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Dissertations / Theses on the topic 'Aluminosilicate'
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1
Mogili, Sravya. "Sol-Gel Synthesis of Aluminosilicate Glasses." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1584733.
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<p> The main goal of this research project is to synthesize aluminosilicate glass materials that are doped with praseodymium. To be useful for optical studies, these glass materials must be optically transparent, strong enough to be handled and polished, and free of cracks. An advantage of the sol-gel process is that we have control over the amount of doping. However, a disadvantage of the sol-gel process is that cracking often occurs during the drying step. </p>
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Cooper, Emma. "Renewable routes to porous aluminosilicate materials." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3936/.
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The objectives of this project were to synthesise zeolites and aluminosilicate materials from silicon sources derived from biomass ashes. These materials will have great potential as catalysts and adsorbents. In order to begin this study it was necessary to find and optimise a technique for extraction of silicon to an alkali silicate solution from biomass ashes. It was then necessary to develop a technique for analysis of the alkali silicate solutions. This was done using calibration of integrals from infrared spectra. An optimisation of the synthesis of Zeolite X from a rice hull ash derived alkali silicate was developed and these materials were analysed and characterised using XRD, N2 Adsorption porosimetry, X‐Ray Fluorescence Spectroscopy, and X‐Ray Photoelectron Spectroscopy. An in‐depth study of the surface of the ash derived and reference Zeolite X was undertaken using in situ small molecule probing FT‐IR. It was found that although the materials were similar there was a significant difference due to the presence of a strongly bonded carbonate species in the pores of the bio‐derived zeolite. Synthesis of a Miscanthus ash derived mesoporous silica, MCM‐41, was successfully achieved which was comparable to its conventionally synthesised equivalent. Both displayed ordered hexagonal pores and high surface areas. A study on addition of different sources of aluminium found that it was possible to introduce aluminium into the structure successfully. Included in this study was the addition of the waste product ‘red clay’ as an aluminium source. Another mesoporous silica, SBA‐15 was synthesised from a Miscanthus ash derived alkali silicate. It was necessary to optimise the synthesis to adapt to the different pH systems of the conventional method and bio‐derived alkali silicate solutions. This was achieved and a bio‐derived SBA‐15 material with ordered hexagonal pores was produced.
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Zhang, Siqi. "The effect of boron substitution on the structure of calcium-aluminosilicate calcium-fluoro-aluminosilicate glasses and glass-ceramics." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7173/.
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This work focuses on the effect of boron substitution for aluminium on the structure o£ a series of fluorine-free (4.5Si02-3A12O3-1.5P205-5Ca0) and fluorine-containing (4.5Si02-3A1203-1.5P205-3Ca0-2CaF2) glasses and the resultant glass ceramics has been studied by using a combination of analytical tools like helium pycnometer, FTIR, Raman, XRD, multinuclear MAS-NMR spectroscopy and thermal analysis by DSC and TGA. The morphology of the crystal phases was observed by ESEM, and the identification of the composition observed was achieved by EDX. The density of both boron-substituted aluminium glasses and glass ceramics decreased with increasing boron content. The glass transition temperature decreased generally with an increase of boron substitution in fluorine-free glasses. When the sintering temperature was raised to 1100°C, the calcium phosphate (C'4P20 9) phase transferred to the tricalcium phosphate [Ca3(P04)2] phase, and anorthite and aluminium phosphorus phases were crystallised. The fluorapatite phase was the first phase to be formed in the fluorine-containing glass ceramics, and with the sintering temperature raised to 1100°C, the mullite and aluminium phosphorus phases were crystallised. All the NMR results investigate the structure of boron-substituted glasses and glass-ceramics which are agree with XRD results. ESEM and EDX analysis showed changes in the composition of glass ceramics with boron substitution.
4
Azizi, Seyed Naser. "NMR studies of silicate & aluminosilicate solutions." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4946/.
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The work described in this thesis deals with the use of (^29)Si and (^27)Al NMR to obtain information about the chemical structure of aqueous silicate and aluminosilicate solutions. This has extended the knowledge gained in previous studies. A wide range of alkaline and tetraalkylammonium hydroxide silicate and aluminosilicate solutions (mostly also containing sodium) has been examined. Such solutions are shown to contain a large range of anions. The first highly-resolved (^27)Al NMR spectra of alkaline aluminosilicate solutions are presented and discussed. The linewidths and number of resolved lines are shown to depend critically on several factors, especially the pH and Si:Al ratio, as well as the concentration of various components. At least thirteen separate peaks or bands are observed at the optimum conditions of pH~10.35 and Si:Al = 1. Tentative assignments of some bands are presented, based on (^27)Al and (^29)Si shift omparability, (^27)Al linewidths and (^27)Al spin-lattice relaxation measurements. Relative intensities of the various (^27)Al signals are given for the pH ~10.35 solution. A correlation of (^27)A1 and (^29)Si chemical shifts has been established. Dilution effects and dynamic equilibria are considered for the aluminosilicate solutions. Trends in the spectra with changing concentrations of the various components have been identified. Under certain conditions, additional peaks are observed. Two of these are tentatively assigned to aluminium nuclei in "three-membered" rings. Moreover, a few very sharp hues (i.e. with very low electric field gradients), currently of unknown origin, are observed in several spectra. At certain concentrations chemical exchange can be shown to take place. The effects of tetraalkylammonium (TAA) and alkali metal cations on the equilibrium distribution of aluminosilicate oligomers in aqueous alkaline aluminosilicate solutions have been investigated using evolution with time of Al-27 NMR spectra. The results indicate that there are no observable differences in the initial distribution of aluminosilicate species (i.e. immediately following solution mixing) involving a mixture of TAA and Na cations and those involving alkali metal cations alone. However, in the latter case, this distribution, in contrast to those for TAA/Na solutions, is not stable, the species quickly re-equilibrating, giving broad signals of q(^3) and perhaps q(^4) type. The effect of Al and Si concentration on the formation of gel in?aluminosilicate solutions is also investigated with ^^Al NMR spectra. It is shown that the gel time strongly depends on the Al concentration and the temperature. A graph of Al and Si concentrations with gel time has been established.Silicon-29 NMR spectra have been obtained for more than 20 aqueous alkaline silicate solutions containing methanol. A signal assigned to CH(_3)OSi(OH)(_3) or one of its deprotonated congeners is studied in detail for the first time for the solution conditions involved. Its appearance has been monitored as a function of the solution composition. The equilibrium constant for its formation is of the order of 0.65. The effects of alcohol, silicate and TAAOH concentration and of the nature of the alkylammonium base on this reaction have been investigated.
5
Sulaiman, Shamsul Kamal. "Preparation of synthetic zeolites from aluminosilicate materials." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427789.
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Prasad, S. "Studies on aluminosilicate and aluminophosphate molecular sieves." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1991. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2996.
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Evans, Amanda Jayne. "The preparation, characterisation and catalytic study of silver incorporated zeolites and ordered mesoporous materials." Thesis, Keele University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288435.
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Le, Gac Alexandre. "Comportement sous irradiation des verres d'aluminosilicate." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX047/document.
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La compréhension des effets d’irradiation dans les verres d’oxyde est importante dans le domaine du conditionnement des déchets nucléaire et requière l’évaluation du rôle des formateurs de réseau, principalement le silicium, le bore et l’aluminium, mais aussi du rôle des éléments alcalins et alcalino-terreux qui peuvent agir en tant que modificateurs de réseau ou compensateurs de charge. Les verres d’aluminoborosilicates ont été très étudiés et le rôle des changements de coordinence du bore sur l’évolution structurale du verre sous irradiation a été souligné. Cependant, il n’y a que peu d’études sur les verres d’aluminosilicates et presque qu’aucune information sur l’influence de l’aluminium et de ses compensateurs de charge sur l’évolution du réseau sous irradiation. Ce travail de thèse a donc pour objectif de déterminer les effets de la teneur en aluminium et du type de compensateurs de charge (ici les ions sodium et calcium) sur l’évolution de la structure des verres d’aluminosilicates sous irradiation. Afin de comprendre les différents phénomènes dans les verres d’oxyde complexes, 13 verres simplifiés, composés d’oxydes de SiO2, Al2O3, Na2O et CaO, ont été élaborés. Ainsi, l’influence des rapports Na2O/CaO et Al2O3/SiO2 et de la teneur en Al2O3 ont été investigués. Pour simuler les désintégrations alpha et comparer les dommages électronique et balistique, des irradiations externes aux ions He2+ d’énergie 5 MeV et aux ions Au4+ d’énergie 7 MeV ont été réalisées sur les verres. Des irradiations aux électrons ont également été faites afin d’obtenir des échantillons irradiés en volume par des collisions électroniques à faible pouvoir d’arrêt<br>The understanding of radiation effects in oxide glasses is important in nuclear waste conditioning field and requires the evaluation of the role of the glass formers, mainly silicon, boron and aluminum, but also of the alkali and alkali-earth elements that can act either as modifier elements or charge compensators. Aluminoborosilicate glasses were highly studied and the role of boron coordination changes on structural evolution under irradiation was highlighted. However, there are only few studies on aluminosilicate glasses and almost no information about the influence of aluminum and its charge compensators on the glassy network evolution under irradiation. The goal of this work is therefore to determine the effects of aluminum content and type of charge compensators (here, Na and Ca cations) on the aluminosilicate glass structure evolution under irradiation. To understand the different phenomena in complex oxide glasses, 13 simplified glasses, composed of SiO2, Al2O3, Na2O and CaO oxides, were elaborated. Hence, the influence of Na2O/CaO and Al2O3/SiO2 ratios, and Al2O3 content, were investigated. To simulate alpha decays and compare electronic and ballistic damage, external irradiations at room temperature with 5 MeV He2+ and 7 MeV Au4+ were performed on glasses. 2.5 MeV electron irradiations were also done to obtain bulk samples irradiated by electronic collisions at low stopping power
9
Hinds, Chantal Simonette. "ESR studies of radical adsorbed on aluminosilicate catalysis." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243865.
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Rappensberger, Csaba Ferenc. "Novel rare-earth aluminosilicate glasses and glass-ceramics." Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/56937/.
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Dvoyashkin, Muslim, Ryan Wood, Clifford R. Bowers, et al. "Gas transport in aluminosilicate nanotubes by diffusion NMR." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185914.
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Diffusion of tetrafluoromethane in aluminosilicate nanotubes was studied by means of 13C pulsed field gradient (PFG) NMR at 297 K. The measured data allow the estimation of the diffusivity of tetrafluoromethane inside the nanotubes as well as the diffusivity for these molecules undergoing fast exchange between many nanotubes. The results support the assumption about the one-dimensional nature of the tetrafluoromethane diffusion inside nanotubes.
