Composition Of Oxide Layer Research Articles

Effect of Nanosize SiO2 Particles Added into Electrolyte on the Composition and Morphology of Oxide Layers Formed in Alloy AK6M2 Under Microarc Oxidizing

Oxide layers formed on AK6M2 aluminum-silicon alloy by microarc oxidizing (MO) are studied. The chemical and phase compositions and the morphology of the layers deposited from a base-composition electrolyte with different contents of added SiO2 powder are determined. It is shown that high-temperature phases form in the oxide layer at a specific concentration of SiO2 nanoparticles. This indicates elevation of the effective temperature in the zone of synthesis of the oxide layers in the process of MO. The addition of nanosize particles of SiO2 into the electrolyte influences positively the operating characteristics of the formed oxide layer.

Effect of rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn alloy anodes during copper electrowinning

The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the properties of the anodes and rolling techniques during copper electrowinning. The anode process was investigated via anodic polarization curves, cyclic voltammetry curves, electrochemical impedance spectra, and corrosion tests. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. Observable variations in the electrocatalytic activity and reaction kinetics of anodes during electrowinning indicated that the electrochemical behavior of the anodes was strongly affected by the rolling technology. An increase in the rolling number tended to decrease the oxygen evolution overpotential and the corrosion rate of the anodes. These trends are contrary to that of the apparent exchange current density. Furthermore, the intensities of diffraction peaks associated with PbO, PbOx, and α-PbO2 tended to increase with increasing rolling number. In addition, the rolled anodes exhibited a more uniform microstructure. Compared with one-way rolled anodes, the eight-time cross rolled anodes exhibited better electrocatalytic activity and improved corrosion resistance.

Characterization Of Oxide Layers Produced On The AISI 321 Stainless Steel After Annealing

Abstract In this study, the structure, chemical composition and topography of oxide layers produced on the surface of the AISI 321 austenitic steel in the annealing process were analyzed. Heat treatment was done at 980°C temperature for 1 hour time in different conditions. The annealing was done in a ceramic furnace in oxidation atmosphere and in vacuum furnaces with cylindrical molybdenum and graphite chambers. The analysis was carried out using the following methods: a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray spectrometer (EDX), an X-ray diffractometer (XRD), a secondary ion mass spectrometer with time-of-flight mass analyzer (TOF SIMS) and an atomic force microscope (AFM). The oxide layer formed during annealing of the AISI 321 steel at 980°C consisted of sub-layers, diversified in the chemical composition. The thickness of the oxidized layer is depended on the annealing conditions. In a ceramic furnace in oxidation atmosphere, the thickness of the oxide layer was of 300-500 nm, in a vacuum furnace with molybdenum and graphite heating chambers, it ranged from 40 to 300 nm and from a few to 50 nm, respectively. TOF SIMS method allows to get average (for the surface of 100 μm × 100 μm) depth profiles of concentration of particular elements and elements combined with oxygen. In oxide layers formed in vacuum furnaces there are no iron oxides. Titanium, apart from being bounded with carbon in carbides, is a component of the oxide layer formed on the surface of the AISI 321 steel.

Effect of processing parameters on pore opening and mechanism of voltage pulse detachment of nanoporous anodic alumina

The free-standing through-hole porous alumina membranes (PAMs) were fabricated by two-step self-organized anodization of aluminum in oxalic acid followed by the subsequent voltage pulse detachment performed in an environmental-friendly solution based on HClO4 and C2H5OH. The effects of oxalic acid concentration used for anodic oxide synthesis and the chemical composition of the barrier oxide layer on the effective detachment of PAMs were studied. On the other hand, the voltage detachment conditions such as applied voltage, number of pulses, and temperature of electrolyte were tested as parameters which might affect the detachment of PAMs and their bottom side morphology. It was found that the voltage detachment process is affected by applied detachment voltage while the bottom surface morphology of detached PAMs is influenced by oxalic acid concentration used for anodization, the chemical composition of the barrier oxide layer, and the time gap between anodization and detachment (storage period). Furthermore, it was revealed that number of applied pulses and electrolyte temperature maintained during the detachment have a little effect on the morphology of PAM films. The most feasible and detailed mechanism of the voltage pulse detachment, considering the individual stages of the process, was proposed. At the beginning, the mechanism was related to an electric field assisted dissolution of oxide enhanced by its chemical dissolution induced by Joule's heating. These processes occur at the pore bottoms upon application of the voltage pulse and results in pore widening and thinning of the barrier layer. Then, after the electrical breakdown of the barrier layer, the intensive electropolishing of aluminum at the metal/oxide interface takes place.

