Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a comp...Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a composite catalyst consisting of Fe/ZnCr_(2)O_(4)(Fe modified ZnCr_(2)O_(4)spinel)oxide and H-ZSM-5 zeolite.Impregnation of only 3 wt%of Fe onto ZnCr_(2)O_(4)can remarkably increase CO conversion without sacrificing the aromatics selectivity.Oxygen vacancy concentration is improved after impregnating Fe.The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr_(2)O_(4)spinel oxide.The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species,which can be continuously transformed to aromatics in H-ZSM-5.This study provides a new insight into the design of highly efficient catalyst for syngas conversion.展开更多
A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion e...A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide （PI） membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130m W/m2 with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.展开更多
Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-po...Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.展开更多
<div style="text-align:justify;"> A high-efficiency ridged magnetically insulated transmission line oscillator (RMILO) is proposed and investigated theoretically and numerically in this paper. In the R...<div style="text-align:justify;"> A high-efficiency ridged magnetically insulated transmission line oscillator (RMILO) is proposed and investigated theoretically and numerically in this paper. In the RMILO, ridge-disk vanes are introduced to enhance the power efficiency. Theoretical investigation shows that the ridge-disk can enhance the coupling impedance of the slow-wave structure (SWS), and so enhance the power efficiency. Moreover, the ridge has a weak influence on frequency, so, it influences little on the tunability of the MILO. In simulation, when the applied voltage is increased to 807 kV, the RMILO can get the 3 dB tunable frequency range with 7.6 - 13.9 GHz and the 3 dB tuning bandwidth with 58.6% which has an increase of 27.6% compared with the conventional MILO. So, the tuning performance of the RMILO is more superior. Besides, the RMILO gets the maximum output power of 7.1 GW, the corresponding power efficiency is 22.6% and the frequency is 1.400 GHz. Furthermore, when the applied voltage is increased to 807 kV, high-power microwave with a power of 13.5 GW, frequency of 1.400 GHz, and ef?ciency of 24.5% is generated, which has an increase of 20.2% compared with the conventional MILO. The simulation results con?rm the ones predicted by theoretical analysis. </div>展开更多
The phenomenon of liquid metal“heartbeat”oscillation presents intriguing applications in microfluidic devices,drug delivery,andminiature robotics.However,achieving high vibrational kinetic energy outputs in these sy...The phenomenon of liquid metal“heartbeat”oscillation presents intriguing applications in microfluidic devices,drug delivery,andminiature robotics.However,achieving high vibrational kinetic energy outputs in these systems remains challenging.In this study,we developed a graphite ring electrode with V-shaped inner wall that enables wide-ranging control over the oscillation performance based on droplet size and the height of the V-shape.The mechanism driving the heartbeat is defined as a dynamic process involving the transformation of the oxide layer.Through electrochemical analysis,we confirmed three distinct states of the heartbeat and introduced a novel model to elucidate the role of the V-shaped structure in initiating and halting the oscillations.A comprehensive series of experiments explored how various factors,such as droplet volume,voltage,tilt angle,and V-shape height,affect heartbeat performance,achieving a significant conversion from surface energy to vibrational kinetic energy as high as 4732 J m^(-2) s^(-1).The increase in energy output is attributed to the synergistic effect of the V-shape height and droplet size on the oscillations.These results not only advance our understanding of liquidmetal droplet manipulation but also pave the way for designing high-speed microfluidic pumping systems.展开更多
In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high meth...In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high methanation performance. CO conversion could reach up to 90% on 25 wt% MoO3/ZrO2 catalyst, much higher than that on the conventional 25 wt% MoO3/Al2O3 catalyst. The Mo-based catalysts were characterized by XRF, XRD, Raman, BET, TEM and H2-TPR etc. It was found that MoO3 particles were highly dispersed on ZrO2 support for 25 wt% MoO3/ZrO2 catalyst prepared at 65-85℃ because of its relatively larger pore size, which contributed to a high CO conversion. Meanwhile, when MoO3 loading exceeded the monolayer coverage, the formed crystalline MoO3 and ZrM020g might block the micropores of the catalyst and make the methanation activity declined. These results are useful for preparing highly efficient catalyst for CO methanation process.展开更多
