In this work,the thermodynamic,mechanical properties and electronic behaviors of D022-TiAl3 doped with W and 15 groupⅣM(M=C,Ge,Pb,Si and Sn)dopants are investigated by DFT methods.We established that ductility can be...In this work,the thermodynamic,mechanical properties and electronic behaviors of D022-TiAl3 doped with W and 15 groupⅣM(M=C,Ge,Pb,Si and Sn)dopants are investigated by DFT methods.We established that ductility can be improved using multi-doping approach and revealed the mechanisms behind such brittle-to-ductile transition.In addition,it is found that there is linearity between changes in Young’s modulus and tensile/compre s sive strain ratio.An alternate insight into brittle-to-ductile transition during ductile mode cutting of brittle materials is proposed.展开更多
This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5...This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/)_5Bi_(1/5))_(x)O_(2-δ)(GSEYB)system.This system holds promise as a solid electrolyte material for low and medium-temperature solid oxide fuel cells.The powders of Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/5)Bi_(1/5))_(x)O_(2-δ)(x=0,0.10,0.15,0.20,0.25,0.30)were synthesized using the solid-phase reaction method.The GSEYB electrolytes were comprehensively investigated for their phase structure,microstructure,oxygen vacancy concentration,and ionic conductivity using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and impedance spectroscopy.XRD diffraction patterns confirm a cubic fluorite-type structure with Fm3m space groups in all multi-doped systems.After sintering at 1400℃for 10 h,the relative density of doped samples exceeds 96%.In terms of electrical properties,the Ce_(0.75)Gd_(0.05)Sm_(0.05)Er_(0.05)Y_(0.05)Bi_(0.05)O_(2-δ)(x=0.25)electrolyte exhibits the highest ionic conductivity(σ_(t)=4.45×10^(-2)S/cm)and the lowest activation energy(E_(a)=0.79 eV)at 800℃.The coefficient of thermal expansion of the developed electrolyte aligns well with that of the commonly used electrode materials.This compatibility positions it as a highly promising candidate for utilization as an electrolyte material in solid oxide fuel cells(SOFCs).展开更多
LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such...LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface morphology.TEM images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.展开更多
Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sin...Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.展开更多
Metal doping for active sites exhibits remarkable potential for improving the hydrogen evolution reaction(HER).Multi-doping and the use of a conductive substrate can further modulate catalytic performance.Herein,Nb-Co...Metal doping for active sites exhibits remarkable potential for improving the hydrogen evolution reaction(HER).Multi-doping and the use of a conductive substrate can further modulate catalytic performance.Herein,Nb-CoSe well dispersed in N-doped carbon nanospheres(NCs,Nb-CoSe@NC)was synthesized to serve as a conductive substrate and facilitated good dispersion of active sites for the HER.Nb doping can also change the electronic structure of CoSe,which facilitates the activity for the HER.In order to further improve the conductivity and intrinsic activity of Nb-CoSe@NC,dual,nonmetal doping was realized through gas sulfurization to prepare hierarchical Nb-CoSeS@NC.The prepared Nb-CoSeS@NC,with a core-shell structure,exhibited a low overpotential of 115 mV at 10 mA cm–2,which is smaller than that of the most doped catalysts.In addition,NCs not only improved the dispersion and conductivity of the catalyst but also prevented metal corrosion in an electrolyte,thus facilitating the long-term stability of Nb-CoSeS@NC.Moreover,the synergistic effect of the multi-doping of Nb,S,and Se was explained.This work provides a promising,multi-doping strategy for the large-scale application of transition-metal-based electrocatalysts for the HER.展开更多
LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>x</sub>Cr<sub>y</sub>Mn<sub>2-x-y</sub>O<sub>4</sub> (x = 0.50;y = 0.05 - 0.50) powders have been synt...LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>x</sub>Cr<sub>y</sub>Mn<sub>2-x-y</sub>O<sub>4</sub> (x = 0.50;y = 0.05 - 0.50) powders have been synthesized via sol-gel method for the first time using Myristic acid as chelating agent. The synthesized samples have been taken to physical and electrochemical characterization such as thermo gravimetric analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical characterization viz., electrochemical galvanostatic cycling studies, electrochemical impedance spectroscopy (EIS) and differential capacity curves (dQ/dE). XRD patterns of LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>x</sub>Cr<sub>y</sub>Mn<sub>2-x-y</sub>O<sub>4</sub> confirm high degree of crystallinity with good phase purity. FESEM image of undoped pristine spinel lucidly depicts cauliflower morphology with good agglomerated particle size of 50 nm while 0.5-Cu doped samples depict the pebbles morphology. TEM images of the spinel LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>0.5</sub>Cr<sub>0.05</sub>Mn<sub>1.45</sub>O<sub>4</sub> authenticate that all the synthesized particles via sol-gel method are nano-sized (100 nm) with spherical surface and cloudy particles morphology. The LiMn<sub>2</sub>O<sub>4</sub> samples calcined at 850℃ deliver the high discharge capacity of 130 mA·h/g with cathodic efficiency of 88% corresponds to 94% columbic efficiency in the first cycle. Among all four compositions studied, LiCu<sub>0.5</sub>Cr<sub>0.05</sub>Mn<sub>1.45</sub>O<sub>4</sub> delivers 124 mA·h/g during the first cycle and shows stable performance with a low capacity fade of 1.1 mA·h/g cycle over the investigated 10 cycles.展开更多
