Yazar "Karazehir, T." seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • [ X ]
    Öğe
    Electrochemical and semiconducting properties of multifunctional smart conductive fabrics based on polypyrrole
    (Wiley, 2024) Sagirli, F. Z. Engin; Karazehir, T.; Sarac, A. S.
    We have fabricated multifunctional conductive fabrics composed of polypyrrole/BaTiO3/poly(acrylonitrile-co-methylacrylate) (PPy/BaTiO3/P(AN-co-MA)(PBA) utilizing a simple process including dip coating and in situ chemical polymerization of pyrrole, which oxidized both ammonium persulfate (APS) and ammonium persulfate + iron (III) chloride (APS + FeCl3) for flexible and wearable textile applications. The influence of the oxidant nature, PPy content, and BaTiO3 on the surface structures, electrochemical, and semiconducting characteristics of the fabrics was examined using scanning electrochemical microscopy (SEM), electrochemical impedance spectroscopy (EIS), and the Mott-Schottky (M-S) studies. The study revealed that the size of the polymer nanostructures on fabric has an impact on the electrochemical impedance properties. Specifically, a decrease in diameter (when FeCl3 + APS is used) or the formation of more compact swelling surface structures (when only APS is used) is associated with changes in the conductivity of the coated fabric. Based on the EIS tests, the composite coating (S0.1, S0.2, and S0.3) with FeCl3 has a higher electrical conductivity compared to the coating with APS (PBA). The M-S tests indicate that the semiconducting characteristics of coated fabrics are dependent upon the kind of oxidant, the amount of PPy, and the presence of BaTiO3. The results of this study indicated that, poly(acrylonitrile-co-methylacrylate) acts as an important interfacial material to prevent the aggregation of BaTiO3 and the size of obtained nanostructures leads to variation in the electrochemical impedance properties, due to presence of ammonium persulfate and FeCl3 and also, depend on pyrrole content and BaTiO3, which is related to the change in conductivity of coated fabric. image
  • [ X ]
    Öğe
    Evaluation of hydrogen storage performance of ZrTiVNiCrFe in electrochemical and gas-solid reactions
    (Pergamon-Elsevier Science Ltd, 2020) Zadorozhnyy, V; Sarac, B.; Berdonosova, E.; Karazehir, T.; Lassnig, A.; Gammer, C.; Zadorozhnyy, M.
    In the present study, the hydrogen storage performance of multi-principal-component ZrTiVNiCrFe alloy produced through rapid solidification has been examined by electro-chemical methods and gas-solid reactions. XRD and EBSD analyses reveal the hexagonal Laves phase structure (type C14) with average grain size of 300 nm and root-mean-square microstrain of 0.19%. Cyclic voltammetry and electrochemical impedance spectroscopy analyses in the hydrogen sorption/desorption region give insight to the sorption/desorption kinetics and the change in the desorption charge in terms of the applied potential. The pressure-composition isotherms measured in course of gas-solid reaction confirm the hydrogen storage capacity reaching 1.6 wt% at the first hydrogenation at room temperature, then reducing to 1.3-1.4% during subsequent cycling. According to the calorimetric titration study, there is a significant hysteresis primarily caused by the non-equilibrium character of the hydrogenation process. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
  • [ X ]
    Öğe
    Porosity and thickness effect of Pd-Cu-Si metallic glasses on electrocatalytic hydrogen production and storage
    (Elsevier Sci Ltd, 2021) Sarac, B.; Karazehir, T.; Yuece, E.; Muehlbacher, M.; Sarac, A. S.; Eckert, J.
    This contribution places emphasis on tuning pore architecture and film thickness of mesoporous Pd-Cu- Si thin films sputtered on Si/SiO2 substrates for enhanced electrocatalytic and hydrogen sorption/desorp-tion activity and their comparison with the state-of-the-art thin film electrocatalysts. Small Tafel slope of 43 mV dec-1 for 1250 nm thick coating on 2 gm diameter pores with 4.2 gm interspacing electrocatalyst with comparable hydrogen overpotentials to the literature suggests its use for standard fuel cells. The lar-gest hydrogen sorption has been attained for the 250 nm thick electrocatalyst on 5 gm pore diameter with 12 gm interspacing (2189 gC cm-2 per CV cycle), making it possible for rapid storage systems. Moreover, the charge transfer resistance described by an equivalent circuit model has an excellent cor-relation with Tafel slopes. Along with its very low Tafel slope of 42 mV dec-1 10 nm thick electrocatalyst on 2 gm diameter pores with 4.2 gm interspacing has the highest capacitive response of ti 0.001 S sn cm-2 and is promising to be used as a nano-charger and hydrogen sensor. The findings of Si/SiO2 supported mesoporous Pd-based metallic glass (MG) assemblies suggest a similar design applicability for crystalline systems and other MG types. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).