Dissertations / Theses on the topic 'Synthetic aluminosilicates'

Made available in DSpace on 2017-07-21T20:43:50Z (GMT). No. of bitstreams: 1 Luiz Cezar Lima Junior.pdf: 4959123 bytes, checksum: 8ba169401ed3c8565f7d14d0d74e19c1 (MD5) Previous issue date: 2016-08-29<br>Geopolymers, or ‘inorganic polymers’, considered an alternative cementing system to the convention Portland cement, are formed due to the dissolution, under a high alkali solution, of natural raw materials containing aluminosilicate species. The product of this reaction is the obtainment of a synthetic aluminosilicate product, manufactured under low temperature or even at room temperature. A wide range of materials can be used as precursors as well as alkali activators. The present work focuses on the obtainment of inorganic polymers with innovative precursors, based on different residues of several industrial sectors, such as glass manufacturing, ceramic claddings, and also with local minerals found in abundance on the region of the Campos Gerais. The development of an alternative cementing system will be directly applied on materials to be used as external cladding of steel/wood-based modular structures for residential/commercial buildings, replacing similar materials made from ordinary Portland cement, aiming and industrial application for this product. The obtained product presented similar/superior physical-mechanical properties when compared to its opponent products, with an average flexural strength of 11,73 MPa and a water absorption of 13,50%, being the first value intermediate and the second the best in comparison with commercial products. The use of temperature during curing cycle for increasing the properties of the geopolymeric cement was successfully tested, resulting on more dense and stable structures. Samples showed an increase in flexural strength from 1,83 MPa to 10,15MPa comparing curing cycles at room temperature and at 65ºC, which indicates that temperature works as a setting accelerator for the tested recipe of geopolymers.<br>Geopolímeros, ou ‘polímeros inorgânicos’, considerados um sistema cimentante alternativo ao cimento Portland convencional, são materiais formados a partir da dissolução de matérias-primas naturais à base de aluminossilicatos em uma solução alcalina. O resultado desta reação é a formação de um aluminossilicato sintético, produzido a baixas temperaturas ou mesmo sob temperatura ambiente. Diferentes matérias-primas naturais e sintéticas podem ser utilizadas como precursores e fonte de álcalis. O presente trabalho tem por objetivo o desenvolvimento de polímeros inorgânicos a partir de precursores inovadores, utilizando-se de resíduos de diversos setores da indústria, tais como da fabricação de vidro, da indústria de revestimentos cerâmicos, e também de insumos locais disponíveis em abundância na região dos Campos Gerais. O sistema cimentante obtido foi utilizado para a obtenção de placas de revestimento em construções em estrutura modular de aço ou madeira, substituindo produtos similares produzidos a partir de cimento Portland convencional, e visando uma aplicação industrial deste. O produto obtido apresentou propriedades físico-mecânicas semelhantes e até superiores às dos produtos concorrentes, com uma resistência à flexão média de 11,73 MPa e uma absorção de umidade média de 13,50%, sendo o primeiro valor intermediário e o segundo o melhor dentre os produtos comerciais. O uso de temperatura para aumento das propriedades físico-mecânicas do cimento geopolimérico foi testado com sucesso, resultando em estruturas mais compactas e estáveis. Houve um aumento de resistência mecânica de 1,83 MPa para 10,15 MPa comparando-se ciclos de cura sob temperatura ambiente e a 65ºC, indicando que a temperatura funciona como um acelerador de cura dos geopolímeros testados.

<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>

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.

