Person: ESMER, KADİR
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ESMER
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KADİR
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Publication Metadata only Tungsten Trioxide Reinforced Epoxy Composites with Increased Dielectric Permittivity and Conductivity(2022-09-04) ŞAHİN, NAZLICAN; ESMER, KADİR; ŞAHİN N., KARABUL Y., KILIÇ M., GÜVEN ÖZDEMİR Z., ESMER K.This study focuses on the improvement of ac electrical properties of epoxy polymer matrix for energy storage applications by reinforcing it with WO3 micro particles. The Bragg diffraction peaks represents to the triclinic structure of WO3 particles. The particle dimensions are between 600 and 800 nm. The samples have been prepared by using the mixture of liquid bisphenol A-epichlorohydrin epoxide resin and isophorone diamine in 2:1 ratio. To prepare composites, µ-WO3 have been added at a rate of 5%, 10%, 20%, and 30% by mass. Electrical investigation of epoxy composites containing WO3 included the real and imaginary components of complex permittivity function, loss tangent, the real and imaginary components of complex electrical modulus, and conductivity in the frequency range of 20 Hz-15 MHz. As a result, it has been determined that among other composites, the composite having 20% WO3 particle addition has the highest Ɛ´ and Ɛ´´ values in the low frequency range. On the other hand, compared to pure epoxy, the highest conductivity values have been observed in ac conductivity in the mid and low frequency regions with 20% and 30% WO3 additives, respectivelyPublication Metadata only Investigation of spectral output of Er3+ and Yb3+/Er3+ doped TeO2-ZnO-BaO glasses for photonic applications(ROYAL SOC CHEMISTRY, 2021) ESMER, KADİR; Dogan, Anil; Yildirim, Saniye Merve; Erdem, Murat; Esmer, Kadir; Eryurek, GonulEr3+ and Yb3+/Er3+ doped TeO2-ZnO-BaO glasses were synthesized using the melt quenching technique with two different Er3+ concentrations. The refractive index was calculated to be around 2.14 from the optical band gap energies of the glasses. Under 975 nm laser excitation, weak blue, strong green and red emissions were observed in the visible region, while broadband emission around 1530 nm was recorded in the near infrared region. The increase in red emission intensity as a result of energy transfer from Yb3+ ions to Er3+ ions in Yb3+/Er3+ co-doped glasses is clearly reflected in the change in color coordinates. The temperature sensing abilities of the glasses were determined from the intensity ratios of light emitted from thermally coupled energy levels (H-2(11/2) and S-4(3/2)) of Er3+ ions. The highest absolute sensitivity was determined as 0.0046 K-1 at 453 K for Er3+ doped glass and 0.0067 K-1 at 353 K for Yb3+/Er3+ co-doped glass. These results show that Er3+ and Yb3+/Er3+ doped TeO2-ZnO-BaO glasses are promising candidates for both lighting and optical temperature sensors.Publication Open Access Structural and dielectrical behavior of polypyrrole/huntite composites(2023-04-01) MADAKBAŞ, SEYFULLAH; ŞAHİN, NAZLICAN; ESMER, KADİR; Madakbaş S., Şahin N., Türk Z., Esmer K., Şen F.In order to characterize stable composites that will contribute to industrial applications, polypyrrole (PPy)/huntite composites were prepared by the physical method. Polypyrrole (PPy)/huntite composites were produced at various huntite concentrations (10, 20, 30, 40 wt.%). Polypyrrole/huntite was characterized by Fourier transform infrared spectroscopy (FTIR), Thermal Gravimetric Analyses (TGA), Differential Thermal Analyses (DTA), Scanning electron microscopy (SEM), and dielectrical properties were investigated by Impedance Analyzer at the room temperature. The FTIR spectra show that huntite mineral coordinate with polymers through carbonate groups. TGA results indicate the main cause of mass loss can be moisture in the samples and unreacted pyrrole monomer. SEM images show that the composites have a granular and spherical geometry. Dielectric measurements showed that at lower frequencies dielectric constants decrease exponentially with an increase in frequency and this behavior indicates that the effect of interfacial polarization becomes more predominant at a lower frequency.Publication Metadata only Thermal and dielectric properties of flexible polyimide nanocomposites with functionalized nanodiamond and silver nanoparticles(2023-05-01) BİRTANE, HATİCE; MADAKBAŞ, SEYFULLAH; ESMER, KADİR; KAHRAMAN, MEMET VEZİR; Birtane H., Cigil A. B., Madakbaş S., Esmer K., Kahraman M. V.In the present study, amine groups were first modified to diamond and silver nanoparticles using APTMS to improve their homogeneous dispersion and compatibility in polyamic acid. Flexible polyimide nanocomposite films were successfully prepared by adding modified nanodiamond and silver nanoparticles to 4,4 \"-(1,3-phenylenedioxy) dianiline and benzophenone-3,3 \",4,4 \"-tetracarboxylic dianhydrides with different proportions. The effects of added amine-modified nanoparticles on dielectric constant and thermal stability were investigated. With SEM analysis, nanoparticles were homogeneously distributed on the polyimide surface and the presence of Si atom resulting from APTMS modification is clearly seen with the SEM-EDAX results. Considering the thermal resistance, the maximum decomposition temperature of the nano particle-free PI film was found to be 501 degrees C, while the thermal decomposition temperatures of the PI nanocomposite film that contains 1% m-Ag and the PI film that contains 5% m-ND, 502 degrees C and 505 degrees C, respectively. Also, it was seen that the dielectric constants of the prepared nanocomposite films that contain m-Ag NP decrease with increasing m-Ag NP ratio, and the dielectric constants of the films