Local atomic structure evolution of pure gadolinium(Gd)and yttrium(Y)during solidification was investigated by using ab initio molecular dynamics(AIMD)simulation.The calculated results indicate that the local short-ra...Local atomic structure evolution of pure gadolinium(Gd)and yttrium(Y)during solidification was investigated by using ab initio molecular dynamics(AIMD)simulation.The calculated results indicate that the local short-range order(SRO)in liquid Gd and Y is similar to some transitional metals with an asymmetric shape of the second peak in static structure factors.Moreover,the formation of icosahedral local motifs as a function of temperature decreases the diffusivity,which explains the connection between structure evolution and dynamic properties.In examining the topological structures of both systems,we demonstrate that small atomic displacement leads to two different types of topological sixfold rings in liquid and solid states.All analyses yield a systematic study about rare earth metals Gd and Y at the atomic level.展开更多
Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers ...Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.展开更多
The nature of a built-in electric field within supported metal catalysts plays a crucial role in regulating gas adsorption and electron transfer during the gas-sensing process.Herein,we found an electron-supply redepl...The nature of a built-in electric field within supported metal catalysts plays a crucial role in regulating gas adsorption and electron transfer during the gas-sensing process.Herein,we found an electron-supply redeployment phenomenon involving the reversal of direction of a built-in electric field between the metal palladium species and the outer S atoms in ZnS,resulting in a marked hydrogen sensing difference.It was found that Pd nanoparticles embedded into Pd NP-ZnS can induce spontaneous electron transfer from S atoms to Pd species to generate an electron-deficient sulfur(S(2-δ)-)surface.Conversely,atomically dispersed Pd species(Pd_(1)-ZnS)prefer to generate electron-rich sulfur(S^((2+δ)-))sites and thus reverse the built-in electric field.Theoretical calculations demonstrate that the electron-rich S(S^((2+δ)-))surface can reduce the occupancy of antibonding orbitals in the S-Hads bond and enhance the bond energy of S-Hads,thus increasing the adsorption of hydrogen.Additionally,in situ Raman,ex situ X-ray photoelectron spectroscopy and DFT analysis demonstrate that S^((2+δ)-)sites in Pd_(1)-ZnS samples can undergo strong electron transfer with hydrogen during the sensing process.Ultimately,Pd_(1)-ZnS sensors exhibit extremely high response values(9.66/20 ppm)and fast response recovery times(5.1 s/1.8 s to 400 ppm)for hydrogen gas at a working temperature of 170℃.展开更多
基金supported by the National Science and Technology Major Project of China(2017-Ⅶ-0008-0102,2019-Ⅵ-0023-0140)Independent Research and Development Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2021-Z12)+2 种基金the National Natural Science Foundation of China(12074241,52130204,11929401,51861145315)the Science and Technology Commission of Shanghai Municipality(19010500500,20501130600)the Key Research Project of Zhejiang Laboratory(2021PE0AC02)。
文摘Local atomic structure evolution of pure gadolinium(Gd)and yttrium(Y)during solidification was investigated by using ab initio molecular dynamics(AIMD)simulation.The calculated results indicate that the local short-range order(SRO)in liquid Gd and Y is similar to some transitional metals with an asymmetric shape of the second peak in static structure factors.Moreover,the formation of icosahedral local motifs as a function of temperature decreases the diffusivity,which explains the connection between structure evolution and dynamic properties.In examining the topological structures of both systems,we demonstrate that small atomic displacement leads to two different types of topological sixfold rings in liquid and solid states.All analyses yield a systematic study about rare earth metals Gd and Y at the atomic level.
基金supported by the National Natural Science Foundation of China under grant No.59783002by the Natural Science Foundation of Henan under grant Nos.200510465008 and 0523021200.
文摘Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.
基金supported by the National Natural Science Foundation of China(62271299)Shanghai Sailing Program(22YF1413400).
文摘The nature of a built-in electric field within supported metal catalysts plays a crucial role in regulating gas adsorption and electron transfer during the gas-sensing process.Herein,we found an electron-supply redeployment phenomenon involving the reversal of direction of a built-in electric field between the metal palladium species and the outer S atoms in ZnS,resulting in a marked hydrogen sensing difference.It was found that Pd nanoparticles embedded into Pd NP-ZnS can induce spontaneous electron transfer from S atoms to Pd species to generate an electron-deficient sulfur(S(2-δ)-)surface.Conversely,atomically dispersed Pd species(Pd_(1)-ZnS)prefer to generate electron-rich sulfur(S^((2+δ)-))sites and thus reverse the built-in electric field.Theoretical calculations demonstrate that the electron-rich S(S^((2+δ)-))surface can reduce the occupancy of antibonding orbitals in the S-Hads bond and enhance the bond energy of S-Hads,thus increasing the adsorption of hydrogen.Additionally,in situ Raman,ex situ X-ray photoelectron spectroscopy and DFT analysis demonstrate that S^((2+δ)-)sites in Pd_(1)-ZnS samples can undergo strong electron transfer with hydrogen during the sensing process.Ultimately,Pd_(1)-ZnS sensors exhibit extremely high response values(9.66/20 ppm)and fast response recovery times(5.1 s/1.8 s to 400 ppm)for hydrogen gas at a working temperature of 170℃.
