Dissertations / Theses: 'Lithium silicates'

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Lu, Hong Materials Science &amp Engineering Faculty of Science UNSW. "Formation of ??-eucryptite and ??-spodumene from topaz mixtures." Awarded by:University of New South Wales. School of Materials Science and Engineering, 2006. http://handle.unsw.edu.au/1959.4/25141.

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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.

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Bastian, Luc. "Impact des variations de la mousson Africaine sur l’érosion chimique des silicates dans le bassin versant du Nil depuis 100.000 ans." Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4101/document.

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L’objectif de cette thèse est de déterminer une reconstruction de l’altération continentale dans le bassin du Nil depuis 100.000 ans, afin de mieux comprendre l’impact des variations climatiques sur les sols, les apports à la Méditerranée et le cycle du carbone. Ce travail repose sur une étude géochimique fine des argiles extraites d’archives sédimentaires du delta du Nil sur une échelle de temps de 100.000 ans. Il repose sur une approche inédite du couplage d’un traceur de source (isotopes du néodyme) et de traceurs d’altérations (isotopes du lithium). Les résultats de cette étude mettent en évidence une réponse rapide de l’altération continentale aux variations hydro-climatique en Afrique du Nord. De plus, les changements climatiques en Atlantique Nord et du ralentissement de l’AMOC ont eu une influence importante sur la diminution de l’intensité d’altération continentale dans le bassin du Nil. A l’actuel, les taux d’altération, et la consommation de CO2 associée, des trapps d’Ethiopie sont relativement faibles par rapport aux autres régions basaltiques. Nos résultats montrent cependant que durant l’African Humid Period, la consommation de CO2 dans cette région était 2 à 3 fois plus importante qu’aujourd’hui. Cela indique que les trapps d’Ethiopie ont pu jouer un rôle non négligeable dans le cycle du CO2, et en particulier lors des périodes de fort runoff. Enfin, des développements analytiques ont été réalisés afin de pouvoir exploiter les compositions isotopiques en lithium des carbonates biogéniques marins, comme nouveaux traceurs des apports en eau douce du Nil. Les résultats obtenus suggèrent une influence des effets dits « vitaux » et des processus de diagénèse
This thesis presents a reconstruction of the chemical weathering in the Nile basin since 100.000 years. His objective is to better understand the impact of climatic variations on chemical weathering, to better. This work is based on the geochemistry study on marine core recorded in the Nile delta, on a time scale of 100.000 years. It use a novel approach with the coupling of à source tracer (εNd) and chemical weathering tracers (δ7Li and elementary ratios) on the fine fraction (< 2µm). In addition, it was analyzed samples of each actual Nil sources and a core sample from Tana Lack (Ethiopie). The results of this studies have enabled to reconstruct the chemical weathering variations in the Nile basin since 100.000 years. It show a rapid respond of chemical weathering to climate variations. This was also observed by important impact of North Atlantic climate variations on the decrease of chemical weathering in the Nile basin. At present, the chemical weathering flux and the CO2 consumption of the Ethiopian traps are low comparted to the other basaltic regions, as the Deccan. However, our results show that during the most humid periods (African Humid Period) the CO2 consumption was 2 to 3 time higher than today. This indicates that the Ethiopian traps could be have played a non-negligible role in the global CO2 cycle during the Cenozoic, and principally during the most humid periods in North Africa. Finally, analytical developments have been realized to be able to exploit the lithium isotopes on biogenic carbonates as a new tracer of Nile water flood. The results suggest an influence of “vital” effect and diagenetic process

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Carmo, Lucas Sátiro do. "Dosimetria termoluminescente de altas doses de raios gama, raios beta, feixe de prótons e de nêutrons epitérmicos utilizando minerais naturais de silicatos e dosímetros de LiF: Mg, Cu, P (MCP)." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-09102015-084259/.

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No mundo de hoje, onde o uso da radiação de diversas naturezas está generalizado, a quantificação da energia depositada por essas diferentes radiações se tornou uma atividade de grande importância, principalmente quando a faixa de energia é considerada elevada, estas altas energias de radiação estão presentes, geralmente, em aceleradores de partículas, reatores nucleares e em irradiadores industriais, por exemplo. Este trabalho tem como objetivo medir altas doses de radiação de raios gama, feixes de elétrons e feixes de prótons utilizando duas variedades de um silicato natural (água-marinha e goshenita) e medir altas doses de nêutrons epitérmicos de alta fluência utilizando dosímetros de Fluoreto de Lítio dopados com Mg, Cu e P (MCP). A técnica utilizada para medir a dose absorvida por esses materiais foi a termoluminescência. As irradiações com raios- γ provenientes de fontes de 60Co foram de 100 kGy a 2000 kGy para a água-marinha e de 600 kGy a 2000 kGy para a goshenita, os resultados de intensidade TL vs Dose mostram que a partir de certa dose - 250 kGy e 1234,8 kGy para água-marinha e goshenita, respectivamente - o sinal TL começa a decrescer. Foi observado neste trabalho que, estes materiais quando irradiados com tais doses e posteriormente irradiados com doses baixas de alguns Gys até cerca de 400-500 Gy, o sinal TL decresce regularmente, podendo ser utilizado na dosimetria das radiações nessa faixa de dose. Para a irradiação de feixe de prótons e de feixe de elétrons foram utilizados dosímetros em placa de goshenita e dosímetros de pastilhas de água-marinha, a carga do feixe de prótons vai de 20 a 216 μC e a dose do feixe de elétrons vai de 10 kGy a 70 kGy. As irradiações com nêutrons epitérmicos utilizando LiF: Mg, Cu, P foram realizadas no reator IEA-R1/IPEN com fluências de 1014 a 1017 n/cm² e a quantificação das doses absorvidas foram realizadas utilizando o método UHTR (Ultra High Temperature Ratio).
In the present days the usage of ionizing radiation from several different sources is spread all over the world. The measurement of the absorbed energy from these radiations became a very important task, mainly when the dose range is considered being in a very high level. These high energies of radiation are associated with particles accelerators, nuclear reactors and industrial irradiators, for example. This work is concerned for measuring high-doses of gamma radiation, electron beams and proton beams using two varieties of a natural silicate (aqua-marine and goshenite) and measuring effects of high-fluence neutrons using LiF: Mg, Cu, P (MCP) detectors. Thermoluminescence was employed to measure the absorbed dose for irradiations with gamma rays ranging from 100 kGy up to 2000 kGy for aquamarine and from 600 kGy and 2000 kGy for goshenite. The TL intensity reaches maximum at 250 kGy in aquamarine and at 1234 kGy for goshenite; this means that for doses larger than 250 kGy in aquamarine and 1234 kGy in goshenite the TL intensity drops. However, the descending part can be used in very high dose dosimetry. Furthermore, has been observed in this study that starting with aquamarine irradiated with 250 kGy and goshenite with 1234 kGy, the subsequent irradiation with doses from low to 400-500 Gy produces a regularly decreasing TL intensity, so that it can be used in radiation dosimetry from low to 400-500 Gy doses. For proton beams, goshenite were used. The beam charge ranges from 20 a 216 μC. For electron beams small pressed pellets of aquamarine were used. The dose ranges from 10 kGy to 70 kGy. The epithermal neutron irradiation was performed at IEA-R1 research reactor at IPEN and MCP-LiF detectors were used to measure the absorbed dose. A method called UHTR (Ultra High Temperature Ratio) was employed for calculating the amount of energy absorbed by the dosimeter. The fluence of epithermal neutrons ranges from 1014 a 1017 n/cm².

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Riquieri, Hilton. "Impacto do processo de cristalização na microestrutura e na resistência à flexão de cerâmicas de silicato de lítio reforçadas por zircônia." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152526.

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O objetivo deste trabalho foi avaliar o silicato de lítio reforçado por zircônia quanto a sua microestrutura e as mesmas propriedades mecânicas em diferentes fases de cristalização. Cento e vinte amostras de discos de silicato de lítio reforçado por zircônia foram usinados de acordo com as normas ISO 6872 (12x1,2mm) para o ensaio de flexão biaxial. Foram separados em 4 grupos de acordo com a fase de cristalização. Grupo I: 30 amostras de Celtra pré cristalizado (CNC); Grupo II: 30 amostras de Celtra cristalizado (CC); Grupo III: 30 amostras de Suprinity Não Cristalizado (SNC) e Grupo IV: 30 amostras de Suprinity Cristalizado (SC). Os corpos de prova foram submetidos ao ensaio mecânico de flexão biaxial e em seguida realizadas análises qualitativas e quantitativas. Por meio microscopia eletrônica de varredura, microscopia eletrônica com emissão de campo MEV-FEG, EDS e difração de raios X (n=4), foi realizada a caracterização completa dos materiais e análise morfológica da microestrutura para todos os grupos. Para as análises estatísticas foram utilizados o módulo Weibull (m) e resistência característica (σ0).
The objective of this work was to evaluate the lithium silicate reinforced by zirconia as to its microstructure and the same mechanical properties in different phases of crystallization. One hundred and twenty samples of zirconia-reinforced lithium silicate discs were machined according to ISO 6872 (12x1,2mm) standards for the biaxial flexural test. They were separated into 4 groups according to the crystallization step. Group I: 30 samples of Pre-Crystallized Celtra (CPC); Group II: 30 samples of Crystallized Celtra (CC); Group III: 30 samples of Uncrystallized Suprinity (SNC) and Group IV: 30 samples of Crystallized Suprinity (SC). The specimens were submitted to the mechanical biaxial flexion test and qualitative and quantitative analyzes were performed. Scanning Electron Microscopy, Electron Microscopy with Field emission SEM-FEG, EDS and X-ray diffraction (n = 4) were carried out to characterize the materials and morphological analysis of the microstructure for all groups. The Weibull (m) and characteristic resistance (σ0) were used for the statistical analysis.

