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Thomas M Tillotson - One of the best experts on this subject based on the ideXlab platform.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Journal of Colloid and Interface Science, 2005Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micrometer particles and nonvolatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface enhanced Raman spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 μm pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Published in: Journal of Colloid and Interface Science vol. 282 no. 1 February 1 2005 pp. 80-86, 2004Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micron particles and non-volatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface Enhanced Raman Spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 micron pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid. This reduction in magnitude of the Surface attractive potential is in agreement with our observation that the phosphoric acid etch followed by detergent wash results in a decrease in Surface-adsorbed sub-micron particulates.
Philippe Marcus - One of the best experts on this subject based on the ideXlab platform.
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Origin of nanoscale heterogeneity in the Surface Oxide film protecting stainless steel against corrosion
npj Materials Degradation, 2019Co-Authors: Frédéric Wiame, Vincent Maurice, Philippe MarcusAbstract:Stainless steels are widely used as metal components owing to self-protection in aggressive environments, provided by an extremely thin Surface Oxide film enriched in chromium Oxide. Yet, despite decades of research, the mechanisms distributing the chromium enrichment at small length scale are poorly understood, although it may cause loss of stability and local failure of the corrosion resistance. Here we apply high resolution Surface analysis to investigate at small time and length scales the nucleation and growth mechanisms of the Surface Oxide on a model stainless steel. Starting from an Oxide-free Surface, we report the direct observation of the Oxide nucleation and local oxidation of chromium, which governs the nanoscale heterogeneity of the growing Surface Oxide by chromium pumping from the atomic terraces to the steps for preferential Cr(III) Oxide nucleation and subsequently by segregation from the atomic planes below to grow the Cr(III) layer incompletely saturating the stainless steel Surface. This work provides new insight on corrosion chemistry, by evidencing local chemical and structural defects self-generated at the nanoscale by the building process of the protective Oxide barrier, and affecting the passive film stability.
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Stainless steel Surface structure and initial oxidation at nanometric and atomic scales
Applied Surface Science, 2019Co-Authors: Li Ma, Frédéric Wiame, Vincent Maurice, Philippe MarcusAbstract:The durability of passivable metals and alloys is often limited by the stability of the Surface Oxide film, the passive film, providing self-protection against corrosion in aggressive environments. Improving this stability requires to develop a deeper understanding of the Surface structure and initial Surface reactivity at the nanometric or atomic scale. In this work we applied scanning tunneling microscopy to unravel the Surface structure of a model stainless steel Surface in the metallic state and its local modifications induced by initial reaction in dioxygen gas. The results show a rich and complex structure of the Oxide-free Surface with reconstructed atomic lattice and self-organized lines of Surface vacancies at equilibrium. New insight is brought into the mechanisms of initial oxidation at steps and vacancy injection on terraces leading to Cr-rich Oxide nuclei and locally Cr-depleted terraces, impacting the subsequent mechanism of chromium enrichment essential to the stability of the Surface Oxide.
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Passivation-Induced Physicochemical Alterations of the Native Surface Oxide Film on 316L Austenitic Stainless Steel
Journal of The Electrochemical Society, 2019Co-Authors: Zuocheng Wang, Vincent Maurice, Francesco Di-franco, Antoine Seyeux, Sandrine Zanna, Philippe MarcusAbstract:Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the Surface Oxide film providing corrosion resistance to 316L stainless steel. The as-prepared Surface is covered by a ∼2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated Oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have bandgap values of 3.0 and 2.6−2.7 eV, respectively, and the Oxide film would behave as an insulator. Electrochemical passivation in sulfuric acid solution causes the preferential dissolution of Fe(III) resulting in the thickness decrease of the outer layer and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III) enrichment of the inner layer causes loss of photoactivity and improved corrosion protection with the anodic shift of the corrosion potential and the increase of the polarization resistance by a factor of ∼4. Aging in the passive state promotes the Cr enrichment in the inner barrier layer of the passive film.
