Intensive power ultrasound is introduced to Zr46.75Cu46.75Al6.5bulk metallic glass(BMG)as an easy-procurable,non-destructive physical method to modulate its atomic rearrangement and shear deformation behavior.The micr...Intensive power ultrasound is introduced to Zr46.75Cu46.75Al6.5bulk metallic glass(BMG)as an easy-procurable,non-destructive physical method to modulate its atomic rearrangement and shear deformation behavior.The microstructure after ultrasonic excitation with amplitude about 15μm in 20 k Hz for 2 h is characterized by large amount of Cu10Zr7 nanocrystals with size of 20–50 nm embedded in the glass matrix.This leads to a sharp increase in the critical stress for the first pop-in event of shear banding,and thus simultaneously improves both compressive plasticity and yield strength.Our findings provide a novel approach for overcoming the strength-ductility trade-off dilemma.展开更多
The absence of efficient red-emitting micrometer-scale light emitting diodes(LEDs),i.e.,LEDs with lateral dimensions of 1μm or less is a major barrier to the adoption of microLEDs in virtual/augmented reality.The und...The absence of efficient red-emitting micrometer-scale light emitting diodes(LEDs),i.e.,LEDs with lateral dimensions of 1μm or less is a major barrier to the adoption of microLEDs in virtual/augmented reality.The underlying challenges include the presence of extensive defects and dislocations for indium-rich InGaN quantum wells,strain-induced quantum-confined Stark effect,and etch-induced surface damage during the fabrication of quantum well microLEDs.Here,we demonstrate a new approach to achieve strong red emission(>620 nm)from dislocation-free N-polar InGaN/GaN nanowires that included an InGaN/GaN short-period superlattice underneath the active region to relax strain and incorporate more indium within the InGaN dot active region.The resulting submicrometer-scale devices show red electroluminescence dominantly from an InGaN dot active region at low-to-moderate injection currents.A peak external quantum efficiency and a wall-plug efficiency of 2.2%and1.7%were measured,respectively,which,to the best of our knowledge,are the highest values reported for a submicrometer-scale red LED.This study offers a new path to overcome the efficiency bottleneck of red-emitting microLEDs for a broad range of applications including mobile displays,wearable electronics,biomedical sensing,ultrahigh speed optical interconnect,and virtual/augmented reality.展开更多
Introduction Operation target beam power of China Spallation Neutron Source(CSNS),as the China's first 100 kW beam power pulsed neutron source,is now larger than 80 kW.During the beam power upgrading process of CS...Introduction Operation target beam power of China Spallation Neutron Source(CSNS),as the China's first 100 kW beam power pulsed neutron source,is now larger than 80 kW.During the beam power upgrading process of CSNS to 50 kW from 2018 to 2019,many improvements have been made for the front end of CSNS.Results The improvements mainly focus on solving the problems of ion source instability and the radio frequency quadrupole(RFQ)sparking caused by the pre-chopped beam into RFQ.展开更多
基金the National Natural Science Foundation of China(Nos.51727803,51922089 and 51972275)the Key Research Plan in Shanxi Province(No.2018GY-104)。
文摘Intensive power ultrasound is introduced to Zr46.75Cu46.75Al6.5bulk metallic glass(BMG)as an easy-procurable,non-destructive physical method to modulate its atomic rearrangement and shear deformation behavior.The microstructure after ultrasonic excitation with amplitude about 15μm in 20 k Hz for 2 h is characterized by large amount of Cu10Zr7 nanocrystals with size of 20–50 nm embedded in the glass matrix.This leads to a sharp increase in the critical stress for the first pop-in event of shear banding,and thus simultaneously improves both compressive plasticity and yield strength.Our findings provide a novel approach for overcoming the strength-ductility trade-off dilemma.
文摘The absence of efficient red-emitting micrometer-scale light emitting diodes(LEDs),i.e.,LEDs with lateral dimensions of 1μm or less is a major barrier to the adoption of microLEDs in virtual/augmented reality.The underlying challenges include the presence of extensive defects and dislocations for indium-rich InGaN quantum wells,strain-induced quantum-confined Stark effect,and etch-induced surface damage during the fabrication of quantum well microLEDs.Here,we demonstrate a new approach to achieve strong red emission(>620 nm)from dislocation-free N-polar InGaN/GaN nanowires that included an InGaN/GaN short-period superlattice underneath the active region to relax strain and incorporate more indium within the InGaN dot active region.The resulting submicrometer-scale devices show red electroluminescence dominantly from an InGaN dot active region at low-to-moderate injection currents.A peak external quantum efficiency and a wall-plug efficiency of 2.2%and1.7%were measured,respectively,which,to the best of our knowledge,are the highest values reported for a submicrometer-scale red LED.This study offers a new path to overcome the efficiency bottleneck of red-emitting microLEDs for a broad range of applications including mobile displays,wearable electronics,biomedical sensing,ultrahigh speed optical interconnect,and virtual/augmented reality.
文摘Introduction Operation target beam power of China Spallation Neutron Source(CSNS),as the China's first 100 kW beam power pulsed neutron source,is now larger than 80 kW.During the beam power upgrading process of CSNS to 50 kW from 2018 to 2019,many improvements have been made for the front end of CSNS.Results The improvements mainly focus on solving the problems of ion source instability and the radio frequency quadrupole(RFQ)sparking caused by the pre-chopped beam into RFQ.
