Liste des documents
Effect of annealing temperature on the microstructureevolution, mechanical and wear behavior of NiCr–WC–CoHVOF-sprayed coatings
In the present work, the effect of annealing temperature on the microstructure, mechanical and tribological properties of NiCr–WC–Co coatings produced by the high-velocity oxy-fuel (HVOF) technique has been investigated. X-ray diffraction and scanning electron microscopy revealed the dissolution of WC into the NiCr matrix to form W2C and Cr3C2 with the annealing process. This dissolution became complete at 800 °C. The mechanical properties of the coatings were investigated using nano-indentation and Vickers fracture toughness measurements. These measurements suggested that the hardness, Young’s modulus, and fracture toughness values increased because of the newly formed carbide phases as a result of the dissolution of the WC particles.The overall properties of the coatings were found to be optimum for annealing temperatures of 800 °C. The wear mechanism appears to be abrasive in the as-sprayed coating, and it becomes a combination of an abrasive and oxidative wear with increasing the annealing temperature Voir les détails
Mots clés : HVOF;, WC coating:, Annealing;, Wear resistance;, Nano-indentation
Investigation of diclofenac sodium adsorption by a purified Algerian diatomite using hydrochloric acid
The objective of this investigation is to use hydrochloric acid (HCl) at different concentration as a chemical treatment for the Algerian diatomite (DE) in order to get it ready for further applications oriented towards pharmaceutical aspects. Commercial diclofenac sodium (DS) is used to study adsorption on DE in aqueous laboratory conditions. It is found that DE contains roughly 60% SiO2 and 13% CaO. Its morphology is characterized by a porous structure composed of several broken and compacted diatomic aggregates, containing cylindrical and alveolus forms of varying diameters, girdle bands and other clayey compounds. The hydrochloric acid treatment is proven to be one attractive choice as it entails a significant raise of SiO2 and facilitates reducing most of impurities. After 10% HCl (DE-10) treatment of crude DE, the amount of SiO2 increased by over 64%. The result showing DS adsorption as a function of time is optimal for DE-10 as the quantity of the absorbed DS on treated DE (qt ) reached 60 mg/g and maintained this equilibrium level from 90 up to 120 min. The pseudo second order model has been successfully applied. The quantity of the absorbed DS on treated DE at equilibrium (qe ) and the pseudo second order rate constant (k2) for the case DE-10 are found 114.94 mg/g and 1.3 10−4 g mg−1 min−1 respectively. Voir les détails
Mots clés : diatomite, hydrochloric acid treatment, diclofenac sodium, adsorption, pseudo second order model
The Microstructure, Texture and Mechanical Propertiesof Friction Stir Welded Aluminum Alloy
The microstructure and texture of 7075-T6 FSW weld with optimal parameters are investigatedusing optical microscopy, electron back scatter diffraction and neutron diffraction. The mechanical proper-ties are characterized through microhardness, nanoindent ation and ultrasonic tests. The friction stir weldingis performed at a nominal rotational speed of 1400 rpm and a traverse speed of 60 mm/min. The nugget zonecontained fine, equiaxed and fully recrystallized grains. The texture of the base material mainly consisted ofCube and rotated Goss components. However, in the nugget zone, the dominant texture components were Band among common shear orientations. Elastic modulus was measured by ultrasonic and nanoindentationmethods. The ultrasonic method being nondestructive, easy, inexpensive and fast. It is found that a littleincrease of Young modulus is observed in nugget zone compared to base metal. Voir les détails
Mots clés : Aluminum alloy, FSW, microstructure, texture, Microhardness, Young modulus
CoSoTIA Project: Decision Support for the Choice of Concentrated Solar Technologies for Electricity Generation
