Lithium metal batteries(LMBs)and anode-free LMBs(AFLMBs)present a solution to the need for batteries with a significantly superior theoretical energy density.However,their adoption is hindered by low Coulombic efficie...Lithium metal batteries(LMBs)and anode-free LMBs(AFLMBs)present a solution to the need for batteries with a significantly superior theoretical energy density.However,their adoption is hindered by low Coulombic efficiency(CE)and rapid capacity fading,primarily due to the formation of unstable solid electrolyte interphase(SEI)layer and Li dendrite growth as a result of uneven Li plating.Here,we report on the use of a stoichiometric Ti_(3)C_(2)T_(x)(S-Ti_(3)C_(2)T_(x))MXene coating on the copper current collector to enhance the cyclic stability of an anode-free lithium metal battery.The S-Ti_(3)C_(2)T_(x)coating provides abundant nucleation sites,thereby lowering the overpotential for Li nucleation,and promoting uniform Li plating.Additionally,the fluorine(-F)termination of S-Ti_(3)C_(2)T_(x)participates in the SEI formation,producing a LiF-rich SEI layer,vital for stabilizing the SEI and improving cycle life.Batteries equipped with S-Ti_(3)C_(2)T_(x)@Cu current collectors displayed reduced Li consumption during stable SEI formation,resulting in a significant decrease in capacity loss.AFLMBs with S-Ti_(3)C_(2)T_(x)@Cu current collectors achieved a high initial capacity density of 4.2 mAh cm^(-2),70.9%capacity retention after 50 cycles,and an average CE of 98.19%in 100 cycles.This innovative application of MXenes in the energy field offers a promising strategy to enhance the performance of AFLMBs and could potentially accelerate their commercial adoption.展开更多
Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices.However,the application of graphene fillers is limited by their restr...Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices.However,the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions.In this study,a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process.A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL^(−1)for graphene ink.The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49×10^(4)S m^(−1)and maintains high conductivity under mechanical bending,compressing,and fatigue tests.Based on the as-prepared graphene ink,a printed electrochemical sodium ion(Na^(+))sensor that shows high potentiometric sensing performance was fabricated.Further,by integrating a wireless electronic module,a prototype Na^(+)-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer.The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost,reproducible,and large-scale printing of flexible and wearable electronic devices.展开更多
The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field...The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.展开更多
A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire ...A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage(Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.展开更多
Nanostructured materials are being actively developed,while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications.This study propose an industrial app...Nanostructured materials are being actively developed,while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications.This study propose an industrial approach to rapidly fabricate high-strength large-size nanostructured metal matrix composites and attempts to investigate and optimize the deposition process and strengthening mechanism.Here,advanced nanocrystalline aluminum matrix composites(nanoAMCs)were assembled for the first time by a novel nano-additive manufacturing method that was guided by numerical simulations(i.e.the in-flight particle model and the porefree deposition model).The present nanoAMC with a mean grain size<50 nm in matrix exhibited hardness eight times higher than the bulk aluminum and shows the highest hardness among all Al–Al2O3 composites reported to date in the literature,which are the outcome of controlling multiscale strengthening mechanisms from tailoring solution atoms,dislocations,grain boundaries,precipitates,and externally introduced reinforcing particles.The present high-throughput strategy and method can be extended to design and architect advanced coatings or bulk materials in a highly efficient(synthesizing a nanostructured bulk with dimensions of 50×20×4 mm^(3) in 9 min)and highly flexible(regulating the gradient microstructures in bulk)way,which is conducive to industrial production and application.展开更多
We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition.Using electron microscopy,the microstructural evolution upon varying the process parameters,especially laser power and powde...We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition.Using electron microscopy,the microstructural evolution upon varying the process parameters,especially laser power and powder feed rate,was investigated in relation to crack formation.Cladding layers showing dilution rates of more than 5%contained cracks due to the formation of the brittle Co_(2)Ti intermetallic phase.The observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co_(2)Ti phase,as determined by density functional theory and nanoindentation.Furthermore,an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles,while a deficient laser energy resulted in a lack of fusion.Neither cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225–300 W,for which the dilution rate was minimized to less than 5%.For such samples,the cladding layers comprised pureα-Ti and a uniform CoT i interface with Co_(2)Ti islands.展开更多
