The Superhydrophobic Research Of The Controllable Surface Microstructures Based On Amorphous Alloy

The superhydrophobicity with self-cleaning property that origined from "lotus effect"has become one of the hottest research issues in materials and bionic fields. Thissuperhydrophobicity is actually determined by two crucial factors, namely surface energyand surface structures. Till now, most superhydrophobicity focus on polymers, glasses andcarbon nanotubes, etc. However, these materials not only with short lifespan, but lack ofpractical applications, caused of their low mechanical strengths and poor bondingstrengths between the superhydrophobic film and the substrate. Metal crystal materials cannot be used to fabricate superhydrophobic surface with micro-nano structures due to theeffect of grain size effect. On the contrary, amorphous alloy not only exhibit goodmechanical properties and anti-corrosion resistance, but also show good processingformability in supercooled liquid region （SCLR）, which ensure that the micro-nanoprecision can be realized. All these properties of metallic glass exhibit a wide potentialapplication prospect in superhydrophobicity.In this dissertation the Pd₄₀Cu₃₀Ni₁₀P₂₀and Zr₃₅Ti₃₀Be_26.75Cu_8.25alloys wererespectively prepared by vacuum induction melting or arc-melting, followed by coppermould casting. The glassy structures of the as-cast alloys were verified by X-raydiffraction （XRD）, the thermal responses of the BMGs were investigated by differentialscanning calorimetry （DSC）. The essential contact angles （CA） of smooth surfaces weremeasured by contact angle measurements（SL2000）, then the relative surface energies ofeach alloy was calculated by Owens–Wendt theory.A series of honeycomb like patterns with various pitches were hot-embossed on thesilicon master moulds that were produced through deep reactive ion（DRI） etching. Themorphologys of the hot-embossed patterns were subsequently characterized by scanningelectron microscope（SEM） and laser scanning confocal microscope （Keyence VK-X200 series）; the surface contact angles were measured by contact angle measurements. Theresults showed that the maximum contact angle reached to153.8°for the patternedPd-based BMG surface. This phenomenon was well rationalized in terms of the modifiedCassie-Baxter theory by considering the surface energy gradient.Considering the influence of amorphous alloys’ surface energies, the honeycombpatterns were also hot-embossed on a Zr-based BMG surface. It was only133.8°,exhibiting a hydrophobicity rather than superhydrophobicity. To improve the contact angle,the surface micro-patterns was etched by HG solution and a micro/nano-hierarchicalstuctures was fabricated, exhibiting a maximum contact angle with about152.7°. Throughanalyzing of the stress of the droplet on the micro/nano-hierarchical surface, and buildinga composite model from the viewpoint of the total energy, the werrability on the Zr-basedBMG surface was illustratued. Furthermore, the maximum contact angle remainedunmoved even when the surface was overturned, which opened a window for the possibleapplication of transfering small liquid droplet used as a "mechanical hand".