Reaction selectivity studies on nanolithographically-fabricated platinum model catalyst arrays (open access)

Reaction selectivity studies on nanolithographically-fabricated platinum model catalyst arrays

In an effort to understand the molecular ingredients of catalytic activity and selectivity toward the end of tuning a catalyst for 100% selectivity, advanced nanolithography techniques were developed and utilized to fabricate well-ordered two-dimensional model catalyst arrays of metal nanostructures on an oxide support for the investigation of reaction selectivity. In-situ and ex-situ surface science techniques were coupled with catalytic reaction data to characterize the molecular structure of the catalyst systems and gain insight into hydrocarbon conversion in heterogeneous catalysis. Through systematic variation of catalyst parameters (size, spacing, structure, and oxide support) and catalytic reaction conditions (hydrocarbon chain length, temperature, pressures, and gas composition), the data presented in this dissertation demonstrate the ability to direct a reaction by rationally adjusting, through precise control, the design of the catalyst system. Electron beam lithography (EBL) was employed to create platinum nanoparticles on an alumina (Al{sub 2}O{sub 3}) support. The Pt nanoparticle spacing (100-150-nm interparticle distance) was varied in these samples, and they were characterized using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM), both before and after reactions. The TEM studies showed the 28-nm Pt nanoparticles with 100 and 150-nm interparticle spacing on …
Date: May 15, 2004
Creator: Grunes, Jeffrey Benjamin
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Characterization of the molecular structure and mechanical properties of polymer surfaces and protein/polymer interfaces by sum frequency generation vibrational spectroscopy and atomic force microscopy (open access)

Characterization of the molecular structure and mechanical properties of polymer surfaces and protein/polymer interfaces by sum frequency generation vibrational spectroscopy and atomic force microscopy

Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and other complementary surface-sensitive techniques have been used to study the surface molecular structure and surface mechanical behavior of biologically-relevant polymer systems. SFG and AFM have emerged as powerful analytical tools to deduce structure/property relationships, in situ, for polymers at air, liquid and solid interfaces. The experiments described in this dissertation have been performed to understand how polymer surface properties are linked to polymer bulk composition, substrate hydrophobicity, changes in the ambient environment (e.g., humidity and temperature), or the adsorption of macromolecules. The correlation of spectroscopic and mechanical data by SFG and AFM can become a powerful methodology to study and engineer materials with tailored surface properties. The overarching theme of this research is the interrogation of systems of increasing structural complexity, which allows us to extend conclusions made on simpler model systems. We begin by systematically describing the surface molecular composition and mechanical properties of polymers, copolymers, and blends having simple linear architectures. Subsequent chapters focus on networked hydrogel materials used as soft contact lenses and the adsorption of protein and surfactant at the polymer/liquid interface. The power of SFG is immediately demonstrated in experiments which identify the chemical …
Date: May 15, 2004
Creator: Koffas, Telly Stelianos
Object Type: Thesis or Dissertation
System: The UNT Digital Library
MAG-GATE System for Molten metal Flow Control (open access)

MAG-GATE System for Molten metal Flow Control

The need for improved active flow control has been recognized as part of the Steel Industry Technology Roadmap. Under TRP 9808 for the American Iron and Steel Institute and the Department of Energy, Concept Engineering Group Inc. has developed MAG-GATE{trademark}, an electromagnetic system for active molten metal flow control. Two hot steel tests were successfully conducted in 2003 at the Whemco Foundry Division, Midland, PA. Approximately 110,000 pounds of 0.2% carbon steel were poured through the device subject to electromagnetic flow control. Excellent agreement between predicted and actual flow control was found. A survey of the molten metal flow control practices at 100 continuous casters in North America was also conducted in 2003. This report summarizes the results of the development program to date. Preliminary designs are described for the next step of a beta test at an operating billet/bloom or slab caster.
Date: May 15, 2004
Creator: Nathenson, Richard D.
Object Type: Report
System: The UNT Digital Library
Infrared Imaging for the Detection of Radioactive Material in Various Storage Containers (open access)

Infrared Imaging for the Detection of Radioactive Material in Various Storage Containers

Three separate tests were conducted in 2003 and 2004 at the Plutonium Finishing Plant (PFP) at the Hanford, Washington site to determine if infrared imaging can be used to detect the presence of radioactive material in various storage containers. The tests were conducted at the two most common infrared wavelength ranges used for nondestructive evaluations, 3-5 microns and 8-12 microns. The results of the tests indicate that infrared imaging can be used to detect the presence of stored radioactive materials. However, the temperature difference between the end plates and the ambient temperature is generally not large, about 1 F. Some of the end plates were much hotter than others, probably due to the amount, type, and location of the material stored in them and any packing material also stored in the containers. Although there was consistency between the three tests, there were also some inconsistencies, probably due to reflections and emissivity differences in the surface of the en d plates. There was excellent consistency between the random temperature measurements made with a contact thermocouple and the infrared image. In addition, testing with the radio-reflectors indicated that the presence of stored radioactive materials in the middle of the canister can be …
Date: May 15, 2004
Creator: Peters, Timothy J.
Object Type: Report
System: The UNT Digital Library