Aqueous zinc-ion batteries encounter issues with the formation of Zn dendrites and parasitic reactions at Zn anodes.To address these issues,coating Zn anodes with two-dimensional(2D)nanocarbon materials,such as graphe...Aqueous zinc-ion batteries encounter issues with the formation of Zn dendrites and parasitic reactions at Zn anodes.To address these issues,coating Zn anodes with two-dimensional(2D)nanocarbon materials,such as graphene,has proven effective in ensuring uniform current distribution and facilitating charge transfer.While direct growth of 2D nanocarbon on Zn substrates offers significant advantages,it remains challenging due to Zn's low melting point(420℃).In this study,as a first proof-ofconcept,a unique sonochemical route was developed to directly grow crystalline-amorphous mixed 2D nanocarbon films,named“Leopard-patterned graphene,”on Zn substrates.This unique structure provides uniform nucleation sites while maintaining high Zn^(2+) ion permeability,mitigating dendrite formation.In Zn symmetric coin cell tests,the Zn electrodes coated with Leopard-patterned graphene maintained stable cycling for over 2000 h at a constant current density of 3mA cm^(−2).This study introduces an innovative approach for bottom-up synthesis of 2D nanocarbon on Zn substrates under ambient conditions and demonstrates its potential to address critical challenges in Zn-ion battery performance.The findings provide insights into advanced electrode design strategies for next-generation energy storage devices.展开更多
In this study,the texture of a rolled Mg alloy is effectively modified through the application of precompression and subsequent annealing treatment,leading to a remarkable improvement in the bending formability of the...In this study,the texture of a rolled Mg alloy is effectively modified through the application of precompression and subsequent annealing treatment,leading to a remarkable improvement in the bending formability of the alloy at room temperature.Precompression induces lattice reorientation through{10-12}twinning,and annealing treatment reduces the stored strain energy of the precompressed material,which results in the formation of a stable grain structure with two dominant texture components.With an increase in precompression,the tensile strain in the outer region of the bending samples is accommodated to a greater extent due to more pronounced{10-12}twinning and basal slip.As a result,the bending formability of the material at room temperature improves with greater precompression.The variation in microstructure,texture,and bending behavior in relation to the degree of precompression is discussed in detail.展开更多
The combination of graphene with conductive nanoparticles, forming graphene–nanoparticle hybrid materials, offers a number of excellent properties for advanced engineering applications. A novel and simple method was ...The combination of graphene with conductive nanoparticles, forming graphene–nanoparticle hybrid materials, offers a number of excellent properties for advanced engineering applications. A novel and simple method was developed to deposit 10 wt% tin-doped indium tin oxide(ITO) nanoparticles on graphene. The method involved a combination of a solution-based environmentally friendly electroless deposition approach and subsequent vacuum annealing. A stable organic-free solution of ITO was prepared from economical salts of In(NO_3)_3H_2 O and SnCl_4. The obtained ITO nanostructure exhibited a unique architecture, with uniformly dispersed 25–35 nm size ITO nanoparticles, containing only the crystallized In_2O_3 phase. The synthesized ITO nanoparticles–graphene hybrid exhibited very good and reproducible optical transparency in the visible range(more than 85%) and a28.2% improvement in electrical conductivity relative to graphene synthesized by chemical vapor deposition. It was observed that the ITO nanoparticles affect the position of the Raman signal of graphene, in which the D, G, and 2 D peaks were redshifted by 5.65, 5.69, and 9.74 cm^(-1),respectively, and the annealing conditions had no significant effect on the Raman signatures of graphene.展开更多
