Liste des documents
A systematic DFT study of (Ti3/2RE1/2)AlC alloys: A new database foradjustable mechanical and electronic properties
In this study, ab initio calculations based on Pseudo-Potential Density Functional Theory (PP-DFT) method arecarried out in order to highlight the partial substitution effect of Rare Earth (RE) elements in the well-known 211-MAX phase of Ti2AlC. The considered elements are Y, Sc and RE = La, Ce, Pr, Nd, Sm, Eu, Gd leading to (Ti3/2RE1/2)AlC alloys. According to the obtained results, the (Ti3/2RE1/2)AlC alloys are significantly less compressibleunder uniaxial stress along x and z axes. They exhibit high resistance to shearing along <001> direction. Inaddition, the calculated heat capacity for (Ti3/2RE1/2)AlC alloys increases with respect to the temperature, amaximum is found in the temperature range 200–300 K. Localized states occur in (Ti3/2RE1/2)AlC alloys due tothe f states filling of the rare earth elements. The magnetic moment of (Ti3/2RE1/2)AlC compounds increasesaccording to 4f n (n=2 for Ce to n=7 for Gd) filling. Our findings provide a theoretical database for new tunableproperties of (Ti3/2RE1/2)AlC alloys. Voir les détails
Mots clés : DFT, Rare earth elements, (Ti3/2Re1/2)AlC, mechanical properties, Localized States, Magnetic moment
Preparation and characteristics of synthesized hydroxyapatite from bovine bones and by co-precipitation method
Hydroxyapatite (HA, (Ca10(PO4)6(OH)2) is a widely studied bioceramic due to its biocompatibility, bioactivity, and chemical similarity to the mineral component of bone. Generally, hydroxyapatite can be made from several natural and synthetic sources. The objective of this study is to prepare hydroxyapatite powders from different precursors (natural or chemical). Hydroxyapatite was synthetized by co-precipitation method, the chemical precursors of which are [Ca(NO3)2.4H2O, (NH4)2HPO4] and the natural source was bovine bone. Bovine hydroxyapatite (BHA) was extracted from the bovine bone bio-waste via thermal method and milling process. Synthesized HA (SHA) was prepared by co-precipitation method with the pH 10.0 of mother liquor. The prepared powders were characterized using various analytical techniques such as XRD, FTIR spectroscopy, thermogravimetry (TG), and scanning electron microscope (SEM). These techniques provide information about the structural, chemical, morphological and physicochemical of each of the prepared powders. The use of co-precipitation method produced a low crystallinity of HA while the thermal method increased crystallinity. On the other hand, the results showed that the Ca / P ratio of synthetic hydroxyapatite (SHA) as well as that of bovine bone source (BHA) was also stoichiometric. Voir les détails
Mots clés : hydroxyapatite, Bovine bone, synthesis, co-precipitation, thermal decomposition.
