【问】[490]近日在查阅《朗文当代高级英语辞典》(外研社,2070页)中有关than作连词的用法时,发现其中第三个用法是这样描述的:"hardly/scarcely/no sooner...than...(一……就……),例如:Nosooner had I mailed the letter than I ...【问】[490]近日在查阅《朗文当代高级英语辞典》(外研社,2070页)中有关than作连词的用法时,发现其中第三个用法是这样描述的:"hardly/scarcely/no sooner...than...(一……就……),例如:Nosooner had I mailed the letter than I realized展开更多
你可能认为hardly是hard派生出来的副词吧，其实不然。下面就请你来做一做这几道题。请选用hard或hardly填空。1．Lucy＿＿＿studies：but her sister studies＿＿＿＿.2．Theworkisvery＿＿＿＿＿forme．3．He＿＿＿＿goes to bed befo...你可能认为hardly是hard派生出来的副词吧，其实不然。下面就请你来做一做这几道题。请选用hard或hardly填空。1．Lucy＿＿＿studies：but her sister studies＿＿＿＿.2．Theworkisvery＿＿＿＿＿forme．3．He＿＿＿＿goes to bed before 11：00 in the evening．展开更多
The acquisition,analysis,and prediction of the radar cross section(RCS)of a target have extremely important strategic significance in the military.However,the RCS values at all azimuths are hardly accessible for non-c...The acquisition,analysis,and prediction of the radar cross section(RCS)of a target have extremely important strategic significance in the military.However,the RCS values at all azimuths are hardly accessible for non-cooperative targets,due to the limitations of radar observation azimuth and detection resources.Despite their efforts to predict the azimuth-dimensional RCS value,traditional methods based on statistical theory fails to achieve the desired results because of the azimuth sensitivity of the target RCS.To address this problem,an improved neural basis expansion analysis for interpretable time series forecasting(N-BEATS)network considering the physical model prior is proposed to predict the azimuth-dimensional RCS value accurately.Concretely,physical model-based constraints are imposed on the network by constructing a scattering-center module based on the target scattering-center model.Besides,a superimposed seasonality module is involved to better capture high-frequency information,and augmenting the training set provides complementary information for learning predictions.Extensive simulations and experimental results are provided to validate the effectiveness of the proposed method.展开更多
Hard carbon(HC)is widely used in sodium-ion batteries(SIBs),but its performance has always been limited by lowinitial Coulombic efficiency(ICE)and cycling stability.Cathode compensation agent is a favorable strategy t...Hard carbon(HC)is widely used in sodium-ion batteries(SIBs),but its performance has always been limited by lowinitial Coulombic efficiency(ICE)and cycling stability.Cathode compensation agent is a favorable strategy to make up for the loss of active sodium ions consumed byHCanode.Yet it lacks agent that effectively decomposes to increase the active sodium ions as well as regulate carbon defects for decreasing the irreversible sodium ions consumption.Here,we propose 1,2-dihydroxybenzene Na salt(NaDB)as a cathode compensation agent with high specific capacity(347.9 mAh g^(-1)),lower desodiation potential(2.4–2.8 V)and high utilization(99%).Meanwhile,its byproduct could functionalize HC with more C=O groups and promote its reversible capacity.Consequently,the presodiation hard carbon(pHC)anode exhibits highly reversible capacity of 204.7 mAh g^(-1) with 98%retention at 5 C rate over 1000 cycles.Moreover,with 5 wt%NaDB initially coated on the Na3V2(PO4)3(NVP)cathode,the capacity retention of NVP + NaDB|HC cell could increase from 22%to 89%after 1000 cycles at 1 C rate.This work provides a new avenue to improve reversible capacity and cycling performance of SIBs through designing functional cathode compensation agent.展开更多
Pore structure engineering has been acknowledged as suitable approach to creating active sites and en-hancing ion transport capabilities of hard carbon anodes.However,conventional porous carbon materials exhibit high ...Pore structure engineering has been acknowledged as suitable approach to creating active sites and en-hancing ion transport capabilities of hard carbon anodes.However,conventional porous carbon materials exhibit high BET and surface defects.Additionally,the sodium storage mechanism predominantly occurs in the slope region.This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries.In our work,we prepared a novel“core-shell”carbon framework(CNA1200).Introducingclosedporesand carboxylgroupsinto coal-basedcarbon materials to enhance its sodium storage performance.The closed pore structure dominates in the“core”structure,which is attributed to the timely removal of sodium hydroxide(NaOH)to prevent further for-mation of active carbon structure.The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region.And the“shell”structure originates from coal tar pitch,it not only uniformly connects hard carbon particles together to improve cycling stability,but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region.CNA1200 has ex-cellent electrochemical performance,it exhibits a specific capacity of 335.2 mAh g^(−1)at a current density of 20 mA g^(−1)with ICE=51.53%.In addition,CNA1200 has outstanding cycling stability with a capac-ity retention of 91.8%even when cycling over 200 times.When CNA1200 is used as anode paired with Na_(3)V_(2)(PO_(4))_(3)cathode,it demonstrates a capacity of 109.54 mAh g^(−1)at 0.1 C and capacity retention of 94.64%at 0.5 C.This work provides valuable methods for regulating the structure of sodium-ion battery(SIBs)anode and enhances the potential for commercialization.展开更多
