In this study,the mechanism of the reduction-diffusion reaction in a Sm-Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)by the low...In this study,the mechanism of the reduction-diffusion reaction in a Sm-Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)by the low-temperature diffusion-reduction(LTRD)process using LiCl-KCl eutectic molten salts.Firstly,the Sm-Fe phase transformation depending on the Sm-Fe composition,the LTRD temperature,and time was investigated,and it is found that the obtained metastable phase is only TbCu_(7)-type SmFe_(~8.5),which is not a Fe-rich phase.This Fe content does not change even after an expended LTRD process,and the metastable TbCu_(7)-type SmFe_(~8.5)tends to transform to the stable Sm_(2)Fe_(17)phase.In addition,it is found that the Sm-Fe phase starts to synthesize from the Sm-rich phase in the order of SmFe_(2),SmFe_(3),and SmFe_(8.5)as the LTRD temperature increases(when the time was 10 h)or the LTRD time increases(when the temperature was 550℃).Core-shell-like particles are observed in the case of a short LTRD time,and the core and the shell are Fe and the Sm-rich Sm-Fe phase,respectively,indicating that the Sm-rich phase begins to produce on the surface of the Fe particles.It is difficult to synthesize a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)phase with the Sm-Fe binary system,suggesting that a different approach,such as addition of other elements,will be necessary.展开更多
L1_(0)-ordered FeNi alloy with a high uniaxial magnetic anisotropy and large magnetic moment is a promising candidate for rare-earth-free permanent magnets applications.However,the synthesis of this chemically ordered...L1_(0)-ordered FeNi alloy with a high uniaxial magnetic anisotropy and large magnetic moment is a promising candidate for rare-earth-free permanent magnets applications.However,the synthesis of this chemically ordered phase remains a longstanding challenge because of its low chemical order-disorder transition temperature(200-320℃).Although a non-equilibrium synthetic route based on a nitrogen topotactic reaction has been proposed as a valid approach,the volume fraction and degree of chemical ordering of the product phase are limited.Herein,we propose a promising approach that promotes the efficient formation of L1_(0)-ordered nitride phase in FeNi nanopowders by introducing a quenching treatment during a low-oxygen induction thermal plasma process.The quenched FeNi nanopowders possessed much smaller powder sizes(40.4 vs 74.0 nm),exhibited higher number densities of nanotwins(39.8%vs 24.1%)and formed much larger volume fraction(33.6 wt.%vs 0.6 wt.%)of ordered phase than the unquenched nanopowders.Notably,quenching-induced high-density nanotwins led to the dominant coverage of serrated{001}crystal facets over the surfaces of the FeNi nanopowders.Such unique features substantially accelerated the formation of the L1_(0)-ordered nitride phase in the FeNi nanopowders because the{001}crystallographic orientation had the highest nitrogen diffusivity.This work provides not only a valid synthetic approach for mass production of the L10-ordered nitride phase in FeNi nanopowders but also novel insights into the crystal-defect-assisted nitridation of nanomaterials.展开更多
Two-dimensional(2D)carbon nanostructures play a critical role in energy-related applications,but developing facile and efficient strategies to synthesize these kinds of nanostructures is extremely rare.Herein,ultrathi...Two-dimensional(2D)carbon nanostructures play a critical role in energy-related applications,but developing facile and efficient strategies to synthesize these kinds of nanostructures is extremely rare.Herein,ultrathin carbon nanoribbons(CNRibs),with a thickness of 2–6 nm and length over 100 nm,have been strategically fabricated via a one-step pyrolysis of one-dimensional(1D)metal–organic framework nanorods(MOF NRods).Manipulating the diameters of MOF NRods will result in the formation of porous carbon nanostructures in 1D or 2D morphologies.Functional CNRibs with N doping or metal active site immobilization have also been studied.The CNRibs decorated with iron nanoclusters and single atoms have been used as excellent catalysts for the oxygen reduction reaction under both alkaline and acidic conditions,as well as zinc–air batteries.This work gives deep insights into the structural evolution from 1D to 2D morphology,providing an efficient approach to fabricate low-dimensional nanomaterials with controllable morphologies and functionalities for electrochemical applications.展开更多
文摘In this study,the mechanism of the reduction-diffusion reaction in a Sm-Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)by the low-temperature diffusion-reduction(LTRD)process using LiCl-KCl eutectic molten salts.Firstly,the Sm-Fe phase transformation depending on the Sm-Fe composition,the LTRD temperature,and time was investigated,and it is found that the obtained metastable phase is only TbCu_(7)-type SmFe_(~8.5),which is not a Fe-rich phase.This Fe content does not change even after an expended LTRD process,and the metastable TbCu_(7)-type SmFe_(~8.5)tends to transform to the stable Sm_(2)Fe_(17)phase.In addition,it is found that the Sm-Fe phase starts to synthesize from the Sm-rich phase in the order of SmFe_(2),SmFe_(3),and SmFe_(8.5)as the LTRD temperature increases(when the time was 10 h)or the LTRD time increases(when the temperature was 550℃).Core-shell-like particles are observed in the case of a short LTRD time,and the core and the shell are Fe and the Sm-rich Sm-Fe phase,respectively,indicating that the Sm-rich phase begins to produce on the surface of the Fe particles.It is difficult to synthesize a Fe-rich TbCu_(7)-type SmFe_(x)(x>9)phase with the Sm-Fe binary system,suggesting that a different approach,such as addition of other elements,will be necessary.