Multi-color emissions(or broadband emissions)from a single-phase phosphor with a single activator are an unfamiliar idea compared with those from multi-color-center materials.A single activator that is located in diff...Multi-color emissions(or broadband emissions)from a single-phase phosphor with a single activator are an unfamiliar idea compared with those from multi-color-center materials.A single activator that is located in different crystallographic sites of a single-phase phosphor,however,could lead to multimodal emission peaks for multi-color(or broadband)emissions.The discovery of a single-phase-single-activator-broadband-phosphor is rare,and it is regarded as difficult to accomplish.The present investigation introduces a novel single-phase-single-activator-broadband-phosphor(Ca_(1.624)Sr_(0.376)Si_(5)O_(3)N_(6):Eu^(2+))and provides an in-depth examination of the energy transfer between different crystallographic sites which is the governing mechanism for the broadband emissions.Structural analysis is backed up by density functional theory(DFT)calculations,which validate the structural model of the discovered novel phosphor.Rate-equation modeling is introduced based on particle swarm optimization(PSO)to provide a complete quantitative analysis for the mechanism of the energy transfer.展开更多
Deep learning(DL)models trained with synthetic XRD data have never accomplished a satisfactory quantitative XRD analysis for the exact prediction of a constituent-phase fraction in unknown multiphase inorganic compoun...Deep learning(DL)models trained with synthetic XRD data have never accomplished a satisfactory quantitative XRD analysis for the exact prediction of a constituent-phase fraction in unknown multiphase inorganic compounds,although DL-based phase identification has been successful.Here,we report a novel data-driven XRD analysis protocol involving a convolutional neural network(CNN)for exact phase identification and other machine learning(ML)techniques for accurate phase-fraction prediction.A key concept behind this reliable,pragmatic protocol is training with a huge amount of cheap synthetic data and testing with a small amount of expensive real-world experimental data.The protocol was applied to a Li-La-Zr-O quaternary compositional system that involves 218 ICSD-registered inorganic compounds,some of which are known as solid electrolyte materials.Synthetic data-driven XRD analysis has achieved a test accuracy of 96.47% for phase identification and a mean square error(MSE)of 0.0018 and an R2 of 0.9685 for phase-fraction regression.Real-world data tests have led to a phase-identification accuracy of 91.11% and a phase-fraction regression MSE of 0.0024 with an R^(2) of 0.9587.展开更多
In the recent development of electrochemical capacitors,battery-type electrode materials are considered to be promising materials owing to their comparable energy density and the ability to deliver significant power c...In the recent development of electrochemical capacitors,battery-type electrode materials are considered to be promising materials owing to their comparable energy density and the ability to deliver significant power compared to batteries.Herein,we report the applicability of nickel molybdate(NiMoO_(4))nanostructures as battery-type positive electrodes for the development of supercapatteries.The nickel molybdate nanostructures were synthesized by a facile coprecipitation technique and the structural and electrochemical properties were modified with appropriate heat treatment.The sample heat treated for 500℃ shows good crystallization of the NiMoO_(4) phase with a partial flower-like nanostructure compared with as-synthesized(bare)and 400℃ heat-treated samples.Moreover,the 500℃ sample-based electrode shows better battery-like electrochemical performances with a maximum specific capacity of 554 C g^(-1),which is higher compared to the other two electrodes.The supercapattery designed using the 500℃ NiMoO_(4) sample as the positive electrode and heteroatom enriched biowaste activated carbon as the negative electrode exhibited excellent electrochemical performances.The resultant supercapattery exhibited a maximum specific capacity value of 341 C g^(-1) at 1 A g^(-1) discharge specific current and showed an excellent specific energy of~64.07 W h kg^(-1) for a specific power of 0.676 kW kg^(-1) with<100%specific capacity retention even after 5000 charge/discharge cycles.展开更多
Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference(EMI)shielding materials in future mobility and wearable applications to prevent signal no...Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference(EMI)shielding materials in future mobility and wearable applications to prevent signal noise,transmission inaccuracy,system malfunction,and health hazards.Here,we report on the synthesis of lightweight and flexible flash-induced porous graphene(FPG)with excellent EMI shielding performance.The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films,forming 5×10 cm^(2)-size porous graphene with a hollow pillar structure in a few milliseconds.The resulting material demonstrated low density(0.0354 g cm^(−3))and outstanding absolute EMI shielding effectiveness of 1.12×10^(5) dB cm^(2) g^(−1).The FPG was characterized via thorough material analyses,and its mechanical durability and flexibility were confirmed by a bending cycle test.Finally,the FPG was utilized in drone and wearable applications,showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body.展开更多
