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Article Citation - WoS: 6Citation - Scopus: 6Low-Temperature Thermo Luminescence Studies on Tlins2 Layered Single Crystals(Polish Acad Sciences inst Physics, 2014) Isik, M.; Delice, S.; Gasanly, N. M.Thermoluminescence characteristics of TlInS2 layered single crystals grown by the Bridgman method were investigated in the low temperature range of 10-300 K. The illuminated sample with blue light (approximate to 470 nm) at 10 K was heated at constant heating rate. Curve fitting, initial rise and various heating rate methods were used to determine the activation energy of the trap levels. All applied methods showed good consistency about the presence of five trapping centers located at 14, 19, 350, 420, and 520 meV. Behavior of the TL curve for various heating rates was investigated. Traps distribution has also been studied. The activation energies of the distributed trapping centers were found to be increasing from 14 to 46 meV.Article Citation - WoS: 15Citation - Scopus: 15Deep Traps Distribution in Tlins2 Layered Crystals(Polish Acad Sciences inst Physics, 2009) Isik, M.; Gasanly, N. M.; Ozkan, H.The trap centers and distributions in TlInS2 were studied in the temperature range of 100-300 K by using thermally stimulated currents technique. Experimental evidence was found for the presence of three trapping centers with activation energies 400, 570, and 650 meV. Their capture cross-sections were determined as 6.3 x 10(-16), 2.7 x 10(-12), and 1.8 x 10(-11) cm(2), respectively. It was concluded that in these centers retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of hole traps was revealed from the analysis of the thermally stimulated current data obtained at different light excitation temperatures. This experimental technique provided a value of 800 meV/decade for the trap distribution.Conference Object Citation - WoS: 2Citation - Scopus: 2Morphological Differences and Their Effects on the Mechanical Properties of Titanium Oxides Thin Film Obtained via Anodization Process(Polish Acad Sciences inst Physics, 2016) Sarica, N.; Ozturk, Z. Z.; Bindal, C.; Ucisik, A. H.It is well known that anodization process is helpful for obtaining metallic oxides on the metal surfaces. The advantages of this process are used in this study to obtain rough surfaces consisting of titanium oxides and solid solutions of titanium and oxygen. Two different voltages were applied to a pure titanium foil during two process time periods. In all process conditions, titanium oxide thin films were successfully obtained on the base material. Depending on the duration of the process and the voltages applied, the amount and the sizes of oxide particles were changed. EDX analysis combined with SEM and AFM clearly showed that rough surfaces were obtained. Having rough surfaces would be helpful for bonding to another material. However, in the micro-nano scale it is clear that the inhomogeneous mechanical and chemical properties were obtained, most probably resulting in inhomogeneous crack initiation.Article Analysis of Thermoluminescence Glow Peaks in Β-Irradiated Tlgases Crystals(Polish Acad Sciences inst Physics, 2016) Isik, M.; Yildirim, T.; Gasanly, N. M.Thermoluminescence properties of TlGaSeS layered single crystals were investigated in the temperature range of 280-720 K. Thermoluminescence glow curve exhibited three peaks with maximum temperatures of approximate to 370, 437, and 490 K. Curve fitting, initial rise and peak shape methods were used to determine the activation energies of the trapping centers. All applied methods resulted with energies around 0.82, 0.91, and 0.99 eV. Dose dependence of the thermoluminescence intensity was also examined for the doses in the range of 0.7-457.6 Gy. Peak maximum intensity of the observed peak around 370 K showed an increase up to a certain dose and then a decrease at higher doses. This non-monotonic dose dependence was discussed under the light of a reported model in which different kinds of competition between radiative and nonradiative recombination centers during excitation or heating stages of the thermoluminescence process are explained.Article Compositional Dependence of Optical Modes Frequencies in T1gax< Layered Mixed Crystals (0 ≤ x ≤ 1)(Polish Acad Sciences inst Physics, 2014) Isik, M.; Gasanly, N. M.; Korkmaz, F.The infrared transmittance and Raman scattering spectra in TlGaxIn1-xS2 (0 <= x <= 1) layered mixed crystals grown by the Bridgman method were studied in the frequency ranges of 400-2000 and 250-400 cm(-1), respectively. The bands observed at room temperature in IR transmittance spectra of TlGaxIn1-xS2 were interpreted in terms of multiphonon absorption processes. The dependences of the frequencies of IR- and Raman-active modes on the composition of TlGaxIn1-xS2 mixed crystals were also established. The structural characterization of the mixed crystals was investigated by means of X-ray diffraction measurements and compositional dependence of lattice parameters was revealed.Article Citation - WoS: 1Citation - Scopus: 