Mehmet Ari - Academia.edu (original) (raw)

Papers by Mehmet Ari

Cumhuriyet Science Journal, 2013

For the first time, the structural and electrical properties of Pb-Al-Sn composite system for co... more For the first time, the structural and electrical properties of Pb-Al-Sn composite system for constant tin concentrations were investigated in this work. The electrical conductivity of the samples depending on temperature was measured by four-point probe, and it was found that the conductivity decreases almost linearly with the temperature. The structural properties of the samples were determined by Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Energy Dispersive X - ray Analysis (EDX). The SEM micrographs of the samples illustrated smooth surfaces with a clear grain boundary. The crystal structure of the samples was indexed in face-centered cubic (fcc) by using XRD data. The cell parameters and the grain sizes were determined from the XRD patterns. In addition, the temperature coefficients of electrical resistivities were obtained determined, which were independent of the compositions of the composit...

Bu calismanin amaci; zamanla ozellikleri bozulmayan ve calisma sartlari altinda iyonik iletkenlig... more Bu calismanin amaci; zamanla ozellikleri bozulmayan ve calisma sartlari altinda iyonik iletkenligini koruyan elektrolit/elektrolitler tespit etmektir. Bu dogrultuda, (Bi2O3)1-xy(Ho2O3)x(Dy2O3)y uclu sistemin (x=%11, 12, 13, 14 mol ve y=% 4, 3, 2, 1 mol, katki konsantrasyonu) numuneleri katihal reaksiyonu ile 48 saat 750°C isil isleme tabi tutularak hazirlandi. Kati Oksit Yakit Hucresi (SOFC) icin en iyi kati elektrolit ozelliklere sahip olabilecek numunelerin yapisal ozellikleri X-isinlari difraktometresi (XRD), elektriksel ozellikleri dort-nokta metodu ve termal ozellikleri diferansiyel termal analiz (TG / DTA) olcum sistemleri ile olculdu. XRD olcumleri 48 saat 750°C isil islem sonucunda butun numuneler δ- Bi2O3 fazinda kararli oldugunu gosterdi. The aim of this study is to find an electrolyte which does not have any degradation in its properties with time this maybe caused either interaction between the different electrochemical cell materials or by instability of the ionic condu...

Journal of the Australian Ceramic Society, 2019

Bi 2 O 3) 1-x-y (Dy 2 O 3) x (Tm 2 O 3) y ternary systems as electrolytes were synthesized at 750... more Bi 2 O 3) 1-x-y (Dy 2 O 3) x (Tm 2 O 3) y ternary systems as electrolytes were synthesized at 750°C by the solid-state ceramic synthesis method. Eight (Bi 2 O 3) 1-x-y (Dy 2 O 3) x (Tm 2 O 3) y (x = 0.1, 0.2) and (y = 0.05, 0.1, 0.15, 0.2) electrolytes at different ratios were investigated. The structural, electrical, and thermal properties of these eight electrolytes for solid oxide fuel cells (SOFCs) were characterized by means of a X-ray powder diffractometer (XRD), the four point-probe technique (4PPT), and thermal gravimetry/ differential thermal analysis (TG/DTA). Results of XRD measurements showed that the δ-Bi 2 O 3 (cubic) phase with a stable structure was dominantly obtained for all of the samples. As a result of the temperature-dependent electrical measurements of these ternary systems, it was found that electrical conductivity decreases with increasing molar ratio of Tm 2 O 3. The highest electrical conductivity was found for the sample of the (Bi 2 O 3) 0.85 (Dy 2 O 3) 0.10 (Tm 2 O 3) 0.05 system as 0.349 (Ω cm) −1 at 750°C. The lowest activation energy was found for the same sample as 0.68 eV.

Cumhuriyet Science Journal, 2017

The structural, electrical, thermal, mechanical properties and micro-hardness of five different s... more The structural, electrical, thermal, mechanical properties and micro-hardness of five different samples of Sn-Pb-Al ternary alloys (Sn-[x] wt. % Pb-10 wt. % Al) (x=40, 30, 20 and 10) with constant Al concentrations, and the eutectic Sn-Pb-Al (Sn 61.82 Pb 38.10 Al 0.08) ternary alloy were investigated. The electrical conductivity of the samples, depending on temperature, was measured using the four-point probe technique (4PPT). The temperature dependence of the thermal conductivities of the samples was shown using the Wiedemann-Franz (W-F) law with the data obtained from electrical measurements. Scanning Electron Microscope (SEM), X-ray diffraction (XRD), and Energy Dispersive X-ray Analysis (EDX) measurements were carried out to reveal the surface morphology, crystal structure, cell parameters, grain sizes, and chemical compositions. Tensile tests were carried out to determine the ultimate tensile strengths depending on the particle size of each component in the alloys. The results of the micro-hardness tests were found using a Vickers test machine for each component of the alloys.