The ffect of tin-oxide(SnO)nanoparticles,which are obtained by indium-tin-oxide(ITO)treatment,on the p-GaN surface of GaN-based flip-chip blue micro-light-emitting diode(μ-LED)arrays is investigated.A thin Ag layer i...The ffect of tin-oxide(SnO)nanoparticles,which are obtained by indium-tin-oxide(ITO)treatment,on the p-GaN surface of GaN-based flip-chip blue micro-light-emitting diode(μ-LED)arrays is investigated.A thin Ag layer is deposited on the ITO-treated p-GaN surface by sputtering.SnO nanoparticles originate from inho-mogencous Schottly barrier heights(SBHs)at Ag/p-GaN contact.Therefore,efective SBH is reduced,which causes carrier transport into theμ-LED to enhance.10 nm thick ITO-treatedμ-LEDs show better optoelectronic characteristics among fabricated u-LEDs owing to improved ohmic contact and highly reflective p-type reflectors.Basically,SnO nanoparticles help to make good ohmic contact,which results in improved carrier transport intoμ-LEDs and thus results in increased optoelectronic performances.展开更多
Cathode materials in potassium ion batteries(KIBs)generally exhibit low charge storage capabilities when compared with cathode materials implemented in lithium or sodium ion batteries.In this work,K_(0.78)Fe_(1.60)S_(...Cathode materials in potassium ion batteries(KIBs)generally exhibit low charge storage capabilities when compared with cathode materials implemented in lithium or sodium ion batteries.In this work,K_(0.78)Fe_(1.60)S_(2)is described as a high capacity KIB cathode that exhibits mixed anion/cation redox behaviors during charge/discharge(C/D).When charged to 3.2 V vs.K/K^(+),K^(+)extraction occurs along with simultaneous oxidations of S^(2−)to S_(2)^(2−)and Fe(II)to Fe(III).During subsequent discharge to 1.5 V,this process is reversed,in addition to a further reduction of Fe(II)to Fe(I).After a few C/D cycles,K_(0.78)Fe_(1.6)0S_(2)reversibly delivers 0.69 K^(+)with a capacity of 100.5 mA h g^(−1)(i.e.,K_(0.20)Fe_(1.6)0S_(2)⇆K_(0.89)Fe_(1.6)0S_(2)).The evolution of S_(2)−and Fe(II)valence states along with a lack of discernable changes in crystallographic dimensions clearly confirms the concomitant redox of anions and cations with C/D.Density functional theory calculations also validate the possibility of mixed redox reactions in K_(0.78)Fe_(1.6)0S_(2).Unique structural features of K_(0.78)Fe_(1.60)S_(2)(layers consisting of edge-shared FeS_(4)tetrahedra with partial Fe vacancies)result in high K^(+)diffusion coefficients that are unprecedented(ca.10^(−9)cm^(2)s^(−1)),which contributes to an excellent rate capability(56.3 mA h g^(−1)at 1000 mA^(g−1)vs.100.5 mA h g^(−1)at 20 mA g^(−1)).Nudged elastic band calculations also reveal that the diffusion preferentially occurs along[100]directions with a low activation energy barrier of 0.41 eV.展开更多
The prediction of excitation band edge wavelength(EBEW)and peak emission wavelength(PEW)for Eu^(2+)-activated phosphors is intricate in practice,although a theoretical interpretation has been well established.A data-d...The prediction of excitation band edge wavelength(EBEW)and peak emission wavelength(PEW)for Eu^(2+)-activated phosphors is intricate in practice,although a theoretical interpretation has been well established.A data-driven approach could be of great help for EBEW and PEW prediction.We collected 91 Eu^(2+)-activated phosphors,the host structures of which exhibit a single activator site and the EBEW and PEW of which are available at the critical activator concentration.We extracted 29 descriptors(input features)that implicate the elemental and structural traits of phosphor hosts,and set up an integrated machine-learning(ML)platform consisting of 18 ML algorithms that allowed prediction of the EBEW and PEW as well as the DFT-calculated band gap(Eg).The acquired dataset involving 91 phosphors was insufficient for the 29-input-feature problem and the real-world data collected from the literature have a so-called dirty nature due to inaccurate,unstandardized experiments.Despite an unavoidable paucity of data and the dirty-data problems of real-world data-based ML implementation,we obtained acceptable holdout dataset test results for PEW predications such as R^(2)>0.6,MSE<0.02,and test_R^(2)/training_R^(2)>0.77 for four ML algorithms.The EBEW and E_(g)predictions returned slightly better test results than these PEW examples.展开更多
