Yazar "Eskizeybek, V." seçeneğine göre listele
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Öğe EVALUATING INTERFACIAL PERFORMANCE OF CARBON-EPOXY COMPOSITES BY FIBER BUNDLE TESTS: THE IMPACT OF NANOFILLER DIMENSION AND SURFACE CHEMISTRY(International Committee on Composite Materials, 2023) Sas, H.S.; Özbilen, M.; Eskizeybek, V.[No abstract available]Öğe Fast production of ZnO nanorods by arc discharge in de-ionized water and applications in dye-sensitized solar cells(Elsevier Science Sa, 2014) Sonmezoglu, S.; Eskizeybek, V.; Toumiat, A.; Avci, A.Fast production of the ZnO nanorods by bottom up approach using arc discharge method in de-ionized water was carried out. Structural analysis showed that the obtained ZnO powder exhibits crystallize in the hexagonal wurtzite structure with (101) preferential orientation. Furthermore, transmission electron microscopy observations showed that rod-like structure is the abundant form with a bimodial grain size distribution around 10 and 30 nm. Optical characterization of the as-synthesized ZnO nanorods revealed the existence of the two absorption and photoluminescence (PL) bands both located at UV spectral region attributed to the two grain size distributions. In addition, the two additional visible bands PL spectrum located at 430 and 492 nm are attributed the interstitial zinc and oxygen vacancies; respectively. Dye sensitized solar cells (DSSCs) were successfully produced via different ruthenium based dyes and ferrocene liquid electrolyte by using of as synthesized ZnO nanorods modified photoanodes. It has been found that DSSCs made with N719 dye is the most efficient with photoconversion of approximately 7% compared to the other dyes. Such nanorod form of the ZnO nanostructures with ruthenium dyes resulted in significant improvements of the device performance in terms of electron transportation and UV light absorption. This work would explore feasible routes to synthesize efficient metal-oxide nanostructures for opto-electronic or other related applications. Published by Elsevier B. V.Öğe Optical Constants of Thin Film Prepared by the Cd(OH)2 Nanowires Synthesized Using the Arc Discharge Method(Amer Scientific Publishers, 2014) Akin, U.; Safak, H.; Eskizeybek, V.; Avci, A.; Yuksel, O. F.The optical constants of thin film prepared by cadmium hydroxide nanoparticles spray coated on the glass substrate held about at 100 degrees C temperature have been investigated using the optical transmission and reflection spectra. The transmission spectrum exhibits that the film has a high transparency (similar to 80%) at the infrared region. From standard optical analysis, direct band gap energy of Cd(OH)(2) was found as 3.13 eV, and also, it was seen that the calculated refractive index varies between 1.65 and 2.15 throughout the spectral region considered. The dispersion parameters such as oscillator energy, dispersion energy, and static and high frequency refractive index were determined in regard to the Wemple DiDomenico single oscillator model. Finally, some dielectric parameters of material such as relaxation time, dissipation (loss) factor, volume and surface energy loss functions and optical conductivity were calculated.Öğe Void entrapment into air pathways in partially impregnated prepregs in the Out-Of-Autoclave process(DEStech Publications, 2014) Cender, T.A.; Eskizeybek, V.; J, J.; Gangloff; Advani, S.G.Out-of-Autoclave (OOA) thermoset prepreg manufacturing of aerospace quality parts is performed under low pressures, which makes it more susceptible to void formation and growth as compared to high pressure autoclave processing. Thus, OOA prepregs are intentionally partially impregnated with resin, with the goal to distribute the resin such that a completely connected network of empty channels is formed in the initial material. This network serves as pathways for evacuation of gases entrapped in the laminate before consolidation and cure. This work investigates how mechanically entrapped air can be removed from partially impregnated OOA prepreg laminates before oven curing. First, a model of void evacuation time is derived to estimate the time necessary to apply vacuum to remove air from within the laminate before placing it in the oven. Next, a flow visualization technique is presented where the resin film of the partially impregnated OOA prepreg is pressed into the fabric, while recording the resin flow on the dry side. This quantifies the degree of resin impregnation with processing time. A relationship between degree of resin impregnation and gas permeability is presented which influences the evacuation time necessary to remove air from the system. A large panel (1.2m long) was fabricated in which low and high evacuation times were employed based on the model physics. The void content was quantified along the length via sectioning/polishing/image analysis and shown to have a void content of 1%. The results of this study should prove useful to develop optimal vacuum application times and temperature and pressure cycles for void reduction and removal during processing of prepregs.