<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&deg;C and the temperature is raised to 150&deg;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>

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 MartaLPS_partes_autorizadas_pelo autor.pdf: 1296900 bytes, checksum: ae142b4d715f0718971945acd4c853ad (MD5) Previous issue date: 2009-06-01<br>Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico<br>The mesoporous molecular sieves of MCM-41 and AlMCM-41 type are considered as promising support for metal in the refining processes of petroleum-based materials as catalysts and adsorbents for environmental protection. In this work the molecular sieves MCM-41 and AlMCM-41 were synthesized by replacing the source of silica conventionally used, for quartz, an alternative and abundant, and the use of waste from the production of diatomaceous earth, an aluminum-silicate, as a source aluminum, due to abundant reserves of diatomaceous earth in the state of Rio Grande do Norte in the city of Cear?-Mirim, with the objective of producing high-value materials that have similar characteristics to traditional commercial catalysts in the market. These materials were synthesized by the method of hydrothermal synthesis at 100 ? C for 7 days and subjected to calcination at 500 ? C for 2 hours under flow of nitrogen and air. The molecular sieves were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TG), adsorption of N2 (BET and BJH methods), spectroscopy in the infra red (FTIR), microscopy scanning electron (SEM) and transmission electron microscopy (TEM). The analysis indicated that the synthesized materials showed characteristic hexagonal structure of mesopores materials with high specific surface area and sort and narrow distribution of size of pores<br>As peneiras moleculares mesoporosas do tipo MCM-41 e AlMCM-41 s?o consideradas promissoras como suporte para metais em processos de refino de materiais a base de petr?leo, como catalisadores e como adsorventes para prote??o ambiental. Neste trabalho foram sintetizadas as peneiras moleculares MCM-41 e AlMCM-41 atrav?s da substitui??o da fonte de s?lica convencionalmente utilizada, por quartzo, uma fonte alternativa e abundante, e pela utiliza??o do rejeito da produ??o de diatomita, um alumino-silicato, como fonte de alum?nio, devido a abundante reserva de diatomita no estado do Rio Grande do Norte, no munic?pio de Cear?-Mirim, com o objetivo de produzir materiais de alto valor agregado que apresentam caracter?sticas semelhantes aos catalisadores comerciais tradicionalmente existentes no mercado. Estes materiais foram sintetizados pelo m?todo de s?ntese hidrot?rmica a 100 ?C por 7 dias, e submetidos a calcina??o a 500 ?C por 2 horas sob fluxo de nitrog?nio e ar. As peneiras moleculares foram caracterizadas por difra??o de raios-X (DRX), an?lises t?rmicas diferencial (DTA) e termogravim?trica (TG), fisissor??o de N2, (M?todos de BET e BJH), espectroscopia na regi?o do infra vermelho (FTIR), microscopia eletr?nica de varredura (MEV) e microscopia eletr?nica de transmiss?o (MET). As an?lises indicaram que os materiais sintetizados apresentaram estrutura hexagonal caracter?stica dos materiais mesoporosos, com elevadas ordena??o e ?rea superficial espec?fica e estreita distribui??o de tamanho de poros

Nanotubes have numerous potential applications in areas such as biotechnology, electronics, photonics, catalysis and separations. There are several challenges to be overcome in order to realize their potential, such as: (1) Synthesis of monodisperse (in diameter and in length) single-walled nanotubes; (2) Quantitative understanding of the mechanism of formation and growth of nanotubes; (3) Capability to engineer the nanotube size; (4) Low temperature synthesis process; and (5) Synthesis of impurity free nanotubes. Our investigation focuses on a class of metal oxide (aluminosilicate/germanate) nanotubes, which are; single walled nanotubes with monodisperse inner and outer diameters, can be synthesized in the laboratory by a low temperature (95ºC) process in mildly acidic aqueous solutions, and their formation timescales is hours, which makes it convenient as a model system to study the mechanisms of nanotube formation. This work is focused on obtaining a qualitative and quantitative understanding of the mechanism of formation of aluminosilicate and aluminogermanate nanotubes. In order to achieve this overall objective, this thesis consists of the following aspects: (1) A systematic phenomenological study of the growth and structural properties of aluminosilicate and aluminogermanate nanotubes. The constant size and increasing nanotube concentration over the synthesis time strongly suggest that these nanotubular are assembled through self-assembly process. (II) Investigation of the mechanism of formation of single-walled aluminogermanate nanotubes provided the central phenomena underlying the formation of these nanostructures: (1) the generation (via pH control) of a precursor solution containing chemically bonded precursors, (2) the formation of amorphous nanoscale (~ 6 nm) condensates via temperature control, and (3) the self-assembly of short nanotubes from the amorphous nanoscale condensates. (III) Synthesis of mixed metal oxide (aluminosilicogermanate) nanotubes with precise control of elemental composition, diameter and length of the product nanotubes. (IV) Preliminary work towards generalization of the kinetic model developed for aluminogermanate nanotubes to a larger class of metal oxide nanotubes. It was found that the size of nanotubes is dependent on the amount of precursors that can be packed in a single ANP and in turn depends on the size of the ANP.