A flexible electromagnetic interference(EMI)shielding film was innovatively fabricated using both low melting temperature solder arrays and amorphous soft magnet particulates consolidated on a polyethylene terephthala...A flexible electromagnetic interference(EMI)shielding film was innovatively fabricated using both low melting temperature solder arrays and amorphous soft magnet particulates consolidated on a polyethylene terephthalate(PET)substrate.First,the IneSneBi solder arrays presented a low melting point of 99.4C,which enabled attachment to the heat-sensitive plastic substrate without any thermal damage,and a low electrical resistivity of 14.1 mU cm,making them very effective at interrupting EM waves.Second,the solder arrays with a high thermal conductivity of 61.2 W/(m$K)at 298.15 K were also useful as a thermal conductor for a heat sink.Thus,the solder arrays provide efficient electrical and thermal channels for electron transport induced by abruptly or consistently created EM waves due to suddenly turning on and the long term operation of electronics,respectively.Third,the Fe-based magnetic particulates were added and resulted in effective saturation magnetization of 161.1 emu/g,remanence of 2.9 emu/g,and coercivity of 12.5 G,thus were able to disturb the EM pathway because of their soft magnetic properties.Consequently,the hybrid EMI shielding film with exceptionally high electrical and thermal conductivity and superior soft magnetic properties provided remarkable shielding effectiveness of 102.5 dB at 10.2 GHz.展开更多
基金supported by the Korean Institute of Energy Technology Evaluation and Planning (KETEP),Korean Government (MOTIE)(RS-2023-00303581)the National Research Foundation of Korea (NRF)the Ministry of Science and ICT (MIST)(Project Number:RS-2025-02223634)
文摘Aqueous zinc-ion batteries encounter issues with the formation of Zn dendrites and parasitic reactions at Zn anodes.To address these issues,coating Zn anodes with two-dimensional(2D)nanocarbon materials,such as graphene,has proven effective in ensuring uniform current distribution and facilitating charge transfer.While direct growth of 2D nanocarbon on Zn substrates offers significant advantages,it remains challenging due to Zn's low melting point(420℃).In this study,as a first proof-ofconcept,a unique sonochemical route was developed to directly grow crystalline-amorphous mixed 2D nanocarbon films,named“Leopard-patterned graphene,”on Zn substrates.This unique structure provides uniform nucleation sites while maintaining high Zn^(2+) ion permeability,mitigating dendrite formation.In Zn symmetric coin cell tests,the Zn electrodes coated with Leopard-patterned graphene maintained stable cycling for over 2000 h at a constant current density of 3mA cm^(−2).This study introduces an innovative approach for bottom-up synthesis of 2D nanocarbon on Zn substrates under ambient conditions and demonstrates its potential to address critical challenges in Zn-ion battery performance.The findings provide insights into advanced electrode design strategies for next-generation energy storage devices.
基金This work was supported by a National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP,South Korea)(No.2019R1A2C1085272)the R&D Center for Valuable Recycling(Global-Top R&BD Program)of the Ministry of Environment of Korea(No.2016002220003).
文摘In this study,the texture of a rolled Mg alloy is effectively modified through the application of precompression and subsequent annealing treatment,leading to a remarkable improvement in the bending formability of the alloy at room temperature.Precompression induces lattice reorientation through{10-12}twinning,and annealing treatment reduces the stored strain energy of the precompressed material,which results in the formation of a stable grain structure with two dominant texture components.With an increase in precompression,the tensile strain in the outer region of the bending samples is accommodated to a greater extent due to more pronounced{10-12}twinning and basal slip.As a result,the bending formability of the material at room temperature improves with greater precompression.The variation in microstructure,texture,and bending behavior in relation to the degree of precompression is discussed in detail.
