Propriedades óticas dos sistemas cerâmicos atuais e suas aplicações em dentes naturais

A estética representa uma qualidade cada vez mais requisitada pela sociedade na atualidade. A busca pela aparência ideal expandiu-se também na medicina dentária, aumentando as exigências por resultados perfeitos. A medicina dentária tem desenvolvido novas técnicas e novos materiais com a ambição de reproduzir as propriedades estéticas e funcionais dos dentes naturais. Os sistemas totalmente cerâmicos têm sido alvo de grande entusiasmo dado as suas características inerentes. O seu potencial na reabilitação oral estética tem derrotado as suas antecessoras metalocerâmicas. À semelhança do esmalte e da dentina, os sistemas totalmente cerâmicos exibem boas propriedades óticas de translucidez, opacidade, fluorescência e opalescência, resultado da interação com a luz. Ainda que não seja possível dissociar as propriedades óticas das propriedades mecânicas de um dente natural para o sucesso de uma restauração, a heterogeneidade das cerâmicas têm sido exitosas enquanto sistema que combina diferentes propriedades para diferentes indicações clínicas. Esta variabilidade deve-se a diferentes composições químicas e a diferentes processos de fabricação, entre outros, que acentuam ou atenuam qualidades em cada sistema totalmente cerâmico. Este trabalho pretende abordar e comparar os sistemas cerâmicos atuais (cerâmicas com base em sílica, cerâmicas com base de alumina, cerâmicas com base em zircónia) de acordo com as suas propriedades óticas e a consequente aplicação clínica tendo em conta as características dos dentes naturais.

Hybrid materials for biomedical applications

The increased longevity of humans and the demand for a better quality of life have led to a continuous search for new implant materials. Scientific development coupled with a growing multidisciplinarity between materials science and life sciences has given rise to new approaches such as regenerative medicine and tissue engineering. The search for a material with mechanical properties close to those of human bone produced a new family of hybrid materials that take advantage of the synergy between inorganic silica (SiO4) domains, based on sol-gel bioactive glass compositions, and organic polydimethylsiloxane, PDMS ((CH3)2.SiO2)n, domains. Several studies have shown that hybrid materials based on the system PDMS-SiO2 constitute a promising group of biomaterials with several potential applications from bone tissue regeneration to brain tissue recovery, passing by bioactive coatings and drug delivery systems. The objective of the present work was to prepare hybrid materials for biomedical applications based on the PDMS-SiO2 system and to achieve a better understanding of the relationship among the sol-gel processing conditions, the chemical structures, the microstructure and the macroscopic properties. For that, different characterization techniques were used: Fourier transform infrared spectrometry, liquid and solid state nuclear magnetic resonance techniques, X-ray diffraction, small-angle X-ray scattering, smallangle neutron scattering, surface area analysis by Brunauer–Emmett–Teller method, scanning electron microscopy and transmission electron microscopy. Surface roughness and wettability were analyzed by 3D optical profilometry and by contact angle measurements respectively. Bioactivity was evaluated in vitro by immersion of the materials in Kokubos’s simulated body fluid and posterior surface analysis by different techniques as well as supernatant liquid analysis by inductively coupled plasma spectroscopy. Biocompatibility was assessed using MG63 osteoblastic cells. PDMS-SiO2-CaO materials were first prepared using nitrate as a calcium source. To avoid the presence of nitrate residues in the final product due to its potential toxicity, a heat-treatment step (above 400 °C) is required. In order to enhance the thermal stability of the materials subjected to high temperatures titanium was added to the hybrid system, and a material containing calcium, with no traces of nitrate and the preservation of a significant amount of methyl groups was successfully obtained. The difficulty in eliminating all nitrates from bulk PDMS-SiO2-CaO samples obtained by sol-gel synthesis and subsequent heat-treatment created a new goal which was the search for alternative sources of calcium. New calcium sources were evaluated in order to substitute the nitrate and calcium acetate was chosen due to its good solubility in water. Preparation solgel protocols were tested and homogeneous monolithic samples were obtained. Besides their ability to improve the bioactivity, titanium and zirconium influence the structural and microstructural features of the SiO2-TiO2 and SiO2-ZrO2 binary systems, and also of the PDMS-TiO2 and PDMS-ZrO2 systems. Detailed studies with different sol-gel conditions allowed the understanding of the roles of titanium and zirconium as additives in the PDMS-SiO2 system. It was concluded that titanium and zirconium influence the kinetics of the sol-gel process due to their different alkoxide reactivity leading to hybrid xerogels with dissimilar characteristics and morphologies. Titanium isopropoxide, less reactive than zirconium propoxide, was chosen as source of titanium, used as an additive to the system PDMS-SiO2-CaO. Two different sol-gel preparation routes were followed, using the same base composition and calcium acetate as calcium source. Different microstructures with high hydrophobicit were obtained and both proved to be biocompatible after tested with MG63 osteoblastic cells. Finally, the role of strontium (typically known in bioglasses to promote bone formation and reduce bone resorption) was studied in the PDMS-SiO2-CaOTiO2 hybrid system. A biocompatible material, tested with MG63 osteoblastic cells, was obtained with the ability to release strontium within the values reported as suitable for bone tissue regeneration.

