Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosp...Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn3 Al2 Ge2 O10:0.02 Cr3+,RE(RE=Ce3+,Dy3+,Tb3+,Eu3+)and Zn3 Al2 Ge2 O10:0.02 Cr3+,Mn2+are observed.The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect,and the nephelauxetic effect is dominant.Therefore,the emission FWHM decreases with the increasing concentration of Mn2+/Tb3+/Eu3+in Zn3 Al2 Ge2 O10:0.02 Cr3+,and for Zn3 Al2 Ge2 O10:0.02 Cr3+,Ce3+and Zn3 Al2 Ge2 O10:0.02 Cr3+,Dy3+,it is a constant.The variation of Zn3 Al2 Ge2 O10:0.02 Cr3+,Tb3+is more obvious than that of Zn3 Al2 Ge2 O10:0.02 Cr3+,Eu3+,because Tb3+ion has smaller electronegativity.Thus,the tunable luminescence of Cr3+can be realized by co-doping different ions.And these phosphors have potential applications in light-emitting diodes for plant growth.展开更多
A warm-white emitting persistent luminescence phosphor Lu3Al2Ga3O12：Pr^3＋ was synthesized by solid state method at 1600 °C in air. The refined crystal structure of Lu3Al2Ga3O12 host was solved by X-ray diffract...A warm-white emitting persistent luminescence phosphor Lu3Al2Ga3O12：Pr^3＋ was synthesized by solid state method at 1600 °C in air. The refined crystal structure of Lu3Al2Ga3O12 host was solved by X-ray diffraction（XRD）. The photoluminescence spectra, decay curve and thermoluminescence were investigated. It was revealed that the persistent luminescence originated from the f-f transitions of Pr^3＋ emitters at Lu^3＋ sites in LuO8 polyhedrons, and it showed white color due to the ^3P0→^3H4, ^3P1→^3H5, ^3P0→^3H5, ^3P0→^3H6, ^3P0→^3F2, ^3P0→^3F3 and ^3P0→^3F4 transitions of Pr^3＋ emitters in a wide range. The persistent luminescence of Pr^3＋ in this host could be promoted by f-d transition（278 nm） but f-f transitions, due to the different thermal activation energy. The persistent luminescence of the optimal sample could be actually recorded for 3 h by the definition of 0.32 mcd/m^2 and was visible for more than 7 h by dark-adapted vision in darkness. The initial depth of the dominant shallow traps was calculated to be about 0.56 eV, which is suitable for persistent luminescence. The different roles of the shallow and deep traps on the persistent decay process were investigated. Accordingly, the persistent luminescence processes and mechanism of the as-synthesized Lu3Al2Ga3O12：Pr^3＋ phosphors were proposed.展开更多
The principal refractive indices and the thermal refractive index coefficients for Be3Al2Si6O18 crystal doped with 1.01wt% Cr2O3 have been accurately measured by the auto-collimation method at wavelengths of 0.488, 0....The principal refractive indices and the thermal refractive index coefficients for Be3Al2Si6O18 crystal doped with 1.01wt% Cr2O3 have been accurately measured by the auto-collimation method at wavelengths of 0.488, 0.53975, 1.064, 1.0795 and 1.3414 μm, and temperatures of 308.2, 328.6, 359.1 and 395.4 K respectively. Based on the measured results of principal indices of 0.488, 0.6328, 1.0795 and 1.3414μm, the Sellmeier’s equations and the thermal refractive index coefficients have been obtained, and the result has been proven to be accurate by error analysis.展开更多
The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed...The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.展开更多
A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive material.The effects of Bi_(2)O_(3)in the PT...A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive material.The effects of Bi_(2)O_(3)in the PTFE/Al/Bi_(2)O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar test.The microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2)O_(3).The results indicate that the PTFE/Al/Bi_(2)O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2)O_(3)and Al/Bi_(2)O_(3)over the PTFE/Al reactive materials,thereby promoting reactions.The excessive aluminum in the ternary system is beneficial for increasing energy release.The ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2)O_(3)is closely related to the material fracture.The dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.展开更多
文摘为研究稀土发光纳米晶的微观结构和形貌对发光性能的影响,用凝胶-微波干燥法和凝胶-烘箱干燥法制备了花状形貌的Sr3Al2O6晶体.研究了微波干燥和烘箱干燥两种不同的干燥方式对溶胶-凝胶法制备的Sr3Al2O6∶Eu2+发光粉体粒径、形貌、团聚程度、干燥时间及发光性能等的影响,结果表明采用微波干燥不仅可以大大缩短干燥所需时间,而且有利于减弱Sr3Al2O6∶Eu2+发光粉料的团聚和团聚程度,制得了颗粒分散均匀、团聚程度低、发光强度高的Sr3Al2O6∶Eu2+花状形貌粉体.研究了Sr3Al2O6∶Eu2+发光粉体的新型形貌对发光性能的影响,微波干燥法制备的均匀分散的花状形貌发光粉体发光强度高,余辉时间长达20 min.