Biomass-derived hard carbon is becoming promising anodes for potassium-ion batteries(PIBs)thanks to their resource abundance.Yet,it is a big challenge to improve the charge carrier kinetics of the disordered carbon la...Biomass-derived hard carbon is becoming promising anodes for potassium-ion batteries(PIBs)thanks to their resource abundance.Yet,it is a big challenge to improve the charge carrier kinetics of the disordered carbon lattice in hard carbon.Herein,confined pitch-based soft carbon in pollen-derived hard carbon(PSC/PHC)is synthesized by vapor deposition strategy as anodes for PIBs.The ordered pitch-based soft carbon compensates for the short-range electron conduction in hard carbon to enhance the charge transfer kinetics,and the externally disordered pollen-derived hard carbon alleviates the volume change of soft carbon during cycling.Benefiting from the synergistic effect of soft and hard carbon,as well as the reinforced structure of order-in-disordered carbon,the PSC/PHC obtained with deposition time of 0.5 h(PSC/PHC-0.5)displays an excellent rate capability(148.7 mAh g^(-1)at 10 A g^(-1))and superb cycling stability(70%retention over 2000 cycles at 1 A g^(-1)).This work offers a unique insight in tuning the microcrystalline structure of soft-hard carbon anode for advanced PIBs.展开更多
The pore structure and pseudo-graphitic phase(domain size and content)of a hard carbon anode play key roles in improving the plateau capacity of sodium-ion batteries(SIBs),while it is hard to regulate them effectively...The pore structure and pseudo-graphitic phase(domain size and content)of a hard carbon anode play key roles in improving the plateau capacity of sodium-ion batteries(SIBs),while it is hard to regulate them effectively and simultaneously.This study delves into the synthesis of hard carbons with tailored microstructures from esterified sodium carboxymethyl cellulose(CMC-Na).The hard carbon(EHC-500)with maximized pseudo-graphitic content(73%)and abundant uniformly dispersed closed pores was fabricated,which provides sufficient active sites for sodium ion intercalation and pore filling.Furthermore,minimized lateral width(L_(a))of pseudo-graphitic domains in EHC-500 is simultaneously realized to improve the accessibility of sodium ions to the intercalation sites and filling sites.Therefore,the optimized microstructure of EHC-500 contributes to a remarkable reversible capacity of 340 mAh/g with a high plateau capacity of 236.7 mAh/g(below 0.08 V).These findings underscore the pivotal role of microcrystalline structure and pore structure in the electrochemical performance of hard carbons and provide a novel route to guide the design of hard carbons with optimal microstructures towards enhanced sodium storage performance.展开更多
The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with...The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with a hard combination,a numerical model is developed in this study.The indoor model test verified the accuracy of the numerical model.The influence laws of different hard combinations,train operating speeds and modes were studied and evaluated accordingly.The results show that the frequency corresponding to the peak vibration acceleration level of each floor of the superstructure property is concentrated at 10–20 Hz.The vibration response decreases in the high-frequency parts and increases in the lowfrequency parts with increasing distance from the source.Furthermore,the factors,such as train operating speed,operating mode,and hard combination type,will affect the vibration of the superstructure.The vibration response under the reversible operation of the train is greater than that of the unidirectional operation.The operating speed of the train is proportional to its vibration response.The vibration amplification area appears between the middle and the top of the superstructure at a higher train speed.Its vibration acceleration level will exceed the limit value of relevant regulations,and vibration-damping measures are required.Within the scope of application,this study provides some suggestions for constructing subway stations and superstructures.展开更多
