Browsing by Author "Sabikoglu, I"

Now showing 1 - 17 of 17
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    Piezoelectric properties of the new generation active matrix hybrid (micro-nano) composites
    Parali, L; Sabikoglu, I; Kurbanov, MA
    A hybrid piezoelectric composite structure is obtained by addition of nano-sized BaTiO3, SiO2 to the micro-sized PZT and polymers composition. Although the PZT material itself has excellent piezoelectric properties, PZT-based composite variety is limited. Piezoelectric properties of PZT materials can be varied with an acceptor or a donor added to the material. In addition, varieties of PZT-based sensors can be increased with doping polymers which have physical-mechanical, electrophysical, thermophysical and photoelectrical properties. The active matrix hybrid structure occurs when bringing together the unique piezoelectric properties of micro-sized PZT with electron trapping properties of nano-sized insulators (BaTiO3 or SiO2), and their piezoelectric, mechanic and electromechanic properties significantly change. In this study, the relationship between the piezoelectric constant and the coupling factor values of microstructure (PZT-PVDF) and the hybrid structure (PZT-PVDF-BaTiO3) composite are compared. The d(33) value and the coupling factor of the hybrid structure have shown an average of 54 and 62% increase according to microstructure composite, respectively. In addition, the d(33) value and the coupling factor of the hybrid structure (PZT-HDPE-SiO2) have exhibited about 68 and 52% increase according to microstructure composite (PZT-HDPE), respectively. (C) 2013 Elsevier B.V. All rights reserved.
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    Modeling of thorium (IV) ions adsorption onto a novel adsorbent material silicon dioxide nano-balls using response surface methodology
    Kaynar, ÜH; Sabikoglu, I; Kaynar, SÇ; Eral, M
    The silicon dioxide nano-balls (nano-SiO2) were prepared for the adsorption of thorium (IV) ions from aqueous solution. The synthesized silicon dioxide nano-balls were characterized by Scanning Electron Microscopy/Energy Dispersive X-ray, X-ray Diffraction, Fourier Transform Infrared and BET surface area measurement spectroscopy. The effects of pH, concentration, temperature and the solid-liquid ratio on the adsorption of thorium by nano-balls were optimized using central composite design of response surface methodology. The interaction between four variables was studied and modelled. Furthermore, the statistical analysis of the results was done. Analysis of variance revealed that all of the single effects found statistically significant on the sorption of Th(IV). Probability F-values (F=4.64-14) and correlation coefficients (R-2=0.99 for Th(IV)) indicate that model fit the experimental data well. The ability of this material to remove Th(IV) from aqueous solution was characterized by Langmuir, Freunlinch and Temkin adsorption isotherms. The adsorption capacity of thorium (IV) achieved 188.2 mg g(-1). Thermodynamic parameters were determined and discussed. The batch adsorption condition with respect to interfering ions was tested. The results indicated that silicon dioxide nano-balls were suitable as sorbent material for adsorption and recovery of Th(IV) ions from aqueous solutions. (C) 2016 Elsevier Ltd. All rights reserved.
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    Dielectric behaviors at microwave frequencies and Mossbauer effects of chalcedony, agate, and zultanite
    Parali, L; Sabikoglu, I; Tucek, J; Pechousek, J; Novak, P; Navarik, J
    In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emission spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and Fe-57 Mossbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm(-1) to 4000 cm(-1) range, epsilon' values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, epsilon' and epsilon '' values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. Fe-57 Mossbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions.
