The commercialization of proton exchange membrane water electrolysis(PEMWE)for green hydrogen production hinges on the development of low-cost,high-performance titanium porous transport layers(PTLs).This study introdu...The commercialization of proton exchange membrane water electrolysis(PEMWE)for green hydrogen production hinges on the development of low-cost,high-performance titanium porous transport layers(PTLs).This study introduces a triple-layer Ti-PTL with a graded porous structure and a 75%ultra-high porosity backing layer,fabricated through tape casting and roll calendering.This triple-layer PTL,composed of a microporous layer,an interlayer,and a highly porous backing layer,enhances catalyst utilization,mechanical integrity,and mass transport.Digital twin technology using X-ray revealed increased contact area and triple-phase boundary at the interface with the catalyst layer,significantly improving oxygen evolution reaction kinetics.Numerical simulations demonstrated that the strategically designed porous structure of the triple-layer PTL facilitates efficient oxygen transport,mitigates oxygen accumulation,and improves reactant accessibility.Electrochemical evaluations showed improved performance,achieving 127 mV reduction in voltage at 2 A cm^(-2)compared to a commercial PTL,highlighting its potential to enhance PEMWE efficiency and cost-effectiveness.展开更多
This study explores,for the first time,the influence of various C1 gases,such as methane(CH_(4)),carbon dioxide(CO_(2)),and biogas(CH4+CO_(2)),on catalytic pyrolysis of plastic waste(polypropylene)to evaluate their po...This study explores,for the first time,the influence of various C1 gases,such as methane(CH_(4)),carbon dioxide(CO_(2)),and biogas(CH4+CO_(2)),on catalytic pyrolysis of plastic waste(polypropylene)to evaluate their potential in producing aromatic hydrocarbons.Also,this study used the 0.5 wt%,1 wt%,3 wt%,and 5 wt%Ga-modified ZSM-5 catalyst and its reduction-oxidation processed catalysts owing to their promising catalytic properties.According to the results,the highest yield(39.5 wt%)of BTEX(benzene,toluene,xylene,and ethylbenzene)was achieved under CH4 over RO-GHZ(1)catalyst among all tested conditions.The reduction-oxidation process not only promotes a significant reduction of the Ga-size but also induces its diffusion inside the pore,compared to GHZ(1).This leads to the formation of highly active GaO^(+)ionic species,balancing the Lewis/Brönsted ratio,thereby accelerating the aromatization reaction.The effect of Ga loading on the RO-GHZ catalyst was also evaluated systematically,which showed a negative impact on the BTEX yield owing to the lowering in the concentration of active GaO+species.A detailed catalyst characterization supports the experimental results well.展开更多
The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be mo...The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be more complex,necessitating new theoretical frameworks,though key empirical evidence remains elusive.In this study,we used microdroplets to investigate the crystallization of sodium halides(NaCl,NaBr,and NaI)under homogeneous nucleation conditions across a wide range of supersaturations.In the evaporating droplet,NaCl follows the classical nucleation pathway,whereas NaBr and NaI exhibit the formation of an intermediate phase prior to the nucleation of anhydrous and hydrous single crystals,respectively.Optical and computational analyses indicate that these intermediate phases are liquid crystal phases composed of contact ion pairs.These findings establish a new theoretical framework for crystal nucleation and growth and offer methods to control nucleation pathways,enabling us to achieve desired crystals regardless of specific conditions.展开更多
Holographic microscopy has emerged as a vital tool in biomedicine,enabling visualization of microscopic morphological features of tissues and cells in a label-free manner.Recently,deep learning(DL)-based image reconst...Holographic microscopy has emerged as a vital tool in biomedicine,enabling visualization of microscopic morphological features of tissues and cells in a label-free manner.Recently,deep learning(DL)-based image reconstruction models have demonstrated state-of-the-art performance in holographic image reconstruction.However,their utility in practice is still severely limited,as conventional training schemes could not properly handle out-of-distribution data.Here,we leverage backpropagation operation and reparameterization of the forward propagator to enable an adaptable image reconstruction model for histopathologic inspection.Only given with a training dataset of rectum tissue images captured from a single imaging configuration,our scheme consistently shows high