Thin Film Deposition on Open‐Cell Foams by Atmospheric Pressure Dielectric Barrier Discharges

Abstract

Thin films are deposited on open‐cell polyurethane (PU) foams using an atmospheric pressure dielectric barrier discharge (DBD) fed with helium and hexafluoropropene (C3F6). During deposition processes, a foam substrate is sandwiched between the dielectric‐covered electrodes of a parallel plate DBD reactor, so that the discharge can ignite also inside its three‐dimensional (3D) interconnected porous structure. This affords the deposition of a fluorocarbon coating on both the exterior and interior of the foam. Scanning electron microscopy (SEM) observations allow estimating the thickness of the coating deposited on the foam struts, while X‐ray photoelectron spectroscopy (XPS) analyses show moderate changes in surface chemical composition moving from the outer to the inner surfaces of the plasma‐treated foams under all explored experimental conditions.

Thin film deposition at atmospheric pressure using dielectric barrier discharges: Advances on three-dimensional porous substrates and functional coatings

“…Rectangular foam strips, having a thickness of 5 mm and a width along the gas flow direction of 10 mm, were used as substrates. 39) The XPS analysis of the pristine foam showed carbon, oxygen, and nitrogen surface atomic concentrations of about 78, 19, and 3%, respectively. The high resolution C 1s XPS spectrum can be curve-fitted with the dominant hydrocarbon component (C-C=C-H) at 284.8 ± 0.2 eV, and other three peaks centered at 285.7 ± 0.2 eV (C-N), 286.5 ± 0.2 eV (C-O), and 289.0 ± 0.2 eV (very likely ascribed to both urethane and ester functionalities of the polyurethane material).…”

“…57,58) Therefore, we carried out an explorative study focused on the PECVD of fluorocarbon coatings onto the entire 3D network of open-cell foams (i.e., on their outer and inner surfaces) using a dielectric barrier discharge. 39) To enlighten the potential of the DBD as a plasma inside complex porous materials, the following initial decisions were taken regarding the substrate to be treated, the thin film to be deposited, the DBD reactor and deposition conditions:…”

“…The high resolution C 1s XPS spectrum can be curve-fitted with the dominant hydrocarbon component (C-C=C-H) at 284.8 ± 0.2 eV, and other three peaks centered at 285.7 ± 0.2 eV (C-N), 286.5 ± 0.2 eV (C-O), and 289.0 ± 0.2 eV (very likely ascribed to both urethane and ester functionalities of the polyurethane material). 39) (ii) The fluorocarbon coating was deposited by a DBD fed with helium and hexafluopropropene (C 3 F 6 ) at flow rates of 6000 and 6 sccm, respectively. The choice of a fluoropolymer was motivated by the need to clearly distinguish the plasmadeposited coating from the underlying polyurethane substrate when the surface composition of the plasma-treated foam was investigated by XPS.…”

“…6,35,37) (iii) The deposition processes were carried out using a DBD reactor with a parallel plate electrode configuration and lateral gas injection, described previously in full detail. 6,39) In particular the DBD electrode system consisted of two parallel plate electrodes (120 × 120 mm 2 electrode area, 5 mm gas gap) both covered with a 0.635 mm thick alumina plate (dielectric barrier). The feed mixture was introduced in the 39) discharge zone through a slit and pumped through a second slit positioned on the opposite side (i.e., lateral gas injection).…”

“…(i) The PECVD of fluoropolymers on open-cell polyurethane foams, 39) showing the DBD potentiality for thin film deposition on the outer and inner surfaces of complex threedimensional porous substrates.…”