By taking tetragonal tungsten bronze(TTB)phase Nb_(18)W_(16)O_(93)as an example,an improved solid-state sintering method at lower temperature of 1000℃for 36 h was proposed via applying nanoscale raw materials.XRD,SEM...By taking tetragonal tungsten bronze(TTB)phase Nb_(18)W_(16)O_(93)as an example,an improved solid-state sintering method at lower temperature of 1000℃for 36 h was proposed via applying nanoscale raw materials.XRD,SEM and XPS confirm that the expected sample was produced.GITT results show that the lithium-ion diffusion coefficient of Nb_(18)W_(16)O_(93)(10−12 cm^(2)/s)is higher than that of the conventional titanium-based anode,ensuring a relatively superior electrochemical performance.The lithium-ion diffusion mechanism was thoroughly revealed by using density functional theory simulation.There are three diffusion paths in TTB phase,among which the interlayer diffusion with the smallest diffusion barrier(0.46 eV)has more advantages than other typical anodes(such as graphite,0.56 eV).The relatively smaller lithium-ion diffusion barrier makes TTB phase Nb_(18)W_(16)O_(93)become a potential highspecific-power anode material.展开更多
Compounds Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 with filled tetragonal tungsten bronze structure were prepared,and the dielectric characteristics and ferroelectric transition were investigated.Both ceramics displayed wea...Compounds Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 with filled tetragonal tungsten bronze structure were prepared,and the dielectric characteristics and ferroelectric transition were investigated.Both ceramics displayed weak frequency dependence in room temperature dielectric constant,which decreased from 125 to 118 for Sr4Eu2Ti4Nb6O30,from 206 to 195 for Sr5EuTi3Nb7O30 in the frequency range of 10 kHz to 1 MHz.The present ceramics showed a diffuse ferroelectric phase transition.The frequency independent transition temperature （Tm） indicated the above compounds had no relaxor property.The diffuseness （γ） was 1.45 and 1.64 for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 respectively.The weak ferroelectric of the present materials are indicated from the P-E hysteresis loops,and a small 2Pr of 0.596 μC/cm2 and 0.068 μC/cm2 were observed for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 respectively.展开更多
This work studied the feasibility of producing a dual-phase aluminium bronze alloy and the use of selected treatments to manipulate the mechanical properties of the produced alloy using local techniques, as a potentia...This work studied the feasibility of producing a dual-phase aluminium bronze alloy and the use of selected treatments to manipulate the mechanical properties of the produced alloy using local techniques, as a potential replacement for con- ventional structural materials, particularly steels. Sand casting was used and was found to be effective based on its ad- vantages of low cost, ease of use and flexibility in the production of a dual-phase aluminium bronze alloy with pre-selected composition of 11% Al content. Cold deformation of 10 and 20% degrees and selected heat treatments were used on the cast alloy to influence its mechanical properties. The selected heat treatments are solution heat treat- ment, normalising, and ageing. The results showed that normalising gave the optimum mix of tested mechanical proper- ties with ultimate tensile strength in the range of 325 MPa, elongation of around 60% and Rockwell hardness values of 46.5 - 63.7 HRc, making this alloy suitable as alternatives to steel in low/medium strength structural applications.展开更多
A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room tempera...A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm,α =β =γ =90° .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃ ,which is lower than that of B NaNb5O30.展开更多
基金the Key R&D Program of Shaanxi Province,China(No.2019ZDLGY04-05)the Natural Science Foundation of Shaanxi Province,China(No.2019JLZ-01)+1 种基金the Fundamental Research Funds for the Central Universities of China(Nos.19GH020302,3102019JC005,3102021ZD0401,3102021TS0406)the Science,Technology,and Innovation Commission of Shenzhen Municipality,China(No.JCYJ20180508151856806).
文摘By taking tetragonal tungsten bronze(TTB)phase Nb_(18)W_(16)O_(93)as an example,an improved solid-state sintering method at lower temperature of 1000℃for 36 h was proposed via applying nanoscale raw materials.XRD,SEM and XPS confirm that the expected sample was produced.GITT results show that the lithium-ion diffusion coefficient of Nb_(18)W_(16)O_(93)(10−12 cm^(2)/s)is higher than that of the conventional titanium-based anode,ensuring a relatively superior electrochemical performance.The lithium-ion diffusion mechanism was thoroughly revealed by using density functional theory simulation.There are three diffusion paths in TTB phase,among which the interlayer diffusion with the smallest diffusion barrier(0.46 eV)has more advantages than other typical anodes(such as graphite,0.56 eV).The relatively smaller lithium-ion diffusion barrier makes TTB phase Nb_(18)W_(16)O_(93)become a potential highspecific-power anode material.
基金Funded by the the National Natural Science Foundation of China(No.50762002,50962004,21061004)the Natural Science Foundation of Gunangxi Province (No3.0832003Z,0832001)ICDD Grant-in-Aid Program
文摘Compounds Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 with filled tetragonal tungsten bronze structure were prepared,and the dielectric characteristics and ferroelectric transition were investigated.Both ceramics displayed weak frequency dependence in room temperature dielectric constant,which decreased from 125 to 118 for Sr4Eu2Ti4Nb6O30,from 206 to 195 for Sr5EuTi3Nb7O30 in the frequency range of 10 kHz to 1 MHz.The present ceramics showed a diffuse ferroelectric phase transition.The frequency independent transition temperature （Tm） indicated the above compounds had no relaxor property.The diffuseness （γ） was 1.45 and 1.64 for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 respectively.The weak ferroelectric of the present materials are indicated from the P-E hysteresis loops,and a small 2Pr of 0.596 μC/cm2 and 0.068 μC/cm2 were observed for Sr4Eu2Ti4Nb6O30 and Sr5EuTi3Nb7O30 respectively.
文摘This work studied the feasibility of producing a dual-phase aluminium bronze alloy and the use of selected treatments to manipulate the mechanical properties of the produced alloy using local techniques, as a potential replacement for con- ventional structural materials, particularly steels. Sand casting was used and was found to be effective based on its ad- vantages of low cost, ease of use and flexibility in the production of a dual-phase aluminium bronze alloy with pre-selected composition of 11% Al content. Cold deformation of 10 and 20% degrees and selected heat treatments were used on the cast alloy to influence its mechanical properties. The selected heat treatments are solution heat treat- ment, normalising, and ageing. The results showed that normalising gave the optimum mix of tested mechanical proper- ties with ultimate tensile strength in the range of 325 MPa, elongation of around 60% and Rockwell hardness values of 46.5 - 63.7 HRc, making this alloy suitable as alternatives to steel in low/medium strength structural applications.
文摘A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm,α =β =γ =90° .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃ ,which is lower than that of B NaNb5O30.