基金partially supported by the National Research Foundation,Prime Minister’s Office,Singapore under its Marine Science Research and Development program(Award No.MSRDPP28)the Ministry of Education,Singapore under Tier 2 program(Award No.MOE2018-T2-1-163)。
文摘In this work,the thermodynamic,mechanical properties and electronic behaviors of D022-TiAl3 doped with W and 15 groupⅣM(M=C,Ge,Pb,Si and Sn)dopants are investigated by DFT methods.We established that ductility can be improved using multi-doping approach and revealed the mechanisms behind such brittle-to-ductile transition.In addition,it is found that there is linearity between changes in Young’s modulus and tensile/compre s sive strain ratio.An alternate insight into brittle-to-ductile transition during ductile mode cutting of brittle materials is proposed.
基金supported by the Guangdong Provincial Basic and Applied Basic Research Foundation(2021A1515010671,2020A1515011221)the Guangdong Provincial Key Discipline Research Capacity Enhancement Project(2021ZDJS071)the Guangdong Provincial College Innovation Project(2021KTSCX122,2022KQNCX077)。
文摘This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/)_5Bi_(1/5))_(x)O_(2-δ)(GSEYB)system.This system holds promise as a solid electrolyte material for low and medium-temperature solid oxide fuel cells.The powders of Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/5)Bi_(1/5))_(x)O_(2-δ)(x=0,0.10,0.15,0.20,0.25,0.30)were synthesized using the solid-phase reaction method.The GSEYB electrolytes were comprehensively investigated for their phase structure,microstructure,oxygen vacancy concentration,and ionic conductivity using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and impedance spectroscopy.XRD diffraction patterns confirm a cubic fluorite-type structure with Fm3m space groups in all multi-doped systems.After sintering at 1400℃for 10 h,the relative density of doped samples exceeds 96%.In terms of electrical properties,the Ce_(0.75)Gd_(0.05)Sm_(0.05)Er_(0.05)Y_(0.05)Bi_(0.05)O_(2-δ)(x=0.25)electrolyte exhibits the highest ionic conductivity(σ_(t)=4.45×10^(-2)S/cm)and the lowest activation energy(E_(a)=0.79 eV)at 800℃.The coefficient of thermal expansion of the developed electrolyte aligns well with that of the commonly used electrode materials.This compatibility positions it as a highly promising candidate for utilization as an electrolyte material in solid oxide fuel cells(SOFCs).
基金support given under the "Brain Pool Program of the Korean Federation of Science and Technology Societies" (KOFST), Republic of South Koreasupported by the Human Resources Development Program (No. 20124010203270) of the Korea Institute of Energy Technology EvaluationPlanning (KETEP) grant funded by the Korea Government Ministry of Trade, Industry and Energy
文摘LiMnOand LiNiAlyMnO（x= 0.50;y = 0.05-0.50） powders have been synthesized via facile solgel method using Behenic acid as active cheiating agent.The synthesized samples are subjected to physical characterizations such as thermo gravimetric analysis（TG/DTA）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,field-emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM） and electrochemical studies viz.,galvanostatic cycling properties,electrochemical impedance spectroscopy（EIS） and differential capacity curves（dQ/dE）.Finger print XRD patterns of LiMnOand LiNiAlMnOfortify the high degree of crystallinity with better phase purity.FESEM images of the undoped pristine spinel illustrate uniform spherical grains surface morphology with an average particle size of 0.5 μm while Ni doped particles depict the spherical grains growth（50nm） with ice-cube surface morphology.TEM images of the spinel LiMnOshows the uniform spherical morphology with particle size of（100 nm） while low level of Al-doping spinel（LiNio.5Alo.05Mn1.45O4） displaying cloudy particles with agglomerated particles of（50nm）.The LiMnOsamples calcined at 850℃ deliver the discharge capacity of 130 mAh/g in the first cycle corresponds to 94%coiumbic efficiency with capacity fade of 1.5 mAh/g/cycle over the investigated 10 cycles.Among all four dopant compositions investigated,LiNiAlMnOdelivers the maximum discharge capacity of 126 mAh/g during the first cycle and shows the stable cycling performance with low capacity fade of 1 mAh/g/cycle（capacity retention of 92%） over the investigated 10 cycles.Electrochemical impedance studies of spinel LiMnOand LiNiAlMnOdepict the high and low real polarization of 1562 and 1100 Ω.
