Sciences des matériaux
Investigation of Structural and Superconducting Properties ofBiSrCa(Ti)CuO Superconducting Ceramics from Sol-Gel Method
Superconducting Bi2Sr2Ca1-xTixCu2Oceramics samples have been prepared by Sol-Gel methods; (using citrateprocess).The influences of the preparation conditions of compound oxide powder on structural andsuperconducting properties have been investigated by x ray diffraction (XRD), Scanning Electron Microscopy(SEM)equipped with EDS.The critical transition temperatures T8have been determined by resistivity versustemperature measurements. Cell parameters samples were calculated from XRD patterns. The polyacrylamid gelmakes the citrate process easier, more rapid and affords the possibility of synthesis of high quality oxidepowders.c Voir les détails
Mots clés : Superconducting, Sol-Gel - Polyacrylamide Gel
Development of a magnetron sputtering system for in-situ deposition of thin multilayerscoatings.
In house Physical Vapor DepositionDualMagnetron Sputtering System (PVD-DMSS) was designed and manufactured based on basis criteria, relevant on R&D and industrial systems, and on the feedback experience acquired from operation of an old classical physical vapor deposition system of our laboratory. Its permit to elaborate in situ multilayer’s thin films without breaking vacuum and with varying several operation parameters, namely the inter-electrode distance, substrate rotation, polarization and the heating of substrate. The sputtering chamber of developed PVD-DMSS has a volume of about 10 liter; equipped with many accesses (for loading/unloading of samples, for the control of operation parameters and for the installation of diagnosis instruments). The PVD-DMSS is also equipped with two planar balanced magnetron cathodes providing magnetic field of 400mT, the cathodes can be powered by either a radiofrequency alternative current or continuous current, and connected to a high vacuum system. Monolayer’s and multilayer’s Nickel and Titanium thin films obtained and the results of plasma diagnosis make obvious that the PVD-DMSS developed allows a good level of operation flexibility as well as obtaining reproducible thin films and multilayer with a desired quality. Voir les détails
Mots clés : Magnetron sputtering, thin film, plasma diagnostic, PVD system design
Study of corrosion resistance of carbon steel in albian water solution in the presence of Chimec as corrosion inhibitor
The N80 steel has been generally used as the main construction material for down hole tubular, flow lines and transmission pipelines in petroleum industry. Electrochemical polarization and electrochemical impedance spectroscopy measurements were performed in order to obtain information on the corrosion behaviour of steel N 80 in the presence of a penetrating Chimec corrosion inhibitor. The investigation was performed in albian water from a well in the Hassi-Messaoud region, in the presence and absence of inhibitor and the effect of temperature on the corrosion was investigated. The electrochemical results indicate that the inhibitor is able to penetrate through the reinforcing steel, minimising steel corrosion. Voir les détails
Mots clés : Corrosion inhibitors, N80 Steel, Albian water, electrochemical impedance spectroscopy.
Corrosion performance and electrochemical stability of 316L in body fluid
Metal implants are the best choice for the long-term replacement of hard tissue, such as hip and knee joints, because of their excellent mechanical properties. 316L stainless steel is widely accepted as biocompatible metal implants. The aim of this work is to study the biocompatibility of 316L stainless steel, for the manufacture of screw plates having high chromium and low carbon contents; in a simulated blood medium (Ringer’s solution). The specimen having a cylindrical shape, has been characterized by a spectral analysis for the identification of the chemical composition, a mechanical characterization (hardness Rockwell), physicochemical (X-ray diffraction), and finally electrochemical measurements (monitoring the free potential evolution, plots of polarization curves and electrochemical impedance spectroscopy (EIS) measurements were conducted after 4h, 6h, 24h, 48h, 168h, 215h, 10 days and 15 days of immersion in Ringer's solution. The influence of parameters such as electrolytic medium, pH, agitation of the medical device (screw plates used in orthopedics) has studied. Very low current densities were obtained, indicating the formation of a passive layer. Impedance spectra, represented in the Nyquist plan, exhibited a single constant system suggesting the formation of one layer. Voir les détails
Mots clés : Implants, stainless steel, biocompatibility, Ringer’s solution, X-ray diffraction
Studies of Iron Diselenide Thin Films Deposited by Thermal Evaporation
Iron diselenide (FeSe) composite thin films have been formed onto ultrasonically and chemical cleaned glass substrates by thermal evaporation technique from powder. This latter was prepared by mechanical alloying. The structural evolution of a binary alloy with nominal composition FeSe2 prepared by ball milling was investigated as a function of milling time. The structural properties of the powders and the films were ascertained by x-ray diffraction method. The XRD patterns showed that for milling times up to 1 h, the FeSe phase is formed. The band gap E estimated from optical absorption data was between 0.8–1.01 eV, depending on preparation conditions such as substrate temperature. High optical absorption coefficients (> 104 cm− 1g) were found. Voir les détails
