Papers by Keyword: Oxidation Rate

Abstract: In this work, we study the impact of the dose rate on the electrical properties of aluminum (p-body, p⁺-body-contact) and phosphorous (n-source/drain) implanted 4H-SiC. We find no significant differences for dose rates ranging from 1×10¹¹ cm^-2s^-1 to 2−7×10¹² cm^-2s^-1. AFM scans across implanted and non-implanted regions after thermal oxidation and subsequent oxide etching reveal a clear dependence of the oxidation rate on the conduction type and doping concentration. In addition, we observe an increasing (decreasing) oxidation rate for increasing doping concentrations of the n-type (p-type) ion implanted areas.

Abstract: Step-controlled growth of 4H-SiC epitaxial layers leads to the formation of a step-bunched morphology along the surface with larger macrosteps, composed of smaller microsteps of several Si-C bilayer heights. As thermal oxidation is an orientation-dependent process, a multi-faceted surface is expected to exhibit a different oxidation behavior compared to a perfectly planar surface. In this work, step-bunched surfaces after oxidation are investigated by high-resolution atomic force microscopy (HR-AFM) and transmission electron microscopy (TEM) indicating a morphological change in the early stages of thermal oxidation. An orientation-dependent oxidation model is used to correctly describe variations of the oxide thicknesses at isolated macrosteps.

Abstract: The oxidation behavior of photovoltaic ribbon was measured for 48 hours over the temperature range of 300°C to 800°C using thermogravimetric apparatus (TGA). It was found that weigh-gained of both samples was found to be increased with increasing temperature and it was dramatically increased at 800°C for 30 minutes of initial oxidation time. Pure copper with 99.55% purity was successfully recovered from the photovoltaic ribbon of spent solar module using cyclic oxidation method.

Abstract: The oxidation rate of pure copper was measured for 48 hours over the temperature range of 500°C to 700°C using thermogravimetric apparatus by means of continuous and discontinuous oxidation methods. It was found that weigh-gained of both samples was found to be increased with increasing temperature and rate laws were determined to be parabolic and linear rate law each other. The comparison of oxidation rate of copper was shown to be higher in discontinuous that in continuous process due to direct oxidation through the oxide scale and copper substrate.

Abstract: The oxide film on implant surface of biomedical titanium alloy is crucial to its bioactivity and biocompatibility in human body. A new method is proposed to obtain titanium oxide film by cutting process in oxygen-enriched atmosphere. A gas mixing system is firstly developed to provide oxygen-argon mixed gas to the flank face of insert during turning. The results show that oxygen-enriched atmosphere promote the oxidation reaction of titanium element. Thicker oxide film can be obtained in oxygen-enriched condition than that in natural atmosphere. The corrosion resistance is also improved significantly by this method in electrochemical test.

Abstract: 4H-SiC(000-1) C-face was oxidized in H₂O and H₂ mixture gas (H₂ rich wet ambient) for the first time. H₂ rich wet ambient was formed by the catalytic water vapor generator (WVG) system, where the catalytic action instantaneously enhances the reactivity between H₂ and O₂ to produce H₂O. The dependence of SiC oxidation rate on the H₂O partial pressure was investigated. We fabricated 4H-SiC C-face MOS capacitor and MOSFET by the H₂ rich wet re-oxidation following the dry O₂ oxidation. The density of interface traps was reduced and the channel mobility was improved in comparison with the conventional O₂ rich wet oxidation.

Abstract: The oxidation behaviors and kinetics of in-situ β-Sialon bonded Al₂O₃-C refractories were investigated by TGA techniques via isothermal oxidation experiments at different temperatures. The results show that the oxidation process of in-situ β-Sialon bonded Al₂O₃-C refractories can be divided into three stages: oxidation reaction rate controlling stage, reaction and diffusion controlling stage, and diffusion controlling stage. The oxidation rate controlled by the reaction rate has no obvious changes as the temperature increases. The oxidation rate controlled by the reaction rate and the diffusion rate together has a trend of decline, so is the oxidation rate controlled by the diffusion rate.

Abstract: The effect of different mass transfer ways in landfill leachate treatment by electrochemical oxidation was studied, the electrochemical oxidation rate, current efficiency and energy consumption were mainly discussed by four different mass transfer ways—including higher pressure water jet electrode, aeration, mixing and natural convection. The results show that mass transfer way has an important influence for NH4+-N and CODcr removal in electrochemical oxidation landfill leachate, high pressure water jet has high current efficiency, oxidation rate and lower energy consumption, which is 7.41 mg/L.min, 48% and 0.11 Kwh/gNH4+-N in electrolytic 6 hours, respectively. Different mass transfer ways have different mass transfer coefficient, improving mass transfer coefficient could increase transfer rate and the overall efficiency of system.

Abstract: By means of magnetron sputtering, the Fe-Y coatings containing 15.4%, 20.7% and 32.7% Y (atom fraction), were deposited on stainless steels. The sputtered coatings were investigated by discontinuous weigh measurement. The results indicate that the oxidation kinetics can be divided into three stages, of which the first and second stages obey the parabolic rate law, while the oxidation kinetic curves of the last stage nearly exhibits horizontal lines. With the increase of the content of Y, the oxidation rate obviously increases. The external scale of the three kinds of alloys is substantially similar. After 24-h oxidation at 800 °C under 1 atm of air, the surface of sputtered coating is mainly transformed into three types of oxide scales, of which the thin outermost layer was Fe2O₃, the innermost is YFeO₃ mixed with double oxides including FeO or Fe3O₄. Single Y₂O₃ layer was not formed on the surface or in the alloys. The results were disscussed by taking into account the defects in the metal oxide, the self-diffusion of the elements in the alloys, and the low diffusion of yttrium in iron.

Abstract: For a number of chromia and alumina forming high temperature alloys and coatings, recent studies revealed, that in some cases the specimen/component or coating thickness may substantially affect the growth rates of the surface oxides. For the alumina formers the thickness dependence is mainly governed by depletion of oxygen active elements such as Y, Zr, Hf, Mg which are either intentionally added alloying elements or manufacturing related alloy impurities. In the case of the chromia forming materials, which tend to exhibit a more substantial dependence of oxidation rate on specimen/component thickness, depletion of minor alloying additions is also an important factor to be considered. However, for these alloys relaxation of oxide growth stresses by plastic deformation of the metallic substrates seems to be the dominant parameter which governs the observed behaviour.