We experimentally compare the output abilities of lightly and heavily doped Ti：Sapphire（Ti：S） amplifiers with diameters as large as 150 mm. Although a lightly doped Ti：S is more favorable to overcome parasitic la...We experimentally compare the output abilities of lightly and heavily doped Ti：Sapphire（Ti：S） amplifiers with diameters as large as 150 mm. Although a lightly doped Ti：S is more favorable to overcome parasitic lasing（PL）and transverse amplified spontaneous emission（TASE）, the self-phase-modulation（SPM） effect becomes more pronounced when a longer crystal is used. Recompression of the amplified, stretched pulses can be seriously affected by the SPM effect. We then propose a temporal multi-pulse pump scheme to suppress PL and TASE in a thin, heavily doped Ti：S crystal. This novel temporal multi-pulse pump technique can find potential applications in 10 PW chirped-pulse amplification laser systems.展开更多
A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for...A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for lithium-ion batteries, Li0.95Fe0.95Ti0.05PO4 exhibited improved rate capability.展开更多
Ti-doped WO3 films were prepared by the mid-frequency dual-target magnetron sputtering method. The structure and electrochromic properties of the Ti-doped WO3 films were analysed by X-Ray diffraction （XRD）, Raman sp...Ti-doped WO3 films were prepared by the mid-frequency dual-target magnetron sputtering method. The structure and electrochromic properties of the Ti-doped WO3 films were analysed by X-Ray diffraction （XRD）, Raman spectroscopy, spectrophotometer, cyclic chronoam- perometry and atomic force microscopy （AFM）. The results indicate that the erystallinity decrease after the doping of titanium, the channels for ion injection and extraction increase, the responding speed with 5.1% titanium doped becomes faster, and its circle life increases more than four times compared with the undoped WO3 film. In the coloured state, the W-O-W bonds decrease, but the W = O bonds increase. Since the W-O-W bonds break down for Li＋ ions＇ injection and more W = O bonds form, it is more convenient to inject Li＋ ions into the Ti-doped film than undoped film because more W-O-W bonds break down in the coloured state.展开更多
Density functional theory （DFT） calculations are conducted to explore the interaction of H2 with pure and Tidoped WO3 （002） surfaces. Four top adsorption models of H2 on pure and Ti-doped WO3 （002） surfaces are ...Density functional theory （DFT） calculations are conducted to explore the interaction of H2 with pure and Tidoped WO3 （002） surfaces. Four top adsorption models of H2 on pure and Ti-doped WO3 （002） surfaces are investigated respectively, they are adsorption on bridging oxygen Olc, absorption on plane oxygen O2c, absorption on 5-fold W5c （Ti）, and absorption on 6-fold W6c. The most stable and H2 possible adsorption structure in the pure surface is H-end oriented to the surface plane oxygen O2c site, while the favourable adsorption sites for H2 in a Ti-doped surface is not only an O2c site but also a W6c site. The adsorption energy, the Fermi energy level EF, and the electronic population are investigated and the H2-sensing mechanism of a pure-doped WO3 （002） surface is revealed theoretically： the theoretical results are in good accordance with our existing experimental results. By comparing the above three terms, it is found that Ti doping can obviously enhance the adsorption of H2. It can be predicted that the method of Ti-doped into a WO3 thin film is an effective way to improve WO3 sensor sensitivity to H2 gas.展开更多
Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The p...Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The physicochemical properties of the Sb-SnO2 coating were markedly influenced by different amounts of Sb dopant. The electrodes, which contained 5% Sb dopant in the coating, presented a much more homogenous surface and much smaller mud-cracks, compared with Ti/Sb-SnO2 electrodes containing 10% or 15% Sb dopant, which exibited larger mud cracks and pores on the surface. However, the main microstructure remained unchanged with the addition of the Sb dopant. No new crystal phase was observed by X-ray diffraction （XRD）. The electrochemical oxidation of 4-chlorophenol on the Ti/SnO2 electrode with 5% Sb dopant was inclined to electrochemical combustion; while for those containing more Sb dopant, intermediate species were accumulated. The electrodes with 5% Sb dopant showed the highest efficiency in the bulk electrolysis of 4-chlorophenol at a current density of 20 mA/cm^2 for 180 min; and the removal rates of 4-chlorophenol and COD were 51.0% and 48.9%, respectively.展开更多
Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the le...Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and densified the microstructure with a decreased grain size. The highest relative density reached more than 90%. The highest piezoelectric dielectric coefficient d33 and planar mode electro-mechanical coupling coefficient kp were 110 pC/N and 19.5%,which were obtained in the NKNT ceramic with 1 mol% Ti. The piezoelectric properties of the NKNT ceramics were enhanced by aging in air for a period of time owing to the compensation of oxygen vacancies.展开更多
The as-prepared Ti-Zr hydride powder is used as dopant to improve hydrogen storage properties of NaAlH4 upon mechanical milling under argon atmosphere. The as-milled sample is investigated by X-ray diffraction(XRD),sc...The as-prepared Ti-Zr hydride powder is used as dopant to improve hydrogen storage properties of NaAlH4 upon mechanical milling under argon atmosphere. The as-milled sample is investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Sievert's technology test. It is observed that Ti-Zr hydride doped NaAlH4 discharges 2.7% and 4.0%(mass fraction) of hydrogen in 40 min and 11 h at 160 ℃,respectively,and keeps its reversible dehydrogenation capacity at 4.0%(mass fraction) after 10 hydrogenation/dehydrogenation cycles. These results show the Ti-Zr hydride doped NaAlH4 has good reversible hydrogen storage capacity and kinetics. XRD and SEM investigations also show that the doped Ti-Zr hydride uniformly distributes in NaAlH4 substrate and keeps stable during the hydrogenation/dehydrogenation cycle,indicating that Ti-Zr hydride plays the main surface-catalytic role on improving reversible hydrogen storage properties of NaAlH4.展开更多
Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling st...Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling stability and rate performance. Doped Ti4^＋ ions can improve the long-term cycling stability and rate performance of the Li-rich oxides materials with obvious capacity fading. The electrochemical performance in LixNi2-4x/3Sbx/3O2 can benefit a lot from the nanohighway, which is a kind of nanoscale 0-TM diffusion channels in the transition metal layer and provides low diffusion barrier pathways for the lithium diffusion. In this work, the doping effect of Ti on the structure and electrochemical properties in Li1.15Ni0.47Sb0.38O2 is studied. The Ti-stabilized Li1.15-xNi0.47TixSb0.38O2 （x=0, 0.01, 0.03 and 0.05） have been prepared by a solid-state method and the Li1.03Ni0.47Sb0.38Ti0.03O2 sample exhibits outstanding electrochemical performance with a larger reversible discharge capacity, better rate capability and cyclability. Synchrotron-based XANES, combined with ab initio calculations in the multiple-scattering flame- work, reveals the Ti ions have been doped into the Li-site in the lithium layer and formed a distortion TiO6 octahedron. This TiO6 local configuration in the lithium can keep the stability of nanohighway in the electrochemical pro- cess. In particular, the Lil.03Ni0.47Sb0.38Ti0.03O2 compound can deliver a discharge capacities 132 and 76 mAh/g at 0.2 and 5 C, respectivly. About 86% capacity retention occurs at 1 C rate after 500 cycles. This work suggests capacity fading in the oxide cathode materials can be suppressed to construct and stabilize the nanohighway.展开更多
High-voltage high-nickel lithium layered oxide cathodes show great application prospects to meet the ever-increasing demand for further improvement of the energy density of rechargeable lithium-ion batteries(LIBs)main...High-voltage high-nickel lithium layered oxide cathodes show great application prospects to meet the ever-increasing demand for further improvement of the energy density of rechargeable lithium-ion batteries(LIBs)mainly due to their high output capacity.However,severe bulk structural degradation and undesired electrode-electrolyte interface reactions seriously endanger the cycle life and safety of the battery.Here,2 mol%Ti atom is used as modified material doping into LiNi_(0.8)Co_(0.2)Mn_(0.2O2)(NCM)to