Effects of Oxide Layer Composition and Radial Compression on Nickel Release in Nitinol Stents

There is a public health need to understand the effects of surface layer thickness and composition on corrosion in nickel-containing medical devices. To address this knowledge gap, five groups of Nitinol stents were manufactured by various processing methods that altered the titanium oxide layer. The following surfaces were created: >3500 nm thick mixed thermal oxide (OT), ~420 nm thick mixed thermal oxide (SP), ~130 nm thick mixed thermal oxide (AF), ~4 nm thick native oxide (MP), and an ~4 nm thick passivated oxide (EP). Radially compressed and not compressed devices were evaluated for nickel (Ni) ion release in a 60-day immersion test. The results indicated that OT stents released the most Ni, followed by stents in the SP and AF groups. For OT and SP stents, which exhibited the thickest oxide layers, radial compression significantly increased Ni release when compared to non-compressed stents. This result was not observed in AF, MP, SP stents indicating that the increased Ni release may be explained by cracking of the thicker oxide layers during crimping. Strong correlations were observed between oxide layer thickness and cumulative Ni release. These findings elucidate the importance of oxide layer thickness and composition on uniform corrosion of laser-cut Nitinol stents.

Oxidation of α-brass: A photoelectron spectroscopy study

The oxidation of Cu0.7Zn0.3(111) exposed to O2 at low pressure (7.0×10−7mbar) and higher pressure (1mbar) both at 400K has been investigated by photoelectron spectroscopy. The results evidenced a preferential oxidation of Zn at the surface in agreement with the literature and Zn segregation to the surface. Moreover, a systematic fitting procedure of high-resolution spectra enabled us to decompose the Zn 2p core-level peak into metallic and oxide components in order to follow the growth of the oxide. By combining these results with careful analysis of the Zn L3M45M45 Auger transition, we evidenced the formation of a discontinuous ZnO layer (3D ZnO islands) in both pressure conditions. Measurements of the O 1s peak for two photon energies using synchrotron radiation allowed us to identify interface and bulk components. Changes in the Zn 3d level and valence band during the initial steps of oxidation were also followed. We show that not only thermodynamics but also kinetic effects have to be considered to describe this complex oxidation process. The importance of the role played by the structural quality of the sample on the composition, growth kinetic and structure of the surface oxide layer is evidenced.

Characterization of dielectric layers grown at low temperature by atomic layer deposition

Dielectric films, such as hafnium dioxide (HfO2), aluminum oxide (Al2O3), zirconium dioxide (ZrO2), titanium dioxide (TiO2) and their composite layers are deposited on polycrystalline and amorphous substrates by the atomic layer deposition (ALD) method. We demonstrate that the use of this technology guarantees a uniform and controlled surface coverage in the nanometer scale at low temperatures (in our case, below 100°C). Modification of the composition of oxide layers allows the deposition of materials with quite different absorption coefficients, refractive indexes and dielectric constants. In particular, we demonstrate structural, electrical and optical properties of dielectric layers and test metal-oxide-semiconductor structures with these oxide materials. Our good quality dielectric layers, obtained at low-temperature ALD, are characterized by a high dielectric constant (above 10), very smooth surface, wide energy gap (above 3eV), low leakage current (in the range of 10−8 A/cm2 at 1V), high dielectric strength (even 6 MV/cm) and high refractive indexes (above 1.5 in the visible spectral range).

