The impact of the presence of TiO2 and SiO2 nanoparticles on the properties of fluorocarbon films synthesized by atmospheric pressure plasma in argon and helium is investigated in this study. The hydrophobicity, chemical composition and roughness of the films are analyzed by Water Contact Angle (WCA), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and profilometry. As expected, a significant impact of the nanoparticles on the roughness and therefore on the hydrophobicity of the films is observed and so regardless their nature. However, we show that the impact of the nanoparticles is different whether He or Ar are use as plasmagen gas, as He doesn't induce a significant intrinsic roughness, whereas Ar does. We show that the presence of SiO2 nanoparticles underneath the deposited film has no influence on the chemical composition of the films whatever the deposition time, the plasma power and the carrier gas (helium or argon) are. On the contrary, the presence of TiO2 nanoparticles leads to the degradation of the coatings over time. The influence of the plasma power of the discharge and the deposition time is also discussed. Finally, superhydrophobic coatings are synthesized by increasing the concentration of nanoparticles underneath the deposited films.

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 O_2 is added to the plasma, which simultaneously decreases the total etching. The deposition of C_xF_y 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.

TiO2 films were synthesized by atmospheric dielectric barrier discharge (DBD) plasma at room temperature. The morphology and chemical composition of TiO2 films were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Effect of the oxygen ratio and deposition time was investigated. It is showed that the content of O2 is an important parameter in the formation of a porous structure. The study of the deposition time could lead to the understanding of the mechanisms of nucleation and growth of TiO2 nanoparticles in the plasma and formation of films on the substrate.

The influence of SiO2 and TiO2 nanoparticles on the atmospheric pressure PECVD of C6F12 precursor is investigated. Chemical and hydrophobic properties of the films synthesized by atmospheric plasma are studied by XPS, WCA and profilometry. The roughness of the samples appears as a crucial parameter since its increase promotes the creation of superhydrophobic coatings.

Among various surface modification techniques, plasma can be used as a source for tailoring the surface properties of diverse materials. HDPE and fluoropolymer surfaces have been treated by the post-discharge of an atmospheric RF-plasma torch supplied with helium and oxygen gases. The plasma-treated surfaces were characterized by measurements of mass losses, water contact angles, x-ray photoelectron spectroscopy and atomic force microscopy. This experimental approach correlated with an optical characterization of the plasma phase allowed us to propose etching mechanisms occurring at the post-discharge/polymer interface. We discuss how competitive and synergistic effects can result from the oxidation and/or the roughening of the surface but also from the excimer VUV radiation, the He metastable species and the O radicals reaching the plasma-polymer interface.

The influence of ambient air on the flowing afterglow of an atmospheric pressure Ar/O2 radiofrequency plasma has been investigated experimentally. Spatially resolved mass spectrometry and laser induced fluorescence on OH radicals were used to estimate the intrusion of air in between the plasma torch and the substrate as a function of the torch-to-substrate separation distance. No air is detected, within the limits of measurement uncertainties, for separation distances smaller than 5 mm. For larger distances, the effect of ambient air can no longer be neglected, and radial gradients in the concentrations of species appear. The Ar 4p population, determined through absolute optical emission spectroscopy, is seen to decrease with separation distance, whereas a rise in emission from the N2(C–B) system is measured. The observed decay in Ar 4p and N2(C) populations for separation distances greater than 9mm is partly assigned to the increasing collisional quenching rate by N2 and O2 molecules from the entrained air. Absorption measurements also point to the formation of ozone at concentrations from 10^14 to 10^15 cm-3, depending both on the injected O2 flow rate and the torch-to-substrate separation distance.

In the present study, the feasibility of synthesizing chlorinated films by a dielectric barrier discharge at atmospheric pressure is assessed. Two different liquid monomers (hexachlorobuta-1,3-diene C4Cl6 and 1,1,1,2-tetrachloroethane C2H2Cl4) are tested and results show that organic coatings rich in chlorine can be deposited. The correlation and complementarity of water contact angle, X-ray photoelectron spectroscopy, secondary ion mass spectrometry and ellipsometry techniques have provided information to compare the properties of the perchlorinated layers built up from monomers with different Cl/C ratios and hydrogen concentrations. The bond dissociation energies of C-Cl-2, C-Cl and C-C/C=C/C-H are used to provide an explanation for the differences in films structure recorded by X-ray photoelectron spectroscopy and secondary ion mass spectrometry. Finally, dynamic-secondary ion mass spectrometry complemented by ellipsometry is used to calculate a deposition rate ranging from 40 to 70 nm/min depending on the plasma conditions. These measurements also show a good homogeneity of the film throughout its thickness. (C) 2013 Elsevier Ltd. All rights reserved.

A comparative study of polytetrafluoroethylene (PTFE) surfaces treated by the post-discharge of He and He-O(2) plasmas at atmospheric pressure is presented. The characterization of treated PTFE surfaces and the species involved in the surface modification are related. In pure He plasmas, no significant change of the surface has been observed by X-ray photoelectron spectroscopy (XPS), dynamic water contact angles (dWCA) and atomic force microscopy (AFM), in spite of important mass losses recorded. According to these observations, a layer-by-layer physical etching without any preferential orientation is proposed, where the highly energetic helium metastables are the main species responsible for the scission of -(CF(2))(n)- chains. In He-O(2) plasmas, as the density of helium metastables decreases as a function of the oxygen flow rate, the treatment leads to fewer species ejected from the PTFE surfaces (in agreement with mass loss measurements and the detection of fluorinated species onto aluminum foil). However, the dWCA and AFM measurements show an increase in the hydrophobicity and the roughness of the surface. The observed alveolar structures are assumed to be caused by an anisotropic etching where the oxygen atoms etch mainly the amorphous phase.

The post-discharge of an RF plasma torch supplied with helium and oxygen gases is characterized by mass spectrometry, optical emission spectroscopy and electrical measurements. We have proved the existence of a dc current in the post-discharge (1–20 µA), attributed to the Penning ionization of atmospheric nitrogen and oxygenated species. The mechanisms ruling this dc current are investigated through experiments in which we discuss the influence of the O2 flow rate, the He flow rate and the distance separating the plasma torch from a material surface located downstream.