Liste des publications
Mechanism for phosphorus deactivation in silicon-based Schottkydiodes submitted to MW-ECR hydrogen plasma
Current work reveals the deactivation mechanism of phosphorus in silicon-based Schottky diodes. Microwave plasma power(P) was fixed at 650 W to observe the variation in different operational parameters of diodes such as initial phosphorusconcentration, flux and hydrogenation temperature (TMWH) and process time (t). The analysis of variation in concentrationof phosphorus by hydrogenation has been carried out by capacitance–voltage (C–V) measurements to monitor the dopingactivation/deactivation. The results clearly show that the atomic species H+H is dominant in the reactors MW-ECR plasma.Therefore, the rates and depth of neutralization were obtained in the low phosphorus-doped silicon sample. The H becomesH0 and prefers an interaction with another H0 instead of gaining an electron to become a negative ion. The hydrogenationtemperature study indicates that the deactivation rate of phosphorus is achieved in a complex manner. Indeed, as the hydrogenationtemperatureincreases,deactivationof phosphorus also increasestill saturationat 250 °C.Athigher temperature,lowor evenno phosphorus–hydrogen complexexistsdue totheirthermaldissociation. The same behaviorwasconfirmedbylonghydrogenation. Voir les détails
Mots clés : MW-ECR plasma, Hydrogenation, phosphorus deactivation, C–V measurement
Dissimilar Welding between 2205 Duplex Stainless Steel and API X52High Strength Low Alloy Steel
This work purposes to investigate the microstructure and the mechanical behavior ofdissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength lowalloy steel API X52. The joining was produced by shielded metal arc welding process using twodifferent filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy,scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysisperformed at the API X52/weld metal interface showed an evident gradient of Cr and Ni betweenfusion and type II boundaries, where the highest hardness value was recorded. Voir les détails
Mots clés : Dissimilar metals welding; 2205 duplex stainless steel; API X52 HSLA steel; Heataffected zone
Study of thin Films of Nickel Oxide (NiO) Deposited bythe Spray Pyrolysis Method
Abstract: In this work, thin films of nickel oxide (NiO) were deposited by a simple and inexpensive technique, which is spraypyrolysis on ordinary glass substrates heated to a fixed temperature of 500 °C, from a solution containing nickel nitrate hexahydrateas a precursor dissolved in distilled water with deferent values of concentrations. The NiO thin films obtained were characterized todetermine the structure with X-ray diffraction technique (XRD), the absorption domain (UV-Visible Spectroscopy), and the surfacemorphology (SEM). The X-ray diffraction patterns confirm the presence of NiO phase with preferential orientation along the (111)direction. The optical gap for nickel oxide calculated with a concentration of 0.1 M from the measurement of optical absorption is 3.6eV, which is quite comparable to the value of the ratio. Voir les détails
Mots clés : NiO, Thin films, Spray pyrolysis
Vibration for detection and diagnosis bearing faults using adaptive neurofuzzy inference system
The fault diagnosis of electrical machines is a primordial and necessary task in industry. Thefailure is unbearable because it causes, incontestably, decrease in production and increases costrepair. Induction motors are the most important equipment in industry, where reliability andsafe operation is desirable, for maintenance, such as detection, and diagnosis of mechanical andelectrical defects of electric drives. The several techniques are adopted and frequency analysis isthe most widely used. Artificial intelligence techniques was gained popularity last decay’s innumerous applications. The presented results show the detected and diagnosed, of the bearingfaults of the induction motor, based on Adaptive Neuro-Fuzzy Inference System. The vibrationsanalysis of the induction machine using the Artificial Intelligence Techniques, combining neuralnetworks and fuzzy logic has been applied successfully. The designed ANFIS network showsabout 99% accurate results as validated by Mat lab / Simulink simulation Voir les détails
Mots clés : diagnosis, fault, vibration, bearing
Rhodamine (B) photocatalysis under solar light on high crystallineZnO films grown by home-made DC sputtering.
ZnO thin films were deposited by home-made DC sputtering of zinc target under mixed gases(Argon, Oxygen) plasma on glass substrates. Films were deposited by varying oxygen partialpressure (PO2) from 0.09 to 1.3 mbar in the deposition chamber, at a fixed substrate temperatureof 100 °C. The samples were characterized by photoluminescence (PL), X-ray diffraction (XRD),optical transmissions (UV–vis), scanning electron microscopy (SEM) and electrical (Hall effect)measurements. The results indicate that by varying the oxygen pressure in the depositionchamber, the films show a precise and well defined photoluminescence emissions for each rangeof pressure covering almost the entire visible domain (UV, UV-Violet, Violet, Blue, and Red) withhigh intensities. Moreover, the deposited films have different defects levels. The XRD analysisindicates that the films are well grown along the c-axis peak, but with different crystallinequality. Optical measurements reveal a high transmission, up to 90%, in the spectral regionbetween 400 and 2500 nm and a large variation of the optical band gap (3.16 – 4.34 eV). As anapplication of the deposited ZnO films, the photo-catalytic degradation of a synthetic solution ofRhodamine B (RhB) poured on a ZnO thin film was successfully achieved and an elimination rateof 38% was obtained after exposing the film to solar light for 3 h. Voir les détails
Mots clés : ZnO thin films, sputtering, Photoluminescence, Rhodamine (B), Solar light, Photocatalysis.
