Laser-induced periodic surface structures(LIPSS)have gained increasing attention in the field of micro/nano fabrication,although achieving sub-100-nm period LIPSS with high uniformity remains a significant challenge.I...Laser-induced periodic surface structures(LIPSS)have gained increasing attention in the field of micro/nano fabrication,although achieving sub-100-nm period LIPSS with high uniformity remains a significant challenge.In this work,towards deep-subwavelength LIPSS on highly oriented pyrolytic graphite(HOPG),we demonstrate that ultra-uniform nanogratings of sub-50-nm periods and near-10-nm groove widths can be stably prepared via 800-nm femtosecond laser scanning irradiation with a high-NA objective lens under water immersion.The resulting nanogratings of strong polarization dependence,exhibiting exceptional surface flatness,period stability,and structural integrity,tend to appear at near-damage-threshold fluence regime with an appropriate effective pulse number.It turns out that the water immersion condition can significantly reduce the thermal effects of femtosecond laser ablation on HOPG,and thus via a mild,incubation-like scanning ablation process occurring in the nanogrooves with a continuous or jumping manner,this deep-subwavelength grating can achieve robust elongation growth,ensuring its long-range uniformity as well as minimal deposited debris and structural defects.Interestingly,the different incubation extension mechanisms for the mutually perpendicular and parallel settings between scanning direction and laser polarization bring not only distinct effective-pulse-number windows and somewhat different grating qualities,but also different extension stabilities in nanograting stitching via overlapping scanning lines and thus the optimal scanning strategy of parallel setting for large-area processing.In short,this study presents a convenient laser-processing approach for high precision fabrication of sub-50-nm gratings on HOPG,which would provide new insights into micro/nano-fabrication for optoelectronic metasurfaces and physics of the interaction between ultrafast laser and graphite.展开更多
The strength-ductility trade-off in low-Mn lightweight steels is a significant challenge due to the low thermal stability of austenite and the presence ofδ-ferrite.Two types of low-Mn lightweight steels containing V ...The strength-ductility trade-off in low-Mn lightweight steels is a significant challenge due to the low thermal stability of austenite and the presence ofδ-ferrite.Two types of low-Mn lightweight steels containing V and NbVMo microalloying elements were developed by warm rolling.Among these,NbVMo steel demonstrated superior properties,achieving a tensile strength of~1.2 GPa and a product of strength and elongation exceeding 45 GPa%.In-depth mechanism analysis by atom probe tomography and quasi-in-situ electron backscatter diffraction revealed that different microalloying compositions influence the mechanical properties by strengtheningδ-ferrite,refining retained austenite and homogenizing matrix strain.In NbVMo steel,δ-ferrite strengthening is attributed to the synergistic effects of(V,Mo,Cr,Nb)C composite precipitation,fine NbC and MoC precipitates,and the solid solution strengthening of Mo.These mechanisms collectively contribute to a higher yield strength andδ-ferrite microhardness compared to V steel.Consequently,δ-ferrite and the surrounding matrix in NbVMo steel exhibit coordinated elongation during deformation,enhancing the ductility.The improved microstructural and strain uniformity in NbVMo steel mitigates stress concentration effects onδ-ferrite deformation and serves as a barrier that delays the transformation of retained austenite.In contrast,the retained austenite in V steel exhibits a blocky morphology with larger grain sizes,resulting in lower stability.Combined with localized stress concentrations due to non-uniform strain distribution,this leads to premature transformation of retained austenite to alleviate stress,ultimately impairing elongation and the continuity of strain hardening.Furthermore,the precipitation mechanisms of(V,Mo,Cr,Nb)C composite precipitates are elucidated.展开更多
Kagome magnets are of growing interest due to their topological electronic structures and unconventional magnetic behavior.Here,we report on the anomalous Hall effect(AHE)in the kagome ferromagnet MgMn_(6)Sn_(6),which...Kagome magnets are of growing interest due to their topological electronic structures and unconventional magnetic behavior.Here,we report on the anomalous Hall effect(AHE)in the kagome ferromagnet MgMn_(6)Sn_(6),which has a Curie temperature of~290 K and an in-plane easy magnetization axis.Magnetotransport measurements show a positive magnetoresistance(MR)below 50 K,which becomes negative at higher temperatures.An intrinsic anomalous Hall conductivity of 114 S·cm^(-1)is observed in MgMn_(6)Sn_(6) single crystals,consistent with ab initio calculations.Moreover,theoretical predictions indicate that shifting the Fermi level(EF)upward by~70 meV could enhance the AHE to~528 S·cm^(-1).These results position MgMn_(6)Sn_(6) as a promising and tunable platform for exploring topological magnetism and related electronic phenomena.展开更多
Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally va...Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally variable,but there are limited data on how biological communities respond to this variation.Hangzhou Bay,a mediumsized estuary in China,is an ideal place in which to study the response of plankton to small-scale ocean fronts,because three water masses(Qiantang River Diluted Water,Changjiang River Diluted Water,and the East China Sea current) converge here and form dynamic salinity fronts throughout the year.We investigate zooplankton communities,and temperature,salinity and chlorophyll a(Chl a) in Hangzhou Bay in June(wet perio d) and December(dry period) of 2022 and examine the dominant environmental factors that affect zooplankton community spatial variability.We then match the spatial distributions of zooplankton communities with those of salinity fronts.S alinity is the most important explanatory variable to affect zooplankton community spatial variability during both wet and dry periods,in that it contributes>60% of the variability in community structure.Furthermore,the spatial distributions of zooplankton match well with salinity fronts.During December,with weaker Qiantang River Diluted Water and a stronger secondary Changjiang River Plume,zooplankton communities occur in moderate salinity(MS,salinity range 15.6±2.2) and high salinity(HS,22.4±1.7) regions,and their ecological boundaries closely match the Qiantang River Diluted Water front.In June,different zooplankton communities occur in low salinity(LS,3.9±1.0),MS(11.7±3.6) and HS(21.3±1.9) regions.Although the LS region occurs abnormally in the central bay rather than its apex because of the anomalous influence of rising and falling tides during the sampling perio d,the ecological boundaries still match salinity interfaces.Low-salinity or brackish-water zooplankter taxa are relatively more abundant in LS or MS regions,and the biomass and abundance of zooplankton is higher in the MS region.展开更多
By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed amon...By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed among multiple construction projects near residential areas.In this process,the local government played a crucial coordinating role.According to regulations,construction units must include the costs of preventing and controlling construction noise pollution in the project cost.The construction contract should clearly specify the construction unit’s responsibility for noise pollution prevention and control.After signing the contract,the construction unit should promptly undertake relevant measures to minimize disturbances caused by nighttime construction,aiming to reduce the adverse impacts on the community and ensure the smooth progress of the construction project.展开更多
With the increasing severity of arsenic(As)pollution,quantifying the environmental behavior of pollutant based on numerical model has become an important approach to determine the potential impacts and finalize the pr...With the increasing severity of arsenic(As)pollution,quantifying the environmental behavior of pollutant based on numerical model has become an important approach to determine the potential impacts and finalize the precise control strategies.Taking the industrialintensive Jinsha River Basin as typical area,a two-dimensional hydrodynamic water quality model coupled with Soil andWater Assessment Tool(SWAT)model was developed to accurately simulate the watershed-scale distribution and transport of As in the terrestrial and aquatic environment at high spatial and temporal resolution.The effects of hydro-climate change,hydropower station construction and non-point source emissions on Aswere quantified based on the coupled model.The result indicated that higher As concentration areas mainly centralized in urban districts and concentration slowly decreased from upstream to downstream.Due to the enhanced rainfall,the As concentration was significantly higher during the rainy season than the dry season.Hydro-climate change and the construction of hydropower station not only affected the dissolved As concentration,but also affected the adsorption and desorption of As in sediment.Furthermore,As concentration increased with the input of non-point source pollution,with the maximum increase about 30%,resulting that non-point sources contributed important pollutant impacts to waterways.The coupled model used in pollutant behavior analysis is generalwith high potential application to predict and mitigate water pollution.展开更多
