Sciences des matériaux

Nombre total de résultats : 399
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Elaboration Of Laminated Composite Plates By The LRI Process

W. Djerir, R. Halimi, H. Barkat and Ali Badidi Bouda (2018)
Article de conférence

The aim of this work is the elaboration oflaminated composite plates based on the LRI (liquid resininfusion process). This process makes it possible to producelightweight composite plates, with the possibility of theirapplications in the structural parts production of variousdimensions in many industrial sectors such as aeronautics,transport and building. In this process, the use of the adjustabletemperature heating plate replaces the autoclaves required inthe development of composites. In contrast to existing processes,it does not require high pressure during the polymerizationphase. The infusion of the resin is also done automatically by avacuum pump. In addition, because of the absence of a mold onthe upper part, vacuum bag made of nylon or silicone is used.Voir les détails

Mots clés : LCM : Liquid Composite Molding; LRI: Liquid Resin Infusion; laminated composite materials; vacuum pump; glass fiber; carbon fiber.

Puzzle of c-WN phase stabilization

W. RICHI, D. ZANATI (2018)
Article de conférence

In this paper, we present first-principles calculationsthat compare structural and electronic properties of WN inthe NaCl and NbO phases. Our results predict that the NbOstructure of WN is more stable than the NaCl structure withoutdefects, where the enthalpy of formation per formula unit Hf =-0.872eV and 0.616eV for NbO and NaCl structures, respectively.Moreover, the calculated lattice parameters of c-WN are a=4.35A°and a=4.11A° for NaCl and NbO phases, respectively. It is veryclear that the lattice parameter obtained for c-WN in NbO is invery good concordance with that reported experimentally of a =4.14A° . Although the formation energy calculations support thehypothesis of the stability of the NbO phase, the experimental xrayphotoelectron spectroscopy (XPS) electron density of statesfor valence band spectra corresponds to that density of statescalculated for c-WN in NaCl phase. Based on this comparison,more consideration must be taken into account to elucidate thisissue.Voir les détails

Mots clés : Cubic Tungsten nitride ceramics, Firstprinciples calculations, Formation energy


A. Azzi, L. Bahloul, L. Alimi, S. Guerfi, S. Bouyeg, M. Boulkra, A. Grairia (2018)
Article de conférence

The objective of this work is the elaboration of a biomaterial Hydroxyapatite (Ca10 (PO4)6 (OH)2), by a synthetic method of precipitation, (CaCl2, 2H2O) as source of calcium and (Na2HPO4, 12 H2O) as a source of phosphate. After preparation, the powder was calcined at 900 °C for 90 minutes at a speed of 10 °C / min and compacted into pellets 12 mm in diameter and 2 mm thick. Sintered powder at different temperatures (1000 °C, 1100 °C, 1200 °C, and 1300 °C). In order to study the effect of sintering temperature on the microstructure, the physical and morphological properties of the elaborated hydroxyapatite, the density, the porosity, X-ray diffraction (DRX) and the scanning electron microscopy (SEM) were used for the characterization of the powder. The density decreases with the increase of the porosity, in fact the sample densifies easily when the porosity is lowerVoir les détails

Mots clés : hydroxyapatite, SEM, DRX, Porosity, Density


I HADJI, R Badji, M Gaceb, N KHARROUBA, L RABAHIL (2018)
Article de conférence

The main goal of this study is to show the effect of the advancing side (AD) and the retreating side (RT) position on the Residual stresses and local mechanical behavior of dissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different samples were produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloy position regarding the advancing side of the tool. Ultrasonic Method has been used to evaluate Residual Stresses. Method ultrasonic is based on the acoustoelastic effect, which measures the velocity variation of the elastic waves according to the stress state of the material. This can be achieved through a calibration test, which permits the determination of the acoustoelastic coefficient (K). A tensile stress show in heat affected zone (HAZ) and a compression stress in the base metal (BM). Increasing the rotational speed reduces the amplitude of the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is in the advancing side whit 1400 rpm. This has been directly associated to the increase in the heat input and the reduction of the thermal mismatch between different areas of the weld. The microstructure effect of aluminum alloy position acts on the acoustoelastic constant K. The choice of t0 corrects the overestimated residual stresses in the (HAZ) and (N).Voir les détails

Mots clés : residual stresses, FSW, Aluminum alloy, Dissimilar welding

Electroless copper deposition on epoxy glass substrate for electrocatalysis of formaldehyde

C. Dehchar, I. CHIKOUCHE, R. KHERRAT, A. Sahari, A. Zouaoui, A. MERATI (2018)
Article de journal

In this paper, we investigated the characteristics of a structured copper (Cu) ?lm deposited on the surface of an insulating epoxy glass (EG) substrate via a facile electroless plating process. The ?lm produced by this method was found to be of high purity and has a homogeneous microstructure consisting of an assembly of numerous aggregates that vary in size from 1 to 5 mm depending on the electroless deposition time. The electrocatalytic activity of the prepared electrode was investigated for the electrooxidation of formaldehyde using cyclic voltammetry in 0.1 M NaOH solution. Results show that formaldehyde oxidation takes place at a low potential of -0.34 V with large anodic current densities.Voir les détails

Mots clés : copper, electroless plating, Formaldehyde, Oxidation, Thin films

Proposition of a mechanical model to predict the behaviour of a laminate bio composite material

