“Smaller is softer”is a reverse size dependence of strength,defying the“smaller is stronger”tenet.It usually results from surface-mediated displacive or diffusive deformation and is mainly found in some ultra-smal...“Smaller is softer”is a reverse size dependence of strength,defying the“smaller is stronger”tenet.It usually results from surface-mediated displacive or diffusive deformation and is mainly found in some ultra-small-scale(below tens of nanometers)metallic materials.Here,making use of the surface modifi-cation via ion beam irradiation,we bring the“smaller is softer”into being in a covalently-bonded,hard,and brittle material-amorphous Si(a-Si)at a much larger size regime(<∼500 nm).It is manifested as the transition from the quasi-brittle failure to the homogeneous plastic deformation as well as the de-creasing yield stress with sample volume reduction at the submicron-scale regime.An analytical model of hard core/superplastic shell has been proposed to explain the artificially-controllable size-dependent softening.This surface engineering pathway via ion irradiation is not only of particular interest to tai-lor the strength and deformation behaviors in small-sized a-Si or other covalently-bonded amorphous solids but also of practical relevance to the utility of a-Si in microelectronics and microelectromechanical systems.展开更多
The theory of magnetic circuit design, the constitutive equations of a magneto-theological fluid, and the load properties of belt conveyors were used to design a magneto-rheological soft starter test-bed. The magnetic...The theory of magnetic circuit design, the constitutive equations of a magneto-theological fluid, and the load properties of belt conveyors were used to design a magneto-rheological soft starter test-bed. The magnetic field distribution in the working gap was analyzed and the current-speed relationship was investigated. A mathematical model for the time response was deduced. The results show that a linear relationship between current and magnetic field is seen when the magnetic materials are not saturated and the magnetic field is uniform in the working section. The rotation speed of the driven shaft changes linearly with increasing time. The response is rapid and can be as short as milliseconds. This meets the starting requirements of belt conveyors.展开更多
基金The authors acknowledge the support from the National Key R&D Program of China(no.2022YFB3203600)the National Natural Science Foundation of China(no.52272162)+1 种基金the China Postdoctoral Science Foundation(Nos.2021T140535 and 2019M663696)the Alexander von Humboldt Foundation.L.T.thanks Dr.Christoph Meyer and Prof.Vasily Moshnyaga for their help in Raman spectroscopy measurement.M.L.acknowledges the support from Prof.Xixiang Zhang and the nanofabrication core lab at King Abdullah University of Science and Technology for the nanofabrication facilities.
文摘“Smaller is softer”is a reverse size dependence of strength,defying the“smaller is stronger”tenet.It usually results from surface-mediated displacive or diffusive deformation and is mainly found in some ultra-small-scale(below tens of nanometers)metallic materials.Here,making use of the surface modifi-cation via ion beam irradiation,we bring the“smaller is softer”into being in a covalently-bonded,hard,and brittle material-amorphous Si(a-Si)at a much larger size regime(<∼500 nm).It is manifested as the transition from the quasi-brittle failure to the homogeneous plastic deformation as well as the de-creasing yield stress with sample volume reduction at the submicron-scale regime.An analytical model of hard core/superplastic shell has been proposed to explain the artificially-controllable size-dependent softening.This surface engineering pathway via ion irradiation is not only of particular interest to tai-lor the strength and deformation behaviors in small-sized a-Si or other covalently-bonded amorphous solids but also of practical relevance to the utility of a-Si in microelectronics and microelectromechanical systems.
基金supported by the National Natural Science Foundation of China (Nos. 50975275 and 51075386)
文摘The theory of magnetic circuit design, the constitutive equations of a magneto-theological fluid, and the load properties of belt conveyors were used to design a magneto-rheological soft starter test-bed. The magnetic field distribution in the working gap was analyzed and the current-speed relationship was investigated. A mathematical model for the time response was deduced. The results show that a linear relationship between current and magnetic field is seen when the magnetic materials are not saturated and the magnetic field is uniform in the working section. The rotation speed of the driven shaft changes linearly with increasing time. The response is rapid and can be as short as milliseconds. This meets the starting requirements of belt conveyors.