Nanocellulose is a sustainable and eco-friendly nanomaterial derived from renewable biomass. In this study, we utilized the structural advantages of two types of nanocellulose and fabricated freestanding carbonized hy...Nanocellulose is a sustainable and eco-friendly nanomaterial derived from renewable biomass. In this study, we utilized the structural advantages of two types of nanocellulose and fabricated freestanding carbonized hybrid nanocellulose films as electrode materials for supercapacitors. The long cellulose nanofibrils （CNFs） formed a macroporous framework, and the short cellulose nanocrystals were assembled around the CNF framework and generated micro/mesopores. This two-level hierarchical porous structure was successfully preserved during carbonization because of a thin atomic layer deposited （ALD） A1203 conformal coating, which effectively prevented the aggregation of nanocellulose. These carbonized, partially graphitized nanocellulose fibers were interconnected, forming an integrated and highly conductive network with a large specific surface area of 1,244 m2·g-1. The two-level hierarchical porous structure facilitated fast ion transport in the film. When tested as an electrode material with a high mass loading of 4 mg·cm-2 for supercapacitors, the hierarchical porous carbon film derived from hybrid nanocellulose exhibited a specific capacitance of 170 F·g-1 and extraordinary performance at high current densities. Even at a very high current of 50 A-g-l, it retained 65% of its original specific capacitance, which makes it a promising electrode material for high-power applications.展开更多
Ultrasonic power and data transfer is a promising technology for implantable medical devices because of its non-invasiveness,deep penetration depth,and potential for a high-power transmission rate with a low specific ...Ultrasonic power and data transfer is a promising technology for implantable medical devices because of its non-invasiveness,deep penetration depth,and potential for a high-power transmission rate with a low specific absorption rate.However,ultrasound-powered implantable devices still suffer from low power transfer efficiency due to beam misalignment and are limited to short-term use due to the bulkiness of the transmitting transducers.Here,we report the first proof of concept for adaptive positioning and targeting of ultrasound-based implantable devices through ultrasound image guidance.A lightweight patch-type ultrasonic transducer array is fabricated to enable ultrasound imaging and beam-forming during long-term operation.The uniform performance of the array is established through the silicon micromachining process.We demonstrate the complete scheme of imaging,positioning,and targeted power transfer in an ex vivo environment,achieving precise targeting of moving implanted devices through real-time ultrasound imaging.Enhanced power transfer efficiency through the use of patch-type ultrasonic transducers can enhance patient comfort and minimize invasive procedures,opening new applications for ultrasonic-powered implantable devices.展开更多
基金supported by the Creative Research Initiative Program(2015R1A3A2028975)funded by the National Research Foundation of Korea(NRF)+2 种基金supported by LG energy solution-KAIST Frontier Research Laboratory(2022)the National Research Foundation of Korea(NRF)grants(MSIT,NRF-2021M3H4A1A03047333)supported(funded)by the Semiconductor-Secondary Battery Interfacing Platform Technology Development Project of NNFC
文摘Lithium metal batteries(LMBs)and anode-free LMBs(AFLMBs)present a solution to the need for batteries with a significantly superior theoretical energy density.However,their adoption is hindered by low Coulombic efficiency(CE)and rapid capacity fading,primarily due to the formation of unstable solid electrolyte interphase(SEI)layer and Li dendrite growth as a result of uneven Li plating.Here,we report on the use of a stoichiometric Ti_(3)C_(2)T_(x)(S-Ti_(3)C_(2)T_(x))MXene coating on the copper current collector to enhance the cyclic stability of an anode-free lithium metal battery.The S-Ti_(3)C_(2)T_(x)coating provides abundant nucleation sites,thereby lowering the overpotential for Li nucleation,and promoting uniform Li plating.Additionally,the fluorine(-F)termination of S-Ti_(3)C_(2)T_(x)participates in the SEI formation,producing a LiF-rich SEI layer,vital for stabilizing the SEI and improving cycle life.Batteries equipped with S-Ti_(3)C_(2)T_(x)@Cu current collectors displayed reduced Li consumption during stable SEI formation,resulting in a significant decrease in capacity loss.AFLMBs with S-Ti_(3)C_(2)T_(x)@Cu current collectors achieved a high initial capacity density of 4.2 mAh cm^(-2),70.9%capacity retention after 50 cycles,and an average CE of 98.19%in 100 cycles.This innovative application of MXenes in the energy field offers a promising strategy to enhance the performance of AFLMBs and could potentially accelerate their commercial adoption.
