Liste des documents
Study of physico-chemical properties ofdiatomite Algeria: Application to thethermal insulation of liquid steel bath
The purpose of this paper is tocharacterize and to evaluate the diatomitepowder of Sig region (West Algeria) withoutfluorine by powder generally used in tundish tothermal insulation of steel bath contain fluorine,that affecting the environment and health ofworkers. Thermal and physicochemicalcharacterization showed different endothermicand exothermic peaks. The scanning microscopymethod was used and a large porosity wasobserved, which is very beneficial for improvingthe thermal conductivity of the product. The trialindustrial in steelwork with diatomite powder,showed a weak loss temperature of steel (10 °Cmax), and filled fully function in thermalinsulation of the steel bath Voir les détails
Mots clés : diatomite, fluorine, Tundish, steelwork, thermal insulation, DSC
Diagnosis of AC corrosion on the buried pipeline due to the high voltage power line
This paper studies the electromagnetic effect of the high voltage power line on the X70 Steel pipeline and the factors affecting this interference. The induced voltage onto the pipeline was calculated for different separation distance between conductors, the existence of the earth wire, separation distance between transmission line and pipeline and the parallelism length. The induced AC current density was calculated function to the induced voltage, the soil resistivity, and the holiday diameter. The electrochemical characters of the X70 steel with and without influence of the alternating currents were studied in simulated soil solution. The results indicate that the AC density accelerate the corrosion degree of X70 steel in simulated soil solution comparing with that in the absence of the AC density. Voir les détails
Mots clés : Power lines, interference, induced voltage, induced current density, AC corrosion.
Numerical study of air preheating effect on NOx emissions in a heating furnace
This work aims to evaluate the reduce pollutant emission by steel reheating furnaces and operating process of the diffusion flame industrials burners. The example developed here is particularly interested in the influence of the air preheating temperature on NOx emissions as well as the dynamic characteristics and heat flow. The study was conducted on an industrial gas burners 250kilowatt. Numerical simulations are per formed using the computer code FLUENT, using the turbulence standard k-ε model coupled to turbulent combustion ED (Eddy Dissipation). The probability density function PDF model (6 species and reactions 3) with a chemical equilibrium model. The results obtained for different air preheat temperatures show that NOx emissions depend on the air preheat temperature. Voir les détails
Mots clés : pollutant emission, industrials burners, turbulent combustion
Simulation of cracks detection in tubes by eddy current testing
The means of detection must ensure controls either during initial construction, or at the time of exploitation of all parts.The Non destructive testing (NDT) gathers the most widespread methods for detecting defects of a part or review the integrity of astructure.In the areas of advanced industry (aeronautics, aerospace, nuclear …),assessing the damage of materials is a key point to control durability and reliability of parts and materials in service.In this context, it is necessary to quantify the damage and identify thedifferent mechanisms responsible for the progress of this damage. It is therefore essential to characterize materials and identify the most sensitive indicators attached to damage to prevent their destruction and use themoptimally.In this work, simulation by finite elements method is realized with aim to calculate the electromagnetic energy of interaction: probe and piece (with/without defect). From calculated energy, we deduce the real and imaginary componentsof the impedance which enables to determine the characteristic parameters of a crack in various metallic parts. Voir les détails
Mots clés : Eddy Current, Non-destructive testing (NDT), Cracks, Finite, Element Method
Microstructure and Magnetic Properties of NiP Alloys
Ni-P alloys were prepared by electrodeposition on a copper substrate at different plating conditions (applied potential and deposition time). The morphology, composition, microstructure, structure, and magnetic properties of the films were investigated by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, and vibrating sample magnetometry, respectively. The phosphorous content is about 8.6–12.2 at.%. The deposits exhibit either a nanocomposite structure where Ni(P)–1 and Ni(P)–2 solid solutions are embedded into an amorphous matrix, or a mixture of Ni2P phosphide and Ni(P)–1 and Ni(P)–2 solid solutions. The coercivity and magnetization are plating condition dependent. All samples exhibit a soft magnetic character with coercivity lower than 58 Oe. The squareness ratio Mr/Ms values that are in the range 0.019–0.123 correspond to a multidomain (<0.1) for all samples except sample B (−1.15 V, 10 min) which falls into a pseudo-single domain (Mr/Ms = 0.123). Voir les détails
Mots clés : Electrodeposition Ni-P alloys Microstructure Magnetic properties X-ray diffraction
Physical investigations on perovskite LaMnO3-δ sprayed thin films for spintronic applications
