Back stress has been proven to be the primary mechanism for superior mechanical properties of heterogeneous structures,but its quantitative contribution remains vague.The main purpose of this work is to clarify the co...Back stress has been proven to be the primary mechanism for superior mechanical properties of heterogeneous structures,but its quantitative contribution remains vague.The main purpose of this work is to clarify the contributions of back stress components,i.e.,intergranular residual stress and intragranular back stress,to the mechanical properties of heterogeneous structures based on the crystal plasticity theory.The results show that the intragranular back stress is smaller than the intergranular residual stress but contributes significantly to the strain hardening of the heterogeneous bimodal structures.In addition,the contributions of misorientation and grain size to back stress are quantitatively analyzed,and the near-linear relationship between hetero-deformation induced hardening and strain gradient is found.These findings emphasize the es-sential role of the intragranular back stress induced by strain gradient and provide an in-depth understanding of the elaborate roles of back stress in heterogeneous structures.展开更多
Mechanical property of coarse grained and nano/ultrafine grained alloy 690 and their corrosion resistance after immersion in high temperature borate buffer solution were investigated. The grain refinement significantl...Mechanical property of coarse grained and nano/ultrafine grained alloy 690 and their corrosion resistance after immersion in high temperature borate buffer solution were investigated. The grain refinement significantly enhances the tensile strength of the alloy 690. In addition, the grain refinement facilitates the formation of the deformation twin which improves the ductility of the alloy 690. It has been found that the grain refinement promotes to form more Cr2 O3 on the surface of the alloy 690 in high temperature borate buffer solution. At the same time, the grain refinement inhibits the formation of spinel type oxides.More hematite type oxides formed on nano/ultrafine grained alloy 690 improves its corrosion resistance in borate buffer solution. The hematite type oxides have a lower concentration of point defect than that of the spinel type oxides, which results in an excellent corrosion resistance of nano/ultrafine grained alloy 690. These results are supported by the Mott-Schottky analysis and the point defect model.展开更多
The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrotherma...The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrothermal method, while large-scale ZnCoOnanowires arrays homogeneously aligned and separated adequately on Ni foam coated with graphene. This ZnCoOnanowire structure exhibited superior supercapacitors properties. The excellent supercapacitors were mainly attributed to the large specific surface and the porosity on the nanowires which promoted the electrons and ions transportation. In addition, graphene improved conductivity of substrate for current collecting.展开更多
For the assessment of the carbon dioxide (CO2) storage potential of water-filled reservoir rocks (i.e., saline aquifers), it should be first important step for a thorough understanding of the effect of water content o...For the assessment of the carbon dioxide (CO2) storage potential of water-filled reservoir rocks (i.e., saline aquifers), it should be first important step for a thorough understanding of the effect of water content on CO2/water/rock interactions during CO2 injection. The purpose of this study is to examine the CO2 sorption amount for Kimachi sandstone and Berea sandstone at different water content using the manometric method at temperature of 50?C and pressures of up to 20 MPa. Our results document that a significant quantity of CO2 was sorbed on the two types of sandstone on all water-saturated bases, which corresponded to the amount adsorbed on the air-dry basis. Also, all the wet samples had significantly higher sorption capacity than the theoretical values calculated from the solubility model based on dissolution of CO2 in pore water and the pore-filling model, which assumes that the pore volume unoccupied by water is filled with CO2. Furthermore, the observations indicated a certain degree of correlation between the sorbed amount and the water content, except at pressures below the critical point for Berea sandstone. This investigation points out that CO2 sorption is a possible mechanism in CO2 geological storage even under water-saturated conditions and that the mechanism of sorption on silica and silicate minerals plays an essential role in the reliable and accurate estimation of the CO2 storage capacity of water-saturated reservoirs.展开更多
