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.

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

Thesis (Ph. D.)--Michigan State University. Dept. of Chemistry, 2006. / Title from PDF t.p. (viewed on Apr. 16, 2009) Includes bibliographical references. Also issued in print.

Thesis (Ph.D.)--Washington State University. / Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, September 2009. / Electronic version restricted until 21st September 2010.

This thesis deals with the various attempts to expand the ADOR (Assembly, Disassembly, Organisation and Reassembly) process. This includes the use of the ADOR process to incorporate new elements into a zeolite framework, the expansion of the ADOR process to other germanosilicate frameworks, and the first ever synthesis of a new ADORable germanosilicate and its subsequent daughters. Chapter 4 deals with the expansion of the ADOR process to the already known ADORable zeolite UTL, using the organisation and reassembly steps to incorporate Al and P, resulting in the formation of a zeolite-AlPO hybrid with distinct silicate layers connected by AlPO based s4r linkages. The material was shown to contain Al and P species and was unstable to acidic medium, atypical of the wholly silica zeolite frameworks produced by the ADOR process. MAS NMR studies showed the presence of both tetrahedral P and Al species in the material and that the presence of Si-OH groups was limited. Indicating that the layers had been reconnected with Al and P now present, forming a zeolite-AlPO hybrid. 29 Si-enriched materials were synthesised to confirm the presence of P-O-Si bonds, through 2D MAS NMR correlation experiments; however, results were limited due to the lack of signal strength. Chapter 5 deals with attempts to expand the ADOR process by applying the ADOR process to other already known germanosilicates. It was found that the non-ideal ADORable candidates NUD-1 and ITQ-33 were unable to undergo a controlled disassembly process, primarily due to their high Ge content and distribution of d4r/d3r. The zeolites ITQ-38 and IM-20 showed more promise. Both could undergo disassembly to form a layered material, which could then be organised and reassembled to form new materials. However, these materials were shown to not form perfect daughter zeolites and had a high degree of disorder. This was associated with the complexity of the ADOR process and the many factors that play a role in each step. Chapter 6 deals with the use of a family of SDAs (with the same biphenyl backbone) to synthesise new ADORable zeolites. The synthesis of the SDAs and their use in various zeolite syntheses was discussed. The potential of these SDAs for the synthesis of new zeolites was then evaluated. The investigations were relatively successful with the successful formation of an ADORable zeolite, which was already known, UTL. However, the suitability of such SDAs also put into question, due to their instability under hydrothermal conditions. Chapter 7 discussed the first successful a priori synthesis of a parent germanosilicate and its daughter zeolites by the ADOR process. The successful synthesis of an ADORable zeolite (SAZ-1) was conducted with the use of an imidazolium-naphthalene based SDA. Investigations were first conducted into changing the synthesis condition, exploring the impact of these changes on the resulting products, and optimising the synthesis conditions to favour the formation of the new zeolite SAZ-1. These investigations led to the new zeolite framework SAZ-1, which showed similarities to the zeolites NUD-2 and CIT-13, which were developed simultaneously by other institutions. The properties of the SAZ-1 framework were discussed and were found to be highly suitable for the ADOR process. SAZ-1 was then successfully disassembled, organised, and reassembled to form two new daughter zeolites SAZ-2 and SAZ-3. The alumination of SAZ-1P to form aluminated SAZ-2 and SAZ-3 was also attempted. Both zeolites showed an increase in catalytic activity, compared to the typical pure-silica daughter zeolites. The layers of SAZ- 1P were also able to undergo the same shifting process as seen for the ‘unfeasible' zeolites IPC-9 and IPC-10, but the resultant products were not as ordered as these previous examples. This in addition to the previous work highlighted some of the non-ideal properties of SAZ-1 compared to other ADORable zeolites, like UTL.

Made available in DSpace on 2015-05-14T16:53:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-09-09Bitstream added on 2015-05-14T16:58:45Z : No. of bitstreams: 1 000821898.pdf: 1301763 bytes, checksum: d28b4fd5d34abcdbe6e39a7e3297aee3 (MD5) / 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... / 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

An investigation was conducted on the mechanisms of bond formation between alloys of nickel and single crystals of alumina. Nickel-titanium, nickel-chromium, and nickel-zirconium powder mixtures were cleaned with purified hydrogen gas at 800°C and were individually melted under vacuum (10⁻⁵ m.m. of Hg) in contact with alumina. Interfacial energy measurements at 1500°C were made by the sessile-drop method. The bond surfaces were examined by X-ray fluorescence and X-ray diffraction techniques. The bond formation in all cases appeared to involve two basic mechanisms - metal solute segregation and interfacial reaction. By interfacial measurements and X-ray fluorescence analyses, the solute atoms, titanium and chromium, were shown to be selectively adsorbed at the metal-ceramic interface. Interfacial reaction products were detected by X-ray diffraction methods. The adsorbed titanium reacted with the alumina to produce an interfacial layer of alpha titanium sesqui oxide (⍺-Ti₂0₃). Adsorbed chromium similarly reacted with the alumina to form an interfacial compound. However, this compound could not be identified. With nickel-zirconium alloys, the violence of the reaction between zirconium and alumina made experimental measurements impossible. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

No description available.

No description available.