Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In...Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In this study,a comprehensive and systematic investigation was conducted,by encompassing the analysis of hot deformation mechanisms,along with the microstructure evolution and magnetoc aloric properties of hot-rolled La-Fe-Co-Si alloy.The La_(1.05)Fe_(11.2)Co_(0.7)Si_(1.38)alloy was examined using multiscale mechanical analysis to assess the effects of temperature.A series of macroscale hot compression and microscale nanoindentation tests were performed to access global and local mechanical properties,including variations in hardness and indentation modulus of the primaryα-Fe and secondary 1:1:1 phases up to 800℃.A significant decrease in hardness and elastic recovery of the secondary phase was observed between 600and 800℃,above half of its melting point(1113℃),suggesting pronounced flow softening in both theα-Fe and 1:1:1 phases.Additionally,a novel multi-step annealing process was introduced for hot-rolled La-Fe-Co-Si alloys,involving partial transient liquid-phase diffusion in the 1:1:1 phase to address deformation-induced defects,such as residualα-Fe and lattice distortions in the 1:13 phase,which have not been previously reported.As a result,a primary La(Fe,Co,Si)13phase with a volume fraction of97.5%was achieved after multi-step annealing,compared to 87.5%using conventional annealing.Correspondingly,the magnetocaloric properties were restored,with the Curie temperature(TC)recovering from 276 to 268 K and the maximum magnetic entropy change(ΔSM)increasing from 7.56 to 8.67 J kg^(-1)K^(-1)under a 2 T magnetic field.展开更多
Regulating luminescent dynamics of lanthanide-based luminescent materials via external stimuli is of great significance in the fields of optical thermometry and high-level anti-counterfeiting.However,it is still a hug...Regulating luminescent dynamics of lanthanide-based luminescent materials via external stimuli is of great significance in the fields of optical thermometry and high-level anti-counterfeiting.However,it is still a huge challenge to realize multimodal emissions with tunable color outputs from a single activator in simple structures via smart dynamic control of photon transition processes.Herein,we present a mechanistic strategy to achieve multimodal luminescence of Er^(3+)activators with color-switchable outputs in a non-core-shell host.Under the control of excitation dynamics(λ_(ex)=980,808,1532,377 nm),the population among the intermediate en ergy levels of Er^(3+)and the interaction between Er^(3+)and Yb^(3+)could be precisely modulated through energy transfer and migration processes,leading to the generation of colortunable multimodal luminescence upon diverse excitation modes(non-steady-state,single-/dual-wavelength steady,thermal activation).Inspired by its special luminescent performance,the as-obtained material exhibits great potential in noncontact thermometry,multimodal anticounterfeiting,and high-capacity information encryption by performing a series of proof-of-concept experiments.Our findings might provide a conceptual model to modulate the luminescent dynamics in a simple-structured system for the generation of color-adjustable multimodal emissions,which is convenient for the development of advanced luminescent materials toward versatile cuttingedge applications.展开更多
基金financially supported by the Fundamental Research Program of the Korea Institute of Materials Science(No.PNKA330)
文摘Although hot-rolled La(Fe,Co,Si)13-based alloys are promising magnetocaloric materials for solidstate cooling with near-net shaping capabilities,their underlying hot deformation mechanisms remain largely unexplored.In this study,a comprehensive and systematic investigation was conducted,by encompassing the analysis of hot deformation mechanisms,along with the microstructure evolution and magnetoc aloric properties of hot-rolled La-Fe-Co-Si alloy.The La_(1.05)Fe_(11.2)Co_(0.7)Si_(1.38)alloy was examined using multiscale mechanical analysis to assess the effects of temperature.A series of macroscale hot compression and microscale nanoindentation tests were performed to access global and local mechanical properties,including variations in hardness and indentation modulus of the primaryα-Fe and secondary 1:1:1 phases up to 800℃.A significant decrease in hardness and elastic recovery of the secondary phase was observed between 600and 800℃,above half of its melting point(1113℃),suggesting pronounced flow softening in both theα-Fe and 1:1:1 phases.Additionally,a novel multi-step annealing process was introduced for hot-rolled La-Fe-Co-Si alloys,involving partial transient liquid-phase diffusion in the 1:1:1 phase to address deformation-induced defects,such as residualα-Fe and lattice distortions in the 1:13 phase,which have not been previously reported.As a result,a primary La(Fe,Co,Si)13phase with a volume fraction of97.5%was achieved after multi-step annealing,compared to 87.5%using conventional annealing.Correspondingly,the magnetocaloric properties were restored,with the Curie temperature(TC)recovering from 276 to 268 K and the maximum magnetic entropy change(ΔSM)increasing from 7.56 to 8.67 J kg^(-1)K^(-1)under a 2 T magnetic field.
基金financially supported by the Natural Science Foundation of Jiangsu Province(No.BK20211280)the National Natural Science Foundation of China(No.51702074)Science Fund for Distinguished Young Scholars,Nanjing Forestry University。
文摘Regulating luminescent dynamics of lanthanide-based luminescent materials via external stimuli is of great significance in the fields of optical thermometry and high-level anti-counterfeiting.However,it is still a huge challenge to realize multimodal emissions with tunable color outputs from a single activator in simple structures via smart dynamic control of photon transition processes.Herein,we present a mechanistic strategy to achieve multimodal luminescence of Er^(3+)activators with color-switchable outputs in a non-core-shell host.Under the control of excitation dynamics(λ_(ex)=980,808,1532,377 nm),the population among the intermediate en ergy levels of Er^(3+)and the interaction between Er^(3+)and Yb^(3+)could be precisely modulated through energy transfer and migration processes,leading to the generation of colortunable multimodal luminescence upon diverse excitation modes(non-steady-state,single-/dual-wavelength steady,thermal activation).Inspired by its special luminescent performance,the as-obtained material exhibits great potential in noncontact thermometry,multimodal anticounterfeiting,and high-capacity information encryption by performing a series of proof-of-concept experiments.Our findings might provide a conceptual model to modulate the luminescent dynamics in a simple-structured system for the generation of color-adjustable multimodal emissions,which is convenient for the development of advanced luminescent materials toward versatile cuttingedge applications.