Hard carbon (HC) has been considered as promising anode material for sodium-ion batteries (SIBs).The optimization of hard carbon’s microstructure and solid electrolyte interface (SEI) property are demonstrated effect...Hard carbon (HC) has been considered as promising anode material for sodium-ion batteries (SIBs).The optimization of hard carbon’s microstructure and solid electrolyte interface (SEI) property are demonstrated effective in enhancing the Na+storage capability,however,a one-step regulation strategy to achieve simultaneous multi-scale structures optimization is highly desirable.Herein,we have systematically investigated the effects of boron doping on hard carbon’s microstructure and interface chemistry.A variety of structure characterizations show that appropriate amount of boron doping can increase the size of closed pores via rearrangement of carbon layers with improved graphitization degree,which provides more Na+storage sites.In-situ Fourier transform infrared spectroscopy/electrochemical impedance spectroscopy (FTIR/EIS) and X-ray photoelectron spectroscopy (XPS) analysis demonstrate the presence of more BC3and less B–C–O structures that result in enhanced ion diffusion kinetics and the formation of inorganic rich and robust SEI,which leads to facilitated charge transfer and excellent rate performance.As a result,the hard carbon anode with optimized boron doping content exhibits enhanced rate and cycling performance.In general,this work unravels the critical role of boron doping in optimizing the pore structure,interface chemistry and diffusion kinetics of hard carbon,which enables rational design of sodium-ion battery anode with enhanced Na+storage performance.展开更多
Enamel demineralization,the formation of white spot lesions,is a common issue in clinical orthodontic treatment.The appearance of white spot lesions not only affects the texture and health of dental hard tissues but a...Enamel demineralization,the formation of white spot lesions,is a common issue in clinical orthodontic treatment.The appearance of white spot lesions not only affects the texture and health of dental hard tissues but also impacts the health and aesthetics of teeth after orthodontic treatment.The prevention,diagnosis,and treatment of white spot lesions that occur throughout the orthodontic treatment process involve multiple dental specialties.This expert consensus will focus on providing guiding opinions on the management and prevention of white spot lesions during orthodontic treatment,advocating for proactive prevention,early detection,timely treatment,scientific follow-up,and multidisciplinary management of white spot lesions throughout the orthodontic process,thereby maintaining the dental health of patients during orthodontic treatment.展开更多
To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software ...To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.展开更多
This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data o...This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data of the hard carbons were obtained by charge/discharge tests and the materials were characterized by XRD,gas adsorption,true density tests and SAXS.In particular,the fitting of SAXS gave a series of structural parameters which showed good characterization.The related test details are given with the structural data of the hard carbons and the electrochemical performance of the sodium-ion batteries.展开更多
As an emerging electrochemical energy storage technology,potassium-ion batteries(PIBs),which are considered a“beyond Li-ion”battery system,have attracted tremendous attention due to their potential for providing a h...As an emerging electrochemical energy storage technology,potassium-ion batteries(PIBs),which are considered a“beyond Li-ion”battery system,have attracted tremendous attention due to their potential for providing a high energy density,and having abundant resource,and a low cost.However,their commercialization is hindered by the lack of practical anode materials.Among various reported anodes,conventional carbon materials,including graphite,soft carbon,and hard carbon,have emerged as promising candidates because of their abundance,low cost,high conductivity,and tunable structures.However,these materials have problems such as a low initial Coulombic efficiency,significant volume expansion,and unsatisfactory cyclability and rate performance.Various strategies to solve these have been explored,including optimizing the interlayer spacing,structural design,surface coating,constructing a multifunctional framework,and forming composites.This review provides a comprehensive overview of the recent progress in conventional carbon anodes,highlighting structural design strategies,mechanisms for improving the electrochemical performance,and underscores the critical role of these materials in promoting the practical application of PIBs.展开更多
The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performan...The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performance.However,there is still disagreement regarding the sodium storage mechanism in the low-voltage plateau region of HC anodes,and the structure-performance relationship between its complex multiscale micro/nanostructure and electrochemical behavior remains unclear.This paper summarizes current research progress and the major problems in understanding HC’s microstructure and sodium storage mechanism,and the relationship between them.Findings about a universal sodium storage mechanism in HC,including predictions about micropore-capacity relationships,and the opportunities and challenges for using HC anodes in commercial SIBs are presented.展开更多
