Yazar "Ari, Mehmet" seçeneğine göre listele

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    Indium phosphide nanofibers prepared by electrospinning method: Synthesis and characterization
    (WILEY-V C H VERLAG GMBH, 2014) Evcin, Atilla; Bezir, Nalan Cicek; Kayali, Refik; Ari, Mehmet; Kepekci, Deniz Belkis
    Nine sets of (3 x 3) InP nanofiber samples have been successfully prepared at three different voltages (20, 25, 30 kV) and at three separate heights (5, 7, 10 cm) by electrospinning with a constant precursor flow rate of 0.3 mLh(-1). The crystalline structure, thermal, morphologies and nanostructure, electrical, and optical properties of the samples are characterized by X-ray powder diffractometer (XRD) and thermal gravity-differential scanning calorimeter (TG-DSC), scanning electron microscopy (SEM), by Four-Point Probe Technique (FPPT,) and ultraviolet/visible spectrometry (UV/VIS), respectively. From these measurements, we have found the formation of stoichiometric nanostructured InP with zinc-blende structure and having lattice parameter of a = 5.874 angstrom, weight loss of 64.59% and crystallization temperature of 500 degrees C, average fiber diameter of 65.82 nm, the activation energies, E-a, of the samples, and band gap energy, E-g, of the nanofibers developed at constant applied voltage 30 kV. The band gap energies determined at different distances 5, 7, and 10 cm are found to be as 1.29, 1.37, and 1.30 eV, respectively.
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    Measurement and Prediction of the Thermal and Electrical Conductivity of Al-Zr Overhead Line Conductors at Elevated Temperatures
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2019) Kahveci, Osman; Cadirli, Emin; Ari, Mehmet; Tecer, Hicran; Gunduz, Mehmet
    In the present work, the thermal conductivity and electrical resistivity of the Al-0.25 Zr (wt.%) alloy have been investigated from 300 K to 600 K. The variations of thermal conductivity (K-total) with temperature were measured by using a radial heat flow furnace. The electrical resistivity (rho) measurements of the alloy depending on the temperature were performed using the standard four-point probe method. The electrical conductivity (sigma) was obtained by using the measured electrical resistivity. The thermal conductivity and the electrical resistivity coefficients were determined from the graphs of thermal and electrical resistivity versus temperature for the alloy. The electronic thermal conductivity (K-e) values were obtained from the Wiedemann-Franz and Smith-Palmer equations, and the values of K-L were obtained by subtracting K-e fromthe measured values (K-total). K-total is dominated by Ke, and K-e varies between 208-198 W/mK. The K-L decreases from 7.99 to 1.77 W/m K, and s varies between 1.41x10(7)-2.80x10(7) Omega(-1)m(-1) in the range of temperature 373-600 K. The enthalpy of fusion (Delta H) and the specific heat capacity (C-p) during the transformation were determined. Thermal diffusivity (alpha) changes were calculated as a function of temperature from these obtained thermal data.
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    Temperature and Thickness Effects on Electrical Properties of InP Films Deposited by Spray Pyrolysis
    (IOP PUBLISHING LTD, 2009) Kayali, Refik; Ari, Mehmet; Oeztas, Mustafa; Bedir, Metin; Aksoy, Funda
    InP film samples are prepared by spray pyrolysis technique using aqueous solutions of InCl(3) and Na(2)HPO(4), which are atomized with compressed air as carrier gas onto glass substrates at 500 degrees C with different thicknesses of the films. The structural properties of the samples are determined by x-ray diffraction (XRD). It is found that the crystal structure of the InP films is polycrystalline hexagonal. The orientations of all the obtained films are along the c-axis perpendicular to the substrate. The electrical measurements of the samples are obtained by dc four-probe technique on rectangular-shape samples. The effects of temperature on the electrical properties of the InP films are studied in detail.