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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 MgB2samples 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 (Jc) of the as-sintered samples has been investigated. An enhancement of Jcat high field has been observed in MgB2samples containing CNTs prepared with fine Mg powders, whereas the values of Jcin the sample prepared using the coarser Mg powders was slightly decreased. These results contrast significantly with measurements on pure, undoped, MgB2samples prepared from the same Mg precursor powders. They suggest that carbon substitution into the MgB2lattice, which accounts for increased flux pinning, and therefore Jc, is more effective in precursor Mg powders with a larger surface area. Rather surprisingly, the so-called fishtail effect, observed typically in MgB2single 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 MgB2and (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: 22 Jun 2018 20:29
DOI: