By using molecular dynamics computer simulation at atomic level, the effects of single dislocation and dipole dislocations on nucleation and growth of martensitic transformation have been studied. It was found that o...By using molecular dynamics computer simulation at atomic level, the effects of single dislocation and dipole dislocations on nucleation and growth of martensitic transformation have been studied. It was found that only the location of tension or compression stress fields of the dislocations are favorable for martensite nucleation in NiAl alloy and the dislocations can move to accommodate partly the transformation strain during the nucleation and growth of martensite. Combined with the molecular dynamics simulation, a two dimensional simulation for martensite morphology based on a dislocation model has been performed. Many factors related to martensitic transformation were considered, such as supercooling, interface energy, shear strain, normal strain and hydrostatic pressure. Different morphologies of martensites, similar to lath, lenticular, thin plate, couple-plate and lenticular couple-plate martensites observed in Fe-C and Fe-Ni-C alloys, were obtained.展开更多
The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental results.I...The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental results.In numerical simulation aspect, finite difference(FD)method and modified cellular automaton(MCA)model were used to simulate the macro-temperature field, micro-concentration field,nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting operations.From the observed casting experiment,the preliminary grain morphologies are the directional columnar grains by the VCC process.The solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.展开更多
Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blo...Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of i PP and i PP/nano-CaCO_3 microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for i PP/nano-CaCO_3 composites, especially at high CO_2 concentration and back pressure, low mold temperature and injection speed, and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process, with the application of the measured ScCO_2 solubility and diffusion data for i PP and i PP/nano-Ca CO_3 composites respectively. For neat i PP, the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However, for i PP/nano-CaCO_3 composites, the correction factor for nucleation activation energy F and the pre-exponential factor of nucleation rate f_0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f_0 can be used to predict the microcellular injection molding process for i PP/nano-CaCO_3 composites by Moldex 3D.展开更多
We build a general multi-length-scale morphology model with mixing phase and pure phase fibril structure,and simulate corresponding organic solar cells performance.Systematical multi-length-scale morphology optimizati...We build a general multi-length-scale morphology model with mixing phase and pure phase fibril structure,and simulate corresponding organic solar cells performance.Systematical multi-length-scale morphology optimization process by changing the proportion of mixing phase and pure phase in different period width cases shows a clear correlation between period width and device performance that a smaller period width with appropriate proportion of mixing phase and fibril structure is advantageous to achieve high-performance devices.Experiments on multiple donor/acceptor blends have been carried out by varying the composition and processing condition,which afford good structure-performance correlation that supports the model prediction.It is demonstrated that building such a multi-length-scale morphology merging the synergistic effects of mixing and pure phases is indeed an imperative avenue to improve device efficiency.展开更多
Morphological transformations of amphiphilic AB diblock copolymers in mixtures of a common solvent （S1） and a selective solvent （S2） for the B block are studied using the simulated annealing method. We focus on th...Morphological transformations of amphiphilic AB diblock copolymers in mixtures of a common solvent （S1） and a selective solvent （S2） for the B block are studied using the simulated annealing method. We focus on the morphological transformation depending on the fraction of the selective solvent Cs2, the concentration of the polymer Cp, and the polymers-solvent interactions εij （i = A, B; j = S1, S2）. Morphology diagrams are constructed as functions of Cp, Cs2, and/or εAs2. The copolymer morpho- logical sequence from dissolved → sphere → rod → ring/cage → vesicle is obtained upon increasing Cs2 at a fixed Cv. This morphology sequence is consistent with previous experimental observations. It is found that the selectivity of the selective solvent affects the self-assembled microstructure signifi- cantly. In particular, when tile interaction εBS2 is negative, aggregates of stacked lamellae dominate the diagram. The mechanisms of aggregate transformation and the formation of stacked lamellar ag- gregates are discussed by analyzing variations of the average contact numbers of the A or B monomers with monomers and with molecules of the two types of solvent, as well as the mean square end-to-end distances of chains. It is found that the basic morphological sequence of spheres to rods to vesicles and the stacked lamellar aggregates result from competition between the interfacial energy and the chain conformational entropy. Analysis of the vesicle structure reveals that the vesicle size increases with increasing Cp or with decreasing Cs2, but remains almost unchanged with variations in εAS2.展开更多
文摘By using molecular dynamics computer simulation at atomic level, the effects of single dislocation and dipole dislocations on nucleation and growth of martensitic transformation have been studied. It was found that only the location of tension or compression stress fields of the dislocations are favorable for martensite nucleation in NiAl alloy and the dislocations can move to accommodate partly the transformation strain during the nucleation and growth of martensite. Combined with the molecular dynamics simulation, a two dimensional simulation for martensite morphology based on a dislocation model has been performed. Many factors related to martensitic transformation were considered, such as supercooling, interface energy, shear strain, normal strain and hydrostatic pressure. Different morphologies of martensites, similar to lath, lenticular, thin plate, couple-plate and lenticular couple-plate martensites observed in Fe-C and Fe-Ni-C alloys, were obtained.
