Yazar "Gargouri, Mohamed" seçeneğine göre listele

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    Influence of V2O5 loading on the dielectric properties and AC conductivity of TiO2
    (Springer, 2024) Ates, Ayten; Ben Brahim, Khawla; Oueslati, Abderrazek; Gargouri, Mohamed
    The interaction between TiO2 and V2O5 can not only improve the physico-chemical properties of the material but also the dielectric and conductive properties of the material. For this purpose, TiO2 samples with 5, 7, and 10 wt% V2O5 were prepared by the impregnation method to investigate the dielectric properties and AC conductivity. The phase composition and morphology of the V2O5/TiO2 samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM)-scanning transmission electron microscope (STEM). Regardless of the vanadium content, the samples exhibit non-spherical structures and particles with size in the range of 60-200 nm. The small V2O5 peaks in XRD were detected at 7.0 and 10 wt% V2O5. In addition, the specific surface area for 5 and 7 wt% V2O5 was determined to be 9.2 m2/g, but at 10 wt% V2O5 the surface area of the sample decreases to 7.5 m2/g as the titanium dioxide pores are filled by vanadium. The DR-UV-Vis spectra of V2O5/TiO2 samples showed that the sample with 5 wt% V2O5 has isolated tetrahedrally coordinated V5+ species and increasing the V2O5 loading leads to the formation of octohedrally coordinated V5+ species in V2O5 clusters. Comparison of the Raman spectra of V2O5/TiO2 and TiO2 samples showed the formation of alpha-V2O5 on the TiO2. In addition, a detailed analysis of the Nyquist diagrams shows how sensitively the electrical properties of the materials react to changes in temperature and frequency. Jonscher's power law is used to analyze alternating current and conductivity, and it is found that the fluctuation of the exponent s adequately describes the conduction mechanism and agrees with CBH models. As the TiO2 concentration increases, the value of the activation energy generated decreases. The higher presence of Ti4+ ions due to the increase in molar volume is the cause of this increase in charge carrier mobility. The effect of the grain and grain boundary on the overall impedance is revealed by a dielectric study, which also confirms that the combination of titanium dioxide and vanadium oxide nanoparticles improves the dielectric and AC conductivity of the samples.
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    Investigation of structural, morphology, and conduction mechanism of GO–Fe3O4–TiO2 composite material
    (2023) Ateş, Ayten; ben brahim, Khawla; Keklikcioğlu Çakmak, Neşe; Oueslati, Abderrazek; Gargouri, Mohamed
    The graphene oxide composite (GO), iron oxide (Fe3O4), and titanium dioxide (TiO2) were prepared by the sol–gel process. The surface of GO is coated with TiO2 and Fe3O4 nanoparticles, and the composite contains 10.26% C, 23.70% O, 57.17% Ti, and 8.87% Fe. The formation of anatase TiO2 and magnetite Fe3O4 on the surface of GO was detected by XRD and Raman analysis. The N2 adsorption–desorption isotherm and pore size distribution results showed the formation of a mesoporous material with a specifc surface area of 233.3 m2 /g, a total pore volume of 0.298 cm3 /g, and an average pore diameter of 7.7 nm. The GO–Fe3O4– TiO2 composite’s dielectric characteristics were examined in the frequency and temperature ranges of 0.1 Hz–5 MHz and 293–373 K, respectively. The Nyquist plot suggests the non-Debye conduction behaviour, which may be related to the distribution of relaxation times within the composite material. The contribution of grains and grain boundaries to the total conductivity is confrmed by impedance spectroscopy. Jonscher’s power law was used to examine AC conductivity graphs, and the variation in the exponent “s” revealed that CBH models accurately characterize the conduction mechanism in the composite. The dielectric measurements reveal Maxwell–Wagner polarization and a thermal-activated relaxation process.