基金supported by the Basic Science Research Program of the National Research Foundation(NRF)of Koreafunded by the Ministry of Education(NRF-2014R1A6A1030419 and NRF-2015R1D1A1A01061005)
文摘The combination of graphene with conductive nanoparticles, forming graphene–nanoparticle hybrid materials, offers a number of excellent properties for advanced engineering applications. A novel and simple method was developed to deposit 10 wt% tin-doped indium tin oxide(ITO) nanoparticles on graphene. The method involved a combination of a solution-based environmentally friendly electroless deposition approach and subsequent vacuum annealing. A stable organic-free solution of ITO was prepared from economical salts of In(NO_3)_3H_2 O and SnCl_4. The obtained ITO nanostructure exhibited a unique architecture, with uniformly dispersed 25–35 nm size ITO nanoparticles, containing only the crystallized In_2O_3 phase. The synthesized ITO nanoparticles–graphene hybrid exhibited very good and reproducible optical transparency in the visible range(more than 85%) and a28.2% improvement in electrical conductivity relative to graphene synthesized by chemical vapor deposition. It was observed that the ITO nanoparticles affect the position of the Raman signal of graphene, in which the D, G, and 2 D peaks were redshifted by 5.65, 5.69, and 9.74 cm^(-1),respectively, and the annealing conditions had no significant effect on the Raman signatures of graphene.
基金supported by the Creative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by the the Ministry of Science,ICT,and Future Planning(2015M3D1A1069705)partly by a NRF grant(2018R1C1B6006943).
文摘Multi-color emissions(or broadband emissions)from a single-phase phosphor with a single activator are an unfamiliar idea compared with those from multi-color-center materials.A single activator that is located in different crystallographic sites of a single-phase phosphor,however,could lead to multimodal emission peaks for multi-color(or broadband)emissions.The discovery of a single-phase-single-activator-broadband-phosphor is rare,and it is regarded as difficult to accomplish.The present investigation introduces a novel single-phase-single-activator-broadband-phosphor(Ca_(1.624)Sr_(0.376)Si_(5)O_(3)N_(6):Eu^(2+))and provides an in-depth examination of the energy transfer between different crystallographic sites which is the governing mechanism for the broadband emissions.Structural analysis is backed up by density functional theory(DFT)calculations,which validate the structural model of the discovered novel phosphor.Rate-equation modeling is introduced based on particle swarm optimization(PSO)to provide a complete quantitative analysis for the mechanism of the energy transfer.
基金supported by the Creative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT,and Future Planning(2015M3D1A1069705 and 2019H1D8A2106002)partly by the Alchemist Project(20012196),and the Digital manufacturing platform(N0002598)funded by MOTIE,Korea.
文摘Deep learning(DL)models trained with synthetic XRD data have never accomplished a satisfactory quantitative XRD analysis for the exact prediction of a constituent-phase fraction in unknown multiphase inorganic compounds,although DL-based phase identification has been successful.Here,we report a novel data-driven XRD analysis protocol involving a convolutional neural network(CNN)for exact phase identification and other machine learning(ML)techniques for accurate phase-fraction prediction.A key concept behind this reliable,pragmatic protocol is training with a huge amount of cheap synthetic data and testing with a small amount of expensive real-world experimental data.The protocol was applied to a Li-La-Zr-O quaternary compositional system that involves 218 ICSD-registered inorganic compounds,some of which are known as solid electrolyte materials.Synthetic data-driven XRD analysis has achieved a test accuracy of 96.47% for phase identification and a mean square error(MSE)of 0.0018 and an R2 of 0.9685 for phase-fraction regression.Real-world data tests have led to a phase-identification accuracy of 91.11% and a phase-fraction regression MSE of 0.0024 with an R^(2) of 0.9587.
基金Creative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and Future(NRF-2015M3D1A1069710)Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2014R1A6A1030419),Republic of Korea.
