Sciences et génie des matériaux

Nombre total de résultats : 68
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Synthesis of Lead-Free Ceramicsof the Perovskite Type for PiezoelectricApplications by Conventional Solid-StateReaction

K. Sedda, R. Djafar, K. Boumchedda, F. Boukazouha, M. Latef  (2020)

Structural properties of BaTiO3, CaTiO3 and Ba0.85Ca0.15Ti0.9Zr0.1O3 prepared by conventional solid state reaction technique, at different calcinations temperatures 1100, 1150 and 1280 °C and sintering temperatures (1200and 1300 °C) are studied. These compositions were selected because of theirinteresting piezoelectric properties. To follow the decomposition process of theprecursor, a differential thermal analysis coupled with thermogravimetric analysis (ATG-ATD) was performed. Structural parameters are analyzed by X-raydiffraction (XRD) and scanning electron microscopy (SEM). The obtained resultsshowed clearly the synthesis of the perovskite phase. The diffractogram illustratesthat BCTZ symmetry is both cubic with a Pm-3 m space group and orthorhombic with a R3m space group, the calculated phase rates are respectively 10% and90%. The results allowed us to specify the effect of sintering temperatures on thestructural properties of ceramics. Voir les détails

Mots clés : Lead free ceramics, synthesis, ;, microstructure, Perovskite

Cu2O addition and sintering temperature dependence of structural,microstructural and dielectric properties of CaCu3Ti4O12 ceramics

R. Djafar, K. Boumchedda, A. Chaouchi, D. Fasquelle, K. Sedda, S. Brahimi, K. Khalfaoui, M. Bououdina  (2020)

This study is aimed in the replacement of commonly used (CuO) by Cu2O in the synthesis of perovskiteCaCu3Ti4O12 (CCTO) phase by the solid-state reaction method. The XRD analysis of powder calcined at 1100 ?Cand ceramics sintered at different temperatures show that the CCTO phase was well crystallized with thepresence of small quantities of additional phases. The SEM/EDS analysis of prepared pellets show that the formation of Cu2O/CuO phase occurs above 950 ?C, resulting in enhanced densifcation at 1050 ?C (>96%).However, it is found that the Cu2O-based CCTO begins to degrade around 1090 ?C. The densifcation aftersintering at 1050 ?C reaches 96%, meanwhile dielectric constant and loss tangent values are optimum in the lowfrequency range (<103 Hz); i.e. 13378 and 0.177, respectively. This favors the use of Cu2O instead of CuO inCCTO ceramics for applications at low frequencies. Voir les détails

Mots clés : Ceramics, CCTO, powder metallurgy, XRD and SEM, Dielectric properties

Criterion for cathodic protection of 25CD4/Inconel 182 system

D. ALLOU, D. Miroud, M. Ouadah, B. Cheniti, S. Bouyegh  (2020)

This study aims to investigate the cathodic protection criterion of a galvanic system of low alloy steel 25CD4substrate /Inconel 182 austenitic stainless-steel ?ller metal couple obtained using Shield Metal Arc Welding(SMAW) process. The microstructure investigation revealed the presence of Type II boundary along the steelsubstrate/Inconel interface where high carbon content and high hardness were recorded. The electrochemicaltests evaluated in marine environment (3.5% NaCl) at room temperature revealed that the corrosion potential(E) of the interface was between the steels substrate and the Inconel 182 ?ller metal ones, On the other hand,the current density (Icorr) and corrosion rate were slightly higher in the overlaid area. In order to determine thesystem protection criterion, chronopotentiometry method was introduced. It was found that the cathodic protectioncriterion for the assembly is based on the criterion of the least noble materialwhich is the steel substrate.corr Voir les détails

Mots clés : cathodic protection, 25CD4, Inconel 182, overlay, Cronopotentiometry.

Study and development of a new process for the treatment and purification of industrial effluents contaminated by metals by electrodeposition

Souad brick chaouche, Ahmed HADDAD, AICHA BENSMAILI  (2019)
Article de conférence

