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1.
Seoung-Soo Lee Ho-In Park Chung-Hyung Joh Song-Ho Byeon 《Journal of solid state chemistry》2007,180(12):3529-3534
Three different synthetic methods, the liquid phase process in HCl solution, the solvothermal reaction, and the surfactant-assisted solvothermal reaction, were explored to selectively control the particle shape and to enhance the luminescence intensity of the PbFCl-type red-emitting oxychloride phosphors LnOCl:Eu (Ln=La and Gd). The solvothermal pressure facilitated the low-temperature crystallization of the rod-shape particles for both Ln=La and Gd. It is noted that LaOCl:Eu nanorods show highly porous particle surface and quite low photoemission intensity. In contrast, the solvothermal synthesis could highly enhance the red-emission of GdOCl:Eu with no porous surface so as to be comparable to that of commercial Y2O3:Eu phosphor. An addition of surfactant material during solvothermal reaction yielded a rhomboidal-shape phosphor particles with no porous surface for both Ln=La and Gd. Interestingly, the elimination of surface porosity by using a surfactant significantly increased the emission intensity of LaOCl:Eu. It is proposed that the application of solvothermal technique for the synthesis of the PbFCl-type oxychloride phosphors is very effective to selectively control the particle shape and consequently to enhance the photoemission intensity if we use an appropriate surfactant material. 相似文献
2.
Yasushi Joh Koichi Harada Heimei Yuki Shunsuke Murahashi 《Journal of polymer science. Part A, Polymer chemistry》1971,9(4):1089-1102
The polymerization of isobutyl vinyl ether by vanadium trichloride in n-heptane was studied. VCl3 ? LiCl was prepared by the reduction of VCl4 with stoichiometric amounts of BuLi. This type of catalyst induces stereospecific polymerization of isobutyl vinyl ether without the action of trialkyl aluminum to an isotactic polymer when a rise in temperature during the polymerization was depressed by cooling. It is suggested that the cause of the stereospecific polymerization might be due to the catalyst structure in which LiCl coexists with VCl3, namely, VCl3 ? LiCl or VCl2 ? 2LiCl as a solid solution in the crystalline lattice, since VCl3 prepared by thermal decomposition of VCl4 and a commercial VCl3 did not produce the crystalline polymer and soluble catalysts such as VCl4 in heptane and VCl3 ? LiCl in ether solution did not yield the stereospecific polymer. It was found that some additives, such as tetrahydrofuran or ethylene glycol diphenyl ether, to the catalyst increased the stereospecific polymerization activity of the catalysts. Influence of the polymerization conditions such as temperature, time, monomer and catalyst concentrations, and the kind of solvent on the formed polymer was also examined. 相似文献
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A. Morozov T. Heindl J. Wieser R. Krücken A. Ulrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):51-57
Continuous and pulsed 12 keV electron beams were used to excite nitrogen
within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure
dependence of the ratio of photon fluxes for emission from vibrational
levels v'=0 and 1 of the C 3Π u state has been studied. The
results confirm the presence of a collisional excitation mechanism
populating v'=0, 1 in addition to electron impact excitation. Rate constants
of (1.27 ±0.04)×10-11 cm3s-1 [ v'=0] and
(2.68 ±0.08)×10-11 cm3s-1 [ v'=1] were measured for
C 3Π u quenching by ground state nitrogen. For electron beam
conditions relative excitation efficiencies of 1:0.59:0.22 for
vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are
compared with the predictions given by a vibrational relaxation model. 相似文献
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