Infrared Extinction Coefficients of Aerosolized Conductive Flake Powders and Flake Suspensions having a Zero-Truncated Poisson Size Distribution.

摘要

High-aspect-ratio aluminum, graphite, and brass flake powders were disseminated into an aerosol chamber and their infrared extinction coefficients were measured. Suspensions, which were prepared by stirring and sonicating the flake powders into ethanol, were also disseminated into the aerosol chamber as droplets that quickly evaporated, leaving aerosols that were used for extinction measurement. A twin-fluid atomizing nozzle was used to disseminate all materials into a stirred 190 cu m cylindrical aerosol chamber. After dispersion by the nozzle and thorough chamber mixing with a low speed fan, spectral aerosol transmittance and concentration were simultaneously measured to obtain spectral extinction coefficients. Zero-truncated Poisson distributions were used to describe the population of flakes in aerosol particles that were produced by evaporation of suspension droplets. The geometric optics expression for flake extinction coefficient also provided a way to obtain the average agglomerate thickness from aerosol extinction coefficient measurements. This information was then interpreted in terms of single flakes and flake aggregates that coalesced when suspension droplets evaporated and briefly coagulated. Aerosols formed by disseminating dry powders formed agglomerates consisting of 1.3 to 3 flakes per particle, and dried suspension droplet aerosols formed larger agglomerates consisting of 2 to 5 flakes per particle.