Er^（3＋） doped Y_2Ti_2O_7 phosphors were prepared by the high temperature solid state reaction method at 1500℃.X-ray diffraction and luminescence spectra were used to characterize the properties of samples.Due to t...Er^（3＋） doped Y_2Ti_2O_7 phosphors were prepared by the high temperature solid state reaction method at 1500℃.X-ray diffraction and luminescence spectra were used to characterize the properties of samples.Due to the layer distribution of Y^（3＋） ions in the pyrochlore Y_2Ti_2O_7 crystal,Er^（3＋） ions,replacing Y^（3＋） in Y_2Ti_2O_7 crystal,could realize high-concentration doping by suppressing energy migration between layers to minimize concentration quenching.Investigation on the upconversion characteristic of Y_2Ti_2O_7：Er^（3＋）showed that the optimal doping concentration of Er^（3＋） was up to 28 mol.%.Y_2Ti_2O_7：0.28 Er^（3＋） exhibited both dominating red emission under 980 and 1550 nm excitation.The brightness of Y_2Ti_2O_7：0.28Er^（3＋） were 4 times（980 nm） and 7 times（1550 nm） higher than that of Y_2Ti_2O_7：0.05Er^（3＋）.And Y_2Ti_2O_7：Er^（3＋） presented much better red emission color purity and stability under 1550 nm excitation.展开更多
A Y2O3 particle enhanced Ni/TiC composite coating was fabricated in-situ on a TC4 Ti alloy by laser surface cladding. The phase component, microstructure, composition distribution and properties of the composite layer...A Y2O3 particle enhanced Ni/TiC composite coating was fabricated in-situ on a TC4 Ti alloy by laser surface cladding. The phase component, microstructure, composition distribution and properties of the composite layer were investigated. The composite layer has graded microstructures and compositions, due to the fast melting followed by rapid solidification and cooling during laser cladding. The TiC powders are completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The size of TiC dendrites decreases with increasing depth. Y2O3 fine particles distribute in the whole clad layer. The Y2O3 particle enhanced Ni/TiC composite layer has a quite uniform hardness along depth with a maximum value of HV1380, which is 4 times higher than the initial hardness. The wear resistance of the Ti alloy is significantly improved after laser cladding due to the high hardness of the composite coating.展开更多
Nanosized Gd2(1–x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties we...Nanosized Gd2(1–x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...展开更多
Polycrystalline samples of Y0.6Gd0.4Ba2-xNbxCu3O7-y(YGBNCO) with different Nb contents (x = 0.05, 0.10, 0.15, 0.20, and 0.25) were prepared using the usual solid state reaction technique. The structure for all samples...Polycrystalline samples of Y0.6Gd0.4Ba2-xNbxCu3O7-y(YGBNCO) with different Nb contents (x = 0.05, 0.10, 0.15, 0.20, and 0.25) were prepared using the usual solid state reaction technique. The structure for all samples was characterized by XRD and SEM. The electrical properties were measured by the FPP method in the temperature range from 70 to 130 K. The lattice constant of b remains almost unchanged and a and c increases with the increase of Nb content with x ≤ 0.10. The zero resistance transition temperature and Jc decrease with increasing Nb content. But superconductivity did not suppress. As the Nb content in the samples increases, it gives a diffused phase indicating a niobium perovskite phase and it is a small amount of unidentified phase.展开更多
基金supported by Research Program of Application Foundation(Main subject)of Ministry of Transport of China(2015329225090)the National Natural Science Foundation of China(11504039,51502031)Fundamental Research Funds for the Central Universities(3132015150,3132015153,3132015139,3132016349)
文摘Er^（3＋） doped Y_2Ti_2O_7 phosphors were prepared by the high temperature solid state reaction method at 1500℃.X-ray diffraction and luminescence spectra were used to characterize the properties of samples.Due to the layer distribution of Y^（3＋） ions in the pyrochlore Y_2Ti_2O_7 crystal,Er^（3＋） ions,replacing Y^（3＋） in Y_2Ti_2O_7 crystal,could realize high-concentration doping by suppressing energy migration between layers to minimize concentration quenching.Investigation on the upconversion characteristic of Y_2Ti_2O_7：Er^（3＋）showed that the optimal doping concentration of Er^（3＋） was up to 28 mol.%.Y_2Ti_2O_7：0.28 Er^（3＋） exhibited both dominating red emission under 980 and 1550 nm excitation.The brightness of Y_2Ti_2O_7：0.28Er^（3＋） were 4 times（980 nm） and 7 times（1550 nm） higher than that of Y_2Ti_2O_7：0.05Er^（3＋）.And Y_2Ti_2O_7：Er^（3＋） presented much better red emission color purity and stability under 1550 nm excitation.
基金Projects (51101096, 51002093) supported by the National Natural Science Foundation of ChinaProject (1052nm05000) supported by Special Foundation of the Shanghai Science and Technology Commission for Nano-Materials ResearchProject (J51042) supported by Leading Academic Discipline Project of the Shanghai Education Commission, China
文摘A Y2O3 particle enhanced Ni/TiC composite coating was fabricated in-situ on a TC4 Ti alloy by laser surface cladding. The phase component, microstructure, composition distribution and properties of the composite layer were investigated. The composite layer has graded microstructures and compositions, due to the fast melting followed by rapid solidification and cooling during laser cladding. The TiC powders are completely dissolved into the melted layer during melting and segregated as fine dendrites when solidified. The size of TiC dendrites decreases with increasing depth. Y2O3 fine particles distribute in the whole clad layer. The Y2O3 particle enhanced Ni/TiC composite layer has a quite uniform hardness along depth with a maximum value of HV1380, which is 4 times higher than the initial hardness. The wear resistance of the Ti alloy is significantly improved after laser cladding due to the high hardness of the composite coating.
基金supported by Cultivating Innovative Talents for Colleges & Universities of Henan Province (2002006)Open Research Foundation of Henan University
文摘Nanosized Gd2(1–x)Eu2xTi2O7:yV5+ phosphors were prepared via sol-gel method and characterized with X-ray diffraction,Raman spectroscopy,diffuse reflectance spectra and photoluminescence spectra.Their PL properties were investigated as functions of the Eu3+ doping concentration and annealing temperature.The results indicated that the as-prepared samples showed a strong emission of Eu3+ under the irradiation of 303 nm.For Eu3+-doped Gd2Ti2O7,the orange emission at 586 nm was the strongest,which was correspond...
文摘Polycrystalline samples of Y0.6Gd0.4Ba2-xNbxCu3O7-y(YGBNCO) with different Nb contents (x = 0.05, 0.10, 0.15, 0.20, and 0.25) were prepared using the usual solid state reaction technique. The structure for all samples was characterized by XRD and SEM. The electrical properties were measured by the FPP method in the temperature range from 70 to 130 K. The lattice constant of b remains almost unchanged and a and c increases with the increase of Nb content with x ≤ 0.10. The zero resistance transition temperature and Jc decrease with increasing Nb content. But superconductivity did not suppress. As the Nb content in the samples increases, it gives a diffused phase indicating a niobium perovskite phase and it is a small amount of unidentified phase.
