Yazar "Ari, M." seçeneğine göre listele

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    Dependence of electrical and thermal conductivity on temperature in directionally solidified Sn-3.5 wt% Ag eutectic alloy
    (SPRINGER, 2011) Cadirli, E.; Sahin, M.; Kayali, R.; Ari, M.; Durmus, S.
    Sn-3.5 wt% Ag alloy was directionally solidified upward with a constant growth rate (V = 16.5 mu m/s) and a temperature gradient (G = 3.3 K/mm) in a Bridgman-type growth apparatus. The variations of electrical resistivity (rho) with temperature in the range of 293-476 K for the directionally solidified Sn-3.5 wt% Ag eutectic alloy was measured. The measurements indicate that the electrical resistivity of the directionally solidified Sn-Ag eutectic solder increases with increasing temperature. The variations of thermal conductivity of solid phases versus temperature for the same alloy was determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of electrical conductivity. From the graphs of electrical resistivity and thermal conductivity versus temperature, the temperature coefficient of electrical resistivity (alpha (TCR) ) and the temperature coefficient of thermal conductivity (alpha (TCT) ) for the same alloy were obtained. According to experimental results, the electrical and thermal conductivity of Sn-Ag eutectic solder linearly decrease with increasing the temperature. The enthalpy of fusion (Delta H) and the change of specific heat (Delta C (P) ) during the transformation at the studied alloy were determined from heating curve during the transformation from eutectic solid to eutectic liquid by means of differential scanning calorimeter (DSC).
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    Investigation of microhardness and thermo-electrical properties in the Sn-Cu hypereutectic alloy
    (SPRINGER, 2010) Cadirli, E.; Boyuk, U.; Engin, S.; Kaya, H.; Marasli, N.; Ari, M.
    Sn-3 wt% Cu hypereutectic alloy was directionally solidified upward with different growth rates (2.24-133.33 mu m/s) at a constant temperature gradient (4.24 K/mm) and with different temperature gradients (4.24-8.09 K/mm) at a constant growth rate (7.64 mu m/s) in the Bridgman-type growth apparatus. The measurements of microhardness of directionally solidified samples were obtained by using a microhardness test device. The dependence of microhardness HV on the growth rate (V) and temperature gradient (G) were analyzed. According to these results, it has been found that with the increasing the values of V and G the value of HV increases. Variations of electrical resistivity (rho) and electrical conductivity (sigma) for casting samples with the temperature in the range of 300-500 K were also measured by using a standard dc four-point probe technique. The variation of Lorenz coefficient with the temperature for Sn-3 wt% Cu hypereutectic alloy was determined by using the measured values of electrical and thermal conductivities. The enthalpy of fusion for same alloy was determined by means of differential scanning calorimeter from heating trace during the transformation from eutectic liquid to eutectic solid.
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    Investigation of Structural and Electrical Properties of (Bi2O3)1-x-y(CeO2)x(Eu2O3)y Electrolytes for Solid Oxide Fuel Cells
    (Polish Acad Sciences Inst Physics, 2019) Islek, Y.; Ozen, M. Kasikci; Kayali, R.; Ari, M.
    In the present study, CeO2 and Eu2O3 doped Bi2O3 composite materials for solid oxide fuel cells were investigated. (Bi2O3)(1-x-y)(CeO2)(x) (Eu2O3)(y) ternary systems (x = 0.01, 0.03, 0.05, 0.07, 0.09, 0.11 and y = 0.11, 0.09, 0.07, 0.05, 0.03, 0.01 dopant concentrations) were fabricated at different temperatures (650, 700, 750, and 800 degrees C) using conventional solid-state synthesis techniques. Characterization of these electrolyte samples were carried out by X-ray powder diffraction, differential thermal analysis/thermal gravimeter, and the four-point probe technique measurements. X-ray powder diffraction measurements showed that nearly all the samples have alpha+beta+gamma phase except the samples with tetragonal beta-phase sintered at 700, 750 degrees C and 750, 800 degrees C with the dopant ratios (x = 0.07, y = 0.05) and (x = 0.09, y = 0.03), respectively. Four-point probe technique measurements showed that the measured ionic conductivity of the stable samples vary in the range 1.05 x 10(-1)-4.76 x 10(-1) S/cm. Additionally, the activation energy values of the samples were calculated with the help of the Arrhenius equation adapted to the logs graphics versus 1000/T varying in the range 0.7799-0.8746 eV. This result shows that there is a good relationship between the activation energy values and conductivity values.