RESUMO
We present the discovery of Ba5CaFe4O12, a new iron-based oxide with remarkable properties as a low-temperature driven oxygen storage material (OSM). OSMs, which exhibit selective and rapid oxygen intake and release capabilities, have attracted considerable attention in chemical looping technologies. Specifically, chemical looping air separation (CLAS) has the potential to revolutionize oxygen production as it is one of the most crucial industrial gases. However, the challenge lies in utilizing OSMs for energy-efficient CLAS at lower temperatures. Ba5CaFe4O12, a cost-competitive material, possesses an unprecedented 5-fold perovskite-type A5B5O15-δ structure, where both Fe and Ca occupy the B sites. This distinctive structure enables excellent oxygen intake/release properties below 400 °C. This oxide demonstrates the theoretical daily oxygen production rate of 2.41 mO23 kgOSM-1 at 370 °C, surpassing the performance of the previously reported material, Sr0.76Ca0.24FeO3-δ (0.81 mO23 kgOSM-1 at 550 °C). This discovery holds great potential for reducing costs and enhancing the energy efficiency in CLAS.
RESUMO
Upconversion photoluminescence (UCPL) of rare-earth ions has attracted much attention due to its potential application in cell labeling, anti-fake printing, display, solar cell and so forth. In spite of high internal quantum yield, they suffer from very low external quantum yield due to poor absorption cross-section of rare-earth ions. In the present work, to increase the absorption by rare earth ions, we place the emitter layer on a diffractive array of Al nanocylinders. The array is designed to trap the near infrared light in the emitter layer via excitation of the plasmonic-photonic hybrid mode, a collective resonance of localized surface plasmons in nanocylinders via diffractive coupling. The trapped near-infrared light is absorbed by the emitter, and consequently the intensity of UCPL increases. In sharp contrast to the pure localized surface plasmons which are bound to the surface, the hybridization with diffraction allows the mode to extend into the layer, and the enhancement up to 9 times is achieved for the layer with 5.7 µm thick. This result explicitly demonstrates that coupling the excitation light to plasmonic-photonic hybrid modes is a sensible strategy to enhance UCPL from a thick layer.
RESUMO
The oxygen intake/release characteristics were systematically studied for Ca2AlMnO5+δ samples synthesized under precisely controlled oxygen pressures. Both the oxygen storage capacity (OSC) and operating temperature were systematically lowered as the oxygen pressure in the firing atmosphere increased. Notably, the sample fired under a 1% O2 atmosphere exhibited sufficiently large OSC and superior oxygen intake/release kinetics to the pristine sample synthesized in an anaerobic condition. The high-angle annular dark-field scanning TEM observation revealed that the samples contain defects in their atomic arrangement when fired in oxygen-rich atmospheres. This result indicates that the oxygen intake/release characteristics of Ca2AlMnO5+δ are sensitive to the synthesis condition and widely tunable even without chemical substitutions.