Part I, Solution Route to Advanced Ceramics ; Part II, A Study of the Photodissociation of Phosphine

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Date
1990
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Publisher
University of Alabama Libraries
Abstract

I. Solution Routes to Advanced Ceramics:

The solution-based synthesis of ceramic powders is one method of controlling and improving their properties. Examples of two different classes of advanced ceramics, the bismuth-based family of high-temperature (high-Tc) superconductors and the ceramic matrix composite (CMC) "TiAlON", have been prepared using solution-based routes. The resulting materials were characterized using four-probe (ac) resistance versus temperature, x-ray powder diffraction, scanning electron microscopy, and surface area analysis.

The solution-synthetic method for the high-Tc superconductors is based on well defined, soluble, stable and readily available metallorganic precursors. The materials prepared by this method exhibited higher densities and showed slight improvements in electrical properties when compared to those obtained from conventional solid-state methods. The "TiAION" composite prepared from the solution synthesis presented here was found to have greater surface area, which is indicative of smaller particle size, than the corresponding samples obtained from solid-state processing techniques. Such improvements in the characteristics of ceramic materials are an expected consequence of solution preparation and were the goal of this research.

II. A Study of the Photodissociation of Phosphine:

The photochemistry of phosphine (PH3) is of interest for a variety of reasons, including the presence of the molecule in the atmosphere of Jupiter and Saturn and potential applications in the growth of semiconductors via metallorganic chemical vapor deposition (MOCVD).

The ground electronic state PH2 resulting from the photodissociation of phosphine was studied by laser induced fluorescence (LIF) spectroscopy. Results of this work indicate that little or no PH2 is created in this state as a direct result of photodissociation, but instead is formed by secondary processes. Possible sources include chemical reactions and relaxation from excited vibrational and electronic states. The kinetics of secondary processes were studied by collecting LIF signal as a function of delay time between creation and detection of the fragment.

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Electronic Dissertation
Keywords
Ceramic materials, Phosphine
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