reform LiNi_(0.6)Co_(0.2)Mn_(0.18)Ti_(0.02)O_(2)(NCM-Ti)and address the long-standing inherent problem.At a high cut-off voltage of 4.5 V,NCM-Ti delivers a higher capacity retention ratio(91.8%vs.82.9%)after 150 cycles and a superior rate capacity(118 vs.105 mAh·g^(-1))at the high current density of 10 C than the pristine NCM.The designed high-voltage full battery with graphite as anode and NCM-Ti as cathode also exhibits high energy density(240 Wh·kg^(-1))and excellent electrochemical performance.The superior electrochemical behavior can be attributed to the improved stability of the bulk structure and the electrode-electrolyte interface owing to the strong Ti-O bond and no unpaired electrons.The in-situ X-ray diffraction analysis demonstrates that Ti-doping inhibits the undesired H2-H3 phase transition,minimizing the mechanical degradation.The ex-situ TEM and X-ray photoelectron spectroscopy reveal that Ti-doping suppresses the release of interfacial oxygen,reducing undesired interfacial reactions.This work provides a valuable strategic guideline for the application of high-voltage high-nickel cathodes in LIBs.展开更多
文摘We experimentally compare the output abilities of lightly and heavily doped Ti：Sapphire（Ti：S） amplifiers with diameters as large as 150 mm. Although a lightly doped Ti：S is more favorable to overcome parasitic lasing（PL）and transverse amplified spontaneous emission（TASE）, the self-phase-modulation（SPM） effect becomes more pronounced when a longer crystal is used. Recompression of the amplified, stretched pulses can be seriously affected by the SPM effect. We then propose a temporal multi-pulse pump scheme to suppress PL and TASE in a thin, heavily doped Ti：S crystal. This novel temporal multi-pulse pump technique can find potential applications in 10 PW chirped-pulse amplification laser systems.
文摘A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for lithium-ion batteries, Li0.95Fe0.95Ti0.05PO4 exhibited improved rate capability.
文摘Ti-doped WO3 films were prepared by the mid-frequency dual-target magnetron sputtering method. The structure and electrochromic properties of the Ti-doped WO3 films were analysed by X-Ray diffraction （XRD）, Raman spectroscopy, spectrophotometer, cyclic chronoam- perometry and atomic force microscopy （AFM）. The results indicate that the erystallinity decrease after the doping of titanium, the channels for ion injection and extraction increase, the responding speed with 5.1% titanium doped becomes faster, and its circle life increases more than four times compared with the undoped WO3 film. In the coloured state, the W-O-W bonds decrease, but the W = O bonds increase. Since the W-O-W bonds break down for Li＋ ions＇ injection and more W = O bonds form, it is more convenient to inject Li＋ ions into the Ti-doped film than undoped film because more W-O-W bonds break down in the coloured state.
基金supported by the National Natural Science Foundation of China (Grant Nos.60771019 and 60801018)the Tianjin Key Research Program of Application Foundation and Advanced Technology,China (Grant No.11JCZDJC15300)+1 种基金the Tianjin Natural Science Foundation,China (Grant No.09JCYBJC01100)the New Teacher Foundation of the Ministry of Education,China (Grant No.200800561109)
文摘Density functional theory （DFT） calculations are conducted to explore the interaction of H2 with pure and Tidoped WO3 （002） surfaces. Four top adsorption models of H2 on pure and Ti-doped WO3 （002） surfaces are investigated respectively, they are adsorption on bridging oxygen Olc, absorption on plane oxygen O2c, absorption on 5-fold W5c （Ti）, and absorption on 6-fold W6c. The most stable and H2 possible adsorption structure in the pure surface is H-end oriented to the surface plane oxygen O2c site, while the favourable adsorption sites for H2 in a Ti-doped surface is not only an O2c site but also a W6c site. The adsorption energy, the Fermi energy level EF, and the electronic population are investigated and the H2-sensing mechanism of a pure-doped WO3 （002） surface is revealed theoretically： the theoretical results are in good accordance with our existing experimental results. By comparing the above three terms, it is found that Ti doping can obviously enhance the adsorption of H2. It can be predicted that the method of Ti-doped into a WO3 thin film is an effective way to improve WO3 sensor sensitivity to H2 gas.
