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Fishtail effects and improved critical current density in polycrystalline bulk MgB<inf>2</inf>containing carbon nanotubes

Cai, Q and Liu, Y and Ma, Z and Cardwell, DA (2013) Fishtail effects and improved critical current density in polycrystalline bulk MgB<inf>2</inf>containing carbon nanotubes. Physica C: Superconductivity and its Applications, 492. pp. 6-10. ISSN 0921-4534

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Abstract

Bulk, polycrystalline MgB 2 samples containing 2.5 wt.% multi-walled carbon nanotubes (CNTs) have been prepared by conventional solid state reaction at 800 °C. The effect of Mg precursor powders composed of two different particle sizes on the critical current density (J c ) of the as-sintered samples has been investigated. An enhancement of J c at high field has been observed in MgB 2 samples containing CNTs prepared with fine Mg powders, whereas the values of J c in the sample prepared using the coarser Mg powders was slightly decreased. These results contrast significantly with measurements on pure, undoped, MgB 2 samples prepared from the same Mg precursor powders. They suggest that carbon substitution into the MgB 2 lattice, which accounts for increased flux pinning, and therefore J c , is more effective in precursor Mg powders with a larger surface area. Rather surprisingly, the so-called fishtail effect, observed typically in MgB 2 single crystals and in the (RE)BCO family of high temperature superconductors (HTSs), was observed in both sets of CNT-containing polycrystalline samples as a result of lattice defects associated with C substitution. Significantly, analytical fits to the data for each sample suggest that the same flux pinning mechanism accounts for the fishtail effect in polycrystalline MgB 2 and (RE)BCO. © 2013 Elsevier B.V. All rights reserved.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div C > Materials Engineering
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:09
Last Modified: 23 Nov 2017 04:08
DOI: