Low surface energy coatings covalently bonded on diamond-like carbon films

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfluorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp² sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PFPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).