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    Comparative Analyses of Few West Turkish Varieties of Pomegranate (Punica granatum L.) Peels for Phenolic Content Using Liquid Chromatography
    Yenil, N; Yemies, F; Sabikoglu, I; Memon, N; Güler, A
    In this work, the amounts of phenolic compounds in the peels of four different pomegranate varieties grown in ozdere-Izmir, Turkey were investigated for the first time. Three different extraction processes namely reflux, ultrasonic bath and mixing, were carried out with dry and fresh pomegranate peels for two different periods of 4 and 12 h. The best results for ellagic acid, hesperidin, and quercetin, except resveratrol, were observed in refluxing extraction in MeOH. It is seen that the amounts of ellagic acid obtained from the dry samples are quite good in shorter extraction time (4-h) as 2778, 3376, 5024 and 3115 mu g/g, when compared to fresh samples where reduced amounts were obtained as 973, 2046, 3232 and 1822 mu g/g. Similarly, the highest ellagic acid quantities were observed in dry and fresh samples as named of Izmir 8; 2624 mu g/g and 8761 mu g/g, respectively by using HPLC-DAD for longer extraction time (12-h) which was found to negatively affect the phenolics for fresh samples. In fresh samples, extraction is rapid and long heating causes deterioration. As expected, the amount of ellagic acid was higher in the dry ones. The flavonoids hesperidin and quercetin were detected in quite well amounts for most of the samples, also hesperidin was in high as about 85.5 and 73.3 mu g/g in one of the samples. Fifteen different phenolics such as ellagic acid, hesperidin, quercetin, resveratrol, catechin, epicatechin, gallocatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, cyanidin, delphinidin, malvidin, myricetin, caffeic acid, caftaric acid, p-coumaric acid, gallic acid and ferulic acid were investigated. The antioxidant activity and total phenolic content analyses were also conducted in the methanolic supernatant extracts. DPPH inhibitions of all extracts varied from 47.22% to 93.83% at 4-h and from 36.88% to 94.96% at 12-hour extractions. Furthermore, ANOVA analyzes for ellagic acid and some catechin derivatives was conducted.
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    A digital measurement system based on laser displacement sensor for piezoelectric ceramic discs vibration characterization
    Parali, L; Pechousek, J; Sabikoglu, I; Novak, P; Navarik, J; Vujtek, M
    This study describes the innovative design of a digital measurement system based on a laser displacement sensor (LDS) as a vibrometer which is capable to measure a dynamic displacement response dependence on a stimulated vibration. The frequency response of a piezoelectric ceramic disc is obtained by processing the input/output signals obtained from the function generator and digital oscilloscope (digitizer) cards driven by a personal computer. Resonant frequencies of vibration are achieved utilizing the swept-sine signal excitation following the peak values in the signal response measured by LDS. The analogue signal from LDS controller represents directly a mechanical vibration of a piezoceramic disc. The test measurement results indicate that the system can distinguish resonance frequencies of piezoelectric ceramic discs up to 40 kHz with the resolution 1 Hz. Piezoelectric coefficient d(33) and its linearity along the excited voltage amplitudes have been calculated by the applied methods as a demonstration of a successful system concept. The results achieved are in compliance with the reference value declared by the manufacturer of the piezoceramic disc. (C) 2015 Elsevier GmbH. All rights reserved.
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    Photoluminescence investigations of Li2SiO3:Ln (Ln=Er3+, Eu3+, Dy3+, Sm3+) phosphors
    Sabikoglu, I; Ayvacikli, M; Bergeron, A; Ege, A; Can, N
    In this study, we report a comprehensive structural and photoluminescence (PL) study on lithium metasilicate (Li2SiO3) phosphor ceramics doped with four rare earth (RE) ions. X-ray diffraction (XRD) patterns show a dominant phase, characteristic of the orthorhombic structure Li2SiO3 compound and the presence of dopants has no effect on the basic crystal structure of the material. The first excited state Er3+ luminescence at 1.54 mu m arises from a sharp atomic-like radiative transition between the I-4(13/2) state and the I-4(15/2) state (ground level) under a 532 nm line of an Ar ion laser excitation. Sm doped samples showed Sm3+ emission characteristics corresponding to the some (4)G(5/2) -> H-6(j) (j = 5/2.9/2,11/2) transitions indicating a strong crystal-field effect. PL spectra of Eu doped material exhibited peaks corresponding to the D-5(0) -> F-7(j) (j similar or equal to 0,1,2,3 and 4) transitions under 405 nm excitation. The dominant red color emission at 612 nm from the hypersensitive (D-5(0) -> F-7(2)) transition of Eu3+ indicates the inversion antisymmetry crystal field around Eu3+ ion, which is favorable to improve the red color purity. Dy doped samples showed the Dy3+ emission characteristic due to the F-4(9/2) -> H-6(13/2) transition. Their relative intensity ratios also suggested the presence of a symmetric environment around the metal ion. We suggest that lithium metasilicate has enough potential candidates to be a phosphor material. (C) 2012 Elsevier B.V. All rights reserved.
