Abderrafik Nemamcha | University 8 May 1945 Guelma (original) (raw)

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Papers by Abderrafik Nemamcha

Research paper thumbnail of Effect of deposition conditions on the properties of Ni–Mo–W coatings as electrocatalysts for hydrogen evolution reaction

Journal of Applied Electrochemistry, Jul 30, 2021

WO 3 is a widely considered photocatalytic material for water purification. In this paper, nanocr... more WO 3 is a widely considered photocatalytic material for water purification. In this paper, nanocrystalline WO 3 films were deposited on a glass slide by the mid-frequency reactive magnetron sputtering method. The aim is to determine the photocatalytic activities of the films, which are controlled by the process parameters (oxygen flow and substrate bias). The annealed films reveal a hexagonal structure and have some absorptivity in the visible region. The field emission scanning electron microscopy pattern shows that the films exhibit a uniform, smooth surface. The photocatalytic properties of the prepared films were evaluated by the photodecolorization of methylene blue. The films exhibit the best activity at an oxygen flow rate of 30 sccm and a substrate bias of −50 V. The reason is that this film can create more electron-hole pairs as a result of the greater absorption of visible light, which enhances the photocatalytic performance. Based on the results, a possible photocatalytic mechanism has been proposed.

Research paper thumbnail of Sonochemical Synthesis of Pd<SUB>50</SUB>Cu<SUB>50</SUB> Bimetallic Nanoparticles

Research paper thumbnail of Morphology and Rietveld analysis of nanostructured Co-Ni electrodeposited thin films obtained at different current densities

Surface and Coatings Technology, 2017

Co-Ni thin films were synthetized by electrodepostion on Cu substrate from chloridesulphate bath ... more Co-Ni thin films were synthetized by electrodepostion on Cu substrate from chloridesulphate bath containing thiourea as additive. The effects of applied current density (J = 1, 2, 3 and 4 A/dm 2) on the composition, morphology, microstructure and formation mechanism of deposited films were investigated by EDX, SEM and XRD techniques respectively. The EDX results indicate that the codeposition phenomenon of Co-Ni coatings can be illustrated as slightly anomalous electrodepositing behavior. The SEM micrographs show that the deposits are well adherent and exhibit a compact surface with a cauliflower-like appearance and changes from rough to smooth surface with the rise of current density. The structural investigation is performed through the Rietveld refinement of XRD patterns using MAUD program. The results reveal the formation of both HCP Co phase, FCC Co(Ni), HCP Co(Ni) and HCP Co(S) solid solutions (SS). The HCP SS formation mechanism is described by the diffusion of Ni and S atoms along c axis of HCP Co crystal lattice. The increase of current density causes a lattice distortion revealed by an increase of the lattice parameters of different

Research paper thumbnail of Optimization of electrodeposited Co–Ag coatings microhardness using Taguchi and ANOVA methods

Materials Research Express, 2019

Research paper thumbnail of Synthesis of Palladium Nanoparticles by Sonochemical Reduction of Palladium(II) Nitrate in Aqueous Solution

Journal of Physical Chemistry B, 2006

The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irra... more The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irradiation of palladium(II) nitrate solution. The starting solutions were prepared by the addition of different concentrations of palladium(II) nitrate in ethylene glycol and poly(vinylpyrrolidone) (PVP). The resulting mixtures were irradiated with ultrasonic 50 kHz waves in a glass vessel for 180 min. The UV-visible absorption spectroscopy and pH measurements revealed that the reduction of Pd(II) to metallic Pd has been successfully achieved and that the obtained suspensions have a long shelf life. The protective effect of PVP was studied using Fourier transform infrared (FT-IR) spectroscopy. It has been found that, in the presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The effect of the initial Pd(II) concentration on the Pd nanoparticle morphology has been investigated by transmission electron microscopy. It has been shown that the increase of the Pd(II)/PVP molar ratio from 0.13 x 10(-3) to 0.53 x 10(-3) decreases the number of palladium nanoparticles with a slight increase in particle size. For the highest Pd(II)/PVP value, 0.53 x 10(-3), the reduction reaction leads to the unexpected smallest nanoparticles in the form of aggregates.

