Yazar "Solmaz, Reyhan" seçeneğine göre listele

Listeleniyor 1 - 4 / 4
  • Küçük Resim
    Öğe
    Characterization and corrosion studies of ternary Zn?Ni?Sn alloys
    (University of Science and Technology Beijing, 2020) Solmaz, Reyhan; Karahan, Billur Deniz
    Nine distinct zinc-nickel-tin films with different compositions have been galvanostatically electrodeposited. The films have been characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Their corrosion potentials and densities have been estimated using Tafel extrapolation. Next, the electrochemical behaviors of the films (deposited through the electrolytes containing 0, 6, 8, and 10 g/L SnCl2?6H2O) have been examined based on cyclic voltammetry (CV) measurements. Further, these films have been immersed in 3.5wt% NaCl solution for 1 h, 1 d, 7 d, 14 d, 28 d, and 42 d followed by application of Tafel extrapolation and electrochemical impedance spectroscopy (EIS) tests on each aged sample. Finally, to analyze the morphologies and the compositions of the oxide films covering the surfaces of the 42-d aged films, FT-IR and SEM analyses have been performed. The results indicated that the Zn–Ni–Sn film produced through the bath including 6 g/L SnCl2?6H2O exhibits superior corrosion resistance because of the high Ni content in the presence of Sn that promotes the barrier protection capability of the deposit.
  • Küçük Resim
    Öğe
    Corrosion behavior of Ni–Fe–Mo deposits obtained under different electrodeposition conditions
    (Springer, 2021) Solmaz, Reyhan; Karahan, Billur Deniz
    Ternary Ni-Fe-Mo coatings have been proposed for anti-corrosion applications to replace chromium coating. To analyze the effects of deposition current and duration six different Ni-Fe-Mo films have been electrodeposited on copper foils. Their morphologies, structures, and chemical compositions of the films have been characterized. Potentiodynamic polarization is applied on each coating and electrochemical impedance spectroscopy is applied to discuss their corrosion resistances. Ni-Fe-Mo film that is produced at the lowest current density (5 mA.cm(-2)) for 5 min. exhibits a more positive corrosion potential and higher charge transfer resistance. To shed some lights on aging mechanism, the film has been aged for 70 days. The enhanced protective properties of the film is attributed to its fine, crack free morphology with high Mo content. The existences of Fe2O3, MoO2, MoO3, and NiO in the passive layer substantiate the improved barrier protection ability of the film.
  • Küçük Resim
    Öğe
    Effect of vinylene carbonate as electrolyte additive for Mn2O3/NiMnO3 anodes of lithium-ion batteries
    (Springer Heidelberg, 2021) Solmaz, Reyhan; Karahan, Billur Deniz
    This study reports for the first time the production and characterization of Mn2O3/NiMnO3 (MO/NMO) powders by the hydrothermal method and the enhanced performance of this electrode upon the addition of 15 vol% vinylene carbonate (VC) into the electrolyte. Cyclic voltammetry and electrochemical impedance spectroscopy tests show that the lithiation mechanism of MO/NMO changes upon the presence of VC in the electrolyte. The galvanostatic tests' results reveal that when half-cells have been tested with 15 vol% VC-containing electrolyte the anode delivers higher discharge capacity (793 mAh g(-1) at 100 mA g(-1), 535 mAh g(-1) at 400 mA g(-1)) and capacity retention, in comparison to that of the standard electrolyte. Finally, XRD and post-SEM analyses' outcomes substantiate that the addition of VC into the standard electrolyte promotes the formation of a stable electrode/electrolyte interface. The improved solid electrolyte interface (SEI) properties caused by VC addition prevent any peel off and/or delamination, resulting in high electrochemical performance over cycles.
  • Küçük Resim
    Öğe
    Fabrication of nickel manganese cobalt oxide (NMCO) anodes for lithium-ion batteries via hydrothermal process
    (Springer, 2020) Solmaz, Reyhan; Karahan, Billur Deniz; Keleş, Özgül
    Nickel manganese cobalt oxide (NMCO) powders have been fabricated by hydrothermal method followed by a calcination. The present work reports for the first time in the open literature, the effects of ammonium fluoride (NH4F) amount and calcination temperature on the NMCO powder's size and morphology. In this regard, the NMCO composite powders are designed to optimize their performances as anode materials for lithium ion batteries. The morphology, composition and structure of powders have been characterized by scanning electron microscopy, X-ray fluorescence and X-ray diffractometry, respectively. Cyclic voltammetry, galvanostatic and impedance spectroscopy tests have been employed to investigate the lithiation mechanism of the composite electrode. The results reveal that the lowest amount of NH4F (1.5 mmol) in the precursor solution and the lowest calcination temperature (250 degrees C) lead to form NMCO rods with 100 nm diameter and 3-5 mu m length. This newly designed rod-shaped NMCO powder presents a high rate performance. The average discharge/charge capacities are 1224/1129, 968/939, 856/826, and 744/712 mAh g(-1)when the current load increases from 50 to 100, 200 and 400 mA g(-1), respectively.