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Moakes, Greg. "Study of Lithium Solvation Environments in Water-saturated Nitrobenzene." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14105.

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It was found that there exist three major water environments when water is dissolved in nitrobenzene. 2H NMR has proved that these solvatomers exist irrespective of whether lithium salt is added to the system. 7Li NMR experiments suggested that the first solvatomer is majority nitrobenzene, the second a mixed solvation shell consisting of nitrobenzene and water and the third solvatomer is a large water aggregated at the glass surface. The mixed solvation state is short lived and is promoted by addition of water of by supersaturating the system upon cooling. This is a high energy state and decays either into the homogenous bulk NB state or to the surface of the glass wall, depending on if glass surface is present. In the 7Li NMR experiments, the hydrophobicity of the salt, determined by the anion, affects the relative intensity of the three 7Li resonances. Addition of lithium serves to promote hydrogen bonding in the majority nitrobenzene solvatomer, as confirmed by FTIR and neutron diffraction studies. There is no evidence that it has an effect on the size of the mixed solvatomer or the water aggregate immobilized on the glass surface. A reasonable hypothesis is that lithium exchanges between the water species which are formed independent of lithium involvement. The system is summarized as follows: Below critical water concentration (~200mM) nitrobenzene/water is a homogeneous distribution of water molecules in nitrobenzene. Addition of lithium salt to such a system has two main affects. First, the lithium promotes hydrogen bonding between the dissolved water molecules, as confirmed by FTIR and neutron scattering. Second, the hydrogen bonded water may precipitate causing microheterogeneity of the system, leading to a second resonance observed in both the 2H and 7Li NMR spectra (LiNB/W). In the presence of glass, a third solvation state can nucleate at the glass surface; this solvation state has character even closer to that of bulk water (LiW). These two supplementary solvation states can be artificially induced by either adding aliquots of water or cooling.

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PORFIRIO, TATIANE C. "Preparação e caracterização microestrutural e dielétrica da perovsquita CaCusub(3)Tisub(4)Osub(12)." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/24066.

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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Henchiri, Soufian. "Les isotopes du lithium, traceurs de la zone critique de la Terre : du local au global." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC201.

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La Zone Critique de la Terre désigne la fine pellicule recouvrant sa surface, à l’interface du cycle de l’eau, de lithosphère et de la biosphère. Cette couche est produite à sa base par altération chimique et détruite à son sommet par érosion mécanique. Parce que le lithium et ses isotopes ont la particularité de se partager entre la phase dissoute et la phase solide au cours des réactions d’interactions eaux-roches, nous explorons, dans cette thèse, le potentiel des isotopes du lithium dissous dans les rivières comme traceurs des processus d’altération chimique des continents. Nous nous sommes focalisés, dans un premier temps, sur le Bassin Congolais. Cette étude met en évidence le caractère équivoque de la réponse de la composition isotopique du Li (δ7Li) dissous des rivières aux topographies plates (et aux intensités d’altération élevées). Deux valeurs extrêmes de δ7Li dissous sont, en effet, produites dans le bassin du Congo, qui tracent deux styles d’altération continentale distincts, dans lesquels les processus d’altération chimique sont différents. D’autre part, nous proposons une nouvelle estimation du flux moyen de Li et de sa composition isotopique moyenne exportés à l’océan par les rivières aujourd’hui (5,5×1010 g.an−1 et 19±2‰, respectivement). Nous montrons que le δ7Li dissous dans les grands fleuves est contrôlé, au premier ordre, par la réincorporation du Li dans les minéraux secondaires (dans les sols et les plaines d’inondation) et, d’une manière équivoque, de l’intensité d’altération. En outre, l’étude des δ7Li dissous dans les rivières drainant les îles volcaniques (Islande, Java, Martinique, Sao Miguel et Réunion) montre que l’hydrothermalisme continental, générant des eaux très concentrées en Li avec une valeur basse de δ7Li (car très peu fractionnée par rapport à la roche mère basaltique), influence le δ7Li dissous des rivières des îles volcaniques et peut avoir un impact significatif sur le flux de Li (et son δ7Li) transféré(s) à l’océan à l’échelle globale. Enfin, nous proposons une interprétation de l’augmentation de l’ordre de 9‰ qu’a connue la signature isotopique du Li de l’eau de mer au cours du Cénozoïque à l’aide d’un modèle de boîtes simple de l’océan et au regard de nos résultats. Il émane de ce travail de thèse que les isotopes du Li dissous dans les rivières prouvent là encore leur capacité à être de bons traceurs des régimes d’altération des roches silicatées continentales (et ce, même en contexte anthropisé, comme le montre notre étude du bassin de l’Orgeval, en Seine-et-Marne). Le Li et ses isotopes constituent donc des traceurs prometteurs de la Zone Critique de la Terre et des paléo-processus d’altération chimique ainsi que de l’évolution géodynamique des continents voire des grands mouvements verticaux affectant la lithosphère continentale
The Critical Zone of the Earth is the layer covering its surface, at the interface between the water cycle, the lithosphere and the biosphere. This layer is produced at its base by chemical weathering and destroyed at its top by mechanical erosion. We explore the potential of lithium isotopes dissolved in rivers as tracers of continental chemical weathering processes as lithium and its isotopes are highly fractionated between the dissolved and solid phases during water-rock interaction processes. First, we are focused on the Congo Bassin. This study demonstrates the equivocal response of the isotopic composition of the riverine dissolved Li isotope compositions (δ7Li) to flat topography (and high weathering intensities). Two extreme values of dissolved δ7Li are produced in the Congo Basin, which trace two distinct continental weathering styles in which chemical weathering processes are different. On the other hand, we refined the mean flux of Li and its average isotopic signature exported to the ocean by rivers today (5.5×1010 g. an-1 et 19±2‰, respectively). We show that dissolved δ7Li in large rivers is controlled, at first-order, by the re-incorporation of Li into secondary weathering minerals (in soils and floodplains) and in, an equivocal way, of the weathering intensity. Moreover, the study of dissolved δ7Li in rivers draining volcanic islands (Iceland, Java, Martinique, Sao Miguel and Reunion) shows that continental hydrothermal activity, producing waters with high Li concentration with low value of δ7Li (as low fractionated towards the basaltic bedrock), influences the dissolved δ7Li in rivers of volcanic islands and can have an impact on the Li flux (and its δ7Li) transferred to the ocean on a global scale. Finally, by using a simple box model of the ocean and our results, we suggest an interpretation of the 9‰ increase of seawater δ7Li during the Cenozoic. This thesis highlights that riverine dissolved Li isotopes confirm once again their capacity to be powerful tracers of the weathering regimes of continental silicate rocks (even in anthropized context, as showed by our study of the Orgeval catchment, in Seine-et-Marne). Li and its isotopes are thus promising tracers of the Critical Zone of the Earth and the chemical weathering paleo-processes as well as the long-term geodynamic evolution of the continents or even the large vertical movements affecting the continental lithosphere

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Moritani, Kimikazu. "Study on Production and Reactions of Radiation-induced Defects in Ceramic Materials." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/77998.

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Gaddam, Anuraag. "Structure and crystallization of multicomponent lithium silicate glasses." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21819.

