Thesis (Ph.D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 113-119). Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Christine E. Schmidt. Vita. Includes bibliographical references.

No description available.

Silicone rubber is a promising candidate for the next generation of electrical insulators on account of the prolonged hydrophobicity of the polymers. However, microalgae biofouling is always a concern for high voltage insulators installed in coastal regions. To understand how microalgae species interact with polymer surfaces that are used in electrical insulator applications, a study has been conducted to determine the interactions of a benthic and a pelagic algal species with polydimethylsiloxane surfaces. The adhesion strength of algal species were quantified with two different types of flow cells employed for our studies. These two types of flow cells are microfluidic chips and a laser-cut flow cell chamber, which provide a high and low wall shear stress, respectively. A video analysis software was designed to automate all aspects of the flow rate profile, data acquisition, and image analysis. Pristine poly(dimethyl siloxane) (PDMS), deionized water-exposed PDMS, and salt solution-exposed PDMS samples were used as substrates in adhesion experiments. The results indicate that surface hydrophobicity played a critical role in adhesion strength. At low shear stress, both B. braunii and T. rotula cells demonstrate a strongest adhesion strength onto the pristine PDMS surface, while show the weakest adhesion strength onto the salt solution exposed PDMS surface. At high shear stress, all PDMS surfaces provide an equal adhesion environment to the both species. / Graduate / 2021-12-11

Removing pyrite from coal and pyrrhotite from pentlandite play a critical role in coal and nickel production, respectively, to meet the stringent restriction on SO2 emission. The present project investigates first the mechanism of xanthate adsorption on gold using Atomic Force Microscope (AFM), then the depression of pyrite and pyrrhotite using the synthetic polymers developed by Cytec Industries. The results show that for xanthate/gold system, dixanthogen is the only species that renders the surface hydrophobic. Chemisorbed xanthate is observed on the gold surface but is hydrophilic. The synthetic polymers may adsorb on pyrite and pyrrhotite possibly through the hydrophobic interaction between the hydrophobic moiety of the polymer and the mineral surface that has been hydrophobized by collector adsorption. The hydrophilic moieties of the polymer are exposed to the aqueous phase and render the surface hydrophilic. / Master of Science

No description available.

