Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - Scopus: 1Production and Dispersion of Plasma Functionalized Carbon Nanotubes in Pan Fiber Spinning Solution With Different Surfactants(MMOB Tekstil Mühendisleri Odası, 2022) Kutlu, Bengi; Akşit, Aysun; Özyüzer, Lütfi; Yağmurcukardeş, Nesli; Selamet, YusufIn this study, the distribution of plasma-functionalized multi-walled carbon nanotubes in polyacrylonitrile nanocomposite fibers produced by wet spinning method using different surfactants (Triton-X and sodium dodecyl sulfate) was investigated. Firstly, we produced CNTs by chemical vapor deposition (CVD) technique. Secondly, low-pressure plasma functionalization of CNTs was realized. Finally, nanocomposite polyacrylonitrile fibers doped by CNTs were obtained using wet spinning technique. Properties of produced carbon nanotubes, functionalized carbon nanotubes and nanocomposite polyacrylonitrile fibers were examined by the analyses of chemical composition, surface structure, structural and mechanical properties.Article Study of the Effect of Various Chemical Polishing Treatments on Mbe-Grown Cdte/Gaas (211)b Heterostructures(Sakarya University, 2020) Bilgilisoy, E.; Özçeri, E.; Tarhan, E.A three-inch-diameter high quality CdTe thin film was grown on a GaAs (211)B substrate by molecular beam epitaxy (MBE) in ultra-high vacuum conditions. The CdTe/GaAs (211)B heterostructure was then cut into several sample pieces. A few as-grown sample pieces were subjected to chemical etching solutions which created etch pits on the surface. The scanning electron microscopy images of such samples were used to calculate the etch pit densities on the surface. In addition, several as-grown samples were subjected to chemical polishing treatments under different conditions to quantify the removal of O and Te-O structures from the surface. Atomic force microscopy was used to determine as-grown and polished surface morphology and the polish rate of chemical solutions. A study of the surface stoichiometry and the chemical composition of the as-grown and polished CdTe (211)B surfaces were carried out by using X-ray photoelectron spectroscopy. Bulk structural qualities of the as-grown and polished samples were studied in terms of the vibrational and phonon modes via confocal Raman spectroscopy. From a comparative analyses of the results, the best chemical polishing conditions for the MBE-grown CdTe (211)B heterostructure were determined. © 2020, Sakarya University. All rights reserved.Article Mıknatıssal Saçtırma Sistemi ile Metal Kaplanan Polipropilen Liflerin Antistatik ve Antibakteriyel Özellikleri(TMMOB Tekstil Mühendisleri Odası, 2010) Özyüzer, Lütfi; Meriç, Zeynep; Selamet, Yusuf; Kutlu, Bengi; Cireli, AysunTekstil liflerini modifiye ederek, katma değeri yüksek, fonksiyonel teknik tekstil elde etmek için çeşitli yöntemler kullanılmaktadır. Örneğin, antistatik tekstiller, lifler içerisine iletken parçaçık katkılama ile elde edilebileceği gibi çeyreye kimyasal olarak zarar vermemesi dolayısıyla vakumda mıknatıssal saçtırma ile yüzeyi istenilen metali ince film olarak yüzeye kaplayarak da elde edilebilir. Bu çalışmada çapları 65 fim olan multifilament sentetik polipropilen liflerin yüzeyleri yüksek vakum altında nanometre kalınlığında Cr ve Ag gibi elektriksel iletken metal filmler ile kaplanmış ve elektriksel iletkenlik ve antibakteriyel özellikleri incelenmiştir.Article Citation - WoS: 4The Synthesis of Ferromagnetic La0.75ca0.25mno3 Nanowires by a Sol-Gel Method(National Institute of Optoelectronics, 2010) Atalay, Funda E.; Yağmur, V.; Atalay, Selçuk; Kaya, Harun; Tarı, Süleyman; Avşar, D.In this study, densely packed La0.75Ca0.25MnO3 (LCMO) nanowires were synthesized within a porous anodic aluminum oxide (AAO) template by means of a sol-gel method using nitrate as raw material and ethylene glycol as the chelating agent. It was observed from measurements of hysteresis curves that the magnetic behavior of the LCMO nanowire arrays was strongly dependent on the pH of