The interactions between a plate-like precipitate and two twin boundaries(TBs)({1012},{1121}) in magnesium alloys are studied using molecular dynamics(MD) simulations. The precipitate is not sheared by {1012} TB, but ...The interactions between a plate-like precipitate and two twin boundaries(TBs)({1012},{1121}) in magnesium alloys are studied using molecular dynamics(MD) simulations. The precipitate is not sheared by {1012} TB, but sheared by {1121} TB. Shearing on the(110) plane is the predominant deformation mode in the sheared precipitate. Then, the blocking effects of precipitates with different sizes are studied for {1121} twinning. All the precipitates show a blocking effect on {1121} twinning although they are sheared, while the blocking effects of precipitates with different sizes are different. The blocking effect increases significantly with the increasing precipitate length(in-plane size along TB) and thickness, whereas changes weakly as the precipitate width changes. Based on the revealed interaction mechanisms, a critical twin shear is calculated theoretically by the Eshelby solutions to determine which TB is able to shear the precipitate. In addition, an analytical hardening model of sheared precipitates is proposed by analyzing the force equilibrium during TB-precipitate interactions. This model indicates that the blocking effect depends solely on the area fraction of the precipitate cross-section, and shows good agreement with the current MD simulations. Finally, the blocking effects of plate-like precipitates on the {1012} twinning(non-sheared precipitate), {1121} twinning(sheared precipitate) and basal dislocations(non-sheared precipitate) are compared together. Results show that the blocking effect on {1121} twinning is stronger than that on {1012} twinning, while the effect on basal dislocations is weakest. The precipitate-TB interaction mechanisms and precipitation hardening models revealed in this work are of great significance for improving the mechanical property of magnesium alloys by designing microstructure.展开更多
In polycrystalline magnesium(Mg)and Mg alloys,as the grain size decreases,the grain boundary(GB)mediated plasticity including GB sliding and GB migration becomes the dominant deformation mechanism.In this study,the mo...In polycrystalline magnesium(Mg)and Mg alloys,as the grain size decreases,the grain boundary(GB)mediated plasticity including GB sliding and GB migration becomes the dominant deformation mechanism.In this study,the motion of[1100]symmetric tilt GBs in Mg bicrystals is investigated using molecular dynamics(MD)simulations.The effects of GB misorientation angle and temperature are considered.At low/room temperatures and varied GB misorientation angles in the range ofθ≥58.36°,the GB migration occurs via the shear coupling with the invariant plane of{0001};At 35.80°<θ<58.36°,both the GB migration and GB sliding happen and the invariant plane changes from{0001}plane to[1122]plane;At 26.54°≤θ≤35.80°,the GB migrates with the invariant plane of[1122];Finally,atθ<26.54°,the GB sliding becomes the main deformation mechanism.At 700 K,the GB sliding occurs at the misorientation angles in the range ofθ<58.36θ;while the GB migration occurs at the misorientation angles ofθ≥58.36°.By comparing the energy barriers of GB migration and GB sliding,it yields that the deformation mode with a low energy barrier always happens,which leads to the transition of deformation modes and agrees well with the MD simulation results.展开更多
Ships and other mobile pollution sources emitted massive ultrafine and low-resistivity particles containing black carbon(BC),which were harmful to human health and were difficult to capture by conventional electrostat...Ships and other mobile pollution sources emitted massive ultrafine and low-resistivity particles containing black carbon(BC),which were harmful to human health and were difficult to capture by conventional electrostatic precipitators(ESPs).In this study,nanoscale carbon black was adopted as simulated particles(SP)with similar physicochemical properties for black carbon emitted from ships(SP-BC)to investigate the feasibility of using an ESP with square-grooved collecting plates for the removal of SP-BC at low backpressures.The increased applied voltage significantly improved the total collection of SP-BC whereas may also promote the conversion of relatively larger particle size SP-BC into nano-size below 20nm.The outlet number concentration of SP-BC under 27 kV at 130℃was three times that of the inlet.While the reduction of the flow rate could strengthen the capture of SP-BC below20 nm,and under the combined action of low flow rate and maximum applied voltage,the collection efficiency of 20-100 nm SP-BC could exceed 90%.In addition,the escape and capture characteristics of SP-BC under long-term rapping were revealed.The square-grooved collecting plate could effectively restrain the re-entrainment of collected SP-BC generated by rapping,and the nanoscale SP-BC was trapped in the grooves after rapping.The results could provide insights into the profound removal of massive nanoscale black carbon emissions from mobile sources.展开更多