Application of PIGE, BS and NRA techniques to oxygen profiling in steel joints using deuteron beam

In order to study the oxygen content and to characterize the oxygen depth profile on the surface of welded steel joints in the function of the applied shielding gases, particle induced gamma-ray emission (PIGE), backscattering spectrometry (BS) and nuclear reaction analysis (NRA) methods were used. The measurements were carried out at 1.0, 1.4 and 1.8MeV deuteron energies. From the PIGE oxygen and carbon elemental maps (1000×1000μm2) taken with a beam of 2×2μm2 beam size, oxygen rich regions were chosen for the depth profile analysis. The investigated depth was ∼6μm using particle detection (BS, NRA), which was extended to ∼11μm with the application of the differential-PIGE method, using the numerical integration of experimental cross-section data. The oxygen depth profiles show systematic discrepancy in the oxide layer thickness and composition between the two different kind of shielding gases.

Optimization of the 3-Point Bending Failure of Anodized Aluminum Formed in Tartaric/Sulphuric Acid Using Doehlert Design

The bending failure of anodized aluminum in tartaric/sulphuric acid bath was modeled using Doehlert design. Bath temperature, anodic current density, sulphuric acid, and tartaric acid concentrations were retained as variables. Thickness measurements and 3-point bending experiments were conducted. The deflection at failure (D f) and the maximum load (F m) of each sample were, then, deducted from the corresponding flexural responses. The treatment of experimental results has established mathematical models of second degree reflecting the relation of cause and effect between the factors and the studied properties. The optimum path study of thickness, deflection at failure, and maximum load, showed that the three optima were opposite. Multicriteria optimization using the desirability function was achieved in order to maximize simultaneously the three responses. The optimum conditions were: C tar = 18.2 g L−1, T = 17.3 °C, J = 2.37 A dm−2, C sul = 191 g L−1, while the estimated response values were e = 57.7 µm, D f = 5.6 mm, and F m = 835 N. Using the established models, a mathematical correlation was found between deflection at failure and thickness of the anodic oxide layer. Before bending tests, aluminum oxide layer was examined by scanning electron microscopy (SEM) and atomic force microscopy. After tests, the morphology and the composition of the anodic oxide layer were inspected by SEM, optical microscopy, and glow-discharge optical emission spectroscopy.

Effect of Ca on the Behavior of Double Oxide Film Defects in Commercially Pure Aluminum Melt

The change in the composition of oxide layers and the possibility of the formation of bonding between the two layers of a double oxide film defect when held in Al-0.01 and 0.05 wt pct Ca melt was investigated, and the thermodynamics of the transformations occurring in the Al-Ca-Al2O3 system was studied. The defect was modeled experimentally by maintaining two aluminum oxide layers in contact with one another in the liquid metal at 1023 K (750 °C) for times ranging from 5 seconds to 50 hours. Any changes in the composition and morphology of these layers were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the initial Al2O3 layer started to transform to a mixture of calcium aluminates in both alloys when the Al bars were still in the solid state. This transformation caused the two oxide layers to bond with each other gradually after the bars melted. The degree of bonding, however, was not consistent between the repetitions of the experiments, which was attributed to the difference between the initial H content of the melt on different experimental days.

Characterisation of coloured TiOx/Ti/glass systems

This paper presents a study of the optical properties, microstructure and chemical composition of titanium oxide layers deposited on Ti film using gas injection magnetron sputtering (GIMS). The samples are examined by means of spectroscopic ellipsometry, atomic force microscopy and X-ray photoelectron spectroscopy. The investigation is complemented by colorimetric measurements. The influence of deposition time on the thickness of dielectric layers has been found. A comprehensive analysis of effective dielectric functions of titanium and titanium oxide films is presented. The thickness of titanium oxide film ranges from 13nm to 54nm and directly determines the colour of a sample from gold to blue, respectively.

