Study On Preparation Principles And Methods Of Multi-coupling Bionic Hydrophobic Metal Surfaces

Hydrophobic and super-hydrophobic surfaces have considerable technological potentialfor various applications ranging from self-cleaning materials to microfluidic devices andbiomaterials due to their extremely good water-repellent properties. A number of studieshave been carried out to produce artificially bionic roughness-induced hydrophobic surfaces.Especially, more and more attention on hydrophobic properties in metal and alloy materialswith high surface energy were arose up because of their great importance in daily life as wellas in various industrial and biological applications such as self-cleaning characteristics.Therefore, building a hydrophobic surface on the metal or alloy substrate with high surfaceenergy become an emerging area in recent years and research focus. The wettability of metaland alloy surfaces depends strongly on multi-coupling of microscopy and/or microstructureand chemical composition of solid surface. Based on the bionics coupling theory, the thesisis engaged to reparation and research of bionic coupling hydrophobic surfaces in aluminumalloy and steel materials by using a variety of experimental methods. The main work of thethesis is listed as following:1,The resultant surfaces of lotus leaves were characterized by means of scanningelectron microscopy (SEM), laser scanning confocal microscopy (LSCM), x-rayphotoelectron spectrograph (XPS) and water contact angle measurements (WCA). Theresults show that the chemical composition of the surface of lotus leaves covered with alayer of waxy grain is much similar to their converse surfaces, and the difference is that thelotus leaves surface micro/nanostructure with micron mastoid morphology and a number ofnano-velvet mastoid is main factor affecting the wettability on the converse surface onlywith a single terrace-like morphology of lotus leaves. Based on the phenomenon of lotus leaves, the two models were established for coupling bionic hydrophobicity. The one iscomposed of non-smooth morphology, microstructure and low-energy materials, and theother is composed of micro morphology and micro/nano composite structure.2,Bionic alumina samples were fabricated on convex dome type aluminum alloysubstrate by using a hard anodizing technique. The resultant surfaces were characterized bymeans of scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM)and water contact angle measurements (WCA). The measurement of the wetting propertyshowed that the water contact angle of the unmodified as-anodized alumina bionic samplesincreases from90°to137°with increasing anodizing time. The increased water contractangle with anodizing time arises from the gradual formation of the hierarchical structure orcomposite structure. The structure is composed of the micro-scaled alumina columns andpores and the change in the height of columns and the depth of pores. The water contactangle increases significantly from96°to152°when the samples were modified withself-assembled monolayer of octadecanethiol (ODT), showing a change in the wettabilityfrom hydrophobicity to super-hydrophobicity.3,A hydrophobic surface was fabricated on etched aluminum alloy by using a hardanodizing technique. The resultant surfaces were characterized by means of scanningelectron microscopy (SEM), field scanning electron microscopy (FESEM), x-rayphotoelectron spectrograph (XPS), laser scanning confocal microscopy (LSCM) and watercontact angle measurements (WCA). The results show that cater-like pits and submicronporous aluminum films constitute a hierarchical rough aluminum surface after etching andsubsequent anodizing treating. The hierarchical micro/nanostructure exhibits excellenthydrophobic properties with water contact angles of about148ｏ. And, the etchedaluminum alloy substrate exhibits hydrophobic properties with water contact angles of about118ｏ. Without the low-energy treatment, the coupling surface gets very close surfaceroughness and hydrophobicity with the same as the lotus leaf lower surface.4,A electrochemical deposition process and thermal oxidation technology were used to fabricate rough surfaces and obtain excellent hydrophobic with an average water contactangle of150°on polycrystalline carbon steel substrates. The resultant surfaces werecharacterized by means of scanning electron microscopy (SEM), x-ray photoelectronspectrograph (XPS), laser scanning confocal microscopy (LSCM) and water contact anglemeasurements (WCA). The results show that the uniformity distributed micrometer-scalecauliflower clusters bodies were found to be consist of further nanometer scale oxidizedcopper spherical monomer on the oxidized copper substrate. This special structure is muchsimilar to that of the lotus leaf. The oxidized copper film with the hierarchicalmicro/nanostructure exhibits excellent super-hydrophobic properties with water contactangle of about150°.5,Based on the biological coupling and its bionic principles and laws, multi-couplingbionic hydrophobic characteristics mechanism on metal surface are proposed and thecommon law are revealed, to achieve the transformation of high-energy surface fromhydrophilic to hydrophobic.