The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulation...The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulations are carried out to elucidate the underlying cause of this phenomenon,namely grain boundary embrittlement due to Zn segregation at iron(Fe)grain boundaries.A machine learning moment tensor interatomic potential for the Fe-Zn binary system is developed,based on which the thermodynamics of grain boundary segregation is evaluated.The yielded segregation energy spectrum of Zn in BCC Fe reveals the quantitative relationship between the average segregation concentration of Zn at Fe grain boundaries and the macroscopic Zn content,temperature,and fraction of grain boundary atoms.It suggests a strong thermodynamic driving force for Zn segregation at the Fe grain boundaries,which correlates directly with the grain boundary energy:high-energy grain boundaries can accommodate a large amount of Zn atoms,while low-energy grain boundaries exhibit a certain degree of repulsion to Zn.Kinetically,Zn enters the grain boundaries more easily through diffusion than by penetration.Nonetheless,the grain boundary embrittlement caused by Zn penetration is more severe than that by Zn diffusion.The embrittlement effect generally increases linearly with the increase in Zn concentration at the grain boundary.Altogether,it suggests that the LME in steels induced by grain boundary segregation of Zn emerges as a combined consequence of Zn melt penetration and solid-state diffusion of Zn atoms.展开更多
Amorphous solids exhibit scale-free avalanches,even under small external loading,and thus can work as suitable systems to study critical behavior and universality classes.The abundance of scale-free avalanches in the ...Amorphous solids exhibit scale-free avalanches,even under small external loading,and thus can work as suitable systems to study critical behavior and universality classes.The abundance of scale-free avalanches in the entire elastic tension regime of bulk metallic glass(BMG)samples has been experimentally observed using acoustic emission(AE)measurements.In this work,we compare the statistics of avalanches with those of earthquakes,and find that they both follow the Gutenberg–Richter law in the statistics of energies and Omori’s law of aftershock rates,and share the same characteristics in the distribution of recurrence times.These resemblances encourage us to propose the term“glass-quake”to describe avalanches in elastically loaded BMGs.Furthermore,our work echoes the potential universality of critical behavior in disordered physical systems from atomic to planetary scales,and motivates the use of elastic loaded BMGs as valuable laboratory simulators of seismic dynamics.展开更多
Bismuth vanadate(BiVO_(4))is a promising photoanode material for efficient photoelectrochemical(PEC)water splitting,whereas its performance is inhibited by detrimental surface states.To solve the problem,herein,a low-...Bismuth vanadate(BiVO_(4))is a promising photoanode material for efficient photoelectrochemical(PEC)water splitting,whereas its performance is inhibited by detrimental surface states.To solve the problem,herein,a low-cost organic molecule 1,3,5-benzenetricarboxylic acid(BTC)is selected for surface passivation of BiVO_(4) photoanodes(BVOs),which also provides bonding sites for Co^(2+)to anchor,resulting in a Co-BTC-BVO photoanode.Owing to its strong coordination with metal ions,BTC not only passivates surface states of BVO,but also provides bonding between BVO and catalytic active sites(Co^(2+))to form a molecular cocatalyst.Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer.The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm^(2) at 1.23 V vs.reversible hydrogen electrode(RHE)and a low onset potential of 0.22 VRHE under AM 1.5 G illumination,which ranks among the best photoanodes coupled with Co-based cocatalysts.This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52071204)Natural Science Foundation of Shanghai Municipal(No.22ZR1428700)SJTU Kunpeng&Ascend Center of Excellence,and MaGIC of Shanghai Jiao Tong University.
文摘The liquid metal embrittlement(LME)of advanced high-strength steels caused by zinc(Zn)has become a critical issue hindering their widespread application in the automotive industry.In this study,atomic-scale simulations are carried out to elucidate the underlying cause of this phenomenon,namely grain boundary embrittlement due to Zn segregation at iron(Fe)grain boundaries.A machine learning moment tensor interatomic potential for the Fe-Zn binary system is developed,based on which the thermodynamics of grain boundary segregation is evaluated.The yielded segregation energy spectrum of Zn in BCC Fe reveals the quantitative relationship between the average segregation concentration of Zn at Fe grain boundaries and the macroscopic Zn content,temperature,and fraction of grain boundary atoms.It suggests a strong thermodynamic driving force for Zn segregation at the Fe grain boundaries,which correlates directly with the grain boundary energy:high-energy grain boundaries can accommodate a large amount of Zn atoms,while low-energy grain boundaries exhibit a certain degree of repulsion to Zn.Kinetically,Zn enters the grain boundaries more easily through diffusion than by penetration.Nonetheless,the grain boundary embrittlement caused by Zn penetration is more severe than that by Zn diffusion.The embrittlement effect generally increases linearly with the increase in Zn concentration at the grain boundary.Altogether,it suggests that the LME in steels induced by grain boundary segregation of Zn emerges as a combined consequence of Zn melt penetration and solid-state diffusion of Zn atoms.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51801122 and 52071210)the Science Challenge Project(Grant No.TZ2018001)the Science and Technology Commission of Shanghai(Grant No.21ZR1430800).
文摘Amorphous solids exhibit scale-free avalanches,even under small external loading,and thus can work as suitable systems to study critical behavior and universality classes.The abundance of scale-free avalanches in the entire elastic tension regime of bulk metallic glass(BMG)samples has been experimentally observed using acoustic emission(AE)measurements.In this work,we compare the statistics of avalanches with those of earthquakes,and find that they both follow the Gutenberg–Richter law in the statistics of energies and Omori’s law of aftershock rates,and share the same characteristics in the distribution of recurrence times.These resemblances encourage us to propose the term“glass-quake”to describe avalanches in elastically loaded BMGs.Furthermore,our work echoes the potential universality of critical behavior in disordered physical systems from atomic to planetary scales,and motivates the use of elastic loaded BMGs as valuable laboratory simulators of seismic dynamics.
基金support from the National Natural Science Foundation of China(No.51672173,U1733130)Shanghai Science and Technology Committee(Nos.21ZR1435700,18520744700, 18JC1410500)Shanghai Jiao Tong University Medical Engineering Cross Research Program(No.YG2023ZD18).
文摘Bismuth vanadate(BiVO_(4))is a promising photoanode material for efficient photoelectrochemical(PEC)water splitting,whereas its performance is inhibited by detrimental surface states.To solve the problem,herein,a low-cost organic molecule 1,3,5-benzenetricarboxylic acid(BTC)is selected for surface passivation of BiVO_(4) photoanodes(BVOs),which also provides bonding sites for Co^(2+)to anchor,resulting in a Co-BTC-BVO photoanode.Owing to its strong coordination with metal ions,BTC not only passivates surface states of BVO,but also provides bonding between BVO and catalytic active sites(Co^(2+))to form a molecular cocatalyst.Computational study and interfacial charge kinetic investigation reveal that chemical bonding formed at the interface greatly suppresses charge recombination and accelerates charge transfer.The obtained Co-BTC-BVO photoanode exhibits a photocurrent density of 4.82 mA/cm^(2) at 1.23 V vs.reversible hydrogen electrode(RHE)and a low onset potential of 0.22 VRHE under AM 1.5 G illumination,which ranks among the best photoanodes coupled with Co-based cocatalysts.This work presents a novel selection of passivation layers and emphasizes the significance of interfacial chemical bonding for the construction of efficient photoanodes.
