The inelastic deformations of shape memory alloys(SMAs)always show poor controllability due to the avalanche-like martensite transformation,and the effective control for the deformation of precision de-vices has been ...The inelastic deformations of shape memory alloys(SMAs)always show poor controllability due to the avalanche-like martensite transformation,and the effective control for the deformation of precision de-vices has been not yet mature.In this work,the phase field method was used to investigate the shape memory effects(SMEs)of NiTi SMAs undergoing grain size(GS)engineering,to obtain tunable one-way and stress-assisted two-way SMEs(OWSME and SATWSME).The OWSME and SATWSME of the systems with various gradient-nanograin structures and bimodal grain structure,as well as that with geometric gradients were simulated.The simulated results indicate that due to the GS dependences of martensite transformation and reorientation,the occurrence and expansion of martensite reorientation,martensite transformation and its reverse can be efficaciously controlled via the GS engineering.When combining the GS engineering and geometric gradient design,since the effects of GS and stress gradient can be su-perimposed or competing,and the responses of martensite reorientation,martensite transformation and its reverse to this are different,the OWSME and SATWSME of the geometrically graded systems with various nanograin structures can exhibit different improvements in controllability.In short,the reorienta-tion hardening modulus during OWSME is increased and the transformation temperature window during SATWSME is widened by GS engineering,indicating the improved controllability of SMEs.The optimal GS engineering schemes revealed in this work provide the basic reference and guidance for designing tun-able SMEs and producing NiTi-based driving devices catering to desired functional performance in various engineering fields.展开更多
To address the high cost and limited electrochemical endurance of Pt-based electrocatalysts,the appropriate introduction of transition metal-based compounds as supports to disperse and anchor Pt species offers a promi...To address the high cost and limited electrochemical endurance of Pt-based electrocatalysts,the appropriate introduction of transition metal-based compounds as supports to disperse and anchor Pt species offers a promising approach for improving catalytic efficiency.In this study,sub-1 nm Pt nanoclusters were uniformly confined on NiO supports with a hierarchical nanotube/nanosheet structure(Pt/NiO/NF)through a combination of spatial domain confinement and annealing.The resulting catalyst exhibited excellent electrocatalytic activity and stability for hydrogen evolution(HER)and urea oxidation reactions(UOR)under alkaline conditions.Structural characterization and density functional theory calculations demonstrated that sub-1 nm Pt nanoclusters were immobilized on the NiO supports by Pt–O–Ni bonds at the interface.The strong metal-support interaction induced massive charge redistribution around the heterointerface,leading to the formation of multiple active sites.The Pt/NiO/NF catalyst only required an overpotential of 12 and 136 mV to actuate current densities of 10 and 100 mA cm^(-2) for the HER,respectively,and maintained a voltage retention of 96%for 260 h of continuous operation at a current density of 500 mA cm^(-2).Notably,in energy-efficient hydrogen production systems coupled with the HER and UOR,the catalyst required cell voltages of 1.37 and 1.53 V to drive current densities of 10 and 50 mA cm^(-2),respectively—approximately 300 mV lower than conventional water electrolysis systems.This study presents a novel pathway for designing highly efficient and robust sub-nanometer metal cluster catalysts.展开更多
基金The National Natural Science Foundation of China(12022208)the Project funded by China Postdoctoral Science Foundation(2022M712243)the Fundamental Research Funds for the Cen-tral Universities are acknowledged.
文摘The inelastic deformations of shape memory alloys(SMAs)always show poor controllability due to the avalanche-like martensite transformation,and the effective control for the deformation of precision de-vices has been not yet mature.In this work,the phase field method was used to investigate the shape memory effects(SMEs)of NiTi SMAs undergoing grain size(GS)engineering,to obtain tunable one-way and stress-assisted two-way SMEs(OWSME and SATWSME).The OWSME and SATWSME of the systems with various gradient-nanograin structures and bimodal grain structure,as well as that with geometric gradients were simulated.The simulated results indicate that due to the GS dependences of martensite transformation and reorientation,the occurrence and expansion of martensite reorientation,martensite transformation and its reverse can be efficaciously controlled via the GS engineering.When combining the GS engineering and geometric gradient design,since the effects of GS and stress gradient can be su-perimposed or competing,and the responses of martensite reorientation,martensite transformation and its reverse to this are different,the OWSME and SATWSME of the geometrically graded systems with various nanograin structures can exhibit different improvements in controllability.In short,the reorienta-tion hardening modulus during OWSME is increased and the transformation temperature window during SATWSME is widened by GS engineering,indicating the improved controllability of SMEs.The optimal GS engineering schemes revealed in this work provide the basic reference and guidance for designing tun-able SMEs and producing NiTi-based driving devices catering to desired functional performance in various engineering fields.
文摘To address the high cost and limited electrochemical endurance of Pt-based electrocatalysts,the appropriate introduction of transition metal-based compounds as supports to disperse and anchor Pt species offers a promising approach for improving catalytic efficiency.In this study,sub-1 nm Pt nanoclusters were uniformly confined on NiO supports with a hierarchical nanotube/nanosheet structure(Pt/NiO/NF)through a combination of spatial domain confinement and annealing.The resulting catalyst exhibited excellent electrocatalytic activity and stability for hydrogen evolution(HER)and urea oxidation reactions(UOR)under alkaline conditions.Structural characterization and density functional theory calculations demonstrated that sub-1 nm Pt nanoclusters were immobilized on the NiO supports by Pt–O–Ni bonds at the interface.The strong metal-support interaction induced massive charge redistribution around the heterointerface,leading to the formation of multiple active sites.The Pt/NiO/NF catalyst only required an overpotential of 12 and 136 mV to actuate current densities of 10 and 100 mA cm^(-2) for the HER,respectively,and maintained a voltage retention of 96%for 260 h of continuous operation at a current density of 500 mA cm^(-2).Notably,in energy-efficient hydrogen production systems coupled with the HER and UOR,the catalyst required cell voltages of 1.37 and 1.53 V to drive current densities of 10 and 50 mA cm^(-2),respectively—approximately 300 mV lower than conventional water electrolysis systems.This study presents a novel pathway for designing highly efficient and robust sub-nanometer metal cluster catalysts.