Four machine learning algorithms were used to predict the solid solution phases of high-entropy alloys(HEAs).To improve the model accuracy,the K-fold cross validation was adopted.Results show that the K-nearest neighb...Four machine learning algorithms were used to predict the solid solution phases of high-entropy alloys(HEAs).To improve the model accuracy,the K-fold cross validation was adopted.Results show that the K-nearest neighbor algorithm can effectively distinguish body-centered cubic(bcc)phase,face-centered cubic(fcc)phase,and mixed(fcc+bcc)phase,and the accuracy rate is approximately 93%.Thereafter,CoCrFeNi_(2)Al_(x)(x=0,0.1,0.3,1.0)HEAs were prepared and characterized by X-ray diffractometer and energy disperse spectrometer.It is found that their phases are transformed from fcc phase to fcc+bcc phase,which is consistent with the prediction results of machine learning.Furthermore,the influence of Al content on the microstructure and tribological properties of CoCrFeNi_(2)Al_(x)(x=0,0.1,0.3,1.0)HEAs was evaluated.Results reveal that with the increase in Al content,the nanohardness and microhardness increase by approximately 45%and 75%,respectively.The elastic limit parameter H/Er increases from 0.0216 to 0.030,whereas the plastic deformation resistance parameter H^(3)/E_(r)^(2) increases from 0.0014 to 0.0045,which demonstrates an improvement in nanohardness with the increase in Al addition amount.In addition,the wear rate decreases by 35%with the increase in Al addition amount.This research provides a new idea with energy-saving and time-reduction characteristics to prepare HEAs.展开更多
Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects ...Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects on its surface cause irreversible electrolyte consump-tion and an uneven solid electrolyte interphase film.An advanced molecular engineering strategy to coat hard carbon with polycyclic aromatic mo-lecules is reported.Specifically,polystyrene-based carbon microspheres(CSs)were first synthesized and then coated with polycyclic aromatic mo-lecules derived from coal tar pitch by spray-drying and followed by oxidation.Compared to the traditional CVD coating meth-od,this molecular framework strategy has been shown to reduce the number of defects on the surface of CSs without sacrifi-cing internal storage sites and suppressing transport kinetics in hosting the sodium ions.Besides the lower surface defect con-centration,the synthesized hybrid carbon microspheres(HCSs)have a larger grain size and more abundant closed pores,and have a higher reversible sodium storage capacity.A HCS-P-60%electrode has a capacity of 332.3 mAh g^(-1)with an initial Cou-lombic efficiency of 88.5%.It also has a superior rate performance of 246.6 mAh g^(-1)at 2 C and a 95.2%capacity retention after 100 cycles at 0.2 C.This work offers new insights into designing high-performance hard carbon microsphere anodes,advan-cing the commercialization of sodium-ion batteries.展开更多
文摘【问】[490]近日在查阅《朗文当代高级英语辞典》(外研社,2070页)中有关than作连词的用法时,发现其中第三个用法是这样描述的:"hardly/scarcely/no sooner...than...(一……就……),例如:Nosooner had I mailed the letter than I realized
文摘你可能认为hardly是hard派生出来的副词吧，其实不然。下面就请你来做一做这几道题。请选用hard或hardly填空。1．Lucy＿＿＿studies：but her sister studies＿＿＿＿.2．Theworkisvery＿＿＿＿＿forme．3．He＿＿＿＿goes to bed before 11：00 in the evening．
基金National Natural Science Foundation of China(61921001,62201588,62022091)。
文摘The acquisition,analysis,and prediction of the radar cross section(RCS)of a target have extremely important strategic significance in the military.However,the RCS values at all azimuths are hardly accessible for non-cooperative targets,due to the limitations of radar observation azimuth and detection resources.Despite their efforts to predict the azimuth-dimensional RCS value,traditional methods based on statistical theory fails to achieve the desired results because of the azimuth sensitivity of the target RCS.To address this problem,an improved neural basis expansion analysis for interpretable time series forecasting(N-BEATS)network considering the physical model prior is proposed to predict the azimuth-dimensional RCS value accurately.Concretely,physical model-based constraints are imposed on the network by constructing a scattering-center module based on the target scattering-center model.Besides,a superimposed seasonality module is involved to better capture high-frequency information,and augmenting the training set provides complementary information for learning predictions.Extensive simulations and experimental results are provided to validate the effectiveness of the proposed method.
