Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper,the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness p...Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper,the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated.Atheoretical model is proposed to study wetting transitions.The results of theoretical analysis are compared with those of experimentindicating that the proposed model can effectively predict the wetting transition.Furthermore,a numerical simulationbased on the meso scale Lattice Boltzmann Method(LBM)is performed to study dynamic contact angles,contact lines,andlocal velocity fields for the case that a droplet displays on the micro structured surface.A spherical water droplet with r=15μmfalls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·sand aninitial vertical distance of 20μm from droplet centre to the top of pots.In spite of a higher initial velocity,the droplet can stillstay in a Cassie state;moreover,it reaches an equilibrium state at t≈17.5 ms,when contact angle is 153.16°which is slightlylower than the prediction of Cassie-Baxter’s equation which givesθ=154.40°.展开更多
In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption characteristics...In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption characteristics.Several characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second phase.Compressive tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous Mg-Zn-Y.The experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second phase.When the Y content increases,different Mg-Zn-Y ternary phases appear:I-phase(Mg_(3)Zn_(6)Y),W-phase(Mg_(3)Zn_(3)Y_(2)),and LPSO phase(Mg_(12)ZnY).When the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 MJ/m^(3)to 10.97 MJ/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second phase.However,the average energy absorption efficiency is independent of the Y content.In addition,the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing temperature.The compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the struts.The deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.展开更多
基金supported by the Royal Society(UK)-NSFC(China)joint project,2009-2011by China Natural Science Foundation major International collaborative project 2010-2013 under grant No.50920105504
文摘Natural surfaces with super hydrophobic properties often have micro or hierarchical structures.In this paper,the wettingbehaviours of a single droplet on biomimetic micro structured surfaces with different roughness parameters are investigated.Atheoretical model is proposed to study wetting transitions.The results of theoretical analysis are compared with those of experimentindicating that the proposed model can effectively predict the wetting transition.Furthermore,a numerical simulationbased on the meso scale Lattice Boltzmann Method(LBM)is performed to study dynamic contact angles,contact lines,andlocal velocity fields for the case that a droplet displays on the micro structured surface.A spherical water droplet with r=15μmfalls down to a biomimetic square-post patterned surface under the force of gravity with an initial velocity of 0.01 m·sand aninitial vertical distance of 20μm from droplet centre to the top of pots.In spite of a higher initial velocity,the droplet can stillstay in a Cassie state;moreover,it reaches an equilibrium state at t≈17.5 ms,when contact angle is 153.16°which is slightlylower than the prediction of Cassie-Baxter’s equation which givesθ=154.40°.
基金supported by"The National Key Research and Development Program of China(No.2018 YFA0703300)""Science and Technology Project of Education Department of Jilin Province(No.JJKH20231086KJ)"Development Project of Jilin Province(No.2021C038-4)。
文摘In this study,interconnected porous Mg-2Zn-xY alloys with different phase compositions were prepared by various Y additions(x=0.4,3,and 6 wt.%)to adjust the compressive properties and energy absorption characteristics.Several characterization methods were then applied to identify the microstructure of the porous Mg-Zn-Y and describe the details of the second phase.Compressive tests were performed at room temperature(RT),200℃,and 300℃to study the impact of the Y addition and testing temperature on the compressive properties of the porous Mg-Zn-Y.The experimental results showed that a high Y content promotes a microstructure refinement and increases the volume fraction of the second phase.When the Y content increases,different Mg-Zn-Y ternary phases appear:I-phase(Mg_(3)Zn_(6)Y),W-phase(Mg_(3)Zn_(3)Y_(2)),and LPSO phase(Mg_(12)ZnY).When the Y content ranges between 0.4%and 6%,the compressive strength increases from 6.30MPa to 9.23 MPa,and the energy absorption capacity increases from 7.33 MJ/m^(3)to 10.97 MJ/m^(3)at RT,which is mainly attributed to the phase composition and volume fraction of the second phase.However,the average energy absorption efficiency is independent of the Y content.In addition,the compressive deformation behaviors of the porous Mg-Zn-Y are altered by the testing temperature.The compressive strength and energy absorption capacity of the porous Mg-Zn-Y decrease due to the softening effect of the high temperature on the struts.The deformation behaviors at different temperatures are finally observed to reflect the failure mechanisms of the struts.