文摘L1_(0)-ordered FeNi alloy with a high uniaxial magnetic anisotropy and large magnetic moment is a promising candidate for rare-earth-free permanent magnets applications.However,the synthesis of this chemically ordered phase remains a longstanding challenge because of its low chemical order-disorder transition temperature(200-320℃).Although a non-equilibrium synthetic route based on a nitrogen topotactic reaction has been proposed as a valid approach,the volume fraction and degree of chemical ordering of the product phase are limited.Herein,we propose a promising approach that promotes the efficient formation of L1_(0)-ordered nitride phase in FeNi nanopowders by introducing a quenching treatment during a low-oxygen induction thermal plasma process.The quenched FeNi nanopowders possessed much smaller powder sizes(40.4 vs 74.0 nm),exhibited higher number densities of nanotwins(39.8%vs 24.1%)and formed much larger volume fraction(33.6 wt.%vs 0.6 wt.%)of ordered phase than the unquenched nanopowders.Notably,quenching-induced high-density nanotwins led to the dominant coverage of serrated{001}crystal facets over the surfaces of the FeNi nanopowders.Such unique features substantially accelerated the formation of the L1_(0)-ordered nitride phase in the FeNi nanopowders because the{001}crystallographic orientation had the highest nitrogen diffusivity.This work provides not only a valid synthetic approach for mass production of the L10-ordered nitride phase in FeNi nanopowders but also novel insights into the crystal-defect-assisted nitridation of nanomaterials.
基金This work was financially supported by the National Institute of Advanced Industrial Science and Technology(AIST),Jiangsu University(4023000046)Shenzhen Key Laboratory of Micro/Nano-Porous Functional Materials(SKLPM)(ZDSYS20210709112802010)+2 种基金China Postdoctoral Science Foundation(2022TQ0126 and 2022M721375)Guangdong Grants(2021ZT09C064)the National Key Research and Development Project(2022YFA1503900).
基金The authors are thankful to Dr.Takeyuki Uchida for microscopic measurements,and AIST and Guangdong-Hong Kong-Macao Joint Laboratory(grant no.2019B121205001)for financial support.
文摘Two-dimensional(2D)carbon nanostructures play a critical role in energy-related applications,but developing facile and efficient strategies to synthesize these kinds of nanostructures is extremely rare.Herein,ultrathin carbon nanoribbons(CNRibs),with a thickness of 2–6 nm and length over 100 nm,have been strategically fabricated via a one-step pyrolysis of one-dimensional(1D)metal–organic framework nanorods(MOF NRods).Manipulating the diameters of MOF NRods will result in the formation of porous carbon nanostructures in 1D or 2D morphologies.Functional CNRibs with N doping or metal active site immobilization have also been studied.The CNRibs decorated with iron nanoclusters and single atoms have been used as excellent catalysts for the oxygen reduction reaction under both alkaline and acidic conditions,as well as zinc–air batteries.This work gives deep insights into the structural evolution from 1D to 2D morphology,providing an efficient approach to fabricate low-dimensional nanomaterials with controllable morphologies and functionalities for electrochemical applications.
