Characterization Of Surface Oxide Films Research Articles

Electrochemical Characterization of Surface Oxide Films Formed on Silicon Electrodes in 3% Sodium Chloride

The study focused on the effect of cooling rate on the behaviour of oxide layers formed on silicon (Si) electrodes in 3% Sodium Chloride. All analysis conducted by electrochemical and spectral techniques confirmed that the stability of the silicon oxide film is influenced by the cooling kinetic used in the manufacturing process of Si material. The electronic structure model studied by Mott-Schottky measurements describes the passive film as a hetero-junction (p-n) composed of a metal/Si oxides interface and Si hydroxides/electrolyte interface.

Effect of High Temperature Oxidation Process on Corrosion Resistance of Bright Annealed Ferritic Stainless Steel

The corrosion resistance of stainless steels is determined by the thickness, structure, composition and electronic properties of the oxide layers grown on their surface and isolating the metallic substrate from the environment. In the present work, ex situ XPS (X-Ray Photoelectron Spectroscopy) and ToF-SIMS (Time of Flight Secondary Ions Mass Spectrometry) have been combined to in situ PCS (PhotoCurrent Spectroscopy) in order to perform an integrated physicochemical characterization of surface oxide films grown on bright annealed ferritic stainless steel (AISI 434) as-received and after thermal post-treatment in air. The surface oxide film on as-received samples has a bilayer structure with an inner layer close to pure Cr(III) oxide and an outer layer of mixed Fe(III) and Cr(III) oxide enriched in Cr. After thermal post-treatment in air at 350°C and 550°C, the surface oxide films thicken and the outer layers are enriched in Fe(III). Linear voltammetry and electrochemical impedance spectroscopy analysis evidence a decrease of the polarization resistance in the passive range, a cathodic shift of the corrosion potential and an increased cathodic current after thermal post-treatment. The bilayer structure, composition and electronic properties of these surface oxide films and their modifications are discussed to rationalize their corrosion behavior.

First experiences on characterization of surface oxide films in powder particles by Glow Discharge Optical Emission Spectroscopy (GD-OES)

The surface characteristics of the powder particles play a key role on the processing of the powders to consolidated products and on the final properties achieved for the material. Characterization of surface oxide films by techniques commonly used such as X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy provide reliable information on the surface films, but they are time-consuming methods and the analyzed areas are very limited. In this evaluation, the potential of the depth profile analysis by Glow Discharge Optical Emission Spectroscopy (GD-OES) is experimented for loose powder particles for the first time. Hitherto, the lack of a sample preparation technique has hindered the use of this powerful surface analysis technique for loose powder.

Characterization of surface oxide films and oxygen distribution in α–W nanopowders produced in a DC plasma reactor from an oxide feedstock

Surface oxide films on α–W nanopowders (average particle size 60nm) have been characterized with X-ray photoelectron spectroscopy (XPS), evolved gas analysis (EGA), and high-resolution transmission electron microscopy (HRTEM). The nanopowders were synthesized from a tungsten trioxide feedstock in a DC thermal plasma reactor operating with a hydrogen-bearing plasma gas. The as-synthesized materials were annealed either under a vacuum or flowing hydrogen, passivated by exposure to trace amounts of oxygen in an argon-filled glove box, and stored in dry air for 1month. Based on XPS analysis, the formed films were composed of a tungsten trioxide (WO3) ranging in thickness from 0.4 to 1.5nm as a function of the post-synthesis history. Based on EGA analysis, the surface oxygen uptake of the nanopowders varied from 0.6 to 2.0mgm−2, which is consistent with the measured film thickness. HRTEM revealed the amorphous nature of the oxide films and their uniform distribution over the surface of the individual particles. The materials contained small amounts of bulk oxides due to the incomplete conversion of the feedstock in the plasma process, and the bulk and surface oxides were differentiated using EGA.

Synthesis and characterization of surface oxide films on CoGa(100)

It has been shown that a Ga2O3 film forms on the surface of CoGa alloy crystals when exposed to oxygen (Pan, 2001 and Vlad, 2010). In this work we report the results of the characterization of surface oxides on CoGa(100) using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), and ion scattering spectroscopy (ISS). The oxides were synthesized using either O2 or NO2 as the oxidant at 300K or in excess of 700K. ISS scans showed that cobalt was always present in the top surface layer regardless of oxidation conditions. XPS showed that depending on the oxidant and the temperature, the composition of the oxide films vary depending on oxidation treatment, with some oxides being nearly all Ga2O3 and ordered with a sharp LEED pattern consisting of (2×1) domains rotated by 90º and others being Co–Ga mixed oxides that gave no diffraction pattern.

