Title: Competition of the nano-inclusions and the effects on critical current density in Ni and SiC co-doped MgB2 bulks

Authors: Qi Cai; Yongchang Liu; Qianying Guo; Zongqing Ma

Addresses: State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science and Engineering, Tianjin University, Tianjin, 300354, China ' State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science and Engineering, Tianjin University, Tianjin, 300354, China ' State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science and Engineering, Tianjin University, Tianjin, 300354, China ' State Key Lab of Hydraulic Engineering Simulation and Safety, School of Materials Science and Engineering, Tianjin University, Tianjin, 300354, China

Abstract: Samples of (MgB2)0.96Ni0.04 + x wt% SiC (with x = 0, 2, 5 and 10) were sintered at 750°C for 30 min, and the phase composition, microstructures, and superconducting properties were investigated. The highest critical current density (Jc) was obtained in the sample with 2 wt% SiC doping, owing to the precipitation of the nanoscale MgNi2.5B2 and Mg2Si on the edge of regular grains. The generation of the two impurities displayed a competition, and consequently the MgNi2.5B2 is refined to be effective pinning centre, which is in contrast to its influence in the Ni-doped sample. Results from differential thermal analysis and modified Flynn-Wall-Ozawa method also supported our explanation, and the best fitting mechanism function of solid-solid reaction in this system was ascertained. We conclude that 'Avrami-Erofeev, n = 2' is the best fitting mechanism function, indicating random nucleation followed by an instantaneous growth of nuclei. The function of the described mechanism, G(α), is 2[−ln(1 − α)]1/2, (α is the product fraction), which is different from that of pure MgB2.

Keywords: MgB2 superconductors; magnesium diboride; nano-inclusions; kinetics; critical current density; nanotechnology; nickel; Ni; silicon carbide; SiC; phase composition; microstructure; superconducting properties.

DOI: 10.1504/IJNT.2016.080362

International Journal of Nanotechnology, 2016 Vol.13 No.10/11/12, pp.832 - 844

Published online: 12 Nov 2016 *

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