Surface wettability of macroporous anodized aluminum oxide
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BUIJNSTERS , Josephus Gerardus, ZHONG, Rui, TSYNTSARU, Natalia, CELIS, Jean-Pierre. Surface wettability of macroporous anodized aluminum oxide. In: ACS Applied Materials and Interfaces, 2013, vol. 5, p. 0. ISSN -. DOI: https://doi.org/10.1021/am4001425
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ACS Applied Materials and Interfaces
Volumul 5 / 2013 / ISSN - /ISSNe 1944-8244

Surface wettability of macroporous anodized aluminum oxide

DOI:https://doi.org/10.1021/am4001425

Pag. 0-0

Buijnsters Josephus Gerardus1, Zhong Rui1, Tsyntsaru Natalia12, Celis Jean-Pierre1
 
1 Catholic University of Leuven (KU Leuven),
2 Institute of Applied Physics, Academy of Sciences of Moldova
 
 
Disponibil în IBN: 11 iulie 2023


Rezumat

The correlation between the structural characteristics and the wetting of anodized aluminum oxide (AAO) surfaces with large pore sizes (>100 nm) is discussed. The roughness-induced wettability is systematically examined for oxide films grown by a two-step, high-field anodization in phosphoric acid of three different concentrations using a commercial aluminum alloy. This is done for the as-synthesized AAO layers, after various degrees of pore widening by a wet chemical etching in phosphoric acid solution, and upon surface modification by either Lauric acid or a silane. The as-grown AAO films feature structurally disordered pore architectures with average pore openings in the range 140-190 nm but with similar interpore distances of about 405 nm. The formation of such AAO structures induces a transition from slightly hydrophilic to moderately hydrophobic surfaces up to film thicknesses of about 6 μm. Increased hydrophobicity is obtained by pore opening and a maximum value of the water contact angle (WCA) of about 128 is measured for AAO arrays with a surface porosity close to 60%. Higher surface porosity by prolonged wet chemical etching leads to a rapid decrease in the WCA as a result of the limited pore wall thickness and partial collapse of the dead-end pore structures. Modification of the AAO surfaces by Lauric acid results in 5-30 higher WCA's, whereas near-superhydrophobicity (WCA ∼146) is realized through silane coating. The "rose petal effect" of strongly hydrophobic wetting with high adhesive force on the produced AAO surfaces is explained by a partial penetration of water through capillary action into the dead-end pore cavities which leads to a wetting state in-between the Wenzel and Cassie states. Moreover, practical guidelines for the synthesis of rough, highly porous AAO structures with controlled wettability are provided and the possibility of forming superhydrophobic surfaces is evaluated

Cuvinte-cheie
anodic aluminum oxide (AAO), hard anodization, Macropores, surface modification, wet chemical etching, wettability