The present study proposes an alternative eco-friendly method to prepare a thin composite coating based on graphene embedded in siloxane polymers which can be used as application for the corrosion protection of steel. The nanocomposite coatings were elaborated by a dielectric barrier discharge using a nebulized colloidal suspension of graphene nanosheets (GNs) dispersed in hexamethyldisiloxane (HMDSO) used as the precursor for the polymer matrix. After obtaining a stable colloidal solution, it was nebulized into the plasma reactor to form a plasma polymer (pp) coating from HMDSO (ppHMDSO) in which GNs were incorporated (GN@ppHMDSO) on the mild steel substrate. The chemical structure of the hybrid coatings was characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectrometry. Raman spectra of GNs and GN@ppHMDSO coatings suggest the existence of charge transfer between the GNs and the HMDSO matrix. Furthermore, scanning electron microscopy confirms the synthesis of micro/nanocomposite with a fairly homogeneous dispersion of the GNs in the polymer matrix. The corrosion resistance of the samples was evaluated by electrochemical impedance spectroscopy which showed that the hybrid coatings GN@ppHMDSO deposited by a one-step atmospheric pressure plasma process, presented excellent anticorrosion performance with 99.99% of protection efficiency.

Polypropylene (PP) particles are used for various purposes, however, the good mechanical properties of PP are counterbalanced by a poor wettability. The wettability of PP particles was therefore improved by an atmospheric pressure blown-arc air plasma jet treatment in a new designed homemade Wurster fluidized bed reactor (Wurster-FBR). This reactor, was used to treat 200 g of particles per batch. The surface free energy of PP particles determined by the Zisman method showed an increase from 30.7 to 38.6 mN m −1 after 120 s of treatment. XPS results showed a 5% increase of the atomic concentration of oxygen on the surface of the treated particles. In order to describe the process, a 2D axisymmetric nonisothermal k-ε turbulent model was used to determine the velocity field, pressure, and temperature profile of the gas phase inside the reactor. Furthermore an Eulerian-Eulerian multiphasic CFD model was added to determine the dynamics of the particles inside the reactor, and the results were compared with fast imaging, thermocouple, and anemometry measurements. These investigations are very important to monitor the homogeneity of the particle treatments, to determine the average effective treatment time for each particle and to avoid overheating of thermally sensitive PP. K E Y W O R D S atmospheric pressure plasma, CFD modeling, polymer surface treatment and coating technology, Wurster fluidised-bed reactor