Liste des publications
Effect of Geometrical Parameters on Vortex Fluidic Oscillators Operating with Gases and Liquids
The fluidic oscillator is an interesting device developed for passive flow measurement. These microsystems can produce a high oscillating jet frequency with high flow velocity. The main advantages of fluidic oscillators are that no moving parts is included in the device. Commercial CFD code FLUENT was used to perform analysis of flows in fluidic oscillator. Numerical simulations were carried out for different flow conditions, where water and air were used as working fluids. The oscillation frequencies were identified by the discrete fast Fourier transform method (FFT). Furthermore a low-pressure vortex of fluid flow in the oscillating chamber was observed. The effect of the operating pressure and the oscillating chamber shape on the fluidic oscillator performance is investigated. Moreover the velocity fluctuations of the feedback flows through both feedback channels and the output were determined quantitatively. In addition, the behaviour of the low-pressure vortex in both models is analysed. Also, numerical result revealed small vortices are developed at the end of nozzle while oscillation, which maintains the deflection of jet flow between attachments wall. Comparison of our numerical simulations with available results showed reasonably and good agreement. Voir les détails
Mots clés : fluidic oscillator, CFD, oscillating chamber, vortex, size effect, Coanda effect.
Copper removal in solution by sawdust: kinetic and thermodynamic study
This study presents the results obtained when okoumé sawdust is used for the removalof copper contained in wastewater. The tests show that one gram of sawdust can fix29.56 mg of copper, according to the Langmuir model with kinetics of the pseudo firstorder where the time of the pseudo equilibrium is reached after 40 minutes of agitation.The elimination is envisaged in batch mode, at 20 ° C, a stirring speed of 200 rpm, atpH value of 4.4 and a particle size between 500 ≤ Ø < 700μm. Measured results alsoreveal that external diffusion controls the speed of the overall process of adsorption anddiffusion into the pores is not the only mechanism limiting kinetics. The thermodynamicstudy shows that this sorption is spontaneous , exothermic and that no changes havebeen made in the structure of the sawdust Voir les détails
Mots clés : Cooper, adsorption, sawdust, water, pollution
Elaboration and characterization of ITO electrode modi?ed bytransition metal dispersed into polyaniline thin ?lms
This work presents the characteristics of composite materials thin ?lms of polyaniline (PAni) andnickel (Ni) particles deposited onto indium tin oxide (ITO) substrate. The electropolymerizationof aniline was performed in acidic medium by potentiodynamic methods. The nickel particleswere electrochemically deposited on the surface of PAni/ITO by reducing metal ions (Ni) usinga potentiostatic method from a separate solution. The e?ect of applied potential as well as immersingtime of complexation on the amount of nickel dispersed was investigated. Di?erentcharacterization techniques were employed to study the electrochemical behavior and surfacecharacteristics of the Ni-PAni/ITO thin ?lms such as Electrochemical Impedance Spectroscopy(EIS), Cyclic Voltammetry, Fourier Transform Infrared Spectroscopy (FTIR), UV–visSpectroscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).The morphology of the obtained composites shows a uniform dispersion of nickel particlesonto the polyaniline matrix and reveals that the immersing times of complexation has a signi?cante?ect on the amount of incorporated particles. The impedance spectroscopy study revealsthat the conductivity of the composite ?lm increases with the amount of nickel incorporated.UV–vis and FTIR results con?rm the presence of PAni and Ni particles on theelectrode surface. Voir les détails
Mots clés : polyaniline, Electro-polymerization, Nickel particles, Chronoamperometry, Materials composites
Tribological behaviour of a continuous hot dip galvanized steel
The aim of this work is to investigate the tribological behaviour of a continuous hot dip galvanizedsteel. This paper presents a fundamental study of the characteristics of zinc coating in terms ofmorphology, surface roughness and tribological behavior according to process parameters typical ofindustrial processes continuous galvanization. The morphology of the zinc coating was observed byscanning electron microscope (SEM), optical microscopy, and the mechanical properties of thecoating layers were determined by nanoindentation. The tribological tests were carried out on arotating ball-disk tribometer under loads of 1, 2, 3Nwith a sliding distance of 15, 30 and 50 m. Theresults showed a marked increase of the coefficient of friction with increasing applied load. Under thesame conditions, wear slightly increased due to the hardness of intermetallic phases. The resultspresented show that heating promotes the diffusion of iron in the zinc coating giving shape to a binaryalloy Fe–Zn whose characteristics depend on the parameters; moreover, it is proved that thetribological characteristics of the surface of the metal blank in terms of coefficient of friction dependon the temperature of the contact pressure. Voir les détails