1Photovoltaic Effect and Space Charge Limited Current Analysis in Tlgate2 Crystals(Polish Acad Sciences inst Physics, 2012) Qasrawi, A. F.; Yaseen, T. R.; Eghbariy, B.; Gasanly, N. M.Anisotropic space charge limited current density analysis and photovoltaic effect in TlGaTe2 single crystals has been investigated. It is shown that, above 330 K, the crystal exhibits intrinsic and extrinsic type of conductivity along (c-axis) and perpendicular (a-axis) to the crystal's axis, respectively. The current density (J) is found to be space charge limited. It is proportional to the square and three halves power of voltage (V) along the a- and c-axis, respectively. Along the a-axis and at sufficiently low electric field values, the activation energy of the current density is found to depend on the one half power of electric field. At high electric fields, the activation energy is field invariant. This behavior is found to be due to the Pool Frenkel effect and due to a trap set located at 0.26 eV, respectively. Along the c-axis the crystal is observed to operate under the Child Langmuir space charge limited regime. TlGaTe2 crystals are found to exhibit photovoltaic properties. The open circuit photovoltage is recorded as a function of illumination intensity at room temperature.Conference Object Citation - WoS: 6Citation - Scopus: 6Influence of Cu and Ni Alloying on the Microstructure and Mechanical Properties of Austempered Ductile Iron Castings(Polish Acad Sciences inst Physics, 2019) Yalcin, M. A.; Cetin, B.; Davut, K.Austempered ductile cast iron (ADI) offers a good combination of high tensile and fatigue strength, good ductility, toughness, wear resistance and damping characteristics, lower density in an economical way. This excellent combination of properties is due to the specific microstructure of ADI; which is composed of spheroidal graphite particles on an ausferritic matrix. The ausferrite consists of acicular ferrite and high carbon retained austenite; which is produced via austempering heat treatment after casting. The alloying additions of Cu or Cu + Ni increases austemperability, which means completely ausferritic structures can be produced on larger cross-sections. In the present study the effect of the alloying additions of Cu and Cu + Ni on mechanical properties and microstructure of ADI was studied. For that purpose, Y-block specimens having a lean composition, 0.8% Cu and 0.8% Cu + 0.4% Ni alloying additions were cast. After austempering treatment, mechanical tests, fractographic and metallographic examinations were performed. The results show that the Cu + Ni alloyed specimen has higher strength and elongation. The lean alloy on the other hand, has the highest nodularity and matrix hardness but the lowest strength and ductility. Those differences in mechanical properties were attributed to the fraction and morphology of the retained austenite regions of the matrix.Conference Object Citation - WoS: 11Citation - Scopus: 12Characterization of Uhwpe-tio2 Composites Produced by Gelation/Crystallization Method(Polish Acad Sciences inst Physics, 2017) Efe, G. Celebi; Bindal, C.; Ucisik, A. H.In this study, ultra-high molecular weight polyethylene (UHMWPE) - TiO2 composites reinforced with TiO2 particles with weight ratios of 0.5, 1 and 2% were produced by gelation/crystallization method in decalin+antioxidant solution of UHMWPE at 150 degrees C, for 40 min by using magnetic stirrer. The gel mixture was cooled in an aluminum tray embedded in iced water under ambient conditions and dried in an oven at 130 degrees C for 90 min to remove any residual trace of decalin. Distribution and elemental analyses of TiO2 particles in polymer matrix was examined by SEM-EDS. Crystallization behavior was investigated by differential scanning calorimetry (DSC). Based on the results, TiO2 particles in the UHMWPE have accelerated the crystallization, acting as nucleating agents, with increment from 56% for UHMWPE to 63.5% for UHMWPE-2 wt% TiO2. The present bond types in composites were analyzed by Raman spectroscopy and the results are in good agreement with literature. Uniaxial tensile tests were performed to determine Young's modulus of UHMWPE-TiO2 composites. It was found that Young's modulus of UHMWPE was increased from 52 MPa to 800 MPa with the addition of TiO2 particles.Conference Object Characterization of Thin Film Boron Nitride Coatings and Observation of Graphite-Like Boron Nitride(Polish Acad Sciences inst Physics, 2019) Durkaya, G.; Efeoglu, I.; Ersoy, K.; Cetin, B.; Kurtuldu, H.Cubic boron nitride is a coating solution to improve wear performances in demanding engineering applications. In order to achieve the best performance from this thin film system, the physical dynamics behind the phase compositions, phonon dynamics, surface quality, interfacial effects and stoichiometric relations should be understood. In this study, for this purpose, physical vapor deposition grown BN thin films were studied in detail using the Raman spectroscopy, atomic force microscopy, and scanning electron microscopy techniques.