For applications of MoS2 in batteries, supercapacitors, electrocatalysts, solar cells and water quality sensors, a substantially increased conductivity is required in order to achieve reasonable currents. Popularly, the metallic 1T-MoS2 phase is used, which can be prepared via a lithium intercalation process, requiring inert atmosphere processing and safety procedures. In this thesis, I demonstrate a safer and more efficient process to yield conductive MoS2 (c-MoS2). This simple and effective way to prepare few layer c-MoS2 utilizes ambient conditions and 0.06 vol% aqueous hydrogen peroxide. Part of the research effort has been to enhance the conductivity of MoS2 using the idea of green solvents (like pure water). The bulk conductivities of both peroxide and water exfoliated MoS2 are up to seven orders of magnitude higher than that of the semiconducting 2H-MoS2 phase. The samples were characterized with Hall measurements, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Trace amounts of hydrogen molybdenum bronze (HxMoO3-y) and sub stoichiometric MoO3-y were shown to help tune the conductivity of the nanometer-scale thin films without impacting the sulfur-to-molybdenum ratio. c-MoS2 was further functionalized with thiols to determine the number of residual reactive sites. I also studied the mechanism of surface functionalization of MoS2 with diazonium molecules (both direct and in-situ approach) to understand the surface properties of our material and tune the chemical and mechanical properties of conductive MoS2. An important goal of my work is to control the conductivity of the MoS2 thin films in safe and facile ways that enable their application in low-cost chemiresistive sensors for liquid environments. I fabricated chemiresistive sensors with centimeter channel lengths while maintaining low measurement voltages for pH sensing. I further measured the catalytic activity of c-MoS2 films in 0.5 M H2SO4 electrolyte solution using linear sweep voltammetry (LSV) which showed a lower Tafel value at 10 mA/cm2 current density. The lower Tafel value demonstrated that c-MoS2 has potential to use as catalyst for hydrogen evolution reaction. My study furthers the understanding of conductive forms of MoS2 and opens up a new pathway for next generation electronic and energy conversion devices. / Thesis / Doctor of Philosophy (PhD) / For applications of MoS2 in batteries, supercapacitors, electrocatalysts, solar cells and water quality sensors, a substantially increased conductivity is required in order to achieve reasonable currents. Popularly, the metallic 1T-MoS2 phase is used, which can be prepared via a lithium intercalation process, requiring inert atmosphere processing and safety procedures. In this thesis, I demonstrate a safer and more efficient process to yield conductive MoS2 (c-MoS2). This simple and effective way to prepare few layer c-MoS2 utilizes ambient conditions and 0.06 vol% aqueous hydrogen peroxide. Part of the research effort has been to enhance the conductivity of MoS2 using the idea of green solvents (like pure water). The bulk conductivities of both peroxide and water exfoliated MoS2 are up to seven orders of magnitude higher than that of the semiconducting 2H-MoS2 phase. The samples were characterized with Hall measurements, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Trace amounts of hydrogen molybdenum bronze (HxMoO3-y) and sub stoichiometric MoO3-y were shown to help tune the conductivity of the nanometer-scale thin films without impacting the sulfur-to-molybdenum ratio. c-MoS2 was further functionalized with thiols to determine the number of residual reactive sites. I also studied the mechanism of surface functionalization of MoS2 with diazonium molecules (both direct and in-situ approach) to understand the surface properties of our material and tune the chemical and mechanical properties of conductive MoS2. An important goal of my work is to control the conductivity of the MoS2 thin films in safe and facile ways that enable their application in low-cost chemiresistive sensors for liquid environments. I fabricated chemiresistive sensors with centimeter channel lengths while maintaining low measurement voltages for pH sensing. I further measured the catalytic activity of c-MoS2 films in 0.5 M H2SO4 electrolyte solution using linear sweep voltammetry (LSV) which showed a lower Tafel value at 10 mA/cm2 current density. The lower Tafel value demonstrated that c-MoS2 has potential to use as catalyst for hydrogen evolution reaction. My study furthers the understanding of conductive forms of MoS2 and opens up a new pathway for next generation electronic and energy conversion devices.

No description available.

Call number: LD2668 .T4 1986 A53 / Master of Science / Chemical Engineering

The stationary phase on chemically modified supports for liquid chromatography is described as a mixture of the surface-bonded species, the active unmodified surface, and associated mobile phase components. Each of these three factors in stationary phase formation is examined and improved qualitative and quantitative descriptions of the stationary phase are provided. The role of the active unmodified surface was examined by synthesizing a carbon support and chemically modifying it with octyl groups. The modified carbon had a greater affinity for lipophilic probes than an octyl silica. The lipophilicity of the octyl carbon was attenuated relative to the unmodified carbon. The physical state of the bonded species in C(,18) and C(,8) packings was studied using carbon-13 NMR. Peak widths of 2-7 ppm indicated a liquid-like nature but with restricted movement. Only the 7 to 10 carbons in a C(,18) chain farthest from the surface were sufficiently motile to produce a signal. The C(,8) packing showed more rigid chains with only the top 3 or 4 carbons responding. The liquid-like nature of a C(,18) chain increased with the lipophilic character of the solvent, indicating that solvation of the bonded species was directly related to the mobile phase composition. Changes in temperature had little effect on the physical state of the bonded species, but chromatographic enthalpy measurements showed that changes in stationary phase composition could be induced by warming the column and held by subsequent cooling. Quantitative measurements of stationary phase compositions revealed linear distribution isotherms for the organic modifiers methanol, acetonitrile, and tetrahydrofuran. Chromatographic selectivities for homologous n-alkanols correlated linearly with organic modifier concentrations in the stationary phases. The stationary phase volumes, which increased with increasing modifier concentrations, are interpreted as constituting filling of the pores in the support with a gradient of modifier enrichment toward the surface.