Mots clés : galvanized steel, wear, roughness, Nanoindentation, intermetallic phases
Thermal Treatment Effect on Tribological and Corrosion Performances of 13Cr5Ni2Mo Super- Martensitic Stainless Steel
Wear behavior of 13Cr5Ni2Mo supermartensitic stainless steel (SMSS) were investigated in air and in argillaceous paste at room temperature. Prior to wear testing, the samples were subjected to two treatments, namely; quenching followed by double tempering. A pin-on- disc test rig was used to conduct the wear test with a tribo-pair consisting of supermartensitic stainless steel sliding against itself. It was observed that the microstructure of the thermally treated samples mainly consisted of tempered martensite and carbides. Wear results showed that oxidative and abrasive wear dominated the wear process of the treated samples in both dry conditions and in argillaceous paste. Additionally corrosion tests were performed in 5.0% NaCl solution via potentiodynamic polarization tests. It was found that the passive film formation provides a good corrosion resistance to the samples. Voir les détails
Mots clés : Martensitic Stainless Steel, Thermal Treatments, wear, corrosion
Degradation of C.I. Acid Red 51 and C.I. Acid Blue 74 in Aqueous Solution by Combination of Hydrogen Peroxide, Nanocrystallite Zinc Oxide and Ultrasound Irradiation
Journal of Advanced Oxidation Technologies2018; 21(1)www.jaots.netDOI:10.26802/jaots.2017.0022Journal of Advanced Oxidation Technologies 2018; 21(1)Article ID-20170022Article:Degradation of C.I. Acid Red 51 and C.I. Acid Blue 74 in Aqueous Solution by Combination of Hydrogen Peroxide, Nanocrystallite Zinc Oxide and Ultrasound IrradiationInsaf Ould Brahim*1,3, Mohamed Belmedani1,Ahmed Haddad3, Hocine Hadoun2,Ahmed Belgacem11Laboratory of transfer phenomena, Faculty of Mechanical and Processes Engineering, University of Sciences and Technology Houari Boumediene, BP n 32 El Alia bab ezzouar 16111 Algiers, Algeria2Nuclear Research Center of Algiers, 2 Bd Frantz Fanon, 16035, Algiers, Algeria3Research Center in Industrial TechnologiesCRTI, P.O.Box 64, Cheraga 16014 Algiers, Algeria *iouldbrahim@gmail.comPhone: 00213-20-77-67Fax: 00213-21-34 -20-19AbstractThis study illustrates the degradation of food dyes, C.I. Acid Red 51 (erythrosine E127) and C.I. Acid Blue 74 (indigo carmine E132) by sonocatalysis using an ultrasonic frequency of 37 kHz and a power of 150 W in the presence of heterogeneous catalysts ZnO and peroxide hydrogen (H2O2). The adsorption process for the two dyes on the ZnO nanocrystalline which satisfies the Freundlich model appears not effective because the elimination of the two food dyes does not exceed 35%. In order to improve the removal, the sonocatalytic process (AD-OX) has been investigated. At this purpose, effect of operating parameters such as initial dye concentrations, H2O2(0-0.75M) and initial pH on the sonochemical degradation was investigated. It was observed that when the adsorption-catalysis was assisted by the ultrasonic and H2O2 a considerable yields has been achieved and about 86% and 97% of E127 and E132 were removed for 10 mg L-1and 50 mg L-1respectively. To understand the behavior of dye degradation, structure of the zinc catalyst before and after the sonocatalytic process was characterized by meanX-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM).Results showed thatthe ZnO particles before and after sonocatalysis were crystallized in the hexagonal wurtzite phase and the size distribution indicates that most of the particles are in the range of 300 and 600 nm. Finally, ADMI and COD analysis were performed in order toquantify the residual color in solution and evaluate the efficiency of the dye mineralization. Results showed that the treatment of food dyes by US-ZnO-H2O2process increased color degradation (ADMI)and mineralization efficiency (COD) by more than 50% and 76% respectively. Voir les détails
Mots clés : Advanced oxidation process, sonocatalysis
Correlation Between the Pitting Potential Evolution and σσ Phase Precipitation Kinetics in the 2205 Duplex Stainless Steel
