Papers by Keyword: Oxide Growth

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Authors: Noraziana Parimin, Esah Hamzah, Astuty Amrin
Abstract: The isothermal oxidation behaviour on two different temperature of Fe-33Ni-19Cr alloy was studied in this work. The present paper focuses on the isothermal oxidation behaviour at 700oC and 900oC. The oxidized samples were subjected to oxidation experiment under isothermal conditions for 500 hours. Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD) technique were employed in this study to analyse the oxidation behaviour of oxidized samples. The kinetics of oxidation followed the parabolic rate law which represent diffusion controlled oxide growth rate. Results indicate that Fe-33Ni-19Cr alloy oxidized at 700oC possess a better oxidation resistance with low Kp value of 2.39 x 10-7 mg2cm-4s-1. The oxide scale formed during oxidation were generally complex consists of several oxide phases. The samples morphologies of oxidized samples were influenced by the alloy structure and expose conditions. An elemental EDX line scan analysis of samples oxidized at 900oC indicated four different oxide layers composes of several oxide structure with evidence of internal oxide precipitates composed of Al-rich oxide phase.
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Authors: J. Balmain, C. Savall, Régine Molins, C. Séverac, C. Haut, Anne Marie Huntz
125
Authors: Jian Sun, Ying Qiang Xu, Wan Zhong Li, Kai Lv
Abstract: Thermal barrier coating systems (TBCs) are widely used in turbines. However, premature failures have impaired the use of TBCs and cut down their lifetime. The thermally grown oxide layer (TGO) thickening and the material thermal expansion misfit under thermal cyclic loading significantly affect the interfacial stress field and stability of TBCs. In this study, the stability evaluation method of TBCs under thermal cyclic loading based on energy is established using the visco-elastoplastic and shakedown theorem. The semicircular shape interface is used to simplify the complicated interfacial undulations in FEA model. And actual TGO thickness obtained from experiment is used to simulate the bond coat oxidation. Then the effect of TGO thickening on the stability and stress field of TBCs under thermal cyclic loading is analyzed through the numerical simulation. It is concluded that estimating from the stress-strain evolution behavior, the local stability of the TBCs decreases with the TGO thickening, and assessing from energy, TBCs shows instable with TGO thickening.
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Authors: Christophe Girardeaux, Brice Sarpi, Sébastien Vizzini
Abstract: Generation of ultra-thin oxide layers (in the nanometer range) is currently a technological lock for numerous applications such as microelectronics, spintronics or even molecular electronics. A precise study of the stages of growth of Mg is essential before studying the growth of the oxide. In this work we report and discuss an experimental study of the very first stages of Mg growth onto Si(100) by Scanning Tunneling Microscopy-Spectroscopy (STM-STS), Auger Electron Spectroscopy (AES) and Low Energy Electron Diffraction (LEED). First, we have shown that an amorphous underlayer is formed onto the silicon substrate for Mg deposits of 0.25 monolayers (ML). This underlayer is attributed to a Mg2Si silicide formed at RT during Mg deposition. Then, using an original growth method based on alternate cycles of magnesium monolayer adsorption and room temperature (RT) oxidation, we did grow ultra-thin magnesium oxide films onto Si(100). Our study revealed that the ultra-thin Mg2Si layer at the MgO/Si(100) interface acts as a diffusion barrier and prevents oxidation of the highly-reactive silicon during magnesium oxide growth.
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Authors: Jeffery W. Butterbaugh, Steven L. Nelson, Thomas J. Wagener
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