基金Projects supported by the National Natural Science Foundation of China(61575019,11474018,61775013),ChinaThe authors express the thanks to the Fundamental ResearchFunds for the Central Universities under Grant No. 2018YJS166,China and the Fundamental Research Funds for the Central Universitieswith the Grant No. 2016JBM066,No. 2017RC015, No.2017JBZ105, China.
文摘Ce3+/Dy3+/Tb3+/Eu3+/Mn2+and Cr3+ions co-doped Zn3 Al2 Ge2 O10 phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn3 Al2 Ge2 O10 phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn3 Al2 Ge2 O10:0.02 Cr3+,RE(RE=Ce3+,Dy3+,Tb3+,Eu3+)and Zn3 Al2 Ge2 O10:0.02 Cr3+,Mn2+are observed.The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect,and the nephelauxetic effect is dominant.Therefore,the emission FWHM decreases with the increasing concentration of Mn2+/Tb3+/Eu3+in Zn3 Al2 Ge2 O10:0.02 Cr3+,and for Zn3 Al2 Ge2 O10:0.02 Cr3+,Ce3+and Zn3 Al2 Ge2 O10:0.02 Cr3+,Dy3+,it is a constant.The variation of Zn3 Al2 Ge2 O10:0.02 Cr3+,Tb3+is more obvious than that of Zn3 Al2 Ge2 O10:0.02 Cr3+,Eu3+,because Tb3+ion has smaller electronegativity.Thus,the tunable luminescence of Cr3+can be realized by co-doping different ions.And these phosphors have potential applications in light-emitting diodes for plant growth.
基金Project supported by the National Natural Science Foundation of China(10904057)the Fundamental Research Funds for Central Universities(Lzjbky-2015-112,Lzjbky-2015-113)the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China(041105,041106)
文摘A warm-white emitting persistent luminescence phosphor Lu3Al2Ga3O12：Pr^3＋ was synthesized by solid state method at 1600 °C in air. The refined crystal structure of Lu3Al2Ga3O12 host was solved by X-ray diffraction（XRD）. The photoluminescence spectra, decay curve and thermoluminescence were investigated. It was revealed that the persistent luminescence originated from the f-f transitions of Pr^3＋ emitters at Lu^3＋ sites in LuO8 polyhedrons, and it showed white color due to the ^3P0→^3H4, ^3P1→^3H5, ^3P0→^3H5, ^3P0→^3H6, ^3P0→^3F2, ^3P0→^3F3 and ^3P0→^3F4 transitions of Pr^3＋ emitters in a wide range. The persistent luminescence of Pr^3＋ in this host could be promoted by f-d transition（278 nm） but f-f transitions, due to the different thermal activation energy. The persistent luminescence of the optimal sample could be actually recorded for 3 h by the definition of 0.32 mcd/m^2 and was visible for more than 7 h by dark-adapted vision in darkness. The initial depth of the dominant shallow traps was calculated to be about 0.56 eV, which is suitable for persistent luminescence. The different roles of the shallow and deep traps on the persistent decay process were investigated. Accordingly, the persistent luminescence processes and mechanism of the as-synthesized Lu3Al2Ga3O12：Pr^3＋ phosphors were proposed.
基金the National Natural Science Foundation of China (Grant No. 60278025).
文摘The principal refractive indices and the thermal refractive index coefficients for Be3Al2Si6O18 crystal doped with 1.01wt% Cr2O3 have been accurately measured by the auto-collimation method at wavelengths of 0.488, 0.53975, 1.064, 1.0795 and 1.3414 μm, and temperatures of 308.2, 328.6, 359.1 and 395.4 K respectively. Based on the measured results of principal indices of 0.488, 0.6328, 1.0795 and 1.3414μm, the Sellmeier’s equations and the thermal refractive index coefficients have been obtained, and the result has been proven to be accurate by error analysis.
文摘The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.
基金the National Natural Science Foundation of China (Grant No.12002045)State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology (Grant No.QNKT22-09)。
文摘A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive material.The effects of Bi_(2)O_(3)in the PTFE/Al/Bi_(2)O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar test.The microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2)O_(3).The results indicate that the PTFE/Al/Bi_(2)O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2)O_(3)and Al/Bi_(2)O_(3)over the PTFE/Al reactive materials,thereby promoting reactions.The excessive aluminum in the ternary system is beneficial for increasing energy release.The ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2)O_(3)is closely related to the material fracture.The dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.
