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    Electrical characterization of ZnO/NiO p-n junction prepared by the sol-gel method
    (Springer Heidelberg, 2017) Akyuzlu, A. Merih; Dagdelen, Fethi; Gultek, Ahmet; Hendi, A. A.; Yakuphanoglu, Fahrettin
    ZnO and NiO films were synthesized on fluourine-doped tin oxide (FTO) glass substrate by the sol-gel method. The surface morphology of the films was investigated by atomic force microscopy. The optical band gaps of the ZnO and NiO films were found to be 3.198 and 3.827eV, respectively. A ZnO/NiO p-n junction diode was prepared and electrical charge transport mechanism of the diode was analyzed using thermionic emission and Norde functions. The ideality factor, barrier height and series resistance of the diode were determined to be 6.46, 1.036eV and 39.1 M , respectively. The obtained results indicate that ZnO/NiO p-n junction can be used as transparent diode for optic communications.
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    Investigation of Electrochemical and Thermal Properties of Ti50Ni40-xZr10Nbx SMAs
    (Springer, 2024) Abdullah, Shakhawan Salih; Balci, Esra; Qader, Ibrahim Nazem; Dagdelen, Fethi
    Titanium and its alloys have already been widely used as implant materials due to their outstanding mechanical characteristics, thermal properties, and biocompatibility. In this study, Ti50Ni40-xZr10Nbx (x = 1, 3, 5 at.%) shape memory alloys (SMAs) with a constant atomic percentage of Ti and Zr were investigated. For investigation of the structural properties of produced SMAs, scanning electron microscope (SEM-EDX) analysis, optical microscope (OM) images, and x-ray diffraction (XRD) pattern were taken. B2, B19', beta-Nb, and Ti2N phases were detected in all alloys. In SEM-EDX and OM research, it was determined that beta-Nb phase increased in dendritic structure as the Nb ratio increased. For the biocompatibility levels of alloys, the corrosion test method was carried out with the potentiodynamic test, which is one of the electrochemical methods. Tafel test and electrochemical impedance spectroscopy in a simulated body fluid (SBF) showed that the Nb additive increased the corrosion resistance of the alloy. Phase transformation temperatures (PTTs) of these alloys were investigated by using differential scanning calorimetry (DSC) measurements. In DSC research, it was determined that the alloys have a shape memory effect (SME), and the PPTs of the alloys decreased as the Nb ratio increased.