reconstruction performance even with the input hologram of diverse tissue types at different pathological states captured under various imaging configurations.Using the proposed adaptation technique,we show that the diagnostic features of cancerous colorectal tissues,such as dirty necrosis,captured with 5×magnification and a numerical aperture(NA)of 0.1,can be reconstructed with high accuracy,whereas a given training dataset is strictly confined to normal rectum tissues acquired under the imaging configuration of 20×magnification and an NA of 0.4.Our results suggest that the DL-based image reconstruction approaches,with sophisticated adaptation techniques,could offer an extensively generalizable solution for inverse mapping problems in imaging.展开更多
Bipolar plates(BPs)are essential multifunctional components in vanadium redox flow batteries(VRFBs)that require excellent electrical conductivity,low permeability,and strong solid support for the stack.However,convent...Bipolar plates(BPs)are essential multifunctional components in vanadium redox flow batteries(VRFBs)that require excellent electrical conductivity,low permeability,and strong solid support for the stack.However,conventional BPs are based on graphite sheets,which provide mechanical properties and corrosion resistance but have limitations in terms of electrical conductivity.Although carbon nanotubes(CNTs)have excellent properties,CNT composites with low CNT volume fractions(10–20%)have increased electrolyte permeability and limited electrical conductivity improvement,resulting in low durability and efficiency for VRFBs.This study proposes a novel concept of horizontally aligned CNT nanocomposite bipolar plate(HACN-BP)to address these issues.The HACN-BPs feature an optimized conduction path with a CNT volume fraction of 59%,resulting in reduced manufacturing time while demonstrating superior conductivity and permeability compared to conventional BPs.Furthermore,integrated HACN-BP mitigates ohmic loss that occurs in the BPs,thereby mitigating the potential drop by 40%.Therefore,the utilization of HACN-BP shows superior performance compared to recent studies,a substantial improvement of more than 6%in energy efficiency and 14%in capacity over conventional BP.展开更多
The harsh corrosive environment and sluggish oxygen evolution reaction(OER)kinetics at the anode of proton exchange membrane water electrolysis(PEMWE)cells warrant the use of excess Ir,thereby hindering large-scale in...The harsh corrosive environment and sluggish oxygen evolution reaction(OER)kinetics at the anode of proton exchange membrane water electrolysis(PEMWE)cells warrant the use of excess Ir,thereby hindering large-scale industrialization.To mitigate these issues,the present study aimed at fabricating a robust low-Ir-loading electrode via one-pot synthesis for efficient PEMWE.The pre-electrode was first prepared by alloying through the co-electrodeposition of Ir and Co,followed by the fabrication of Ir–Co oxide(Co-incorporated Ir oxide)electrodes via electrochemical dealloying.Two distinct dealloying techniques resulted in a modified valence state of Ir,and the effects of Co incorporation on the activity and stability of the OER catalysts were clarified using density functional theory(DFT)calculations,which offered theoretical insights into the reaction mechanism.While direct experimental validation of the oxygen evolution mechanism remains challenging under the current conditions,DFT-based theoretical modeling provided valuable perspectives on how Co incorporation could influence key steps in oxygen evolution catalysis.The Ir–Co oxide electrode with a selectively modulated valence state showed impressive performance with an overpotential of 258 mV at 10 mA cm^(−2),a low Tafel slope of 29.4 mV dec^(−1),and stability for 100 h at 100 mA cm^(−2)in the OER,in addition to a low overpotential of 16 mV at−10 mA cm^(−2)and high stability for 24 h in the hydrogen evolution reaction.The PEMWE cell equipped with the bifunctional Ir–Co oxide electrode as the anode and cathode exhibited outstanding performance(11.4 A cm^(−2)at 2.3 Vcell)despite having a low noble-metal content of 0.4 mgNM cm^(−2).展开更多
