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Conference Object Non-Invasive 3d Optical Measurement of Round Surfaces(Polish Acad Sciences inst Physics, 2019) Kurtuldu, H.; Durkaya, G.; Cetin, B.Precise measurement of wear profiles in large areas of round surfaces such as shafts, suspension bars and high-deviation geometry surfaces is a challenge in manufacturing engineering. An optical measurement method is developed to overcome this challenge. This method, relying on angular reconstruction of scattered light profiles, is used for the measurement of irregular wear in quality testing of round surfaces which provides information on estimating the surface lifetime after prolonged use. This approach achieves a 3D depth accuracy better than 50 mu m in suspension bars with diameters up to 50 mm from an imaging distance of 250 mm.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.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.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.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 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.Conference Object Investigating the Effect of Auto-Focus and Auto-Threshold Algorithms in Advanced Nodularity Analysis of Austempered Ductile Iron Castings(Polish Acad Sciences inst Physics, 2019) Cetin, B.; Kurtuldu, H.; Durkaya, G.; Davut, K.Austempered ductile iron castings have a wide range of application fields including defense and heavy-duty industries due to their promising mechanical properties. Austempered ductile iron castings could provide excellent combination of high strength, toughness, and wear resistance at the same time. Unlike other spheroidal ductile cast irons, austempered ductile iron castings need to be processed by a special austempering heat treatment which enables the verification of the conformity of the nodularity level after the casting operations. Previous studies have shown that wide area mappings for determining nodularity are crucial to eliminate the representativeness problems. In this sense, some precautions should be taken for the accuracy of results in large scale nodularity examination. In this study, the effect of auto-thresholding and auto-focusing algorithms on the advanced nodularity analysis is investigated. The results suggest that auto-thresholding and auto-focusing methods have significant contributions for determining average nodularity levels and average graphite sizes.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.
