into MgB 2 via several carbon sources, such as carbohydrates, [ 25 ] carbon allotropes, [ 26 ] graphene oxides, [ 27 ] SiC, [ 28 ] coronene, [ 29 ] toluene, [ 7 ] etc. The nature of the precursor boron powder also plays crucial role in the formation of the final matrix.…”

Novel nanometer-level uniform amorphous carbon coating for boron powders by direct pyrolysis of coronene without solvent

“…or RF plasma produced25,[27][28][29] B powders. The J c values are expected to be further enhanced by adjustment of the thickness of carbon layer, which will be described in our late paper.But in this paper, we just want to introduce this uniform amorphous carbon coating method and show its potential applications in many fields as introduced in introduction section.Any particles, if they keep stable and do not react with coronene below the temperature of carbon coating formation (about 600 °C), could be coated with carbon by the method developed in this study.…”

Doping-Induced Isotopic Mg11B2 Bulk Superconductor for Fusion Application

“…Glycine (C2H5NO2, Glycine) was doped into MgB2 bulks by a series of techniques in our previous study [12,13]. MgB 2 bulks and wires with carbon addition, for instance, malic acid [8], graphene, coronene, or glucose [9][10][11], have been under investigation, motivated by the potential response of carbon atoms (compared to boron) to donate their additional valence electrons to the σ conduction band. Glycine (C 2 H 5 NO 2 , Glycine) was doped into MgB 2 bulks by a series of techniques in our previous study [12,13].…”

“…Additionally, because of the reaction 10 B + n → 7 Li + He (gas) under the heavy irradiation condition, 10 B can no longer guarantee the stability of the MgB 2 superconducting magnet. 10 B isotope is transformed to 7 Li and He by the neutron irradiation, while 11 B isotope is stable against the neutron irradiation without nuclear transformation and can reduce nuclear heating from 2.58 to 0.13 W/cm 3 [22].…”