基金supported by National Natural Science Foundation of China(No.22278308 and 22109114)Open Foundation of Shanghai Jiao Tong University Shaoxing Research Institute of Renewable Energy and Molecular Engineering(Grant number:JDSX2022023).
文摘Hard carbon(HC)is widely used in sodium-ion batteries(SIBs),but its performance has always been limited by lowinitial Coulombic efficiency(ICE)and cycling stability.Cathode compensation agent is a favorable strategy to make up for the loss of active sodium ions consumed byHCanode.Yet it lacks agent that effectively decomposes to increase the active sodium ions as well as regulate carbon defects for decreasing the irreversible sodium ions consumption.Here,we propose 1,2-dihydroxybenzene Na salt(NaDB)as a cathode compensation agent with high specific capacity(347.9 mAh g^(-1)),lower desodiation potential(2.4–2.8 V)and high utilization(99%).Meanwhile,its byproduct could functionalize HC with more C=O groups and promote its reversible capacity.Consequently,the presodiation hard carbon(pHC)anode exhibits highly reversible capacity of 204.7 mAh g^(-1) with 98%retention at 5 C rate over 1000 cycles.Moreover,with 5 wt%NaDB initially coated on the Na3V2(PO4)3(NVP)cathode,the capacity retention of NVP + NaDB|HC cell could increase from 22%to 89%after 1000 cycles at 1 C rate.This work provides a new avenue to improve reversible capacity and cycling performance of SIBs through designing functional cathode compensation agent.
基金the National Natural Science Foundation of China(No.21978164,22078189 and 22105120)the Outstanding Youth Science Fund of Shaanxi Province(No.2021JC-046)and the Special Support Program for high level talents of Shaanxi Province+3 种基金the Innovation Support Program of Shaanxi Province(2021JZY-001)the Key Research and Development Program of Shaanxi Province(No.2020GY-243)the Special Research Fund of Education Department of Shaanxi(No.20JK0535)the National High-end Foreign Expert Project(No.GDW20186100428).
文摘Pore structure engineering has been acknowledged as suitable approach to creating active sites and en-hancing ion transport capabilities of hard carbon anodes.However,conventional porous carbon materials exhibit high BET and surface defects.Additionally,the sodium storage mechanism predominantly occurs in the slope region.This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries.In our work,we prepared a novel“core-shell”carbon framework(CNA1200).Introducingclosedporesand carboxylgroupsinto coal-basedcarbon materials to enhance its sodium storage performance.The closed pore structure dominates in the“core”structure,which is attributed to the timely removal of sodium hydroxide(NaOH)to prevent further for-mation of active carbon structure.The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region.And the“shell”structure originates from coal tar pitch,it not only uniformly connects hard carbon particles together to improve cycling stability,but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region.CNA1200 has ex-cellent electrochemical performance,it exhibits a specific capacity of 335.2 mAh g^(−1)at a current density of 20 mA g^(−1)with ICE=51.53%.In addition,CNA1200 has outstanding cycling stability with a capac-ity retention of 91.8%even when cycling over 200 times.When CNA1200 is used as anode paired with Na_(3)V_(2)(PO_(4))_(3)cathode,it demonstrates a capacity of 109.54 mAh g^(−1)at 0.1 C and capacity retention of 94.64%at 0.5 C.This work provides valuable methods for regulating the structure of sodium-ion battery(SIBs)anode and enhances the potential for commercialization.
