Liste des communications
Structural modification and magnetic properties enhancement with Er3+, of sol-gel TiO2 thin films
Nano-crystalline un-doped and erbium doped TiO2 thin films were dip-coated on glass substrates by sol-gel method. The films were annealed at 450 °C during 1 hour. DSC results show that the crystallization effectuates at 339°C for un-doped TiO2, whereas for erbium doped TiO2 the crystallization occurs earlier with two separated exothermic. XRD diagrams illustrate that un-doped and erbium doped TiO2 crystallize in anatase phase only and indicate that the crystallite size decreases from 24 to 21 nm as a function of the increase in Er3+ content. This result is confirmed by Raman spectra. Moreover, the VSM results indicate, on one hand, a ferromagnetic behaviour of the un-doped TiO2. On the other hand, the incorporation of Erbium leads to an enhancement of the ferromagnetic behaviour. It is worthy to mention that the weak Er3+ doping (0.1 at.%) is the high ordered magnetically with highest saturation magnetization of 1.92 memu. Both elaborated TiO2 and Er:TiO2 films show good structural properties and have a diluted magnetic semiconductors structure. The films are promising for the possible applications in optoelectronic devices. Voir les détails
Mots clés : TiO2 doped Er3+, Structural properties, sol-gel, Magnetic Properties, oxygen vacancies.
SURFACE CONDITIONS EFFECT ON THE CORROSION BEHAVIOUR OF STEEL REBAR IN SIMULATED CONCRETE PORE SOLUTION
In order to study a surface conditions effect on the corrosion behaviour of steel rebar, electrochemical tests were carried out in simulated concrete pore solution using samples with two different surfaces: polished and corroded (as received). The obtained results show that the oxide layer has a negative effect on the corrosion behaviour of reinforcement steel. This effect can be explained by the fact that the oxides provoke a decrease of the electrolyte resistance at the metal/concrete interface and reduce the re-passivating ability. In addition, the oxide layer acts as a physical barrier against the diffusion of hydroxyl ions, which prevents the realkalinization phenomenon. Voir les détails
Mots clés : corrosion, concrete, steel, chloride, rust.
Synthesis of Nano Particles CuO by sol-gel process and studies their Characterizations Structural
The aim of this work is synthesis and characterization of the copper oxide powders “CuO” and its composite thin film of (CuO/PMMA), by (sol-gel) process (wet-chemistry route, using (Cu (CH3COO) 2, H2O), as precursor and DMF (CH3) NC (OH), as solvent, the obtained powder has undergone a heat treatment annealing to 450°C. The structural analysis by X-Ray diffraction and the Fourier transform infrared (FTIR) reveal the single phase monoclinic structure of CuO, the average crystallite size of the powder annealed to 450 C° is 16,76nm. Voir les détails
Mots clés : CuO, CuO/PMMA, thin film, powders, (sol-gel) process, structural analysis.
Fabrication and characterization of pure ZnO thin films deposited by Sol – gel method
ZnO thin films were prepared via Sol-gel method and were deposited on an ordinary glass substrate using dip coating technique. These films undergo optical annealing using UV irradiation during 2 hours. The starting materials used were zinc acetate dehydrate, 2-methoxyethanol which was used as solvent as well as the mono-ethanolamine (MEA) as stabilizer. Xraydiffraction study shows that all the films prepared in this work have a preferential orientation situated at 34° and correspond to (002) plan of the hexagonal Wurtzite structure, with lattice constants a = b = 3.02 Å, c = 5.20 Å. The optical band gap energy of the thin films was found to be a direct allowed transition ~3.23 eV. These values belong to the blue shift absorbance. Moreover, the photoluminescence measurement reveals that the prepared samples exhibit intense emission band in the visible and near UV. This observation led us to practical applications in the area of optoelectronic. Voir les détails
Mots clés : Photoluminescence, band gap, ZnO, sol-gel method
Time-varying ultimate strength of aging sheet pile considering corrosion effect
Steel Sheet pile walls are widely used in excavation support systems, cofferdams, cut-off walls under dams, slope stabilization, water front structures, and floodwall. Corrosion in sheet pile leads to severe degradation processes which usually affect both the ultimate and serviceability limit state performance of the structure. Recent developments in mathematical modeling strategies, in association with in situ thickness measurements, have significantly enhanced the qualitative understanding of the corrosion processes at various locations within marine structures. A comprehensive mathematical model is developed that allows capturing all the main effects of corrosion. Voir les détails
Mots clés : Sheet pile, corrosion, Mathematical, modeling
Behaviour of the electric arc for different times and for different values of welding currents