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Doutoramento em Ciência e Engenharia de Materiais
A presente tese tem como objetivo adquirir uma compreensão aprofundada acerca do processo de cristalização de vidros à base de silicato de lítio com a adição de pequenas quantidades de outros componentes. Os principais componentes investigados neste estudo são os óxidos de Mn, Al, B e P. Estudaram-se os efeitos de cada um destes componentes na estrutura do vidro, na separação de fases líquido-líquido, nos processos de nucleação e crescimento de cristais, na microestrutura e no conjunto das fases cristalinas formadas. Os vitro-cerâmicos utilizados neste estudo são produzidos a partir de amostras tridimensionais de vidro fundido e vertido em moldes, ou a partir de pós de frita obtida por arrefecimento dos fundidos em água. A adição de óxidos de Mn aos vidros de silicato de lítio resulta na criação de entidades moleculares individuais de Mn. Por conseguinte, estas entidades moleculares dificultam o todo o processo de cristalização do vidro. Óxidos de Al e B são incorporados na rede de vidro como formadores de rede. Estes componentes, por conseguinte, também diminuem a tendência do vidro para a cristalização. O P2O5 também desempenha um papel de formador de rede do vidro. No entanto, ele aumenta a tendência do vidro para a cristalização. Dá-se uma ênfase especial ao estabelecimento de correlações entre a estrutura do vidro e seu comportamento na cristalização. Estes esforços levaram à introdução de um novo modelo matemático baseado na mecânica estatística para descrever a estrutura de vidro. O modelo foi desenvolvido principalmente para silicatos binários e mais tarde estendido para composições de silicatos multicomponentes.
The present thesis is aimed at gaining an in-depth understanding of the crystallization process in multicomponent lithium silicate based glasses when other components are added in small amounts. The added components investigated in this study are oxides of Mn, Al, B and P. The effects of each of these components on glass structure, liquid-liquid phase separation, crystal nucleation, crystal growth, microstructure and phase assemblage are studied. The glass ceramics used in this study are produced by both bulk glasses obtained by melt quenching as well as by powder methods from glass frits. Oxides of Mn when added to lithium silicate glasses result in creating individual Mn molecular entities. Consequently, these molecular entities hinder the overall crystallization ability of the glass. Oxides of Al and B are incorporated into glass network as network formers. These components consequently decrease the overall crystallization ability of the glass. P2O5 is also incorporated into glass network as network former. However, it increases the overall crystallization ability of the glass. Particular emphasis is given to establishing correlations between glass structure and its corresponding crystallization behaviour. These efforts led to introducing a new mathematical model based on statistical mechanics for describing the glass structure. The model was primarily developed for binary silicates and later on extended to multicomponent silicates.

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Reid, William B. "The electrical characteristics of lithium silicate glasses." Thesis, University of Aberdeen, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328008.

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The electrical behaviour of a series of lithium silicate glasses has been characterised by the versatile a.c. impedance technique. The advantage of using a combination of complex plane and spectroscopic plots in the data analysis is shown. The compositional dependence of the conductivities of the phase separated glasses, which exhibit complex two-phase spinodal decomposition or nucleation and growth textures, is related to the volume fraction of the phases present in the conduction pathway and the tortuosity of the effective medium. The compositional dependence of the conductivities of homogeneous lithium silicate glasses is accounted for by postulating a glass structure composed of silicate anion clusters which are surrounded by a lithia-rich phase which constitutes the preferred conduction pathway. Annealing effects are also reported. The effect of surface roughness on the response of the electrode/electrolyte interface, a phenomenon originally reported by de Levie, and contact problems between the metal electrode and the glass electrolyte are discussed. Novel results regarding the effect of gold electrode recrystallisation on the a.c. response of glass electrolytes are reported. The a.c. impedance technique is shown to be a very useful, surface sensitive tool for monitoring interfacial phenomena such as atmospheric corrosion and surface ion-exchange. The technique is also successfully applied to studies of the mechanism of glass-ceramic formation, where the identification of surface crystallisation products and residual glass, by electrical measurement, is possible. Conclusive evidence for the presence of an effective medium conduction mechanism (percolation theory) in the inhomogeneous glass-ceramic, is given. The electrical data are corroborated by electron microscopy, x-ray diffractometry, energy dispersive x-ray analysis and Fourier Transform Infrared Spectroscopy.

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Myalo, Zolani. "Graphenised Lithium Iron Phosphate and Lithium Manganese Silicate Hybrid Cathode Systems for Lithium-Ion Batteries." University of the Western Cape, 2017. http://hdl.handle.net/11394/6036.

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Magister Scientiae - MSc (Chemistry)
This research was based on the development and characterization of graphenised lithium iron phosphate-lithium manganese silicate (LiFePO4-Li2MnSiO4) hybrid cathode materials for use in Li-ion batteries. Although previous studies have mainly focused on the use of a single cathode material, recent works have shown that a combination of two or more cathode materials provides better performances compared to a single cathode material. The LiFePO4- Li2MnSiO4 hybrid cathode material is composed of LiFePO4 and Li2MnSiO4. The Li2MnSiO4 contributes its high working voltage ranging from 4.1 to 4.4 V and a specific capacity of 330 mA h g-1, which is twice that of the LiFePO4 which, in turn, offers its long cycle life, high rate capacity as well as good electrochemical and thermal stability. The two cathode materials complement each other's properties however they suffer from low electronic conductivities which were suppressed by coating the hybrid material with graphene nanosheets. The synthetic route entailed a separate preparation of the individual pristine cathode materials, using a sol-gel protocol. Then, the graphenised LiFePO4-Li2MnSiO4 and LiFePO4-Li2MnSiO4 hybrid cathodes were obtained in two ways: the hand milling (HM) method where the pristine cathodes were separately prepared and then mixed with graphene using a pestle and mortar, and the in situ sol-gel (SG) approach where the Li2MnSiO4 and graphene were added into the LiFePO4 sol, stirred and calcined together.
2021-04-30

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Roß, Sebastian [Verfasser]. "Lithium conductivity characteristics of amorphous lithium silicate and lithium alumosilicate materials and their compaction / Sebastian Roß." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1068347899/34.

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13

Iqbal, Yaseen. "Early stages of crystallisation in lithium silicate glasses." Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245649.

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14

Burgner, Lori Lynn. "Crystallization kinetics of lithium disilicate and sodium silicate glasses." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/279818.

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The formation of metastable crystalline phases in lithium disilicate glass has been a subject of controversy for decades. Here, one aspect of this problem relating to the stability of these non-equilibrium phases when glasses are heated for extended time periods in the nucleation regime is addressed. The results of a systematic experimental investigation on the persistence of metastable phases and the factors that may influence the appearance of such phases, e.g., water content, impurities, glass composition, and glass preparation procedure are presented. Growth rates of lithium disilicate crystals in lithium disilicate glass are measured as a function water concentration in the glass and of temperature in the deeply undercooled regime. The growth rate data obtained in this work are combined with data reported in the literature and used to assess the applicability of standard models of crystal growth for the description of experimental results over a very broad temperature range. The reduced growth rate versus undercooling graph is found to consist of three regimes. For undercoolings less than 140°C, the reduced growth rate curve is suggestive of either 2-D surface nucleation or screw dislocation growth. For undercoolings greater than 400°C, the reduced growth rate plot suggests the operative crystal growth mechanism is 2-D surface nucleation, but detailed calculations cast doubt upon this conclusion. In the intermediate undercooling range, there appears to be some sort of transitional behavior for which none of the standard models appear to be applicable. Further, it is observed that small differences in the viscosity data employed can produce enormous differences in the predicted growth rates at larger undercoolings. Results of the kinetic analyses conducted herein seem to indicate that the nature of the kinetic rate coefficient used in the standard growth models may be incorrect. Nucleation rates of sodium metasilicate crystals in a sodium silicate glass of composition 43Na₂O57SiO₂ (mol%) are investigated using the development technique. The results of this study are compared with the nucleation rate results recently obtained for this composition using a novel DTA method. The two techniques are found to agree within experimental error.

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15

Ruales, Mary Cristina. "Design of a Low Power – High Temperature Heated Ceramic Sensor to Detect Halogen Gases." FIU Digital Commons, 2007. http://digitalcommons.fiu.edu/etd/33.

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The design, construction and optimization of a low power-high temperature heated ceramic sensor to detect leaking of halogen gases in refrigeration systems are presented. The manufacturing process was done with microelectronic assembly and the Low Temperature Cofire Ceramic (LTCC) technique. Four basic sensor materials were fabricated and tested: Li2SiO3, Na2SiO3, K2SiO3, and CaSiO3. The evaluation of the sensor material, sensor size, operating temperature, bias voltage, electrodes size, firing temperature, gas flow, and sensor life was done. All sensors responded to the gas showing stability and reproducibility. Before exposing the sensor to the gas, the sensor was modeled like a resistor in series and the calculations obtained were in agreement with the experimental values. The sensor response to the gas was divided in surface diffusion and bulk diffusion; both were analyzed showing agreement between the calculations and the experimental values. The sensor with 51.5%CaSiO3 + 48.5%Li2SiO3 shows the best results, including a stable current and response to the gas.

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16

Ramos, Aline. "Nucleation et croissance cristallines dans un verre sio::(2)-al::(2)o::(3)-li::(2)o : etude par microscopie electronique a haute resolution et absorption des rayons x." Paris 6, 1988. http://www.theses.fr/1988PA066504.

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Etude des premieres etapes de la cristallisation dans un verre du systeme sio::(2)-al::(2)o::(3)-li::(2)o(mgo) dans lequel de faibles quantites de titane et de zirconium sont introduites comme elements nucleants

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17

Ndipingwi, Miranda Mengwi. "Graphol and vanadia-linkedzink-doped lithium manganese silicate nanoarchitectonic platforms for supercapatteries." University of Western cape, 2020. http://hdl.handle.net/11394/7236.

