Kinds Of Oxide Films Research Articles

An Electrochemical Impedance Spectroscopic Study of Oxide Films in Liquid Metal

Electrochemical impedance spectroscopy (EIS) is a powerful technique for the non-destructive, dynamic measurement of electrochemical corrosion behavior in condensed environments, and is a demonstrated, in situ method for monitoring oxide films formed on metal surfaces in liquid metals. To characterize this capability, the impedance properties of three kinds of oxide films (anodic titanium oxide films, deposited Fe2O3 films, and thermally oxidized Fe samples) in liquid metals were examined using the EIS technique. The results show that the impedance response is related to the oxide film thickness and quality. The impedance of thin oxide films ( 200 nm) shows that the oxide film without cracks is stable in LBE and protects the substrate from corrosion. EIS is a promising method for accessing the electrochemical behavior of oxide films on metals and alloys in liquid metals.

Tin oxide coverage on tin whisker surfaces, measurements and implications for electronic circuits

Purpose – This paper aims to evaluate the morphology and thickness of oxides that form on the surfaces of tin whiskers. The problems related to the growth of tin whiskers are stated, and the relevance of oxide layers adhering to whiskers is discussed. Design/methodology/approach – Modern laboratory methods including focused ion beam sectioning, energy dispersive spectroscopy and X-ray photoelectron spectroscopy have been used to characterise the composition of oxides present on the surfaces of 48-year-old whiskers. These very old whiskers had nucleated and grown on electronic equipment stored at ambient temperatures. They were compared to the oxide layers on newly grown 2-week-old whiskers. Findings – A dual oxide film, consisting of stannous and stannic oxides, was found present on both the old and the new whiskers. Measurements of oxide thickness were established for both generations of whiskers and these were noted to be similar to those films present on pure, cleaned bulk tin. Research limitations/implications – Only very new and very old whiskers, and their oxide films, were the focus of this investigation. However, sufficient data were gained to predict the effect both kinds of oxide films would have during whisker bridging between conductors and the risk of short circuits. Thick oxide films (order of 30 nm) may have a greater resistance to shorting, but they will be more difficult to remove during solder dipping (with respect to whisker mitigation). Practical implications – A knowledge of the oxide thickness on growing/gyrating tin whiskers will provide the electronics industry with data useful for establishing the risk of short circuits. It will also be useful during the forensic work associated with component and assembly failure analysis. Originality/value – The data resulting from this study are unique. They are of value to others who may require knowledge of the morphology, composition and thickness of oxides present on tin whiskers of different vintage.

Wear and corrosion behavior of Mg–Gd–Y–Zr alloy treated by mixed molten-salt bath

A novel kind of oxide film was successfully prepared on the Mg–Gd–Y–Zr alloy by mixed molten-salt bath treatment. The composition and microstructure of the film were studied by XRD and SEM. Wear and corrosion behavior of the modified surface film was evaluated. According to XRD and SEM analysis, it was confirmed that the oxide film resulted in uniform distribution of MgO phase. The implantation of MgO phase in the film is expected to harden the surface and retard the dissolution behavior greatly in NaCl solution, and acts as an artificial compact and continuous passive film with the thickness of tens of microns.

An atomic force microscopy study of DNA hairpin probes monolabelled with gold nanoparticle: Grafting and hybridization on oxide thin films

First and original results are reported regarding the surface evolution of two kinds of oxide film after covalent grafting and hybridization of hairpin oligonucleotide probes. These hairpin probes were monolabelled with a 1.4 nm gold nanoparticle. One kind of oxide film was rough Sb doped SnO 2 oxide film and the other kind was smooth SiO 2 film. Same process of covalent grafting, involving a silanization step, was performed on both oxide surfaces. Atomic force microscopy (AFM) was used to study the evolution of each oxide surface after different steps of the process: functionalization, probe grafting and hybridization. In the case of rough SnO 2 films, a slight decrease of the roughness was observed after each step whereas in the case of smooth SiO 2 films, a maximum of roughness was obtained after probe grafting. Step height measurements of grafted probes could be performed on SiO 2 leading to an apparent thickness of around 3.7 ± 1.0 nm. After hybridization, on the granular surface of SnO 2, by coupling AFM with SEM FEG analyses, dispersed and well-resolved groups of gold nanoparticles linked to DNA duplexes could be observed. Their density varied from 6.6 ± 0.3 × 10 10 to 2.3 ± 0.3 × 10 11 dots cm −2. On the contrary, on smooth SiO 2 surface, the DNA duplexes behave like a dense carpet of globular structures with a density of 2.9 ± 0.5 × 10 11 globular structures cm −2.

