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ZrO2:Yb3+ nanocrystalline phosphors with high concentrations of ytterbium ions were prepared using the sol-gel method. X-ray diffraction, high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to characterize the nanocrystalline phosphors annealed at 1000°C. Unit-cell distortion and changes in the crystalline structure of the monoclinic zirconia to tetragonal zirconia, and subsequently cubic zirconia, were observed with increased Yb concentration. Yb ions were randomly distributed into the lattice of the crystalline structure. No segregation of Yb2O3 phase was observed. The substitution of Zr atoms by Yb atoms on different crystalline phases was confirmed by the experimental results and theoretical simulations of HRTEM and HAADF-STEM.
An Al58Cu25Fe17 alloy composition was produced by conventional casting technique. In order to take advantage from the hydrogen-environmental embrittlement reaction, which affects these alloys, this research was carried out subjecting prealloyed powders to wet-ball milling. Through these experiments it has been possible to evaluate the particle size reduction as consequence of hydrogen fracture and milling energy. The morphological and structural characteristics of the samples were performed using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The experimental results indicate that the samples with higher contents of humidity have a good particle size reduction. With the increment of milling time, the particle size was diminished even more reaching nanometer size scale.
Direct evidence of the transformation of WOx species in WO3 nanoclusters on WOx–ZrO2 system was achieved by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy on samples obtained by a conventional precipitation method and annealed from 560 to 800 °C. WO3 Nanoclusters with 2-nm crystal size orthorhombic structure were identified on the ZrO2 surface after annealing at 800 °C.