Investigation Of Oxidation Process Research Articles

Transmission electron microscopy investigation of oxidation of (110)NiAl single crystal with wedge-shaped profile

Low energy electron diffraction (LEED), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX), and electron energy loss spectroscopy (EELS) investigations of oxidation processes in (110)NiAl single crystal of wedge like shape, i.e., on the sample’s areas of different thickness, were carried out. It was found that in the result of several cycles of ion etching, annealing and oxidation the upper layer of (110)NiAl is enriched with Ni. With the increase of Ni concentration from 50 to 100 at. %, the stoichiometry of the near surface area changes and the new phases of Ni3Al and Ni with Al doping are formed one after another. Up to Ni content of 75 at. % the defects concentration in the near-surface area increases and above 75 at. % it drops again. This leads to the change in orientation and azimuth direction of aluminum oxide (alumina). By varying the conditions of γ-Al2O3 epitaxial growth on (110)NiAl with (100), (110), and (111) orientations, we found that this oxide can be grown with different azimuthal directions, for example [440](111)γ-Al2O3 ∥ [002](110)NiAl and [440](111)γ-Al2O3 ∥ [022](110)NiAl.

Investigation of oxidation process in self‐terminating gate recess wet etching technique for AlGaN/GaN normally‐off MOSFETs

A self-terminating gate recess wet etching technique with thermal oxidation of the AlGaN/GaN layer followed by etching in potassium hydroxide (KOH) solution was recently proposed by the present authors for normally-off AlGaN/GaN metal–oxide semiconductor field effect transistors (MOSFETs). In this present reported work, the oxidation process inside the AlGaN/GaN heterostructure involved in this technique was analysed using several material characterisation methods. The measurement results show that the concentration and depth of the O element distribution increase with increased thermal oxidation temperature. It is worth noting that after 650°C oxidation almost no O element could be found in the GaN layer and the O element mainly locates in the AlGaN layer with an obvious correlation between the distribution of Al and O elements, where the Al(Ga)-oxide was detected by X-ray photoelectron spectroscopy, which could be etched by 70°C KOH. Thus, self-terminating wet etching on the AlGaN/GaN material is achieved.

Investigation of oxidation processes in non-stoichiometric lithium–titanium ferrites using TG analysis

Using non-isothermal thermogravimetry (TG), the oxidation kinetics of oxygen-deficient lithium-titanium ferrospinel, Li0.649Fe1.598Ti0.5Zn0.2Mn0.051O4-d, manufac- tured by ceramic engineering is investigated. The oxidation annealing of powder samples is performed in air. Accord- ing to the X-ray phase analysis, the processes giving rise to variations in oxygen content occur within single-phase spinel structure. The experimental kinetic results are pro- cessed using the Netzsch Thermokinetics software. The oxidation rate constants and the effective coefficients of atmospheric oxygen diffusion into the ferrites are deter- mined. The effective activation energy E of oxygen dif- fusion is found to be 1.95 eV. It is demonstrated that an increase in the oxygen non-stoichiometry parameter d as a result of recovery annealing of ferrite powders in vacuum at T = 1,070 K for 2 h gives rise to a slight decrease in E down to 1.89 eV. The activation energy of oxygen grain- boundary diffusion is identified by the electroconduction method. The resulting value 1.93 eV is fairly consistent with that obtained by TG.

Bioremedation of Oil and Oil Products Bacterial Species of the Genus Pseudomonas

In the article the results of investigation of oxidation processes of crude-oil by bacteria of genus Pseudomonas: Pseudomonas mendocina H-3, Pseudomonas sp. H-7, Pseudomonas stutzeri H-10, Pseudomonas aeruginosa H-14, Pseudomonas alcaligenes H-15 and Pseudomonas sp H-16. It was shown that these microorganisms are capable to oxidize oil’s hydrocarbons and oil products. It means that the bacteria may be used for bioremediation of oil-pollutant soils.

Investigation of oxidation process and properties of indium and tin-based thin-film heterostructures

Solid-phase processes in thin films (∼200 nm) based on tin and indium oxides (ITO structures) prepared by magnetron sputtering from a composite target (93 at % In and 7 at % Sn) and by layer-by-layer deposition of In/Sn/Si and Sn/In/Si structures from two magnetrons in a single vacuum cycle have been investigated in the work under their oxidation in an oxygen flow. Two ways of optically transparent semiconductor film formation have been compared using near-edge fundamental absorption spectroscopy, x-ray diffraction analysis, and electron microscopy and dynamics of the change in their optical and structure properties has been studied. In the case of oxidation of the layer-by-layer deposited structures, the heterogeneous phase composition of the film is confirmed both by the XRD data and by the optical results. Only wide-band-gap phases with an energy of direct transitions of 3.5–3.6 eV have been found in the films prepared by magnetron sputtering from a composite target after their oxidation. These wide-band-gap phases are associated with In2O3 oxide and a tin-doped indium oxide compound.

