No description available.

Feldspar minerals are framework aluminosilicates that comprise approximately 60 percent of the Earth's crust. The elastic and thermodynamic properties of this important mineral group are needed for the interpretation of seismic wave velocities, for understanding cation partioning patterns and for the determination of phase boundaries and reactions involving feldspars in the Earth's crust. Until recently, no systematic approach has been applied to describe the structural behavior of feldspars as a function of pressure, temperature and composition. In this thesis, high-pressure and high-temperature X-ray diffraction data were collected for feldspars over a range of compositions which has led to the development a structural model that allows one to predict the structural evolution of feldspars at depth in the Earth's crust. Specifically, the equations of state have been determined for two plagioclase feldspars (An20 and An78) with different states of Al/Si ordering using single-crystal X-ray diffraction. This study has shown that the introduction of Al,Si disorder into plagioclase structures at constant composition softens the structure by 4(1)% for An0, 2.5(9)% for An20 and is essentially zero for An78 compositions. The effect of pressure on the structure of an ordered An20 was also determined up to 9.15 GPa using single-crystal X-ray diffraction and it was found that the dominant compression mechanism involves tilting of the AlO4 and SiO4 tetrahedra. Similarly, high-temperature single-crystal X-ray diffraction data collected from an ordered An26 plagioclase and powder X-ray diffraction collected on a suite of Na-rich plagioclases that were refined using the Rietveld method indicate that the major structural response to increased temperature involves tilting of the tetrahedra. Building on ideas originally proposed by Dr. Helen Megaw, the changes in the conformation of the tetrahedral framework of feldspars can be described in terms of four distinct tilt systems of rigid tetrahedra. This model demonstrates that the fundamental reason for the observed anisotropy and volume change of feldspars lies in the topology of the tetrahedral framework with the greatest contribution attributed to tilt systems 2 and 3. / Ph. D.

A method of extracting gallium from a Virginia feldspar has been determined. The steps in this method are: 1. Grinding of the ore to a very small particle size (200 mesh) 2. Extraction of gallium by “leaching” the ore with sodium hydroxide 3. Acidification of the sodium hydroxide solution with hydrochloric acid and subsequent extraction of the acid solution with ether to separate the gallium from aluminum, vanadium, and titatium, and other metals 4. Removal of iron by precipitation of ferrous sulphide with hydrogen sulphide 5. Precipitation of gallium by cupferron 6. Ignition of the cupferron precipitate to gallium oxide / M.S.

M.S.

published_or_final_version / abstract / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Made available in DSpace on 2015-04-01T12:17:41Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2182019 bytes, checksum: f16ae6c6befcaa27f593134ca7fa0f5d (MD5) Previous issue date: 2013-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Brazil is one of the references in the world market of ceramic tiles, ranking second in production and consumption. Only in 2012 were produced 865.9 million square feet, for a total installed capacity of 1.004 million square meters. An important aspect of the ceramic industry in the global context, is the continuous technological development, the widespread use of ceramics in various applications and environments and the increasing incorporation of waste from other sectors, giving sustainability concepts in the industry. Brazil produces on average 980 000 tonnes of glass packaging a year and has about a recycling rate of 47%. This study aimed to present one more option to the use of waste glass, which is still poorly recycled in Brazil, analyzing the influence of the replacement of feldspar in a ceramic, for residue from glass bottles are not returnable to the market. We tested three different percentages of glass waste, but also the influence on the behavior of the residue the technological properties with variation of firing temperature. Previously, all materials used in this work were characterized by the techniques of X-ray fluorescence, X-ray diffraction, thermal analysis and particle size. After established formulations, manufacturing and burning the bodies of the test piece, checked the technological properties and microstructure of established formulations. The results indicate that the glass waste has the potential to be used as a flux alternative to replace feldspar in the production of ceramic tiles for different purposes, according to NBR 13817/1997. / O Brasil é uma das referências no mercado mundial de revestimentos cerâmicos, ocupando a segunda posição em produção e consumo. Só no ano de 2012 foram produzidos 865,9 milhões de metros quadrados, para uma capacidade instalada de 1.004 milhões de metros quadrados. Um aspecto importante da indústria cerâmica, no contexto mundial, é o contínuo desenvolvimento tecnológico, a disseminação do uso de cerâmica em diferentes aplicações e ambientes e a crescente incorporação de resíduos provenientes de outros setores, dando conceitos de sustentabilidade no setor. O Brasil produz em média 980 mil toneladas de embalagens de vidro por ano e possui, aproximadamente, um índice de reciclagem de 47%. Este trabalho teve como objetivo apresentar mais uma opção para o aproveitamento do resíduo de vidro, que ainda é pouco reciclado no Brasil,analisando a influência da substituição do feldspato, em uma massa cerâmica, por resíduo de vidro proveniente de garrafas não retornáveis ao mercado. Foram testadas três diferentes percentuais de resíduo de vidro, como também a influência no comportamento do resíduo nas propriedades tecnológicas com a variação de temperatura de queima. Previamente, todos os materiais utilizados no trabalho foram caracterizados pelas técnicas de fluorescência de raios X, difração de raios X, análise térmica e granulométrica. Após estabelecidas as formulações, confecção e queima dos corpos-de-prova, foram verificadas as propriedades tecnológicas e microestruturais das formulações estabelecidas. Os resultados obtidos apontam que o resíduo de vidro apresentou potencial de ser utilizado como fundente alternativo em substituição ao feldspato, na produção de revestimentos cerâmicos para diferentes finalidades, de acordo com a norma NBR 13817/1997.

