Sciences des matériaux
Physico-chemical study of a welding assembly of the low alloy steels
The welding is inevitable in the realization of electric centrals, several processes of welding were developed, with the extension of the branches of industry, whose choice depends on several parameters in particular the nuance of metals to be assembled, the thicknesses of parts to be welded, the position of welding, the type of preparation of parts and available energy source. The realization of the resistant high-security junctions on the severe mechanical conditions of corrosion, resistance and creep requires to make numerous study.Our study consists in making a weld on a low alloy steel, used in power plants, by using two processes in the electric arc, GTAW (Gas Tungsten Arc Welding) and SMAW (Shielded Metal Arc Welding).This joint of weld was characterized by the various techniques usually used such as, the optical microscopy, electronic microscopy with sweeping scanning (MEB) coupled with the EDS, as the mechanical characterization by the macro-hardness Vickers. Voir les détails
Mots clés : welding, proceeded GTAW and SMAW, physic-chemical, element of addition, low alloy steel, Metallography, SEM.
Solid state synthesis of ZnO nanostructures: effect of temperature on the structural and Optical properties
Among the different approaches to synthesize nanostructured ZnO, the solid state synthesis isone of the simplest methods to elaborate the ZnO nanoparticles. In this work we obtainednanostructured ZnO by aforesaid method using zinc nitrate tetrahydrate ZnO(NO3)2 asprecursor. The influence of calcination temperatures as 300, 400, 500 and 600°C, on thecrystallite size and the optical properties was investigated by X-Ray diffraction and UV–visible spectroscopy, respectively. The results obtained by XRD confirm that the diameter ofnanocrystallites was affected by the calcinations temperature. The UV–visible absorbancespectra of the synthesized samples reveals that the calcinations temperature plays a significantrole in the absorption characteristics, and influences the optical band-gap of the samples.Raman and FT-IR spectroscopy were performed to investigate the structural, vibrational andchemical properties of the ZnO nanostructures. Voir les détails
Mots clés : ZnO nanostructure, FTIR, UV-Vis, solid state synthesis
Structural and microstructural characterization of Algerian diatomite
Diatomite is a sedimentary rock composed of fossilized skeletons of diatoms which are microscopic unicellular alga. Due to its useful physical and chemical characteristics, it is used in a wide range of industrial applications. Raw diatomite samples were taken from SIG region of Algeria. Chemical composition, morphology, structure and specific surface area are determined by X-ray fluorescence, scanning electron microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and N2-adsorption-desorption analysis, respectively. The XRF results indicate that the raw diatomite is mainly composed of silica (>60%) and CaO (>14%). The XRD pattern reveals a mixture of amorphous silica and crystalline phases such as quartz and tridimite. The surface area, pore volume and pore size are 26.4 m2/g, 0.204cm3/g and 30.82 nm, respectively. Voir les détails
Mots clés : diatomite, characterization, pore, FTIR
Study of composite with metallic matrix WC/W2C- 20W-20Ni realized by spontaneous infiltration of the bronze alloy Cu-30Mn-3P.
The improved performance and duration of an impregnated tool for the mineral drilling requires thorough understanding of the mechanisms involved in the consolidation of powder mixtures in the liquid phase sintering cycle (FPL). The elements used for the manufacture of the active parts of these tools are usually made from mixtures of loose powders based on WC / W-Ni. The spontaneous infiltration process is the most appropriate method offers a big possibility of shapes due to molding. It lets to have considerable density of the metal matrix composite (MMC) constituting the active head and increase its resistance to erosion and abrasion.This work consists to develop a metal matrix composite which can constitute the active part of a drilling tool impregnated by the infiltration of industrial process SILP (Sintering by Infiltration of an appropriate mixture of Loose Powders). The mixture of loose powders (WC/W2C-W-Ni) is infiltrated under hydrogen by a manganese bronze (Cu-30Mn-3P) and then characterized by DTA, optical microscopy, SEM coupled with EDS, HRA hardness and micro-hardness Hv0.1. Voir les détails
Mots clés : Matrix Composite Material (MMC), SILP process, Matrix, Powder Free, alloying element, sintering in liquid phase (FPL), multi-material, physical chemistry.
