The Experts below are selected from a list of 42948 Experts worldwide ranked by ideXlab platform
F Climent - One of the best experts on this subject based on the ideXlab platform.
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effects of thickness coating on the electrochemical behaviour of thermal spray cr3c2 nicr coatings
Surface & Coatings Technology, 2002Co-Authors: J M Guilemany, Javier Fernandez, J Delgado, Assis Vicente Benedetti, F ClimentAbstract:Abstract Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1] , [2] . In this paper, electrochemical ac and dc experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr3C2–NiCr Layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a Thicker Layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr3C2–NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited Layer. Electrochemical measurements, such as Open-Circuit Potential (EOC), Polarisation Resistance (Rp) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCl media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited Layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena.
A J Epstein - One of the best experts on this subject based on the ideXlab platform.
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corrosion protection of iron steel by emeraldine base polyaniline an x ray photoelectron spectroscopy study
Synthetic Metals, 1997Co-Authors: Mats Fahlman, S Jasty, A J EpsteinAbstract:The emeraldine base form of polyaniline has been used as a corrosion protecting undercoat on steel and iron samples. Using X-ray photoelectron spectroscopy, the anti-corrosion performance of various application methods of the emeraldine base Layer was studied, as well as the mechanism for corrosion protection. Emeraldine base polyaniline undercoats were found to offer corrosion protection for both the cold rolled steel and iron samples. The degree of protection did vary depending on the thickness of the iron oxide Layer at the polymer/metal interface as well as on the thickness of the top oxide Layer. The best results were achieved when both the top and interfacial oxide Layers were removed prior to the polymer deposition. The mechanism for corrosion protection was found to be anodic, i.e., the polyaniline film withdraws charge from the metal, passivating its surfaces against corrosion. For all samples studied, iron as well as cold rolled steel, the iron oxide structure consisted of a thin (~15 A) Layer of Fe2O3 followed by a Thicker Layer of Fe3O4 at the pure steel (iron) interface. Large values (up to ~1.5 cm) of throwing power were obtained for emeraldine base protected cold rolled steel.
Abdelkader Elhanaoui - One of the best experts on this subject based on the ideXlab platform.
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acoustic scattering from immersed composite cylindrical shells existence of zero group velocity circumferential waves
Composite Structures, 2017Co-Authors: Said Agounad, El Houcein Aassif, Younes Khandouch, Dominique Decultot, G Maze, Abdelkader ElhanaouiAbstract:Abstract Some Lamb waves in a plate and some circumferential waves in a one-Layer cylinder are characterized by the resonance frequencies where the group velocity is vanishing while the phase velocity remains finite. This paper investigates on the existence of these special waves which call zero group velocity waves (ZGV waves) in the case of the copper/polymer composite cylindrical shell immersed in water and filled with air. The acoustic scattering of a plane wave from this composite cylindrical shell is analyzed in the reduced frequency range ( 0.1 k 1 a 1 200 ; k 1 is the wave number and a 1 is the outer radius of the composite cylindrical shell). The study of the respective influence of the inner Layer thickness (polymer) and the outer Layer thickness (copper) shows that the existence of these waves is a function of these thicknesses. Moreover, this study depicts that the dispersion curves of the considered biLayer shell tend towards the dispersion curves of the one-Layer cylindrical shell made from the material of the Thicker Layer of the bi-Layer cylindrical shell (polymer or copper). The time-frequency representation of smoothed pseudo Wigner-Ville (SPWV) is used to extract some properties of the circumferential waves propagating in and around the bi-Layer cylindrical shell. The obtained results by this representation are in good agreement with those obtained by the theoretical approach.
J M Guilemany - One of the best experts on this subject based on the ideXlab platform.
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effects of thickness coating on the electrochemical behaviour of thermal spray cr3c2 nicr coatings
Surface & Coatings Technology, 2002Co-Authors: J M Guilemany, Javier Fernandez, J Delgado, Assis Vicente Benedetti, F ClimentAbstract:Abstract Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1] , [2] . In this paper, electrochemical ac and dc experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr3C2–NiCr Layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a Thicker Layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr3C2–NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited Layer. Electrochemical measurements, such as Open-Circuit Potential (EOC), Polarisation Resistance (Rp) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCl media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited Layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena.
Sean C Solomon - One of the best experts on this subject based on the ideXlab platform.
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microearthquake characteristics and crustal velocity structure at 29 n on the mid atlantic ridge the architecture of a slow spreading segment
Journal of Geophysical Research, 1995Co-Authors: Cecily J Wolfe, Geraldine M Purdy, Douglas R Toomey, Sean C SolomonAbstract:We report the results of a microearthquake and seismic tomography experiment conducted along the southern half of the Mid-Atlantic Ridge segment at 29°N and aimed at investigating the relationship of earthquake and seismic structural characteristics to spreading processes. The seismic velocity structure is obtained from two-dimensional (2-D) and three-dimensional (3-D) tomographic inversions of travel times from shots along an axial refraction line. Inversion solutions indicate that the velocity structure in the lower crust is heterogeneous, with higher velocities and relatively thin crust near the segment end and lower velocities and a Thicker Layer 3 near the central bathymetrie high. The thickness of the lower crust at the segment end is asymmetric across axis, with thinner crust beneath the inside corner. The indicated variations in crustal thickness are consistent with those inferred from mantle Bouguer gravity anomalies. The microearthquakes located along axis during the 41-day recording period cluster in three separate along-axis regions: (1) the southern segment end near 28°55′N, (2) the central along-axis topographic high at 29°11′N, near and north of the Broken Spur hydrothermal vent field, and (3) a region midway between, beneath a volcano near 29°02′N. The greatest level of microearthquake activity was in a diffuse zone off axis beneath the inside corner of a nontransform offset. This pattern of off-axis microearthquake activity, and the cross-axis asymmetry in crustal thickness at the segment end, support tectonic models in which normal faulting and consequent crustal thinning occur preferentially at inside corner regions. Anomalous focal mechanisms for microearthquakes beneath the along-axis volcano and the significant seismicity beneath the axial volcanic ridge at the segment center, in contrast, may be the result of volcanic and hydrothermal processes, such as magma movement or thermal stresses generated near cooling plutons. A comparison of microearthquake characteristics with residual gravity data and velocity structure leads to the hypothesis that microearthquakes associated with areas of thin crust near the segment end and inside corner are dominantly tectonic in nature, whereas microearthquakes associated with volcanic and hydrothermal processes are more likely to occur toward the segment center in areas of greater rates of magma supply and Thicker crust. Along axis, well-resolved focal depths determined with a 3-D velocity model range from 3 to 6 km beneath the seafloor and do not shoal toward the segment center. These observations indicate that the thermal structure of the crust along this slow spreading ridge segment is not in steady state.
