Liste des publications
Surface performances of Ti-6Al-4V substrates coated PVD multilayered filmsin biological environments
Multilayered and nanostructured coatings of Ti based alloys (oxides and nitrides) are elaborated and tested for increasing protective properties such as corrosion and wear resistances. A pin-on-disc tribometer was used to evaluate the wear resistance in Hank's solution against bovine bone. Corrosion behavior in Hank's solution was determined by potentiodynamic and electrochemical impedance spectroscopy techniques. Besides, the specimen surfaces were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) microanalyses. The results showed that optimal tribological properties were obtained in the case of coatings having TiN as top layer. The main wear mechanism was abrasive third bodywear. In vitro corrosion tests at 37 °C showed that the better corrosion resistance was obtained when TiN was the top layer. However all of them exhibited good tribological properties, good corrosion resistance and then may be promising options for biomedical applications. Voir les détails
Mots clés : PVD coatings, oxides, Nitrides, Biomaterials, tribology, corrosion
Effect of calcium phosphate synthesis conditions on its physico-chemical properties and evaluation of its antibacterial activity
The antibacterial activity of non-stoichiometric calcium phosphate particles prepared by precipitationunder controlled experimental conditions at pH ?∼ ?9 and sintered at high temperature was studiedagainst Staphylococcus aureus bacteria. The effects of operating parameters developed according to anexperimental design of Plackett-Burman type on the physicochemical characteristics and the capacityto inhibit bacterial growth were identi fi ed using a thermal analysis ( TGA-DTA-DSC) , x-rayDiffraction( XR) , Raman Spectroscopy, Scanning Electron Microscope(SEM ) and the Kirby BauerMethod. The XRD spectrum shows that the synthetic crystalline nanoparticles powders consist ofmultiphasic calcium phosphateβ -TCP/β -CPP/OCP / HA and that the average particle size is between56 and 123 nm calculated by the Debay-Shearer equation. The Raman spectrum of sintered powdershows the main absorption bands that are assigned to the asymmetric / symmetric P-O stretchingvibrations in PO4− 3and the symmetric O-H stretching mode of the hydroxyl group in addition ofCa-PO4and Ca-OH modes. The samples were found to possess different morphologies consisting ofnano-rods of different lengths, semi / spherical structures and fine granules, in addition to irregularclusters. The antibacterial tests results showed that the high concentration calcium phosphate powderexhibited better antibacterial activity against Staphylococcus aureus bacteria with inhibition zonesranging from 0.2 –0.7 cm. Voir les détails
Mots clés : Biomaterials, calcium phosphate, Antibacterial Activity, nanoparticles
Effect of thermal spray process on chemical composition, magnetic behaviour, structure and mechanical properties of coatings based on milled Fe, Co a nd Al2O3 powder
Coated steel substrate by FeCo/Al2O3 nanoparticle with various Co concentrations realized by a thermal spraying process, preliminary powder alloy was elaborated by mechanical alloying technique for 20 h of milling time. The aims of this work are to study the effect of thermal spraying process and mechanical alloying on chemical composition, magnetic behaviour, structure and mechanical properties of coating. After mechanical alloying, the crystallite sizes of the powder were decreased from 18 to 7 nm and the lattice strains increased from 0.36 to 0.56%. This is due to the phenomenon of diffusion of cobalt in the iron lattice and the milling effect. After thermal spraying, many different phases appeared in the coating, such as Al2FeO4, CoAl2O4, CoFe and CoFe2O4. Magnetic behaviour was influenced by this change in the chemical composition of coating. The maximum saturation magnetization was found in Fe40Co20(Al2O3)40 sprayed powder, however, the minimum coercivity was found in Fe50Co10(Al2O3)40 sprayed powder. Mchanical properties parameters such as microhardeness and Young’s modulus were enhanced by the change in chemical composition during mechanical alloying and thermal spraying process. Voir les détails
Mots clés : FeCo/Al2O3 nanoparticle coating, Mechanical Alloying, Thermal Spraying, magnetic behaviour, structural and mechanical parameters
Simulation analysis of a high efficiency GaInP/Si multijunction solar cell
The solar power conversion efficiency of a gallium indium phosphide (GaInP)/silicon (Si) tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithic structures. In particular, to interconnect the bottom and top sub-cells of the monolithic tandem, a gallium arsenide (GaAs)-based tunnel-junction, i.e. GaAs(n+)/GaAs(p+), which assures a low electrical resistance and an optically low-loss connection, has been considered. The J–V characteristics of the single junction cells, monolithic tandem, and mechanically stacked structure have been calculated extracting the main photovoltaic parameters. An analysis of the tunnel-junction behaviour has been also developed. The mechanically stacked cell achieves an efficiency of 24.27% whereas the monolithic tandem reaches an efficiency of 31.11% under AM1.5 spectral conditions. External quantum efficiency simulations have evaluated the useful wavelength range. The results and discussion could be helpful in designing high efficiency monolithic multijunction GaInP/Si solar cells involving a thin GaAs(n+)/GaAs(p+) tunnel junction. Voir les détails
Mots clés : GaInP/Si, tandem solar cells, power efficiency, numerical simulations
Modelling and performance analysis of a GaN-based n/p junction betavoltaic cell
In this work, we optimized the performance of a gallium nitride (GaN)-based n/p junction betavoltaic cell irradiated by the radioisotope nickel-63 (Ni63). In particular, we developed a lab-made software starting from an analytical model that takes into account a set of fundamental physical parameters for the cell structure. The simulations reveal that, by using a Ni63 radioisotope source with a 25 mCi/cm² activity density emitting a flux of beta-particles with an average energy of 17.1 KeV, the cell performs a conversion efficiency (η) in excess of 26%, thus approaching the theoretical limit for a GaN-based device. The other electrical parameters of the cell, namely the short-circuit current density (Jsc), open-circuit voltage (Voc), and maximum electrical power density (Pmax) are 240 nA/cm², 2.87 V, and 660 nW/cm², respectively. The presented analysis can turn useful for understanding the theoretical background needed to better face GaN-based betavoltaic cell design problems. Voir les détails
Mots clés : analytical modelling, Gallium nitride, betavoltaic cell, nickel-63 radioisotope, radioactivity density
Criterion for cathodic protection of 25CD4/Inconel 182 system
This study aims to investigate the cathodic protection criterion of a galvanic system of low alloy steel 25CD4substrate /Inconel 182 austenitic stainless-steel ?ller metal couple obtained using Shield Metal Arc Welding(SMAW) process. The microstructure investigation revealed the presence of Type II boundary along the steelsubstrate/Inconel interface where high carbon content and high hardness were recorded. The electrochemicaltests evaluated in marine environment (3.5% NaCl) at room temperature revealed that the corrosion potential(E) of the interface was between the steels substrate and the Inconel 182 ?ller metal ones, On the other hand,the current density (Icorr) and corrosion rate were slightly higher in the overlaid area. In order to determine thesystem protection criterion, chronopotentiometry method was introduced. It was found that the cathodic protectioncriterion for the assembly is based on the criterion of the least noble materialwhich is the steel substrate.corr Voir les détails
Mots clés : cathodic protection, 25CD4, Inconel 182, overlay, Cronopotentiometry.