12
Bheemala, Veera Manesh. "Sol-Gel Synthesis of Lanthanide-Doped Aluminosilicate Glasses." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1601351.
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<p> Doping Praseodymium into Al-Si glass has potential applications in permanent holographic data storage and other optical devices. For this we are using the sol-gel method to produce glass monoliths at relatively low temperatures. The silicon precursor is tetraethylorthosilicate (TEOS) and aluminum tri-sec butoxide (ATSB) is the aluminum precursor. TEOS is hydrolyzed in ethanol with HCl as a catalyst. ATSB is then added, as well as praseodymium chloride in water. To prevent cracking we use dimethyl formamide (DMF) as a drying control chemical additive (DCCA). The solution is poured into a polymethylpentene cylinder and maintained at 40°C and the temperature is raised to 150°C to dry and shrink the sample. Samples prepared by this method are amorphous, as indicated by X-ray diffraction. The final aim of this research is to produce optically clear, fracture less monoliths by varying aging, shape and drying conditions.</p>
13
Newlands, Katrina. "The early stage dissolution characteristics of aluminosilicate glasses." Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=227976.
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To reduce CO2 emissions the cement industry has for decades diluted the Portland cement fraction of concrete binders with Supplementary Cementitious Materials (SCM). Defining the reactivity of these aluminosilicate-based materials and their interaction with clinker phases has however challenged the research community and limited their replacement levels. In the present study, to quantify the reactivity of SCMs during early hydration, aluminosilicate glasses with compositions representative of blast furnace slag and fly ash systems were synthesised and exposed to different activator solutions in a continuously stirred closed system reactor for a period up to 3 h. Solution compositions were measured from the very first minutes of dissolution with complementary solid surface analysis. The experimental conditions were designed to avoid precipitation, however an initial Ca maximum in the first 30 min of exposure to the activating solution was a common feature in most dissolution profiles with a subsequent rapid decline, most likely attributable to Ca-reincorporation on the reacting surface. Surface specific analysis confirmed Ca enrichment on the surface and also detected Al enrichment, suggesting the formation of a Ca-modified aluminosilicate phase by a dissolution reprecipitation mechanism on the surface of the glass. Differing chemistries are thought to be responsible for the Ca and Al re-integration on the reacting surface depending on the pH of the solution; near-neutral conditions favour Ca-readsorption and surface condensation reactions, whereas alkaline solutions favour Ca-reintegration via covalently bound phases. The Ca concentration in solution was also observed to control glass alteration. Decreased dissolution rates were in fact observed as Ca concentrations in solution were increased supporting the formation of a C-A-S-H phase on the surface, the formation of which was instead suppressed when a Ca chelating chelating agent (EDTA) was added to the solution resulting in increased glass dissolution. Experiments using in situ AFM and LAOICPOMS are also reported and the significance of the findings to the early hydration reactions of a blended cement system is discussed.
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Dvoyashkin, Muslim, Ryan Wood, Clifford R. Bowers, et al. "Gas transport in aluminosilicate nanotubes by diffusion NMR." Diffusion fundamentals 16 (2011) 85, S. 1-6, 2011. https://ul.qucosa.de/id/qucosa%3A13830.
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Diffusion of tetrafluoromethane in aluminosilicate nanotubes was studied by means of 13C pulsed field gradient (PFG) NMR at 297 K. The measured data allow the estimation of the diffusivity of tetrafluoromethane inside the nanotubes as well as the diffusivity for these molecules undergoing fast exchange between many nanotubes. The results support the assumption about the one-dimensional nature of the tetrafluoromethane diffusion inside nanotubes.
15
Jerez, Briones Jorge Antonio. "Aluminosilicate-coated silica sand for reactive transport experiments." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Spring2005/J-J%5FBriones%5F050305.pdf.
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Hogan, Mari 1965. "Chemical synthesis and densification of cesium aluminosilicate powders." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277275.
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Pollucite (CsAlSi₂O₆) is a refractory phase within the Cs₂O-Al₂O₃-SiO₂. It melts at >1900°C and also has a reported thermal expansion value of 15 x 10⁻⁷/°C. These qualities make it suitable for study as a high temperature structural ceramic. Amorphous powders were synthesized by a novel sol-gel process in the Cs₂O-Al₂O₃-SiO₂ system. Gels were produced from tetraethoxysilane (TEOS), Aluminum chelate, and Cs-acetate. Powders were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), chemical, differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The glass transition and crystallization temperatures were determined to be 945°C and 1026°C, respectively, for the amorphous powders. Pollucite and mullite phases were observed by XRD of bulk glass-ceramics. A density of 3.02 gm/cm³ was observed for the hot pressed material. Dielectric constants in the frequency range 1kHz-1MHz were found to be in the range of 5.23 to 5.78 for the as hot pressed and heat treated samples. Thermal expansion coefficients were also determined.
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Novikov, Alexey. "Structure and dynamics of aluminosilicate glasses and melts." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2041/document.
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Trois systèmes ternaires (SAS, BAS et ZAS) ont été étudiés dans le cadre de la thèse. Les principaux objectifs étaient l’élaboration et la caractérisation de verres aluminosilicatés de Sr, Ba et Zn peu étudiés auparavant. Une étude systématique a été réalisée sur des aluminosilicates vitreux et dans certains cas sur des aluminosilicates fondus avec différents rapports MO/Al₂O₃ (M = Sr, Ba, Zn) et SiO₂/Al₂O₃. Les compositions étudiées couvrent une partie significative des diagrammes ternaires (des silicates aux verres peralumineux, des compositions pauvres en silice à celles riches en silice). Cela a permis d'accroître nos connaissances sur les domaines de vitrification de ces systèmes. Afin d’obtenir des informations sur la structure et les propriétés macroscopiques des verres SAS, BAS et ZAS, une approche multi-technique a été mise en place. Une telle approche permet d’avoir une vue d’ensemble sur les systèmes étudiés et de trouver des origines nano- à microscopiques aux propriétés macroscopiques. La spectroscopie de résonance magnétique nucléaire, la diffractométrie de neutrons et la spectroscopie Raman ont été utilisées au cours de la thèse afin de sonder l'échelle à courte et à moyenne distance. Les propriétés macroscopiques mesurées ont été : la densité, la viscosité et la température de transition vitreuse. Les données issues de cette thèse permettent une meilleure compréhension des changements de structures et des propriétés macroscopiques des verres aluminosilicatés produits par les variations de MO/Al₂O₃ ou SiO₂/Al₂O₃, ou par la nature des cations non-formateurs de réseau<br>Three ternary systems (SAS, BAS and ZAS) have been investigated within the framework of the PhD thesis. The main goals were the elaboration and characterization of previously poorly studied Sr, Ba and Zn aluminosilicate glasses. A systematic study has been carried out on glasses and in some cases on melts with various MO/Al₂O₃ (M = Sr, Ba, Zn) and SiO₂/Al₂O₃ ratios. The compositions studied cover a significant part of the ternary diagrams (from silicates to peraluminous glasses, from silica-poor to silica-rich compositions). This allowed expanding our knowledge of the vitrification domains in these systems. In order to obtain information on the structure and macroscopic properties of SAS, BAS and ZAS glasses, a multi-technique approach has been implemented. Such approach allows having a broad view on the systems and finding nano- to microscopic origins of macroscopic properties. The techniques used during the thesis probe short- (NMR, ND) to medium-range (Raman) scale and among the properties studied were density, viscosity and glass transition temperature. The data resulting from this thesis provides a better understanding of the changes in the structure and macroscopic properties of the aluminosilicate glasses produced by variations in MO/Al₂O₃ or SiO₂/Al₂O₃, or by the nature of non-network forming cation
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Gharzouni, Ameni. "Contrôle de l'attaque des sources aluminosilicates par la compréhension des solutions alcalines." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0054/document.
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Cette étude a été menée afin d’identifier les paramètres qui permettent de contrôler la réaction de géopolymérisation et les propriétés d’usage des matériaux finaux. Différentes sources aluminosilicates et solutions alcalines ont donc été sélectionnées afin d’évaluer leur réactivité. Ensuite, une étude de faisabilité des matériaux consolidés a été initiée pour identifier les zones d’existence des matériaux géopolymères dans le diagramme ternaire Si/Al/M/O. L’évolution des échantillons au cours de la formation a été suivie par analyses thermiques (ATD-ATG), pour quantifier l’énergie nécessaire à la formation des oligomères, et par spectroscopies infrarouge et résonance magnétique nucléaire afin de déterminer la nature des réseaux formés et le taux de la réaction. Une forte corrélation a été mise en évidence entre la réactivité des précurseurs, la structure locale et poreuse et les propriétés mécaniques. Ces données ont été exploitées pour valoriser d’une part une argile tunisienne de faible réactivité et d’autre part pour recycler un déchet géopolymère dans des nouvelles formulations<br>This study was undertaken to identify the parameters that control the geopolymerization reaction and the working properties of the final materials. To do this, various aluminosilicate sources and alkaline solutions have been studied to exacerbate their reactivity. Then a feasibility study of the consolidated materials was conducted to identify the geopolymer existence domain in Si-Al-M / O ternary diagram. The evolution of samples during formation was monitored by thermal analysis (DTA-TGA), to quantify the required energy for oligomer formation, and infrared and nuclear magnetic resonance spectroscopies to determine the nature of formed networks and the reaction rate. A strong correlation was evidenced between the precursors reactivity, the local and porous structure and the mechanical properties. The obtained results have been exploited to use poorly reactive Tunisian clay as alternative aluminosilicate source and also to reuse geopolymer waste in new formulations
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Johnson, Geoffrey Mark. "Synthesis and characterisation of aluminosilicate and framework modified sodalites." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242210.
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Yang, C. "The pre-nucleation of aluminosilicate zeolites : a theoretical approach." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1391057/.
