Sciences des matériaux

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A systematic DFT study of (Ti3/2RE1/2)AlC alloys: A new database foradjustable mechanical and electronic properties

C. Meftah, N. Iles, L. Rabahi, M. Gallouze, H.I. Feraoun, M. Drir  (2022)
Publication

In this study, ab initio calculations based on Pseudo-Potential Density Functional Theory (PP-DFT) method arecarried out in order to highlight the partial substitution effect of Rare Earth (RE) elements in the well-known 211-MAX phase of Ti2AlC. The considered elements are Y, Sc and RE = La, Ce, Pr, Nd, Sm, Eu, Gd leading to (Ti3/2RE1/2)AlC alloys. According to the obtained results, the (Ti3/2RE1/2)AlC alloys are significantly less compressibleunder uniaxial stress along x and z axes. They exhibit high resistance to shearing along <001> direction. Inaddition, the calculated heat capacity for (Ti3/2RE1/2)AlC alloys increases with respect to the temperature, amaximum is found in the temperature range 200–300 K. Localized states occur in (Ti3/2RE1/2)AlC alloys due tothe f states filling of the rare earth elements. The magnetic moment of (Ti3/2RE1/2)AlC compounds increasesaccording to 4f n (n=2 for Ce to n=7 for Gd) filling. Our findings provide a theoretical database for new tunableproperties of (Ti3/2RE1/2)AlC alloys. Voir les détails

Mots clés : DFT, Rare earth elements, (Ti3/2Re1/2)AlC, mechanical properties, Localized States, Magnetic moment

Numerical study of polymer coating by UV photopolymerization.

K.HAMLAOUI, B.BOUCHOUL, L.Lamiri, R.KHOUATRA  (2022)
Article de conférence

Polymer-based coatings are used to protect a structure or device against mechanical attacks such as scratches, abrasion and erosion or against chemical attacks such as humidity, temperature, UV rays. This work concerns the development by photopolymerization UV of new coating materials based on a polymer as (Polyurethane Acrylate, oligomers) deposited on heat-sensitive materials such as thermoplastics (PC; PMMA,). Now, the polymers, which are already used in thermal powder coating. They generally show very high melting temperatures (around 200 °C). They will not be suitable for depositing on supports sensitive to high temperatures without risk of damaging them. In this work, we proposed a numerical study of the effect of different synthesis parameters (energy and applied UV rays, exposure time, temperature, external medium, etc.) on the conversion rate to a 3D mesh (crosslinking rate) and model optimization of coating parameters on heat-sensitive substrates. Voir les détails

Mots clés : polymers, coatings polymer, photopolymerization UV

Synthesis, Characterization, and Photocatalytic Activity ofBa-Doped BiFeO3 Thin Films.

KHIAT Abdelmadjid, Felicia Gheorghiu Boughelout Abderrahmane.  (2022)
Publication

Abstract: In the present paper, Bi1-xBaxFeO3 (BBFO) thin films (where x = 0, 0.02 and 0.05) wereprepared by a combined sol-gel and spin-coating method. The influence of Ba substitutions on thestructural, microstructural, optical properties, and photocatalytic activity of BiFeO3 thin films hasbeen studied. X-ray diffraction pattern correlated with FTIR analysis results confirms that all thefilms have a perovskite structure of rhombohedral symmetry with an R3m space group. Atomicforce microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate thesurface morphology and reveals microstructural modifications with the increase in Ba concentration.The optical properties show that the band gap is narrowed after doping with Ba ions and decreasesgradually with the increase of doping content. The photocatalytic investigations of depositedfilms revealed that Ba doping of BFO material leads to the enhancement of photocatalytic response.The present data demonstrates that Bi1-xBaxFeO3 (BBFO) thin films can be used in photocatalyticapplications. Voir les détails

Mots clés : perovskites; films; optical properties; doped BaTiO3; photocatalytic activity

Effet du traitement de vieillissement sur l’évolution microstructurale et le comportement électrochimique des aciers inoxydables 2101, 2205 et 2507.

F.Z.ROUIBI  (2021)
Mémoire de Master

this work, the effect of ageing treatment on the microstructural evolution, morphology and potential distribution of LDX2101, SDX2205 and SDSS 2507 stainless steels is investigated. The heat treatment is carried out in two stages: solution treatment for one hour, then water quenching followed by ageing at 750°C for 2101 and 850°C for 2205 and 2507, for 24 hours holding time. Metallographical characterization is conducted using optical microscopy and scanning electron microscopy (SEM) as well as XRD analysis to identify the phases and precipitates formed after treatment. In order to study the effect of ageing on the morphological changes, magnetic behavior and potential distribution on the surfaces of the treated steels, different modes of atomic force microscopy (AFM) are used. The results showed a clear increase in roughness with a very heterogeneous potential distribution due to microstructural changes as a result of the formation of precipitates and secondary phases Voir les détails

Mots clés : LDX2101, SDX2205, SDSS 2507 stainless steels, The heat treatment

Comportement mécanique et métallurgique des jonctions hétérogènes soudées par friction rotative

A. CHERIFI, R. BELHOCINE  (2020)
Mémoire de Master

Rotational friction welding is a solid state welding process, which has seen spectacular development in various industries. It offers the possibility of producing very high quality solder joints in an extremely short time. The objective of this work is to improve the operating parameters of this process by changing the friction time (periods) and fixing the other parameters namely the speed of rotation [round per minute], the forging time [s], the friction and forging pressure [MPa]. The major problem with the disimmilar assembly of aluminum and stainless steel alloys is the low mechanical strength in the welded joint, due to the formation of certain unwanted inter-metal compounds during welding. An experimental procedure was used to obtain an Al6013-T8 /304L stainless steel welded joint with and without copper insertion. Different characterization methods were used namely x-ray diffraction, optical microscopy, HV microhardness and tensile testing. The Al6013-T8 side microstructure reveals the formation of two zones, the HAZ and the TMAZ at the center of the junction, unlike 304L stainless steel, which has not undergone any mechanical deformation. The microhardness of Al6013-T8 increased in the vicinity of the junction, and tensile testing revealed that the mechanical characteristics of the joints increase with increasing friction time. Voir les détails