Influence of dry friction on the wear behavior of X52steel—experimental study and simulation using response surfacesmethod
Friction and wear phenomena alter the behavior of the material surface, where certain relevant parameters which characterizethe surface are influenced. Therefore, the objective of this work is to identify the parameters most influencing the frictioncoefficient (f), the wear rate (Ws), and the volume parameters (Vmc and Vvv) during the friction test. The friction tests werecarried out by adopting the methodology of 23complete planes with three factors (D, V, and Py), at two levels each. Theresults show a decrease in the wear rate when all three factors are at their highest level and a decrease in the friction coefficientwhen using minimum load on speed long distances. In addition, the mathematical models developed allow to reveala correlation between the test parameters (D, V, and Py), and the responses studied (f, Ws) in their study field. Moreover,the volume parameters Vmc and Vvv were evaluated during the tests, and the morphology of the worn surface shows thatthe friction under a load of 1 N leads to the predominance of an abrasive wear mechanism, while a load of 10 N promotesan adhesive wear mechanism. Voir les détails
Mots clés : Complete plans, modeling, friction coefficient, Wear rate, volume parameters
Effect of erosion parameters on the surface direction texture-Study by experimental plans
The aim of this work is to study the effect of solid particle impact erosion parameters of sand on the isotropy parameter "Std" which presents the direction of surface texture. The experimental methodology adopted for this experimental work is the Box Behnken plan with three factors, each at three levels (-1, 0 and +1), the parameters considered are: time "t", pressure "P" and angle of impact "θ". 3D roughness measurements were carried out using a laser source profilometer type Cyper-Technologie-CT100, in order to characterize the different surfaces after erosion test. The statistical analysis was carried out using the Mini Tab software, where a mathematical model was established showing the relationship between the input parameters (t, P, θ) and the output parameter "Std". This model predicts the "Std" response in the field of study as well as the parameters of the sandblasting regime. The results show the significant effect of the impact angle on "Std" and the interaction between the different parameters in the study domain, of which the highest value of "Std" is equal to 130 ° for an average time combined with low pressure and impact angle. Voir les détails
Mots clés : erosion, topography, roughness surface, Mathematical model, Box plans
Tribocorrosion Dependence on Porosity of TiNi Alloysin Phosphate‑Buffered Saline Solution
Degradations of implants during their service life lead to rejection because of corrosion and wear-related problems, i.e., toxicions and wear particles released into the human body. In this case, tribocorrosion tests are appropriate ways to investigate thesynergistic effect of the corrosion and wear phenomena, on the material implant in simulated body fluids. This study aims toanalyze the bio-tribology as well as the tribocorrosion performances of porous TiNi alloys, fabricated from elemental powdermixture (Ti, Ni) by powder metallurgy. The effect of the level in porosity, resulting from four (04) different cold pressing, wasinvestigated against alumina ball in phosphate-buffered saline solution (PBS) at 37 °C. SEM/EDS microstructural analysesrevealed the presence of various phases with TiNi as the predominant phase. Obtained results showed that the lowest frictioncoefficient was recorded for the sample with 33% in porosity rate when sliding against an alumina ball in dry conditions. Ahigh tribocorrosion resistance for all the studied TiNi compositions was also observed. Based on the corrosion parametersand the wear rate, the composition with the highest porosity exhibited the optimum performance. Voir les détails
Mots clés : TiNi alloys, Biotribolgy, Tribocorrosion, Porosity
Mechanical properties and bio‑tribological performance of PVD (Ta/ZrN)n multilayer coatings on UHMWPE in bovine serum lubrication
This work investigated the tribological performance of (Ta/ZrN)n multilayer coatings against ultrahigh molecular weight polyethylene (UHMWPE) material. Three multilayer coatings with different designs were deposited on Ti-6Al-4V substrate and subjected to wear testing under lubrication of diluted bovine calf serum. The results revealed an improvement in wear resistance of (Ta/ZrN) multilayer coatings and low coefficient of friction under an applied load of 1 N. High hardness, excellent biotribological properties, and low residual stresses were obtained in the multilayer coating with the thinnest ZrN as the topmost layer of 100 nm. This work demonstrates that Ta/ZrN multilayers can be promising coatings for prosthesis applications. Voir les détails
Mots clés : PVD coating, Ta/ZrN, UHMWPE, wear
Synthesis and tribocorrosion performances of multilayer (Ta/ZrN)n coatings