The C oSoTIA (Concentrated Solar Technologies for I ndustrial Appli-cations) project initiated by the CRTI center in collaboration with the URMPEunit concerns the s tudy and development of CSP s olar concentrators f or indus-trial applications. I n t he present work, we present decision s upport t ools f or thechoice of a s olar concentration t echnology for s ites i n Algeria. T hey will be usedfor t he comparison between diff erent t echnologies of solar concentration e.g.:cylindro-parabolic, parabolic, s olar tower, etc. T he models used include projectcosts and site characteristics; they incorporate also engineering knowledge (eco-nomic, social, t echnical and environmental). The i nformation needed for decision-making produced by these t ools i s: the t otal cost of the project, i ndicators witheconomic, social, t echnical and environmental aspects. The case s tudies presentedwere conducted under t he SAM Advisor environment, which was developed t oevaluate the capacities t o i mplement C SP project i n order to produce expertisefor t he diff erent actors t hrough an application on a given s ite (by t he client). Fourcase sites i n Algeria and f or two t ypes of s olar concentrator plant are studied andpresented. A comparative study was conducted and for each s ite the best C SP wasdeduced and commented. Voir les détails
Mots clés : Decision support, Multicriteria analysis, Solar concentration, CSP, SAM Advisor
Weldability, microstructure, and residual stress in Al/Cu and Cu/Alfriction stir spot weld joints with Zn interlayer
In this work, the effect of lap joint configuration and Zn interlayer addition on the microstructure, the residual stress state, and thequality of Al/Cu (configuration #1) and Cu/Al (configuration #2) friction stir spot welds (FSSW) was investigated. The studyrevealed the close dependency of the weld joint quality on the pin length and Zn addition. The higher the pin plunge depth is, thegreater the obtained tensile shear strength. The Zn addition reduced sensibly the thickness of Al2Cu layer (from 10 to 2 μm) andfavored the formation of the Al4.2Cu3.2Zn0.7 precipitate that hindered the formation of detrimental Al4Cu9compounds. Materialflow analysis revealed the presence of an intermixing zone containing thin continuous intermetallic layer (approximately 2.07 μm) at the weld interface of configuration #1. Meanwhile, the Cu material was covered by the Zn layer, which resultedin a hardness increase (228 HV) at the stirred zone. In addition, a significant increase of the tensile shear strength from 1650 to 3600 N was noticed (an improvement rate of ≈ 118%). Conversely, in configuration #2, the Zn foil was squeezed out of the spotweld interface resulting in the absence of material intermixing, discontinuous intermetallic layer, low hardness level (140 HV),and weak improvement rate of the shear strength (≈ 53%). The Zn interlayer addition resulted in a quasi-symmetric distribution ofthe residual stresses and shifted their nature from tensile stresses (+ 60 MPa) to compressive ones ( − 10 MPa). Voir les détails
Mots clés : FSSW, aluminum, copper, Zinc interlayer, Tensile shear, microstructure, intermetallic Compounds, residual stress
Particle Swarm Optimization of Fuzzy Fractional PDµ+I Controllerof a PMDC Motor for Reliable Operation of Wire-Feeder Units ofGMAW Welding Machine
In this article, we consider the development of an optimal control approach based on fuzzy fractional PDµ+I controller to improve thespeed error-tracking and control capability of a permanent magnet DC Motor (PMDC) driven wire-feeder systems (WFSs) of gas metal arc welding(GMAW) process. The proposed controller employs an optimized fractional-order proportional derivative + integral (PDµ+I) controller that serves toeliminate oscillations, overshoots, undershoots and steady state fluctuations of the PMDC motor and makes the wire-feeder unit (WFU) has fast andstable starting process as well as excellent dynamic characteristics. The fixed controller parameters are meta-heuristically selected via a particleswarm optimization (PSO) algorithm. Numerical simulations are performed in MATLAB/SIMULINK environment and the performance of the proposedfuzzy fractional PDµ+I controller is validated. The simulation tests clearly demonstrate the significant improvement rendered by the proposed fuzzyPDµ+I controller in the wire-feeder system's reference tracking performance, torque disturbance rejection capability and robustness against modeluncertainties. Voir les détails
