The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual o...The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 μm/s to 1500 μm/s. Indeed, dendrite to cell transition follows this sequence： dendrites→→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.展开更多
Biological and synthetic surfactants were compared in terms of their ability to reduce interfacial tension, change the thermodynamic characteristics of a pre-conditioned surface, and to modify the rheological properti...Biological and synthetic surfactants were compared in terms of their ability to reduce interfacial tension, change the thermodynamic characteristics of a pre-conditioned surface, and to modify the rheological properties of their respective formulations at two different temperatures. Both classes of suffactants were able to reduce the inteffacial tension of their formulations to a similar level. However, the biosurfactants were more effective than the synthetics surfactants. Biosurfactants also altered the surface properties of stainless steel, rendering it hydrophilic. Microbial adhesion to stainless steel conditioned with biosurfactants was found to be thermodynamically unfavorable for all microbial strains tested. A linear relationship between shear stress and shear rate was obtained across a range of experimental conditions for all surfactant mixtures, indicating that all formulations behaved as Newtonian fluids.展开更多
基金Project(SKLSP201418)supported by the Fund of the State Key Laboratory of Solidification Processing in North China University of Technology,ChinaProjects(51171151,51331005)supported by the National Natural Science Foundation of China
文摘The solid-liquid interracial morphology evolution was investigated in directional solidification （DS） of Al-1.5%Cu alloy （mass fraction）. The results show that the solidified microstructural evolution is gradual other than sharp, and the microstructure patterns are interesting and diversiform at the pulling rate ranging from 30 μm/s to 1500 μm/s. Indeed, dendrite to cell transition follows this sequence： dendrites→→banded cellular dendrites→elongated cells and part of dendrites→main elongated cells and little dendrites. Moreover, the present microstructure is not normal microstructure as we saw before. Further, according to the experimental phenomenon, the dendrite to cell transition was studied theoretically. Dendrite tip shape is an important parameter to characterize the dendrite to cell transition. As the dendrite to cell transition is far from equilibrium solidification, non-equilibrium solidification is taken into consideration in calculation. Finally, it is speculated that the dendrite to cell transition would occur at the minimum tip radius.
文摘Biological and synthetic surfactants were compared in terms of their ability to reduce interfacial tension, change the thermodynamic characteristics of a pre-conditioned surface, and to modify the rheological properties of their respective formulations at two different temperatures. Both classes of suffactants were able to reduce the inteffacial tension of their formulations to a similar level. However, the biosurfactants were more effective than the synthetics surfactants. Biosurfactants also altered the surface properties of stainless steel, rendering it hydrophilic. Microbial adhesion to stainless steel conditioned with biosurfactants was found to be thermodynamically unfavorable for all microbial strains tested. A linear relationship between shear stress and shear rate was obtained across a range of experimental conditions for all surfactant mixtures, indicating that all formulations behaved as Newtonian fluids.
