Liste des publications
Inhibition Effect of 2,2’-bipyridyl on the Corrosion of austenitic Stainless Steel in 0.5M H2 SO4
The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails
Mots clés : AISI309, 2, 2'-Bipyridyl, corrosion, EIS, Tafel
Numerical simulation study of a high efficient AlGaN-based ultraviolet photodetector
In this paper, a two-dimensional (2D) numerical simulation study of a p+-n-n+ AlGaN-based ultraviolet (UV) photodetector, which is designed to achieve true solar blindness with a cutoff wavelength of 0.31 µm, is presented. The device performance is evaluated by investigating both the current density-voltage characteristics and the spectral response (SR). The proposed structure is optimized in terms of the fundamental geometrical and doping parameters. During the simulations, it was found that the detector is sensitive to the UV rays in the 0.155-0.37 µm wavelength range and the spectral response can reach 0.156 AW-1 under a light intensity of 1 Wcm-2 at zero-bias voltage and room temperature. This SR peak value increases further under reverse bias conditions. The temperature effect on the detector SR and the impact of an explicit trap concentration located into the p+ and n-region are also investigated. The spectral response decreases for a temperature exceeding 420 K. At the same time, the SR reference values begin to be affected only for acceptor and donor trap densities that are much higher than the local (total) doping concentration. Voir les détails
Mots clés : AlGaN, Numerical simulation, Photodetector, Spectral response, Trap Density
Electroless copper deposition on epoxy glass substrate for electrocatalysis of formaldehyde
In this paper, we investigated the characteristics of a structured copper (Cu) ?lm deposited on the surface of an insulating epoxy glass (EG) substrate via a facile electroless plating process. The ?lm produced by this method was found to be of high purity and has a homogeneous microstructure consisting of an assembly of numerous aggregates that vary in size from 1 to 5 mm depending on the electroless deposition time. The electrocatalytic activity of the prepared electrode was investigated for the electrooxidation of formaldehyde using cyclic voltammetry in 0.1 M NaOH solution. Results show that formaldehyde oxidation takes place at a low potential of -0.34 V with large anodic current densities. Voir les détails
Mots clés : copper, electroless plating, Formaldehyde, Oxidation, Thin films
Inhibition Effect of 2,2’-bipyridyl on the Corrosion of Austenitic Stainless Steel in 0.5M H2SO4
The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules' adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails
Mots clés : AISI309, 2, 2'-Bipyridyl, EIS, Tafel, corrosion, inhibition
Computational insights about the dynamic behavior for the inclusion process of deprotonated and neutral aspirin in β-cyclodextrin
Molecular dynamics was used to study the inclusion of neutral and deprotonated aspirin into the β-cyclodextrin (β-CD) cavity. The molecular dynamic simulation allows following the time dependent behavior of the formation of the inclusion complex. For both complexes, we find a reasonable and a realistic pattern of the complexation. The calculations show a single pathway consisting of a no reversible binding process leading to the complexation of aspirin. Whereas for deprotonated aspirin it has been observed a reversible binding, in which one way leads to the binding form, and the reverse way to the unbinding form. Throughout the simulation, the penetration of aspirin (ASA) or deprotonated aspirin (ASA−) inside the cavity occurs only with a phenyl ring entering first through the wider or narrower rim. The determination of free energy using unbiased and biased simulations of the corresponding inclusion processes gives more favorable inclusion process of aspirin than deprotonated aspirin. The inclusion of the guest molecule is found deeply embedded within ASA:β-CD complex whereas it is partial in ASA−:β-CD complex. Also, the orientation A of both complexes is found more favorable of ca. 1.9 kcal/mol, and of ca. 0.8 kcal/mol, respectively for neutral and deprotonated complex. Aspirin molecule establish one H-bond between the hydrogen carboxylic atom and one oxygen atom of primary hydroxyl group of β-CD; this H-bond is detected during about 20% of the simulation period. In addition, we found that water molecules in the first solvation layer are implied with hydrogen carboxylic atom and the keto oxygen atoms within H-bonds. While, water molecules of the second solvation layer is in interact with the O1 and O2 oxygen atoms of aspirin. Accordingly, based on the obtained results we can consider that the hydrophobic/hydrophilic interactions are the most important driving forces of the complexation assisted by stabilizing H-bonds. Voir les détails
Mots clés : Aspirin, Cyclodextrin, Inclusion complexes, Molecular dynamic simulation, Umbrella sampling, Hydrogen bonding
Experimental and numerical analysis of mode?I interlaminar fractureof composite pipes
A common industrial production process for composites is filament winding, widely used for the production of axially symmetriccomponents. In these composite components, delamination is a predominant failure mechanism. The current workfocuses on investigating experimentally the effect of the initial crack and fiber bridging length on the mode-I delaminationresistance curve (R-curve) behavior of various double cantilever beam (DCB) specimens. For this purpose, the magnitudesof initiation and propagation fracture toughness (GIC-init and GIC-prop) and the compliance C are calculated. DCB specimenswith a stacking sequence of [± 50]6 and various initial crack lengths of a0 = 33, 37, 59 and 70 mm are manufactured from areal composite pipe using filament winding process. In order to evaluate the critical energy release rate in mode-I, variousfracture tests are conducted on these specimens. The greatest bridging zone length dues to good penetration of two adjacentlayers of the delamination interface. Moreover, the results indicate that the fiber bridging length has a significant effect onthe GIC and the largest value of fiber bridging causes a large fracture toughness value. Finally, numerical simulations areperformed using finite element (FE) method and GIC-init measurements obtained experimentally are compared to the numericalfindings. The numerical displacements and GIC-init, calculated from the numerical displacements, are found to be in goodagreement compared to the experimental results. Voir les détails