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Density Functional Theory (DFT) and the Conductor-like Screening Model (COSMO) have been employed to investigate the structural geometry and thermodynamical properties for the condensation reactions of aluminosilicates in the prenucleation of forming aluminosilicate zeolites. We report the relative structures and energies of clusters containing between one and six Si/Al atoms and the effect on them of the interplay of the Na+ ions and intramolecular hydrogen bonds. Our result reveals that with the exception of the dimer, “Lowensteinian” clusters (without the Al-O-Al linkage) are more energetically favourable than “non-Lowensteinian” clusters (which contain such bridges) in the gas phase. The stability of aluminosilicate clusters is strongly affected by the COSMO solvation, with the solvent influencing their conformations. In COSMO solvation, all the most stable clusters follow not only Lowenstein’s rule, but also Dempsey’s rule. The condensation reactions are involved key aluminosilicate species: the Si(OH)4 or Al(OH)4Na monomers and AlSiO(OH)6Na dimer, where we investigate reactions with the four, six, double four and double six rings to form a series of fused rings in both the gas phase and COSMO solvation. Our calculations suggests that the Al(OH)4Na monomer does not participate in these condensation reactions as such participation would generate structures that contradict Lowenstein’s rule; in contrast, on the basis of our results we propose that the condensation reactions occur via the AlSiO(OH)6Na dimer. As a result, employing the AlSiO(OH)6Na dimer, which could be responsible for forming aluminosilicate aggregates studies the nucleation mechanism of zeolite A. the rational mechanism for nucleated self-assembly for zeolite A is that the double four ring, which is probably the main initial ring in the nucleation stage could be formed by the successive condensation reactions of the AlSiO(OH)6Na dimer, tetramer, four ring, four-four ring, tri-four ring, and open double four ring. Furthermore, to consider the alkalinity in the nucleation and crystal growth of aluminosilicate zeolites, our supposition is that the AlSiO2(OH)5Na2 dimer would play the key role in the relative condensation reactions for deprotonated open clusters (the dimers, trimers and tetramers) and rings (the four rings).
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Mountfort, Francesca. "The acousto-optic interaction in aluminosilicate-based optical fibres." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/400628/.
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In fibre optic technology there is a drive to innovate more sophisticated telecommunications and narrow linewidth laser application systems. Brillouin scattering, with its low threshold powers - the lowest of all nonlinear processes - presents a fundamental barrier, in many cases, to achieving desired efficiencies. Aluminosilicate fibres have presented the possibility of thwarting this effect. The incorporation of aluminium oxide into silica fibre is not new. Historically its been used in applications requiring the deposition of rare-earth ions in the fibre core; mostly broad bandwidth fibre amplifier applications. However, with its unique acoustic properties - optically waveguiding and acoustically anti-waveguiding - it possesses the promise of minimising the interplay between optical and acoustic modes, thereby mitigating Brillouin scattering. The work presented in this thesis is an investigation of the acousto-optic interaction in a variety of different aluminosilicate single-mode optical fibres. These fibres include aluminosilicate, ytterbium-doped aluminosilicate, aluminophosphosilicate, ytterbium-doped aluminophosphosilicate as well as an aluminosilicate PANDA-type optical fibre wherein the position of the two stress rods changes longitudinally. A heterodyne coherent detection technique was used to measure the spontaneous Brillouin spectrum of these fibres. The characterisation of this work is distinctive in that, rather than using the Brillouin Stokes signal to measure the Brillouin spectrum, the Brillouin anti-Stokes signal was used. The Stokes Brillouin signal experiences gain with an increase in power, and hence the Brillouin spectrum experiences exhibits gain narrowing effects. However, characterising the Brillouin spectra with an increase in power using the Brillouin anti-Stokes signal reveals a spectral broadening. The Brillouin spectrum of these fibres were exhaustively characterised according to the Brillouin frequency shift and linewidth with changes in temperature, strain and input power.
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Hu, Ruiqi. "Aluminosilicate Nanotubes for Water Desalination: Effects of Functional Groups." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543536995672758.
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Ktafi, Imane. "Mastering Photoinduced Transformations by Femtosecond Laser in Aluminosilicate Glasses." Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASF011.
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La transformation volumique dans les verres optiques peut être réalisée de manière sélective grâce à l'écriture directe par laser femtoseconde. Cette méthode constitue un outil idéal pour fonctionnaliser le verre et permettre une série d'applications dans des domaines tels que la micro-optique, le stockage optique de données ou les capteurs optiques. En ce qui concerne ce dernier domaine, les modifications induites par laser femtoseconde peuvent être utilisées pour fabriquer des dispositifs optiques fonctionnant dans des environnements extrêmes. La structuration du verre en nanoréseaux ou sous forme de cavités peut résister à des températures avoisinant 1100 °C pendant plusieurs dizaines d'heures, après quoi elles se dégradent. Dans ce contexte, les aluminosilicates binaires ont montré des perspectives prometteuses avec une stabilité thermique remarquable, surpassant celle de certaines silices pures (par exemple, le Suprasil CG). Cela représente une stabilité thermique anormalement élevée par rapport aux modélisations actuellement effectuées via l'équation de Rayleigh-Plesset. Dans le cadre de cette thèse, une nouvelle composition est étudiée dans ce travail : un verre aluminosilicate (60%Al₂O₃ - 40%SiO₂ en molaire) et fabriqué par lévitation aérodynamique. Cette composition étend la gamme des compositions précédemment étudiées, tout en présentant une stœchiométrie de cristallisation congruente en une phase mullite 3:2. Cette thèse établit d'abord les relations existantes entre les propriétés optiques des verres aluminosilicates (biréfringence, variations d'indice de réfraction) et les modifications structurales (cristallisation, séparation de phase, migration chimique etc.). Au niveau fondamental, cette approche complète les connaissances déjà acquises sur la formation de nanoréseaux poreux. De plus, la retardance optique est systématiquement étudiée sous une large gamme de paramètres laser. Une analyse comparative a été réalisée en utilisant le verre de silice (Suprasil CG) comme matériau de référence. Notamment, le verre aluminosilicate a montré des valeurs de retardance atteignant 100 nm, soit environ le double de celles observées dans les verres aluminosilicates étudiés précédemment. La spectroscopie Raman et la microscopie électronique ont révélé la formation de nanoréseaux alternant une phase amorphe riche en SiO₂, avec une phase cristallisée riche en Al₂O₃ (phase mullite 3:2). Ces structures biréfringentes, observées pour la première fois dans ce type de verre, offrent de nouvelles informations sur les mécanismes sous-jacents à la formation des nanoréseaux. Elles peuvent également être induites dans des verres ternaires ZrO₂-Al₂O₃-SiO₂, et présentent une stabilité thermique jusqu'à 1300 °C pendant 30 minutes. Même après effacement de la structure biréfringente en température, un contraste d'indice positif résiduel persiste jusqu'à 1650 °C dans l'aluminosilicate étudié. Cette observation sans précédent ouvre de nouvelles perspectives pour des composés optiques ultra-stables.À ce jour, deux principaux types de nanoréseaux ont été identifiés. La possible coexistence des nanoréseaux poreux observés majoritairement dans les silicates, et ceux cristallisés partiellement comme dans le cadre de cette thèse, reste mal connue, car les études précédentes rapportaient leur apparition dans des verres distincts. Cependant, la famille des verres aluminosilicates offre désormais un cadre pour comprendre leur interrelation. Les simulations rapportées dans cette thèse décrivent les conditions nécessaires pour atteindre une cristallisation partielle du verre et explorent les mécanismes liant la formation des nanoréseaux à la cristallisation. Les résultats fournissent également des lignes directrices pour concevoir des nanoréseaux résistants aux hautes températures<br>Volume transformation in optical glasses can be selectively achieved using femtosecond (fs) laser direct writing. This method is an ideal tool to functionalize glass and enable a series of applications in fields like micro-optics, microfluidic, optical data storage, or optical sensing. With respect to the latter, fs-laser induced modifications can be employed to fabricate optical devices operating in harsh environments. Glass structuring into nanogratings or voids can withstand temperatures around 1100 °C for a few 10s of hours, after which they deteriorate. In this context, binary aluminosilicates have shown promising perspective with outstanding thermal stability surpassing pure silica (e.g., Suprasil CG). This is an anomalously high thermal stability based on current modeling using Rayleigh-Plesset Equation. Consequently, in this Thesis a new composition is studied, being an aluminosilicate glass fabricated by aerodynamic levitation with a molar composition of 60%Al₂O₃ - 40%SiO₂. This composition extends to the compositional range previously investigated, while presenting a congruent crystallization ratio into a 3:2 mullite phase. This thesis first establishes the existing relationships between optical properties in aluminosilicate glasses (birefringence, refractive index changes) and structural modifications (crystallization, phase separation, elemental migration, etc.). From a fundamental point of view, this approach will complete the knowledge already acquired on the formation of porous nanogratings. Moreover, optical retardance is systematically investigated under a broad range of laser parameters. A comparative analysis was conducted using silica glass (Suprasil CG) as a reference material. Notably, the aluminosilicate glass exhibited retardance values reaching up to 100 nm, approximately double those observed in previously studied aluminosilicate glasses. Raman spectroscopy and electron microscopy revealed the formation of nanogratings, composed of alternating SiO₂-rich amorphous layers and Al₂O₃-enriched layers. The latter are predominantly crystallized in a 3Al₂O₃:2SiO₂ mullite phase. These birefringent structures, observed for the first time in this glass system, offer new insights into the underlying mechanisms of nanogratings formation. They were also induced in ZrO₂-Al₂O₃-SiO₂ glasses and exhibit thermal stability up to 1300 °C for 30 minutes. Even after erasure of the birefringent structure, a residual positive refractive index contrast persists up to 1650 °C in the binary aluminosilicate glass. This unprecedented observation of a persistent refractive index contrast opens new avenues for ultra-stable glass-based optical components.The coexistence between porous nanogratings, commonly observed in silicate glasses, and partially crystalline ones found in this study, still remain been unclear, as previous studies reported their existence in independent glasses. However, the aluminosilicate glass family now offers a testbed for understanding their interrelation. Simulations reported in this Thesis describe the necessary conditions to reach partial glass crystallization and explore the mechanisms linking nanograting formation to crystallization. The findings also provide guidelines for designing high-temperature-resistant nanogratings
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Gentile, Paul Steven. "Investigation of aluminosilicate refractory for solid oxide fuel cell applications." Diss., Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/gentile/GentileP1210.pdf.
Full textAbstract:
Stationary solid oxide fuel cells (SOFCs) have been demonstrated to provide clean and reliable electricity through electro-chemical conversion of various fuel sources (CH₄ and other light hydrocarbons). To become a competitive conversion technology the costs of SOFCs must be reduced to less than $400/kW. Aluminosilicate represents a potential low cost alternative to high purity alumina for SOFC refractory applications. The objectives of this investigation are to: (1) study changes of aluminosilicate chemistry and morphology under SOFC conditions, (2) identify volatile silicon species released by aluminosilicates, (3) identify the mechanisms of aluminosilicate vapor deposition on SOFC materials, and (4) determine the effects of aluminosilicate vapors on SOFC electrochemical performance. It is shown thermodynamically and empirically that low cost aluminosilicate refractory remains chemically and thermally unstable under SOFC operating conditions between 800°C and 1000°C. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) of the aluminosilicate bulk and surface identified increased concentrations of silicon at the surface after exposure to SOFC gases at 1000°C for 100 hours. The presence of water vapor accelerated surface diffusion of silicon, creating a more uniform distribution. Thermodynamic equilibrium modeling showed aluminosilicate remains stable in dry air, but the introduction of water vapor indicative of actual SOFC gas streams creates low temperature (<1000°C) silicon instability due to the release of Si(OH)₄ and SiO(OH)₂. Thermal gravimetric analysis and transpiration studies identified a discrete drop in the rate of silicon volatility before reaching steady state conditions after 100-200 hours. Electron microscopy observed the preferential deposition of vapors released from aluminosilicate on yttria stabilized zirconia (YSZ) over nickel. The adsorbent consisted of alumina rich clusters enclosed in an amorphous siliceous layer. Silicon penetrated the YSZ along grain boundaries, isolating grains in an insulating glassy phase. XPS did not detect spectra shifts or peak broadening associated with formation of new Si-Zr-Y-O phases. SOFC electrochemical performance testing at 800-1000°C attributed rapid degradation (0.1% per hour) of cells exposed to aluminosilicate vapors in the fuel stream predominately to ohmic polarization. EDS identified silicon concentrations above impurity levels at the electrolyte/active anode interface.
