Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 3Citation - Scopus: 3Mgb2 Superconducting Thin Films Grown by Magnetron Sputtering(National Institute of Optoelectronics, 2007) Ulucan, Savaş; Okur, Salih; Okur, Salih; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this study, we report the growth and properties of MgB2 thin films on polycrystalline Al2O3 substrates. A composite MgB2 target was produced by MgB2 and Mg powder mixing, using a hot pressing technique. MgB2 thin films were grown on Al 2O3 substrates by d.c. magnetron sputtering, without heating the substrate. To enhance the superconducting properties of the as-grown films and to increase the crystal quality, an ex-situ anneal process was applied. The crystal structure of the thin films was determined by X-ray diffraction. The resistivity versus temperature of the deposited MgB2 thin films was studied to examine the transition temperatures of the films under various magnetic fields. The effects of the annealing temperature and annealing time on the electrical properties of MgB2 thin films are revealed.Article Citation - WoS: 6Citation - Scopus: 11Electrical and Mechanical Properties of Superconducting Mgb2/Mg Metal Matrix Composites(IOP Publishing Ltd., 2006) Eğilmez, Mehmet; Okur, Salih; Özyüzer, Lütfi; Tanoğlu, Metin; Tanoğlu, Metin; Özyüzer, Lütfi; Okur, Salih; Kamer, Orhan; Öner, Yıldırhan; 04.05. Department of Pyhsics; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyMgB2/Mg composites were prepared using a metal matrix composite fabrication method that offers the potential to produce superconducting wires as an alternative approach to the powder in tube process. To obtain composites, MgB2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical die under the pressure of 0.5 and 1.0GPa for two hours at various temperatures. The x-ray diffraction technique was used for phase identification. Temperature dependence of resistivity and magnetization measurements were carried out to determine superconducting properties. The effects of composite fabrication temperature and the addition of the Mg on the mechanical properties of MgB2/Mg composites were investigated. For this purpose, the compressive mechanical testing was performed to measure the elastic modulus and fracture strength values of the composites. It was found that the relative weight fraction of the Mg and the fabrication conditions of the composites have considerable effect on the superconducting and mechanical properties of the composites.Conference Object Citation - WoS: 3Citation - Scopus: 2Fabrication of Superconducting Mgb2 From Boron Oxide (b 2o3), and Its Microstructural and Electrical Characterization(National Institute of Optoelectronics, 2005) Yavaş, Mert; Okur, Salih; Özyüzer, Lütfi; Kalkancı, Mihriban; Özyüzer, Lütfi; Okur, Salih; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe discovery of superconducting MgB2 (39 K) draws attention to it as a new material for applications based on superconductivity. Many researchers successfully synthesized MgB2 using commercial boron and magnesium. In this study, elementary boron was obtained via an acid leaching process, after reacting B2O3, and Mg in an argon atmosphere at 800°C. Energy Dispersive X-ray Spectroscopy (EDX) results revealed that the powder obtained from the reaction was boron in 92% purity with magnesium as the major impurity. Superconducting MgB2 was produced from this boron and magnesium, in an argon atmosphere at 900°C, by a conventional solid-state reaction. Superconducting MgB2 powders were compressed in a dye to pellets by a hot pressing technique at 500°C and 1 GPa. The microstructural properties of the MgB2 were determined by X-ray Diffraction Spectroscopy, EDX, and Scanning Electron Microscopy techniques. The electrical properties of the fabricated MgB 2 were examined by resistivity measurements in a closed-cycle cryopump system, between 20 and 300 K. The critical temperature (Tc) of the MgB2 pellets was around 32 K.Conference Object Citation - WoS: 2Citation - Scopus: 2Microstructural and Electrical Characterization of Ti and Mg Doped Cu-Clad Mgb2 Superconducting Wires(National Institute of Optoelectronics, 2005) Okur, Salih; Kalkancı, Mihriban; Özyüzer, Lütfi; Eğilmez, Mehmet; Özyüzer, Lütfi; Okur, Salih; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe recent studies on Ti doping