Engineering Commons^™

Controlled-Stress Large-Area Pulsed Laser Deposition Of Yttria Stabilized Zirconia, Paul C. Rounsavall

Theses and Dissertations

The US Air Force has need of parabolic-shaped membrane mirrors for surveillance satellites. The current polymer membrane technology has been unable to overcome shape deformation problems caused by intrinsic stresses from the membrane casting and mounting processes. One proposed solution was to coat the membrane mirrors with a stressed coating to compensate for shape deformations. Thus, the research presented in this dissertation produced controlled-stress large-area pulsed laser deposition (PLD) grown thin films on polymer substrates and investigated optical time-of-flight (TOF) sensor systems and Raman spectroscopy for control for the PLD process with respect to thin film stress. Initially, the PLD-grown …

Electrical Activation Studies Of Silicon Implanted Alx Gal-X N And Coimplanted Gan, Elizabeth A. Chitwood

Theses and Dissertations

A comprehensive study of the electrical activation of silicon implanted Al_xGa_1-xN was performed as a function ion dose, anneal temperature, and aluminum mole fraction, Also, GaN coimplanted with silicon and nitrogen was investigated. Room temperature Hall effect measurements were used to determine carrier concentration and mobility. All the samples had a 500 Å encapsulant of AlN, and were implanted at room temperature with 200 keV silicon ions at doses ranging from 1x10¹³ to 1x10¹⁵ /sq cm. The GaN was also implanted with nitrogen under the same conditions in doses of 9x10¹² to 9x10 …

Luminescence Studies Of Ion-Implanted Gallium Nitride And Aluminum Gallium Nitride, Erin N. Claunch

Theses and Dissertations

Recently, research on the wide bandgap semiconductors such as GaN and Al(x)Ga(1-x)N became very popular for their applications on various devices. Therefore comprehensive and systematic luminescence studies of Si implanted Al_xGa_1-xN, Mg doped GaN, and Si+N implanted GaN grown on sapphire substrates by molecular beam epitaxial method have been made as a function of ion dose and anneal temperature.

Pure Iron Electrolyzed From Scrap Iron Chips And Its Corrosion Characteristics, Wei-Min Cao, Ren-He Yin, Hui-Ceng Yan, Zhi-Qiang Ye

Journal of Electrochemistry

The high purity electrolytic iron was made from scrap iron chips. Electrolytic conditions of pure iron were determined in chloride baths and the highest purity was 99.983% by chemical analysis. Pure iron had very compact texture and high mechanical strength by SEM figures of cross section. In deaerated 0.5 kmol·m-3H2SO4 and 0.5 kmol·m-3NaCl solutions, the corrosion rate of iron decreased with increasing purity.

Localized Charge Transfer In Csau·Nh3:  1h And 133cs Nuclear Magnetic Resonance, Steffen Kramer, Michael Mehring, Anja V. Mudring, Martin Jansen

Anja V. Mudring

We report results from 1H and 133Cs nuclear magnetic resonance (NMR) studies on CsAu·NH3. This compound has recently been synthesized and belongs to the family of ammoniates. The intense blue color of the material, which is not observed in the parent compounds, suggests that a charge-transfer electronic state is formed. The 1H NMR line shape and relaxation rates are found to be very similar to the corresponding properties in pure ammonia. However, the 133Cs-NMR properties of CsAu·NH3 strongly deviate from the corresponding ones in CsAu, and we show that the former can be interpreted consistently within a localized charge distribution …

Thermal Assessment Of Silicon-Based Composite Materials Used In Photovoltaics, Pavlos K. Bataglannis

Theses

Photovoltaics are devices that convert sunlight directly to electricity. It is well established that the conversion efficiency of mono and poly-crystalline silicon-based photovoltaic modules is inversely related to their temperature. Substantial improvements in operational performance can thus be achieved if the thermal energy accumulating in the material can be effectively dissipated.

Accurate modelling of modules would allow possible methods of thermal dissipation to be evaluated, and as a crucial component of the model, the thermal properties of the constituent materials of PV modules needed to be known. Special consideration needed to be given to the interfaces between dissimilar materials and …