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Philosophiae Doctor - PhD
Energy storage technologies are rapidly being developed due to the increased awareness of global warming and growing reliance of society on renewable energy sources. Among various electrochemical energy storage technologies, high power supercapacitors and lithium ion batteries with excellent energy density stand out in terms of their flexibility and scalability. However, supercapacitors are handicapped by low energy density and batteries lag behind in power. Supercapatteries have emerged as hybrid devices which synergize the merits of supercapacitors and batteries with the likelihood of becoming the ultimate power sources for multi-function electronic equipment and electric/hybrid vehicles in the future. But the need for new and advanced electrodes is key to enhancing the performance of supercapatteries. Leading-edge technologies in material design such as nanoarchitectonics become very relevant in this regard. This work involves the preparation of vanadium pentoxide (V2O5), pristine and zinc doped lithium manganese silicate (Li2MnSiO4) nanoarchitectures as well as their composites with hydroxylated graphene (G-ol) and carbon nanotubes (CNT).
2023-12-01

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18

Fernandes, Hugo Alexandre Gonçalves da Rocha. "Development of lithium disilicate based glass-ceramics." Doctoral thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/11207.

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Doutoramento em Ciência e Engenharia dos Materiais
O principal objectivo deste estudo foi o desenvolvimento de vitrocerâmicos à base de dissilicato de lítio no sistema Li2O-K2O-Al2O3-SiO2 contendo uma razão molar SiO2/Li2O muito afastada da do dissilicato de lítio (Li2Si2O5) usando composições simples e a técnica tradicional de fusão-vazamento de vidro de forma a obter materiais com propriedades mecânicas, térmicas, químicas e eléctricas superiores que permitam a utilização destes materiais em diversas aplicações funcionais. Investigou-se o fenómeno de separação de fases, a cristalização e as relações estrutura-propriedades de vidros nos sistemas Li2O-SiO2, Li2O-Al2O3-SiO2 e Li2O-K2O-Al2O3-SiO2. Os vidros nos sistemas Li2O-SiO2 e Li2O-Al2O3-SiO2 apresentaram fraca densificação e resultaram em materiais frágeis, contrastando com a boa sinterização dos vidros no sistema Li2O-K2O-Al2O3-SiO2. Pequenas adições de Al2O3 e K2O ao sistema Li2O-SiO2 permitiram controlar a separação de fases devido à formação de espécies de Al(IV) que confirmaram o papel de Al2O3 como formador de rede. Os compactos de pó de vidro das composições contendo Al2O3 e K2O tratados termicamente resultaram em vitrocerâmicos bem densificados, apresentando dissilicato de lítio como a principal fase cristalina, e valores de resistência mecânica à flexão, resistência química e condutividade eléctrica (173-224 MPa, 25-50 mg/cm2 e ~2´10-18 S/cm, respectivamente) que possibilitam a utilização destes materiais em diversas aplicações funcionais. A adição de P2O5, TiO2 e ZrO2 ao sistema Li2O-K2O-Al2O3-SiO2 como agentes nucleantes revelou que os vidros contendo apresentaram cristalização em volume, com a formação de metassilicato de lítio a temperaturas mais baixas e dissilicato de lítio para as temperaturas mais elevadas, enquanto a adição de zircónia reduz o grau de segregação, aumenta a polimerização da matriz vítrea e desloca o valor de Tg para temperaturas superiores, inibindo a cristalização.
The purpose of the present study was developing lithium disilicate based glass-ceramics in the system Li2O-K2O-Al2O3-SiO2 featuring SiO2/Li2O molar ratios far beyond that of lithium disilicate (Li2Si2O5) stoichiometry using simple compositions and traditional glass melt-quenching technique in order to get enhanced mechanical, thermal, chemical and electrical properties which allow the use these materials in functional applications. Phase separation phenomena as well as the crystallization behaviour and structure-properties relations of glasses in Li2O-SiO2, Li2O-Al2O3-SiO2 and Li2O-K2O-Al2O3-SiO2 glass systems were investigated. The experimental glasses in Li2O-SiO2 and Li2O-Al2O3-SiO2 systems exhibited poor densification ability resulted in porous samples of brittle nature, contrasting with well sintered glass-powder compacts obtained from glasses in the Li2O-K2O-Al2O3-SiO2 system. Small additions of Al2O3 and K2O to glasses in the in the system Li2O-SiO2 allowed to control an extent of the phase separation due to the formation of tetrahedral four-coordinated Al(IV) species confirming the role of Al2O3 as network former. Moreover, Al2O3- and K2Ocontaining sintered glass powder compacts resulted in well-densified and mechanically strong fine-grained glass-ceramics with lithium disilicate as the major crystalline phase, mechanical strength of 173-224 MPa, chemical resistance of 25-50 mg/cm2 and low total conductivity (~2´10-18 S/cm) making the materials suitable for a number of practical applications. The effects of single additions of P2O5, TiO2 and ZrO2 as nucleating agents in the Li2O-K2O-Al2O3-SiO2 system revealed that addition of P2O5 led to bulk crystallization, with the formation of lithium metasilicate at lower temperatures and lithium disilicate at higher temperatures while the addition of zirconia reduces the degree of segregation, increases the polymerization of the glassy matrix, and shifts Tp to higher temperatures hindering crystallization.

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19

Ndipingwi, Miranda Mengwi. "Graphol and vanadia-link zin doped lithium manganese silicate nanoarchitectonic platforms for supercapatteries." University of the Western Cape, 2020. http://hdl.handle.net/11394/7611.

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Doctor Educationis
Energy storage technologies are rapidly being developed due to the increased awareness of global warming and growing reliance of society on renewable energy sources. Among various electrochemical energy storage technologies, high power supercapacitors and lithium ion batteries with excellent energy density stand out in terms of their flexibility and scalability. However, supercapacitors are handicapped by low energy density and batteries lag behind in power. Supercapatteries have emerged as hybrid devices which synergize the merits of supercapacitors and batteries with the likelihood of becoming the ultimate power sources for multi-function electronic equipment and electric/hybrid vehicles in the future. But the need for new and advanced electrodes is key to enhancing the performance of supercapatteries. Leading edge technologies in material design such as nanoarchitectonics become very relevant in this regard. This work involves the preparation of vanadium pentoxide (V2O5), pristine and zinc doped lithium manganese silicate (Li2MnSiO4) nanoarchitectures as well as their composites with hydroxylated graphene (G-ol) and carbon nanotubes (CNT).
2023-12-02

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20

Stewart, Joseph A. "Variation in silicate weathering across the Oligocene-Miocene boundary : evidence from lithium and neodymium isotopes." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/351811/.

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21

Kashkari, Afnan. "Comparison of Load-to-Fracture Values and Fracture Characterization of Monolithic Zirconia, Lithium Disilicate, and Zirconia-Reinforced Lithium Silicate Glass-Ceramic CAD/CAM Crowns." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469039766.

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22

Chen, Chao-Hsu. "Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700110/.

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Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and grain boundary in lithium lanthanum titanate (LLT) solid state electrolytes. The effects of defect concentration on the structure and lithium ion diffusion behaviors in LLT were systematically studied and the lithium ion self-diffusion and diffusion energy barrier were investigated by both dynamic simulations and static calculations using the nudged elastic band (NEB) method. The simulation results show that there exist an optimal vacancy concentration at around x=0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static NEB calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8-10% when lithium ions pass through. By designing perovskite structures with large bottleneck sizes can lead to materials with higher lithium ion conductivities. The structure and diffusion behavior of lithium silicate glasses and their interfaces, due to their importance as a grain boundary phase, with LLT crystals were also investigated by using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. Lithium ion diffusion energy barrier at the interface was found to be dominated by the glass phase.

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23

Barker, Michael Francis. "Crystallization of lithium alumino-silicate glasses and the formation of photomachinable glass ceramics of controlled thermal expansion." Thesis, University of Sheffield, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362506.

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24

Stjerndahl, Mårten. "Stability Phenomena in Novel Electrode Materials for Lithium-ion Batteries." Doctoral thesis, Uppsala University, Department of Materials Chemistry, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8214.

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Li-ion batteries are not only a technology for the future, they are indeed already the technology of choice for today’s mobile phones, laptops and cordless power tools. Their ability to provide high energy densities inexpensively and in a way which conforms to modern environmental standards is constantly opening up new markets for these batteries. To be able to maintain this trend, it is imperative that all issues which relate safety to performance be studied in the greatest detail. The surface chemistry of the electrode-electrolyte interfaces is intrinsically crucial to Li-ion battery performance and safety. Unfortunately, the reactions occurring at these interfaces are still poorly understood. The aim of this thesis is therefore to increase our understanding of the surface chemistries and stability phenomena at the electrode-electrolyte interfaces for three novel Li-ion battery electrode materials.

Photoelectron spectroscopy has been used to study the surface chemistry of the anode material AlSb and the cathode materials LiFePO₄ and Li₂FeSiO₄. The cathode materials were both carbon-coated to improve inter-particle contact. The surface chemistry of these electrodes has been investigated in relation to their electrochemical performance and X-ray diffraction obtained structural results. Surface film formation and degradation reactions are also discussed.

