Investigation of the Effects of Gas versus Liquid Deposition in an Aerosol-Assisted Corona Deposition Process

The particle size of polymethylhydrogen siloxane (PHMS) and hexamethyldisiloxane (HMDSO) droplets nebulised into an atmospheric pressure plasma was investigated using laser particle imaging. At low precursor flow rates the volatile HMDSO monomer is shown to be vapourised by the nebulisation process and no discrete aerosol droplets enter the plasma. This results in a standard gas phase PECVD process. As the precursor flow rate increases, liquid aerosol droplets are detected in the plasma. The diameter and number of droplets is largely unaffected by exposure to the plasma and intact droplets exit the plasma and impact directly on the substrate. The change in precursor flow is found to significantly alter the surface morphology of the deposited coatings with minimal impact upon the coating chemistry.