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Öğe Design, fabrication, and testing of MgB2/Fe racetrack coils(Ieee-Inst Electrical Electronics Engineers Inc, 2018) Karaboğa, Fırat; Yetiş, Hakan; Akdoğan, Mustafa; Gajda, Daniel; Belenli, İbrahimWe fabricated four superconducting racetrack coils wound by bare in situ MgB2/Fe mono and multifilamentary wires produced in our laboratory by using the wind-and-react method. Transport measurements in self-field were performed in a liquid helium dewar. The magnetic field flux density B = 25 mT for I = 92 A was measured to verify how the current flowed inside the coil for one of the coils by means of a cryogenic axial Hall sensor placed into the central bore region of the coil. The coil with 36 turns wound by mono MgB2/Fe wire of l = 24 m has a highest current-carrying capacity of more than 150 A at T = 4.2 K and self-field among the coils. The coils fabricated by multifilamentary wires have relatively low engineering critical current values of I-ce = 67 A for 18 + 1 and I-ce = 57 A for 4 + 5 superconducting/copper filament wires at T = 4.2 K in self-field. Our results form essential contribution toward determination of the possible use of low-cost MgB2/Fe wires in low-field superconductor coil applications.Öğe Effect of the initial filling density on the critical current of in-situ Fe/MgB2 wires(Elsevier Science Sa, 2015) Akdoğan, Mustafa; Yetiş, Hakan; Gajda, Daniel; Karaboğa, Fırat; Ülgen, Asaf Tolga; Demirtürk, Emine; Belenli, İbrahimWe report a comparative study on the fabrication of in-situ monofilamentary superconducting Fe sheathed MgB2 wires as a function of the initial tube filling density. The wire samples are fabricated by means of a standard Powder-in-Tube (PIT) method with two different initial powder filling densities. Transport measurements are applied under high magnetic fields, of up to 10 T, obtained in a Bitter magnet. We find that increasing the initial filling density improved the critical current of the Fe/MgB2 wires, and a high I-c (4.2 K) = 140 A at B = 5 T is achieved. (C) 2015 Elsevier B.V. All rights reserved.Öğe Formation of high-field pinning centers in superconducting MgB2 wires by using high hot isostatic pressure process(Springer, 2017) Gajda, Daniel; Morawski, Andrzej; Zaleski, Andrzej Janusz; Akdoğan, Mustafa; Yetiş, Hakan; Karaboğa, Fırat; Belenli, İbrahimThis paper demonstrates the effects of hot isostatic pressure (HIP) on the structure and transport critical parameters of in situ MgB2 wires without a barrier. Our results show that only HIP and nano-boron allow the formation of more high-field pinning centers, which lead to the increase in critical current density (J (c)) at high applied magnetic fields. Nano-boron and annealing at a low pressure increase the J (c) in the low magnetic field. This indicates that nano-particles create more high-field pinning centers. In addition, the results show that nano-boron improves the connection between the grains. Scanning electron microscope results show that HIP increases the reaction rate between Mg and B, density, and homogeneity of the MgB2 material. Additionally, HIP allows to create a structure with small grains and voids and eliminates the significance of the number of voids. High isostatic pressure allows to obtain high J (c) of 10 A/mm(2) (at 4.2 K) in 10 T and increases irreversible magnetic field (B (irr)) and upper critical field (B (c2)). Measurements show that these wires have high critical temperature of 37 K.Öğe Improvement of in-situ Fe/MgB2 monofilamentary wires by internal Mg-coating process(Elsevier Science Sa, 2017) Karaboğa, Fırat; Avcı, Doğan; Yetiş, Hakan; Akdoğan, Mustafa; Gajda, Daniel; Belenli, İbrahimIn the present work, we have studied on the use of internally Mg-coated and uncoated iron tubes in processing of in-situ mono filamentary Fe/MgB2 wires by means of transport measurements and structural analysis methods. For coated wires, the starting Fe tube is internally coated by magnesium before PIT process is applied and these wires with 0.81 mm in diameter are heat treated at different annealing temperatures and times. The main idea behind this work is to investigate the possible role of Mg coating on inhibition of Fe2B phase formation and its contribution to granular structure of MgB2 core. The transport and superconducting properties in the presence of external magnetic field are well improved for Mg-coated wire samples in comparison to the uncoated wire samples. The structural and surface analyses of Mg-coated wires reveal that the Fe2B formation still exists at the interface region. The results are interpreted in terms of effects of excess magnesium, internal Mg vapor pressure, homogeinity of Mg coating process, and heat treatment conditions. The highest engineering critical current density J(ce)(4.2 K) is obtained as greater than 5.4 x 10(4) A/cm(2) at mu H-0 = 4 T among the coated samples.