基金partly supported by the National Natural Science Foundation of China(52072002,52372037,and 22108003)the Postdoctoral Fellowship Program of CPSF(GZC20230015)+2 种基金the Outstanding Scientific Research and Innovation Team Program of Higher Education Institutions of Anhui Province(2023AH010015)the Excellent Young Talents Fund Program of Higher Education Institutions of Anhui Province(2023AH030026)financial support from the Anhui International Research Center of Energy Materials Green Manufacturing and Biotechnology。
文摘Biomass-derived hard carbon is becoming promising anodes for potassium-ion batteries(PIBs)thanks to their resource abundance.Yet,it is a big challenge to improve the charge carrier kinetics of the disordered carbon lattice in hard carbon.Herein,confined pitch-based soft carbon in pollen-derived hard carbon(PSC/PHC)is synthesized by vapor deposition strategy as anodes for PIBs.The ordered pitch-based soft carbon compensates for the short-range electron conduction in hard carbon to enhance the charge transfer kinetics,and the externally disordered pollen-derived hard carbon alleviates the volume change of soft carbon during cycling.Benefiting from the synergistic effect of soft and hard carbon,as well as the reinforced structure of order-in-disordered carbon,the PSC/PHC obtained with deposition time of 0.5 h(PSC/PHC-0.5)displays an excellent rate capability(148.7 mAh g^(-1)at 10 A g^(-1))and superb cycling stability(70%retention over 2000 cycles at 1 A g^(-1)).This work offers a unique insight in tuning the microcrystalline structure of soft-hard carbon anode for advanced PIBs.
基金financial support of the National Natural Science Foundation of China(NSFC,No.21905278)the Natural Science Foundation of Hunan Province(No.2023JJ30015).
文摘The pore structure and pseudo-graphitic phase(domain size and content)of a hard carbon anode play key roles in improving the plateau capacity of sodium-ion batteries(SIBs),while it is hard to regulate them effectively and simultaneously.This study delves into the synthesis of hard carbons with tailored microstructures from esterified sodium carboxymethyl cellulose(CMC-Na).The hard carbon(EHC-500)with maximized pseudo-graphitic content(73%)and abundant uniformly dispersed closed pores was fabricated,which provides sufficient active sites for sodium ion intercalation and pore filling.Furthermore,minimized lateral width(L_(a))of pseudo-graphitic domains in EHC-500 is simultaneously realized to improve the accessibility of sodium ions to the intercalation sites and filling sites.Therefore,the optimized microstructure of EHC-500 contributes to a remarkable reversible capacity of 340 mAh/g with a high plateau capacity of 236.7 mAh/g(below 0.08 V).These findings underscore the pivotal role of microcrystalline structure and pore structure in the electrochemical performance of hard carbons and provide a novel route to guide the design of hard carbons with optimal microstructures towards enhanced sodium storage performance.
基金National Natural Science Foundation of China under Grant No.51578463。
文摘The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with a hard combination,a numerical model is developed in this study.The indoor model test verified the accuracy of the numerical model.The influence laws of different hard combinations,train operating speeds and modes were studied and evaluated accordingly.The results show that the frequency corresponding to the peak vibration acceleration level of each floor of the superstructure property is concentrated at 10–20 Hz.The vibration response decreases in the high-frequency parts and increases in the lowfrequency parts with increasing distance from the source.Furthermore,the factors,such as train operating speed,operating mode,and hard combination type,will affect the vibration of the superstructure.The vibration response under the reversible operation of the train is greater than that of the unidirectional operation.The operating speed of the train is proportional to its vibration response.The vibration amplification area appears between the middle and the top of the superstructure at a higher train speed.Its vibration acceleration level will exceed the limit value of relevant regulations,and vibration-damping measures are required.Within the scope of application,this study provides some suggestions for constructing subway stations and superstructures.
