A geometric analysis technique for crystal growth and microstructure development in single-crystal welds had been previously developed.And the effect of welding conditions on the tendency of stray grains formation dur...A geometric analysis technique for crystal growth and microstructure development in single-crystal welds had been previously developed.And the effect of welding conditions on the tendency of stray grains formation during solidification was researched.In the present work,these analytical methods were further extended.Combined with an original vectorization method,a 3D Rosenthal solution was used to determine thermal conditions of the welds.Afterward,the dendrite growth orientation,the dendrite growth velocity and the thermal gradient along dendrite direction were calculated and lively plotted.Finally,the tendency of stray grains formation in the solidification front was forecasted and its distribution was presented with a 3D plot.The results indicate that substrate orientation has some impacts on the crystal growth pattern,dendrite growth velocity,distribution of thermal gradient and stray grain.Based on the research methods proposed in this work,any substrate crystallographic orientation can be studied,and predicted stray grains distribution can be visualized.展开更多
Effects of Re on the formation of surface eutectics have been investigated by using Ni-base single crystal superalloys with different Re additions. It was found that Re promotes the segregation of Al and Ta to the eut...Effects of Re on the formation of surface eutectics have been investigated by using Ni-base single crystal superalloys with different Re additions. It was found that Re promotes the segregation of Al and Ta to the eutectic melt, leading to an increase of the surface and internal eutectics. In addition, the addition of Re also increased the freezing range, the local solidification time, and the permeability of the dendritic network within the mushy zone. These factors ultimately promoted the outflow of the interdendritic residual liquid with the action of solidification shrinkage, and led to the formation of more surface eutectics. In contrast, the addition of Re had no obvious influence on the surface eutectic microstructures.展开更多
A vectorization analysis technique for crystal growth and microstructure development in single-crystal weld was developed in our previous work. Based on the vectorization method, crystal growth and stray grain distrib...A vectorization analysis technique for crystal growth and microstructure development in single-crystal weld was developed in our previous work. Based on the vectorization method, crystal growth and stray grain distribution in laser surface remelting of single crystal superalloy CMSX-4 were investigated in com- bination of simulations with experimental observations. The energy distribution of laser was taken into consideration in this research. The experimental results demonstrate that the simulation model applies well in the prediction of dendrite growth direction. Moreover, the prediction of stray grain distribution works well except for the region of dendrites growing along the [100] direction.展开更多
The adsorption of one monolayer Fe atoms on an ideal GaAs (100) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on Ga- and As-terminatedsurfa...The adsorption of one monolayer Fe atoms on an ideal GaAs (100) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on Ga- and As-terminatedsurface are considered separately. A monolayer of S atoms is used to saturate the dangling bonds on one of the supercellsurfaces. Energies of adsorption systems of an Fe atom on different sites are calculated, and the charge transfers areinvestigated. It is found that Fe-As interaction is stronger than Fe-Ga interaction and Fe atoms prefer to be adsorbed onthe As-terminated surface. It is possible for the adsorbed Fe atoms to sit below the As-terminated surface resulting inan Fe-Ga-As mixed layer. The layer projected density states are calculated and compared with that of the clean surface.展开更多
In the current study, two novel Knoevenagel condensation products of substituted napthofuran-2-carbaldehydes were designed, synthesized and characterized. In order to study the intermolecular interactions of titl...In the current study, two novel Knoevenagel condensation products of substituted napthofuran-2-carbaldehydes were designed, synthesized and characterized. In order to study the intermolecular interactions of title compounds, single crystals were grown by slow evaporation solution growth technique at </span><span style="font-family:Verdana;">r</span><span style="font-family:Verdana;">oom temperature and crystal structure has been determined by single crystal X-ray diffraction technique. Both the molecule</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> crystallize in the