AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Classifying Nanoparticles with the Aerodynamic Aerosol Classifier: Monodisperse Classification without Particle Charge Artifacts
JASON S. OLFERT, Charlie Lowndes, Jonathan Symonds, Kingsley Reavell, Mark Rushton, University of Alberta
Abstract Number: 28 Working Group: Instrumentation and Methods
Abstract The Aerodynamic Aerosol Classifier (AAC) classifies particles by their relaxation time (or aerodynamic diameter). The AAC consists of two rotating coaxial cylinders. The aerosol enters through a gap in the inner cylinder and is carried axially by particle-free sheath flow. Between the rotating cylinders, the centrifugal force causes the particles to move in the radial direction. Particles with a narrow range of aerodynamic diameters exit the classifier through a gap in the outer cylinder with the sample flow. Particles with larger aerodynamic diameters impact and adhere to the outer cylinder and particles with smaller aerodynamic diameters exit the classifier with the exhaust flow.
Unlike the differential mobility analyser (DMA) or centrifugal particle mass analysers (CPMA or APM) the classification does not depend on the electrical charge state of the particles. Therefore, the AAC is a preferred classifier where a truly monodisperse aerosol is desired.
Previously work has shown theoretical models of the transfer function of the AAC, experimental validation of those transfer functions, and tandem measurements using an AAC and DMA to measure particle mass, effective density, mass-mobility exponent, and dynamic shape factor.
In previous work most of the measurements were made between ~100–1000 nm in aerodynamic diameter due to the limited rotational speed of the first prototype AAC. Recently, a new prototype AAC has been developed with a much higher maximum rotational speed.
The AAC was tested using a scanning mobility particle sizer (SMPS). Atomized NaCl was passed through the AAC operating at a fixed rotational speed. Aerodynamic diameters ranging down to 23 nm were successfully measured.