Soft strain sensors that can transduce stretch stimuli into electrical readouts are promising as sustainable wearable electronics.However,most strain sensors cannot achieve highly-sensitive and wide-range detection of...Soft strain sensors that can transduce stretch stimuli into electrical readouts are promising as sustainable wearable electronics.However,most strain sensors cannot achieve highly-sensitive and wide-range detection of ultralow and high strains.Inspired by bamboo structures,anti-freezing microfibers made of conductive poly(vinyl alcohol)hydrogel with poly(3,4-ethylenedioxythiphene)-poly(styrenesulfonate)are developed via continuous microfluidic spinning.The microfibers provide unique bamboo-like structures with enhanced local stress to improve both their length change and resistance change upon stretching for efficient signal conversion.The microfibers allow highlysensitive(detection limit:0.05%strain)and wide-range(0%-400%strain)detection of ultralow and high strains,as well as features of good stretchability(485%strain)and anti-freezing property(freezing temperature:-41.1°C),fast response(200 ms),and good repeatability.The experimental results,together with theoretical foundation analysis and finite element analysis,prove their enhanced length and resistance changes upon stretching for efficient signal conversion.By integrating microfluidic spinning with 3D-printing technique,the textiles of the microfibers can be flexibly constructed.The microfibers and their 3D-printed textiles enable highperformance monitoring of human motions including finger bending and throat vibrating during phonation.This work provides an efficient and general strategy for developing advanced conductive hydrogel microfibers as highperformance wearable strain sensors.展开更多
Single-phase concentrated solid solution alloys(SP-CSAs),including high-entropy alloys,have received extensive attention due to their excellent irradiation resistance.In this work,displacement cascade simulations are ...Single-phase concentrated solid solution alloys(SP-CSAs),including high-entropy alloys,have received extensive attention due to their excellent irradiation resistance.In this work,displacement cascade simulations are conducted using the molecular dynamics method to study the evolution of defects in Ni-based SP-CSAs.Compared with pure Ni,the NiCr,NiCo,and NiCu alloys exhibit a larger number of Frankel pairs(FPs)in the thermal peak stage,but a smaller number of surviving FPs.However,the NiFe alloy displays the opposite phenomenon.To explain these different observations for NiFe and other alloys,the formation energy and migration energy of interstitials/vacancies are calculated.In the NiFe alloy,both the formation energy and migration energy barrier are higher.On the other hand,in NiCr and other alloys,the formation energy of interstitials/vacancies is lower,as is the migration energy barrier of interstitials.The energy analysis agrees well with previous observations.The present work provides new insights into the mechanism behind the irradiation resistance of binary Ni-based SP-CSAs.展开更多
The total internal reflection(TIR)behavior of interface shear waves is crucial for ensuring the reliability of dielectric elastomer(DE)devices.However,due to the complex force-electric coupling and large deformation o...The total internal reflection(TIR)behavior of interface shear waves is crucial for ensuring the reliability of dielectric elastomer(DE)devices.However,due to the complex force-electric coupling and large deformation of DEs,the TIR behavior of shear waves in heterogeneous force-electric interface models is still unclear.This study modeled an elastic/DE bi-material interface to analyze the trajectory of out-of-plane shear waves.Employing Dorfmann and Ogden’s nonlinear electroelastic framework and the related linear small incremental motion theory,a method has been developed to control the TIR behavior of interface shear waves.It has been found that the TIR behavior is significantly influenced by the strain-stiffening effect induced by biasing fields.Consequently,a biasing field principle involving preset electric displacement and pre-stretch has been proposed for TIR occurrence.By controlling the pre-stretch and preset electric displacement,active regulation of TIR behavior can be achieved.These results suggest a potential method for achieving autonomous energy shielding to improve the reliability of DE devices.展开更多
