No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1927. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The calcination of calcium carbonate in a cement or a lime kiln uses approximately two to four times the theoretical quantity of energy predicted from thermodynamic calculation depending upon the type of the kiln used (1.4 x 10^6 Btu/ton theoretical to 6 x 10^6 Btu/ton actual). The objective of this research was to attempt to reduce the energy required for the calcination by 1. decreasing the calcination temperature of calcium carbonate, and/or 2. increasing the rate of calcination at a specific temperature. Assuming a catalytic enhancement of 20 percent in the industrial applications, an energy savings of 300 million dollars annually in the United States could be reached in the cement and lime industries. Three classes of compounds to date have shown a positive catalytic effect on the calcination of calcium carbonate. These include alkali halides, phospho- and silico-molybdate complexes, and the fused carbonates system.

No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Chemistry. University of the Witwatersrand, Johannesburg. May 2016 / In this research project, the morphogenesis and polymorphism of calcium carbonate (CaCO3) and its subsequent use as a template in the fabrication of hollow carbon spheres (HCS) is reported. A series of ratios (i.e. 5:0, 5:1, 5:2, 5:3, 5:4, 5:5, and 0:5) of binary solvent mixtures consisting of polar aprotic (dimethylformamide and dimethyl sulfoxide) and polar protic (methanol, ethanol, isopropanol, and 2-butanol) solvents, with 10% PEG200 as a crystal modifier, were used to influence the morphogenesis and polymorphism of precipitated CaCO3 (PCC). The PCC products were characterised using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), and laser Raman spectroscopy. An increase in the ratio of the polar protic solvent (methanol, ethanol, isopropanol, and 2-butanol) relative to the polar aprotic solvent (DMF & DMSO) within the binary solvent mixture favored the formation of vaterite particles of different morphologies, while an increase in the ratio of polar aprotic solvent (DMF & DMSO) within the binary solvent mixture favored the precipitation of rhombohedral calcite crystals. Time-resolved ex situ PXRD and SEM measurements revealed that the nucleation and phase transformation of the CaCO3 under polar protic and aprotic solvents followed the dissolution-reprecipitation mechanism. The major phase transformation occurred within 3 hours after mixing the precursor solutions. The effect of poly (4-styrenesulfonic acid) (PSSA) as an additive in the crystallisation of CaCO3 at different temperatures (i.e. 30, 40, 75, and 100 °C) and different crystallisation times (3, 6, 12, and 24 hrs) was investigated. The as-synthesised CaCO3 products were subjected to: SEM, laser Raman spectroscopy, PXRD, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The crystallisation of CaCO3 in the presence of PSSA resulted in the self-assembly of vaterite particles into spherical bulk crystals. Varying the crystallisation temperature led to different particle attachment (CPA) pathways, which in turn resulted in bulk crystal morphologies that varied. Changes in the crystallisation temperature were found to not have changed the polymorphism of the precipitated CaCO3 due to the kinetic stabilisation effects of PSSA, instead hollow vaterite spheres formed at 75 and 100 °C. The possibility to synthesise HCS using CaCO3 as a template under chemical vapour deposition (CVD) at different temperatures (i.e. 600, 700 and 800 °C) was, for the first time, demonstrated. The evolution of CO2(g) from the decomposition of the template during CVD resulted in the formation of a rough surface topography on the carbon shell of the HCS. This surface roughness increased with the increase in the reaction temperature due to the increased rate of CaCO3 decomposition. The structural integrity of the spherical template was not affected by the CO2(g) evolution during carbonisation at all the reaction temperatures. The as-synthesised HCS at 600, 700, and 800 °C gave specific BET surface areas of: 193, 55, and 51 m2/g, respectively. / MT2016

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 214-219). Available also in a digital version from Dissertation Abstracts.

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This thesis has studied aspects of biomineralisation, covering the inorganic mineral, the organic matrix, the possible use of phospholipid bilayer vesicles to control mineralisation, calcium and other metal binding to an antibiotic ionophore, Lasalocid-A and a study of a known inhibitor of biomineralisation, the glycopeptide antifreeze found in the plasma of fish which live under polar conditions. The mineral systems studied have been calcium carbonate formations in otoconia and otoliths, crystals which form part of the balance organs of the inner ear, and coccoliths, the earliest eukariotic formation of calcium carbonate, from an alga. Both these systems have been studied by ultra-high resolution electron microscopy with the observation that both types of structures grow in a unique manner, quite distinct from their geological counterparts; indeed the coccolith system involves two distinct mechanisms of growth for different parts of its structure, which is only 2 μm in diameter. Mechanisms of growth of both biominerals are proposed. The study of the organic matrix was less successful in that it was not possible to fully characterise an acidic matrix protein, but it has been shown that the soluble matrix consists of many polypeptide chains cross-linked together, which undergo a conformational change on dissolution from the insoluble matrix on which they lie in vivo and consequently give in vitro results which do not mimic the in vivo condition. Equally, the use of vesicles to control the formation of calcium carbonate was shown to be possible on occasion, but lipids are very unstable in the presence of calcium and no means of stabilising the system to produce consistent results was determined. Two studies were made by ¹H-nmr, the metal-ion complexes of the ionophore Lasalocid-A and the antifreeze glycopeptide of polar fish, in order to demonstrate principles of the handing of isolated ions and of crystallisation inhibition. In both cases, the biological action of the system was mimicked and followed by nmr and a mechanism for their function proposed.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Robert H. Pelton. Includes bibliographical references. Also available online.

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Robert H. Pelton. Includes bibliographical references. Also available online.