Currently, Electrochemical methods find wide application in the treatment of industrial effluents to reduce their organic matter content, in inorganic sulfur compounds and nitrogen, or in harmful metals for the environment. Electrochemistry is not only applied to wastewater, but also on contaminated soils, incineration residues or sewage sludge wastewater from the metallurgical industry. Electrochemistry has proved its effectiveness, which allowed him to integrate the environmental industry. Environmental electrochemical technologies allow to control pollution, to recycle materials, to carry out the rehabilitation of sites, monitoring (monitors and sensors for gases and liquids), the efficient conversion of energy, the prevention of corrosion, removal of contaminants and disinfection of water. Electrochemical processes can therefore be efficient and economical when properly designed, and they integrate harmoniously with the environmental industry. These processes require compact installations and can thus integrate into existing industrial waste treatment chains. The present work aims so the elaboration of an electrochemical process of treatment and purification of industrial effluents contaminate with metals. Indeed, the use of this technique can allow both the elimination of these metals by electroplating on a cathode, a recovery of metals, a saving of precipitation reagents and a reduction in the amount of sludge to be removed, as well as surface treatments where the applications concern gold recovery, silver, copper, cadmium, nickel, zinc, iron and lead ... etc. The metal that can be recovered in the form of valorizable cathodes, which allows the depollution of the environment. This work requires in-depth studies of design considerations and the development of an electrolytic cell. Voir les détails

Mots clés : electrochemical, environment, pollution

Analyses physico-chimique et rhéologique des boues d'épuration des eaux uséesde la ville de Guelma

CHIBANI Sana (2010)
Mémoire de magister

In general, the sludge must be of agronomic interest, for this it must be easier to use, it means that sludge can be easily stored, transported and spread easily. More than the knowledge of the dry matter content, viscosity and physico-chemical composition are necessary to process optimization of storage and application techniques. However, the variable quality of output sludge treatment plant makes the heterogeneous volumes involved in the context of agricultural development.This study aims mainly to identify the rheological and physico-chemical parameters ofsludge. The quality of wastewater, treated wastewater and sludge is often determined by a set of physicochemical parameters. Applied to the treatment plant of Guelma city, il showed significant heterogeneity over months. For protection against wastewater pollution, they must be treated before being discharged into the environment by biological techniques of activated sludge. The purified water can be used for various purposes (irrigation, industry, etc ....), especially for Guelma’s zone which is agricultural.Our work is involved in the study and the characterization of wastewater entering the treatment plant and water discharges after treatment of the city of Guelma and in addition of the study and the characterization of sludge during treatment. Physical and chemical indicators of pollution are determined i.e.: the BOD5, COD, TSS, VSS, TKN, OPO4--, NO2 -, NO3 -, K +, Cl-... and the temperature, pH, dissolved oxygen, conductivity. This study is carried out for two months.Our results suggest that wastewater is polluted by organic pollution characterized by partially degradable waste and sludge is rich organic matter and mineral. Rheological study also showed that sludge is linear viscous and elastic behaviour.Finally, the use of sewage sludge has enabled is the best method of treatment because of its large reduction in pollution load Voir les détails

Mots clés : Keywords: sewage disposal, water treatment, physicochemical indicator, activated sludge.

Etude et caractérisation de l’interface lors du soudage de matériauxmétalliques non ferreux :

MEBTOUCHE Ahmed (En préparation)
Thèse de doctorat

Le procédé, appelé soudage par friction, se présente comme un bon choixpour le soudage des matériaux métalliques ferreux non ferreux, parfois nonsoudables pour certaines séries d’alliage d’aluminium.Ce procédé s’effectue à l’état pâteux, sans atteindre la fusion, et il permet desouder des dissemblables et d’éviter les inconvénients inhérents aux procédésde soudage conventionnels.Le choix, des paramètres du mode opératoire, ainsi que l’originalité dans cetravail restent déterminants pour apporter une innovanteCe travail porte sur la caractérisation non destructive et destructive del’interface des soudures obtenues, représente notre zone d’intérêt. Voir les détails

Mots clés : friction

Comparative investigation of the Ni and the Fe effect on the structure andmechanical response of a WC-W-Ni hardmetal obtained by infiltration

H. Bouchafaa, D. Miroud, S. MATO, Z. Boutaghou, B. Cheniti, F.J. PÉREZ, G. ALCALÁ  (2019)

In the present work, and in order to enhance the efficiency of drilling tools for the oil and gas industry, theinfluence and performance of Ni and Fe during spontaneous infiltration on a WC-W-Ni composite materialmechanical behaviour was addressed. Solid-state activity of Fe and Ni during infiltration exhibits partial dissolution in the metallic binder. The chemical affinity between Fe and Ni, provided by the Fe powder and thebinder respectively, derived on the formation of the (Fe, Ni) solid solution and FeNi3 intermetallic precipitates inthe particle/matrix diffusion region, with a hardness (12 GPa) close to that of WC and high elastic modulus (230 GPa). Furthermore, the diffusion of Fe to the matrix leads to the formation of sub-micrometer precipitatesof α-Fe with some (Ni, Mn) in solid solution and of Ni3Sn with a small amount of Cu dissolved, driving to anincrease of about 30% in its elastic modulus, and without appreciable effect in the hardness observed. Voir les détails

