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Nombre total de résultats : 451
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Mechanism for phosphorus deactivation in silicon-based Schottkydiodes submitted to MW-ECR hydrogen plasma

D.BELFENNACHE, D.MADI, N.BRIHI, M.S.Aida, M.A.SAEED (2018)
Article de journal

Current work reveals the deactivation mechanism of phosphorus in silicon-based Schottky diodes. Microwave plasma power(P) was fixed at 650 W to observe the variation in different operational parameters of diodes such as initial phosphorusconcentration, flux and hydrogenation temperature (TMWH) and process time (t). The analysis of variation in concentrationof phosphorus by hydrogenation has been carried out by capacitance–voltage (C–V) measurements to monitor the dopingactivation/deactivation. The results clearly show that the atomic species H+H is dominant in the reactors MW-ECR plasma.Therefore, the rates and depth of neutralization were obtained in the low phosphorus-doped silicon sample. The H becomesH0 and prefers an interaction with another H0 instead of gaining an electron to become a negative ion. The hydrogenationtemperature study indicates that the deactivation rate of phosphorus is achieved in a complex manner. Indeed, as the hydrogenationtemperatureincreases,deactivationof phosphorus also increasestill saturationat 250 °C.Athigher temperature,lowor evenno phosphorus–hydrogen complexexistsdue totheirthermaldissociation. The same behaviorwasconfirmedbylonghydrogenation.Voir les détails

Mots clés : MW-ECR plasma, Hydrogenation, phosphorus deactivation, C–V measurement

Poly Chlorure de Vinyle (PVC) Plastifié par des Mélanges des Plastifiants d’origineBiosourcés : Synthèse et Caractérisation

Boussaha BOUCHOUL, Mohamed Tahar BENANIBA (2016)
Article de journal

L’huile de tournesol époxydée (HTE) avec un indice d’oxyrane de 4,5 a été synthétisée à partir de l’huile de tournesol vierge et l’eau oxygénée (H2O2) en présence de l’acide formique. L’HTE est utilisée avec le di esters isosorbide (DEI) comme un système plastifiant biosourcé dans le PVC en combinaison avec un plastifiant classique soit le di-éthyle-2-hexyle phthalates (DEHP).Après fabrication des films (0,5 mm d’épaisseurs) de différents pourcentages des plastifiants dans un mélangeur à deux cylindres, on a réalisé les essais de la migration et d’excudation des plastifiants des formulations obtenues. La migration des plastifiants biosourcés (DEI ou HTE) en combinaison avec le DEHP est suivie par les tests de volatilité, d’extraction et de lessivage. Les pertes des masses des formulations plastifiées réalisées obtenues par les différents modes de caractérisation à savoir: la volatilité, l’extraction dans l’eau distillée et dans la gazoline et le lessivage dépendent de la pression devapeur, de la masse moléculaire, de la solubilité, de la compatibilité et de la structure chimique du plastifiant.Voir les détails

Mots clés : PVC, Biosourcé, Epoxydation, plastifiants

Thermal and mechanical properties of bio-basedplasticizers mixtures on poly (vinyl chloride)

Boussaha BOUCHOUL, Mohamed Tahar BENANIBA, Valérie MASSARDIER (2017)
Article de journal

The use of mixtures of nontoxic and biodegradable plasticizers coming from natural resources is a good way to replaceconventional phthalates plasticizers. In this study, two secondary plasticizers of epoxidized sunflower oil (ESO)and epoxidized sunflower oil methyl ester (ESOME) were synthesized and have been used with two commerciallyavailable biobased plasticizers; isosorbide diesters (ISB) and acetyl tributyl citrate (ATBC) in order to produce flexiblePVC. Different mixtures of these plasticizers have been introduced in PVC formulations. Thermal, mechanical andmorphological properties have been studied by using discoloration, thermogravimetric analysis (TGA), differentialscanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile - strain and scanning electronmicroscopy (SEM). Studies have shown that PVC plasticization and stabilization were improved by addition ofplasticizers blends containing ISB, ATBC, ESO and ESOME. An increase in the content of ESO or ESOME improvedthermal and mechanical properties, whereas ESOME/ATBC formulations exhibited the best properties.Voir les détails

Mots clés : PVC, epoxidized sunflower oil, epoxidized sunflower oil methyl ester, isosorbide diesters, acetyl tributyl citrate.

