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Title:Solid-State Nuclear Magnetic Resonance Studies of Quadrupolar Nuclei in Inorganic Systems (Nmr)
Author(s):Timken, Hye Kyung Cho
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Physical
Abstract:Solid-state nuclear magnetic resonance (NMR) has been used to study a variety of systems of chemical, physical, and geological interest, including zeolites, metasilicates, and semiconductors. Among the nuclei studied were $\sp $O, $\sp{27}$Al, $\sp{69}$Ga and $\sp{71}$Ga. The general motivations for this research were to broaden solid-state NMR into new nuclei, especially quadrupolar nuclei, and to examine how quadrupolar NMR can be used as a structural tool. The research involved several applications, brief descriptions of which are presented below.
Quadrupolar echo techniques were applied in order to resolve chemically non-equivalent sites in solids which have nearly identical chemical shifts. Oxygen-17 NMR studies of zeolites and related systems demonstrated that the $\sp $O NMR spectra of these systems consist of resonances from chemically distinct oxygen species, Si ($\sp $O) Si and Si ($\sp $O) Al for aluminosilicates; Si ($\sp $O) Si and Si ($\sp $O) Ga for gallosilicates; and Al ($\sp $O) P for the AlPO$\sb{4}$ zeolite analogs. From $\sp{69}$Ga and $\sp{71}$Ga NMR studies of gallium analog zeolites we have characterized the framework gallium sites (Ga(OSi)$\sb{4}$), and have obtained NMR parameters essentially by carrying out a "frequency dependence" study at one magnetic field strength by observing the different apparent chemical shifts of $\sp{69}$Ga and $\sp{71}$Ga. We have measured and interpreted the variable-temperature spin-lattice relaxation times (T$\sb{1}$) of $\sp{27}{\rm Al}$ in zeolites. The major relaxation mechanism is due to the quadrupolar interaction. For hydrated zeolites, the motions of the hydrated water in zeolites gives rise to a fluctuating electric field gradient at the framework Al nuclear sites. From $\sp $O NMR studies of a series of alkaline earth metasilicates, we have characterized the different oxygen sites encountered (one bridging oxygen and two distinct non-bridging oxygens). Finally, we have applied $\sp{69}$Ga and $\sp{71}$Ga NMR to a series of gallium-containing III-V semiconductors. By applying the magic-angle sample-spinning technique, we can selectively remove some specific linebroadening mechanisms and the contribution of each mechanism (dipolar, first-order and second-order quadrupolar, pseudodipolar, and exchange interaction) may be more accurately estimated.
Issue Date:1987
Description:213 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
Other Identifier(s):(UMI)AAI8721769
Date Available in IDEALS:2014-12-15
Date Deposited:1987

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