基金Project supported by the Institute of Environmental Engineering,Peking University and China Postdoctoral Science Foundation(No.2005037032)
文摘Ti/Sb-SnO2 anodes were prepared by thermal decomposition to examine the influence of the amount of Sb dopant on the structure and electrocatalytic capability of the electrodes in the oxidation of 4-chlorophenol. The physicochemical properties of the Sb-SnO2 coating were markedly influenced by different amounts of Sb dopant. The electrodes, which contained 5% Sb dopant in the coating, presented a much more homogenous surface and much smaller mud-cracks, compared with Ti/Sb-SnO2 electrodes containing 10% or 15% Sb dopant, which exibited larger mud cracks and pores on the surface. However, the main microstructure remained unchanged with the addition of the Sb dopant. No new crystal phase was observed by X-ray diffraction （XRD）. The electrochemical oxidation of 4-chlorophenol on the Ti/SnO2 electrode with 5% Sb dopant was inclined to electrochemical combustion; while for those containing more Sb dopant, intermediate species were accumulated. The electrodes with 5% Sb dopant showed the highest efficiency in the bulk electrolysis of 4-chlorophenol at a current density of 20 mA/cm^2 for 180 min; and the removal rates of 4-chlorophenol and COD were 51.0% and 48.9%, respectively.
基金the National Natural Science Foundation of China (No. 50842028)the National High-Tech Research and Development Program of China (No. 2006AA03Z436).
文摘Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and densified the microstructure with a decreased grain size. The highest relative density reached more than 90%. The highest piezoelectric dielectric coefficient d33 and planar mode electro-mechanical coupling coefficient kp were 110 pC/N and 19.5%,which were obtained in the NKNT ceramic with 1 mol% Ti. The piezoelectric properties of the NKNT ceramics were enhanced by aging in air for a period of time owing to the compensation of oxygen vacancies.
基金Projects(2006AA05Z131 2006AA05Z144) supported by the National High-Tech Research and Development Program of China
文摘The as-prepared Ti-Zr hydride powder is used as dopant to improve hydrogen storage properties of NaAlH4 upon mechanical milling under argon atmosphere. The as-milled sample is investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM) and Sievert's technology test. It is observed that Ti-Zr hydride doped NaAlH4 discharges 2.7% and 4.0%(mass fraction) of hydrogen in 40 min and 11 h at 160 ℃,respectively,and keeps its reversible dehydrogenation capacity at 4.0%(mass fraction) after 10 hydrogenation/dehydrogenation cycles. These results show the Ti-Zr hydride doped NaAlH4 has good reversible hydrogen storage capacity and kinetics. XRD and SEM investigations also show that the doped Ti-Zr hydride uniformly distributes in NaAlH4 substrate and keeps stable during the hydrogenation/dehydrogenation cycle,indicating that Ti-Zr hydride plays the main surface-catalytic role on improving reversible hydrogen storage properties of NaAlH4.
基金Supporting information for this article is available on the WWW under http：//dx.doi.org/10. 1002/cjoc.201700265 or from the author.Acknowledgement This work was partly supported by the Science Fund for Creative Re search Groups of NSF C （No. 11321503）, the National Key Research and Development Program of China （No. 2016YFA0401004）, the National Natural Science Foundation of China （NSFC No. 11275227, U1632103）, and the Youth Innovation Promotion Association CAS （No. 2014927）.
