Yazar "Kara, Emre" seçeneğine göre listele
Listeleniyor 1 - 5 / 5
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Bi-2223 Süperiletken Seramiklerde Peletizasyon Basıncının Yapısal, Elektriksel ve Mekanik Özellikler Üzerine Etkisi(2022) Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirBu çalışmada Bi-2223 tozlar farklı peletizasyon basınç değerleri ile külçe formuna getirilmiş ardından külçeler 840ºC’de 36 saat tavlanmıştır. Basıncın Bi-2223 külçelerin yapısal, mekanik ve elektriksel özellikleri üzerine etkileri incelenmiştir. Yapısal analizlerin değerlendirilmesi için X-ışını Kırınımı (XRD) spektroskopisi ölçümleri kullanılmıştır. Mekanik analizler için oda sıcaklığında Vickers Mikrosertlik ölçümleri yapılmıştır. Elektriksel analizlerde ise dört kontak I-V ölçümleri kullanılmıştır. Elde edilen sonuçlara göre, Bi-2223 kristal faz yoğunluğunun, sertlik değerinin ve elektrik taşıma kapasitesinin basınca ciddi bir şekilde bağlı olduğu görülmüştür. Bu bağlamda, basıncın artması ile sertlik değerlerinin kristal yapıdaki faz geçişlerine ve yüzey artık basınç gerilim bölgelerinin artışına bağlı olarak yükseldiği tespit edilmiştir. Ayrıca, hesaplanan elastisite modülü ve akma dayanımı gibi genel mekanik performans değerlerinin basınca bağlı olarak arttığı gözlemlenmiştir. Bu bulgu kristal yapıda hali hazırda var olan kovalent ve özellikle iyonik bağ kuvvetlerinin artmasının sonucu olabilir. Bununla birlikte, numunelerin plato limit bölgelerinde yükten bağımsız mikrosertlik değerleri Meyer yasası, Orantılı Numune Direnç (OND) ve Indentation Induced Cracking (IIC) yöntemleri ile analiz edilmiştir. Analiz sonucunda IIC modelin gerçek mikrosertlik değerlerini incelemede daha başarılı olduğu bulunmuştur. Kritik akımın uygulanan basıncın artması ile düştüğü gözlemlenmiştir. Örneklerin yoğunlukları Arşimet yasası kullanılarak ölçülmüştür. Teknolojik kullanım alanına bağlı olarak külçe Bi-2223 örneklerin üretiminde uygulanması gereken optimum basınç değeri detaylarıyla tartışılmıştır.Öğe BSCCO süperiletkenlere nikel oksit katkısının yapısal, mekanik ve elektriksel özellikleri üzerine etkileri(Bolu Abant İzzet Baysal Üniversitesi, 2022) Kara, Emre; Terzioğlu, Rıfkı; Doğan, Muhsin UğurBu tez çalışmasında, Bi tabanlı süperiletken seramiklerin temel özellikleri üzerine nikel oksit (NiO) katkısının etkileri araştırılarak, süperiletkenlik ve elektriksel performansının geliştirilmesi hedeflenmektedir. Bu hedef doğrultusunda NİO metalik bileşeni Bi-2223 seramiklerinin üzerine katı hal reaksiyon yöntemi ile 0.0-1.2 molar oranları arasında NiO eklemesi yapılmıştır. NiO katkısı yapılan Bi-2223 seramik örneklerin yapısal, mekanik, elektriksel, manyetik ve süperiletken özellikleri üzerindeki etkileri sistematik olarak yorumlanarak çalışma sonlandırılmıştır. Süperiletken örnekler X-ışını kırınımı (XRD), taramalı elektron mikroskobu (SEM), elektriksel özdirenç (R-T), manyetizasyon (M-H) ve dinamik Vickers mikrosertlik ölçümleri gerçekleştirilerek analiz edilmiştir.Öğe Evolution of basic features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy ceramic systems with NiO impurity(Springer, 2023) Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirIn the current work, we have investigated the role of different nickel oxide (NiO)(x) impurity addition levels (0 & LE; x & LE; 1.2) on the fundamental crystallographic, morphological, electrical, magnetic, critical current density, and superconducting features of Bi1.8Pb0.4Sr2Ca2.2Cu3Oy (Bi-2223) by the temperature-dependent electrical resistivities (& rho;-T), X-ray diffraction data (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and magnetic hysteresis (M-H) measurements for the first time. The NiO-added Bi-2223 ceramics have been produced by the standard solid-state reaction method at 840 & DEG;C for 36 h in the air atmospheric conditions. EDX investigations have demonstrated that there appear no extra contamination and additional phases for any anionic or cation-including phases. Besides, the Ni impurity concentration has been observed to increase systematically depending on the impurity amount. Thus, the NiO impurities have been added to the ceramic matrix as requested. Similar findings have been confirmed by the XRD examinations. The experimental results have pointed out the multiple substitution reaction of Ni-sites with the Bi-sites, Ca-sites, and Cu-sites in the Bi-2223 system. Moreover, the experimental results have shown that all the fundamental features are strongly dependent upon the NiO addition level due to the variation of Cu-O-2 interlayer bonding forces, grain alignment distributions, mobile carrier concentrations in the in-plane Cu-O-2 layer x(2)-y(2) bands, and coupling probabilities between the adjacent layers in the crystal structure. Similarly, the induction of new impurity phase formations, grain boundaries, modulation of Bi-O double layers, spin fluctuations, inhomogeneities, structural defects, and non-recoverable structural problems have also triggered the decrease in the main characteristic quantities. On this basis, the microstructural morphology and related crystallographic features have been noted to degrade with the impurity. Furthermore, the presence of NiO impurity has resulted in a decrement in the flux-pinning centers due to the increase in the lower resistance regions against the flux drifts in the bulk crystal system. All in all, the addition of NiO impurity in the Bi-2223 ceramic matrix is not a good idea for the improvement in the fundamental features of the Bi-2223 superconducting structure.