Influence of extracellular polymeric substances (EPS) from Pseudomonas NCIMB 2021 on the corrosion behaviour of 70Cu–30Ni alloy in seawater

Copper alloys, often used in cooling circuits of industrial plants using seawater as coolant, can be affected by biocorrosion induced by biofilm formation. Extracellular polymeric substances (EPS) produced by bacteria play a fundamental role in the different stages of biofilm formation, maturation and maintenance. The influence of loosely bound (LB) and tightly bound (TB) EPS, extracted from marine Pseudomonas NCIMB 2021, on the electrochemical behaviour of 70Cu–30Ni (wt.%) alloy in static artificial seawater (ASW) and on the chemical composition of oxide layers was studied by combined electrochemical measurements (polarization curves, EIS) and surface analysis (XPS, ToF-SIMS). Results were compared with those obtained in the presence of bovine serum albumin (BSA), a model protein. Compared to 70Cu–30Ni alloy in static ASW without biomolecules, for which a thick duplex oxide layer (outer redeposited Cu2O layer and inner oxidized nickel layer) is shown, the presence of BSA, TB EPS and LB EPS leads to a mixed oxide layer (oxidized copper and nickel) with a lower thickness. In the biomolecules-containing solutions, this oxide layer is covered by an adsorbed organic layer, mainly composed of proteins. A model is proposed to analyse impedance data obtained at the corrosion potential. The fitting procedure of impedance diagrams allows extracting the anodic charge transfer resistance, from which the corrosion current density can be calculated. The results show a slow-down of the anodic reaction in the presence of biomolecules (BSA, TB EPS and LB EPS), and a corrosion inhibition effect by LB EPS and to a lesser extent by BSA. No detrimental effect is evidenced with TB EPS.

Synthesis and Electrochemical Characterization of P2- and O3-Phase Na2/3Fe1/2Mn1/2O2 Layered Oxide

The commercial success of Li-ion batteries over last decades leads to large investments in developing safer battery with bigger capacity and less expensive materials and the application of Li-ion battery is being explored for EV and beyond these days[1]. However, expending the use of Li-based battery to a large electricity storage system for grid support may be more realistic if more abundant earth element could be utilized. One of the fine candidate to replace Li ion in large scale battery facility would be Na ion which is one of the most abundant element in earth´s crust[2] and sea water.Layered oxides, NaMO2 (M = Cr, Mn, Fe, Co, Ni, and mixture of 2-3 transition metal) show one of the largest capacities among the Na-ion cathode candidates due to their structural simplicity. Particularly, Na(FeMn)O2[3] is of great interest because Fe and Mn are abundant and environmentally benign. Recently, one of the largest capacities was reached with P2-phase Na2/3Fe1/2Mn1/2O2[4]. O3-phase of the same composition, however, could not be prepared because each phase depends on the Na concentration[3].Here, we report synthesis and direct comparison of electrochemistry between P2- and O3-phase Na2/3Fe1/2Mn1/2O2. The pure phases of P2 and O3 are confirmed by XRDs as shown in figure 1 and we have obtained a similar electrochemical performance in terms of capacity and cyclability for both phases. Our focus is to rationalize electrochemical behavior based on the structural types and Na surrounding environment while keeping the composition of oxide layer the same. Figure 1. XRD pattern matching of a) P2-Na2/3Fe1/2Mn1/2O2 and b) O3-Na2/3Fe1/2Mn1/2O2.[1] M. Armand, J.-M. Tarascon, Nature, 451, 652 (2008).[2] S. R. Taylor, Geochim. Cosmochim. Acta., 28, 1273 (1964).[3] J. S. Thorne, R. A. Dunlap, M. N. Obrovac, J. Electrochem. Soc., 160, A361 (2013).[4] N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada, S. Komaba, Nature Mater., 11, 512 (2012).