The frost-driven self-fracture of ionomer-bound carbon electrodes compromises the mechanical stability of electrochemical systems under subzero conditions.This study suggests that the mechanical degradation of ionomer...The frost-driven self-fracture of ionomer-bound carbon electrodes compromises the mechanical stability of electrochemical systems under subzero conditions.This study suggests that the mechanical degradation of ionomer-bound carbon electrodes under subfreezing conditions is primarily driven by damage within the ionomer binder phase rather than within the nanopores.This damage occurs owing to the expansion of confined water upon freezing.Reducing the size of the freezable water domains significantly enhances the mechanical robustness.Structural and mechanical analyses reveal that thermal reconfiguration effectively modifies the ionomer nanostructure,leading to an approximately 30%reduction in water uptake and improved resistance to frost-induced self-fracturing.Nanostructural analyses further confirm that crystallized packing in the ionomer binder minimizes the number of water retention sites,thereby restricting the buildup of internal stress during freezing.Consequently,the elongation of the as-prepared electrodes reduces by approximately 65%after freezing at−10℃,whereas that of the thermally reconfigured electrodes is above 90%of its initial value with minimal deterioration.These findings highlight the critical role of ionomer-phase engineering in improving the low-temperature durability of ionomer-bound carbon electrodes,providing a scalable strategy applicable to fuel cells,water electrolyzers,and next-generation energy storage systems without requiring antifreezing agents.展开更多
Extensively explored for their distinctive pseudocapacitance characteristics,MXenes,a distinguished group of 2D materials,have led to remarkable achievements,particularly in the realm of energy storage devices.This wo...Extensively explored for their distinctive pseudocapacitance characteristics,MXenes,a distinguished group of 2D materials,have led to remarkable achievements,particularly in the realm of energy storage devices.This work presents an innovative Pseudocapacitive Sensor.The key lies in switching the energy storage kinetics from pseudocapacitor to electrical double layer capacitor by employing the change of local pH(-log[H^(+)])in MXene-based flexible supercapacitors during bending.Pseudocapacitive sensing is observed in acidic electrolyte but absent in neutral electrolyte.Applied shearing during bending causes liquid-crystalline MXene sheets to increase in their degree of anisotropic alignment.With blocking of H+mobility due to the higher diffusion barrier,local pH increases.The electrochemical energy storage kinetics transits from Faradaic chemical protonation(intercalation)to non-Faradaic physical adsorption.We utilize the phenomenon of capacitance change due to shifting energy storage kinetics for strain sensing purposes.The developed highly sensitive Pseudocapacitive Sensors feature a remarkable gauge factor(GF)of approximately 1200,far surpassing conventional strain sensors(GF:~1 for dielectric-cap sensor).The introduction of the Pseudocapacitive Sensor represents a paradigm shift,expanding the application of pseudocapacitance from being solely confined to energy devices to the realm of multifunctional electronics.This technological leap enriches our understanding of the pseudocapacitance mechanism of MXenes,and will drive innovation in cutting-edge technology areas,including advanced robotics,implantable biomedical devices,and health monitoring systems.展开更多
Next-generation artificial tactile systems demand seamless integration with neuromorphic architectures to support on-edge computation and high-fidelity sensory signal processing.Despite significant advancements,curren...Next-generation artificial tactile systems demand seamless integration with neuromorphic architectures to support on-edge computation and high-fidelity sensory signal processing.Despite significant advancements,current research remains predominantly focused on optimizing individual sensor elements,and systems utilizing single neuromorphic components encounter inherent limitations in enhancing overall functionality.Here,we present a vertically integrated in-sensor processing platform,which combines a three-dimensional antiferroelectric field-effect transistor(AFEFET)device with an aluminum nitride(AlN)piezoelectric sensor.展开更多
A wearable health monitoring system is a promising device for opening the era of the fourth industrial revolution due to increasing interest in health among modern people.Wearable health monitoring systems were demons...A wearable health monitoring system is a promising device for opening the era of the fourth industrial revolution due to increasing interest in health among modern people.Wearable health monitoring systems were demonstrated by several researchers,but still have critical issues of low performance,inefficient and complex fabrication processes.Here,we present the world’s first wearable multifunctional health monitoring system based on flash-induced porous graphene(FPG).FPG was efficiently synthesized via flash lamp,resulting in a large area in four milliseconds.Moreover,to demonstrate the sensing performance of FPG,a wearable multifunctional health monitoring system was fabricated onto a single substrate.A carbon nanotube-polydimethylsiloxane(CNT-PDMS)nanocomposite electrode was successfully formed on the uneven FPG surface using screen printing.The performance of the FPG-based wearable multifunctional health monitoring system was enhanced by the large surface area of the 3D-porous structure FPG.Finally,the FPG-based wearable multifunctional health monitoring system effectively detected motion,skin temperature,and sweat with a strain GF of 2564.38,a linear thermal response of 0.98Ω℃^(-1) under the skin temperature range,and a low ion detection limit of 10μM.展开更多
Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BC...Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3μm,and small amounts(<4 vol.%)of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27%and 87%at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm^(3),while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50%of the yield strength of the AlxCrNbVMo RHEAs.展开更多
Dual-fuel premixed charge compression ignition (DF-PCCI) combustion has been proven to be a viable alternative to conventional diesel combustion in heavy-duty compression ignition engines due to its low nitrogen oxide...Dual-fuel premixed charge compression ignition (DF-PCCI) combustion has been proven to be a viable alternative to conventional diesel combustion in heavy-duty compression ignition engines due to its low nitrogen oxides (NOx) and particulate matter (PM) emissions. When natural gas (NG) is applied to a DF-PCCI engine, its low reactivity reduces the maximum pressure rise rate under high loads. However, the NG–diesel DF-PCCI engine suffers from low combustion efficiency under low loads. In this study, an injection strategy of fuel supply (NG and diesel) in a DF-PCCI engine was investigated in order to reduce both the fuel consumption and hydrocarbon (HC) and carbon monoxide (CO) emissions under low load conditions. A variation in the NG substitution and diesel start of energizing (SOE) was found to effectively control the formation of the fuel–air mixture. A double injection strategy of diesel was implemented to adjust the local reactivity of the mixture. Retardation of the diesel pilot SOE and a low fraction of the diesel pilot injection quantity were favorable for reducing the combustion loss. The introduction of exhaust gas recirculation (EGR) improved the fuel economy and reduced the NOx and PM emissions below Euro VI regulations by retarding the combustion phasing. The combination of an NG substitution of 40%, the double injection strategy of diesel, and a moderate EGR rate effectively improved the combustion efficiency and indicated efficiency, and reduced the HC and CO emissions under low load conditions.展开更多
This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evalu...This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evaluation is carried out by comparing fracture loci constructed by fracture criteria to experimental results of A12024-T351. Comparison demonstrates that the Modified Mohr-Coulomb criterion and a newly proposed criterion provide sufficient predictabil- ity of fracture strain. Moreover, evaluation is emphasized on the predicted cut-off value for stress triaxiality. The evaluation demonstrates that the Cockcroft-Latham, Brozzo, Oh, Ko-Huh and the new criteria coupled a reasonable cut-off value for ductile materials.展开更多
基金supported by the collaborative research project of Hyundai Motor Company.Also,this work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00406086,RS-2024-00338569,and RS-2024-00467191)。
文摘The commercialization of proton exchange membrane water electrolysis(PEMWE)for green hydrogen production hinges on the development of low-cost,high-performance titanium porous transport layers(PTLs).This study introduces a triple-layer Ti-PTL with a graded porous structure and a 75%ultra-high porosity backing layer,fabricated through tape casting and roll calendering.This triple-layer PTL,composed of a microporous layer,an interlayer,and a highly porous backing layer,enhances catalyst utilization,mechanical integrity,and mass transport.Digital twin technology using X-ray revealed increased contact area and triple-phase boundary at the interface with the catalyst layer,significantly improving oxygen evolution reaction kinetics.Numerical simulations demonstrated that the strategically designed porous structure of the triple-layer PTL facilitates efficient oxygen transport,mitigates oxygen accumulation,and improves reactant accessibility.Electrochemical evaluations showed improved performance,achieving 127 mV reduction in voltage at 2 A cm^(-2)compared to a commercial PTL,highlighting its potential to enhance PEMWE efficiency and cost-effectiveness.