Mots clés : Filament wound composite, Critical energy release rate, Propagation energy release rate, DCB specimen, Fiber bridging
Thermal spray metallisation of carbon fibre reinforced polymer composites Effect of top surface modification on coating adhesion and mechanical properties
Thermal Spray TS processes are used to enhance the surface properties of Polymer Matrix Composites. However, poor adhesion and mechanical degradation are usually experienced. The main objective of this work is to investigate the effect of the modification of the top surface of Carbon Fibre Reinforced Polymer CFRP substrate on the TS deposition of metallic coatings. CFRP composite panels were manufactured with different upper layers I pure epoxy overflow layer, II pure copper powder filler layer, III mixture copper and stainless steel powder filler layer, and IV aluminium mesh layer. The top layers of the CFRP substrates were manufactured during the forming process. Arc Spray, one of the TS processes, was used to deposit zinc coating onto the manufactured CFRP panels. The substrates were sandblasted before the TS process to enhance the adhesion of the deposited zinc to the substrate. The quality of the coatings including adhesion and mechanical properties was investigated using tensile adhesion and bending test, respectively. The porosity, microstructure, morphology and surface fracture of the metallised CFRP coupons were characterized using optical and electronical microscopy techniques. The results obtained revealed that pure epoxy top layer did not resist to sandblasting prior to TS process, contrary to the substrates with fillers and mesh top layer. Moreover, the aluminium based mesh layer improved the adhesion strength by about 50 percent. Bending test results indicated that coating on CFRP composites decreased their mechanical properties. However, the use of a metallic mesh layer reduced the degradation effect of spraying. Voir les détails
Mots clés : CFRP composite, Zn coating, Arc spray, Filler layer, Adhesion strength
Electrochemical behavior, characterization and corrosion protection properties of poly(bithiophene + 2-methylfuran) copolymer coatings on A304 stainless steel
Polybithiophene (PBTh), poly(2-methylfuran) (PMeFu) and poly(bithiophene + 2-methylfuran) noted poly(BTh + MeFu) copolymer films were synthesized by electrochemical deposition on 304-stainless steel, from an acetonitrile (ACN) solution containing 10−2 m bithiophene, 10−2 m 2-methylfuran and 10−1 m lithium perchlorate (LiClO4), by cyclic voltammetry (CV) between 0 V and 2 V vs. SCE, with a scan rate of 50 mV · s−1. The copolymers coated were studied in a corrosive sulfuric acid medium (H2SO4 1 N) using the potensiodynamique polarization method and the electrochemical impedance spectroscopy (EIS). Copolymers coated characterization was performed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The polarization curves show that the copolymer film formed on A304, shifts the corrosion potential towards more positive potentials. The presence of the poly(BTh + MeFu) improves the corrosion resistance of the metal in a corrosive medium, H2SO4. This protection against corrosion is caused by the barrier effect of the layer of copolymer, which covers the surface of the A304 stainless steel against the aggressive ions of the corrosive medium. Voir les détails
Mots clés : 2-methylfuran, bithiophene, copolymers, protection against corrosion, stainless steel.
SIMULATION STUDY OF SUPER-RESOLUTION IN HYDROPHONE MEASUREMENTS OF PULSED ULTRASONIC FIELDS
In order to carry out reliable measurements of pulsed ultrasonic fields, the use of a piezoelectric hydrophone as receiver is recommended. However, due the finite size of the receiver aperture the measured acoustic pressure is affected by spatial averaging on the surface active face. The aim of this work is to deconvolve the spatial effects of the receiver hydrophone in order to reconstruct the pulsed ultrasonic field with a better spatial resolution. Hereby, the linear pulsed pressure field radiated in water by wideband planar transducers of 19 mm diameter, with central frequencies fc=2.25 MHz and fc=15 MHz are considered. The receivers are PVDF membrane hydrophones of 25 µm - thickness with rectangular and circular apertures. The results of this study show the strong dependency of the reconstruction quality upon the signal-to-noise ratio (SNR). Generally, the quality of the reconstruction decreases with decreasing SNR. Good reconstruction quality has been obtained with correlation coefficient larger than 0.9936 when the “acquired” signals are not too much noisy (SNR=60dB). In this case, improvement of the spatial resolution by a factor of 5 and 9 respectively could be reached. The reconstruction quality depends also upon the hydrophone dimensions, the axial distance to the source, the central frequency and the spectral frequency bandwidth of the pressure pulse. Voir les détails
Mots clés : Super-resolution, spatial inverse filter, spatial Wiener filter, PVDF hydrophone, pulsed ultrasonic field, ultrasonic field reconstruction.
A Bayesian Mumford–Shah Model for Radiography ImageSegmentation
This paper investigates the segmentation of radiographic images using a level set method based on a BayesianMumford–Shahmodel. The objective is to separate regions in an image that have very close arithmetic means, where a model based on thestatistical mean is not effective. Experimental results show that the proposed model can successfully separate such regions,in both synthetic images and real radiography images. Voir les détails
Mots clés : Level set