Mots clés : FeSe, Solar energy materials, Mechanical Alloying, Thermal evaporation, Thin films
DURABILITY OF CONCRETE UNDER THE INFLUENCE OF SULPHATES ATTACK IN THE REGION OF OUARGLA – ALGERIA
Several damages were found on remediation networks (pipes and manholes) in Ouargla -Algeria, due a to product quality of concrete and aggressive external environment. The objective of this work is to study the sustainability of pipes for sanitation networks in this region under the effect of sulfates attack (especially HS). To do this, Sulphate resisting cement (SRC) specimens have been preserved in the real world and the results were compared with those of control specimens. According to the study, we concluded that the cement concrete SRC submitted acceptable mechanical properties in wastewater compared to concrete witnesses and penetration of aggressive agents rather slow, where a small decline in mechanical compressive strength from 3% to the duration of 365 days of storage. But the exposure of cement concrete SRC to H2S gas, shows a degradation accelerated concrete under the effect of HS gas in particular after 90 days of age, when a 40% regression of approximately compressive strength compared witnesses specimens at the age of 365 days. Voir les détails
Mots clés : Durability, sulphate resisting cement (SRC), sanitation, waste water, HS gas, H2S gas
DIAGNOSIS OF DAMAGE OF METAL STRUCTURES UNDER THE INFLUENCE OF CORROSION IN THE REGION OF DJIJEL
The region of Djijel is characterized by a Mediterranean climate, its winters are cold and rainy unlike its autumns. It is also famous for its dry summers with a temperature ranging between 20 °C and 35 °C in summer, and average relative humidity of the air is high and can reach about 70%. Several physical and chemical damages were observed on the metal structures implanted in the Djijel region, these changes have directly affected their sustainability, such as: corrosion of steel profiles or reinforced concrete frames, cracks or/and coating bursting under the effect of alkali-aggregate reactions or corrosion of steel. In this study, we show some pictures from damage caused by corrosion of metal structures, then we explain the main causes of corrosion of steel profiles or degradation of reinforced concrete, and finally we propose some solutions or recommendations to avoid or reduce this structural damage Voir les détails
Mots clés : Durability, corrosion, metal structures, humidity
Application of new azomethine as corrosion inhibitor on mild steel in acidic medium: Electrochemical, thermodynamic and SEM investigations.
1-(4-Nitrphenylo-imino) -1 (phenylhydrazono) - propan-2-one (NOAM) was studied as a corrosion inhibitor for the protection of mild steel in 1 M HCl solution by means of weight loss, polarization and electrochemical impedance spectroscopy. The inhibition efficiency was found to increase with increasing inhibitor concentrations and decreases with increasing temperatures. Some thermodynamic and kinetic parameters were calculated and discussed. The adsorption of inhibitor on mild steel surface, obeyed the Langmuir adsorption isotherm. Polarization studies showed that inhibitor behave as mixed-type inhibitor. Scanning electron microscopy (SEM) was performed for surface analysis of the uninhibited and inhibited mild steel samples. Voir les détails
Mots clés : corrosion, inhibition, electrochemical, SEM
Effect of some experimental conditions on the electroplated Mn-Bi film composition
In this study, the effect of some experimental parameters on the electrodeposition of Mn-Bi thin film from a mixed sulfate-nitrate bath was investigated under direct potentiostatic mode based on the previous published paper. The plating bath is characterized by the presence of some additives like boric acid and ammonium sulfate. Cyclic voltammety is used to the electrochemical analysis, the chemical composition and the morphology of the films obtained at different experimental conditions were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The deposits have a cauliflower appearance with a heterogeneous distribution of manganese and bismuth. The Mn and Bi content in the deposit estimated by the EDS analysis revealed that the film composition depend strongly on the applied potential and the pH bath but no significant variation is obtained with varying the deposition time. Voir les détails
Mots clés : Mn-Bi, electrodeposition, Cyclic voltammety, EDS, MEB
Friction and wear behaviors of TiCN coating treated by R.F magnetron sputtering
Titanium carbonitride (TiCN) coatings combine high hardness and wear resistance, low friction, good corrosion resistance and high adhesion strength with substrate. These unique properties make TiCN coatings a good solution for the applications requiring high abrasion and wear resistance. In this study, we present the effect of the negative bias applied to the substrate on the microstructure, friction and wear behaviors of the TiCN coating. The elaboration of our films has been carried out by reactive magnetron sputtering (R.F) at 13,56MHz, using a gas mixture of methane, nitrogen and argon. The film deposition has been done on the XC38 steel substrates. The deposited layers were characterized by XRD analysis, potentiodynamic polarization and tribometer. Voir les détails
Mots clés : Thin films, Magnetron, sputtering, Hard coating, TiCN, corrosion, friction and wear.