Graduation Year

2008

Document Type

Thesis

Degree

M.S.Ch.E.

Degree Granting Department

Chemical Engineering

Major Professor

Vinay K. Gupta, Ph.D.

Committee Member

Scott Campbell, Ph.D.

Committee Member

Babu Joseph, Ph.D.

Keywords

Settling velocity, Turbidometer, Titania, Ceria, Pnipam

Abstract

Sedimentation is one of many characterization tools used to test materials in nanotechnology. Characterization of settling behavior is complex as there are many variables which can affect sedimentation. In our research, we focused on sedimentation in colloidal systems with the aid of an optical turbidometer. Nanoparticles of CeO2 (Ceria Oxide) and TiO2 (Titanium Dioxide) are embedded onto a polymeric matrix of a thermally responsive microgel of poly(N-isopropylacrylamide) (PNIPAM) and interpenetrating chains of poly(acrylic acid) to create novel composites. The composites are loaded with the inorganic oxide nanoparticles at different weight percent from a low value of 10 weight % to 75 weight %. The loading of the colloidal particles affects the sedimentation rate. In this thesis a turbidomenter is used to characterize the settling rate, which is an important characteristic for application of these new composites.

TiO2 is a key constituent in many industrial products; cosmetics, paints, ceramics and used in waste water remediation. It is a potent photocatalyst which breaks down almost any organic compound when exposed to ultraviolet light. By combining nanoparticles of TiO2 with microgels of a polymer, the composites can facilitate use and recovery of the catalyst. Gravity settling of these loaded composites provides an easy separation of TiO2 nanoparticles. In this context, characterization of settling plays an important role. CeO2 composites are used to polish oxide coatings in the semiconductor industry and sedimentation of the composite particles is important as it can affect the efficiency of the planarization process. Therefore, measuring sedimentation of these composites is necessary.

In this study, the settling behavior is measured optically for a variety of conditions that differ in loading of inorganic nanoparticles within the microgels, temperature of the solution, and concentration of particles in solution. The overall goal is to understand the sedimentation behavior of these novel composites and facilitate their use in industrial processes.

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