Optical characterization of FeCo nanostructured
Fe–Co alloys are important optical and magnetic materials that have been widely used in industry. The material nanostructured has showed a superior magnetic and optic properties Compared to polycrystalline materials. However, optical and magnetic properties of materials nanostructured are affected by their microstructure such as grain size, internal strain and crystal structure. This, studies on synthesis of materials nanostructured with controlled microstructure are obligatory for a significant improvement. MA is a method with a lot of advantage that it can be simply and fabricate large amounts of nanostructured powders in small time. In the present work, starting with two powder mixtures of Fe and Co produced by Mechanical alloying. Voir les détails
Mots clés : optical and magnetic properties, Fe–Co alloys nanostructured
Synthèse et caractérisation de nano-hydroxyapatite
Plusieurs procédés de synthèse chimique ont été développés pour préparer la poudre hydroxyapatite (HA) en utilisant divers types de sources de calcium (Ca) et de phosphate (PO4). Dans le présent travail, nous rapportons les conditions d’élaboration d’une poudre nanométrique de HA en utilisant la coquille d’œuf de poule comme source de Ca. La synthèse a été effectuée à partir de la réaction chimique de Ca(OH)2 obtenu après traitement thermique des coquilles et l’acide phosphorique H3PO4, en présence de L’EDTA comme agent chélateur et le NH4OH pour ajuster le pH. Les produits ont été caractérisés par diffraction des rayons X et microscopie électronique à balayage. Voir les détails
Mots clés : hydroxyapatite, nano-poudre, synthèse par voie humide, DRX, MEB
Effet des paramètres de synthèse sur les propriétés d’un biomatériau type phosphate de calcium : Hydroxyapatite
L’hydroxyapatite (HA) a été largement utilisée dans des applica-tions biomédicales pendant plus de quatre décennies, elle présente un intérêt croissant dû à ses propriétés favorables telles que la bioactivité, la biocompatibilité, ostéoconduction et l’ostéointégration. Divers procédés ont été rapportés pour prépa-rer des poudres du HA synthétiques. Du fait qu’in vivo, les pro-priétés biologiques et mécaniques du HA soient très sensibles à ses caractéristiques structurelles, la bonne exploitation de ce matériau bioactif dans le domaine biomédical nécessite encore un effort à déployer. Dans ce travail de recherche, nous avons élaboré deux poudres d’hydroxyapatite par voie humide, en variant le temps d’agitation : 72 h en continu et 48 h avec des périodes de vieillis-sement. Les spectres DRX montrent que les deux poudres ont la même stœchiométrie, les observations MEB nous permettent d’identifier la forme et la taille des cristallites. Voir les détails
Mots clés : hydroxyapatite, biomatériaux, céramiques, double décom-position, voie humide.
Characterization of the Algerian diatomite by XRD, FTIR and XRF For use in water filtration
Diatomite (Kieselguhr) consists of fossilized diatoms residues of hard-shelled algae type, is used as a filter aid, liquids absorbent, reinforcing filler in plastics and rubber, porous support for chemical catalysts, and a thermal insulating. The purpose of this paper is studying the structural and chemical composition of this material; by means of elemental analysis, in order to identify and quantify the chemical elements and the structural composition of the crude diatomite of the Sig region (western Algeria) by analytical methods such as X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray fluorescence (XRF) in order to be exploited in a large scale for water filtration. Voir les détails
Mots clés : diatomite, characterization, structural, chemical composition, filtration.
VALUATION OF MILL SCALE AS IRON PIGMENTS FOR PAINTING ANTICORROSIVE
The mill scale is a steelmaking byproduct. This work focuses on the valuation of the steel waste and its transformation to a usable product in the field of anti-corrosion paints.These iron oxides have been examined as a pigment and corrosion inhibitor in both types of solvent based paints with different concentrations (1%, 3%, 7%, 15%) to determine the best formulation. Their properties were compared to that of an anticorrosion paint trademark based on iron oxide.For this purpose various techniques of mechanical and physical-chemical analysis were used:- Grinding is applied to pieces of mill scale for very fine powders (<32μm);- The particle size of the milled scale analysis, to determine their particle size distribution;- A primary electrochemical method used to evaluate the performance and scale vis-à-vis the phenomenon of corrosion behavior;- A UV-Visible spectroscopic method for determining the concentration of total dissolved iron.The experimental results showed that the anti-corrosion properties or rather inhibition efficiency increases with increasing concentration of the mill scale in the tested paints.Keywords: mill scale, corrosion inhibitor, spectroscopic, electrochemical analysis. Voir les détails
Mots clés : mill scale, corrosion inhibitor, spectroscopic, electrochemical analysis
Influence des traitements thermiques après soudage sur le comportement mécanique d'un acier faiblement allié au chrome molybdène.
Les aciers faiblement alliés au Chrome Molybdène sont des matériaux qui résistent au fluage et à la corrosion à haute température. En effet un faible pourcentage des éléments (Cr, Mo) lors de soudage provoque des changements dans la microstructure ainsi que le comportement mécanique. L’objectif de ce travail est de mettre en évidence l'influence des traitements thermiques sur l'évolution de la microstructure et le comportement mécanique d'un assemblage par soudage à l’arc électrique d'un acier faiblement allié au chrome-molybdène. L'évolution de la microstructure avant et après traitements thermiques seront suivi par des analyses micrographiques, tandis que le comportement mécanique sera caractérisé par les essais de traction, de résilience et de dureté. Voir les détails
Mots clés : Soudage à l’arc électrique, acier faiblement allié, éléments d’addition, physico-chimique, traitement thermique.