139 research outputs found
Structure and phase stability of nanocrystalline Ce1âxLnxO2âx/2âÎŽ (Ln = Yb, Lu) in oxidizing and reducing atmosphere
The structure and phase evolution of nanocrystalline Ce1âxLnxO2âx/2âÎŽ (Ln = Yb, Lu, x = 0 â 1) oxides upon heating in H2 was studied for the first time. Up to 950 °C the samples were single-phase, with structure changing smoothly with x from fluorite type (F) to bixbyite type (C). For the Lu-doped samples heated at 1100 °C in the air and H2, phase separation into coexisting F- and C-type structures was observed for ~0.40 < x < ~0.70 and ~0.25 < x < ~0.70, respectively. It was found also that addition of Lu3+ and Yb3+ strongly hinders the crystallite growth of ceria during heat treatment at 800 and 950 °C in both atmospheres. Valency of Ce and Yb in Ce0.1Lu0.9O1.55âÎŽ and Ce0.95Yb0.05O1.975âÎŽ samples heated at 1100 °C was studied by XANES and magnetic measurements. In the former Ce was dominated by Ce4+, with small contribution of Ce3+ after heating in H2. In the latter, Yb existed exclusively as 3+ in both O2 and H2
Effect of surrounding environment on atomic structure and equilibrium shape of growing nanocrystals: gold in/on SiO2
We report on the equilibrium shape and atomic structure of thermally-processed Au nanocrystals (NCs) as determined by high resolution transmission electron microscopy (TEM). The NCs were either deposited on SiO2surface or embedded in SiO2layer. Quantitative data on the NCs surface free energy were obtained via the inverse Wulff construction. Nanocrystals inside the SiO2layer are defect-free and maintain a symmetrical equilibrium shape during the growth. Nanocrystals on SiO2surface exhibit asymmetrical equilibrium shape that is characterized by the introduction of twins and more complex atomic defects above a critical size. The observed differences in the equilibrium shape and atomic structure evolution of growing NCs in and on SiO2is explained in terms of evolution in isotropic/anisotropic environment making the surface free energy function angular and/or radial symmetric/asymmetric affecting the rotational/translational invariance of the surface stress tensor
The Enigma of Sexual Desire, Part 1: A Brief Review of Classical, Historical, Philosophical, and Literary Perspectives
Valence band splitting in wurtzite InP nanowires observed by photoluminescence and photoluminescence excitation spectroscopy
RelatĂłrio de estĂĄgio em farmĂĄcia comunitĂĄria
RelatĂłrio de estĂĄgio realizado no Ăąmbito do Mestrado Integrado em CiĂȘncias FarmacĂȘuticas, apresentado Ă Faculdade de FarmĂĄcia da Universidade de Coimbr
Ueber lineare homogene Differentialgleichungen mit algebraischen Relationen zwischen den Fundamentalintegralen.
Krankengeschichten und HeilausgÀnge nach Resection und Exstirpation des Ganglion Gasseri. Neuralgie-Recidiv nach Ganglion-Exstirpation
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