Chimie
Approche expérimentale et théorique de l’inhibition de la corrosion de l’aluminium en milieu alcalin
The objective of this thesis is the study of the properties of the cocamidopropyl betaine surfactant. The CPAB has been evaluated as a corrosion inhibitor of the aluminum used in the AL-Air batteries in KOH 1M, by means of the open circuit potential (OCP), of curves dynamic potential polarization of TAFEL and measurements by electrochemical impedance spectroscopy. The results revealed that the processus is limited by pure activation, that the CPAB inhibitor behaves as an effective cathodic inhibitor and that the inhibitory efficiency obtained from the different methods increases with increasing inhibitor concentration. The adsorption of the inhibitor on the aluminum surface follows Langmuir adsorption indicating monolayer adsorption. The theoretical study showed that the Cocamidopropyl betaine could serve as an effective corrosion inhibitor for aluminum in an alkaline solution. Voir les détails
Mots clés : inhibitor, corrosion, aluminum, curves dynamic potential polarization of TAFEL, EIS, CPAB.
On the corrosion behaviour of as-cast and heat-treated Mg-RE alloys in 0.9% NaCl solution
The microstructure and corrosion behaviour of as-cast and heat-treated Mg-1.44Ndand Mg-1.43Ce (wt.%) alloys in 0.9% NaCl (wt.%) solution were investigated usingelectrochemical tests, X-ray diffraction (XRD) and scanning electron microscopy,combined with energy-dispersive X-ray spectroscopy (SEM-EDS). The as-castmicrostructure of both alloys revealed the presence of second phases. Heat treatmentat 535°C for 6 h led to a more uniform distribution of the second phases in Mg-1.44Ndalloy and their dissolution along the grains boundaries in the Mg-1.43Ce alloy. As aresult, the corrosion resistance was improved in the heat-treated alloys. Accordingly,the corrosion resistance values for the heat-treated alloys were much higher than thoseof the as-cast alloys, indicating that the heat-treated alloys were less susceptible to thecorrosion. Also, the heat-treated Mg-1.43Ce alloy seems to have very good corrosionresistance (26890 Ω cm 2 ) compared to the Mg-1.44Nd alloy (6156 Ω·cm 2 ) bypreventing pitting corrosion along the grains boundaries. The corrosion product wasmade up mainly of magnesium hydroxide Mg(OH) 2 and magnesium oxide MgO andmore uniform corrosion morphology were found in the heat-treated alloys. Voir les détails
Mots clés : Corrosion resistance Heat treatment Magnesium alloy NaCl solution Rare earth
Chemical sensor array modeling. Quartz crystal microbalance sensors.
The primary objective of the paper is to develop Gibbs- Duhem like equations for the interactions between Quartz Crystal Microbalance (QCM) based sensor array and a mixture of vapors. These differential equations connect the variations of the sensors partial sensitivities or the sensors response with the gas mixture components concentrations. Furthermore, Thermodynamic models in the case of conducting polymer sensors, whose multi-component adsorption follows the generalized adsorption model of Langmuir have been deduced, these are differential equations that connect the adsorption entropies to the selectivities of the sensors and coefficients of standardization at constant temperature Voir les détails
Mots clés : chemical sensor array, Quartz Crystal Microbalance sensors, gas mixture, modeling, equations of Gibbs-Duhem, adsorption entropy
Thermodynamic investigation on the adhesion and corrosion inhibitionproperties of a non-steroidal anti-inflammatory drug in HCl electrolyteapplied on mild steel material
In this paper, the inhibition mechanism of a pharmaceutical agent, piroxicam, on the corrosion behavior of carbon steel in HCl (1M) solution was investigated. The weight loss technique and quantum chemical calculations were carried out. The determined inhibition efficiency at 298 K was 86.90 % for a concentration of 600 ppm. The adsorption mode of the drug obeys to the Langmuir isotherm model. The free energy of adsorption (ΔGads = −32.84 kJ mol?¹) revealed a spontaneous process with a mixed interaction type, physical and chemical. The thermodynamic parameters (ΔHads and ΔSads) governing the adsorption phenomenon and metal dissolution were investigated and discussed through thermodynamic and kinetic principles. The ΔHads and ΔSads were respectively −17.86 kJ mol?¹ and 50.27 J mol?¹ K?¹ which indicates an exothermic process and an increased disorder at the interface. The DFT method was used to determine the adsorption centers of the chemical structure of the drug. EHOMO (−6.448 eV) reveals a high tendency of the drug to share its electrons with the metal. In addition, the SEM analysis was carried out for the surface characterization of the carbon steel after immersion into the aggressive medium in the absence and presence of the drug substance. Voir les détails
Mots clés : Mild steel, Weight loss, adsorption, DFT
Tamanrasset’s Clay Characterization and Use as Low Cost, Ecofriendlyand Sustainable Material for Water Treatment: Progress and Challengein Copper Cu (II)
In this study, the adsorption of copper Cu (II) from aqueous solution, on Tamanrasset’sclay which is low cost adsorbent, was studied using batch experiments. The adsorption study includesboth equilibrium adsorption isotherms and kinetics. The characterization of the adsorbent necessitatedseveral methods such as X-Ray Diffraction, Scanning Electron Microscopy coupled with EnergyDispersive X-ray, BET for specific surface area determination, Fourier transform infraredspectroscopy and thermogravimetric analysis. Indeed, various parameters were investigated such ascontact time, initial metal ion concentration, mass of solid, pH of the solution and temperature. Theadsorption process as batch study was investigated under the previews experimental parameters. Theresults revealed that the adsorption capacity of Cu2+ is maximized at naturel pH of metal 5.5. Removalof copper by the clay of Tamanrasset (kaolinite) achieved equilibrium within 50 minutes; the resultsobtained were found to be fitted by the pseudo-second order kinetics model. The equilibrium processwas well described by the Langmuir model and the maximum adsorption capacity was found to be26.59 mg/g. Voir les détails