Research paper thumbnail of PVP Protective mechanism of palladium nanoparticles obtained by sonochemical process

Physics Procedia, 2009

ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has b... more ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has been investigated using Fourier Transform Infrared Spectroscopy (FT-IR). Palladium nanoparticles have been obtained by ultrasonic irradiation of Pd(NO(3))(2) solution in presence of ethylene glycol (EG) and PVP. The sonochemical reduction process of palladium ions (Pd(II)) to palladium atoms (Pd(0)) can be explained by considering the intense ultrasonic waves that are strong enough to produce cavitation: formation, growth and collapse of bubbles. The UV-Visible absorption spectroscopy revealed that the reduction of Pd (II) to metallic Pd has been successfully achieved. The FT-IR spectroscopy spectra analysis show that, in presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The transmission electron microscopy (HRTEM) and electron-dispersive X-ray (EDX) results confirm the dispersion, the nanometric size and the composition of the obtained palladium particles. (C) 2009 Elsevier B.V. All rights reserved

Research paper thumbnail of Stacking faults and structure analysis of ball-milled Fe–50%Co powders

Materials Chemistry and Physics, 2010

ABSTRACT Stacking faults probability, structure and microstructure parameters of different phases... more ABSTRACT Stacking faults probability, structure and microstructure parameters of different phases of ball milled Fe–50%Co powders have been quantitatively evaluated by X-ray diffraction profile analysis. It is observed that after short milling time, Co is found to undergo an allotropic transformation from FCC to HCP form. The Rietveld whole profile fitting results reveal an increase of the stacking fault probability with increasing milling time and that twin faults are more prevalent than deformation ones. In addition to the reduction of crystallite size to the nanometer level and the increase of internal strain, prolonged milling leads to the formation of a BCC Fe(Co) solid solution with a high dislocations density (3.8×1017m−2).

Research paper thumbnail of Magnetic properties of nanostructured ball-milled Fe and Fe 50 Co 50 alloy

Journal of Physics: Condensed Matter, 2006

Nemamcha by Abderrafik Nemamcha

Research paper thumbnail of Effect of deposition conditions on the properties of Ni–Mo–W coatings as electrocatalysts for hydrogen evolution reaction

Journal of Applied Electrochemistry, Jul 30, 2021

WO 3 is a widely considered photocatalytic material for water purification. In this paper, nanocr... more WO 3 is a widely considered photocatalytic material for water purification. In this paper, nanocrystalline WO 3 films were deposited on a glass slide by the mid-frequency reactive magnetron sputtering method. The aim is to determine the photocatalytic activities of the films, which are controlled by the process parameters (oxygen flow and substrate bias). The annealed films reveal a hexagonal structure and have some absorptivity in the visible region. The field emission scanning electron microscopy pattern shows that the films exhibit a uniform, smooth surface. The photocatalytic properties of the prepared films were evaluated by the photodecolorization of methylene blue. The films exhibit the best activity at an oxygen flow rate of 30 sccm and a substrate bias of −50 V. The reason is that this film can create more electron-hole pairs as a result of the greater absorption of visible light, which enhances the photocatalytic performance. Based on the results, a possible photocatalytic mechanism has been proposed.

Research paper thumbnail of Sonochemical Synthesis of Pd<SUB>50</SUB>Cu<SUB>50</SUB> Bimetallic Nanoparticles

Research paper thumbnail of Morphology and Rietveld analysis of nanostructured Co-Ni electrodeposited thin films obtained at different current densities

Surface and Coatings Technology, 2017

Co-Ni thin films were synthetized by electrodepostion on Cu substrate from chloridesulphate bath ... more Co-Ni thin films were synthetized by electrodepostion on Cu substrate from chloridesulphate bath containing thiourea as additive. The effects of applied current density (J = 1, 2, 3 and 4 A/dm 2) on the composition, morphology, microstructure and formation mechanism of deposited films were investigated by EDX, SEM and XRD techniques respectively. The EDX results indicate that the codeposition phenomenon of Co-Ni coatings can be illustrated as slightly anomalous electrodepositing behavior. The SEM micrographs show that the deposits are well adherent and exhibit a compact surface with a cauliflower-like appearance and changes from rough to smooth surface with the rise of current density. The structural investigation is performed through the Rietveld refinement of XRD patterns using MAUD program. The results reveal the formation of both HCP Co phase, FCC Co(Ni), HCP Co(Ni) and HCP Co(S) solid solutions (SS). The HCP SS formation mechanism is described by the diffusion of Ni and S atoms along c axis of HCP Co crystal lattice. The increase of current density causes a lattice distortion revealed by an increase of the lattice parameters of different