Domain pattern is the carrier of electromechanical property.A novel domain pattern will open a gate for ferroelectric nano device.A distinctive topological domain pattern termed as hierarchical vortex(Hvo)has been fou...Domain pattern is the carrier of electromechanical property.A novel domain pattern will open a gate for ferroelectric nano device.A distinctive topological domain pattern termed as hierarchical vortex(Hvo)has been found in polycrystalline ferroelectric based on the first-principles-based atomistic method.The Hvo pattern displays a unique structure,which is a flux-closing vortex encircle an anti-vortex or a vortex and anti-vortex pair(VA).Each Hvo structure could be regarded as a single vortex to forming a vortex-anti-vortex pair with anti-vortex or forming a vortex-vortex array with the vortex.The mechanism of HVo obtained in polycrystalline ferroelectric has been found that the grain boundary(GB)equals the domain wall when the first-order vortex is in the vortex.The HVo will open a new view of the domain topology pattern and its evolution.展开更多
This paper develops the adhesive contact theory for a one-dimensional hexagonal quasicrystal half-space punched by a spherical indenter on the basis of the classical adhesive contact models involving the Johnson–Kend...This paper develops the adhesive contact theory for a one-dimensional hexagonal quasicrystal half-space punched by a spherical indenter on the basis of the classical adhesive contact models involving the Johnson–Kendall–Roberts(JKR)model,the Maugis–Dugdale(MD)model and the Derjaguin–Muller–Toporov(DMT)model.By using the superposition principle combined with the Griffith energy balance,all the significant physical quantities for adhesive contact,such as the energy release rate,indentation force,penetration depth,contact radius and pull-out force,are obtained for different models.The result for the DMT model is derived from the MD solution through a limiting procedure.A numerical calculation is carried out to verify the present analytical solutions,to compare different contact models,and to analyze the influence of the phason field on the results.It is indicated that the effect of the phason field on the result for the MD model is pronounced,especially for a small contact radius.However,the phason effect on the JKR and DMT results is not significant.The present solution can serve as a theoretical basis for nano-indentation and atomic force microscopy to measure the material properties of quasicrystals.展开更多
In this paper,molecular dynamics simulations are performed to investigate the decomposition of(c+a)dislocations on both pyramidal-Ⅰ and pyramidal-Ⅱ planes.The pyramidal-Ⅰ dislocations are decomposed into(c)and(a)di...In this paper,molecular dynamics simulations are performed to investigate the decomposition of(c+a)dislocations on both pyramidal-Ⅰ and pyramidal-Ⅱ planes.The pyramidal-Ⅰ dislocations are decomposed into(c)and(a)dislocations under shear stress at 0-400 K,which all reside on the basal plane.At 500-700 K,the dislocations are transited onto the basal plane at zero stress,then decomposed into(c)and(a)dislocations under shear loading.In particular,at 700 K,the dislocation is possibly decomposed spontaneously at zero stress.For the pyramidal-Ⅱ dislocations,the core is glissile below 400 K.At 500 K,the dislocation is transited onto the basal plane under shear loading.At 600-700 K,basal(c+a)dislocation is formed at zero stress,but then decomposed under shear loading.The dislocation core energy is calculated to explain the observations.It is found that the energy of decomposed(c+a)dislocation is high,the energy of pyramidal(c+a)dislocation is intermediate,and the energy of basal(c+a)dislocation is low.Our results provide new insights into the behaviors of pyramidal dislocations and temperature effects.展开更多
Two-dimensional(2D)multiferroic materials are recognized as promising candidates for nextgeneration nanodevices due to their tunable magnetoelectric coupling and distinctive physical phenomena.In this study,we propose...Two-dimensional(2D)multiferroic materials are recognized as promising candidates for nextgeneration nanodevices due to their tunable magnetoelectric coupling and distinctive physical phenomena.In this study,we proposed a novel 2D multiferroic van der Waals heterostructure(vdWH)by stacking atomic layers of ferroelectric In_(2)Se_(3)and ferromagnetic MnI3.Using first-principles calculations,we found that theMnI3/In_(2)Se_(3)vdWH exhibit robust metallic conductivity across various spin and polarization states,preserving the distinctive band characteristics of isolated In_(2)Se_(3)and MnI_(3).展开更多
基金financial support from National Natural Science Foundation of China (12072211)Sichuan Province Science and Technology Project (2020JDJQ0029)。