Acousto-optic modulation of optical reflection properties in fiber Bragg gratings and the application in fiber lasers

This thesis aims to investigate the interaction of acoustic waves and fiber Bragg gratings (FBGs) in standard and suspended-core fibers (SCFs), to evaluate the influence of the fiber, grating and modulator design on the increase of the modulation efficiency, bandwidth and frequency. Initially, the frequency response and the resonant acoustic modes of a low frequency acousto-optic modulator (f < 1.2 MHz) are numerically investigated by using the finite element method. Later, the interaction of longitudinal acoustic waves and FBGs in SCFs is also numerically investigated. The fiber geometric parameters are varied and the strain and grating properties are simulated by means of the finite element method and the transfer matrix method. The study indicates that the air holes composing the SCF cause a significant reduction of the amount of silica in the fiber cross section increasing acousto-optic interaction in the core. Experimental modulation of the reflectivity of FBGs inscribed in two distinct SCFs indicates evidences of this increased interaction. Besides, a method to acoustically induce a dynamic phase-shift in a chirped FBG employing an optimized design of modulator is shown. Afterwards, a combination of this modulator and a FBG inscribed in a three air holes SCF is applied to mode-lock an ytterbium doped fiber laser. To improve the modulator design for future applications, two other distinct devices are investigated to increase the acousto-optic interaction, bandwidth and frequency (f > 10 MHz). A high reflectivity modulation has been achieved for a modulator based on a tapered fiber. Moreover, an increased modulated bandwidth (320 pm) has been obtained for a modulator based on interaction of a radial long period grating (RLPG) and a FBG inscribed in a standard fiber. In summary, the results show a considerable reduction of the grating/fiber length and the modulator size, indicating possibilities for compact and faster acousto-optic fiber devices. Additionally, the increased interaction efficiency, modulated bandwidth and frequency can be useful to shorten the pulse width of future all-fiber mode-locked fiber lasers, as well, to other photonic devices which require the control of the light in optical fibers by electrically tunable acoustic waves.

Síntese de sensores, funcionalização de nanopartículas e fibras óticas para reconhecimento de aniões

O trabalho descrito nesta dissertação envolve a síntese e caracterização de novos macrociclos tetrapirrólicos e afins com potencial aplicação como quimiossensores de aniões, tanto em solução como quando suportados em diferentes materiais. As porfirinas e ftalocianinas ocupam um lugar de destaque nesta dissertação, pelo que no primeiro capítulo, é feita uma revisão bibliográfica acerca das suas metodologias de síntese bem como das suas principais características e aplicações, nomeadamente como quimiossensores de aniões. No segundo capítulo é discutida a síntese e caracterização dos compostos porfirínicos e ftalocianinicos com grupos amina ou poliamina, posteriormente utilizados como hospedeiros de aniões. Descrevem-se, pormenorizadamente, os métodos de síntese, purificação e caracterização estrutural dos diversos compostos sintetizados. No terceiro capítulo realizaram-se os estudos de complexação com aniões em solução e determinaram-se as respetivas constantes de afinidade. Os compostos sintetizados apresentam capacidade de interagir com diferentes aniões. As porfirinas testadas apresentam elevadas constantes de afinidade para o anião di-hidrogenofosfato, mesmo em soluções aquosas quando testadas com cristais piezoelétricos. No caso das ftalocianinas verificou-se que estas interagem com vários aniões e apresentam propriedades cromogénicas, podendo mesmo distinguir aniões cianeto em soluções contendo água. No quarto capítulo estudou-se a imobilização dos quimiossensores, que demonstraram maior eficácia nos estudos de reconhecimento em solução, em diferentes materiais. Primeiro foi estudada a imobilização dos quimiossensores em nanopartículas de sílica (com e sem núcleo magnético) e testada a sua capacidade como sensor de aniões em solução. Numa segunda parte foi estudada a imobilização em fibras óticas. Estas, além das suas excecionais propriedades físico-químicas, têm a vantagem de poderem ser integradas em diferentes estruturas e/ou equipamentos de análise. Na ultima parte desta dissertação encontra-se a descrição da síntese e caracterização de novos conjugados porfirina-C60-OligoDNA com potencial aplicação em transferência eletrónica. Foram sintetizados e caracterizados novos compostos porfirina-OligoDNA e C60-OligoDNA. Esta parte do trabalho foi realizada no “Institute of Advanced Energy” na Universidade de Quioto, Japão.