the solution. As it has been reported that bulk polycrystalline La0.75Ca0.25MnO3 samples have a Curie temperature of 224 K [1], it is interesting to find that nanowires produced at pH 3 show ferromagnetic properties at room temperatureArticle Multicolor Photometric Behavior of the Young Stellar Object V1704 Cygni(Bulgarian Acad Sciences, Inst Astronomy, 2018) Ibryamov, Sunay; Semkov, Evgeni; Peneva, Stoyanka; Karadeniz, UğurResults from BV RI photometric observations of the pre-main sequence star V1704 Cyg collected during the time period from August 2010 to December 2017 are presented. The star is located in the star-forming HII region IC 5070 and it exhibits photometric variability in all optical passbands. After analyzing the obtained data, V1704 Cyg is classified as a classical T Tauri star.Article Citation - WoS: 2Citation - Scopus: 2The Synthesis of Super-Hydrophilic and Hard Mgb2 Coatings as an Alternative To Electroless Nickel Coatings(Slovenska Akademia Vied, 2018) Bülbüll, Ferhat; Güney, M.; Jafarpour, SomaiyehIn this study, we report the electroless deposition using an alternative technique for the fabrication of hard and super-hydrophilic MgB2 films. MgB2 films on AZ91 magnesium alloys were prepared using an electroless bath containing magnesium diboride nanopowders, sodium hypophosphite, sodium succinate, sodium acetate, and dimethyl sulfoxide. The electroless deposition was carried out in a bath kept at a bath temperature of 95 degrees C for 60 min. After deposition, the coated samples were annealed at 300 degrees C for 60 min to investigate crystallization, morphology, and the changes in the hardness and wettability. The phase composition, morphology, the hardness, and the contact angle of produced coatings were studied by X-ray diffractometer, scanning electron microscopy, microhardness tester, and contact angle measurement system, respectively. The coatings exhibited a dense and nodular structure with strong grain connections. As-deposited and annealed MgB2 films showed an orientation with the (101) reflection, and the highest hardness value (500 HV0.01) was obtained from the annealed coating. Both synthesized coatings had a super-hydrophilic surface.Article Citation - WoS: 18Citation - Scopus: 17Cnt Incorporated Polyacrilonitrile/Polypyrrole Nanofibers as Keratinocytes Scaffold(Trans Tech Publications, 2019) İnce Yardımcı, Atike; Aypek, Hande; Öztürk, Özgür; Yılmaz, Selahattin; Özçivici, Engin; Meşe, Gülistan; Selamet, YusufPolypyrrole (PPy) is an attractive scaffold material for tissue engineering with its non-toxic and electrically conductive properties. There has not been enough information about PPy usage in skin tissue engineering. The aim of this study is to investigate biocompatibility of polyacrilonitrile (PAN)/PPy nanofibrous scaffold for human keratinocytes. PAN/PPy bicomponent nanofibers were prepared by electrospinning, in various PPy concentrations and with carbon nanotube (CNT) incorporation. The average diameter of electrospun nanofibers decreased with increasing PPy concentration. Further, agglomerated CNTs caused beads and disordered parts on the surface of nanofibers. Biocompatibility of these PAN/PPy and PAN/PPy/CNT scaffolds were analyzed in vitro. Both scaffolds provided adhesion and proliferation of keratinocytes. Nanofiber diameter did not significantly influence the morphology of cells. However, with increasing number of cells, cells stayed among nanofibers and this affected their shape and size. In this study, we demonstrated that PAN/PPy and PAN/PPy/CNT scaffolds enabled the growth of keratinocytes, showing their biocompatibility.Article Citation - WoS: 2Citation - Scopus: 2Comparison of Photocatalytic Properties of Tio2 Thin Films and Fibers(EDP Sciences, 2016) Özdemir, Mehtap; Kurt, Metin; Özyüzer, Lütfi; Aygün, GülnurEfficiency of solar panels degrades as a result of organic contamination such as airborne particles, bird droppings and leaves. Any foreign object on photovoltaic panels reduces the