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    Irradiated rGO electrode-based high-performance supercapacitors: Boosting effect of GO/rGO mixed nanosheets on electrochemical performance
    (Elsevier Sci Ltd, 2022) Karaman, Onur; Kariper, I. Afsin; Korkmaz, Satiye; Karimi-Maleh, Hassan; Usta, Metin; Karaman, Ceren
    Supercapacitors are seemed to be one of the most promising choices as an energy storage system. However, there is still a gap in enhancing its energy density values and cyclic stabilities throughout a facile approach. Herein, it was aimed to propose a facile and effective way to fabricate high-energy supercapacitor electrode material based on reduced graphene oxide (rGO) nanostructure. Bearing this in mind, the bulk rGO powder was irradiated by various beam sources including Co-60, Am-241, Na-22, and Sr-90, and the resultant irradiated rGO samples were utilized as the electrode active material to fabricate symmetrical supercapacitor cells. The irradiated rGO samples were characterized both physicochemically and electrochemically. The physicochemical characterizations revealed that as a consequence of the irradiation, both GO and rGO nanosheets were formed in the resultant powder and the d-spacing of the graphene nanosheets were expanded. The highest electrochemical performance metrics were acquired for Sr-90 irradiated rGO electrode-based supercapacitor cell with the specific capacitance value of 585.44F.g ? 1 at 0.2 A.g ? 1, and outstanding capacitance retention performance of 97.14% for the 5000th CV cycles at 200 mV.s ? 1. Moreover, the energy density and power density values were comparable to other commercial energy storage systems such as lead-acid and nickel-metal hybrid batteries. Hence, it can be speculated that these pioneering breakthroughs could pave the way for cutting-edge high-energy supercapacitors based on rGO-derivatives with superior electrochemical performance metrics, as well as engineering of highperformance rGO-based materials to be employed in various energy applications.
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    Radioactive rays shielding film: coating on amorphous glass
    (Springer, 2020) Kariper, I. Afsin; Meydaneri Tezel, Fatma; Usta, Metin
    In this study, boron and lead compounds were coated on amorphous glass. Chemical bath deposition method was used for coating. Films were produced in the baths with pH: 9-12. Some of the produced films were directly analyzed, whereas some of them were analyzed after annealing at 500 degrees C. The characterization of the films was performed by XRD, while surface characterization was performed by SEM and EDX analysis. The study was finalized by performing radioactive analyzes of the films. Am-241 isotopes were used as the radioactive source for Alpha rays, Co-60 for Gamma rays and Sr-90 for Beta rays. According to the results, it was found that the films produced at pH: 9-10 had low optical transmittance but were able to absorb alpha and beta particles considerably. However, despite the high optical permeability of the films produced at pH: 11-12, their absorption of radioactive particles was found to be lower than the others. As a result, it was found that the absorption characteristics of the films produced at baths with different pH depend on the relative rate of boron and lead elements found on the surface.