effect on the critical current density (Jc) of MgB2 composite superconductors prepared under ambient pressure has shown an important enhancement at 20 K. In the present work, we have fabricated Ti and Mg doped superconducting MgB2 wires by packing reacted MgB2 and Ti or Mg powders together inside Cu tubes with a diameter of 6 mm. The tubes were then cold worked by rolling or drawing to smaller diameters. The prepared Cu-clad Ti and Mg added MgB 2 superconducting wires were annealed at various temperatures to enhance the grain connectivity of the MgB2 bulk materials. The effect of the sintering time has been investigated for high performance characteristics of superconducting Cu-clad Ti and Mg added MgB2 wires. The microstructural evaluation of the superconducting wires has been carried out using XRD and SEM equipped with EDX analysis system. The interfacial properties between Cu sheath and superconducting core was characterized using SEM-EDX. Furthermore, the influence of the presence of Ti and Mg on Tc has been investigated to understand the structural and electronic properties of superconducting Ti and Mg doped MgB2 wires.Conference Object Citation - WoS: 3Citation - Scopus: 3Low-Field Behavior of Ti-Added Mgb2/Cu Superconducting Wires(Institute of Electrical and Electronics Engineers Inc., 2005) Gençer, Ali; Kılıç, Ahmet; Okur, Salih; Özyüzer, Lütfi; Özyüzer, Lütfi; Belenli, İbrahim; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe report on low-field magnetic properties of Ti-added (0-20 wt.% of Ti) Cu-clad MgB2 superconducting wires. Wires were produced by mixing appropriate amount of Ti and reacted MgB2 powder which was then placed inside Cu tubes with a diameter of 6 mm. The tubes were then cold worked by rolling or drawing to smaller diameters and then annealed at various temperatures to enhance the grain connectivity. XRD studies show that Ti addition results in new but minor phases. We have then measured ac susceptibilities in the temperature range between 20 K and 40 K in ac fields of 20-1600 A/m. The data show that an additional loss mechanism is established with Ti-addition. The calculated ac losses are increasing with increasing Ti-content in the main superconducting matrix.Article Citation - WoS: 10Citation - Scopus: 9Structural and Low-Field Magnetic Characterization of Superconducting Mgb2 Wires(Elsevier Ltd., 2004) Kılıç, Ahmet; Okur, Salih; Özyüzer, Lütfi; Okur, Salih; Uzun, Orhan; Özyüzer, Lütfi; Gençer, Ahmet; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologySuperconducting MgB2 composite wires were prepared by packing blend of MgB2 inside of Cu tubes using powder in tube (PIT) method. The produced samples of the wires were then characterised by using SEM, XRD and AC susceptibility measurements, The measured fundamental susceptibility is compared with Bean model. We have obtained an empirical functions for the penetration field Hp = Hα(1-t)β, where t is the reduced temperature. In addition, ac losses were calculated at the same fixed temperatures to compare theoretical solutions. There is a qualitative agreement between the experimental results and theory.Conference Object Citation - WoS: 6Citation - Scopus: 5Electrical and Microstructural Properties of Superconducting Mgb 2/Mg Composites(Trans Tech Publications, 2004) Eğilmez, Mehmet; Günel, Aylin; Özyüzer, Lütfi; Tanoğlu, Metin; Özyüzer, Lütfi; Tanoğlu, Metin; Okur, Salih; 04.05. Department of Pyhsics; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyMgB2/Mg composites were prepared to improve mechanical properties of brittle superconducting MgB2. MgB2 and Mg powders were mixed at different weight ratios and uniaxially pressed in a cylindrical dye at 0.5 GPa and at various temperatures for two hours to prepare MgB2/Mg composites. X-ray diffraction, SEM and EDX were used for phase identification and microstructural characterization. In addition to the main MgB2 and Mg phases, the microstructural studies have indicated the presence of a minor amounts of second phases, namely MgO and B-rich compounds. The surface morphology, grain size and porosity ratio of the samples prepared under various temperatures were also investigated. The resistivity measurements were performed in the range of room temperature to 15 K. The effect of excess Mg and secondary phases on critical temperature of MgB2/Mg composites were studied.