Type
Text
Type
Thesis
Advisor
Gersappe, Dilip | Gouma, Pelagia-Irene (Perena) | Sokolov, Jonathan.
Date
2014-12-01
Keywords
Engineering
Department
Department of Materials Science and Engineering.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/76328
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
Abstract
Acetone is one of the biomarkers in our breath that may be used to control metabolic disorders, such as diabetes. Sensors that monitor acetone in breath with high specificity and high sensitivity are needed for this purpose. It has been found previously by our research group that nanostructure epsilon-phase WO3 -based sensors are highly selective to acetone compared to other volatile organic compounds found in breath. Since doping in metal oxides usually present stability issues in the long-term operation of a gas sensor, pure epsilon-WO3 is being explored as the sensing element of choice for develop a non-invasive method to monitor diabetes based on breath acetone monitoring. However, epsilon-WO3 is a thermodynamically unstable polymorph of the WO3 system at room temperature. Thus rapid solidification processing was employed in this project to synthesize pure epsilon-WO3 nanopowders. This thesis focuses on using flame spray pyrolysis to produce pure epsilon-WO3 nanoparticles that can be stable at high temperatures. The flame spray pyrolysis is a scalable nanomanufacturing process that allows the precursor chemicals (solute) to react with oxygen and the product to nucleate in the reactor when it is far away from the flame source. The advantage of flame spray pyrolysis is that it provides large temperature gradient for the product to nucleate and short residence time for its sintering; therefore, the metastable phase, epsilon-WO3, could be synthesized directly from a range of precursors (solutes) in a single step, by increasing the nucleation rate and reducing the residence time. In this work, isopropanol, xylene and a mixture of them have been used as the precursor solvent materials. Tungsten isopropoxide's raman spectroscopy and XRD analysis showed that the mixing of xylene with tungsten isopropoxide could produce the epsilon; phase at room temperature and that was stable at high temperature following heat treatment. It could be the reason that the xylene has higher evaporative rate than isopropanol so that creating the higher temperature gradient. In addition, ferroelectric testing on the sample that contains the epsilon-WO3 has been conducted. The testing device was served as a parallel-plate capacitor that has gold and copper as top and bottom electrode and the thickness is controlled by the thickness of thin film. The ferroelectric test result does not show the typical butterfly curve on the capacitance. It could be the reason that the film for the device is not thick enough so that a lot of defects to create the current leakage. Another possibility is that the particle size may be too small to observe ferroelectric effects. Suggestions for further studies that build on the current results are also made. | 66 pages
Recommended Citation
Liao, Wen Ling, "Processing and Characterization of ε -WO3 Processed by Flame Spray Pyrolysis" (2014). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 2252.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/2252