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  • Küçük Resim
    Öğe
    Atomization and combustion behavior of nanofuel droplets containing perovskite-type nanoparticles
    (Elsevier Ltd, 2023) Küçükosman, Rıdvan; Akçay, Aleyna; Yontar, Ahmet Alper; Ünlü, Cumhur Gökhan; Ocakoglu, Kasım
    Metal and metal oxide nanoparticles (NPs) are promising agents for reducing energy consumption and pollution in applications where combustion power generation is provided. This study focuses on the production of new generation perovskite-type metal oxide NPs with enhanced catalytic activity customized for combustion and investigation of their catalytic performance for gasoline. The droplet scale combustion experiments were carried out at ambient temperature, atmospheric pressure and under normal gravity, the experimental processes were recorded with an optical system consisting of a high-speed camera and a thermal camera with a spectral range of 7.5–14 ?m, and the combustion and atomization behavior of the nanofuel droplets were characterized. Perovskite-type NPs were produced by sol-gel technique in varying stoichiometric ratios (LaMnO3, La1- XNdXMnO3, La1-XBaXMnO3, Nd1-XBaXMnO3, La0.5NdXBa0.5-XMnO3, x = 0, 0.3) to confirm their catalytic activity’s effect on gasoline droplets’ combustion behavior. Structural characterization of the obtained five different NPs was carried out by SEM and XRD techniques. Chemical analysis, surface area measurements, and spectral properties of the samples were determined by XPS, BET, and UV–Vis spectroscopy, respectively. The results showed that all perovskite-type NPs have particle size range of 25–40 nm. La0.7Nd0.3MnO3 NPs had the highest oxygen adsorption ability and La0.5Nd0.3Ba0.2MnO3 NPs had the largest surface area (393.4898 m2 /g). Perovskite type NPs tended to increase ignition delay and extinction times. The maximum flame temperature of fuel droplets loaded with La0.5Nd0.3Ba0.2MnO3 NPs was 469 ?C. This temperature was 274 ?C higher than the maximum flame temperature of the pure gasoline droplet. The outcomes demonstrated that, with the right catalyst design, perovskite-type NPs can perform better as powerful oxidizers and high energy combustion catalysts.
  • Küçük Resim
    Öğe
    Investigation of graphene-coated Ag/AgCl electrode performance in surface electromyography measurement
    (Elsevier, 2022) Alcan, Veysel; Harputlu, Ersan; Ünlü, Cumhur Gökhan; Ocakoğlu, Kasım; Zinnuroğlu, Murat
    Conventional silver-silver chloride (Ag/AgCl) electrodes are widely used for recording surface electromyography (sEMG) with a conductive gel. However, for long-term sEMG recording, the gel has some disadvantages that cause high impedance. Therefore, the dry electrodes have been alternatively purposed to overcome these disadvantages. Recently, the nanomaterial-based dry electrodes have been developed for long term electrophysiological signal recording. In the present study, we aimed to develop a graphene-coated Ag/AgCl electrode for long-term recording. We transferred single layer graphene (SLG) on the Ag/AgCl electrode surface by using chemical vapor deposition and confirmed this process by Raman scattering spectroscopy and scanning electron microscopy. We then compared the graphene-coated Ag/AgCl and conventional Ag/AgCl electrodes by evaluating median motor nerve conduction studies (mNCS) and their impedance. The charge transfer resistance (Rct) for the Ag/AgCl electrode (4170 ?) was much higher than graphene-coated Ag/AgCl electrode (Rct = 24.6 ?). For median mNCS measurements without gel, the graphene-coated Ag/AgCl electrode provided a better amplitude of distal and proximal compound muscle action potential (28.3 mV and 25.8 mV, respectively) than the Ag/AgCl electrode (21.8 mV and 20.9 mV, respectively). Consequently, the present study suggests promising results in terms of the usability of graphene-coated Ag/AgCl electrodes for long-term monitoring and wearable systems applications of sEMG. In future studies, we aim to investigate clinical applicability of graphene-coated sEMG electrodes that include extended clinical settings and larger study population.