Browsing by Author "Şentürk, Ufuk"

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Bir fosfor dönüşümlü beyaz led paketi
(Türk Patent ve Marka Kurumu, 2020) Demir, Mustafa Muammer; Güner, Tuğrul; Şentürk, Ufuk
Bu buluş bir fosfor dönüşümlü beyaz LED paketi ile, özellikle fosfor kullanım miktarını azaltmayı ve ışık rengi sıcaklığının ayarlanmasını sağlayan cam küre formunda optik elemanlar içeren bir fosfor dönüşümlü beyaz LED paketi ile ilgilidir.
Characterization and expansion behaviour of perlite
(Izmir Institute of Technology, 2016-07) Gül, Dilek; Şentürk, Ufuk; Demir, Mustafa Muammer
Perlite is a silica-based organic glass. When it is instantaneously heated, it shows expansion by releasing a certain amount of water. Approximately 70% of perlite reserves in the world are found in Turkey. The porous structure of expanded perlite leads to use this material in many industrial areas; therefore, this is highly advantageous from the economic standpoint. In this study, the expansion behaviours of perlite samples, which were taken from İzmir (Bergama Mine), Kütahya (Avdan Mine), and Erzincan (Mollatepe Mine) were both characterized and investigated in the laboratory. The instrumentation techniques, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Optic Microscope were used to characterize the perlite. The determination of the amorphous and crystal structure of perlite, the chemical composition of perlite, the measurement of loss of mass, the morphological characterization of perlite, and the form of raw and expanded perlite samples were obtained by XRD, XRF, TGA, SEM and Optic Microscopy, respectively. Four different heat treatments as 600 ˚C, 800 ˚C , 900 ˚C and 1000 ˚C and four different sizes 400-500 μm, 315-400 μm, 200-315 μm and 160-200 μm were conducted in the laboratory and the their bulk volumes and densities were compared before and after heat treatment. The perlite sample from Bergama 01 showed the largest expansion in all samples. As results of the analyses, the amount of crystal and water release in the perlite which had an influence on expansion process were consistent with the literature. The analyses were conducted until 1000 ˚C due to forming sinter above softening temperature. Additionally, the expanded perlite samples in the industrial furnace were compared with the expanded perlite samples in the laboratory more porous structure was observed. As a conclusion, the perlite samples from the different regions of Turkey were characterized and analyzed in terms of expansion behaviour in this study.
Investigation od the surfaces of dealkalized and wethered float glass
(Izmir Institute of Technology, 2016-07) Seziş, Ümmügülsüm; Şentürk, Ufuk; Zareie, Hadi M.
In this study, the effects of surface dealkalization due to SO2 or SO3 gas treatment of commercial soda lime silica float glass on the weathering behavior was investigated. Only the air side of the glass was studied. The changes in the glass surface were analyzed for their topography and structure. The surface topography was studied using atomic force microscopy (AFM). The findings show the formation of micro-cracks on the surfaces of as-produced glass surfaces when treated with sulfur gas. The weathered surfaces show an increased roughness with increased weathering. The surface structure was investigated using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, specular reflectance infrared (SR-IR) spectroscopy, and micro-Raman spectroscopy techniques The results of the studies, ATR-FTIR and SR-IR techniques provided a reasonable insight on the surface structural changes while micro-Raman spectroscopy failed to detects these differences. ATR-FTIR and SR-IR the overall comparison of the effects of peak position with and without sulfur gas treatment suggests a wide scatter within each group. This scatter implies that sulfur gas treatment does not have any statistically significant effects. Also, the change in peak positions are no clear evidence of a decreasing or increasing peak position as the weathering period is increased by weathering effect. Additionally, the calculated penetration depth is found to be ~0,6-1 μm for these techniques. Namely, the penetration depth greater than the surface modification was observed. The results showed was not significantly affected by the surface dealkalization and weathering reactions. The analysis of the surface topography using AFM technique showed the formation of micro-cracks like features on the surfaces of sulfur treated glasses. These features are thought to occur under the sodium sulfate salt residue that is formed during the high temperature dealkalization reactions on the surface. Results sample preparation, i.e. cleaning, was found to have a significant effect on the surface properties. A method has been developed to minimize the effects of sample preparation on the surface of the glass.
Investigation of biological and organic molecular assembly
(Izmir Institute of Technology, 2016-07) Mendirek, Gizem; Zareie, Hadi; Şentürk, Ufuk
Self-assembled monolayers (SAMs) are well-defined and ordered films of molecules that are spontaneously deposited on a surface. By designing molecules with desired head groups for binding specific surfaces, such SAMs can be interesting for a lot of applications such as molecular electronics and biosensors. In this study, SAMs of organic and biological molecules have been investigated. SAMs of thiophenol, a newly designed Schiff base (E)-4-((4-(phenylethynyl)benzylidene)amino)benzenethiol molecule, a newly designed 4-(4,7-di(thiophen-2-yl)-1H-benzo[d]imidazol-2-yl)benzaldehyde monomer were studied. Mixed SAMs of biotin and streptavidin and graphite binding peptide assemblies are also studied. SAMs were prepared by solution phase method. The gold surface and graphite surface were used as a substrate, because they are both chemically inert to oxidation and flat surfaces. Scanning Tunneling Microscope (STM) was the main experimental technique used here. It was used to obtain images of SAMs at an atomic scale. Scanning Tunneling Spectroscopy (STS) was used to provide information about the local density of states of molecules. Spectroscopic Ellipsometry (SE) was used to measure the monolayer thickness. Contact Angle Measurements was used to determine the surface wettability. X-Ray Photoelectron Spectroscopy (XPS) was used to analyze surface chemistry of SAMs. Surface-Enhanced Raman Spectroscopy (SERS) was used to identify the molecules on a surface.