High Temperature Oxidation Behavior of SUS310S Austenitic Stainless Steel

The oxidation behavior of SUS310S austenitic stainless steels was studied in isothermal conditions at different temperatures between 800oC and 1100oC for 96h in air. The oxidation kinetics was analyzed, the surface and cross-section of the oxide scale grown by oxidation were characterized by using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffusion (XRD) and X-ray photoelectron spectroscopy (XPS). The SUS310S steel has high oxidation resistance at 800oC and with the increase of the temperature, the parabolic rate constants is constantly increasing. Examination of the morphology and composition of oxide layers reveals a double-layer structure, The inner layer is mainly chromium oxide (Cr2O3) and is covered by an uneven thinness outer layer of manganese-chromium or iron-chromium spinel oxide.

Electrochemical behavior of rolled Pb–0.8%Ag anodes in an acidic zinc sulfate electrolyte solution containing Cl− ions

In this study, the oxygen evolution kinetics and oxide layer properties of Pb–0.8%Ag rolled-alloy anodes were investigated during 15d of galvanostatic electrolysis in an acidic zinc sulfate electrolyte solution containing 600mg·L−1 Cl− ions. Cyclic voltammetry, quasistationary polarization, and electrochemical impedance spectroscopy were used to investigate the anode process. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. The observable variations in the electrocatalytic activity and reaction kinetics of the anodes during electrolysis indicate the formation and stabilization of the anodic oxide layer. With prolonged electrolysis, the oxygen evolution overpotential in the anodes mainly exhibited a decreasing trend, which is contrary to the trend of the electrode surface exchange current density. This depolarization may have been caused by the increasing roughness of the anodic surface and the catalytic effects of α-PbO2 and β-PbO2. As electrolysis continued, the cathodic peak (α-PbO2→PbSO4) mainly showed an increasing trend and gradually moved toward the negative direction. After 15days of electrolysis, the oxide layers exhibited a severely corrosive microstructure with plenty of cavities and etch pits. The uniform, well-defined crystal grains and regularity were not appeared. The phase composition of the anodic oxide layer was formed after 6d of electrolysis. α-PbO2 proved to be the main peak and showed preferential growth orientations along the (111) planes of the anodic oxide layer.

Oxidation states of GaAs surface and their effects on neutral beam etching during nanopillar fabrication

We have investigated a new process for fabricating GaAs sub-20 nm nanopillars that uses a top–down combination of a bio-template and damage-free neutral beam etching. A two-dimensional array of nanoparticles composed of a protein shell embedded with a metal oxide core was formed on the top of a GaAs surface treated by neutral beam oxidation. Because of device requirements, three low-temperature oxygen techniques were investigated for removing the protein shell prior to the etching process: oxygen radical, oxygen neutral beam, and low-temperature oxygen annealing in vacuum (LT-OAV). X-ray photoelectron spectroscopy was used to monitor the effects of the different treatments on the GaAs surface. While the three processes could efficiently remove a protein shell, subsequent oxidation of the GaAs surface showed some differences in the oxide layer composition. Therefore, LT-OAV was selected considering its lower gallium oxide formation. A hydrogen radical process was then performed at temperatures lower than 400 °C to remove the oxide layer prior to etching. This process completely removed arsenide oxide and only residual gallium oxide was found on the surface afterwards. Etching was performed using a pure chlorine neutral beam of GaAs samples with metal oxide core etching masks. We found that control of the Ga-oxide amount on the surface is the key parameter for controlling the diameter and the density of nanopillars. Finally, high-aspect ratio nanopillars using stacked layers of GaAs and AlGaAs were obtained and showed no damage layer.

