Chemomechanics of materials is an exciting and fast growing field where mechanics meets chemistry. This perspective presents a brief overview of recent advance in the study of materials chemomechanics. We identify cha...Chemomechanics of materials is an exciting and fast growing field where mechanics meets chemistry. This perspective presents a brief overview of recent advance in the study of materials chemomechanics. We identify challenges and opportunities for tackling the long-standing and emerging problems for the field.展开更多
Measuring the temperature and deformation synchronously at elevated temperatures is technically challenging and has become a major concern in the evaluation of mechanical properties. In this study, a simple, easy-to-i...Measuring the temperature and deformation synchronously at elevated temperatures is technically challenging and has become a major concern in the evaluation of mechanical properties. In this study, a simple, easy-to-implement, yet effective monochromatic pyrometry is established for non-contact and full-field temperature measurements, which can significantly reduce the error caused by the camera’s channel crosstalk that commonly occurs in the existing improved two-color method. In addition, hightemperature digital image correlation, combined with band-pass filtering and monochromatic illumination, is applied for deformation measurement. Subsequently, an experimental system was set up to validate the accuracy of the proposed method,which consists of a CCD camera for image capturing, a blue bandpass filter for radiation suppression, blue light irradiation for light compensation, and an infrared pyrometer for temperature recording. The results of the thermal heating experiment on the C/SiC sample proved that the selection of camera channel R in monochromatic pyrometry can reduce the error by channel crosstalk,and the proposed method is applicable for synchronous measurement of temperature and deformation.展开更多
The application of silicon as ultrahigh capacity electrodes in lithiumion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a resul...The application of silicon as ultrahigh capacity electrodes in lithiumion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a result of its large volumetric change during lithiation and delithiation. Graphene coating is one feasible technique to mitigate the mechanical degradation of Si anode and improve its conductivity. In this paper, first-principles calculations are performed to study the atomic structure, charge transfer and sliding strength of the interface between lithiated silicon and graphene. Our results show that Li atoms segre- gate at the （lithiated） Si-graphene interface preferentially, donating electrons to graphene and enhancing the interfacial sliding resistance. Moreover, the interfacial cohesion and sliding strength can be further enhanced by introducing single-vacancy defects into graphene. These findings provide insights that can guide the design of stable and efficient anodes of silicon/graphene hybrids for energy storage applications.展开更多
High-entropy alloys, a new class of metallic materials, exhibit excellent mechanical properties at high temperatures. In spite of the worldwide interest, the underlying mechanisms for temperature dependence of mechani...High-entropy alloys, a new class of metallic materials, exhibit excellent mechanical properties at high temperatures. In spite of the worldwide interest, the underlying mechanisms for temperature dependence of mechanical properties of these alloys remain poorly understood. Here, we systemically investigate the mechanical behaviors and properties of Al_(1.2)CrFeCoNi(comprising a body-centered cubic phase) and Al_(0.3)CrFeCoNi(comprising a face-centered cubic phase) single-crystal micropillars with three orientations([100], [110], and [111]) at temperatures varying from 300 to 675 K by using in situ compression of micropillars inside a scanning electron microscope. The results show that the yield stresses of Al_(1.2)CrFeCoNi micropillars are insensitive to temperature changes, and their flow stresses and work hardening rates increase slightly with increasing temperature from 300 to550 K, which differs from the typical temperature dependence of yield/flow stresses in metals and alloys. In contrast,Al_(0.3)CrFeCoNi micropillars exhibit typical thermal softening. Furthermore, it is found that the Al_(1.2)CrFeCoNi micropillars exhibit a transition from homogenous deformation to localized deformation at a critical temperature, while the Al_(0.3)CrFeCoNi micropillars always maintain a well-distributed and fine slip deformation. Detailed transmission electron microscopy analyses reveal that dynamic recrystallization(involving dislocation tangles, and formation of dislocation cell structures and sub-grains)plays a key role in the observed temperature insensitivity of the yield stress and increasing flow stress(and work hardening rate)with increasing temperature in the Al_(1.2)CrFeCoNi micropillars, and that thermally activated dislocation slip leads to thermal softening of the Al_(0.3)CrFeCoNi micropillars. The differences in deformation modes and temperature dependence of the mechanical properties between Al_(1.2)CrFeCoNi and Al_(0.3)CrFeCoNi essentially originate from the differences in dislocation activities and slip systems since the two alloys adopt different phases. Our findings provide key insights in the temperature dependence of mechanical properties and deformation behaviors of high-entropy alloys with body-centered cubic and face-centered cubic phases.展开更多
文摘Chemomechanics of materials is an exciting and fast growing field where mechanics meets chemistry. This perspective presents a brief overview of recent advance in the study of materials chemomechanics. We identify challenges and opportunities for tackling the long-standing and emerging problems for the field.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11625207 and 11972326)the Fundamental Research Funds for the Central Universities(Grant No.2652019071)。
文摘Measuring the temperature and deformation synchronously at elevated temperatures is technically challenging and has become a major concern in the evaluation of mechanical properties. In this study, a simple, easy-to-implement, yet effective monochromatic pyrometry is established for non-contact and full-field temperature measurements, which can significantly reduce the error caused by the camera’s channel crosstalk that commonly occurs in the existing improved two-color method. In addition, hightemperature digital image correlation, combined with band-pass filtering and monochromatic illumination, is applied for deformation measurement. Subsequently, an experimental system was set up to validate the accuracy of the proposed method,which consists of a CCD camera for image capturing, a blue bandpass filter for radiation suppression, blue light irradiation for light compensation, and an infrared pyrometer for temperature recording. The results of the thermal heating experiment on the C/SiC sample proved that the selection of camera channel R in monochromatic pyrometry can reduce the error by channel crosstalk,and the proposed method is applicable for synchronous measurement of temperature and deformation.
