21st International Symposium on Fluorine Chemistry & 6th International Symposium on Fluorous Technologies – Como, Italy- August 23-28, 2015

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Macro- and Microscopic Investigation of Anti-icing Properties of Anodized Aluminum Surfaces

Daan Heskes¹, Valentina Rizzi², Matteo Chiesa¹, Walter Navarrini², Maria Vittoria Diamanti², Marco Stefancich¹

¹ Laboratory for Energy and NanoScience (LENS), Institute for Future Energy Systems (iFES), Masdar Institute of Science and Technology, P.O.Box 54224, Abu Dhabi, UAE

²Dipartimento di Chimica, Materiali ed Ingegneria Chimica ”G. Natta”, Politecnico di Milano, via L. Mancinelli, 7, 20131 Milano, Italy

In this work the (anti-)icing properties of anodized aluminium with different surface chemistries are investigated. In order to obtain anti icing coatings use is made of the surface chemistry as well as the structure of the surface, which are often also related to the hydrophobicity of surface [1]. Recently it was shown that anodized alumina surface, which have a honeycomb like surface structure, can exhibit superhydrophobic properties [2]. In addition to the structural part of the coating also different surfaces chemistries are investigated; bare alumina, silanized and perfluorinated anodized alumina surfaces as well as liquid impregnated surfaces. Characterization is done macroscopically as well as microscopically. Macroscopically the ice adhesive energy, the contact angle and contact angle hysteresis is experimentally measured. The ice adhesive energy is obtained by subjecting the iced samples to a guided impact test. On the Microscopic scale the properties of the surface are investigated using different methods of Atomic Force Microscopy. In order make fully use of the Atomic Force Microscopy imaging also the different surface chemistries on flat samples are examined. First the surface topography of the sample probed to obtain the surface roughness. Using Scanning Kelvin Probe Microscopy the surface potential of the different samples are mapped [3]. Combining these scales of measurement can enhance the understanding of these kinds of surfaces.

1. Farhadi, S., M. Farzaneh, and S. Kulinich, Anti-icing performance of superhydrophobic surfaces. Applied Surface Science, 2011. 257(14): p. 6264-6269.
2. Leese, H., et al., Wetting Behaviour of Hydrophilic and Hydrophobic Nanostructured Porous Anodic Alumina. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2012.
3. Suzuki, S., et al., Hydrophobicity and freezing of a water droplet on fluoroalkylsilane coatings with different roughnesses. Langmuir, 2007. 23(17): p. 8674-8677.

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17th European Symposium on Fluorine Chemistry – Paris – July 21-25, 2013

Perfluoropolyethers as hydrophobizing agents for Fuel Cells carbonaceous functional materials

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Functionalization of Carbonaceous Materials with High Fluorine Content Organic Peroxides

M. Sansotera ^a, W. Navarrini ^a, P. Metrangolo ^a, G. Resnati ^a, C. Bianchi ^b, A. Guarda ^c

^a Dip-CMIC ”Giulio Natta”, Politecnico di Milano, via Mancinelli 7, 20131 Milan, Italy;

^b Department of Physical Chemistry and Electrochemistry, University of Milan, via Golgi 19, 20133, Milan, Italy

^c R&D Centre, Solvay Solexis, viale Lombardia 20, 20021 Bollate (MI), Italy

E-mail: maurizio.sansotera@polimi.it

Perfluorodiacyl peroxides and perfluoropolyether peroxides (FOMBLIN peroxides) are suitable organic peroxides for direct linkage of perfluoroalkyl and perfluoropolyether chains on unsaturated substrates through a radical pathway. Highly graphitic carbon black and a-C:H diamond-like carbon are carbonaceous materials characterized by sp² hybridized carbon atoms in the structure. Consequently a chemical treatment with high fluorine content organic peroxides allows the introduction of fluorinated groups onto carbonaceous substrates with carbon-carbon bond formation [1]. Depending on the peroxide involved during the treatment, several fluorinated chains, i.e. perfluoroethyl, CF₃CF₂-, perfluoro-n-propyl, CF₃CF₂CF₂-, perfluoro-iso-propyl, (CF₃)₂CF-, and perfluoropolyether residual, has been covalently linked on the surface of such carbonaceous materials. Functionalization of carbon black transfers the typical hydrophobic properties of perfluorinated chains to the carbon black surface even preserving its conductive properties. This chemical treatment on diamond-like carbon films produces a covalently linked protective layers with the typical lubricant properties of perfluorinated compounds.

[1] Navarrini W., Sansotera M., Metrangolo P., Cavallotti P., Resnati G. WO 2009/019243 A1.