The influence of the interface exchange coupling on the magnetization reversal process for a FePt/α-Fe/FePt tri-layer structure has been studied through a micromagnetic approach.The analytical formula of the nucleati...The influence of the interface exchange coupling on the magnetization reversal process for a FePt/α-Fe/FePt tri-layer structure has been studied through a micromagnetic approach.The analytical formula of the nucleation field has been derived.It is found that the nucleation field increases as the interface coupling constant rises.Especially when the thickness of the soft layer is small,the influence of the exchange coupling on the nucleation field is significant.The angular distributions of the magnetization for various exchange coupling constants have been obtained by numerical calculation.It is found that the angular distribution of the magnetization is discontinuous at the interface of the hard and soft layers.In the meantime,the pinning field decreases with the increase of the thickness of the soft layer and the exchange coupling constant.展开更多
A phase-field method was employed to study the influence of elastic field on the nucleation and microstructure evolution. Two kinds of nucleation process were considered： one using fixed nucleation probability and th...A phase-field method was employed to study the influence of elastic field on the nucleation and microstructure evolution. Two kinds of nucleation process were considered： one using fixed nucleation probability and the other calculated from the classical nucleation theory. In the latter case, the simulated results show that the anisotropic elastic strain field yields significant effects on the behavior of nucleation. With a large lattice misfit between the matrixes and the precipitates, the nucleation process does not appear fully random but displays some spatial correlation and has a preference for the elastic soft direction. However, with a small lattice misfit, this bias does not look quite clear. On the contrary, in the case of fixed nucleation probability, the elastic field has no influence on the nucleation process. The lattice mismatch also exerts influences on the microstructure morphology： with lattice mismatch becoming larger, the microstructure proves to align along the elastic soft direction.展开更多
The influence of a high magnetic field(HMF)on the nucleation kinetics of paramagnetic aluminum and diamagnetic zinc melts has been investigated by differential thermal analysis(DTA).It is found that the application of...The influence of a high magnetic field(HMF)on the nucleation kinetics of paramagnetic aluminum and diamagnetic zinc melts has been investigated by differential thermal analysis(DTA).It is found that the application of an HMF increases the undercooling of pure aluminum and pure zinc at the same heatingcooling rates.Moreover,the quantitative analysis of activation energy calculated from the DTA results using the Kissinger method manifests that the HMF reduces the activation energy of pure aluminum and pure zinc.Regardless of magnetism,the nucleation frequency under an HMF is higher than that without an HMF.Furthermore,the increase in undercooling under the HMF is mainly attributed to the increase of the contact angle,calculated by the functional relationship between the cooling rate and undercooling.This result is consistent with the increase of the calculated nucleation work for pure aluminum and pure zinc.Additionally,the increase in undercooling caused by the HMF is partly ascribed to the magnetic field-induced suppression of thermal convection in the undercooled melt.展开更多
A travel ing magnetic field, a power ultrasonic field, and a compound field were used separately during the horizontal continuous casting process of Al-1wt.%Si al oy. The samples obtained were characterized using an o...A travel ing magnetic field, a power ultrasonic field, and a compound field were used separately during the horizontal continuous casting process of Al-1wt.%Si al oy. The samples obtained were characterized using an optical microscope, a scanning electron microscope, a tensile testing machine, and an electron probe microscopic analyzer to test the microstructures, properties, and element distribution of the samples. The results show that the application of a single ifeld can enhance the mechanical properties and reduce the segregation of Si element in Al-1wt.%Si alloy to some extent. The application of a compound field can obtain the best reifnement and homogeneity of the Si element in the al oy, leading to the highest increase of tensile strength and elongation among the three applied ifelds. The mechanism of the action of external ifelds on the reifnement of microstructures and homogeneity of the Si element is discussed and the compound ifeld is considered to be an effective method to achieve high quality Al alloys.展开更多
The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled ...The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled metallic melts with respect to undercooling was studied respectively based on two kinds of forms of local free energy density. The calculation results show that, with the increase of undercooling, the critical nucleus does not show bulk properties, and the nucleation barrier height decreases gradually and deviates more and more from that predicted by the classical nucleation theory in both cases. The physical spinodal occurs for a specific form of the local free energy density, where the nucleation barrier height vanishes when the undercooling reaches a critical value and the reduced nucleation barrier height can be expressed by a function of the ratio of undercooling to critical undercooling.展开更多