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    Measurements of Environmental Pollution in Industrial Area Using Magnetic Susceptibility Method
    Kucer, N; Sabikoglu, I; Can, N
    Gaziemir district of Izmir, the Aegean Free Zone, is an industry center of approximately 295 companies that operate in lots of fields such as production, maintenance-repair, trade and that provide 1/3 of total employment in 21 free zones in Turkey. In this study, magnetic susceptibility values of soil samples taking from environment of various factories in Aegean Free Zone have been determined. Magnetic susceptibilities of samples in low and high frequency have been measured by Bartington MS2B magnetic susceptibility measurement device. All of the samples have showed ferromagnetic characteristics and also their pseudosingle-domain structures and super paramagnetic granule additives have been determined by evaluating their graphics connected to frequency.
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    Determination of optical and structural properties of lithium silicate ceramics with different ratios of Sm doped
    Sabikoglu, I
    In this study, the synthesis and luminescence characterization of Samarium (Sm3+) doped lithium metasilicate (Li2SiO3) phosphor ceramic were investigated. It was presented and discussed the results obtained on the luminescence and other optical studies such as X-ray diffraction (XRD), optical absorption and luminescence properties of Li2SiO3:Sm3+ phosphor ceramic. The Li2SiO3 compound was shown a characteristic phase in XRD. The doping in the lithium compound was not having a significant effect on the basic crystal structure of the material. The maximum photoluminescence (PL) emission for Sm3+ doped Li2SiO3 was observed at 554, 583, 641, 725 nm and bore resemblance to the visible region of the spectrum. The glow curves of all synthesized materials have a complex peak structure after being irradiated with a Sr-90-Y-90 beta source. In addition, the peak between 400 and 600 nm was seen in the radioluminescence (RL) spectrum because of a wide peak thought to be caused by silicate. (C) 2022 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved.
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    FTIR and VSM properties of samarium-doped nickel ferrite
    Sabikoglu, I; Parali, L
    Nickel Ferrite (NiFe2O4) doped with Samarium (Sm) (0.2, 0.3, 0.4, 0.5 mol.%) was prepared by the conventional solid-state reaction. The crystal structure, surface morphology, infrared spectrum of absorption, and magnetic properties of samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and vibrating sample magnetometer (VSM). XRD patterns were indexed with inverse spinel cubic phase with the space group of Fd-3m of nickel ferrite. The average grain size was about 5-10 mu m. FTIR spectral study on the NiFe2O4 ferrite phase was recorded between 350 cm(-1) and 4000 cm(-1). Two fundamental absorption bands of the ferrites were appeared at 450 cm(-1) and 1000 cm(-1) characteristic of metal vibrations. VSM measurements show that the NiFe2O4 doped with Sm 0.3% has the highest value of saturation magnetization. It is also easily demagnetized due to the low value of coercivity field it has. Both NiFe2O4 doped with Sm 0.2 mol.% and 0.4 mol.% materials have same values of coercivity field. However, NiFe2O4 doped with Sm 0.4 mol.% material has the comparatively high value of saturation magnetization than NiFe2O4 doped with Sm 0.2%, also this material was hardly demagnetized, and has highest coercivity field.
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    Synthesis of Eu and Dy doped Sr3B2SiO8 using solid state reaction and investigation of radio and photoluminescence properties of these materials
    Sabikoglu, I
    Sr3B2SiO8 host material doped with separately Eu3+, Dy3+ synthesized by conventional solid state synthesis methods at 1100 degrees C. According to the results of XRD, samples have both of the Sr3B2SiO8 phase and the SrSiO3 phase (Multi-phase MP). Although there is significant amount of impurity concentration, expected energy transitions were obtained from the samples which are doped with Eu3+ and Dy3+. Both samples were performed to the radioluminescence (RL) and photoluminescence (PL) measurements. Measurement results, they were both in harmony with each other. Eu:Sr3B2SiO8 (MP) phosphor has D-5(0) -> F-7(j) (j = 0, 1, 2, 3 and 4) transitions and Dy: Sr3B2SiO8 (MP) phosphor has F-4(9/2) -> H-6(J) (j = 9/2, 11/2, 13/2 and 15/2) transitions. Dy: Sr3B2SiO8 (MP) phosphor synthesized by conventional solid state synthesis method and the RL and PL properties were examined for the first time. (C) 2012 Elsevier B. V. All rights reserved.