Electromagnetic topological chiral edge states mimicking the quantum Hall effect have attracted a great deal of attention due to their unique features of free backscattering and immunity against sharp bends and defect...Electromagnetic topological chiral edge states mimicking the quantum Hall effect have attracted a great deal of attention due to their unique features of free backscattering and immunity against sharp bends and defects.However,the matching techniques between classical waveguides and the topological one-way waveguide deserve more attention for real-world applications.In this paper,a highly efficient conversion structure between a classical rectangular waveguide and a topological one-way waveguide is proposed and demonstrated at the microwave frequency,which efficiently converts classical guided waves to topological one-way edge states.A tapered transition is designed to match both the momentum and impedance of the classical guided waves and the topological one-way edge states.With the conversion structure,the waves generated by a point excitation source can be coupled to the topological one-way waveguide with very high coupling efficiency,which can ensure high transmission of the whole system(i.e.,from the source and the receiver).Simulation and measurement results demonstrate the proposed method.This investigation is beneficial to the applications of topological one-way waveguides and opens up a new avenue for advanced topological and classical integrated functional devices and systems.展开更多
Biaxially oriented polypropylene(BOPP)thin film is the predominant dielectric material used in film capacitive energy storage for pulsed power engineering and power conver-sions due to its remarkable high dielectric s...Biaxially oriented polypropylene(BOPP)thin film is the predominant dielectric material used in film capacitive energy storage for pulsed power engineering and power conver-sions due to its remarkable high dielectric strength and low conduction loss.However,the design rating of BOPP film capacitors in high power density conversion systems operated also under high temperature is still based on the empirical criteria due to the lack of systematic mechanism studies at elevated temperature.In this work,the temperature-dependent electrical conduction in tenter and bubble BOPP films up to their break-down strength was systematically studied using a specialised circuitry featuring dynamic gain-controlled capacitive current cancellation.Both tenter and bubble BOPP films exhibit an extended trap-limited conduction region at the high electric field,followed subsequently with a trap-filled limited conduction until breakdown.This trap-filled-limited conduction presents characteristics of carriers transport with detrimental high mobility and soaring conduction loss.Overall,the shallow localised states revealed by the Arrhenius analysis,the large bandgap,and high barrier height of BOPP film together render its exceptional electrical integrity.In comparison,the enhanced crystallinity and larger crystallite sizes in tenter BOPP produced by the sequential stretching result in a higher upper operational temperature and slightly higher breakdown strength than bubble BOPP,suggesting the important role of processing induced enhancements to intrinsic properties of molecular origin.This study provides insights into the high-field charac-teristics of BOPP films at elevated temperature with promising learning outcomes useful to the expedited designs of the next generation polymer films for capacitive energy storages.展开更多
Perovskite tandem solar cells(TSCs)hold substantial promise for surpassing the efficiency limits of single-junction solar cells.Nevertheless,achieving high open-circuit voltage(VOC)in wide-bandgap perovskite devices r...Perovskite tandem solar cells(TSCs)hold substantial promise for surpassing the efficiency limits of single-junction solar cells.Nevertheless,achieving high open-circuit voltage(VOC)in wide-bandgap perovskite devices remains a challenge due to significant VOC-losses.Here,we introduce a heterogeneous interface anchoring strategy aimed at enhancing interfacial properties by incorporating a silane coupling agent between the perovskite and hole transport layers.Trimethoxysilane(TMOS),an amphiphilic molecule,strengthens interfacial adhesion through enhanced chemical interactions,thereby promoting efficient hole extraction.Additionally,the terminal functional groups of TMOS molecules interact with lead ions,modulating the perovskite film crystallization and improving their overall quality.Devices treated with TMOS exhibit a marked reduction in non-radiative recombination,leading to a significant increase in VOC.Notably,3-cyanopropyltrimethoxysilane(CN-TMOS)optimizes the uniformity and interfacial contact of the perovskite film,achieving a VOC of 1.345 V and a power conversion efficiency(PCE)of 19.69%.The corresponding VOC-loss,relative to the bandgap,is reduced to 0.425 V,one of the lowest values reported for wide-bandgap perovskite single-junction solar cells.Extending this strategy to all-perovskite TSCs,we achieve a PCE of 28.45%and exceptional operational stability,retaining over 90%of the initial efficiency after 500 h of continuous operation under 1 sun illumination.展开更多