that contain m-ND increase with increasing m-ND ratio.Publication Metadata only Structural and dielectrical properties of PMMA/TiO2 composites in terms of free volume defects probed by positron annihilation lifetime spectroscopy(SAGE PUBLICATIONS LTD, 2021) TAV, CUMALİ; Kaya, A. U.; Kosem, G.; Yener, M. Y.; Tav, C.; Yahsi, U.; Esmer, K.A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introduced into a poly(methyl methacrylate) (PMMA) matrix by solvent (CHCl3) mixing under slow mechanical stirring, and the resulting suspension was used to cast free-standing PMMA/TiO2 composite films. Filler contents from 0 wt% to 7.5 wt% were selected, since TiO2 particles could not be previously suspended in chloroform at higher concentrations by ultrasonic agitation. Optical and dielectric properties of composites were determined by ultraviolet (UV)-visible and dielectric spectrometry. In the UV region, 450% improvement of UV absorption was achieved in the TiO2/PMMA composite compared with neat PMMA. The structural properties and hole-free volume of the composites were determined by X-ray diffractometry and positron annihilation lifetime spectroscopy, respectively. The particle size and homogeneous dispersion of the particles in the polymer matrix were related to the hole-free volume of the PMMA.Publication Open Access Structural and Dielectric Properties of Eu3+, B3+ co-doped CoNb2O6 Ceramic(2024-04-01) EKMEKÇİ, METE KAAN; ESMER, KADİR; İLHAN M., EKMEKÇİ M. K., ESMER K.The boron co-doped CoNb2O6:xEu3+, yB3+ (x=1, 3, 6, 9, 12 mol%, y=10 mol%) ceramics were obtained by the molten salt method, which has advantageous properties such as short reaction time, low sintering temperature, improved homogeneity, and crystallinity. The ceramic samples were examined by structural and dielectric analyses. In X-ray diffractions, the orthorhombic columbite type CoNb2O6 structure was obtained, and also a minor EuNbO4 phase was detected with increasing Eu3+ doping concentrations. Additionally, increasing Eu3+ concentration led to a slight increase in crystallite size, and two theta peak shifts occurred towards higher angles associated with shrinkage in the lattice or reduction in the lattice constant. In SEM examinations, a slight increase was observed in grain sizes from 1 to 9 mol% Eu3+ in the range of 1-30 m, while some decrease occurred in grain sizes at 12 mol%, and there was an evident increase in plate-shaped and elongated grains. The dielectric constant (ε') of the ceramic samples increased with increasing Eu3+ concentration and reached approximately 35 and 0.24 at 20 Hz for 9 mol% Eu3+, respectively. The increase in dielectric loss with increasing Eu3+ was associated with an increase in ionic conductivity, in which Eu3+ substitution does not suppress oxygen vacancies or make them more ordered.Publication Open Access Spectral investigation of Yb3+/Ho3+/Tm3+:Y2Si2O7 upconverting nanophosphors for the usage of temperature sensing(2023-02-28) ERDEM, MURAT; ESMER, KADİR; ERDEM M., ESMER K., Eryürek G.© 2023, Turkish Chemical Society. All rights reserved.Rare earth (Yb3+, Ho3+, Tm3+) yttrium disilicate phosphors were produced by sol-gel technique and heated at 1050 °C temperature. The sizes of the phosphors vary between 20-30 nm according to the images obtained from the Transmission Electron Microscope. The up-conversion (UC) emissions of the nanopowders were measured in the range of 500–900 nm wavelength under 950 nm laser excitation. A linear increase with power was observed in the emission intensity ratio depending on the laser excitation power. Using the FIR technique, the phosphor’s temperature was determined by the heating effect caused by the laser pump power. Due to the change in intensity ratio versus temperature, the temperature sensitivity at 428 K was calculated as 0.781x10-2K-1 and it was suggested that it can be used as a promising temperature sensor probe in photonic devices.Publication Metadata only Investigation of spectral properties of Er3+/Yb3+ CO-doped TeO2-B2O3-NbO5-ZnO-WO3-TiO2 glass systems(2022-10-04) ERDEM, MURAT; ESMER, KADİR; CANER T. F., Sümer I., Doğan A., ERDEM M., ESMER K., ERYÜREK G.Publication Metadata only Structural characterization and dielectric parameters of polyindole/WO3 nanocomposites(WILEY, 2021) ESMER, KADİR; Erdonmez, Seda; Karabul, Yasar; Kilic, Mehmet; Ozdemir, Zeynep Guven; Esmer, KadirIn the present study, polyindole/tungsten trioxide (PIn/WO3) nanocomposites have been prepared and characterized in the context of their structural properties as well as frequency-dependent (ac) electrical features for the first time. While PIn polymer has been synthesized by chemical oxidative polymerization, WO3 nanorods have been obtained by using the hydrothermal method. Several studies, that is, transmission electron microscopy, Fourier transform infrared, energy dispersive X-ray, X-ray diffraction analysis, scanning electron microscopy, dielectric properties on these PIn/WO3 nanocomposites have been carried out. These investigations showed the average particle size of WO3 between 15.36 and 44.71 nm. The pure PIn and WO3 were compatible with the surface morphology of the PIn and WO3 reported in the scientific literature. The dielectric analyses have been carried out in the context of both the real and imaginary components of complex permittivity and electrical modulus. The epsilon ' values of all PIn/WO3 composites have been observed lower than that of pure Pln and epsilon ' decreased with the increasing amount of WO3 in the PIn matrix for the low-frequency range. Electric modulus analysis showed that the increase in M ' value with frequency implies a tendency to reach a Mmax ' value which can be interpreted as short-range mobile charge carriers perform the electrical conductivity.