monoclinic centrosymmetric space group </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;">2</span><sub><span style="font-size:12px;font-family:Verdana;">1</span></sub><span style="font-family:Verdana;">/</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;"> with one molecule in the asymmetric unit. In compound </span><b><span style="font-family:Verdana;">[4] </span></b><span style="font-family:Verdana;">the molecules are connected via bifurcated C-H···O=C and C-H···N=C</span></span><span style="font-family:Verdana;"> </span><span style="font-family:""><span style="font-family:Verdana;">H-bonds and van der Waals interactions forming a layered structure, whereas in compound </span><b><span style="font-family:Verdana;">[5a</span></b></span><span style="font-family:Verdana;"><b>]</b></span><span style="font-family:""><span style="font-family:Verdana;"> the molecular conformation is stabilized via intramolecular C-H···O H-bond and molecule interacts with other molecule generated via 2</span><sub><span style="font-size:12px;font-family:Verdana;">1</span></sub><span style="font-family:Verdana;">-screw </span><i><span style="font-family:Verdana;">via</span></i><span style="font-family:Verdana;"> bifurcated C-H···O=</span></span><span style="font-family:Verdana;">C along with C-H···N=C H-bonds, which are interacting with nitro- of ot</span><span style="font-family:Verdana;">her molecule generated via same symmetry operation, forming bifurcated C-H···O-N </span><span style="font-family:Verdana;">H-bonds, which helps in formation of molecular sheet-like structure.</span><span style="font-family:Verdana;">Further, in order to understand the various type</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> and nature of intermolecular interactions</span><span style="font-family:Verdana;"> in the supramolecular structure Hirshfeld</span><span style="font-family:Verdana;"> surface analysis</span><span style="font-family:Verdana;"> and fingerprint plot analysis was carried out.展开更多
The adsorption of a half monolayer of Mg atoms on the Si（100）-（2×1） surface is studied by using the self-consistent tight binding linear muffin-tin orbital method.Energies of the adsorption systems of Mg atom...The adsorption of a half monolayer of Mg atoms on the Si（100）-（2×1） surface is studied by using the self-consistent tight binding linear muffin-tin orbital method.Energies of the adsorption systems of Mg atoms on the different sites are calculated.It has been found that the adsorbed Mg atoms are more favorable on the cave site above the surface than any other sites on the Si（100）-（2×1） surface and a metastable shallow site also exists above the surface.This is in agreement with the experimental results.The charge transfer and the layer projected density of states are also studied.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51401210 and51271186)the National High Technology Research and Development Program of China(No.2014AA041701)
文摘A geometric analysis technique for crystal growth and microstructure development in single-crystal welds had been previously developed.And the effect of welding conditions on the tendency of stray grains formation during solidification was researched.In the present work,these analytical methods were further extended.Combined with an original vectorization method,a 3D Rosenthal solution was used to determine thermal conditions of the welds.Afterward,the dendrite growth orientation,the dendrite growth velocity and the thermal gradient along dendrite direction were calculated and lively plotted.Finally,the tendency of stray grains formation in the solidification front was forecasted and its distribution was presented with a 3D plot.The results indicate that substrate orientation has some impacts on the crystal growth pattern,dendrite growth velocity,distribution of thermal gradient and stray grain.Based on the research methods proposed in this work,any substrate crystallographic orientation can be studied,and predicted stray grains distribution can be visualized.
基金supported by the National Natural Science Foundation of China (Nos. 51271186 and 51001103)
文摘Effects of Re on the formation of surface eutectics have been investigated by using Ni-base single crystal superalloys with different Re additions. It was found that Re promotes the segregation of Al and Ta to the eutectic melt, leading to an increase of the surface and internal eutectics. In addition, the addition of Re also increased the freezing range, the local solidification time, and the permeability of the dendritic network within the mushy zone. These factors ultimately promoted the outflow of the interdendritic residual liquid with the action of solidification shrinkage, and led to the formation of more surface eutectics. In contrast, the addition of Re had no obvious influence on the surface eutectic microstructures.