For AlSb, it has been shown that most of the surface layer deposition occurs between 0.50 and 0.01 V vs. Li°/Li⁺ and that cycling performance improves when the lower cut-off potential of 0.50 V is used instead of 0.01 V. For both LiFePO₄ and Li₂FeSiO₄, the surface layer has been found to be very thin and does not provide complete surface coverage. Li₂CO₃ was also found on the surface of Li₂FeSiO₄ on exposure to air; this was found to disappear from the surface in a PC-based electrolyte. These results combine to give the promise of good long-term cycling with increased performance and safety for all three electrode materials studied.

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25

Lyness, Christopher. "Novel lithium-ion host materials for electrode applications." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1921.

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Two novel lithium host materials were investigated using structural and electrochemical analysis; the cathode material Li₂CoSiO₄ and the LiMO₂ class of anodes (where M is a transition metal ion). Li₂CoSiO₄ materials were produced utilising a combination of solid state and hydrothermal synthesis conditions. Three Li₂CoSiO₄ polymorphs were synthesised; β[subscript(I)], β[subscript(II)] and γ₀. The Li₂CoSiO₄ polymorphs formed structures based around a distorted Li₃PO₄ structure. The β[subscript(II)] material was indexed to a Pmn2₁ space group, the β[subscript(I)] polymorph to Pbn2₁ and the γ₀ material was indexed to the P2₁/n space group. A varying degree of cation mixing between lithium and cobalt sites was observed across the polymorphs. The β[subscript(II)] polymorph produced 210mAh/g of capacity on first charge, with a first discharge capacity of 67mAh/g. It was found that the β[subscript(I)] material converted to the β[subscript(II)] polymorph during first charge. The γ₀ polymorph showed almost negligible electrochemical performance. Capacity retention of all polymorphs was poor, diminishing significantly by the tenth cycle. The effect of mechanical milling and carbon coating upon β[subscript(II)], β[subscript(I)] and γ₀ materials was also investigated. Various Li[subscript(1+x)]V[subscript(1-x)]O₂ materials (where 0≤X≤0.2) were produced through solid state synthesis. LiVO₂ was found to convert to Li₂VO₂ on discharge, this process was found to be strongly dependent on the amount of excess lithium in the system. The Li₁.₀₈V₀.₉₂O₂ material had the highest first discharge capacity at 310mAh/g. It was found that the initial discharge consisted of several distinct electrochemical processes, connected by a complicated relationship, with significant irreversible capacity on first discharge. Several other LiMO₂ systems were investigated for their ability to convert to layered Li₂MO₂ structures on low voltage discharge. While LiCoO₂ failed to convert to a Li₂CoO₂ structure, LiMn₀.₅Ni₀.₅O₂ underwent an addition type reaction to form Li₂Mn₀.₅Ni₀.₅O₂. A previously unknown Li₂Ni[subscript(X)]Co[subscript(1-X)]O₂ structure was observed, identified during the discharge of LiNi₀.₃₃Co₀.₆₆O₂.

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26

Fosu, Allen Yushark. "Development of a Chloride Route for Lithium Extraction from Spodumene." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0094.

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Le lithium est un composant majeur des batteries Li-ion, utilisées dans la fabrication de nombreux appareils électroniques portables. La transition énergétique entraîne le passage des véhicules thermiques aux véhicules électriques et hybrides, qui repose principalement sur l'utilisation de batteries Li-ion pour le stockage réversible de l'énergie. Le développement des véhicules électriques basés sur la technologie lithium-ion est à l'origine d'une demande record de sel de lithium (principalement carbonate et hydroxyde de lithium). Le spodumène est la principale source de lithium à partir de minerais. Son traitement nécessite une transformation de phase de la forme α à la forme β, suivie d'un grillage conduisant à la formation d'un sel de lithium après des étapes de lixiviation, de purification et de récupération. Dans cette thèse, le concentré de spodumène de la région de Pilbara en Australie occidentale a été caractérisé pour le traitement thermique et hydrométallurgique. Le traitement thermique est responsable de la formation de fissures dans les grains qui deviennent plus visibles avec l'augmentation de la température. La désintégration du matériau, la fusion et l'agglomération avec les minéraux contenus dans la gangue ont également été observées en augmentant la température jusqu'à 1050 °C. Des énergies d'activation apparentes de 655±20 kJ mol-1 ont été calculées pour la transformation de l'α-spodumène, ce qui confirme une forte dépendance à la température pour les transformations polymorphes du spodumène. Par la suite, nous avons étudié une voie alternative aux méthodes conventionnelles (procédé à l'acide sulfurique) pour traiter le concentré de spodumène dans le but de réduire la consommation d'énergie élevée des étapes de transformation de phase et de grillage au sulfate. Pour ce faire, nous avons procédé à la chloration directe de l'α-spodumène avec du chlorure de calcium, suivie d'une lixiviation à l'eau du résidu pour récupérer le chlorure de lithium. L'analyse du résidu obtenu après lixiviation a indiqué que la forme α était le seul polymorphe présent, ce qui suggère que l'extraction se fait directement à partir de la phase α. Dans des conditions optimales, un traitement thermique à 1000 °C pendant 60 minutes du concentré de spodumène en présence de chlorure de calcium à un rapport molaire chlorure de calcium/spodumène de 2,0 est nécessaire pour extraire près de 90 % du lithium et récupérer 85 % dans la liqueur de lixiviation. Une énergie d'activation apparente d'environ 122±6 kJ mol-1 a été calculée pour des températures allant de 800 à 950 ℃. La liqueur obtenue après lixiviation a été purifiée par échange d'ions et extraction par solvant afin de récupérer du chlorure de lithium d'une pureté suffisante pour être considéré comme un précurseur dans la production de matériaux pour batteries au lithium-ion
Lithium is a major component of Li-ion batteries, used in the manufacture of many portable electronic devices. The energy transition is driving the shift from thermal to electric and hybrid vehicles, which relies mainly on the use of Li-ion batteries for reversible energy storage. The development of electric vehicles based on lithium-ion technology is responsible for a record demand for lithium salt (mainly lithium carbonate and hydroxide). Spodumene is the main source of lithium from ores. Its processing requires a phase transformation from α-form to β-form, followed by roasting leading to the formation of a lithium salt after a leaching, purification, and recovery steps. In this thesis, spodumene concentrate from the Pilbara region of Western Australia was characterized for thermal and hydrometallurgical processing. Heat treatment is responsible for the formation of cracks in the grains which become more noticeable with increasing temperature. Disintegration of the material, melting and agglomeration with minerals contained in the gangue have also been observed by increasing the temperature up to 1050 °C. Apparent activation energies of 655±20 kJ mol-1 was calculated for the transformation of α-spodumene which confirms a strong temperature dependence for polymorphic transformations of spodumene. Subsequently, we investigated an alternative route to conventional methods (sulphuric acid process) to treat the spodumene concentrate with the aim of reducing the high energy consumption of the phase transformation and sulphate roasting steps. This was achieved by direct chlorination of α-spodumene with calcium chloride, followed by water leaching of the residue to recover lithium chloride. Analysis of the residue obtained after leaching indicated that the α-form was the only polymorph present, suggesting that extraction occurs directly from the α-phase. Under optimal conditions, heat treatment at 1000 °C for 60 minutes of the spodumene concentrate in the presence of calcium chloride at a calcium chloride/spodumene molar ratio of 2.0 is required to extract nearly 90% of lithium and recover 85% in the leach liquor. An apparent activation energy of about 122±6 kJ mol-1 was calculated for temperatures ranging from 800 to 950 ℃. The liquor obtained after leaching was purified by ion exchange and solvent extraction to recover lithium chloride of sufficient purity for consideration as a precursor in the production of lithium-ion battery materials

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27

Bohlin, Madeleine Sassaya. "Silicate weathering in the Himalayas : constraints from the Li isotopic composition of river systems." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270728.

