Browsing by Author "Gunen A."

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    Structural and mechanical characterization of Bi1.75Pb 0.25Sr2Ca2Cu3-xSnxO 10+y superconductor ceramics using Vickers microhardness test
    (2013-11-01) Koralay H.; Arslan A.; Cavdar S.; Ozturk O.; Asikuzun E.; Gunen A.; Tasci A.T.
    In this work we investigated the role of Sn doping on mechanical and structural properties of Bi1.75Pb0.25Sr2Ca 2Cu3-xSnxO10+y (x = 0.0, 0.1, 0.3 and 0.5) superconducting ceramic material. All samples were fabricated with glass ceramic method. The prepared samples were characterized by using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffractometer (XRD) and static microhardness indenter. Surface morphology, orientation of grains, and elemental composition analysis of the samples were made by SEM and EDS measurements, respectively. Texturing and lattice parameters a and c were determined by XRD measurements. Load dependent and load independent microhardness, elastic modulus, yield strength and fracture toughness were obtained by hardness measurements. In this work we focused on Vickers microhardness measurements in order to characterize the mechanical properties of our samples. Experimental results of Vickers microhardness measurements were analyzed by using Meyer's law, the elastic/plastic deformation model, proportional sample resistance model (PSR), modified PSR model and Hays-Kendall (HK) approach. From these analyses, HK approach was determined as the most successful model describing the mechanical properties of our samples. Finally in this study, the changes on the mechanical and microstructural properties of Sn doped Bi-2223 superconductors and their possible reasons were also discussed in detail. © 2013 Springer Science+Business Media New York.
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    Scopus
    The effect of pbse addition on the mechanical properties of Bi-2212 superconductors
    (2012-10-01) Cavdar S.; Deniz E.; Koralay H.; Ozturk O.; Erdem M.; Gunen A.
    The effects of PbSe addition and heat treatment on the structure and mechanical properties of Bi-2212 superconductors are analyzed. Glass ceramic method is used to produce PbSe added samples. The mechanical properties are derived using Vickers microhardness measurement results. Well known analysis methods like Meyer's law, PSR (Proportional Sample Resistance) Model, EDP (Elastic/ Plastic DeformationModel), Hays-Kendall approach and IIC (Indentation-Induced Cracking Model) are used to calculate load independent microhardness values of the samples. HK approach produces successful results for the samples A, E, F, G and H indicating ISE (Indentation Size Effect) behavior. The IIC model successfully explains RISE (Reverse Indentation Size Effect) behavior for the samples B, C and D. RISE behavior is observed only for the samples where the plastic deformation is dominant. ISE behavior is observed for the samples where both elastic and plastic deformation are produced. The results of XRD and SEM analysis show improvement with PbSe addition in the crystal structures and surface morphologies of superconducting samples. © Springer Science+Business Media, LLC 2012.