Materials Research, 2019

In the present work, the thermal conductivity and electrical resistivity of the Al-0.25 Zr (wt.%)... more 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 (ρ) measurements of the alloy depending on the temperature were performed using the standard four-point probe method. The electrical conductivity (σ) 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 σ varies between 1.41x10 7-2.80x10 7 Ω-1 m-1 in the range of temperature 373-600 K. The enthalpy of fusion (ΔH) and the specific heat capacity (C p) during the transformation were determined. Thermal diffusivity (α) changes were calculated as a function of temperature from these obtained thermal data.

Current Applied Physics, 2016

In the present work, the ternary system of (Bi 2 O 3) 1ÀxÀy (Sm 2 O 3) x (Yb 2 O 3) y was investi... more In the present work, the ternary system of (Bi 2 O 3) 1ÀxÀy (Sm 2 O 3) x (Yb 2 O 3) y was investigated. For the production and stabilization of the fcc-type solid solution, nano-Sm 2 O 3 and nano-Yb 2 O 3 were doped into nano-Bi 2 O 3 by solid-state synthesis techniques. The XRD results showed that the crystallographic structure of the samples had displayed a fluorite type face-centered cubic d-Bi 2 O 3 phase. The phase stability was also checked by the DTA measurements. The temperature dependent electrical conductivity results revealed that the maximum electrical conductivity observed for the sample of the nanostructure-(Bi 2 O 3) 0.8 (Sm 2 O 3) 0.1 (Yb 2 O 3) 0.1 system was 5.39 Â 10 À2 (ohm.cm) À1 at 650 C. The results also show that the lowest activation energy was 0.7062 eV and the lowest crystallite size was 31.62 nm for the nanostructure-(Bi 2 O 3) 0.75 (Sm 2 O 3) 0.1 (Yb 2 O 3) 0.15 system. Consequently, the face-centered cubic stable d-phase-(Bi 2 O 3) 0.8 (Sm 2 O 3) 0.1 (Yb 2 O 3) 0.1 is the optimal dopant amount due to the relatively good stability and oxygen ionic conductivity obtained, which are two of our major concerns for the electrolyte layer of solid oxide fuel cells (SOFCs).

Phase Transitions, 2016

In this study, (Bi 2 O 3) 1¡x¡y (Sm 2 O 3) x (CeO 2) y ternary system was synthesized by using so... more In this study, (Bi 2 O 3) 1¡x¡y (Sm 2 O 3) x (CeO 2) y ternary system was synthesized by using solid-state reaction method. Structural, morphological, thermal and electrical properties of the samples were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy, thermo gravimetry/ differential thermal analyzer and four-probe method. The XRD measurement results indicated that the samples (x D 10À15, y D 5À10À15À20) had cubic d-phase crystallographic structure. The phase stability of the samples was checked by the differential thermal analyzer measurements, which indicates most of the samples have stable d-Bi 2 O 3 phase. The electrical conductivity measurement results showed that the electrical conductivity increased with mol% CeO 2 molar ratio at a fixed molar ratio of Sm 2 O 3. The highest electrical conductivity obtained for the (Bi 2 O 3) 0.65 (Sm 2 O 3) 0.15 (CeO 2) 0.20 system was 1.55 £ 10 ¡2 (V.cm) ¡1 at 600 C. The activation energies were also calculated at low temperature range (350À650 C) which vary from 1.1325 to 1.4460 eV and at high temperature (above 650 C) which vary from 0.4813 to 1.1071 eV.

Surface Review and Letters, 2017

The structural, surface and transport properties of Sn–Ag alloys were investigated by X-ray diffr... more The structural, surface and transport properties of Sn–Ag alloys were investigated by X-ray diffraction (XRD), radial heat flow, energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and four-point probe techniques. We observed that the samples had tetragonal crystal symmetry except for the pure Ag sample which had cubic crystal symmetry, and with the addition of Ag the cell parameters increased slightly. Smooth surfaces with a clear grain boundary for the samples were shown on the SEM micrographs. The grain sizes of pure Ag, [Formula: see text]-Sn and the formed Ag3Sn intermetallic compound phase for Sn–[Formula: see text] wt.% Ag [[Formula: see text], 3.5] binary alloys were determined to be 316[Formula: see text]nm, between 92[Formula: see text]nm and 80[Formula: see text]nm and between 36[Formula: see text]nm and 34[Formula: see text]nm, respectively. The values of electrical resistivity for pure Sn, pure Ag and Sn–[Formula: see text] wt.% Ag [[Formula: see ...

Cerâmica, 2011

Electrical conductivity of tetragonal β-phase (Bi2O3)1-x(Eu2O3)x (0.01 ≤ x ≤ 0.10 %mol) ceramic s... more Electrical conductivity of tetragonal β-phase (Bi2O3)1-x(Eu2O3)x (0.01 ≤ x ≤ 0.10 %mol) ceramic systems were investigated. The temperature and doping concentration dependences of the electrical conductivity were studied by four-point probe technique. The electrical conductivity increases with the increasing doping concentration and temperature. The highest value of the electrical conductivity is 0.013 Ω-1cm-1 (x = 0.05, 750 ºC) for the β-phase at 670 ºC and 0.57 Ω-1cm-1 (x=0.05, 800 ºC) in binary systems at 690 ºC. The phase transition which manifests itself by the jump in the conductivity curves was seen and verified by differential thermal analysis measurements. The activation energies of the samples were found to be about 0.71-1.57 eV.