文摘This study explores,for the first time,the influence of various C1 gases,such as methane(CH_(4)),carbon dioxide(CO_(2)),and biogas(CH4+CO_(2)),on catalytic pyrolysis of plastic waste(polypropylene)to evaluate their potential in producing aromatic hydrocarbons.Also,this study used the 0.5 wt%,1 wt%,3 wt%,and 5 wt%Ga-modified ZSM-5 catalyst and its reduction-oxidation processed catalysts owing to their promising catalytic properties.According to the results,the highest yield(39.5 wt%)of BTEX(benzene,toluene,xylene,and ethylbenzene)was achieved under CH4 over RO-GHZ(1)catalyst among all tested conditions.The reduction-oxidation process not only promotes a significant reduction of the Ga-size but also induces its diffusion inside the pore,compared to GHZ(1).This leads to the formation of highly active GaO^(+)ionic species,balancing the Lewis/Brönsted ratio,thereby accelerating the aromatization reaction.The effect of Ga loading on the RO-GHZ catalyst was also evaluated systematically,which showed a negative impact on the BTEX yield owing to the lowering in the concentration of active GaO+species.A detailed catalyst characterization supports the experimental results well.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2021R1C1C2006535)supported by the Korea Basic Science Institute(National Research Facilities and Equipment Center)grant funded by the Korea government(MSIT)(No.RS-2024-00403164)supported by the National Research Foundation of Korea grant funded by the Korea government,Ministry of Science and ICT(Development of Nanofiber Yarn Based Compound Sensor as a Comprehensive Wearable Healthcare Solution)(Grant No.RS-2024-00357296).
文摘The crystallization of ionic crystals has traditionally been explained by Gibbs's classical nucleation theory.However,recent observations of intermediate phases during nucleation suggest that the process may be more complex,necessitating new theoretical frameworks,though key empirical evidence remains elusive.In this study,we used microdroplets to investigate the crystallization of sodium halides(NaCl,NaBr,and NaI)under homogeneous nucleation conditions across a wide range of supersaturations.In the evaporating droplet,NaCl follows the classical nucleation pathway,whereas NaBr and NaI exhibit the formation of an intermediate phase prior to the nucleation of anhydrous and hydrous single crystals,respectively.Optical and computational analyses indicate that these intermediate phases are liquid crystal phases composed of contact ion pairs.These findings establish a new theoretical framework for crystal nucleation and growth and offer methods to control nucleation pathways,enabling us to achieve desired crystals regardless of specific conditions.
基金supported by the Samsung Research Funding and Incubation Center of Samsung Electronics(Grant No.SRFC-IT2002-03)the Samsung Electronics Co.,Ltd.(Grant No.IO220908-02403-01)+2 种基金the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(Grant Nos.NRF-RS-2021-NR060086 and NRF-RS-2023-00251628)the Bio&Medical Technology Development Program of the National Research Foundation funded by the Korean government(MSIT)(Grant No RS-2024-00397673)the KAIST-CERAGEM Next Generation Healthcare Research Center.
文摘Holographic microscopy has emerged as a vital tool in biomedicine,enabling visualization of microscopic morphological features of tissues and cells in a label-free manner.Recently,deep learning(DL)-based image reconstruction models have demonstrated state-of-the-art performance in holographic image reconstruction.However,their utility in practice is still severely limited,as conventional training schemes could not properly handle out-of-distribution data.Here,we leverage backpropagation operation and reparameterization of the forward propagator to enable an adaptable image reconstruction model for histopathologic inspection.Only given with a training dataset of rectum tissue images captured from a single imaging configuration,our scheme consistently shows high reconstruction performance even with the input hologram of diverse tissue types at different pathological states captured under various imaging configurations.Using the proposed adaptation technique,we show that the diagnostic features of cancerous colorectal tissues,such as dirty necrosis,captured with 5×magnification and a numerical aperture(NA)of 0.1,can be reconstructed with high accuracy,whereas a given training dataset is strictly confined to normal rectum tissues acquired under the imaging configuration of 20×magnification and an NA of 0.4.Our results suggest that the DL-based image reconstruction approaches,with sophisticated adaptation techniques,could offer an extensively generalizable solution for inverse mapping problems in imaging.