基金support by U.S. Department of Energy through DOE EPSCo R Implementation Grant No. DESC0007074by the Assistant Secretary for Energy Efficiency and Renewable Energy, Vehicle Technologies Office of the U.S. Department of Energy under Contract No. DE-AC0205CH11231+2 种基金Subcontract No 7056410 under the Batteries for Advanced Transportation Technologies (BATT) Programfinancial support from the State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, through Grant No. MCMS-0414G01financial support from the National Basic Research of China through Grant No. 2015CB932500.
文摘The application of silicon as ultrahigh capacity electrodes in lithiumion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a result of its large volumetric change during lithiation and delithiation. Graphene coating is one feasible technique to mitigate the mechanical degradation of Si anode and improve its conductivity. In this paper, first-principles calculations are performed to study the atomic structure, charge transfer and sliding strength of the interface between lithiated silicon and graphene. Our results show that Li atoms segre- gate at the （lithiated） Si-graphene interface preferentially, donating electrons to graphene and enhancing the interfacial sliding resistance. Moreover, the interfacial cohesion and sliding strength can be further enhanced by introducing single-vacancy defects into graphene. These findings provide insights that can guide the design of stable and efficient anodes of silicon/graphene hybrids for energy storage applications.
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financial support from the National Natural Science Foundation of China (Grant Nos. 11522218, 11720101002)the Beijing Natural Science Foundation (Grant No. Z180014)+1 种基金the National Science and Technology Major Project (Grant No. 2017-VI-0003-0073)financial support from the National Science Foundation (Grant No. DMR-1709318)。
文摘High-entropy alloys, a new class of metallic materials, exhibit excellent mechanical properties at high temperatures. In spite of the worldwide interest, the underlying mechanisms for temperature dependence of mechanical properties of these alloys remain poorly understood. Here, we systemically investigate the mechanical behaviors and properties of Al_(1.2)CrFeCoNi(comprising a body-centered cubic phase) and Al_(0.3)CrFeCoNi(comprising a face-centered cubic phase) single-crystal micropillars with three orientations([100], [110], and [111]) at temperatures varying from 300 to 675 K by using in situ compression of micropillars inside a scanning electron microscope. The results show that the yield stresses of Al_(1.2)CrFeCoNi micropillars are insensitive to temperature changes, and their flow stresses and work hardening rates increase slightly with increasing temperature from 300 to550 K, which differs from the typical temperature dependence of yield/flow stresses in metals and alloys. In contrast,Al_(0.3)CrFeCoNi micropillars exhibit typical thermal softening. Furthermore, it is found that the Al_(1.2)CrFeCoNi micropillars exhibit a transition from homogenous deformation to localized deformation at a critical temperature, while the Al_(0.3)CrFeCoNi micropillars always maintain a well-distributed and fine slip deformation. Detailed transmission electron microscopy analyses reveal that dynamic recrystallization(involving dislocation tangles, and formation of dislocation cell structures and sub-grains)plays a key role in the observed temperature insensitivity of the yield stress and increasing flow stress(and work hardening rate)with increasing temperature in the Al_(1.2)CrFeCoNi micropillars, and that thermally activated dislocation slip leads to thermal softening of the Al_(0.3)CrFeCoNi micropillars. The differences in deformation modes and temperature dependence of the mechanical properties between Al_(1.2)CrFeCoNi and Al_(0.3)CrFeCoNi essentially originate from the differences in dislocation activities and slip systems since the two alloys adopt different phases. Our findings provide key insights in the temperature dependence of mechanical properties and deformation behaviors of high-entropy alloys with body-centered cubic and face-centered cubic phases.