Mots clés : Metal matrix composites, Liquid-solid reactions, Precipitation, powder metallurgy, diffusion, mechanical properties

Comportement à l'usure des boulets de broyage moulés et forgés Caractérisation et comparaison

Article de conférence

Les secteurs miniers sidérurgiques et cimentiers utilisent de grandes installations pour préparer la matière première et la rendre aussi fine que possible pour répondre à des exigences de process bien définies. Généralement deux types de boulets sont utilisés, les boulets de fonderie et les boulets forgés. Les boulets de fonderie sont en fonte au chrome par contre les boulets forgés sont en acier. Ces derniers sont fournis en différentes granulométrie et composition chimique. En cours de broyage, les boulets subissent des sollicitations différentes qui se résument en un impact une abrasion une friction ainsi que d’autres types d’usure. La tenue à l’usure de ces deux types de boulets est différente du fait qu’ils ne présentent pas le même type de microstructure. Les boulets en fonte au chrome sont constitués d’une microstructure mixte composée d’un réseau de carbure contenu dans une matrice à prédominance martensitique par contre les boulets en acier, la phase carbure existe en proportion très minime. La microstructure est constituée d’un mélange de martensite et bainite.Dans ce travail, nous présentons une étude comparative sur le comportement à l’usure les boulets en fonte au chrome et les boulets en acier forgé. Des caractérisations chimique, métallographique et microstructurales par DRX sont effectuées pour définir la composition chimique, le type de microstructure, la nature et la proportion des phases microstructurales existantes. Des mesures de dureté et des essais d’abrasion et de frottement sont aussi réalisés afin d’évaluer le comportement à l’usure des deux matériaux étudiés. Les résultats obtenus révèlent une large différence du point de vue composition chimique et composants microstructuraux. Les essais d’usure ont montré que les boulets en fonte au chrome et les boulets en acier forgé manifestent un comportement à l’usure qui diffère selon le type d’usure subit. Les boulets en fonte au chrome résistent mieux au frottement par contre les boulets forgés ont une meilleure résistance à l’abrasion. Voir les détails

Mots clés : Boulets moulés;, boulets forgés;, microstructure;, usure;

Synthèse et caractérisations de nouvelles générations de céramiques piézoélectriques sans plomb

SEDDA kamal (En préparation)
Thèse de doctorat

Dans ce travail de thèse, nous proposons d’élaborer de nouvelles céramiques piézoélectriques sans plomb, d’étudier l’influence des procédés d’élaboration et des conditions de synthèse de ces céramiques sur les propriétés physiques, microstructurales, diélectriques, piézoélectriques et ferroélectriques. Diverses techniques disponibles nous permettront de mener à bien ces travaux de recherche, que ce soient des techniques d’élaboration (synthèse en voie solide, sol-gel, …) ou des techniques de caractérisation (DRX, MEB, MET, STEM-EDX, ATD-TG, caractérisations diélectriques, piézoélectriques et ferroélectriques).En plus de cette étude fondamentale de nouvelles céramiques sans plomb, une application pourrait être développée : la conception de transformateurs piézoélectriques. Cette partie de l’étude passe d'abord par le choix d’une structure, le dimensionnement géométrique, suivis de la fabrication des prototypes (plusieurs architectures seront proposées) pour finir enfin par la détermination de leurs performances (gain, rendement, puissance). Voir les détails

Mots clés : synthèse, Céramique piézoélectriques, Système BCTZ, Caractérisation, microstructure

Metallic Coating for Carbon Fiber Reinforced Polymer Matrix Composite Substrate

Amine REZZOUG, Said ABDI, Nadjet BOUHELAL, Ismail DAOUD  (2016)

This paper investigates the application of metallic coatings on high fiber volume fraction polymer matrix composites. For the grip of the metallic layer, a method of modifying the surface of the composite by introducing a mixture of copper and steel powder filler powders which can reduce the impact of thermal spray particles. The powder was introduced to the surface at the time of the forming. Arc spray was used to project the zinc coating layer.The substrate was grit blasted to avoid poor adherence. The porosity, microstructure, and morphology of layers are characterized by optical microscopy, SEM and image analysis. The samples were studied also in terms of hardness and erosion resistance. This investigation did not reveal any visible evidence damage to the substrates. The hardness of zinc layer was about 25.94 MPa and the porosity was around 6.70 percent. The erosion test showed that the zinc coating improves the resistance to erosion. Based on the results obtained, we can conclude that thermal spraying allows the production of protective coating on PMC. Zinc coating has been identified as acompatible material with the substrate. The filler powders layer protects the substrate from the impact of hot particles and allows avoiding the rupture of brittle carbon fibers. Voir les détails

Mots clés : Arc spray, coating, composite, erosion