The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating fi...The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating filled with benzotriazole loaded metal-organic frameworks(BTA-MOFs)functionalized graphene oxide nanoribbons(GONR)that exhibit active anti-corrosion,act as a barrier to corrosive ion,and enhance wear resistance.The GONR@BTA-MOFs composite is synthesized through chemically etching multi-walled carbon nanotubes and subsequent electrostatic self-assembly corrosion inhibitors loaded MOFs onto the GONR.The composite demonstrates improved compatibility with epoxy resins compared to carbon nanotubes.The anti-corrosion performance of the composite coating is investigated using electrochemical impedance spectroscopy.After immersing in a 3.5 wt.%NaCl solution for 25 d,the alternating current impedance of the composite coating is three orders of magnitude higher than that of pure epoxy resin.Simultaneously,the controlled release of the corrosion inhibitor retards the deterioration of the coating after localized damage occurrence,which functions as active corrosion protection.The GONR@BTA-MOFs/EP composite coating exhibits the highest corrosion potential of-0.188 V and the lowest corrosion current of 3.162×10^(−9)A cm^(−2)in the Tafel test.Tribological studies reveal a reduction in the friction coefficient from 0.62 to 0.08 after incorporating GONR@BTA-MOFs in the coating,with the wear volume being seven times lower than that of pure epoxy resin.The excellent lubrication effect of the nanomaterials reduces the coefficient of friction of the coating,thereby improving the abrasion resistance of the coating.The synergy between the self-lubrication of the two-dimensional layered fillers and the corrosion resistance of the smart inhibitor containers suggests a promising strategy for enhancing the performance of epoxy resins under complex working conditions.展开更多
Increasing environmental concerns about limiting harmful emissions has necessitated sulfur-and phosphorus-free green lubricant additives.Although boron-containing compounds have been widely investigated as green lubri...Increasing environmental concerns about limiting harmful emissions has necessitated sulfur-and phosphorus-free green lubricant additives.Although boron-containing compounds have been widely investigated as green lubricant additives,their macromolecular analogs have been rarely considered yet to develop environmentally friendly lubricant additives.In this work,a series of boron-containing copolymers have been synthesized by free-radical copolymerization of stearyl methacrylate and isopropenyl boronic acid pinacol ester with different feeding ratios(S_(n)-r-B_(m),n=1,m=1/3,1,2,3,5,9).The resulting copolymers of S_(n)-r-B_(m)(n=1,m=1/3,1,2,3,5)are readily dispersed in the PAO-10 base oil and form micelle-like aggregates with hydrodynamic diameters ranging from 9.7 to 52 nm.SRV-IV oscillating reciprocating tribological tests on ball-on-flat steel pairs show that compared with the base oil of PAO-10,the friction coefficients and wear volumes of the base oil solutions of S_(n)-r-B_(m)decrease considerably up to 62%and 97%,respectively.Moreover,the base oil solution of S_(1)-r-B_(1)exhibits an excellent load-bearing capacity of(850±100)N.These superior lubricating properties are due to the formation of protective tribofilms comprising S_(n)-r-B_(m),boron oxide,and iron oxide compounds on the lubricated steel surface.Therefore,the boron-containing copolymers can be regarded as a novel class of environmentally friendly lubricating oil macroadditives for efficient friction and wear reduction without sulfur and phosphorus elements.展开更多
基金supported by grants from Natural Science Foundation of Guangdong Province(Grant No.2021A1515012335)National Natural Science Foundation of China(NSFC)(Grant No.11274400)+2 种基金Pearl River S&T Nova Program of Guangzhou(Grant No.201506010059)State Key Laboratory of Optoelectronic Materials and Technologies(Sun Yat-Sen University)(Grant No.OEMT-2024-ZTS-01)State Key Laboratory of High Field Laser Physics(Shanghai Institute of Optics and Fine Mechanics)。