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Chemical weathering of silicate rock consumes atmospheric CO2 and supplies the oceans with cations, thereby controlling both seawater chemistry and climate. The rate of CO2 consumption is closely linked to the rate of CO2 outgassing from the planetary interior, providing a negative feedback loop essential to maintaining an equable climate on Earth. Reconstruction of past global temperatures indicates that a pronounced episode of global cooling began ~50 million years ago, coincident with the collision of India and Asia, and the subsequent exhumation of the Himalayas and Tibet. This has drawn attention to the possible links between exhumation, erosion, changes in silicate weathering rates, and climate. However, many of the present-day weathering processes operating on the continents remain debated and poorly constrained, hampering our interpretations of marine geochemical archives and past climatic shifts. To constrain the controls on silicate weathering, this thesis investigates the lithium (Li) isotopic composition of river waters, suspended sediments and bed load sediments in the Alaknanda river basin, forming the headwaters of the Ganges. Due to the large fractionation of Li isotopes in the Earth’s surface environment, Li is sensitive to small changes in silicate weathering processes. As a consequence of the pronounced gradients in climate (rainfall and temperature) and erosion across the basin, the river waters show large variations in their Li isotopic composition (δ7Li), ranging from +7.4 to +35.4‰, covering much of the observed global variation. This allows a detailed investigation of the controls on Li isotope fractionation, and by extension silicate weathering. The Li isotopic composition is modelled using a one-dimensional reactive transport model. The model incorporates the continuous input of Li from rock dissolution, removal due to secondary mineral formation, and hydrology along subsurface flow paths. Modelling shows that the Li isotopic variations can be described by two dimensionless variables; (1) the Damköhler number, ND, which relates the silicate dissolution rate to the fluid transit time, and (2) the net partition coefficient of Li during weathering, kp, describing the partitioning of Li between secondary clay minerals and water, which is primarily controlled by the stoichiometry of the weathering reactions. The derived values of the controlling parameters ND and kp, are investigated over a range of climatic conditions and on a seasonal basis, shedding light onto variations in the silicate weathering cycle. In a kinetically limited weathering regime such as the Himalayan Mountains, both climate and erosion exert critical controls the weathering intensity (the fraction of eroded rock which is dissolved) and the weathering progression (which minerals that are being weathered), and consequently the fractionation of Li isotopes and silicate weathering in general. Modelling of the Li isotopic composition provides an independent estimate of the parameters which control silicate weathering. These estimates are then used to constrain variables such as subsurface fluid flux, silicate dissolution rates, fluid transit times and the fraction of rock which is weathered to form secondary clay minerals. The simple one-dimensional reactive transport model therefore provides a powerful tool to investigate the minimum controls on silicate weathering on the continents.

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28

Iliushchenko, Valeriia. "Povrchového ošetření cementových systémů vybranými roztoky křemičitanů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414120.

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Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu.

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29

Nytén, Anton. "Low-Cost Iron-Based Cathode Materials for Large-Scale Battery Applications." Doctoral thesis, Uppsala University, Department of Materials Chemistry, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6842.

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There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O₂-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO₄. A second and in some ways even more attractive material - Li₂FeSiO₄ - has emerged during the course of this work.

An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li₂FeSiO₄. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li₂FeSiO₄ and LiFeSiO₄, but with the structure of the original Li₂FeSiO₄ transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li₂FeSiO₄ and the delithiated on LiFeSiO₄ structure provide an interesting insight into the experimental result.

Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO₄ and Li₂FeSiO₄ after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling.

LiFePO₄ and Li₂FeSiO₄ should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.

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CARMO, LUCAS S. do. "Dosimetria termoluminescente de altas doses de raios gama, raios beta, feixe de prótons e de nêutrons epitérmicos utilizando minerais naturais de silicatos e dosímetros de LiF: Mg, Cu, P (MCP)." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/25192.

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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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31

Maouacine, Koceila. "Matériaux hybrides poreux silice/polymère comme électrolytes pour batterie lithium-ion tout solide." Electronic Thesis or Diss., Aix-Marseille, 2023. http://www.theses.fr/2023AIXM0024.

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La conception de batteries lithium-ion utilisant un électrolyte solide est actuellement l’une des voies les plus étudiées pour s’affranchir des problèmes de sécurité lié à ces dispositifs. Dans ces travaux de thèse, nous proposons une nouvelle approche d'élaboration d'un électrolyte hybride poreux silice/polymère, contenant une fraction massique plus élevée de silice mésoporeuse que de polymère. Deux morphologies de matériaux hybrides de silice ont été étudiées : sous forme de poudres compressées (pastilles) et sous forme de films minces. Dans la première partie du travail, une poudre de silice hybride a été synthétisée puis calcinée pour libérer la porosité. La silice mésoporeuse a, ensuite, été fonctionnalisée par imprégnation en solution avec différents polymères de type PEG de faible poids moléculaire puis, par un sel de lithium, le LiTFSI. Les poudres hybrides ont été compressées sous forme de pastilles, présentant une porosité inter- et intraparticulaire. Il a été montré que, les pastilles hybrides présentent des propriétés de conductivité ionique prometteuse lorsque les porosités inter et intraparticulaires sont remplies par le complexe PEG-LiTFSI pour PEG de faible masse molaire (300-600 g/mol). Dans la seconde partie, des films de silice mésoporeuse ont été déposés sur une électrode de carbone vitreux en utilisant une électrode à disque rotatif (RDE). Après avoir caractérisé ces films du point des propriétés texturales et de la microstructure, ces derniers ont été fonctionnalisés par le complexe PEG-LiTFSI via un procédé d’imprégnation et l’étude préliminaire de leur conductivité ionique a été réalisée
The design of lithium-ion batteries using a solid electrolyte is currently one of the most studied ways to overcome safety problem of these devices. In this thesis work, we propose a new approach to develop a porous silica/polymer hybrid electrolyte, containing a higher weight fraction of mesoporous silica than polymer. Two morphologies of silica hybrid materials were studied: as compressed powders (pellets) and as thin films. In the first part of the work, a hybrid silica powder was synthesized and then calcined to liberate the porosity. The mesoporous silica was then functionalized with different polymers of PEG of low molecular weight then by a simple solution impregnation. The hybrid powders were shaped as pellets, presenting inter- and intra-particle porosity. It was shown that the hybrid pellets present promising ionic conductivity properties when the inter- and intraparticle porosities are filled with the PEG-LiTFSI complex for PEG of low molar mass (300-600 g/mol). In the second part, mesoporous silica films were deposited on a glassy carbon electrode using a rotating disc electrode (RDE). After the characterization of these films from a textural properties and a microstructure point of view, they were functionalized by the PEG-LiTFSI complex via an impregnation process and the preliminary study of their ionic conductivity was performed

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32

Guarda, Guilherme Bottene 1987. "Influência das sucessivas termo-prensagens nas propriedades mecânicas, transmissão da luz e análise microestrutural da ceramica prensada reforçada por di-silicato de lítio = Influence of repetead heat-pressing on mechanical properties, light transmission and microstructural analysis of pressable ceramic reforced by lithium disilicate." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289559.

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Orientador: Lourenço Correr Sobrinho
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O objetivo neste estudo foi avaliar a dureza Vickers, resistência à flexão biaxial, análise microestrutural e transmissão da luz da cerâmica vítrea prensada por calor após repetidas re-prensagem. Discos de cerâmica de IPS e.max Press (12,0 mm de diâmetro x 0,9 mm de espessura) foram prensadas e usadas como grupo controle (TP1). Sprues e botões cerâmicos restantes da primeira prensagem foram reaproveitados e utilizados para confecionar os grupos testes de re-prensagem (TP2 e TP3). Todos os procedimentos das termoprensagens foram feitas de acordo com as recomendações do fabricante. O teste de resistência à flexão biaxial (BFS) foi realizado para determinar a resistência dos discos cerâmica vítrea prensada (TP1) e re-prensada (TP2). Doze amostras por grupo (n=12) foram testadas, com velocidade de aplicação de carga de 0,5 mm/min., na máquina de ensaio universal (Instron). Para o teste de dureza Vickers foi realizado em um mucrodurômetro HMV 2 (Shimadzu) com carga de 500 gf por 15 segundos. Dez discos de cerâmica vítrea foram foram confeccionadas para primeira prensagem (TP1) e dez para cada reprensagem (TP2 e TP3), realizando 5 endentações por amostras. As características de superfície foram analisadas em MEV. Características de irradiancia e de espectro de luz transmitida através da cerâmica foram medidos utilizando-se um medidor de energia e um espectrômetro de luz. Os dados foram submetidos à analise de variância e teste de Tukey post-hoc (p <0,05). Os valores BFS em MPa (média e desvio-padrão) foram para TP1 (279,7 ±12,5), para TP2 (230,3 ±7,1) e para TP3 (220,8± 8,6). Os valores de TP1 foram significativamente maiores que os grupos TP2 e TP3. Os valores de dureza Vickers foram para TP1 (638,1 ±11,5), para TP2 (592,6± 6,6) e para TP3 (590,4 ±7,6). A dureza de TP1 foi significativamente maior que os grupos TP2 e TP3. As micrografias do material cerâmico em MEV mostrou aumento no tamanho e concentração dos cristais de disilicato de lítio (LeDiSi) após re-prensagem. A análise das imagens, re-prensagem mostrou homogeneidade na distribuição dos cristais de disilicato de lítio e aumento na densidade dos cristais. Redução na transmissão da luz foi detectada com aumento da espessura da cerâmica, alterações na emissão foi observada após repetidas prensagens. Conclui-se que a reutilização de material em repetidas re-prensagens diminuiu significativamente as propriedades de resistência à flexão biaxial e a dureza da cerâmica reforçada por di-silicato de lítio IPS e.max Press, alterou a microestrutura e influenciou na transmissão da luz através da cerâmica
Abstract: The aim of this study was to evaluate the Vickers hardness, biaxial flexural strength, microstructural analysis and light transmission of heat-pressed glass-ceramic material after repeated pressing. Ceramic discs of IPS e.max Press (12.0 mm in diameter x 0.9 mm thickness) were heat-pressed and used as control (HP1). Sprue and button parts of the heat-pressed material were retrieved and used for repeated heat-pressing to construct discs of two and three re-pressed groups (HP2 and HP3). All the heat-pressed casting procedures were performed according to the manufacturers' instructions. A biaxial flexural strength (BFS) test was performed to determine the strength of pressed (HP1) and re-pressed (HP2 and HP3) glass-ceramic disc specimens (n = 12) at a crosshead speed of 0.5 mm/min., in the universal testing machine (Instron). Vickers hardness test was conducted in a microhardness tester HMV-2 (Shimadzu) with a load of 500 g applied for 15 s. Ten glass-ceramic discs were made for pressed (HP1) and ten for re-pressed (HP2 and HP3) and five indentations were made for each disc. Surface characteristics were examined with SEM. Light irradiance and spectrum characteristics transmitted through ceramic were measured using a power meter and a light spectrometer. Data were submitted to ANOVA and Tukey¿s post-hoc test (p<0.05). The BFS values in MPa (mean ± standard deviation) were HP1 (279.7±12.5); HP2 (230.3±7.1) and HP3 (220.8±8.6). HP1 was significantly higher than HP2 and HP3. The VH values were HP1 (638.1±11.5); HP2 (592.6±6.6) and HP3 (590.4±7.6). HP1 was significantly higher than HP2 and HP3. In conclusion, repeated heat-pressing treatment produce a statistically significant decreased in the biaxial flexural strength and Vickers hardness of the IPS e.max Press glass-ceramic, microstructural alterations and alterations in light transmission throughout ceramic discs
Doutorado
Materiais Dentarios
Doutor em Materiais Dentários

