The Cu-10 %Fe-1.5 %Ag in situ composite with high strength, high conductivity and low cost was prepared, and its hot deformation behavior was investi- gated by isothermal compression test with true strain of 0.69, tem...The Cu-10 %Fe-1.5 %Ag in situ composite with high strength, high conductivity and low cost was prepared, and its hot deformation behavior was investi- gated by isothermal compression test with true strain of 0.69, temperature range of 750-950℃ and strain rate of 0.002-1.000 s-1. The flow stress-strain response shows the characterization of dynamic recrystallization （DRX）, and the peak stress increases gradually with deformation tem- perature decreasing and strain rate increasing. The defor- mation activation energy of the composite for DRX is calculated as 241.864 kJ.mo1-1. The constitutive relation of the composite was got by Arrhenius equation. Further- more, according to the dynamic material modeling and Kumar-Prasad＇s instability criteria, the processing map was constructed and the unsafe regions for hot deformation were analyzed. Based on the processing map and microstructural evolution, the optimal parameter range for hot deformation processing is 750-863℃ at the strain rate of 0.002-0.013 s-1.展开更多
Excavation with tunnel boring machine(TBM)can generate vibrations,causing damages to neighbouring buildings and disturbing the residents or the equipment.This problem is particularly challenging in urban areas,where T...Excavation with tunnel boring machine(TBM)can generate vibrations,causing damages to neighbouring buildings and disturbing the residents or the equipment.This problem is particularly challenging in urban areas,where TBMs are increasingly large in diameter and shallow in depth.In response to this problem,four experimental campaigns were carried out in different geotechnical contexts in France.The vibration measurements were acquired on the surface and inside the TBMs.These measurements are also complemented by few data in the literature.An original methodology of signal processing is pro-posed to characterize the amplitude of the particle velocities,as well as the frequency content of the signals to highlight the most energetic bands.The levels of vibrations are also compared with the thresholds existing in various European regulations concerning the impact on neighbouring structures and the disturbance to local residents.展开更多
Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity.Herein,we present a synthesis of NiSe_(2)-Ce_(2)(CO_(3))_(2)O hetero...Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity.Herein,we present a synthesis of NiSe_(2)-Ce_(2)(CO_(3))_(2)O heterostructure and demonstrate the efficacy of interfacial Ce_(2)(CO_(3))2O in promoting the formation of catalytically active centers to improve oxygen evolution activity.In-situ Raman spectroscopy shows that incorporation of Ce_(2)(CO_(3))2O into NiSe_(2) causes a cathodic shift of the Ni^(2+)→Ni~(3+) transition potential.Operando electrochemical impedance spectroscopy reveals that strong electronic coupling at heterogeneous interface accelerates charge transfer process.Furthermore,density functional theory calculations suggest that actual catalytic active species of NiOOH transformed from NiSe_(2),which is coupled with Ce_(2)(CO_(3))_(2)O,can optimize electronic structure and decrease the free energy barriers toward fast oxygen evolution reaction(OER) kinetics.Consequently,the resultant NiSe_(2)-Ce_(2)(CO_(3))_(2)O electrode exhibits remarkable electrocatalytic performance with low overpotentials(268/304 mV@50/100 mA cm^(-2)) and excellent stability(50 mA cm^(-2) for 120 h) in the alkaline electrolyte.This work emphasizes the significance of modulating the dynamic changes in developing efficient electrocatalyst.展开更多
The silicon carbide(SiC)crystal growth is a multiple-phase aggregation process of Si and C atoms.With the development of the clean energy industry,the 4H-SiC has gained increasing attention as it is an ideal material ...The silicon carbide(SiC)crystal growth is a multiple-phase aggregation process of Si and C atoms.With the development of the clean energy industry,the 4H-SiC has gained increasing attention as it is an ideal material for new energy automobiles and optoelectronic devices.The aggregation process is normally complex and dynamic due to its distinctive formation energy,and it is hard to study and trace back in a non-destructive and comprehensive way.Here,this work developed a non-destructive and deep learning-enhanced characterization method of 4H-SiC material,which was based on micro-CT scanning,the verification of various optical measurements,and the convolutional neural network(ResNet-50 architecture).Harmful defects at the micro-level,polytypes,micropipes,and carbon inclusions could be identified and orientated with more than 96%high performance on both accuracy and precision.The three-dimensional visual reconstruction with quantitative analyses provided a vivid tracing back of the SiC aggregation process.This work demonstrated a use-ful tool to understand and optimize the SiC growth technology and further enhance productivity.展开更多
基金financially supported by the National Natural Science Foundation of China(No.50571035)the National High-Tech Research and Development Project (No.2006AA03Z528)
文摘The Cu-10 %Fe-1.5 %Ag in situ composite with high strength, high conductivity and low cost was prepared, and its hot deformation behavior was investi- gated by isothermal compression test with true strain of 0.69, temperature range of 750-950℃ and strain rate of 0.002-1.000 s-1. The flow stress-strain response shows the characterization of dynamic recrystallization （DRX）, and the peak stress increases gradually with deformation tem- perature decreasing and strain rate increasing. The defor- mation activation energy of the composite for DRX is calculated as 241.864 kJ.mo1-1. The constitutive relation of the composite was got by Arrhenius equation. Further- more, according to the dynamic material modeling and Kumar-Prasad＇s instability criteria, the processing map was constructed and the unsafe regions for hot deformation were analyzed. Based on the processing map and microstructural evolution, the optimal parameter range for hot deformation processing is 750-863℃ at the strain rate of 0.002-0.013 s-1.