High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared b...High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal.As compared with traditional carbon materials,this MB exhibited ultra-high specific surface area(2693 m^(2)g^(−1))and mesopore volume of mesopore(0.81 cm^(3)g^(−1))with a narrow distribution(2-5 nm),responsible for the high dispersion of binary Cu-Mo_(2)C sites,CO_(2)adsorption and mass transfer in the reaction system.Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo_(2)C binary sites(~6.1 nm)on the surface of MB.Cu+species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo_(2)C and Cu.These were advantageous to the intrinsic activity and stability of the Cu-Mo_(2)C binary sites and their accessibility to the reactant molecules.Under the RWGS reaction conditions of 500℃,atmospheric pressure,and 300,000 ml/g/h gas hour space velocity,the CO_(2)conversion rate over Cu-Mo_(2)C/MB reached 27.74×10^(-5)molCO_(2)/gcat/s at very low H_(2)partial pres-sure,which was more than twice that over traditional carbon supported Cu-Mo_(2)C catalysts.In addition,this catalyst exhibited 99.08%CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity.This study offers a new development strategy and a promising candidate for industrial RWGS.展开更多
A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency（PCE）.The internal quantum efficiency,the series resistance,and the thermal resistance were theoretically opt...A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency（PCE）.The internal quantum efficiency,the series resistance,and the thermal resistance were theoretically optimized.The series resistance and the thermal resistance were greatly decreased by optimizing the thickness of the P-waveguide and the P-cladding layers.The internal quantum efficiency was increased by introducing a novel strain-compensated GaAs0.9P0.1/InGaAs quantum well.Experimentally,a single 1-cm bar with 20% fill factor and 900 μm cavity length was mounted P-side down on a microchannel-cooled heatsink,and a peak PCE of 60% is obtained at 26.3-W continuous wave output power.The results prove that this novel asymmetric waveguide structure design is an efficient approach to improve the PCE.展开更多
Organic diradicaloids with unique open-shell structures and properties have been widely used in organic electronics and spintronics.However,their advantageous optical properties have been explored less in the biomedic...Organic diradicaloids with unique open-shell structures and properties have been widely used in organic electronics and spintronics.However,their advantageous optical properties have been explored less in the biomedical field.In this work,the photothermal conversion behaviors of a boron-containing organic diradicaloid(BOD)are reported.BOD can assemble with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)to form rodlike nanoparticles(BOD NPs).These as-prepared BOD NPs exhibit high photothermal conversion capability and robust photothermal stability.Notably,they possess morphological superiority,which guarantees the effective photothermal therapy of tumors.This work thus demonstrates the promise of organic diradicaloids as efficient photothermal agents for biomedical applications.展开更多
By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L-band amplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing ...By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L-band amplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.展开更多
Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amp...Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amplifier and enhance the power of the amplified laser.Furthermore,the role of the 4f system in the passive spherical aberration compensation and its effect on the amplified laser are discussed in detail.The results indicate that the amplification efficiency is enhanced by incorporating a 4f system in a double-pass amplifier and placing a 0?reflector only at the focal point of the single-pass amplified laser.This method also effectively uses the heat from the gain medium(neodymiumdoped yttrium aluminium garnet)of the amplifier to compensate the spherical aberration of the amplified laser.展开更多
For practicability of the high power microwave source,a C-band backward wave oscillator（BWO） which has high conversion efficiency is designed.When the axial guiding magnetic field is 0.83 T,the electron energy and t...For practicability of the high power microwave source,a C-band backward wave oscillator（BWO） which has high conversion efficiency is designed.When the axial guiding magnetic field is 0.83 T,the electron energy and the beam current of the diode are respectively 80 keV and 2.1 kA,a microwave output power of 100 MW at 7.4 GHz microwave frequency with 65% conversion efficiency is achieved in simulation.展开更多