基金National Key Research and Development Program of China (2022YFE0206300)National Natural Science Foundation of China (U21A2081,22075074, 22209047)+3 种基金Guangdong Basic and Applied Basic Research Foundation (2024A1515011620)Hunan Provincial Natural Science Foundation of China (2024JJ5068)Foundation of Yuelushan Center for Industrial Innovation (2023YCII0119)Student Innovation Training Program (S202410532594,S202410532357)。
文摘Hard carbon (HC) has been considered as promising anode material for sodium-ion batteries (SIBs).The optimization of hard carbon’s microstructure and solid electrolyte interface (SEI) property are demonstrated effective in enhancing the Na+storage capability,however,a one-step regulation strategy to achieve simultaneous multi-scale structures optimization is highly desirable.Herein,we have systematically investigated the effects of boron doping on hard carbon’s microstructure and interface chemistry.A variety of structure characterizations show that appropriate amount of boron doping can increase the size of closed pores via rearrangement of carbon layers with improved graphitization degree,which provides more Na+storage sites.In-situ Fourier transform infrared spectroscopy/electrochemical impedance spectroscopy (FTIR/EIS) and X-ray photoelectron spectroscopy (XPS) analysis demonstrate the presence of more BC3and less B–C–O structures that result in enhanced ion diffusion kinetics and the formation of inorganic rich and robust SEI,which leads to facilitated charge transfer and excellent rate performance.As a result,the hard carbon anode with optimized boron doping content exhibits enhanced rate and cycling performance.In general,this work unravels the critical role of boron doping in optimizing the pore structure,interface chemistry and diffusion kinetics of hard carbon,which enables rational design of sodium-ion battery anode with enhanced Na+storage performance.
基金funded with National Key R&D Program of China(2022YFC2405904)National Natural Science Foundation of China(11932012,and 32171348).
文摘Enamel demineralization,the formation of white spot lesions,is a common issue in clinical orthodontic treatment.The appearance of white spot lesions not only affects the texture and health of dental hard tissues but also impacts the health and aesthetics of teeth after orthodontic treatment.The prevention,diagnosis,and treatment of white spot lesions that occur throughout the orthodontic treatment process involve multiple dental specialties.This expert consensus will focus on providing guiding opinions on the management and prevention of white spot lesions during orthodontic treatment,advocating for proactive prevention,early detection,timely treatment,scientific follow-up,and multidisciplinary management of white spot lesions throughout the orthodontic process,thereby maintaining the dental health of patients during orthodontic treatment.
基金Funded by the National Natural Science Foundation of China(No.52172007)。
文摘To analyze the impact of bubbles on the mechanical behavior of glasses,by controlling the refining time,we prepared three borosilicate glasses with the same composition and different porosity.By the analysis software integrated within the optical microscope,the diameter and number of the bubbles on the surface of three borosilicate glasses were quantified.From the hardness and crack initiation resistance(CR),we built the relationship between the porosity and the mechanical performance of these borosilicate glasses.
基金supported by the National Natural Science Foundation of China(22379157)CAS Project for Young Scientists in Basic Research(YSBR-102)+2 种基金Institute of Coal Chemistry,Chinese Academy of Sciences(SCJC-XCL-2023-13,SCJCXCL-2023-10)Talent Projects for Outstanding Doctoral Students to Work in Shanxi Province(E3SWR4791Z)Fundamental Research Program of Shanxi Province(202403021222485).
文摘This data set collects,compares and contrasts the capacities and structures of a series of hard carbon materials,and then searches for correlations between structure and electrochemical performance.The capacity data of the hard carbons were obtained by charge/discharge tests and the materials were characterized by XRD,gas adsorption,true density tests and SAXS.In particular,the fitting of SAXS gave a series of structural parameters which showed good characterization.The related test details are given with the structural data of the hard carbons and the electrochemical performance of the sodium-ion batteries.
