We investigate a minute magneto hydro-dynamic mixer with relatively rapid mixing enhancement experimentally and analytically. The mixer is fabricated with brass and polymethyl methacrylate （PMMA） layers. A secondary...We investigate a minute magneto hydro-dynamic mixer with relatively rapid mixing enhancement experimentally and analytically. The mixer is fabricated with brass and polymethyl methacrylate （PMMA） layers. A secondary flow is generated by using the Lorentz force in the fluids. The efficiency of mixing is greatly improved due to the large increase of the contact area between two mixing fluids. The micro particle image velocimetry technique is employed to measure the fluid flow characteristics in the micro-channel. Numerical simulation is performed based on the theoretical model of the computational fluid dynamics and the electromagnetic field theory. The experimental results are in good agreement with the numerical results, which indicates that the mixing area is enlarged by the driving of Lorentz force and the mixing can be enhanced.展开更多
The dynamic behavior of octahedral gold nanopartides （NPs） and nanoparticle clusters （NPCs） in aqueous solution is studied by in-situ liquid-cell transmission electron microscopy （TEM）. The octahedral Au NPs/NPC...The dynamic behavior of octahedral gold nanopartides （NPs） and nanoparticle clusters （NPCs） in aqueous solution is studied by in-situ liquid-cell transmission electron microscopy （TEM）. The octahedral Au NPs/NPCs show preferential orientations in the liquid cell, due to the interaction with the SiNx window. The Au NPs show long-range reversible hopping and three-dimensional （3D） rotational motions in the liquid environment. At the same time, the Au NPCs and NPs perform slow stick-sUp and stick-roU motions, respectivel~ with a centripetal trend. The centripetal motions were explained by a liquid evaporation-induced radial flow model in which the NPCs/NPs trajectories are controlled by Stokes forces and surface friction by the silicon nitride window. The calculated radius-dependent force （Fc） on the NPCs/NPs shows a semi-linear correlation with the distance r between the NPCs/NPs and the center of mass, accompanied with stochastic fluctuations, in agreement with the model predictions. This work thus demonstrates the effectiveness of in situ liquid-cell TEM for the in-depth understanding of complicated liquid flow and force interactions in nanomaterials.展开更多
文摘We investigate a minute magneto hydro-dynamic mixer with relatively rapid mixing enhancement experimentally and analytically. The mixer is fabricated with brass and polymethyl methacrylate （PMMA） layers. A secondary flow is generated by using the Lorentz force in the fluids. The efficiency of mixing is greatly improved due to the large increase of the contact area between two mixing fluids. The micro particle image velocimetry technique is employed to measure the fluid flow characteristics in the micro-channel. Numerical simulation is performed based on the theoretical model of the computational fluid dynamics and the electromagnetic field theory. The experimental results are in good agreement with the numerical results, which indicates that the mixing area is enlarged by the driving of Lorentz force and the mixing can be enhanced.
文摘The dynamic behavior of octahedral gold nanopartides （NPs） and nanoparticle clusters （NPCs） in aqueous solution is studied by in-situ liquid-cell transmission electron microscopy （TEM）. The octahedral Au NPs/NPCs show preferential orientations in the liquid cell, due to the interaction with the SiNx window. The Au NPs show long-range reversible hopping and three-dimensional （3D） rotational motions in the liquid environment. At the same time, the Au NPCs and NPs perform slow stick-sUp and stick-roU motions, respectivel~ with a centripetal trend. The centripetal motions were explained by a liquid evaporation-induced radial flow model in which the NPCs/NPs trajectories are controlled by Stokes forces and surface friction by the silicon nitride window. The calculated radius-dependent force （Fc） on the NPCs/NPs shows a semi-linear correlation with the distance r between the NPCs/NPs and the center of mass, accompanied with stochastic fluctuations, in agreement with the model predictions. This work thus demonstrates the effectiveness of in situ liquid-cell TEM for the in-depth understanding of complicated liquid flow and force interactions in nanomaterials.