The low cycle fatigue strength properties of the additively manufactured Ti-6Al-4V alloy are experimentally investi-gated under proportional and nonproportional multiaxial loading.The fatigue tests were conducted usin...The low cycle fatigue strength properties of the additively manufactured Ti-6Al-4V alloy are experimentally investi-gated under proportional and nonproportional multiaxial loading.The fatigue tests were conducted using hollow cylinder specimens with and without heat treatments,at room temperature in air.Two fatigue tests were conducted:one for proportional loading and one for nonproportional loading.The proportional loading was represented by a push-pull strain path(PP)and the nonproportional loading by a circle strain path(Cl).The failure lives of the additively manufactured specimens were clearly reduced drastically by internal voids and defects.However,the sizes of the defects were measured,and the defects were found not to cause a reduction in fatigue strength above a critical size.The fracture surface was observed using scanning electron microscopy to investigate the fracture mechanisms of the additively manufactured specimens under the two types of strain paths.Different fracture patterns were recognized for each strain paths;however,both showed retention of the crack propagation,despite the presence of numerous defects,probably because of the interaction of the defects.The crack propagation properties of the materials with numerous defects under nonproportional multiaxial loading were clarified to increase the reliability of the additively manufactured components.展开更多
The abundant nitrogen in the Earth’s atmosphere can be interpreted as the result of endothermic nuclear transmutation of carbon and oxygen atom pairs in (Ca, D) CO3 or CaCO3 aragonite lattice of Earth’s crust from t...The abundant nitrogen in the Earth’s atmosphere can be interpreted as the result of endothermic nuclear transmutation of carbon and oxygen atom pairs in (Ca, D) CO3 or CaCO3 aragonite lattice of Earth’s crust from the Archean era to the present time, by physical catalytic help of excited electrons e* generated by stick sliding due to plate tectonics and geoneutrinos ν by the radioactive decay of elements such as uranium and thorium in Earth’s mantle: through a nuclear attraction effect that is due to deuteron catalysis of nitrogen formation. The relationship between the critical temperature T and the critical pressure P for the nuclear transmutation is expressed as 7253 × e-0.014P, and the formation of nitrogen in the mantle is possible at temperatures ≥ 2510 K and pressure ≥ 58 GPa.展开更多
Using machine learning to predict and design materials is an important mean of accelerating material development.One way to improve the accuracy of machine learning predictions is to introduce material structures as d...Using machine learning to predict and design materials is an important mean of accelerating material development.One way to improve the accuracy of machine learning predictions is to introduce material structures as descriptors.However,thecomplexity ofcomputing material structures limits the practical use of these models.To address this challenge and improve prediction accuracy in small data sets,we develop a generative network framework:Elemental Features enhanced and Transferring corrected data augmentation in Generative Adversarial Networks(EFTGAN).Combining the elemental convolution technique with Generative Adversarial Networks(GAN),EFTGAN provides a robust and efficient approach for generating data containing elemental and structural information that can be used not only for data augmentation to improve model accuracy,but also for prediction when the structures are unknown.Applying this framework to the FeNiCoCrMn/Pd high-entropy alloys,we successfully improve the prediction accuracy in a small data set and predict the concentrationdependent formation energies,lattices,and magnetic moments in quinary systems.This study provides a new algorithm to improve the performance and usability of deep learning with structures as inputs,which is effective and accurate for the prediction and development of materials for small data sets.展开更多
When developing deep learning models for accurate property prediction,it is sometimes overlooked that some material physical properties are insensitive to the local atomic environment.Here,we propose the elemental con...When developing deep learning models for accurate property prediction,it is sometimes overlooked that some material physical properties are insensitive to the local atomic environment.Here,we propose the elemental convolution neural networks(ECNet)to obtain more general and global element-wise representations to accurately model material properties.It shows better prediction in properties like band gaps,refractive index,and elastic moduli of crystals.To explore its application on high-entropy alloys(HEAs),we focus on the FeNiCoCrMn/Pd systems based on the data of DFT calculation.The knowledge from less-principal element alloys can enhance performance in HEAs by transfer learning technique.Besides,the element-wise features from the parent model as universal descriptors retain good accuracy at small data limits.Using this framework,we obtain the concentration-dependent formation energy,magnetic moment and local displacement in some sub-ternary and quinary systems.The results enriched the physics of those high-entropy alloys.展开更多