文摘As an emerging electrochemical energy storage technology,potassium-ion batteries(PIBs),which are considered a“beyond Li-ion”battery system,have attracted tremendous attention due to their potential for providing a high energy density,and having abundant resource,and a low cost.However,their commercialization is hindered by the lack of practical anode materials.Among various reported anodes,conventional carbon materials,including graphite,soft carbon,and hard carbon,have emerged as promising candidates because of their abundance,low cost,high conductivity,and tunable structures.However,these materials have problems such as a low initial Coulombic efficiency,significant volume expansion,and unsatisfactory cyclability and rate performance.Various strategies to solve these have been explored,including optimizing the interlayer spacing,structural design,surface coating,constructing a multifunctional framework,and forming composites.This review provides a comprehensive overview of the recent progress in conventional carbon anodes,highlighting structural design strategies,mechanisms for improving the electrochemical performance,and underscores the critical role of these materials in promoting the practical application of PIBs.
文摘The advantages of sodium-ion batteries(SIBs)for large-scale energy storage are well known.Among possible anode materials,hard carbon(HC)stands out as the most viable commercial option because of its superior performance.However,there is still disagreement regarding the sodium storage mechanism in the low-voltage plateau region of HC anodes,and the structure-performance relationship between its complex multiscale micro/nanostructure and electrochemical behavior remains unclear.This paper summarizes current research progress and the major problems in understanding HC’s microstructure and sodium storage mechanism,and the relationship between them.Findings about a universal sodium storage mechanism in HC,including predictions about micropore-capacity relationships,and the opportunities and challenges for using HC anodes in commercial SIBs are presented.
基金National Natural Science Foundation of China(52201177)Hebei Province Department of Education Fund(QN2024264)Natural Science Foundation of Hebei Province(E2022201010)。
文摘Four machine learning algorithms were used to predict the solid solution phases of high-entropy alloys(HEAs).To improve the model accuracy,the K-fold cross validation was adopted.Results show that the K-nearest neighbor algorithm can effectively distinguish body-centered cubic(bcc)phase,face-centered cubic(fcc)phase,and mixed(fcc+bcc)phase,and the accuracy rate is approximately 93%.Thereafter,CoCrFeNi_(2)Al_(x)(x=0,0.1,0.3,1.0)HEAs were prepared and characterized by X-ray diffractometer and energy disperse spectrometer.It is found that their phases are transformed from fcc phase to fcc+bcc phase,which is consistent with the prediction results of machine learning.Furthermore,the influence of Al content on the microstructure and tribological properties of CoCrFeNi_(2)Al_(x)(x=0,0.1,0.3,1.0)HEAs was evaluated.Results reveal that with the increase in Al content,the nanohardness and microhardness increase by approximately 45%and 75%,respectively.The elastic limit parameter H/Er increases from 0.0216 to 0.030,whereas the plastic deformation resistance parameter H^(3)/E_(r)^(2) increases from 0.0014 to 0.0045,which demonstrates an improvement in nanohardness with the increase in Al addition amount.In addition,the wear rate decreases by 35%with the increase in Al addition amount.This research provides a new idea with energy-saving and time-reduction characteristics to prepare HEAs.
文摘Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects on its surface cause irreversible electrolyte consump-tion and an uneven solid electrolyte interphase film.An advanced molecular engineering strategy to coat hard carbon with polycyclic aromatic mo-lecules is reported.Specifically,polystyrene-based carbon microspheres(CSs)were first synthesized and then coated with polycyclic aromatic mo-lecules derived from coal tar pitch by spray-drying and followed by oxidation.Compared to the traditional CVD coating meth-od,this molecular framework strategy has been shown to reduce the number of defects on the surface of CSs without sacrifi-cing internal storage sites and suppressing transport kinetics in hosting the sodium ions.Besides the lower surface defect con-centration,the synthesized hybrid carbon microspheres(HCSs)have a larger grain size and more abundant closed pores,and have a higher reversible sodium storage capacity.A HCS-P-60%electrode has a capacity of 332.3 mAh g^(-1)with an initial Cou-lombic efficiency of 88.5%.It also has a superior rate performance of 246.6 mAh g^(-1)at 2 C and a 95.2%capacity retention after 100 cycles at 0.2 C.This work offers new insights into designing high-performance hard carbon microsphere anodes,advan-cing the commercialization of sodium-ion batteries.