'Co-authored by Paolo R. Zafred, Stephen W. Sofie, Camas F. Key, and Richard J. Smith.'
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Sanghera, J. S. "Electrical properties of aluminosilicate glazes containing niobium doped titanium dioxide." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37846.
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Chakraborty, Sumit. "Multicomponent cation diffusion in aluminosilicate garnets: Theory, experiments and applications." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185214.
Full textAbstract:
Results from experiments in this work have been combined with existing data to yield tracer diffusivities of divalent cations in natural multicomponent garnets at 10-40 kb, 1100 - 1475°C. For the garnet compositions studied in this work, the activation energy for tracer diffusion of Mn < Fe ≃ Mg, while activation volumes increase in the order Mg < Fe < Mn. These data may be used with theoretical models to calculate the full multicomponent diffusion coefficient matrix as a function of pressure, temperature, composition and oxygen fugacity. An analytical model has been developed to describe the relaxation of compositional zoning in metapelitic garnets during metamorphism. It is found that a significant amount of relaxation occurs during heating and the composition at the core of a garnet crystal is disturbed very early in the process. The extent of relaxation depends on a number of factors which include the grain size, the initial shape of the compositional profile, details of the thermal history and the textural mode of occurrence of the garnet. Complications such as oscillations in a compositional profile may be explained by the mathematical form of the equations describing the process. Graphical representation of the results of this model have been provided that allow quick and easy determination of the extent of relaxation or time scale of metamorphic processes. Calculations using the diffusion data indicate that Fe-Mg exchange geothennometry and Sm-Nd geochronology involving garnets may not yield the peak metamorphic conditions for certain geologically realistic situations. Model calculations on natural assemblages suggest that the diffusion data may be used to yield infonnation on metamorphic processes ranging from time scales to crystal growth rates during metamorphism. Veracity of P-T paths calculated from garnet zoning may also be checked using the diffusion data. Illustrative examples of such calculations have been provided.
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Beatty, Kirk Matthew 1962. "Processing of copper aluminosilicate glasses to produce glass-copper structures." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278284.
Full textAbstract:
Copper aluminosilicate (composition Cu₂O·Al₂O₃·6SiO₂) glass was melted in an alumina crucible at 1500°C and air cooled in situ. A layer of cupric oxide was grown on the polished glass surface and its thickness measured using a scanning electron microscope (SEM). The thickness of the oxide layer was found to increase parabolically with time, with a temperature dependency that was compatible with the diffusion of copper through the layer. The cupric oxide layer was reduced to copper on roughened and polished glass surfaces using a gas mixture of 3% H₂ and 97% N₂, resulting in a glass substrate coated by copper. Adherence of the copper layer to the polished glass substrate was found to be poor. However, adherence was found to increase by roughening the surface before oxidation. Additions of NiO and CaO to the base glass were not detrimental to the production of the copper film.
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Gibbons, Martina M. "Studies on the crystallization of zeolites and zeotypes." Thesis, University of Wolverhampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341865.
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Besnard, Clémence. "Elaboration de composites céramiques oxyde/oxyde par caléfaction." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0162/document.
Full textAbstract:
De manière générale, les composites oxyde/oxyde sont la plupart du temps élaborés par frittage, par voie sol-gel ou par infiltration en phase gazeuse, CVI (« Chemical vapor infiltration »). Ces techniques d’élaboration comportent de nombreuses étapes engendrant un temps long d’élaboration ce qui peut entraîner une détérioration des propriétés du composite. Cette thèse s’intéresse à un procédé original et rapide de densification de préformes fibreuses développé par le Commissariat à l’Energie Atomique et aux énergies alternatives (CEA) : la caléfaction. Ce procédé est connu pour élaborer des composites C/C ou C/SiC à partir d’un précurseur liquide. Cependant, la possibilité d’élaborer des composites oxyde/oxyde n’a jamais été testée. L’objectif de ce travail est d’étudier la réalisation de composites oxydes/oxydes par ce procédé. Plusieurs matrices ont été réalisées telles que la silice, l’alumine et le système ternaire aluminosilicate de baryum, BaSi2Al2O8. Plusieurs paramètres expérimentaux ont été étudiés tels que la température d’élaboration, le temps de manipulation et la composition du précurseur. Des caractérisations microstructurales et physico-chimiques ont permis de caractériser les matériaux élaborés. Plusieurs modifications ont été apportées au montage expérimental afin de permettre une meilleure reproductibilité des essais et un meilleur suivi thermique lors de l’élaboration de matrice oxyde<br>Nowadays, oxide/oxide composites are most of the time developed by sintering, sol-gel process or CVI (Chemical Vapor Infiltration). These techniques include many steps of synthesis leading to a long time of synthesis and possible deteriorations of the properties of the composite. This thesis focuses on an original and rapid process developed by French Alternative Energies and Atomic Energy Commission (CEA): the film boiling chemical vapor infiltration. This technique is already used to synthesize C/C and C/SiC composites but works have never focused on oxide/oxide composites. The main goal of this thesis is to synthesize oxide/oxide composites by film boiling chemical vapor infiltration. Works were focused on alumina, silica and barium aluminosilicate matrices. Several experimental parameters were studied: temperature, time and liquid precursor. Microstructural and physicochemical characterizations were done on composites. Several modifications of the experimental setup have been made in order to allow a better reproducibility of the tests and a better thermal monitoring
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Oppici, Maria A. "Sodium sulfate hot corrosion of silicon carbide fiber-reinforced calcium aluminosilicate." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA297663.
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Kapilasharmi, Era. "Investigation of Interactions between Liquid Iron Containing Oxygen and Aluminosilicate Refractories." Doctoral thesis, KTH, Materials Science and Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3625.
Full textAbstract:
<p>The present work was initiated to investigate runnerrefractory corrosion by molten steel. The aim was to understandthe mechanism of inclusion formation during ingot casting. Thework is also of interest to other unit processes in steelmaking, where refractory corrosion and erosion are seriousproblems. The oxides investigated in the present work werealumina, silica and mullite, which are the main components inrunner refractory. In addition, industrial refractory materialwas investigated.</p><p>Two types of experiments were conducted. The first, "rodexperiments", involved dipping a rod of the oxide into an ironbath containing varying amounts of oxygen. After quenching, therods were examined through SEM/EDS analysis. In the second setsof experiments, the wetting behaviour of molten iron onrefractory oxides was investigated by means of the sessile-dropmethod. The reactions were followed in static as well asdynamic modes through contact angle measurements. Temperatureand oxygen partial pressure were, besides time the parametersthat were investigated in the present study. Oxygen partialpressure was defined by introducing a gas mixture of CO-CO<sub>2</sub>-Ar into the furnace.</p><p>The experimental studies were preceded by a thermodynamicinvestigation of the refractory systems, in order to get afundamental understanding of the reactions that occurred. Phasestability diagrams for the systems were constructed based onthe data available in literature. The diagrams showed that thereaction between alumina and oxygen containing iron would leadto the formation of hercynite at a critical oxygen level in themetal. With silica, the reaction would lead to the formation offayalite. In the mullite case, the reaction products would behercynite at moderate oxygen levels in the melt and hercynitetogether with fayalite at slightly higher oxygenpotentials.</p><p>For all substrates, the contact angles started decreasing asthe surface-active oxygen came into contact with the iron drop.At a critical level of oxygen in the metal, a reaction productstarted forming at the drop/substrate interface. The reactionproducts were identified through SEM/EDS analysis and werefound to be in agreement with thermodynamic predictions. In thecase of SiO<sub>2</sub>substrate, there were also deep erosion tracksalong the periphery of the drops, probably due to Marangoniflow.</p><p>Alumina-graphite refractory reactions with molten iron werealso investigated through Monte Carlo simulations. The resultsshowed that, with increased alumina content in the refractory,the carbon dissolution into the melt decreased. Further, thewetting behaviour at the interface was found to be an importantfactor to considerably reduce the carbon dissolution fromalumina-graphite refractories.</p><p>The experimentation was extended to the commercialrefractories used in the ingot casting process at UddeholmTooling AB, Sweden. The analysis of the plant trial samplesindicates that there is less likelihood of a strong corrosionof the refractories that could lead to a significant populationof inclusions in the end product. The impact of the presentexperimental results on refractory erosion is discussed. Theimportance of the results to clean steel processing anddevelopment of new generation refractories are alsopresented.</p>
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Schomborg, Lars [Verfasser]. "Aluminosilicate borohydrides : NaBH4 embedded in sodalite and gel structures / Lars Schomborg." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1077608209/34.
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Maybodi, Abdolraouf Samadi. "NMR studies of silicate and aluminosilicate solutions as precursors for zeolites." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5400/.
Full textAbstract:
The search for a detailed understanding of the mechanism of zeolite synthesis has, over the past two decades, promoted many investigations into the species present in (alumino)silicate solutions. It is generally accepted that dissolved (alumino)silicate species are involved as precursors in the nucleation of zeolites. Several techniques have been employed to understand the mechanism of formation of these complex structures. NMR spectroscopy has been shown to be a very powerful tool for the detection and characterization of (alumino)silicate species in the solutions in question. This thesis presents a comprehensive study of certain silicate solutions employmg (^29)Si NMR which has extended the knowledge gained in previous studies. The role of structure-direction on the distribution of silicate species in silicate solutions is discussed, the results providing more understanding of this effect. The effects of pH, temperature, Si/cation ratio and silica concentration on the distribution of silicate anions were also studied.Aluminium-27 NMR was applied to investigate the local structure about alummium atoms in a series of alumino silicate solutions with Si:Al mole ratios pertinent to zeolite synthesis. The kinetics of the reaction of aluminate with silicate anions have been studied by investigating the temporal evolutions of (^29)Al NMR spectra and by 2D NMR exchange spectroscopy. Structural analyses of two new silicate crystals were carried out by single-crystal X-ray diffraction. Liquid- and solid-state NMR spectroscopy were employed to characterize the mother liquors, the powdered polycrystalline products, and their melts.The Zeolite SUZ-9 was characterized by application of multinuclear magnetic resonance spectroscopy : (^29)Si, (^27)Al, (^13)C and (^1)H NMR spectra of this zeolite were studied.
