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    Comparative study of the magnetic stiffness, levitation and guidance force properties of single and multi seeded YBCOs for different HTS-PMG arrangements
    (Elsevier Ltd, 2015) Ozturk K.; Sahin E.; Abdioglu M.; Kabaer M.; Celik S.; Yanmaz E.; Kucukomeroglu T.
    Abstract It is crucial to improve the magnetic levitation, guidance and stiffness performances of the HTS Maglev systems for real-scale applications. In this study, the magnetic levitation force, guidance force and magnetic stiffness values were determined for single and multi-seeded YBCOs on different PMGs in ZFC regime and different cooling heights (CHs) after the magnetic flux distributions simulation of the using PMGs. Implemented study showed that the additional downward PMs make an enhancing contribution on the magnetic levitation force, guidance force and magnetic stiffness of both single and multi-seeded YBCOs. It was also determined that both the force and stiffness ratios of multi-seeded YBCO to single-seeded YBCO increase with increasing CH, indicating that the multi-seeded YBCO has much more interaction domain than single-seeded at higher gaps. It is considered that the results obtained in this study are very useful in technological applications of Maglev and bearing systems, because there is no detailed study on the magnetic stiffness, levitation and guidance force comparison to clarify electromagnetic behavior of single and multi-seeded YBCOs for different HTS-PMG arrangements. © 2015 Elsevier B.V.
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    Improvement in levitation force performance of bulk MgB2 superconductors through coronene powder adding
    (Elsevier Ltd, 2017) Erdem O.; Abdioglu M.; Guner S.B.; Celik S.; Kucukomeroglu T.
    The effect of coronene (C24H12) addition on the levitation force properties of MgB2 superconductor has been investigated for the first time in this study. The polycrystalline disk-shaped MgB2 + y wt % C24H12 samples (y = 0, 2, 4, 6, 8, 10), were synthesized by a pellet/closed tube method at 850 °C under Ar atmosphere, after hot pressing at 200 °C. XRD analysis indicates a decrease in lattice parameters of coronene added samples and confirms substitution of carbon in boron sites. An increase in lattice strain and a decrease in grain size are observed due to the carbon substitution effect. Vertical and lateral levitation force measurements under zero-field-cooled and field-cooled regimes were carried out at different temperatures of 20, 25 and 30 K. It was found that the coronene addition significantly increases the high-field critical current density of MgB2. The Jc values were obtained as 4.6 × 103 Acm?2 and 1.3 × 104 Acm?2 for pure and 4 wt % coronene added samples at 20 K and 4 T. In addition, the levitation force measurements show that 4 wt % coronene adding is very effective in increasing both the vertical and lateral levitation force performances at 20 K. The maximum levitation force for 4 wt % coronene added sample corresponds to 7.58 N/g whereas the reference sample shows 6.73 N/g at 20 K in ZFC regime. The results point out that the hydrocarbon of C24H12 is an effective carbon-containing additive for MgB2 and can be useful for optimizing the levitation performance of MgB2 superconductors for potential applications. © 2017 Elsevier B.V.