A red-emitting phosphor GdNbO4:Eu3+,Bi3+ was prepared by a high temperature solid-state reaction technique. The phosphor was characterized by X-ray diffraction (XRD), particle size analyzer and fluorescence spect...A red-emitting phosphor GdNbO4:Eu3+,Bi3+ was prepared by a high temperature solid-state reaction technique. The phosphor was characterized by X-ray diffraction (XRD), particle size analyzer and fluorescence spectrometer. The single phase of GdNbO4:Eu3+,Bi3+ was obtained at 1150~C and the average particle diameter was about 2.30 μm. Excitation and emission spectra reveal that the phosphor can be ef- ficiently excited by ultraviolet (UV) light (394 nm) and emit the strong red light of 612 nm due to the Eu3+ transition of SD0~TF2. The opti- mum content of Eu3+ doped in the phosphor GdNbOn:Eu3+ is 20mo1%. The phosphor Gdo.80NbO4:0.20Eu3+,0.03Bi3+ shows much stronger photoluminescence intensity and better chromaticity coordinates (x=0.642, 0.352) than GdNbO4:Eu3+. It is confirmed that Gdo.80NbO4:0.20Eu3+,0.03Bi3+ is a potential candidate for near-UV chip-based white light emitting diodes.展开更多
Ultrasonic effect on microstructure evolution and mechanical properties of Mg-6Zn-0.5Y magnesium alloy was investigated.The results show that ultrasonic treatment can significantly modify the as-cast microstructure of...Ultrasonic effect on microstructure evolution and mechanical properties of Mg-6Zn-0.5Y magnesium alloy was investigated.The results show that ultrasonic treatment can significantly modify the as-cast microstructure of Mg-6Zn-0.5Y alloy.With the application of ultrasonic treatment,the primary a-Mg phase transforms from coarse dendrites to nearly fine equiaxed grains,and the continuous I-phase atα-Mg boundaries is modified into discontinuous one.Interestingly,the area fraction of I-phase decreases after ultrasonic treatment.Besides,the tensile properties of Mg-6Zn-0.5Y alloy are apparently improved after ultrasonic treatment.Compared to those of the untreated alloy,the ultimate tensile strength and elongation of Mg-6Zn-0.5Y alloy are improved by 67%and 56%,respectively.展开更多
The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, E...The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, EPMA, X-ray EDS, XRD and FTIR. The corrosion behavior was evaluated using weight-loss measurement, hydrogen evolution, electrochemical and pH measurements, The results demonstrate that the microstructure for both ZMT614-1,5Nd alloy and ZMT614-0.5Y alloy is characterized by α-Mg and intermetallic compounds, most of which are distributed along the grain boundaries. These second phases contain Mg2Zn, Mg2Zn11, Mg2Sn and single metal Mn, together with Mg12Nd phase for the ZMT614-1.5Nd alloy, and with Mg24Y5 phase for the ZMT614-0.5Y alloy. Honeycomb-like corrosion product layers form. The corrosion resistance of the ZMT614-0.5Y alloy is higher than that of the ZMT614-1.5Nd alloy, which is ascribed to the addition of the element Y into the alloy delaying the corrosion initiation in comparison to that of Nd element in the alloy.展开更多
The Mg–9Al–5Sn-xSb(x=0.0,0.3,0.6,1.0,1.5 wt%)alloys were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The effects of Sb additions on the microstructure and mechanic...The Mg–9Al–5Sn-xSb(x=0.0,0.3,0.6,1.0,1.5 wt%)alloys were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The effects of Sb additions on the microstructure and mechanical properties of the Mg–9 Al–5 Sn alloys were investigated by optical microscopy,X-ray diffraction,transmission electron microscopy,scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer.The results indicated that the phasesα-Mg matrix,Mg2Sn,Mg_(3)Sb_(2) and Mg17 Al12 exist in the as-cast Sb-containing alloys.Sb addition results in the precipitation of Mg_(3)Sb_(2).The dendritic size of these alloys decreases with the addition of Sb.Both their ultimate tensile strength and yield strength of extruded alloys increase,and their elongation decreases gradually with increasing the content of Sb.The better mechanical properties of the as-extruded alloys were achieved due to the refined grains and the formation of dispersive second phases Mg_(3)Sb_(2).展开更多
The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile t...The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile tests were simulated by the finite element method(FEM)to calculate the critical damage values(Dc)of the CockcroftLatham criterion to predict the occurrence of fracture defects.Finally,the effects of temperature and strain rate on Dc were analyzed to predict the critical damage value’s evolution.The results demonstrate that the critical damage value changes in the range of 0.188-0.718.It increases as strain rate decreases at constant temperature,and increases with the increase of temperature under certain strain rate,but is more sensitive to the temperature.展开更多
基金financial supports from the National Natural Science Foundation of China(Nos.U1764253,51971044,U1910213,52001037,U2037601)the Qinghai Scientific&Technological Program,China(No.2018-GX-A1)the Natural Science Foundation of Chongqing,China(No.cstc2019jcyjmsxm X0234)。
基金Project(2016YFB0301101)supported by the National Key Research and Development Program of ChinaProjects(51571040,U1764253,51531002)supported by the National Natural Science Foundation of China。
基金the National Natural Science Foundation of China(Nos.U1764253,U2037601,52001037 and 51971044)the National Defense Basic Scientific Research Program of China+1 种基金the Chongqing Science and Technology Commission,China(No.cstc2017zdcyzdzx X0006)the Qinghai Science and Technology Program,China(No.2018-GX-A1)。
基金the National"12th Five-year"Science and Technology Support Program of China(No.2011BAE22B03-3)the Project of Chong qing Scientific and Technological Commission(No.CSTC2010AA4048)
文摘A red-emitting phosphor GdNbO4:Eu3+,Bi3+ was prepared by a high temperature solid-state reaction technique. The phosphor was characterized by X-ray diffraction (XRD), particle size analyzer and fluorescence spectrometer. The single phase of GdNbO4:Eu3+,Bi3+ was obtained at 1150~C and the average particle diameter was about 2.30 μm. Excitation and emission spectra reveal that the phosphor can be ef- ficiently excited by ultraviolet (UV) light (394 nm) and emit the strong red light of 612 nm due to the Eu3+ transition of SD0~TF2. The opti- mum content of Eu3+ doped in the phosphor GdNbOn:Eu3+ is 20mo1%. The phosphor Gdo.80NbO4:0.20Eu3+,0.03Bi3+ shows much stronger photoluminescence intensity and better chromaticity coordinates (x=0.642, 0.352) than GdNbO4:Eu3+. It is confirmed that Gdo.80NbO4:0.20Eu3+,0.03Bi3+ is a potential candidate for near-UV chip-based white light emitting diodes.
