Yosef badali | İstanbul Ticaret Üniversitesi (original) (raw)

Papers by Yosef badali

Piezoelektrik özelliği olan poliviniliden florür (PVDF) malzemenin; sertlik, termal dayanıklık ve... more Piezoelektrik özelliği olan poliviniliden florür (PVDF) malzemenin; sertlik, termal dayanıklık ve elektriksel özelliğini geliştirmek bu çalışmanın esas amacını oluşturmaktadır. PVDF, elektriksel olarak yalıtkan, yüksek korozyona dirençli, esnek, düşük üretim maliyeti ve zehirsiz olması nedeniyle yeni nesil piezoelektrik malzeme uygulamalarında tercih edilen polimerdir. Ancak piezoelektrik yük sabiti ve sertlik değerlerinin istenilen seviyelerde olmaması bu malzemenin kullanılmasına bazı kısıtlamalar getirmiştir. Bu nedenle yapılan bu çalışmada grafen, bor, seryum ve erbiyum katkı maddesi olarak polimer içine eklenip nanokompozit malzeme üretilmiştir ve elektro-eğirme tekniğini kullanarak tamamen homojen bir yapı elde edilmiştir. Dört kristal fazından oluşan yarı kristal PVDF polimere, grafen katkılaması; bu polimerin polar olmayan α fazından polar β fazına bir geçiş yapmasına neden olmaktadır. Bu β fazı, malzemenin piezoelektrik özelliğinden sorumludur, dolayısıyla gr...

Journal of Building Engineering

International Journal of Numerical Methods for Heat & Fluid Flow

Purpose Heat exchangers (HEs) which provide heat transfer and transfer energy through direct or i... more Purpose Heat exchangers (HEs) which provide heat transfer and transfer energy through direct or indirect contact between fluids have an essential role in many processes as a part of various industries from pharmaceutical production to electronic devices. Using nanofluid as working fluid and integrating different types of turbulators could be used to upgrade the thermal effectiveness of HEs. Recently, to obtain more increment in thermal effectiveness, hybrid nanofluids are used that are prepared by mixing two or more various nanoparticles. The purpose of this experimental and numerical study is investigating different scenarios for improving the effectiveness of a concentric U-tube type HE. Design/methodology/approach In the numerical section of this study, different turbulator modifications, including circular and quarter circular rings, were modeled to determine the effect of adding turbulator on thermal performance. In addition, Al2O3/water and SiO2/water single and Al2O3–SiO2/wat...

Farklı nanokompozit arayüzey tabakalı Au/(Bi2O3-x:PVA)/4H-SiC (MPS) (x=Sm, Sn, Mo) yapılar spin-k... more Farklı nanokompozit arayüzey tabakalı Au/(Bi2O3-x:PVA)/4H-SiC (MPS) (x=Sm, Sn, Mo) yapılar spin-kaplama yöntemi ile üretilmiştir. Hazırlanan yapıların I-V karakteristiklerden elde edilen doygunluk akımı (I0), engel yüksekliği (B0), idealite faktörü (n), seri ve şönt dirençleri (Rs ve Rsh) ve rektifiye oranı (RR) gibi ana elektriksel parametreleri, arayüzey tabakada kullanılan farklı nanomateryale bağlı olarak değişimi incelenmiştir. Tüm yapılar için cheung ve norde fonksiyonlarından elde edilen n,  B0 and Rs değerleri karşılaştırılmıştır. Arayüzey durumlarının enerji dağılım profili (Nss‒(Ec-Ess)); doğru beslem (I‒V), voltaja bağlı bariyer yüksekliği (e(V)) ve idealite faktörü (n(V)) verileri dikkate alınarak elde edilmiştir. Ek olarak, hazırlanan yapıların muhtemel akım iletim mekanizmasını belirlemek için Ln(I)‒Ln(V) eğrileri çizilmiştir. Ayrıca tüm yapıların C‒V ve G/‒V ölçümleri de yapılmıştır. Ters beslem C-2‒V...

Journal of Physics and Chemistry of Solids

Journal of Physics and Chemistry of Solids, 2021

Applied Physics A, 2021

To determine the influence of the thin polymer interface film on the electrical and dielectric ch... more To determine the influence of the thin polymer interface film on the electrical and dielectric characteristics of the Al/p-Si MS structure, the Graphene doped (Bi2Te3–Bi2O3–TeO2): PVP film was deposited on the silicon substrate using the spin-coating method. The mean size of these nanostructures was found less than 50 nm using the XRD method. EDX profile shows that the structure of Bi2Te3–Bi2O3–TeO2 consists of the bismuth (Bi), tellurium (Te), and oxygen (O) atoms and also not consists of other impurities or compounds. The key electrical and dielectric parameters of metal–semiconductor (MS) and metal-polymer/semiconductor nanocomposite structures were examined using I–V and Z–f analyses. The values of saturation-current (I0), barrier-height (BH) at zero-bias (ΦB0), ideality factor (n), series and shunt resistances (Rs, Rsh) data for both structures were derived from the I–V experiments at ± 6 V voltage scales and compared with them. The energy distributions of interface state density (Dit) were also acquired from the voltage-dependent ΦB(V) and n(V) data. Finally, the frequency dependence of complex dielectric (e* = e′ − je″) and electric modulus (M* = M′ + jM″), dielectric loss tangent (tanδ), and ac electrical conductivity (σac) values were evaluated from the C–f and G/ω–f experiments for both structures at 102–106 Hz frequency scale. The results depict that the Bi2Te3–Gr: PVP organic layer improves the quality of the MS structure as it reduces the leakage current, n, and Dit and increases the Rsh, BH, and e′.

Journal of Materials Science: Materials in Electronics, 2020

In this work, Au/4H–SiC Schottky diodes with different Bi2O3–x:PVA (x = Sm, Sn, Mo) thin insulato... more In this work, Au/4H–SiC Schottky diodes with different Bi2O3–x:PVA (x = Sm, Sn, Mo) thin insulator interface layer were produced for the fabrication of metal/insulator/semiconductor (MIS) structures. The effect of different Bi2O3–x:PVA interfacial layer deposited between metal and semiconductor on important optical and electrical parameters of Schottky diodes was investigated. The main electrical parameters of the prepared structures such as the saturation current (I0), the barrier height (ΦB0), ideality factor (n), and series and shunt resistance (Rs and Rsh) were obtained from the I‒V characteristics. The discrepancies in these parameters can be ascribed to the use of different nanomaterials as an interlayer. Moreover, the values of n, ΦB0, and Rs were also extracted by using Cheung and Norde functions and obtained results were compared with each other. The energy dependence of interface states [Nss vs (Ec − Ess)] was investigated by taking into account the voltage dependence of Φe(V) and n(V). In addition, Ln(I)–Ln(V) plots were drawn to specify the possible current transport mechanisms of the prepared structures. Experimental results show that the Schottky structures with (Bi2O3–Sn:PVA) and (Bi2O3–Sm:PVA) interlayers yield higher RR and Rsh values and lower Io values. This provides an evidence to performance increase in MS structures.