Measurement methods for surface oxides on SUS 316L in simulated light water reactor coolant environments using synchrotron XRD and XRF

Synchrotron X-ray diffraction (XRD) and X-ray fluorescent (XRF) measurement techniques have been used for non-destructive characterization of surface oxide films on Type 316L austenitic stainless steels that were exposed to simulated primary water environments of pressurized water reactors (PWR) and boiling water reactors (BWR). The layer structures of the surface spinel oxides were revealed ex situ after oxidation by measurements made as a function of depth. The layer structure of spinel oxides formed in simulated PWR primary water should normally be different from that formed in simulated BWR water. After oxidation in the simulated BWR environment, the spinel oxide was observed to contain NiFe2O4 at shallow depths, and FeCr2O4 and Fe3O4 at deeper depths. By contrast, after oxidation in the simulated PWR primary water environment, a Fe3O4 type spinel was observed near the surface and FeCr2O4 type spinel near the interface with the metal substrate. Furthermore, by in situ measurements during oxidation in the simulated BWR environment, it was also demonstrated that the ratio between spinel and hematite Fe2O3 can be changed depending on the water condition such as BWR normal water chemistry or BWR hydrogen water chemistry.

Characterization of Surface Oxide Films and Cell Toxicity Evaluations with a Quenched Titanium Surface

This study characterizes the surface of the oxide film that forms on titanium metal through the use of thermal and quenching treatments in cold water and investigates the effects of the surface characteristics and cellular interactions of a modified titanium surface. A range of sample groups were prepared in heat treatments of pure titanium at 600°C, 700°C, 800°C, 900°C, and 1000°C and subsequent quenching in cold water. The surface topography, roughness, crystallite size and crystal intensity were found to depend on the heating temperature. An increased surface roughness was observed with increases in the heating temperature and the quenching. The surface roughness was in the range of 0.15 μm–1.07 μm. In vitro cell responses were evaluated with mouse osteoblast MC3T3 cells in terms of cell proliferation and differentiation. MTT assays showed an increase in the living cell density and proliferation upon heating and quenching the titanium surface. The results of this study indicate that the cell toxicity was sensitive to the surface roughness and that it decreased as the roughness of the Ti increased.

Characterization of air-formed surface oxide film on Ti–29Nb–13Ta–4.6Zr alloy surface using XPS and AES

The surface oxide film on a Ti–29Nb–13Ta–4.6Zr alloy (TNTZ) was precisely characterized using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to understand the composition and chemical state of the surface oxide film of TNTZ. For comparison, the component metals, titanium, niobium, tantalum, and zirconium, were also characterized to consider the effect of those on the formation of the surface oxide film on their alloy. The characterization of the surface oxide films on TNTZ and its component revealed the following issues. The surface oxide film on TNTZ consists of a composite oxide that contains titanium, niobium, tantalum, and zirconium but forms continuous layer and is very thin, ca. 3.7 nm. The oxide film is not completely oxidized because it contains various valences of cations. In particular, the oxidation of tantalum is inhibited in the oxide. Tantalum is enriched in the substrate in TNTZ just under the surface oxide because of this inhibition in the oxidation. The formation of the surface oxide film in TNTZ is predominantly governed by titanium. The preferential oxidation of an element is not always dependent on the initial oxidation potential of that element, the relationship between the oxidation energy from a smaller valence to a larger valence, and the dehydration process. In other words, a complicated competition governs the resultant composition of surface oxide.

Characterization of Surface Oxide Film Formed on Ti–8Fe–8Ta–4Zr

We have already developed a novel β-type titanium alloy, Ti–8Fe–8Ta–4Zr, for biomedical applications. Ti–8Fe–8Ta–4Zr showed higher strength than conventional biomedical titanium alloys, such as Ti–6Al–4V ELI, Ti–6Al–7Nb, and Ti–13Nb–13Zr. In addition, the alloy also showed higher corrosion resistance than cp-Ti and Ti–6Al–4V ELI in Hanks’ solution. In particular, the breakdown potential of the alloy (the pitting potential) was over 3.5 V vs. SCE (saturated calomel electrode) and much higher than those of cp-Ti and Ti–6Al–4V ELI. A slightly active region was observed at about 1.7 V vs. SCE that may be related to the high breakdown potential.In this study, the surface oxide films on Ti–8Fe–8Ta–4Zr after anodic polarization at 1 and 3 V in Hanks’ solution were characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy to elucidate the high corrosion resistance mechanism of the alloy in Hanks’ solution. In addition, the surface oxide film on the alloy before anodic polarization was also characterized for comparison.The surface oxide film on Ti–8Fe–8Ta–4Zr is grown with anodic polarization. Calcium phosphate is formed on the alloy after polarization. The corrosion resistance of the alloy after polarization at a potential above 1.7 V is improved by the concentration of iron and titanium in the surface oxide film. A titanium hyper-oxidized layer with a low iron concentration is observed within the surface oxide film. This layer is generated with polarization and worked as a corrosion-protective layer. The slight active region on the polarization curve may be caused by the dissolution of iron and titanium.