The random distributed-feedback fiber laser(RFL) is a new approach to obtain a high-power stable supercontinuum(SC) source.To consider both structure simplification and high-power SC output,an innovative structure ach...The random distributed-feedback fiber laser(RFL) is a new approach to obtain a high-power stable supercontinuum(SC) source.To consider both structure simplification and high-power SC output,an innovative structure achieving a kilowatt-level SC output in a single-stage RFL with a half-open cavity is demonstrated in this paper.It consists of a fiber oscillator,a piece of long passive fiber and a broadband coupler,among which the broadband coupler acting as a feedback device is crucial in SC generation.When the system has no feedback,the backward output power is up to298 W under the pump power of 1185 W.When the feedback is introduced before the pump laser,the backward power loss can be reduced and the pump can be fully utilized,which could promote forward output power and conversion efficiency significantly.Under the maximum pump power of 1847 W,a 1300 W SC with spectrum ranging from 887 to1920 nm and SC conversion efficiency of 66% is obtained.To the best of our knowledge,it is the simplest structure used for high-power SC generation,and both the generated SC output power and the conversion efficiency are highest in the scheme of the half-opened RFL output SC.展开更多
基金the financial support from the National Natural Science Foundation of China(Grant No.21978285,21991093,21991090),the‘‘Transformational Technologies for Clean Energy and Demonstration”the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics(STA)reaction is still challenging.Herein,we report a 57.5%CO conversion along with 74%aromatics selectivity over a composite catalyst consisting of Fe/ZnCr_(2)O_(4)(Fe modified ZnCr_(2)O_(4)spinel)oxide and H-ZSM-5 zeolite.Impregnation of only 3 wt%of Fe onto ZnCr_(2)O_(4)can remarkably increase CO conversion without sacrificing the aromatics selectivity.Oxygen vacancy concentration is improved after impregnating Fe.The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr_(2)O_(4)spinel oxide.The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species,which can be continuously transformed to aromatics in H-ZSM-5.This study provides a new insight into the design of highly efficient catalyst for syngas conversion.
基金Supported by the National Natural Science Foundation of China under Grant No 11335003
文摘A polymeric nanopore membrane with selective ionic transport has been proposed as a potential device to convert the chemical potential energy in salinity gradients to electrical power. However, its energy conversion efficiency and power density are often limited due to the challenge in reliably controlling the size of the nanopores with the conventional chemical etching method. Here we report that without chemical etching, polyimide （PI） membranes irradiated with GeV heavy ions have negatively charged nanopores, showing nearly perfect selectivity for cations over anions, and they can generate electrical power from salinity gradients. We further demonstrate that the power generation efficiency of the PI membrane approaches the theoretical limit, and the maximum power density reaches 130m W/m2 with a modified etching method, outperforming the previous energy conversion device that was made of polymeric nanopore membranes.
基金supported by the National Natural Science Foundation of China(Grant No.61671457)
文摘Frequency tunability has become a subject of concern in the field of high-power microwave（HPM） source research.However, little information about the corresponding mode converter is available. A tunable circularly-polarized turnstilejunction mode converter（TCTMC） for high-power microwave applications is presented in this paper. The input coaxial TEM mode is transformed into TE（10） mode with different phase delays in four rectangular waveguides and then converted into a circularly-polarized TE（11） circular waveguide mode. Besides, the rods are added to reduce or even eliminate the reflection. The innovations in this study are as follows. The tunning mechanism is added to the mode converter, which can change the effective length of rectangular waveguide and the distance between the rods installed upstream and the closest edge of the rectangular waveguide, thus improving the conversion efficiency and bandwidth. The conversion efficiency of TCTMC can reach above 98% over the frequency range of 1.42 GHz–2.29 GHz, and the frequency tunning bandwidth is about 47%. Significantly, TCTMC can obtain continuous high conversion efficiency of different frequency points with the change of tuning mechanism.
