Thesis (M.Sc.), Memorial University of Newfoundland, 2000. / Bibliography: leaves 155-160.

No description available.

In the past decade, the field of NMR spectroscopy has seen the emergence of ever more powerful superconducting magnets, which has opened the door for the observation of many traditionally challenging or non-receptive nuclei. In this dissertation, a variety of ionic solids with organic coordination environments are investigated using quadrupolar solid-state NMR experiments with an ultrahigh-field magnet (21.1 T). Two general research directions are presented including a 79/81Br solid-state NMR study of a series of 6 triphenylphosphonium bromides for which single-crystal X-ray structures are reported herein. A second research direction is also presented wherein alkaline-earth metal (25Mg, 43Ca, and 87Sr) solid-state NMR is used to characterize a systematic series of 16 aryl and alkyl carboxylates. In both studies, the quadrupolar nuclei studied are deemed “exotic” due to their unreceptive nature to NMR spectroscopic analysis including low natural abundances, large quadrupole moments, or low resonance frequencies. A variety of coordination modes to alkaline-earth metals, including N-atom coordination, are characterized herein for the first time using alkaline-earth metal solid-state NMR. In all cases, the electric field gradient (EFG) and chemical shift (CS) tensors are characterized and correlated to structural features such as interatomic distances measured from the crystal structure of the compound under study. In all of the projects undertaken herein, the gauge-including projector-augmented-wave density functional theory (GIPAW DFT) method is used, which allows for the prediction and rationalization of the experimental EFG and CS tensor parameters based on the input crystal structure. In the case of 43Ca solid-state NMR experiments reported in this dissertation, a linear correlation between the calculated and experimental 43Ca quadrupolar coupling constants, CQ, is used as a calibration curve for GIPAW DFT calculations performed on the 18 structural models currently available for the vaterite polymorph of CaCO3. Vaterite cannot be fully characterized by X-ray diffraction alone; therefore an NMR crystallography protocol is used in order to identify the model that best accounts for 43Ca solid-state NMR experiments performed on vaterite. It is expected that the conclusions from this dissertation can be used for future studies involving structural refinement and elucidation of solid materials containing challenging quadrupolar nuclei.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18088号 / 理博第3966号 / 新制||理||1572(附属図書館) / 30946 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 下林 典正, 教授 土`山 明, 准教授 三宅 亮 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

No description available.

Amorphous calcium carbonate (ACC) precipitation is modeled using particle nucleation, growth, and aggregation. The particles are tracked in terms of their radial size and particle density using direct quadrature method of moments (DQMOM). Four separate nucleation models are implemented and are compared to experimental data. In discord with a recent study, it is shown that classical nucleation, coupled with equilibrium chemistry, is in good agreement with experimental data. Novel nucleation mechanisms are presented which fit the experimental data with slightly greater accuracy. Using equilibrium chemistry it is shown that the equilibrium value of ACC is pKeq = 7.74 at 24C, which is a factor of two smaller than the originally published equilibrium constant. Additionally, legacy equilibrium chemistry expressions are shown to accurately capture the fraction of calcium carbonate ions formed into ACC nano-clusters. The density, solubility, and water content of ACC are discussed in a brief review, finding that a wide variety of properties are reported in the literature. Based on literature findings, it is proposed that the broad variety of reported properties may be due to ACC having several unique thermodynamic states. Compelling evidence is presented exposing errors made by experimentalists studying the calcium carbonate system. The errors correct for mistakes of experimental kinetic data of the chemical-potential cascade of calcium carbonate due to the formation of meta-stable phases. Correlations are presented which correct for these mistakes. A time-scale analysis shows the overlapping of kinetic scales and mixing scales within the calcium carbonate system. The kinetic scales are based on classical nucleation theory, coupled with diffusion limited growth. The mixing scales were computed using one-dimensional turbulence (ODT).