No description available.

<p> In this study the experiments were designed to measure the geochemical and surface charge (zeta potential) changes with time for two crushed samples of feldspar (Na-fs and K-fs) over the pH range of most natural waters (5 to 9). These experiments show: </p> <p> (a) the importance of adsorption/desorption phenomena in both short-term and long-term feldspar dissolution, and probably for chemical weathering in general; </p> <p> (b) that the generalized curve which characterizes the geochemical data (an initial rapid rise to a peak followed by a decrease to a lower, either constant or later increasing value) is consistent with a consideration of the adsorption/desorption process (i.e., the formation of the double layer) taking place at the feldspar surface and with the simple dissolution of the mineral; </p> <p> (c) that the cation-silica ratios (Na₂O/SiO₂, K₂O/SiO₂, CaO/SiO₂) of the solution compared to those in the original feldspar indicate an initially incongruent dissolution which tends towards congruency during the latter part of the experiments. </p> <p> From information in the Iiterature and the results of these experiments. it may be concluded that: </p> <p> (a) the most important or master variables in chemical weathering are abrasion, minerologic or crystallographic factors such as twinning, exsolution regions, impurities, fractures and grain size, and solution composition and concentration. pH does not appear to be a master variable in most natural waters, especially for long-term weathering, and the chemical composition of the mineral phase is also not a good criterion for predicting weathering behaviour; and </p> <p> (b) the most extreme chemical weathering should occur in a high energy environment, either for physical reasons (i.e., high abrasion due to extreme relief) or for chemical reasons (i.e., high rainfall). </p> / Thesis / Master of Science (MSc)

The optically stimulated luminescence (OSL) characteristics of a suite of quartz and feldspar samples from a range of modern glaciofluvial sediments have been explored to determine the use of OSL as a depositional pathway tracer. Paraglacial and subglacial source material and various glaciofluvial deposits have been analysed from the glacial catchments of Bergsetbreen, Fåbergstølsbreen, and Nigardsbreen as well as the Fåbergstølsgrandane sandur, Jostedalen, Norway. The OSL distribution signatures have been characterised through exploration of sample skewness, kurtosis and overdispersion, and dose distributions of the different depositional settings and source materials are distinct for both quartz and feldspar. Residual ages are greatest for feldspar, indicating significant potential age overestimation where feldspar is used to date glaciofluvial deposits. Sample dose distributions and overdispersion characteristics are driven by source sediment properties, whereas residual ages are controlled by transport and depositional processes. Those transport and depositional processes which result in significant light exposure, also influence dose distributions, and processes that sort sediments least effectively have the highest residual doses. Sample OSL characteristics, transport distance and grain size distributions have been investigated using factor analysis, as a means of predicting sediment source, facies, depositional process and deposit type. Although the depositional processes of the quartz samples can be clearly differentiated based upon OSL characteristics, factor analyses of feldspar and grain size characteristics are inconclusive. The application of quartz OSL to the Norwegian samples was limited by its very poor luminescence sensitivity. Quartz is the preferred mineral for OSL, however, despite the plethora of successful quartz OSL applications, the precise origin of the UV/blue luminescence emission, measured during OSL, remains unclear. The origins of this emission and controls on its intensity were explored using a variety of spectroscopic techniques including photoluminescence, cathodoluminescence, radioluminescence (RL), ionoluminescence (IL) and x-ray excited optical luminescence (XEOL). Exciting sample luminescence at a range of energies enables exploration of the different donor centres responsible for the luminescence emission. Cathodoluminescence and RL emission spectra are similar, comprising broad emissions at 1.5, 2.0 and 2.7 eV (detection in the UV part of the spectrum was not possible for these experiments). Ionoluminescence emission spectra were dominated by the ~ 3.3 eV emission, which is a component of the signal conventionally monitored during OSL. This emission depleted as a function of dose, to the benefit of the red emission (1.8-2.0 eV) for all samples throughout IL, and similar observations were made for the 3.4 eV emission observed from the XEOL emission spectra. The XEOL spectra are dominated by an emission at ~ 3.8 eV, not widely reported for quartz, which has tentatively been attributed to peroxy linkages. Differences between the IL and XEOL emission spectra are interpreted as evidence for the presence of multiple excited states.