sunlight entering the absorbing surface of the solar panels. Since this leads to a major problem decreasing in energy production, solar panels should be cleaned. The self-cleaning method can be preferred. There are some methods to clean the surface of solar panels. Among the self-cleaning materials, TiO2 is the most preferable ones because of its powerful photocatalytic properties. In this study, photocatalytic TiO2 were produced in two different nanostructures: nanofibers and thin films. TiO2 nanofibers were successfully produced by electrospinning. TiO2 thin films were fabricated by reactive magnetron sputtering technique. Both TiO2 nanofiber and thin film structures were heat-treated to form TiO2 in anatase phase at 600 °C for 2 h in air. Then, they were evaluated by SEM analyses for morphology, X-ray diffraction (XRD) analyses for phase structures, X-ray photoelectron spectroscopy (XPS) for the chemical state and atomic concentration, and UV-spectrometer for photocatalytic performance. The results indicate that photocatalytic and transmittance properties of TiO2 thin films are better than those of nanofibers. Consequently, TiO2 based thin films exhibit better performance for solar cell applications due to the surface cleanliness.Conference Object Graphene-Based Integrated Electronic, Photonic and Spintronic Circuit(SPIE, 2013) Potasz, P.; Güçlü, Alev Devrim; Özfidan, Işıl; Korkusinski, Marek; Hawrylak, PawelTo create carbon-based nanoscale integrated electronic, photonic, and spintronic circuit one must demonstrate the three functionalities in a single material, graphene quantum dots (GQDs), by engineering lateral size, shape, edges, number of layers and carrier density. We show theoretically that spatial confinement in GQDs opens an energy gap tunable from UV to THz, making GQDs equivalent to semiconductor nanoparticles. When connected to leads, GQDs act as single-electron transistors. The energy gap and absorption spectrum can be tuned from UV to THz by size and edge engineering and by external electric and magnetic fields. The sublattice engineering in, e.g., triangular graphene quantum dots (TGQDs) with zigzag edges generates a finite magnetic moment. The magnetic moment can be controlled by charging, electrical field, and photons. Addition of a single electron to the charge-neutral system destroys the ferromagnetic order, which can be restored by absorption of a photon. This allows for an efficient spin-photon conversion. These results show that graphene quantum dots have potential to fulfill the three functionalities: electronic, photonic, and spintronic, realized with different materials in current integrated circuits, as well as offer new functionalities unique to graphene.Article Fabrication of Bi2212 Single Crystal Bolometer for Detection of Terahertz Waves(Springer Verlag, 2017) Semerci, Tuğçe; Demirhan, Yasemin; Miyakawa, Nobuaki; Wang, Huabing; Özyüzer, LütfiTerahertz (THz) radiation is in powerful region of electromagnetic spectrum because of prosperous application areas yet deficiency still exists about sources and detectors in despite of improvements of the research field in this range. This gap can be filled by focusing on development of THz detectors. Therefore, bolometers were preferred through many detectors due to detection sensitivity above 1 THz. In this study, Bi2Sr2CaCu2O8+δ (Bi2212) single crystals were used to fabricate THz bolometric detector. Bi2212 single crystals were transferred on sapphire substrate by cleavage process and e-beam lithography and ion beam etching were used to fabricate the microchip clean room facilities. Customdesigned cryogenic cryostat was used for a-b axis electrical and THz response measurements with liquid nitrogen cooled system. After electrical measurements, Bi2212 microchips detected the signals using Stefan-Boltzmann Lamp and response time were calculated. This study have shown with our experimental results that Bi2212 single crystals are potential candidates for THz bolometric detectors.