Στο πλαίσιο της παρούσας εργασίας έγινε προσπάθεια για την ανάπτυξη αναλυτικών μεθοδολογιών με στόχο την ταυτοποίηση και την ποσοτική ανάλυση σε περιπτώσεις ταυτόχρονης συνύπαρξης και των τριών φάσεων του άνυδρου κρυσταλλικού ανθρακικού ασβεστίου. Η Φασματοσκοπία Raman και η Φασματοσκοπία Υπερύθρου ήταν οι δύο αναλυτικές τεχνικές οι οποίες χρησιμοποιήθηκαν σαν βάση για την ανάπτυξη των ανάλογων αναλυτικών μεθοδολογιών. Η χρήση της Φασματοσκοπίας Raman οδήγησε στην ανάπτυξη μιας μη καταστροφικής αναλυτικής μεθοδολογίας, στην οποία όμως μόνο τα σχετικά ποσοστά των τριών φάσεων έγινε δυνατόν να προσδιοριστούν. Για την δημιουργία των ευθειών αναφοράς, κατασκευάστηκαν δυαδικά μίγματα, ενώ χρησιμοποιήθηκαν οι κορυφές στα 711cm-1 για τον ασβεστίτη, στα 700cm-1 για τον αραγωνίτη και στα 750cm-1 για τον βατερίτη. Τα όρια ανίχνευσης προσδιορίστηκαν 0.13mol%, 0.18mol% και 1.3mol% για τον ασβεστίτη, αραγωνίτη και βατερίτη αντίστοιχα, ενώ τα σφάλματα κατά τον προσδιορισμό τριαδικού μίγματος γνωστής σύστασης βρέθησαν να είναι 1.6mol% για τον ασβεστίτη, 0.3mol% για τον αραγωνίτη και 1.1mol% για τον βατερίτη. Στην προσπάθεια επιλογής των κατάλληλων δονήσεων Raman, έγινε μελέτη των φασμάτων Raman των καθαρών κρυσταλλικών φάσεων και απόδοση των κορυφών. Τέλος με την χρήση της Φασματοσκοπίας IR έγινε δυνατός ο προσδιορισμός των απόλυτων ποσοστών των τριών φάσεων, κάνοντας χρήση των δονήσεων στα 714cm-1 για τον ασβεστίτη, στα 700cm-1 και 714cm-1 για τον αραγωνίτη και στα 745cm-1 για τον βατερίτη. Οι απόρροφητικότητες των κορυφών (σε mg-1CaCO3 mm-2) βρέθηκαν ίσες με: α 63.38 714 = για τον ασβεστίτη, α .30 700 = 19 και α .43 714 = 40 για τον αραγωνίτη και α .79 745 = 21 για τον βατερίτη. Τα όρια ανίχνευσης (σε mgCaCO3/mm2) προσδιορίστηκαν σε: 714 -4 C O.A. =6.6 ×10 για τον ασβεστίτη, 700 -3 A O.A. =2.2 ×10 και 714 -3 A O.A. =1.1×10 για τον αραγωνίτη και 745 -3 V O.A. =1.9 ×10 για τον βατερίτη. / In the present work new analytical methodologies were developed for the study of calcium carbonate polymorphs (calcite, aragonite, vaterite). Two vibrational techniques were employed for the simultaneous quantitative analysis of mixtures of crystalline materials; Raman Spectroscopy (non-destructive technique), Infrared Spectroscopy (destructive technique). Using binary mixtures from known quantities of the crystal phase the calibration curves were constructed using the Raman bands at 711cm-1 for calcite, 700cm-1 for aragonite and 750cm-1 for vaterite. Detection limits (DL) were found to be 0.13, 0.18 and 1.3mol % for calcite, aragonite and vaterite, respectively, while the relative errors in determining the mol % of a known ternary mixture of calcium carbonate polymorphs were 1.6% for calcite, 0.3% for aragonite and 1.1% for vaterite. Infrared Spectroscopy was used, in order to determinate the absolute concentration of the calcium carbonate crystal phases, using the bands at 714cm-1 for calcite, at 700cm- 1 and 714cm-1 for aragonite and at 745cm-1 for vaterite. The asborptivities were found to be α 63.38 714 = for calcite, α .30 700 = 19 and α .43 714 = 40 for aragonite and α .79 745 = 21 for vaterite. The detection limits were also established and found to be 714 -4 C D.L. = 6.6 ×10 for calcite, 700 -3 A D.L. = 2.2 ×10 and 714 -3 A D.L. =1.1×10 for aragonite and 745 -3 V D.L. = 1.9 ×10 for vaterite.

