Yazar "Polat, Yusuf" seçeneğine göre listele

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    Centrifugally spun hydroxyapatite/carbon composite nanofiber scaffolds for bone tissue engineering
    (Iop Publishing Ltd, 2024) Akgul, Yasin; Stojanovska, Elena; Calisir, Mehmet Durmus; Polat, Yusuf; Kilic, Ali
    In recent years, advancements in tissue engineering have demonstrated the potential to expedite bone matrix formation, leading to shorter recovery times and decreased clinical challenges compared to conventional methods. Therefore, this study aims to develop composite carbon nanofibers (CNFs) integrated with nano-hydroxyapatite (nHA) particles as scaffolds for bone tissue engineering applications. A key strategy in achieving this objective involves harnessing nanofibrous structures, which offer a high surface area, coupled with nHA particles expected to accelerate bone regeneration and enhance biological activity. To realize this, polyacrylonitrile (PAN)/nHA nanofibers were fabricated using the centrifugal spinning (C-Spin) technique and subsequently carbonized to yield CNF/nHA composite structures. Scanning Electron Microscopy (SEM) confirmed C-Spin as a suitable method for PAN and CNF nanofiber production, with nHA particles uniformly dispersed throughout the nanofibrous structure. Carbonization resulted in reduced fiber diameter due to thermal decomposition and shrinkage of PAN molecules during the process. Furthermore, the incorporation of nHA particles into PAN lowered the stabilization temperature (by 5 degrees C-20 degrees C). Tensile tests revealed that PAN samples experienced an approximately 80% increase in ultimate tensile strength and a 187% increase in modulus with a 5 wt.% nHA loading. However, following carbonization, CNF samples exhibited a 50% decrease in strength compared to PAN samples. Additionally, the addition of nHA into CNF improved the graphitic structure. The incorporation of nHA particles into the spinning solution represents a viable strategy for enhancing CNF bioactivity.
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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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    Mechanical and dynamic mechanical thermal properties of ensete fiber/woven glass fiber fabric hybrid composites
    (Elsevier Sci Ltd, 2021) Negawo, Tolera A.; Polat, Yusuf; Akgul, Yasin; Kilic, Ali; Jawaid, M.
    This study aimed to identify the effects of the stacking sequences on mechanical and dynamic mechanical properties of ensete/glass hybrid composites. The composites were fabricated by using 4 layers of carded ensete web and woven glass fabric by Vacuum-assisted resin transfer molding method. Mechanical and dynamic mechanical properties of hybrid composites were characterized. The test results showed that hybridization of ensete web with glass woven fabrics enhanced the mechanical properties of ensete composites. The morphology of fractured samples reveals that higher glass fibers pullout than ensete fibers in hybrid composites. The flexural properties also increased when glass fiber hybridized with ensete fiber and the optimum values obtained when it is used as the skin of the composite.The composites stacked as glass-ensete-glass (GEEG) showed higher storage modulus as compared to glass-ensete (GGEE) ensete composites whereas loss modulus of the composites reinforced with glass fiber exhibited the maximum value of 407 MPa and the height of the damping curve decreased in GEEG composite. Experimental studies showed that the ensete/glass fiber hybrid polyester composites can be used as load-bearing structures and components where high resistance to deformations and thermal stability is necessary.
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    Solution blown nanofibrous air filters modified with glass microparticles
    (Sage Publications Inc, 2021) Polat, Yusuf; Calisir, Mehmet; Gungor, Melike; Sagirli, Merve N.; Atakan, Raziye; Akgul, Yasin; Demir, Ali
    High-pressure drop and lower dust holding capacity reduce the performance of nanofibrous air filters. For that reason, this study was carried out to form filters with high-quality factor and high dust holding capacity, thanks to the glass particle additives. In this study, as an approach to such modifications, fluffy nanofiber webs were produced via solution blowing. Polyamide 6 (PA6) was chosen as the base for the nanofibrous mats, where glass microparticles were embedded as an additive to reduce web solidity. The effects of glass microparticle embedding on the filtration performance and pressure drop of the mats were investigated. SEM analysis was performed to analyze nanofiber diameter and morphology. Also, the barrier properties of samples were examined by air filtration and air permeability tests. Findings showed that the addition of glass particles did not alter fiber morphology significantly. However, lowering the pressure drop resulted in higher air permeability and better filtration performance in terms of the quality factor. Glass particles embedded composite samples exhibited a higher quality factor compared to the neat PA6 sample, and the PA6 + 5%GP sample has the highest quality factor value around 0.43. The filtration efficiency of this sample was 99.97% at an expense of 187.3 Pa pressure drop. The obtained enhancement was conducted to the lower solidity of composite webs which was 36% lower for the PA6 + 5%GP sample.