In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external ...In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external magnetic field on the solidification is characterized by the critical temperature and radial distribution functions.Our computational results show that under external magnetic field,the solidification point tends to decrease significantly.By further analyzing the diffusion coefficients and viscosity,we attribute the effect to the stronger fluctuation of liquid iron atoms driven by the external magnetic field.展开更多
We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the und...We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the underneath ITO substrate have two different nucleation rates in the initial stage of heterogeneous nucleation process, the subsequent ZnO growth on the quick nucleating area takes place under diffusion control and is able to confine the synthesis of ZnO nanorods to specific locations. The concentrations of zinc nitrate and HMT are well adjusted to show the possibility of the new route for the patterning of the ZnO nanorods. Furthermore, the nanorods pattern was characterized by X-ray diffraction and photoluminescence and the performance of field emission property from ZnO nanorod patterns was investigated. The ZnO nanorods pattern with a good alignment also shows a good field enhancement behavior with a high value of the field enhancement factor.展开更多
Multi-hierarchical self-assembly （MHSA） is a key process responsible for the spontaneous formation of many complex structures. However, because of the complexity of the process, the underlying mechanism remains larg...Multi-hierarchical self-assembly （MHSA） is a key process responsible for the spontaneous formation of many complex structures. However, because of the complexity of the process, the underlying mechanism remains largely unclear. Thus, a deeper understanding of MHSA is required, especially for the preparation of MHSA systems via bottom-up methodologies. We show here, experimentally and theoretically, that the complex-formation MHSA of peptide nanotube films can be controlled solely by manipulating the experimental parameter of humidity. Furthermore, we identify growth-front nucleation （GFN; the formation of new grains at the perimeter） as the physical background for the observed morphological transitions by correlating experimental observations with phase-field modeling of the morphological evolution. Our findings indicate a simple way to control multi-hierarchical morphologies, crucial for the employment of bottom-up techniques in constructing complex structures for practical applications.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 10747007)the Scientific Research Foundation for Returned Overseas Chinese Scholars,State Education Ministry
文摘The influence of the interface exchange coupling on the magnetization reversal process for a FePt/α-Fe/FePt tri-layer structure has been studied through a micromagnetic approach.The analytical formula of the nucleation field has been derived.It is found that the nucleation field increases as the interface coupling constant rises.Especially when the thickness of the soft layer is small,the influence of the exchange coupling on the nucleation field is significant.The angular distributions of the magnetization for various exchange coupling constants have been obtained by numerical calculation.It is found that the angular distribution of the magnetization is discontinuous at the interface of the hard and soft layers.In the meantime,the pinning field decreases with the increase of the thickness of the soft layer and the exchange coupling constant.
基金National Natural Science Foundation of China (50401013)
文摘A phase-field method was employed to study the influence of elastic field on the nucleation and microstructure evolution. Two kinds of nucleation process were considered： one using fixed nucleation probability and the other calculated from the classical nucleation theory. In the latter case, the simulated results show that the anisotropic elastic strain field yields significant effects on the behavior of nucleation. With a large lattice misfit between the matrixes and the precipitates, the nucleation process does not appear fully random but displays some spatial correlation and has a preference for the elastic soft direction. However, with a small lattice misfit, this bias does not look quite clear. On the contrary, in the case of fixed nucleation probability, the elastic field has no influence on the nucleation process. The lattice mismatch also exerts influences on the microstructure morphology： with lattice mismatch becoming larger, the microstructure proves to align along the elastic soft direction.
基金financially supported by the National Natural Science Foundation of China(Nos.51571056,51904183 and 51690164)“Shuguang Program”from Shanghai Municipal Education Commission+1 种基金China Postdoctoral Science Foundation(Nos.2018M640375 and 2019T120330)the Shanghai Science and Technology Committee Grant(Nos.19XD1401600 and 19010500300)。
文摘The influence of a high magnetic field(HMF)on the nucleation kinetics of paramagnetic aluminum and diamagnetic zinc melts has been investigated by differential thermal analysis(DTA).It is found that the application of an HMF increases the undercooling of pure aluminum and pure zinc at the same heatingcooling rates.Moreover,the quantitative analysis of activation energy calculated from the DTA results using the Kissinger method manifests that the HMF reduces the activation energy of pure aluminum and pure zinc.Regardless of magnetism,the nucleation frequency under an HMF is higher than that without an HMF.Furthermore,the increase in undercooling under the HMF is mainly attributed to the increase of the contact angle,calculated by the functional relationship between the cooling rate and undercooling.This result is consistent with the increase of the calculated nucleation work for pure aluminum and pure zinc.Additionally,the increase in undercooling caused by the HMF is partly ascribed to the magnetic field-induced suppression of thermal convection in the undercooled melt.