基金supported financially by the National Natural Science Foundation of China(Nos.U1537212,51971013,51590894and 51425102)the National Key Research and Development Program of China(No.2016YFB0300901)。
文摘Rare earth oxides doped hafnia ceramics,with a formula of Hf0.76LnxY0.24-xO1.88(Ln=Gd,Yb,Gd+Yb or La+Yb),were prepared by solid state sintering at 1500℃.The effects of the rare earth oxides on the microstructures,sintering resistance,and thermo-physical properties of the doped hafnia ceramics were investigated.Results show that the Gd-Y,Yb-Y or Gd-Yb-Y co-doped hafnia ceramics remain the same defect fluorite(F)structure,while the La-Yb-Y co-doped hafnia revealing coexistence of pyrochlore(P)and fluorite structures.Yb-Y co-doped samples exhibited much better sintering resistance compared with Gd-Y and Gd-Yb-Y co-doped samples.The coexistence of P and F phases is beneficial to improved sintering capability.The thermal conductivities of the Gd-Y,Yb-Y and Gd-Yb-Y doped samples are relatively lower(1.4-1.7 W m^(-1)K^(-1)at 1200℃),but for the La-Yb-Y co-doped samples,the thermal conductivity increases dramatically with temperature due to increased thermal radiation at high-temperature.The average thermal expansion coefficients(TECs)of the Gd-Y,Yb-Y and Gd-Yb-Y co-doped samples are as high as10.3×10^(-6)K^(-1) in temperature range between 200-1200℃.
文摘Metal doping for active sites exhibits remarkable potential for improving the hydrogen evolution reaction(HER).Multi-doping and the use of a conductive substrate can further modulate catalytic performance.Herein,Nb-CoSe well dispersed in N-doped carbon nanospheres(NCs,Nb-CoSe@NC)was synthesized to serve as a conductive substrate and facilitated good dispersion of active sites for the HER.Nb doping can also change the electronic structure of CoSe,which facilitates the activity for the HER.In order to further improve the conductivity and intrinsic activity of Nb-CoSe@NC,dual,nonmetal doping was realized through gas sulfurization to prepare hierarchical Nb-CoSeS@NC.The prepared Nb-CoSeS@NC,with a core-shell structure,exhibited a low overpotential of 115 mV at 10 mA cm–2,which is smaller than that of the most doped catalysts.In addition,NCs not only improved the dispersion and conductivity of the catalyst but also prevented metal corrosion in an electrolyte,thus facilitating the long-term stability of Nb-CoSeS@NC.Moreover,the synergistic effect of the multi-doping of Nb,S,and Se was explained.This work provides a promising,multi-doping strategy for the large-scale application of transition-metal-based electrocatalysts for the HER.
文摘LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>x</sub>Cr<sub>y</sub>Mn<sub>2-x-y</sub>O<sub>4</sub> (x = 0.50;y = 0.05 - 0.50) powders have been synthesized via sol-gel method for the first time using Myristic acid as chelating agent. The synthesized samples have been taken to physical and electrochemical characterization such as thermo gravimetric analysis (TG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical characterization viz., electrochemical galvanostatic cycling studies, electrochemical impedance spectroscopy (EIS) and differential capacity curves (dQ/dE). XRD patterns of LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>x</sub>Cr<sub>y</sub>Mn<sub>2-x-y</sub>O<sub>4</sub> confirm high degree of crystallinity with good phase purity. FESEM image of undoped pristine spinel lucidly depicts cauliflower morphology with good agglomerated particle size of 50 nm while 0.5-Cu doped samples depict the pebbles morphology. TEM images of the spinel LiMn<sub>2</sub>O<sub>4</sub> and LiCu<sub>0.5</sub>Cr<sub>0.05</sub>Mn<sub>1.45</sub>O<sub>4</sub> authenticate that all the synthesized particles via sol-gel method are nano-sized (100 nm) with spherical surface and cloudy particles morphology. The LiMn<sub>2</sub>O<sub>4</sub> samples calcined at 850℃ deliver the high discharge capacity of 130 mA·h/g with cathodic efficiency of 88% corresponds to 94% columbic efficiency in the first cycle. Among all four compositions studied, LiCu<sub>0.5</sub>Cr<sub>0.05</sub>Mn<sub>1.45</sub>O<sub>4</sub> delivers 124 mA·h/g during the first cycle and shows stable performance with a low capacity fade of 1.1 mA·h/g cycle over the investigated 10 cycles.