Recently, substantial attention has been paid to the strain sensitivity of the carbon nanotubes＇ （CNTs＇） electronic properties. In this study, the relationships between the geometric structures and electronic stat...Recently, substantial attention has been paid to the strain sensitivity of the carbon nanotubes＇ （CNTs＇） electronic properties. In this study, the relationships between the geometric structures and electronic states of zigzag CNTs under uniaxial compressive strain were investigated. We found that different factors dominate the electronic states of zigzag CNTs depending on the strain regions： the initial stage of the strain loading, which lasts until column-buckling deformation begins, and the strain regions corresponding to column- and shell-buckling deformations. Because shell-buckling deformation significantly increases the re-orbital angle, the angle between the π orbital axis vectors of adjacent atoms, strong localization of the density of states （LDOS） occurs in the buckled area. We also analyzed the current able to pass through deformed CNTs using a tight-binding-based Green＇s function approach and determined that the current can be significantly suppressed by applying uniaxial compressive strain. Our method of predicting the electronic state of a deformed CNT based on the π-orbital angle is expected to be useful for predicting the electronic properties of CNT-based electronic devices and sensors.展开更多
The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dy...The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dynamics simulation,etc,applied to homogeneous and heterogeneous systems.Firstly,we examined the elastic properties based on electronic structure calculations in a homogeneous system and attributed the physical origin of the loss of ductility with increasing Si content to the combined effects of magneto-volume and D03 ordering.As a typical example of a heterogeneity forming a microstructure,we focus on grain boundaries,and segregation behavior of Si atoms is studied through high-precision electronic structure calculations.Two kinds of segregation sites are identified:looser and tighter sites.Depending on the site,different segregation mechanisms are revealed.Finally,the dislocation behavior in the Fe-Si alloy is investigated mainly by molecular dynamics simulations combined with electronic structure calculations.The solid-solution hardening and softening are interpreted in terms of two kinds of energy barriers for kink nucleation and migration on a screw dislocation line.Furthermore,the clue to the peculiar work hardening behavior is discussed based on kinetic Monte Carlo simulations by focusing on the preferential selection of slip planes triggered by kink nucleation.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52222505,52321002,and 52005185)the Natural Science Foundation of Shanghai(Grant No.23ZR1415500)+2 种基金the China Scholarship Council(Grant No.202106740014)the Innovation Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-02-E00068)Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No.YESS20200029).
文摘Back stress has been proven to be the primary mechanism for superior mechanical properties of heterogeneous structures,but its quantitative contribution remains vague.The main purpose of this work is to clarify the contributions of back stress components,i.e.,intergranular residual stress and intragranular back stress,to the mechanical properties of heterogeneous structures based on the crystal plasticity theory.The results show that the intragranular back stress is smaller than the intergranular residual stress but contributes significantly to the strain hardening of the heterogeneous bimodal structures.In addition,the contributions of misorientation and grain size to back stress are quantitatively analyzed,and the near-linear relationship between hetero-deformation induced hardening and strain gradient is found.These findings emphasize the es-sential role of the intragranular back stress induced by strain gradient and provide an in-depth understanding of the elaborate roles of back stress in heterogeneous structures.
文摘Mechanical property of coarse grained and nano/ultrafine grained alloy 690 and their corrosion resistance after immersion in high temperature borate buffer solution were investigated. The grain refinement significantly enhances the tensile strength of the alloy 690. In addition, the grain refinement facilitates the formation of the deformation twin which improves the ductility of the alloy 690. It has been found that the grain refinement promotes to form more Cr2 O3 on the surface of the alloy 690 in high temperature borate buffer solution. At the same time, the grain refinement inhibits the formation of spinel type oxides.More hematite type oxides formed on nano/ultrafine grained alloy 690 improves its corrosion resistance in borate buffer solution. The hematite type oxides have a lower concentration of point defect than that of the spinel type oxides, which results in an excellent corrosion resistance of nano/ultrafine grained alloy 690. These results are supported by the Mott-Schottky analysis and the point defect model.
文摘The graphene coating was deposited on the surface of Ni foam using the chemical vapor deposition process. A large amount of flower-like ZnCoOmicrospheres with short nanowires were formed on bare Ni foam by hydrothermal method, while large-scale ZnCoOnanowires arrays homogeneously aligned and separated adequately on Ni foam coated with graphene. This ZnCoOnanowire structure exhibited superior supercapacitors properties. The excellent supercapacitors were mainly attributed to the large specific surface and the porosity on the nanowires which promoted the electrons and ions transportation. In addition, graphene improved conductivity of substrate for current collecting.
