Artificial 2D Flux Pinning Centers in MgB₂ Induced by Graphitic-Carbon Nitride Coated on Boron for Superconductor Applications

Abstract

Systemic investigation was carried out on the microstructure, superconducting properties, and flux pinning mechanism of MgB 2 in situ fabricated with magnesium and g-C 3 N 4 coated boron as precursors. The encapsulation of the boron powders with g-C 3 N 4 was achieved by polycondensation of urea on boron powders. The g-C 3 N 4 decomposes during the MgB 2 fabrication to induce two-dimensional few-carbon layer, dispersed nanoparticles, and carbon-rich phases in the matrix to enhance the flux pinning force and H irr of MgB 2 , which accounts for the in-field critical current density (J c (H)) increase compared to the pure MgB 2 . The carbon layers acting as artificial twodimensional flux pinning centers, have demonstrated high flux pinning efficiency to increase the J c (H) of MgB 2 superconductors. KEYWORDS: MgB 2 superconductor, two-dimensional flux pinning center, g-C 3 N 4 , critical current density, connectivity

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

“…17c, d). Li et al [104] employed the g-C 3 N 4 coated boron as precursor, to synthetize MgB 2 at 850 °C. The coating layer of g-C 3 N 4 was decomposed to 2D few-carbon layer which demonstrated high flux pinning efficiency as 2D flux pinning centers in MgB 2 (Fig.…”

Carbon-Coating Layers on Boron Generated High Critical Current Density in MgB2 Superconductor

“…Few-layer carbon sheets, which were produced by the g-C 3 N 4 decomposition, improve the J c ( H ) performance and the flux-pinning force. Meanwhile, carbon substitution on the boron site induced by g-C 3 N 4 increases the upper critical field ( H c2 ), while the thickness of the 2D flux-pinning centers are randomly generated during the coating process of graphene and g-C 3 N 4 . Kim et al prepared carbon-coated boron powder by plasma technology and successfully prepared uniform carbon-doped MgB 2 at 600 °C, which improved the magnetic field carrying capacity of MgB 2 .…”

Various effects of aliphatic amino acids on the critical current of the MgB2 superconductor

“…A more nuanced view appears from several reports dealing with graphene coated or generally carbon-encapsulated boron powders, which conclude to partial carbon-boron substitution in MgB2 and a residual carbon layer at the surface of the MgB2 grains that generates two-dimensional surface pinning centers and suppresses grain growth [33][34][35][36][37]. In the case of carbon nitride (C3N4) coated boron powders, BN nano-inclusions also form and contribute to performance enhancement [38], while for mixing of multiwall carbon nanotubes (MWCNT) to precursor powders, some MWCNTs remain inside the final MgB2 grains and influence the flux pinning mechanism [39].…”