Date of Thesis

2015

Thesis Type

Masters Thesis

Degree Type

Master of Science in Chemical Engineering

First Advisor

Timothy M. Raymond

Second Advisor

Ryan Snyder

Keywords

Atmospheric aerosol, Particle, Nanoparticle, Size, Morphology, Atomic force microscope, AFM, Dicarboxylic acid, Cycling relative humidity, Drying

Abstract

Atmospheric aerosol particles have been known to influence the Earth's climate directly and indirectly. The magnitude of these effects strongly depends on their size, morphology, and their interaction with water at different relative humidities, yet our knowledge of them is largely limited. Moreover, many industrial processes such as food, personal care, and pharmaceuticals require a general knowledge of particles' size and morphology. Therefore, an investigation of these characteristics is essential to both industrial and atmospheric applications. Different techniques have been used to study these physical characteristics of particles; nevertheless, these studies did not extend their analysis to the effects of different drying rates. Drying rates in this thesis are referring to different drying processes with different starting droplets and conditions. It was not the objective of this study to quantify the drying rates; therefore, the term was used to generally simplify the descriptions of two different drying processes. The thesis' goal was to investigate the effect of drying rate on size and morphology of a few inorganic, amino acid and dicarboxylic acid (C3-C7) nanoparticles through the use of a scanning mobility particle spectrometer and an atomic force microscope. The hypothesis was that some chemical compounds resulted in different morphologies depending on the drying rates. Experimental results confirmed this hypothesis. Particularly, the even dicarboxylic acid particles (C4 and C6) did not change while the odd dicarboxylic acid particles (C3, C5 and C7) did. Both amino acids (glutamic acid and L-leucine) results showed that their size stayed the same. However, AFM images of glutamic acid showed some changes in their morphology. Finally, CaCl2 and NH4Cl exhibited no change while NH4NO3 results indicated that the particles might have crystallized into two forms depending on the drying rates.

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