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101.
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Xinguo ZhangLianghao Fei Jianxin ShiManglian Gong 《Physica B: Condensed Matter》2011,406(13):2616-2620
A series of Eu2+-activated Ba2Mg(BO3)2 yellow phosphors were prepared by a high temperature solid-state reaction. The phosphor emits intense yellow light under near ultraviolet excitation. Large Stokes shift can be attributed to the asymmetric nature of the Eu site and the lack of rigidity in the host. The concentration self-quenching mechanism of Ba2Mg(BO3)2:Eu2+ is d-d interaction and the critical transfer distance is calculated to be about 12.29 Å. Prototype light-emitting diodes were fabricated by coating the Ba2Mg(BO3)2:0.07Eu2+ phosphor onto ∼370 nm-emitting InGaN chips. The LEDs exhibit intense yellow-emitting under a forward bias of 20 mA. The results indicate that Eu2+-activated Ba2Mg(BO3)2 is a candidate as a yellow component for fabrication of near-UV white light-emitting diodes. 相似文献
103.
Development of long-life-cycle tablet ceramic adsorbent for geosmin removal from water solution 总被引:1,自引:0,他引:1
Rongzhi ChenQiang Xue Zhenya Zhang Norio SugiuraYingnan Yang Miao LiNan Chen Zhao Ying Zhongfang Lei 《Applied Surface Science》2011,257(6):2091-2096
In this study, the tablet ceramic adsorbent (TCA), a silica/iron(III) oxide composite material, has been developed for geosmin (GSM) removal from the water solution. The physicochemical characteristics of TCA were examined with XRD, SEM, EDX and BET analyses. The sorption characteristics of GSM on TCA were investigated in a batch system. Attempts have been made to understand the adsorption kinetics, the effect of initial GSM concentration, solution pH, and reaction time.The batch experiments equilibrium data were well fitted to the Lagergren kinetic equation, which indicate the first-order nature adsorption. Over 82% of the GSM was removed by the TCA within 600 min at an initial concentration of 200 ng/L with 20 g/L of TCA dose. The batch and regeneration study indicated that the TCA is a cost-effective GSM adsorbent with sufficient mechanical strength to retain its physical integrity after long-time adsorption, and high regeneration performance for long-life-cycle application. Almost no second contamination (toxic sludge or leached iron) was observed after adsorption, and the gas resultant of thermal regeneration is harmless to atmospheric environment. 相似文献
104.
Jiaqing ZhuangZhiguo Xia Haikun LiuZepeng Zhang Libing Liao 《Applied Surface Science》2011,257(9):4350-4353
Green-emitting phosphors Ca3SiO4Cl2:Eu2+ were prepared by the high temperature solid-state method. Sol-gel process was adopted to encapsulate the as-prepared phosphors with tetraethylorthosilicate (TEOS) as silicon coating reagent. Fluorescence spectrometer, scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) patterns were employed to characterize the emission spectra, the surface morphologies and the phase structures, respectively. The chemical stability testing was operated by the method of soaking the phosphors in deionized water and roasting them at different temperatures. The results indicated that the surfaces of the green phosphors were evenly coated by SiO2 and the phase structure of the coated phosphors remained the same as the uncoated samples. The luminance centre of Eu2+ did not shift after surface treatment and the luminance intensity of coated phosphors was lower than that of the uncoated samples. The results demonstrated that the water-resistance stability of the coated phosphor was improved to some degree because the pH value and the luminance intensity variation were both smaller than the uncoated phosphor after steeping within the same time. Moreover, the thermal stability of coated phosphors was enhanced obviously compared to the original samples based on the temperature dependent emission spectra measurement. 相似文献
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The optimization of the elaboration conditions of a new family of highly emissive white phosphors based on glassy yttrium aluminum borates (g-YAB) compositions is presented. Their preparation from solutions is based on the polymeric precursor method (modified Pechini process), involving non-toxic and low cost precursors. The resulting resins were first dried at moderate temperatures followed by two-step annealing treatments of the obtain powders under controlled atmospheres: a first pyrolysis under nitrogen followed by a calcination under oxygen. This favored the gradual oxidation of organic moieties coming from starting materials, avoiding uncontrolled self-combustion reactions, which generate localized hot spots. This prevented phase segregations and the formation of pyrolytic carbon or carbonates, which are strongly detrimental to the luminescence properties. Thus, coupled chemical analyses and luminescence characterizations showed the high chemical homogeneity of the resulting powders and their intense emissions in the whole visible range. These emissions can be tuned from blue to warm white by adjusting the calcination temperature that is an important advantage for the development of LED devices. We showed that impurities of monovalent and divalent cations act as quenching emission centers for these phosphors. Therefore, by increasing the purity grade, we significantly enhanced the PL emissions leading to high internal quantum yields (80–90%). Finally, cathodoluminescence emissions showed the homogeneous dispersion of emitting centers in the g-YAB matrix. 相似文献
108.
In this study, an orange-red silicate phosphor that is used in light emitting diodes (LEDs) was coated with a SiO2 blocking layer via a sol-gel reaction of tetra-ethyl ortho-silicate (TEOS) to investigate its reliability as an encapsulant. A sol-gel coating protects the phosphor surface from moisture and reactive materials and improves the reliability of the phosphor. The efficacy of the phosphor coating following an 85 °C and 85 relative humidity (Rh)% test decreased by 7%, whereas an uncoated phosphor coating decreased by 35%. A SiO2 sol-gel coating decreases the luminous efficiency by a small amount with each coating. 相似文献
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