Publications Scientifiques
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Item Effect of alkaline carbonate-based activators on the properties of one-part ternary hybrid cement(Elsevier, 2024) Oualit, Mehena; Sarri, ArezkiThis paper investigates the use of solid alkaline carbonates (Na2CO3 and K2CO3) as activators for the production of one-part hybrid cement from a combination of three precursors: blast furnace slag, metakaolin, and clinker. The impact of activator dosage and the nature of the alkaline cation (Na+ or K+) on the compressive strength (Cs) and microstructure of the elaborated materials was studied. The results indicate that the highest Cs values are achieved with 5 % Na2CO3. The analysis of the reaction products’ microstructure reveals that the inclusion of Na2CO3 mainly produces (N,C)-A-S-H and C-A-S-H cementitious gels, along with metastable carboaluminates and different types of calcium carbonate. Additionally, the presence of K2CO3 results in the creation of hemicarboaluminate.Item Wear Behavior and Microstructure of Thermally Sprayed NiCrBSiFeC and Composite NiCrBSiFeC-WC(Co) Coatings(2021) Abderrahmane, Abderrahmane; Gaceb, Mohamed; Cheikh, Mohammed; Le roux, SabineIn this work, a study was carried out on the friction and wear behavior of flame thermal sprayed NiCrBSiFeC-WC(Co) composite and NiCrBSiFeC coatings subjected to severe wear conditions. For this purpose, flame remelted samples were tested in reciprocating wear conditions based on a cylinder-on-flat configuration. The wear assessment of the coatings was achieved using scanning electron microscopy (SEM) and 3D optical profilometry. The microstructure and the mechanical properties of the coatings were investigated using SEM, EDS and XRD techniques as along with indentation tests. The tribological behavior of the substrate and the coatings was successfully studied thanks to wear tests conducted on an adapted multi test apparatus. The results show that both NiCrBSiFeC and composite coatings induced a significant increase in the steel substrate hardness and wear resistance due to the formation of precipitates with high hardness well dispersed within an ultra-crystalline structure. Besides, adding WC(Co) to NiCrBSiFeC leads to a composite coating with hardness and wear resistance further improved. In return, it increases the coefficient of friction (COF) and the coatings’ roughness. Furthermore, improvements in the surface hardness, the roughness and the coating-substrate adhesion were attained after the remelting process for both NiCrBSiFeC and NiCrBSiFeC-WC(Co) coatings. Wear tracks investigations indicated that reciprocating dry sliding based on cylinder-on-flat test configuration promote several wear mechanisms that may occur simultaneously.Item Structure, Microsctructure and Magnetic Properties of Ternary (Fe0.6Al0.4)100-xSix Nanostructured Powders: Effect of Si Addition(2019) Boukherroub, N.; Hemmous, M.; Guittoum, A.; Martínez-Blanco, D.; Souami, N.; Gorria, P.; Blanco, J.A.Nanostructured (Fe0.6Al0.4)100-xSix powders with x= 0, 5, 10, 15 and 20 at.% were elaborated by means of mechanical alloying for a fixed milling time of 72 h. We have investigated the effect of silicon addition on the microstructure and magnetic properties of these ternary alloys. X-ray diffraction experiments reveal that these powders are single-phase disordered solid solutions with body centered cubic crystal structure. The lattice parameter diminishesalmost linearly as the Si content increases. The mean crystallite size,, is around three times smaller for the samples with higher amount of Si (≈ 10 nm) compared with that of the binary alloy (27 nm). Moreover, the volume fraction of grain boundaries (fgb) seems to be higher with increasing the Si content, as well as both dislocation density (ρ) and lattice microstrain (<ε>),that follow alinear trend. The SEM images show that the Si helps in refining the shape and size of the powder particles, leading to a nearly homogeneous small particles.The addition of Si strongly affects the value of the saturation magnetization, Ms, that falls nearly an order of magnitude for the sample with 20 at.% Si, while the coercivity remains almost unchanged. The Mössbauer spectra show the presence of a sextet (ferromagnetic phase) and a singlet or a doublet (non ferromagnetic phase), except for the sample corresponding to x = 10, where only one singlet is observed in the spectrum.Item Hydrothermal synthesis of co nanoparticles : structure, morphology and magnetic properties(World Scientific, 2021) Bouelkreb, I.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Blanco, J. A.; Boukherroub, N.We have investigated the crystal structure, the microstructural and morphological characteristics, as well as the magnetic properties of Co nanoparticles (NPs) synthesized by a hydrothermal method. A series of samples has been elaborated for different concentrations of sodium hydroxide. The analysis of X-ray diffraction patterns, using two different wavelengths, has evidenced the coexistence of both α-Co and β-Co phases in the samples. The lattice parameter for both phases is in good agreement with those values expected for their bulk Co counterparts; the grain sizes of NPs were found to be dependent on the NaOH concentration. The scanning electron microscope micrographs show that Co NPs are agglomerated forming micrometer-sized entities whose shape evolves, indicating that the synthesis process affects the morphology of the powdered samples. Magnetic measurements indicate that the coercivity is slightly larger, HC>200 Oe, for Co NPs with dendritic-like shape, probably due to an increase in the magnetocrystalline anisotropyItem Dissimilar FSW of AA2024 and AA7075 : effect of materials positioning and tool deviation value on microstructure, global and local mechanical behavior(Springer, 2021) Hadji, Idir; Badji, Riad; Gaceb, Mohamed; Cheniti, BillelIn this work, the effect of material location and tool deviation on global and local mechanical behavior of dissimilar AA2024/ AA7075 friction stir weld joints was investigated. The results showed that increasing the tool deviation value up to 1 mm towards the soft material, fixed in