基金the National Research Foundation of Korea(NRF)Grant funded by the Ministry of Science and ICT(No.2021R1A2C1009926)“Basic project(referring to projects performed with the budget directly contributed by the Government to achieve the purposes of establishment of Government-funded research Institutes)”+3 种基金supported by the KOREA RESEARCH INSTITUTE of CHEMICAL TECHNOLOGY(KRICT)(SS2042-10)Basic research project(Project:21-3212-1)of the Korea institute of GeoscienceMineral resources funded by the Ministry of Science and ICT of Koreaby Nanomedical Devices Development Project of NNFC in 2021.
文摘Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices.However,the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions.In this study,a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process.A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL^(−1)for graphene ink.The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49×10^(4)S m^(−1)and maintains high conductivity under mechanical bending,compressing,and fatigue tests.Based on the as-prepared graphene ink,a printed electrochemical sodium ion(Na^(+))sensor that shows high potentiometric sensing performance was fabricated.Further,by integrating a wireless electronic module,a prototype Na^(+)-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer.The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost,reproducible,and large-scale printing of flexible and wearable electronic devices.
基金Project supported by the 2010 Yeungnam University Research Grant,Korea
文摘The measurement and prediction of gas pulsations are performed along the discharge pipeline of a reciprocating compressor for a refrigerator. A regression based experimental model of the one-dimensional acoustic field is developed. First, the conventional method for gas pulsation measurement and prediction, which separates the incident and reflected wave of acoustic waves traveling in the frequency domain, is discussed. Then, regression based on our proposed simple model, which is able to predict gas pulsation compared to the conventional method, is introduced for the analysis of a reciprocating compressor(The conventional method requires the value of sound speed in the piping line for the reciprocating compressor). A numerical prediction is made for the regression method. Three power spectrum values along the discharge pipeline are used for analysis, and two values are used for verification. Our results are in a good agreement with the conventional method.
基金support by National High Technology Research and Development Program of China (No. 2011AA050504)the analysis supports from Instrumental Analysis Center of SJTU
文摘A vertical carbon nanotube field-effect transistor(CNTFET) based on silicon(Si) substrate has been proposed and simulated using a semi-classical theory. A single-walled carbon nanotube(SWNT) and an n-type Si nanowire in series construct the channel of the transistor. The CNTFET presents ambipolar characteristics at positive drain voltage(Vd) and n-type characteristics at negative Vd. The current is significantly influenced by the doping level of n-Si and the SWNT band gap. The n-branch current of the ambipolar characteristics increases with increasing doping level of the n-Si while the p-branch current decreases. The SWNT band gap has the same influence on the p-branch current at a positive Vd and n-type characteristics at negative Vd. The lower the SWNT band gap, the higher the current. However, it has no impact on the n-branch current in the ambipolar characteristics. Thick oxide is found to significantly degrade the current and the subthreshold slope of the CNTFETs.
基金received from Inno Tech Alberta (Dr Gary Fisher)the Major Innovation Fund (MIF) Program+5 种基金Imperial Oilthe Province of Alberta-Ministry of Jobs,Economy and Innovationthe Natural Science and Engineering Research Council of Canadafinancial support from Youth Talent Promotion Project of China Association for Science and Technology(Grant No. YESS20200120)the Youth Innovation Promotion Association CAS (Grant Nos. 2022189)Distinguished Scholar Project of Institute of Metal Research CAS (Grant No.2019000179)
文摘Nanostructured materials are being actively developed,while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications.This study propose an industrial approach to rapidly fabricate high-strength large-size nanostructured metal matrix composites and attempts to investigate and optimize the deposition process and strengthening mechanism.Here,advanced nanocrystalline aluminum matrix composites(nanoAMCs)were assembled for the first time by a novel nano-additive manufacturing method that was guided by numerical simulations(i.e.the in-flight particle model and the porefree deposition model).The present nanoAMC with a mean grain size<50 nm in matrix exhibited hardness eight times higher than the bulk aluminum and shows the highest hardness among all Al–Al2O3 composites reported to date in the literature,which are the outcome of controlling multiscale strengthening mechanisms from tailoring solution atoms,dislocations,grain boundaries,precipitates,and externally introduced reinforcing particles.The present high-throughput strategy and method can be extended to design and architect advanced coatings or bulk materials in a highly efficient(synthesizing a nanostructured bulk with dimensions of 50×20×4 mm^(3) in 9 min)and highly flexible(regulating the gradient microstructures in bulk)way,which is conducive to industrial production and application.