文摘For the assessment of the carbon dioxide (CO2) storage potential of water-filled reservoir rocks (i.e., saline aquifers), it should be first important step for a thorough understanding of the effect of water content on CO2/water/rock interactions during CO2 injection. The purpose of this study is to examine the CO2 sorption amount for Kimachi sandstone and Berea sandstone at different water content using the manometric method at temperature of 50?C and pressures of up to 20 MPa. Our results document that a significant quantity of CO2 was sorbed on the two types of sandstone on all water-saturated bases, which corresponded to the amount adsorbed on the air-dry basis. Also, all the wet samples had significantly higher sorption capacity than the theoretical values calculated from the solubility model based on dissolution of CO2 in pore water and the pore-filling model, which assumes that the pore volume unoccupied by water is filled with CO2. Furthermore, the observations indicated a certain degree of correlation between the sorbed amount and the water content, except at pressures below the critical point for Berea sandstone. This investigation points out that CO2 sorption is a possible mechanism in CO2 geological storage even under water-saturated conditions and that the mechanism of sorption on silica and silicate minerals plays an essential role in the reliable and accurate estimation of the CO2 storage capacity of water-saturated reservoirs.
基金Supported by Japan Society for the Promotion of Science KAKENHI(Grant No.18H05256).
文摘The low cycle fatigue strength properties of the additively manufactured Ti-6Al-4V alloy are experimentally investi-gated under proportional and nonproportional multiaxial loading.The fatigue tests were conducted using hollow cylinder specimens with and without heat treatments,at room temperature in air.Two fatigue tests were conducted:one for proportional loading and one for nonproportional loading.The proportional loading was represented by a push-pull strain path(PP)and the nonproportional loading by a circle strain path(Cl).The failure lives of the additively manufactured specimens were clearly reduced drastically by internal voids and defects.However,the sizes of the defects were measured,and the defects were found not to cause a reduction in fatigue strength above a critical size.The fracture surface was observed using scanning electron microscopy to investigate the fracture mechanisms of the additively manufactured specimens under the two types of strain paths.Different fracture patterns were recognized for each strain paths;however,both showed retention of the crack propagation,despite the presence of numerous defects,probably because of the interaction of the defects.The crack propagation properties of the materials with numerous defects under nonproportional multiaxial loading were clarified to increase the reliability of the additively manufactured components.
文摘The abundant nitrogen in the Earth’s atmosphere can be interpreted as the result of endothermic nuclear transmutation of carbon and oxygen atom pairs in (Ca, D) CO3 or CaCO3 aragonite lattice of Earth’s crust from the Archean era to the present time, by physical catalytic help of excited electrons e* generated by stick sliding due to plate tectonics and geoneutrinos ν by the radioactive decay of elements such as uranium and thorium in Earth’s mantle: through a nuclear attraction effect that is due to deuteron catalysis of nitrogen formation. The relationship between the critical temperature T and the critical pressure P for the nuclear transmutation is expressed as 7253 × e-0.014P, and the formation of nitrogen in the mantle is possible at temperatures ≥ 2510 K and pressure ≥ 58 GPa.
基金supported by the National Natural Science Foundation ofChina(grant no.92270104)partially by Grant-in-Aids for Scientific Research on innovative Areas on High Entropy Alloys through the grant number P18H05454 of JSPS,Japan.Authors acknowledge the Center of High Performance Computing,Tsinghua University and the Center for Computational Materials Science of the Institute for Materials Research,Tohoku University for the support of the supercomputing facilities.Figure 1 is drawn by FigDraw.
