W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hy...W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO3(c-WO3),and the c-WO3 particles have c-WO3 whiskers attached to the surface.This kind of whiskers is essential for c-WO3 to be reduced directly to tungsten and also helpful to obtain W-Y2O3 powders with small size and good uniformity.展开更多
Using polyethylene glycol (PEG) as the surfactant, Bi3.84W0.1606.24 up-conversion luminescence nano-crystal co-doped with Yb^3+ and Ho^3+ ions was synthesized by the hydrothermal method. The structure and properti...Using polyethylene glycol (PEG) as the surfactant, Bi3.84W0.1606.24 up-conversion luminescence nano-crystal co-doped with Yb^3+ and Ho^3+ ions was synthesized by the hydrothermal method. The structure and properties of luminescence powder were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was of cubic system when the sample was synthesized at a low temperature and the particle size was about 30 nm. The results showed that adding surfactants was useful to improve the powder agglomeration and the grain crystal was spherical. The green emission peak at 546 nm and red emission peak at 655 nm, corresponding to the (^5F4, ^5S2)→^5I8 and the ^5F5→^5I8 transitions of Ho^3+, respectively, were simultaneously observed at room temperature under excitation of 980 nm semiconductor laser. The up-conversion luminescence intensity was the strongest when the concentration ratio of yb^3+/Ho^3+ was 6:1 and the concentration of Ho3+ ion was 1.5 tool.%. The up-conversion mechanism was also studied. The green and red emission peaks were the two-photon absorption according to the relationship between the pump power and the luminescence intensity.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51822404 and 51574178)the Science and Technology Program of Tianjin(No.18YFZCGX00070)+1 种基金the Natural Science Foundation of Tianjin(No.18JCYBJC17900)the Seed Foundation of Tianjin University(Nos.2018XRX-0005 and 2019XYF-0066).
文摘W-Y2O3 composite nanopowders prepared via wet chemical method exhibit unique morphologies and micro structures.The yttrium addition during chemical reaction process affects not only the composition of tungsten acid hydrate precursors,but also the reduction property of tungsten oxide transformed from precursors.In this study,the morphology evolution of the samples with and without yttrium during reduction process has been studied,and it is found that the addition of yttrium can exert a strong influence on the reduction route of tungsten oxide and the final morphology of tungsten particles.The cause of the difference of reduction route and tungsten particle morphology is also analyzed.It is suggested that the composition of the samples with yttrium at the beginning of reduction is pure cubic system WO3(c-WO3),and the c-WO3 particles have c-WO3 whiskers attached to the surface.This kind of whiskers is essential for c-WO3 to be reduced directly to tungsten and also helpful to obtain W-Y2O3 powders with small size and good uniformity.
基金supported by Jilin Science Bureau (20070515)Changchun Science Bureau (20091510)
文摘Using polyethylene glycol (PEG) as the surfactant, Bi3.84W0.1606.24 up-conversion luminescence nano-crystal co-doped with Yb^3+ and Ho^3+ ions was synthesized by the hydrothermal method. The structure and properties of luminescence powder were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was of cubic system when the sample was synthesized at a low temperature and the particle size was about 30 nm. The results showed that adding surfactants was useful to improve the powder agglomeration and the grain crystal was spherical. The green emission peak at 546 nm and red emission peak at 655 nm, corresponding to the (^5F4, ^5S2)→^5I8 and the ^5F5→^5I8 transitions of Ho^3+, respectively, were simultaneously observed at room temperature under excitation of 980 nm semiconductor laser. The up-conversion luminescence intensity was the strongest when the concentration ratio of yb^3+/Ho^3+ was 6:1 and the concentration of Ho3+ ion was 1.5 tool.%. The up-conversion mechanism was also studied. The green and red emission peaks were the two-photon absorption according to the relationship between the pump power and the luminescence intensity.