Öğe Influence of amorphous boron grain size, high ısostatic pressure, annealing temperature, and filling density of unreacted material on structure, critical parameters, n-value, and engineering critical current density in MgB2 wires(MDPI, 2021) Gajda, Daniel; Zaleski, Andrzej Janusz; Morawski, Andrzej; Malecka, Malgorzata; Akdoğan, Mustafa; Karaboğa, Fırat; Avcı, Doğan; Yetiş, Hakan; Belenli, İbrahimOur results show that a lower density of unreacted Mg + B material during an Mg solid-state synthesis reaction leads to a significant reduction in the quantity of the superconducting phase and lowers the homogeneity of the superconducting material. It also significantly reduces the irreversible magnetic field (B-irr), critical temperature (T-c), upper magnetic field (B-c2), engineered critical current density (J(ec)), and n-value, despite high isostatic pressure (HIP) treatment and the use of nanoboron in the sample. Our measurements show that samples with large boron grains with an 8% higher density of unreacted Mg + B material allow better critical parameters to be achieved. Studies have shown that the density of unreacted material has little effect on B-irr, T-c, B-c2, J(ec), and the n-value for an Mg liquid-state synthesis reaction. The results show that the critical parameters during an Mg liquid-state synthesis reaction depend mainly on grain size. Nanoboron grains allow for the highest B-irr, T-c, B-c2, J(ec), and n-values. Scanning electron microscopy (SEM) images taken from the longitudinal sections of the wires show that the samples annealed under low isostatic pressure have a highly heterogeneous structure. High isostatic pressure heat treatment greatly improves the homogeneity of MgB2.Öğe The influence of HIP process on critical parameters of MgB2/Fe wires with big boron grains and without barriers(Elsevier Science Sa, 2016) Gajda, Daniel; Morawski, Andrzej; Zaleski, Andrzej Janusz; Akdoğan, Mustafa; Yetiş, Hakan; Karaboğa, Fırat; Belenli, İbrahimWe show transport results of the critical temperature (T-c), irreversible magnetic field (B-irr), upper critical field (B-c2), critical current density (J(c)) and the pinning force (F-p) for undoped MgB2 wires without barriers. The results of SEM show that the hot isostatic pressure process increases the density and uniformity of MgB2 materials. Hot isostatic pressure allows for obtaining small grains and increasing the number of connections between the grains, accelerated reaction rate and limits the diffusion of Fe atoms into MgB2 material from the adjacent sheath. The pressure of 1.1 GPa increases T-c quite significantly in high magnetic field range of 6-12 T, improves the B-irr and B-c2 and increase the J(c) at 4.2 K and 20 K of about three times. Our results may be important for this field since many MgB2 wires are made from big grains of boron greater than 1 mu m. Moreover, our research can be important for the production of MgB2 wires for the International Thermonuclear Experimental Reactor with boron B-11. (C) 2016 Elsevier B.V. All rights reserved.Öğe An innovative approach to fabricate MgB2/Fe IMD wires by magnesium powder method(Elsevier, 2020) Yetiş, Hakan; Avcı, Doğan; Karaboğa, Fırat; Gajda, Daniel; Akdoğan, Mustafa; Belenli, İbrahimA novel method is presented for the production of the in-situ MgB2/Fe mono-core internal magnesium diffusion (IMD) processed wires by using Mg powder instead of Mg rod to accomplish internal diffusion of magnesium into semi-crystalline boron powder. The MgB2/Fe wires were cold drawn to 0.81 mm diameter. The structural investigation of superconducting MgB2 layers was completed using X-ray diffraction and scanning electron microscopy. There are no traces of unreacted magnesium in the central region after Mg/B reaction. The use of magnesium powder increases the reaction rate and provides rapid Mg diffusion. The Mg powder method is also effective in reducing boron-rich regions in MgB2 IMD wires.Öğe Investigation of Layered Structure Formation in MgB2 Wires Produced by the Internal Mg Coating Process under Low and High Isostatic Pressures(Mdpi, 2024) Gajda, Daniel; Babij, Michal; Zaleski, Andrzej; Avci, Dogan; Karaboga, Firat; Yetis, Hakan; Belenli, IbrahimCurrently, MgB2 wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB2 wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction.Öğe Optimized superconducting MgB2 joint made by IMD technique(IOP Publishing Ltd, 2023) Avcı, Doğan; Yetiş, Hakan; Gajda, Daniel; Babij, Michal; Tran, Lan Maria; Karaboğa, Fırat; Aksoy, Canan; Zaleski, Andrzej; Belenli, İbrahimA novel type of superconducting joining technique has been introduced to join unreacted internal Mg diffusion (IMD) single-core MgB2 wires. Our method is based on fabricating a small diameter joint mould obtained by deforming an Nb/Cu composite tube with a longitudinal semi-cylindrical Mg and B core into a thick round wire. The small diameter of the joint provided advantages such as rapid cooling, low resistance, and the unique core design inside the joint ensured a uniform MgB2 phase formation. Scanning electron microscope analysis revealed that the IMD MgB2 wires had excellent contact with the superconducting MgB2 bulk material inside the joint. The joint resistance, calculated from the decay of the trapped magnetic field over time, is a quite low value of 6.44 × 10−16 Ω at 20 K. The transport critical current (Ic) of the joint is 62 A at 20 K under a self-magnetic field, and the n-value of the joint is 66 at 20 K under 1.5 T. The results showed that the Ic of our joint can be determined precisely, regardless of whether the magnetic field is applied from low to high or from high to low value during I–V measurements.Öğe The significant influence of packing density of unreacted Mg+2B mixture and heat treatment conditions on some of critical parameters for MgB2/Fe wires(Elseiver Science SA, 2021) Gajda, Daniel; Zaleski, Andrzej Janusz; Morawski, Andrzej; Czujko, Tomasz; Avcı, Doğan; Karaboğa, Fırat; Akdoğan, Mustafa; Yetiş, Hakan; Belenli, İbrahimOur research show that the higher packing density of the unreacted material (Mg +2B) by 8%, especially for Mg in the solid state, allows to eliminate the large number of large voids (20 mu m), improves the homogeneity and density of the MgB2 superconducting material, allows to obtain a greater number and longer lengths of connections between MgB2 grains, eliminates the formation of the intermetallic phase (iron borides), allows to obtain MgB2 grains of a uniform size and shape, increase irreversible magnetic field (Birr), critical temperature (T-c) and upper magnetic field (B-c2). Research show that spherical grains significantly reduce the number of inter-grain connections in the material with low and high density of unreacted material and allows to obtain the more superconducting phase. Research shows that MgB2 grains with a plate-like and rectangular shape allow to obtain more connections between the grains. Studies show that thermal treatment under high iso-static pressure does not allow to obtain the large amount of superconducting phase for the unreacted material of low density. Moreover, studies show that the high packing density of unreacted material and thermal treatment under high isostatic pressures (0.8 GPa and 1.1 GPa) allow to obtain a large amount of superconducting phase even for Mg in the solid state. Additionally, studies points that heat treatment under medium isostatic pressure (0.3 GPa) significantly reduce B-irr and B-c2. Our results are important for long superconducting wires made by using the powder-in-tube (PIT) technique. Because they indicate that the higher packing density of the unreacted material (Mg +2B) will allow to obtain a the superconducting material with greater homogeneity and density, and improve the critical parameters e.g. coils. (C) 2021 Elsevier B.V. All rights reserved.Öğe Transport and structural properties of MgB2/Fe wires produced by redesigning internal Mg diffusion process(IOP Publishing Ltd, 2022) Yetiş, Hakan; Avcl, Do?an; Karabo?a, Flrat; Aksoy, Canan; Gajda, Daniel; Martínez, Elena; Tanylldlzl, Fatih MehmetWe report transport, electromechanical, and structural properties of single core MgB2/Fe wire produced using a new fabrication method, called designed internal Mg diffusion (IMD) process, which relies on the use of non-stoichiometric Mg + B pellets with excess Mg in place of a central Mg rod used in the standard IMD method. Structural analysis revealed the successful formation of a porous MgB2 structure in the center and a dense circular MgB2 layer surrounding this structure in the designed-IMD wire. Fast transport I-V measurements showed that the designed IMD method increased engineering critical current density (J e) up to twice that of the IMD wires in self-field. The central porous MgB2 structure shared the applied current and indirectly behaved as an internal stabilizer against quench damage at high applied currents. © 2022 IOP Publishing Ltd.Öğe Use of amorphous boron and amorphous nano boron powder mixture in fabrication of long in-situ MgB2/Fe wires(Elsevier Ltd, 2017) Mustafa, Akdoğan; Yetiş, Hakan; Gajda, Daniel; Karaboğa, Fırat; Rogacki, Krzysztof; Morawski, Andrzej; Belenli, İbrahimWe report a study on the structural and transport properties of long in situ MgB2/Fe wires that are prepared by use of amorphous boron and nano amorphous boron powders with 50–50% weight ratio. The wire samples are fabricated by means of a standard Powder-in-Tube (PIT) method. Transport measurements are applied under high magnetic fields, of up to 9 T, obtained in a Bitter magnet. We find that use of a mixture of the amorphous boron and amorphous nano boron precursor powders at equal amounts is very promising way to fabricate long wires without any degradation in transport engineering Jcevalues in the presence of low and moderate magnetic fields. © 2017 Elsevier B.V.