Oxygen deficient LaMnO3 thin films were successfully grown on glass substrate by spray pyrolysis at 460 °C. XRD studies show oxygen vacancies corresponding to the orthorhombic La4Mn4O11 with (040) preferential orientation. Optical properties were investigated through optical band gap and Urbach energy. The dispersion of the refractive index was discussed in terms of both Cauchy and Wemple & Di-domenico models. Raman spectroscopy shows the band positions corresponding to LaMnO3 with a shift related to oxygen deficiency. Electrical properties were quantified using impedance spectroscopy technique within frequency range of 5 Hz–13 MHz at various temperatures. Both the DC conductivity and relaxation frequency were thermally activated with activation energy around 0.9 eV. Also, AC conductivity was investigated through Jonscher law. Finally, magnetic measurements at room temperature using vibrating sample magnetometer (VSM) technique show ferromagnetic behavior of these ternary sprayed thin films. Voir les détails
Mots clés : Thin films, Magnetic Properties, Raman spectroscopy, Impedance spectroscopy, X-ray diffraction, Dielectric properties
EFFET DE LAMINAGE A CHAUD SURLE COMPORTEMENT DE LARECRYSTALLISATION DE L’ACIERINOXYDABLE FERRITIQUE TYPE 409
The behavior of the static recrystallization of this ferritic stainless steel type 409 which contains precipitateswas examined using hot rolling test of a single pass. Hot rolling tests were carried out at temperature of 870°C from athickness of 15mm to 8,4mm and 4,7mm thickness at a controled strain rate of 3.3s-1. The recrystallized volumeincreases with the increase of the reduction and the holding time after hot rolling. Nucleation of recrystallising grainsappears to be associated with triple points and grain boundaries. This material displays a slower rate of recrystallisationand this is attributed to the presence of titanium Voir les détails
Mots clés : ferritic stainless steel type 409, precipitates, deformation variables, hot rolling, dynamic recovery, static recovery, static recrystallization
Beta to alpha transformation kinetics and microstructure of Ti-6Al-4Valloy during continuous cooling
In the present paper, an approach based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model hasbeen developed and applied to study the transformation kinetics of the b phase in Ti-6Al-4V titaniumalloy during cooling. To this purpose, Differential Scanning Calorimetry (DSC) tests have been conductedusing a set of cooling rates ranging from 10 to 50 C/min. This approach allows the kinetics parameters,particularly the activation energy, to be calculated from a single DSC test using a simple linear regression.The microstructural analysis indicates that the microstructure is dominated by the a Widmanstatten €morphology (aW). Microstructural observations along with the calculated values of the Avrami index andof the activation energy suggest that the growth of the aW platelets obeys a mixed mode combining thevanadium diffusion and a displacive mechanism. Voir les détails
Mots clés : Continuous cooling, KJMA model, additivity rule, diffusion, Displacive mechanism
Energetics of atomic hydrogen absorption in C15-Fe2Zr Laves phases with ternary additions: A DFT study
The pseudo-potential Density Functional Theory (DFT) method using the GeneralizedGradient Approximation (GGA) was applied to investigate hydrogen absorption trends inthe cubic C15-ZrFe2 Laves phase in the presence of several ternary additions. The effect ofthe ternary addition on the stability of the Laves phase was investigated. The relativestability of atomic hydrogen at various interstitial sites was determined taking into accountthe type of ternary addition for different H contents in the hydrides. The results wereanalyzed and particular attention was given to the formation and binding energies ofhydrogen. It was found that hydrogen prefers the 96g site in the clean C15-Fe2Zr, and itsabsorption leads to decrease the heat of formation of the formed hydrides with occurrenceof phase separation around 6H/fu. This effect was enhanced by the presence of ternaryadditions. Moreover, alloys with Be, V, Cr, Mn, Y and Tc elements at the Fe sites were foundto absorb hydrogen up to 6H/fu. More interestingly, the cohesion of hydrogen atoms wasfound to be very sensitive to the third element nature. The hydrides with V, Y, and moreparticularly Tc and Ru have exhibited interesting energetics which would be very attractivefor practical applications. Voir les détails
Mots clés : Laves Phases, Hydrogen absorption, Atomic defects, Relative stability, DFT
Purification and detoxification of petroleumrefinery wastewater by electrochemical process
The treatment of synthetic oily wastewater having the characteristics of a typical petrochemicalwastewater (PRW) by electrocoagulation (EC) using iron and aluminum electrodes was conducted inan electrolytic reactor equipped with fluid recirculation. During the treatment, the emulsion stabilitywas followed by the measurement of Zeta potential and particle sizes. Effects of some operatingconditions such as electrodes material, current density and electrolysis time on removal efficiencies ofturbidity and chemical oxygen demand (COD) were investigated in details. The PRW purification byEC process was found most effective using aluminum as anode and cathode, current density of 60A/m2 and 30 min of electrolysis time. Under these conditions, the process efficiencies were 83.52%and 99.94% respectively for COD and turbidity removals which correspond to final values of 96 mgO2/L and 0.5 NTU. A moderate energy consumption (0.341 kWh) was needed to treat 1 m3 of PRW.Besides, the ecotoxicicity test proved that toxic substances presented in the PRW, and those inhibitingthe germination growth of whet, were eliminated by the EC technique. Voir les détails
Mots clés : petroleum wastewater purification, electrocoagulation, energy consumption, ecotoxicity test.