基金financially supported by the Key Project of Science and Technology Department of Henan Province(142102210449)the Key Project of Science and Technology of Henan Educational Committee,China(No.13A150518)the Postdoctoral Science Foundation of Henan Province
文摘A travel ing magnetic field, a power ultrasonic field, and a compound field were used separately during the horizontal continuous casting process of Al-1wt.%Si al oy. The samples obtained were characterized using an optical microscope, a scanning electron microscope, a tensile testing machine, and an electron probe microscopic analyzer to test the microstructures, properties, and element distribution of the samples. The results show that the application of a single ifeld can enhance the mechanical properties and reduce the segregation of Si element in Al-1wt.%Si alloy to some extent. The application of a compound field can obtain the best reifnement and homogeneity of the Si element in the al oy, leading to the highest increase of tensile strength and elongation among the three applied ifelds. The mechanism of the action of external ifelds on the reifnement of microstructures and homogeneity of the Si element is discussed and the compound ifeld is considered to be an effective method to achieve high quality Al alloys.
基金supported by the National Natural Science Foundation of China(Grant No. 51101059)China Postdoctoral Science Foundation (Grant No.20110490874)
文摘The phase-field model of a liquid-to-solid transition was constructed where the model parameters were linked quantitatively to the interfacial properties, and the variation of nucleation barrier height in undercooled metallic melts with respect to undercooling was studied respectively based on two kinds of forms of local free energy density. The calculation results show that, with the increase of undercooling, the critical nucleus does not show bulk properties, and the nucleation barrier height decreases gradually and deviates more and more from that predicted by the classical nucleation theory in both cases. The physical spinodal occurs for a specific form of the local free energy density, where the nucleation barrier height vanishes when the undercooling reaches a critical value and the reduced nucleation barrier height can be expressed by a function of the ratio of undercooling to critical undercooling.
基金funded by the National Natural Science Foundation of China(No.22173057 for Yongle Li and No.51690164 for Xi Li)the Foundation of Shanghai Science and Technology Commission(No.21JC1402700 and No.21DZ2304900 for Yongle Li)supported by Open Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University。
文摘In this work,the solidification of liquid iron with or without external magnetic field was investigated by using two molecular dynamics methods,namely direct cooling and two-phase simulation.The influence of external magnetic field on the solidification is characterized by the critical temperature and radial distribution functions.Our computational results show that under external magnetic field,the solidification point tends to decrease significantly.By further analyzing the diffusion coefficients and viscosity,we attribute the effect to the stronger fluctuation of liquid iron atoms driven by the external magnetic field.
文摘We provide a new way to prepare ZnO nanorods pattern from the solution composed of hexamethylenetetramine （HMT） and Zn（NO3）2. The substrate is ITO substrate covered by well ordered Au islands. Since Au and the underneath ITO substrate have two different nucleation rates in the initial stage of heterogeneous nucleation process, the subsequent ZnO growth on the quick nucleating area takes place under diffusion control and is able to confine the synthesis of ZnO nanorods to specific locations. The concentrations of zinc nitrate and HMT are well adjusted to show the possibility of the new route for the patterning of the ZnO nanorods. Furthermore, the nanorods pattern was characterized by X-ray diffraction and photoluminescence and the performance of field emission property from ZnO nanorod patterns was investigated. The ZnO nanorods pattern with a good alignment also shows a good field enhancement behavior with a high value of the field enhancement factor.
基金Acknowledgements This work has been supported by the Israel Science Foundation （No. 434/12） and by the National Agency for Research, Development, and Innovation, Hungary under contract OTKA-K-115959.
文摘Multi-hierarchical self-assembly （MHSA） is a key process responsible for the spontaneous formation of many complex structures. However, because of the complexity of the process, the underlying mechanism remains largely unclear. Thus, a deeper understanding of MHSA is required, especially for the preparation of MHSA systems via bottom-up methodologies. We show here, experimentally and theoretically, that the complex-formation MHSA of peptide nanotube films can be controlled solely by manipulating the experimental parameter of humidity. Furthermore, we identify growth-front nucleation （GFN; the formation of new grains at the perimeter） as the physical background for the observed morphological transitions by correlating experimental observations with phase-field modeling of the morphological evolution. Our findings indicate a simple way to control multi-hierarchical morphologies, crucial for the employment of bottom-up techniques in constructing complex structures for practical applications.