Research paper thumbnail of Optimization of electrodeposited Co–Ag coatings microhardness using Taguchi and ANOVA methods

Materials Research Express, 2019

Research paper thumbnail of Synthesis of Palladium Nanoparticles by Sonochemical Reduction of Palladium(II) Nitrate in Aqueous Solution

Journal of Physical Chemistry B, 2006

The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irra... more The sonochemical synthesis of stable palladium nanoparticles has been achieved by ultrasonic irradiation of palladium(II) nitrate solution. The starting solutions were prepared by the addition of different concentrations of palladium(II) nitrate in ethylene glycol and poly(vinylpyrrolidone) (PVP). The resulting mixtures were irradiated with ultrasonic 50 kHz waves in a glass vessel for 180 min. The UV-visible absorption spectroscopy and pH measurements revealed that the reduction of Pd(II) to metallic Pd has been successfully achieved and that the obtained suspensions have a long shelf life. The protective effect of PVP was studied using Fourier transform infrared (FT-IR) spectroscopy. It has been found that, in the presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The effect of the initial Pd(II) concentration on the Pd nanoparticle morphology has been investigated by transmission electron microscopy. It has been shown that the increase of the Pd(II)/PVP molar ratio from 0.13 x 10(-3) to 0.53 x 10(-3) decreases the number of palladium nanoparticles with a slight increase in particle size. For the highest Pd(II)/PVP value, 0.53 x 10(-3), the reduction reaction leads to the unexpected smallest nanoparticles in the form of aggregates.

Research paper thumbnail of PVP Protective mechanism of palladium nanoparticles obtained by sonochemical process

Physics Procedia, 2009

ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has b... more ABSTRACT The protective effect of polyvinylpyrrolidone (PVP) on the palladium nanoparticles has been investigated using Fourier Transform Infrared Spectroscopy (FT-IR). Palladium nanoparticles have been obtained by ultrasonic irradiation of Pd(NO(3))(2) solution in presence of ethylene glycol (EG) and PVP. The sonochemical reduction process of palladium ions (Pd(II)) to palladium atoms (Pd(0)) can be explained by considering the intense ultrasonic waves that are strong enough to produce cavitation: formation, growth and collapse of bubbles. The UV-Visible absorption spectroscopy revealed that the reduction of Pd (II) to metallic Pd has been successfully achieved. The FT-IR spectroscopy spectra analysis show that, in presence of ethylene glycol, the stabilization of the nanoparticles results from the adsorption of the PVP chain on the palladium particle surface via the coordination of the PVP carbonyl group to the palladium atoms. The transmission electron microscopy (HRTEM) and electron-dispersive X-ray (EDX) results confirm the dispersion, the nanometric size and the composition of the obtained palladium particles. (C) 2009 Elsevier B.V. All rights reserved

Research paper thumbnail of Stacking faults and structure analysis of ball-milled Fe–50%Co powders

Materials Chemistry and Physics, 2010

ABSTRACT Stacking faults probability, structure and microstructure parameters of different phases... more ABSTRACT Stacking faults probability, structure and microstructure parameters of different phases of ball milled Fe–50%Co powders have been quantitatively evaluated by X-ray diffraction profile analysis. It is observed that after short milling time, Co is found to undergo an allotropic transformation from FCC to HCP form. The Rietveld whole profile fitting results reveal an increase of the stacking fault probability with increasing milling time and that twin faults are more prevalent than deformation ones. In addition to the reduction of crystallite size to the nanometer level and the increase of internal strain, prolonged milling leads to the formation of a BCC Fe(Co) solid solution with a high dislocations density (3.8×1017m−2).

Research paper thumbnail of Magnetic properties of nanostructured ball-milled Fe and Fe 50 Co 50 alloy

Journal of Physics: Condensed Matter, 2006