Nebulization of Nanocolloidal Suspensions for the Growth of Nanocomposite Coatings in Dielectric Barrier Discharges

Abstract

The nebulization of colloidal suspensions is analyzed by dynamic light scattering, scanning, and transmission electron microscopies. While primary agglomeration can be important for many nanoparticle-solvent couples, our results indicate that for TiO 2 nanoparticles dispersed in water, secondary agglomeration also occurs during nebulization. When nebulization is realized immediately after sustaining a plane-toplane dielectric barrier discharge at atmospheric pressure, the collection efficiency of TiO 2 nanoparticles increases due to the presence of a remanent electric field between the two electrodes. Finally, these findings are used to deposit SiO 2 -TiO 2 nanocomposite thin films by alternating the deposition of dense silicalike layers in a Townsend discharge and the collection of TiO 2 nanoparticles through nebulization of the nanocolloidal suspension.

Control of composite thin film made in an Ar/isopropanol/TiO2 nanoparticles dielectric barrier discharge by the excitation frequency

“…However, in our case, the NPs are bigger than in reference (>100 nm). Therefore, we believe that the simulations are of strong interest to take into account the aggregation of the NPs contained in the droplets after atomization . The gas flow is laminar, thus the gas velocity profile is taken as parabolic as shown in Figure .…”

“…Moreover, using a nebulization chamber or a wall impactor removes the bigger droplets and therefore the bigger aggregates. For this reason, an alcohol is chosen as solvent and polymerizable liquid in this study which aims to contribute to a better control of the integration of NPs aggregates thanks to the electrostatic force induced by the plasma voltage …”

“…The advantage of the method is that immiscible precursors can be used but it presents the disadvantage that the properties, size, and shape of the NPs are difficult to control together with the interface between the matrix and the NPs . A second approach consists of creating an aerosol of NPs in suspension in a polymerizable liquid and to inject it in the plasma . As the NPs are synthesized independently of the plasma, their characteristics can be well controlled.…”

“…However, as it is shown by Fanelli et al, a suitable solvent is necessary to create an appropriate aerosol of NPs suspension. Furthermore, if the NPs are not properly functionalized, they aggregate during the evaporation of the aerosol droplet . In the end, these aggregates are included in the matrix.…”

“…The first one consists of functionalizing the NPs. This functionalization can be steric, in which long chain are grafted on the NPs surface, or electrostatic, in which ionic charges are added on the NPs to induce repulsive forces . The solvent is also a key parameter to limit the agglomeration rate as shown by Dowling et al Small amounts of alcohol increase the stability of TiO 2 NPs suspensions.…”