文摘Laser-induced periodic surface structures(LIPSS)have gained increasing attention in the field of micro/nano fabrication,although achieving sub-100-nm period LIPSS with high uniformity remains a significant challenge.In this work,towards deep-subwavelength LIPSS on highly oriented pyrolytic graphite(HOPG),we demonstrate that ultra-uniform nanogratings of sub-50-nm periods and near-10-nm groove widths can be stably prepared via 800-nm femtosecond laser scanning irradiation with a high-NA objective lens under water immersion.The resulting nanogratings of strong polarization dependence,exhibiting exceptional surface flatness,period stability,and structural integrity,tend to appear at near-damage-threshold fluence regime with an appropriate effective pulse number.It turns out that the water immersion condition can significantly reduce the thermal effects of femtosecond laser ablation on HOPG,and thus via a mild,incubation-like scanning ablation process occurring in the nanogrooves with a continuous or jumping manner,this deep-subwavelength grating can achieve robust elongation growth,ensuring its long-range uniformity as well as minimal deposited debris and structural defects.Interestingly,the different incubation extension mechanisms for the mutually perpendicular and parallel settings between scanning direction and laser polarization bring not only distinct effective-pulse-number windows and somewhat different grating qualities,but also different extension stabilities in nanograting stitching via overlapping scanning lines and thus the optimal scanning strategy of parallel setting for large-area processing.In short,this study presents a convenient laser-processing approach for high precision fabrication of sub-50-nm gratings on HOPG,which would provide new insights into micro/nano-fabrication for optoelectronic metasurfaces and physics of the interaction between ultrafast laser and graphite.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.FRF-BD-25-001)Development and Application of Ultra-High Strength Hot Stamping Steel Strip for Automobiles(Grant No.20232BCJ22030)Manufacturing and Application Innovation and Integration of High-Safety Automotive Steel(Grant No.24431002D).
文摘The strength-ductility trade-off in low-Mn lightweight steels is a significant challenge due to the low thermal stability of austenite and the presence ofδ-ferrite.Two types of low-Mn lightweight steels containing V and NbVMo microalloying elements were developed by warm rolling.Among these,NbVMo steel demonstrated superior properties,achieving a tensile strength of~1.2 GPa and a product of strength and elongation exceeding 45 GPa%.In-depth mechanism analysis by atom probe tomography and quasi-in-situ electron backscatter diffraction revealed that different microalloying compositions influence the mechanical properties by strengtheningδ-ferrite,refining retained austenite and homogenizing matrix strain.In NbVMo steel,δ-ferrite strengthening is attributed to the synergistic effects of(V,Mo,Cr,Nb)C composite precipitation,fine NbC and MoC precipitates,and the solid solution strengthening of Mo.These mechanisms collectively contribute to a higher yield strength andδ-ferrite microhardness compared to V steel.Consequently,δ-ferrite and the surrounding matrix in NbVMo steel exhibit coordinated elongation during deformation,enhancing the ductility.The improved microstructural and strain uniformity in NbVMo steel mitigates stress concentration effects onδ-ferrite deformation and serves as a barrier that delays the transformation of retained austenite.In contrast,the retained austenite in V steel exhibits a blocky morphology with larger grain sizes,resulting in lower stability.Combined with localized stress concentrations due to non-uniform strain distribution,this leads to premature transformation of retained austenite to alleviate stress,ultimately impairing elongation and the continuity of strain hardening.Furthermore,the precipitation mechanisms of(V,Mo,Cr,Nb)C composite precipitates are elucidated.
基金Project supported by the National Natural Science Foundation of China(Grant No.12204347)National Key Research and Development Program of China(Grant No.2022YFA1402600)the Fund from Beijing National Laboratory for Condensed Matter Physics(Grant No.2023BNLCMPKF011)。
文摘Kagome magnets are of growing interest due to their topological electronic structures and unconventional magnetic behavior.Here,we report on the anomalous Hall effect(AHE)in the kagome ferromagnet MgMn_(6)Sn_(6),which has a Curie temperature of~290 K and an in-plane easy magnetization axis.Magnetotransport measurements show a positive magnetoresistance(MR)below 50 K,which becomes negative at higher temperatures.An intrinsic anomalous Hall conductivity of 114 S·cm^(-1)is observed in MgMn_(6)Sn_(6) single crystals,consistent with ab initio calculations.Moreover,theoretical predictions indicate that shifting the Fermi level(EF)upward by~70 meV could enhance the AHE to~528 S·cm^(-1).These results position MgMn_(6)Sn_(6) as a promising and tunable platform for exploring topological magnetism and related electronic phenomena.
