Browsing by Author "Pechousek, J"

Now showing 1 - 7 of 7
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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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    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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    Characterization ofβ-PVDF-based nanogenerators along with Fe2O3NPs for piezoelectric energy harvesting
    Ongun, MZ; Parali, L; Oguzlar, S; Pechousek, J
    beta-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).
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    Affordable and customizable electrospinning set-up based on 3D printed components
    Skoumal, V; Pechousek, J; Parali, L; Koç, M
    The 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.
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    Estimating elasticity modulus of the piezo ceramic disc (PCD) using basic mathematical modelling
    Parali, L; Sari, A; Malgaca, L; Pechousek, J; Latal, F
    The 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.
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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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    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.