Effects of charge and size on condensation of supersaturated water vapor on nanoparticles of SiO2

Abstract

The effects of size and charge on the condensation of a supersaturated water vapor on monodisperse nanoparticles of SiO(2) were investigated in a flow cloud chamber. The dependences of the critical supersaturation S(cr) on particle size at diameters of 10, 12, and 15 nm as well as on charge and charge polarity are determined experimentally. A novel electrospray aerosol generator was developed to generate a high concentration of SiO(2) nanoparticles of less than 10 nm by electrospraying silicon tetraethoxide (STE) ethanol solution followed by the thermal decomposition of STE. The effects of liquid flow rate, liquid concentration, flow rate of carrier gas, and liquid conductivity on the particle size distribution and concentration were examined. For charged particles, the nucleation occurs at a critical supersaturation S(cr) lower than that on neutral particles, and the charge effect fades away as particle size increases. The charge effect is stronger than the theoretical predictions. In addition, a sign preference is detected, i.e., water vapor condenses more readily on negatively charged particle, a trend consistent with those observed on ions. However, both effects of charge and charge polarity on S(cr) are stronger than that predicted by Volmer's theory for ion-induced nucleation.

The role of hydrogen bonding in nanocolloidal amorphous silica particles in electrolyte solutions

“…For example, even after 30 min the layer was still growing on the silica particles. It might be possible that the growth of hydration/hairy layer on silica nanoparticles suspended in solution is much faster because it is shown experimentally that small (7.12 nm) silica particles are strongly hydrated compared to the large (16.5 nm) silica particles [55,56]. This increased hydration of small particles is due to the increased curvature at the particle solution interface.…”

A modified expression for the steady-state heterogeneous nucleation rate

“…We choose three groups of experimental data reported in the literature: the first group (Koutsky, Walton, & Baer, 1965) shows the relationship between the critical supersaturation and the wetting degree of flat surface in the nucleation of water, the second group (Chen & Cheng, 2007) shows the relationship between the critical supersaturation and the particle radius in the nucleation of water, and the last group (Schobesberger et al, 2010) 6. Comparison of predicted and measured critical supersaturations S cri as functions of nucleation temperature T in the heterogeneous nucleation of npropanol on Ag particles whose radii are (a) 2 nm and (b) 4 nm, respectively.…”

An adsorption theory of heterogeneous nucleation of water vapour on nanoparticles

“…Chem. Phys., 16, 135-143, 2016 www.atmos-chem-phys.net/16/135/2016/ sorption measurements of Naono et al (1994) was of a grade treated at 800 • C. On the other hand, the silica nanoparticles used in the nucleation experiments were produced by two different techniques: oxidation of SiCl 4 at 1000 • C , and thermal decomposition of silicon tetraethoxide at 800 • C (Chen and Tao, 2000;Chen and Cheng, 2007). Apparently, the adsorption parameters determined from the data of Naono et al (1994) are appropriate for these aerosols.…”