Nerine J Cherepy - One of the best experts on this subject based on the ideXlab platform.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Journal of Colloid and Interface Science, 2005Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micrometer particles and nonvolatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface enhanced Raman spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 μm pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Published in: Journal of Colloid and Interface Science vol. 282 no. 1 February 1 2005 pp. 80-86, 2004Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micron particles and non-volatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface Enhanced Raman Spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 micron pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid. This reduction in magnitude of the Surface attractive potential is in agreement with our observation that the phosphoric acid etch followed by detergent wash results in a decrease in Surface-adsorbed sub-micron particulates.
Gregory Jerkiewicz - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Duality of Platinum Surface Oxides in the Oxygen Reduction and Hydrogen Oxidation Reactions
Electrocatalysis, 2017Co-Authors: Sadaf Tahmasebi, Ashley A. Mcmath, Julia Drunen, Gregory JerkiewiczAbstract:In polymer electrolyte membrane fuel cells (PEMFCs), the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) take place on the Surface of platinum nanoparticles (Pt-NPs) residing on carbon support. Polycrystalline platinum (Pt(poly)) serves as a model polyoriented system due to its randomly oriented grains separated by grain boundaries, and research using Pt(poly) creates important background knowledge that is used to identify and understand electrochemical phenomena occurring in fuel cells. In this study, we report new results on the electrochemical behavior of Pt(poly) in 0.50 M H_2SO_4 aqueous solution saturated with reactive gases, namely O_2(g) and H_2(g). We analyze the influence of the potential scan rate over a broad range of values (1.00–50.0 mV s^−1) on the cyclic voltammetry (CV) behavior of Pt(poly). A comparative analysis of the impact of dissolved O_2 and H_2 on the electrochemical behavior of Pt(poly) is performed using CV profiles and capacitance transients. Their analysis reveals the existence of new features that are observed in the potential range corresponding to the Pt Surface Oxide formation and reduction. The results indicate that the Pt Surface Oxide reveals catalytic duality because it acts both as an inhibitor and a catalyst in both the ORR and HOR. In the case of the ORR, the anodic-going transients reveal that the process becomes inhibited as the Pt Surface Oxide develops, while in the cathodic-going transients, the reduction of Pt Surface Oxide significantly (ca. 65%) increases the reaction rate. In the case of the HOR, the anodic-going transients also reveal that the process becomes inhibited as the Pt Surface Oxide develops, while in the cathodic-going transients, the reduction of Pt Surface Oxide increases (ca. 15%) the reaction rate. The catalytic effect can be attributed either to changes in the Surface electronic structure that accompanies the Surface Oxide reduction or to short-lived increase in the electrochemically active Surface area. Graphical Abstract ᅟ
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Surface science and electrochemical analysis of nickel foams
ACS Applied Materials & Interfaces, 2012Co-Authors: Michal Grden, Mohammad Alsabet, Gregory JerkiewiczAbstract:Open-pore nickel (Ni) foams are characterized using Surface science and electrochemical techniques. A scanning electron microscopy analysis reveals interconnected Ni struts that generate small and large pores of ca. 50 and 500 μm in size, respectively. An X-ray photoelectron spectroscopy (XPS) analysis of the Surface-chemical composition of the Ni foams shows that there are oxidized and metallic sections within their Surfaces despite being prepared by sintering in an oxidizing atmosphere at a high temperature and being stored in moist air. The ratio of the areas of oxidized and metallic sections is evaluated using XPS data. Chemical etching of the Ni foams results in removal of the native Surface Oxide/hydrOxide without altering the three-dimensional structure; it also increases the roughness (R) of the Surfaces of Ni struts giving rise to an increase in the electrochemically active Surface area (Aecsa). Thermal treatment of Ni foams in an H2(g) atmosphere at 500 °C reduces the native Surface Oxide/hydrox...