Welding is a permanent joiningprocess used to join different materials like metals, alloysor plastics, togetherat their contacting surfacesby application of heat and or pressure. The study of welding processes currently appears as an area of research both open and complex because it requires to share of knowledge in different fields of physics and mechanics.Thus, the description of one of the most commonly used processes,the arc welding, involves physical phenomena as varied as the study of plasmas, magnetic and hydrodynamic interactions, the description and quantification of heat transfer, etc. The aim of our work is the treatment of the influence of welding time and welding current on the form of the arc, voltage and current density in the GTWA process. For this, we realize a numerical study to determine the arc forms, the voltage and the current density, in which we use the finite element method for the calculation, using Comsol software. The Main results obtained are: 1-The arc shape and evolution of isothermal change with increasing weld time.2-The distribution of the voltage and the current density between the torch and the plate weld obtained by simulation are the same with the results presented in the literature. Voir les détails
Mots clés : arc welding, GTAW process, welding current, modeling, Finite elements method, COMSOL Multiphysics
ILLUSTRATION OF SQUAR-WAVE VOLTAMMETRY AS AN EFFICIENTANALYTICAL METHOD FOR NANOMOL AMOUNT HIGH DETECTION OF HEAVY METALS FOR ENVIRONMENTAL APPLICATIONS
Square wave voltammetry (SWV) has been widely used in the development of electrochemical sensors and biosensors in recent years due to its high selectivity and sensitivity. It is of great interest and importance to rapidly and sensitively detect disease-related biomarkers, environmental pollutants (e.g., heavy metals and other chemical contaminants), which are severely detrimental to human and animal life and the environment as a whole. Voir les détails
Mots clés : Square wave voltammetry, Molecularly imprinted, Molecularly imprinted polymers, Detection, environment
Improvement in Nano-hardness and Corrosion Resistance of of XC48 Samples by Plasma Immersion Ion Implantation
In this work, Nitrogen Plasma Immersion Ion Implantation (PIII) treatment of (XC48) Carbon steel was performed in a vacuum chamber with an inductive RF source (l3.56 MHz) at low pressure in order to investigate the influence of the process conditions on the corrosion properties of this studied material. The X-rays diffraction analysis revealed the presence of several nitride phases (Fe3N and FeN) formed onto implanted samples. The mechanical characterization of the processed samples showed an increase of 450 % in the nanohardness.A low corrosion rate is obtained denoting an improvement in the corrosion resistance behavior. These results are particularly interesting since they were obtained for relatively low bias voltages and processing time. Voir les détails
Mots clés : Plasma nitriding, Low Carbon Steel, Nanohardness, corrosion resistance, Negative DC bias voltage
The comparative study between the inhibitive effect of sodium molibdate and sodium vanadate on the corrosion behaviour of aluminium alloy in chloride medium
The effect of molybdate and vanadate inhibitor ions on the corrosion of aluminium alloy in near-neutral chloride solution has been studied using measurements of the open circuit potential and its variation with time, electrochemical impedance measurements and polarization curves. In addition, scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray photoelectrons were used for surface analysis. The results show that both inhibitors present an interesting protective effect against pitting corrosion of aluminum. However the effect of molybdate is more significant than the one of vanadate. This inhibitive effect is reflected through the substantial reduction of both the rate of pit nucleation and the current rise characterizing the pit propagation progress. Voir les détails
Mots clés : corrosion, aluminum, chlorides, inhibitors, molybdate, vanadate
Elaboration and characterization of nanosized RuO2-TiO2 powder by Sol Gel route
Mixed metal oxide, RuO2-TiO2 powders were successfully synthesized via a sol gel method and reflux process by using hydrolysis of titanium oxide nanopowders (prepared in the first stage by sol gel route) with its mixture anatase and rutile phases and RuCl3 as rhutenium source in water and alcohol. Nanopowders thus prepared are characterized by X-ray diffraction, UV solid, SEM, ATG and FT-IR techniques. The XRD spectrum confirms the complete conversion of RuCl3 to RuO2 with the presence of TiO2 in its anatase phase only, which is due to the conversion of rutile TiO2 to anatase TiO2. The crystallite size calculated from Debye-Scherrer’s formula is 9 nm. UV solid study show that the characteristic absorption bands of TiO has a low intensity; this is only due to the strong absorption of RuO2 by contribution to titanium oxide. It is reported an increase in absorption intensity with the RuO2 content. This can be attributed to the external effect of resonance related to the excitation of electron collective oscillations in the RuO2 nanoparticles by the electric field of the electromagnetic wave. Voir les détails
Mots clés : nanopowders, sol gel, RuO2-TiO2