文摘Recent success and application of the percolation theory have highlighted cation-disordered Li-rich oxides as high energy density cathode materials. Generally, this kind of cathode materials suffer from low cycling stability and rate performance. Doped Ti4^＋ ions can improve the long-term cycling stability and rate performance of the Li-rich oxides materials with obvious capacity fading. The electrochemical performance in LixNi2-4x/3Sbx/3O2 can benefit a lot from the nanohighway, which is a kind of nanoscale 0-TM diffusion channels in the transition metal layer and provides low diffusion barrier pathways for the lithium diffusion. In this work, the doping effect of Ti on the structure and electrochemical properties in Li1.15Ni0.47Sb0.38O2 is studied. The Ti-stabilized Li1.15-xNi0.47TixSb0.38O2 （x=0, 0.01, 0.03 and 0.05） have been prepared by a solid-state method and the Li1.03Ni0.47Sb0.38Ti0.03O2 sample exhibits outstanding electrochemical performance with a larger reversible discharge capacity, better rate capability and cyclability. Synchrotron-based XANES, combined with ab initio calculations in the multiple-scattering flame- work, reveals the Ti ions have been doped into the Li-site in the lithium layer and formed a distortion TiO6 octahedron. This TiO6 local configuration in the lithium can keep the stability of nanohighway in the electrochemical pro- cess. In particular, the Lil.03Ni0.47Sb0.38Ti0.03O2 compound can deliver a discharge capacities 132 and 76 mAh/g at 0.2 and 5 C, respectivly. About 86% capacity retention occurs at 1 C rate after 500 cycles. This work suggests capacity fading in the oxide cathode materials can be suppressed to construct and stabilize the nanohighway.
基金This work is financially supported by the National Key R&D Program of China(No.2017YFE0198100)the National Natural Science Foundation of China(Nos.21975250 and 52072145)+4 种基金the Beijing Natural Science Foundation(No.2214061)the Scientific and Technological Developing Project of Jilin Province,China(No.YDZJ202101ZYTS185)the Capital Construction Fund Projects within the Budget of Jilin Province,China(No.2021C037-2)the Open Project Program of Key Laboratory of Preparation and Application of Environmental Friendly Materials(Jilin Normal University),Ministry of Education,China(No.2020005)the Open Program of State Key Laboratory of Metastable Materials Science and Technology(Yanshan University),China(No.202110).
文摘High-voltage high-nickel lithium layered oxide cathodes show great application prospects to meet the ever-increasing demand for further improvement of the energy density of rechargeable lithium-ion batteries(LIBs)mainly due to their high output capacity.However,severe bulk structural degradation and undesired electrode-electrolyte interface reactions seriously endanger the cycle life and safety of the battery.Here,2 mol%Ti atom is used as modified material doping into LiNi_(0.8)Co_(0.2)Mn_(0.2O2)(NCM)to reform LiNi_(0.6)Co_(0.2)Mn_(0.18)Ti_(0.02)O_(2)(NCM-Ti)and address the long-standing inherent problem.At a high cut-off voltage of 4.5 V,NCM-Ti delivers a higher capacity retention ratio(91.8%vs.82.9%)after 150 cycles and a superior rate capacity(118 vs.105 mAh·g^(-1))at the high current density of 10 C than the pristine NCM.The designed high-voltage full battery with graphite as anode and NCM-Ti as cathode also exhibits high energy density(240 Wh·kg^(-1))and excellent electrochemical performance.The superior electrochemical behavior can be attributed to the improved stability of the bulk structure and the electrode-electrolyte interface owing to the strong Ti-O bond and no unpaired electrons.The in-situ X-ray diffraction analysis demonstrates that Ti-doping inhibits the undesired H2-H3 phase transition,minimizing the mechanical degradation.The ex-situ TEM and X-ray photoelectron spectroscopy reveal that Ti-doping suppresses the release of interfacial oxygen,reducing undesired interfacial reactions.This work provides a valuable strategic guideline for the application of high-voltage high-nickel cathodes in LIBs.
