Yazar "Ozkan, Ali Osman" seçeneğine göre listele

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    20 kHz Unipolar Pulsed Field Surface Flashover Characteristics of Polymer Nanocomposites in Subatmospheric Pressure Helium
    (IEEE, 2014) Ozkan, Ali Osman; Ozcan, Muciz; Auad, Maria; Kirkici, Hulya
    The high performance electrical insulation materials and structures in power systems must be free from unwanted and unpredictable dielectric breakdown through the insulation as well as over the dielectric surfaces, and along the interfaces. Surface flashover, another form of breakdown, usually occurs over the surface of insulator between the energized electrodes, and is usually triggered by the stresses caused by the field at the insulator/electrode/ambient interfaces. Studies of surface flashover at sub-atmospheric pressures are specifically important for aerospace systems and vehicles operating in this regime. In this work we present surface flashover characteristics of two different polymer nanodielectrics filled with either TiO2 or Al2O3 nanoparticles. A 20 kHz pulsed, unipolar field is applied across the electrodes positioned on top of the sample with a 0.5 cm gap distance in sub-atmospheric pressure helium. The plasma characteristics, such as voltage, current and optical emission waveforms are recorded. Breakdown voltage as a function of pressure, frequency and duty cycle of the applied field is presented. Differences between the surface breakdown of TiO2 and Al2O3 filled samples are studied and results are presented. Furthermore, frame-by-frame images of the optical emission during the breakdown events are recorded and presented.
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    The Influence of Al2O3 and TiO2 Additives on the Electrical Resistivity of Epoxy Resin-Based Composites at Low Temperature
    (Wiley-V C H Verlag Gmbh, 2019) Eker, Yasin Ramazan; Ozcan, Muciz; Ozkan, Ali Osman; Kırıkçı, Hülya
    Electrical insulation is a major security problem in aerospace applications where temperature can reach relatively low values. Epoxy resins are well known as easily formable dielectric materials and can be used to prepare complex insulator parts. In this study, the electrical performance of bisphenol A/epichlorohydrin epoxy resin matrix-based nanocomposites containing 1, 3, or 6 wt% titanium oxide (TiO2) or aluminium oxide (Al2O3) nanofillers are investigated. Composites are characterized with thermogravimetric analysis, scanning electron microscopy-coupled electron dispersive spectroscopy, and confocal Raman spectroscopy. Furthermore, the role of additives and their ratio on the resistivity performance of the composites are evaluated from 77 to 500 K by applying a direct current voltage from 1 to 20 V. It is observed that the electrical properties of the matrix are directly influencing the insulation performance of the nanocomposite. For example, the abrupt decrease at 370 K of the positive temperature coefficient of the resin for all nanocomposites. It is found that the most resistive composite contains 3 wt% TiO2 nanoparticles with a value above 3.7.10(10) omega from 77 to 370 K at 20 V. As a result, this work gives information on to the choice of appropriate insulator materials in extreme working conditions.