Date on Master's Thesis/Doctoral Dissertation

12-2019

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Committee Chair

Willing, Gerold

Committee Co-Chair (if applicable)

Williams, Stuart

Committee Member

Williams, Stuart

Committee Member

Watters, James

Author's Keywords

Colloid; nanoparticle; haloing; silsesquioxane

Abstract

Colloidal suspensions typically contain a multi-phase system of solid particles suspended in a liquid medium. Colloids are widely used in industrial applications such as inks, paints, motor oils, foods, cosmetics, and many more. Colloidal systems are typically formed by the interaction of the attractive van der Waals forces and one or more repulsive forces. These repulsive forces include electrostatic repulsion, steric hindrance, and nanoparticle haloing. Nanoparticle Haloing (NPH) is a phenomenon discovered in 2001 as a viable method to stabilize colloidal systems of uncharged silica microparticles using highly charged zirconia nanoparticles. For this thesis the effects of NPH were tested and compared between ground-based experiments and experiments conducted in microgravity aboard the International Space Station (ISS). This study found that for the same bimodal sample of 0.055 vol% nanoparticles and 1 vol% microparticles, the time for the system to reach steady state was 30 minutes in gravity settling conditions versus less than three minutes in a microgravity environment. This indicated that the ground experiments were better mixed due to sonication than the microgravity samples, which used magnetic stir bar mixing. The data presented herein illustrates the effects of microgravity on the NPH system and the viability of nanoparticle haloing as a stabilization mechanism for future applications such as high performance quantum-dot solar cells (QDSS). This study notes key factors for colloidal systems in microgravity and lays the groundwork for future nanoparticle haloing experiments. During the experiment potential issues were noted such as illumination, image capture rate, and the mixing iv apparatus. For each issue a recommendation is made for future work in nanoparticle haloing colloidal systems in a microgravity environment.

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