Surface Characterization of Magnesium Anodized in a 10M KOH Electrolyte

Magnesium (Mg) is a promising implant material for orthopedic applications due to its biodegradability and desirable mechanical properties. However, in order for Mg to have widespread clinical applications, engineering solutions that address the rapid degradation in physiological environments and promote bone-forming activity are needed. The objective of this study was to develop an anodization process using a toxicant-free electrolyte to modulate nanoscale surface features and surface chemistry on Mg. Anodic polarization and potentiostatic anodization tests were used to evaluate the effect of applied potential on surface morphology of Mg in a 10 M KOH electrolyte. Nucleation of oxides as a function of anodization duration was also investigated in order to optimize the synthesis process. The alkaline electrolyte used for anodization of Mg offers an alternative to commercial processes that use hazardous elements. The anodized samples were annealed to investigate the effect of thermal treatments on surface morphology and chemical composition. The nanostructure and chemical composition of the anodized and annealed Mg substrates were characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy. Our results showed that the nanostructures and chemical composition of anodically-generated oxide layers on Mg are specific to each oxidation process in a 10 M KOH electrolyte. Furthermore, results indicated that anodization durations of two hours generated surface oxide layers with homogeneous topography on the Mg substrates atapplied potentials of 0.5 V, 1.5 V and 2 V.. This study showed a promising approach for creating nanoscale surface features on Mg for improved bioactivity and degradation property.

A Study on the Effect of Heat Treatment and Magneto-Electropolishing on in-Vitro Corrosion and Surface Properties of Ternary Nitinol

The development of new materials with tailored properties has found wide application in the medical, automobile and electronic industries. Ternary Nitinol alloys are a class of such emerging materials that require further research and development for application in such industries. Heat treatment is known to affect their transformation temperature, oxide layer composition, wettability and flexibility that directly impact their biocompatibility, performance and ease of installation. Magneto-electropolishing affords a thin and compact oxide layer that renders corrosion resistance, nano-textured morphology with reduced thrombogenicity. This investigation assessed the effect of heat treatment and magneto-electropolishing on the surface chemistry and corrosion resistance of NiTi10Ta. Martensitic phase transformation, a crucial parameter that determines the alloy’s application was determined using a differential scanning calorimeter (DSC). Electrochemical impedance spectroscopy (EIS) and potentiodynamic tests were performed as per ASTM standards to assess corrosion resistance. Surface topography, morphology, surface chemistry and crystallinity were determined using atomic force microscopy (AFM), scanning electron microscopy (SEM)/ Energy-dispersive X-ray spectroscopy (EDS) and x-ray diffraction (XRD) respectively.

Surface characterisation of Ti–15Mo alloy modified by a PEO process in various suspensions

This paper reports on the surface modification of a Ti–15Mo alloy by plasma electrolytic oxidation (PEO). This process was carried out in solutions of 0.1M Ca(H2PO2)2 with various concentrations of tricalcium phosphate (Ca3(PO4)2), wollastonite (CaSiO3), or silica (SiO2) using voltages of up to 350V. The surface microstructure (SEM, cross-section of coating), roughness and chemical composition (energy-dispersive X-ray spectroscopy, thin layer X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy) of the porous oxide layers were investigated. The concentration of powder added to the solution changed the chemical composition and morphology of PEO coatings on the Ti–15Mo alloy surface. Calcium and phosphorous compounds were detected in the coatings formed on the substrate by the PEO process at 300V.

Emissivity, catalycity and microstructural characterization of ZrB2–SiCfiber based UHTC at high temperature in a non-equilibrium air plasma flow

ZrB2-based Ultra-High Temperature Ceramics (UHTC) could be used at temperatures above 2000K, a typical limit of most structural ceramics such as SiC-coated C/C composites. In particular, UHTC are candidate materials for thermal protection systems (TPS) for the new sharp-shaped hypersonic re-entry vehicles. Among the open points of research on UHTC materials is the characterization of surface properties like emissivity and catalycity in the high temperature range. High emissivity and low surface catalycity towards the exothermal recombination of oxygen atoms will improve the material performance in re-entry conditions by reducing temperature gradients and thermal stresses.In this paper are presented and discussed the experimental results of emissivity and catalycity of two different UHTC materials based upon the ZrB2–SiCfiber composition with different sintering additives (Si3N4 or ZrSi2). Microstructural characterization by SEM, XRD and XPS have shown oxidation-induced surface modifications with oxide layers composed of silica with trace amounts of boron oxide and zirconia if the maximum reached temperature is lower than about 1800K and only zirconia for higher temperatures. The differences in the oxide layer composition may account for the different thermal radiative properties and catalytic behavior.