Mots clés : Rotational friction welding, the speed of rotation, the forging time

Etude mécanique et microstructurale des soudures des alliages d'aluminium soudées par friction

S. BENDOUMA, G.GUERMAT  (2020)
Mémoire de Master

This work is related to the study of the friction welding process. This type of welding has many applications in different branches of industry. This process has many advantages. First, the very high quality assemblies can be made. In addition, this process is much faster than any other conventional processes. Furthermore, it can be completely automated so that constant quality is guaranteed. The aim of this study is the optimization of the parameters of friction welding: (by varying the friction time [s] and the rotational speed [rpm], forging time [s] and the friction pressure and forging [MPa] remain constant). An experimental procedure was used to obtain a welded junction (alu-alu), the alloy used is Al 6013-T8. We used several characterization methods, simple but effective and suitable for this kind of research work; such as microstructural characterization by optical microscope and mechanical characterization namely microhardness and tensile testing. We observed that the microstructure has three zones (TMAZ, HAZ and MDZ), The microhardness profile has a certain homogeneity and the tensile tests have shown that the tensile strength, elongation and elastic limit increase with increased friction time. In general, the mechanical properties are influenced by the overall effect of the metallographic structure of the weld. The latter is closely linked to the process parameters. Voir les détails

Mots clés : Friction welding, 6013-T8 alloy, Welded joint, mechanical properties, microstructure, Microhardness

Effet de l’application d’une peinture anti-corrosion sur le comportement électrochimique de l’acier au carbone en milieu acide

M. BOUKANDOURA, O. NACHI  (2019)
Mémoire de Master

In this work, we are interested in the evolution of the surface roughness of steel (mechanically polished (A2, A3) and shot-blasted (A2G, A3G)) and the thickness of the paint applied to different surface states (mechanically polished (A2P, A3P) and shot blasted (A2GP, A3GP)). Shows that the roughness of grit-carbon steel surfaces is greater than the mechanically polished ones. Although the evolution of the thickness of the paint deposited on mechanically polished and shot-blasted carbon steel, depending on the grade of polishing paper,), shows that the thicknesses of paint deposited on carbon steel surfaces shot blasted are larger than those polished mechanically. The characterization of the samples was determined by scanning electron microscopy (SEM), showing that the surface state of mechanically polished steel (A3) is much better than that of shot-blasted steel (A3G). The surface analysis by SEM also shows that the coatings applied on the shot-blasted steel (A3GP) have a much better morphology than those applied on mechanically polished steel (A3P), and the metallographic micrographic analysis shows that the thickness of the coatings of paints obtained on shot-blasted steel are superior than that obtained on mechanically polished steel, The effect of mechanical polishing and shot blasting on the behavior of carbon steel with respect to corrosion by the use of two electrochemical techniques: potentiodynamic method and electrochemical impedance spectroscopy (EIS). mechanically polished and shot-blasted steel with and without coating for better resistance to corrosion in hydrochloric acid medium. Spectral analyzes by FTIR, shows the evolution of chemical bonds and functional groups present in the paint applied to steel. Voir les détails

Mots clés : surface roughness of steel, shot-blasted steel (A3G), electron microscopy (SEM)

Elaboration et caractérisation des composites stratifiés à base de fibres de carbone et de fibres de verre à usage aéronautique

A. r. OUKAZI  (2019)
Mémoire de Master

This work is based on the elaboration and the characterization of different types of laminated composites based on epoxy resin, carbon fiber and glass fiber. These composites differ based on three essential parameters, including the type of reinforcements used, the orientation of the constituent fibers reinforcements and the heat treatment temperature at which these laminated composites were exposed. The characterization is then done to see the influence of these elaboration parameters on the physical and dynamic behaviors of this laminated composite materials developed during and after the solicitation. For this, we used nondestructive testing methods such as ultrasound and microscopy and destructive methods such as tensile and bending tests. The results obtained from the various tests were the subject of comparative interpretations followed by interesting perspectives. Voir les détails

Mots clés : Laminated composites, carbon fiber, Glass fiber, Epoxy resin, nondestructive test, mechanic tests

Détection, positionnement, localisation et identification des défauts dans les matériaux solides par ultrasons

L. GHOUDELBOURK  (2019)
Mémoire de Master

In this study, we have been adapted to the various techniques of non-destructive testing and especially non-destructive ultrasonic testing by contact of a piezoelectric transducer with welded parts (different types of welding). This method can detect, locate, dimension and identify defects in the weld seam after going through several steps such as calibration and tracing of the distance amplitude curve. The ultimate goal of this control is to accept or reject controlled parts according to international standards Voir les détails

Mots clés : Non-Destructive testing, piezoelectric transducer, different types of welding

Contrôle du joint de soudure d’un pipeline par ultrasons

L. GHOUDELBOURK  (2019)
Mémoire de Master

In this study, we have been adapted to the various techniques of non-destructive testing and especially non-destructive ultrasonic testing by contact of a piezoelectric transducer with welded parts (welded pipe). This method can detect, locate, dimension and identify defects in the weld seam after going through several steps such as calibration and tracing of the distance amplitude curve. The ultimate goal of this control is to accept or reject controlled parts according to international standards Voir les détails

Mots clés : Non-Destructive testing, - ultrasonic testing, welded pipe