Liste des publications
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
Power control strategy of a photovoltaic system with battery storage system
In this paper, an intelligent approach based on fuzzy logic has been developed to ensure operation at the maximum power point of a PV system under dynamic climatic conditions. The current distortion due to the use of static converters in photovoltaic production systems involves the consumption of reactive energy. For this, separate control of active and reactive powers using a proportional-integral controller is applied. Using batteries for energy storage in the photovoltaic system has become an increasingly promising solution to improve energy quality: current and voltage. For this purpose, the energy management of batteries for regulating the charge level under dynamic climatic conditions has been studied. The research presented in this paper provides an important contribution to the application of fuzzy theory to improve the power and performance of a hybrid system comprising a grid-connected PV, battery, and energy management strategy. Therefore, to highlight the advantage of the FL-MPPT studied in this paper, its performance has been compared and analyzed with conventional P&O and NNT algorithms. Simulation results are carried out in MatLab/Simulink tools. According to the analysis of the results, a better energy quality has been proven. Voir les détails
Mots clés : Battery storage, Energy management, Energy storage, MPPT control, Performance, photovoltaic System
A0 Lamb Mode Tracking to Monitor Crack Evolution in Thin Aluminum Plates Using Acoustic Emission Sensors
This paper presents a real time monitoring methodology to identify the location of acoustic emission (AE) sources generated by microcracks created within an aluminum plate when submitted to a tensile load. The real time detection of the AE hits was performed by means of a network of piezoelectric sensors distributed on the surface of the plate. The proposed localization approach is based on the combination of the time-frequency analysis of the detected AE hits with an extended Kalman filter (EKF). The spatial coordinates of the AE sources were determined by solving a set of nonlinear equations, where the extended Kalman filter is based on an iterative calculation. By considering the statistics related to the estimation of the coordinates’ errors, results show that the proposed method is in agreement with the experimental observations related to the propagation of the crack when the aluminum plate is under load. Voir les détails
Mots clés : Acoustic Emission (AE), AE events localization, Continuous Wavelet Transform (CWT), crack propagation, Extended Kalman Filter (EKF), Lamb waves, tensile test
Argon flow rate effects on the optical waveguide properties of DC sputtered TiO2 thin films
TiO2 thin films were successfully prepared by DC sputtering using pure titanium target in mixed gases (Argon, Oxygen) plasma on glass substrates. The films were deposited at a constant substrate temperature (350 °C) with different Argon flow rate values (15, 30, 45, and 60 sccm). Raman spectroscopy analysis shows that all films crystallized in the Anatase phase. The crystallinity was found to improve with increasing Argon flow rate up to 45 sccm and then deteriorate sharply at 60 sccm. The crystallite size varied between 9.1 and 9.7 nm. Atomic force microscopy (AFM) revealed that the roughness fluctuated between 1.30 and 6.01 nm with an overall increase. The grain shape went from sharp needles like shape to dome like shape with an enlargement in their size by up to 60 nm. The UV–Vis spectrophotometer displayed that the films were highly transparent. The optical band gap ranged from 3.65 to 3.49 eV. Prism coupler analysis exhibited single guided modes in both transverse electric and transverse magnetic polarizations for the sample prepared at 15 sccm Argon flow rate and bi-guided modes in both polarizations for the rest of the samples. Both ordinary and extraordinary refractive indices decreased over Argon flow by 9.912% and 6.441% respectively. The thickness, porosity as well as the birefringence where found to increase by 155 nm, 16.16% and 0.0832 respectively as Argon flow rate went from 15 to 60 sccm. Voir les détails
Mots clés : Ar flow rate, DC sputtering, Prism coupler, Refractive indices, TiO2, waveguides
Antibacterial activity of intermetallic NixMgy and NiO–MgO phases in nickel-magnesium oxide nanocomposites
This work focuses on Ni–Mg metallic nanomaterials and NiO–MgO composites, especially on their antibacterial activity against Escherichia coli (E. coli (G-)) and Staphylococcus aureus (S. aureus (G+)) in relation with their size and structure. They are generated by impregnation of nickel formate, followed by either calcination (T = 100–600 °C) or gamma-irradiation at room temperature. In samples prepared by calcination at temperatures T ≤ 300 °C or irradiation, the structural study by XRD and HRTEM reveals the presence of nanoscaled Ni–Mg intermetallic phases: NiMg2, Ni2Mg and NiMg6.33 (2–4 nm diameter) and magnesium hydroxide Mg(OH)2. At T > 300 °C, only the NiO–MgO solid solution is formed. Bare MgO and NiO–MgO nanoparticles exhibit a bacterial activity only against E. coli and S. aureus, respectively. In contrast, the Ni–Mg intermetallic phases of high specific area, that are present in irradiated (T = 20 °C) or calcined (T ≤ 300 °C) samples, exhibit a significant antibacterial activity against both E. coli and S. aureus. Voir les détails
Mots clés : Antibacterial Activity, Gamma radiolysis, intermetallic Compounds, NiO–MgO, Ni–Mg
Effects of Erbium Incorporation on Structural, Surface Morphology, and Degradation of Methylene Blue Dye of Magnesium Oxide Nanoparticles
This paper reports the chemical synthesis of MgO and Er-doped MgO nanoparticles (NPs) by the sol–gel method. Their microstructural, optical characterization and the evaluation of their photocatalytic activity are presented. The synthesized NPs were characterized by means of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Environmental Scanning Electron Microscopy (ESEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX), UV–Visible and Photoluminescence (PL) spectroscopy. The effective synthesis of cubic MgO compound is attested by XRD, FTIR and electron diffraction in TEM. Er2O3 cubic secondary phase is found in the 2 and 3 wt% Er-doped MgO samples. The average size of the roundish cuboid-shaped crystallites decreases from 50 to 32 nm upon the incorporation of the rare earth element (TEM, XRD). Concomitantly, the size of flakes in which the NPs do agglomerate follows the same trend (ESEM). UV–Visible results show that the calculated band-gap energy of the NPs was in the 5.23 to 5.35 eV range. PL analysis showed that all samples have visible emissions owing to the formation of defects in the MgO band-gap. The photocatalytic activity against methylene blue dye was evaluated under UV light irradiation. The photocatalytic results showed an improvement in degradation efficiency with the addition of erbium in samples, with a maximal MB dye removal for the 3 wt% Er-doped MgO sample after 90 min irradiation. The performance is ascribed to a higher separation of the photo-generated (electron–hole) and larger surface area. Voir les détails
Mots clés : Erbium, methylene blue, MgO, Photocatalytic activity, X-ray diffraction