Browsing by Author "Parali, L"
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Item Piezoelectric and magnetoelectric properties of PVDF/NiFe2O4 based electrospun nanofibers for flexible piezoelectric nanogeneratorsParali, L; Donmez, CED; Koç, M; Aktürk, SIn this study, flexible piezoelectric nanogenerators (PNGs) were fabricated using the composite fibers which were prepared by combining polyvinylidene difluoride (PVDF) and nickel ferrite (NiFe2O4) nanoparticles (NPs) at a concentration of 1, 3, 5, 7, and 10 wt%. The piezoelectric properties of PNG indicate that the PVDF/NiFe2O4 fibers containing NiFe2O4 NPs at a concentration of 10 wt% has a higher power efficiency of 5.4% at 20 Hz compared to that of the pure PVDF fibers at 10 Hz, under the same resistive load of 2.5 M omega. The magnetoelectric properties of PNG show that the PNG with PVDF+7 wt%NiFe2O4 supplied the highest electrical power of 0.40 mu W under a resistive load of 750K omega & nbsp;while it reached a maximum voltage value of 17.50 mV at the same load resistive load for a low-level magnetic field of 50 Hz frequency.Item Fabrication and Characterization of High Performance PVDF-based flexible piezoelectric nanogenerators using PMN-xPT (x:30, 32.5, and 35) particlesParali, L; Koç, M; Akça, EFlexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobatelead titanate Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-xPT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 mu W) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 mu W) at 15 Hz under the same resistance load of 1 M omega. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy.Item Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer-Metal Nitride/Carbide CompositesParali, L; Kurbanov, MA; Bayramov, AA; Tatardar, FN; Sultanakhmedova, RI; Xanlar, HGHigh-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt-ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.Item 2D/3D Direct Writing of Thermoplastics through Electrohydrodynamic PrintingParali, L; Koç, M; Yildiz, ZThis paper describes a novel electro hybrid mechanical system which consists of the following components: electrohydrodynamic printing combined with the fused deposition modeling, electrospinning, and electrospray. The electrohydrodynamic printing section with the fused deposition modeling of the electro hybrid mechanical system was used to obtain fibers from thermoplastics such as polylactic acid, thermoplastic polyurethane, polyethylene terephthalate-glycol, acrylonitrile-butadiene-styrene copolymer, and high impact polystyrene. This study reports the changes in the 2D array and the 3D scaffold structure of the samples and exhibits their characteristics and performance evaluations by comparing them under the same production conditions.Item Piezoelectric properties of the new generation active matrix hybrid (micro-nano) compositesParali, L; Sabikoglu, I; Kurbanov, MAA 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.Item Dielectric behaviors at microwave frequencies and Mossbauer effects of chalcedony, agate, and zultaniteParali, L; Sabikoglu, I; Tucek, J; Pechousek, J; Novak, P; Navarik, JIn 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.Item A digital measurement system based on laser displacement sensor for piezoelectric ceramic discs vibration characterizationParali, L; Pechousek, J; Sabikoglu, I; Novak, P; Navarik, J; Vujtek, MThis 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.Item Characterization ofβ-PVDF-based nanogenerators along with Fe2O3NPs for piezoelectric energy harvestingOngun, MZ; Parali, L; Oguzlar, S; Pechousek, Jbeta-phase polyvinylidene fluoride (PVDF) nanogenerators along with various concentrations (0.2, 0.4, 0.6, and 0.8 wt%) of iron oxide (Fe2O3) nanoparticles were produced using the electrospinning technique. The characterization of the free- and doped-nanogenerators was examined by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and(57)Fe Mossbauer spectroscopy, dielectric measurements, and piezoelectric effect analysis. All the analyses demonstrated that the structural transition in the specimens at doping ratios are above the critical concentration of 0.4% by wt. of Fe(2)O(3)NPs in PVDF, superparamagnetic behavior of the iron oxide particles in the composite. Utilization of the beta-PVDF along with Fe(2)O(3)NPs (0.4 wt%) exhibited higher piezoelectric properties with respect to the free form and the other additive concentrations. Considering the piezoelectric properties of the nanogenerator, the output voltage of the beta-PVDF in the presence of the 0.4 wt% of Fe(2)O(3)NPs reaches up to 1.39 V by increasing the peak amplitude to almost 50% while the undoped beta-PVDF nanogenerator reveals almost to 0.93 V at the same impact frequency (6-7 Hz).Item Affordable and customizable electrospinning set-up based on 3D printed componentsSkoumal, V; Pechousek, J; Parali, L; Koç, MThe widespread use of electrospinning, a technique widely used for fabricating micro/nanofibrous materials, has been limited by the high acquisition costs of commercial equipment. This study introduces an accessible alternative by leveraging 3D-printing technology, providing detailed insights into the design and functionality of each component. Specifically, a cost-effective syringe pump, a rotating collector that allows fiber orientation control, and a user-friendly control unit are described. The affordability and customizability of the proposed setup are emphasized, demonstrating its versatility in accelerating material research. Experimental results on