Desenvolvimento de processos oxidativos avançados para degradação de agrotóxicos em meio aquoso

Atualmente há uma crescente preocupação quanto à qualidade dos recursos hídricos, e essa notória inquietação se deve em parte ao aumento na demanda e consumo de água a nível global, uma vez que o crescimento econômico, juntamente com o desenvolvimento tecnológico, agrícola e industrial conduz a poluição ambiental. Neste contexto, os agrotóxicos, apresentam um alto fator de risco para a qualidade dos recursos hídricos, pois essas substâncias geralmente são tóxicas e não biodegradáveis. Diante deste cenário, um dos maiores desafios nos dias atuais é a eliminação de uma parte significativa, dessa poluição, a qual é causada por esses contaminantes orgânicos tóxicos. O processo clássico de oxidação biológica falha na eliminação de compostos tóxicos, bem como de contaminantes orgânicos recalcitrantes. Além disso, os processos físico-químicos, como a adsorção em carvão ativado, floculação, e a filtração por membranas, apenas transferem esses contaminantes de fase, sem que ocorra a sua destruição. Sendo assim, surge a necessidade da adoção de técnicas que possam ser destrutivas a essas espécies. Os Processos Oxidativos Avançados, surgem como um caminho alternativo para diminuir e eliminar os resíduos desses contaminantes orgânicos. Por tanto, tiveram-se como objetivos neste trabalho: (i) desenvolver e otimizar um processo Fenton empregando ferro zero e peróxido de hidrogênio (Fe0 /H2O2) (ii) utilizar como fonte de ferro zero para o processo Fenton limalha de ferro, a qual é um resíduo da atividade metalúrgica na cidade de Rio Grande (iii) otimizar o tempo de reação (TR) e tempo de homogeneização (TH) para a Fotocatálise Heterogênea empregando um catalisador de sílica dopada com dióxido de titânio e dicloreto de tris (2,2-bipiridina) rutênio II (iv) desenvolver um método cromatográfico empregando LC-DAD para realizar o monitoramento da degradação dos agrotóxicos (v) empregar a LC-MS/MS para confirmar a degradação dos agrotóxicos e monitorar a formação de produtos (vi) empregar IC para monitorar a formação de espécies iônicas (vii) realizar a determinação de COT para estimar a mineralização do carbono orgânico dissolvido. Para tanto, um total de seis agrotóxicos foram selecionados para a o estudo de degradação: bentazona, carbofurano, clomazona, diurom, tebuconazole e piraclostrobina. O sistema Fe0 /H2O2 desenvolvido para a degradação dos agrotóxicos mostrou ser eficiente. A eficiência de degradação foi fortemente afetada pelo pH, massa de limalha de ferro e concentração de peróxido de hidrogênio. As melhores condições para a degradação foram: pH 2,0, 5 mmol L-1 H2O2 e 2,0 g de limalha de ferro. No tempo total de 20 min o carbono orgânico total foi reduzido levando a mineralização de 55%, com taxas de degradação que variaram de 51 a 100%. A utilização de recirculação no sistema Fe0 /H2O2 elevou a taxa de degradação dos agrotóxicos bentazona e carbofurano. As taxas variaram de 93 a 100% de degradação, com um tempo total de reação de 120 min, chegando a 63% de mineralização. O sistema TiO2/UV também mostrou-se adequado a degradação dos agrotóxicos. As condições ótimas foram 20 mg de catalisador, pH 7, TH de 15 min e TR de 110 min. O sistema apresentou taxas de degradação que variaram de 71 a 99,98%. Levando a mineralização de 97,60% da demanda de carbono orgânico.

