Physics Commons^™

Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat

Graduate College Dissertations and Theses

Small molecule organic semiconductors such as phthalocyanines and their derivatives represent a very interesting alternative to inorganic semiconductor materials for the development of flexible electronic devices such as organic thin field effect transistors, organic Light Emitting Diodes and photo-voltaic cells. Phthalocyanine molecules can easily accommodate a variety of metal atoms as well in the central core of the molecule, resulting in wide range of magnetic properties. Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to sub-micron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. However, this can be overcome by …

The Interaction Mechanisms Of A Screw Dislocation With A Defective Coherent Twin Boundary In Copper, Qiongjiali Fang

Graduate College Dissertations and Theses

Σ3{111} coherent twin boundary (CTB) in face-centered-cubic (FCC) metals and alloys have been regarded as an efficient way to simultaneously increase strength and ductility at the nanoscale. Extensive study of dislocation-CTB interaction has been carried out by a combination of computer simulations, experiments and continuum theory. Most of them, however, are based on the perfect CTB assumption. A recent study [Wang YM, Sansoz F, LaGrange T, et al. Defective twin boundaries in nanotwinned metals. Nat Mater. 2013;12(8):697-702.] has revealed the existence of intrinsic kink-like defects in CTBs of nanotwinned copper through nanodiffraction mapping technique, and has confirmed the effect of …

Numerical Simulations Of Reacting Flow In An Inductively Coupled Plasma Torch, Maximilian Dougherty

Graduate College Dissertations and Theses

In the design of a thermal protection system for atmospheric entry, aerothermal heating presents a major impediment to efficient heat shield design. Recombination of atomic species in the boundary layer results in highly exothermic surface-catalyzed recombination reactions and an increase in the heat flux experienced at the surface. The degree to which these reactions increase the surface heat flux is partly a function of the heat shield material. Characterization of the catalytic behavior of these materials takes place in experimental facilities, however there is a dearth of detailed computational models for the fluid dynamic and chemical behavior of such facilities. …

Experimental Investigation And Analysis Of High-Enthalpy Nitrogen Flow Over Graphite, Andrew Lutz

Graduate College Dissertations and Theses

The high-enthalpy flow generated by hypersonic vehicles traveling within the Earth's atmosphere inherently delivers an elevated heat flux to the vehicle surface. In addition to conductive heating, the liberated energy generated by various exothermic chemical reactions occurring at the vehicle surface further augment the total heat load. Quantifying the rates at which these reactions take place is imperative and remains a significant challenge as developers attempt to design the next generation of thermal protection systems.

This study focused on nitrogen recombination and carbon nitridation, as these reactions are ubiquitous to the most aggressive atmospheric re-entry trajectories in which carbon-based ablative …

Density Functional Theory Study Of Dilute Transition Metal Phthalocyanines, Daniel Burrill

Graduate College Dissertations and Theses

Organometallic (OM) crystals are studied in fields ranging from spintronics to photovoltaics. This thesis focuses on studying a particular class of OM crystals known as transition metal-phthalocyanines (TM-Pc) - a molecular crystal composed of chains of planar OM molecules with a transition metal center and four coordinated pyrrole-aromatic rings joined by nitrogen atoms, similar to porphyrin. The structure resembles a dish rack pattern where the planar TM-Pcs of adjacent chains are oriented nearly perpendicular to each other. While TM-Pcs have been studied for decades due to their interesting optical properties and applications as dyes, there has been recent interest in …

Spatiotemporally Periodic Driven System With Long-Range Interactions, Owen Dale Myers

Graduate College Dissertations and Theses

It is well known that some driven systems undergo transitions when a system parameter is changed adiabatically around a critical value. This transition can be the result of a fundamental change in the structure of the phase space, called a bifurcation. Most of these transitions are well classified in the theory of bifurcations. Among the driven systems, spatiotemporally periodic (STP) potentials are noteworthy due to the intimate coupling between their time and spatial components. A paradigmatic example of such a system is the Kapitza pendulum, which is a pendulum with an oscillating suspension point. The Kapitza pendulum has the strange …