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Öğe Directional solidification of pure succinonitrile and succinonitrile- salol alloys(2001) Karaca I.; Çadirli E.; Kaya H.; Maraşli N.Pure succinonitrile (SCN) and succinonitrile-salol alloys with four different concentrations of salol were unidirectionally solidified at five different growth rates in a temperature gradient. The microstructure parameters, viz., the primary dendrite arm spacing ?1, dendrite tip radius R and mushy zone depth d, were measured. The dependence of the microstructure parameters on the solidification parameters for pure SCN and SCN-Salol alloys were determined via linear regression analysis. The results are compared with published data.Öğe Effects of Growth Rates and Compositions on Dendrite Arm Spacings in Directionally Solidified Al-Zn Alloys(Springer Boston, 2017) Acer E.; Çadırlı E.; Erol H.; Kaya H.; Gündüz M.Dendritic spacing can affect microsegregation profiles and also the formation of secondary phases within interdendritic regions, which influences the mechanical properties of cast structures. To understand dendritic spacings, it is important to understand the effects of growth rate and composition on primary dendrite arm spacing (?1) and secondary dendrite arm spacing (?2). In this study, aluminum alloys with concentrations of (1, 3, and 5 wt pct) Zn were directionally solidified upwards using a Bridgman-type directional solidification apparatus under a constant temperature gradient (10.3 K/mm), resulting in a wide range of growth rates (8.3–165.0 µm/s). Microstructural parameters, ?1 and ?2 were measured and expressed as functions of growth rate and composition using a linear regression analysis method. The values of ?1 and ?2 decreased with increasing growth rates. However, the values of ?1 increased with increasing concentration of Zn in the Al-Zn alloy, but the values of ?2 decreased systematically with an increased Zn concentration. In addition, a transition from a cellular to a dendritic structure was observed at a relatively low growth rate (16.5 µm/s) in this study of binary alloys. The experimental results were compared with predictive theoretical models as well as experimental works for dendritic spacing. © 2017, The Minerals, Metals & Materials Society and ASM International.Öğe Investigation of the thermo-electrical properties of A707 alloys(Elsevier B.V., 2019) Çadırlı E.; Kaya H.; Büyük U.; Şahin M.; Üstün E.; Gündüz M.In the present work, the thermal conductivity, electrical conductivity, enthalpy of fusion, specific heat capacity and thermal diffusivity of the A707 alloy (Al–4.5 Zn–1.2 Mg–0.15 Cr–0.15 Zr wt.%) have been investigated. Phase identification of the studied alloy was investigated with energy dispersive X-ray analysis and X-ray diffraction techniques. Thermal conductivity of as-cast A707 alloy was measured using Comparison Cut Bar Method in the temperature range of 300–800 K. With the increase of temperature, thermal conductivity decreased gradually in as-cast A707 alloy. The electrical conductivities of the sample were obtained with the Wiedemann–Franz equation by using the measured thermal conductivity values. Thermal conductivity coefficients for the alloy were obtained from the graphs of thermal conductivity versus temperature. The enthalpy of fusion and the specific heat capacity during the transformation were also determined. Thermal diffusivity changes were calculated as a function of temperature through the obtained thermal data. © 2019 Elsevier B.V.Öğe The effects of a continuous 1-h a day 900-MHz electromagnetic field applied throughout early and mid-adolescence on hippocampus morphology and learning behavior in late adolescent male rats(Elsevier B.V., 2018) Keleş A.İ.; Yıldırım M.; Gedikli Ö.; Çolakoğlu S.; Kaya H.; Baş O.; Odacı E.The purpose of this study was to investigate hippocampus morphology and changes in learning behavior in male rats in late adolescence exposed to the effect of a continuous 1-h a day 900-megahertz (MHz) electromagnetic field (EMF). Twenty-four male Sprague Dawley rats aged 3-weeks were divided equally into control, sham and EMF groups. EMF group rats were exposed to a 900-MHz EMF inside an EMF cage, while the sham group rats were placed in the same cage but were not exposed to such an effect. No procedure was performed on the control group. Following 25-day application of EMF, passive avoidance, 8-arm radial maze and Y-maze tests were applied to determine rats’ learning and memory performances. Open field and rotarod tests were applied to assess locomotor activity. At the end of the tests, the animals’ brains were removed. Sections were taken and stained with toluidine blue. The regions of the hippocampus were subjected to histopathological evaluation. At histopathological examination, impairments of pyramidal and granular cell structures were observed in the EMF group hippocampus. No significant change was observed in learning, memory or locomotor behavior in any group. In conclusion, 900-MHz EMF applied in early and mid-adolescence causes no changes in learning, memory or locomotor behavior. © 2018 Elsevier B.V.