Carbonate geochemistry plays an important role in understanding environmental conditions during the time of precipitation. The studies for this dissertation research were focused on carbonate precipitation and crystallization in different chemical and physical environments. The first project aimed to precipitate aragonite at low oxygen levels to identify a correlation between partitioning of trace elements and anoxic and suboxic conditions. The second study focused on the precipitation of amorphous calcium carbonate in varying magnesium concentrations to determine the identity of crystalline material after transformation of ACC. Lastly, the third project was developed to understand transformation of CaCO3 polymorphs. Specifically, whether or not geochemistry is retained from one polymorph to the next. All projects could aid in development of paleoproxies to be used for determining past environmental and climatic conditions in the past.

No description available.

L'objectif de cette thèse était de synthétiser des particules de carbonate de calcium (CaCO3) poreuses pour applications industrielles comme charge dans du papier à cigarette, ainsi que pour l'encapsulation d’'arômes. Nous avons cherché à maîtriser les paramètres de synthèse pour obtenir de la vatérite de taille contrôlée. Nous avons étudié sa transformation à haute température et dans l’'eau, car ce polymorphe est métastable. La transition de phase vatérite/calcite a été étudié par DRX et imagerie par diffraction des rayons X cohérents qui permet d’accéder à l’'image en 3D des particules. Nous avons montré que la vatérite de taille 1 à 2µm présentant 20% de porosité peut être synthétisée de façon reproductible. Les particules préparées ont été introduites comme charge dans du papier à cigarette pour évaluer l’'impact de nouvelles formes de CaCO3 sur les propriétés physiques du papier ainsi que sur la réduction des certains composées nocifs contenus dans la fumée. Nous avons développé l’analyse conjointe de l’'absorption et de la diffraction des rayons X pour estimer la charge réelle introduite ainsi que la porosité des papiers. Nous avons démontré que l’'utilisation de CaCO3 sous forme des sphères poreuses permet d’'augmenter la diffusivité du papier et de réduire l’'émission de CO dans la fumée principale.L’encapsulation d'arômes par la co-cristallisation et l'inclusion moléculaire dans le carbonate de calcium a été aussi étudiée. Nous avons montré que CaCO3 peut être utilisé comme matrice d’'imprégnation d'arômes avec une efficacité d’'encapsulation de plus que 55%. Les particules aromatiques ont été après ajoutées dans le papier pour évaluation sensorielle. / The aim of this thesis was to synthesize porous calcium carbonate (CaCO3) particles for industrial applications as fillers for cigarette paper as well as a matrix for flavour encapsulation. We show that we can control the fabrication of porous particles of vaterite with a given size by tuning the parameters of synthesis. After the synthesis, the stability of vaterite in aqueous solution and at high temperature was studied. The phase transition was analyzed by XRD and coherent X-ray diffraction imaging that allows us to have a 3D-image of the particles. Finally, particles of 1-2 μm size with 20% porosity were reproducibly synthesized. Prepared vaterite particles were introduced as a filler in cigarette paper, with the goal to evaluate their impact on the physical properties of papers as well as on the reduction of some harmful compounds during the smoking. It was demonstrated that the use of vaterite can increase the diffusivity of paper and reduce the CO emission in the mainstream smoke. We also show that the use of X-ray absorption and diffraction can provide an estimation of the filler fraction and porosity of the papers in a non-destructive way. The encapsulation of flavours in CaCO3 particles was performed by co-crystallization and molecular inclusion. It was demonstrated that CaCO3 can be used as a matrix for flavour impregnation with more than 55% of encapsulation efficiency. Flavoured particles was added in paper for sensory evaluation. We shown that it is possible, to flavour the final product with flavoured calcium carbonate particles.