Liste des publications

Nombre total de résultats :666
Pertinence Titre A-Z Plus récents Plus anciens
10 25 50
Année de publication
et

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

A. Younes, N.Dilmi, A.BOUAMER  (2020)
Publication

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

M Benaicha, L Dehimi, F Pezzimenti, F Bouzid  (2020)
Publication

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

F. Bouzid, F. Pezzimenti, L. Dehimi  (2020)
Publication

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

D. ALLOU, D. Miroud, M. Ouadah, B. Cheniti, S. Bouyegh  (2020)
Publication

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

A. Allali, M. AISSANI, N. MESRATI, B. Othmani, M. Medkour, I. Boukhadouni, A. Khiali  (2020)
Publication

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

Omar Fethi BENAOUDA, Azzedine Bendiabdellah, KAHLA SAMI  (2019)
Publication

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

OULD BRAHIM Insaf, Belmedani Mohamed, Hadoun Hocine, Belgacem Ahmed, Haddad Ahmed  (2019)
Publication

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

OULD BRAHIM Insaf, Belmedani Mohamed, Hadoun Hocine, Belgacem Ahmed and Haddad Ahmed  (2019)
Publication

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

Effect of heat treatment on surface hardness and tribologicalbehavior of XC38 steel—approach by the experiments plans

M Bourebia, S Meddah, H Hamadache, A Taleb, A Gharbi, L Laouar  (2019)
Publication

This work aims at predicting the micro-hardness of XC38steel using the experiments plans as well asstudy of tribological behavior of thissteel. The heat treatments were considered by adopting thefactorial plans 22 methodology at two factors (temperature ‘T’ and holding time ‘t’), each at two levels(-1, +1). The results obtained allowed lead to a mathematical model predicting the micro-hardness‘Hv’ in every point of the study field. Moreover, the curves of the responses surfaces clearly show theinfluence of two factors studied (T, t) on ‘Hv’. Mechanical characterization of treated samples showedasignificant increase in the micro-hardness, which achieve to 76% for the treated sample at 850 °Cduring 2 h compared to untreated state. An investigation of wear tracks morphology shows thatfriction under a load of 10 N results in predominant adhesive wear, while a load of 2 N favorabrasive wear. Voir les détails

Mots clés : heat treatment, factorial plans, prediction, superficial hardness, tribological behavior

Characterization of the Polylactic acid stretched uniaxial and annealed by Raman spectrometry and Differential scanning calorimetry

A. Bouamer, N. Benrekaa, A.Younes, H. Amar  (2019)
Publication

In this work, we have been interested in the characterization of the effect of heat treatment and mechanical treatment on the crystallinity of polylactic acid (PLA) film by two techniques, DSC and Raman spectroscopy. The results obtained by the DSC for the stretched film shows the appearance of a broad peak of crystallization around 120 °C, a rise in melting peak in a significant way, which shows that the uniaxial stretching has increased the crystallinity of the PLA, whereas for the annealed film appearance of a double melting peak. The result obtained by Raman spectroscopy shows new peaks appears at 922 cm−1 and 540 cm-1 after stretching and annealed process, indicating the crystallization process. Voir les détails

Mots clés : PLA, glass transition, Raman spectroscopy, DSC