Organic coatings from acetylene at atmospheric pressure: UV light versus plasma

A versatile pilot-scale reactor has been designed in such a way that it can be readily converted from a dielectric barrier discharge “PECVD” operating mode into a photoinitiated “PICVD” one; in the latter, low-pressure mercury (Hg) lamps replace the high-voltage glow discharge plasma. Both processes operate at ambient temperature and atmospheric pressure, 100 kPa, using acetylene (C2H2) monomer. In both sets of experiments, it was found that efficient gas-to-solid conversion can occur in the form of a nanoparticulate amorphous hydrocarbon polymer-like material. It was found that in the PICVD case, great care was required to exclude even traces of O2 contamination, because it not only reduced the growth rate of solid, but the latter then became highly oxidized ([O] ~50 at.%) and water-soluble.