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33

Yu-WenShen and 沈郁文. "Synthesis of Needle-Shaped Lithium Iron Silicate for Lithium-Ion Battery Application." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/80797093939465041675.

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碩士
國立成功大學
化學工程學系碩博士班
101
Li2FeSiO4 was prepared by the hydrothermal method from LiOH, FeSO4, and amorphous SiO2 at 180℃for 3 day. The influences of synthesis conditions (cheating agent, hydrothermal temperature, precursors, and the mix of the precursors) were systematically examined. Carbon coated Li2FeSiO4(LFS/C) was synthesized from a mixture of as-prepared Li2FeSiO4 and resin or sucrose in solvent via a simple mixing, then calcinated under high-temperature treatment. The resulting Li2FeSiO4/resin (LFS/r) and Li2FeSiO4/sucrose (LFS/s) samples were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. When tested as lithium-ion battery cathodes, the discharge capacity of the LFS/r and LFS/s samples can reach 163 and 144 mAh /g, respectively, in the voltage window of 1.5−4.7 V at the rate of 0.06 C. Furthermore, when the charge voltage set to 4.1 V, the gap between charge and discharge capacity disappeared, that it is good for battery. The result shows that the best voltage window for Li2FeSiO4 is about from 1.8 V to 4.1 V.

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Chen, Chih-Chung, and 陳志仲. "Zinc-Rich Lithium-Silicate Coatings for Corrosion Prevention of Steel." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/19286010103326949761.

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碩士
國立臺灣海洋大學
河海工程學系
94
Abstract In order to prevent the corrosion of the steel structure of rocket launch site, NASA developed the zinc-rich inorganic silicate coating materials during 1970. The silicate is used to form the coating and zinc powder is added as the color agent. After hardening, it becomes a hard material and can resist to mechanical erosion. In addition, it can prevent corrosion since zinc can performed as the sacrificed anode. In the process, no organic solution is used and this meets the environmental requirement. Owing to the above-mentioned merits, the zinc-rich inorganic silicate coating has a bright future and is worth studying. In this study, we evaluate the influences for different moduli of lithium silicate (LiO/SiO2) and different mass ratio of lithium silicate to zinc on the coating-forming ability, the corrosion prevention capability and durability (especially to the varying weather condition). The following factors are considered to evaluate the performance of the coating: coating-forming ability, workability, mechanical behavior, resistance to highly alkali or acid solution and weather-resistance. The experiments include setting time, coating thickness, hardness, adhesive test, corrosion, open circuit potential, linear DC corrosion rate, micro-scale analysis and chemical analysis for the corrosion product. Experiment results show that the mass ratio of lithium silicate to zinc influences the workability and coating-forming ability significantly. The coating will debond, crack as the mass ratio of lithium silicate to zinc becomes too low. When the mass ratio of lithium silicate to zinc becomes too high, the workability of coating becomes doubtful and the coating will become sticky and hard to mix such that it is difficult to put a uniform layer of coating on the surface of steel. Meanwhile, the modulus of lithium silicate (LiO/SiO2) will affect the mechanical performance of coating as well as the capability of cathodic protection. Lower modulus will have a coating with a nicer thickness, hardness, viscosity and adhesive property. In addition, the cathodic protection can last longer.

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Galoustov, Karen. "A detailed study of the lithiation of iron phosphate as well as the development of a novel synthesis of lithium iron silicate as cathode material for lithium-ion batteries." Thèse, 2011. http://hdl.handle.net/1866/5875.

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Dans cette thèse nous démontrons le travail fait sur deux matériaux de cathodes pour les piles lithium-ion. Dans la première partie, nous avons préparé du phosphate de fer lithié (LiFePO4) par deux méthodes de lithiation présentées dans la littérature qui utilisent du phosphate de fer (FePO4) amorphe comme précurseur. Pour les deux méthodes, le produit obtenu à chaque étape de la synthèse a été analysé par la spectroscopie Mössbauer ainsi que par diffraction des rayons X (DRX) pour mieux comprendre le mécanisme de la réaction. Les résultats de ces analyses ont été publiés dans Journal of Power Sources. Le deuxième matériau de cathode qui a été étudié est le silicate de fer lithié (Li2FeSiO4). Une nouvelle méthode de synthèse a été développée pour obtenir le silicate de fer lithié en utilisant des produits chimiques peu couteux ainsi que de l’équipement de laboratoire de base. Le matériau a été obtenu par une synthèse à l’état solide. Les performances électrochimiques ont été obtenues après une étape de broyage et un dépôt d’une couche de carbone. Un essai a été fait pour synthétiser une version substituée du silicate de fer lithié dans le but d’augmenter les performances électrochimiques de ce matériau.
In this thesis, we demonstrate work on two different cathode materials for lithium-ion batteries. First, the synthesis of lithium iron phosphate (LiFePO4) is reproduced from literature using two lithiation methods starting with amorphous iron phosphate (FePO4). For both reactions, the product at each step of the synthesis was analyzed using Mössbauer Spectroscopy and X-ray diffraction in order to gain further insight of the reaction mechanism. The results of this work were published in Journal of Power Sources. The second cathode material of interest was lithium iron silicate (Li2FeSiO4). A novel synthetic method was developed to produce lithium iron silicate cost effectively starting with low cost precursors and basic laboratory equipment. The material was synthesized using a solid- state synthesis after milling and carbon coating, electrochemical performance was evaluated. An attempt was made to synthesize off-stoichiometric lithium iron silicate in order to increase the electrochemical performance of the material.

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Wu, Shang-Ru, and 吳尚儒. "Development of Lithium Silicate to Capture Carbon Dioxide Integrated with Wasted Heat Recovery System." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/90476668377465746895.

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碩士
國立雲林科技大學
環境與安全衛生工程系
103
The carbon capture and storage (CCS) have attracted considerable attention especially at high temperature. In this study, lithium orthosilicate (Li4SiO4) which synthesized by solid state method and sol-gel method has been selected as a sorbent due to its high reactivity. Li/Si ratio, calcination temperature and calcination time are the key experimental parameters. The contribution of each parameter on the CO2 capture capacity and the regeneration experiments were conducted using Taguchi method. Moreover, designing a CO2 capture circulatory system with wasted heat recovery, and use the operating parameters from the calcium looping demonstration to calculate the require amount of Li4SiO4, heat value and regeneration mass flow. Finally, the sensitivity analysis has been carried out for the parameters of exhaust gas flow rate, CO2 content and heat lost. Li4SiO4 has showed superior CO2 capture capacity and remained stable absorption capacity at four times cycles, which synthesized by solid state method. Calcination temperature would cause a considerable influence of absorption capacity and though adding excess lithium is unable to increase the absorption capacity, it would enhance the absorption rate and regeneration capacity. In contract, Calcination time is the most influential parameter for Li4SiO4 in sol-gel method showing better absorption capacity at 550 ºC. However, the Li4SiO4 prepared by sol-gel method has the poor regeneration capacity due to the low particle size. In order to determinate the required amount of Li4SiO4 and regeneration flow rate, two equations were derived and verified by using the experimental data. In sensitivity analysis, the required amounts of Li4SiO4 and regeneration flow rate are linear with exhaust gas flow rate and CO2 content, and the ratio of regeneration flow rate and exhaust gas flow rate is approximately equal to the CO2 content. However, the variation of exhausted gas composition would influence the gas density, affecting the result of calculation. In contract, the heat recovered rate is nonlinear with regeneration flow rate. In characteristics analysis, pure Li4SiO4 can be obtained by solid state method; on the other hand, the sorbents prepared by sol-gel method would cause a product of Li2SiO3. However, sol-gel method provides the better absorption rate at 600 – 650 ºC.