Investigation of Oxidation Process of Ultrathin Amorphous and/or Nano-Crystalline Silicon Films

AbstractA series experiments were conducted and reported here on how to employ quartz crystal microbalance (QCM) as a highly mass sensitive sensor to study a-Si film and Si nanocrystals oxidation under ambient oxygen. An experimental calibration procedure has been developed to prevent problems with QCM systems during routine study. With the help of pulsed laser deposition (PLD) technique, one can purposely deposit a thin layer of a heavy element as an insitu calibrant which can be analyzed by RBS quantitatively for QCM. The errors resulted from manufacture's sensor, non-repeatable sensor mounting and handling, temperature cycling history from run to run and so on will be effectively eliminated. Our preliminary results indicate that the oxidation process of a-Si thin films has two stages. A fast oxidation associated with surface and near surface oxidation followed by a slow oxidation. The former is depends on the oxygen vapor pressure in the chamber and the later is oxygen diffusion controlled process.

Investigation of oxidation process on plasma treated thin Al-films by GIXR and GIXRD

The sensitivity of grazing incidence X-ray reflectometry (GIXR) for amorphous as well as crystalline layers and for layer formations in the nm-range combined with information about structural states by grazing incidence X-ray diffractometry (GIXRD) enable these methods to study interfaces and surface layers. Thin aluminium layers (30–60 nm) were deposited on Si by thermal evaporation. These Al-layers were plasma oxidized for 5 h with interruptions every hour. The plasma treatments were carried out in a 2.45 GHz microwave discharge (SLAN-slot antenna) with different plasma types (Ar, O2) at low temperatures. In this way a thin oxide layer additional to the native alumina on the top was formed. The properties of the oxide layers such as thickness, roughness and density were studied by GIXR. The chemical composition was investigated by GIXRD and XPS. In addition AFM was used for surface topography observations. All these methods were applied before and after the plasma treatment. The properties of the thin Al-oxide layers were found to depend on the type of plasma but in all cases plasma leads to a smoothing of the films as well as an increasing of the thickness of the upper alumina layer.

Investigation of oxidation processes of steels under laboratory and industrial conditions

Investigation of oxidation processes of steels under laboratory and industrial conditions

Investigation of oxidation processes of steels under laboratory and industrial conditions

One of the most important factors in the oxidation process of steels is the chemical composition of the material. The effect of the chemical elements present in the steel on the characteristic features of the oxide layers has been investigated by several researchers, and it was proved that these elements play an important role not only in the development of the oxide layers but also in the adhesion of these layers to the base metal. From the point of view of industrial users, this property is of great importance, since after the different heat treatments and manufacturing steps the oxide layer should be removed. In the experimental work presented in this paper, the structure and composition of oxide layers formed under laboratory and industrial conditions were investigated. The aim of these experiments was to determine which parameters influence the adhesion of the oxide layers. During the tests, x-ray diffraction and energy-dispersive spectroscopy were applied. It was shown that alloying elements, especially silicon, have a large effect to the removability of the scale.

Influence of surface morphology on the oxidation of metal electrodes studied by in-situ grazing incidence x-ray diffractometry

The successful application of in-situ grazing incidence x-ray diffractometry (GIXD) for the investigation of oxidation processes at copper electrodes in pH 12 electrolytes is demonstrated. A penetration/escape depth of about 1 μm could be detected for a smooth polycrystalline copper foil and an x-ray incidence angle of 1.7°. Oxide layers generated at overpotentials less than about 0.5 V in respect to the equilibrium formation potentials of Cu2O or CuO, respectively, showed a dependence of the crystalline oxide formation on the defect density of the copper substrate. Highly disordered ground or polished specimens exhibited an order of magnitude higher GIXD reflexes from crystalline Cu2O than electrodeposited copper. Beyond overpotentials of 0.5 V, this epitaxial information for the Cu2O crystal growth became irrelevant. Further, GIXD turned out to be an appropriate tool to monitor atmospheric corrosion processes under thin humidity films with oxygen access. When oxygen diffusion through the polymer window membrane is allowed, oxygen reduction led to the concurrent formation of a crystalline CuO phase coexisting with amorphous Cu(OH)2 and Cu2O, though the potential was kept in the region of Cu2O.

Selection of composite stabilizer for automotive gasolines

An important and very promising approach in expanding the volume of automotive gasoline production is the incorporation of products from secondary processes, namely, pyrolysis, coking, catalytic cracking and thermal cracking. Naturally, the addition of such components gives a very sharp reduction of the gasoline`s oxidation resistance. To stabilize this sort of blended gasoline, new and highly efficient antioxidants, are required. The selection of antioxidants for this purpose is hampered by the lack of information on the mechanisms of mixed-fuel oxidation and the action of stabilizers under these conditions. Since the investigation of oxidation processes involves extended test periods, it becomes important to obtain an objective evaluation of stabilizer efficiency by standard methods, and to improve these methods. The work reported here was aimed at finding and evaluating (by standard methods) a new stabilizer for A-76 automotive gasoline containing unstable catalytic naphtha; the work was also aimed at improving the standard methods. This program consisted of several stages.