Synthesis, optical properties, and energy transfer of Ce 3+/Tb3+ co-doped MyGdFx (M = Li, Na, K)

Through a solid-state reaction method, the Ce3+/Tb3+ co-doped MyGdFx (M = Li, Na, K; x = 3, 4, 6; y = 0, 1, 3) system samples have been synthesized by controlling the annealing temperatures and the ratios of raw materials. The samples were characterized by X-ray diffraction (XRD) patterns, photoluminescence (PL) excitation and emission spectra as well as luminescent dynamic decay curves. The experimental results suggest that the LiF is more difficult to react with the prepared material compared that of NaF or KF under similar reaction conditions. The samples crystallized in different crystalline phases. The energy transfer from Ce 3+ to Tb3+ or Ce3+ to Gd3+ to Tb3+ has been observed in all the samples. The Ce3+ and Tb3+ present different optical properties for they are sensitive to the local environment. In addition, the deduced lifetime of Tb3+ 5D4 → 7F5 transition decreases in the same system samples with the annealing temperature increasing. The deduced lifetime of Tb3+ 5D4 → 7F5 also decreases with the increase of the KF concentration in the KF system samples. ? 2014 Elsevier B.V. All rights reserved

High Temperature conversion of fats: Cracking, gasification, esterification and transesterification

Burning fossil fuels increases the concentration of carbon dioxide in the atmosphere. Alternative sources of energy are necessary to control global warming. Diverse synthetic methods transform vegetable oils and animal fats, inexpensive carbon sources to biofuels. This chapter reviews the main chemical and thermal processes that transform triglycerides into fuels. We collected the most cited and recent scientific publications about transesterification, thermal and catalytic cracking, and gasification reactions and their respective technologies