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    Adsorption of thorium (IV) by amorphous silica; response surface modelling and optimization
    Kaynar, UH; Sabikoglu, I
    The amorphous SiO2 (200-300nm) was synthesized as an absorbent and thorium adsorption of SiO2 was investigated using experimental and RSM method. The SiO2 particles were made for the adsorption of thorium from aqueous solutions, and characterized by particle size measurement, XRD and SEM. The adsorption of thorium process was optimized with RSM method. The correlation between four variables was modeled and studied. Under optimum conditions, the adsorption capacity of SiO2 particles was found to be 134.4mg/g, the correlation coefficient (R-2) and the F value was obtained 0.96 and 1.98x10(-6), respectively. In addition, the adsorption isotherms were examined.
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    Energy Harvesting Sensor - PZT0,5M0,5(M:PVC, PP, PVDF) Composite Thick Film Equipped With SiO2
    Sabikoglu, I
    PZT (Lead zircon titanate) material has been used fOr many years because of its unique piezoelectric properties especially in conversion of electrical energy to mechanical energy and vice versa, and it is the most used material in this piezoelectric area. 'these kinds of piezoelectric materials, which can be produced as thin or thick film, have a wide range of uses in electronics such as; ultrasonic applications, in aircraft air -flames, structural health monitoring, and in energy harvesting as actuators or transducers, due to its large surface area and -flexibility. In this study, composite thick films were produced with PZT piezoelectric material by using different polymers. In addition, synthesized in nano size the Si02 (silicon dioxide) spheres were added to the films. PZT-5H (Navy Type VI) piezoelectric materials were made into film by inciting method with the different polymers (Polyvinyl chloride - PVC, Polypropylene - PP, and Polyvinylidene fluoride - PVDF). The SiO: spheres, which have about 120nm particle size, were added to this polymer PZT films at a rate of 1%. In present study, invert microscope images and scanning electron microscope (SEM) images of the films were obtained, in addition to this, the capacitance, dielectric constant, resonance and anti-resonance frequencies and effective efficiencies were calculated with a homemade system. It can be decided that the produced films can he used as low frequency actuators or transducer in energy harvesting system.
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    Statistical analysis and susceptibility properties of heavy/light metal pollution in surface seawater of Izmir Bay
    Sabikoglu, I
    The inner bay of Izmir is known as the part between Sasali/Karsiyaka coastline and Guzelbahce/Bayrakli. It is used extensively in transportation. There is constant ferry transportation and an international port operates in this region. There are also a few streams that flow into the inner bay. Therefore, the inner bay can be exposed to continuous chemical pollutants, and these wastes can intensively be observed in its natural structure. In this study, the magnetic susceptibility values and elemental analyses of the samples taken from the surface sea waters of the inner bay coastline were performed. Silicon, strontium, and manganese elements were mostly observed in the samples. The greatest susceptibility values were seen in the Bostanli ferry port and Goztepe ferry. In addition, the standard deviation and correlation coefficient values of the samples were calculated and discussed. According to the correlation coefficient value, it can be said that there is a positive correlation between metal ion ratios and magnetic susceptibility.