基金supported by the Nano&Material Technology Development Program through the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS-2023-00260461)supported by ANSYS,Airbus,Embraer,Lockheed Martin,Saab AB,Saertex,and Teijin Carbon America through MIT’s Nano-Engineered Composite aerospace STructures(NECST)Consortium,USAsupported in part by the U.S.Army Research Office through the Institute for Soldier Nanotechnologies at MIT,under Cooperative Agreement Number W911NF-18-2-0048,and was carried out in part using MIT.-nano’s facilities.
文摘Bipolar plates(BPs)are essential multifunctional components in vanadium redox flow batteries(VRFBs)that require excellent electrical conductivity,low permeability,and strong solid support for the stack.However,conventional BPs are based on graphite sheets,which provide mechanical properties and corrosion resistance but have limitations in terms of electrical conductivity.Although carbon nanotubes(CNTs)have excellent properties,CNT composites with low CNT volume fractions(10–20%)have increased electrolyte permeability and limited electrical conductivity improvement,resulting in low durability and efficiency for VRFBs.This study proposes a novel concept of horizontally aligned CNT nanocomposite bipolar plate(HACN-BP)to address these issues.The HACN-BPs feature an optimized conduction path with a CNT volume fraction of 59%,resulting in reduced manufacturing time while demonstrating superior conductivity and permeability compared to conventional BPs.Furthermore,integrated HACN-BP mitigates ohmic loss that occurs in the BPs,thereby mitigating the potential drop by 40%.Therefore,the utilization of HACN-BP shows superior performance compared to recent studies,a substantial improvement of more than 6%in energy efficiency and 14%in capacity over conventional BP.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(RS-2024-00340074,RS-2024-00409901,2022M3I3A1081901,and RS-2024-00413272)。
文摘The harsh corrosive environment and sluggish oxygen evolution reaction(OER)kinetics at the anode of proton exchange membrane water electrolysis(PEMWE)cells warrant the use of excess Ir,thereby hindering large-scale industrialization.To mitigate these issues,the present study aimed at fabricating a robust low-Ir-loading electrode via one-pot synthesis for efficient PEMWE.The pre-electrode was first prepared by alloying through the co-electrodeposition of Ir and Co,followed by the fabrication of Ir–Co oxide(Co-incorporated Ir oxide)electrodes via electrochemical dealloying.Two distinct dealloying techniques resulted in a modified valence state of Ir,and the effects of Co incorporation on the activity and stability of the OER catalysts were clarified using density functional theory(DFT)calculations,which offered theoretical insights into the reaction mechanism.While direct experimental validation of the oxygen evolution mechanism remains challenging under the current conditions,DFT-based theoretical modeling provided valuable perspectives on how Co incorporation could influence key steps in oxygen evolution catalysis.The Ir–Co oxide electrode with a selectively modulated valence state showed impressive performance with an overpotential of 258 mV at 10 mA cm^(−2),a low Tafel slope of 29.4 mV dec^(−1),and stability for 100 h at 100 mA cm^(−2)in the OER,in addition to a low overpotential of 16 mV at−10 mA cm^(−2)and high stability for 24 h in the hydrogen evolution reaction.The PEMWE cell equipped with the bifunctional Ir–Co oxide electrode as the anode and cathode exhibited outstanding performance(11.4 A cm^(−2)at 2.3 Vcell)despite having a low noble-metal content of 0.4 mgNM cm^(−2).
