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    A Facile Approach to Produce Activated Carbon from Waste Textiles via Self-Purging Microwave Pyrolysis and FeCl3 Activation for Electromagnetic Shielding Applications
    (Mdpi, 2024) Sert, Sema; Gultekin, Sirin Siyahjani; Gultekin, Burak; Kaya, Deniz Duran; Korlu, Aysegul
    This study aims to convert composite textile structures composed of nonwoven and woven fabrics produced from cotton-jute wastes into activated carbon textile structures and investigate the possibilities of using them for electromagnetic shielding applications. To this end, the novel contribution of this study is that it shows that directly carbonized nonwoven textile via self-purging microwave pyrolysis can provide Electromagnetic Interference (EMI) shielding without any processing, including cleaning. Textile carbonization is generally achieved with conventional heating methods, using inert gas and long processing times. In the present study, nonwoven fabric from cotton-jute waste was converted into an activated carbon textile structure in a shorter time via microwaves without inert gas. Due to its polar structure, FeCl3 has been used as a microwave absorbent, providing homogeneous heating in the microwave and acting as an activating agent to serve dual purposes in the carbonization process. The maximum surface area (789.9 m(2)/g) was obtained for 5% FeCl3. The carbonized composite textile structure has a maximum of 39.4 dB at 1 GHz of EMI shielding effectiveness for 10% FeCl3, which corresponds to an excellent grade for general use and a moderate grade for professional use, exceeding the acceptable range for industrial and commercial applications of 20 dB, according to FTTS-FA-003.
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    Developing Biopolymer-Based Electrolytes for Supercapacitor and Dye-Sensitized Solar Cell Applications
    (Amer Chemical Soc, 2023) Konwar, Subhrajit; Singh, Pramod K.; Dhapola, Pawan; Singh, Abhimanyu; Savilov, Serguei V.; Yahya, Muhd Zu Azhan; Gultekin, Sirin Siyahjani
    This paper deals with the synthesis, characterization, and application of low-viscosity ionic liquids as dopants and biopolymers as the host. The biopolymer used in the present study is cornstarch, while the ionic liquid 1-ethyl 3-methylimidazolium thiocyanate (EMIm(+)SCN(-)) is used to develop an electrochemical double-layer capacitor (EDLC) and a dye-sensitized solar cell (DSSC). Different weight ratios of the ionic liquid are incorporated in the polymer host to develop a highly conducting ionic-liquid-doped biopolymer electrolyte (ILBPE). Electrical, structural, and photoelectrochemical characterizations are carried out in detail. Electrochemical impedance spectroscopy (EIS) shows that doping different weight ratios of the ionic liquid enhances the ionic conductivity and conductivity maxima observed at a weight ratio of 80 of the ionic liquid, with an ionic conductivity value of 2.6 x 10(-4) S cm(-1). X-ray diffraction (XRD) and polarized optical microscopy (POM) affirm a reduction in the crystallinity, while thermogravimetric analysis (TGA) shows thermal stability of the ILBPE beyond 200 degrees C. In addition, the 80% ILBPE-based EDLC exhibits a specific capacitance of 140 F g(-1-) , an energy density of 23.13 Wh kg(-1) , and a power density of 3600 W kg(-1) calculated based on galvanostatic charge-discharge (GDC), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) studies. Moreover, the photovoltaic performance of the DSSC is investigated by using J-V analysis and EIS measurements, while the overall power conversion efficiency is determined as 4% under standard conditions (AM 1.5).
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    One-step preparation of binder-free nickel-containing graphene foam electrode for supercapacitors
    (Wiley, 2024) Gultekin, Sirin Siyahjani; Karimi, Aziz Ahmad; Can, Mustafa; Demic, Serafettin
    In this study, a nickel hydroxide (Ni(OH)2)-modified reduced graphene oxide (rGO) foam electrode for supercapacitor application is presented. The electrode was prepared without using a binder through a one-step process with three different ratios (NirGO1, NirGO2, and NirGo3). To compare the supercapacitor performance of the obtained graphene foam electrodes, rGO and rGO:carbon black (CB) standard electrodes with PVDF-HFP binder were also prepared. All electrodes were then characterized structurally (XPS, EDS, RAMAN, XRD, and FT-IR) and morphologically (SEM). Structural characterizations demonstrated that the Ni-containing electrodes were in alpha-Ni(OH)2:rGO structure. In addition, NirGO3 exhibited a specific capacitance of 800 F g-1 which is relatively the highest performance between the foam electrodes, while rGO:CB presented a specific capacitance of 900 F g-1. The results demonstrated that with the method proposed for electrode development, it was possible to obtain comparable results with the standard electrode rGO:CB. image