Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Research Project Üstüniletken magnezyum borür (MgB2) tellerinin yüksek akım ve yüksek manyetik alan uygulamaları için geliştirilmesi(2008) Okur, Salih; Tarhan, Enver; Büyükköse, Serkan; Özyüzer, Lütfi; Tanoğlu, Metin; Emirdağ, Mehtap[No Abstract Available]Research Project Nanokompozit malzemelerin polimer ve tabakalı kil yapılardan geliştirilmesi ve karakterizasyonu(2009) Tanoğlu, Metin; Okur, Salih[No Abstract Available]Article Citation - WoS: 11Citation - Scopus: 13Effect of Cnt Incorporation on Pan/Ppy Nanofibers Synthesized by Electrospinning Method(TÜBİTAK, 2020) İnce Yardımcı, Atike; Tanoğlu, Metin; Yılmaz, Selahattin; Selamet, YusufIn this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution. The functionalized CNTs were well dispersed within the nanofibers and aligned along the direction of nanofibers. Therefore, beads formation on nanofibers decreased. The impedance of the nanofibers was found to decrease with the PPy content and CNT addition. These nanofibers had a great potential to be used as an electrochemical actuator or a tissue engineering scaffold.Article Citation - WoS: 17Citation - Scopus: 17Monitoring the Doping and Diffusion Characteristics of Mn Dopants in Cesium Lead Halide Perovskites(American Chemical Society, 2018) Güner, Tuğrul; Akbalı, Barış; Özcan, Mehmet; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, HasanCesium lead perovskites, in the form of CsPbX3 or Cs4PbX6, have been widely used for various optoelectronic applications due to their exceptionally good optical properties. In this study, the effect of Mn doping on the structural and optical properties of cesium lead halide perovskite crystals are investigated from both experimental and theoretical points of view. It is found that adding MnCl2 during the synthesis not only leads to a Mn-driven structural phase transition from Cs4PbBr6 to CsPbCl3 but also triggers the Br- to Cl- halide exchange. On the other hand, it is observed that, under UV illumination, the color of Mn-doped crystals changes from orange to blue in approximately 195 h. While the intensity of Mn-originated photoluminescence emission exponentially decays in time, the intensity of CsPbCl3-originated emission remains unchanged. In addition, diffusive motion of Mn ions results in both a growing population of MnO2 at the surface and transition of the host into a cesium-rich Cs4PbCl6 phase.Article Citation - WoS: 15Citation - Scopus: 14Development of Electrically Conductive and Anisotropic Gel-Coat Systems Using Cnts(Elsevier Ltd., 2013) İnce Yardımcı, Atike; Tanoğlu, Metin; Selamet, YusufElectrical conductivity of an unsaturated thermoset polyester based gel-coat system containing 0.05 wt.% of carbon nanotubes (CNTs) was investigated. The CNTs used were synthesized by chemical vapor deposition method by methane decomposition and Raman characterization showed that they were mostly single walled and high quality. To disperse CNTs in the gel-coat resin, 3-roll milling technique was used. It was found that as the CNTs are added to gel-coat system, resistivity value decreases significantly while neat gel-coat showed a high resistivity. By the application of an AC electrical field during curing process, it was attempted to align CNTs in the gel-coat resin and an electrically anisotropic polymer was obtained. © 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 12A Microstructural Study of Surface Hydration on a Magnesia Refractory(Elsevier Ltd., 2010) Sütçü, Mücahit; Akkurt, Sedat; Okur, SalihHydration of the surface of a periclase refractory was studied in a controlled humidity atmosphere (92% relative humidity) at 26 °C for up to 92 h. The effect of humidity on the specimens was examined using a scanning probe microscope (SPM) and a scanning electron microscope (SEM), which showed that the degree of hydration was noticeably less in the intergranular bond phase compared to the periclase crystallites. The SPM study indicated significant growth of hydrates on the refractory grain surface. Growth rate of the hydrate layer was least on (0 0 1) orientation, higher for the (1 0 3) orientation, and highest for the (1 0 1) oriented grain. The rate