A Method to Study Agglomerate Breakup and Bounce During Impaction

The impaction behavior of agglomerates plays a significant role in nanoparticle technology. In order to be able to evaluate the process of de-agglomeration, the agglomerates are impacted onto a surface and forces are estimated from the breakup of the agglomerates. Several studies have used this principle; however, the simultaneous bounce and breakup of the agglomerates has received little attention. In this study, a method was devised to study both agglomerate breakup and bounce during impaction. In this method, the agglomerates were impacted onto an impaction plate located in a single stage micro-orifice uniform deposit impactor and the bounced particles were collected into a sampling chamber specially designed for this task. This way, the properties of the deposited and bounced particles can be examined with transmission electron microscopy, but in addition, the bounced particles can be analyzed with online measurement instruments, such as the scanning mobility particle sizer. Titanium dioxide (TiO 2 ) and copper particles were used to test and validate the system, and the first impaction behavior results with this system were acquired using TiO 2 agglomerates. It was evident that the agglomerates broke up during impaction under the conditions used in this study; the diameter of the particles decreased from 269 nm to 143 nm. It was found that half of the particles bounced. The particle diameter and the fractal dimension of the bounced particles were very similar to those of the particles that did not bounce. Copyright 2012 American Association for Aerosol Research