Characterization of surface oxide films on titanium and adhesion of osteoblast

The relationship between surface characteristics of titanium and initial interactions of titanium-osteoblasts was investigated. Titanium plates were heat-treated in different oxidation atmospheres. The third passage rabbit osteoblasts were cultured on the titanium plates for 24 h. After the heat-treatment, the crystal structure of the surface oxide films on titanium was identified using X-ray diffractometer and X-ray photoelectron spectroscopy (XPS). The surface roughness of titanium was measured with a profilometer. The surface energy was obtained by measurement of contact angles and calculation with Owens–Wendt–Kaeble's equation. The amount of surface hydroxyl (OH) s groups was examined using XPS. The change of binding energy of the some elements on the substrate surface suggested that the interactions between the cells and the titanium involved chemical reactions. The greater surface roughness, higher surface energy and more surface hydroxyl groups resulted in greater numbers of adhered osteoblasts and higher cell activity. Compared to the acidic hydroxyl (OH) a groups in (OH) s groups and the dispersion component of the total surface energy, the basic hydroxyl (OH) b groups and the polar component play more important roles in the osteoblast–titanium interaction.

Characterization of surface oxide films on titanium and bioactivity.

Biological properties of titanium implant depend on its surface oxide film. In the present study, the surface oxide films on titanium were characterized and the relationship between the characterization and bioactivity of titanium was studied. The surface oxide films on titanium were obtained by heat-treatment in different oxidation atmospheres, such as air, oxygen and water vapor. The bioactivity of heat-treated titanium plates was investigated by immersion test in a supersaturated calcium phosphate solution. The surface roughness, energy morphology, chemical composition and crystal structure were used to characterize the titanium surfaces. The characterization was performed using profilometer, scanning electronic microscopy, ssesile drop method, X-ray photoelectron spectroscopy, common Bragg X-ray diffraction and sample tilting X-ray diffraction. Percentage of surface hydroxyl groups was determined by X-ray photoelectron spectroscopy analysis for titanium plates and density of surface hydroxyl groups was measured by chemical method for titanium powders. The results indicated that heat-treatment uniformly roughened the titanium surface and increased surface energy. After heat-treatment the surface titanium oxide was predominantly rutile TiO(2), and crystal planes in the rutile films preferentially orientated in (1 1 0) plane with the highest density of titanium ions. Heat-treatment increased the amount of surface hydroxyl groups on titanium. The different oxidation atmospheres resulted in different percentages of oxygen species in TiO(2), in physisorbed water and acidic hydroxyl groups, and in basic hydroxyl groups on the titanium surfaces. The immersion test in the supersaturated calcium phosphate solution showed that apatite spontaneously formed on to the rutile films. This revealed that rutile could be bioactivated. The analyses for the apatite coatings confirmed that the surface characterization of titanium has strong effect on bioactivity of titanium. The bioactivity of the rutile films on titanium was related not only to their surface basic hydroxyl groups, but also to acidic hydroxyl groups, and surface energy. Heat-treatment endowed titanium with bioactivity by increasing the amount of surface hydroxyl groups on titanium and its surface energy.

In-situ and ex-situ characterization of surface oxide films on AB5-type metal hydride electrodes

Abstract The surface oxide films on AB 5 -type metal hydride electrodes have been investigated by means of in-situ and ex-situ techniques such as in-situ laser scanning photoelectrochemical microscopy (PEM), ex-situ scanning tunneling microscopy (STM) and in-situ confocal Raman spectroscopy. The results indicated that the growth of surface oxide films can be monitored by using in-situ photoelectrochemical methods. Both laser-scanning photoelectrochemical microscopic and confocal Raman microscopic results showed that crack sites on the electrode surface are more feasible to be oxidized than other smooth sites under electrochemical conditions. In addition, the primary surface oxide layer on fresh metal hydride electrode was found to be composite metal oxides with nickel oxide as its main component.

Passivity of stainless steel

AbstractPassivity behavior in austenitic stainless steel has been studied both with bulk metal samples and by characterization of surface oxide films stripped from the stainless steel in various states of passivity. Electrochemical measurements of (1) break‐through potentials, (2) resistance to pit initiation and (3) solution potential change with time provide a direct indication of the passivity state and point to the presence and influence of surface films in the control of passivity and corrosion behavior.Protective surface films have been isolated and characterized with respect to structure and chemical composition. Microgravimetric techniques have been applied to the determination of the kinetics of formation of oxide films on activated stainless steel surfaces. The influence of adsorption on the over‐all process of film formation has been carefully considered on the basis of the kinetic data. A concept for the state of passivity of stainless steel is presented on the basis of data on gas adsorption, film properties and alloy composition.