Superconductivity and its large scale applications.
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Scopus Publications
Scopus Publications
The role of individual Er and Tb incorporation in CO2 gas-sensing properties of hydrothermally grown ZnO nanorods Fatih Bulut, Özgür Öztürk, Şükrü Çelik, Gürcan Yıldırım, Selim Acar Journal of Sol Gel Science and Technology, 2026 This study systematically investigated the role of independently doped Erbium (Er) and Terbium (Tb) incorporation on the structural, morphological, optical, and carbon dioxide (CO2) gas-sensing properties of ZnO nanorods synthesized by the hydrothermal method with dopant concentrations of 0, 1, 3, 5, and 7 wt%. X-ray diffraction (XRD) analysis confirmed the successful substitutional incorporation of Er and Tb ions into the ZnO lattice, preserving the hexagonal wurtzite structure without the formation of secondary phases, except at the highest Tb concentration. These findings are in good agreement with scanning electron microscopy (SEM) results, which revealed vertically aligned ZnO nanorods with uniform spatial distribution and apparent diameters below 100 nm. Further, dopant incorporation significantly influenced nanorod morphology and interfacial characteristics, including variations in diameter uniformity, surface charge homogeneity, and ZnO shell composition and thickness due to differences in ionic radii, valence states, and outer-shell electron configurations of the Er³⁺ and Tb³⁺ dopant ions. This modified local strain fields and defect chemistry within the ZnO matrix. Optical characterization also showed a systematic reduction in optical bandgap energy with increasing dopant content. This is consistent with bandgap narrowing induced by enhanced carrier concentration and defect-related band tailing, accompanied by noticeable changes in optical transmittance. CO2 gas-sensing experiments displayed that rare-earth doping markedly enhanced sensor performance compared to that of undoped ZnO nanorods. In particular, 5 wt% Er-doped semiconductor exhibited the highest sensitivity, along with rapid response and recovery times, indicating an optimal balance between surface reactivity, charge transport, and defect-mediated adsorption-desorption dynamics. To sum up, the experimental results and theoretical approach obtained highlighted Er- and Tb-doped ZnO nanorods as promising low-cost, chemically stable, and high-performance sensing materials for CO2 detection in environmental and industrial monitoring applications.
Magnetic levitation force and trapped field properties of multiseeded YBCO with triangular arrangement of seeds Murat Abdioglu, Sait Baris Guner, Kemal Ozturk, Chiaming Yang, Ingann Chen, Sukru Celik International Journal of Applied Ceramic Technology, 2022 Abstract Although there are studies in literature using different number of seeds with different arrangements, especially line and rectangular, it is seen that there is no detailed study handling the levitation force together with trapped field properties of triangular arrangement of seed in YBCO. Therefore, to further investigate the magnetic properties of seeded YBCO superconductors, we have fabricated cylindrical YBCO (YBa 2 Cu 3 O 7 ) superconductors with triangular arrangement of the seeds with different seed distances. Maximum levitation force values were obtained as 39.4 N and 57.1 N, while the maximum guidance force values were obtained as −4.6 N, and −8.7 N, respectively, with single‐seeded and triangular‐seeded samples with seed distance of 14 mm. It was determined that the trapped field, levitation force, and guidance force firstly decreased from the single‐seeded sample to the triangular‐seeded sample with small seed distance and then increased with increasing seed distance. Increased field trapping and levitation force performances in the triangular‐seeded samples with suitable seed distance indicate that the triangular arrangement of seeds is an eligible method to produce larger dimension YBCO samples with bigger shielding current radius and bigger averaged trapped field values.
Design and Experimental Studies on Superconducting Maglev Systems with Multisurface HTS-PMG Arrangements Murat Abdioglu, Kemal Ozturk, Mehmet Ekici, Burcu Savaskan, Sukru Celik, Ahmet Cansiz IEEE Transactions on Applied Superconductivity, 2021 In this article, we have designed and constructed a new multisurface (MS) high temperature superconductor (HTS) Maglev measurement system to investigate the enhancement of magnetic force properties of Maglev systems via MS HTS configurations above conventional permanent magnetic guideway (PMG). We have investigated both the static force and stiffness behavior and dynamic response characteristics of these MS HTS-PMG arrangements in different field cooling heights (FCHs). Optimum cooling height is determined as FCH 20-30 for both six- and four-HTS configurations. The maximum levitation force values of HTS-PMG arrangement with six-HTS were obtained bigger than that of four-HTS in the unit cryostat volume of MS arrangement, indicating that the HTSs at the bottom side of the cryostat make contribution to the loading capacity of Maglev systems. In the present article, it is observed that the magnetic flux density of bottom surface in addition to upper surface of the PMG can make a contribution to loading performance, vertical and lateral stability of Maglev systems. It is thought that the designed measurement facility and results of this study will be beneficial to increase the magnetic flux density in the unit volume via MS HTS-PMG arrangements for future design and construction of the HTS Maglev systems.
Superconducting and levitation force characterisation of pyrene added MgB2 bulk superconductors Ozge Erdem, Sait Baris Guner, Sukru Celik, Tayfur Kucukomeroglu Cryogenics, 2020 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 (1 1 0) peak observed at 2θ ≈ 59.9◦ 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 (Jc) increased after C16H10 addition. The Jc value at 20 K and 4 T was obtained about two times higher (8.54 × 103 A/cm2) 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.