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    Absorption and photoluminescence spectroscopy of Er3+-doped SrAl2O4 ceramic phosphors
    Ayvacikli, M; Khatab, A; Ege, A; Sabikoglu, I; Henini, M; Can, N
    A spectroscopic characterization of Er3+-doped SrAl2O4 phosphor materials synthesized by a solid-state reaction method with Er concentrations varying from 0.1 to 1 mol% has been performed by studying photoluminescence (PL) in the temperature range 10 to 360 K and absorption spectra. PL signals containing five emission bands at 1492, 1529, 1541, 1558, and 1600 nm, respectively, have been observed at room temperature for Er3+ transitions in the near infrared region. The samples exhibit a main luminescence peak at 1.54 mu m, which is assigned to recombination via an intra-4f Er3+ transition. Sharp bands centered at around 378, 488, 521, 651, 980, 1492, and 1538 nm in the absorption spectra can be associated with transitions from I-4(15/2) level to H-2(9/2), F-4(7/2), H-2(11/2), F-4(9/2), I-4(11/2), H-2(11/2), and I-4(13/2) levels, respectively. The sharp emission peaks and excellent luminescence properties show that SrAl2O4 is a suitable host for rare-earth-doped phosphors, which may be suitable for optical applications.
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    The effect of neodymium substitution on the structural and magnetic properties of nickel ferrite
    Sabikoglu, I; Parali, L; Malina, O; Novak, P; Kaslik, J; Tucek, J; Pechousek, J; Navarik, J; Schneeweiss, O
    Nickel ferrite NiFe2O4 is a typical soft magnetic ferrite with high electrical resistivity used as high frequency magnetic material. Neodymium (Nd3+) doped NiFe2O4 materials were fabricated using solid state reaction. The properties of the obtained material were investigated by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FT-IR), magnetic measurements on SQUID and Mossbauer spectroscopy. It was found that the material consists of two different phases: Nd3+ doped NiFe2O4 and NdFeO3. The Nd3+ ions occupy cation sites of the NiFe2O4 inverse spinel structure. NdFeO3 phase occurred when the level of Nd3+ atoms exceed a percolation limit. The presence of both phases was confirmed by SEM observations. The Mossbauer spectra analysis showed two sextets, which can be ascribed to iron atoms in tetrahedral and octahedral positions. From their intensities it is concluded that Nd3+ occupies octahedral sites in the spinel structure of NiFe2O4, which were originally occupied by Ni2+. (C) 2015 The Authors. Published by Elsevier GmbH.
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    Piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites
    Mamedov, HA; Parali, L; Kurbanov, MA; Bayramov, AA; Tatardar, FN; Sabikoglu, I
    In this study, piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic composites have been investigated. The results show that composites based on crystallizable polymers, such as PVDF, HDPE, and PP dispersed by semiconductors and ferropiezoelectric fillers have piezoresistive and posistor properties, respectively. At low pressure, charge carriers tunneling through the located thin polymer among filler particles into the barrier define the conductivity of the composite. When pressure value is increased from 0 to 1 MPa, the thickness of the interlayer decreases and tunnel conductivity descends exponentially depending on barrier height. The piezoresistor sensitivity of a composite based on PVDF-70 vol % + Si-30 vol % is higher than a composite based on HDPE-70 vol % + Ge-30 vol %. Furthermore, the posistor properties of polymer composites dispersed by ferropiezoceramic are determined as the maximum resistance that varies significantly with temperature. Posistor effect in composites based on polymer + ferropiezoceramic is associated with the height of the barrier layer, which changes according to properties of filler, polymer, and dielectric permittivity of two-phase composites. The highest specific resistance related to HDPE-70 vol % + BaTiO3-30 vol % composite was observed at similar to 403 K.
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    Calibration of gamma-ray detectors using Gaussian photopeak fitting in the multichannel spectra with a LabVIEW-based digital system
    Schlattauer, L; Parali, L; Pechousek, J; Sabikoglu, I; Celiktas, C; Tektas, G; Novak, P; Jancar, A; Prochazka, V
    This paper reports on the development of a gamma-ray spectroscopic system for the (i) recording and (ii) processing of spectra. The utilized data read-out unit consists of a PCI digital oscilloscope, personal computer and LabVIEW (TM) programming environment. A pulse-height spectra of various sources were recorded with two NaI(T1) detectors and analyzed, demonstrating the proper usage of the detectors. A multichannel analyzer implements the Gaussian photopeak fitting. The presented method provides results which are in compliance to the ones taken from commercial spectroscopy systems. Each individual hardware or software unit can be further utilized in different spectrometric user-systems. An application of the developed system for research and teaching purposes regarding the design of digital spectrometric systems has been successfully tested at the laboratories of the Department of Experimental Physics.