Abstract View
Frequency-Dependent Humidity Response in Ultraviscous and Gel Particles
CRAIG SHELDON, Chelsea Price, Ryan Davis, James F. Davies, University of California, Riverside
Abstract Number: 475
Working Group: Aerosol Chemistry
Abstract
The amount of water within an aerosol particle, determined by the relative humidity (RH), affects many aspects of an its characteristics. At low RH, the physical state of an aerosol can be crystalline, amorphous, or a combination of the two, such as in a gel, depending on the composition of the particle. These states are associated with slow diffusive mass transport, with implication for equilibration times and chemical reaction rates.
This research explores the relaxation times of various mixtures of inorganic and organic components of liquid particles exposed to changes in RH. For particles that form ultraviscous states, it is expected that the relaxation time will increase continuously with decreasing RH as diffusion rate decreases. However, if the particle experiences a phase change, to a gel state for example, relaxation time may change in a non-continuous manner. In a gel state, water transport will become restricted by slow percolation through pores within the particle, increasing the relaxation time. In this work we measure the response of levitated particles to RH oscillations (±2.5%) in a linear quadrupole electrodynamic balance to explore the relaxation time of these particles over a full range of RH. The response time following gel formation will be a function of both diffusive mass transport and percolation and detailed analysis may provide insight into the microstructure of the gel.