Study of the effect burnishing on superficial hardness and hardening of S355JR steel using experimental planning

Mounira Bourebia, abdeljalille bouri, Hamid Hamadache, Sihem ACHOURI, lakheder laouer, amel gherbi, Oualid GHELLOUDJ (2019)
Article de journal

Surface hardness plays an important role in lifetime of a mechanical piece subjected to friction and wear. Indeed, the hardness can be improved by superficial plastic deformation processes (SDP), such as mechanical surface treatment "MST", in particular the ball burnishing. However, the treatment result of is conditioned by mastery of operation thus ensuring treated piece good mechanical and geometric properties. Experimental work was carried out by applying the ball burnishing process on steel tensile specimens S355JR, in order to observe the influence of treatment parameters regime on surface hardness ‘Hv’ and the effect of latter on tensile behavior of this steel. Two parameters of regime were considered namely: burnishing force "Py" and number of passes "i". The relationship between these parameters and microhardness measured at "Hv" surface has been highlighting using factorial plans 22. Moreover a mathematical model has been obtained allowing prediction of response (Hv) as well as optimization of parameters of treatment regime. The experimental results showed that for surface hardness Hv it is possible to reach a 45% improvement rate for a burnishing force py = 20 Kgf and a number of passages i = 3 for this material. Regarding behavior of material during tensile test, for a low burnishing force (py = 10N) and a number of passes (i = 5), the section further weakening (S = 4.14), proof than ductility of material has decreased.Voir les détails

Mots clés : Surface hardness, factorial designs, ball burnishing, Mathematical model, tensile behaviour

ZnO nanoparticles and biocidal effect of nanostructured ZnO filmson Escherichia coli

Nabila Bouasla, Sihem Abderrahmane, Sameh Athmani, Amel Oulabbas, Mohamed Bououdina (2018)
Article de journal

The biocidal effect of ZnO nanostructured films was studied using Escherichia coli ATCC 43897. TheZnO nanoparticles were synthesized in diethylene glycol by using zinc acetate forced hydrolysis.X-ray diffraction analysis confirmed the formation of single wurtzite-type ZnO phase with a crystallitesize of 20.59 nm. Transmission electron microscopy observations revealed spherical-shaped particlesin the nanoscale regime with a mean particle size of 21.96 nm. It was found that the addition oftrioctylphosphine during synthesis favored much improved dispersion of ZnO nanoparticles, withsmaller particle size; that is, 16.28 nm. Meanwhile, ZnO film grown onto glass substrate by spin-coatingrevealed single phase with the formation of aggregates (≈700) having mushroom-like morphologyformed of very fine particles in the nanoscale regime. The as-deposited nanostructured films exhibiteda hydrophilic character. The classical bacteriological and electrochemical impedance spectroscopymeasurements enabled the biocidal effect of ZnO nanostructured films with 94% inactivation efficiencyafter 90 min of contact time.Voir les détails

Mots clés : ZnO; Spin-coating; Nanostructured film; Biocide effect; E. coli; EIS

Endurance and Damage in Fatigue of Symmetrical Configuration 2P-2V-2P Perlon-Glass-Acrylic Composite Laminates of Orthopaedic Use

Bachir Redjel, Sihem ACHOURI (2019)
Article de journal

In this paper, an experimental characterization of fatigue behaviour on prismatic specimens of a symmetrical laminated composite material perlon- glass- acrylique 2P-2V-2P for orthopaedic use is conducted. Cyclic repeated solicitation is employed corresponding to applied minimum stress σmin equal zero. The various loading levels imposed on the specimens are 80%, 70%, 60%, 55%, 45%, 35% and 25% of the value of the static failure strength measured in flexure. A significant scatter characterizes the results of material fatigue lifetime. That is the consequence of the heterogeneity of the material structure. The scattered phenomenon prevents any prediction of the lifetime with a good probability using Wohler equation. This enables defining a constant degradation rate by 10% cycle decade. The microstructure morphology study through microscopic observations is also discussed and analyzed. The damage state in fatigue is characterized by a combination of density and orientation of micro-cracks. This damage is mainly due to mechanisms complexity of matrix micro-cracking, inter facial exfoliation, debonding and delamination. The damage evolution stages in the case of cyclic loading have the same nature than those found in static loading but have different chronology and scaleVoir les détails

Mots clés : perlon, acrylic, Orthopaedic, fatigue, Scatter

Natural extract of Opuntia ficus indica as green inhibitor for corrosion ofXC52 steel in 1M H3PO4

Amel Oulabbas, Abd errahmane Sihem (2019)
Article de journal

The purpose of this study is to evaluate the anti-corrosive effect of natural extract of Opuntia Ficus Indica (O.F.I) for XC52steel in 1M H3PO4. Experimental work has been achieved by weight loss, potentiodynamic polarization and EISmeasurement, as well as SEM surface characterization. Among the results obtained, we can mention an inhibitory efficiencyof 90% by gravimetric method and 83.9% by electrochemical method at 10% (v/v) of O.F.I. Moreover, The O.F.I extract actsas a mixed inhibitor; however, adsorption free enthalpy indicates a physisorption. The adsorption obeys the Langmuirisotherm model. These results have been improved by SEM micrographsVoir les détails

