Yazar "Calisir, Mehmet D." seçeneğine göre listele

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    Centrifugally spun silica (SiO2) nanofibers for high-temperature air filtration
    (Taylor & Francis Inc, 2019) Tepekiran, Beyza Nur; Calisir, Mehmet D.; Polat, Yusuf; Akgul, Yasin; Kilic, Ali
    In this study, silica-based nanofibers were produced via centrifugal spinning (C-spin) and subsequent calcination. The produced heat resistant media was challenged with NaCl nanoparticles to investigate their filtration performance. To obtain inorganic SiO2 nanofibers, C-spun organic PVP-TEOS nanofibers were calcinated at 300-600 degrees C. Effects of solution concentration and calcination temperature on crystallinity, morphology and air filtration performance of nanofibers were investigated. Scanning electron microscopy (SEM) analysis was performed to analyze fiber diameter and morphology of nanofibrous webs. Differential thermal analysis (DTA) was realized for the thermal behavior of samples. Moreover, X-ray diffraction (XRD) and Fourier transform infrared spectra (FTIR) analysis were realized for further characterization. In addition to the chemical and morphological analysis, the ductility of the samples was investigated via tensile tests. Finally, calcinated webs were challenged with 0.4 mu m salt particles to analyze their filtration performance. The calcinated 5 wt% TEOS/PVP silica nanofiber webs were more brittle due to three times lower precursor content. Therefore, flexibility (percent elongation) of 15 wt%TEOS/PVP sample was nearly five times higher than 5 wt%TEOS/PVP sample. The calcinated 15 wt%TEOS/PVP sample showed the highest filtration performance among all the silica nanofibers. The average fiber diameter of the optimized web was found to be the lowest, which is around 521 +/- 308 nm, which resulted in enhanced filtration efficiency around 75.89%. Copyright (c) 2019 American Association for Aerosol Research
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    Clogging performance of micro/nanofibrous laminated composite air filter media
    (Sage Publications Inc, 2022) Calisir, Mehmet D.; Gungor, Melike; Toptas, Ali; Donmez, Utkay; Kilic, Ali; Karabuga, Semistan
    The performance of fibrous filter media relies on factors such as particle capture efficiency, pressure drop and clogging time. Fiber diameter, porosity and packing density are important web-based factors to improve final filtration performance. In this study, composite nonwoven webs were produced using spunbonded, meltblown and electroblown mats to obtain filter media with different fiber diameter, porosity and packing density. Such a layered composite approach caused huge differences in porosity and packing density, which resulted with improved clogging performance. The average fiber diameter was found to be 65 +/- 19.4 nm for electroblown layer (N), while that was 1.17 +/- 0.38 mu m for meltblown (M) and 17.64 +/- 2.65 mu m for spunbond (S) layers. NM (nanofiber+meltblown) configuration provided 12-13% lower mean flow pore size, which resulted in faster clogging compared to NS (nanofiber + spunbond) mats. The thicker nanofibrous layer resulted in lower pore size and quality factor. Additionally, the composite samples showed a faster-rising pressure drop than the thick microfibrous mats due to smaller pores that clogged quickly. It was also shown that nanofiber coating causes a linear increase in pressure drop with dust loading, while microfibrous samples exhibited smooth plateau and linear increase after clogging point. Nanofiber layer facilitates cake formation which causes more difficult airflow, and lower dust holding capacity. Among the layered composite mats, the NM configurations were found to be more advantageous due to higher initial filtration efficiency and almost similar dust loading performance.
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    Enhancing filtration performance of submicron particle filter media through bimodal structural design
    (Wiley, 2024) Toptas, Ali; Calisir, Mehmet D.; Gungor, Melike; Kilic, Ali
    Depth filtration is a widely utilized mechanism for submicron aerosol filtration using disposable filter cartridges and facemasks. The filter media should be carefully engineered to reach high filtration efficiency and dust-loading capacity at the expense of a low-pressure drop (Delta P). Filter media with bimodal fiber diameter distribution enhance particle capture by creating small pores with tiny fibers, while microfibers improve airflow, reduce Delta P, and increase the effective filter area for particle retention. In this study, bimodal filters were achieved through the homogeneous distribution or layered use of nanofibers and microfibers. The impact of the bimodal design was explored using fibrous mats produced through melt-blowing, solution-blowing, and electroblowing methods. Keeping the basis weight of filter samples at 30 gsm, using four-layered filters (4L) improved air permeability compared to single-layer samples. The 4L sample exhibited the highest performance, achieving 99.52% efficiency at 148 Pa. Moreover, replacing the melt-blown layer with bimodal mats in the 4L design increased the filtration efficiency to 99.61% keeping Delta P nearly the same. The corona discharge treatment yielded the highest efficiency (99.99%) in the 4BML sample, even after 1 month the efficiency was maintained at 99.90%, highlighting the advantage of bimodal fiber distribution in electret filters.HighlightsFour-layered filter (4L) structures resulted in improved air permeability.Bimodal layer (BL) achieved by adding SB nanofibers into the melt blowing.BL in 4L structure increased the efficiency from 99.52% to 99.61%.Modified BL sample (4BML) provides the highest QF (0.044 Pa-1) after 1 month. Production of the layered bimodal mats in different structural designs and their filtration performance.image
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    Submicron aerosol filtration performance of centrifugally spun nanofibrous polyvinylpyrrolidone media
    (Sage Publications Inc, 2021) Melike, Gungor; Calisir, Mehmet D.; Akgul, Yasin; Selcuk, Sule; Ali, Demir; Kilic, Ali
    In this study, polyvinylpyrrolidone-based nanofibrous air filter media were produced via centrifugal spinning and subsequently stabilized by thermal cross-linking process. Samples were produced using solutions with three different polymer concentrations (5, 10 and 20 wt.%) and three different rotational speeds (4000, 6000 and 8000 r/min). After obtaining the optimum web structure with the lowest average fiber diameter and the most uniform distribution, the webs were later thermally cross-linked in order to stabilize polyvinylpyrrolidone against the degradative effects of water. In addition, the webs were subjected to dissolvability tests to see the efficacy of cross-linking treatment. Morphological, structural and chemical characterizations of the polyvinylpyrrolidone webs were performed by SEM, XRD and FTIR, respectively. Finally, filter efficiency and pressure drop were measured to assess filter performance. The results have shown that the lowest average fiber diameter is obtained at the highest rotational speeds. Subsequent thermal cross-linking treatment has been found to prevent fibers from dissolving in water. The produced water-resistant, environmentally friendly polyvinylpyrrolidone nanofibrous filter media has had a satisfactory filtration performance with a high filter efficiency of 99.995% and a high quality factor of 0.39 mm H2O-1.