基金The National Key Research and Development Program of China under contact No.2021YFC3101702the Natural Science Foundation of Zhejiang Province under contact Nos LY22D060006 and LY14D060007+1 种基金the Key R&D Program of Zhejiang under contact No.2022C03044the Project of Long-term Observation and Research Plan in the Changjiang Estuary and Adjacent East China Sea (LORCE) under contact No.SZ2001。
文摘Ocean fronts play important roles in nutrient transport and in the shaping ecological patterns.Frontal zones in small bays are typically small in scale,have a complex structure,and they are spatially and temporally variable,but there are limited data on how biological communities respond to this variation.Hangzhou Bay,a mediumsized estuary in China,is an ideal place in which to study the response of plankton to small-scale ocean fronts,because three water masses(Qiantang River Diluted Water,Changjiang River Diluted Water,and the East China Sea current) converge here and form dynamic salinity fronts throughout the year.We investigate zooplankton communities,and temperature,salinity and chlorophyll a(Chl a) in Hangzhou Bay in June(wet perio d) and December(dry period) of 2022 and examine the dominant environmental factors that affect zooplankton community spatial variability.We then match the spatial distributions of zooplankton communities with those of salinity fronts.S alinity is the most important explanatory variable to affect zooplankton community spatial variability during both wet and dry periods,in that it contributes>60% of the variability in community structure.Furthermore,the spatial distributions of zooplankton match well with salinity fronts.During December,with weaker Qiantang River Diluted Water and a stronger secondary Changjiang River Plume,zooplankton communities occur in moderate salinity(MS,salinity range 15.6±2.2) and high salinity(HS,22.4±1.7) regions,and their ecological boundaries closely match the Qiantang River Diluted Water front.In June,different zooplankton communities occur in low salinity(LS,3.9±1.0),MS(11.7±3.6) and HS(21.3±1.9) regions.Although the LS region occurs abnormally in the central bay rather than its apex because of the anomalous influence of rising and falling tides during the sampling perio d,the ecological boundaries still match salinity interfaces.Low-salinity or brackish-water zooplankter taxa are relatively more abundant in LS or MS regions,and the biomass and abundance of zooplankton is higher in the MS region.
文摘By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed among multiple construction projects near residential areas.In this process,the local government played a crucial coordinating role.According to regulations,construction units must include the costs of preventing and controlling construction noise pollution in the project cost.The construction contract should clearly specify the construction unit’s responsibility for noise pollution prevention and control.After signing the contract,the construction unit should promptly undertake relevant measures to minimize disturbances caused by nighttime construction,aiming to reduce the adverse impacts on the community and ensure the smooth progress of the construction project.
基金supported by the National Key Research and Development Program of China(No.2017YFC1502504)the National Natural Science Foundation of China(No.41877531).
文摘With the increasing severity of arsenic(As)pollution,quantifying the environmental behavior of pollutant based on numerical model has become an important approach to determine the potential impacts and finalize the precise control strategies.Taking the industrialintensive Jinsha River Basin as typical area,a two-dimensional hydrodynamic water quality model coupled with Soil andWater Assessment Tool(SWAT)model was developed to accurately simulate the watershed-scale distribution and transport of As in the terrestrial and aquatic environment at high spatial and temporal resolution.The effects of hydro-climate change,hydropower station construction and non-point source emissions on Aswere quantified based on the coupled model.The result indicated that higher As concentration areas mainly centralized in urban districts and concentration slowly decreased from upstream to downstream.Due to the enhanced rainfall,the As concentration was significantly higher during the rainy season than the dry season.Hydro-climate change and the construction of hydropower station not only affected the dissolved As concentration,but also affected the adsorption and desorption of As in sediment.Furthermore,As concentration increased with the input of non-point source pollution,with the maximum increase about 30%,resulting that non-point sources contributed important pollutant impacts to waterways.The coupled model used in pollutant behavior analysis is generalwith high potential application to predict and mitigate water pollution.