Mots clés : corrosion, Opuntia ficus indica, EIS, green inhibitor, XC52 steel

Effect of Biobased Plasticizers on Thermal, Mechanical, andPermanence Properties of Poly(vinyl chloride)

Boussaha BOUCHOUL, Mohamed Tahar BENANIBA, Valérie MASSARDIER (2014)
Article de journal

Phthalates can be replaced by other harmless andenvironmentally friendly plasticizers, such as isosorbidediesters (ISB), and epoxidized sunflower oil (ESO),which has been proved an efficient stabilizer for poly(vinyl chloride) (PVC) in helping to prevent degradationduring processing. Formulations based on PVC withdifferent amounts of ISB, ESO, and di-(2-ethylhexyl)phthalate (DEHP) from 0 to 60 parts by weight per hundredparts of resin were realized. To make PVC flexiblewith partial amounts of the debated phthalates asplasticizers, we use a combination of DEHP, ISB, andESO. Effects of these two biobased plasticizers, ISBand ESO, and their mixture with DEHP on thermal stabilityby measuring discoloration degrees and thermalgravimetric analysis, on mechanical properties suchtensile strength, elongation at break, and hardness,were characterized. Plasticizer permanence propertiesof PVC compounds were studied. Studies showed thatprocessibility and flexibility were improved by the additionof a plasticizer system (ISB, ESO, and DEHP). Anincrease in the content of ISB and/or ESO increasedthermal and mechanical properties, whereas compositionswith ternary compositions of ISB/ESO/DEHP (15/15/30) exhibited the best performance properties.Voir les détails

Mots clés : PVC, Sunflower oil, Leaching, Volatility

Impact of the inhomogeneous structure of the active layer on the transfer characteristic of polysilicon TFT's

Hadjira Tayoub, asmaa bensmain, Baya Zebentout, Zineb Benamara (2012)
Article de journal

Recently polycrystalline silicon (pc-Si) thin film transistors (TFT's) have emerged as the devices of choice for many applications. The TFT's made of a thin un-doped polycrystalline silicon film deposited on a glass substrate by the Low Pressure Chemical Vapor Deposition technique LPCVD have limits in the technological process to the temperature <; 600°C. The benefit of pc-Si is to make devices with large grain size. Unfortunately, according to the conditions during deposition, the pc-Si layers can consist of a random superposition of grains of different sizes, where grains boundaries parallels and perpendiculars appear. In this paper, the transfer characteristics IDS-VGS are simulated by solving a set of two-dimensional (2D) drift-diffusion equations together with the usual density of states (DOS: exponential band tails and Gaussian distribution of dangling bonds) localized at the grains boundaries. The impact of thickness of the active layer on the distribution of the electrostatic potential, the effect of density of intergranular traps states and grain size on the TFT's transfer characteristics IDS-VGS have been also investigated.Voir les détails

Mots clés : Transistor TFT, 2D simulation, heterogeneous structure, Grain Size, transfer characteristic

Discoloration of Azo Dye Solutions by Adsorption on Activated Carbon Prepared from the Cryogenic Grinding of Used Tires

OULD BRAHIM Insaf, BELMEDANI AHMED, Belgacem Ahmed, Hadoun Hocine, SADAOUI ZAHRA (2014)
Article de journal

This present work reports a study about the adsorption of cationic dye (Methylene blue) by activated carbon prepared from the cryogenic grinding of used tires. Characterization of the obtained activated carbon by chemical analysis, FTIR and SEM, was studied and resumed that the activated carbon was mesoporous. The effect of various experimental parameters such as contact time, solution pH, adsorbent dose and dye concentration, on the dye adsorption uptake on the activated carbon has been investigated using batch adsorption experiments. According to the experiments results, it was shown, that equilibrium was achieved in less than 114 min. The effect of pH investigated for values ranging from 2 to 11, showed maximum adsorption for pH 11. The equilibrium adsorption isotherms models of Langmuir, Freundlich and Dubinin-Radushkevich, were tested for the quantitative description of the dye adsorption. The Langmuir isotherm provided the best fit for dye adsorption onto the prepared activated carbon and the maximum adsorption capacity was found to be 30.21 mg.g-1. The results show that the produced activated carbon from used tire is an alternative low-cost adsorbent for removing dyes from solutions.Voir les détails

Mots clés : adsorption, FTIR, SEM