Aujourd’hui, les difficultés pour établir des liens entre caractéristiques des nanomatériaux et réponses biologiques sont principalement issues du manque de contrôle de la synthèse des nanomatériaux, ne permettant pas de faire varier leurs paramètres physico-chimiques clés une à une.Pour identifier certains mécanismes gouvernant la toxicité des nanomatériaux nous avons utilisé un nanotube inorganique modèle dont la synthèse est bien contrôlée : les Ge-imogolites. Les effets de la longueur, du nombre de parois, de la cristallinité et de la composition chimique des Ge-imogolites ont été étudiés sur une bactérie des sols: Pseudomonas brassicacearum. Il a été identifié que la présence de sites réactifs (en bordure de tubes) induit une toxicité due à une interaction forte des nanotubes avec les cellules bactériennes, ainsi que la génération d’espèces réactives de l’oxygène. Ajouter des sites réactifs via la présence de défauts structuraux augmente la dégradation des tubes ainsi que la rétention d’éléments nutritifs essentiels, ce qui augmente leur toxicité. Enfin, l’ajout de fer dans leur structure transforme les Ge-imogolites en source de fer, qui sont dégradées et deviennent promoteurs de croissance. Dans tous ces cas, les interactions entre nanomatériaux et cellules ont été identifiées comme cruciales pour comprendre et prévenir les effets des nanomatériaux. Ce travail de thèse a également permis de mettre en avant la capacité de nouveaux outils pour le suivi de l’internalisation de nanomatériaux dans les organismes<br>Only a few studies of (eco)toxicology linked the physico-chemical properties of nanoparticles to the toxicity mechanisms or the stress they induce. Moreover, no clear conclusions can be drawn at present because of the variability of nanoparticles used in studies. The present study used the inorganic Ge-imogolite nanotubes as a model compound. The toxic effects of length, number of walls, structural defects, and chemical composition were assessed towards the soil bacteria Pseudomonas brassicacearum. Several mechanisms modulating the toxicity of Ge-imogolite were then identified. Indeed, reactive sites at the tube ends induce a slight toxicity via a strong cell interaction and the generation of reactive oxygen species. Creating vacant sites on the surface of Ge-imogolite (ant thus increasing the number of reactive sites), appears to cause a deficiency of nutrients in the culture media correlated with a higher degradation of the tubes, leading to a high bacterial growth decrease. Finally, structural iron incorporation into Ge-imogolite transforms them into an iron source, being degraded and becoming growth promoters. In this work, the new tools capacities for the study of nanomaterials/cells interaction have been studied

碩士<br>國立臺北科技大學<br>資源工程研究所<br>99<br>Inorganic polymer is an amorphous to semi-crystalline aluminosilicate material which is conventionally synthesized from the mixture of kaolinite, quartz and alkaline solution. The structure of this material is similar to the framework of zeolites and the composition is closed to that of natural minerals, in which is named “Geopolymer”. Geopolymer materials are formed by geopolymerisation via the gelation of Si and Al dissolved in alkaline solutions with raw materials which are rich in silicon and aluminum contents. Potassium aluminosilicate are synthesized using pure chemicals with different molar ratios of Si to Al in order to study the variation in structural matters. In general potassium silicate solutions made of silica fume in KOH(aq) react with potassium aluminate solutions made of Al powders in KOH(aq) to form potassium aluminosilicate raw powders. After heat-treatment, these raw powders are then dissolved and reacted with KOH solution to form potassium aluminosilicate materials. XRD, FT-IR, 29Si and 27Al MAS-NMR spectroscopy were carried out for analyzing the composition and structure of products, respectively.

