Yazar "Tas, Mahmut" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • Küçük Resim Yok
    Öğe
    Graphene and graphene oxide-coated polyamide monofilament yarns for fiber-shaped flexible electrodes
    (Taylor & Francis Ltd, 2019) Tas, Mahmut; Altin, Yasin; Bedeloğlu, Ayşe
    In this study, polyamide monofilament yarn of 3000 tex was coated with graphene oxide (GO) nanomaterial using dip-coating method. The graphene oxide layer was then reduced with green chemical reduction method, resulting in a reduced graphene oxide-coated monofilament yarn. The properties of the graphene oxide and reduced graphene oxide-coated polyamide monofilament yarns were characterized by performing physical, electrical, optical, and morphological investigations. The lowest sheet resistance was measured from seven-layer graphene-coated polyamide monofilament yarn as 3.09 k omega/sq. Moreover, it was measured that 90 degrees and 180 degrees bent seven-layer graphene-coated polyamide monofilament yarns had 3.57 and 3.81 k omega/sq sheet resistance, respectively. Additionally, while PA monofilament yarn has 73.5% transmittance at 550 nm; seven-layer GO and seven-layer graphene have 18.8 and 4.5%, respectively, as expected. On the other hand, the contact angle increased with the reduction of graphene oxide layer on monofilament yarn. The fabricated graphene-coated polyamide monofilament yarns can be used in electrotextiles, solar cells, sensors, and OLEDs as fiber-shaped flexible electrodes.
  • Küçük Resim Yok
    Öğe
    Reduction of graphene oxide thin films using a stepwise thermal annealing assisted by L-ascorbic acid
    (Elsevier Science Sa, 2019) Tas, Mahmut; Altin, Yasin; Bedeloğlu, Ayşe
    In this study, an environmental and economical multi-step reduction method has been developed for the reduction of graphene oxide thin films more efficiently. Within the scope of the method, the graphene oxide films produced were subjected to the process of chemical reduction with L-ascorbic acid (Vitamin C) as the first step and then to the process of thermal reduction that can be performed through progressive thermal annealing without any need for special atmospheric conditions as the second step. In addition, the impact of L-ascorbic acid solutions with different molarities (5, 25, 50, 100, 200, 400 and 800 mM) on the conductivity of the reduced graphene oxide produced was examined and compared with hydrazine hydrate for the same concentrations. Besides, the impact of different thermal annealing temperatures (70 degrees C, 120 degrees C and 300 degrees C) and the process of intermediate drying on the conductivity of the reduced graphene oxide thin films were investigated. The results show that the graphene oxide thin films were best reduced through 800 mM L-ascorbic acid and progressive thermal annealing combination (at 70 degrees C, 120 degrees C and 300 degrees C respectively) and that 13.2 k Omega/sq. surface resistivity was achieved and that the intermediate heating at 120 degrees C made at least 10% positive contribution to this.
  • Küçük Resim Yok
    Öğe
    Solution-processed transparent conducting electrodes with graphene, silver nanowires and PEDOT:PSS as alternative to ITO
    (Elsevier Science Sa, 2016) Altin, Yasin; Tas, Mahmut; Borazan, Ismail; Demir, Ali; Bedeloğlu, Ayşe
    Novel transparent electrodes, including graphene, silver nanowires (AgNWs) and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) serving as the low-cost and flexible alternative to indium tin oxide (ITO) are of interest to the organic electronic industry in recent years. In this paper, transparent, flexible and conductive nanocomposite electrodes were fabricated by using different combinations of graphene, AgNWs, PEDOT:PSS materials via spin coating technique. Optical, morphological and electrical properties of solution-processed electrodes were characterized. Transparent conductive electrode (TCE) based on PEDOT:PSS/AgNW/graphene construction exhibited 216.67 Omega/sq sheet resistance with-83% transparency. Additionally, after 100 cycles of bending, the sheet resistance of PEDOT:PSS/AgNW/graphene electrode on the flexible polyethylene terephthalate (PET) substrate was found to be about 223 Omega/sq, while conventional ITO-coated PET substrate exhibited 83,050 Omega/sq resistance, which was about 400 times more than that of resistance before bending. Optical and electrical measurements showed that obtained nanocomposite electrodes may be promising alternatives to ITO to be used in flexible optoelectronic devices. (C) 2016 Elsevier B.V. All rights reserved.