基金supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT)(Grant Nos.2022R1A2C3009087 and 2022R1F1A1073173)the Korean Institute of Energy Technology Evaluation and Planning (KETEP)+1 种基金the Ministry of Trade,Industry & Energy (MOTIE) of the Republic of Korea (Grant No. RS-2024-00394769)the research grant of Kongju National University in 2022
文摘The frost-driven self-fracture of ionomer-bound carbon electrodes compromises the mechanical stability of electrochemical systems under subzero conditions.This study suggests that the mechanical degradation of ionomer-bound carbon electrodes under subfreezing conditions is primarily driven by damage within the ionomer binder phase rather than within the nanopores.This damage occurs owing to the expansion of confined water upon freezing.Reducing the size of the freezable water domains significantly enhances the mechanical robustness.Structural and mechanical analyses reveal that thermal reconfiguration effectively modifies the ionomer nanostructure,leading to an approximately 30%reduction in water uptake and improved resistance to frost-induced self-fracturing.Nanostructural analyses further confirm that crystallized packing in the ionomer binder minimizes the number of water retention sites,thereby restricting the buildup of internal stress during freezing.Consequently,the elongation of the as-prepared electrodes reduces by approximately 65%after freezing at−10℃,whereas that of the thermally reconfigured electrodes is above 90%of its initial value with minimal deterioration.These findings highlight the critical role of ionomer-phase engineering in improving the low-temperature durability of ionomer-bound carbon electrodes,providing a scalable strategy applicable to fuel cells,water electrolyzers,and next-generation energy storage systems without requiring antifreezing agents.
基金supported by NRF-2021M3H4A1A03047333 and NRF-2022R1F1A1075084 of the National Research Foundation(NRF)of Korea funded by the Ministry of Science and ICT,Koreasupported by Semiconductor-Secondary Battery Interfacing Platform Technology Development Project of NNFC.
文摘Extensively explored for their distinctive pseudocapacitance characteristics,MXenes,a distinguished group of 2D materials,have led to remarkable achievements,particularly in the realm of energy storage devices.This work presents an innovative Pseudocapacitive Sensor.The key lies in switching the energy storage kinetics from pseudocapacitor to electrical double layer capacitor by employing the change of local pH(-log[H^(+)])in MXene-based flexible supercapacitors during bending.Pseudocapacitive sensing is observed in acidic electrolyte but absent in neutral electrolyte.Applied shearing during bending causes liquid-crystalline MXene sheets to increase in their degree of anisotropic alignment.With blocking of H+mobility due to the higher diffusion barrier,local pH increases.The electrochemical energy storage kinetics transits from Faradaic chemical protonation(intercalation)to non-Faradaic physical adsorption.We utilize the phenomenon of capacitance change due to shifting energy storage kinetics for strain sensing purposes.The developed highly sensitive Pseudocapacitive Sensors feature a remarkable gauge factor(GF)of approximately 1200,far surpassing conventional strain sensors(GF:~1 for dielectric-cap sensor).The introduction of the Pseudocapacitive Sensor represents a paradigm shift,expanding the application of pseudocapacitance from being solely confined to energy devices to the realm of multifunctional electronics.This technological leap enriches our understanding of the pseudocapacitance mechanism of MXenes,and will drive innovation in cutting-edge technology areas,including advanced robotics,implantable biomedical devices,and health monitoring systems.
基金supported by the National Research Foundation of Korea(No.2021R1A2C2095322)supported by Grant Nos.RS-2023-00260527,RS-2023-00231985,RS2023-00235655,RS-2024-00406007supported by BK21 FOUR(Connected AI Education&Research Program for Industry and Society Innovation,KAIST EE,No.4120200113769)。
文摘Next-generation artificial tactile systems demand seamless integration with neuromorphic architectures to support on-edge computation and high-fidelity sensory signal processing.Despite significant advancements,current research remains predominantly focused on optimizing individual sensor elements,and systems utilizing single neuromorphic components encounter inherent limitations in enhancing overall functionality.Here,we present a vertically integrated in-sensor processing platform,which combines a three-dimensional antiferroelectric field-effect transistor(AFEFET)device with an aluminum nitride(AlN)piezoelectric sensor.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Ministry of Science,ICT and Future Planning(MSIT)(RS-2024-00408989,RS-2023-00278906,and RS-2023-00217661)the Center for Universitywide Research Facilities(CURF)at Jeonbuk National University for High-Resolution In Vivo Micro-Computed Tomography(Skyscan 1276,BRUKER).