The comparison of levitation and lateral force of bulk and cut-pasted bulk GdBCO samples at different temperatures Sait Barış Güner, Murat Abdioğlu, Kemal Öztürk, Şükrü Çelik Journal of Alloys and Compounds, 2020 In this work, in the first time, we have investigated the levitation and lateral force properties of bulk and cut-pasted bulk GdBCO samples at different temperatures and different cooling heights (CH) to determine the effect of cut-pasted process on the magnetic levitation force behaviour. The measurements of superconducting characteristics indicated that the attractive and repulsive force values of cut-pasted GdBCO sample are slightly lesser than those of GdBCO bulk sample. The maximum repulsive and attractive force values obtained as 15.45 N and −4.56 N for GdBCO bulk and as 14.78 N and −3.92 N for cut-pasted GdBCO samples at 37 K. Although there are many fabrication methods as melt-textured growth (MTG), top seeded infiltration growth (TSIG) and TSMG to produce large HTS samples, the desired large sample size and the sample shape compatible with the superconducting magnetic bearing systems are not still sufficient for the technological applications. In this study, the performed cut-pasted process and obtained magnetic levitation force data can be using for the increment sample size and the desired sample shape in the needed different geometry and size for superconducting magnetic bearing systems.
IR laser line scanning treatments to improve levitation forces in MgTi0.06B2 bulk materials K. Ozturk, C. Aksoy, L.A. Angurel, B. Savaskan, E. Martínez, A. Badía-Majós, G.F. de la Fuente, B. Guner, C.E.J. Dancer, S. Celik Journal of Alloys and Compounds, 2019 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, Jc, which were estimated from isothermal magnetic hysteresis loops. A significant increment of both vertical (Fz) and lateral (Fx) magnetic levitation forces was achieved. Numerical calculations were performed to understand the experimental behaviour and to clarify how an improvement of Jc 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.
Investigation of magnetic force properties between different PMGs and multi-seeded YBCO superconductors with different seed distances M. Abdioglu, K. Ozturk, S.B. Guner, S. Celik, T. Kucukomeroglu Physica C Superconductivity and Its Applications, 2019 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.
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 K. Ozturk, S.B. Guner, M. Abdioglu, M. Demirci, S. Celik, A. Cansiz Journal of Alloys and Compounds, 2019 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 20 mm 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.
Investigation on superconducting and magnetic levitation force behaviour of excess Mg doped-bulk MgB2 superconductors Sait Barış Güner, Burcu Savaşkan, Kemal Öztürk, Şükrü Çelik, Canan Aksoy, Fırat Karaboğa, Ezgi Taylan Koparan, Ekrem Yanmaz Cryogenics, 2019 A series bulk samples of MgB2 + x wt% of Mg (x = 0, 5, 10, 15, 20 and 30) were fabricated by solid state reaction method. The structural and electromagnetic properties of MgB2 samples were studied using X-ray diffraction (XRD), scanning electronic microscope (SEM), electrical resistivity (R-T), magnetic hysteresis (M-H), magnetic levitation (Fz) force and lateral force (Fx) measurements. The maximum repulsive and attractive force values of 15 wt% of excess magnesium MgB2 sample compared to the other samples imply that the intergranular connection between grains enhanced while pore and microcrack density decreased which brings an increase in the values of the radius of a shielding current loop (r) and the critical current density (Jc). It was determined that to obtain the enhancement of the micro and macro structure properties, causing to the higher critical current density, and the maximum levitation and lateral force values, the optimum excess magnesium content was 15 wt% into sample. It is thought that an addition of 10–15% excess magnesium can be tried for spark plasma or other methods –as a further research– and the results showed a potential to guide the researchers to study on the material-fabrication and the magnetic bearing system.
Enhanced Magnetic Levitation and Guidance Force in MgB2 Bulks by Synthetic Engine Oil Immersion Burcu Savaşkan, Ezgi Taylan Koparan, Sait Barış Güner, Kemal Öztürk, Şükrü Çelik Journal of Superconductivity and Novel Magnetism, 2019 We have used ‘Synthetic engine oil’ as a rich easily accessible carbon source and investigated the effect of engine oil on the microstructure, critical current density (Jc), vertical levitation force (Fz) and guidance force (Fx) properties of MgB2 superconductor. The polycrystalline disk-shaped MgB2 bulk samples have been prepared using two-step solid-state reaction process. After the first heating process, MgB2 bulk samples immersed in the engine oil for different durations (30, 120, 300 and 1440 min). XRD analysis indicated the decreasing of lattice parameters of samples and confirmed C substitution in boron sites. Vertical levitation and guidance force measurements were carried out with both Field-cooling (FC) and zero-field-cooling (ZFC) regimes at different temperatures of 20, 24 and 28 K. It was found that engine oil addition slightly increases the levitation and guidance force properties. The Fz$F_{z}$ values were obtained as 11.17 and 11.58 N for pure and MgB2 sample immersed for 30 min at 20 K in ZFC regime. In addition, the MgB2 sample immersed for 300 min in engine oil showed the highest Jc$J_{c}$ value of 5.3×104$5.3\\times 10^{4}$ A cm− 2 at 15 K and self-field and showed the highest guidance force value of 4.14 N at 20 K. These finding suggest that synthetic engine oil is a cost-effective and promising method to improve the levitation and guidance force performance as well as the critical current density of MgB2 bulk superconductor.