基金financially supported by the National Great Theoretic Research Project of China(No.2013CB632200)the Sharing Fund of Chongqing University's Large-Scale Equipment(No.2013063009)
文摘Ultrasonic effect on microstructure evolution and mechanical properties of Mg-6Zn-0.5Y magnesium alloy was investigated.The results show that ultrasonic treatment can significantly modify the as-cast microstructure of Mg-6Zn-0.5Y alloy.With the application of ultrasonic treatment,the primary a-Mg phase transforms from coarse dendrites to nearly fine equiaxed grains,and the continuous I-phase atα-Mg boundaries is modified into discontinuous one.Interestingly,the area fraction of I-phase decreases after ultrasonic treatment.Besides,the tensile properties of Mg-6Zn-0.5Y alloy are apparently improved after ultrasonic treatment.Compared to those of the untreated alloy,the ultimate tensile strength and elongation of Mg-6Zn-0.5Y alloy are improved by 67%and 56%,respectively.
基金Acknowledgements This research was financially supported by the National Natural Science Foundation of China (Grant No. 5124 1001 ), the Natural Science Foundation of Shandong Province (Grant No. ZR2011EMM004), the Open Foundation of State Key Laboratory for Corrosion and Protection (Grant No. SKLCP21012KF03), SDUST Research Fund and Taishan Scholarship Project of Shandong Provincc (Grant No. TS20110828).
文摘The microstructure evaluation, surface morphology, chemical compositions and phase analysis of the biomedical Mg-6Zn-IMn-4Sn-1.5Nd/0.5Y (ZMT614- 1.5Nd/0.5Y) alloys were investigated by means of optical microscopy, EPMA, X-ray EDS, XRD and FTIR. The corrosion behavior was evaluated using weight-loss measurement, hydrogen evolution, electrochemical and pH measurements, The results demonstrate that the microstructure for both ZMT614-1,5Nd alloy and ZMT614-0.5Y alloy is characterized by α-Mg and intermetallic compounds, most of which are distributed along the grain boundaries. These second phases contain Mg2Zn, Mg2Zn11, Mg2Sn and single metal Mn, together with Mg12Nd phase for the ZMT614-1.5Nd alloy, and with Mg24Y5 phase for the ZMT614-0.5Y alloy. Honeycomb-like corrosion product layers form. The corrosion resistance of the ZMT614-0.5Y alloy is higher than that of the ZMT614-1.5Nd alloy, which is ascribed to the addition of the element Y into the alloy delaying the corrosion initiation in comparison to that of Nd element in the alloy.
基金financially supported by the National Natural Science Foundation of China(Nos.51531002 and 51571040)the National Great Theoretic Research Project(No.2013CB632200)+4 种基金the National Great Engineering Research Project(No.2016YFB0301101)the Ministry of Education of China(No.SRFDR 20130191110018)the Chongqing Municipal Government(No.CSTC2013JCYJC60001,CEC Project,Two River Scholar Project and The Chief Scientist Studio Project)the Fundamental Research Funds for the Central universities(No.106112016CDJXZ138811)the Science and Technology Key Projects of Henan Province(No.172102210425)。
文摘The Mg–9Al–5Sn-xSb(x=0.0,0.3,0.6,1.0,1.5 wt%)alloys were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The effects of Sb additions on the microstructure and mechanical properties of the Mg–9 Al–5 Sn alloys were investigated by optical microscopy,X-ray diffraction,transmission electron microscopy,scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer.The results indicated that the phasesα-Mg matrix,Mg2Sn,Mg_(3)Sb_(2) and Mg17 Al12 exist in the as-cast Sb-containing alloys.Sb addition results in the precipitation of Mg_(3)Sb_(2).The dendritic size of these alloys decreases with the addition of Sb.Both their ultimate tensile strength and yield strength of extruded alloys increase,and their elongation decreases gradually with increasing the content of Sb.The better mechanical properties of the as-extruded alloys were achieved due to the refined grains and the formation of dispersive second phases Mg_(3)Sb_(2).
基金financially supported by the National Great Theoretic Research Project(No.2013CB632200)the National Science&Technology Support Project(No.2011BAE 22B01-3)+1 种基金the International Cooperation Project(No.2010DFR 50010)the Sharing Fund of Chongqing University’s Large-Scale Equipment。
文摘The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile tests were simulated by the finite element method(FEM)to calculate the critical damage values(Dc)of the CockcroftLatham criterion to predict the occurrence of fracture defects.Finally,the effects of temperature and strain rate on Dc were analyzed to predict the critical damage value’s evolution.The results demonstrate that the critical damage value changes in the range of 0.188-0.718.It increases as strain rate decreases at constant temperature,and increases with the increase of temperature under certain strain rate,but is more sensitive to the temperature.