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Surface Oxide growth at platinum electrodes in aqueous h2so4 reexamination of its mechanism through combined cyclic voltammetry electrochemical quartz crystal nanobalance and auger electron spectroscopy measurements
Electrochimica Acta, 2004Co-Authors: Gregory Jerkiewicz, Gholamreza Vatankhah, Jean Lessard, Manuel P Soriaga, Yeonsu ParkAbstract:Abstract The mechanism of platinum Surface electro-oxidation is examined by combined cyclic-voltammetry (CV), in situ electrochemical quartz-crystal nanobalance (EQCN) and ex situ Auger electron spectroscopy (AES) measurements. The CV, EQCN and AES data show that the charge density, interfacial mass variation and intensity of the O-to-Pt AES signal ratio increase in a continuous, almost linear manner as the potential is raised from 0.85 to 1.40 V. In addition, the charge density, mass variation and O-to-Pt signal ratio profiles follow each other, thus indicating that the Surface oxidation proceeds by a progressive coordination of O-containing species to the Pt substrate. The coupled CV and EQCN measurements lead to in situ determination of the molecular weight of the interfacial species; these were identified as chemisorbed O (Ochem) at 0.85≤E≤1.10 V and as O2− in the form of a Surface PtO at 1.20≤E≤1.40 V. The AES results reveal that the first half-monolayer of Ochem is formed through discharge of H2O molecules and such formed Ochem resides on the Pt Surface. Subsequent discharge of H2O molecules leads to formation of the second half-monolayer of Ochem that is accompanied by the interfacial place exchange of Ochem and Surface Pt atoms; this process results in the development of a quasi-3D Surface PtO lattice comprising Pt2+ and O2−. AES data demonstrate that the place-exchange process occurs in the 1.10–1.20 V potential range. The experimentally determined molecular weight of the species added to the Surface is 15.8 g mol−1, which points to O and to anhydrous PtO as the Surface Oxide formed.
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Independence of formation and reduction of monolayer Surface Oxide on Pt from presence of thicker phase-Oxide layers
Journal of Electroanalytical Chemistry, 1991Co-Authors: Brian E. Conway, Germano Tremiliosi-filho, Gregory JerkiewiczAbstract:Abstract On Pt Surfaces at which thick, phase-Oxide types of films have been generated by strong anodic oxidation, it is shown that, following incomplete reduction of the Oxide layer over the quasi-2-D Oxide reduction region, a regeneration of the quasi-2-D Surface Oxide can be achieved with the thick phase-Oxide layer remaining intact. The nature of the behaviour observed indicates that first the 2-D Oxide film must be formed with the 3-D film being subsequently generatable upon and above it under strong anodic polarization conditions. Upon reduction, the 2-D film is first reduced beneath the thick Oxide film, independently of subsequent reduction of the latter. These results suggest an independence of the 2-D processes occurring at the Pt-metal interface from the quasi-3-D film growth processes that can also take place, leading to thick films having electrochemical stabilities substantially greater than that of the quasi-2-D underlying film.
Anthony P Esposito - One of the best experts on this subject based on the ideXlab platform.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Journal of Colloid and Interface Science, 2005Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micrometer particles and nonvolatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface enhanced Raman spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 μm pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid.
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characterization of an effective cleaning procedure for aluminum alloys Surface enhanced raman spectroscopy and zeta potential analysis
Published in: Journal of Colloid and Interface Science vol. 282 no. 1 February 1 2005 pp. 80-86, 2004Co-Authors: Nerine J Cherepy, Tien H Shen, Anthony P Esposito, Thomas M TillotsonAbstract:We have developed a cleaning procedure for aluminum alloys for effective minimization of Surface-adsorbed sub-micron particles and non-volatile residue. The procedure consists of a phosphoric acid etch followed by an alkaline detergent wash. To better understand the mechanism whereby this procedure reduces Surface contaminants, we characterized the aluminum Surface as a function of cleaning step using Surface Enhanced Raman Spectroscopy (SERS). SERS indicates that phosphoric acid etching re-establishes a Surface Oxide of different characteristics, including deposition of phosphate and increased hydration, while the subsequent alkaline detergent wash appears to remove the phosphate and modify the new Surface Oxide, possibly leading to a more compact Surface Oxide. We also studied the zeta potential of <5 micron pure aluminum and aluminum alloy 6061-T6 particles to determine how Surface electrostatics may be affected during the cleaning process. The particles show a decrease in the magnitude of their zeta potential in the presence of detergent, and this effect is most pronounced for particles that have been etched with phosphoric acid. This reduction in magnitude of the Surface attractive potential is in agreement with our observation that the phosphoric acid etch followed by detergent wash results in a decrease in Surface-adsorbed sub-micron particulates.