Mots clés : GMAW process, Wire-feeder System (WFS), fuzzy fractional PDµ+I controller, Particle Swarm Optimization (PSO) algorithm
Cu2O addition and sintering temperature dependence of structural,microstructural and dielectric properties of CaCu3Ti4O12 ceramics
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
Synthesis of Lead-Free Ceramicsof the Perovskite Type for PiezoelectricApplications by Conventional Solid-StateReaction
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
STRUCTURAL AND MAGNETIC PROPERTIES OF Fe60–xNix(ZnO)40NANOCOMPOSITES PRODUCED BY MECHANICAL MILLINGAND COATED BY THERMAL SPRAYING ON A STEEL SUBSTRATE
This work aims to study the effect of mechanical milling of Fe, ZnO, and Ni elemental powders andthermal spraying processes on chemical composition, structural properties, and magnetic behaviorof the Fe60–xNix(ZnO)40 coatings. As the first step, the FeNi/ZnO composite was synthesized bymechanical alloying process, and afterward, the milled powder was coated by a thermal sprayingtechnique on a steel substrate. Obtained samples were characterized by the methods of X-raydiffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS),atomic force microscopy (AFM), and with help of vibrating sample magnetometer (VSM). Aftermechanical milling, the crystallite size of the powder decreased from 18 to 10 nm, while the latticestrain increased from 0.31 to 0.59%, and a new solid solution FeNi formed after 20 h of milling dueto diffusion of nickel into the iron lattice. After the thermal spraying process, different phasesappeared in a surface coating such as ZnFe2O4, NiFe2O4, and FeNi. The magnetic and structuralproperties of the coated powders are influenced by the change in chemical composition. Thus, theincrease of Ni concentration improved the soft magnetic performance of the coating significantly.The highest saturation magnetization was determined in Fe40Ni20(ZnO)40 sprayed powder. However,the smallest coercivity appeared in Fe50Ni10(ZnO)40 sprayed powder. Voir les détails
Mots clés : FeNi/ZnO nanoparticle coating, Mechanical Alloying, Thermal Spraying, magnetic behavior, Structural properties
THE EFFECT OF Ti ADDITION ON MICROSTRUCTUREAND MAGNETIC PROPERTIES OF NANOCRYSTALLINEFeAl40 ALLOY POWDERS PREPAREDBY MECHANICAL ALLOYING
Recent research on nanocrystalline FeAl alloys has shown that these alloys are of high importancedue to their promising structural and mechanical properties, particularly magnetic behavior. Thiswork aims at studying the synthesis, structural and magnetic characterization of nanocrystallineFeAl alloy powders, prepared by a mechanical alloying process (MA), as well as the effect of Tiaddition on the magnetic properties of a compound. The powder morphology, phase transformation,crystallite size, micro-stress evolution, and magnetic properties were investigated by X-raydiffraction (XRD), scanning electronic microscopy (SEM), and vibrating samples magnetometer(VSM). It has been found that at the final stage of mechanical alloying the bcc-disordered FeAlphase and nanocrystalline Fe(Al, Ti) solid solution occurred for the FeAl40 and FeAl40Ti3 alloys,respectively. The milling time and the addition of titanium affect the powder morphology anddecrease the size of the particles. The average crystallites size of 17.2 and 11.2 nm was reached atthe end of 30 h of milling, and the lattice strain increased up to 0.3 and 0.21% for the FeAl40 andFeAl40Ti3 alloys, respectively. Also, the magnetic properties attributed to microstructural changeswere investigated. It has been established that the change in magnetic behavior occurs mainly due tothe formation of a supersaturated Fe(Al, Ti) solid solution. Magnetic properties of the samples arehighly influenced by the addition of the Ti element into FeAl40 alloy, as well. The magnetism of theFeAl40Ti3 compound is reported to be higher than that of FeAl40. Voir les détails
Mots clés : Mechanical Alloying, nanocrystalline materials, lattice strain, crystallite size, magnetic behavior.