Chimie
Métallurgie, Corrosion et Fatigue de l’Acier Inoxydable Austénitique 316Let de Ses Joints Soudés
Ce travail de thèse a pour objectif d’une part, de mettre en évidence l’influence du métal d’apport sur la microstructure, le comportement mécanique ainsi que la résistance à la corrosion des joints soudés en acier inoxydable austénitique 316L, et de montrer d’autre part l’utilité de la corrélation d’images numériques (DIC) comme technique de caractérisation complémentaire lors des essais de fatigue menés sur des joints soudés avec et sans défauts de soudage. Les résultats ont révélé que l'utilisation d’ER308LN à la place d’ER316LN en tant que métal d’apport, est bénéfique pour améliorer la résistance au choc du joint soudé. La zone fondue et le joint soudé obtenus avec le métal d’apport ER308LN ont également montré des valeurs plus élevées de potentiel de piqûre.Les essais de fatigue menés à l’air sur le métal de base AISI316L ont montré que la propagation des microfissures est transgranulaire, alors que dans un milieu salin, les fissures s’amorcent au niveau de plusieurs sites dans la microstructure du matériau tels que les joints de grains, les joints de macles et les bandes de glissement. L’utilisation de la DIC comme technique de caractérisation complémentaire des joints soudés a indiqué que la géométrie et le volume occupé par un défaut de soudage interne, tels que l’inclusion, peuvent affecter la résistance à la fatigue par la concentration de contrainte autour du défaut de soudage occupant le plus grand volume dans la zone étudiée. Par ailleurs, la zone de localisation de l'inclusion dans le joint soudé agit directement sur l’amorçage de la fissure. Selon les tests de Fatigue-DIC réalisés sur des joints soudés sains, il a été possible de conclure que la déformation se localise tout au long des zones microstructurales dans le joint soudé jusqu’à une valeur limite de force imposée, au-delà de laquelle la déformation majeure serait entièrement localisée dans la zone fondue. Voir les détails
Mots clés : métal d’apport, joint soudé, comportement mécanique, résistance à la corrosion, fatigue, défauts de soudage, DIC.
VALORISATION DE COPRODUIT ISSU DE LA FABRICATION D’ACIER AU NIVEAU DU COMPLEXE SIDERURGIQUE D’EL-HADJAR ET APPLICATION DANS LA PEINTURE ANTICORROSIVE
Le but de ce travail est la valorisation d’un coproduit issu de la fabrication d’acier du complexe sidérurgique d’El-Hadjar, à savoir la calamine. Dans cette étude nous avons utilisé un mélange composé de ce produit et d’un pigment de fer afin d’obtenir un pigment d’oxyde de fer pour application dans le domaine de la peinture anticorrosive. Plusieurs essais ont été menés sur des mélanges préparés avec différents pourcentages de pigment de fer et de calamine. Les différentes caractéristiques de cette peinture ont été réalisé (extrait sec, densité, viscosité, test de corrosion). Les résultats obtenus montrent que l’utilisation de ce nouveau mélange comme pigment anti corrosif donne des résultats encourageant. Voir les détails
Mots clés : Pigment de fer, peinture anticorrosive, oxyde de fer, calamine
ÉTUDES STRUCTURALE ET MORPHOLOGIQUE DU DECHET INDUSTRIEL SIDERURGIQUE : SCORIE
Les scories sont générées lors de la purification de l’acier suite à l’introduction d’additions riches en calcium tels que le calcaire ou la chaux. Ces matériaux réagissent avec les composés indésirables tels que l’aluminium ou le silicium et forment des composés complexes non-métalliques de densité inférieure à celle du fer et de l’acier. L’objectif principal de ce présent travail est l’étude des caractéristiques de coproduit provenant de l’usine sidérurgiques El-Hadjar (scorie). La caractérisation de scorie choisis va être effectuée par la microscopie optique pour l’étude morphologique, la diffraction par rayon X pour la caractérisation physique et chimique, l’identification des différentes liaisons chimiques ( Al-O, Ca-O, et Si-O )se fait par spectrométrie infrarouge Voir les détails
Mots clés : caractérisation, Scorie, Propriétés chimiques, Déchets sidérurgiques
METALLURGICAL AND ELECTROCHEMICAL BEHAVIOR OF S295 STEEL TUBES IN STEEL COOLING CIRCUITS
