Synthesis and texturization processes of (super)-hydrophobic fluorinated surfaces by atmospheric plasma
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Viville and R. Lazzaroni Service de Chimie des Matériaux Nouveaux, Université de Mons-UMONS/Materia Nova, 20 Place du Parc, 7000 Mons, Belgium
M. Raes and H. Terryn Department of Metallurgy, Electrochemistry and Materials Science (SURF), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussel, Belgium (Received 12 June 2015; accepted 24 August 2015)
The synthesis and texturization processes of fluorinated surfaces by means of atmospheric plasma are investigated and presented through an integrated study of both the plasma phase and the resulting material surface. Three methods enhancing the surface hydrophobicity up to the production of super-hydrophobic surfaces are evaluated: (i) the modification of a polytetrafluoroethylene (PTFE) surface, (ii) the plasma deposition of fluorinated coatings and (iii) the incorporation of nanoparticles into those fluorinated films. In all the approaches, the nature of the plasma gas appears to be a crucial parameter for the desired property. Although a higher etching of the PTFE surface can be obtained with a pure helium plasma, the texturization can only be created if O2 is added to the plasma, which simultaneously decreases the total etching. The deposition of CxFy films by a dielectric barrier discharge leads to hydrophobic coatings with water contact angles (WCAs) of 115°, but only the filamentary argon discharge induces higher WCAs. Finally, nanoparticles were deposited under the fluorinated layer to increase the surface roughness and therefore produce super-hydrophobic hybrid coatings characterized by the nonadherence of the water droplet at the surface.
I. INTRODUCTION
Super-hydrophobic thin films are attractive in applications where water-repellent, anti-fouling, and self-cleaning properties are desirable. A super-hydrophobic surface is one that repels water to such an extent that the droplet is almost spherical and easily rolls across the surface. They are generally characterized by a high water contact angle (WCA) (.150°) and a low tilting angle or a low contact angle hysteresis (,10°); the hysteresis being defined by the difference between the advancing contact angle and the receding contact angle.1 The highest known WCA of a smooth low-energy surface is comprised between 110° and 120° depending on the chemical group present at the surface (CH3, CF2, CF3).2 Super-hydrophobic surfaces are therefore obtained by combining rough surface morphology and low surface energy coatings.2 Such coatings have been deposited using wet chemistry Contributing Editor: Akira Nakajima a) Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2015.279 J. Mater. Res., Vol. 30, No. 21, Nov 13, 2015
with low surface energy materials but these methods usually require multiple processing steps and utilize solvents.3–6 The use of plasmas is then a very promising synthetic route to produce super-hydrophobic surfaces since this approach has the advantage of reducing the number of steps required to modify the sur
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