Classic and local analysis of corrosion behaviour of graphite and stainless steels in polluted phosphoric acid

In phosphoric acid solution (40% H3PO4), the corrosion behaviour of graphite and stainless steels was studied by the use of different electrochemical methods, namely polarization curve analysis, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The combined effect of chemical impurities and the increase of medium temperature was studied to approach the real conditions in the process of phosphoric acid manufacturing. It was found that the current density measured by polarization curves increased with the presence of chloride and sulphate ions in the acid solution whatever the tested material. Compared to stainless steels, graphite had the best corrosion resistance in polluted phosphoric acid. However, for graphite the increase of temperature from 20 to 80 ◦C induced an increase of the corrosion rate and potential and a decrease of the resistance confirmed by EIS results. Subsequently, local currents were detected at the surface of the sample by using the scanning vibrating electrode technique. From the data obtained, graphite surface manifested a distinctive behaviour from that of stainless steels. A generalized corrosion was occurred on graphite whereas a localized corrosion was observed for stainless steels. These results show a clear interest of graphite as component material in some of the equipments of the phosphoric acid industry

THE IMPORTANCE OF PHYSIOLOGICAL TRAITS IN ASSOCIATION WITH METABOLISM IN THE DEVELOPMENT OF SPEED ENDURANCE AMONG MIDDLE DISTANCE RUNNERS

This study sets up to investigate the importance of physiological traits in relation to metabolism in the development of speed endurance among runners at middle-distances. It aims at determining the level of physiological traits which are associated with metabolism among runners; in addition of developing the required physical attributes especially speed endurance. Accordingly, the researchers have administered two main physiological tests: The River index test and the Shannon flash back heart curve test to a sample of 15 runners from the athletics games club of Blida (Algeria). Their age range varies between 17 and 18 years.  Article visualizations

Preparation and characterization of electrolytic alumina deposit on austenitic stainless steel

Conversion coating modified by alumina has been studied as a way for improving the resistance to thermal oxidation of an austenitic stainless steel. Conversion coating, characterized by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. The influence of the current density and treatment time on alumina deposit was studied using statistical experimental designs like Doehlert uniform shell design. After heating, coatings present a continuous composition gradient with refractory compounds at the surface. The behavior at high temperature (1000 8C) of the alumina coating was investigated. The presence of alumina increases the oxidation resistance of an austenitic stainless steel at 1000 8C. The morphology and the chemical composition of the deposit are analyzed. Results on the thermal stability of coating on austenitic stainless steel are presented

Investigations on composition and morphology of electrochemical conversion layer/titanium dioxide deposit on stainless steel

In this study, the formation and characterization of conversion coatings modified by a sol-gel TiO2 deposit were investigated as a way to develop a new photocatalyst for water and air depollution. The conversion coating, characterised by strong interfacial adhesion, high roughness and high surface area facilitates the sol-gel deposition of titania and enhances its adhesion to the substrate. The conversion treatment is carried out in an acid solution. Observation by Scanning Electron Microscopy (SEM) reveals a rough surface with pores and cavities. According to SIMS measurements, the thickness of the initial conversion layer is evaluated at about 1.5 μm. On this pre-functionalised support, the titanium dioxide was deposited by the sol-gel method. The roughness measurements coupled with SIMS analysis allowed a precise evaluation of the surface state of the final layers. The coating consists of two layers: a TiO2 outer layer and an inner layer containing iron chromium oxides. Characterization by X-ray diffraction (XRD) showed the existence of the TiO2 anatase structure as the main compound

QCOF: New RPL Extension for QoS and Congestion-Aware in Low Power and Lossy Network

Low power and lossy networks (LLNs) require a routing protocol under real-time and energy constraints, congestion aware and packet priority. Thus, Routing Protocol for Low power and lossy network (RPL) is recommended by Internet Engineering Task force (IETF) for LLN applications. In RPL, nodes select their optimal paths towards their preferred parents after meeting routing metrics that are injected in the objective function (OF). However, RPL did not impose any routing metric and left it open for implementation. In this paper, we propose a new RPL objective function which is based on the quality of service (QoS) and congestion-aware. In the case paths fail, we define new RPL control messages for enriching the network by adding more routing nodes. Extensive simulations show that QCOF achieves significant improvement in comparison with the existing objective functions, and appropriately satisfies real-time applications under QoS and network congestion.info:eu-repo/semantics/publishedVersio

An efficient protection of stainless steel against corrosion: Combination of a conversion layer and titanium dioxide deposit

In the present work, a novel process has been developed to improve the corrosion properties of ferritic stainless steels. Titanium oxide coatings have been deposited onto stainless steel by sol–gel process after a pre-functionalization of the substrate in a conversion bath. Gel titania was prepared by hydrolysis of a titanium butoxide through a sol–gel process. Duplex systems "conversion layer/uniform TiO2 coating" have been prepared on stainless steels using a dipping technique and thermal post-treatments at 450 °C. The preparation of sol–gel coatings with specific chemical functions offers tailoring of their structure, texture and thickness and allows the fabrication of large coatings. The morphology and structure of the coatings were analysed using scanning electron microscopy with field effect gun (SEM-FEG), Mass spectroscopy of secondary ions (SIMS) and X-ray diffraction (XRD). The anticorrosion performances and the ageing effects of the coatings have been evaluated in neutral and aggressive media by using several normalized tests. The results show that the conversion layer was not sufficient to protect steel but sol–gel TiO2 coatings, anchored on the metal substrate via the conversion layer, show good adhesion with the substrate and act as a very efficient protective barrier against corrosion. So, duplex layers with TiO2 nanoparticle coatings on steels exhibit an excellent corrosion resistance due to a ceramic protective barrier on metal surface. Analysis of the data indicates that the films act as geometric blocking layers against exposure to the corrosive media and increase drastically the lifetime of the substrate

Estimation paramétrique pour le diagnostic des processus : Application à la bobine à noyau de fer

International audienceLe travail présenté dans cet article concerne la mise en oeuvre d'une méthodologie de diagnostic des procédés industriels basée sur l'estimation paramétrique. Cette technique s'appuie sur une modélisation de la signature de défaut en associant au mode commun (modèle sain) un mode différentiel (modèle de défaut) qui traduit le dysfonctionnement. L'identification des paramètres du modèle commun indique donc l'état dynamique du système, tandis que le suivi d'évolution des paramètres du mode différentiel permet la détection et la localisation du déséquilibre. Notre méthodologie a été validée expérimentalement sur une bobine à noyau de fer dédiée au diagnostic des défauts de type réduction et court-circuit de spires

The Spiny Lobster, Palinurus mauritanicus (Gruvel, 1911) from Algerian West Coasts: A Species to Protect.

The study of the biometric characteristics of the pink lobster, Palinurus mauritanicus allowed us to define some parameters related to reproduction and growth of a noble little-known species in the Mediterranean, which is not protected in Algeria, and tends to be scarce. To avoid future a pronounced decline in the fishable stock and allow a rational balance of specimens attending island fishing areas; our recommendations are based on observations made ??during sampling process that are resumed as follows: prohibit throughout the year capture of berried females, and returned them to water in case of accidental trawl capture, closing the lobster fishing during periods of reproduction and egg maturation (July, August an