Nanopartículas hibrídas para sistemas de drug delivery inteligentes

A nanotecnologia é uma ciência multidisciplinar que consiste na otimização das propriedades da matéria permitindo assim o desenvolvimento de sistemas com um tamanho manométrico. A aplicação da nanotecnologia na medicina surge como um campo de pesquisa que esta a gerar um grande interesse, principalmente em sistemas de libertação controlada de fármacos. A nanotecnologia, e a sua aplicação na área da nanomedicina, em particular em drug delivery systems, tem sido alvo de um desenvolvimento acentuado. A administração de fármacos ocorre sobretudo por via oral ou por injeção direta no organismo. O percurso destes fármacos desde do local de entrada no organismo até ao tecido-alvo obriga que estes entrem em contato com os outros tecidos podendo interagir com eles. Deste modo, esta interação química pode produzir efeitos indesejáveis no organismo e reduzir a capacidade de ação do fármaco. Tem-se verificado, nas últimas décadas, um grande desenvolvimento de sistemas que contornam estes problemas, tais como a quantidade e o período de administração do fármaco bem como o seu local de libertação e atuação específicos. Este estudo surge com esta necessidade de se desenvolver sistemas de libertação controlada de fármacos. O objetivo destes sistemas inteligentes é controlar a libertação de fármacos por um dado período de tempo, a dose, a diminuição da toxidade, o aumento da permanência em circulação e o aumento da eficácia terapêutica através da libertação progressiva e controlada do fármaco por administrações menos frequentes. Além de todas estas vantagens, a administração destes sistemas possibilita a libertação dos fármacos em locais específicos, tais como em tumores e, assim, minimizar os efeitos colaterais indesejados dos fármacos em outros tecidos. O presente trabalho visa o desenvolvimento de novos biomateriais utilizando nanopartículas mesoporosas de sílica (MSN) e nanopartículas (NPs) metálicas de ouro para a aplicação a sistemas de libertação controlada de fármacos. Para isto, estudou-se a libertação de doxorrubicina (DOX) encapsulada em NPs e nanocápsulas mesoporosas de sílica tanto em solução como em superfícies como em vidro. Os resultados obtidos mostraram que as NPs apresentam uma grande capacidade de encapsulação com 36 ng DOX/mg partícula. O tempo de libertação em superfície (vidro) foi estimado em 50 horas enquanto que em solução obteve-se um período inferior a 10 horas. Em relação as NPs de ouro pode-se observar como estas promovem a libertação do fármaco ao serem irradiadas mediante um laser. Deste modo, estas NPs podem ser úteis para sistemas de libertação controlada de fármacos e para várias aplicações na nanomedicina.

Síntese, caracterização e estudo da regeneração do silicoaluminofosfato-11 (SAPO-11)

heterogeneous catalyst such as a silicoaluminophosphate, molecular sieve with AEL (Aluminophosphate eleven) structure such as SAPO-11, was synthesized through the hydrothermal method starting from silica, pseudoboehmite, orthophosphoric acid (85%) and water, in the presence of a di-isopropylamine organic template. For the preparation of SAPO-11 in a dry basis it was used as reactants: DIPA; H3PO4; SiO4; Pseudoboehmite and distilled water. The crystallization process occurred when the reactive hydrogel was charged into a vessel and autoclaved at 200ºC for a period of 72 hours under autogeneous pressure. The obtained material was washed, dried and calcined to remove the molecular sieves of DIPA. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), nitrogen adsorption (BET) and thermal analysis (TG/DTG). The acidic properties were determined using adsorption of nbutylamine followed by programmed thermodessorption. This method revealed that SAPO-11 shows an acidity that ranges from weak to moderate. However, a small quantity of strong acid sites could be detected there. The deactivation of the catalysts was conducted by artificial coking followed by the cracking of the n-hexane in a fixed bed with a continuous flow micro-reactor coupled on line to a gas chromatograph. The main products obtained were: ethane, propane, isobutene, n-butane, n-pentane and isopentane. The Vyazovkin (model-free) kinetics method was used to determine the regeneration and removal of the coke

Otimização e análise mecânica de pastas geopoliméricas para uso em poços sujeitos à injeção cíclica de vapor

Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and thermal stability. Basic geopolymeric formulations can be found in the literature, which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21° for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3 for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204ºF (400ºC) and geopolymeric slurries are viable above 500ºF (260ºC)

Obtenção de filtro cerâmico a partir da diatomita e casca de arroz carbonizada visando tratamento de efluente têxtil

