Showing papers by "Anabela G. Rolo published in 2006"
TL;DR: In this article, the evolution of photoluminescence (PL) emission from CdS quantum dots embedded in silica glass with time was studied, and an increase of PL emission was observed due to the passivation of non-radiative recombination centres.
13 citations
TL;DR: In this paper, thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt-ferrite concentrations (x).
Abstract: Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt ferrite concentrations (x). The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinnel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation was observed. As the concentration of the cobalt ferrite increased, the grain size of the BaTiO3 phase decreased, from 91nm to 30nm, up to 50% CoFe2O4 concentration, beyond which the BaTiO3 grain size take values in the range 30-35nm. On the other hand the cobalt ferrite grain size did not show a clear trend with increasing cobalt ferrite concentration, fluctuating in the range 25nm to 30nm. The lattice parameter of the CoFe2O4 phase increased with increasingx. However, it was always smaller than the bulk value indicating that, in the films, the cobalt ferrite was under compressive stress that was progressively relaxed with increasing CoFe2O4 concentration. The magnetic measurements showed a decrease of coercive field with increasingx, which was attributed to the relaxation of the stress in the films and to the increase of particle agglomeration in bigger polycrystalline clusters with increasing cobalt ferrite concentration.
1 citations
TL;DR: In this article, the kinetics of the isothermal crystallization from the melt at different crystallisation temperatures and the melting behavior of Poly(vinylidene fluoride) (PVDF) in the alpha phase has been investigated.
Abstract: The kinetics of the isothermal crystallization from the melt at different crystallisation temperatures and the melting behaviour of Poly(vinylidene fluoride) (PVDF) in the alpha phase has been investigated. The variation of the microstructure of the samples crystallized at different temperatures was monitored with time by Optical Microscopy. The correlation between microstructure and kinetic parameters allows the tailoring of the microstructure by choosing the crystallisation conditions of the samples. Raman and Infrared Transmission Spectroscopy also show the appearance of the γ-phase for higher crystallisation temperatures. The influence of the crystallisation kinetics on the degree of crystallinity of the samples will be also presented and discussed.