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Luk, Kathryn Michelle. "The encapsulation of nuclear waste in a magnesium aluminosilicate glass-ceramic." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342511.
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Rizeq, Rizeq George. "Alkali-induced agglomeration of aluminosilicate particles during coal combustion and gasification." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185278.
Full textAbstract:
This study focuses on the effect of alkali adsorption on the agglomeration of particles of bauxite, kaolinite, emathlite, lime, and two types of coal ash. An agglomeration (adhesion) temperature is defined which characterizes the adhesion propensity of particles. Using a small fluidized bed, a unique experimental technique is developed to measure this agglomeration point in-situ. The effects of alkali adsorption on the agglomeration characteristics of the substrates are determined. The agglomeration temperature of all substrates decreases as the alkali content increases. At low alkali loadings, alkali adsorption enhances particle agglomeration by forming new compounds of lower melting points. At high alkali concentrations, adhesion and agglomeration are caused by a layer of molten alkali which covers the exterior of the particles. Alkali surface composition of particles is studied using a Scanning Auger Microprobe (SAM). Results indicate that the alkali surface concentration decreases as agglomeration temperature increases. SAM depth profiling data provides information on the variations of alkali loading across particles. These results show that an alkali surface product layer is formed where most of the alkali adsorbed is concentrated. The use of additives to scavenge alkali vapors is further studied in a pilot scale downflow combustor under more typical combustion conditions. SAM surface analyses of additive particles indicate three mechanisms of alkali capture. Alkali adsorption by reaction, alkali surface condensation, and alkali nucleation and coagulation with additive particles. These mechanisms may occur independently or simultaneously depending primarily on the alkali vapor concentration and the temperature profile along the combustion furnace. A mathematical model is developed to represent the kinetics and mechanisms of the alkali adsorption and agglomeration process. Modeling results indicate that the adsorption-reaction process is influenced by diffusion of alkali through the surface product layer. The model predictions of the alkali adsorbed as a function of minimum agglomeration temperature agree very well with the experimental results. Alkali-additive interactions in a downflow combustor are also modeled to predict the mechanisms of alkali capture and the overall alkali removal efficiency. Model predictions of the alkali capture agree well with the experimental results.
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Renggli, Christian Josef. "Volcanic gases and the reaction of sulfur dioxide with aluminosilicate glasses." Phd thesis, Canberra, ACT : The Australian National University, 2018. http://hdl.handle.net/1885/147744.
Full textAbstract:
Volcanic gases are an important part of the volatile cycle in
active planetary systems and contribute significantly to the
mobilization and transport of metals to planetary surfaces. On
Earth, Venus, Mars and Io, SO2 is the most abundant corrosive
species in volcanic gases, and basalts are ubiquitous on these
planetary bodies. The reaction between SO2 and silicate rocks
forms oxidized sulfate and reduced sulfide. This reaction is a
key process in the formation of porphyry deposits. In volcanic
eruption plumes SO2 reacts with volcanic ash and is scavenged
onto the surface of the ash particles. Knowledge of the reaction
mechanisms between volcanic gas and rocks, minerals and glasses,
and processes controlling the metal mobilization and transport in
volcanic gas can constrain models of volatile and metal budgets
of planetary crusts and surfaces.
Using thermochemical modelling, I present a new model for the
composition of volcanic gas on the Moon and compare it to a
terrestrial volcanic gas from Erta Ale volcano (Ethiopia). The
main species in lunar volcanic gas are H2, S2 and CO. This
finding is in contrast to previous studies which suggested that
CO was the sole driver of explosive volcanic eruptions on the
Moon. This lunar volcanic gas has a lower capacity for metal
transport compared to the Cl- and H2O-rich volcanic gas from Erta
Ale volcano.
To identify how SO2-glass reactions occur at high temperature and
to investigate what might promote and limit these reactions, I
present results from an experimental study. Pure SO2 was reacted
with silicate glasses in the system anorthite-diopside-albite and
with Fe-bearing natural basaltic glasses.
The sulfate reaction products are relatively enriched in Ca
compared to the silicate glass composition, in particular in
experiments with Fe-free anorthite-diopside glasses. On these
Fe-free glasses CaSO4 is the sole observed phase in the coatings
at 800 °C, whereas at 600 °C minor amounts of MgSO4 were
detected. At 800 °C, the flux of Ca from the silicate glass to
the surface exceeds that of Mg by a factor of up to 330, whereas
at 600 °C this factor is only 3. The rate of reaction is not
constant, decreasing by an order of magnitude from 1 h to 24 h at
800 °C.
The reaction of SO2 with tholeiitic basalt glasses produces
coatings of CaSO4, MgSO4, Na2SO4 and oxides including Fe2O3 and
TiO2. In addition, the reaction modifies the basalt glass because
Ca, Mg and Na are lost to the coating. This results in the
nucleation of crystalline spherulites and needles including SiO2,
Al2O3, as well as Fe-Na-rich and Mg-rich pyroxenes.
VIII
The results suggest that the structural properties of the
silicate glass substrate control the diffusive transport of Ca,
Na, Mg, Fe and Ti to the surface which in turn controls the
overall reaction rate and the formation of sulfates, oxides and
silicates. These findings can be applied to predicting reactions
on planetary surfaces and at shallow levels within their crusts.
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Hiet, Julien. "Motifs structuraux dans des verres modèles pour le stockage des actinides." Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00454383.
Full textAbstract:
Les matrices vitreuses aluminosilicatées de lanthanides {SiO2 -Al2O3 - (CaO) - Y2O3 - La2O3} constituent, une matrice potentielle d'intérêt nucléaire, dans le cadre du stockage des déchets des actinides. Alors que de nombreuses études sont encore menées pour établir leurs propriétés macroscopiques (durabilité, mécanismes de vitrification, etc...), nous nous sommes attachés à décrire l'environnement proche des noyaux qui composent le réseau, c'est-à-dire leur structure à une échelle locale. Les verres aluminosilicatés sont constitués de tétraèdres d'aluminium et de silicium. Plus précisément, ils sont constitués d'entités Qn(mAl) silicium et d'entités qn(mSi) aluminium. Cependant, il est rare d'aboutir à une description en ces termes. La Résonance Magnétique Nucléaire haute résolution solide (RMN MAS 27Al et 29Si) est un des moyens d'y parvenir. Nous proposons ici le développement de séquences d'impulsions permettant l'identification de ces unités puis la description de leurs connectivités via leurs liaisons chimiques, basées sur le filtrage des cohérences MultiQuanta associées aux couplages scalaires J2 (Si-O-Si) et J2 (Si-O-Al). Cette approche RMN permet donc d'affiner la compréhension des réseaux aluminosilicatés quels qu'ils soient. Couplé à la spectroscopie RAMAN, elle a pu ensuite nous servir comme référence pour établir la structure et le comportement à long terme de ces matrices, suite à des expériences de lixiviation statique et d'irradiation a pratiquées au cyclotron du CEMHTI.
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Reddy, Allu Amarnath. "Alkaline-earth aluminosilicate-based glass and glass-ceramic sealants for functional applications." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/15217.
Full textAbstract:
Doutoramento em Ciência e Engenharia dos Materiais<br>The planar design of solid oxide fuel cell (SOFC) is the most promising one due
to its easier fabrication, improved performance and relatively high power
density. In planar SOFCs and other solid-electrolyte devices, gas-tight seals
must be formed along the edges of each cell and between the stack and gas
manifolds. Glass and glass-ceramic (GC), in particular alkaline-earth alumino
silicate based glasses and GCs, are becoming the most promising materials for
gas-tight sealing applications in SOFCs. Besides the development of new
glass-based materials, new additional concepts are required to overcome the
challenges being faced by the currently existing sealant technology. The
present work deals with the development of glasses- and GCs-based materials
to be used as a sealants for SOFCs and other electrochemical functional
applications. In this pursuit, various glasses and GCs in the field of diopside
crystalline materials have been synthesized and characterized by a wide array
of techniques. All the glasses were prepared by melt-quenching technique
while GCs were produced by sintering of glass powder compacts at the
temperature ranges from 800−900 ºC for 1−1000 h. Furthermore, the influence
of various ionic substitutions, especially SrO for CaO, and Ln2O3 (Ln=La, Nd,
Gd, and Yb), for MgO + SiO2 in Al-containing diopside on the structure,
sintering and crystallization behaviour of glasses and properties of resultant
GCs has been investigated, in relevance with final application as sealants in
SOFC. From the results obtained in the study of diopside-based glasses, a bilayered
concept of GC sealant is proposed to overcome the challenges being
faced by (SOFCs). The systems designated as Gd−0.3 (in mol%:
20.62MgO−18.05CaO−7.74SrO−46.40SiO2−1.29Al2O3 − 2.04 B2O3−3.87Gd2O3)
and Sr−0.3 (in mol%: 24.54 MgO−14.73 CaO−7.36 SrO−0.55 BaO−47.73
SiO2−1.23 Al2O3−1.23 La2O3−1.79 B2O3−0.84 NiO) have been utilized to realize
the bi-layer concept. Both GCs exhibit similar thermal properties, while differing
in their amorphous fractions, revealed excellent thermal stability along a period
of 1,000 h. They also bonded well to the metallic interconnect (Crofer22APU)
and 8 mol% yttrium stabilized zirconium (8YSZ) ceramic electrolyte without
forming undesirable interfacial layers at the joints of SOFC components and
GC. Two separated layers composed of glasses (Gd−0.3 and Sr−0.3) were
prepared and deposited onto interconnect materials using a tape casting
approach. The bi-layered GC showed good wetting and bonding ability to
Crofer22APU plate, suitable thermal expansion coefficient (9.7–11.1 × 10–6
K−1), mechanical reliability, high electrical resistivity, and strong adhesion to the
SOFC componets. All these features confirm the good suitability of the
investigated bi-layered sealant system for SOFC applications.<br>A concepção planar de células de combustível de óxido sólido (SOFC) é a
mais promissora devido a sua fabricação mais fácil, um melhor desempenho e
uma densidade de potência relativamente elevada. Nas SOFCs planares e
outros dispositivos de electrólitos sólidos são necessárias vedações estanques
ao gás ao longo das arestas de cada uma das células e entre os tubos de
distribuição de gás e de pilha. Materiais vítreos e vitrocerâmicos (GC), em
particular com composições baseadas em aluminosilicatos alcalino-terrosos,
estão entre os materiais mais promissores para aplicações de vedação à prova
de gás em SOFCs. Além do desenvolvimento de novos materiais à base de
vidros e vitrocerâmicos, são também necessários novos conceitos para
superar os desafios enfrentados pela tecnologia selante atualmente existente.
