Neutron diffraction study of water freezing on aircraft engine combustor soot

Abstract

The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction.

Ice nucleation by particles immersed in supercooled cloud droplets

“…Aerosol particles resulting from combustion are complex and highly variable, ranging from elemental carbon through to complex mixtures of organic and inorganic materials. [281][282][283][284] In part, this reflects the varied sources of combustion aerosol, with contributions from fossil fuel burning as well as biomass burning for domestic use and in wildfires. The terminology associated with combustion aerosol is at times confusing in the literature, but here we use the terms defined by Andreae and Gelencse´r.…”

Icephobic materials: Fundamentals, performance evaluation, and applications

“…With the assistance of Cassie-Baxter wetting model, the actual solid / liquid contact area decreases greatly and therefore leads to less probability to trigger heterogeneous ice nucleation. Overall, the nanostructured hydrophobic or superhydrophobic surface exhibits a strong ability to inhibit ice nucleation, and such ability is affected by the 61 / 141 size of nanostructures and the actual solid / liquid contact area [200,201]. Reprinted with the permission of Ref.…”

Ice Nucleation Activities of Carbon-Bearing Materials in Deposition Mode: From Graphite to Airplane Soot Surrogates

“…Alternative measurements [38][39] include the amount of adsorbed water (in terms of monolayers) at a given RH. In addition, ice nucleation abilities were shown to depend upon temperature regimes, where black carbon samples were found non-active in mixed-phase clouds (MPCs) regimes (above -38°C) but potentially active in cirrus clouds (CCs) regimes 40 (below -38°C).…”

“…Therefore, a sample can be observed as being active from its ice nucleation onset yet exhibiting only a few ice crystals over the whole aerosol population and over the time of the experiment. Alternative measurements , include the amount of adsorbed water (in terms of monolayers) at a given RH. In addition, ice nucleation abilities were shown to depend upon temperature regimes, where black carbon samples were found nonactive in mixed-phase clouds (MPCs) regimes (above −38 °C) but potentially active in CC regimes (below −38 °C).…”