Öğe Evolution of operable slip systems, lattice strain fields and morphological view of Bi-2223 ceramic system with optimum NiO addition(Elsevier, 2023) Mercan, Ali; Kara, Emre; Doğan, Muhsin Uğur; Kaya, Şenol; Terzioğlu, Rıfkı; Erdem, Ümit; Yıldırım, Gürcan; Terzioğlu, CabirThe current work extensively reveals the influence of different nickel oxide (NiO) impurity addition levels on the morphological, microstructural, key mechanical performance, and mechanical characteristic properties of Bi1.8Pb0.4Ca2.2Sr2Cu3Oy (Bi-2223) ceramics using scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Vickers micro-indentation (Hv) hardness measurements. It was observed that the addition of NiO impurity in the Bi-2223 crystal structure affected seriously the fundamental characteristic features. In the case of the optimum NiO concentration level of x = 0.1, the Bi-2223 materials exhibited the best crystallinity quality and coupling strengths between the adjacent layers, the most uniform surface view, and the densest, and the smoothest crystal structure. Similarly, the compound was noted to possess the hardest, highest mechanical strength, durable tetragonal phase, resistance toward failure by fatigue, and elastic recovery properties. Besides, it was observed that the characteristic Bi-2223 superconducting phase fraction and stabilization of the tetragonal crystal system reached the maximum level for the optimum concentration. Moreover, optimum NiO particles brought about a considerable increase in the number of operable slip systems, surface residual compressive force regions, and lattice strain fields. Correspondingly, the mobility of defects was blocked significantly depending on the preference of defects through transcrystalline regions. Additionally, optimum addition strengthened the typical indentation size effect due to the improvement of the recovery mechanism. In this regard, the NiO-added sample exhibited the least response to the applied loads. Thus, the Bi-2223 sample with the optimum NiO concentration was found to present the highest hardness parameter of 0.496 GPa, greatest elastic deformation value of 16.493 GPa, largest stiffness value of 1.044 MN/m, and smallest contact depth of 5.849 mu m. On the other hand, after the optimum concentration level of x = 0.1, there appeared serious increase in problems including internal defects, impurity residues, microscopic structural problems, and connection problems between the grains. All experimental findings were theoretically supported by semi-empirical mechanical methods. To sum up, the addition of NiO particles was noticed to increase the potential application areas of Bi-2223 ceramicÖğe Refinement of some basic features of Zr surface-layered Bi-2223 superconductor with diffusion annealing temperature(Springer, 2022) Orhan, Emre; Kara, Emre; Kaya, Şenol; Doğan, Muhsin Uğur; Terzioğlu, Rıfkı; Yıldırım, Gürcan; Terzioğlu, CabirThis study aims to investigate the influences of diffusion annealing temperatures on structural, morphological, electrical, and superconducting features of Zr surface-layered Bi-2223 ceramics. The present study also covers an in-depth understanding of correlations between disorders and transition temperatures. The Zr diffusion is carried out via an annealing process between 650 and 840 degrees C. The observed results depict that the Zr ions can easily diffuse into the deeper level of Bi-ceramics and possible Zr/Bi substitution has occurred due to the driving force of high thermal energy. Besides, it is found that the Zr diffusion improves the general crystallinity quantities of Bi-2223 ceramic up to 800 degrees C annealing temperature. In addition, better intergranular couplings with a smoother plate-like structure are extensively observed in surface morphology for the samples annealed at 800 degrees C. Significant refinements of both basic electrical resistivity, hole carrier densities, and critical temperatures with narrow transitions are also obtained for the Zr surface-layered Bi-2223 ceramics after the 800 degrees C annealing process. The obtained improvements in critical fundamental features can be attributed to the optimum pairing mechanism, best crystal structure quality, ideal Cu-O-2 interlayer coupling strengths, and enhanced interaction between adjacent superconductive layers. Besides, the first-order derivative of electrical resistivity versus temperature graphs indicates that the best annealing temperature enables to triggers to stabilize the superconductivity in the homogeneous regions. It can be concluded that the Zr impurity diffusion at 800 degrees C is promising for the improvement in the basic features of Bi-2223 superconducting systems for future applications in superconductor technology.