文摘Excavation with tunnel boring machine(TBM)can generate vibrations,causing damages to neighbouring buildings and disturbing the residents or the equipment.This problem is particularly challenging in urban areas,where TBMs are increasingly large in diameter and shallow in depth.In response to this problem,four experimental campaigns were carried out in different geotechnical contexts in France.The vibration measurements were acquired on the surface and inside the TBMs.These measurements are also complemented by few data in the literature.An original methodology of signal processing is pro-posed to characterize the amplitude of the particle velocities,as well as the frequency content of the signals to highlight the most energetic bands.The levels of vibrations are also compared with the thresholds existing in various European regulations concerning the impact on neighbouring structures and the disturbance to local residents.
基金financially National Natural Science Foundation of China (52363028, 21965005)Volkswagen Foundation (Freigeist Fellowship 89592)+2 种基金Natural Science Foundation of Guangxi Province (2021GXNSFAA076001)Guangxi Technology Base and Talent Subject (GUIKE AD23023004, GUIKE AD20297039)Innovation Project of Guangxi Graduate Education (Nos. YCSW2024219, YCBZ2024082)。
文摘Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity.Herein,we present a synthesis of NiSe_(2)-Ce_(2)(CO_(3))_(2)O heterostructure and demonstrate the efficacy of interfacial Ce_(2)(CO_(3))2O in promoting the formation of catalytically active centers to improve oxygen evolution activity.In-situ Raman spectroscopy shows that incorporation of Ce_(2)(CO_(3))2O into NiSe_(2) causes a cathodic shift of the Ni^(2+)→Ni~(3+) transition potential.Operando electrochemical impedance spectroscopy reveals that strong electronic coupling at heterogeneous interface accelerates charge transfer process.Furthermore,density functional theory calculations suggest that actual catalytic active species of NiOOH transformed from NiSe_(2),which is coupled with Ce_(2)(CO_(3))_(2)O,can optimize electronic structure and decrease the free energy barriers toward fast oxygen evolution reaction(OER) kinetics.Consequently,the resultant NiSe_(2)-Ce_(2)(CO_(3))_(2)O electrode exhibits remarkable electrocatalytic performance with low overpotentials(268/304 mV@50/100 mA cm^(-2)) and excellent stability(50 mA cm^(-2) for 120 h) in the alkaline electrolyte.This work emphasizes the significance of modulating the dynamic changes in developing efficient electrocatalyst.
基金Fundamental Research Funds for the Central Universities,Grant/Award Number:20720220036National Key Research and Development Program of China,Grant/Award Number:2021YFB3401604+1 种基金Key Scientific and Technological Program of Xiamen,Grant/Award Number:3502Z20231014Innovation Program for Quantum Science and Technology,Grant/Award Number:2021ZD0303400。
文摘The silicon carbide(SiC)crystal growth is a multiple-phase aggregation process of Si and C atoms.With the development of the clean energy industry,the 4H-SiC has gained increasing attention as it is an ideal material for new energy automobiles and optoelectronic devices.The aggregation process is normally complex and dynamic due to its distinctive formation energy,and it is hard to study and trace back in a non-destructive and comprehensive way.Here,this work developed a non-destructive and deep learning-enhanced characterization method of 4H-SiC material,which was based on micro-CT scanning,the verification of various optical measurements,and the convolutional neural network(ResNet-50 architecture).Harmful defects at the micro-level,polytypes,micropipes,and carbon inclusions could be identified and orientated with more than 96%high performance on both accuracy and precision.The three-dimensional visual reconstruction with quantitative analyses provided a vivid tracing back of the SiC aggregation process.This work demonstrated a use-ful tool to understand and optimize the SiC growth technology and further enhance productivity.
