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Atomic substitutions in synthetic apatite; insights from solid-state NMR spectroscopy

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dc.contributor.advisor Phillips, Brian L en_US
dc.contributor.advisor Nekvasil, Hanna en_US
dc.contributor.author Vaughn, John en_US
dc.contributor.other Department of Geosciences en_US
dc.date.accessioned 2017-09-20T16:53:10Z
dc.date.available 2017-09-20T16:53:10Z
dc.date.issued 2016-12-01 en_US
dc.identifier.uri http://hdl.handle.net/11401/77644 en_US
dc.description 173 pg. en_US
dc.description.abstract Apatite, Ca5(PO4)3X (where X = F, Cl, or OH), is a unique mineral group capable of atomic substitutions for cations and anions of varied size and charge. Accommodation of differing substituents requires some kind of structural adaptation, e.g. new atomic positions, vacancies, or coupled substitutions. These structural adaptations often give rise to important physicochemical properties relevant to a range of scientific disciplines. Examples include volatile trapping during apatite crystallization, substitution for large radionuclides for long-term storage of nuclear fission waste, substitution for fluoride to improve acid resistivity in dental enamel composed dominantly of hydroxylapatite, and the development of novel biomaterials with enhanced biocompatibility. Despite the importance and ubiquity of atomic substitutions in apatite materials, many of the mechanisms by which these reactions occur are poorly understood. Presence of substituents at dilute concentration and occupancy of disordered atomic positions hinder detection by bulk characterization methods such as X-ray diffraction (XRD) and infrared (IR) spectroscopy. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an isotope-specific structural characterization technique that does not require ordered atomic arrangements, and is therefore well suited to investigate atomic substitutions and structural adaptations in apatite. In the present work, solid-state NMR is utilized to investigate structural adaptations in three different types of apatite materials; a series of near-binary F,Cl apatite, carbonate-hydroxylapatite compositions prepared under various synthesis conditions, and a heat-treated hydroxylapatite enriched in 17O. The results indicate that hydroxyl groups in low-H, near binary F,Cl apatite facilitate solid-solution between F and Cl via column reversals, which result in average hexagonal symmetry despite very dilute OH concentration (~2 mol percent). In addition, 19F NMR spectra indicate that fluorine occupies a complex distribution of atomic positions, which give rise to complex 19F peak shapes owing to varied F-Ca distance. 13C NMR analysis of carbonate-hydroxylapatite indicates that AB-type carbonate hydroxylapatite can be prepared without the presence of sodium or heat treatment. Isotopic 17O enrichment of hydroxylapatite and 17O NMR analysis reveals distinct signals corresponding to phosphate and hydroxyl oxygens, and heat treatment under vacuum results in loss of hydroxyl signal due to decomposition to tricalcium phosphate, which was observed by powder X-Ray diffraction (PXRD). en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Geochemistry -- Materials Science -- Inorganic chemistry en_US
dc.subject.other apatite, nuclear magnetic resonance, solid solution, solid state NMR en_US
dc.title Atomic substitutions in synthetic apatite; insights from solid-state NMR spectroscopy en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Parise, John B en_US
dc.contributor.committeemember Hurowitz, Joel en_US
dc.contributor.committeemember Rakovan, John en_US
dc.contributor.committeemember . en_US

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