Multilayer thin coatings (~3 µm in thickness) were deposited using reactive radio frequency magnetron sputteringon Ti-6Al-4 V substrate for biomaterial applications. Films are a combination of hard zirconium nitride with pure tantalum, used to manage interfacial stress and to avoid crack growth. Alternating hard/ductile material is a biomimetic design inspired by nature(nacre-inspired materials). Tribocorrosion tests were performed in Hank’s solution at 37 C, under open circuit potential by using a ball-on-disk reciprocating tribometer. A tendency to high resistance against corrosion was found for all the samples. Coatings with a top 100 nm thick ZrN layer showed more noble potential as well as a reduction of both the friction coefficient and the wear rate during the sliding phase. The principal wear mechanism is related to a tribocorrosion layer formation. Voir les détails
Mots clés : Multilayer coating, Biomaterial, Tribocorrosion, Tantalum, Zirconium nitride, Magnetron sputtering
A probabilistic approach to estimate the remaining life and reliability of corroded pipelines
Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental to calculate the interval between two consecutive inspections. A total of 798 internal and external corrosion defects have been detected, using the Magnetic Flux Leakage intelligent inspection tool, over 48 km of a pipeline length located in the west region of Algeria. The statistical analysis has shown that there is a strong correlation between the corrosion defect length and the corrosion defect circumferential width, with a significant correlation coefficient equal to 82.87%. A probabilistic methodology is presented for the assessment of the remaining life of a corroded pipeline transporting gas, and a finite element method (FEM) was used to assess the pipeline failure pressure. The numerical FEM modeling results were compared with the commonly used codes-models for calculating limit pressure to establish a more realistic and accurate engineering model. The reliability analysis of an API 5L X60 steel made Algerian natural gas pipeline, in service for thirty years, and exposed to active corrosion attack, is presented. The sensitivity analysis of the basic random variables within the nonlinear limit state function was carried out to bring out the relative contribution of each variable affecting the remaining life of corroded pipelines. The reliability analysis is carried out by using Breitung’s formula, based on the second-order reliability method (SORM). The reliability assessment of the corroded pipeline is based on the usage of the notched failure assessment diagram (NFAD), different codes for the calculation of the failure pressure, and the numerical results using the finite element analyses (FEA) software ANSYS. Voir les détails
Mots clés : Corrosion defects, pipelines, Remaining life, Probability of failure, Reliability, Probabilistic approach
Experimental Study Of The Effect Of Shot Peening Parameters On The Surface Texture - Influence On The Adhesion Of A Paint Coating
The investigation presented in this paper focuses on the effect of surface texture on the adhesion of a paint coating as well as the influence of shot peening regime parameters on the surface isotropy indicator "Str" and on the fractal dimension "Df". The tests have been organized according to full factorial designs 23, where three parameters have been examined, at their two levels (min, max), namely the pressure (P), the angle of attack (θ) and the time (t). 3D roughness measurements have been carried out to characterize the different surfaces after a shot peening operation. A mathematical model linking the input parameters (P, θ, t) and the output parameter "Str", in the study area has been established, and the fractal dimension (Df) has been used for the surface characterization. Paint deposit has been applied to surfaces and adhesion tests have been carried out. The results show the significant effect of the impact angle on "Str", and the interaction between the different parameters in the studied area. Furthermore, the greatest bond strength has been obtained with the sample 3 (F = 4.25 N / mm2), whose the isotropy indicator "Str" is equal to 0.6438 and the fractal dimension Df = is about 1.768. Voir les détails
Mots clés : surface texture, fractal dimension, shot peening, Adhesion
STUDY OF CIGS PSEUDO-HOMOJUNCTION THIN FILM SOLAR CELL USING SCAPS-1D
) have been used as indicators to evaluate the device performances. Simulation outcomes have proved that for a best performance for CIGS P-HTFSC device, the optimal thickness for CIGS and ODC layers should be small than 2 µm and few nm, respectively, while the optimal defect concentration within the layer should be 10hThe present modelling study reports the performance of defected CIGS pseudo-homojunction thin film solar cell (P-HTFSC) and determines its optimum parameters for high performance using the Scaps-1D software under the AM1.5 illumination and the operating temperature of 300 K. To focus the discussion on the optimal parameters (thickness, doping concentrations, deep/interface defect concentrations and bandgap) for the ZnO, CdS, ODC and CIGS thin film layers, cross sectional (1D) simulations have been performed on the ZnO/CdS/ODC/CIGS P-HTFSC device for obtaining its optimal structure that confers high light-into-electricity conversion efficiency. The four light J-V characteristics (short-circuit current: JSC, open-circuit voltage: VOC, fill factor: FF and conversion efficiency:13 cm-3 and between 1013 cm-3-1018 cm-3, respectively. Voir les détails
Mots clés : CIGS, J-V characteristics, ODC, Pseudo-homojunction, Scaps-1D