文摘<div style="text-align:justify;"> A high-efficiency ridged magnetically insulated transmission line oscillator (RMILO) is proposed and investigated theoretically and numerically in this paper. In the RMILO, ridge-disk vanes are introduced to enhance the power efficiency. Theoretical investigation shows that the ridge-disk can enhance the coupling impedance of the slow-wave structure (SWS), and so enhance the power efficiency. Moreover, the ridge has a weak influence on frequency, so, it influences little on the tunability of the MILO. In simulation, when the applied voltage is increased to 807 kV, the RMILO can get the 3 dB tunable frequency range with 7.6 - 13.9 GHz and the 3 dB tuning bandwidth with 58.6% which has an increase of 27.6% compared with the conventional MILO. So, the tuning performance of the RMILO is more superior. Besides, the RMILO gets the maximum output power of 7.1 GW, the corresponding power efficiency is 22.6% and the frequency is 1.400 GHz. Furthermore, when the applied voltage is increased to 807 kV, high-power microwave with a power of 13.5 GW, frequency of 1.400 GHz, and ef?ciency of 24.5% is generated, which has an increase of 20.2% compared with the conventional MILO. The simulation results con?rm the ones predicted by theoretical analysis. </div>
基金National Natural Science Foundation of China,Grant/Award Number:51901009。
文摘The phenomenon of liquid metal“heartbeat”oscillation presents intriguing applications in microfluidic devices,drug delivery,andminiature robotics.However,achieving high vibrational kinetic energy outputs in these systems remains challenging.In this study,we developed a graphite ring electrode with V-shaped inner wall that enables wide-ranging control over the oscillation performance based on droplet size and the height of the V-shape.The mechanism driving the heartbeat is defined as a dynamic process involving the transformation of the oxide layer.Through electrochemical analysis,we confirmed three distinct states of the heartbeat and introduced a novel model to elucidate the role of the V-shaped structure in initiating and halting the oscillations.A comprehensive series of experiments explored how various factors,such as droplet volume,voltage,tilt angle,and V-shape height,affect heartbeat performance,achieving a significant conversion from surface energy to vibrational kinetic energy as high as 4732 J m^(-2) s^(-1).The increase in energy output is attributed to the synergistic effect of the V-shape height and droplet size on the oscillations.These results not only advance our understanding of liquidmetal droplet manipulation but also pave the way for designing high-speed microfluidic pumping systems.
基金supported by the Tianjin Municipal Science and Technology Commission(14JCZDJC37500)
文摘In this study, different methods were used to prepare MoO3/ZrO2 catalysts for sulfur resistant methanation reaction. It was found that MoO3/ZrO2 catalyst prepared by one-step co-precipitation method achieved high methanation performance. CO conversion could reach up to 90% on 25 wt% MoO3/ZrO2 catalyst, much higher than that on the conventional 25 wt% MoO3/Al2O3 catalyst. The Mo-based catalysts were characterized by XRF, XRD, Raman, BET, TEM and H2-TPR etc. It was found that MoO3 particles were highly dispersed on ZrO2 support for 25 wt% MoO3/ZrO2 catalyst prepared at 65-85℃ because of its relatively larger pore size, which contributed to a high CO conversion. Meanwhile, when MoO3 loading exceeded the monolayer coverage, the formed crystalline MoO3 and ZrM020g might block the micropores of the catalyst and make the methanation activity declined. These results are useful for preparing highly efficient catalyst for CO methanation process.
基金supported by the National Natural Science Foundation of China(No.62171082)the Natural Science Foundation of Sichuan Province(No.2022NSFSC0483)。
文摘Electromagnetic topological chiral edge states mimicking the quantum Hall effect have attracted a great deal of attention due to their unique features of free backscattering and immunity against sharp bends and defects.However,the matching techniques between classical waveguides and the topological one-way waveguide deserve more attention for real-world applications.In this paper,a highly efficient conversion structure between a classical rectangular waveguide and a topological one-way waveguide is proposed and demonstrated at the microwave frequency,which efficiently converts classical guided waves to topological one-way edge states.A tapered transition is designed to match both the momentum and impedance of the classical guided waves and the topological one-way edge states.With the conversion structure,the waves generated by a point excitation source can be coupled to the topological one-way waveguide with very high coupling efficiency,which can ensure high transmission of the whole system(i.e.,from the source and the receiver).Simulation and measurement results demonstrate the proposed method.This investigation is beneficial to the applications of topological one-way waveguides and opens up a new avenue for advanced topological and classical integrated functional devices and systems.
基金Office of Naval Research,Grant/Award Numbers:N00014-17-1-2656,N00014-23-1-2292,N00014-23-1-2346,N00014-23-1-2348。
文摘Biaxially oriented polypropylene(BOPP)thin film is the predominant dielectric material used in film capacitive energy storage for pulsed power engineering and power conver-sions due to its remarkable high dielectric strength and low conduction loss.However,the design rating of BOPP film capacitors in high power density conversion systems operated also under high temperature is still based on the empirical criteria due to the lack of systematic mechanism studies at elevated temperature.In this work,the temperature-dependent electrical conduction in tenter and bubble BOPP films up to their break-down strength was systematically studied using a specialised circuitry featuring dynamic gain-controlled capacitive current cancellation.Both tenter and bubble BOPP films exhibit an extended trap-limited conduction region at the high electric field,followed subsequently with a trap-filled limited conduction until breakdown.This trap-filled-limited conduction presents characteristics of carriers transport with detrimental high mobility and soaring conduction loss.Overall,the shallow localised states revealed by the Arrhenius analysis,the large bandgap,and high barrier height of BOPP film together render its exceptional electrical integrity.In comparison,the enhanced crystallinity and larger crystallite sizes in tenter BOPP produced by the sequential stretching result in a higher upper operational temperature and slightly higher breakdown strength than bubble BOPP,suggesting the important role of processing induced enhancements to intrinsic properties of molecular origin.This study provides insights into the high-field charac-teristics of BOPP films at elevated temperature with promising learning outcomes useful to the expedited designs of the next generation polymer films for capacitive energy storages.
