Browsing by Subject "Titanium dioxide"
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Item Developing model architectures via atomic layer deposition to investigate interfacial electrochemical processes in lithium-ion batteries(2015-05) Charlton, Matthew Robert; Stevenson, Keith J.; Johnston, Keith P; Mullins, C Buddie; Crooks, Richard M; Rose, Michael JThis dissertation describes the development of thin film electrodes with well-defined structures and geometries (architectures) to aid in the assessment of complex charge transfer processes in lithium ion battery systems. Titanium dioxide (TiO₂) anodes and vanadium pentoxide (V₂O₅) cathodes are synthesized via atomic layer deposition (ALD) onto transparent and opaque carbon films and used as model interfacial systems to investigate the chemical and electrochemical properties of lithium ion (Li-ion) coupled electron transfer processes at the electrode/electrolyte interface. The superior film quality and precise control over structure and chemistry afforded by ALD allow tuning of the electrode properties to facilitate coupling of analysis methods and provide new insights. A combination of analytical techniques, including cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF SIMS), and ultraviolet-visible (UV-Vis) absorption spectrophotometry, is used to elucidate mechanistic information about charge storage processes. Electrochemical investigations of TiO₂ lithiation coupled with high-resolution, spatially resolved surface analytical techniques demonstrate that in situ formation of hydrofluoric acid (HF) during cycling can alter the lithiation process and introduce partial lithiation by conversion reaction as a result of HF co-intercalation. The relationship between electrode material length scale (thickness) and the balance between charge storage via bulk intercalation versus surface pseudocapacitance is also determined for TiO₂. Combined CV and UV-Vis absorption spectrophotometry are used to investigate optical and electronic transitions in transparent V₂O₅ cathodes as a function of lithiation.Item Effects of photocatalysis on concrete surfaces(2012-05) Terpeluk, Alexandra Lee; Juenger, Maria C. G.; Fowler, David W.Highway air pollution is a significant environmental threat that has staggering implications for human health worldwide. Photocatalytic materials have the potential to reduce air pollution levels near major highways using ultraviolet radiation. This project, funded by the Texas Department of Transportation, evaluated photocatalytic efficiency and durability of several commercially-available photocatalytic coatings for use on concrete structures near highways. The research presented in this thesis involved obtaining concrete highway barriers and creating concrete slabs for outdoor testing and laboratory chamber testing. Three commercially-available coatings were applied to the specimens for testing: Keim Soldalit ME paint, TxActive Stucco Cement, and Pureti Clean. Field sites were set up near major highways in Houston and Austin, Texas. Durability and photocatalytic efficiency were regularly monitored at the field sites using ion chromatography and spectrophotometry. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were conducted on samples from each of the specimens taken before and after placement at the field sites in order to understand durability of the photocatalytic materials that were exposed outdoors. SEM results from this research project revealed that the photocatalytic material in the TxActive stucco and Keim paint remained in their original distribution after the exposure period, while the photocatalytic material in the Pureti Clean product appeared to decrease. XRD results remained fundamentally consistent for all coatings. Ion chromatography results showed that TxActive specimens had the highest surface levels of nitrates and nitrites between rainfall events, which indicates photocatalytic activity. Spectrophotometry results revealed a decrease in brightness for the Keim paint-coated specimens and no change or an increase in brightness for the TxActive stucco over time. The spectrophotometry results indicate how many surface contaminants are accumulating on the surface of a specimen, and thereby how efficiently sunlight is reaching the surface and activating the photocatalytic process. Results obtained from this research project may be influential in the selection of a means for reducing highway pollution in Texas.