This work is studying the layers of cerium oxide (doped with platinum) prepa- red by magnetron sputtering on different types of substrates. Attention is focused mainly on modes of growth and morfology of (Pt−)CeO2 layers. The study was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specimens (lamellas) were created by using focused ion beam (FIB) with respect to transparency for electron beam and material contrast. The emphasis was on elimination of redeposition and minimize the amorphous layer of lamella. Representation of elements was determined by energy-dispersive spectroscopy (EDX) and electron-energy loss spectroscopy (EELS). 1

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第20484号 / エネ博第353号 / 新制||エネ||70(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 木村 晃彦, 教授 星出 敏彦, 教授 今谷 勝次 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

In the present study, the formation and the evolution of lamellar structures in different Al-Ag alloys were investigated by transmission electron microscopy (TEM). Plates of the hexagonal [gamma] phase form semi-coherently on the {111} planes of the face centered cubic lattice of the alloy after the formation of Guinier-Preston zones. Guinier-Preston zones are metastable coherent preprecipitates which are silver rich in the aluminum-rich Al-Ag alloys. The decomposition of aluminum rich Al-Ag alloys, particularly the sequence of the later stages of precipitate formation was studied. With scanning electron microscopy and high-resolution transmission electron microscopy the development of the [gamma] phase was investigated. Samples cut from different Al-Ag alloys were homogenized at temperatures between 530 degrees C to 560 degrees C to obtain a single phase f.c.c solid solution. The samples were then quenched to room temperature, followed by heat treatments at temperatures between 140 degrees C and 220 degrees C for varying lengths of times. While Guinier-Preston zones increase in diameter with increasing aging duration, silver rich platelets of the [gamma] phase form. The [gamma] phase is the next metastable phase in the decomposition sequence before finally the [gamma] phase transforms to the stable silver-rich phase, termed [gamma]. For samples with silver contents above 12 at.% a parallel lamellar alignment of fine [gamma] plates and Alrich matrix is found after extended heat treatments. For all alloys with Ag concentrations below 12 at.% individual [gamma] plates are found on all four possible (111) planes of the [alpha] matrix. A method is presented to calibrate the medium-magnification high-angle annular dark-field contrast in scanning transmission electron microscopy. This calibration allows for the quantitative measurement of plate thicknesses from high-angle annular dark-field scanning transmission electron micrographs of Ag2Al plates inclined to the electron beam. Results from these measurements are in good agreement with direct bright-field micrographs of plates viewed edge-on.

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