文摘The purpose of this study is to predict the morphologies in the solidification process for Cu-0.6Cr(mass fraction,%)alloy by vacuum continuous casting(VCC)and verify its accuracy by the observed experimental results.In numerical simulation aspect, finite difference(FD)method and modified cellular automaton(MCA)model were used to simulate the macro-temperature field, micro-concentration field,nucleation and grain growth of Cu-0.6Cr alloy using real data from actual casting operations.From the observed casting experiment,the preliminary grain morphologies are the directional columnar grains by the VCC process.The solidification morphologies by MCAFD model are in agreement with the result of actual casting experiment well.
基金Supported by the National High Technology Research and Development Program of China(2012AA040211)the National Natural Science Foundation of China(21306043)+2 种基金the Research Fund for the Doctoral Program of Higher Education of China(2012007412001920130074110013)the Fundamental Research Funds for the Central Universities
文摘Microcellular injection molding of neat isotactic polypropylene(iPP) and isotactic polypropylene/nano-calcium carbonate composites(i PP/nano-CaCO_3) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of i PP and i PP/nano-CaCO_3 microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for i PP/nano-CaCO_3 composites, especially at high CO_2 concentration and back pressure, low mold temperature and injection speed, and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process, with the application of the measured ScCO_2 solubility and diffusion data for i PP and i PP/nano-Ca CO_3 composites respectively. For neat i PP, the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However, for i PP/nano-CaCO_3 composites, the correction factor for nucleation activation energy F and the pre-exponential factor of nucleation rate f_0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f_0 can be used to predict the microcellular injection molding process for i PP/nano-CaCO_3 composites by Moldex 3D.
基金supported by the National Natural Science Foundation of China(51973110,21734009,22109094,21905102)the Program of Shanghai Science and Technology Commission Science and Technology Innovation Action Plan(20ZR1426200,20511103800,20511103802,20511103803)+1 种基金the Natural Science Foundation of Shandong Province,China(ZR2019LFG005)Key Research Project of Shandong Province(2020CXGC010403)。
文摘We build a general multi-length-scale morphology model with mixing phase and pure phase fibril structure,and simulate corresponding organic solar cells performance.Systematical multi-length-scale morphology optimization process by changing the proportion of mixing phase and pure phase in different period width cases shows a clear correlation between period width and device performance that a smaller period width with appropriate proportion of mixing phase and fibril structure is advantageous to achieve high-performance devices.Experiments on multiple donor/acceptor blends have been carried out by varying the composition and processing condition,which afford good structure-performance correlation that supports the model prediction.It is demonstrated that building such a multi-length-scale morphology merging the synergistic effects of mixing and pure phases is indeed an imperative avenue to improve device efficiency.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 21204040, 20904027, 21574071, 21528401, 20925414, and 91227121）, the Pro- gram for Changjiang Scholars and Innovative Research Team in University of China （PCSIRT） （Grant No. IRT1257）, and the 111 Project （Grant No. B16027）.
文摘Morphological transformations of amphiphilic AB diblock copolymers in mixtures of a common solvent （S1） and a selective solvent （S2） for the B block are studied using the simulated annealing method. We focus on the morphological transformation depending on the fraction of the selective solvent Cs2, the concentration of the polymer Cp, and the polymers-solvent interactions εij （i = A, B; j = S1, S2）. Morphology diagrams are constructed as functions of Cp, Cs2, and/or εAs2. The copolymer morpho- logical sequence from dissolved → sphere → rod → ring/cage → vesicle is obtained upon increasing Cs2 at a fixed Cv. This morphology sequence is consistent with previous experimental observations. It is found that the selectivity of the selective solvent affects the self-assembled microstructure signifi- cantly. In particular, when tile interaction εBS2 is negative, aggregates of stacked lamellae dominate the diagram. The mechanisms of aggregate transformation and the formation of stacked lamellar ag- gregates are discussed by analyzing variations of the average contact numbers of the A or B monomers with monomers and with molecules of the two types of solvent, as well as the mean square end-to-end distances of chains. It is found that the basic morphological sequence of spheres to rods to vesicles and the stacked lamellar aggregates result from competition between the interfacial energy and the chain conformational entropy. Analysis of the vesicle structure reveals that the vesicle size increases with increasing Cp or with decreasing Cs2, but remains almost unchanged with variations in εAS2.
