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Öğe Effect of Adding on the Critical Current Density and Lateral Levitation Force of Bulk(Springer/Plenum Publishers, 2015) Savaskan, B.; Koparan, E. Taylan; Guner, S. B.; Celik, S.; Ozturk, K.; Yanmaz, E.We fabricated malic acid -added bulks by wet mixing and Two-step solid state reaction method. The effects of adding malic acid on , behaviour and lateral levitation force features of bulk have been investigated. A systematic decrease in the critical temperature with increasing adding level confirms the substitution of C at the B site of . While the 4 wt% sample showed the best of at 4 T and 5 K, 15 wt% sample showed uncompetitive lower critical current density , which ascribes the poor connectivity due to the excessive unsubstituted C distribution at grain boundaries and the presence of high MgO amount. At 24 and 28 K, the 4 and 6 wt% malic-acid-added samples exhibit a higher lateral force than pure sample. Based on the observed values of M-H, (H) and lateral levitation force , it can be concluded that the 4 wt% malic-acid-added sample is the best of the studied samples.Öğe Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors(Springer, 2016) Koparan, E. Taylan; Savaskan, B.; Guner, S. B.; Celik, S.We present a detailed investigation of the effects of Bi2Sr2Ca1Cu2O8+kappa (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB2 obtained by hot press method. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 10 wt%) of the total MgB2. Moreover, we present MgB2 bulk samples fabricated by using different production methods including hot pressing method to our knowledge. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano-boron (B) powder and Bi-2212 powder which are produced by hot press method. As a result of hot press process, compact pellet samples were manufactured. The vertical and lateral levitation force measurements were executed at the temperatures of 20, 24 and 28 K under zero-field-cooled (ZFC) and field-cooled (FC) regimes for samples with various adding levels. At 24 K and 28 K under ZFC regime, the 2 wt% Bi-2212 added sample exhibits a higher vertical levitation force than the pure sample. Bi-2212 added MgB2 samples compared to the pure sample have lower attractive force values in FC regime. The magnetic field dependence of the critical current density J(c) was calculated from the M-H loops for Bi-2212 added MgB2 samples. The 2 wt% Bi-2212 added sample has the best levitation and critical current density performance compared to other samples. The critical temperature (T-c) has slightly dropped from 37.8 K for the pure MgB2 sample to 36.7 K for the 10 wt% of Bi-2212 added sample. The transition temperature slightly decreases when Bi-2212 adding level is increased.Öğe IR laser line scanning treatments to improve levitation forces in MgTi0.06B2 bulk materials(Elsevier Science Sa, 2019) Ozturk, K.; Aksoy, C.; Angurel, L. A.; Savaskan, B.; Martinez, E.; Badia-Majos, A.; de la Fuente, G. F.Infrared (IR) laser-line scanning has been widely used to induce different surface microstructures in a broad range of materials. In this work, this laser configuration was applied on the surface of MgTi0.06B2 bulk samples in order to ascertain its effects on their superconducting properties, particularly on the magnetic levitation forces. The microstructural changes produced by this type of laser treatment were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). It was observed that the thermal treatment induced by the laser improves grain connectivity in a layer of material just below the irradiated surface, in agreement with the observed improvement in critical current density values, J(c), which were estimated from isothermal magnetic hysteresis loops. A significant increment of both vertical (F-z) and lateral (F-x) magnetic levitation forces was achieved. Numerical calculations were performed to understand the experimental behaviour and to clarify how an improvement of J(c) near the surface can improve the magnetic levitation force of these materials. In addition, the same studies were carried out in similar bulk samples but with nano-sized silver particle additions of 3 and 6 wt %, in the outer ring of the bulk, observing also an improvement of the levitation forces, albeit less than in samples without Ag because of the better performance of the original samples after laser treatment. These results are relevant to those studying superconductor fabrication and material fabrication modelling, essential for the development of technological applications of superconductors, and are based on microstructure control via application of a recently developed laser-line scan method. (C) 2019 Elsevier B.V. All rights reserved.Öğe The investigation on the regional nanoparticle Ag doping into MgTi0.06B2 bulk for improvement the magnetic levitation force and the bulk critical current(Elsevier Science Sa, 2017) Ozturk, K.; Dancer, C. E. J.; Savaskan, B.; Aksoy, C.; Guner, B.; Badica, P.; Aldica, G.Fabrication methods are important way to improve structural and superconducting properties of MgB2 such as critical current, magnetic levitation force (MLF) and magnetic field trapping capability. Although the graded fabrication technique has been used for single-grain bulk YBCO superconductor to improve critical current and bulk superconducting properties, similar technique as regional doping has not been used for bulk MgB2, until now. In this study, nanoparticle silver doping was carried out in to the bulk MgTi0.06B2 superconductor by using in-situ solid state reaction and partial graded (regional) doping method together, to improve the radius independent uniform bulk current density and the magnetic levitation force as well as the structural properties of the MgB2 bulk superconductors. Both the J(c)(0) self-field critical current and F-p (mu H-0) pinning force density values enhanced in comparison with the inner region values, when the nanoparticle Ag doping is carried out in to the outer section of the sample. Addition to the enhancement of the structural and the micro electromagnetic properties as J(c)(0) and Fp (mu H-0), our study also focused on the improved of the bulk Jc and the radius of shielding current loop r, to improve bulk electromagnetic properties as the levitation force. It is seen that the structural properties enhanced and both the vertical levitation force and the lateral guidance force value increased with Ag doping to the outer section of MgTi0.06B2 sample. On the other hand, the increasing ratio of the lateral guidance force of 19.7% and the vertical levitation force of 10.8% of the sample with 3 wt% Ag-doped than the undoped one points out that the regional doping method to the outer section is very suitable for guidance force applications, which is important in the magnetic bearing application such as Maglev and magnetic energy storage systems. (C) 2017 Elsevier B.V. All rights reserved.Öğe The size effect on the magnetic levitation force of MgB2 bulk superconductors(Elsevier Sci Ltd, 2016) Savaskan, B.; Koparan, E. T.; Guner, S. B.; Celik, S.; Yanmaz, E.In this study, the size effect on the magnetic levitation performance of disk-shaped MgB2 bulk superconductors and permanent magnets was investigated. MgB2 samples with varying diameters of 13 mm, 15 mm and 18 mm, each of which were 2 g in mass, were prepared by two-step solid state reaction method. Vertical levitation force measurements under both zero-field-cooled (ZFC) and field-cooled (FC) regimes were carried out at different temperatures of 20, 24 and 28 K. It was determined that the levitation force of the MgB2 strongly depends on both the diameters of the sample and the permanent magnet. In ZFC regime, the maximum levitation force value for the permanent magnet and the sample 18 mm in diameters reached to the 8.41 N at 20 K. In addition, in FC regime, attractive and repulsive force increased with increasing diameters of the sample and the permanent magnet. In that, the sample with 18 mm in diameter showed the highest attractive force value -3.46 N at 20 K and FC regime. The results obtained in this study are very useful in magnetic levitation devices as there is no detailed study on the size of superconductors and permanent magnets. (C) 2016 Elsevier Ltd. All rights reserved.