基金the support of the KAIST GCO_(2) RE(Global Center for Open Research with Enterprise)grant funded by the Ministry of Science and ICT(N11200010)National Research Foundation of Korea(NRF)[grant number NRF-2019R1A2C1002165]。
文摘We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition.Using electron microscopy,the microstructural evolution upon varying the process parameters,especially laser power and powder feed rate,was investigated in relation to crack formation.Cladding layers showing dilution rates of more than 5%contained cracks due to the formation of the brittle Co_(2)Ti intermetallic phase.The observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co_(2)Ti phase,as determined by density functional theory and nanoindentation.Furthermore,an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles,while a deficient laser energy resulted in a lack of fusion.Neither cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225–300 W,for which the dilution rate was minimized to less than 5%.For such samples,the cladding layers comprised pureα-Ti and a uniform CoT i interface with Co_(2)Ti islands.
文摘Nanocellulose is a sustainable and eco-friendly nanomaterial derived from renewable biomass. In this study, we utilized the structural advantages of two types of nanocellulose and fabricated freestanding carbonized hybrid nanocellulose films as electrode materials for supercapacitors. The long cellulose nanofibrils （CNFs） formed a macroporous framework, and the short cellulose nanocrystals were assembled around the CNF framework and generated micro/mesopores. This two-level hierarchical porous structure was successfully preserved during carbonization because of a thin atomic layer deposited （ALD） A1203 conformal coating, which effectively prevented the aggregation of nanocellulose. These carbonized, partially graphitized nanocellulose fibers were interconnected, forming an integrated and highly conductive network with a large specific surface area of 1,244 m2·g-1. The two-level hierarchical porous structure facilitated fast ion transport in the film. When tested as an electrode material with a high mass loading of 4 mg·cm-2 for supercapacitors, the hierarchical porous carbon film derived from hybrid nanocellulose exhibited a specific capacitance of 170 F·g-1 and extraordinary performance at high current densities. Even at a very high current of 50 A-g-l, it retained 65% of its original specific capacitance, which makes it a promising electrode material for high-power applications.
基金supported by the Korea Medical Device Development Fund grant funded by the Korea government(the Ministry of Science and ICT,the Ministry of Trade,Industry and Energy,the Ministry of Health&Welfare,Republic of Korea,the Ministry of Food and Drug Safety)(202011B01,RS-2020-KD000007)by the K-Brain Project of the National Research Foundation(NRF)funded by the Korean government(MSIT)(RS-2023-00262568)+3 种基金by a grant of the Korea Dementia Research Project through the Korea Dementia Research Center(KDRC)funded by the Ministry of Health&Welfare and Ministry of Science and ICT,Republic of Korea(RS-2024-00355871)by Nanomedical Devices Development Project of NNFC(1711197701)by Samsung Electronics.
文摘Ultrasonic power and data transfer is a promising technology for implantable medical devices because of its non-invasiveness,deep penetration depth,and potential for a high-power transmission rate with a low specific absorption rate.However,ultrasound-powered implantable devices still suffer from low power transfer efficiency due to beam misalignment and are limited to short-term use due to the bulkiness of the transmitting transducers.Here,we report the first proof of concept for adaptive positioning and targeting of ultrasound-based implantable devices through ultrasound image guidance.A lightweight patch-type ultrasonic transducer array is fabricated to enable ultrasound imaging and beam-forming during long-term operation.The uniform performance of the array is established through the silicon micromachining process.We demonstrate the complete scheme of imaging,positioning,and targeted power transfer in an ex vivo environment,achieving precise targeting of moving implanted devices through real-time ultrasound imaging.Enhanced power transfer efficiency through the use of patch-type ultrasonic transducers can enhance patient comfort and minimize invasive procedures,opening new applications for ultrasonic-powered implantable devices.