O presente trabalho visa dar um contributo nesse sentido, propondo soluções
de vedação para SOFCs e outras aplicações electroquímicas. Para o efeito,
foram sintetizados vários vidros e GCs à base de diópsido, os quais foram
caracterizados por recurso a uma grande variedade de técnicas. Todos os
vidros foram preparados por fusão, enquanto os GCs foram produzidos por
sinterização (tratamento térmico) de compactos de pó de vidro nas faixas de
temperatura de 800 − 900 ºC por 1 − 1000 h. Além disso, foram estudados os
efeitos de diversas substituições iónicas, especialmente de CaO por SrO, e de
MgO + SiO2 por Ln2O3 (Ln = La, Nd, Gd, e Yb), em composições de
aluminosilicatos à base de diópsido na estrutura, sinterização e cristalização
dos vidros e nas propriedades dos GCs resultantes com particular relevância
para as propriedades de vedação em SOFCs. Com base nos resultados
obtidos neste estudo, foi possível propor um novo conceito de selante
vritrocerâmico em bi-camadas que visa ultrapassar os desafios enfrentados
pelos vedantes actualmente usados em SOFCs. Os sistemas designados por
Gd−0,3 (em % molar: 20,62 MgO−18,05 CaO−7,74 SrO−46,40 SiO2−1,29
Al2O3−2,04 B2O3−3,87 Gd2O3) e Sr−0,3 (em % molar: 24,54 MgO−14,73
CaO−7,36 SrO−0,55 BaO−47,73 SiO2−1,23 Al2O3−1,23 La2O3−1,79 B2O3−0,84
NiO) foram seleccionados para realizar o conceito de bi-camada. Ambos os
GCs exibem propriedades térmicas semelhantes, e excelente estabilidade
térmica ao longo de um período de 1.000 horas, mas diferem nas suas
fracções vítreas/cristalinas. Eles revelaram também elevada aptidão para se
ligarem à interconexão metálica (Crofer22APU) e ao electrólito sólido (zircónia
estabilizada com 8 mol% de ítria (8YSZ) sem a formação de camadas
interfaciais indesejáveis entre os diferentes componentes das SOFCs. Duas
camadas separadas compostas pelos vidros (Gd−0,3 e Sr−0.3) foram
preparadas e depositadas sobre as interconexões metálicas através de uma
abordagem tape casting. As bi-camadas vitrocerâmicas mostram boa
capacidade de molhamento e ligação à placa Crofer22APU, coeficientes de
expansão térmica adequados (9,7−11,1 × 10−6 K−1), confiabilidade mecânica,
elevada resistividade eléctrica, e uma forte adesão aos componentes da
SOFC. Todas estas características confirmam a boa adequação do sistema
selante bi-camadas investigado para aplicações em SOFCs.
39
Rowles, Matthew Ryan. "The structural nature of aluminosilicate inorganic polymers: a macro to nanoscale study." Thesis, Curtin University, 2004. http://hdl.handle.net/20.500.11937/1641.
Full textAbstract:
Aluminosilicate inorganic polymers (AIPs) are network heteropolymers consisting of Si04 and AlO4 tetrahedra linked by a shared oxygen. The use of these materials as a cementing agent, toxic waste storage and fibre reinforced material, amongst a multitude of prospective applications, has grown in recent years. The utilisation of AIPs is hampered by a lack of knowledge about their formation and structure. In order to allow the materials to achieve their full potential, the way in which the material behaves and forms under different conditions must be elucidated. The basic questions that this study aimed to answer were: 1) How does the structure of these AIPs change with composition? and 2) Can this change in structure explain the material properties of the AIP? The AIPs investigated in the study covered the molar composition ranges Si:Al ratio = 1 - 3 and Na:Al ratio = 0.5 - 2. They were made by the sodium hydroxide activation of metakaolinite, derived from the dehydroxylation of kaolinite. The Si content of the AIP was altered by the addition of amorphous silica fume via the activation solution. The study considered the structural nature of the AIPs at the macro, micro and nanoscales, and found that the structure changed at all scales and with all compositions. The nature of the AIP structure was studied at the macroscale utilising compressive strength testing. The results from this work showed that the compressive strength of the AIPs varied systematically with the chemical composition. The strengths recorded ranged from 0.4 ± 0.2 MPa for a sample with Si:Al:Na molar ratios = 1.08:1:0.5, to 64 ± 3 MPa for a sample with Si:Al:Na molar ratios = 2.5:1:1.3. The higher strengths measured exceed those exhibited by Portland cement pastes. The microstructure of the AIPs was investigated by scanning electron microscopy and energy dispersive spectroscopy.Microscopy showed that the microstructure variations correlated with the compressive strength. In general, AIPs with low compressive strengths exhibited an inhomogeneous two-phase microstructure; grain and matrix. The grain phase consisted of undissolved metakaolinite, whilst the matrix was the fully formed inorganic polymer. AIPs with high compressive strengths exhibited a microstructure that was more homogeneous than the samples with low compressive strength. The compressive strength of the AIPs depended on both the chemical composition and the level of residual MK present in the microstructure. EDS microanalysis showed that the composition of the two phases was significantly different, and that the differences depended on the overall composition of the AIP. EDS results also demonstrated that the impurity elements present in the metakaolinite were affected by the polymerisation process. Soluble elements such as Ca and Mg were found primarily in the matrix, indicating that they had leached out of the metakaolinite grains, whereas insoluble elements such as Fe and Ti were found primarily in the grains. The nanoscale structure of the AIPs was examined by solid-state nuclear magnetic resonance (NMR) and x-ray scattering (XRS). The NMR measurements revealed that the average coordination of Si varied according to the composition of the AIP, whereas the coordination of Al was constant. Na is present in the network in both hydrated and non-hydrated forms. It is postulated that the variation in the Si coordination can be explained by the formation of Si-O-Na bonds with Na forming an ionic bond with 0 in the polymer network. Radial distribution function (RDF) analysis of the XRS patterns revealed little difference in the structure of the different AIPs beyond ~2.5 Å.Unfortunately, the data were of insufficient resolution to allow for a full evaluation of the differences in the Si-O and Al-O bonds between different AIPs. However, the trends present in the shape and position of the RDF peak corresponding to the Si-O and Al-O bonds do follow the composition of the AIP. It has been shown that a variety of experimental techniques can be used in concert to obtain information on the structural nature of AIPs. To this end, it has been found that the compressive strength of AIPs can be optimised, and that the microstructure of the AIPs changes systematically with variations in the compressive strength. An improved model for the structure of AIPs has also been proposed.
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Rowles, Matthew Ryan. "The structural nature of aluminosilicate inorganic polymers: a macro to nanoscale study." Curtin University of Technology, Department of Applied Physics, 2004. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16061.
Full textAbstract:
Aluminosilicate inorganic polymers (AIPs) are network heteropolymers consisting of Si04 and AlO4 tetrahedra linked by a shared oxygen. The use of these materials as a cementing agent, toxic waste storage and fibre reinforced material, amongst a multitude of prospective applications, has grown in recent years. The utilisation of AIPs is hampered by a lack of knowledge about their formation and structure. In order to allow the materials to achieve their full potential, the way in which the material behaves and forms under different conditions must be elucidated. The basic questions that this study aimed to answer were: 1) How does the structure of these AIPs change with composition? and 2) Can this change in structure explain the material properties of the AIP? The AIPs investigated in the study covered the molar composition ranges Si:Al ratio = 1 - 3 and Na:Al ratio = 0.5 - 2. They were made by the sodium hydroxide activation of metakaolinite, derived from the dehydroxylation of kaolinite. The Si content of the AIP was altered by the addition of amorphous silica fume via the activation solution. The study considered the structural nature of the AIPs at the macro, micro and nanoscales, and found that the structure changed at all scales and with all compositions. The nature of the AIP structure was studied at the macroscale utilising compressive strength testing. The results from this work showed that the compressive strength of the AIPs varied systematically with the chemical composition. The strengths recorded ranged from 0.4 ± 0.2 MPa for a sample with Si:Al:Na molar ratios = 1.08:1:0.5, to 64 ± 3 MPa for a sample with Si:Al:Na molar ratios = 2.5:1:1.3. The higher strengths measured exceed those exhibited by Portland cement pastes. The microstructure of the AIPs was investigated by scanning electron microscopy and energy dispersive spectroscopy.<br>Microscopy showed that the microstructure variations correlated with the compressive strength. In general, AIPs with low compressive strengths exhibited an inhomogeneous two-phase microstructure; grain and matrix. The grain phase consisted of undissolved metakaolinite, whilst the matrix was the fully formed inorganic polymer. AIPs with high compressive strengths exhibited a microstructure that was more homogeneous than the samples with low compressive strength. The compressive strength of the AIPs depended on both the chemical composition and the level of residual MK present in the microstructure. EDS microanalysis showed that the composition of the two phases was significantly different, and that the differences depended on the overall composition of the AIP. EDS results also demonstrated that the impurity elements present in the metakaolinite were affected by the polymerisation process. Soluble elements such as Ca and Mg were found primarily in the matrix, indicating that they had leached out of the metakaolinite grains, whereas insoluble elements such as Fe and Ti were found primarily in the grains. The nanoscale structure of the AIPs was examined by solid-state nuclear magnetic resonance (NMR) and x-ray scattering (XRS). The NMR measurements revealed that the average coordination of Si varied according to the composition of the AIP, whereas the coordination of Al was constant. Na is present in the network in both hydrated and non-hydrated forms. It is postulated that the variation in the Si coordination can be explained by the formation of Si-O-Na bonds with Na forming an ionic bond with 0 in the polymer network. Radial distribution function (RDF) analysis of the XRS patterns revealed little difference in the structure of the different AIPs beyond ~2.5 Å.<br>Unfortunately, the data were of insufficient resolution to allow for a full evaluation of the differences in the Si-O and Al-O bonds between different AIPs. However, the trends present in the shape and position of the RDF peak corresponding to the Si-O and Al-O bonds do follow the composition of the AIP. It has been shown that a variety of experimental techniques can be used in concert to obtain information on the structural nature of AIPs. To this end, it has been found that the compressive strength of AIPs can be optimised, and that the microstructure of the AIPs changes systematically with variations in the compressive strength. An improved model for the structure of AIPs has also been proposed.