文摘In the recent development of electrochemical capacitors,battery-type electrode materials are considered to be promising materials owing to their comparable energy density and the ability to deliver significant power compared to batteries.Herein,we report the applicability of nickel molybdate(NiMoO_(4))nanostructures as battery-type positive electrodes for the development of supercapatteries.The nickel molybdate nanostructures were synthesized by a facile coprecipitation technique and the structural and electrochemical properties were modified with appropriate heat treatment.The sample heat treated for 500℃ shows good crystallization of the NiMoO_(4) phase with a partial flower-like nanostructure compared with as-synthesized(bare)and 400℃ heat-treated samples.Moreover,the 500℃ sample-based electrode shows better battery-like electrochemical performances with a maximum specific capacity of 554 C g^(-1),which is higher compared to the other two electrodes.The supercapattery designed using the 500℃ NiMoO_(4) sample as the positive electrode and heteroatom enriched biowaste activated carbon as the negative electrode exhibited excellent electrochemical performances.The resultant supercapattery exhibited a maximum specific capacity value of 341 C g^(-1) at 1 A g^(-1) discharge specific current and showed an excellent specific energy of~64.07 W h kg^(-1) for a specific power of 0.676 kW kg^(-1) with<100%specific capacity retention even after 5000 charge/discharge cycles.
基金supported by the Technology Development Program of MSS (S3207363)supported by the Wearable Platform Materials Technology Center (WMC) (NRF-2022R1A5A6000846)+3 种基金National Research Foundation of Korea (NRF) grant funded by the Korea government (MSITMinistry of Science and ICT) (No. NRF-2020M3C1B8081519)supported by the MSIT, Korea, under the ITRC (Information Technology Research Center) support program (IITP-2020-0-01778)supervised by the IITP (Institute of Information & Communications Technology Planning & Evaluation).
文摘Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference(EMI)shielding materials in future mobility and wearable applications to prevent signal noise,transmission inaccuracy,system malfunction,and health hazards.Here,we report on the synthesis of lightweight and flexible flash-induced porous graphene(FPG)with excellent EMI shielding performance.The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films,forming 5×10 cm^(2)-size porous graphene with a hollow pillar structure in a few milliseconds.The resulting material demonstrated low density(0.0354 g cm^(−3))and outstanding absolute EMI shielding effectiveness of 1.12×10^(5) dB cm^(2) g^(−1).The FPG was characterized via thorough material analyses,and its mechanical durability and flexibility were confirmed by a bending cycle test.Finally,the FPG was utilized in drone and wearable applications,showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body.
基金National Research Foundation of Korea(NRF-2014R1A6A1030419,NRF-2018R1D1A3A03000779)Korea.Evaluation Institute of Industrial Technology(20004946).
文摘The ffect of tin-oxide(SnO)nanoparticles,which are obtained by indium-tin-oxide(ITO)treatment,on the p-GaN surface of GaN-based flip-chip blue micro-light-emitting diode(μ-LED)arrays is investigated.A thin Ag layer is deposited on the ITO-treated p-GaN surface by sputtering.SnO nanoparticles originate from inho-mogencous Schottly barrier heights(SBHs)at Ag/p-GaN contact.Therefore,efective SBH is reduced,which causes carrier transport into theμ-LED to enhance.10 nm thick ITO-treatedμ-LEDs show better optoelectronic characteristics among fabricated u-LEDs owing to improved ohmic contact and highly reflective p-type reflectors.Basically,SnO nanoparticles help to make good ohmic contact,which results in improved carrier transport intoμ-LEDs and thus results in increased optoelectronic performances.
基金supported by Creative Materials Discovery Program through the National Research Foundation of Korea funded by the Ministry of Science,ICT and Future(2015M3D1A1069710)Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education(NRF-2014R1A6A1030419)the NRF grant funded by the Korea government(2018R1C1B6006943).
