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排序方式: 共有345条查询结果,搜索用时 312 毫秒
61.
循环流化床提升管中固体颗粒停留时间的分布 总被引:9,自引:1,他引:9
在内径140mm,高10m的循环流化床提升管中,采用磷光颗粒示踪法对床内固体颗粒的停留时间分布进行了测定。在气速1.5~9.0m/s,固体循环量10~140kg/m2s的范围内,实验测得的停留时间分布曲线均有明显的双峰分布。这种双峰分布是由于提升管中弥散颗粒和颗粒团共同作用的结果。本文提出的一维两组分扩散叠加模型可较好地描述提升管中固体的混合行为。考察了在实验条件下,操作条件对固体混合行为的影响。发现:气速及固含对颗粒的轴向Peclet数影响不大,提升管中颗粒的返混主要是由于颗粒团引起的。将研究结果与近期文献报道的其他研究进行了对比 相似文献
62.
Xinguo Zhang Xiaoxiao Wang Jinqing Huang Jinxin Shi Menglian Gong 《Optical Materials》2009,32(1):75-78
A series of halosilicate phosphor, Ba5SiO4(F,Cl)6:Eu2+, were synthesized by a solid state reaction. Excited by 370-nm light, Ba5SiO4Cl6:Eu2+ exhibits a broad emission band peaking at 440 nm. Partial substitution of Cl− with F− in the host lattice leads to red-shift in the emission band with centering wavelength from 440 nm to 503 nm. The possible mechanism for the luminescence change was discussed based on the XRD patterns. Blue and green LEDs were fabricated by combination of a 370 nm-emitting near UV chip and the optimal Ba5SiO4Cl6:Eu2+ and Ba5SiO4(F3Cl3):Eu2+, respectively. This series of phosphors is considered as a promising blue and green component used in fabrication of near UV-based white LEDs. 相似文献
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A novel green phosphor Mg2GeO4:Tb3+ with pure phase was prepared by the solid state reaction. The luminescence properties were investigated in detail. The diffusion reflection spectra of the undoped and Tb3+ doped Mg2GeO4 phosphors were recorded, the result reveals that there is an absorption band superposition of the host material and Tb3+ ion. The study on the excitation and diffusion spectra shows that there is an effective energy transfer from the host material to Tb3+ ion. Under 277 and 172 nm excitation, the phosphor presents predominant green emission at 543 and 547 nm respectively. The excitation intensity at 172 nm is about 1.8 times of that at 272 nm. The promising luminescence properties make it a candidate for application in Plasma Display Panel. 相似文献
66.
Jack Silver Robert Withnall George R.Fern Paul G Harris Terry G.Ireland Anthony Lipman 《电子器件》2008,31(1):161-165
文章介绍了两种移植和可控纳米沉积荧光粉颗粒和纳米铁电体颗粒的载体.第一种载体是一种可以悬浮和沉积合成的具有亚微米级尺寸大小的荧光粉颗粒的油墨.解决了该油墨的聚集和沉降问题,并发现该油墨具有良好的液流学性能,从而可用于印刷高分辨率的荧光粉.测量了相关的单个象素的阴极发光密度以评定这种丝网印刷油墨的可重复性.第二种载体是一种粘结剂,这种粘结剂不仅可以携带 30 μm 以及更大的尺寸的电致发光的荧光粉,还可以携带纳米铁电体颗粒.这种新型的粘结剂可应用于不需要额外的绝缘反射层的低造价的 EL 显示器.从衬底按要求将发射层剥下来就形成了柔性薄膜,将该薄膜置于两电极之间,仍可保持其电致发光的活性.该粘结剂薄膜可以很容易地印刷和定型制成显示屏. 相似文献
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Yiting Tao Sasa Yan Ying Du Panting Wang Danping Chen 《Ceramics International》2021,47(13):18030-18036
In this study, Eu2+/Al3+-, Eu2+/Tb3+-, and Eu2+/Tb3+/Al3+-doped high silica glasses were prepared, and the effect of Al3+ on the spectroscopic properties of Eu2+ and Tb3+ and the energy transfer of Eu2+→Tb3+ was investigated. The results revealed that the addition of Al3+ increased the luminescent intensity of the Eu2+-doped glass by approximately 400 times. An obvious Eu2+→Tb3+ energy transfer occurred in the Eu2+/Tb3+-doped high silica glass, whose transfer efficiency can reached 66.9%. However, the efficiency continuously decreased as the Al3+ concentration increased, and eventually, it dropped to 7.2%. These phenomena can be explained by the following: Al3+ not only disperses Eu2+ but also changes the field strength and symmetry of its neighboring environment, thus increasing its emission intensity. Moreover, Al3+ destroys the strong dipole–dipole interactions between Eu2+ and Tb3+ in high silica glass due to its dispersive ability, which inhibits the energy transfer of Eu2+→Tb3+. This indicates that a small amount of Al3+ can significantly modify the neighboring environment of Eu2+ and change its light-emitting characteristics, potentially yielding efficient blue and green phosphors excited by near-ultraviolet light for use in white light-emitting diodes. 相似文献
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A comparison study on the axial and lateral mixing of wide-size-distribution (WSD) particles with normal-size-distribution (NSD) FCC particles is presented. The fines smaller than 20 μm contribute 24.5% in volume in the WSD particles. Phosphor tracer method is used. The axial backmixing of the WSD is slightly lower than the NSD. However, the lateral solids Peclet number increases linearly with the increase of the content of fines smaller than 20 μm because of the serious agglomeration of the fines, which leads to very poor lateral mixing for the WSD particles. And the solids lateral mixing for the WSD particles decreases significantly with increasing solids fraction. These results show that the particle size and the particle-size-distribution is a very important factor that controls the lateral solids mixing and hence the heat and mass transfer in lateral direction, which should be taken into full consideration in the riser reactor. And the NSD may be a good particle size distribution for the FCC riser, the lateral solids mixing of which is satisfactory in the reactor. 相似文献
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