基金financially supported by the National Natural Science Foundation of China (NSFC) under grant Nos. 51401210 and 51271186the National High Technology Research and Development Program (863 Program) of China under grant No. 2014AA041701
文摘A vectorization analysis technique for crystal growth and microstructure development in single-crystal weld was developed in our previous work. Based on the vectorization method, crystal growth and stray grain distribution in laser surface remelting of single crystal superalloy CMSX-4 were investigated in com- bination of simulations with experimental observations. The energy distribution of laser was taken into consideration in this research. The experimental results demonstrate that the simulation model applies well in the prediction of dendrite growth direction. Moreover, the prediction of stray grain distribution works well except for the region of dendrites growing along the [100] direction.
文摘The adsorption of one monolayer Fe atoms on an ideal GaAs (100) surface is studied by using the self-consistent tight-binding linear muffin-tin orbital method. The Fe adatom chemisorption on Ga- and As-terminatedsurface are considered separately. A monolayer of S atoms is used to saturate the dangling bonds on one of the supercellsurfaces. Energies of adsorption systems of an Fe atom on different sites are calculated, and the charge transfers areinvestigated. It is found that Fe-As interaction is stronger than Fe-Ga interaction and Fe atoms prefer to be adsorbed onthe As-terminated surface. It is possible for the adsorbed Fe atoms to sit below the As-terminated surface resulting inan Fe-Ga-As mixed layer. The layer projected density states are calculated and compared with that of the clean surface.
文摘In the current study, two novel Knoevenagel condensation products of substituted napthofuran-2-carbaldehydes were designed, synthesized and characterized. In order to study the intermolecular interactions of title compounds, single crystals were grown by slow evaporation solution growth technique at </span><span style="font-family:Verdana;">r</span><span style="font-family:Verdana;">oom temperature and crystal structure has been determined by single crystal X-ray diffraction technique. Both the molecule</span><span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> crystallize in the monoclinic centrosymmetric space group </span><i><span style="font-family:Verdana;">P</span></i><span style="font-family:Verdana;">2</span><sub><span style="font-size:12px;font-family:Verdana;">1</span></sub><span style="font-family:Verdana;">/</span><i><span style="font-family:Verdana;">c</span></i><span style="font-family:Verdana;"> with one molecule in the asymmetric unit. In compound </span><b><span style="font-family:Verdana;">[4] </span></b><span style="font-family:Verdana;">the molecules are connected via bifurcated C-H···O=C and C-H···N=C</span></span><span style="font-family:Verdana;"> </span><span style="font-family:""><span style="font-family:Verdana;">H-bonds and van der Waals interactions forming a layered structure, whereas in compound </span><b><span style="font-family:Verdana;">[5a</span></b></span><span style="font-family:Verdana;"><b>]</b></span><span style="font-family:""><span style="font-family:Verdana;"> the molecular conformation is stabilized via intramolecular C-H···O H-bond and molecule interacts with other molecule generated via 2</span><sub><span style="font-size:12px;font-family:Verdana;">1</span></sub><span style="font-family:Verdana;">-screw </span><i><span style="font-family:Verdana;">via</span></i><span style="font-family:Verdana;"> bifurcated C-H···O=</span></span><span style="font-family:Verdana;">C along with C-H···N=C H-bonds, which are interacting with nitro- of ot</span><span style="font-family:Verdana;">her molecule generated via same symmetry operation, forming bifurcated C-H···O-N </span><span style="font-family:Verdana;">H-bonds, which helps in formation of molecular sheet-like structure.</span><span style="font-family:Verdana;">Further, in order to understand the various type</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> and nature of intermolecular interactions</span><span style="font-family:Verdana;"> in the supramolecular structure Hirshfeld</span><span style="font-family:Verdana;"> surface analysis</span><span style="font-family:Verdana;"> and fingerprint plot analysis was carried out.
文摘The adsorption of a half monolayer of Mg atoms on the Si（100）-（2×1） surface is studied by using the self-consistent tight binding linear muffin-tin orbital method.Energies of the adsorption systems of Mg atoms on the different sites are calculated.It has been found that the adsorbed Mg atoms are more favorable on the cave site above the surface than any other sites on the Si（100）-（2×1） surface and a metastable shallow site also exists above the surface.This is in agreement with the experimental results.The charge transfer and the layer projected density of states are also studied.