基金supported by the National Key R&D Program of China(2023YFE0111500)the National Natural Science Foundation of China(52321006,T2394480,T2394484,22109143,22475196,and 22479131)+9 种基金the Joint Fund for Provincial Science and Technology R&D Program of Henan(242301420051)the Opening Project of the State Key Laboratory of Advanced Technology for Float Glass(2022KF04)the China Postdoctoral Innovative Talent Support Program(BX2021271)the China Postdoctoral Science Foundation(2022M712851)the Graduate Education Reform Project of Henan Province(2023SJGLX136Y)the Key R&D Special Program of Henan Province(241111242000)the Program for Science&Technology Innovation Talents in Universities of Henan Province(25HASTIT005)the Henan Provincial Excellent Youth Science Foundation(252300421172)the Training Plan for Young Backbone Teachers of Zhengzhou University(2023zDGGJS017)and the Joint Research Project of Puyang Shengtong Juyuan New Materials Co.,Ltd.(20230128A).
文摘Perovskite tandem solar cells(TSCs)hold substantial promise for surpassing the efficiency limits of single-junction solar cells.Nevertheless,achieving high open-circuit voltage(VOC)in wide-bandgap perovskite devices remains a challenge due to significant VOC-losses.Here,we introduce a heterogeneous interface anchoring strategy aimed at enhancing interfacial properties by incorporating a silane coupling agent between the perovskite and hole transport layers.Trimethoxysilane(TMOS),an amphiphilic molecule,strengthens interfacial adhesion through enhanced chemical interactions,thereby promoting efficient hole extraction.Additionally,the terminal functional groups of TMOS molecules interact with lead ions,modulating the perovskite film crystallization and improving their overall quality.Devices treated with TMOS exhibit a marked reduction in non-radiative recombination,leading to a significant increase in VOC.Notably,3-cyanopropyltrimethoxysilane(CN-TMOS)optimizes the uniformity and interfacial contact of the perovskite film,achieving a VOC of 1.345 V and a power conversion efficiency(PCE)of 19.69%.The corresponding VOC-loss,relative to the bandgap,is reduced to 0.425 V,one of the lowest values reported for wide-bandgap perovskite single-junction solar cells.Extending this strategy to all-perovskite TSCs,we achieve a PCE of 28.45%and exceptional operational stability,retaining over 90%of the initial efficiency after 500 h of continuous operation under 1 sun illumination.
基金National Natural Science Foundation of China(32101474,42377249)National Key Research and Development Program of China(2023YFD2201605).
文摘High conversion rate and selectivity are challenges for CO_(2)utilization through catalytic reverse water gas shift(RWGS)reaction.Herein,a novel mesoporous biochar(MB)supported Cu-Mo_(2)C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal.As compared with traditional carbon materials,this MB exhibited ultra-high specific surface area(2693 m^(2)g^(−1))and mesopore volume of mesopore(0.81 cm^(3)g^(−1))with a narrow distribution(2-5 nm),responsible for the high dispersion of binary Cu-Mo_(2)C sites,CO_(2)adsorption and mass transfer in the reaction system.Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo_(2)C binary sites(~6.1 nm)on the surface of MB.Cu+species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo_(2)C and Cu.These were advantageous to the intrinsic activity and stability of the Cu-Mo_(2)C binary sites and their accessibility to the reactant molecules.Under the RWGS reaction conditions of 500℃,atmospheric pressure,and 300,000 ml/g/h gas hour space velocity,the CO_(2)conversion rate over Cu-Mo_(2)C/MB reached 27.74×10^(-5)molCO_(2)/gcat/s at very low H_(2)partial pres-sure,which was more than twice that over traditional carbon supported Cu-Mo_(2)C catalysts.In addition,this catalyst exhibited 99.08%CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity.This study offers a new development strategy and a promising candidate for industrial RWGS.