文摘Using machine learning to predict and design materials is an important mean of accelerating material development.One way to improve the accuracy of machine learning predictions is to introduce material structures as descriptors.However,thecomplexity ofcomputing material structures limits the practical use of these models.To address this challenge and improve prediction accuracy in small data sets,we develop a generative network framework:Elemental Features enhanced and Transferring corrected data augmentation in Generative Adversarial Networks(EFTGAN).Combining the elemental convolution technique with Generative Adversarial Networks(GAN),EFTGAN provides a robust and efficient approach for generating data containing elemental and structural information that can be used not only for data augmentation to improve model accuracy,but also for prediction when the structures are unknown.Applying this framework to the FeNiCoCrMn/Pd high-entropy alloys,we successfully improve the prediction accuracy in a small data set and predict the concentrationdependent formation energies,lattices,and magnetic moments in quinary systems.This study provides a new algorithm to improve the performance and usability of deep learning with structures as inputs,which is effective and accurate for the prediction and development of materials for small data sets.
基金This research was supported by the Tohoku-Tsinghua Collaborative Research Funds,the National Natural Science Foundation of China under Grant No.92270104the Tsinghua University Initiative Scientific Research Program,Grants-in-Aid for Scientific Research on Innovative Areas on High Entropy Alloys through the grant number P18H05454 of JSPS。
文摘When developing deep learning models for accurate property prediction,it is sometimes overlooked that some material physical properties are insensitive to the local atomic environment.Here,we propose the elemental convolution neural networks(ECNet)to obtain more general and global element-wise representations to accurately model material properties.It shows better prediction in properties like band gaps,refractive index,and elastic moduli of crystals.To explore its application on high-entropy alloys(HEAs),we focus on the FeNiCoCrMn/Pd systems based on the data of DFT calculation.The knowledge from less-principal element alloys can enhance performance in HEAs by transfer learning technique.Besides,the element-wise features from the parent model as universal descriptors retain good accuracy at small data limits.Using this framework,we obtain the concentration-dependent formation energy,magnetic moment and local displacement in some sub-ternary and quinary systems.The results enriched the physics of those high-entropy alloys.
文摘Recently, substantial attention has been paid to the strain sensitivity of the carbon nanotubes＇ （CNTs＇） electronic properties. In this study, the relationships between the geometric structures and electronic states of zigzag CNTs under uniaxial compressive strain were investigated. We found that different factors dominate the electronic states of zigzag CNTs depending on the strain regions： the initial stage of the strain loading, which lasts until column-buckling deformation begins, and the strain regions corresponding to column- and shell-buckling deformations. Because shell-buckling deformation significantly increases the re-orbital angle, the angle between the π orbital axis vectors of adjacent atoms, strong localization of the density of states （LDOS） occurs in the buckled area. We also analyzed the current able to pass through deformed CNTs using a tight-binding-based Green＇s function approach and determined that the current can be significantly suppressed by applying uniaxial compressive strain. Our method of predicting the electronic state of a deformed CNT based on the π-orbital angle is expected to be useful for predicting the electronic properties of CNT-based electronic devices and sensors.
基金supported by the JST Industry-Academia Collaborative Programs,“Materials Strength from Hamiltonian”,and by the Elements Strategy Initiative for Structural Materials(ESISM)through MEXT,Japansupported by a Grant-in-Aid for Scientific Research on Innovative Area“Bulk Nanostructured Metals”and by the Computational Materials Science Initiative(CMSI),MEXT,Japanthe K computer provided by the RIKEN Advanced Institute for Computational Science through the HPCI System Research project(Project ID:hp130016,hp140233,hp150235).
文摘The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dynamics simulation,etc,applied to homogeneous and heterogeneous systems.Firstly,we examined the elastic properties based on electronic structure calculations in a homogeneous system and attributed the physical origin of the loss of ductility with increasing Si content to the combined effects of magneto-volume and D03 ordering.As a typical example of a heterogeneity forming a microstructure,we focus on grain boundaries,and segregation behavior of Si atoms is studied through high-precision electronic structure calculations.Two kinds of segregation sites are identified:looser and tighter sites.Depending on the site,different segregation mechanisms are revealed.Finally,the dislocation behavior in the Fe-Si alloy is investigated mainly by molecular dynamics simulations combined with electronic structure calculations.The solid-solution hardening and softening are interpreted in terms of two kinds of energy barriers for kink nucleation and migration on a screw dislocation line.Furthermore,the clue to the peculiar work hardening behavior is discussed based on kinetic Monte Carlo simulations by focusing on the preferential selection of slip planes triggered by kink nucleation.
