Wetting Behaviours of a Single Droplet on Biomimetic Micro Structured Surfaces

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= 15 μmfalls 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 20 μm 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 gives θ=154.40°.

Wetting Behaviour of Glasses on Nanostructured Silicon Surfaces

The behavior of molten glass on nanostructured silicon surface is of essential importance for the fabrication of a strong bond interface between glass （or glass-based ceramic tapes） and silicon. It was found that typical glasses do not wet the silicon surface that is always coated with a thin silica layer. It is shown that the high surface tension of molten glasses at high temperatures in combination with the dewetting surface of the structured silicon prohibits the formation of an interlocking bond between the two substrates. The theory of wetting can be applied to molten glasses, too. As a consequence, a similar solution as for liquids is investigated： the surface has to be chemically modified to become wettable. Investigations with sputtered metals on the nanostructured silicon improve wetting of the surface and result in a better bond homogeneity of the SiCer compound during sintering with low pressure.

The influence of substrate and atmosphere on the properties of FeSiB(Cu,Nb) alloy melts

The surface tensions and contact angles of Fe_(78)Si_9B_(13) and Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy melts were studied as a function of temperature in various atmospheres(vacuum, Ar and N_2 gas) and on different substrates(Si C, Al_2O_3 and BN). It is indicated that Si_3N_4, NbN, Fe_2 Al B and B_(13)C_2 are generated as new phases at the interface between the melt and substrate, and reactive wetting behaviour exists during the heating process. The surface tensions of two alloy melts on BN substrate both firstly decrease and then increase along with increasing temperature, leading to V-shaped surface tension versus temperature, which results from atomic diffusion effects in the surface layer during the oxidation of BN and formation of C-rich layer. Comparably, the surface tensions on Al_2O_3 and Si C substrates decrease with increasing temperature throughout the entire temperature range. Among three substrates, BN exhibits the mildest wetting behaviour. The vacuum environment has the strongest protective effect on melt stability among the tested atmospheres. These findings enrich our knowledge about the effects of the substrate and atmosphere on Fe-based alloy melts at a high temperature, and provide theoretical reference for designing jet nozzles in melt-spinning techniques.