Mots clés : adsorption, Clay, copper, kinetic, Isotherms
Investigation of some physical properties of pure and Co-doped MoO3 synthesized on glass substrates by the spray pyrolysis method
Pristine and Cobalt (Co)-doped MoO3 nanofilms were synthesized on glass substrates using the spray pyrolysis method. The nanometric pristine MoO3 films were prepared from the 10−2 M.L-1 solution of ammonium molybdate tetrahydrate [(NH4)6Mo7O24,4H2O] in distilled water. Co-doping at 0.5, 0.75 and 1% was achieved by adding cobalt (II) chloride hexahydrate (Cl2CoH12O6) in the pristine solution. The structure and the morphology of the films were investigated by means of X-ray diffraction and atomic force microscopy: two pronounced (020) and (040) peaks corresponding to the orthorhombic structure phase of α-MoO3 were detected. The AFM observations revealed the formation of micro-plates, parallel to the surface plane, with a roughness ranging from 33?nm to 54?nm. Optical properties were investigated through reflectance, transmittance and photoluminescence measurements. The optical band gap, the Urbach energy and the refractive index were deduced from these measurements. The presence of oxygen vacancies was revealed from the interband transitions in the blue and green domains. Co-doped MoO3 nanofilms showed ferromagnetic behavior. The photocatalytic degradation of an aqueous solution of methylene blue (MB) under UV irradiation, in the presence of Co-MoO3 nanomfilms, has been carried out using UV–vis spectrometery: the intensity of the absorption peak recorded at 660?nm decreased with the increase of the UV-illumination time while the color of the initial MB solution was drastically waned. Voir les détails
Mots clés : Spray pyrolysis method, MoO3 nanofilms, optical properties, Magnetic Properties
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
Simulation and Modeling of Uncertainties in the Calibration
Sensitivity analysis and uncertainty estimation are ofmajor importance for the declaration of conformity of finishedproducts. Models must be sought to analyze the test data. Themain objective of this work is to establish reliable models toanalyze our experimental data and validate them. So we havestudied and used the Monte Carlo and Bootstrap simulationmethods, we have been able to realize programs that calculate theuncertainty according to the ISO 8466 standard on X-rayfluorescence spectrometer samples from the URASM CRTIchemical analysis laboratory. Programs and interfaces are madewith Matlab (GUI). Voir les détails
Mots clés : simulation, Uncertainties, Monte Carlo, Bootstrap, calibration
Etude de l'applicabilité de différents procédés électrochimiques et d'oxydation avancée pour le traitement de rejet de la raffinerie d'Alger
La demande mondiale de produits pétroliers est en constante d’augmentation, et elle entraîne une exposition dangereuse pour l’environnement. Ces produits génèrent des quantités importantes d’eau lors du processus de raffinage, qui posent de sérieux problèmes dans le traitement biologique du fait de leur résistance à la biodégradation et/ou d’effets toxiques sur les processus microbiens. La persistance de certaines molécules non biodégradables présentes dans ces rejets pourrait entraîner une toxicité pour l'être humain et son environnement. Pour cette raison, les eaux usées de raffineries nécessitent l’emploi de traitements avant de les rejeter dans l’environnement. Les procédés électrochimiques ainsi que les procédés d'oxydation avancée sont parmi les procédés appliqués pour traiter ce type de polluant. L’étude paramétrique appliquant le procédé d’électrocoagulation nous a permis d’optimiser les paramètres étudiés. Après 30 minutes d’électrolyse, pour une densité du courant de 60 A/m2, pH de solution de 5.83 (pH original), une concentration de chlorure de sodium de 1.5 g/L et une distance entre les électrodes fixée à 10 mm, les valeurs finales de la DCO et de la turbidité sont respectivement 208 mg d’O2/L et 1.12 NTU, avec une consommation énergétique égale à 0.323 kWh/kg DCO, soit 0.341 kWh/m3. Voir les détails
Mots clés : effluents industriels, DCO, radicaux hydroxyles, procédés électrochimiques
PLASTICIZING OF POLYLACTIC ACID (PLA) BIOPOLYMER WITH CITRATE ESTERS
Triethyl citrate (TEC) and acetyl tributyl citrate (ATBC) were used as plasticizer for Polylactic acid (PLA). The treated and plasticized PLA at various concentrations were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), melt ?ow index (MFI) and thermogravimetric analysis (TGA). Differential scanning calorimetry was used to evaluate the crystallinity and thermal property of all the samples. It was found that the glass transition temperature (Tg) and the melting temperature (Tm) decreased as the amount of citrate esters increased. Additionally, the presence of TEC or ATBC tended to increase the crystallinity of PLA. This result was supported by x-ray diffraction. DMA of plasticized PLA indicates that a decrease in Tg is obtained with increasing plasticizer content, Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated PLA. The TGA results indicated that ATBC and TEC promoted a decrease in thermal stability of the PLA. Voir les détails
Mots clés : Polylactic acid (PLA), Plasticizer; Citrate esters; Crystallinity, Triethyl Citrate (TEC), Acetyl Tributyl Citrate (ATBC)