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Pure, MgO doped and B2C3 doped monocalcium, dicalcium, and tricalcium silicates were prepared with different glass contents. Characterization of the anhydrous materials was carried out using optical microscopy, infrared absorption spectroscopy, and X-ray powder diffraction. The hydration of these compounds was studied as a function of the glass contents. The hydration studies were conducted at 25°C. Water/solid ratios of 0.5, 1, 10, and 16 were used for the various experiments. The hydration behavior was monitored through calorimetry, conductometry, pH measurements, morphological developments by scanning electron microscopy, phase development by X-ray powder diffraction, and percent combined water by thermogravimetry. A highly sensitive ten cell pseudo-adiabatic microcalorimeter was designed and constructed for early hydration studies. Conductometry was found to be of great utility in monitoring the hydration of monocalcium silicate and the borate doped dicalcium silicates.

Orientador: Osvaldo Magro Filho / Banca: Celso Kooji Sonoda / Banca: Sonia Regina Panzarini Barioni / Banca: Luiz Guilherme Brentegani / Banca: Osny Ferreira Júnior / Resumo: Objetivos: Avaliar o processo de reparo alveolar em ratas ovarectomizadas após implante com Biosilicato cristalino. Materiais e Métodos: Sessenta ratas foram divididas em quatro grupos (n = 15) de acordo com o tratamento: Grupo 1- ratas submetidas à cirurgia sham com alvéolos preenchidos com coágulo; Grupo 2-ratas submetidas à cirurgia sham com alvéolos preenchidos com Biosilicato cristalino; Grupo 3-ratas ovarectomizadas com alvéolos preenchidos com coágulo; e Grupo 4- ratas ovarectomizadas com alvéolos preenchidos com Biosilicato cristalino. Após 7, 14 e 28 dias os animais foram sacrificados e análises histomorfométricas (histologia e histometria) e imunoistoquímicas (Osteopontina e Osteocalcina) foram realizadas. A comparação dos resultados foi realizada utilizando o programa estatístico Assistat 2013 para Windows através da Análise de Variância e teste de Mann-Whitney, com resultados significantes sendo encontrados quando p≤0.05. Resultados: No período de 7 dias, os Grupos 1 e 3 apresentaram resultados superiores e estatisticamente maiores do que os Grupos 2 e 4 (p<0.05) quanto à formação óssea. Após o período de 14 dias as diferenças estatísticas mantiveram-se, com os Grupos 1 e 3 apresentando diferença estatisticamente significante maiores aos Grupos 2 e 4 (p<0.05). Aos 28 dias, a diferença estatística significativa permaneceu entre os mesmo Grupos estudados, sendo que nos grupos implantados com o Biosilicato cerca de 60% do alvéolo já havia sido preenchido por osso novo. A imunoistoquímica revelou expressão das proteínas Osteocalcina e Osteopontina, principalmente nos animais submetidos à cirurgia de ovarectomia. Conclusões: Os Grupos 1 e 3 foram os que apresentaram os melhores resultados durante todo o estudo, com o Biosilicato cristalino apresentando resultado favorável na reparação... / Abstract: Objectives: To evaluate the process of alveolar repair in ovariectomized rats after implantation with Biosilicate. Materials and Methods: Sixty rats were divided into four groups (n = 15) according to treatment: Group 1 - rats underwent sham surgery with alveoli filled with blood clot; Group 2 - rats underwent sham surgery with alveoli filled with crystalline Biosilicate; Group 3 - ovariectomized rats with alveoli filled with blood clot; Group 4 - ovariectomized rats with alveoli filled with crystalline Biosilicate. After 7, 14 and 28 days the animals were sacrificed and histomorphometric analysis (histology and histometric) and immunohistochemical (Osteopontin and Osteocalcin) were measured . The comparison of the results was performed using the statistical program Assistat 2013 for Windows by Analysis of Variance and Mann-Whitney tests, with significant results being found when p ≤ 0:05 . Results: During the 7- day period, Groups 1 and 3 showed better and significantly higher results in bone formation than Groups 2 and 4 (p<0.05). After 14 days the statistical differences remained between Groups 1 and 3 and Groups 2 and 4 (p<0,05). At 28 days, the statically difference remained significant between the same Groups, while the groups implanted with Biosilicate presented about 60% of the socket filled by new bone. Immunohistochemistry revealed expression of proteins osteocalcin and osteopontin, especially in animals subjected to ovariectomy surgery. Conclusions: Groups 1 and 3 were those with the best results throughout the study, with the crystalline Biosilicate presenting favorable result in bone repair without bioglass resorption. The immunohistochemical analysis showed that animals subjected to ovariectomy had a higher signaling in Ostecalcina and Osteopontin proteins / Doutor