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Saintonge, Arnaud. "Élaboration d’un composite oxyde/oxyde à matrice d'aluminosilicate de baryum et fibres d'alumine." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0243.
Full textAbstract:
Dans l’industrie de l’aéronautique et de la défense, les applications thermostructurales nécessitent des matériaux toujours plus performants, alliant résistance mécanique, réfractarité et légèreté. Pour répondre à ces exigences, les matériaux composites à matrice céramique tout oxyde (OCMC) sont prometteurs. Parmi les matrices de ces OCMC, l'aluminosilicate de baryum (BAS) se distingue par ses propriétés physiques intéressantes, notamment en tant que matériau pour radômes. Cependant, pour rendre ce matériau fonctionnel à haute température, proche de sa température de fusion (1750°C), il est essentiel de le renforcer avec un matériau thermochimiquement stable et doté d'une architecture adaptée. Plusieurs thèses antérieures ont permis de maîtriser la phase hexagonale du BAS. La nature chimique du renfort présentant la stabilité souhaitée avec le BAS a été identifiée et des OCMC Al2O3/BAS à renfort fibreux 1D, 2D ont commencé à être élaborés. Toutefois, pour obtenir des matériaux ayant des propriétés accrues pour des conditions thermostructurales sévères, il est nécessaire de réaliser ces OCMC avec une architecture « 3D » du renfort. Le sujet présenté porte sur la réalisation d'un tel composite avec une architecture complexe (3D) du renfort fibreux et sur l'évaluation de ses propriétés. Pour répondre à cet objectif, ces travaux de recherche incluent : l'étude du frittage du BAS-H afin d’anticiper son comportement en tant que matrice, l'amélioration de son comportement rhéologique en suspension afin de favoriser son infiltration dans une préforme de renforts fibreux, et la mise en place d'un procédé d'imprégnation adapté aux renforts 3D. À la suite de ces études, la fabrication d'OCMC Al2O3/BAS a été réalisée, mettant en évidence des caractéristiques prometteuses en lien avec l'application<br>In the aerospace and defense industry, thermostructural applications require increasingly high-performance materials, combining mechanical strength, refractoriness, and lightness. To meet these demands, all-oxide ceramic matrix composites (OCMC) are considered promising candidates. Among the matrices for these OCMCs, barium aluminosilicate (BAS) stands out due to its advantageous physical properties, particularly as a material for radomes. However, to make this material functional at high temperatures, close to its melting point (1750°C), it is essential to reinforce it with a thermochemically stable material that has an appropriate architecture. Previous theses have successfully mastered the hexagonal phase of BAS. The chemical nature of the reinforcement, which offers the desired stability with BAS, has been identified, and OCMC Al2O3/BAS composites with 1D and 2D fibrous reinforcements have been developed. However, to achieve materials with enhanced properties under severe thermostructural conditions, these OCMCs need to be produced with a "3D" reinforcement architecture. This work focuses on the development of such a composite with a complex (3D) fiber reinforcement architecture and the evaluation of its properties. To achieve this, the research involves studying the sintering of BAS-H to predict its behavior as a matrix, improving its rheological behavior in suspension to facilitate infiltration into the fibrous reinforcement preform, and implementing an impregnation process suitable for 3D reinforcements. Following these studies, the fabrication of OCMC Al2O3/BAS was completed, demonstrating promising characteristics for the intended application
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Predescu, Ligia. "Adsorption of nitrogen, methane, and carbon monoxide on aluminosilicate and aluminophosphate molecular sieves." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10115.
Full textAbstract:
Considering the difficulties associated with the experimental determination of binary mixture adsorption isotherms, pure-gas adsorption information becomes vital in the prediction of these isotherms and the corresponding phase equilibria necessary in the design of adsorptive separation units. Experimental equilibrium isotherms describing the adsorption of pure N$\rm\sb2,\ CH\sb4,$ and CO in a natural aluminosilicate molecular sieve (clinoptilolite from Cuba) and two synthetic small-pore aluminophosphate molecular sieves (AlPO$\sb4$-17 and AlPO$\sb4$-18) have been determined using the volumetric method at 40$\sp\circ$C over a pressure range up to about 1000 mm Hg, and subsequently fitted with the Langmuir and Flory-Huggins Vacancy Solution Theory equations. Additional Langmuir and FH-VST fits of equilibrium isotherms previously measured over the same pressure range at room temperature and 40$\sp\circ$C to describe the equilibrium adsorption of the same three adsorbates in two aluminosilicate molecular sieves (natural clinoptilolite from Turkey and zeolite 5A), as well as in a medium-pore aluminophosphate molecular sieve AlPO$\sb4$-11 were also obtained. The Freundlich equation was found to yield a better fit than either the Langmuir or FH-VST equations for the experimental adsorption isotherms of N$\sb2$ and CO on AlPO$\sb4$-17. The higher observed capacities of the aluminosilicate molecular sieves, compared to the aluminophosphates, were attributed to the energetic heterogeneity conferred by the presence of framework-charge compensating cations. The model parameters obtained by fitting the experimental pure-component adsorption isotherms permitted the prediction of the mixture adsorption phase diagrams and the binary adsorption isotherms by the Extended Langmuir Model and the Flory-Huggins Vacancy Solution Model for the three possible binary mixtures at 101.3 kPa total pressure and the pure-component adsorption temperatures investigated. The Ideal Adsorbed Solution Theory was also applied with the explanation of the behaviour predicted by each model for each adsorption system was attempted. (Abstract shortened by UMI.)
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Villalobos, Guillermo Roberts. "Strength enhancement of nicalon reinforced lithium aluminosilicate containing a Ta₂O₅ second phase." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19969.
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Dickson, Johnbull Otah. "The role of secondary aluminosilicate minerals in technetium-99 immobilization in radioactive waste." Thesis, Washington State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3640335.
Full textAbstract:
<p> Corroding waste tanks at select U.S. Department of Energy's nuclear waste facility have leaked highly alkaline tank waste solutions containing radionuclides and other contaminants into subsurface sediments. These tank wastes react with subsurface sediments to form secondary mineral phase(s) (feldspathoids), which may play key role in the transport of contaminants through the vadose zone and aquifers. Although transformation of secondary precipitates in subsurface sediments has been extensively studied, however, there is lack of knowledge about the role of feldspathoid selectivity in controlling the long-term fate and transport of key anionic radionuclides in the subsurface. The overarching objectives of this dissertation were to (1) determine secondary mineral transformation with aging time, alkalinity, anion identity and selectivity, and (2) quantify the competitive incorporation of ReO<sub>4</sub><sup>- </sup> (a chemical analogue for Tc-99) into mineral phase(s) as a function of anion composition, size and selectivity under simulated waste leaks. The key results of this work showed that alkalinity, time and anion composition play important role in mineral transformation that control the mobility of key radionuclide species in the environment. Nitrate in 16 mol OH<sup>- </sup>/kg solution favored cancrinite nucleation while in 1 mol OH<sup> -</sup>/kg solution fostered mixed cancrinite/sodalite formation. The sequestering capacity of sodalite for ReO<sub>4</sub><sup>-</sup> was ∼5 times higher than that of cancrinite. The immobilized ReO<sub>4</sub><sup>-</sup> in the sodalite cages was not easily exchanged with other competing anions. Due to the less distortion to the β-cage, sodalite displayed stronger preference for smaller competing anions relative to the larger ReO<sub>4</sub><sup> -</sup> anion. The selectivity of the mixed sodalite cage for ReO<sub>4 </sub><sup>-</sup> was largely driven by the difference in anion radii (DIR) and increases in the following order: Cl<sup>-</sup><NO<sub> 3</sub><sup>-</sup><MnO<sub>4</sub><sup>-</sup> and CO<sub>3</sub><sup> 2-</sup><SO<sub>4</sub><sup>2-</sup><WO<sub>4</sub><sup>2-</sup> for the monovalent and divalent anions respectively. When the DIR between ReO<sub>4</sub><sup>-</sup> and competing anions was less than ∼12%, then ReO<sub>4</sub><sup>-</sup> incorporation into sodalite was significant. The results imply that anion size is the major factor that determines sodalite anion compositions and that ReO<sub>4</sub><sup>-</sup> is likely to serve as a suitable analogue for TcO<sub>4</sub><sup>-</sup></p>
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Jermy, Mark Christopher. "Structural studies of alkali aluminosilicate glasses using advanced scattering, resonance and computational techniques." Thesis, University of Kent, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337317.
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Read, Michael J. (Michael Joseph) 1975. "Adsorption and conformation change of short helical peptides on silica and aluminosilicate surfaces." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29914.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.<br>Includes bibliographical references (p. 194-206).<br>Motivated by the challenges in understanding important features of protein adsorption, the interactions between (-helical peptides and a carefully selected set of model surfaces were studied. The peptide sequences contained three blocks of two to five residues each, with the side chains of the N-terminal and C-terminal blocks having negative and positive charges, respectively, and the central block having uncharged side chains. The conformation of a variety of such peptides was studied in solution by circular dichroism (CD) and H nuclear magnetic resonance (NMR) spectroscopy, in order to characterize the degree of xc-helicity in solution, as a function of temperature, pH, and chemical denaturant (urea) concentration. Intramolecular electrostatic interactions arising from the charged side chains, together with the central block of gc-helix-forming alanine residues, were found to stabilize oc-helicity. These interactions were balanced by the natural tendency toward disordered structures, which resulted in fractional oc-helicities between 25% and 50% when in solution. Adsorption isotherms for the peptide Ac-DDDDAAYAARRRR-Am on amorphous colloidal silica nanoparticles were studied in detail. A greater amount of peptide was adsorbed at basic pH than at neutral pH. The was fit with Langmuir and Frumkin isotherms, and the free energy, enthalpy, and entropy of adsorption were calculated. The enthalpy of adsorption at pH 9 (-17 kJ mol'1) was consistent with calculations of the electrostatic interaction between the screened silica surface charge and the dipolar charge distribution on the peptide arising from the charged side chains.<br>The entropy of adsorption at pH 9 (15 J mol'l K-) arose in part from conformational changes which were observed in the CD and NMR spectra of adsorbed molecules. Solution 1H NMR spectra of peptide adsorbed to colloidal silica resolved resonances from aspartate and alanine, but not from arginine; this was shown to arise from selective immobilization of positively-charged arginine side chains due to electrostatic interactions with the negatively-charged silica, which resulted in a specific orientation of the peptide on the surface. Conformationally-sensitive resonances from aspartate and alanine residues displayed peak shifts characteristic of reduced ac-helicity. The CD spectra of adsorbed peptides also indicated a decrease in oc-helicity. Taken together, these measurements supported the view that loss of o-helicity of adsorbed molecules propagates from the arginine terminus, which is directly adjacent to the surface, into the alanine and arginine segments, which extend into solution. Because conformational changes have important implications for the functionality of adsorbed molecules, the extent of c-helicity loss was measured quantitatively as a function of temperature and pH for the peptide Ac-DDDDAAAARRRRR-Am. At neutral pH, the c-helicity of adsorbed peptides decreased with increasing temperature, much like the behavior observed for peptides in solution. In contrast, at basic pH, the ca-helicity of adsorbed peptides increased with increasing temperature. These results were interpreted using a statistical model based on modifications to existing theories of the helix-coil transition to include residue-specific electrostatic interactions between the surface and charged peptide side chains.<br>by Michael J. Read.<br>Ph.D.