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Singh, Shashwat. "Study of the Effect of Different Nucleating Agents On Lithium Alumino-Silicate Glass-Ceramic System." Thesis, 2013. http://ethesis.nitrkl.ac.in/5137/1/109CR0610.pdf.

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Lithium AluminoSilicate (LAS) Glass ceramic (GC) finds use in kitchenware, cooktop panels and telescope mirror because of its characteristic of very low and sometime zero thermal expansion coefficient (TEC) in the application temperature range. In this project work, conventional melt-quenching technique has been used for the development of the LAS base glass. After controlled crystallization, LAS GC has been developed using titania and/ zirconia as a nucleating agent and their effect has been studied in the presence of yittria. Here the yittria content has been varied from 1-3 wt% with corresponding variation in titania (2-4 wt%) or zirconia (2-4 wt%). Effects of temperature and time on crystallization have also been studied followed by the effect of crystallization on thermal expansion co-efficient of the developed glass ceramics. Developed crystalline phases were â-Spodumene and â-quartz solid solution (ss) which has been authenticated by X-ray diffractometer. TEC of the GC has been measured and studied using Dilatometer in the temperature range of 25oC to 750oC and its surface hardness has been measured at 0.5Kgf using Vickers indentation method.

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Choudhary, Abhisek. "Synthesis and characterization of lithium silicate ceramic for the test blanket module (tbm) in fusion reactors." Thesis, 2012. http://ethesis.nitrkl.ac.in/4462/1/M.Tech(R)_Abhisek_Choudhary.pdf.

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Lithium-based ceramic, Li4SiO4, is being considered as promising solid breeder materials in the tritium breeding blanket of thermonuclear fusion reactors, because of its high Li- density, high thermal conductivity and prominent tritium release rate at low temperatures between 300 and 500oC, its low activation characteristics, low thermal expansion coefficient and high thermal conductivity. For tritium recovery purpose samples having 85-90% of true density with open porosity (around 5%) is required. Uniform small grain size distribution (having diameter between 2-4μm) is preferable as activation energy for tritium diffusion through grain is higher compared to grain boundary. Solid state method requires higher calcination temperature, producing coarser particle and impurity, which adversely affects in achieving high sintered density (above 85% of theoretical density) and forms large grain size with entrapped closed pore inside the grain. In the current work Li4SiO4 powder was synthesized by solution combustion technique using cheaper precursor of silica i.e. from rice husk ash (an agricultural waste). We found that by controlling the metal to citrate ratio of the solution and calcination temperature of the as-burnt powder phase purity can be achieved. The particle size of Li4SiO4 powder (prepared at M/C=1.4) was found to be 100-200 nm with low surface area (2m2/gm). It was found that Li4SiO4 powder can be sintered at a temperature as low as 900oC with a density ~ 85% of the theoretical density. Phase stability in the sintered sample was studied. Attempts were made to minimize the lithium loss from the sintered specimens. Moisture reactivity studies were conducted together with FTIR spectroscopy on calcined powder to find out the moisture affinity of the samples. Kinetics of the initial stage of sintering from the shrinkage data has been analyzed to find out the sintering mechanism. Thermal diffusivity measured by laser flash method. Thermal conductivity value depends on the density of the sample. AC impedance method has been used to characterize electrical property of the sintered sample as tritium diffusion is related to the Li+ ion conductivity in Li4SiO4.

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Choudhary, Abhisek. "Synthesis and characterization of lithium silicate ceramic for the test blanket module (TBM) in fusion reactors." Thesis, 2012. http://ethesis.nitrkl.ac.in/4472/1/M.Tech(R)_Abhisek_Choudhary.pdf.

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Lithium-based ceramic, Li4SiO4, is being considered as promising solid breeder materials in the tritium breeding blanket of thermonuclear fusion reactors, because of its high Li- density, high thermal conductivity and prominent tritium release rate at low temperatures between 300 and 500oC, its low activation characteristics, low thermal expansion coefficient and high thermal conductivity. For tritium recovery purpose samples having 85-90% of true density with open porosity (around 5%) is required. Uniform small grain size distribution (having diameter between 2-4μm) is preferable as activation energy for tritium diffusion through grain is higher compared to grain boundary. Solid state method requires higher calcination temperature, producing coarser particle and impurity, which adversely affects in achieving high sintered density (above 85% of theoretical density) and forms large grain size with entrapped closed pore inside the grain. In the current work Li4SiO4 powder was synthesized by solution combustion technique using cheaper precursor of silica i.e. from rice husk ash (an agricultural waste). We found that by controlling the metal to citrate ratio of the solution and calcination temperature of the as-burnt powder phase purity can be achieved. The particle size of Li4SiO4 powder (prepared at M/C=1.4) was found to be 100-200 nm with low surface area (2m2/gm). It was found that Li4SiO4 powder can be sintered at a temperature as low as 900oC with a density ~ 85% of the theoretical density. Phase stability in the sintered sample was studied. Attempts were made to minimize the lithium loss from the sintered specimens. Moisture reactivity studies were conducted together with FTIR spectroscopy on calcined powder to find out the moisture affinity of the samples. Kinetics of the initial stage of sintering from the shrinkage data has been analyzed to find out the sintering mechanism. Thermal diffusivity measured by laser flash method. Thermal conductivity value depends on the density of the sample. AC impedance method has been used to characterize electrical property of the sintered sample as tritium diffusion is related to the Li+ ion conductivity in Li4SiO4.

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Bhatia, Dishu. "Effect of TiO2 and ZrO2 Addition on Phase Evolution, Densification and Microstructure of Lithium Silicate Ceramics." Thesis, 2015. http://ethesis.nitrkl.ac.in/7290/1/2015_Effect_Bhatia.pdf.

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Lithium ortho-silicate (Li4SiO4) powder was synthesized using cheaper source of silica like rice husk ash through solid-state reaction of Li2CO3 (Lithium Carbonate) and SiO2 (Silica). Phase pure powder could be produced at 800oC calcined for 4h. In this report we studied the phase evolution, densification and corresponding micro structural properties in Li4SiO4 on the addition of TiO2 and ZrO2 nano powder by solid-state mixing process. The obtained powders are pressed and sintered at three different temperatures i.e. 900oC, 950oC, 1000oC. The structural, micro structural and mechanical properties of above samples were investigated by X-ray Diffraction, Field Emission Scanning Electron Microscopy and Diametric Tensile Strength measurement respectively. It is observed that densification and diametric tensile strength (DTS) values of the Solid-state mixing of 1wt% nano TiO2 and ZrO2 to Li4SiO4 showed 76% and 81% of the theoretical density and DTS values of 3.9MPa and 4.1Mpa at 1000oC, which is less than that of the pure Li4SiO4 samples.

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Abdulwahed, Abdulaziz. "The effect of repetitive firing cycles on physical and optical properties of zirconia reinforced lithium silicate ceramics." Thesis, 2019. https://hdl.handle.net/2144/37991.

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This study’s objective was to evaluate repetitive firing cycles’ effects on the translucency, light’s absorption coefficient, and flexural strength of zirconia-reinforced lithium silicate ceramics. Two zirconia-reinforced lithium silicate ceramics and one lithium disilicate glass-ceramic were tested. Blocks of all materials were sectioned into tiles with different thicknesses and subjected to up to five firing cycles using the firing schedule indicated in the manufacturer’s user instructions. Light transmission ratio (T) and absorption coefficients were determined using a spectrophotometer. Further, bars were sectioned from blocks of all materials and tested for three-point-bend flexural strength using a Universal Testing Machine (Instron), and flexural strength was calculated from load at failure. Factorial ANOVA and Tukey’s HSD tests were conducted to analyze light transmission and flexural strength, while regression was used to analyze the absorption coefficient. Weibull parameters and fractographic analysis also were investigated. The results showed that repetitive firing cycles reduced e.max® and Vita Suprinity’s® translucency, but not that of Celtra® Duo, which showed no significant difference. All materials of greater thickness exhibited less translucency, and e.max® CAD had the highest mean light transmission; however, it was not significantly different than Celtra® Duo. Repetitive firing cycles showed more absorption coefficient of light with Vita Suprinity® and e.max®, except for Celtra® Duo, which showed no difference. Vita Suprinity® showed the highest absorption coefficient; however, it was not significantly different than e.max® CAD. Repetitive firing cycles had no significant effect on flexural strength. High and low flexural strength samples for all materials showed similar characteristics with respect to crack propagation patterns, and fracture origins. In conclusion, repetitive firing cycles decreased both e.max® and Vita Suprinity’s® translucency significantly. Repetitive firing cycles increased e.max® and Vita Suprinity’s® absorption coefficient significantly, particularly at shorter wavelengths. Repetitive firing cycles did not increase flexural strength statistically significantly. Vita Suprinity® showed an inherent and more homogeneous flaw-distribution in the first two firing cycles compared to the distribution of flaws in the other two materials.

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Dissertations / Theses on the topic 'Lithium silicates'

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