the advancing side, improved the material mixing quality and enhanced the grain refine- ment in the stir zone. It was found that the highest ultimate tensile strength was obtained when the AA7075 alloy was fixed in the retreating side for 1-mm tool deviation towards the AA2024 alloy. Above this deviation value, a gradual decrease of the global mechanical properties of the weld joints was noticed. The digital image correlation (DIC) technique coupled to tensile testing revealed an improvement of local strain in the stir zone as well as the heat-affected zones of the dissimilar joints when the AA2024 alloy was positioned in the advancing sideItem Impact of the nature of fibers on the physicomechanical behavior and durability of cement matrices(Springer, 2021) Aboutair, Wafaa; Chaid, Rabah; Perrot, ArnaudIn this paper, the strength of concrete prismatic and cylinders concrete and reinforced with steel and polypropylene fibers are presented. Also, hybrid fibers with crimped steel and polypropylene were used in concrete matrix to study its improvements in strength and durability properties. The steel, polypropylene, and hybrid consisting of polypropylene and steel (crimped) fibers of various proportions by volume of cement were used in concrete mixes. Besides cubes, cylinders of 160 mm diameter X 320 mm high of concrete were cast with steel fiber, polypropylene fiber, and hybrid fiber, respectively, by volume of cement. The water absorption test was conducted on 28 and 90 days, and the test results show that the addition of steel and polypropylene fibers to concrete exhibits better performance. The test results show that use of steel fiber-reinforced concrete improves compressive strength and split tensile strength. The durability of such concrete is also improvedItem Study of the acoustical and thermo-mechanical properties of dune and river sand concretes containing recycled plastic aggregates(Elsevier Ltd, 2020) Boucedra, A.; Bederina, M.; Ghernouti, Y.The main objective of this work is the development of a new sand concrete whose aggregates consist only of river (0/4 mm) or dune (0/63 mm) sand and recycled plastic aggregates (0/3.15 mm). The work has both ecological and economical interest, without forgetting the technological interest which can certain materials provide. Indeed, what is new in our case is the addition of plastic aggregates to sand concrete as well as the study of the acoustic properties of this material. Different compositions have been studied by replacing (in volume) the mineral sand with plastic aggregates. The envisaged proportions are: 0%, 25%, 50% and 75%. The work focused mainly on the study of the effect of the addition of plastic aggregates on the properties of the river sand concrete and dune sand concrete, such as the thermo-mechanical properties and microstructure, with particular emphasis on studying the acoustic properties. The results obtained showed that, although the compressive strength of the studied composites is slightly reduced, their qualities in thermal insulation and acoustics absorption are significantly improved. For substitutions of up 75%, the sound absorption coefficient and the noise reduction coefficient (NRCs) ranged between 0.15 and 0.6 and between 0.28 and 0.39 respectively. Based on the obtained results, the final product is a lightweight concrete which can be classified, according to ISO 11654, into the sound absorption classes D and E. It is able to integrate among the new building materials and to contribute to sustainable development, particularly in local construction (arid regions). In conclusion, the recycled plastic waste and the dune sand can be a suitable alternative to the classic building materialsItem Effects of calcined halloysite nano-clay on the mechanical properties and microstructure of low-clinker cement mortar(Elsevier, 2018) Allalou, Sara; Kheribet, Rabia; Benmounah, AbdelbakiThis paper explores the effects of calcined halloysite nano-clay (CHNC) on the physico-mechanical properties and microstructure of high volume slag (HVS) cement mortar. The principal objective of this research is to constitute a low-clinker cement mortar with high mechanical properties. Ordinary Portland cement clinker blended with 70% of ground granulated blast furnace slag (GBFS) was partially substituted with CHNC in ratios of 0%, 1%, 2%, 3%, 4%, 5% and 6% by weight. The results showed that the early age and long-term mechanical strengths of the slag cement mortars were significantly improved by the presence of CHNC. The slag cement containing 5 mass % of CHNC possessed the highest improvement of the mechanical properties and microstructure of hardened cement pastes and mortars. It was suggested that the higher pozzolanic activity of CHNC particles and the nucleation of calcium hydrosilicate (C–S–H) caused the enhanced strength developmentItem Microstructure, corrosion and magnetic behavior of an aged Dual-Phase stainless steel(Springer, 2018) Ziouche, Aicha; Haddad, A.; Badji, Riad; M. Zergoug, M. Zergoug; Zoubiri, N.; Bedjaoui, W.; Abaidia, Seddik-El-HakItem Microstructure and mechanical behavior in dissimilar 13Cr/2205 stainless steel welded pipes(Elsevier, 2015) Bettahar, K.; Bouabdallah, Mounira; Badji, R.; Gaceb, M.; Kahloun, C.; Bacroix, B.Thiswork aims to investigate the microstructure and themechanical behavior of dissimilar 13Cr Supermartensitic/2205 Duplex stainless steelwelded pipes. A wide variety ofmicrostructures resulting fromboth solidification and solid state transformation is induced by the fusion welding process across the weld joint. The tensile tests show that the deformation process of the dissimilarweld joint ismainly controlled by the two basematerials: the duplex steel at the beginning of the deformation and the supermartensitic one at its end. This is confirmed by the microtensile tests showing the overmatching effect of the weld metal. The fatigue tests conducted on dissimilar welded specimens led us to conclude that the weld metal is considered as a weak link of the weld joint in the high cycle fatigue regime. This is supported by its lower fatigue limit compared to the two basematerials that exhibit a similar fatigue behavior