文摘Cathode materials in potassium ion batteries(KIBs)generally exhibit low charge storage capabilities when compared with cathode materials implemented in lithium or sodium ion batteries.In this work,K_(0.78)Fe_(1.60)S_(2)is described as a high capacity KIB cathode that exhibits mixed anion/cation redox behaviors during charge/discharge(C/D).When charged to 3.2 V vs.K/K^(+),K^(+)extraction occurs along with simultaneous oxidations of S^(2−)to S_(2)^(2−)and Fe(II)to Fe(III).During subsequent discharge to 1.5 V,this process is reversed,in addition to a further reduction of Fe(II)to Fe(I).After a few C/D cycles,K_(0.78)Fe_(1.6)0S_(2)reversibly delivers 0.69 K^(+)with a capacity of 100.5 mA h g^(−1)(i.e.,K_(0.20)Fe_(1.6)0S_(2)⇆K_(0.89)Fe_(1.6)0S_(2)).The evolution of S_(2)−and Fe(II)valence states along with a lack of discernable changes in crystallographic dimensions clearly confirms the concomitant redox of anions and cations with C/D.Density functional theory calculations also validate the possibility of mixed redox reactions in K_(0.78)Fe_(1.6)0S_(2).Unique structural features of K_(0.78)Fe_(1.60)S_(2)(layers consisting of edge-shared FeS_(4)tetrahedra with partial Fe vacancies)result in high K^(+)diffusion coefficients that are unprecedented(ca.10^(−9)cm^(2)s^(−1)),which contributes to an excellent rate capability(56.3 mA h g^(−1)at 1000 mA^(g−1)vs.100.5 mA h g^(−1)at 20 mA g^(−1)).Nudged elastic band calculations also reveal that the diffusion preferentially occurs along[100]directions with a low activation energy barrier of 0.41 eV.
基金supported by the Creative Materials Discovery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT,and Future Planning(2015M3D1A1069705),(2021R1A2C1011642)and(2021R1A2C1009144)partly by the Alchemist Project(20012196)Digital manufacturing platform(N0002598)funded by MOTIE,Korea.
文摘The prediction of excitation band edge wavelength(EBEW)and peak emission wavelength(PEW)for Eu^(2+)-activated phosphors is intricate in practice,although a theoretical interpretation has been well established.A data-driven approach could be of great help for EBEW and PEW prediction.We collected 91 Eu^(2+)-activated phosphors,the host structures of which exhibit a single activator site and the EBEW and PEW of which are available at the critical activator concentration.We extracted 29 descriptors(input features)that implicate the elemental and structural traits of phosphor hosts,and set up an integrated machine-learning(ML)platform consisting of 18 ML algorithms that allowed prediction of the EBEW and PEW as well as the DFT-calculated band gap(Eg).The acquired dataset involving 91 phosphors was insufficient for the 29-input-feature problem and the real-world data collected from the literature have a so-called dirty nature due to inaccurate,unstandardized experiments.Despite an unavoidable paucity of data and the dirty-data problems of real-world data-based ML implementation,we obtained acceptable holdout dataset test results for PEW predications such as R^(2)>0.6,MSE<0.02,and test_R^(2)/training_R^(2)>0.77 for four ML algorithms.The EBEW and E_(g)predictions returned slightly better test results than these PEW examples.
基金This study was partially sup-ported by the Korea Institute of Materials Science(KIMS).This work was mainly supported by the National Research Council of Science&Technology(NST)grant(No CRC-15-03-KIMM)of the Ministry of Science,ICTand Future Planning(MSIP)in the Korea government.This research was also supported by the Korea Institute of Industrial Technology(KTTECH)internal project(Grant No.P]A18350).
文摘A flexible electromagnetic interference(EMI)shielding film was innovatively fabricated using both low melting temperature solder arrays and amorphous soft magnet particulates consolidated on a polyethylene terephthalate(PET)substrate.First,the IneSneBi solder arrays presented a low melting point of 99.4C,which enabled attachment to the heat-sensitive plastic substrate without any thermal damage,and a low electrical resistivity of 14.1 mU cm,making them very effective at interrupting EM waves.Second,the solder arrays with a high thermal conductivity of 61.2 W/(m$K)at 298.15 K were also useful as a thermal conductor for a heat sink.Thus,the solder arrays provide efficient electrical and thermal channels for electron transport induced by abruptly or consistently created EM waves due to suddenly turning on and the long term operation of electronics,respectively.Third,the Fe-based magnetic particulates were added and resulted in effective saturation magnetization of 161.1 emu/g,remanence of 2.9 emu/g,and coercivity of 12.5 G,thus were able to disturb the EM pathway because of their soft magnetic properties.Consequently,the hybrid EMI shielding film with exceptionally high electrical and thermal conductivity and superior soft magnetic properties provided remarkable shielding effectiveness of 102.5 dB at 10.2 GHz.