D.ZELMATI, W.Ghelloudj, K.BEDOUD, M.HASSANI (2018)
Article de conférence

The purpose of this paper is to develop a mechanical model able to predict the mechanical behaviour of a laminate bio-composite material reinforced by the flax fibres without necessity to the expensive experimental test. A numerical comparative modelling based on finite element method is conducted by using in one hand a several stacking sequences, and in the other hand a growing plies number in order to estimate the lateral deflexion U3 in each plies of the bio-composite subjected to compression load. Meanwhile, the proposed mathematical model can be used as a power tool decision in design and the ensuring of the structure integrity.Voir les détails

Mots clés : Bio-composite, laminate, flax, modeling

Structure, magnetic and microwave studies of mechanically alloyed powders Fe45Ni35Co20

Ahmed HADDAD, Insaf Ouldbrahim, Mohamed Azzaz (2018)
Article de journal

Nanocrystalline Fe-35 wt%Ni-20 wt%Co has been prepared by using a high-energy planetary ball mill with increasing milling time from 4 to 36 h. Microstructural characterisations showed the development of an face-centred cubic nanostructured Fe-35 wt%Ni-20 wt%Co alloy with an average crystallite size of 8 nm. The magnetic investigation revealed that the nanostructures obtained from a milling time of 36 h have the highest magnetic saturation and the lowest coercive field. In addition, the hardness and the electromagnetic absorption of the Fe-35 wt%Ni-20 wt%Co alloy were found to increase with the milling time. These evolutions could be attributed to the crystallite size and the strain variations in the samples during milling.Voir les détails

Mots clés : nanostructure, magnetic, nanocristalline, Mechanical Alloying, Fe, Co

Elaboration and characterization of a refractory based on Algerian kaolin: evolution with heat treatments up to 1450°C

S. LADJAMA, A. Grid, N.Touati, A.Meberek, H.Rezzag, S.Bouchoucha (2018)
Article de conférence

Abstract:In order to meet the needs of the local market in terms of renovation of ovens for different uses, we propose the valorization of natural resources through the development of local products that meet industrial requirements and international standards and therefore the reduction of the import bill. Refractory ceramics based on silica-alumina are the subject of our study. The chemical characteristics of kaolin known as DD1, from eastern Algeria were examined. The results showed that kaolin DD1 has an alumina content of 40%, and 37.23% of silica. Thermodifferential and thermogravimetric analysis (ATD and ATG) confirm the mineralogical results obtained by X-ray diffraction (XRD) of the sintered samples at different temperatures namely 1200, 1300, 1350, 1400 and 1450° C; ATD peaks characteristic of a kaolinite are present.X-ray diffraction analysis showed that the refractory samples are composed of mullite and cristobalite. The different treatments lead to the formation of mullite, from 1200 ° C the beginning of the crystallization of the mullite and the densification of the sample due to the sintering phenomenon are marked. At sintering temperature greater than or equal to 1200 ° C, mullite constitutes the dominant phase of the material. The intensity of the peak at 21.6 °, corresponding to the cristobalite that remains and its intensity increases as the cooking temperature increases, according to the literature at a temperature> 1400 ° C cristobalite melts in the amorphous phase which leads to the formation of the vitreous phase which causes the degradation of the refractorinessVoir les détails

Mots clés : Keywords: Refractory ceramics, silica-alumina, Kaolin, sintering temperature, characterization.

Electrocatalytic oxidation of ascorbic acid at polypyrrole thin film incorporating palladium particles

Charif DEHCHAR, Imene CHIKOUCHE, Rochdi KHERRAT, Saida ZOUGAR, Ahmed ZOUAOUI (2017)
Article de journal

In this paper, we report a simple sensing strategy for electrochemical determination of ascorbicacid (AA) using a combination of polypyrrole (PPy) thin film and palladium particles composites deposited onto n-doped silicon (Si) substrate. A two-step electrochemical process was employed to synthesize the composite films: At first, PPy film (average thickness 200 nm) was electro-generated on Si substrate from an organic solution of the pyrrole under galvanostatic conditions. Secondly, palladium particles were electrodeposited on PPy/Si surface from a separate solution by chronoamperometry technique. The surface morphology analysis of the obtained composites shows a uniform dispersion of palladium particles onto the polymer matrix and reveals that the electrodeposition time has a significant effect on the amount and size of the incorporated palladium particles. The electrochemical reactivity of the Pd–PPy/Si-modified electrodes towards the oxidation of AA was studied by cyclic voltammetry method in 0.1 M, pH 7.0 phosphate buffer solution. The oxidation current was proportional to the concentration of AA in the range of 0.5–10 mM with a detection limit of 0.2 mM.Voir les détails

Mots clés : ascorbic acid, composite, electrocatalysis, Electropolymerization, palladium, Polypyrrole

Copper-polypyrrole composite films for electrocatalysis of ascorbic acid

Charif DEHCHAR, Imene CHIKOUCHE (2018)
Article de conférence

In this study, we have interested to the electrochemical deposition on an indium tin oxide (ITO) substrate of thin films of polypyrrole functionalized by a dispersion of copper particles. The resulting copper-polypyrrole/ITO modified electrodes were used for the development of an amperometric sensor allowing the detection of ascorbic acid at low concentration ranges. The surface morphology analysis of the obtained deposits showed a homogenous dispersion of copper particles on the polymer film. The electrochemical reactivity of the prepared modified electrode towards the oxidation of ascorbic acid was examined in a solution of 0.1 M pH 7.0 phosphate buffer using cyclic voltammetry and chronoamperometry methods. The catalytic behavior of this electrode manifests by an increase in the peak current of ascorbic acid oxidation as compared to the response of the pristine polypyrrole film; and by an increase in the oxidation current density with increasing the ascorbic acid concentration.Voir les détails

Mots clés : ascorbic acid, copper, electrodeposition, electrocatalysis, Polypyrrole