The aim of this work is to correlate the pitting potential (Epit) evolution with the kinetics ofrphaseprecipitation in the 2205 duplex stainless steel aged at 850°C after solution treatment at 1150°C. Thepotentiodynamic polarization curves indicate a reduction of the pitting corrosion resistance with the agingtime, which is revealed by a decrease in theEpitvalues from 0.65 to 0.40 VSCE. Thus,Epitvalues are used todetermine the kinetics parameters of therphase precipitation. The experimental transformed fractionagrees well with the one calculated by using the modified Kolmogorov–Johnson–Mehl–Avrami equationwith an impingement parameterc= 0.6. Voir les détails
Mots clés : kinetic, KJMA, Pitting corrosion, otentiodynamic polarization, r phase precipitation
ZnO nanoparticles and biocidal effect of nanostructured ZnO filmson Escherichia coli
The biocidal effect of ZnO nanostructured films was studied using Escherichia coli ATCC 43897. TheZnO nanoparticles were synthesized in diethylene glycol by using zinc acetate forced hydrolysis.X-ray diffraction analysis confirmed the formation of single wurtzite-type ZnO phase with a crystallitesize of 20.59 nm. Transmission electron microscopy observations revealed spherical-shaped particlesin the nanoscale regime with a mean particle size of 21.96 nm. It was found that the addition oftrioctylphosphine during synthesis favored much improved dispersion of ZnO nanoparticles, withsmaller particle size; that is, 16.28 nm. Meanwhile, ZnO film grown onto glass substrate by spin-coatingrevealed single phase with the formation of aggregates (≈700) having mushroom-like morphologyformed of very fine particles in the nanoscale regime. The as-deposited nanostructured films exhibiteda hydrophilic character. The classical bacteriological and electrochemical impedance spectroscopymeasurements enabled the biocidal effect of ZnO nanostructured films with 94% inactivation efficiencyafter 90 min of contact time. Voir les détails
Mots clés : ZnO; Spin-coating; Nanostructured film; Biocide effect; E. coli; EIS
Investigation of WC decarburization effect on the microstructure and wear behavior of WC-Ni hardfacing under dry and alkaline wet conditions
The performance of drilling tools hardfacing in different conditions is strongly related to microstructural aspect of the coating and to the adhesion with the substrate. In the present investigation, the manual oxy-acetylene brazing process was employed for AISI 1020 steel hardfacing using WC-Ni. The substrate/hard facing interface was particularly studied which was a Ni-Cr-Al-Mo interlayer prepared by flame thermal spray method. The microstructural results exhibit a good embedding of WC particles into the Ni matrix, where the inter-diffusion of Ni, Cr, and Fe elements at the interface is enhanced using the interlayer. The dissolution and decarburization phenomena of WC particles with the formation of W2C eutectic phase and their effect on the decohesion and pull out of the particles during the wear test were studied. The hardness (HIT) and Young's modulus (EIT) of different parts of the hardfacing were investigated by instrumented nanoindentation. The wear resistance of the surface coatings under alkaline condition using sodium hydroxide (NaOH) basic solution of pH?=?12 is two times higher than under dry condition. Furthermore, the formation of SiO2 third body stripes along the wear track promotes the decrease of the friction coefficient and the volume loss. On the other side, the wear mechanism is adhesive with severe plastic deformation of the Ni matrix in dry condition and oxidative/abrasive wear in alkaline wet condition. Voir les détails
Mots clés : Interface, WC dissolution, Hardfacing, inter-diffusion, Decarburization
Composite adaptive dynamic surface control of nonlinear systems in parametric strict-feedback form
In this paper, a composite adaptive dynamic surface control scheme is developed for a class of parametric strict-feedback nonlinear systems. The proposed composite adaptation law uses both the surface error and the estimation error to update the parameters. In addition, by using the dynamic surface control technique, the problem of the explosion of complexity in the adaptive backstepping design is avoided. It is proved that the proposed scheme guarantees uniform ultimate boundedness of all signals in the closed-loop system with arbitrary small surface error by adjusting the design parameters. Simulation results demonstrate the effectiveness of the proposed approach for an electrohydraulic actuator system. Voir les détails
Mots clés : Composite adaptation law, direct and indirect adaptive control, dynamic surface control, Lyapunov stability, parametric strict-feedback nonlinear systems