of loss of refractory phases by hydration on a (1 0 1) oriented grain was 4.53 nm/h. This material loss may be insignificant for a bulk brick, but is a serious threat for a magnesia castable consisting of fine magnesia powder due to large surface area exposed to humidity or water itself. © 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 17Influence of Crystallographic Orientation on Hydration of Mgo Single Crystals(Elsevier Ltd., 2009) Sütçü, Mücahit; Akkurt, Sedat; Okur, SalihThis study has been performed in order to find out the influence of crystallographic orientation on hydration of MgO single crystal substrates with (1 0 0)-, (1 1 0)-, and (1 1 1)-orientations. The samples were left in a hydration chamber with an 88% relative humidity for 18 h at room temperature. The effect of humidity on the samples was examined by scanning probe microscope (SPM) and scanning electron microscope (SEM) which showed that the degree of hydration was noticeably influenced by the crystallographic orientation. It was found that the MgO with (1 1 1)-orientation has the highest tendency to hydrate than the other orientations. Second most affected sample was (1 1 0) crystal. Loss of MgO on the surface by hydration is most severe when the crystal is oriented in (1 1 1) plane with the maximum hydrate layer thickness of 174 nm after 18 h of exposure.Article Citation - WoS: 38Citation - Scopus: 42Layered Clay/Epoxy Nanocomposites: Thermomechanical, Flame Retardancy, and Optical Properties(John Wiley and Sons Inc., 2008) Kaya, Elçin; Tanoğlu, Metin; Okur, SalihIn this study, layered clay/polymer nano-composites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ion exchange reaction. In this way, Na+ interlay er cations of the clay is exchanged with onium cation of the surfactant that turns the hydrophilic clays (MMT) to organophilic (OMMT) characteristics. Thermal analysis results revealed that the glass transition temperature (Tg) and the dynamic mechanical properties including the storage and loss modulus of the neat epoxy resin increases by the incorporation of clay particles. It was also found that flame resistance of the polymer is improved by the addition of the clay particles.Article Citation - WoS: 3Citation - Scopus: 3Thermostable Tensoresistors of Co Doped Gasb-Fega1.3 Eutectic Composites(Elsevier Ltd., 2008) Rahimov, R. N.; Khalilova, A. A.; Arasly, D. H.; Aliyev, M. I.; Tanoğlu, Metin; Özyüzer, LütfiThe microstructure and tensoresistive properties of GaSb-FeGa1.3 eutectic composites doped with 0.1% Co have been investigated. It was found that the Co impurity atoms mainly accumulate in the metallic inclusions. The length of the inclusions in GaSb-FeGa1.3〈Co〉 was measured to be about half of those in undoped GaSb-FeGa1.3 eutectics. The tensometric characteristics of gauges based on GaSb-FeGa1.3〈Co〉 have been found to be more thermostable than undoped samples. © 2008 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 11Electrical and Mechanical Properties of Superconducting Mgb2/Mg Metal Matrix Composites(IOP Publishing Ltd., 2006) Eğilmez, Mehmet; Özyüzer, Lütfi; Tanoğlu, Metin; Okur, Salih; Kamer, Orhan; Öner, YıldırhanMgB2/Mg composites were prepared using a metal matrix composite fabrication method that offers the potential to produce superconducting wires as an alternative approach to the powder in tube process. To obtain composites, MgB2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical die under the pressure of 0.5 and 1.0GPa for two hours at various temperatures. The x-ray diffraction technique was used for phase identification. Temperature dependence of resistivity and magnetization measurements were carried out to determine superconducting properties. The effects of composite fabrication temperature and the addition of the Mg on the mechanical properties of MgB2/Mg composites were investigated. For this purpose, the compressive mechanical testing was performed to measure the elastic modulus and fracture strength values of the composites. It was found that the relative weight fraction of the Mg and the fabrication conditions of the composites have considerable effect on the superconducting and mechanical properties of the composites.