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Öğe An analysis on the relation between the seed distance and vertical levitation force for the multi-seeded YBCO using the modified advanced frozen image (MAFI) and experimental methods(Elsevier Science Sa, 2019) Ozturk, K.; Guner, S. B.; Abdioglu, M.; Demirci, M.; Celik, S.; Cansiz, A.The higher magnetic levitation force and related stiffness values are very important for Maglev and magnetic bearing applications. Also, larger superconducting surface area is needed for continuous and larger magnetic mediums with different geometries and dimensions in real scale industrial applications of superconducting systems. In this study, the cylindrical YBCO superconductors were fabricated by top-seeded melt growth (TSMG) method in single and two-seeded forms with different seed distances and then the magnetic force and stiffness measurements were carried out by three axes magnetic force measurement system in different cooling heights (CH) of 20mm and 75 mm. Additionally, a new analytical method, based on the magnetic dipole approximation, is proposed to calculate the levitation force in this study, named as Modified Advanced Frozen Image Method (MAFI), since although the Advanced Frozen Image Method in literature can calculate the levitation force with hysteresis, this method does not include the size effect of the superconductor. In the experimental studies, it is seen that the maximum levitation force values obtained by PMG with three PMs (named PMG-1) are more than two times higher than that of obtained with single PM for all samples with different distance of seeds, because of the higher magnetic flux distribution of related PMG arrangement than the single PM. In addition, the maximum magnetic levitation force value firstly increased and then decreased due to current coupling effect weakness by increasing distance of seeds. The calculated analytical levitation force results are not compatible with the experimental results without current coupling effect, but a well agreement is observed when the current coupling effect is taken into account in calculations. Also the MAFI method was tested with different dimensions of superconductors and the obtained results indicated the success of the proposed method. The maximum levitation force values obtained with MAFI method increased with increasing dimensions of HTS and PMs. Thus, one can say that the MAFI method is useful for the levitation force calculations between multi-seeded superconductors and PMGs with different dimensions and for different CHs. As a result, the analytical levitation force values obtained with the MAFI method are agree with the experimental levitation force sufficiently and this method can give fast calculation results without any divergence problem. This method can be thought as an alternative to the numerical calculation methods, having serious divergence problems for much amount and bigger size superconducting samples, therefore it will be useful to clarify bulk superconducting properties as supporter to the experimental studies. (C) 2019 Elsevier B.V. All rights reserved.Öğe Comparative study of the magnetic stiffness, levitation and guidance force properties of single and multi seeded YBCOs for different HTS-PMG arrangements(Elsevier Science Sa, 2015) Ozturk, K.; Sahin, E.; Abdioglu, M.; Kabaer, M.; Celik, S.; Yanmaz, E.; Kucukomeroglu, T.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. (C) 2015 Elsevier B.V. All rights reserved.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 Investigation of magnetic force properties between different PMGs and multi-seeded YBCO superconductors with different seed distances(Elsevier, 2019) Abdioglu, M.; Ozturk, K.; Guner, S. B.; Celik, S.; Kucukomeroglu, T.The magnetic levitation force in vertical direction and guidance force in lateral direction should be increased for enhancing the loading capacity and stability of Maglev systems, respectively. In this study, we have produced multi-seeded YBCO (YBa2Cu3O7) superconductors with two seeds and investigated the effect of seed distance on the vertical levitation force and lateral guidance force properties by using different permanent magnetic guideway (PMG) arrangements. Although there are studies in literature related to different distance, orientation and angle of seeds; there is no detailed study investigating the effect of seed distance on the vertical and lateral magnetic force properties of Maglev systems depending on different types of PMGs. In this study, after the sample fabrication, the optimum PMG arrangement were determined by using numerical simulation to obtain magnetic flux density distribution. It is determined that both maximum levitation and guidance force values firstly increased with increasing the seed distance from 0 to 4 mm and then related forces decreased with increasing the seed distance from 4 to 16 mm but still keep the higher force values than the sample with the seed distances of 0 mm. This situation is clarified as the increasing of the seed distance to an optimum value enhances both the levitation and guidance forces simultaneously and this is very important for levitation force applications because it causes to easy control of the Maglev system in vertical and lateral directions.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 Lateral Position Effect of Auxiliary Permanent Magnets on the Magnetic Force Properties of Cylindrical YBCO(Springer, 2017) Abdioglu, M.; Kabaer, M.; Ozturk, K.; Erdem, O.; Celik, S.The magnetic levitation force (MLF) and the guidance force (GF) should be improved for loading capacity and stability of Maglev systems, respectively. Although there are some ways to increase these properties, using of auxiliary onboard permanent magnets (PMs) can be considered as the most efficient one. The auxiliary PMs increase the MLF significantly but, at the same time, decrease the GF. We have searched a solution to overcome this problem in this study. Firstly, we have determined the optimum vertical positions of the auxiliary PMs and then we have investigated the vertical levitation force and lateral guidance force of hybrid Maglev system depending on lateral position of auxiliary PMs in different cooling heights (CHs). A cylindrical YBCO superconductor, fabricated by a top seeding method with the diameter of 45 mm and the height of 15 mm, was used as a high-temperature superconductor (HTS). The maximum increment rate in MLF and the minimum decrement rate in GF were observed as 277 and 54 %, respectively. The increment in MLF was obtained five times more than the decrement in GF, and this reality points out that the results of this study can be useful for improving the loading capacity and thus enhancing the practical applicability of Maglev systems.Öğe Magnetic properties of the welded joined TSMG Y123+x wt% Y211 (x=20 and 30) bulk superconductors(Elsevier, 2019) Cakir, B.; Ozturk, K.; Guner, S. B.; Celik, S.; Aydiner, A.Although the welding techniques have been used to join for bulk YBCO superconductors with a sintered superconductor, similar technique as a Ag2O added bulk YBCO superconductor fabricated by melt-powder-melt-growth process (MPMG) for using as a solder material has not been used, until now. Also, physical and the bulk superconducting properties of the welded samples have not been investigated. In this study, two 20 wt% Y211 and two 30 wt% Y211 added YBCO main samples were fabricated by cold top seeding-melt-growth (TSMG) method by using an Nd123 seed. Two main samples having the same Y211 addition and welding sample positioned between the main samples stacked and welded thermally with a pressure source simultaneously. It can be seen from the levitation force measurement, making before the welding process, that the 30 wt% Y211 added samples have the larger the maximum repulsive forces values than the 20 wt% Y211 added and Ag2O added welding samples but at the same order. After the welding process the welded samples cut into the specimens, to investigate micro structure and electromagnetic properties, positioned above, on and below of the welding region of the each welded Y123 samples. From the SEM analysis a continuous structural phase was obtained between the solder material and the main samples with a good integration without any boundary gap or defects. The welding process had no negative noticeable effect on T-c of the samples under zero magnetic field, while superconducting transition width (Delta T-c) of the specimen cutting from the 30 wt% Y211 added sample (Y30-ab) is smaller the specimen cutting from the 20 wt% Y211 added sample (Y20-ab) under applied magnetic field points out that Y30-ab is more resistant to the applied field than the Y20-ab because of the 211 addition. In addition, 30 wt% 211 addition ratio is more efficient for welding region and whole welded sample in terms of the supplying uniform superconducting properties as J(c). The obtained results on welded joined bulk superconductor can be beneficial to increase application potential of these superconducting materials in real scale magnetic systems.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.