Experimental investigation of notch effect and ply number on mechanicalbehavior of interply hybrid laminates (glass/carbon/epoxy)
The great advantages of hybrid composite materials reside in the synergistic effect of their constituent materialsand that make them very attractive for advanced applications. Nevertheless, the interactive effect of the intrinsicproperties of each element further complicates understanding of their behavior. In this study, an experimentalanalysis of the mechanical behavior of interply hybrid laminates (glass/carbon/epoxy) and the estimation of thehybridization effect with respect to mono-reinforced laminates were carried out. It has been found that theincorporation of 25% carbon fibers in the glass/epoxy laminates contributes significantly to improving theirtensile mechanical properties but they degrade as the number of glass plies increase. In addition, investigationswere carried out on the sensitivity of these materials to geometric imperfections. To this end, the influence of acircular notch has been highlighted. From the results obtained, it was found that the greatest loss of properties isrecorded for the hybrid materials; however, they remain the most resistant. Voir les détails
Mots clés : Hybrid composite materials, laminates, notch, mechanical properties
Control of Matrix Converter Fed Induction Motor Drive
This paper presents a variable speed control of the squirrel induction machine fed by a three-phase matrix converter. Principle of vector control for induction motor and vector control strategy in synchronous reference frame are described. The use of matrix converter allows the availability of better switching devices, bi-directional power flow and sinusoidal input and output waveform. Also, the advantages of matrix converter are combined with the advantages of the field oriented control technique where Venturini algorithm is applied. We study the operation of the motor in the four regions of speed-torque plane. At this effect, the simulation results of the whole system are carried out with four quadrants of motor operations and the performance results obtained are presented and analyzed. A good performance of induction motor fed by a matrix converter is proved. Voir les détails
Mots clés : matrix converter, induction motor, vector control, modelling, Simulation.
A new time–frequency method for identificationand classification of ball bearing faults
In order to fault diagnosis of ball bearing that is one of the most critical components ofrotating machinery, this paper presents a time–frequency procedure incorporating a newfeature extraction step that combines the classical wavelet packet decomposition energydistribution technique and a new feature extraction technique based on the selection ofthe most impulsive frequency bands. In the proposed procedure, firstly, as a pre-processing step, the most impulsive frequency bands are selected at different bearing conditionsusing a combination between Fast-Fourier-Transform FFT and Short-Frequency Energy SFEalgorithms. Secondly, once the most impulsive frequency bands are selected, the measured machinery vibration signals are decomposed into different frequency sub-bands byusing discrete Wavelet Packet Decomposition WPD technique to maximize the detectionof their frequency contents and subsequently the most useful sub-bands are representedin the time-frequency domain by using Short Time Fourier transform STFT algorithm forknowing exactly what the frequency components presented in those frequency sub-bandsare. Once the proposed feature vector is obtained, three feature dimensionality reductiontechniques are employed using Linear Discriminant Analysis LDA, a feedback wrappermethod and Locality Sensitive Discriminant Analysis LSDA. Lastly, the Adaptive NeuroFuzzy Inference System ANFIS algorithm is used for instantaneous identification andclassification of bearing faults. In order to evaluate the performances of the proposedmethod, different testing data set to the trained ANFIS model by using different conditionsof healthy and faulty bearings under various load levels, fault severities and rotatingspeed. The conclusion resulting from this paper is highlighted by experimental resultswhich prove that the proposed method can serve as an intelligent bearing fault diagnosissystem. Voir les détails
Mots clés : Vibration signal processing Bearing fault diagnosis Bearing faults LDA, LSDA, ANFIS, WPD
Power Control of DFIG Driven by Matrix ConverterUnder Super and Sub Synchronous OperationModes
In this paper, we present the modeling and control of the wind energy conversion systemsbased on the doubly fed induction generator fed by AC/AC matrix converter. Firstly, wedeveloped the models of the different elements of the conversion chain. After, we consider thevector control strategy of the active and reactive powers in order to ensure an optimum operation.Finally, the dynamic model of a doubly fed induction generator and wind turbine grid connectedsystem is determined in the d-q synchronous reference frame.Therefore, the powers control isverified using software Matlab/Simulink. The behaviours of the sub-synchronous and supersynchronous operation modes is presented and discussed. The results prove that the power controlstrategy is well adapted to this kind of system. Voir les détails
Mots clés : wind systems, doubly fed induction generator, Bidirectional DC-DC Converter, Variable Speed Wind Turbine
Structural, microstructural and thermal characterization of Fe- doped ZnO powder nanostructures prepared by mechanical alloying
ZnO powder nanoparticles mechanically alloyed were doped with iron to investigate their structural and microstructural properties using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) for examined 1% Fe doped ZnO. The ZnO starting pure powder exhibited a hexagonal crystal structure with space group p63mc of ZnO, however with the introduction of 1% Fe in the ZnO milled powder, the hexagonal ZnO phase remained unchanged, whereas the microstructural parameters were subject to significant variations due to the introduction of Fe atoms into the ZnO hexagonal matrix to replace oxygen ones. The size of crystallites and microstrains are found milling time dependent. Voir les détails
Mots clés : ZnO, XRD, DSC