Sciences des matériaux
Elaboration and structural study of Ni/SiOCo/SiO2and Ni-Co/SiO2nanocomposites2
The present work examines the structural properties of Ni, Co and Ni-Co supported on silica. The samples areprepared by impregnation, followed by calcination and thermal H- treatment. Several techniques, such as SEM and XRD, are used forthe characterization of the samples at different steps of their elaboration. After impregnation, the X-rays diffraction reveals theformation of nickel and cobalt silicide (NiSi, Co2Si, NiCoSi and Ni20.56Co3.44Si). After calcination, the XRD pattern presents the featuresof nickel and cobalt oxides (NiO, Co3O4, NiCoO2, NiCo2O44and CoO)with an average size of 10-25 nm. After H- treatment, the metallicphases (Ni, Co and Ni0.75Co0.25) appear at T 350°C Voir les détails
Mots clés : nanocomposites, Structural properties, Co 2 Si, NiCoSi, NiO, Co 3 O 4, NiCoO 2, NiCo 2 O 4, Metal/Support interaction.
Comparison of IR Spectra of Five PorcelainCompositions Prepared Using Algerian RawMaterials
The interest in Infrared (IR) spectroscopy is anessential technique for the characterization of ceramic. Its mainadvantage when it comes to studying items is that it is nondestructive:the samples can be investigated without furtherpreparation. IR spectroscopy probes molecular and crystal latticevibrations and therefore is sensitive to the compositions, chemicalenvironment, bonding and crystalline/amorphous structure of asample material. Five Porcelain compositions were studied bynon-destructive infra Raman spectroscopy: kaolin was derivedfrom Debagh deposit (Guelma region), Quartz was derived fromEl Oued region and PF was derived from Ain Barbar deposit(Annaba region) and both commercial Alumina talc. Ramanintensity is a very powerful tool, which allows investigating andcharacterizing the modifications of the structure in covalentbonded compounds. Hence the observed porcelain spectralfeature at ~1050 cm-1is due to SiOfor the five compositions.From our study, as well as the literature reviewed it appears thatinvestigators uniformly confirm the benefits of IR spectroscopyconcerning identification of chemical functional groups of thedifferent chemical compositions. Voir les détails
Mots clés : porcelain, IR, quartz, alumina, talc
Modeling and optimization of the composite plateslaminated by genetic algorithm
Our study made it possible to develop and test a program ofoptimization based on a technique of optimization based on theuse of a genetic algorithm. This program moreover was appliedto the resolution of several types of problems connected to theoptimal design of laminated structures. Among these problems,orientations of the folds, the material and the number of folds asvariable which were already solved . In this work, we havepresented the principles of the genetic algorithm functioning , itsapplication to the laminated composites and to the originaltechnique of coding which allows giving an account of theindustrial constraints of composites development.The flexibility of the general structure of our software allowstreatening the various types of problems like: calculation of themodule of rigidity as well as the factors of buckling and rupture.We develop the OpStrAG software to optimize the characteristicsof rigidity of the laminates and also their constraints towardsrupture and their deformations under a given loading. Voir les détails
Mots clés : composite materials, laminated Plates, Modeling and optimizatio, genetic Algorithm.
A new and economic approach to synthesize andfabricate anorthite based ceramics using kaolin andCaCO3
This new and economic approach to fabricateresistant anorthite based ceramics consists of Algerian kaolinand calcite (CaCO3). The anorthite (CaO·Al2O3E-Mail :zaiou_21 @yahoo.fr·2SiO) basedceramics were obtained by solid state reaction. The startingpowders were sintered at different temperatures (800-1100°C) for 1 h. The optimum sintering conditions gave arelatively higher density (2.64 g/cm3). Different techniqueswere used to investigate the physical proprieties of theprepared anorthite such as: scanning electron microscopy, Xraydiffraction, Raman spectroscopy and tensile strength. Thebest obtained 3 points flexural strength value was about 202MPa for the samples sintered at 1000 °C for 1 h. Furthermore,the best value of Vickers micro-hardness of the samplessintered at 1000 °C was 7.1 GPa. Finally, a correlationbetween microstructure and mechanical properties ofelaborated supports has been discussed. Voir les détails
Mots clés : anorthite, Kaolin, calcite, Sintering, Vickers micro-hardness, tensile strength.