The effluents released by the textile industry have high concentrations of alkali, carbohydrates, proteins, in addition to colors containing heavy metals. Therefore, a filter was prepared aiming primarily to the removal of color. In order to prepare this filter, rice hulls and diatomite were used, which have in their structure, basically amorphous hydrated silica. The silica exists in three crystalline forms: quartz, tridymite and cristobalite. In accordance with the above considerations, this study was divided into two stages; the first corresponds to the preparation of the filter and the second to carry out the tests in the effluent/filter in order to verify the efficiency of the color removal. First, the raw material was subjected to a chemical analysis and XRD, and then the diatomite was mixed, via humid, with a planetarium windmill with 20 %, 40 %, 60 % and 80 % of rice husk ash. To the mixture, 5 % carboxymethylcellulose (CMC) was added as a binder at room temperature. The samples were uniaxially compacted into metallic matrix of 0.3 x 0.1 cm² of area at a pressure of 167 MPa by means of hydraulic press and then sintered at temperatures of 1,000 °C, 1,200 °C and 1,400 °C for 1 h and submitted to granulometry test using laser, linear retraction, water absorption, apparent porosity and resistance to bending, DTA, TMA and XRD. To examine the pore structure of the samples scanning electron microscope (SEM) was used. Also tests were carried out in a mercury porosimeter to verify the average size of the pores and real density of the samples. In the second stage, samples of the effluent were collected from a local industry, whose name will be preserved, located in Igapó, in the State of Rio Grande do Norte - RN. The effluent was first pretreated before filtration and then subjected to a treatment of flotation. The effluent was then characterized before and after filtration, with parameters of color, turbidity, suspended solids, pH, chemical and biochemical oxygen demand (COD and BOD). Thus, through the XRD analysis the formation of cristobalite α in all samples was observed. The best average size of pore was found to be 1.75 μm with 61.04 % apparent porosity, thus obtaining an average 97.9 % color removal and 99.8 % removal of suspended solid

Degradação do PMMA através da reação despolimerização uitlizando catalisadores de óxidos mistos

In this work, mixed oxides were synthesized by two methods: polymeric precursor and gel-combustion. The oxides, Niquelate of Lanthanum, Cobaltate of Lanthanum and Cuprate of Lanthanum were synthesized by the polymeric precursor method, and treated at 300 º C for 2 hours, calcined at 800 º C for 6h in air atmosphere. In gel-combustion method were produced and oxides using urea and citric acid as fuel, forming for each fuel the following oxides Ferrate of Lanthanum, Cobaltato of Lanthanum and Ferrato of Cobalt and Lanthanum, which were submitted to the combustion process assisted by microwave power maximum of 10min. The samples were characterized by: thermogravimetric analysis, X-ray diffraction; fisisorção of N2 (BET method) and scanning electron microscopy. The reactions catalytic of depolymerization of poly (methyl methacrylate), were performed in a reactor of silica, with catalytic and heating system equipped with a data acquisition system and the gas chromatograph. For the catalysts synthesized using the polymeric precursor method, the cuprate of lanthanum was best for the depolymerization of the recycled polymer, obtaining 100% conversion in less time 554 (min), and the pure polymer, was the Niquelate of Lanthanum, with 100% conversion in less time 314 (min). By gel-combustion method using urea as fuel which was the best result obtained Ferrate of Lanthanum for the pure polymer with 100% conversion in less time 657 (min), and the recycled polymer was Cobaltate of Lanthanum with 100 % conversion in less time 779 (min). And using citric acid to obtain the best result for the pure polymer, was Ferrate of Lanthanum with 100% conversion in less time 821 (min and) for the recycled polymer, was Ferrate of Lanthanum with 98.28% conversion in less time 635 (min)

Síntese de pigmentos cerâmicos inorgânicos nanométricos e encapsulados com estrutura core-shell pela rota dos precursores poliméricos

The present work has as objective the development of ceramic pigments based in iron oxides and cobalt through the polymeric precursor method, as well as study their characteristics and properties using methods of physical, chemical, morphological and optical characterizations.In this work was used iron nitrate, and cobalt citrate as precursor and nanometer silica as a matrix. The synthesis was based on dissolving the citric acid as complexing agent, addition of metal oxides, such as chromophores ions and polymerization with ethylene glycol. The powder obtained has undergone pre-ignition, breakdown and thermal treatments at different calcination temperatures (700 °C, 800 °C, 900 °C, 1000 °C and 1100 °C). Thermogravimetric analyzes were performed (BT) and Differential Thermal Analysis (DTA), in order to evaluate the term decomposition of samples, beyond characterization by techniques such as BET, which classified as microporous materials samples calcined at 700 ° C, 800 º C and 900 º C and non-porous when annealed at 1000 ° C and 1100 º C, X-ray diffraction (XRD), which identified the formation of two crystalline phases, the Cobalt Ferrite (CoFe2O4) and Cristobalite (SiO2), Scanning Electron Microscopy (SEM) revealed the formation of agglomerates of particles slightly rounded;and Analysis of Colorimetry, temperature of 700 °C, 800 °C and 900 °C showed a brown color and 1000 °C and 1100 °C violet