文摘A wearable health monitoring system is a promising device for opening the era of the fourth industrial revolution due to increasing interest in health among modern people.Wearable health monitoring systems were demonstrated by several researchers,but still have critical issues of low performance,inefficient and complex fabrication processes.Here,we present the world’s first wearable multifunctional health monitoring system based on flash-induced porous graphene(FPG).FPG was efficiently synthesized via flash lamp,resulting in a large area in four milliseconds.Moreover,to demonstrate the sensing performance of FPG,a wearable multifunctional health monitoring system was fabricated onto a single substrate.A carbon nanotube-polydimethylsiloxane(CNT-PDMS)nanocomposite electrode was successfully formed on the uneven FPG surface using screen printing.The performance of the FPG-based wearable multifunctional health monitoring system was enhanced by the large surface area of the 3D-porous structure FPG.Finally,the FPG-based wearable multifunctional health monitoring system effectively detected motion,skin temperature,and sweat with a strain GF of 2564.38,a linear thermal response of 0.98Ω℃^(-1) under the skin temperature range,and a low ion detection limit of 10μM.
基金the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT of Korea through contracts NRF-2018K2A9A1A06069970,NRF2020R1A5A6017701the Asian Office of Aerospace Research and Development(AOARD)grant funded by the Air Force Office of Scientific Research(AFOSR)through a grant FA2386-19-1-4009。
文摘Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3μm,and small amounts(<4 vol.%)of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27%and 87%at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm^(3),while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50%of the yield strength of the AlxCrNbVMo RHEAs.
基金the Global-Top Project,Development of Advanced Combustion Technology for Global Top Low Emission Vehicle(2016002070001)the Ministry of Environment(MOE)of Korea for financial support by the Center for Environmentally Friendly Vehicle(CEFV)
文摘Dual-fuel premixed charge compression ignition (DF-PCCI) combustion has been proven to be a viable alternative to conventional diesel combustion in heavy-duty compression ignition engines due to its low nitrogen oxides (NOx) and particulate matter (PM) emissions. When natural gas (NG) is applied to a DF-PCCI engine, its low reactivity reduces the maximum pressure rise rate under high loads. However, the NG–diesel DF-PCCI engine suffers from low combustion efficiency under low loads. In this study, an injection strategy of fuel supply (NG and diesel) in a DF-PCCI engine was investigated in order to reduce both the fuel consumption and hydrocarbon (HC) and carbon monoxide (CO) emissions under low load conditions. A variation in the NG substitution and diesel start of energizing (SOE) was found to effectively control the formation of the fuel–air mixture. A double injection strategy of diesel was implemented to adjust the local reactivity of the mixture. Retardation of the diesel pilot SOE and a low fraction of the diesel pilot injection quantity were favorable for reducing the combustion loss. The introduction of exhaust gas recirculation (EGR) improved the fuel economy and reduced the NOx and PM emissions below Euro VI regulations by retarding the combustion phasing. The combination of an NG substitution of 40%, the double injection strategy of diesel, and a moderate EGR rate effectively improved the combustion efficiency and indicated efficiency, and reduced the HC and CO emissions under low load conditions.
文摘This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evaluation is carried out by comparing fracture loci constructed by fracture criteria to experimental results of A12024-T351. Comparison demonstrates that the Modified Mohr-Coulomb criterion and a newly proposed criterion provide sufficient predictabil- ity of fracture strain. Moreover, evaluation is emphasized on the predicted cut-off value for stress triaxiality. The evaluation demonstrates that the Cockcroft-Latham, Brozzo, Oh, Ko-Huh and the new criteria coupled a reasonable cut-off value for ductile materials.