基金supported by the National Natural Science Foundation of China(No.52475216)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515240030)+2 种基金the Natural Science Foundation of Shaanxi Province(No.2024RSCXTD-62)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2022-QZ-04)We would like to thank the Analytical&Testing Center of Northwestern Polytechnical University and the Shaanxi Materials Analysis and Research Center.
文摘The synergy between corrosion protection and wear resistance is an effective strategy for the development of multifunctional coating to withstand complex working conditions.This study reports an epoxy resin coating filled with benzotriazole loaded metal-organic frameworks(BTA-MOFs)functionalized graphene oxide nanoribbons(GONR)that exhibit active anti-corrosion,act as a barrier to corrosive ion,and enhance wear resistance.The GONR@BTA-MOFs composite is synthesized through chemically etching multi-walled carbon nanotubes and subsequent electrostatic self-assembly corrosion inhibitors loaded MOFs onto the GONR.The composite demonstrates improved compatibility with epoxy resins compared to carbon nanotubes.The anti-corrosion performance of the composite coating is investigated using electrochemical impedance spectroscopy.After immersing in a 3.5 wt.%NaCl solution for 25 d,the alternating current impedance of the composite coating is three orders of magnitude higher than that of pure epoxy resin.Simultaneously,the controlled release of the corrosion inhibitor retards the deterioration of the coating after localized damage occurrence,which functions as active corrosion protection.The GONR@BTA-MOFs/EP composite coating exhibits the highest corrosion potential of-0.188 V and the lowest corrosion current of 3.162×10^(−9)A cm^(−2)in the Tafel test.Tribological studies reveal a reduction in the friction coefficient from 0.62 to 0.08 after incorporating GONR@BTA-MOFs in the coating,with the wear volume being seven times lower than that of pure epoxy resin.The excellent lubrication effect of the nanomaterials reduces the coefficient of friction of the coating,thereby improving the abrasion resistance of the coating.The synergy between the self-lubrication of the two-dimensional layered fillers and the corrosion resistance of the smart inhibitor containers suggests a promising strategy for enhancing the performance of epoxy resins under complex working conditions.
文摘Increasing environmental concerns about limiting harmful emissions has necessitated sulfur-and phosphorus-free green lubricant additives.Although boron-containing compounds have been widely investigated as green lubricant additives,their macromolecular analogs have been rarely considered yet to develop environmentally friendly lubricant additives.In this work,a series of boron-containing copolymers have been synthesized by free-radical copolymerization of stearyl methacrylate and isopropenyl boronic acid pinacol ester with different feeding ratios(S_(n)-r-B_(m),n=1,m=1/3,1,2,3,5,9).The resulting copolymers of S_(n)-r-B_(m)(n=1,m=1/3,1,2,3,5)are readily dispersed in the PAO-10 base oil and form micelle-like aggregates with hydrodynamic diameters ranging from 9.7 to 52 nm.SRV-IV oscillating reciprocating tribological tests on ball-on-flat steel pairs show that compared with the base oil of PAO-10,the friction coefficients and wear volumes of the base oil solutions of S_(n)-r-B_(m)decrease considerably up to 62%and 97%,respectively.Moreover,the base oil solution of S_(1)-r-B_(1)exhibits an excellent load-bearing capacity of(850±100)N.These superior lubricating properties are due to the formation of protective tribofilms comprising S_(n)-r-B_(m),boron oxide,and iron oxide compounds on the lubricated steel surface.Therefore,the boron-containing copolymers can be regarded as a novel class of environmentally friendly lubricating oil macroadditives for efficient friction and wear reduction without sulfur and phosphorus elements.
