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    Comparison of Superconducting Properties of Bulk MgB2 Samples with Pyrene Additive Produced by B Powder and C encapsulated B Powder
    (Springer/Plenum Publishers, 2024) Erdem, Ozge
    In this paper, the advantages and disadvantages of using B powder and C encapsulated B powder as a precursor during the production process of MgB2 with the addition of pyrene (C16H10) were investigated. Two MgB2 bulk samples with the addition of 10 wt % C16H10 of 1 g MgB2 were produced by the in-situ method using B powder and C encapsulated B powder. The C encapsulated B powder as a precursor was prepared by adding 10% C16H10 as a C source. From XRD and SEM analysis, a greater increase in MgO phase and a greater decrease in a-lattice parameter were observed for the sample produced with B, compared to the sample produced with C encapsulated B. The curves of critical current density (J(c)) at 5 K showed a similar character for both samples. The J(c) values at 5 K in self field were respectively obtained as 1.52 x 10(5) A/cm(2) and 1.90 x 10(5) A/cm(2) for the samples produced by B and C encapsulated B. The decrement ratio of in-field J(c) at 20 K was less affected by increasing magnetic field for the sample produced using C encapsulated B due to the relatively higher increase in the irreversibility field (H-irr) and the upper critical magnetic field (H-c2) values. The J(c) values at 20 K and 3 T were respectively determined as 1.49 x 10(4) A/cm(2) and 1.93 x 10(4) A/cm(2) for the samples produced with B and C encapsulated B.
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    Superconducting and levitation force characterisation of pyrene added MgB2 bulk superconductors
    (Elsevier Sci Ltd, 2020) Erdem, Ozge; Guner, Sait Baris; Celik, Sukru; Kucukomeroglu, Tayfur
    This research presents the influence of pyrene (C16H10) addition (0, 2, 4, 6, 8, 10 wt%) on the superconducting properties of bulk MgB2. For C16H10 added MgB2 samples, a shrinkage in a-lattice parameters was determined, whereas c-lattice parameters remained practically unchanged. The (110) peak observed at 2 theta approximate to 59.9 degrees slightly shifted to higher angles, the lattice strain increased and the crystallite size reduced after C16H10 addition. By virtue of induced stronger pinning force, the in-field critical current density (J(c)) increased after C16H10 addition. The J(c) value at 20 K and 4 T was obtained about two times higher (8.54 x 10(3) A/cm(2)) for 4 wt% C16H10 added MgB2 sample than that of the pure one. In addition, the variation of levitation force characteristic of MgB2 with increasing C16H10 content was determined at 20, 25 and 30 K. The best vertical levitation force performance in zero-field-cooled regime was obtained as 7.09 N/g at 20 K for 4 wt% C16H10 added MgB2 sample with 13 mm in diameter.