Rutile powders in flaked form were pressed and heated at different temperatures (1000°C to 1300°C) under reducing (H₂/H₂O) atmospheres to study the rate of weight loss, the grain growth and the densification. The weight loss measurements for reduction of rutile to two non-stoichiometric compositions of TiO₁.₉₂ and TiO₁.₉₈ yielded an activation energy for weight loss of 82 ± 2 kcal/mole. No attempt was made to identify the rate-determining step. Previous weight loss measurements carried out in equilibrium conditions produced an enthalpy of 83 ± 10 kcal/mole for the formation of an oxygen ion vacancy. This could suggest that the rate-determining step might be the formation of an oxygen ion vacancy. The grain growth study revealed that the non-stoichiometric composition of TiO₁.₉₂ did not obey the theoretical relation of Burke. The results can be expressed by the following D² - D₀² = Kt°·⁶exp (- 78,000/RT) This activation energy for grain growth is equal to the activation energy for oxygen ion diffusion in TiO₂. This suggests that the oxygen ion diffusion may be the rate-controlling step for grain growth. The densification on sintering was evaluated from linear shrinkage measurements of the compacts during reduction to TiO₁.₉₂. A few models were tried, to find the best fit for the present data. While the photomicrographs suggest the Coble model for bulk diffusion, and the values for the diffusion coefficients are of the right order of magnitude, the activation energy for the rate determining step is about 118 kcal/mole, which is not in agreement with the previous sintering study on rutile. From grain growth data for those compacts reduced to TiO₁.₉₈ at 1200°C and those sintered in open air, it was seen that the diffusion coefficient was not significantly affected by variation of the oxygen partial pressure. This discrepancy in the activation energy value may be explained by a possible error in measurement and other unknown variables which may control the densification process. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 120-124).

The study focused on analysis of microstructure of sintered TiO2 bulk by using XRD, SEM-EBSD, and TEM. The experiment results showed that sintered samples were rutile phase, besides also found growth twins in sintered sample. The twin plane {101 ̅) was confirmed by SEM-EBSD, TEM-SADP and mathematics transformation matrix. Finally traditional contrast analysis was adopted for determining twin boundary were £\-boundaries and displacement vectors R = 1/n[011].

Thesis (Ph. D.)--Murdoch University, 1990. / Thesis submitted to the School of Mathematical and Physical Sciences. Includes bibliographical references (p. 309-322).

Titanium production is a long and complicated process. What we often consider to be the standard method of primary titanium production (the Kroll process), involves many complex steps both before and after to make a useful product from titanium ore. Thus new methods of titanium production, especially electrochemical processes, which can utilize less-processed feedstocks have the potential to be both cheaper and less energy intensive than current titanium production processes. This project is investigating the use of lower-grade titanium ores with the electrochemical MER process for making titanium via a molten salt process. The experimental work carried out has investigated making the MER process feedstock (titanium oxycarbide) with natural titanium ores|such as rutile and ilmenite|and new ways of using the MER electrochemical reactor to \upgrade" titanium ores or the titanium oxycarbide feedstock. It is feasible to use the existing MER electrochemical reactor to both purify the titanium oxycarbide feedstock and produce titanium metal.

Submitted by DOUGLAS HENRIQUE MARCELINO DE AZEVEDO null (fums_draculea@hotmail.com) on 2017-02-17T01:42:07Z No. of bitstreams: 1 Dissertação Mestrado Douglas Azevedo.pdf: 6219487 bytes, checksum: 5015fcd83ed83657a80e79409bb2bdd3 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-02-21T19:57:09Z (GMT) No. of bitstreams: 1 azevedo_dhm_me_ilha.pdf: 6219487 bytes, checksum: 5015fcd83ed83657a80e79409bb2bdd3 (MD5) / Made available in DSpace on 2017-02-21T19:57:09Z (GMT). No. of bitstreams: 1 azevedo_dhm_me_ilha.pdf: 6219487 bytes, checksum: 5015fcd83ed83657a80e79409bb2bdd3 (MD5) Previous issue date: 2016-12-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Com a constante busca o avanço tecnológico para satisfazer as necessidades da nossa sociedade, verifica-se uma preocupação da sociedade com menor degradação do meio ambiente. Em função disso, busca-se um melhor aproveitamento dos recursos naturais, o que, por sua vez, requer tecnologia apropriada. Na indústria optoeletrônica, a utilização de materiais com propriedades ópticas e condutoras cresce continuamente, porém esta tecnologia está fortemente baseada em óxido de índio (In2O3), que é um material bastante caro, já que é naturalmente escasso. Apresente pesquisa pretende contribuir com o conhecimento, em nível microscópio, das propriedades que governam a condutividade de óxidos de chumbo e óxidos de titânio dopados visando sua utilização como óxido transparente condutor, já que titânio e chumbo são mais baratos que o índio. Estudou-se propriedades eletrônicas de filmes finos de dióxido de titânio (TiO2) e dióxido de chumbo (PbO2) em sua principal fase cristalográfica, a fase rutila, em função da superfície exposta, Empregou-se cálculos ab initio dentro da teoria do funcional de densidade (DFT) implementada no programa CRYSTAL14. Procurou-se entender os fatores responsáveis pela condutividade desses materiais e formular propostas que contribuam para a transformação desses materiais em óxidos condutores transparentes. / There is a constant search for technological development to satisfy the need of our society, on the other hand there is a growing concern with environmental conservation. However, the better use of natural sources requires appropriate technology for that.In the optoelectronic industry, the use of materials with optical and conductive properties is continuously increasing, but this technology is strongly based on indium oxide (In2O3), which is a very expensive material, since it is naturally scarce. The present research aims to contribute to the knowledge of the properties that govern the conductivity of lead and titanium oxides at the microscopic level in order to enable its use as a transparent oxide conductor. Electronic properties of thin films of titanium dioxide (TiO2) and lead dioxide (PbO2) in the main crystallographic phase (the rutile phase), depending on the exposed surface was investigated. Ab initio calculations with density functional theory (DFT) implemented in the CRYSTAL14 program have been performed. Factors responsible for the conductivity of these materials have been explored aiming to contribute to the transformation of these materials in transparent conductive oxides.

Thesis (M.S.) in Chemical Engineering--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 69-72).

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Orientador: João Manuel Marques Cordeiro / Resumo: Com a constante busca o avanço tecnológico para satisfazer as necessidades da nossa sociedade, verifica-se uma preocupação da sociedade com menor degradação do meio ambiente. Em função disso, busca-se um melhor aproveitamento dos recursos naturais, o que, por sua vez, requer tecnologia apropriada. Na indústria optoeletrônica, a utilização de materiais com propriedades ópticas e condutoras cresce continuamente, porém esta tecnologia está fortemente baseada em óxido de índio (In2O3), que é um material bastante caro, já que é naturalmente escasso. Apresente pesquisa pretende contribuir com o conhecimento, em nível microscópio, das propriedades que governam a condutividade de óxidos de chumbo e óxidos de titânio dopados visando sua utilização como óxido transparente condutor, já que titânio e chumbo são mais baratos que o índio. Estudou-se propriedades eletrônicas de filmes finos de dióxido de titânio (TiO2) e dióxido de chumbo (PbO2) em sua principal fase cristalográfica, a fase rutila, em função da superfície exposta, Empregou-se cálculos ab initio dentro da teoria do funcional de densidade (DFT) implementada no programa CRYSTAL14. Procurou-se entender os fatores responsáveis pela condutividade desses materiais e formular propostas que contribuam para a transformação desses materiais em óxidos condutores transparentes. / Mestre

No description available.