PREPARATION OF ALUMINA / POLY (ETHYLENE OXIDE) NANOCOMPOSITES WITH CONTROLLED SPACING

Open Access
- Author:
- Shi , Wenjin
- Graduate Program:
- Chemical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 16, 2010
- Committee Members:
- Janna Kay Maranas, Thesis Advisor/Co-Advisor
Janna Kay Maranas, Thesis Advisor/Co-Advisor - Keywords:
- solvent extraction
solvent displacement
miniemulsion
nanocomposites
alumina
PEO - Abstract:
- This thesis describes the production of γ-Al2O3 – poly (ethylene oxide) (PEO) nano-composites by a novel colloidal processing route. PEO is a candidate for use as a solid polymer electrolyte in lithium ion batteries, but the ionic conductivity of pure PEO is too low to be of practical use. The addition of ceramic nanoparticles into the PEO matrix results in increased ionic conductivity. Additionally, the ionic conductivity of these nanocomposites correlates directly with the specific surface area of the dispersed ceramic phase. Therefore, the dispersion and spacing of the ceramic phase in these nanocomposites is of the utmost importance. As ceramic nanoparticles aggregate very easily in PEO, the preparation of highly dispersed nanoparticles composites with well-controlled spacing presents a unique processing challenge. In this work, well dispersed, colloidal suspensions of γ-Al2O3 and PEO nanoparticles were prepared in a common solvent system and were spin cast to evaporate the solvent. The resulting films can then be melted to leave isolated γ-Al2O3 nanoparticles in a continuous PEO matrix. γ-Al2O3 nanoparticles were dispersed in non-polar organic solvent by a solvent extraction technique, while two separate approaches were utilized to prepare the PEO nanoparticle suspensions. A reverse emulsion technique yielded PEO particles from 100 to 300 nm in size, while a solvent displacement method produced average sizes of 100 to 200 nm. Dynamic Light Scattering (DLS) was used to measure the particle size distributions of PEO and alumina nanoparticles in suspension and field emission scanning electron microscopy (FESEM) characterized the resulting polymer nanocomposites. The techniques discussed in this work were developed to test the influence of nanoparticle addition to solid polymer electrolytes [SPEs] by creating a series of samples with controlled, adjustable nanoparticle spacing subsequently. These samples will directly reveal the effects of confinement and surface area on the ionic conductivity of SPEs. A study such as this could reveal how the spacing and dispersion of nanoparticles affects the ionic conductivity of SPEs, as the mechanisms leading to increased conductivity are not well understood. This work focuses heavily on the study of processing methods, surfactant behavior, and dispersion of γ-Al2O3 in a specific set of solvents that show promise for producing well-dispersed PEO nanoparticles. Using this system, γ-Al2O3 -PEO nanocomposites were prepared from γ-Al2O3 and PEO nanospheres in the range of 100 - 300 nm.