Microbubbles are very small bubbles with a diameter of 50 m or less. The important characteristics of microbubbles are their large specific area and small buoyancy, and therefore effective dissolution of gas phase and high adsorption rate are expected. The utilization of microbubbles is useful in improving water environments. Research efforts at a number of institutions have been devoted to the development of microbubble generators. However, in previous microbubble generation devices, complex mechanisms and a high power supply have been required. In this study, a compact and low-power microbubble generator has been developed. Microbubbles were generated by inducing local shear stress in the flow of water through a pipe with slits. Three types of model (slit angle = 30 • , 60 • , and 90 • ) were used in order to investigate the effect of slit angle on the purification technique. The proposed microbubble generator with the slit angle = 60 • showed superior performance for the water purification technique in comparison with the other two models. It was confirmed that microbubble generation was affected by slit angle. Also, in this study, we investigated the electrical property of the gas-water interface, and the -potential of microbubbles was measured by electrophoresis. The results of the floatation experiments were affected by the -potential of the microbubbles.
Remarkable improvements of environmental durability and energy conversion efficiency in silicon solar cells were achieved using ethylene vinyl acetate (EVA) protection film containing poly(methyl methacrylate) (PMMA) polymer beads (PB), which includes hyper-stable luminescent lanthanide coordination polymer [Eu(hfa)3(dpbp)]n (hfa: hexafluoroacetylacetonate, dpbp: 4,4′-bis(diphenylphosphoryl)biphenyl). The shape of PB including [Eu(hfa)3(dpbp)]n (PB-[Eu(hfa)3(dpbp)]n) was observed with SEM. Luminescence performance of EVA protection films including PB-[Eu(hfa)3(dpbp)]n or related lanthanide complexes (previously reported [Eu(hfa)3(dpbp)]n powder, Tb(hfa)3(TPPO)2, Eu(hfa)3(TPPO)2, and Yb(hfa)3(TPPO)2, TPPO: triphenylphosphine oxide) were characterized using emission spectroscopy, quantum yields, and lifetimes. Their durability were evaluated using photophysical measurements after degradation test (85 °C 85% RH). The durability of PB-[Eu(hfa)3(dpbp)]n in EVA film was estimated to be twenty-five years, which is much longer than those of previous lanthanide complexes. The temperature dependency of emission spectra of PB-[Eu(hfa)3(dpbp)]n confirmed that the luminescence properties are maintained even at high temperatures up to 120 °C. Increased value of the solar cell short-circuit current efficiency using EVA protection film containing PB-[Eu(hfa)3(dpbp)]n was found to be 1.1%, which is a drastic increase as a photovoltaic solar system. The EVA protection films with PB-[Eu(hfa)3(dpbp)]n are effective for enhancing the performance of silicon solar cells.
UV durability of luminescent Eu(III) complexes for future solar cell application is estimated using Fourier transform infrared spectroscopy (FT-IR). Sandwich-typed glass cells containing Eu(III) complexes powders under UV irradiation are used for the carbonyl index analysis (calculation of decomposition percentage of organic ligands) using FT-IR measurements. The durability of Eu(hfa) 3 (TPPO) 2 (hfa: hexafluoroacetylacetonate, TPPO: triphenylphospine oxide) is five times larger than that of Eu(tta) 3 (phen) (tta: trifluoromethylthienylacetylacetonate, phen: phenanthroline). Photophysical performance of Eu(III) complexes under UV irradiation is also evaluated using emission lifetimes and external quantum efficiency measurements of the solar cell module using EVA films with Eu(III) complexes. Photo-degradation analysis of luminescent polymer thin films with Eu(III) complexes are demonstrated for the first time.
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