文摘The interactions between a plate-like precipitate and two twin boundaries(TBs)({1012},{1121}) in magnesium alloys are studied using molecular dynamics(MD) simulations. The precipitate is not sheared by {1012} TB, but sheared by {1121} TB. Shearing on the(110) plane is the predominant deformation mode in the sheared precipitate. Then, the blocking effects of precipitates with different sizes are studied for {1121} twinning. All the precipitates show a blocking effect on {1121} twinning although they are sheared, while the blocking effects of precipitates with different sizes are different. The blocking effect increases significantly with the increasing precipitate length(in-plane size along TB) and thickness, whereas changes weakly as the precipitate width changes. Based on the revealed interaction mechanisms, a critical twin shear is calculated theoretically by the Eshelby solutions to determine which TB is able to shear the precipitate. In addition, an analytical hardening model of sheared precipitates is proposed by analyzing the force equilibrium during TB-precipitate interactions. This model indicates that the blocking effect depends solely on the area fraction of the precipitate cross-section, and shows good agreement with the current MD simulations. Finally, the blocking effects of plate-like precipitates on the {1012} twinning(non-sheared precipitate), {1121} twinning(sheared precipitate) and basal dislocations(non-sheared precipitate) are compared together. Results show that the blocking effect on {1121} twinning is stronger than that on {1012} twinning, while the effect on basal dislocations is weakest. The precipitate-TB interaction mechanisms and precipitation hardening models revealed in this work are of great significance for improving the mechanical property of magnesium alloys by designing microstructure.
基金supported by the National Natural Science Foundation of China(Grant Nos.12192210,12192214,and 12072211)。
文摘In polycrystalline magnesium(Mg)and Mg alloys,as the grain size decreases,the grain boundary(GB)mediated plasticity including GB sliding and GB migration becomes the dominant deformation mechanism.In this study,the motion of[1100]symmetric tilt GBs in Mg bicrystals is investigated using molecular dynamics(MD)simulations.The effects of GB misorientation angle and temperature are considered.At low/room temperatures and varied GB misorientation angles in the range ofθ≥58.36°,the GB migration occurs via the shear coupling with the invariant plane of{0001};At 35.80°<θ<58.36°,both the GB migration and GB sliding happen and the invariant plane changes from{0001}plane to[1122]plane;At 26.54°≤θ≤35.80°,the GB migrates with the invariant plane of[1122];Finally,atθ<26.54°,the GB sliding becomes the main deformation mechanism.At 700 K,the GB sliding occurs at the misorientation angles in the range ofθ<58.36θ;while the GB migration occurs at the misorientation angles ofθ≥58.36°.By comparing the energy barriers of GB migration and GB sliding,it yields that the deformation mode with a low energy barrier always happens,which leads to the transition of deformation modes and agrees well with the MD simulation results.
基金supported by the National Natural Science Foundation (No.52076191)Key Research&Development Plan of Shandong Province (No.2020CXGC011401)。
文摘Ships and other mobile pollution sources emitted massive ultrafine and low-resistivity particles containing black carbon(BC),which were harmful to human health and were difficult to capture by conventional electrostatic precipitators(ESPs).In this study,nanoscale carbon black was adopted as simulated particles(SP)with similar physicochemical properties for black carbon emitted from ships(SP-BC)to investigate the feasibility of using an ESP with square-grooved collecting plates for the removal of SP-BC at low backpressures.The increased applied voltage significantly improved the total collection of SP-BC whereas may also promote the conversion of relatively larger particle size SP-BC into nano-size below 20nm.The outlet number concentration of SP-BC under 27 kV at 130℃was three times that of the inlet.While the reduction of the flow rate could strengthen the capture of SP-BC below20 nm,and under the combined action of low flow rate and maximum applied voltage,the collection efficiency of 20-100 nm SP-BC could exceed 90%.In addition,the escape and capture characteristics of SP-BC under long-term rapping were revealed.The square-grooved collecting plate could effectively restrain the re-entrainment of collected SP-BC generated by rapping,and the nanoscale SP-BC was trapped in the grooves after rapping.The results could provide insights into the profound removal of massive nanoscale black carbon emissions from mobile sources.