碩士<br>中原大學<br>化學研究所<br>90<br>Aluminium-incorporated mesoporous molecular sieves SBA-15 have been obtained by direct synthesis at low acid concentration and at room temperature for 72 h and 90℃ for 24 h. The condition of preparing Na+- [Si, Al]-SBA-15 is Al(NO3)3：NaOH =1：1.25. The resulting materials retain the hexagonal order and physical properties of pure siliceous SBA-15. It shows a very narrow pore size distribution with an average mesopore size of 60Å and a high surface area of 800 m2 / g. The condition of preparing H+- [Si, Al]-SBA-15 is Al(NO3)3：TMAOH = 1：1.0. It also shows narrow pore size distribution with an average mesopore size of 70Å and a high surface area of 700 m2/ g .The morphology of Na+-[Si, Al]-SBA-15 or H+-[Si,Al]-SBA-15 controlled by acid concentration shows a variety of morphology such as rod, U-shape, hexagon, donut, ball and coral. The catalytic activity of the prepared [Si,Al]-SBA-15 was evaluated by using the cumene cracking reaction and was much higher than that of MCM-41 analog. The condition of preparing high order [Si,Al]-SBA-15 is Al(NO3)3：Al(OCH(CH3)2)3 = 1：3. The resulting materials retain the hexagonal order and physical properties of pure siliceous SBA-15 and it can find that major part of aluminum in [Si,Al]-SBA-15 can be easily incorporated into framework of SBA-15 without structure deformation. It shows narrow pore size distribution with an average mesopore size of 70Å and a high surface area of 700 m2/ g .

碩士<br>國立中央大學<br>環境工程研究所<br>100<br>This study investigated the feasibility of synthesizing mesoporous molecular sieve, MCM-41, by alkali fusion and hydrothermal processes, using water purification sludge ash (WPSA) and waste glass (WG) as starting Si and Al sources. Aluminum from the WPSA was incorporated into the resultant Al-MCM41, which contributed to the strength and the hydrothermal stability of the MCM-41 structure, and also enhanced the adsorption of organic dye (i.e., methyl blue), as compared to MCM-41 synthesized from pure sodium metasilicate. The proper conditions for the mix ratio of WPSA and WG, alkali fusion/extraction for the preparation of precursor solution, and the hydrothermal process were studied, the resultant Al-MCM-41s were characterized. The residues from the alkali fusion/extraction process were also converted into zeolite (Cancrinite) for a total retrieval. The results indicated WPSA containing Quartz and Illite, was less extractable for Si as compared to the WG, containing amorphous silicates. Accordingly, the increase in WG portion of the starting mixture increased the extracted quantity of Si. It is noted that the proper mix ratio is about 1:1 that may be expected to generate a precursor solution with a suitable range of Si/Al for the synthesis of Al-MCM-41. All the starting materials were tested with TCLP and showed they are safe below the regulatory thresholds. The Al-MCM-41 hydrothermally synthesized with 1:1 mix ratio of the starting materials show that the surface area (860 m2/g), pore diameter (3.16 nm), pore volume (0.85 cm3/g), d100 (3.73 nm), a0(4.31 nm) and wall thickness(1.15 nm) are close to that of pure MCM-41. However, the hydrothermal stability and adsorption of organic dye (methyl blue) outperform that of the pure MCM-41. Furthermore, the impurity such as Na2O, K2O, and Fe2O3, derived from the starting wastes are less or close to 1%, and have no significant effects on the on the synthesis and performance of the Al-MCM-41. In addition, the residues resulted from the alkali fusion/extraction was successfully synthesized into zeolites (Cancrinite and the other unnamed) for a secondary retrieval/recycling purpose, suggesting a total retrieval/recycling of the water purification sludge and waste glass.