TEM study of the structural dependence of the epitaxial passive oxide films on crystal facets in polyhedral nanoparticles of chromium

Nanocubes and partially truncated rhombic dodecahedral nanoparticles of Cr have been studied by electron diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. It is found that the nanoparticles of Cr are enclosed by the epitaxial passive oxide films. The oxide films on 100% truncated nanocubes of Cr with only one kind of facets, {1 0 0} facets, are face-centered cubic (fcc) structured Cr 2O 3 with a lattice constant of 0.407 nm. There are two kinds of oxide films in partially truncated nanoparticles of Cr with two kinds of crystallographic facets, {1 0 0} and {1 1 0}. The same fcc Cr 2O 3 is found on the {1 0 0} facets while the rhombohedral α-Cr 2O 3 is found on the {1 1 0} facets. This is similar to the two kinds of oxides, fcc and rhombohedral Fe 2O 3, which have also been observed in polyhedral nanoparticles of Fe. These passive Cr 2O 3, found in nanoparticles of Cr which have remained unchanged in water for four years, may have important implications for protective oxide films involving Cr.

Formation of atomically smooth surfaces on SrTiO 3 substrates for epitaxial film growth

Preparation of atomically smooth SrTiO 3 substrates is a crucial step for fabricating various high-quality thin films. This step can be in situ accomplished by homoepitaxial growth of several unit cells of SrTiO 3 on commercially available substrates using laser molecular-beam epitaxy. The atomic-level smoothness of as-treated substrates was verified by AFM image and well-defined intensity oscillation in reflection high-energy electron diffraction. This simple procedure can be applied to epitaxy of several kinds of oxide films.

Compatibility of Structural Materials with Li2BeF4 Molten Salt Breeder

Research results on corrosion behavior of Flibe (LiF-BeF2 molten salt) against structural materials are reviewed. Thermodynamic calculation and static experiment were carried out. It was found that some kinds of oxide films may work as a protective scale for ferritic steel. For V-based alloy, on the other hand, no stable oxide film can exist in the presence of Flibe. It was also found that Redox control might protect V-based alloy against corrosion.

Determination of the thickness and refractive index of films on silicon using split-beam ellipsometry

Measurements have been made of the thickness and refractive index of various kinds of oxide films on silicon, using a split-beam ellipsometer. The principles of the method are described with special emphasis on the ease with which measurements can be taken and interpreted. Measurements of film thickness were taken at different wavelengths and showed excellent consistency. The variation of the refractive index of silicon oxide films with composition was investigated, and was found to have a discontinuity in slope.

Dielektrisches verhalten von Ta2O5-Schichten im elektrolyten

Deviations from the normal course of the capacitance and of the equivalent series resistance as a function of the frequency in anodized tantalum measured in dilute aqueous electrolyte solutions, and the dependence of these dielectric properties on the composition of the solution, are explained by a conductivity profile in the oxide. It is assumed that a different kind of oxide film is present at the boundary with the solution, which allows electrolyte to enter. The influence of the second-electrode in the solution (normally Pt) used in these measurements is demonstrated or eliminated by using a second identical oxide film instead of platinum. It follows that the unsymmetrical dc current characteristic of the oxide film has no detectable influence on the measured dielectric properties. In addition a treatment of the oxide layers is given, which makes it possible to obtain reproducible results in different kinds of solution over a longer period of time.