基金support from the National Natural Science Foundation of China(Nos.22278281 and 21991101)Sichuan University(2020SCUNG112)
文摘Soft strain sensors that can transduce stretch stimuli into electrical readouts are promising as sustainable wearable electronics.However,most strain sensors cannot achieve highly-sensitive and wide-range detection of ultralow and high strains.Inspired by bamboo structures,anti-freezing microfibers made of conductive poly(vinyl alcohol)hydrogel with poly(3,4-ethylenedioxythiphene)-poly(styrenesulfonate)are developed via continuous microfluidic spinning.The microfibers provide unique bamboo-like structures with enhanced local stress to improve both their length change and resistance change upon stretching for efficient signal conversion.The microfibers allow highlysensitive(detection limit:0.05%strain)and wide-range(0%-400%strain)detection of ultralow and high strains,as well as features of good stretchability(485%strain)and anti-freezing property(freezing temperature:-41.1°C),fast response(200 ms),and good repeatability.The experimental results,together with theoretical foundation analysis and finite element analysis,prove their enhanced length and resistance changes upon stretching for efficient signal conversion.By integrating microfluidic spinning with 3D-printing technique,the textiles of the microfibers can be flexibly constructed.The microfibers and their 3D-printed textiles enable highperformance monitoring of human motions including finger bending and throat vibrating during phonation.This work provides an efficient and general strategy for developing advanced conductive hydrogel microfibers as highperformance wearable strain sensors.
基金supported by the National Natural Science Foundation of China(12232008,12072211)Foundation of Key laboratory(2022JCJQLB05703)Sichuan Province Science and Technology Project(2023NSFSC0914,2020JDJQ0029).
文摘Single-phase concentrated solid solution alloys(SP-CSAs),including high-entropy alloys,have received extensive attention due to their excellent irradiation resistance.In this work,displacement cascade simulations are conducted using the molecular dynamics method to study the evolution of defects in Ni-based SP-CSAs.Compared with pure Ni,the NiCr,NiCo,and NiCu alloys exhibit a larger number of Frankel pairs(FPs)in the thermal peak stage,but a smaller number of surviving FPs.However,the NiFe alloy displays the opposite phenomenon.To explain these different observations for NiFe and other alloys,the formation energy and migration energy of interstitials/vacancies are calculated.In the NiFe alloy,both the formation energy and migration energy barrier are higher.On the other hand,in NiCr and other alloys,the formation energy of interstitials/vacancies is lower,as is the migration energy barrier of interstitials.The energy analysis agrees well with previous observations.The present work provides new insights into the mechanism behind the irradiation resistance of binary Ni-based SP-CSAs.
基金supported by the National Natural Science Foundation of China(Grant No.12372154)National Science and Technology Major Project(Grant No.J2019-III-0010-0054).
文摘The total internal reflection(TIR)behavior of interface shear waves is crucial for ensuring the reliability of dielectric elastomer(DE)devices.However,due to the complex force-electric coupling and large deformation of DEs,the TIR behavior of shear waves in heterogeneous force-electric interface models is still unclear.This study modeled an elastic/DE bi-material interface to analyze the trajectory of out-of-plane shear waves.Employing Dorfmann and Ogden’s nonlinear electroelastic framework and the related linear small incremental motion theory,a method has been developed to control the TIR behavior of interface shear waves.It has been found that the TIR behavior is significantly influenced by the strain-stiffening effect induced by biasing fields.Consequently,a biasing field principle involving preset electric displacement and pre-stretch has been proposed for TIR occurrence.By controlling the pre-stretch and preset electric displacement,active regulation of TIR behavior can be achieved.These results suggest a potential method for achieving autonomous energy shielding to improve the reliability of DE devices.
基金supported by the National Defense Science&Technology Innovation Zone Project,the Natural Science Foundation of China(Grant No.12072213)the National Science and Technology Major Project(Grant No.J2019-Ⅲ-0010-0054)+1 种基金the National Numerical Windtunnel(Grant No.NNW2019-JT01-023)We thank Zhenhuan Li(Huazhong University of Science and Technology)and Jiangyu Li(Southern University of Science and Technology)for the useful discussion.
基金This work is supported by the Natural Science Foundation of China(No.12072213)National Science and Technology Major Project(J2019-III-0010-0054)the National Numerical Windtunnel(NNW2019-JT01-023).