文摘A novel asymmetric broad waveguide diode laser structure was designed for high power conversion efficiency（PCE）.The internal quantum efficiency,the series resistance,and the thermal resistance were theoretically optimized.The series resistance and the thermal resistance were greatly decreased by optimizing the thickness of the P-waveguide and the P-cladding layers.The internal quantum efficiency was increased by introducing a novel strain-compensated GaAs0.9P0.1/InGaAs quantum well.Experimentally,a single 1-cm bar with 20% fill factor and 900 μm cavity length was mounted P-side down on a microchannel-cooled heatsink,and a peak PCE of 60% is obtained at 26.3-W continuous wave output power.The results prove that this novel asymmetric waveguide structure design is an efficient approach to improve the PCE.
基金National Natural Science Foundation of China,Grant/Award Numbers:52003267,51973214,22175074Natural Science Foundation of Jilin Province,Grant/Award Numbers:YDZJ202101ZYTS027,20220101054JC。
文摘Organic diradicaloids with unique open-shell structures and properties have been widely used in organic electronics and spintronics.However,their advantageous optical properties have been explored less in the biomedical field.In this work,the photothermal conversion behaviors of a boron-containing organic diradicaloid(BOD)are reported.BOD can assemble with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-poly(ethylene glycol)to form rodlike nanoparticles(BOD NPs).These as-prepared BOD NPs exhibit high photothermal conversion capability and robust photothermal stability.Notably,they possess morphological superiority,which guarantees the effective photothermal therapy of tumors.This work thus demonstrates the promise of organic diradicaloids as efficient photothermal agents for biomedical applications.
文摘By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L-band amplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.
基金supported by the National Natural Science Foundation of China(Grant Nos.62075056 and 61927815)the Natural Science Foundation of Hebei Province(Grant Nos.F2023202082 and F2022202035)。
文摘Based on a 4f system,a 0?reflector and a single laser diode side-pump amplifier,a new amplifier is designed to compensate the spherical aberration of the amplified laser generated by a single laser diode side-pump amplifier and enhance the power of the amplified laser.Furthermore,the role of the 4f system in the passive spherical aberration compensation and its effect on the amplified laser are discussed in detail.The results indicate that the amplification efficiency is enhanced by incorporating a 4f system in a double-pass amplifier and placing a 0?reflector only at the focal point of the single-pass amplified laser.This method also effectively uses the heat from the gain medium(neodymiumdoped yttrium aluminium garnet)of the amplifier to compensate the spherical aberration of the amplified laser.
基金Supported by State’s High-Technology Research and Development Project (863)
文摘For practicability of the high power microwave source,a C-band backward wave oscillator（BWO） which has high conversion efficiency is designed.When the axial guiding magnetic field is 0.83 T,the electron energy and the beam current of the diode are respectively 80 keV and 2.1 kA,a microwave output power of 100 MW at 7.4 GHz microwave frequency with 65% conversion efficiency is achieved in simulation.
基金supported by the Natural Science Foundation of Hunan Province(No.2022JJ30653).
文摘The random distributed-feedback fiber laser(RFL) is a new approach to obtain a high-power stable supercontinuum(SC) source.To consider both structure simplification and high-power SC output,an innovative structure achieving a kilowatt-level SC output in a single-stage RFL with a half-open cavity is demonstrated in this paper.It consists of a fiber oscillator,a piece of long passive fiber and a broadband coupler,among which the broadband coupler acting as a feedback device is crucial in SC generation.When the system has no feedback,the backward output power is up to298 W under the pump power of 1185 W.When the feedback is introduced before the pump laser,the backward power loss can be reduced and the pump can be fully utilized,which could promote forward output power and conversion efficiency significantly.Under the maximum pump power of 1847 W,a 1300 W SC with spectrum ranging from 887 to1920 nm and SC conversion efficiency of 66% is obtained.To the best of our knowledge,it is the simplest structure used for high-power SC generation,and both the generated SC output power and the conversion efficiency are highest in the scheme of the half-opened RFL output SC.
