Elsevier

Applied Surface Science

Volume 490, 1 October 2019, Pages 56-60
Applied Surface Science

Full length article
Superoleophobic surfaces via functionalization of electrophoretic deposited SiO2 spheres on smart aluminum substrates

https://doi.org/10.1016/j.apsusc.2019.06.046Get rights and content

Highlights

  • Superoleophobic surfaces have been prepared by an interdisciplinary process.

  • Laser patterned substrates allow self-organized deposition of SiO2 microspheres.

  • Silanization produces surfaces with superoleophobic properties.

  • Extremely large contact angles vs. diiodomethane are reported.

Abstract

Complex, hierarchic microstructures are prepared by electrophoretic deposition of SiO2 microspheres. A subsequent functionalization via sol-gel technique using perfluorsilanes leads to superoleophobic surfaces. A crucial step of the used process is the application of laser-structured aluminum substrates for electrophoretic deposition leading to complex three-dimensional surface structures. After a chemical functionalization step surfaces are generated that exhibit a huge contact angle against diiodomethane of 157° in air. This is significantly larger than the typically used threshold angle for superoleophobicity of 150°.

Section snippets

Methods

Electrophoretic deposition (EPD) is a widespread method to deposit solid particles from a suspension using an electric field [[23], [24], [25], [26], [27], [28]]. Particle migration under the electric field depends on the formation of surface charges. This depends either on the pH used or in general on the extent of particle surface ion adsorption from any ionic additive [24]. To achieve large particle surface charges we add various salts of diphosphoric acid in a starting concentration of not

Experimental

A short pulsed laser source (TRUMPF TruMark5020) is used to structure the surface of an aluminum substrate. The Master Oscillator Fiber Power amplifier architecture of the systems allows a maximum average power of 20 W, a maximum pulse peak power of 14 kW and a maximum pulse energy of 0,8 mJ. For the experiments a single pulse energy of Ep = 250 μJ at a pulse duration tp = 200 ns was set to ablate the material mostly via evaporation of the aluminum. Compared to the use of ultra-short pulsed

Results

Electrophoretic deposition is conducted varying either the used pyrophosphate compound or the surface topography of the anode. We protocol the electrolyte current that is of the order of I = 100 μA or j = 19 mA/dm2 which cumulates after a typical deposition period of t = 15 min to transported charges of about 0.1 C. The number of deposited particles is extracted from microscopy images by counting individuals. Fig. 3 displays the relation between transported charge and deposited particles.

In

Summary

In this work, we prepared superoleophobic surfaces using a combination of physical and chemical surface treatments. First, laser-structured aluminum surfaces are deposited with SiO2 microspheres by electrophoretic deposition. It is found that the evolving particle distribution is strongly controlled by the presence of sharp edges on the surface. In particular, three-dimensional structures could be generated at the rim of laser dimples. The combination of 50 μm sized laser dimples and complex 3d

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