OPTIMIZATION OF THE BEHAVIOR OF BUCKLINGOF THE STRATIFIEES BY GENETIC ALGORITHM
The laminated composite structures which are largely usednowadays, become unstable when they are prone to loadings ofmechanical or thermal nature and flame in the elastic zone.Consequently, buckling has a very great importance whendesigning this kind of structure. In this work, we studied thephenomenon of the buckling which was devoted underinvestigation of the optimization of a composite materiallaminated by the use of a data-processing method based on amathematical theory which uses the stochastic statistics it is thetheory of the genetic algorithms (GA). The objective of this workis, the maximization of the rigidity of the plate laminated bymaximizing the critical load of buckling according to theorientations of the folds. Voir les détails
Mots clés : Composite laminated, optimization, Buckling, genetic Algorithm.
Synthesis and characterization of CuxSixFe2-2xOspinnelferrites produced by the ceramic technic4
Spinel copper ferrites Cu1+xMxFe2-2xO(M=Si) with(0.2 x 0.5) were synthesized by the double sintering ceramic4technique and characterized using X-ray diffraction VSM andSEM, diffraction patterns show that all samples have a singlephase.the magnetic properties of the nanocomposites wereinvestigated, the scanning electron microscope (SEM) with EDSanalyser were performed to show micrographs aggregates andconfirm the stoichiometry of the compound. Voir les détails
Mots clés : Cu-Ti Ferrites, Spinel, XRD, VSM, SEM, EDS
The experimental behavior of slabs strengthened byfiber reinforced polymer (CFRP)
The experimental behaviour of slabsstrengthened by composite fiber reinforced polymer (CFRP)is presented in this paper three concrete slabs of 16 cm x 14cm x 4 cm were made in laboratory conditions. Thedimensions of the patches are calculated so that the ratiopatch XP /YP is proportional to XD/ YD of the slab.Dimensions of the composite patches are: 70x90x1 mm,100x120x1mm, 160x140x1mm, the load is flexionalpunching load. The results given in the form of curves ofloads - displacements measured to the centric of the slabaccording to the force applied; show that the breaking loadand ultimate correspondent displacement are influenced bythe properties of the composite patch and the surface coveredby the composite patch. It is observed that, the breaking loadand ultimate displacement increase with the surface of thepatch and properties of the composite. The third slab havethe best behavior than the rest of slabs, the ratio of thedisplacement between the third and the second slab is 1.39and the ratio between the third and the first slab is 1,95. Voir les détails
Mots clés : Concrete slabs, composites, reinforcement, experiments.
PHYSICO-CHEMICAL ANALYSIS OF COMPOSITEMATERIALS (ALGINATE-BENTONITE-ACTIVATEDCARBON)
New low cost materials consisting of alginate,bentonite and activated carbon were prepared according to theionic gelation method. Physical characteristics of composites werecharacterised by X-ray diffraction, Fourier transform infraredspectroscopy, surface mesurment by Brunauer, Emmett and Tellermethod (BET), and morphological characterization by SEM. Alginatebeads containing activated carbon and bentonite have beensuccessfully applied for water treatment. Voir les détails
Mots clés : encapsulation, composite beads, characterization.
Thermal behavior of Functionally Graded Materials
Mathematical expressions have been used to findthermal behavior of functionally graded plate. Temperaturedistributions are used on the basis of three different types toevaluate the thermal properties of FGMs. Material properties arevary continuously through the thickness according to a powerlaw function, exponential function, and sigmoid function in termsof the volume fraction of the constituents. The computationalmathematical software Matlab.R2014b has been used to carry outthe numerical calculations and the graphs been plotted usingOriginLab.9. Voir les détails
Mots clés : Functionally graded materials, Material properties, Temperature distribution
The effect of Sintering condition on the microstructure and ElectricalConductivity of Apatite- type La9.33(SiO4)6O2ceramic
Rare-earth apatite-type lanthanum silicates, La9.33(SiO4)6O2.is prepared in air by the conventional solid statereaction for solid oxide electrolyte. The microstructure and electrical properties of La2 ,9.33(SiOceramic areinvestigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedancespectroscopy (EIS).The principal objective is the study of the effect of the sintering condition(time, temperature),on the morphology and the electrochemical properties of this phase. La9.33(SiO4)6O2 ceramic consist of ahexagonal apatite type structure and a small amount of a second phase of La2SiO52due to the law temperature ofsintering.Electrical properties of the sample have been studied between 302 and 802°C by the complex impedancemethod. The results of the conductivity measurements obtained between 302 and 605°C are treated first, in thetotal form of the sample, and then, by separating the grain from the grain boundary. Electrical conductivity of theLa9,33(SiO4)6O2apatite-type was found of a value of 1.04 10-3S.cm-1at 605°C. This value is higher than thatobtained with yttria stabilized zirconia(YSZ) at the same intermediate temperatures. Voir les détails
Mots clés : electrolyte, Apatite, Lanthanum silicate, Ionic conductivity