polyvinyl difluoride (PVDF) showcase successful electrospinning, validating the efficacy of the 3D-printed electrospinning device. This innovative solution aims to increase the method's availability and broader utilization in research and development applications.Item The piezoelectric response of electrospun PVDF/PZT incorporated with pristine graphene nanoplatelets for mechanical energy harvestingParali, L; Tatardar, F; Koç, M; Sari, A; Moradi, RFlexible nanogenerators based on electrospun piezoelectric polyvinylidene fluoride (PVDF)/lead zirconium titanate (PZT) incorporated with unmodified graphene nanoplatelets (GNP) were fabricated via the electrospinning method. The microstructural and phase characterizations demonstrated a continuous and homogeneous fiber-shaped composite structure with good interfacial interaction between the GNP and the PVDF/PZT matrix. It was found that the diameter of the PVDF/PZT fibers was on average 270 nm, while the PVDF/PZT/GNP fiber with GNP content of 1.5wt.% had a diameter of approximately 236 nm. The piezoelectric performance evaluations of all nanogenerator devices indicated that the PVDF/PZT/GNP with GNP content of 1.5wt.% nanogenerator had an almost 6 times higher electrical output (8.68 mu W) compared to that of the PVDF/PZT-based nanogenerator (1.51 mu W) at 20 Hz within the same resistance of 2.5 M ohm. Considering its simple and low-cost fabrication technology, high performance, and stable electrical power efficiency, the introduced flexible nanogenerator based on the PVDF/PZT/GNP offers a promising capability of powering portable and wearable electronics.Item Luminescence behaviour and Raman characterization of dendritic agate in the Dereyalak village (Eskisehir), TurkeyParali, L; Guinea, JG; Kibar, R; Cetin, A; Can, NResults are presented for the cathodoluminescence (CL), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and simultaneously two thermal analyses of (DTA/TGA) spectroscopy of dendritic agate which occurs in the Pliocene polymictic conglomerates of the Hoyuklu Formation, North West of the Dereyalak village (Eskisehir, Turkey). Micro-Raman measurements were performed on dendritic agate and then strong quartz and moganite peaks were identified at 465 and 501 cm(-1), respectively. Thermal analysis shows the loss of water and hydroxyl units occurs in 2 distinct stages: at 796 and 808 degrees C. Spatially resolved CL results at room temperature were recorded for chosen 3 different areas. Grey area (100% SiO2) displays the lowest CL emission. Brown area (99.7% SiO2 and 0.3% Fe2O3) contains exsolved non-detected ironed phases such as goethite-lepidochrocite to explain the brown colour and the iron point substitutional defects attributed to the 643 nm CL emission. White outer (98.7% SiO2 and 1.3% Al2O3) would be strongly disordered as observed in the amorphous Raman spectrum containing as inferred from the spectrum CL on the outer areas, particularly non-bridging oxygen hole centres (NBOHC) (317 nm) and [AlO4]degrees/H+ (380 nm) centres produced by large amounts of aluminium in the lattice (1.33% Al2O3). When it comes to collect the data in the time resolved CL spectrum, at least three broad emission bands were detected in: a green band of low intensity at about 496 nm, intense orange band at about 600 nm, and a red band at 670 nm. The CL emission at 670 rim shows some relationships between the hydroxyl or alkali content and the abundance of O-2 (super 3-) centres and E'(1) centres. Another conspicuous observed feature in the CL spectra of agates is the existence of an orange emission band centred at around 600 nm. The predominance of the yellow CL emission band and the high concentration of E'(1) centres are typical for agates formed by acidic volcanism processes. (C) 2011 Elsevier B.V. All rights reserved.Item Fabrication and vibrational energy harvesting characterization of flexible piezoelectric nanogenerator (PEN) based on PVDF/PZTKoç, M; Parali, L; San, OIn this study, polyvinylidene difluoride (PVDF) is doped with different volume levels (10, 20, 30 vol %) of lead zirconate titanate (PZT), and neat PVDF (undoped) electrospun nanofibres are prepared by aligning them through the electrospinning process with a rotating drum collector. All of the produced nanofibres are characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR). The piezoelectric nanogenerator (PEN) devices are fabricated by placing the PVDF/PZT electrospun nanofibres as the dielectric material between two conductive plates. The vibrational energy harvesting analyses of the PEN are defined by taking measurements under various resistive loads. At 15 Hz excitation frequency, the maximum output power of PEN with PVDF+10 vol %PZT reaches 6.35 mu W by increasing the power to 85% under a resistive load of 1M Omega, while the PEN with beta-PVDF has the electrical power of 3.44 mu M at the same load. The PEN based energy generation is a promising source of clean energy generation from mechanical vibrations for powering portable microelectronic applications without an external power supply.Item FTIR and VSM properties of samarium-doped nickel ferriteSabikoglu, I; Parali, LNickel 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.Item The electret effects of crystallized polymer-ferropiezoelectric composite under electric discharge plasmaParali, LThe fluorine-containing polymer composite filled with piezo-ceramics such as PZT-2, PZT-5A, PZT-8 were prepared by a hot pressing method. The electret composites were treated by an electric discharge plasma