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Najwa Gouitaa, Lamcharfi Taj-Dine, Bouayad Lamfaddal, Abdi Farid, Mohamed Ounacer, Mohammed Sajieddine,
Volume 18, Issue 2 (June 2021)

    The structural and dielectric properties of iron and bismuth co-substituted BaTiO3 ceramic with the formula: B0.95Bi0.05Ti1-xFexO3 for x=0.00 to 1.00, synthesis with solid state route, were characterized.     The X-ray diffraction results show a tetragonal phase for x=0.00. While for x=0.40 to 0.80 we observed a coexistence of tree phase tetragonal, hexagonal and pseudo-cubic. And at x=1.00 only the pseudo-cubic phase is present and the other phase disappeared. The Raman results indicate the existence of tetragonal band for x≤0.40, and an appearance of characteristic bands of Fe3+ ions for more than 0.40 of Fe content. The SEM micrographs show an increase in grain size with the increase of Fe content and it reaches a maximum at x=0.40.  And the Mossbauer spectroscopy indicates that our samples is paramagnetic at room temperature and that the Fe is   oxidized under Fe3+ with no existence of Fe2+ and Fe4+ ions. The temperature dependence of dielectric permittivity was investigated in the frequency range from 20 Hz to 2MHz. The results show three dielectric relaxation phase transitions from a rhombohedral ferroelectric to orthorhombic ferroelectric (TR-O) then to a tetragonal ferroelectric phase (at TO-T), and finally to cubic paraelectric at the Curie temperature (TC).  In addition, the temperature of phase transition shifted to the lower temperature with the increase of Fe content for all the phase transitions. And the maximum of dielectric permittivity increases for TR-O while for TT-O and Tm phases transitions, it reaches a maximum at x=0.60 and x=0.80 respectively and then decreases.

Farid Lekmine, Hachemi Ben Temam, Elhachmi Temam,
Volume 18, Issue 3 (September 2021)

Nickel phosphorus alloy coatings were prepared by electrodeposition route from sulfate electrolyte bath at various current densities. SEM studies reveal spherical grains covered the entire surface with uniform distribution. EDX results showed a linear increase of P content in the developed deposits with current density and therefore, enhancing the grains size and drop of the hardness values. XRD studies reveal monocrystalline orthorhombic alloys at a low amount of phosphorus (10.88 wt. %). Corrosion tests show that 1 is the best applied current density giving the nobler Ecorr (-171.4 mV) and the lower icorr (4.64 µA/cm2).
Najwa Gouitaa, Lamcharfi Taj-Dine, Abdi Farid , Ahjyaje Fatima Zahra,
Volume 18, Issue 3 (September 2021)

      In this study we have synthesis the Zr substituted BaTi0.80Fe0.20O3 ceramics at different content of Zr from x=0.00 to 0.10 by using the solid-state route. The room temperature X-ray diffraction results confirmed the coexistence of the two tetragonal and hexagonal phases for x ≤ 0.050 of Zr content. While above 0.050 the hexagonal phase disappears in benefit of tetragonal phase. The Raman results confirmed the formation of these phases obtained with XRD. The scanning electron micrographs consist of both spherical and straight grain forms for x=0.000 to 0.075, and only spherical grain form for x=0.100 attributed to the tetragonal phase. Also, the grain size increases accompanied with a decrease in density of ceramics with increasing Zr content up to 0.050 then decreases accompanied with an increase in density. Detailed studies of dielectric permittivity measurement have provided a presence of two anomalies Te and TR-O at different temperatures, with a relaxation phenomenon and diffuse behavior which is very important for ceramic at x=0.075 of Zr content. The dielectric permittivity values of the two anomalies of Zr substituted BaTi0.80Fe0.20O3 ceramics increase with increase of Zr content and the dielectric loss is minimal at x=0.100 of Zr content. The conductivity increases with the increasing of Zr substitution from 0.025 to 0.075 levels while for x = 0.100 the dielectric conductivity decreases.  And the Cole-Cole analysis indicates a negative thermal resistivity coefficient (NTCR) behavior of these materials and an ideal Debye-type behavior.

Farideh Golbabaie, Somayeh Farhang Dehghan, Majid Habibi Mohraz, Elham Akhlaghi Pirposhteh,
Volume 18, Issue 4 (December 2021)

The present study aims to investigate the role of the electrostatic mechanism in the filtration process of Polyacrylonitrile nanofibers containing single-walled carbon nanotube. The nanofibers were fabricated via electrospinning using 16wt% Polyacrylonitrile polymer (PAN) solution, single-wall carbon nanotubes (SWNT) at a ratio of 99:1 along with N and N-Dimethylformamide solvents. Initial filtration efficiency was tested as per ISO 29463:2011 standard inside a test rig. An electrostatic discharge test was performed via the chemical treatment of the filter media with Isopropyl alcohol in accordance to EN779 standard. Mean initial filtration efficiency of the nanofiber media in the capturing of 100nm and 200nm particles were 95.92% ±2.74 and 97.26% ±1.11 respectively, while for particles between 80nm to 250nm, this was 96.73% ±2.74. The efficiency of the untreated media was 0.2% to 1.2% higher than the PAN/SWNT media after electron discharge using Isopropyl alcohol with an even bigger difference being observed at lower particle size ranges. After treatment with Isopropyl alcohol, the pressure drop of the filtration media was increased from 164.7 Pa to 185.3 Pa. The reduction in filtration efficiency observed after the electrostatic discharge test indicates that the electrical charge of the electrospun nanofibers is influential in its initial efficiency for removing the submicron particles.
Ahabboud Malika, Najwa Gouitaa, Ahjyaje Fatimazahra, Lamcharfi Taj-Dine, Abdi Farid,
Volume 20, Issue 1 (March 2023)

In this paper, Pb1-xFex(Zr0.52Ti0.48)O3 (PFZT) nanopowders, with x from 0.00 up to 0.20, were synthesized by using the sol-gel method. The PFZT samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and impedance spectroscopy. According to the experimental results, PFZT combines rhombohedral and tetragonal symmetries for all the samples without a change in phase structure. The SEM investigation indicated that the grains are homogeneous with regular form and the average grain size of PFZT ceramics changed with Fe concentration. The dielectric characterizations show that the dielectric permittivity increases with increasing temperature, and the Fe amount shifts down the temperature of transition. Moreover, a dielectric resonance phenomenon is observed for all the PFZT ceramics.

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