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.

Human activities since the beginning of the industrial revolution have led to vast amounts of CO₂ being emitted into the atmosphere (May 2023, 424 ppm; NOAA), which is principally responsible for anthropogenic climate change; the effects of which are expected to be globally devastating. In order to combat the unbalanced carbon cycle and reduce the effects of climate change, it is widely accepted that the adoption and use of carbon capture utilization and storage (CCUS) technologies will be necessary to limit warming to 2.0 degrees C (IPCC 2022). Among the industrial sectors to decarbonize, the built environment will be notably challenging, principally due to the challenges associated with reducing the carbon impact of structural materials, such as cement and steel. These construction industries currently account for roughly 8% of global emissions, with projections that this number will increase with a growing global population and more rapid urbanization, especially in developing areas. The abysmal state of U.S. infrastructure decay (ASCE 2021 Grade: C-minus) is also concerning as the replacement of concrete, cement, steel, and asphalt will require and release numerous amounts of carbon; however, this also presents a unique opportunity to deploy CCUS technologies to capture and utilize carbon in the creation of next-generation built-environment materials. These materials include fillers, pozzolans, supplementary cementitious materials (SCMs), and geopolymers such as carbonates, amorphous silica/silicates, bio-chars, and structural allotropes of carbon, like crystalline carbon nanotubes (CNTs) or graphene. The production of these carbon neutral or even carbon-negative materials can be achieved through advanced ex-situ carbon mineralization reaction pathways and novel biomass-to-carbonate conversion technologies, such as alkaline thermal treatment (ATT). In the former, alkaline waste, such as landfilled concrete rich in Ca, can be processed to produce calcium carbonates. This captures atmospheric CO2 and also creates new filler materials which can be incorporated into construction materials. The latter reaction pathway, ATT, takes waste biomass and alkaline wastes as feedstocks and directly converts them into H2 gas and carbonates in a single reaction pathway conducted at moderate conditions (1 atm, 300 degrees C). Although advantageous, both of these synthesis pathways contain unique challenges related to kinetic barriers, conversion issues, mass transfer limitations, and the degree of carbon capture and utilization which can be achieved. Thus, the objective of this study is directed towards overcoming these limitations and coupling these two relatively understudied and novel reaction pathways as a tandem method for carbon sequestration and the creation of new building materials and clean energy. First, the hydrometallurgical processing of waste concrete in a two-step aqueous dissolution and carbonation reactor system is explored. This system is developed and designed to process hydrated waste cement paste, which has extremely high Ca and Si contents. The kinetics of the dissolution process are detailed and the properties of the unreacted residue is examined, revealing a high surface area, amorphous Si-rich material which was shown to be an excellent clinker replacement in new cement mixtures. The dissolution kinetics were fit to a diffusion controlled reactive model, and methods to further increase the elemental extraction of Ca, Al, Fe, and Si, such as internal abrasive media, was also studied. The Ca-rich mother liquor was then carbonated at various conditions using CO₂ gas and the properties, uses, and potential CO₂ capture metrics of these Si-rich residues and calcium carbonates was detailed. In an effort to explore alternative carbon mineralization processes, the use of novel leaching agents, such as regenerable ammoniacal salts was also studied. Typical dissolution and carbonation processes require copious amounts of commodity chemicals, such as acid and base; however, cycling of ammonia/ammonium, similar to the chemistries of the Solvay process, is a promising alternative. The use of ammonium chloride and ammonium bisulfate was studied in the context of material extraction from waste cement paste and subsequent carbonate formation. The process was assessed from a carbon circularity standpoint, revealing significant cost and emissions reductions when compared to conventional carbon mineralization for the treatment of alkaline waste. Additionally, the profiling of carboxylic acid ligands, such as formate, glutamate, acetate, and citrate, to further enhance kinetics during leaching were studied. These agents were found to significantly enhance both of these parameters, resulting in almost 100% of Ca material extraction in a single pass with a sodium citrate ligand. Producing the metastable forms of anhydrous calcium carbonate, such as vaterite and aragonite, was heavily examined in the context of new built-environment building blocks as alternatives to conventional limestone. The production and use of these polymorphs has not been well studied or documented; yet, both vaterite and aragonite are expected to have niche market uses in a carbon-constrained world. The favorable conditions to synthesize vaterite was explored, revealing that a high carbonate to calcium molar ratio is necessary to stabilize this polymorph at ambient reaction conditions. Surface active salt species, such as NH₄+ and sulfate, also had a profound effect on vaterite morphology and stability. Aragonite was successfully stabilized at high carbonation reaction temperatures (~70 degrees C); however, the use of alternative crystallization systems, such as a semi-continuous system vs. traditional batch process was able to produce higher purity aragonite at lower temperatures (40-50 degrees C). The use of crystal seeding also showed remarkable templating abilities and allowed for aragonite production at room temperature (25 degrees C). Both polymorphs were shown to be exceptional fillers for cement through isothermal calorimetry, with aragonite also showing high yield stress development via rheometric testing adding to its potential use in advanced 3-D printed cements, plastics, and papers. The alkaline thermal treatment of waste biomass derived from coastal marine sources was studied to convert biomass into carbonate materials in a carbon-negative manner, while producing H₂ as a valuable product. Various reaction conditions were profiled, including temperature, steam load, hydroxide utilized, and biomass source. A strong correlation was found between carbon conversion/H₂ yield and the basicity of the hydroxide salt, which matched well with thermodynamic calculations performed. These findings were utilized to inform more advanced and refined ATT reaction pathways, coupled with the use of novel regeneration schemes. One potential reactant regeneration pathway is through the use of molten salt electrolysis, in which carbonates are electrosplit into solid carbon (e.g., CNTs) and O₂. Eutectic regenerable alkaline hydroxide mixtures of Li, Na, and K were studied in their ability to convert biomass into electrochemically active carbonate salts mixtures. Interestingly, the content of LiOH in the salt greatly poisoned the biomass conversion potential; however, lithium is the most electroactive carbonate salt for downstream electrolysis. Finally, the electrolytic processing of these biomass-derived carbonate salts was shown to yield high amounts of CNTs, a valuable allotrope of carbon and significant strength enhancer of cementitious materials. Lastly, a brief discussion of the combination of these two reactive pathways in the context of producing low-carbon or even carbon-negative next-generation built environment building materials is performed with respect to a circular material economy and scalability. From the results of these studies, recommendations are made for future research advancements to continue to accelerate CCUS activities and reaction pathways in the realm of the most difficult-to-decarbonize industries, such as the built environment.