文摘Domain pattern is the carrier of electromechanical property.A novel domain pattern will open a gate for ferroelectric nano device.A distinctive topological domain pattern termed as hierarchical vortex(Hvo)has been found in polycrystalline ferroelectric based on the first-principles-based atomistic method.The Hvo pattern displays a unique structure,which is a flux-closing vortex encircle an anti-vortex or a vortex and anti-vortex pair(VA).Each Hvo structure could be regarded as a single vortex to forming a vortex-anti-vortex pair with anti-vortex or forming a vortex-vortex array with the vortex.The mechanism of HVo obtained in polycrystalline ferroelectric has been found that the grain boundary(GB)equals the domain wall when the first-order vortex is in the vortex.The HVo will open a new view of the domain topology pattern and its evolution.
基金supported primarily by the National Natural Science Foundation of China(Nos.12172237,12002273 and 11832007)The supports from Sichuan Science and Technology Program(No.2021YJ0513-BG)+1 种基金2022 Open Project of Failure Mechanics and Engineering Disaster Prevention,Key Lab of Sichuan Provence(No.FMEDP202211)are also gratefully acknowledged.
文摘This paper develops the adhesive contact theory for a one-dimensional hexagonal quasicrystal half-space punched by a spherical indenter on the basis of the classical adhesive contact models involving the Johnson–Kendall–Roberts(JKR)model,the Maugis–Dugdale(MD)model and the Derjaguin–Muller–Toporov(DMT)model.By using the superposition principle combined with the Griffith energy balance,all the significant physical quantities for adhesive contact,such as the energy release rate,indentation force,penetration depth,contact radius and pull-out force,are obtained for different models.The result for the DMT model is derived from the MD solution through a limiting procedure.A numerical calculation is carried out to verify the present analytical solutions,to compare different contact models,and to analyze the influence of the phason field on the results.It is indicated that the effect of the phason field on the result for the MD model is pronounced,especially for a small contact radius.However,the phason effect on the JKR and DMT results is not significant.The present solution can serve as a theoretical basis for nano-indentation and atomic force microscopy to measure the material properties of quasicrystals.
基金The financial support from National Natural Science Foundation of China(12072211)Sichuan Province Science and Technology Project(2020JDJQ0029)is acknowledged.
文摘In this paper,molecular dynamics simulations are performed to investigate the decomposition of(c+a)dislocations on both pyramidal-Ⅰ and pyramidal-Ⅱ planes.The pyramidal-Ⅰ dislocations are decomposed into(c)and(a)dislocations under shear stress at 0-400 K,which all reside on the basal plane.At 500-700 K,the dislocations are transited onto the basal plane at zero stress,then decomposed into(c)and(a)dislocations under shear loading.In particular,at 700 K,the dislocation is possibly decomposed spontaneously at zero stress.For the pyramidal-Ⅱ dislocations,the core is glissile below 400 K.At 500 K,the dislocation is transited onto the basal plane under shear loading.At 600-700 K,basal(c+a)dislocation is formed at zero stress,but then decomposed under shear loading.The dislocation core energy is calculated to explain the observations.It is found that the energy of decomposed(c+a)dislocation is high,the energy of pyramidal(c+a)dislocation is intermediate,and the energy of basal(c+a)dislocation is low.Our results provide new insights into the behaviors of pyramidal dislocations and temperature effects.
基金supported by the National Natural Science Foundation of China(NOs.12202134 and 12372154)the Natural Science Foundation of Hebei Province(NO.A2024407001)the Science Research Project of Hebei Education Department(No.BJK2024032).
文摘Two-dimensional(2D)multiferroic materials are recognized as promising candidates for nextgeneration nanodevices due to their tunable magnetoelectric coupling and distinctive physical phenomena.In this study,we proposed a novel 2D multiferroic van der Waals heterostructure(vdWH)by stacking atomic layers of ferroelectric In_(2)Se_(3)and ferromagnetic MnI3.Using first-principles calculations,we found that theMnI3/In_(2)Se_(3)vdWH exhibit robust metallic conductivity across various spin and polarization states,preserving the distinctive band characteristics of isolated In_(2)Se_(3)and MnI_(3).