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Ren, Mengguo. "Molecular Dynamics Simulations of the Structures and Properties of Aluminosilicate and Borosilicate Glasses." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404517/.
Full textAbstract:
Silicate glasses are the most common glass types and have impact on almost every aspect in our lives: from window, containers, to glass fibers for telecommunications. Unlike their crystalline counterparts, glass materials lack long-range order in their atomic arrangement but their structures do possess short and medium range characteristics that play critical roles in their physical and chemical properties. Despite active development of characterization techniques that have contributed to the understanding of glass structures, there remain key challenges in obtaining essential structural features of glasses. Atomistic computer simulations have become an increasingly important method in elucidating the atomic structures and in interpretation and/or prediction of composition-structure-property relationships of complex materials. In this dissertation, classical molecular dynamic (MD) simulations were used to investigate the atomic structures, dynamic and other properties of two important glass systems—aluminosilicate glasses and borosilicate glasses, which are the basis of most industrial and technologically important glasses. Firstly, a comprehensive study of peralkaline Na2O-Al2O3-SiO2 glass with varying Al2O3/SiO2, Na2O/Al2O3, Na2O/SiO2 ratios has been performed to obtain better understanding of the composition–structure–property relationships in this glass system. More than 99% of Al were 4-coordinated in these glasses, validating that Na+ tend to charge balance [AlO4]- network forming units first and then, excess Na+ was used to create non-bridging oxygen (NBO) on Si. As the drop of Na/Al ratio, the percentage of NBO decreases, indicating an increase of the glass network connectivity. In addition, polyhedral connection probability results show that Al tend to be randomly distributed in the glass structure, suggesting a violation of Lowenstein's rule. These structural properties were further used to explain macroscopic properties of glass, such as change of glass transition temperature (Tg) and hardness (Hv) with glass composition. Secondly, molecular dynamics simulations were used to understand the structural, thermal mechanical and diffusion behaviors of spodumene (LiAlSi2O6) crystalline phases and glasses. It was found that β-LiAlSi2O6 has a structure much closer to the glass phase. The α-LiAlSi2O6 phase, however, has a more closed-packed structure and higher density. The diffusion behaviors were also found to be closely related to the atomic structures. Thirdly, the surface atomic structures of a series of sodium borosilicate glasses were studied using recently developed compositional dependent partial charge potentials. This provides insight into: a) the structural difference between glass surface and bulk glass; b) the evolution of bulk and surface structures as the change of glass composition. Lastly, pressure and temperature effects on the structure and properties of borosilicate glass were investigated in detail. A serial data derived from different compression temperatures and pressures enable us to explore the link between the microstructure and macroscopic physical properties. The results show that compression temperature and pressure play important roles in glass densification process and may result various glass densification mechanism. This dissertation demonstrates that atomistic simulations coupled with effective potentials and careful validations have become an effective method in research and design of complex glass materials.
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Goyal, Gaurav. "Light Olefin Production by Cracking Nannochloris oculata Microalgae using Aluminosilicate Catalysts." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6619.
Full textAbstract:
The global demand and sustainability concerns for producing light olefins encouraged researchers to look for an alternative and sustainable feedstock. Alkenes, such as ethene, propene and butene, are known as light olefins. Olefins are the backbone of the chemical industry because they serve as the chemical building blocks for the manufacture of polymers, fibers, and numerous organic chemicals. Feedstocks such as naphtha, natural gas and liquefied petroleum gas (LPG) are currently used for producing light olefins, but they are non-renewable and hence unsustainable. In contrast, biomass as a potential feedstock for the production of fuels and chemicals is renewable. Microalgae, in particular, are a promising resource due to their fast growth rate and ability to act as a CO2 sink.
The objective of my research was to assess the potential of thermochemical production of the light olefins ethene, propene, and butene from the marine microalga Nannochloris oculata in the absence and presence of catalysts and study the effect of catalyst to cell mass ratio on the production of these chemicals. Thermal cracking was conducted using two catalysts, aluminosilicate (Si/Al) and H-ß zeolite at 400-650 °C in a semi-batch reactor system and gas analysis was performed using mass spectrometry. Cracking of N. oculata by the aluminosilicate catalyst was studied in more detail at catalyst-to-algae mass ratios of zero, 5:1, 10:1 and 20:1 using (Si/Al) catalyst and a comparative study was performed at catalyst-to-algae mass ratio of 10:1 using (Si/Al) and H-ß zeolite catalyst. The formation of light olefins ethene, propene, and butene was quantified. Higher temperature and catalyst to algae ratio led to an increase in the yield of all olefins, although a diminishing effect was observed above 600 °C and a ratio of 5:1. Although ethene was the most significant product, the concentration of all olefins increased significantly, when catalysts were employed in the cracking reaction. Moreover, the comparative study revealed that ethene was the most significant product when (Si/Al) was used and propene was the most significant product when H-ß zeolite was used.
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Sandland, Travis Odin. "Structure of Cl-containing silicate an aluminosilicate glasses: a 35Cl MAS-NMR study /." May be available electronically:, 2004. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Bouchouicha, Hamed. "Élaboration, caractérisation structurale et étude des propriétés de luminescence des verres et des vitrocéramiques alumino-silicatés de calcium dopés à l'europium." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1035/document.
Full textAbstract:
Ce travail de thèse porte sur l'étude des verres alumino-silicatés de calcium dopés à l'europium et le processus de leur cristallisation sous forme des vitrocéramiques dans le cadre de la recherche de nouveaux phosphores pour application LED à émission blanche. Nous avons étudié trois échantillons vitreux avec différentes teneurs en silice et avons élaboré des vitrocéramiques cristallisées. La caractérisation des verres et des vitrocéramiques a été réalisée par différentes techniques expérimentales : l'analyse thermique, la diffraction des rayons X et la spectroscopie de diffusion Raman. Les propriétés spectroscopiques de l'ion europium dans les verres et les vitrocéramiques synthétisés ont été étudiées. Le contrôle de la cristallisation des vitrocéramiques GC34 et GC50 par la diffraction des rayons X a permis d'identifier deux phases la mélilite et l'anorthite. Dans le cas de la vitrocéramique GC7, une seule phase alumino-calcique qui est la mayenite est cristallisée majoritairement. L'étude par la spectroscopie de diffusion Raman a permis d'une part, de suivre l'évolution de la cristallisation pendant les traitements thermiques en surface et en profondeur dans l'ensemble des vitrocéramiques. Nous avons montré que le processus de cristallisation a eu lieu en surface des échantillons et correspond typiquement à une nucléation hétérogène. D'autre part, une étude comparative avec des échantillons naturels analogues prise de la base de données RRUFF nous a permis de valider l'ensemble des résultats trouvés. Dans le cas des vitrocéramiques GC34 et GC50, les mesures des spectres d'émission et les durées de vie de l'ion Eu3+ montrent bien son incorporation dans les phases cristallines formées. L'ion Eu3+ tend à occuper seulement les sites Ca2+ (CN= 8) de la mélilite majoritaire dans la vitrocéramique GC34 alors, qu'il tend à s'incorporer dans les sites Ca2+ (CN= 6 et 7) et Ca2+ (CN=8) respectivement, des phases anorthite et mélilite formées dans la vitrocéramique GC50. Ces résultats ont été confirmés par les mesures d'affinement de raies. L'étude des spectres d'émission de l'ion Eu2+ a permis de mettre en évidence une modification de son environnement durant la cristallisation traduite par son incorporation dans les sites Ca2+ après réduction de l'ion Eu3+ pendant les recuits. Dans le cas de la vitrocéramique GC7, les spectres d'émissions et les mesures du déclin de luminescence de l'ion Eu3+ montrent bien que l'ion Eu3+ est incorporé dans la phase mayenite formée. En terme d'application, les mesures des coordonnées trichromatiques suggèrent que la dévitrification des verres semble être une technique efficace permettant d'obtenir de nouveaux matériaux luminophores (LED blanches) à émission intensifiée (cas des vitrocéramiques GC34 et G50) et accordable en modifiant leur composition et l'excitation<br>This work concerns the study of calcium aluminosilicate glass doped with europium and their process of crystallization as glass-ceramics as part of the search for new phosphors for white LED application. We studied three glass samples with different silica contents and have elaborated crystallized glass-ceramics. Characterization of glasses and glass-ceramics was performed by different experimental techniques: thermal analysis, X-ray diffraction and Raman spectroscopy. The spectroscopic properties of the europium ion in the glass and glass-ceramic synthesized were studied.Control of crystallization of GC34 and GC50 glass-ceramics by X-ray diffraction have been identified two phases, melilite and anorthite. In the case of the GC7 glass-ceramic, a single aluminum calcium phase, mayenite which crystallized predominantly. The study by Raman spectroscopy allowed to follow the evolution of the crystallization during heat treatment in the surface and of glass-ceramics. We have shown that the crystallization process initiate at the surface of the samples and corresponds typically to a heterogeneous nucleation. On the other hand, a comparison with similar natural samples allowed us to validate all the identifications.In the case of GC34 and GC50 glass-ceramics, emission spectra and lifetimes of Eu3+ ion clearly show its incorporation into the new-formed crystalline phases. The Eu3+ ion occupy the Ca2+ sites (CN = 8) in the major mélilite phase of the the GC34 glass-ceramic while, it incorporates the Ca2+ sites (CN = 6 and 7) and Ca2+ (CN = 8) of anorthite and mélilite phases formed in the GC50 glass-ceramic, respectively. These results were confirmed by Fluorescence Line Narrowing (FLN) measurements. The study of emission spectra of the Eu2+ ion allowed highlighting changes during crystallization associated with the reduction of the Eu3+ ions during annealing. In the case of the low silicate GC7 glass-ceramic, emission spectra and lifetimes measurements of the Eu3+ ion show that the Eu3+ ions are incorporated into the mayenite phase. In terms of application, the analyses of the trichromatic coordinates suggest that the glass devitrification appears to be an efficient technique to achieve new white LED phosphor materials with intensified (mainly for GC34 and G50 glass-ceramics) and tunable emission by varying composition and/or excitation