The aging of glassy materials is an inevitable process leading to progressive property degradation.In metallic glasses(MGs),aging-induced property degradation poses a persistent challenge to their applications.Over th...The aging of glassy materials is an inevitable process leading to progressive property degradation.In metallic glasses(MGs),aging-induced property degradation poses a persistent challenge to their applications.Over the years,rejuvenating or even reversing the aged glasses remains a critical elusive goal.Here we report that ultrasonic vibration(UV)treatment can reverse aging in a Zr-based MG within 0.5 s,achieving plasticity up to 14.5%that is 1.5 times that of the as-cast MG.This intriguing plasticity enhancement results from a UV-induced higher-energy state,as evidenced by structural enthalpy recovery,boson peak restoration,and a more disordered structure revealed by the pair distribution functions.This higher-energy state can be properly explained through the framework of‘anti-free volume defects’with a high atomic packing density.Furthermore,we propose a novel‘aging-assisted UV loading’method:pre-aging stabilizes the MG,enabling subsequent UV to amplify plasticity.This strategy achieves exceptional plasticity improvement,demonstrating that controlled aging can paradoxically enhance material properties.展开更多
MOSFETs are widely used in power electronics converters.Due to the high di/dt and dv/dt of the MOSFET and parasitic parameters in the circuit,drain voltage spikes and oscillations will be generated during turn-off,whi...MOSFETs are widely used in power electronics converters.Due to the high di/dt and dv/dt of the MOSFET and parasitic parameters in the circuit,drain voltage spikes and oscillations will be generated during turn-off,which can affect the safety of the device and degrade the system's electromagnetic compatibility.This paper first studies the relationship between drain voltage spike and gate voltage during turn-off.Based on the effect of gate voltage on drain voltage spike,a new active gate driver that optimizes gate voltage is proposed.The proposed active gate driver detects the slope of the drain voltage and generates a positive pulse in the drain current fall phase to increase the gate voltage,thereby suppressing drain voltage spike and oscillation.In order to verify the effectiveness of the proposed active gate driver,a simulation circuit and an experimental platform are constructed and compared with the conventional gate driver.Simulation and experimental results show that the new active gate driver can effectively suppress the drain voltage spike and oscillation of MOSFETs,and can effectively reduce high-frequency EMI.展开更多
基金supported by the NSF of China(Grant Nos.52371160,52401217,52271150,52201185)the Key-Area Research and Development Program of Guangdong Province(Grant No.2024B0101070001)+4 种基金the Applied Research Program of Guangdong Province(Grant No.2019B030302010)the Science and Technology Innovation Commission Shenzhen(Grants Nos.RCJC20221008092730037 and 20220804091920001)the Research Team Cultivation Program of Shenzhen University(Grant No.2023QNT001)Shenzhen Science and Technology Program(JCYJ20240813141413018)Scientific Foundation for Youth Scholars of Shenzhen University.
文摘The aging of glassy materials is an inevitable process leading to progressive property degradation.In metallic glasses(MGs),aging-induced property degradation poses a persistent challenge to their applications.Over the years,rejuvenating or even reversing the aged glasses remains a critical elusive goal.Here we report that ultrasonic vibration(UV)treatment can reverse aging in a Zr-based MG within 0.5 s,achieving plasticity up to 14.5%that is 1.5 times that of the as-cast MG.This intriguing plasticity enhancement results from a UV-induced higher-energy state,as evidenced by structural enthalpy recovery,boson peak restoration,and a more disordered structure revealed by the pair distribution functions.This higher-energy state can be properly explained through the framework of‘anti-free volume defects’with a high atomic packing density.Furthermore,we propose a novel‘aging-assisted UV loading’method:pre-aging stabilizes the MG,enabling subsequent UV to amplify plasticity.This strategy achieves exceptional plasticity improvement,demonstrating that controlled aging can paradoxically enhance material properties.
基金Supported in part by the General Program of National Natural Science Foundation of China under Grant 51577010,51777012in part by the Fundamental Research Funds for the Central Universities under Grant 2017JBM054.
文摘MOSFETs are widely used in power electronics converters.Due to the high di/dt and dv/dt of the MOSFET and parasitic parameters in the circuit,drain voltage spikes and oscillations will be generated during turn-off,which can affect the safety of the device and degrade the system's electromagnetic compatibility.This paper first studies the relationship between drain voltage spike and gate voltage during turn-off.Based on the effect of gate voltage on drain voltage spike,a new active gate driver that optimizes gate voltage is proposed.The proposed active gate driver detects the slope of the drain voltage and generates a positive pulse in the drain current fall phase to increase the gate voltage,thereby suppressing drain voltage spike and oscillation.In order to verify the effectiveness of the proposed active gate driver,a simulation circuit and an experimental platform are constructed and compared with the conventional gate driver.Simulation and experimental results show that the new active gate driver can effectively suppress the drain voltage spike and oscillation of MOSFETs,and can effectively reduce high-frequency EMI.