Mesoestruturas porosas a partir de materiais naturais

The MCM-41 mesoporous synthesis was done using rice hulls ash and chrysotile as natural alternative silica sources. For the using of these sources, chemical and thermic treatments were done in both materials. After chemical and thermic treatments, these materials were employed on the MCM-41 mesoctructures synthesis. The natural materials treated and employed in the synthesis were characterized by several techniques such as X-ray diffraction, N2 adsorption and desorption, scanning electronic microscopy and thermogravimetric analysis. MCM-41 standart samples synthetized with aerosil 200 commercial sílica were used to evaluation. The formed material from rice hulls ash showed values from BET specific area about 468 m².g-1, N2 adsorption and desorption isotherms and loss mass similar to reference materials. The silica from chrysotile calcined and leached was employed to mesoporous materials synthesis. The BET specific area showed values about 700 m².g-1, N2 adsorption and desorption isotherms type IV and loss mass similar to mesoporous materials. The formed material from calcined and leached chrysotile, without calcination, applied to phenol remotion carried high performance liquid chromatography and evaluated with organophilic clays with different treatments. By the characterization techniques were proved that mesoporous materials with lesser order that reference samples. The material formed from rice hulls ash without the calcination step achieved better adsorption results than organophilic clays

Utilização de nanosílica como aditivo estendedor para pastas cimentantes de baixa densidade destinadas à cimentação de poços petrolíferos

Cementing operations are conducted at different times of the well s life and they have high importance, because the functions are fundamental to keep good properties during a long life of the well, such as, maintain the mechanical stability of the well, to promote the isolation hydraulic and support the tubing. In some situations, the rocky zones have low fractures pressures and require the use of lightweight slurries to prevent the hydrostatic pressure in the formation is greater than the pressure of fracture. There are three ways to reduce the density of cement slurries: exterders water additives, microspheres and foamed slurries. The most used extender water additive is sodium bentonite, which is a clay with a good capacity of water absorption and expansion of its volume, the main disadvantage of this additive is the reduction of the strength. Currently, the use of nanoscale particles has received special attention, mainly because they get new functionalities. Following this trend, this paper aims to use a colloidal solution of nano-silica as an exterders water additives for use in oil wells. Slurries were designed with fixed 13lb/gal density and concentration of nano silica 0.1 gpc; 0.4 gpc; 0.7 and 1gpc, the influence of nano-silica was studied at these levels in isolation and combined varying concentrations of CaCl2,. Tests including rheology, stability, strength, thickening time, porosity and permeability. Besides the API tests, microstructural characterizations were performed after 28 days of the slurries, X-ray diffraction (XRD) and scanning electron microscopy (SEM)

Preparação, caracterização e aplicação de derivados do ácido 12- tungstofosfórico suportado em SBA-15

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2016.

Síntese de zeólita A a partir de diatomita como fonte de aluminossilicato

The synthesis of zeolites from natural sources of silicon and aluminum are promising alternative routes to obtain porous or zeolite MCM family. Such materials are typically used in catalytic processes and / or adsorption is to obtain new products or for separation and purification processes thereof. Environmental legislation is becoming stricter and requires the use of materials more efficient, aiming to achieve pollution prevention, by gas or liquid contaminants in the environment. In order to obtain a material with environmentally friendly features, this study aimed at the synthesis of zeolite A, from an amorphous sediment, diatomite, which is found in abundance in the northeast region of Brazil, may be substituted for conventional products the production of zeolite, involving higher costs. The methodology for obtaining the "Zeolite A" using as a source of silica and alumina diatomite is simple, since this is a source of silicon, not requiring therefore a structural driver, but also by heat treatment, only drying conventional to remove water. The "zeolite A" was obtained from diatomite, but as an intermediate step we obtained the sodalite. The characterization was made by the following techniques: EDX, XRD, FT-IR, SEM and determining a specific area by the BET method and the BJH method for checking the diameter of pores. By characterization of the obtained material was first demonstrated the achievement of sodalite and after modification of the same, there was obtained zeolite A