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    Effect of foreign impurity and growth temperatures on hexagonal structure and fundamental properties of ZnO nanorods
    (Wiley, 2024) Seydioglu, T.; Kurnaz, S.; Tokeser, E. Asikuzun; Yildirim, G.; Ozturk, O.
    This study examined the influence of growth temperature and dopant concentration on the properties of Gd- and Ni-doped zinc oxide nanorods (ZnO NRs). ZnO seed layers were deposited on glass substrates using a sol-gel and dip-coating approach. Gd- and Ni-doped ZnO NRs were hydrothermally grown on the seed layers at different temperatures such as 75, 90, and 105 degrees C for a constant growth time of 5 h. The crystal structure, optical, surface morphology views, and electrical properties of the NRs were extensively investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, and four probe experimental methods. The XRD analysis confirmed the successful substitution of Zn2+ ions by Gd3+ and Ni2+ within the ZnO main matrices. The reordering of hexagonal structures with varied electronegativity, ionic radius dimensions, and valence electron states of Gd and Ni dopants affected seriously the fundamental characteristic features of NRs. The SEM images showed that the ZnO NRs grown at 90 degrees C possessed a more favorable surface morphology and well-defined hexagonal shape compared with those grown at other growth temperatures. Higher dopant concentration led to an increase in NR diameter but a decrease in density depending on the increase in the space between the NRs. Additionally, the optical transmittance was found to generally enhance with increasing dopant concentration. The results obtained highlighted the interplay between growth temperature, dopant type and concentration in tailoring the structural, morphological, and optical properties of Gd- and Ni-doped ZnO NRs, paving the way for the development of optimized nanomaterials for various applications.
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    Evolution of fundamental mechanical properties with aliovalent Co/Cu partial substitution and preparation method for Y-123 system
    (Springer, 2024) Ozturk, O.; Safran, S.; Ada, H.; Bulut, F.; Seydioglu, T.; Nefrow, A. R. A.; Akkurt, B.
    This study investigates the effect of aliovalent Co/Cu replacement and preparation method on fundamental mechanical performance features of YBa2Cu3-xCoxO7-delta (Y-123) ceramic system depending on the crack propagation mechanism by Vickers hardness measurements (H-v) and mechanical investigation models for the first time. All the findings are verified by the scanning electron microscopy (SEM) examinations. Besides, the electron-dispersive X-ray (EDX) technique verifies the successful substitution mechanism. Besides, the Vickers hardness parameters improve systematically with the increment in the Co/Cu partial substitution (serving as a barrier) level due to formation of operable slip systems, ionic bond formations, and decrement of stress-amplified strain fields. Moreover, the Y-123 ceramic produced by solid-state reaction method and molecular weight of 0.20% presents the densest and smoothest surface morphology with the largest particle distributions and well-linked cobblestone-like grains. On the other hand, the Y-123 ceramic compounds produced by the sol-gel method are more sensitive and responsive to the indentation test loads. All the findings are wholly supported by the mechanical performance properties, including the shear modulus, resilience, and degree of granularity. Furthermore, the mechanical models indicate that every compound prepared exhibits the untypical reverse indentation size effect (RISE). Additionally, the modeling studies display that the induced cracking (IIC) approach is found to be the most appropriate method to examine true Vickers hardness parameters in the plateau limit regions. All in all, this comprehensive study reports efficiently exploiting the process-structure-property relationships in Y-123 ceramic material design for physical science and mechanical application fields using the aliovalent partial substitution and preparation condition.