Corrosion damage to industrial cooling systems in steel mills is a serious problem for industry and the environment. In order to reduce this phenomenon by the subsequent development of organic-based corrosion inhibitors, a preliminary identification study of the base material and the surrounding environment of the cooling circuits is essential. To monitor the electrochemical behavior of unalloyed steel tubes, we studied the influence of the "industrial cooling water" environment and the most influential physical parameters. This behavior of S295 grade steel will be determined by different stationary and non-stationary electrochemical methods, notably electrochemical impedance spectroscopy. These investigations enabled us on the one hand the metallurgical knowledge of the base material, the nature of the corrosive medium, and on the other hand the evaluation of the potentials and the corrosion rates and to define the different reactions at the metal interface. middle. In conclusion, the tubes studied in unalloyed steel have a low resistance to corrosion under the effect of the aggressiveness of the surrounding environment (Figure 1) in this case industrial cooling water hence the need to introduce corrosion inhibitors in cooling circuits. In our case, we will focus on natural organic inhibitors that ensure an economic and environmental balance. Figure.1: Stationary and frequential electrochemical curves of the material / medium interaction Voir les détails
Mots clés : steel, corrosion, behavior, cooling water, impedance, Temperature
OPTICAL, STRUCTURAL AND MORPHOLOGICAL CHARACTERIZATION OF ELECTRODEPOSITED CUPROUS OXIDE THIN FILMS: EFFECT OF DEPOSITION TIME
The purpose of this work is the development and characterization of a novel electrode material based on copper oxide (Cu2O) for use as electrode in catalytic application. The samples are prepared on an indium doped tin oxide (ITO) glass substrate using a simple electrochemical deposition process from a solution of copper (II) sulfate and citric acid. The Cu2O films are deposited under chronoamperometric control at a potential of −0.50V versus SCE at different deposition times ranging from 2 to 15 minutes. The solution was maintained at a temperature of 60°C and a pH of 11. The effect of the deposition time is mainly examined in terms of the change in structural, morphological and optical properties of the Cu2O films using various characterization techniques. Atomic force microscopy (AFM) images showed that the prepared thin films are homogeneous with a granular shape. Also, the surface of the deposits becomes roughened with increasing deposition time. Scanning electron microscopy (SEM) images showed that the morphology of the prepared thin films is composed of a mixture of cubic and pyramidal shapes regularly distributed over the surface of the substrate. X-ray diffraction (XRD) measurements demonstrated that Cu2O thin films prepared by electrochemical deposition have a pure cubic structure with higher preferred growth orientation (111) and good crystallinity. Characterization by UV-Visible spectroscopy showed that the samples have high absorption in the visible region. The calculated values of the direct band gap are between 1.9 and 2.15 eV. These results represent a good starting point for the development of low cost anode used in catalytic application. Voir les détails
Mots clés : Cu2O thin film, electrodeposition, deposition time, optical properties
Optical and Photo-electrochemical characterization of manganese dioxide/polypyrrole nanocomposite
PPy-coated manganese dioxide (PPy-MnO2) synthesized by depositing PPy on the surface of γ-MnO2 particles in acetonitrile solution containing 10-1M lithium perchlorate (LiClO4) containing a monomer (pyrrole) and semiconductor (MnO2) nanoparticles. The composite materials (MnO2-PPy/ITO) were characterized by different methods including cyclic voltammetry, impedance spectroscopy, chronoamperometry, scanning electron microscopy (SEM). The cyclic voltammogram showed one redox couple characteristic of the oxidation and reduction composite material of composite material. The impedance spectroscopy study showed that the resistance of the film increases with the MnO2 incorporated in the polymer. The morphological analysis of the film surfaces showed that the MnO2 nanoparticle increased the roughness. These results give information on the use possibility of these materials for energy storage and as photovoltaic cells applications. Voir les détails
Mots clés : Manganese dioxide, Polypyrrole, electrodeposition, optical proprieties.