process, formed by crystallization via electro-thermal treatment, and polarized. The surface charge density and the charge relaxation time of the electret composite were investigated using thermostimulated depolarization and their potential differences were defined via a contactless measurement method. According to the obtained experimental results, the stability of the electret charge of a composite based on F42 + PZT-5A is better than a composite based on F3 + PZT-8. (C) 2015 Elsevier B.V. All rights reserved.Item The output performance evaluations of multilayered piezoelectric nanogenerators based on the PVDF-HFP/PMN-35PT using various layer-by-layer assembly techniquesParali, LMultilayered Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and lead magnesium niobate lead titanate Pb (Mg1/3Nb2/3) O3-PbTiO3 (PMN-35PT) composition-based piezoelectric nanogenerators (PNGs) were fabricated as series, parallel, and combined series-parallel connections using various layer-by-layer assembly techniques. Supporting the theoretical approaches with experimental results shows that the fabricated four-layered PNG with parallel connections (4L-P) reached an open-circuit voltage of 0.4 V (VRMS) and a maximum electrical power of 0.3 mu W (PRMS) by drawing a current (IRMS) of 1.46 mu A under a resistive load of 140.2 K omega. Increasing the capacitance and decreasing the impedance with the fabrication of the four-layer PNG by connecting the layers in parallel connection with the support of the impedance matching process led to an increase in electrical output. With the use of an impedance matching system, the piezoelectric performance tests revealed that the 4L-P-based PNG had a 6.7 times greater electrical power efficiency (72.92 mu W) at the vibrational frequency of 20 Hz compared to that of the single-layered PNG (10.82 mu W). Furthermore, the multilayer PNG was successfully used as a wearable sensor for the monitoring of human body motions in real time on an IOT (Internet of Things) platform.Item Vibration Modelling of Piezoelectric Actuator (PEA) Using Simulink SoftwareParali, L; Sari, AThis paper presents to define a vibration modelling of a PEA using MATLAB-Simulink software based on a single degree freedom mechanical model. The experimental vibration displacement values of PEA have been carried out utilizing the swept-sine signal excitation following the peak values in the signal response measured as contactless by the laser displacement sensor. Harmony between the mathematical modelling and experimental values have been observed from 96.6 to 81.4 % between excitation amplitudes of 0.5 and 3.0 V when the vibration modelling of PEA is normally taken into consideration with a linear working range. Therefore, obtained this vibration modelling could be used as training-testing tool for estimating vibration characterization of an actuator under any excitation voltages.Item Estimating elasticity modulus of the piezo ceramic disc (PCD) using basic mathematical modellingParali, L; Sari, A; Malgaca, L; Pechousek, J; Latal, FThe objective of this paper is to determine a mathematical modelling of piezoceramic disc vibration using a single degree freedom mechanical model, with estimation of its elasticity modulus. The experimental vibration displacement values of piezo ceramic disc have been achieved utilizing the swept-sine signal excitation following the peak values in the signal response measured by the laser Doppler vibrometer. Consistency between the mathematical modelling and experimental values have been observed from 97 to 80% between excitation amplitudes of 0.5 and 3.5 V when the mathematical modeling of piezo ceramic disc is normally taken into consideration with a linear working range. The results obtained from experimental studies on resonance frequency are in a compliance with reference value declared by producer of the piezo ceramic disc.Item The piezoelectric properties of three-phase electrospun PVDF/PZT/ Multiwalled Carbone Nanotube composites for energy harvesting applicationsKoç, M; Tatardar, F; Musayeva, NN; Guluzade, S; Sari, A; Parali, LIn this study, the piezoelectric nanogenerators (PENs) based on the PVDF (polyvinylidene fluoride)/PZT (lead zirconate titanate, the particle size of <1 m) incorporated with MWCNT (Multiwalled Carbone Nanotube, Outer diameter: 10 nm, Inner diameter: 4.5 nm, and Length: 3-6 mu m) were produced using the electrospinning method. An 8- phase content of 96.56 % in PVDF electrospun composites was arrived at due to the synergistic effect of the PZT ceramics and the MWCNT nanoparticles. The experimental results showed that a PVDF/PZT/0.7 wt% MWCNT composite with a thickness of 145 mu m based on the PEN had an electrical power efficiency (0.16 mu W) approximately 1.3 times higher at a vibrational frequency of 20 Hz under a resistive load of 46 K Omega as compared to that of the PEN based on the PVDF/PZT composite (0.12 mu W). The PVDF/PZT/MWCNT-based PENs have promising potential for flexible energy transmission and structural health monitoring.Item The effect of neodymium substitution on the structural and magnetic properties of nickel ferriteSabikoglu, I; Parali, L; Malina, O; Novak, P; Kaslik, J; Tucek, J; Pechousek, J; Navarik, J; Schneeweiss, ONickel 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.Item Piezoresistive and posistor effects in polymer-semiconductor and polymer-ferropiezoceramic compositesMamedov, HA; Parali, L; Kurbanov, MA; Bayramov, AA; Tatardar, FN; Sabikoglu, IIn 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.