Solid State Sciences, 2015

The structural, thermal, electrical and mechanical properties and micro-hardness of four differen... more The structural, thermal, electrical and mechanical properties and micro-hardness of four different samples of Al-Sn-Pb ternary alloys (Al-[x] wt. % Sn-10 wt. % Pb) (x=40, 30, 20 and 10) with constant lead concentrations were investigated for four different samples. Electrical resistivity and conductivity were measured by using (four-point probe measurement techniques) 4PPT techniques. The variations of thermal conductivity were determined by Wiedemann-Franz law (W-F) and Smith-Palmer (S-P) equation using the data obtained from electrical properties. The mechanical properties of the same alloys were obtained by the tensile test and the Vickers micro-hardness test.

Materials Characterization, 2008

Abstract The thermophysical transport properties of Cd–Sn alloys have been investigated for six s... more Abstract The thermophysical transport properties of Cd–Sn alloys have been investigated for six samples. The electrical resistivity measurements were obtained by using a standard dc four-point probe technique in the temperature range of 300 K–550 K. The resistivity of samples increases linearly with temperature and the electrical current mainly flows through the Sn phase channel. The electrical conductivity of samples is inversely proportional to temperature. Also, thermal conductivity of the Cd–Sn alloys was determined. The phonon component contribution of thermal conductivity dominates the thermal conduction processes at T T > 500 K. The thermal conductivity of the Cd–Sn alloys also depends on the grain size and grain boundary of the pure Cd and the pure Sn phases in the matrix. The temperature coefficient of resistivity was also determined, which is independent with the alloying elements.

Journal of optoelectronics and adavnced materials, 2009

Résumé/Abstract We present a theoretical model regarding the electron-phonon interactions in n-ty... more Résumé/Abstract We present a theoretical model regarding the electron-phonon interactions in n-type InN at a lattice temperature of 1.5 K. A perturbation-based model with a drifted Maxwellian distribution is used for obtaining the energy loss rates and mobility from ...

Crystal Research and Technology, 2014

Nine sets of (3 × 3) InP nanofiber samples have been successfully prepared at three different vol... more Nine sets of (3 × 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 = 5.874Å, weight loss of 64.59% and crystallization temperature of 500°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.

Continuum Mechanics and Thermodynamics, 2012

In this work, the structural and transport properties of Mg-doped Sn-based alloys have been inves... more In this work, the structural and transport properties of Mg-doped Sn-based alloys have been investigated. The temperature-dependent transport and structural properties of Sn-Mg alloys were investigated for five different samples (Pure Sn, Sn-1.0 wt% Mg, Sn-2.0 wt% Mg, Sn-6.0 wt% Mg and Pure Mg). Scanning electron microscopy (SEM), X-ray diffraction and energy dispersive X-ray analysis measurements were carried out in order to clarify the structural properties of the samples. It was found that the samples had tetragonal crystal symmetry, except for pure Mg which had hexagonal crystal symmetry. We also found that the cell parameters changed slightly with the addition of Mg element. The SEM micrographs of the samples showed that they had smooth surfaces with a clear grain boundary. The electrical and thermal conductivity of the samples were measured by four-point probe and the radial heat flow method, respectively. The electrical resistivity of the samples increased almost linearly with the increasing temperature. The thermal conductivity values ranged between 0.60 and 1.00 W/Km, while they decreased slightly with temperature and increased with Mg composition. The thermal conductivity values of the alloys were in between the values of pure Sn and Mg. The thermal conductivity results of the alloys were compared with other available results, and a good agreement was seen between the results. In addition, the temperature coefficients of electrical resistivity and thermal conductivity were determined; these were independent of the composition of the alloying elements. Keywords Electrical and thermal conductivity • Sn-Mg alloys • Four-point probe method • SEM • XRD Communicated by Andreas Öchsner.

… : Meeting the Climate …, 2008

50 Smart Energy Strategies LaSrFeNi-oxide: a promising cathode material matching proton conductor... more 50 Smart Energy Strategies LaSrFeNi-oxide: a promising cathode material matching proton conductor speci¿ cations for intermediate temperature solid oxide fuel cells Selma Erat1/2 Artur Braun1 EMPAand ETH Zurich, Switzerland Xiaojun Zhang3/4, Steven Y. Sun5, Zhi Liu6, Alwin ...

Archivos argentinos de pediatria, 2016

In childhood, pulmonary thromboembolism (PTE) is an uncommonbut potentially life-threatening dise... more In childhood, pulmonary thromboembolism (PTE) is an uncommonbut potentially life-threatening disease. The greater numbers of venous thromboembolism (VTE) are complications of underlying risk factors such as malignancies, chemotherapy (L-asparaginase), and central venous catheter. We report a patient with acute lymphoblastic leukemia and PTE, who presented with near-syncope, and was successfully treated with low molecular weight heparin and calcium channel blockers.