Experimental, Mechanical Characterizations of Friction Welding of Steel and Aluminium Joints
Rotary friction welding (RFW) is a solid-state joining process which works by rotating one workpiece relative to another while under a compressive axial force, which produces coalescence of materials workpieces. It is considered most viable alternative to overcome the difficulties faced in conventional joining techniques. As it is a solid state welding process, the process does not form molten pool thereby eliminating the solidification errors. It offers many advantages for some manufacturing sectors for a wide range of applications. In this research, we investigated the mechanical and metallurgical characteristics of RFW welded joints for homogenous and heterogeneous assemblies. We have studied A60 steels and 2017A series aluminum alloys. The obtained welds are similar in appearance in that they have several Microstructural distinct zones.So, the results show that by increasing the rotating speed employing 1000 and 1600 rpm, the mechanical properties during the RFW process is lightly improved, favored by the increase in heat flow. In the same specimen, the microhardness distribution is generally viewed lightly changed between center line throw weld of welded tube and close to their boundary line. This is due to the no-uniform of temperature distribution in cross section. Thus, plastic deformation of heated portion of the metal plays an important role in friction welding process and their quality. Microstructural analysis reveals that grain growth in the joint WCZ and in heat affected zone HAZ because of the no-uniform of thermal flux distribution in both directions (transvers and longitudinal of tube). Finally using RFW, the fabricators allow to perform and maintenance the mechanical components with low cost and which it conserves their welding quality compared to the classical fusion welding. Voir les détails
Mots clés : Rotary friction welding (RFW), plasticised material, heat flux, characterization, Microhardness
CONTRIBUTION TO RECONFIGURATION OF FAULT-TOLERANT INVERTER APPLIED TO THE WIND PARK CONNECTED TO THE ELECTRICAL NETWORK
This paper proposes a new diagnostic technique based on Park vectors associated with polar coordinates for the detection and location of open circuit (OC) faults, as well as the integration of fault-tolerant reconfigurable inverter in order to enable continuity of service of the wind farm system. The model used is that of a variable speed wind turbine coupled to a double-fed induction generator (DFIG) connected to the power grid via a fault-tolerant converter to improve performance after the appearance of the fault. This converter is used based on IGBT to obtain an acceptable accuracy with high switching frequencies. This model is well suited for the observation of harmonics and the dynamic performance of the control system over relatively short periods of time (typically hundreds of milliseconds to one second). This method allows extracting the maximum wind energy during a low wind speed by optimizing the turbine speed while minimizing the mechanical stress on the turbine during gusts of wind. To illustrate the diagnostic improvement of fault-tolerant inverter open circuit faults, several results are presented and discussed in this article. Voir les détails
Mots clés : DFIG Turbine, Inverter, diagnosis, Detection, Location, Reconfiguration, fault, Open-Circuit, IGBT
Manufacturing Nanostructured and Microstructured Chitosan Prepared By Milling Shrimp Shell
Nano-products are of great interest in the field of pharmaceutical, corrosion, medecine and engineering. dis research aimed to produce nano-chitosan. Nanocrystallite. Shrimp shells has been prepared by using a high-energy planetary ball with an optimal rotational speed.The raw material was subjected to standard chemical processing for chitin extraction, followed by deacetylation to obtain nanocrystallite chitosan, which is characterized by Scanning Electron Microscope SEM and Fourier Transform Infrared Spectrometry FT-IR. Voir les détails
Mots clés : Shrimp shell, Planetary milling, chitosan, SEM, FT-IR.
Manufacturing Nanostructured and Microstructured Chitosan Prepared By Milling Shrimp Shelll
Nano-products are of great interest in the field of pharmaceutical,corrosion, medecine and engineering.This research aimed to produce nano-chitosan. Nanocrystallite.Shrimp shells have been prepared by using a high-energy planetaryball with an optimal rotational speed.The raw material was subjected to standard chemical processing forchitin extraction, followed by deacetylation to obtain nanocrystallitechitosan, which is characterized by Scanning Electron MicroscopeSEM Fourier, Transform Infrared Spectrometry FT-IRand X-raydiffraction (XRD) Voir les détails
Mots clés : Shrimp shell, Planetary milling, chitosan, SEM, FT-IR, XRD