The production of ??-eucryptite [LiAlSiO4] and ??-spodumene [LiAlSi2O6] from topaz [Al2SiO4(F0.64OH0.36)2, containing ~3 wt% quartz impurity] from Torrington, NSW may be of commercial importance since both lithium aluminosilicates have negative or low coefficients of thermal expansion and are used commercially as raw materials in the glass, ceramics, and metallurgical industries. A review of the literature has revealed that the production of ??-eucryptite and ??-spodumene from topaz has not been reported before. The aim of the present work was to determine the kinetics and reaction mechanisms of formation of ??-eucryptite from topaz + lithium carbonate mixtures and ??-spodumene from topaz + lithium carbonate + silica mixtures. To this end, the related reactions and subsolidus phase equilibria of the Li2O-Al2O3-SiO2 ternary system were determined. The subsolidus phase equilibria for the Li2O-Al2O3-SiO2 ternary system were investigated by literature assessment, experimentation, and thermodynamic calculations. The experimentation confirmed the previously published tentative compatibility relations in the Al2O3 and the SiO2 corners. Thermodynamic calculations were used to define the phase relations in the Li2O corner. Thermodynamic calculations also were used to define the phase equilibria for two binary subsystems, Li2SiO3-LiAlO2 and Li4SiO4-LiAlO2. The decomposition of topaz and formation of ??-eucryptite from topaz + lithium carbonate mixtures and ??-spodumene from topaz + lithium carbonate + silica mixtures were investigated experimentally using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman microspectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM). Confirmatory thermodynamic calculations also were done. One significant finding of the present work was the formation of nanofibres from topaz + lithium carbonate mixtures at 1150???C. These fibres were formed by gas-phase reaction of SiF4 and AlOF produced from the reaction between topaz, lithium carbonate and by reaction of SiO2 and Li(OH), which was produced by Li2O volatilisation. These fibres, which were difficult to analyse, most likely consisted of metastable ???-spodumene solid solution or mullite in the incipient stage of formation. Formation of single-phase ???-spodumene from topaz + lithium carbonate + silica mixtures was observed after heating above 950???C for 24 h. Reaction paths for the formation of ??-spodumene over the temperature range 450???-1550???C were proposed. The formation of single-phase ??-spodumene was not simple and straightforward but a complex process involving several precursor phases. Specifically, there were two reaction mechanisms involving the formation of single-phase ???-spodumene by gas-solid reaction and gas-liquid-solid reaction. The reaction kinetics and thermodynamics of the formation of single-phase ??-spodumene at 750???-950???C were assessed. Essential work supplementary to that associated with the Li2O-Al2O3-SiO2 system consisted of determination of the decomposition mechanism of topaz, which was determined to take place in four stages. Reaction paths for the decomposition of topaz also were proposed. Another significant finding of the present work was the formation of transient single-crystal mullite from topaz + lithium carbonate + silica mixtures at ~600???C, which may be contrasted with the normal temperature range of 1000???-1400???C for formation from clay-based raw materials. This phenomenon occurred via a gas-solid growth mechanism. The present observation suggests a potential low-temperature route for the production of high-purity mullite fibres without glass contamination.

Graduation date: 2004

Thèse doctorat : Matériaux Polymères et Composites : Villeurbanne, INSA : 2003. / Titre provenant de l'écran-titre. Bibliogr. p. 245-258.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 219-237). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Drexel University, 2004. / Includes abstract. Includes bibliographical references (leaves 119-126).

No description available.

Thesis (PhD)--University of South Australia, 1999