Characterization of toughened Poly (lactic acid) PLA/ Polycaprolactone (PCL) with bio-plasticizers (TEC and PEG3)
Triethyl citrate (TEC) and poly (ethylene glycol) (PEG3) were used as plasticizer for Polylactic acid (PLA)/ polycaprolactone (80PLA/20PCL) blends. The treated and plasticized 80PLA/20PCL blends at various concentrations of plasticizers were analyzed were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA), 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 plasticizers increased. Additionally, the presence of TEC or PEG3 tended to increase the crystallinity of PLA. 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 80PLA/20PCL blends. The TGA results indicated that PEG3 and TEC promoted a decrease in thermal stability of the 80PLA/20PCL. Voir les détails
Mots clés : Poly lactic acid (PLA), Polycaprolactone (PCL), Plasticizers vegetable, Biodegradable
Inhibition Efficiency of Cinnamon Oil as a Green Corrosion Inhibitor
The corrosion inhibition efficiency of cinnamon oil for stainless steel 304 L in 0.1 and 1.0 M HCl solutions was investigatedusing electrochemical study and surface electronic observation. The potentiodynamic polarization curves showed that, independentlyof the time of immersion in 1.0% HCl, a reaction to the anode occurred, which was explained by the dissolutionof the metal due to the strong aggressiveness of the medium; the addition of 1% cinnamon oil led to a corrosion efficiencyof 84%. Furthermore, in 0.1 M aggressive medium the tests with addition of inhibitor showed that the inhibition efficiencyincreases (86.6–96.0%) with an increase in the cinnamon oil concentration from 0.5 to 5%. Scanning electron microscopeobservations of metal surface confirmed the existence of a protective adsorbed film of the inhibitor on the steel surface. Cinnamonoil can be proposed as an efficient green inhibitor of corrosion of stainless steel exposed to hydrochloric acid mediums. Voir les détails
Mots clés : Aggressive medium · Cinnamon oil · Corrosion inhibitor · Stainless steel
Quantitative and qualitative analyses of intermolecular interactions in neutral/deprotonated aspirin@β-CD inclusion complexes: QTAIM and NBO analyses
Most of the researches in supramolecular chemistry area are focused on the conventional hydrogen bonds without taking into account unconventional intermolecular interactions. The nature and strength of the conventional and unconventional interactions in inclusion complexes formed between neutral aspirin (ASA) and its deprotonated form (ASA−) with β-cyclodextrin (β-CD) have been studied. It was conducted through combining atoms in molecules (AIM) theoretical criteria suggested by Koch and Popelier and natural bond orbital (NBO) analyses by means of dispersion-corrected density functional theory (DFT-D3) with the functional B3LYP using cc-pvdz basis set in the gas phase. We have found fve intermolecular closedshell interaction groups responsible for neutral ASA:β-CD and deprotonated ASA−:β-CD inclusion complexes stability: One is conventional O–H···O bond group. The four C–H···O, C–H···C, O–H···H–C and C–H···H–C groups are nonconventional. Also, with respect to the Koch and Popelier criteria, some of them present the properties of a hydrogen bond, while others do not. The non-covalent interaction energies are calculated using Espinosa approach. Finally, according to the AIM and NBO analyses, the topological parameters (electron density ρband its Laplacian ∇2ρb), estimated interaction energies (Eint), and the stabilization energy E(2)of both complexes were correlated with the intermolecular bond lengths Voir les détails
Mots clés : β-Cyclodextrin, Aspirin, Inclusion complex, DFT-D3, QTAIM, NBO
A Copper Oxide (CuO) Thin Films Deposited by Spray Pyrolysis Method
A simple and low-cost procedure (spray pyrolysis) was used to elaborate a copper oxide thin films on ordinary glass substrates. A copper nitrate was used and dissolved in two different solutions (Water, Methanol) S1 and S2 respectively in order to obtain an equal concentration; CS1,S2=0.5M. The spray pyrolysis deposition made at fixed temperature T=500°C and different volumes of S1 or S2 on the glass substrates. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectrophotometry were used to determinate the structural, morphological and optical properties of CuO thin films. The X-ray diffraction patterns confirm the presence of the polycrystalline phase of CuO as monoclinic crystal structure with preferential orientation along (110), (002), (111), (200) and (020). Their optical band gaps ranged from 3.95 to 4.02eV for thin films made with S1, and from 1.6 to 1.95eV for thin films made with S2 with a high absorbency in the visible region, which is in agreement with the values of the literature. Voir les détails
Mots clés : Copper oxide, Thin films, Spray pyrolysis, Band Gaps, XRD, SEM.